Views: 0 Author: Site Editor Publish Time: 2021-04-07 Origin: Site
What inherent defects may exist in the raw material of welded steel pipe ?
Mainly include delamination, non-metallic inclusions, segregation, bubbles, gas content, and poor metallographic structure, etc.
How does stratification come about? What is the impact on the quality of steel pipes?
The delamination is caused by the shrinkage cavity defect of the steel ingot. After the steel ingot with shrinkage cavity is rolled into a steel strip, a layered layer is formed in the middle of the section. The internal delamination of the wide coil can be exposed at the edge of the strip after slitting, but it is not easy to find. Delamination defects are obviously exposed during the forming and welding process, causing large longitudinal cracks, and even welding is impossible. Using ultrasonic flaw detection can detect delamination defects. How are non-all inclusions formed? What impact does it have on the quality of steel pipes? Non-metallic inclusions are strip-shaped oxides, sulfides, and brittle and plastic silicates in the metal matrix, which are imperfect steels containing impurities For more reasons. When the steel chain segregation is serious, the non-metallic inclusions in the segregated part are also more serious. Non-metallic inclusions affect the weldability of steel and reduce weldability. There are non-metallic inclusions at the edge of the steel strip. Welded pipe = cracks and cracks appear at the welded seam, and light yellow inclusions can be seen at the cracks after flattening. Special blanks for welded pipes hope to improve the purity of steel, reduce impurities as much as possible, and improve welding performance.
What effect does the full-phase structure of 70 copper strip have on the quality of steel pipes? The metallurgical structure of steel strips is of great significance to the quality of welded pipes. The metallographic structure has a great influence on the welding performance and the quality of the welded seam of the electric welded pipe.The ferrite grain size cannot be too large. If the grain size is too large, the flattening test and the flaring test cannot guarantee to meet the standard requirements; a grain size cannot be too small, otherwise, the welding performance of the metal will be deteriorated due to the growth of the grain boundary, and the grain boundary will be The amount of output (carbides, non-metallic inclusions, gas) entering the central area of the weld increases, causing the weld to become brittle.
The structure of free cementite and troostite martensite has an adverse effect on the quality of welds and hinders the improvement of welded pipe quality. In this case, a martensite structure will appear during welding, which will make the weld brittle, and it is easy to produce welded floor cracks during straightening; even if no cracking occurs when the car is straight, it is easy to flatten test and flaring test. Cracked.
Non-metallic inclusions reduce the weldability.