METHOD FOR THE PRODUCTION OF HIGH-STRENGTH EXTRA-LOW-CARBON COLD-ROLLED STEEL WITH ANNEALING IN BATCH FURNACES Russian patent published in 2021 - IPC C21D8/04 C22C38/58 C22C38/50 

FIELD: metallurgy.

SUBSTANCE: invention relates to the field of metallurgy, in particular to the technology for the production of cold-rolled strip, intended for the manufacture of car parts by stamping. Steel is smelted containing, in wt.%: carbon 0.001-0.006, silicon no more than 0.3, manganese 0.3-1.6, phosphorus no more than 0.1, aluminum no more than 0.1, titanium 0.02-0.12, niobium no more than 0.02, sulfur no more than 0.012, nitrogen no more than 0.012, chromium no more than 0.01, nickel no more than 0.07, copper no more than 0.01, iron and inevitable impurities, the rest. Casting into slabs, hot rolling, coiling, pickling, cold rolling with a total reduction of 65-90% to obtain a strip, recrystallization annealing of the strip in a bell furnace and its tempering are carried out. The recrystallization annealing of the strip is carried out in the temperature range 720-780°С, and the duration of the holding of the strip during recrystallization annealing is calculated by the expression: t=40.201-0.1337σ_r, where t is the exposure duration, h, σ_r is the required level of the yield stress, MPa. Training is carried out with a reduction rate of 0.4-1.2%.

EFFECT: obtaining increased strength characteristics while maintaining high plasticity.

1 cl, 3 tbl, 3 ex