| 摘要 |
A method of producing high strength steel sheet and formed articles fabricated from the sheet and containing about 0.01-0.3 free and uncombined atomic percent Ti, Ni or V as strengthening element, by hot rolling or hot rolling plus cold rolling the sheet within limited temperature ranges, annealing the rolled sheet or formed articles at a temperature of about 1275-1350 DEG F to provide a (111) grain structure, nitriding the annealed sheet or formed article in an annealing furnace at a temperature of about 800-1250 DEG F under fully developed laminar or turbulant gas flow, and controlling the strengthening of the steel article as a function of steel composition, the nitriding gas composition, nitriding time, nitriding temperature, thickness of the steel sheet and depth of strengthening desired, in accordance with specified relationships, to provide a steel article having a 0.2 % off-set yield strength after temper rolling of at least about 40 ksi and an r value in excess of about 1.7 for the cold rolled sheet.
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