In the production process of schedule 40 black large diameter seamless steel pipe, it will also have some common defects. In this article, I will give you a detailed introduction to the common defects of schedule 40 black large diameter seamless steel pipe.
1. The weld size does not meet the requirements
The appearance of the weld is uneven, the width is uneven, the size is too large or too small, and the size of the weld does not meet the requirements.
The reasons are: the edge processing of the large diameter stainless steel pipe is not good; the assembly quality is poor; the welding rod swings unevenly. Improper control of welding specifications, etc.
2. Bite the meat
At the junction of the metal and the edge of the weld there is a deep longitudinal groove called the undercut, and an undercut or undercut. This is caused by excessive welding current intensity, incorrect electrode movement, and inappropriate electrode inclination angle.
Biting is a dangerous defect that reduces the working cross-section of the base metal. In particular, large-diameter thick-walled stainless steel pipes will generate stress concentration at the grooves under the action of dynamic loads, resulting in cracks.
3. Flash
There is excess metal buildup on the edge of the weld that is not fused with the base metal, which is flash. This defect is usually prone to occur in vertical welding and horizontal welding.
The main reasons for the flash are: the electrode melts too fast; the arc is too long; the electrode movement is incorrect; the welding speed is too slow, etc.
4. Not fully welded
A gap or edge of a large diameter thick-walled stainless steel tube that has not been melted by the arc is called incomplete penetration. Schedule 40 black large diameter seamless steel pipe can be divided into root, edge and interlayer according to the part of incomplete penetration.
The main reasons for lack of penetration are: welding current is too small, groove angle is too small, blunt edge is too large, gap is too small, improper electrode angle, large-diameter stainless steel tube is too thick, and automatic submerged arc welding welding deviation. Incomplete penetration defects can reduce the strength of the weld, resulting in cracks and structural damage.