Inventors:
Emil G. Hamburg - Pittsburgh PA
Robert L. Cryderman - McMurray PA
John F. Butler - Bethel Park PA
Assignee:
Jones & Laughlin Steel Corporation - Pittsburgh PA
International Classification:
C21D 600, C21D 714
Abstract:
A steel product having a combination of high strength and formability (as measured by percent tensile uniform elongation) is produced by austenitizing a steel consisting essentially of from 0. 04 to 0. 17% carbon, 0. 8 to 2. 0% manganese, up to 1. 0% silicon, up to 0. 12% vanadium, up to 0. 1% columbium, up to an effective amount of titanium to form titanium carbonitrides, 0. 001 to 0. 025% nitrogen, balance essentially iron and then cooling at a rate of no more than about 70. degree. F/sec. to about 850. degree. F and at a rate of more than about 10. degree. F/sec. to transform the freshly formed austenite to a microstructure of from 10 to 35% by volume of martensite and/or lower bainite (MLB), balance essentially proeutectoid ferrite. Slower cooling rates may be employed to obtain the desired microstructure if a restricted chemical composition is used. The heat-treated steel product is characterized by an ultimate tensile strength of 80,000 p. s. i.