The cylinder block is an important part of the hydraulic cylinder, which is composed of a joint and a chain plate welded to the cylinder tube. As shown in Fig. 1, the materials used for the steel pipes, joints and chain plates of the cylinder block are all 45 steel. The inner hole of the workpiece blank is φ45mm, the outer circle is φ63mm, and the length is 1610mm. Due to the small bore diameter,