| 摘要 |
PROBLEM TO BE SOLVED: To remarkably improve the surface hardness of an austenitic metal without deteriorating the strength and corrosion resistance of a base material and to obtain a hardened surface layer provided with corrosion resistance higher than that of the base metal according to circumstances, prior to carburizing treatment, by holding an austenitic metal in a heating state in a fluorine gas atmosphere and specifying the carburizing temp. SOLUTION: For example, an austenitic stainless steel is heated at 250 to 450 deg.C in a fluorine gas atmosphere, is held in this state and is next subjected to carburizing treatment at <=680 deg.C. Thereafter, pickling treatment is executed according to necessary. In such a way, the surface layer to a depth of 10 to 70μm from the surface of the steel is formed into a carburizing layer having 700 to 1050 (Hv) micro Vickers hardness and composed of austenitic phases free from chromium carbide grains. As for the obtd. carburizing treated product, the surface is hard, and not only the corrosion resistance of the austenitic metal itself is not deteriorated, but also it can respond to a requirement for the hardness of the base material or above according to circumstances.
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