In laser welding, we always run into various issues related to welding seams. So, this article will analyze several common laser welding problems and corresponding solutions for you.
1. Splash
Splash refers to the many metal particles attached to the surface of the material after laser welding is completed. The spatter generated seriously affects the surface quality of the weld and can contaminate and damage the lens.
CAUSES:
1. Directly related to laser power density.
2. The surface of the processed material is not cleaned thoroughly, with oil stains or pollutants.
3. The surface evaporation of the galvanized layer can also cause splashing phenomenon.
SOLUTIONS:
1. Pay attention to cleaning materials before laser welding.
2. Splash is directly related to power density. Reducing welding energy appropriately can reduce spatter.
2. Crack
Continuous laser welding may produce cracks, Such as crystal cracks, liquefaction cracks, and multilateral cracks.
CAUSES:
It is mainly due to excessive shrinkage force before the weld seam fully solidifies.
SOLUTIONS:
Measures such as wire filling and preheating can reduce or eliminate cracks.
3. Porosity
The appearance of pores on the surface of the weld seam is a common defect in laser welding.The formation of pores will weaken the welding strength, resulting in reduced corrosion resistance and unsightly welds.
CAUSES:
1.The laser beam causes metal fluctuations in the welding pool, and when gas trapped in the metal expands and overflows, it will produce pores.
2.In addition, metal films can block the bonding between metals, absorb moisture, and easily generate impurities, which can also cause the formation of pores.
SOLUTIONS:
1. Adjust the appropriate laser power to ensure balanced energy input.
2. When welding thin plates, the welding speed can be increased to reduce the time for gas to expand in the metal.
3. When welding thick plates, with the material already preheated, the welding speed can be appropriately reduced, and the surface of the weld seam can be chemically or mechanically cleaned before welding to reduce the impact of impurities on the welding quality.
4. At the same time, it can be considered to use some protective gases or fluxes to reduce the degree of oxidation, thereby reducing the amount of gas produced.
4. Undercut
In laser welding, if the weld seam is not well bonded to the base material, a groove will appear, and the groove depth is greater than 0.5mm. If the total length of the groove is greater than 10% of the weld seam length or greater than the length required by the acceptance standard, it is called undercutting.
CAUSES:
1. 1.If the welding speed is too fast, the liquid metal in the weld will not redistribute on the back of the small hole, forming undercuts on both sides of the weld.
2. If the gap between welded joints is too large, the amount of molten metal in the joint filling decreases, and it is also prone to undercutting.
3. At the end of laser welding, if the energy decreases too quickly, the small hole is prone to collapse and can also cause local undercutting.
SOLUTIONS:
1. Reduce the bonding gap between welded work pieces.
2. Adjust the laser beam focus to determine the correct spot position
3. Control the laser power and adjust the de-focus position to ensure the welding quality after metal melting, thereby avoiding the occurrence of undercutting.
5. Weld accumulation
The weld seam is clearly overfilled, and the weld seam is too high during welding.
CAUSES:
Wire feeding speed too fast or welding speed too slow during welding
SOLUTIONS:
Increase welding speed or decrease wire feeding speed, or decrease laser power.
6. Welding deviation
The weld metal does not solidify at the center of the joint structure.
CAUSES:
Inaccurate positioning during welding, or inaccurate filling welding time and wire alignment.
SOLUTIONS:
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.
7. Inclusions
Surface inclusion refers to the fact that during the welding process, the visible surface slag mainly appears between layers.
CAUSES:
1.When welding multiple layers and passes, the inter-layer coating is not clean; Or the surface of the previous layer of weld is uneven or the surface of the welded part does not meet the requirements.
2 Improper welding techniques such as low welding input energy and too fast welding speed.
SOLUTIONS:
1. Choose a reasonable welding current and welding speed. When welding multiple layers and passes, it is necessary to clean the inter-layer coating.
2 Polish and remove weld seams with surface slag inclusions, and repair welding if necessary.
8. Lack of fusion or incomplete fusion
The laser welding machine has insufficient penetration during welding.
CAUSES:
1. Lack of laser energy
2. Incorrect focusing lens.
SOLUTIONS:
1. Improving the pulse width and current.
2. Adjusting the focusing amount to approach the focusing position.
9. Flame weakening
The laser welding machine experiences a weakening of flames.
CAUSES:
1. The shutter is not completely repelled.
2. The main optical path laser deviates.
3. The cooling water is contaminated or not replaced for a long time.
4. The focusing lens or laser resonator film is damaged or contaminated.
SOLUTIONS:
1. Check and lubricate the shutter connector.
2. Adjust the main optical path's total reflection and semi reflection apertures.
3. Replace the cooling water.
4. Clean the UV glass tube and xenon lamp.
5. Replace or clean the optical components in a timely manner.
