high hardenability, no temper brittleness, welding is quite good, formation of cold cracking tendency is small, cutting and cold strain plasticity is good. generally used in the hardened and tempered or carburizing and hardening state, for manufacturing in non corrosive medium and the temperature lower than 250℃, containing nitrogen hydrogen mixture of medium high pressure tubes and a variety of fastening pieces, more advanced carburized parts, such as gears, shaft, etc.