HIGH-STRENGTH MULTI-PHASE STEEL FOR COLD OR HOT-ROLLED STEEL STRIP AND METHOD OF MAKING COLD AND HOT-ROLLED STEEL STRIP

摘要

FIELD: metallurgy.SUBSTANCE: invention relates to metallurgy for production of strips of high-strength multi-phase steel, used in automotive industry. To ensure uniform mechanical properties along strip length and increasing moulding properties of cold-rolled or hot-rolled strip is made from steel containing, wt%: 0.060 to ≤ 0.115, Al 0.020 to ≤ 0.060, Si 0.100 to ≤ 0.500, Mn 1.300 to ≤ 2.500, P ≤ 0.025, S ≤ 0.0100, Cr 0.280 to ≤ 0.480, Mo ≤ 0.150, Ti ≥ 0.005 to ≤ 0.050, Nb ≥ 0.005 to ≤ 0.050, B ≥ 0.0005 to ≤ 0.0060, N ≤ 0.0100, rest is iron and unavoidable impurities. Hot-rolled or cold-rolled strip is subjected to continuous annealing by heating in furnace for continuous annealing to 700-900 °C and cooling first, at rate of 15-100 °C/s to intermediate temperature of 200-250 °C, and then at rate of 2-30 °C/s in air to room temperature.EFFECT: providing uniform mechanical properties along length of strip and improved moulding properties.25 cl, 11 dwg