Laser welding machines have excellent welding effects in the field of thin plates, but due to improper operation or incomplete processes, porosity often occurs during the welding process. To solve this problem, the causes of porosity should be analyzed first, and corresponding solutions should be provided based on the reasons.
1、 When using nitrogen as a protective gas
The appearance of pores during laser welding processing is mainly caused by inadequate protective measures. During the welding process, if nitrogen gas is used to assist welding, nitrogen gas will invade the molten pool from the outside. The solubility of nitrogen gas in liquid iron is significantly different from that in solid iron. Therefore, during the cooling and solidification process of the metal; Due to the decrease in nitrogen solubility with temperature, when the molten metal cools to begin crystallization, the solubility will suddenly decrease significantly. At this time, a large amount of gas will precipitate to form bubbles. If the upward velocity of the bubbles is lower than the metal crystallization velocity, pores will be generated.
2、 When using argon gas as a protective gas
The inside of the small hole in laser welding is in an unstable vibration state, and the flow of the small hole and the molten pool is very intense. The metal vapor inside the small hole erupts outward, causing a steam vortex at the opening of the small hole, which rolls the protective gas into the bottom of the small hole. As the small hole moves forward, these protective gases will enter the molten pool in the form of bubbles. When using argon gas for auxiliary welding, due to the low solubility of argon gas, the cooling rate of laser welding is very fast, and bubbles cannot escape in time and remain in the weld seam, forming pores.
When processing on a laser welding machine, the laser welding machine needs to blow out protective gas along the fiber optic axis to prevent oxidation of the weld seam or prevent gas splashing and contaminating the lens after material dissolution. The generation of pores is often caused by improper use of protective gas or operational errors during laser welding processing, and the reasons for the occurrence of pores may vary slightly among different protective gases.