Besides the efficient processing quality brought by laser welding, it is bound to bring some disadvantages at the same time, such as welding cracks, etc., but it can be avoided through certain technical operations, which requires our welding operators to have professional welding technical ability. You know, the laser welding machine uses high-energy pulse laser focusing to melt the metal workpiece to achieve the purpose of welding. Once the operation is improper, It will cause hot cracks or cold cracks, so as a laser welding operator, you must know why these cracks occur.
1. Metallurgical Factors
The characteristics of unbalanced rapid heating and rapid cooling of laser welding make the whole joint in a complex stress state, which constitutes the mechanical factor of joint cracking; Laser welding is also the synthesis of a series of unbalanced processes. In the process of rapid metallurgical solidification, there will inevitably be uneven distribution of components and hardened structures with low crack resistance, which constitute metallurgical factors that promote crack initiation.
2. Mechanical Factors
There are mainly three kinds of cracks produced in the welding process of laser welding machine: product cracks, liquefaction cracks and reheat cracks.
Crystal crack:
It is related to the non-uniformity of composition in the macro area of the weld. The central area of the weld is the place where the liquid phase crystallization is the latest. The columnar crystals on both sides of the weld intersect here. At the same time, a large number of low melting point impurities also accumulate here, forming centerline segregation, which reduces the bonding strength at this place. Under certain mechanical conditions, cracks occur in this part.
Liquefaction crack:
In the near seam zone or the adjacent weld bead heat affected zone of multi-layer and multi pass welding, the low melting point eutectic on the grain boundary is remelted due to the welding thermal cycle, resulting in intergranular cracking under the action of shrinkage force.
Reheat crack:
The cracks produced by reheating the weldment within a certain temperature range after welding (stress relief heat treatment or other heating processes) are called reheat cracks.
Well, through the above brief analysis, I believe that many laser welding operators can learn how to avoid the shortcomings of these cracks during welding, and the actual operation experience is that the majority of laser welding operators need to constantly learn from their daily work. Through long-term experience accumulation, it is bound to give full play to the advantages of laser welding technology, Make full use of laser welding processing technology to bring a higher level of enterprise benefits and quality of life.
