Laser welding is a high-efficiency and precise welding method that uses a high-energy-density laser beam as a heat source. Today, laser welding has been widely used in various industries, such as: electronic parts, automobile manufacturing, aerospace and other industrial manufacturing fields. However, in the process of laser welding, some defects or defective products will inevitably appear. Only by fully understanding these pitfalls and learning how to avoid them can the value of laser welding be better utilized. Today, Hangao Tech (SEKO Machinery) team bring you to have an overview of some main problems occouring when laser welding. Our team have over 20 year experience in automatic industrial pipe rolling and forming machine. If there is any need or doubt about industrial laser welding tube mill line duct machine, welcome to contact us.
10 common laser weld defects, their causes and solutions are as follows:
1. Weld spatter
The spatter produced by laser welding seriously affects the surface quality of the weld seam, which can contaminate and damage the lens. The general performance is: after the laser welding is completed, many metal particles appear on the surface of the material or workpiece, and adhere to the surface of the material or workpiece.
Causes of splashing:
The processed material or the surface of the workpiece is not cleaned, there are oil stains or pollutants, or it may be caused by the volatilization of the material itself.
Solution:
A. Pay attention to cleaning materials or workpieces before laser welding.
B. Splash is directly related to power density. Appropriately reducing welding energy can reduce spatter.
2. Crack
The cracks produced by continuous laser welding are mainly thermal cracks, such as crystal cracks and liquefaction cracks.
Reasons for cracks:
mainly due to excessive shrinkage before the weld is not completely solidified.
Solution:
Measures such as wire filling and preheating can reduce or eliminate cracks.
3. Stoma
Pores on the surface of weld seam are relatively easy defects in laser welding.
Causes of porosity:
A. The molten pool of laser welding is deep and narrow, and the cooling speed is fast. The gas generated in the liquid molten pool has no time to overflow, which easily leads to the formation of pores.
B. The surface of the weld seam is not cleaned, or the zinc vapor of the galvanized sheet evaporates.
Solution:
Clean the surface of the workpiece and the surface of the weld before welding to improve the volatilization of zinc when heated. In addition, the blowing direction will also affect the generation of air holes.
4. Undercut
Undercut refers to: the welding seam is not well combined with the base metal, there is a groove, the depth is greater than 0.5mm, and the total length is greater than 10% of the weld length, or greater than the length required by the acceptance standard.
Undercut reason:
A. The welding speed is too fast, and the liquid metal in the weld will not be redistributed on the back of the small hole, forming undercuts on both sides of the weld.
B. If the assembly gap of the joint is too large, the molten metal in the filling of the joint is reduced, and undercutting is also prone to occur.
C. At the end of laser welding, if the energy drop time is too fast, the small hole is easy to collapse, which will also cause local undercut.
Solution:
A. Control the processing power and speed matching of the laser welding machine to avoid undercutting.
B. The undercut of the weld found in the inspection can be polished, cleaned and repaired to make it meet the requirements of the acceptance standard.
5. Weld accumulation
The weld seam is obviously overfilled, and the weld seam is too high when filling.
Causes of weld accumulation:
Wire feeding speed is too fast or welding speed is too slow during welding.
Solution:
Increase the welding speed or reduce the wire feeding speed, or reduce the laser power.
6. Welding deviation
The weld metal will not solidify in the center of the joint structure.
Reasons for this situation:
Inaccurate positioning during welding, or inaccurate filling welding time and welding 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 welding seam.
7. Weld seam depression
Weld sinking refers to the phenomenon that the weld metal surface is depressed.
Causes of weld sinking:
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, causing part of the base metal to melt.
Solution:
Adjust the light filament matching.
8. Poor weld formation
Poor weld formation includes: poor weld ripples, uneven welds, uneven transition between welds and base metals, poor welds, and uneven welds.
The reason for this situation:
When the weld seam is brazed, the wire feeding is unstable, or the light is not continuous.
Solution:
Adjust the stability of the device.
9. Welding
Weld bead refers to: when the weld trajectory changes greatly, weld bead or uneven forming is prone to appear at the corner.
Causes:
The seam track changes greatly, and the teaching is uneven.
Solution:
Weld under the best parameters, adjust the angle of view to make the corners coherent.
10. Surface slag inclusion
Surface slag inclusions refer to: during the welding process, the skin slag inclusions that can be seen from the outside mainly appear between layers.
Reason analysis of surface slag inclusion:
A. During multi-layer multi-pass welding, the interlayer coating is not clean; or the surface of the previous layer of weld is not smooth or the surface of the weldment does not meet the requirements.
B. Improper welding operation techniques such as low welding input energy and too fast welding speed.
Solution:
A. Choose a reasonable welding current and welding speed. The interlayer coating must be cleaned during multi-layer multi-pass welding.
B. Grinding to remove the weld seam with slag inclusion on the surface, repair welding if necessary.
