ROUND ROLLED BARS OF MEAN-ALLOY STEEL

FIELD: metallurgy, namely production of rolled bars. ^ SUBSTANCE: round rolled bar is made of steel containing, mass %: carbon, 0.17 -0.23; manganese, 0.65 -0.95; silicon, 0.17 - 0.37; chrome, 0.35 - 0.65; nickel, 0.40 - 0.75; molybdenum, 0.15 -0.25; sulfur, 0.020 - 0.040; phosphorus, 0.001 - 0.010; oxygen, 0.001 -0.015; copper, no more than 0.25; arsenic, no more than 0.08; nitrogen, no more than 0.015; iron and inevitable impurities, the balance; at relations oxygen/calcium = 1.45; calcium/sulfur >= 0.065. Rolled bar contains double-layer structure sulfide - sulfide with oxide envelope and it has hardness after quenching in depth 6 mm 32 - 40 HRc, size of real grain 5 - 10 points, diameter - up to 50 mm. Rolled bar has no decarbonized layer. After quenching and tempering rolled bar is characterized by temporary tensile strength, 1180 - 1520 MPa; limit yield, no less than 930 MPa; percentage elongation, no less than 7%; percentage tapering, no less than 59%. ^ EFFECT: improved cutting capability, enhanced hardenability at keeping high technological ductility. ^ 1 ex