Iron-based sintered alloy having excellent machinability

[0001] This is a U.S. national phase application under 35 U.S.C. §371 of International Patent Application No. PCT/JP2004/003094 filed Mar. 10, 2004, and claims the benefit of Japanese Patent Application No. 2003-62854 filed Mar. 10, 2003 which is incorporated by reference herein. The International Application published in Japanese on Sep. 23, 2004 as WO 2004/003094 A1 under PCT Article 21(2).

[0002] The present invention relates to an iron-based sintered alloy having excellent machinability which is used as materials for various machine components.

[0003] With the progress of a sintering technique, various electric components such as yoke and rotor, and various machine components such as pistons for shock absorber, rod guides, bearing caps, valve plates for compressor, hubs, forkshifts, sprockets, toothed wheels, gears and synchronizer hubs have recently been produced using an iron-based sintered alloy obtained by sintering a raw powder mixture. For example, it is known that an iron-based sintered alloy having the composition consisting of pure iron and 0.1 to 1.5% by mass of P, the balance being Fe and inevitable impurities, is used to produce various electric components such as yokes and rotors. It is known that an iron-based sintered alloy having the composition consisting of 0.1 to 1.2% by mass of C, the balance being Fe and inevitable impurities, is used to produce pistons for shock absorber, and lot guides. It is known that an iron-based sintered alloy having the composition consisting of 0.1 to 1.2% by mass of C and 10 to 25% by mass of Cu, the balance being Fe and inevitable impurities, is used to produce bearing caps, and valve plates for compressor. It is known that an iron-based sintered alloy having the composition consisting of 0.1 to 1.2% by mass of C and 0.1 to 6% by mass of Cu, the balance being Fe and inevitable impurities, is used to produce forkshifts, sprockets, gears, toothed wheels, and pistons for shock absorber. It is known that an iron-based sintered alloy having the composition consisting of 0.1 to 1.2% by mass of C, 0.1 to 6% by mass of Cu, 0.1 to 10% by mass of Ni and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities, is used to produce CL cranks, sprockets, gears, and toothed wheels.

[0004] It is known that an iron-based sintered alloy having the composition consisting of 0.1 to 1.2% by mass of C and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities, an iron-based sintered alloy having the composition consisting of 0.1 to 1.2% by mass of C, 0.1 to 10% by mass of Cr and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities, an iron-based sintered alloy having the composition consisting of 0.1 to 1.2% by mass of C, 0.1 to 10% by mass of Ni, 0.1 to 10% by mass of Cr and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities, an iron-based sintered alloy having the composition consisting of 0.1 to 1.2% by mass of C, 0.1 to 6% by mass of Cu, 0.1 to 10% by mass of Ni, 0.1 to 10% by mass of Cr and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities, an iron-based sintered alloy having the composition consisting of 0.1 to 1.2% by mass of C and 0.1 to 10% by mass of Ni, the balance being Fe and inevitable impurities, an iron-based sintered alloy having the composition consisting of 0.1 to 1.2% by mass of C, 0.1 to 10% by mass of Ni and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities, and an iron-based sintered alloy having the composition consisting of 0.1 to 1.2% by mass of C, 0.1 to 6% by mass of Cu and 0.1 to 10% by mass of Ni, the balance being Fe and inevitable impurities, are used as materials of various machine components such as sprockets, gears and toothed wheels.

[0005] Also it is known that an iron-based sintered alloy having the composition consisting of 1.0 to 3.0% by mass of C, 0.5 to 8% by mass of Cu and 0.1 to 0.8% by mass of P, the balance being Fe and inevitable impurities, are used as materials of valve guides.

[0006] Also it is known that an iron-based sintered alloy having the composition consisting of 0.3 to 2.5% by mass of C, 0.5 to 12% by mass of Cr, 0.3 to 9% by mass of Mo, 3 to 14% by mass of W and 1 to 6% by mass of V, the balance being Fe and inevitable impurities, an iron-based sintered alloy having the composition consisting of 0.3 to 2.5% by mass of C, 0.5 to 12% by mass of Cr, 0.3 to 9% by mass of Mo, 3 to 14% by mass of W, 1 to 6% by mass of V and 5 to 14% by mass of Co, the balance being Fe and inevitable impurities, an iron-based sintered alloy having the composition consisting of 0.3 to 2% by mass of C, 0.5 to 10% by mass of Cr, 0.3 to 16% by mass of Mo and 0.1 to 5% by mass of Ni, and one or more kinds selected from among 1 to 5% by mass of W, 0.05 to 1% by mass of Si, 0.5 to 18% by mass of Co and 0.05 to 2% by mass of Nb, the balance being Fe and inevitable impurities, an iron-based sintered alloy having the composition consisting of 0.3 to 2% by mass of C, 0.5 to 10% by mass of Cr, 0.3 to 16% by mass of Mo and 0.1 to 5% by mass of Ni, one or more kinds selected from among 1 to 5% by mass of W, 0.05 to 1% by mass of Si, 0.5 to 18% by mass of Co and 0.05 to 2% by mass of Nb, and 10 to 20% by mass of Cu, the balance being Fe and inevitable impurities, and an iron-based sintered alloy having the composition consisting of 0.3 to 2% by mass of C, 0.1 to 3% by mass of Mo, 0.05 to 5% by mass of Ni and 0.1 to 2% by mass of Co, the balance being Fe and inevitable impurities, are used as materials of valve seats.

[0007] Also it is known that an iron-based sintered alloy having the composition consisting of 15 to 27% by mass of Cr and 3 to 29% by mass of Ni, the balance being Fe and inevitable impurities, an iron-based sintered alloy having the composition consisting of one or more kinds selected from among 15 to 27% by mass of Cr, 3 to 29% by mass of Ni, 0.5 to 7% by mass of Mo and 0.5 to 4% by mass of Cu, the balance being Fe and inevitable impurities, an iron-based sintered alloy having the composition consisting of 10 to 33% by mass of Cr, the balance being Fe and inevitable impurities, an iron-based sintered alloy having the composition consisting of 10 to 33% by mass of Cr and 0.5 to 3% by mass of Mo, the balance being Fe and inevitable impurities, an iron-based sintered alloy having the composition consisting of 10 to 33% by mass of Cr and 0.5 to 3% by mass of Mo, the balance being Fe and inevitable impurities, an iron-based sintered alloy having the composition consisting of 10 to 19% by mass of Cr and 0.05 to 1.3% by mass of C, the balance being Fe and inevitable impurities, an iron-based sintered alloy having the composition consisting of 14 to 19% by mass of Cr and 2 to 8% by mass of Ni, the balance being Fe and inevitable impurities, and an iron-based sintered alloy having the composition consisting of 14 to 19% by mass of Cr and 2 to 8% by mass of Ni, and one or more kinds selected from among 2 to 6% by mass of Cu, 0.1 to 0.5% by mass of Nb and 0.5 to 1.5% by mass of Al, the balance being Fe and inevitable impurities, are used as materials of corrosion-resistant machine components.

[0008] Various machine components made of these conventional iron-based sintered alloys are produced by blending predetermined raw powders, mixing the powders and compacting the powder mixture to obtain a green compact, and sintering the resulting green compact in a vacuum, dissociated ammonia gas, N₂+5% H₂ gas mixture, endothermic gas or exothermic gas atmosphere, and are finally shipped after piercing the required position using a drill and cutting or grinding the surface. Machining such as piercing, cutting or grinding is conducted by using various cutting tools. When machine components have a lot of positions to be cut, cutting tools are drastically worn out, resulting in high cost. Therefore, there has been made a trial of suppressing wear of the cutting tool by a method of adding about 1% of a MnS or MnO powder and sintering the resulting green compact thereby to improve machinability of the cutting tool (see Japanese Patent Application, First Publication No. Hei 3-267354) or a method of adding a CaO—MgO—SiO₂-based complex oxide, thereby to improve machinability (see Japanese Patent Application, First Publication No. Hei 8-260113) of the cutting tool, and thus reducing the cost.

[0009] An iron-based sintered alloy obtained by adding a conventional MnS powder, MnO powder or CaO—MgO—SiO₂-based complex oxide powder and sintering the resulting green compact has machinability, which is improved to some extent, but is not still satisfactory. Therefore, it is required to develop an iron-based sintered alloy having more excellent machinability.

[0010] From such a point of view, the present inventors have intensively studied so as to obtain an iron-based sintered alloy having more excellent machinability, which can be used as materials of various electric and machine components. As a result, they have found that an iron-based sintered alloy containing 0.05 to 3% by mass of a calcium carbonate powder or an iron-based sintered alloy containing 0.05 to 3% by mass of a strontium carbonate powder has more improved machinability.

[0011] The present invention has been made based on such a finding and is characterized by the followings:

• [0012] (1) an iron-based sintered alloy having excellent machinability, comprising 0.05 to 3% by mass of calcium carbonate,
• [0013] (2) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, the balance being Fe and inevitable impurities,
• [0014] (3) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate and 0.1 to 1.5% by mass of P, the balance being Fe and inevitable impurities,
• [0015] (4) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate and 0.1 to 1.2% by mass of C, the balance being Fe and inevitable impurities,
• [0016] (5) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 0.1 to 1.2% by mass of C and 10 to 25% by mass of Cu, the balance being Fe and inevitable impurities,
• [0017] (6) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 0.1 to 1.2% by mass of C and 0.1 to 6% by mass of Cu, the balance being Fe and inevitable impurities,
• [0018] (7) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 0.1 to 1.2% by mass of C, 0.1 to 6% by mass of Cu, 0.1 to 10% by mass of Ni and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities,
• [0019] (8) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 0.1 to 1.2% by mass of C and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities,
• [0020] (9) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 0.1 to 1.2% by mass of C, 0.1 to 10% by mass of Cr and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities,
• [0021] (10) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 0.1 to 1.2% by mass of C, 0.1 to 10% by mass of Ni, 0.1 to 10% by mass of Cr and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities,
• [0022] (11) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 0.1 to 1.2% by mass of C, 0.1 to 6% by mass of Cu, 0.1 to 10% by mass of Ni, 0.1 to 10% by mass of Cr and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities,
• [0023] (12) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 0.1 to 1.2% by mass of C and 0.1 to 10% by mass of Ni, the balance being Fe and inevitable impurities,
• [0024] (13) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 0.1 to 1.2% by mass of C, 0.1 to 10% by mass of Ni and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities,
• [0025] (14) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 0.1 to 1.2% by mass of C, 0.1 to 6% by mass of Cu and 0.1 to 10% by mass of Ni, the balance being Fe and inevitable impurities,
• [0026] (15) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 1.0 to 3.0% by mass of C, 0.5 to 8% by mass of Cu and 0.1 to 0.8% by mass of P, the balance being Fe and inevitable impurities,
• [0027] (16) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 0.3 to 2.5% by mass of C, 0.5 to 12% by mass of Cr, 0.3 to 9% by mass of Mo, 3 to 14% by mass of W and 1 to 6% by mass of V, the balance being Fe and inevitable impurities,
• [0028] (17) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 0.3 to 2.5% by mass of C, 0.5 to 12% by mass of Cr, 0.3 to 9% by mass of Mo, 3 to 14% by mass of W, 1 to 6% by mass of V and 5 to 14% by mass of Co, the balance being Fe and inevitable impurities,
• [0029] (18) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 0.3 to 2% by mass of C, 0.5 to 10% by mass of Cr, 0.3 to 16% by mass of Mo and 0.1 to 5% by mass of Ni, and one or more kinds selected from among 1 to 5% by mass of W, 0.05 to 1% by mass of Si, 0.5 to 18% by mass of Co and 0.05 to 2% by mass of Nb, the balance being Fe and inevitable impurities,
• [0030] (19) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 0.3 to 2% by mass of C, 0.5 to 10% by mass of Cr, 0.3 to 16% by mass of Mo and 0.1 to 5% by mass of Ni, one or more kinds selected from among 1 to 5% by mass of W, 0.05 to 1% by mass of Si, 0.5 to 18% by mass of Co and 0.05 to 2% by mass of Nb, and 10 to 20% by mass of Cu, the balance being Fe and inevitable impurities,
• [0031] (20) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 0.3 to 2% by mass of C, 0.1 to 3% by mass of Mo, 0.05 to 5% by mass of Ni and 0.1 to 2% by mass of Co, the balance being Fe and inevitable impurities,
• [0032] (21) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 15 to 27% by mass of Cr and 3 to 29% by mass of Ni, the balance being Fe and inevitable impurities,
• [0033] (22) an iron-based sintered alloy having excellent machinability with the composition consisting of one or more kinds selected from among 0.05 to 3% by mass of calcium carbonate, 15 to 27% by mass of Cr, 3 to 29% by mass of Ni, 0.5 to 7% by mass of Mo and 0.5 to 4% by mass of Cu, the balance being Fe and inevitable impurities,
• [0034] (23) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate and 10 to 33% by mass of Cr, the balance being Fe and inevitable impurities,
• [0035] (24) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 10 to 33% by mass of Cr and 0.5 to 3% by mass of Mo, the balance being Fe and inevitable impurities,
• [0036] (25) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 10 to 19% by mass of Cr and 0.05 to 1.3% by mass of C, the balance being Fe and inevitable impurities,
• [0037] (26) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 14 to 19% by mass of Cr and 2 to 8% by mass of Ni, the balance being Fe and inevitable impurities,
• [0038] (27) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of calcium carbonate, 14 to 19% by mass of Cr and 2 to 8% by mass of Ni, and one or more kinds selected from among 2 to 6% by mass of Cu, 0.1 to 0.5% by mass of Nb and 0.5 to 1.5% by mass of Al, the balance being Fe and inevitable impurities,
• [0039] (28) an iron-based sintered alloy having excellent machinability, comprising 0.05 to 3% by mass of strontium carbonate,
• [0040] (29) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, the balance being Fe and inevitable impurities,
• [0041] (30) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate and 0.1 to 1.5% by mass of P, the balance being Fe and inevitable impurities,
• [0042] (31) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate and 0.1 to 1.2% by mass of C, the balance being Fe and inevitable impurities,
• [0043] (32) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 0.1 to 1.2% by mass of C and 10 to 25% by mass of Cu, the balance being Fe and inevitable impurities,
• [0044] (33) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 0.1 to 1.2% by mass of C and 0.1 to 6% by mass of Cu, the balance being Fe and inevitable impurities,
• [0045] (34) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 0.1 to 1.2% by mass of C, 0.1 to 6% by mass of Cu, 0.1 to 10% by mass of Ni and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities,
• [0046] (35) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 0.1 to 1.2% by mass of C and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities,
• [0047] (36) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 0.1 to 1.2% by mass of C, 0.1 to 10% by mass of Cr and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities,
• [0048] (37) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 0.1 to 1.2% by mass of C, 0.1 to 10% by mass of Ni, 0.1 to 10% by mass of Cr and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities,
• [0049] (38) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 0.1 to 1.2% by mass of C, 0.1 to 6% by mass of Cu, 0.1 to 10% by mass of Ni, 0.1 to 10% by mass of Cr and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities,
• [0050] (39) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 0.1 to 1.2% by mass of C and 0.1 to 10% by mass of Ni, the balance being Fe and inevitable impurities,
• [0051] (40) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 0.1 to 1.2% by mass of C, 0.1 to 10% by mass of Ni and 0.1 to 6% by mass of Mo, the balance being Fe and inevitable impurities,
• [0052] (41) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 0.1 to 1.2% by mass of C, 0.1 to 6% by mass of Cu and 0.1 to 10% by mass of Ni, the balance being Fe and inevitable impurities,
• [0053] (42) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 1.0 to 3.0% by mass of C, 0.5 to 8% by mass of Cu and 0.1 to 0.8% by mass of P, the balance being Fe and inevitable impurities,
• [0054] (43) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 0.3 to 2.5% by mass of C, 0.5 to 12% by mass of Cr, 0.3 to 9% by mass of Mo, 3 to 14% by mass of W and 1 to 6% by mass of V, the balance being Fe and inevitable impurities,
• [0055] (44) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 0.3 to 2.5% by mass of C, 0.5 to 12% by mass of Cr, 0.3 to 9% by mass of Mo, 3 to 14% by mass of W, 1 to 6% by mass of V and 5 to 14% by mass of Co, the balance being Fe and inevitable impurities,
• [0056] (45) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 0.3 to 2% by mass of C, 0.5 to 10% by mass of Cr, 0.3 to 16% by mass of Mo and 0.1 to 5% by mass of Ni, and one or more kinds selected from among 1 to 5% by mass of W, 0.05 to 1% by mass of Si, 0.5 to 18% by mass of Co and 0.05 to 2% by mass of Nb, the balance being Fe and inevitable impurities,
• [0057] (46) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 0.3 to 2% by mass of C, 0.5 to 10% by mass of Cr, 0.3 to 16% by mass of Mo and 0.1 to 5% by mass of Ni, one or more kinds selected from among 1 to 5% by mass of W, 0.05 to 1% by mass of Si, 0.5 to 18% by mass of Co and 0.05 to 2% by mass of Nb, and 10 to 20% by mass of Cu, the balance being Fe and inevitable impurities,
• [0058] (47) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 0.3 to 2% by mass of C, 0.1 to 3% by mass of Mo, 0.05 to 5% by mass of Ni and 0.1 to 2% by mass of Co, the balance being Fe and inevitable impurities,
• [0059] (48) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 15 to 27% by mass of Cr and 3 to 29% by mass of Ni, the balance being Fe and inevitable impurities,
• [0060] (49) an iron-based sintered alloy having excellent machinability with the composition consisting of one or more kinds selected from among 0.05 to 3% by mass of strontium carbonate, 15 to 27% by mass of Cr, 3 to 29% by mass of Ni, 0.5 to 7% by mass of Mo and 0.5 to 4% by mass of Cu, the balance being Fe and inevitable impurities,
• [0061] (50) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate and 10 to 33% by mass of Cr, the balance being Fe and inevitable impurities,
• [0062] (51) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 10 to 33% by mass of Cr and 0.5 to 3% by mass of Mo, the balance being Fe and inevitable impurities,
• [0063] (52) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 10 to 19% by mass of Cr and 0.05 to 1.3% by mass of C, the balance being Fe and inevitable impurities,
• [0064] (53) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 14 to 19% by mass of Cr and 2 to 8% by mass of Ni, the balance being Fe and inevitable impurities, and
• [0065] (54) an iron-based sintered alloy having excellent machinability with the composition consisting of 0.05 to 3% by mass of strontium carbonate, 14 to 19% by mass of Cr and 2 to 8% by mass of Ni, and one or more kinds selected from among 2 to 6% by mass of Cu, 0.1 to 0.5% by mass of Nb and 0.5 to 1.5% by mass of Al, the balance being Fe and inevitable impurities.

[0066] The iron-based sintered alloys having excellent machinability, which contain 0.05 to 3% by mass of calcium carbonate, according to (1) to (27) of the present invention are produced by blending a calcium carbonate powder having an average particle size of 0.1 to 30 μm with raw powders, mixing these powders and compacting the powder mixture to obtain a green compact, and sintering the resulting green compact in an atmosphere of a nonoxidizing gas such as vacuum, dissociated ammonia gas, N₂+5% H₂ gas mixture, endothermic gas or exothermic gas. The green compact is particularly preferably sintered in an atmosphere of the nonoxidizing gas such as endothermic gas or exothermic gas. The iron-based sintered alloy thus obtained has a structure in which CaCO₃ is dispersed at grain boundary in a basis material of the iron-based sintered alloy. The presence of CaCO₃ in the sintered compact obtained by sintering the green compact can be confirmed by X-ray diffraction.

[0067] The iron-based sintered alloys having excellent machinability, which contain 0.05 to 3% by mass of strontium carbonate, according to (28) to (54) of the present invention are produced by blending a strontium carbonate powder having an average particle size of 0.1 to 30 μm with raw powders, mixing these powders and compacting the powder mixture to obtain a green compact, and sintering the resulting green compact in an atmosphere of a nonoxidizing gas such as vacuum, dissociated ammonia gas, N₂+5% H₂ gas mixture, endothermic gas or exothermic gas. The green compact is particularly preferably sintered in an atmosphere of the nonoxidizing gas such as endothermic gas or exothermic gas. The iron-based sintered alloy thus obtained has a structure in which SrCO₃ is dispersed at grain boundary in a basis material of the iron-based sintered alloy. The presence of SrCO₃ in the sintered compact obtained by sintering the green compact can be confirmed by X-ray diffraction.

[0068] Therefore, the present invention is characterized by the followings: (55) a method for preparing the iron-based sintered alloy having excellent machinability according to any one of (1) to (27), which comprises compacting a raw powder mixture containing 0.05 to 3% by mass of a calcium carbonate powder having an average particle size of 0.1 to 30 μm as a raw powder to obtain a green compact and sintering the resulting green compact in a nonoxidizing gas atmosphere, and (56) a method for preparing the iron-based sintered alloy having excellent machinability according to any one of (28) to (54), which comprises compacting a raw powder mixture containing 0.05 to 3% by mass of a strontium carbonate powder having an average particle size of 0.1 to 30 μm as a raw powder to obtain a green compact and sintering the resulting green compact in a nonoxidizing gas atmosphere.

[0069] The average particle size of the calcium carbonate powder as the raw powder was defined within a range from 0.1 to 30 μm by the following reason. That is, when the average particle size of the calcium carbonate powder exceeds 30 μm, a contact area between the calcium carbonate powder and the basis material decreases and sufficient machinability improving effect is not exerted. On the other hand, when the average particle size of the calcium carbonate powder is less than 0.1 μm, a force of agglomeration increases, and thus the calcium carbonate powder is not uniformly dispersed in the basis material and further machinability improving effect is not exerted, and it is not preferred.

[0070] The average particle size of the strontium carbonate powder as the raw powder was defined within a range from 0.1 to 30 μm by the following reason. That is, when the average particle size of the strontium carbonate powder exceeds 30 μm, a contact area between the strontium carbonate powder and the basis material decreases and sufficient machinability improving effect is not exerted. On the other hand, when the average particle size of the strontium carbonate powder is less than 0.1 μm, a force of agglomeration increases, and thus the strontium carbonate powder is not uniformly dispersed in the basis material and further machinability improving effect is not exerted, and it is not preferred.

[0071] The endothermic gas is a gas containing, as a main component, hydrogen, carbon monoxide and nitrogen, which is obtained by mixing a natural gas, propane, butane or coke oven gas with an air to obtain a gas mixture, and decomposing and converting the gas mixture while passing through a heated catalyst composed mainly of nickel. In this case, since this reaction is an endothermic reaction, a catalyst layer must be heated. The exothermic gas is a gas containing nitrogen as a main component, hydrogen and carbon monoxide, which is obtained by semicombusting a natural gas, propane, butane or coke oven gas with air, and decomposing and converting the combustion gas while passing through a nickel catalyst layer or charcoal layer. In this case, since the temperature of the catalyst increases due to combustion heat of the raw gas, it is not necessary to externally heat the catalyst layer.

[0072] The sintering temperature, at which the iron-based sintered alloy having excellent machinability is sintered, is preferably from 1100 to 1300° C. (more preferably from 1110 to 1250° C.) and this sintering temperature is the temperature which is generally known as a temperature at which the iron-based sintered alloy is sintered.

[0073] The reason why the composition of the CaCO₃ component and the composition of the SrCO₃ component in the iron-based sintered alloy having excellent machinability of the present invention were as limited as described above will now be described.

[0074] CaCO₃ has such an effect that it exists at grain boundary and is uniformly dispersed in a basis material, thereby to improve machinability. When the content is less than 0.05% by mass, sufficient machinability improving effect is not exerted. On the other hand, even when the content exceeds 3.0% by mass, further machinability improving effect is not exerted and the strength of the iron-based sintered alloy rather decreases, and therefore it is not preferred. Therefore, the content of CaCO₃ in the iron-based sintered alloy of the present invention was defined within a range from 0.05 to 3.0% by mass. The content of CaCO₃ is more preferably within a range from 0.1 to 2% by mass.

[0075] SrCO₃ has such an effect that it exists at grain boundary and is uniformly dispersed in a basis material, thereby to improve machinability. When the content is less than 0.05% by mass, sufficient machinability improving effect is not exerted. On the other hand, even when the content exceeds 3.0% by mass, further machinability improving effect is not exerted and the strength of the iron-based sintered alloy rather decreases, and therefore it is not preferred. Therefore, the content of SrCO₃ in the iron-based sintered alloy of the present invention was defined within a range from 0.05 to 3.0% by mass. The content of SrCO₃ is more preferably within a range from 0.1 to 2% by mass.

[0076] Preferred examples of the present invention will now be described with reference to the accompanying drawings. The present invention is not limited to the following examples and, for example, constituent features of these examples may be appropriately combined with each other.

[0077] As raw powders, a CaCO₃ powder having an average particle size shown in Table 1, a CaMgSiO₄ powder having an average particle size of 10 μm, a MnS powder having an average particle size of 20 μm, a CaF₂ powder having an average particle size of 36 μm and a pure Fe powder having an average particle size of 80 μm were prepared. These raw powders were blended according to the formulation shown in Table 1, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 1 to 10 of the present invention, comparative sintered alloys 1 to 2, and conventional sintered alloys 1 to 3.

[0078] Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 1 to 10 of the present invention, the comparative sintered alloys 1 to 2, and the conventional sintered alloys 1 to 3 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

• [0079] Rotating speed: 10000 rpm
• [0080] Feed speed: 0.030 mm/rev.
• [0081] Cutting oil: none (dry).
  The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 1. Machinability was evaluated by the results.

[0082]

	TABLE 1
		Component
	Component ratio of raw powder	ratio of iron-based
	(mass %)	sintered alloy (mass %)
	CaCO3 powder			Fe and	Number of
	Average particle size is			inevitable	piercing
Iron-based sintered alloy	described in parenthesis.	Fe powder	CaCO3	impurities	(times)	Remarks
Products of the	1	0.05 (0.1 μm)	balance	0.03	balance	59	—
present invention	2	0.2 (0.1 μm)	balance	0.18	balance	137	—
	3	0.5 (0.6 μm)	balance	0.48	balance	155	—
	4	1.0 (2 μm)	balance	0.95	balance	203	—
	5	1.3 (0.6 μm)	balance	1.26	balance	196	—
	6	1.5 (2 μm)	balance	1.48	balance	236	—
	7	1.8 (18 μm)	balance	1.76	balance	213	—
	8	2.1 (2 μm)	balance	1.99	balance	176	—
	9	2.5 (18 μm)	balance	2.43	balance	222	—
	10	3.0 (30 μm)	balance	2.97	balance	310	—
Comparative	1	0.02* (40 μm*)	balance	0.01	balance	23	—
products	2	3.5* (0.01 μm*)	balance	3.45*	balance	114	decrease in
							strength
Conventional	1	CaMgSi4: 1	balance	CaMgSi4: 1	balance	38	—
products	2	MnS: 1	balance	MnS: 0.97	balance	27	—
	3	CaF2: 1	balance	CaF2: 1	balance	25	—
The symbol * means the value which is not within the scope of the present invention.

[0083] As is apparent from the results shown in Table 1, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 1 to 10 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 1 to 3 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 1 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 2 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

[0084] As raw powders, a CaCO₃ powder having an average particle size shown in Table 2, a CaMgSiO₄ powder having an average particle size of 10 μm, a MnS powder having an average particle size of 20 μm, a CaF₂ powder having an average particle size of 36 μm and a Fe-0.6 mass % P powder having an average particle size of 80 μm were prepared. These raw powders were blended according to the formulation shown in Table 2, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 11 to 20 of the present invention, comparative sintered alloys 3 to 4, and conventional sintered alloys 4 to 6.

[0085] Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 11 to 20 of the present invention, the comparative sintered alloys 3 to 4, and the conventional sintered alloys 4 to 6 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

• [0086] Rotating speed: 10000 rpm
• [0087] Feed speed: 0.030 mm/rev.
• [0088] Cutting oil: none (dry).
  The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 2. Machinability was evaluated by the results.

[0089]

	TABLE 2
	Component ratio of	Component ratio of
	raw powder	iron-based sintered alloy
	(mass %)	(mass %)
	CaCO3 powder				Fe
	Average particle	Fe-based			and	Number of
Iron-based sintered	size is described	alloy			inevitable	piercing
alloy	in parenthesis.	powder#	CaCO3	P	impurities	(times)	Remarks
Products of the	11	0.05 (0.1 μm)	balance	0.03	0.55	balance	51	—
present invention	12	0.2 (0.1 μm)	balance	0.18	0.58	balance	119	—
	13	0.5 (0.6 μm)	balance	0.48	0.53	balance	158	—
	14	1.0 (2 μm)	balance	0.95	0.53	balance	176	—
	15	1.3 (0.6 μm)	balance	1.28	0.57	balance	140	—
	16	1.5 (2 μm)	balance	1.48	0.57	balance	131	—
	17	1.8 (18 μm)	balance	1.76	0.54	balance	167	—
	18	2.1 (2 μm)	balance	1.99	0.53	balance	121	—
	19	2.5 (18 μm)	balance	2.42	0.55	balance	137	—
	20	3.0 (30 μm)	balance	2.97	0.55	balance	186	—
Comparative	3	0.02* (40 μm*)	balance	0.01*	0.56	balance	27	—
products	4	3.5* (0.01 μm*)	balance	3.42*	0.54	balance	125	decrease in
								strength
Conventional	4	CaMgSi4: 1	balance	CaMgSi4: 1	0.55	balance	33	—
products	5	MnS: 1	balance	MnS: 0.97	0.55	balance	35	—
	6	CaF2: 1	balance	CaF2: 1	0.55	balance	22	—
The symbol * means the value which is not within the scope of the present invention.
#Fe-based alloy powder with the composition of Fe-0.6 mass % P

[0090] As is apparent from the results shown in Table 2, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 11 to 20 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 4 to 6 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 3 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 4 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

[0091] As raw powders, a CaCO₃ powder having an average particle size shown in Table 3, a CaMgSiO₄ powder having an average particle size of 10 μm, a MnS powder having an average particle size of 20 μm, a CaF₂ powder having an average particle size of 36 μm, a Fe powder having an average particle size of 80 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 3, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 21 to 30 of the present invention, comparative sintered alloys 5 to 6, and conventional sintered alloys 7 to 9.

[0092] Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 21 to 30 of the present invention, the comparative sintered alloys 5 to 6, and the conventional sintered alloys 7 to 9 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

• [0093] Rotating speed: 10000 rpm
• [0094] Feed speed: 0.018 mm/rev.
• [0095] Cutting oil: none (dry).
  The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 3. Machinability was evaluated by the results.

[0096]

	TABLE 3
	Component ratio of	Component ratio of iron-based
	raw powder (mass %)	sintered alloy (mass %)
	CaCO3 powder					Fe
	Average particle					and	Number of
Iron-based sintered	size is described	C	Fe			inevitable	piercing
alloy	in parenthesis.	powder	powder	CaCO3	C	impurities	(times)	Remarks
Products of the	21	0.05 (0.1 μm)	0.13	balance	0.03	0.11	balance	80	—
present invention	22	0.2 (0.1 μm)	0.3	balance	0.17	0.24	balance	102	—
	23	0.5 (0.6 μm)	0.6	balance	0.47	0.54	balance	95	—
	24	1.0 (2 μm)	0.8	balance	0.94	0.55	balance	135	—
	25	1.3 (0.6 μm)	1.1	balance	1.22	1.02	balance	197	—
	26	1.5 (2 μm)	1.1	balance	1.43	0.99	balance	208	—
	27	1.8 (18 μm)	1.1	balance	1.69	1.05	balance	191	—
	28	2.1 (2 μm)	1.1	balance	2.09	1.03	balance	220	—
	29	2.5 (18 μm)	1.1	balance	2.3	1.03	balance	174	—
	30	3.0 (30 μm)	1.2	balance	2.91	1.15	balance	180	—
Comparative	5	0.02* (40 μm*)	1.1	balance	0.01*	1.04	balance	22	—
products	6	3.5* (0.01 μm*)	1.1	balance	3.38*	1.01	balance	126	decrease in
									strength
Conventional	7	CaMgSi4: 1 (10 μm)	1.1	balance	CaMgSi4: 1	1.04	balance	37	—
products	8	MnS: 1 (20 μm)	1.1	balance	MnS: 0.97	1.04	balance	45	—
	9	CaF2: 1 (36 μm)	1.1	balance	CaF2: 1	1.04	balance	29	—
The symbol * means the value which is not within the scope of the present invention.

[0097] As is apparent from the results shown in Table 3, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 21 to 30 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 7 to 9 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 5 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 6 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

[0098] As raw powders, a CaCO₃ powder having an average particle size shown in Table 4, a CaMgSiO₄ powder having an average particle size of 10 μm, a MnS powder having an average particle size of 20 μm, a CaF₂ powder having an average particle size of 36 μm, a Fe powder having an average particle size of 80 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 4, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes and subjected to 20% Cu infiltration to obtain iron-based sintered alloys 31 to 40 of the present invention, comparative sintered alloys 7 to 8, and conventional sintered alloys 10 to 12.

[0099] Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 31 to 40 of the present invention, the comparative sintered alloys 7 to 8, and the conventional sintered alloys 10 to 12 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

• [0100] Rotating speed: 10000 rpm
• [0101] Feed speed: 0.018 mm/rev.
• [0102] Cutting oil: none (dry).
  The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 4. Machinability was evaluated by the results.

[0103]

	TABLE 4
		Component ratio of iron-based sintered
	Component ratio of raw powder (mass %)	alloy (mass %)
	CaCO3 powder							Fe	Number
	Average particle							and	of
Iron-based sintered	size is described			Infiltration				inevitable	piercing
alloy	in parenthesis.	C powder	Fe powder	Cu	CaCO3	C	Cu	impurities	(times)	Remarks
Products of the	31	0.05 (0.1 μm)	0.13	balance	20	0.05	0.12	19.5	balance	78	—
present	32	0.2 (0.5 μm)	0.3	balance	20	0.20	0.24	20.2	balance	126	—
invention	33	0.5 (1 μm)	0.6	balance	20	0.49	0.54	20.1	balance	186	—
	34	1.0 (2 μm)	0.8	balance	20	0.97	0.75	19.6	balance	201	—
	35	1.3 (0.5 μm)	1.1	balance	20	1.28	1.05	19.9	balance	210	—
	36	1.5 (2 μm)	1.1	balance	20	1.46	0.99	20.4	balance	176	—
	37	1.8 (18 μm)	1.1	balance	20	1.77	1.05	19.8	balance	197	—
	38	2.1 (2 μm)	1.1	balance	20	2.09	1.07	20.0	balance	189	—
	39	2.5 (18 μm)	1.1	balance	20	2.45	1.07	19.7	balance	160	—
	40	3.0 (30 μm)	1.2	balance	20	2.96	1.15	19.9	balance	152	—
Comparative	7	0.02* (40 μm*)	1.1	balance	20	0.01*	1.04	20.3	balance	23	—
products	8	3.5* (0.01 μm*)	1.1	balance	20	3.45*	1.06	19.6	balance	112	decrease
											in
											strength
Conventional	10	CaMgSi4: 1 (10 μm)	1.1	balance	20	CaMgSi4: 1	1.04	19.8	balance	41	—
products	11	MnS: 1 (20 μm)	1.1	balance	20	MnS: 0.97	1.04	19.8	balance	48	—
	12	CaF2: 1 (36 μm)	1.1	balance	20	CaF2: 1	1.04	19.9	balance	32	—
The symbol * means the value which is not within the scope of the present invention.

[0104] As is apparent from the results shown in Table 4, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 31 to 40 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 10 to 12 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 7 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 8 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

[0105] As raw powders, a CaCO₃ powder having an average particle size shown in Table 5, a CaMgSiO₄ powder having an average particle size of 10 μm, a MnS powder having an average particle size of 20 μm, a CaF₂ powder having an average particle size of 36 μm, a Fe powder having an average particle size of 80 μm, a Cu powder having an average particle size of 25 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 5, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 41 to 50 of the present invention, comparative sintered alloys 9 to 10, and conventional sintered alloys 13 to 15.

[0106] Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 41 to 50 of the present invention, the comparative sintered alloys 9 to 10, and the conventional sintered alloys 13 to 15 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

• [0107] Rotating speed: 10000 rpm
• [0108] Feed speed: 0.030 mm/rev.
• [0109] Cutting oil: none (dry).
  The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 5. Machinability was evaluated by the results.

[0110]

	TABLE 5
		Component ratio of
	Component ratio of raw powder (mass %)	iron-based sintered alloy (mass %)
	CaCO3 powder							Fe	Number
	Average particle							and	of
Iron-based sintered	size is described	Cu	C	Fe				inevitable	piercing
alloy	in parenthesis.	powder	powder	powder	CaCO3	Cu	C	impurities	(times)	Remarks
Products of the	41	0.05 (0.1 μm)	0.2	0.13	balance	0.03	2.0	0.11	balance	53	—
present	42	0.2 (0.1 μm)	2	0.25	balance	0.17	2.1	0.22	balance	122	—
invention	43	0.5 (0.6 μm)	2	0.98	balance	0.47	1.9	0.87	balance	129	—
	44	1.0 (2 μm)	2	0.7	balance	0.94	2.0	0.66	balance	235	—
	45	1.3 (0.6 μm)	2	0.7	balance	1.22	2.0	0.64	balance	250	—
	46	1.5 (2 μm)	4	0.7	balance	1.43	4.0	0.65	balance	220	—
	47	1.8 (18 μm)	5.8	0.7	balance	1.69	5.7	0.65	balance	203	—
	48	2.1 (2 μm)	4	0.7	balance	2.09	3.9	0.64	balance	190	—
	49	2.5 (18 μm)	2	0.98	balance	2.3	2.0	0.88	balance	145	—
	50	3.0 (30 μm)	2	1.2	balance	2.91	2.0	1.15	balance	179	—
Comparative	9	0.02* (40 μm*)	2	0.7	balance	0.01*	1.9	0.65	balance	10	—
products	10	3.5* (0.01 μm*)	2	0.7	balance	3.45*	2.0	0.64	balance	108	decrease in
											strength
Conventional	13	CaMgSi4: 1	2	0.7	balance	CaMgSi4: 1	2.0	0.66	balance	20	—
products	14	MnS: 1	2	0.7	balance	MnS: 0.97	2.0	0.64	balance	14	—
	15	CaF2: 1	2	0.7	balance	CaF2: 1	2.0	0.64	balance	9	—
The symbol * means the value which is not within the scope of the present invention.

[0111] As is apparent from the results shown in Table 5, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 41 to 50 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 13 to 15 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 9 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 10 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

[0112] As raw powders, a CaCO₃ powder having an average particle size shown in Table 6, a CaMgSiO₄ powder having an average particle size of 10 μm, a MnS powder having an average particle size of 20 μm, a CaF₂ powder having an average particle size of 36 μm, a partially diffused Fe-based alloy powder having an average particle size of 80 μm with the composition of Fe-1.5% Cu-4.0% Ni-0.5% Mo and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 6, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 51 to 60 of the present invention, comparative sintered alloys 11 to 12, and conventional sintered alloys 16 to 18.

[0113] Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 51 to 60 of the present invention, the comparative sintered alloys 11 to 12, and the conventional sintered alloys 16 to 18 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

• [0114] Rotating speed: 5000 rpm
• [0115] Feed speed: 0.006 mm/rev.
• [0116] Cutting oil: none (dry).
  The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 6. Machinability was evaluated by the results.

[0117]

	TABLE 6
	Component ratio	Component ratio
	of raw powder (mass %)	of iron-based sintered alloy (mass %)
	CaCO3 powder								Fe	Number
	Average particle		Fe-based						and	of
Iron-based sintered	size is described	C	alloy						inevitable	piercing
alloy	in parenthesis.	powder	powder#	CaCO3	Cu	C	Ni	Mo	impurities	(times)	Remarks
Products of the	51	0.05 (0.1 μm)	0.13	balance	0.03	1.5	0.11	3.9	0.50	balance	48	—
present	52	0.2 (0.1 μm)	0.25	balance	0.18	1.5	0.19	4.0	0.50	balance	153	—
invention	53	0.5 (0.6 μm)	0.98	balance	0.46	1.5	0.85	4.0	0.50	balance	214	—
	54	1.0 (2 μm)	0.5	balance	0.96	1.4	0.47	4.1	0.52	balance	300	—
	55	1.3 (0.6 μm)	0.5	balance	1.25	1.5	0.45	4.0	0.50	balance	287	—
	56	1.5 (2 μm)	0.5	balance	1.45	1.5	0.45	4.0	0.50	balance	324	—
	57	1.8 (18 μm)	0.5	balance	1.72	1.5	0.47	4.0	0.49	balance	274	—
	58	2.1 (2 μm)	0.5	balance	1.89	1.6	0.47	3.8	0.50	balance	257	—
	59	2.5 (18 μm)	1.0	balance	2.32	1.5	0.90	4.0	0.50	balance	231	—
	60	3.0 (30 μm)	1.2	balance	2.89	1.5	1.17	4.0	0.50	balance	267	—
Comparative	11	0.02* (40 μm*)	0.5	balance	0.01*	1.5	0.43	4.1	0.50	balance	5	—
products	12	3.5* (0.01 μm*)	0.5	balance	3.45*	1.5	0.44	4.0	0.51	balance	87	decrease in
												strength
Conventional	16	CaMgSi4: 1	0.5	balance	CaMgSi4: 1	1.5	0.46	4.0	0.50	balance	17	—
products	17	MnS: 1	0.5	balance	MnS: 0.97	1.5	0.47	4.0	0.50	balance	35	—
	18	CaF2: 1	0.5	balance	CaF2: 1	1.5	0.45	4.0	0.48	balance	8	—
The symbol * means the value which is not within the scope of the present invention.
#partially diffused Fe-based alloy powder having an average particle size of 80 μm with the composition of Fe-1.5% Cu-4.0% Ni-0.5% Mo

[0118] As is apparent from the results shown in Table 6, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 51 to 60 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 16 to 18 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 11 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 12 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

[0119] As raw powders, a CaCO₃ powder having an average particle size shown in Table 7, a CaMgSiO₄ powder having an average particle size of 10 μm, a MnS powder having an average particle size of 20 μm, a CaF₂ powder having an average particle size of 36 μm, a Fe-based alloy powder having an average particle size of 80 μm with the composition of Fe-1.5% Mo and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 7, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 61 to 70 of the present invention, comparative sintered alloys 13 to 14, and conventional sintered alloys 19 to 21.

[0120] Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 61 to 70 of the present invention, the comparative sintered alloys 13 to 14, and the conventional sintered alloys 19 to 21 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

• [0121] Rotating speed: 5000 rpm
• [0122] Feed speed: 0.006 mm/rev.
• [0123] Cutting oil: none (dry).
  The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 7. Machinability was evaluated by the results.

[0124]

	TABLE 7
	Component	Component ratio of
	ratio of raw powder (mass %)	iron-based sintered alloy (mass %)
	CaCO3 powder						Fe	Number
	Average particle		Fe-based				and	of
Iron-based sintered	size is described	C	alloy				inevitable	piercing
alloy	in parenthesis.	powder	powder#	CaCO3	C	Mo	impurities	(times)	Remarks
Products of the	61	0.05 (0.1 μm)	0.13	balance	0.03	0.11	1.50	balance	48	—
present invention	62	0.2 (0.1 μm)	0.25	balance	0.19	0.19	1.48	balance	85	—
	63	0.5 (0.6 μm)	0.98	balance	0.48	0.85	1.50	balance	71	—
	64	1.0 (2 μm)	0.5	balance	0.97	0.46	1.50	balance	214	—
	65	1.3 (0.6 μm)	0.5	balance	1.27	0.47	1.50	balance	225	—
	66	1.5 (2 μm)	0.5	balance	1.44	0.45	1.51	balance	201	—
	67	1.8 (18 μm)	0.5	balance	1.72	0.45	1.46	balance	228	—
	68	2.1 (2 μm)	0.5	balance	1.95	0.44	1.50	balance	219	—
	69	2.5 (18 μm)	1.0	balance	2.39	0.90	1.50	balance	170	—
	70	3.0 (30 μm)	1.2	balance	2.91	1.17	1.53	balance	148	—
Comparative	13	0.02* (40 μm*)	0.5	balance	0.01*	0.43	1.51	balance	12	—
products	14	3.5* (0.01 μm*)	0.5	balance	3.45*	0.44	1.50	balance	81	decrease
										in
										strength
Conventional	19	CaMgSi4: 1	0.5	balance	CaMgSi4: 1	0.46	1.51	balance	20	—
products	20	MnS: 1	0.5	balance	MnS: 0.97	0.47	1.50	balance	23	—
	21	CaF2: 1	0.5	balance	CaF2: 1	0.44	1.48	balance	16	—
The symbol * means the value which is not within the scope of the present invention.
#Fe-based alloy powder having an average particle size of 80 μm with the composition of Fe-1.5% Mo

[0125] As is apparent from the results shown in Table 7, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 61 to 70 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 19 to 21 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 13 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 14 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

[0126] As raw powders, a CaCO₃ powder having an average particle size shown in Table 8, a CaMgSiO₄ powder having an average particle size of 10 μm, a MnS powder having an average particle size of 20 μm, a CaF₂ powder having an average particle size of 36 μm, a Fe-based alloy powder having an average particle size of 80 μm with the composition of Fe-3.0% Cr-0.5% Mo and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 8, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an N₂+5% H₂ gas mixture atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 71 to 80 of the present invention, comparative sintered alloys 15 to 16, and conventional sintered alloys 22 to 24.

[0127] Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 71 to 80 of the present invention, the comparative sintered alloys 15 to 16, and the conventional sintered alloys 22 to 24 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

• [0128] Rotating speed: 10000 rpm
• [0129] Feed speed: 0.006 mm/rev.
• [0130] Cutting oil: none (dry).
  The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 8. Machinability was evaluated by the results.

[0131]

	TABLE 8
	Component	Component ratio of
	ratio of raw powder (mass %)	iron-based sintered alloy (mass %)
	CaCO3 powder							Fe	Number
	Average particle		Fe-based					and	of
Iron-based sintered	size is described	C	alloy					inevitable	piercing
alloy	in parenthesis.	powder	powder#	CaCO3	C	Cr	Mo	impurities	(times)	Remarks
Products of the	71	0.05 (0.1 μm)	0.13	balance	0.03	0.11	3.0	0.50	balance	31	—
present	72	0.2 (0.1 μm)	0.25	balance	0.19	0.19	3.0	0.50	balance	105	—
invention	73	0.5 (0.6 μm)	0.98	balance	0.48	0.85	3.0	0.49	balance	121	—
	74	1.0 (2 μm)	0.5	balance	0.97	0.47	3.0	0.50	balance	163	—
	75	1.3 (0.6 μm)	0.5	balance	1.27	0.45	2.9	0.50	balance	186	—
	76	1.5 (2 μm)	0.5	balance	1.44	0.45	3.0	0.51	balance	151	—
	77	1.8 (18 μm)	0.5	balance	1.72	0.44	3.0	0.49	balance	185	—
	78	2.1 (2 μm)	0.5	balance	1.95	0.44	3.1	0.50	balance	196	—
	79	2.5 (18 μm)	1.0	balance	2.39	0.90	3.0	0.50	balance	103	—
	80	3.0 (30 μm)	1.2	balance	2.91	1.17	3.0	0.50	balance	88	—
Comparative	15	0.02* (40 μm*)	0.5	balance	0.01*	0.43	3.1	0.50	balance	3	—
products	16	3.5* (0.01 μm*)	0.5	balance	3.45*	0.45	3.0	0.51	balance	89	decrease in
											strength
Conventional	22	CaMgSi4: 1	0.5	balance	CaMgSi4: 1	0.46	3.0	0.50	balance	16	—
products	23	MnS: 1	0.5	balance	MnS: 0.97	0.47	3.1	0.50	balance	13	—
	24	CaF2: 1	0.5	balance	CaF2: 1	0.44	3.0	0.50	balance	8	—
The symbol * means the value which is not within the scope of the present invention.
#Fe-based alloy powder having a particle size of 80 μm with the composition of Fe-3.0% Cr-0.5% Mo

[0132] As is apparent from the results shown in Table 8, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 71 to 80 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 22 to 24 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 15 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 16 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

[0133] As raw powders, a CaCO₃ powder having an average particle size shown in Table 9, a CaMgSiO₄ powder having an average particle size of 10 μm, a MnS powder having an average particle size of 20 μm, a CaF₂ powder having an average particle size of 36 μm, a Fe-based alloy powder having an average particle size of 80 μm with the composition of Fe-3.0% Cr-0.5% Mo, a Ni powder having an average particle size of 3 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 9, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an N₂+5% H₂ gas mixture atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 81 to 90 of the present invention, comparative sintered alloys 17 to 18, and conventional sintered alloys 25 to 27.

[0134] Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 81 to 90 of the present invention, the comparative sintered alloys 17 to 18, and the conventional sintered alloys 25 to 27 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

• [0135] Rotating speed: 5000 rpm
• [0136] Feed speed: 0.006 mm/rev.
• [0137] Cutting oil: none (dry).
  The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 9. Machinability was evaluated by the results.

[0138]

	TABLE 9
		Component ratio of
	Component ratio of raw powder (mass %)	iron-based sintered alloy (mass %)
	CaCO3 powder									Fe	Number
	Average particle			Fe-based						and	of
Iron-based sintered	size is described			alloy						inevitable	piercing
alloy	in parenthesis.	C powder	Ni powder	powder#	CaCO3	C	Ni	Cr	Mo	impurities	(times)	Remarks
Products of the	81	0.05 (0.1 μm)	0.13	0.2	balance	0.03	0.11	0.2	3.0	0.50	balance	65	—
present	82	0.2 (0.1 μm)	0.25	2	balance	0.19	0.19	2.0	3.0	0.50	balance	93	—
invention	83	0.5 (0.6 μm)	0.98	4	balance	0.48	0.85	4.0	3.0	0.49	balance	89	—
	84	1.0 (2 μm)	0.5	4	balance	0.97	0.47	4.0	3.0	0.50	balance	135	—
	85	1.3 (0.6 μm)	0.5	4	balance	1.27	0.45	3.9	2.9	0.50	balance	112	—
	86	1.5 (2 μm)	0.5	4	balance	1.44	0.45	4.0	3.0	0.51	balance	125	—
	87	1.8 (18 μm)	0.5	4	balance	1.72	0.44	4.0	3.0	0.49	balance	140	—
	88	2.1 (2 μm)	0.5	6	balance	1.95	0.44	6.0	3.1	0.50	balance	177	—
	89	2.5 (18 μm)	1.0	8	balance	2.39	0.90	7.9	3.0	0.50	balance	133	—
	90	3.0 (30 μm)	1.2	9.8	balance	2.91	1.17	9.8	3.0	0.50	balance	109	—
Comparative	17	0.02* (40 μm*)	0.5	4	balance	0.01*	0.43	4.1	3.1	0.50	balance	3	—
products	18	3.5* (0.01 μm*)	0.5	4	balance	3.45*	0.45	4.0	3.0	0.51	balance	101	decrease in
													strength
Conventional	25	CaMgSi4: 1	0.5	4	balance	CaMgSi4: 1	0.46	4.0	3.0	0.50	balance	6	—
products	26	MnS: 1	0.5	4	balance	MnS: 0.97	0.47	4.0	3.1	0.50	balance	8	—
	27	CaF2: 1	0.5	4	balance	CaF2: 1	0.44	4.0	3.0	0.50	balance	8	—
The symbol * means the value which is not within the scope of the present invention.
#Fe-based alloy powder having a particle size of 80 μm with the composition of Fe-3.0% Cr-0.5% Mo

[0139] As is apparent from the results shown in Table 9, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 81 to 90 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 25 to 27 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 17 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 18 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

[0140] As raw powders, a CaCO₃ powder having an average particle size shown in Table 10, a CaMgSiO₄ powder having an average particle size of 10 μm, a MnS powder having an average particle size of 20 μm, a CaF₂ powder having an average particle size of 36 μm, a Fe-based alloy powder having an average particle size of 80 μm with the composition of Fe-3.0% Cr-0.5% Mo, a Cu powder having an average particle size of 25 μm, a Ni powder having an average particle size of 3 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 10, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an N₂+5% H₂ gas mixture atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 91 to 100 of the present invention, comparative sintered alloys 19 to 20, and conventional sintered alloys 28 to 30.

[0141] Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 91 to 100 of the present invention, the comparative sintered alloys 19 to 20, and the conventional sintered alloys 28 to 30 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

• [0142] Rotating speed: 5000 rpm
• [0143] Feed speed: 0.006 mm/rev.
• [0144] Cutting oil: none (dry).
  The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 10. Machinability was evaluated by the results.

[0145]

	TABLE 10
	Component ratio of raw powder (mass %)
	CaCO3 powder	Component ratio of iron-based sintered alloy (mass %)	Number
	Average particle	Cu			Fe-							Fe and	of
Iron-based	size is described	pow-	C	Ni	based							inevitable	piercing
sintered alloy	in parenthesis.	der	powder	powder	alloy #	CaCO3	Cu	C	Ni	Cr	Mo	impurities	(times)	Remarks
Products	91	0.05 (0.1 μm)	0.2	0.13	0.2	balance	0.03	0.2	0.11	0.2	3.0	0.50	balance	34	—
of the	92	0.2 (0.1 μm)	2	0.25	2	balance	0.19	2.1	0.19	2.0	3.0	0.50	balance	87	—
present	93	0.5 (0.6 μm)	2	0.98	4	balance	0.48	1.9	0.85	4.0	3.0	0.49	balance	95	—
invention	94	1.0 (2 μm)	2	0.5	4	balance	0.97	2.0	0.47	4.0	3.0	0.50	balance	150	—
	95	1.3 (0.6 μm)	2	0.5	4	balance	1.27	2.0	0.45	3.9	2.9	0.50	balance	138	—
	96	1.5 (2 μm)	4	0.5	4	balance	1.44	4.0	0.45	4.0	3.0	0.51	balance	143	—
	97	1.8 (18 μm)	5.8	0.5	4	balance	1.72	5.8	0.44	4.0	3.0	0.49	balance	139	—
	98	2.1 (2 μm)	4	0.5	6	balance	1.95	4.0	0.44	6.0	3.1	0.50	balance	155	—
	99	2.5 (18 μm)	2	1.0	8	balance	2.39	2.0	0.90	7.9	3.0	0.50	balance	132	—
	100	3.0 (30 μm)	2	1.2	9.8	balance	2.91	2.0	1.17	9.8	3.0	0.50	balance	129	—
Com-	19	0.02* (40 μm*)	2	0.5	4	balance	0.01*	1.9	0.43	4.1	3.0	0.50	balance	2	—
parative	20	3.5* (0.01 μm*)	2	0.5	4	balance	3.45*	2.0	0.45	4.0	3.0	0.51	balance	119	decrease
products															in strength
Con-	28	CaMgSi4: 1	2	0.5	4	balance	CaMgSi4: 1	2.0	0.46	4.0	3.0	0.50	balance	8	—
ventional	29	MnS: 1	2	0.5	4	balance	MnS: 0.97	2.0	0.47	4.0	3.1	0.50	balance	4	—
products	30	CaF2: 1	2	0.5	4	balance	CaF2: 1	2.0	0.44	4.0	3.0	0.50	balance	11	—
The symbol * means the value which is not within the scope of the present invention.
*Fe-based alloy powder having a particle size of 80 μm with the composition of Fe-3.0% Cr-0.5% Mo

[0146] As is apparent from the results shown in Table 10, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 91 to 100 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 28 to 30 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 19 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 20 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

[0147] As raw powders, a CaCO₃ powder having an average particle size shown in Table 11, a CaMgSiO₄ powder having an average particle size of 10 μm, a MnS powder having an average particle size of 20 μm, a CaF₂ powder having an average particle size of 36 μm, a Fe powder having an average particle size of 80 μm, a Ni powder having an average particle size of 3 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 11, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 101 to 110 of the present invention, comparative sintered alloys 21 to 22, and conventional sintered alloys 31 to 33.

[0148] Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 101 to 110 of the present invention, the comparative sintered alloys 21 to 22, and the conventional sintered alloys 31 to 33 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

• [0149] Rotating speed: 5000 rpm
• [0150] Feed speed: 0.009 mm/rev.
• [0151] Cutting oil: none (dry).
  The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 11. Machinability was evaluated by the results.

[0152]

	TABLE 11
	Component ratio of raw powder (mass %)	Component ratio of iron-based
	CaCO3 powder	sintered alloy (mass %)
	Average particle	Fe and	Number of
Iron-based sintered	size is described	C	Ni	Fe				inevitable	piercing
alloy	in parenthesis.	powder	powder	powder	CaCO3	C	Ni	impurities	(times)	Remarks
Products of	101	0.05 (0.1 μm)	0.13	0.2	balance	0.03	0.11	0.2	balance	43	—
the present	102	0.2 (0.1 μm)	0.25	1	balance	0.19	0.19	1.0	balance	84	—
invention	103	0.5 (0.6 μm)	0.98	3	balance	0.48	0.93	2.9	balance	79	—
	104	1.0 (2 μm)	0.5	3	balance	0.97	0.44	3.0	balance	128	—
	105	1.3 (0.6 μm)	0.5	3	balance	1.27	0.44	3.0	balance	114	—
	106	1.5 (2 μm)	0.5	3	balance	1.44	0.45	3.0	balance	202	—
	107	1.8 (18 μm)	0.5	3	balance	1.72	0.45	3.0	balance	187	—
	108	2.1 (2 μm)	0.5	6	balance	1.95	0.45	6.0	balance	168	—
	109	2.5 (18 μm)	1.0	8	balance	2.39	0.90	8.0	balance	126	—
	110	3.0 (30 μm)	1.2	9.8	balance	2.91	1.11	9.8	balance	99	—
Comparative	21	0.02* (40 μm*)	0.5	3	balance	0.01*	0.45	3.0	balance	5	—
products	22	3.5* (0.01 μm*)	0.5	3	balance	3.45*	0.45	3.0	balance	143	decrease in
											strength
Conventional	31	CaMgSi4: 1	0.5	3	balance	CaMgSi4: 1	0.44	2.9	balance	17	—
products	32	MnS: 1	0.5	4	balance	MnS: 0.97	0.45	3.0	balance	20	—
	33	CaF2: 1	0.5	4	balance	CaF2: 1	0.44	3.0	balance	12	—
The symbol * means the value which is not within the scope of the present invention.

[0153] As is apparent from the results shown in Table 11, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 101 to 110 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 31 to 33 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 21 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 22 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

[0154] As raw powders, a CaCO₃ powder having an average particle size shown in Table 12, a CaMgSiO₄ powder having an average particle size of 10 μm, a MnS powder having an average particle size of 20 μm, a CaF₂ powder having an average particle size of 36 μm, a Fe powder having an average particle size of 80 μm, a Ni powder having an average particle size of 3 μm, a Mo powder having an average particle size of 3 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 12, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 111 to 120 of the present invention, comparative sintered alloys 23 to 24, and conventional sintered alloys 34 to 36.

[0155] Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 111 to 120 of the present invention, the comparative sintered alloys 23 to 24, and the conventional sintered alloys 34 to 36 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

• [0156] Rotating speed: 5000 rpm
• [0157] Feed speed: 0.009 mm/rev.
• [0158] Cutting oil: none (dry).
  The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 12. Machinability was evaluated by the results.

[0159]

	TABLE 12
	Component ratio of raw powder (mass %)
	CaCO3 powder	Component ratio of iron-based sintered alloy
	Average	(mass %)	Number
	particle size is	Fe and	of
Iron-based sintered	described in	C	Ni	Mo	Fe		inevitable	piercing
alloy	parenthesis.	powder	powder	powder	powder	CaCO3	C	Ni	Mo	impurities	(times)	Remarks
Products of the	111	0.05 (0.1 μm)	0.13	0.2	0.2	balance	0.03	0.11	0.2	0.2	balance	55	—
present	112	0.2 (0.1 μm)	0.25	1	0.3	balance	0.19	0.19	1.0	0.3	balance	91	—
invention	113	0.5 (0.6 μm)	0.98	4	0.5	balance	0.48	0.91	4.0	0.5	balance	103	—
	114	1.0 (2 μm)	0.6	4	0.5	balance	0.97	0.55	4.0	0.5	balance	170	—
	115	1.3 (0.6 μm)	0.6	4	0.5	balance	1.27	0.56	4.0	0.5	balance	227	—
	116	1.5 (2 μm)	0.6	4	1	balance	1.44	0.54	3.9	1.0	balance	198	—
	117	1.8 (18 μm)	0.6	4	3	balance	1.72	0.54	3.9	2.7	balance	164	—
	118	2.1 (2 μm)	0.6	6	4.8	balance	1.95	0.55	6.0	4.8	balance	144	—
	119	2.5 (18 μm)	1.0	8	0.5	balance	2.39	0.92	8.0	0.5	balance	159	—
	120	3.0 (30 μm)	1.2	9.8	0.5	balance	2.91	1.14	9.8	0.5	balance	166	—
Comparative	23	0.02* (40 μm*)	0.6	4	0.5	balance	0.01*	0.54	4.0	0.5	balance	11	—
products	24	3.5* (0.01 μm*)	0.6	4	0.5	balance	3.45*	0.54	4.0	0.5	balance	91	decrease in
													strength
Conventional	34	CaMgSi4: 1	0.6	4	0.5	balance	CaMgSi4: 1	0.54	4.0	0.5	balance	22	—
products	35	MnS: 1	0.6	4	0.5	balance	MnS: 0.97	0.55	4.0	0.5	balance	31	—
	36	CaF2: 1	0.6	4	0.5	balance	CaF2: 1	0.55	4.0	0.5	balance	28	—
The symbol * means the value which is not within the scope of the present invention.

[0160] As is apparent from the results shown in Table 12, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 111 to 120 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 34 to 36 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 23 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 24 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

[0161] As raw powders, a CaCO₃ powder having an average particle size shown in Table 13, a CaMgSiO₄ powder having an average particle size of 10 μm, a MnS powder having an average particle size of 20 μm, a CaF₂ powder having an average particle size of 36 μm, a Fe powder having an average particle size of 80 μm, a Ni powder having an average particle size of 3 μm, a Cu powder having an average particle size of 25 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 13, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 121 to 130 of the present invention, comparative sintered alloys 25 to 26, and conventional sintered alloys 37 to 39.

[0162] Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 121 to 130 of the present invention, the comparative sintered alloys 25 to 26, and the conventional sintered alloys 37 to 39 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

• [0163] Rotating speed: 5000 rpm
• [0164] Feed speed: 0.009 mm/rev.
• [0165] Cutting oil: none (dry).
  The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 13. Machinability was evaluated by the results.

[0166]

	TABLE 13
	Component ratio of raw powder (mass %)
	CaCO3 powder	Component ratio of iron-based sintered alloy
	Average	(mass %)	Number
	particle size is	Fe and	of
Iron-based sintered	described in	Cu	C	Ni	Fe		inevitable	piercing
alloy	parenthesis.	powder	powder	powder	powder	CaCO3	Cu	C	Ni	impurities	(times)	Remarks
Products of the	121	0.05 (0.1 μm)	0.2	0.13	0.2	balance	0.03	0.2	0.11	0.2	balance	46	—
present	122	0.2 (0.1 μm)	1	0.25	1	balance	0.17	1.0	0.21	1.0	balance	104	—
invention	123	0.5 (0.6 μm)	1	0.98	3	balance	0.47	1.0	0.91	3.0	balance	136	—
	124	1.0 (2 μm)	1	0.6	3	balance	0.94	0.99	0.55	3.0	balance	157	—
	125	1.3 (0.6 μm)	2	0.8	3	balance	1.22	1.0	0.54	3.0	balance	180	—
	126	1.5 (2 μm)	4	0.6	3	balance	1.43	4.0	0.55	2.9	balance	166	—
	127	1.8 (18 μm)	5.8	0.6	3	balance	1.69	5.7	0.56	3.0	balance	192	—
	128	2.1 (2 μm)	1	0.6	6	balance	1.09	1.0	0.55	6.0	balance	153	—
	129	2.5 (18 μm)	1	1.0	8	balance	2.3	1.0	0.91	8.0	balance	193	—
	130	3.0 (30 μm)	1	1.2	9.8	balance	2.91	1.0	1.13	9.8	balance	179	—
Comparative	25	0.02* (40 μm*)	1	0.6	3	balance	0.01*	1.0	0.55	3.0	balance	7	—
products	26	3.5* (0.01 μm*)	1	0.6	3	balance	3.45*	1.0	0.55	3.0	balance	79	decrease in
													strength
Conventional	37	CaMgSi4: 1	1	0.6	3	balance	CaMgSi4: 1	1.0	0.55	3.0	balance	12	—
products	38	MnS: 1	1	0.6	3	balance	MnS: 0.97	1.0	0.54	3.0	balance	15	—
	39	CaF2: 1	1	0.6	3	balance	CaF2: 1	1.0	0.55	3.0	balance	9	—
The symbol * means the value which is not within the scope of the present invention.

[0167] As is apparent from the results shown in Table 13, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 121 to 130 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 37 to 39 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 25 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 26 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

[0168] As raw powders, a CaCO₃ powder having an average particle size shown in Table 14, a CaMgSiO₄ powder having an average particle size of 10 μm, a MnS powder having an average particle size of 20 μm, a CaF₂ powder having an average particle size of 36 μm, a Fe powder having an average particle size of 80 μm, a Cu—P powder having an average particle size of 25 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 14, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 131 to 140 of the present invention, comparative sintered alloys 27 to 28, and conventional sintered alloys 40 to 42.

[0169] Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 131 to 140 of the present invention, the comparative sintered alloys 27 to 28, and the conventional sintered alloys 40 to 42 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

• [0170] Rotating speed: 10000 rpm
• [0171] Feed speed: 0.009 mm/rev.
• [0172] Cutting oil: none (dry).
  The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 14. Machinability was evaluated by the results.

[0173]

	TABLE 14
	Component ratio of iron-based
	Component ratio of raw powder (mass %)	sintered alloy
	CaCO3 powder	(mass %)	Number
	Average particle	Fe and	of
Iron-based sintered	size is described	C	Cu-P	Fe					inevitable	piercing
alloy	in parenthesis.	powder	powder	powder	CaCO3	C	Cu	P	impurities	(times)	Remarks
Products	131	0.05 (0.1 μm)	1.0	0.7	balance	0.03	0.91	0.6	0.1	balance	77	—
of the	132	0.2 (0.1 μm)	1.5	1.2	balance	0.19	1.44	1.1	0.1	balance	73	—
present	133	0.5 (0.6 μm)	1.5	1.8	balance	0.48	1.46	1.6	0.2	balance	114	—
invention	134	1.0 (2 μm)	2.0	1.8	balance	0.97	1.95	1.6	0.2	balance	203	—
	135	1.3 (0.6 μm)	2.0	2.8	balance	1.27	1.93	2.5	0.3	balance	231	—
	136	1.5 (2 μm)	2.0	2.8	balance	1.44	1.93	2.5	0.3	balance	211	—
	137	1.8 (18 μm)	2.0	3.3	balance	1.72	1.96	3	0.3	balance	274	—
	138	2.1 (2 μm)	2.5	6.0	balance	1.95	2.48	5.4	0.6	balance	177	—
	139	2.5 (18 μm)	2.5	8.0	balance	2.39	2.45	5	0.6	balance	229	—
	140	3.0 (30 μm)	3.0	9.0	balance	2.91	2.99	8.2	0.8	balance	310	—
Comparative	27	0.02* (40 μm*)	1	2.8	balance	0.01*	0.45	2.5	0.3	balance	2	—
products	28	3.5* (0.01 μm*)	1	2.8	balance	3.43*	0.45	2.5	0.3	balance	198	decrease
												in
												strength
Conventional	40	CaMgSi4: 1	1	2.8	balance	CaMgSi4: 1	0.44	2.9	0.3	balance	32	—
products	41	MnS: 1	1	2.8	balance	MnS: 0.97	0.45	3.0	0.3	balance	53	—
	42	CaF2: 1	1	2.8	balance	CaF2: 1	0.44	3.0	0.3	balance	40	—
The symbol * means the value which is not within the scope of the present invention.

[0174] As is apparent from the results shown in Table 14, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 131 to 140 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 40 to 42 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 27 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 28 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

[0175] As raw powders, a CaCO₃ powder having an average particle size of 0.6 μm, a CaF₂ powder having an average particle size of 36 μm and a Fe-6% Cr-6% Mo-9% W-3% V-10% Co-1.5% C powder having an average particle size of 80 μm were prepared. These raw powders were blended according to the formulation shown in Table 15, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in a dissociated ammonia gas atmosphere under the conditions of a temperature of 1150° C. and a retention time of 60 minutes to obtain an iron-based sintered alloy 141 of the present invention, comparative sintered alloys 29 to 30, and a conventional sintered alloy 43.

[0176] Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloy 141 of the present invention, the comparative sintered alloys 29 to 30, and the conventional sintered alloy 43 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

• [0177] Rotating speed: 5000 rpm
• [0178] Feed speed: 0.006 mm/rev.
• [0179] Cutting oil: none (dry).
  The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 15. Machinability was evaluated by the results.

[0180]

	TABLE 15
	Component ratio of raw powder
	(mass %)
	Fe-6% Cr-
	CaCO3 powder	6% Mo-	Component ratio
	Average particle	9% W-3% V-	of iron-based sintered alloy (mass %)
	size	10% Co-		Fe and	Number of
Iron-based sintered	is described in	1.5% C								inevitable	piercing
alloy	parenthesis.	powder	CaCO3	C	Cr	Mo	W	Co	V	impurities	(times)	Remarks
Product of the	141	0.5 (0.6 μm)	balance	0.48	1.5	6	6	9	10	3	balance	158	—
present
invention
Comparative	29	0.02* (40 μm*)	balance	0.01*	1.5	6	6	9	10	3	balance	18	—
products	30	3.5* (0.01 μm*)	balance	3.43*	1.5	6	6	9	10	3	balance	127	decrease in
													strength
Conventional	43	CaF2: 1	balance	CaF2: 1	1.5	6	6	9	10	3	balance	26	—
product
The symbol * means the value which is not within the scope of the present invention.

[0181] As is apparent from the results shown in Table 15, the number of piercing of the cylindrical sintered alloy block for piercing test made of the sintered alloy 141 of the present invention is larger than that of the cylindrical sintered alloy block for piercing test made of the conventional sintered alloy 43 and therefore the sintered alloy of the present invention is excellent in machinability. However, the comparative sintered alloy 29 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 30 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

[0182] As raw powders, a CaCO₃ powder having an average particle size of 0.6 μm, a CaF₂ powder having an average particle size of 36 μm, a Fe-based alloy powder having an average particle size of 80 μm with the composition of Fe-13% Cr-5% Nb-0.8% Si, a Fe powder having an average particle size of 80 μm, a Ni powder having an average particle size of 3 μm, a Mo powder having an average particle size of 3 μm, a Co-based alloy powder having an average particle size of 80 μm with the composition of Co-30% Mo-10% Cr-3% Si, a Cr-based alloy powder having an average particle size of 80 μm with the composition of Cr-25% Co-25% W-11.5% Fe-1% Nb-1% Si-1.5% C, a Co powder having an average particle size of 30 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 16-1, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in a vacuum atmosphere at 0.1 Pa under the conditions of a temperature of 1150° C. and a retention time of 60 minutes to obtain an iron-based sintered alloy 142 of the present invention, comparative sintered alloys 31 to 32, and a conventional sintered alloy 44 shown in Table 16-2.

[0183] Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloy 142 of the present invention, the comparative sintered alloys 31 to 32, and the conventional sintered alloy 44 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

• [0184] Rotating speed: 5000 rpm
• [0185] Feed speed: 0.006 mm/rev.
• [0186] Cutting oil: none (dry).
  The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 16-2. Machinability was evaluated by the results.

[0187]

	TABLE 16-1
	Component ratio of raw powder (mass %)
	CaCO3 powder
	Average particle size is		Co-based	Cr-based				Fe-based
Iron-based sintered	described in	Mo	alloy	alloy	Ni	C	Co	alloy	Fe
alloy	parenthesis.	powder	powder#	powder#	powder	powder	powder	powder#	powder
Product of the	142	0.5 (0.6 μm)	9.0	10	12	3	0.8	3.3	10	balance
present
invention
Comparative	31	0.02* (40 μm*)	9.0	10	12	3	0.8	3.3	10	balance
products	32	3.5* (0.01 μm*)	9.0	10	12	3	0.8	3.3	10	balance
Conventional	44	CaF2: 1	9.0	10	12	3	0.8	3.3	10	balance
product
Fe-based alloy powder#: Fe-13% Cr-5% Nb-0.8% Si
Co-based alloy powder#: Co-30% Mo-10% Cr-3% Si
Cr-based alloy powder#: Cr-25% Co-25% W-11.5% Fe-1% Nb-1% Si-1.5% C
The symbol * means the value which is not within the scope of the present invention.

[0188]

	TABLE 16-2
	Component ratio of iron-based sintered alloy (mass %)	Number of
	Fe and inevitable	piercing
Iron-based sintered alloy	CaCO3	C	Cr	Mo	W	Ni	Si	Co	Nb	impurities	(times)	Remarks
Product of the present	142	0.47	1	6	12	3	3	0.5	11.7	1.1	balance	250	—
invention
Comparative products	31	0.01*	1	6	12	3	3	0.5	11.7	1.1	balance	14	—
	32	3.47*	1	6	12	3	3	0.5	11.7	1.1	balance	140	decrease in
													strength
Conventional	44	CaF2: 1	1	6	12	3	3	0.5	11.7	1.1	balance	31	—
product
The symbol * means the value which is not within the scope of the present invention.

[0189] As is apparent from the results shown in Table 16-1 and Table 16-2, the number of piercing of the cylindrical sintered alloy block for piercing test made of the sintered alloy 142 of the present invention is larger than that of the cylindrical sintered alloy block for piercing test made of the conventional sintered alloy 44 and therefore the sintered alloy of the present invention is excellent in machinability. However, the comparative sintered alloy 31 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 32 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

[0190] As raw powders, a CaCO₃ powder having an average particle size of 0.6 μm, a CaF₂ powder having an average particle size of 36 μm, a Fe-based alloy powder having an average particle size of 80 μm with the composition of Fe-13% Cr-5% Nb-0.8% Si, a Fe powder having an average particle size of 80 μm, a Ni powder having an average particle size of 3 μm, a Mo powder having an average particle size of 3 μm, a Co-based alloy powder having an average particle size of 80 μm with the composition of Co-30% Mo-10% Cr-3% Si, a Cr-based alloy powder having an average particle size of 80 μm with the composition of Cr-25% Co-25% W-11.5% Fe-1% Nb-1% Si-1.5% C, a Co powder having an average particle size of 30 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 17-1, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in a vacuum atmosphere at 0.1 Pa under the conditions of a temperature of 1150° C. and a retention time of 60 minutes and subjected to 18% Cu infiltration to obtain an iron-based sintered alloy 143 of the present invention, comparative sintered alloys 33 to 34, and a conventional sintered alloy 45 shown in Table 17-2.

[0191] Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloy 143 of the present invention, the comparative sintered alloys 33 to 34, and the conventional sintered alloy 45 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

• [0192] Rotating speed: 5000 rpm
• [0193] Feed speed: 0.006 mm/rev.
• [0194] Cutting oil: none (dry).
  The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 17-2. Machinability was evaluated by the results.

[0195]

	TABLE 17-1
	Component ratio of raw powder (mass %)
	CaCO3 powder	Co-
	Average particle size	based	Cr-based		Fe-based
Iron-based sintered	is described in	Mo	alloy	alloy	Ni	C	Co	alloy		Fe
alloy	parenthesis.	powder	powder#	powder#	powder	powder	powder	powder#	Infiltration Cu	powder
Product of the	143	0.5 (0.6 μm)	1.5	5.0	19.0	3.0	1.5	4.4	9.0	18	balance
present
invention
Comparative	33	0.02* (40 μm*)	1.5	5.0	19.0	3.0	1.5	4.4	9.0	18	balance
products	34	3.5* (0.01 μm*)	1.5	5.0	19.0	3.0	1.5	4.4	9.0	18	balance
Conventional	45	CaF2: 1	1.5	5.0	19.0	3.0	1.5	4.4	9.0	18	balance
product
Fe-based alloy powder#: Fe-13% Cr-5% Nb-0.8% Si
Co-based alloy powder#: Co-30% Mo-10% Cr-3% Si
Cr-based alloy powder#: Cr-25% Co-25% W-11.5% Fe-1% Nb-1% Si-1.5% C
The symbol * means the value which is not within the scope of the present invention.

[0196]

	TABLE 17-2
	Component ratio of iron-based sintered alloy (mass %)	Number of
Iron-based sintered											Fe and inevitable	piercing
alloy	CaCO3	C	Cr	Mo	W	Ni	Si	Co	Nb	Cu	impurities	(times)	Remarks
Product of the present	143	0.47	1.8	8	3	4.8	5	0.4	12	1.1	18	balance	346	—
invention
Comparative products	33	0.01*	1.8	8	3	4.8	5	0.4	12	1.1	18	balance	38	—
	34	3.47*	1.8	8	3	4.8	5	0.4	12	1.1	18	balance	205	decrease in
														strength
Conventional product	45	CaF2: 1	1.8	8	3	4.8	5	0.4	12	1.1	18	balance	50	—
The symbol * means the value which is not within the scope of the present invention.

[0197] As is apparent from the results shown in Table 17-1 and Table 17-2, the number of piercing of the cylindrical sintered alloy block for piercing test made of the sintered alloy 143 of the present invention is larger than that of the cylindrical sintered alloy block for piercing test made of the conventional sintered alloy 45 and therefore the sintered alloy of the present invention is excellent in machinability. However, the comparative sintered alloy 33 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 34 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

[0198] As raw powders, a CaCO₃ powder having an average particle size of 0.6 μm, a CaF₂ powder having an average particle size of 36 μm, a Fe powder having an average particle size of 80 μm, a Ni powder having an average particle size of 3 μm, a Mo powder having an average particle size of 3 μm, a Co powder having an average particle size of 30 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 18-1, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in a vacuum atmosphere at 0.1 Pa under the conditions of a temperature of 1150° C. and a retention time of 60 minutes to obtain an iron-based sintered alloy 144 of the present invention, comparative sintered alloys 35 to 36, and a conventional sintered alloy 46 shown in Table 18-2.

[0199] Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloy 144 of the present invention, the comparative sintered alloys 35 to 36, and the conventional sintered alloy 46 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

• [0200] Rotating speed: 5000 rpm
• [0201] Feed speed: 0.006 mm/rev.
• [0202] Cutting oil: none (dry).
  The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 18-2. Machinability was evaluated by the results.

[0203]

	TABLE 18-1
	Component ratio of raw powder (mass %)
	CaCO3 powder
	Average particle size is
Iron-based sintered alloy	described in parenthesis.	Mo powder	Ni powder	C powder	Co powder	Fe powder
Product of the present	144	0.5 (0.6 μm)	2.0	2.0	1.3	1.0	balance
invention
Comparative products	35	0.02* (40 μm*)	2.0	2.0	1.3	1.0	balance
	36	3.5* (0.01 μm*)	2.0	2.0	1.3	1.0	balance
Conventional product	46	CaF2: 1	2.0	2.0	1.3	1.0	balance
The symbol * means the value which is not within the scope of the present invention.

[0204]

	TABLE 18-2
	Component ratio of iron-based	Number
	sintered alloy (mass %)	of
						Fe and inevitable	piercing
Iron-based sintered alloy	CaCO3	C	Mo	Ni	Co	impurities	(times)	Remarks
Product	144	0.46	1.3	2	2	1	balance	287	—
of the present invention
Comparative products	35	0.01*	1.3	2	2	1	balance	27	—
	36	3.43*	1.3	2	2	1	balance	167	decrease in
									strength
Conventional product	46	CaF2: 1	1.3	2	2	1	balance	37	—
The symbol * means the value which is not within the scope of the present invention.

[0205] As is apparent from the results shown in Table 18-1 and Table 18-2, the number of piercing of the cylindrical sintered alloy block for piercing test made of the sintered alloy 144 of the present invention is larger than that of the cylindrical sintered alloy block for piercing test made of the conventional sintered alloy 46 and therefore the sintered alloy of the present invention is excellent in machinability. However, the comparative sintered alloy 35 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 36 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

[0206] As raw powders, a CaCO₃ powder having an average particle size of 0.6 μm, a CaF₂ powder having an average particle size of 36 μm and a SUS316 (Fe-17% Cr-12% Ni-2.5% Mo) powder having an average particle size of 80 μm were prepared. These raw powders were blended according to the formulation shown in Table 19, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in a vacuum atmosphere at 0.1 Pa under the conditions of a temperature of 1200° C. and a retention time of 60 minutes to obtain an iron-based sintered alloy 145 of the present invention, comparative sintered alloys 37 to 38, and a conventional sintered alloy 47.

[0207] Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloy 145 of the present invention, the comparative sintered alloys 37 to 38, and the conventional sintered alloy 47 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

• [0208] Rotating speed: 5000 rpm
• [0209] Feed speed: 0.006 mm/rev.
• [0210] Cutting oil: none (dry).
  The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 19. Machinability was evaluated by the results.

[0211]

	TABLE 19
	Component ratio of raw powder
	(mass %)	Component ratio of
		SUS316	iron-based sintered alloy
	CaCO3 powder	(Fe-17%	(mass %)
	Average particle size	Cr-12%					Fe and	Number of
	is described in	Ni-2.5%					inevitable	piercing
Iron-based sintered alloy	parenthesis.	Mo) powder	CaCO3	Cr	Ni	Mo	impurities	(times)	Remarks
Product of the	145	0.5 (0.6 μm)	balance	0.48	17.1	12.3	2.2	balance	175	—
present invention
Comparative	37	0.02* (40 μm*)	balance	0.01*	17.1	12.3	2.2	balance	6	—
products	38	3.5* (0.01 μm*)	balance	3.43*	17.1	12.3	2.2	balance	105	decrease in
										strength
Conventional	47	CaF2: 1	balance	CaF2: 1	17.1	12.3	2.2	balance	15	—
product
The symbol * means the value which is not within the scope of the present invention.

[0212] As is apparent from the results shown in Table 19, the number of piercing of the cylindrical sintered alloy block for piercing test made of the sintered alloy 145 of the present invention is larger than that of the cylindrical sintered alloy block for piercing test made of the conventional sintered alloy 47 and therefore the sintered alloy of the present invention is excellent in machinability. However, the comparative sintered alloy 37 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 38 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

[0213] As raw powders, a CaCO₃ powder having an average particle size of 0.6 μm, a CaF₂ powder having an average particle size of 36 μm and a SUS430 (Fe-17% Cr) powder having an average particle size of 80 μm were prepared. These raw powders were blended according to the formulation shown in Table 20, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in a vacuum atmosphere at 0.1 Pa under the conditions of a temperature of 1200° C. and a retention time of 60 minutes to obtain an iron-based sintered alloy 146 of the present invention, comparative sintered alloys 39 to 40, and a conventional sintered alloy 48.

[0214] Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloy 146 of the present invention, the comparative sintered alloys 39 to 40, and the conventional sintered alloy 48 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

• [0215] Rotating speed: 5000 rpm
• [0216] Feed speed: 0.006 mm/rev.
• [0217] Cutting oil: none (dry).
  The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 20. Machinability was evaluated by the results.

[0218]

	TABLE 20
		Component ratio
	Component ratio	of iron-based
	of raw powder (mass %)	sintered alloy (mass %)
	CaCO3 powder	SUS430			Fe and	Number of
	Average particle size is	(Fe-17%			inevitable	piercing
Iron-based sintered alloy	described in parenthesis.	Cr) powder	CaCO3	Cr	impurities	(times)	Remarks
Product of the present	146	0.5 (0.6 μm)	balance	0.45	16.7	balance	193
invention
Comparative products	39	0.02 (40 μm*)	balance	0.01*	16.7	balance	24
	40	35* (0.01 μm*)	balance	3.43*	16.7	balance	134	decrease in
								strength
Conventional product	48	CaF2: 1	balance	CaF2: 1	16.7	balance	31
The symbol * means the value which is not within the scope of the present invention.

[0219] As is apparent from the results shown in Table 20, the number of piercing of the cylindrical sintered alloy block for piercing test made of the sintered alloy 146 of the present invention is larger than that of the cylindrical sintered alloy block for piercing test made of the conventional sintered alloy 48 and therefore the sintered alloy of the present invention is excellent in machinability. However, the comparative sintered alloy 39 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 40 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

[0220] As raw powders, a CaCO₃ powder having an average particle size of 0.6 μm, a CaF₂ powder having an average particle size of 36 μm, a C powder having an average particle size of 18 μm and a SUS410 (Fe-13% Cr) powder having an average particle size of 80 μm were prepared. These raw powders were blended according to the formulation shown in Table 21, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in a vacuum atmosphere at 0.1 Pa under the conditions of a temperature of 1200° C. and a retention time of 60 minutes to obtain an iron-based sintered alloy 147 of the present invention, comparative sintered alloys 41 to 42, and a conventional sintered alloy 49.

[0221] Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloy 147 of the present invention, the comparative sintered alloys 41 to 42, and the conventional sintered alloy 49 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

• [0222] Rotating speed: 5000 rpm
• [0223] Feed speed: 0.006 mm/rev.
• [0224] Cutting oil: none (dry).
  The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 21. Machinability was evaluated by the results.

[0225]

	TABLE 21
	Component ratio of raw powder (mass %)	Component ratio of iron-based
	CaCO3 powder		sintered alloy (mass %)
	Average particle size is		SUS410				Fe and	Number of
	described in	C	(Fe-13%				inevitable	piercing
Iron-based sintered alloy	parenthesis.	powder	Cr) powder	CaCO3	Cr	C	impurities	(times)	Remarks
Product of the	147	0.5 (0.6 μm)	0.15	balance	0.49	12.8	0.1	balance	157	—
present invention
Comparative	41	0.02* (40 μm*)	0.15	balance	0.01*	12.8	0.1	balance	10	—
products	42	3.5* (0.01 μm*)	0.15	balance	3.47*	12.8	0.1	balance	115	decrease in
										strength
Conventional	49	CaF2: 1	0.15	balance	CaF2: 1	12.8	0.1	balance	18	—
product
The symbol * means the value which is not within the scope of the present invention.

[0226] As is apparent from the results shown in Table 21, the number of piercing of the cylindrical sintered alloy block for piercing test made of the sintered alloy 147 of the present invention is larger than that of the cylindrical sintered alloy block for piercing test made of the conventional sintered alloy 49 and therefore the sintered alloy of the present invention is excellent in machinability. However, the comparative sintered alloy 41 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 42 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

[0227] As raw powders, a CaCO₃ powder having an average particle size of 0.6 μm, a CaF₂ powder having an average particle size of 36 μm and a SUS630 (Fe-17% Cr-4% Ni-4% Cu-0.3% Nb) powder having an average particle size of 80 μm were prepared. These raw powders were blended according to the formulation shown in Table 22, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in a vacuum atmosphere at 0.1 Pa under the conditions of a temperature of 1200° C. and a retention time of 60 minutes to obtain an iron-based sintered alloy 148 of the present invention, comparative sintered alloys 43 to 44, and a conventional sintered alloy 50.

[0228] Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloy 148 of the present invention, the comparative sintered alloys 43 to 44, and the conventional sintered alloy 50 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

• [0229] Rotating speed: 5000 rpm
• [0230] Feed speed: 0.006 mm/rev.
• [0231] Cutting oil: none (dry).
  The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 22. Machinability was evaluated by the results.

[0232]

	TABLE 22
	Component ratio of raw powder
	(mass %)	Component ratio of iron-based sintered
	CaCO3 powder	alloy (mass %)
	Average particle size							Fe and	Number of
	is described in	#SUS630						inevitable	piercing
Iron-based sintered alloy	parenthesis.	powder	CaCO3	Cr	Ni	Cu	Nb	impurities	(times)	Remarks
Product of the present	148	0.5 (0.6 μm)	balance	0.45	16.8	4.1	4	0.3	balance	143	—
invention
Comparative products	43	0.02* (40 μm*)	balance	0.01*	16.8	4.1	4	0.3	balance	13	—
	44	3.5* (0.01 μm*)	balance	3.43*	16.8	4.1	4	0.3	balance	108	decrease in
											strength
Conventional product	50	CaF2: 1	balance	CaF2: 1	16.8	4.1	4	0.3	balance	16	—
#SUS630 (Fe-17% Cr-4% Ni-4% Cu-0.3% Nb)
The symbol * means the value which is not within the scope of the present invention.

[0233] As is apparent from the results shown in Table 22, the number of piercing of the cylindrical sintered alloy block for piercing test made of the sintered alloy 148 of the present invention is larger than that of the cylindrical sintered alloy block for piercing test made of the conventional sintered alloy 50 and therefore the sintered alloy of the present invention is excellent in machinability. However, the comparative sintered alloy 43 containing CaCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 44 containing CaCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

[0234] As raw powders, a SrCO₃ powder having an average particle size shown in Table 23 and a pure Fe powder having an average particle size of 80 μm were prepared. These raw powders were blended according to the formulation shown in Table 23, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 149 to 158 of the present invention and comparative sintered alloys 45 to 46.

[0235] Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 149 to 158 of the present invention and the comparative sintered alloys 45 to 46 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

• [0236] Rotating speed: 10000 rpm
• [0237] Feed speed: 0.030 mm/rev.
• [0238] Cutting oil: none (dry).
  The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 23. Machinability was evaluated by the results.

[0239]

	TABLE 23
		Component ratio of
	Component ratio	iron-based sintered
	of raw powder (mass %)	alloy (mass %)
	SrCO3 powder			Fe and	Number of
	Average particle size is			inevitable	piercing
Iron-based sintered alloy	described in parenthesis.	Fe powder	SrCO3	impurities	(times)	Remarks
Products of the	149	0.05 (0.1 μm)	balance	0.05	balance	63	—
present invention	150	0.2 (0.5 μm)	balance	0.19	balance	130	—
	151	0.5 (1 μm)	balance	0.49	balance	145	—
	152	1.0 (1 μm)	balance	0.98	balance	212	—
	153	1.3 (0.5 μm)	balance	1.28	balance	190	—
	154	1.5 (2 μm)	balance	1.49	balance	245	—
	155	1.8 (18 μm)	balance	1.80	balance	197	—
	156	2.1 (2 μm)	balance	2.09	balance	188	—
	157	2.5 (18 μm)	balance	2.47	balance	219	—
	158	3.0 (30 μm)	balance	2.99	balance	305	—
Comparative	45	0.02* (40 μm*)	balance	0.01	balance	25	—
products	46	3.5* (0.01 μm*)	balance	3.47*	balance	146	decrease in
							strength
The symbol * means the value which is not within the scope of the present invention.

[0240] As is apparent from the results shown in Table 23, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 149 to 158 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 1 to 3 shown in Table 1 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 45 containing SrCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 46 containing SrCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

[0241] As raw powders, a SrCO₃ powder having an average particle size shown in Table 24 and a Fe-0.6 mass % P powder having an average particle size of 80 μm were prepared. These raw powders were blended according to the formulation shown in Table 24, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 159 to 168 of the present invention and comparative sintered alloys 47 to 48.

[0242] Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 159 to 168 of the present invention and the comparative sintered alloys 47 to 48 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

• [0243] Rotating speed: 10000 rpm
• [0244] Feed speed: 0.030 mm/rev.
• [0245] Cutting oil: none (dry).
  The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 24. Machinability was evaluated by the results.

[0246]

	TABLE 24
	Component ratio of raw powder	Component ratio
	(mass %)	of iron-based
	SrCO3 powder		sintered alloy (mass %)
	Average particle size is	Fe-based			Fe and	Number of
	described in	alloy			inevitable	piercing
Iron-based sintered alloy	parenthesis.	powder#	SrCO3	P	impurities	(times)	Remarks
Products of the	159	0.05 (0.1 μm)	balance	0.04	0.55	balance	51	—
present invention	160	0.2 (0.5 μm)	balance	0.18	0.58	balance	121	—
	161	0.5 (1 μm)	balance	0.49	0.53	balance	167	—
	162	1.0 (1.0 μm)	balance	0.99	0.53	balance	169	—
	163	1.3 (0.5 μm)	balance	1.28	0.57	balance	148	—
	184	1.5 (2 μm)	balance	1.48	0.57	balance	178	—
	165	1.8 (18 μm)	balance	1.79	0.54	balance	159	—
	166	2.1 (2 μm)	balance	2.07	0.53	balance	110	—
	167	2.5 (18 μm)	balance	2.49	0.55	balance	135	—
	168	3.0 (30 μm)	balance	2.99	0.55	balance	178	—
Comparative	47	0.02* (40 μm*)	balance	0.02*	0.56	balance	28	—
products	48	3.5* (0.01 μm*)	balance	3.48*	0.54	balance	163	decrease in
								strength
The symbol * means the value which is not within the scope of the present invention.
#Fe-based alloy powder with the composition of Fe-0.6 mass % P

[0247] As is apparent from the results shown in Table 24, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 159 to 168 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 4 to 6 shown in Table 2 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 47 containing SrCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 48 containing SrCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

[0248] As raw powders, a SrCO₃ powder having an average particle size shown in Table 25, a Fe powder having an average particle size of 80 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 25, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 169 to 178 of the present invention and comparative sintered alloys 49 to 50.

[0249] Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 169 to 178 of the present invention and the comparative sintered alloys 49 to 50 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

• [0250] Rotating speed: 10000 rpm
• [0251] Feed speed: 0.018 mm/rev.
• [0252] Cutting oil: none (dry).
  The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 25. Machinability was evaluated by the results.

[0253]

	TABLE 25
	Component ratio of raw powder (mass %)	Component ratio of iron-based
	SrCO3 powder		sintered alloy (mass %)
	Average particle							Fe and	Number of
Iron-based sintered	size is described	C	Fe					inevitable	piercing
alloy	in parenthesis.	powder	powder	Infiltration Cu	SrCO3	C	Cu	impurities	(times)	Remarks
Products of	169	0.05 (0.1 μm)	0.13	balance	20	0.05	0.12	19.5	balance	83	—
the present	170	0.2 (0.5 μm)	0.3	balance	20	0.20	0.24	20.2	balance	130	—
invention	171	0.5 (1 μm)	0.6	balance	20	0.49	0.54	20.1	balance	175	—
	172	1.0 (2 μm)	0.8	balance	20	0.97	0.75	19.6	balance	203	—
	173	1.3 (0.5 μm)	1.1	balance	20	1.28	1.05	19.9	balance	182	—
	174	1.6 (2 μm)	1.1	balance	20	1.46	0.99	20.4	balance	192	—
	175	1.8 (18 μm)	1.1	balance	20	1.77	1.05	19.8	balance	183	—
	176	2.1 (2 μm)	1.1	balance	20	2.09	1.07	20.0	balance	209	—
	177	2.5 (18 μm)	1.1	balance	20	2.45	1.07	19.7	balance	197	—
	178	3.0 (30 μm)	1.2	balance	20	2.96	1.15	19.9	balance	172	—
Comparative	49	0.02* (40 μm*)	1.1	balance	20	0.01*	1.04	20.3	balance	25	—
products	50	3.5* (0.01 μm*)	1.1	balance	20	3.45*	1.06	19.6	balance	124	decrease in
											strength
The symbol * means the value which is not within the scope of the present invention.

[0254] As is apparent from the results shown in Table 25, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 169 to 178 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 7 to 9 shown in Table 3 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 49 containing SrCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 50 containing SrCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

[0255] As raw powders, a SrCO₃ powder having an average particle size shown in Table 26, a Fe powder having an average particle size of 80 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 26, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes and subjected to 20% Cu infiltration to obtain iron-based sintered alloys 179 to 188 of the present invention and comparative sintered alloys 51 to 52.

[0256] Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 179 to 188 of the present invention and the comparative sintered alloys 51 to 52 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

• [0257] Rotating speed: 10000 rpm
• [0258] Feed speed: 0.018 mm/rev.
• [0259] Cutting oil: none (dry).
  The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 26. Machinability was evaluated by the results.

[0260]

	TABLE 26
		Component ratio
	Component ratio of raw powder (mass %)	of iron-based sintered
	SrCO3 powder		alloy (mass %)
	Average particle size					Fe and	Number of
Iron-based sintered	is described in	C				inevitable	piercing
alloy	parenthesis.	powder	Fe powder	SrCO3	C	impurities	(times)	Remarks
Products of the	179	0.05 (0.1 μm)	0.13	balance	0.05	0.12	balance	75	—
present	180	0.2 (0.5 μm)	0.3	balance	0.20	0.24	balance	110	—
invention	181	0.5 (1 μm)	0.6	balance	0.49	0.54	balance	156	—
	182	1.0 (2 μm)	0.8	balance	0.97	0.75	balance	172	—
	183	1.3 (0.5 μm)	1.1	balance	1.28	1.05	balance	181	—
	184	1.5 (2 μm)	1.1	balance	1.46	0.99	balance	205	—
	185	1.8 (18 μm)	1.1	balance	1.77	1.05	balance	171	—
	186	2.1 (2 μm)	1.1	balance	2.09	1.07	balance	220	—
	187	2.5 (18 μm)	1.1	balance	2.45	1.07	balance	199	—
	188	3.0 (30 μm)	1.2	balance	2.96	1.15	balance	194	—
Comparative	51	0.02* (40 μm*)	1.1	balance	0.01*	1.04	balance	15	—
products	52	3.5* (0.01 μm*)	1.1	balance	3.45*	1.06	balance	122	decrease in
									strength
The symbol * means the value which is not within the scope of the present invention.

[0261] As is apparent from the results shown in Table 26, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 179 to 188 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 10 to 12 shown in Table 4 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 51 containing SrCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 52 containing SrCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

[0262] As raw powders, a SrCO₃ powder having an average particle size shown in Table 27, a Fe powder having an average particle size of 80 μm, a Cu powder having an average particle size of 25 μm and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 27, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 189 to 198 of the present invention and comparative sintered alloys 53 to 54.

[0263] Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 189 to 198 of the present invention and the comparative sintered alloys 53 to 54 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

• [0264] Rotating speed: 10000 rpm
• [0265] Feed speed: 0.030 mm/rev.
• [0266] Cutting oil: none (dry).
  The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 27. Machinability was evaluated by the results.

[0267]

	TABLE 27
	Component ratio of raw powder (mass %)	Component ratio of iron-based
	SrCO3 powder		sintered alloy (mass %)
	Average particle size							Fe and	Number of
Iron-based sintered	is described in	Cu	C	Fe				inevitable	piercing
alloy	parenthesis.	powder	powder	powder	SrCO3	Cu	C	impurities	(times)	Remarks
Products of the	189	0.05 (0.1 μm)	0.2	0.13	balance	0.03	2.0	0.11	balance	48	—
present	190	0.2 (0.5 μm)	2	0.25	balance	0.18	2.1	0.22	balance	127	—
invention	191	0.5 (1 μm)	2	0.98	balance	0.48	1.9	0.87	balance	136	—
	192	1.0 (2 μm)	2	0.7	balance	0.96	2.0	0.68	balance	225	—
	193	1.3 (0.5 μm)	2	0.7	balance	1.25	2.0	0.64	balance	247	—
	194	1.5 (2 μm)	4	0.7	balance	1.46	4.0	0.65	balance	229	—
	195	1.8 (18 μm)	5.8	0.7	balance	1.77	5.7	0.67	balance	213	—
	196	2.1 (2 μm)	4	0.7	balance	2.09	3.9	0.64	balance	200	—
	197	2.5 (18 μm)	2	0.98	balance	2.48	2.0	0.92	balance	179	—
	198	3.0 (30 μm)	2	1.2	balance	2.97	2.0	1.16	balance	154	—
Comparative	53	0.02* (40 μm*)	2	0.7	balance	0.01*	1.9	0.67	balance	8	—
products	54	3.5* (0.01 μm*)	2	0.7	balance	3.47*	2.0	0.65	balance	148	decrease in
											strength
The symbol * means the value which is not within the scope of the present invention.

[0268] As is apparent from the results shown in Table 27, the number of piercing of the cylindrical sintered alloy blocks for piercing test made of the sintered alloys 189 to 198 of the present invention is larger than that of the cylindrical sintered alloy blocks for piercing test made of the conventional sintered alloys 13 to 15 shown in Table 5 and therefore the sintered alloys of the present invention are excellent in machinability. However, the comparative sintered alloy 53 containing SrCO₃ in the content of less than the range defined in the present invention is inferior in machinability because of small number of piercing, while the comparative sintered alloy 54 containing SrCO₃ in the content of more than the range defined in the present invention is excellent in machinability because of large number of piercing, but shows drastically decreased deflection strength, and therefore it is not preferred.

[0269] As raw powders, a SrCO₃ powder having an average particle size shown in Table 28, a partially diffused Fe-based alloy powder having an average particle size of 80 μm with the composition of Fe-1.5% Cu-4.0% Ni-0.5% Mo and a C powder having an average particle size of 18 μm were prepared. These raw powders were blended according to the formulation shown in Table 28, mixed in a double corn mixer and compacted to obtain a green compact, and then the resulting green compact was sintered in an endothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of a temperature of 1120° C. and a retention time of 20 minutes to obtain iron-based sintered alloys 199 to 208 of the present invention and comparative sintered alloys 55 to 56.

[0270] Cylindrical sintered alloy blocks for piercing test each having a diameter of 30 mm and a height of 10 mm, made of the sintered alloys 199 to 208 of the present invention and the comparative sintered alloys 55 to 56 were produced and these cylindrical sintered alloy blocks for piercing test were repeatedly pierced until the drill is damaged, using a high-speed steel drill having a diameter of 1.2 mm, under the following conditions:

• [0271] Rotating speed: 5000 rpm
• [0272] Feed speed: 0.006 mm/rev.
• [0273] Cutting oil: none (dry).
  The number of piercing (maximum number of piercing, lifetime) of one new drill was measured. The results are shown in Table 28. Machinability was evaluated by the results.

[0274]

	TABLE 28
	Component ratio of raw powder
	(mass %)	Component ratio of iron-based sintered alloy
	SrCO3 powder	(mass %)
	Average particle		Fe-based						Fe and	Number of
Iron-based sintered	size is described in	C	alloy						inevitable	piercing
alloy	parenthesis.	powder	powder#	SrCO3	Cu	C	Ni	Mo	impurities	(times)	Remarks
Products of the	199	0.05 (0.1 μm)	0.13	balance	0.03	1.5	0.11	3.9	0.50	balance	51	—
present	200	0.2 (0.5 μm)	0.25	balance	0.18	1.5	0.19	4.0	0.50	balance	148	—
invention	201	0.5 (1 μm)	0.98	balance	0.46	1.5	0.85	4.0	0.50	balance	208	—
	202	1.0 (2 μm)	0.5	balance	0.96	1.4	0.47	4.1	0.52	balance	308	—
	203	1.3 (0.5 μm)	0.5	balance	1.25	1.5	0.45	4.0	0.50	balance	301	—
	204	1.5 (2 μm)	0.5	balance	1.45	1.5	0.45	4.0	0.50	balance	315	—
	205	1.8 (18 μm)	0.5	balance	1.72	1.5	0.47	4.0	0.49	balance	268	—
	206	2.1 (2 μm)	0.5	balance	2.05	1.6	0.47	3.8	0.50	balance	298	—
	207	2.5 (18 μm)	1.0	balance	2.44	1.5	0.90	4.0	0.50	balance	286	—
	208	3.0 (30 μm)	1.2	balance	2.93	1.5	1.17	4.0	0.50	balance	248	—
Comparative	55	0.02* (40 μm*)	0.5	balance	0.01*	1.5	0.43	4.1	0.50	balance	9	—
products	56	3.5* (0.01 μm*)	0.5	balance	3.42*	1.5	0.44	4.0	0.51	balance	130	decrease in
												strength
The symbol * means the value which is not within the scope of the present invention.
#partially diffused Fe-based alloy powder having an average particle size of 80 μm with the composition of Fe-1.5% Cu-4.0% Ni-0.5% Mo