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Power battery shell welding process-pulse welding and continuous welding

At present, battery shells made of aluminum alloy materials account for more than 90% of the entire power battery. The difficulty of welding is that aluminum alloy has extremely high reflectivity to laser, and high pore sensitivity during welding. Some problems and defects will inevitably appear during welding, the most important of which are pores, hot cracks and explosions.

In power battery welding, the welding process technicians will select the appropriate laser and welding process parameters according to the customer’s battery material, shape, thickness, and tensile requirements, including welding speed, waveform, peak value, welding head inclination angle, etc. to set reasonable Welding process parameters to ensure that the final welding effect meets the requirements of power battery manufacturers.

Power Battery Manufacturer China

1) Pulse mode welding

The appropriate welding waveform should be selected during laser welding. Commonly used pulse waveforms include square wave, peak wave, double peak wave, etc. The reflectivity of the aluminum alloy surface to light is too high. When a high-intensity laser beam hits the surface of the material, the metal surface will be 60%-98% of the laser energy is lost due to reflection, and the reflectivity varies with the surface temperature. Generally, sharp wave and double peak wave are the best choice when welding aluminum alloy. The slow-down part behind this welding waveform has a longer pulse width, which can effectively reduce the generation of pores and cracks.

Due to the high reflectivity of aluminum alloy to laser, in order to prevent the vertical reflection of the laser beam from perpendicular incidence and damage the laser focusing mirror, the welding head is usually deflected to a certain angle during the welding process. The diameter of the solder joint and the effective joint surface increase with the increase of the laser tilt angle. When the laser tilt angle is 40°, the largest solder joint and effective joint surface are obtained. The weld penetration depth and effective penetration depth decrease with the laser tilt angle. When it is greater than 60°, the effective weld penetration depth drops to zero. Therefore, tilting the welding head to a certain angle can appropriately increase the weld penetration depth and penetration width.

In addition, when welding, with the welding seam as the boundary, 65% of the laser welding spot offset from the cover plate and 35% of the shell need to be welded, which can effectively reduce the explosion caused by the cover problem.

Power Battery Laser Cutting Lens

2) Continuous mode welding

Since continuous laser welding is not heated like a pulse machine, the crack tendency is not obvious during welding. In order to improve the quality of the weld, continuous laser welding is used. The surface of the weld is smooth and uniform, without spatter, defect, and inside the weld. No cracks were found. In the welding of aluminum alloys, continuous lasers have obvious advantages. Compared with traditional welding methods, the production efficiency is high and no wire is required. Compared with pulsed laser welding, it can solve the defects generated after welding, such as cracks, Porosity, spatter, etc., ensure that the aluminum alloy has good mechanical properties after welding; it will not sag after welding, and the amount of polishing and grinding after welding is reduced, which saves production costs. However, because the continuous laser spot is relatively small, the assembly accuracy of the workpiece is The requirements are higher.

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