Method at Gas Planing

This invention relates to a method of gas planing, especially at spot planing.

Gas planing is applied mostly for removing defects in the surfaces of steel workpieces before the workpieces are passed through a continued refining process, for example rolling. The surface defects of the workpieces have the form of cracks, non-metallic inclusions or the like, which render a deteriorated product unless they are removed prior to the refining of the workpiece. Gas planing can be carried out by means of a combusting gas in such a manner, that the melting of the workpiece is effected by the supply of heat from the combusting gas. Also pure oxygen can advantageously be used for gas planing. Oxygen gas planing, however, requires heating of the workpiece surface to about 1100.degree. C. before the supplied gas per se is capable to continue the planing operation with heat developing from the oxidized iron. The gas flowing out from the nozzle of the planing device applies, in addition to an oxidizing melting effect on the workpiece, also a transporting effect on the melt being formed in front of the planing device. At spot planing only those portions of the workpiece surface are worked which include defects. After the working of a workpiece surface portion with defects, the supply of combusting gas or oxygen is stopped. There is great risk that the melt already formed in front of the planing device adheres to a workpiece surface portion without defects, because there exists no longer the transporting effect of the gas on the melt.

The present invention relates to a method, which applies a transporting removing effect on the melt even after the planing operation has been stopped.

By supplying air after completed planing operation, the transporting removing effect on the melt can be maintained until all melt has been removed. The air preferably is supplied through the passageways and nozzles, which during the planing operation guide the working gas. The air supply also has the effect that oxidization of the workpieces rapidly ceases, which prevents unnecessary removal of material and renders the planing operation easily adjustable.

The arrangement for the supply of air must consist only of a compressed-air container, which via a double-acting switch valve is connected to the gas supply line of the planing device, so that the working gas is throttled at the same time as the air is supplied.

The method according to the invention can be applied to all known gas planing devices utilizing combusting gas or pure oxygen as working medium.

The air sluicing through the planing device advantageously can be combined with turbulent flow and/or with a planing device having portions shielding off in lateral direction.

When the invention is applied together with a device having laterally shielding side portions and where evacuation nozzles are provided, the gas stream remains in the evacuation nozzles until all of the melt has been removed, i.e. even after the oxygen in the main gas stream has been replaced by, for example, air.

It also can be advantageous to direct the air through a nozzle separated from the nozzle guiding the working gas stream.