METHOD OF PRODUCTION OF THE CIRCULAR BAR MADE OUT OF THE MEDIUM ALLOY STEEL Russian patent published in 2006 - IPC C21D8/06 C21C5/52 C22C38/44 

FIELD: metallurgy; methods of production of the circular bars.

SUBSTANCE: the invention is pertaining to the field of metallurgy, in particular, to production of circular hot-rolled hot-calibrated and turned bars made out of the medium alloy steel of the heightened cutability used for manufacture of the high-loaded pinion gears of the car gearbox. The technical result of the invention is production of the structure of the bar ensuring the rational cutting conditions, which will allow to provide the guarantied level of the consuming properties of the pinion gears of the car gearbox. The method of production of the circular bar made out of the medium alloy steel includes: smelting of the steel in the electric furnace, out-of-furnace treatment of the steel in the ladle with a doping, a reduction and blowing by argon, the steel degassing treatment, the continuous steel casting, the hot rolling of the continuous bars with usage of modes of the thermomechanical treatment. According to the invention after the steel degassing conduct the repeated ladle metal reduction by the oxygenated pellets with the subsequent addition of aluminum, sulfur and produce the steel at the following ratio of the components(in mass %): carbon - 0.17-0.23; manganese - 0.65-0.95; silicon - 0.17-0.37; chromium - 0.35-0.65; nickel - 0.40-0.75; molybdenum - 0.15-0.25; sulfur - 0.020-0.040; phosphor - 0.001-0.035; niobium - 0.005-0.02; vanadium - 0.005-0.08; calcium - 0.001-0.010; oxygen - 0.001-0.015; copper - no more than 0.25; arsenic - no more than 0.008; nitrogen - no more than 0.015; iron and the imminent impurities - the rest; at realization of the following ratios: oxygen/calcium = l÷4.5 and calcium/sulfur ≥ 0.065. After the hot rolling realize the finish of the bars including the straightening, monitoring of the surface defects, the selective abrasive cleaning, the whole-size continuous abrasive grinding, turning of the circular bars, reeling of the bars in bundles and cutting the bars into billets of up to 6 meters length with the cutting accuracy ±5 mm.

EFFECT: the invention ensures production of the bars with the structure providing the rational cutting conditions, which guaranty the required level of the consuming properties of the car gearbox pinion gears.