Welded pipe blank is the raw material for manufacturing welded pipe. Its mechanical properties and chemical composition have a far-reaching impact on the quality of welded pipe. Its width is an important factor to determine the weld strength. We usually say that the appropriate width of welded pipe blank refers to the width of a given thickness. The determination of the width is restricted by many factors.

Weld is an important sign of welded pipe quality and the life of welded pipe. Therefore, the analysis and treatment of welding quality defects should be carried out around the weld. The main defects of weld include weld crack, crack, incomplete penetration, overburnt and perforation, weld dislocation and so on.

The welded pipe formed by roller requires the strip to be bent horizontally into a circle, which is realized by a series of rollers with different passes to deform the strip. Each pair of rollers rotates at a certain speed, but the linear speed of the roller surface varies with the rotation radius. The sliding friction between the strip and the forming roller caused by the difference of linear speed is the fundamental reason for the scratch on the welded pipe surface.

The sizing of high frequency straight welded pipe refers to rolling the welded pipe through the special pass roller, and adjusting the irregular size and shape of circular or special-shaped pipe to the finished pipe with regular shape and size meeting the standard requirements. The basic function of sizing process has four aspects.

Because of the characteristics of super cooling and fast welding speed, the equilibrium state is basically removed. If the same chemical composition as the base metal is used as the welding material, the weld metal will have low plasticity, low toughness and high strength mechanical properties.

Influence of welding current on weld formation

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.