Grade 20Cr Steel Composition, Properties, Material Equivalent

20Cr steel is a kind of Chinese GB standard alloy steel. It has good comprehensive mechanical properties after quenching and low temperature tempering: good low temperature impact toughness and temper brittleness is not obvious. When carburizing, the grain of steel has a tendency to grow, so secondary quenching is required to improve the toughness of the core, and it is not suitable for cooling and quenching. When the hardness after normalizing is 170-217 HB, the relative machinability is about 65%. 20Cr steel has good weldability, and generally does not require heat treatment after welding, but parts with a thickness greater than 15mm need to be preheated to 100-150 °C before welding, and tempering heat treatment may not be performed after welding. Compared with 15Cr steel, 20Cr has higher strength and hardenability. The critical hardenable diameter in oil is 4-22mm, and the critical hardenable diameter in water is 11-40mm, but the toughness is poor. The machinability is good under high temperature normalizing or quenching and tempering conditions, but it is poor after annealing. Machine gearbox gears, gear shafts, cams, worms, piston pins, dog clutches, etc.