METHOD OF PRODUCTION OF MERCHANT SHAPES IN FORM OF BARS FROM MEDIUM-CARBON MICRO-ALLOYED STEEL

FIELD: metallurgy; production of round bars used for manufacture of shock absorber rods. ^ SUBSTANCE: proposed method includes melting steel in electric furnace, off-furnace treatment, pouring into ingot molds at protection of jet, hot rolling of ingot, thus obtaining billet followed by rolling, controlled cooling and winding bars in bundles, calibration of bars at deformation degree of 20-25%, unwinding of bars, cutting and straightening and special treatment of surface. Steel contains the following components, mass-%: carbon, 0.40-0.52; manganese, 0.40-0.95; silicon, 0.17-0.37; chromium,, 0.01-0.25; sulfur, 0.020-0.045; vanadium, 0.005-0.020; aluminum, 0.03-0.050; calcium, 0.001-0.010; nitrogen, 0.005-0.015; nickel, up to 0.25; copper, no more than 0.25; molybdenum, no more than 0.10; arsenic, no more than 0.08; phosphorus, no more than 0.030; the remainder being iron and unavoidable admixtures. Calcium-to-sulfur ratio is >=0.065; hot rolling of merchant shaped is completed at temperature of 1000-1050°C followed by fast cooling to 880-900°C and cooling in air to 300°C. Length of bars from bundle of hot-rolled shapes reaches 6 m at accuracy of cutting of ±5 mm. Finishing of shapes includes trimming, check of surfaces for flaws and ultrasonic monitoring of internal defects, selective dressing. ^ EFFECT: enhanced machinability of merchant shapes; enhanced ductility and toughness. ^ 1 ex