Patent ID: 8999085
Filing Date: 2015-04-07
Classification: B32B,B62D,C21D,C22C,C23C,C25D,Y10T

Abstract:
1. A method for manufacturing a high Mn cold-rolled steel strip having superior surface properties and plating characteristics, comprising: homogenizing either a steel ingot or a continuous cast steel slab at 1,050-1,300° C., the steel ingot or the steel slab comprising, by weight%: 0.2-1.5% of C, 10 18 25% of Mn, 1.3-3.0% of Al, 0.45-2.0% of Si, 0.03% or less of P, 0.03% or less of S, 0.040% or less of N, 0.0005-0.010% of Ca, 0.001-0.020% of B, and the balance of Fe and other unavoidable impurities; hot rolling the homogenized steel ingot or steel slab with finish rolling at a finish rolling temperature of 850-950° C. to form a hot-rolled steel strip, followed by coiling the hot-rolled steel strip at a temperature of 700° C. or less; cold rolling the hot-rolled steel strip at a cold rolling reduction ratio of 30-80% to form a cold-rolled steel strip; and continuously annealing the cold-rolled steel strip at a temperature of 600° C. or more and over-aging the annealed steel strip at a temperature lower than the annealing temperature, forming a thin silicon oxide layer which suppresses oxidation of iron and manganese on the surface of the cold-rolled steel strip, wherein the steel strip contains fine aluminum nitrides and spheroidized non-metallic inclusions.