| 摘要 |
PURPOSE:To perform efficiently a stress relief annealing, and to reduce discoloration caused by heating, by heating and cooling rapidly a sheet by a convergent plasma flame to give the shrinkage and deformation while sealing the back surface of a heated part with inert gas or nonoxidizing gas. CONSTITUTION:A plasma arc 5 is ignited between a sheet 1 and an electrode 2, and then a small range of the surface of sheet 1 is heated rapidly while sealing the back surface of a heated part with non-oxidizing gas such as inert gas, gaseous carbon oxide, and gaseous nitrogen, etc. to prevent the back surface from oxidation. The heat inputted to the local part by the plasma arc is rapidly diffused and cooled, and the oxidation accompanying discoloration is prevented. |
