What are the common welding defects?

[McGarrett]

Common welding defects can be divided into two major categories: internal defects and external defects. External defects are located on the outer surface of the weld and can be seen with the naked eye or a low-power magnifying glass, such as weld size not meeting requirements, undercut, weld reinforcement, crater, porosity, cracks, slag inclusion, lack of penetration, lack of fusion, etc. Internal defects are located inside the weld and can be detected through destructive testing or non-destructive testing methods, such as lack of penetration, lack of fusion, porosity, cracks, slag inclusion, etc. Welding defects refer to flaws formed in the weld joint during the welding process, including porosity, slag inclusion, lack of penetration, etc. Defect prevention includes shape imperfections, size imperfections, undercut, and crater, etc. Based on weld defects, welds are classified into three levels: Class B, Class C, and Class D.