Desensitization of Stainless Steels by Laser Surface Heat-Treatment

概要

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Later heating was applied for the desensitization heat-treatment of the surface layer in the sensitized HAZ of Type 304 stainless steel. The degree of sensitization was examined by the EPR technique and the 10% oxalic acid electrolytic etch test. The CO_2 laser with the maximum power of 1.5 kW was used for heat-treatment. Time-Temperature-Desensitization diagrams (TTDS diagrams) for sensitized Type 304 stainless steels were obtained by calculation assuming the chromium diffusion control for desensilization which might occur when the chromium depleted zone was healed up due to dissolution of chromium carbide and chromium diffusion from the matrix being healed at the solution annealing temperatures. TTDS diagrams calculated agree fairly well with ones determined by the corrosion tests. Laser irradiation conditions (e.g., laser power, beam diameter and traveling velocity) required for desensitization of sensitized Type 304 stainless steels were calculated using the additivity rule from the TTDS diagram calculated and the theoretical thermal cycle curve of laser heating derived from the heat conduction theory. After laser beam was irradiated under an optimum condition predicted by calculation, the sensitized HAZ of Type 304 stainless steel restored a complete resistance to intergranular corrosion.
社団法人溶接学会の論文
1986-04-01