① Annealing. Obtain ferrite matrix, improve plasticity, toughness, eliminate stress , and improve cutting performance. ② Normalizing. A pearlite matrix is obtained , which improves strength and wear resistance. ③ Tempering. Obtain the matrix structure of tempered sorbite and good comprehensive mechanical properties, such as main shaft, crankshaft, connecting rod, etc. ④ Austempering . Make parts with complex shapes and high comprehensive performance requirements obtain the matrix structure of lower bainite , as well as comprehensive mechanical properties such as high strength, high hardness, and high toughness, to avoid cracking during heat treatment, such as spindles, crankshafts, gears, etc.