C - Chemistry – Metallurgy – 22 – C
Patent
C - Chemistry, Metallurgy
22
C
C22C 38/14 (2006.01) C21D 7/00 (2006.01) C21D 8/00 (2006.01) C21D 8/04 (2006.01) C22C 38/12 (2006.01)
Patent
CA 2171920
The invention relates to a cold rolled steel sheet having excellent press workability and a method for making the same. The composition of the cold rolled steel sheet includes about 0.001 weight percent or less of carbon (C), about 0.1 weight percent or less of silicon (Si), about 0.3 weight percent or less of manganese (Mn), about 0.05 weight percent or less of phosphorus (P), about 0.003 weight percent or less of sulfur (S), about 0.1 weight percent or less of aluminum (Al), about 0.002 weight percent or less of nitrogen (N), about 0.005 to 0.02 weight percent of titanium (Ti), about 0.001 to 0.01 weight percent of niobium (Nb), and the balance iron and incidental impurities. The total weight percent of carbon, sulfur, and nitrogen is about 0.004 weight percent or less, while the content of titanium, carbon, sulfur and nitrogen satisfy equation: about 4x(carbon weight percent) (titanium weight percent) - 48/14(nitrogen weight percent) - 48/32(sulfur weight percent) about 12x (carbon weight percent). The steel sheet may further contain about 0.0001 to 0.0010 weight percent of boron. The method of the invention includes uniformly heating a steel slab having a composition as described above at a temperature T(K) satisfying the following equation: T(K)x(carbon weight percent+sulfur weight percent) about 4.0, and within a temperature range from about 900 to 1,300°C, hot rolling at a finishing temperature of higher than the AC3 transformation temperature, coiling at a temperature of about 650°C or less, cold rolling after pickling at a rolling reduction rate of about 65 to 90 percent, and recrystallization-annealing at a temperature ranging from about 700 to 950°C.
Kato Toshiyuki
Sakata Kei
Yasuhara Eiko
Jfe Steel Corporation
Smart & Biggar
LandOfFree
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