Power battery laser welding machine Automobile power battery laser welding machine Power battery laser welding
Application area of laser welding machine
Reasonable selection of welding methods and processes for the power battery manufacturing process will directly affect the cost, quality, safety and consistency of the battery. Next, I will sort out the aspects of power battery soldering.
How does laser welding work
The laser welding machine works by using the excellent directionality and high power density of the laser beam. The the laser beam is focused on a small optical system, and the welded portion forms a highly concentrated energy in a very short time. The heat source zone, thereby melting the soldered material and forming a strong solder joint and weld.
The types of laser welding
Heat transfer welding and deep fusion welding
The laser power density is 105~106w/cm2 to form laser thermal conduction welding, and the laser power density is 105~106w/cm2 to form laser deep fusion welding.
Penetration welding and seam welding
For Penetration welding ,The connecter chip does not require punching and are relatively easy to process. Penetration requires a laser welder with a higher power. The penetration depth of penetration welding is lower than that of seam welding, and the reliability is relatively poor.
Compared to penetration welding, seam welding requires a smaller power laser welder. The penetration depth of seam welding is higher than that of penetration welding, and the reliability is relatively good. However, the connecting piece needs to be punched, which is relatively difficult to process.
Pulse welding and continuous welding
Pulse mode welding
The right welding waveform should be chose when laser welding work.The frequently-used impulse waveforms have square wave, peak wave, double peak wave, etc., The reflectivity of aluminum alloy surface to light is too high, when the high intensity laser beam to the surface of the material, the metal surface will have 60% to 98% of the laser energy loss due to reflection, and the reflectivity changes with the surface temperature.Generally, when welding aluminum alloy, the best choice is pointed wave and double peak wave, the slow down part of the pulse width of this welding waveform is longer, which can effectively reduce the formation of pores and cracks.
Since the reflectance of the aluminum alloy to the laser is high, in order to prevent the vertical reflection of the laser beam from causing vertical reflection and damage the laser focusing mirror, the welding head is usually deflected by a certain angle during the welding process. The diameter of the solder joint and the diameter of the effective joint surface increase as the laser tilt angle increases. When the laser tilt angle is 40°, the largest solder joint and the effective joint surface are obtained. The penetration depth and effective penetration of the solder joint decrease with the laser tilt angle. When it is greater than 60°, the effective solder penetration depth is reduced to zero. Therefore, when the welding head is inclined to a certain angle, the weld penetration and the width of the weld can be appropriately increased.
In addition, when welding, take the weld line as the boundary, 65% of the partial cover plate and 35% of the shell shall be welded by laser welding spot, which can effectively reduce the explosion caused by the problem of closing the cover.
Continuous mode welding
Continuous laser welding is not like the sudden cooling of the pulse machine because of its heating process. The crack tendency during welding is not obvious. In order to improve the quality of the weld, continuous laser welding is used. The surface of the weld is smooth and uniform, no splash, no defects, and the inside of the weld. No cracks were found. In the welding of aluminum alloys, the advantages of continuous lasers are obvious. Compared with the traditional welding methods, the production efficiency is high and no wire filling is required. Compared with pulsed laser welding, defects caused by welding, such as cracks, can be solved. Porosity, splashing, etc., to ensure good mechanical properties of the aluminum alloy after welding; no dents after welding, less polishing and polishing after welding, saving production costs, but because the spot of the continuous laser is relatively small, the assembly accuracy of the workpiece The requirements are higher.
In the power battery welding, the welding process technician will select the appropriate laser and welding process parameters according to the customer's battery material, shape, thickness, tensile requirements, etc., including the welding speed, waveform, peak value, tip angle of the welding head, etc. Welding process parameters to ensure that the final welding effect meets the requirements of the power battery manufacturer. Laser welding advantages
Energy concentration, high welding efficiency, high machining accuracy, and large weld width to width ratio. The laser beam is easy to focus, align, and guided by optical instruments. It can be placed at an appropriate distance from the workpiece and can be re-guided between fixtures or obstacles around the workpiece. Other welding methods are not possible due to the above space limitations.
The heat input is small, the heat affected zone is small, the residual stress and deformation of the workpiece are small; the welding energy can be precisely controlled, the welding effect is stable, and the welding appearance is good;
Non-contact welding, fiber transmission, good accessibility and high degree of automation. When welding thin materials or thin-diameter wires, it is not as easy to melt back as arc welding. Due to the principle of “lightweight”, the batteries used in power batteries usually use a lighter aluminum material, and they need to be made “thinner”. Generally, the shell, cover and bottom are required to be less than 1.0 mm. The current basic material thickness of mainstream manufacturers is around 0.8 mm.
High-strength welding is available for a variety of material combinations, especially when welding between copper materials and aluminum materials. This is also the only technology that can weld electroplated nickel to copper.
