Stomata is a problem that we do not want to encounter in the production and processing of laser welding machine, but we have to deal with it. Although the laser welding machine is an electric welding weapon, if the actual operation is unreasonable or the processing technology is not used correctly, the porosity problem is inevitable. To deal with this difficulty, we must first understand the causes caused by stomata, and then explore different solutions for different causes.
The inside of the laser welded hole is in an unstable vibration condition, the flow of the hole and the molten pool is very strong, the metal material vapor inside the hole gushes out, causing the vapor vortex at the interface of the hole, and the maintenance gas (Ar) will be rolled into the bottom of the hole, and the maintenance gas will enter the molten pool in the form of a bubble when the hole moves forward.
Due to the low solubility of Ar, coupled with the rapid cooling rate of laser welding, the bubble can not escape and is residual in the welding, resulting in porosity. The porosity caused by laser welding production process is mainly caused by poor maintenance. In the whole process of electric welding, nitrogen invades the molten pool from the outside, and the solubility of nitrogen in liquid iron is very different from that of nitrogen in solid iron, so it is in the whole process of refrigeration and condensation of metal materials.
Because the solubility of nitrogen decreases with the decrease of temperature, when the molten pool metal material is cooled to gradually crystallize, the solubility will produce a large sudden decrease, then a lot of gas precipitates to produce vapor bubbles, if the up-raising rate of the vapor bubble is lower than the crystallization rate of the metal material, it is converted into pores.
In most laser welding production and processing, the gas supply nozzle of the laser welding machine needs to send maintenance gas to avoid oxidation of the welding air and prevent pollution of the metal material gas environment. Most of the reasons caused by pores are caused by the wrong operation of maintenance gas during laser welding production and processing, but different maintenance gas reasons are slightly different.
In the whole process of laser welding, nitrogen invades the molten pool from the outside, and the solubility of nitrogen in liquid iron is very different from that of nitrogen in solid iron, so it is in the whole process of refrigeration and condensation of metal materials.
Because the solubility of nitrogen decreases with the decrease of temperature, when the molten pool metal material is cooled to gradually crystallize, the solubility will produce a large sudden decrease, then a lot of gas precipitates to produce vapor bubbles, if the up-raising rate of the vapor bubble is lower than the crystallization rate of the metal material, it is converted into pores.
During laser welding, the metal material vapor inside the hole gushes outwards, causing the vapor vortex at the interface of the hole, and the argon is rolled into the bottom of the hole. Along with the hole moving forward, this argon will enter the molten pool in the form of a bubble. Due to the low solubility of argon gas, coupled with the rapid cooling rate of laser welding, the vapor bubble can not escape and is residual in the welding, resulting in porosity.
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