METHOD FOR PRODUCING ROUND ROLLED STOCK OF BORON-CONTAINING STEEL WITH INCREASED DUCTILITY Russian patent published in 2017 - IPC C21D8/06 C22C38/54 

FIELD: metallurgy.

SUBSTANCE: when producing fasteners with cold upsetting, steel is melted containing, wt %: carbon 0.07-0.11, silicon 0.15-0.40, manganese 0.30-0.55, aluminium 0.02-0.05, sulfur 0.005-0.025, phosphorus 0.005-0.025, chromium 0.02-0.15, nickel 0.02-0.30, copper 0.03-0.18, titanium 0.002-0.03, boron 0.001-0.003, molybdenum 0.002-0.03, nitrogen 0.005-0.010, tin 0.001-0.015, lead 0.001-0.010, zinc 0.001-0.018, calcium 0.001-0.003, iron and impurities are the rest, continuous casting of steel is carried out to produce a blank with 150×150 mm section with macrostructure segregation level not more than 2 points, austenization of the blank, rolling on intermediate square cross section 106×106 mm size, continuous cleaning and polishing, heating, rolling the blank into a round profile and cooling in two stages, wherein at first, accelerated cooling by high-pressure water to 850-930°C, and then air cooling with round rolled stock movement rate of 0.4-1.0 m/s and with the possibility for adjusting the cooling intensity depending on the diameter of the rolled bars and the temperature of the surrounding medium. The round rolled product has elongation at least 34% and relative contraction not less than 72%.

EFFECT: increased elastic properties of rolled product makes it possible to ensure the degree of deformation of rolled product at the level of 66 percent.

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