Process for Autogenic Flame Cutting With Oxygen

It is known that the removal of slag from the cutting grove during flame cutting is a limiting factor where cutting speed is concerned. Higher cutting speeds are an advantage with many applications. Thus the cutting speed during autogenic flame cutting of continuous casting ingots is lower than the pull out speed of the ingots. For example, the cutting speed with ingots 200 mm thick amounts to about 0.5 m/min. The pull out speed, on the other hand, amounts to 1.5/2.0 m/min. If the continuous casting ingots are to be cut longitudinally, it is desirable to adapt the cutting speed to the pull out speed.

The objective of the invention is thus to achieve a process for autogenic flame cutting with oxygen according to which the cutting speed can be significantly raised.

The invention proceeds from the idea of linking the high kinetic energy of a liquid jet, which is for example used in water jet cutting, with the technology of autogenic flame cutting. With the use of liquid oxygen, according to the invention, the striking energy can be raised because of the higher densities. Because of the smaller impact area, the striking energy is greater per unit area. The process is purposely carried out so that the amount of liquid oxygen corresponds to the amount of gaseous oxygen needed for the flame cutting. The cold brought in by the liquid oxygen can be tolerated since the heat of vaporization of liquid oxygen is very low. A pre-heater can eventually be installed before the liquid jet nozzle, which permits heating the workpiece so that the surface temperature is raised to the ignition temperature.

The simple FIGURE illustrates in schematic form, an embodiment of the invention, namely the cutting of continuous casting ingots.

Shown is a liquid jet nozzle 1 from which a jet 2 of liquid oxygen with higher velocity exits and impacts the continuous casting ingot 3 to be cut. The supply of liquid oxygen occurs, via an insulated line 4, and of an insulated storage tank 5 for the liquid oxygen. This insulated tank 5 has the usual, not referenced in closer detail, pipe lines and valves for taking up liquid and gaseous oxygen. The liquid oxygen required for the process according to the invention is drawn from the insulated tank 5, via the line 6 and arrives, via the valve 7, at the high pressure pump 8 which raises the pressure of the liquid oxygen to 500 bar. The pressure from pump 8 may be between 200 and 900 bar. The final pressure of the liquid oxygen available at the liquid jet cutting nozzle 1 is regulated by means of the adjustable overflow valve 9. Unused liquid oxygen flows from the overflow valve 9, through the line 10, back into the insulated storage tank 5. Lines leading to the high pressure pump 8 and to the overflow valve 9 are insulated. The insulated line 4 can additionally be surrounded with liquid nitrogen in order to avoid a premature vaporization of the oxygen. Maximum pressures of 300 to 600 bar can be attained with the liquid oxygen pumps commonly on the market. The invention is not, however, restricted to this pressure range, but rather, pressures of 4000 bar and higher, which are known from water jet cutting can be used.

The limiting factor of the cutting speed during flame cutting is the removal of slag from the cutting grove. In order to raise the cutting speed, the oxygen, in the liquid state and at a pressure of from several hundred bar to several thousand bar is directed at the workpiece from a liquid jet cutting nozzle. The striking energy and thus the removal of the slag are thus increased. The liquid jet cutting nozzle can be associated with a pre-heater which raises the surface of the workpiece to the ignition temperature. The preferred application area is the cutting of continuous casting ingots.