The diameter of the weldable workpiece isφ50~300mm and the length is 3000mm.The equipment consists of headstock,bed,pneumatic bracket,pneumatic tailstock,mobile trolley,electric carriage,protective door,mobile operation box,MIG welding gun system,automatic heating device,etc.During welding,one end of the workpiece is clamped by the three-jaw chuck on the main shaft,and the other end is clamped by the top of the pneumatic tailstock,and can be supported by a liftable pneumatic bracket in the middle of the workpiece as required.