STEEL BAND OR SHEET OF IMPROVED STRENGTH AND METHOD FOR PRODUCING THE SAME Russian patent published in 2005 - IPC

FIELD: metallurgy, in particular steel smelting.

SUBSTANCE: invention relates to steel band or sheet of improved strength with essential ferrite-martensite structure wherein martensite part is 4-20 %. Claimed steel contains (mass %) C 0/05-0/2; Si at most 1.0; Mn 0.8-2.0; P at most 0.1; S at most 0.015; N at most 0.005; Cr 0.25-1.0; B 0.002-0.01; Al 0.02-0.4, optionally Ti, and balance: Fe and technological impurities, with the proviso, that when Al content is 0.02-0.06 %, Ti content is at least 2.8xA_N, wherein A_N denotes nitrogen content, and if Ti is absent Al content is 0.1-0.4 %. In one embodiment of invention cold-rolled steel band or sheet is annealed in continuous furnace, and another one hot-rolled steel band or sheet is annealed in continuous furnace at temperature of 750-870⁰C, preferably at 750-850⁰C. Steel band or sheet is cooled from annealing temperature at rate of at least 20⁰C/s and maximum 100⁰C/s.

EFFECT: steel band or sheet of improved strength.

17 cl, 5 tbl, 4 ex