ASTM grade 5140 steel is medium carbon modulated steel and cold heading die steel. The steel is moderately priced and easy to process. It can obtain certain toughness, plasticity and wear resistance after appropriate heat treatment. Normalizing can promote tissue spheroidization and improve the cutting performance of blanks with a hardness less than 160HBS. Tempered at a temperature of 550~570℃, the steel has the best comprehensive mechanical properties. The hardenability of this steel is higher than that of S45C steel, and it is suitable for surface hardening treatments such as high-frequency quenching and flame quenching.

After quenching and tempering, 5140 steel is used to manufacture mechanical parts that bear medium loads and work at medium speeds, such as steering knuckles, rear half shafts of automobiles, and gears, shafts, worms, spline shafts, center sleeves, etc. on machine tools; After quenching and medium-temperature tempering, it is used to manufacture parts that can withstand high load, impact and medium-speed operation, such as gears, spindles, oil pump rotors, slides, collars, etc.; after quenching and low-temperature tempering, it is used to manufacture parts that can withstand heavy loads, Parts with low impact and wear resistance and a physical thickness of less than 25mm on the cross-section, such as worms, spindles, shafts, collars, etc.; are used to manufacture high surface hardness and wear resistance after quenching and tempering and high-frequency surface quenching. Parts without great impact, such as gears, sleeves, shafts, spindles, crankshafts, spindles, pins, connecting rods, screws, nuts, intake valves, etc. In addition, this kind of steel is suitable for manufacturing various transmission parts that undergo carbonitriding treatment, such as gears and shafts with larger diameters and good low-temperature toughness.