A method for the production of high-strength, cold-rolled steel sheet having an improved press the form of the highway

摘要

PURPOSE:To manufacture a cold rolled steel plate with high strength and superior press workability by hot rolling Mn stel of restricted sol. Al and N contents followed by coiling at a suitable temp., cold rolling, annealing and temper rolling under restricted conditions. CONSTITUTION:Steel consising of C 0.005-0.080%, Si=0.30%,Mn 1.6-3.5%, sol. Al 0.02-0.08%, N 0.005-0.020%, and the balance Fe and inevitable impurities is hot rolled, coiled at below 600 deg.C, cold rolled at a reduction ratio above 30%, and annealed by soaking at 660-750 deg.C for more than 30 min, and so on. After being annealed the plate may be temper-rolled at a reduction ratio below 0.5%. By these treatments the grains of the cold rolled plate are made appropriate, and the gamma-value is enhanced. The annealing relieves a strain and provides a ferrite+ martensite two phase structure, resulting in high dent resistance.