MANUFACTURING METHOD OF ROLLED STOCK FROM LOW-ALLOY PLATE STEEL Russian patent published in 2014 - IPC C21D8/02 C22C38/58 

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, and namely to making of plate steel for tubes with wall thickness of up to 39 mm. In order to provide increased cold resistance, high level of resistance to extended ductile rupture, a slab workpiece with thickness of at least 250 mm from steel containing the following, wt %, is used: 0.05-0.12 C, 1.40-1.75 Mn, Si≤0.35, Ni≤0.3, Mo≤0.25, Cu≤0.3, 0.01-0.03 Ti, 0.02-0.08 Nb, V≤0.08, 0.01-0.05 Al, S≤0.05, P≤0.015, Fe and impurities are the rest; with that, quantity of nonmetallic inclusions does not exceed 1.5 points, and quantity of the rest nonmetallic inclusions does not exceed 3 points. Heating temperature of workpieces before roughing-down is set in the range of 1160-1220°C. Roughing-down is performed at 2 stages with a crimping degree per pass of at least 10%. The first roughing-down stage is performed at temperatures of full recrystallisation of at least 980°C till thickness of an intermediate workpiece, which is equal to 40-60% of initial thickness of the slab workpiece. After that, cooling of the intermediate workpiece is performed in the air. The second roughing-down stage is performed at the rolling beginning temperature equal to 870-930°C and corresponding to recrystallisation braking temperature at thermochemical treatment till roll thickness. Finish rolling is performed at the rolling beginning temperature of not more than 830-890°C and at rolling end temperature equal to Ar₃ -50°C to Ar₃ +10°C.

EFFECT: providing increased cold resistance of high level of resistance to extended ductile rupture.

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