MANUFACTURE OF NONMAGNETIC AGE-HARDENING AUSTENITIC STEEL WITH HIGH HARDNESS BY POWDER METHOD

摘要

PURPOSE:To improve the hot hardness of a steel, by using, as starting raw materials, respective pulverized powders, as raw materials, of metals as simple substances, carbides, etc., for producing a steel with a specific composition and by subjecting the above to pressing and heat treatment under respectively prescribed conditions. CONSTITUTION:Pulverized powders as raw materials (powders of Fe, Cr, and Mn, powders of the carbides of Cr, V, Nb, and Ti, graphite powder, etc.) for producing a steel having a composition consisting of 0.65-1.40% C, 10.00-20.00% Mn, one or more kinds (2.00-6.00%, in total, of two or more kinds) among 7.00-15.00% Cr, 2.00-6.00% V, 2.00-6.00% Nb, and 1.80-5.00% Ti, and the balance iron with usual impurities as powdery starting raw materials. These powders are mixed and cold-press- compacted, and the resulting green compact is subjected to sintering which doubles as diffusion treatment (1,050-1,250 deg.C) in vacuum or an hydrogen and further to hot isostatic pressing finish which doubles as diffusion treatment at 1,050-1,250 deg.C. By this method, the carbides of V, Nb, Ti, etc., are refined and the amount of precipitation of the carbides in the course from solution heat treatment to age hardening treatment is increased, by which a nonmagnetic steel having high hardness can be obtained.