The spatter generated by laser welding seriously affects the surface quality of the weld seam, and will pollute and damage the lens. Especially the automotive industry needs to use laser welding technology to process specific materials such as galvanized steel, copper and aluminum. The way to eliminate spatter is to sacrifice the inherent advantages of fiber lasers, but this will reduce processing efficiency. If you often use laser welding to weld various metals in your work, you need to understand the reasons why laser welding machines spatter during welding, and find the best way to eliminate the effects of spatter. We can explore how to resolve this situation.
What is spatter in laser welding process?
Splash is molten metal flying to the outside of the molten pool. After the metal material is heated to the melting temperature, it changes from a solid state to a liquid state, and continues to heat up and transforms into a gaseous state. As the laser beam is continuously heated, the solid metal becomes liquid and forms a molten pool. Then, the liquid metal in the molten pool is heated again to “boil”. Finally, the material again absorbs heat and evaporates, boiling to change the internal pressure, bringing out the surrounding liquid metal and finally creating a “splash”.
Why is there a splash?
1. Some impurities in the welding area may cause spatter during welding.
2. Improper operation of welding equipment, such as improper contact angle with the workpiece and other irregular operations, may also cause spatter during the welding process.
3. The following is a concentrated view on the cause of splashing:
- As the size of the deep melting small orifice decreases, the raised liquid column at the front of the small orifice gradually elongates and breaks, which is the reason for the formation of splashes;
- Some believe that the strong shear force of the laser-induced plume in the small hole acting on the back wall of the small hole is the main reason for promoting the formation of spatter in the molten pool;
- The generation of spatter is related to the extrusion of the laser-induced vaporization recoil pressure on the front wall of the small hole on the molten layer of the front wall and the impact of the steam on the molten pool on the back wall of the small hole;
- The main factor affecting spatter in the process of laser welding aluminum alloy is the laser power density.
What measures can be taken to effectively suppress the formation of spatter?
1. Reduce the laser beam irradiation area, which can effectively reduce spatter. It can reduce the high heat vaporization of the core material temperature and reduce the generation of metal gas. For the welding of stainless steel, the welding quality can be improved by increasing the welding speed, but it will cause large welding deformation and affect the appearance of the weld. Therefore, the laser beam irradiation area can be reduced to reduce welding deformation. In addition, laser welding with pulsed lasers will reduce spattering, because the pulse width is short and the energy density is high, and the pulse width and energy density have little effect on spatter.
2. Adding shielding gas during laser welding can suppress the generation of spatter. When high-purity, high-pressure argon is used as the shielding gas, many small bubbles will appear on the surface of the weld, which can suppress the generation of spatter to a certain extent. In addition, when laser welding is carried out under the protection of argon, the absorption coefficient of argon to laser is very small, and the laser beam can pass through the thicker base material to reach the bottom of the molten pool, thereby reducing the possibility of spatter.
3. Change scan mode and swing welding. Using the laser head to swing can improve the temperature uniformity of the weld seam and avoid local overheating and boiling. It only needs to control the X and Y axes of the motion mechanism to complete the swing of various trajectories.
4. Using high-power density laser beam welding can effectively suppress the generation of spatter. In actual production, the method of reducing the spot diameter of the laser beam is generally used to suppress spattering. This paper studies the formation process of spatter in laser welding and proposes effective suppression measures for various factors in the welding process. In actual production, the above measures can effectively suppress the formation of spatter. At the same time, by optimizing the parameters, the quality of laser welding can be improved and spatter can be reduced.
5. Optimizing welding parameters: Adjusting the power, pulse frequency, focal length and other parameters of the laser equipment can effectively control the spatter problem during the laser welding process. Setting reasonable parameters can reduce spatter and improve weld surface quality.
Particles produced by splashing will also adhere to the molten pool and the surface of the workpiece, which can easily cause changes in surface roughness, scratch the base material, contaminate optical media such as eyepieces, spacers, filters, and frosted glass, and may lead to rework of components in severe cases, component damage, and even cause personal safety and company property loss and other issues. Spatter is directly related to power density, and appropriately reducing welding energy can reduce spatter. If the penetration is insufficient, the welding speed can be reduced. In order to further reduce or eliminate the spatter generated during laser welding, in actual production, parameter settings should be made according to different materials and processes.
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