GB is our standard 40Cr steel, 40Cr steel machinery manufacturing industry is one of the most widely used steel. After quenching with good mechanical properties, good low temperature impact toughness and low notch sensitivity. Hardenability good, when water quenching can hardenability to Ф28 ~ 60mm, when oil quenching can hardenability to Ф15 ~ 40mm. In addition to the external quenching the steel is also suitable cyanide and high-frequency quenching. Good cutting performance, when the hardness of HB174 ~ 229, the relative machinability of 60%. The steel is suitable for the production of medium-sized plastic mold. 40cr characteristics and uses modulation characteristics of carbon steel, cold heading steel mold. The steel affordable, easy processing, the availability of appropriate heat treatment after a certain toughness, ductility and wear resistance. Normalizing can promote tissue ball, improved cutting hardness of less than 160HBS blank. Tempering temperature 550 ~ 570 ℃, the steel has the best mechanical properties. The steel hardenability than 45 steel, suitable for induction hardening, flame hardening and other surface hardening treatment. Use of such steel after quenching medium used in the manufacture withstand moderate speed work load and mechanical parts, such as automotive steering knuckles, and rear axle gears, shafts, worm, spline shaft, sets and other tools on top; by After quenching and tempering for the manufacture of high loads, impact and moderate speeds of parts, such as gears, spindles, oil pump rotor, sliders, rings, etc; after quenching and tempering for the manufacture of heavy duty, low impact and wear resistance, the cross-sectional thickness of the part entities 25mm or less, such as worm, the spindle, the shaft, the collar and the like; and quenched after high-frequency surface hardening for manufacturing a high surface hardness and wear resistance no great impact on the parts, such as gears, sleeves, shafts, shaft, crankshaft, spindles, pins, connecting rods, screws, nuts, intake valves and so on. In addition, this also suitable for the manufacture of steel were carbonitriding treatment of various transmission parts, such as large diameter and low temperature toughness, good gear and shaft.