METHOD FOR MANUFACTURING TENSILE STRENGTH 590MPa CLASS COLD ROLLED DP STEEL WITH EXCELLENT WORKABILITY AND VARIATION OF MECHANICAL PROPERTY

摘要

PURPOSE: A method for manufacturing high-strength hot-rolled DP steel with a tensile strength of about 590MPa and low property deviation is provided to reduce energy consumption by excluding a re-heating process from the processes of the conventional mill. CONSTITUTION: A method for manufacturing high-strength hot-rolled DP steel comprises the steps of: continuously casting steel into a thin slab(a) 30-150mm thick, roughing, heating, finish rolling, cooling, and coiling the thin slab to obtain a hot-rolled strip(b), and picking, cold rolling, continuous annealing, and cooling the hot-rolled strip. In the finish rolling step, rolling speed deviation in a single strip is controlled to 15% or less and the rolling temperature of the final rolling stand is controlled to 20C of a target temperature. In the cooling step, the annealed strip is continuously cooled at a cooling speed of 10-150C/s to a temperature of 200-400C.