Metal treatment – Compositions – Heat treating
Patent
1976-12-21
1979-05-15
Rutledge, L. Dewayne
Metal treatment
Compositions
Heat treating
148 165, 148 166, 148 315, C21D 148
Patent
active
041546296
ABSTRACT:
A process for case hardening martensitic stainless steels comprising the steps of forming non-explosive and neutral or weakly reducing atmosphere consisting essentially of 97.5% to 95% by volume of nitrogen gas, 0.5% to 1.5% by volume of carbon monoxide and 2% to 3.5% by volume of hydrogen gas. The carbon monoxide and hydrogen gases are produced by heat decomposition of an organic solvent mixed with the nitrogen gas. The martensitic stainless steel is heated in this atmosphere at a solution heat treatment temperature in the range 900.degree. C. to 1100.degree. C. for a period required to cause nitriding of a surface thereof to a predetermined depth. The steel is then quenched at a temperature within the range of 150.degree. C. to room temperature, the quenching gas being selected from the group consisting of nitrogen gas and the resulting gaseous atmosphere. As a result of this process, resistance against planar pressure by loads and the strength of the martensitic stainless steel are increased. The stainless steel thus treated has bright surfaces and high corrosion resistance.
REFERENCES:
patent: 2786003 (1957-03-01), Hollingsworth et al.
patent: 3201290 (1965-08-01), Wyss
patent: 3344817 (1967-10-01), Connard
patent: 4006042 (1977-02-01), Kieferle
patent: 4042428 (1977-08-01), Asai et al.
Metals Handbook, 8th. Ed., vol. 2, 1974, pp. 125, 126, 151, 152 and 154.
Asai Takeji
Sakuta Teruyoshi
Yamazumi Kaishu
Kabushiki-Kaisha Fujikoshi
Rutledge L. Dewayne
Sheehan John P.
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