Method For Producing Super High Strength Nano-Precipitation Strengthened, Single Phase Ferritic Steel

Abstract

A hot-rolled steel sheet is defined by the following composition by weight percentage: 0.040%<carbon<0.06%, 1.20%<manganese<1.50%, 0.02%<aluminum<0.04%, 0.09%<titanium<0.15%, 0.15%<silicon<0.40%, 0.00%<copper<0.20%, with the balance being iron and impurities inherent in processing. The hot-rolled steel sheet has a tensile strength equal to or greater than 780 MPa. The elimination of cold rolling and high temperature annealing process is the essence of this innovation for the production of high strength sheet steels down to a thickness of 1.4 mm.

1 . A hot-rolled steel sheet comprises the following composition by weight percentage:
 0.040%<carbon<0.06%,   1.20%<manganese<1.50%,   0.02%<aluminum<0.04%,   0.09%<titanium<0.15%,   0.15%<silicon<0.40%,   0.00%<copper<0.20%, with the balance being iron and impurities inherent in processing; and   the hot-rolled steel sheet has a tensile strength equal to or greater than 780 MPa.   
     
     
         2 . The hot-rolled steel sheet as set forth in  claim 1  having a hole expansion ratio of at least 40%. 
     
     
         3 . The hot-rolled steel sheet as set forth in  claim 2  wherein the hot-rolled steel sheet is hot rolled to a thickness equal to or less than 1.4 mm.