Sep 25, 2020
With the renewal and development of consumer electronic products such as mobile phones, tablet computers, and notebooks, a large number of new processes, new materials, and new structures have been applied. Aluminum alloys have the advantages of light weight, high strength, corrosion resistance, and good formability. It is widely used in the production of structural parts of various consumer electronic products.
Here, a comparison is made between continuous fiber lasers and pulsed lasers, which are widely used in aluminum alloy structural parts of consumer electronics.
1. Welding defects
The main defects of laser welding of aluminum alloy are pores and cracks, which are particularly obvious during pulse laser welding. It is generally believed that the pores produced by laser welding of aluminum alloys are mainly caused by the evaporation of hydrogen pores and low-melting-boiling alloy elements. Aluminum alloy has a high linear expansion coefficient and high welding stress. It is a eutectic alloy and is prone to thermal cracks. Especially in laser pulse spot welding, the action time of a single pulse is short, the thermal cycle speed is fast, and the crack tendency is great. When the fiber laser is used for continuous seam welding of aluminum alloy, the existence time of the molten pool is significantly prolonged, which improves the welding stress and the influence of low melting point substances on welding cracks, and greatly reduces the tendency of cracks in the welding process. At the same time, the extension of the existence time of the molten pool is also conducive to the discharge of gas in the molten pool and reduces the formation of welding pores.
2. Strength and stability
Welding cracks will significantly reduce the strength of welded joints, have a huge impact on the practicability and reliability of the product, and are one of the most harmful welding defects. Fiber laser continuous welding method for welding aluminum alloy can avoid welding cracks and effectively improve the strength and stability of the weld.
The welding tension of fiber laser and pulse laser welding the same aluminum alloy product is compared. After calculation, the average pulling force of the fiber laser is 3.9 times that of the pulsed laser, and the standard deviation of the pulling force data is only 1/3 of that of the pulsed laser. The metallographic analysis of the combination shows that the width of the weld joint of the fiber laser is much smaller than that of the pulsed spot welding, but the tensile force can reach nearly 4 times that of the pulsed laser. This is because: (1) The fiber laser weld is in the length direction There is still an extension on the above, and the actual effective bonding area is not smaller than that of the pulse solder joint; (2) The welding defects such as pores and cracks in the pulse solder joint cause its welding strength to be much lower than the strength of the base material, while the strength of the fiber laser weld material.
3. Welding deformation
Aluminum alloy has a large linear expansion coefficient and is prone to welding deformation. CW fiber laser has excellent beam quality, smaller spot, more concentrated energy, faster speed and smaller heat input, so the product deformation is smaller than traditional CW laser. At the same time, the strength of fiber laser welding aluminum alloy IT component products is much higher than pulse laser.
4. Product appearance
IT component products have higher requirements for appearance, and aluminum alloy materials are affected by element segregation, surface roughness, oxide layer, etc., resulting in inconsistent laser absorption rates on the surface of the workpiece. This phenomenon has a greater impact on laser pulse spot welding. When using pulsed laser spot welding, problems such as unwelded, spattering, smoke and dust are prone to occur, which affect the appearance and performance of the product, and need to be cleaned twice. When the fiber laser continuously welds aluminum alloy, the welding process is more stable, it is not easy to produce splashes and smoke, and it does not need to be cleaned twice. It is better than the pulse laser in appearance and process.
(1) The use of fiber laser for continuous seam welding of aluminum alloy components can avoid defects such as welding cracks and pores that often occur in pulse laser spot welding, and greatly improve the welding strength and stability.
(2) By optimizing the welding parameters of the fiber laser, welding distortion can be reduced and production efficiency improved.
(3) When continuous fiber laser welding aluminum alloy components, the welding seam is smooth and beautiful, and it is not easy to produce splashes, smoke, etc.