Main characteristics of 30CrMo steel pipe seamless steel. This steel has high strength and toughness, high hardenability, and critical hardenable diameter in oil is 15~70mm; steel has good thermal strength, and has sufficient high temperature below 500 °C. Strength, but its strength drops significantly at 550 °C; when the alloying element is at the lower limit, the welding is quite good, but the weldability is medium when it is close to the upper limit, and it needs to be preheated to above 175 °C before welding; the machinability of steel is good, when cold deformation It has medium plasticity; it has the first type of temper brittleness in the range of 300-350 °C during heat treatment; there is a tendency to form white spots.