Why do cracks and pores occur during the welding process of the laser welding machine?

In recent years, laser welding machines have gained widespread popularity in the mechanical manufacturing industry due to their advantages such as no deformation during welding, minimal heat influence, high welding efficiency, and aesthetically pleasing welds. Although they have many benefits, cracks and pores can occur in the welds between the welding base materials if the operators do not operate properly. Today, our editor Ward will show you the reasons for the appearance of cracks and pores in laser welding machines. Pay attention, here are the key points! 

The reasons for cracks in the laser welding machine: 

During the welding process, the laser welding machine will initially generate the following three types of cracks: liquefaction, embrittlement and reheat cracks. The distribution of component composition in the welding area between the crack and the base material of the weld is closely related. The center of the weld is the crystallization zone. The cylindrical joint measurement here intersects, and a large amount of low-melting-point impurities will again accumulate. Therefore, the bonding strength here is relatively low, and cracks will occur under the action of specific tensile force.

The reasons for the formation of pores during welding: 

The pores generated during the welding process will seriously affect the strength of the laser welding and the appearance of the welding material. The formation of pores is mainly due to poor maintenance during the welding process. The laser welding machine mainly uses two types of maintenance gases: nitrogen and argon. 

Nitrogen: If nitrogen is chosen as the maintenance gas, there are significant differences in the solubility of nitrogen in commercial metals and solid metals. Therefore, during the cooling and condensation process of the metal, the solubility of nitrogen is directly proportional to the temperature. The lower the temperature, the smaller the solubility of nitrogen. When the base metal cools and condenses, the solubility will drop sharply, and at this time, the gas will separate in large quantities and form bubbles. If the rising speed of the bubbles is slower than the crystallization speed of the metal, pores will be formed. 

Argon gas: The small hole inside the laser welding machine is in an unstable oscillating state. The flow of the small hole and the molten pool is very intense. The metal vapor inside the small hole is ejected outward, causing a steam vortex at the opening of the small hole, which sucks in the maintenance gas and moves it to the bottom of the small hole along with the movement of the small hole. These maintenance gases will enter the molten pool in the form of bubbles. When using argon gas-assisted welding, due to the low solubility of argon and the fast cooling speed of the laser welding machine, the bubbles cannot escape and remain in the weld seam, forming a gas hole.