Laser welding is an efficient and precise welding method that uses a high-energy density laser beam as the heat source, with advantages such as high efficiency, accuracy, simplicity, and ease of use. Nowadays, laser welding has been widely applied in various industries, such as electronic parts, automotive manufacturing, aerospace and other industrial manufacturing fields.
However, laser welding is not omnipotent, and sometimes processing errors may occur due to operational or parameter settings. Only by fully understanding these defects and learning how to avoid them can the value of laser welding be better realized.
Ten Common Defects and Solutions
Welding spatter
The spatter generated by laser welding seriously affects the surface quality of the weld seam, which can contaminate and damage the lens. Generally, after laser welding is completed, many metal particles appear on the surface of the material or workpiece, adhering to the surface of the material or workpiece.
Splash cause: The surface of the processed material or workpiece has not been cleaned thoroughly, and there are oil stains or pollutants, which may also be caused by the evaporation of the galvanized layer.
Solution: A. Pay attention to cleaning materials or workpieces before laser welding; B. Splash is directly related to power density. Reducing welding energy appropriately can reduce splashing.
Cracks
The cracks generated by continuous laser welding are mainly thermal cracks, such as crystal cracks, liquefaction cracks, etc.
The reason for the occurrence of cracks is mainly due to excessive shrinkage force before the weld is fully solidified.
Solution: Measures such as wire filling and preheating can reduce or eliminate cracks.
Pore
Porosity on the surface of the weld seam is a common defect in laser welding.
The reason for the formation of pores: A. The laser welding molten pool is deep and narrow, and the cooling speed is fast. The gas generated in the liquid molten pool cannot overflow in time, which can easily lead to the formation of pores.
The surface of the weld seam is not cleaned thoroughly, or zinc vapor evaporates from the galvanized sheet.
Solution: Clean the surface of the workpiece and weld seam before welding to improve the evaporation of zinc during heating. In addition, the direction of blowing can also affect the generation of pores.
Undercut
Undercut refers to the occurrence of a groove with a depth greater than 0.5mm due to poor bonding between the weld and the base material, and a total length greater than 10% of the weld length, or greater than the length required by the acceptance standard
Reason for undercut: A. The welding speed is too fast, and the liquid metal in the weld will not redistribute on the back of the small hole, forming undercuts on both sides of the weld.
If the assembly gap of the joint is too large, the molten metal in the joint filling is reduced, and it is also prone to undercutting.
At the end of laser welding, if the energy drops too quickly, the small hole is prone to collapse and can also cause local undercutting.
Solution: A. Control the processing power and speed matching of the laser welding machine to avoid undercutting.
The undercuts found during inspection can be polished, cleaned, and repaired to meet the requirements of the acceptance standards.
Weld accumulation
The weld seam is obviously overfilled, and the weld seam is too high during welding.
The reason for weld seam accumulation: the wire feeding speed is too fast or the welding speed is too slow during welding.
Solution: Increase welding speed or reduce wire feeding speed, or reduce laser power.
Welding deviation
The weld metal will not solidify at the center of the joint structure.
Reason for deviation: inaccurate positioning during welding, or inaccurate filling welding time and wire alignment.
Solution: Adjust the welding position, or adjust the repair welding time and the position of the welding wire, as well as the position of the lamp, welding wire, and weld seam.
Weld depression
Weld depression refers to the phenomenon of a depression on the surface of the weld metal.
Reason for depression: During brazing, the center of the solder joint is poor. The center of the light spot is close to the lower plate and deviates from the center of the weld seam, resulting in partial melting of the base material.
Solution: Adjust the filament matching.
Poor weld formation
Poor weld formation includes: poor weld ripple, uneven and irregular weld seam, uneven transition between weld seam and base metal, poor weld seam, and uneven weld seam.
The reasons for this situation include unstable wire feeding or discontinuous light during weld brazing.
Solution: Adjust the stability of the device.
Weld bead
When the trajectory of the weld seam changes significantly, there is a tendency for weld beads or uneven formation at the corners.
Cause: The weld trajectory changes greatly and the teaching is uneven.
Solution: Weld under the optimal parameters, adjust the viewing angle, and make the corners coherent.
Surface slag inclusion
Surface slag inclusion refers to the fact that during the welding process, the visible surface slag mainly appears between layers.
Analysis of surface slag inclusion reasons: A. During multi-layer and multi-pass welding, the interlayer coating is not clean; Or the surface of the previous layer of welding seam is uneven or the surface of the welded part does not meet the requirements.
Improper welding techniques such as low welding input energy and fast welding speed.
Solution: A. Choose a reasonable welding current and welding speed. It is necessary to clean the interlayer coating during multi-layer and multi-pass welding.
Grind and remove weld seams with surface slag inclusions, and repair welding if necessary.
About HGSTAR: HGSTAR is is a sub-brand of HGTECH.HGTECH the pioneer and leader of laser industrial application in China, and the authoritative provider of global laser processing solutions. We have comprehensively arranged laser intelligent machine, measurement and automation production lines, and smart factory construction to provide overall solutions for intelligent manufacturing.
