MULTI-PHASE STEEL COLD-ROLLED FLAT PRODUCT PRODUCED FROM A MULTI-PHASE STEEL OF THIS TYPE AND METHOD FOR PRODUCING IT

摘要

In order to produce a cold rolled steel plate product having TRIP characteristics and exhibiting improved strength and high fracture elongation at the same time in the composite structure steel according to the present invention, the composite structure steel according to the present invention comprises, in addition to the balance iron and unavoidable impurities, 0.1 to 0.25%, Mn to 1.7 to 2.5%, Si to 1.4 to 2.0%, Al to 0.1%, Cr to 0.1%, Mo to 0.05%, Nb to 0.02 to 0.06% , At least one element in the group "Ti, B, V" according to the conditions of P: at most 0.02%, N: at most 0.01% and optionally Ti: at most 0.1%, B: at most 0.002% And the cast semi-finished product is hot rolled into hot rolled strips by hot rolling starting at an initial temperature of 1100 - 1300 캜 and ending at a final temperature of 820 - 950 캜. The hot-rolled strip is then wound into coils at 400-750 ° C, cold rolled into cold rolled flat products at a cold rolling rate of 30-80% after winding. Cold rolled products are subjected to a continuous annealing treatment at an annealing temperature that is at least 20 ° C higher than the A _C1 temperature and not exceeding the temperature of the steel A _C3, and a heat treatment including an overhanging treatment at an overhanging temperature of 350-500 ° C. The present invention also provides composite textured steels and correspondingly prepared flat plate products suitable for this purpose.