HIGH-STRENGTH COLD-ROLLED STEEL PLATE WITH EXCELLENT UNIFORM RELATIVE ELONGATION AND ABILITY FOR HOLE EXPANSION AND METHOD OF ITS PRODUCTION

摘要

FIELD: metallurgy.SUBSTANCE: invention relates to metallurgy, particularly, to high-strength cold-rolled steel plate used in motor-car production. Plate is made of steel containing in wt %: C: from 0.01 to 0.4, Mn: from 0.001 to 4.0, P: from 0.001 to 0.15, S: from 0.0005 to 0.03, N: from 0.0005 to 0.01, O: from 0.0005 to 0.01, Si and Al at least 0.001 each, and at Si + Al up to below 1.0%, iron and inevitable contaminating admixtures - rest. Steel structure in units of area fractions contains from 5 to 80% of ferrite, from 5 to 80% of beinite and 1% or below martensite, at total content of martensite, pearlite and residual austenite 5% or below. In central part through the metal thickness in range from 5/8 to 3/8 of plate thickness from the steel plate surface the average pole densities of group of orientations from {100}<011> to {223}<110> is 5.0 or below, and pole density of the crystal-lattice orientation {332}<113> is 4.0 or below. Anisotropic index "r" in direction perpendicular to rolling direction (rC) is 0.70 or over, and anisotropic index "r" in the direction at angle 30° to the rolling direction (r30) is 1.10 or below.EFFECT: plate has increased uniform relative elongation and ability for the hole expansion.14 cl, 1 dwg, 5 tbl, 1 ex