Among the various forms of weld, metal streamline is an important display feature. It is a special shape of crystalline structure, formed by local melting or semi melting metal under high temperature and pressure. It is also a comprehensive embodiment of welding extrusion force size and direction, linear energy and welding speed, and has fixed metallurgical characteristics.

In the production process, in addition to the quality of raw materials and the use of advanced submerged arc welding equipment, the production process is also very important, such as steel plate pretreatment: pretreatment of the steel plate such as rust removal, oil removal, and edge grinding to ensure the surface of the steel plate The cleanliness and flatness of the production line; and the core part of the production line "forming" and welding of steel pipes

Production process of submerged arc welded steel pipe and High performance characteristics of submerged arc welded steel pipe

Pipeline scar is a common defect of welded pipe, and its specific manifestations include crush, indentation and scratch.

Submerged arc welding is mainly suitable for flat position welding. If certain tooling aids are used, corner welding and horizontal welding can be realized. The main factors affecting the shape and performance of submerged arc welding seam are welding process parameters and conditions. The welding process parameters affecting the shape and size of submerged arc welding seam include welding current, arc voltage, welding speed and wire diameter.

Hot crack, in the process of weld cooling, because the sulfur and phosphorus impurities in the steel or welding material form a variety of brittle and hard eutectic with low melting point, in the process of weld cooling, the solidified eutectic with low melting point is in a tensile state, which is easy to crack.

Reinforcement is not only the need of welding process, but also has an impact on the safe operation of the vessel, especially the fatigue life. The welding of pressure vessel is mostly multi pass welding (such as manual welding and automatic welding).

A large number of studies have proved that the hydrogen content of the welded joint, the hardening tendency of the steel and the restraint stress of the joint are the three major factors causing the welding delay crack, and the welding delay crack is caused by the joint action of these three factors.

Welding cracks are relatively dangerous welding defects, which seriously affect the performance and safety of welded structures. Many damage accidents of welded structures are caused by welding cracks.

Sometimes, the defects in the actual production of high frequency welded pipe are not caused by one reason, but usually the result of a variety of factors.