Patent ID: 6811624
Filing Date: 2004-11-02
Classification: C21D,C22C,C23C

Abstract:
Method of making an incipient dual phase steel sheet, wherein said steel sheet has the composition, in weight percent, carbon: 0.02-0.20; aluminum: 0.010-0.150; titanium: 0.01 max; silicon: 0.5 max; phosphorous: 0.060 max; sulfur: 0.030 max; manganese: 1.5-2.40; chromium: 0.03-1.50; molybdenum: 0.03-1.50; with the provisos that the amounts of manganese, chromium and molybdenum have the relationship: (Mn+6Cr+10Mo)=at least 3.5%, comprising soaking said steel sheet for 20 to 90 seconds at a temperature within the range of Acl+45Â° F., but at least 1340Â° F. (727Â° C.), to AC1+135Â° F., but no more than 1425Â° F. (775Â° C.), cooling said steel sheet at a rate of at least 1Â° C. per second to a temperature in the range 850-920Â° F., and holding said steel sheet in the range 850-920Â° F. for 20 to 100 seconds.