10 Common Laser Welding Defects Causes and Solutions

Laser welding is a highly efficient and precise welding method using a high energy density laser beam as the heat source. Nowadays, 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 occur. Only by fully understanding these defects and learning how to avoid them can the value of laser welding be better utilized.

10 common laser welding joint defects

10 common laser welding joint defects, their causes and solutions are as follows.

1. Welding spatter

Laser welding spatter seriously affects the surface quality of the weld joint, which will pollute and damage the lens.

General performance: after the completion of laser welding, there are many metal particles attached to the surface of the material or workpiece.

Causes

The surface of the material or workpiece being processed is not cleaned. There are oil stains or contaminants, or it may be caused by the volatilization of the galvanized layer.

Solution

A. Take care to clean the material or workpiece before laser welding.

B. Spatter is directly related to power density. Proper reduction of laser 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.

Causes

Mainly due to excessive shrinkage force before the weld is fully solidified.

Solution

Filling weld, preheating and other measures can reduce or eliminate cracks.

3. Pores

Weld surface porosity is a relatively easy defect in laser welding.

Causes

A. Laser welding molten pool is deep and narrow, and the cooling rate is very fast. The gas generated in the liquid molten pool is not in time to overflow, easily leading to the formation of pores.

B. The weld surface is not cleaned, or zinc vapor evaporates from the galvanized plate.

Solution

Clean the workpiece surface and weld surface before laser welding to improve the volatilization of zinc during hating. In addition, the direction of air blowing will also affect the generation of porosity.

4. Welding undercut

The weld seam and the base material do not combine well, the appearance of bevel, depth greater than 0.5mm, the total length is greater than 10% of the weld length, or greater than the length required by the acceptance standards.

Causes

A. Welding speed is too fast, the liquid metal in the weld will not be redistributed on the back of the small hole, forming undercut on both sides of the weld.

B. The joint assembly gap is too large, the molten metal in the joint filler is reduced.

C. At the end of laser welding, if the energy drop time is too fast, the small hole will easily collapse, which will also cause local undercut.

Solution

A. Control the laser welding machine to match the processing power and speed to avoid undercut.

B. The weld undercut found in the inspection can be polished, cleaned and repaired to make it meet the requirements of the acceptance standards.

5. Weld accumulation

The weld is obviously overfilled.

Causes

Feeding speed is too fast or welding speed is too slow.

Solution

Increase the welding speed or reduce the feeding speed, or reduce the laser power.

6. Welding deviation

The weld metal will not solidify in the center of the joint structure.

Causes

Inaccurate positioning during welding, or inaccurate filling time and alignment.

Solution

Adjust the welding position, or adjust the filler welding time and the position.

7. Weld depression

Weld depression refers to the phenomenon of depression on the surface of the weld metal.

Causes

When brazing, the center of the weld spot is poor. The spot center is close to the lower plate and deviates from the center of the weld, resulting in partial melting of the base material.

Solution

Adjust the matching position.

8. Poor weld formation

Includes: weld ripple, uneven and untidy weld, unsmooth transition between weld and base material.

Causes

When brazing the weld, the feeding is not stable, or the light is not continuous, etc.

Solution

Adjust the stability of the laser welding equipment.

9. Weld bead

When the weld trajectory changes a lot, the corners are prone to weld bead or uneven forming.

Causes

The weld trajectory changes a lot and the shaping is uneven.

Solution

Weld under the best parameters and adjust the angle of view to make the corners coherent.

10. Surface slagging

During the welding process, the slagging can be seen from the outside mainly appears between layers and layers.

Causes

A, multi-layer multi-channel welding, interlayer coating is not clean; or the previous layer of the weld surface is not flat or the surface of the weld does not meet the requirements.

B, welding input energy is low, welding speed is too fast and other improper welding operation techniques.

Solution

A. Select a reasonable welding current and welding speed. Multi-layer multi-pass welding must clean up the interlayer coating.

B. Sanding to remove the surface slag, if necessary, filler welding.