METHOD OF PRODUCTION OF MERCHANT SHAPES IN FORM OF BARS FROM MEDIUM-CARBON STEEL Russian patent published in 2006 - IPC C21D8/06 C22C38/12 C21C5/04 

FIELD: metallurgy; production of round calibrated merchant shapes in form of bars from medium-carbon steel of enhanced machinability for manufacture of shock absorbers.

SUBSTANCE: proposed method includes melting of steel in electric furnace, off-furnace treatment of steel, micro-alloying with sulfur, continuous teeming at protection of jet with argon shield, hot rolling of continuously cast billet in modes of thermo-mechanical treatment and winding of bars in bundles, unwinding of bars, cutting and straightening of bars and special finishing of their surfaces. Proposed steel contains the following components, mass-%: carbon, 0.42-0.50; manganese, 0.50-0.80; silicon, 0.17-0.37; sulfur, 0.020-0.040; phosphorus, 0.001-0.030; aluminum, 0.03-0.05; calcium, 0.001-0.010; oxygen, 0.001-0.015; chromium, no more than 0.25; nickel, no more than 0.25; copper, no more than 0.25; molybdenum, no more than 0.10; arsenic, no more than 0.08; nitrogen, no more than 0.015; the remainder being iron and unavoidable admixtures; ratio of oxygen to calcium, as well calcium to sulfur is determined by the following dependence: oxygen/calcium=1-4.5 and calcium/sulfur≥0.065. In tapping metal from melting unit, it is deeply de-oxidized by aluminum and is alloyed by silicon, manganese and chromium. After bringing the chemical composition of metal to normal in all components but for aluminum and sulfur, metal and slag are subjected to repeated oxidation by oxidized pellets; then, aluminum is added and metal is treated with calcium and is alloyed with sulfur. Machined bars, 6 m long are obtained from bundles of hot-rolled shapes at accuracy of cutting of ±5 mm. Finishing of shapes includes straightening, monitoring of surfaces for defects and ultrasonic monitoring of internal surfaces for defects, random abrasive dressing, continuous abrasive grinding and machining of round bars.

EFFECT: enhanced machinability by wide cutting tools; improved ductility and toughness of steel.

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