1. the determination of welding scheme for rectangular tubes

　　In order to meet the strength requirement, the rectangular tube has a section size of 300 mm Therefore, through investigation and study, the manufacturing process of symmetrical two-half bending of sheet metal into groove-shaped half shell is finally determined, and then CO2 gas shielded welding is adopted.

　　2. welding technology

　　(1) Two symmetrical V-grooved half-pipes are formed by large-scale bending machine, butt welding grooves are processed according to technical requirements, and gaps are reserved for splicing. The design of welded joints is a weak link in welding engineering. Groove form plays an important role in controlling the internal quality of weld and manufacturing quality of welded structure. In groove design, the fusion ratio of base metal, welding space, welding position and comprehensive economic benefit must be considered. The horizontal shrinkage value should be calculated first.