Laser welding is an efficient 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 understanding these defects well and learning how to avoid them can we better exert the value of laser welding. The following Leapion laser manager shares 10 welding defects, causes and corresponding solutions.
The spatter produced by laser welding seriously affects the surface quality of the weld, and 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, which adhere to the surface of the material or workpiece.
Reasons for splashing: the surface of the processed material or workpiece is not cleaned, there are oil stains or pollutants, or it may be caused by the volatilization of the galvanized layer.
Solution: A. Pay attention to cleaning materials or workpieces before laser welding.
B. Spatter is directly related to power density. Appropriate reduction of welding energy can reduce spatter.
The cracks produced in continuous laser welding are mainly thermal cracks, such as crystal cracks, liquefaction cracks, etc.
Reasons for cracks: Mainly caused by the large shrinkage force of the weld before it is completely solidified.
Solution: Wire filling, preheating and other measures can reduce or eliminate cracks.
Porosity on the weld surface is a relatively easy defect in laser welding.
Reasons for the occurrence of pores: A. The molten pool of laser welding is deep and narrow, and the cooling rate is very fast. The gas generated in the liquid molten pool does not have enough time to overflow, which easily leads to the formation of pores.
B. The surface of the weld is not cleaned, or the zinc vapor of the galvanized sheet is volatilized.
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.
Undercut refers to: the weld is not well integrated with the base metal, grooves appear, the depth is greater than 0.5 mm, and the total length is greater than 10% of the weld length, or greater than the length required by the acceptance standard.
Reasons for undercutting: A. If the welding speed is too fast, the liquid metal in the weld will not be redistributed at the back of the small hole, and undercut will be formed on both sides of the weld.
B. If the joint assembly gap is too large, the molten metal in the joint filling is reduced, and the undercut is also prone to occur.
C. At the end of laser welding, if the energy fall time is too fast, the small holes are easy to collapse, which will also cause local undercuts.
Solution: A. Control the processing power and speed of the laser welding machine to match, so that the undercut can be avoided.
B. The undercut of the weld found in the inspection can be polished and cleaned and repaired to make it meet the requirements of the acceptance standard.
There is obviously too much filler material in the welding seam and the welding seam is too high during filling welding.
The cause of weld accumulation: the wire feeding speed is too fast or the welding speed is too slow during welding.
Solution: increase the welding speed or reduce the wire feed speed, or reduce the laser power.
The weld metal does not solidify in the center of the joint structure.
The reason for this situation: inaccurate positioning during welding, or inaccurate alignment of the filler welding time and wire.
Solution: Adjust the welding position, or adjust the position of the fill welding time and wire, as well as the position of the light, wire and weld.
Weld depression refers to the phenomenon of depression on the surface of the weld metal.
The reason for the depression of the weld: during brazing, the center of the welding spot is poor. The center of the spot is close to the lower plate and deviates from the center of the weld, causing part of the base metal to melt.
Solution: adjust the light and silk matching.
Poor welding seam forming includes: poor welding seam corrugation, uneven and untidy welding seam, non-smooth transition between welding seam and base metal, poor welding joint, and uneven welding seam.
The reason for this situation: when the welding seam is brazed, the wire feeding is unstable, or the light is not continuous, etc.
Solution: Adjust the stability of the equipment.
Welding bead refers to: when the trajectory of the welding seam changes greatly, welding bead or uneven forming is likely to appear at the corner.
Cause: The welding seam trajectory changes greatly and the teaching is uneven.
Solution: Weld under the optimal parameters, and adjust the viewing angle to coherently transition corners.
Surface slag inclusion refers to: during the welding process, the skin slag that can be seen from the outside appears mainly between the layers.
Analysis of the reasons for slag inclusion on the surface: A. During multi-layer and multi-pass welding, the coating between layers is not clean; or the surface of the previous layer of weld is uneven or the surface of the weldment does not meet the requirements.
B. Improper welding operation techniques such as low welding input energy and high welding speed.
Solution: A. Choose a reasonable welding current and welding speed. The coating between layers must be cleaned up during multi-layer and multi-pass welding.
B. Grind and remove welds with slag inclusion on the surface, and repair welding if necessary.
In fact, only when we correctly understand the defects produced in the laser welding process and understand the causes of different defects, can we solve the abnormal problems of laser welding in a more targeted manner. So, have you learned the 10 common laser welding defects and solutions shared today? If you want to know more professional questions, welcome to consult Leapion Laser!