Cracks are defects of laser welding. 

There are two main factors that cause weld joint cracking: metallurgical factors and mechanical factors. The characteristics of unbalanced rapid heating and rapid cooling of laser welding make the entire joint in a complex stress state, which constitutes the mechanical factor of joint cracking; laser welding is a combination of a series of unbalanced technological processes. In the process of rapid metallurgical solidification, Uneven composition distribution and hardened structure with low crack resistance will inevitably appear, which constitute metallurgical factors that promote crack initiation.

There are three main types of laser welding cracks: crystalline cracks, liquefaction cracks and thermal cracks. The crystalline cracks are related to the compositional inhomogeneity of the macroscopic area of the weld. The central area of the weld is the last part of the liquid phase crystallization. The columnar crystals on both sides of the weld meet here. At the same time, a large amount of low melting point impurities are also piled up here to form centerline segregation, thereby reducing the bonding strength there. Under certain mechanical conditions, cracks occur in this part.

There are two ways to reduce defects in laser welding cracks: one is to change the welding parameters and improve the quality of the welding machine, and the other is to reasonably improve the alloy system of the material according to the nature of the crack.

Laser welding originated in Germany and has been extensively developed in China. At present, China is the largest consumer of mold laser welding. Laser welding technology is widely used in sheet metal processing, mold welding and repair, aviation, aerospace, metal product manufacturing, etc. It can weld metal materials and some non-metal materials, and has very good welding effects on metal materials. In addition, laser welding Technology can also weld dissimilar materials. Laser welding technology has been widely used in more and more fields.