Welded steel pipe production process is a steel sheet, strip, and other various molding methods using the straight press roll or helical direction curling into a desired cross-sectional shape, and then by means of heat, pressure, different methods of welding weld together to obtain steel. Therefore, defects in the welded steel pipe is divided into two parts: the steel base material defects and weld defects.


1. Steel base material defect
The sheet material defects after rolling and other processes, most of planar, parallel to the surface; their main weakness delamination, inclusions, cracks, folds, etc., which is the most common layered internal defects. Stratification will produce a variety of cracks when the tensile stress perpendicular to the surface of the sheet by the hierarchical will seriously affect the strength of the steel pipe, it is not allowed defects.


2. Weld defects
Weld defects refers to defect during welding or after welding resulting in the weld is divided into cracks, pores, slag, incomplete penetration, incomplete fusion, undercut weld defects. Intensive weld porosity, slag, etc. a dense three-dimensional defects, cracks, lack of fusion and other defects in the case of the flat, great harm. Strip slag, incomplete penetration and other defects in the case of strip, great harm. Pores, slag and other small point-like defects in the case. Weld defects more likely to cause strength steel, plastic and other issues, seriously affecting the quality of steel, welded steel pipe quality directly affect the safe operation and service life of oil and gas pipelines, and thus for weld inspection mainly for welding cracks cracks, pores, slag, incomplete penetration, incomplete fusion and other dangerous flaw detection of defects.