Metal treatment – Stock – Ferrous
Reexamination Certificate
2007-07-27
2010-11-02
Yee, Deborah (Department: 1793)
Metal treatment
Stock
Ferrous
C148S649000, C148S653000, C148S654000, C148S643000, C148S644000, C148S665000, C148S902000
Reexamination Certificate
active
07824508
ABSTRACT:
The present invention provides a fine grain surface layer steel part having a high proof strength ratio equal to or higher than that of conventional quenched and tempered materials, that is, a fine grain surface layer steel part containing, by mass %, C: 0.45% to 0.70%, Nb: 0.01% to 0.60%, Si: 0.10% to 1.50%, Mn: 0.40% to 2.0%, P: 0.10% or less, S: 0.001% to 0.15%, and N: 0.003% to 0.025% and having a balance of Fe and unavoidable impurities, where the surface layer and inside at all or part of the part have structures of different average particle sizes of ferrite crystal grains surrounded by high angle grain boundaries of a misorientation angle of 15 degrees or more and a method of production of that part comprising warm forging locations where strength is required to a predetermined shape at 1000° C. to 800° C. during which working so as to give an equivalent strain of 1.5 or more.
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Takada Hiromasa
Teramoto Shinya
Kenyon & Kenyon LLP
Nippon Steel Corporation
Yee Deborah
LandOfFree
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