Patent ID: 7311789

Claim:
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: 0.8-2.40; 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+10 Mo)=at least 3.5%, comprising soaking said steel sheet for 20 to 90 seconds at a temperature within the range of A C1 +45° F., to A C1 +135° F., cooling said steel sheet at a rate of at least 1° C. per second to a temperature in the range 850-940° F., and holding said steel sheet in the range 850-940° F. for 20 to 100 seconds.