It is very important to choose a suitable laser welding method according to different materials and welding requirements. There are many laser welding parts for power battery, the main material is aluminum alloy, a few parts use copper, nickel and other materials, a few stainless steel as the battery shell, among these materials, nickel and stainless steel laser welding is relatively simple and mature, but there are still many difficulties in the laser welding of aluminum alloy and copper. In addition to the influence of material properties, the state of the welded joint will also have a greater impact on the welding effect. Follow the small make-up to understand.

Power battery laser welding equipment

First, the welding difficulties of different types of materials to be welded and the choice of welding method.

When using aluminum alloy and copper as the welding material, the main reasons for the poor effect of conventional laser welding are as follows.

① Both are highly reflective of fiber laser materials, fiber laser absorption is not high, resulting in poor stability of the welding process;

② Both of the thermal conductivity has a better, weld molding technology is difficult, easy to produce the impact of porosity.

At the same time, there are some differences between the two materials. Relatively speaking, the aluminum alloy on the fiber laser absorption rate is higher than copper, while the thermal conductivity of copper is higher than aluminum alloy, so the two laser welding difficulty of the solution has the same place, there are some differences:.

Laser Welding of Square Aluminum Shells

When the laser welding material is aluminum alloy, choose the laser welding method:.

1. Use a smaller focusing point (0.1 mm ~ 0.3 mm) for welding

2. The welding speed should not be too low, and should be controlled above 60mmu002Fs;

3. use conventional fiber-semiconductor material laser for composite welding;

Use of oscillating welding.

Select laser welding method when laser welding copper;

1. using a smaller focus point (0.02 mm ~ 0.2 mm) for welding

2. Welding speed should be fast, 100 mmu002Fs or more is recommended;

3. Use this swing for welding.

2. Laser welding process of welding material state at the same time the welding difficulties and the choice of welding method.

In this paper, the state of the material to be welded refers to the surface cleanliness of the material and the degree of pretreatment, which can lead to the deterioration of the quality of the weld. Specific results and solutions are as follows.

1. Impurities on the surface of the material

Difficulties:Welds with porosity, sealing performance is not enough, not enough strength; welds with burst points, product scrap.

Solution to the problem: the material to be welded for welding before the need to remove surface oil, water and other impurities.

Laser welding under the collapse

2. Aluminum alloy surface oxides are not cleaned

Difficulty:weld porosity, sealing is not enough, strength is not enough; molding is unstable and the output is reduced.

Solution: Weld the material before the oxide film treatment, then weld as soon as possible.

3. Roughness of material to be welded.

Difficult problem performance: uneven molding, poor appearance quality; easy to lead to welding leakage, no sealing. Solution to China's solution: the material can be processed by computer, and it needs to be flat and without deformation.

Types and requirements of the parts to which the weld belongs

At present, there are three types of mainstream automotive power batteries, namely, square batteries, cylindrical batteries and soft pouch batteries. Square batteries are the most commonly used batteries and the type of battery with the most laser welded parts. The other two types of batteries have a relatively small market share and laser welding demand. The main problems with welds are lack of strength, poor sealing, and poor molding that lead to these problems. Their commonality is due to incorrect choice of welding process, in addition to welding difficulties caused by the structure of the part to be welded and its weld requirements. Specifics and solutions:.

1. flexible packaging battery lugs / busbar laser welding difficulties and programs

Laser welding difficulties: thin material, multiple pieces of overlap welding is easy to virtual welding, resulting in insufficient strength, poor conductivity.

Laser for welding technology to solve the problem solution: control the incoming material flatness; design an excellent performance of the fixture, control the clamping gap.

2.21700 battery cap laser welding difficulties and solutions

Welding difficulties: thin material, easy to burn through, the strength can not reach.

Solution: Control the consistency of the feed, design a good performance fixture, control the fixture gap, choose a small core diameter fiber laser, high-speed vibration reflector (300mm/s or more) welding.

Battery PACK module laser welding

3. Battery PACK module laser through the welding technology difficulties and problem solving solutions

Welding difficulties: high depth of fusion requirements, poor weld formation.

Solution: Select 50μm ~ 100μm laser core, high-speed (80mm / s above) high-power welding.

4. square battery parts laser welding difficulties and solutions

Square battery components liquid injection holes, flip piece, pole post, explosion-proof valve welding difficulties: many air holes, easy to burst, resulting in inadequate sealing.

Solution to the problem: improve the cleanliness of the parts to be welded; selection of 50μm core fiber as a laser,battery pilot machine welding development speed can be improved appropriately.

5. Battery shell sealing laser welding difficulties and solutions

Difficulties in welding: many pores, easy to burst points, resulting in inadequate sealing.

Solution: improve the cleanliness of the parts to be welded, choose 50μm fiber core laser, can be appropriate to improve the welding speed, choose a small fiber core laser + semiconductor laser for composite welding.

Welding difficulties:Square weld corners are easy to burn through, resulting in inadequate sealing.

Problem solution: choose the welding platform that can be accelerated for better performance;battery laser welding machine use a higher welding development speed, shorten the laser irradiation time at the corners.

Welding difficulties: uneven weld molding, processing efficiency is not high enough.

Solution: composite welding selection of small core fiber laser and semiconductor laser.

6. busbar laser welding difficulties and solutions

Welding difficulties: thin material, multi-piece overlap welding is easy to weld the virtual welding, resulting in insufficient strength, poor conductivity.

Problem solving solutions: control the incoming material flatness; design an excellent working performance of the fixture,battery packing machine control the clamping gap. Welding technology difficulties: weld connection width is not perfect enough to lead to management strength development is not enough. Solve the Chinese solution: choose a small core fiber laser, using swing welding.

7. Side plate laser welding difficulties and solutions

Welding difficulties:Welding more parts, high efficiency requirements.

Solution: Choose high-power fiber laser, remote scanning welding.

8. Flexible connection laser welding difficulties and solutions

Welding difficulties: thin material, multi-piece overlap welding is easy to weld, resulting in insufficient strength, poor conductivity.

Solution: control the smoothness of the feed, design a good performance of the fixture, control the fixture gap.

Welding Difficulty: Insufficient weld width leads to insufficient strength.

Solution: choose a small core fiber laser, using swing welding.

The above is about laser welding equipment using different power battery welding field mirror when the different welding methods. Laser welding as a highly efficient and precise connection method, has obvious advantages: high processing efficiency, high processing accuracy, small heat-affected zone, welding deformation is small, the degree of automation and so on. The application of laser welding in automotive power battery welding can greatly improve its safety, reliability and service life.