METHOD OF PRODUCING HOT-ROLLED COLD-RESISTANT ROLLED STOCK Russian patent published in 2022 - IPC C21D8/02 B21B1/26 C22C38/38 C22C38/58 

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, more specifically to rolling production, and can be used in production of hot-rolled coils for electric-welded pipes at wide-strip multi-stand mills, electric-welded pipes intended for operation at negative temperatures, including for arctic application. Method for production of hot-rolled cold-resistant rolled stock includes production of continuously cast slab from steel, slab heating in furnace and its rolling in mill stands roughing group, intermediate semi-finished stock is rolled in the finishing group of mill stands, the obtained rolled stock is cooled and coiled. At that, continuously cast slab with thickness of 70÷110 mm from steel containing, wt. %: carbon from 0.04 to 0.07; silicon from 0.15 to 0.50; manganese from 0.50 to 1.75; aluminium from 0.02 to 0.05; niobium from 0.03 to 0.10; titanium from 0 to 0.015; sulphur not more than 0.005; phosphorus not more than 0.015; nitrogen not more than 0.012; wherein (Si + Mn + 10⋅Nb) = (0.0078⋅σ_B-2.35 + 300⋅Ti²+17⋅Ti) ± 0.2, where Si, Mn, Nb, Ti is the content of silicon, manganese, niobium and titanium in the steel from which the slab is obtained (wt. %); σ_B - target value of ultimate tensile strength of rolled steel, which is a number from a number of numbers from minimum to maximum standardized value of temporary tensile strength of rolled steel (MPa). Slab rolling in the roughing group of mill stands and rolling of the intermediate rolled stock in the finishing group of mill stands is carried out with total relative reductions corresponding to the ratio Σε_finish/Σε_rough = 1.23÷1.57, where Σε_finish - total relative reduction of intermediate semi-finished stock at its rolling in finishing group of mill stands (%); Σε_rough is the total relative reduction of slab at its rolling in roughing group of mill stands (%). Rolling of the intermediate semi-finished stock in the finishing group of stands is started at its temperature T (°C) corresponding to the ratio T = 1117⋅Nb^0.073 ± 20, where Nb is the niobium content in the steel from which the slab is obtained, (wt. %).

EFFECT: increased dispersion and homogeneity of rolled stock formed depending on target value of temporary tensile strength of ferrite-pearlite or ferrite-bainitic structure.

1 cl, 2 ex, 1 tbl