[Laser welding technology] The key technology of new energy vehicle manufacturing

 Automakers face stiff competition and must find ways to cut costs, especially in battery manufacturing. This means that production lines must become faster and more efficient. Assuming that manufacturers have exhausted all the potential of line automation, there is only one way to achieve both goals - by deploying more powerful lasers with greater beam-shaping capabilities, more sophisticated sensors, and ultra-precise dynamic welding machining heads. Of course, this also requires a lot of process knowledge.

In electric vehicles, the battery system cost accounts for nearly 50% of the total vehicle cost, the processing quality in the manufacturing process determines the battery storage capacity and service life, the laser processing technology can improve the welding quality and production efficiency, reduce the welding process splash, improve the reliability, consistency and yield of battery manufacturing, improve the endurance of electric vehicles. Laser welding technology is becoming the key technology of new energy vehicles and their parts in the production and processing process, it is known as "the brightest light, the fastest knife, the most accurate ruler", in terms of reliability, accuracy and efficiency have outstanding advantages.

Taking the current relatively mainstream flat wire drive motor as an example, the laser process involved includes the welding of the silicon steel sheet of the motor, the painting and welding of the hairpin flat wire, and the welding of the motor bus. The high repeatability and reliability of the laser ensure that the motor always achieves excellent electrical conductivity in mass production. For example, in the flat copper wire paint removal process, pulsed laser ablation is a very economical and reliable process scheme, and compared with mechanical processes (such as planing and milling), the paint removal efficiency of laser processing can be increased by more than 80%.

In the field of body, laser welding has long been famous, and now, many advantages such as flexibility, automation, and low production costs make the application of laser wider, from the assembly, body in white, to the production workshop of automotive parts such as seat interior, almost all can see laser applications. Whether it is a new energy vehicle or a traditional fuel vehicle, to meet the two requirements of strength and weight reduction/thinning at the same time, as an example, the mainstream choice for Oems and parts manufacturers is three-dimensional laser cutting.

Laser welding equipment in lithium battery welding application range:

1, battery explosion-proof valve welding

The explosion-proof valve of the battery is a thin-walled valve body on the battery sealing plate. When the internal pressure of the battery exceeds the specified value, the explosion-proof valve body breaks to avoid the battery bursting. The safety valve structure is clever, and this process is extremely strict for laser welding process. Before continuous laser welding was not used, the welding of the battery explosion-proof valve was welded by pulsed laser, and continuous sealing welding was achieved by overlapping and covering the solder joints and solder joints, but the welding efficiency was low and the sealing was relatively poor. The use of continuous laser welding can achieve high-speed and high-quality welding, welding stability, welding efficiency and yield can be guaranteed.

2, battery pole ear welding

The electrodes are usually divided into three materials, the positive electrode of the battery uses aluminum (Al) material, and the negative electrode uses nickel (Ni) material or copper plated nickel (Ni-Cu) material. In the manufacturing process of the power battery, one of the steps is to weld the battery pole and the pole together. In the production of the secondary battery, it is necessary to weld it together with another aluminum safety valve. Welding should not only ensure the reliable connection between the pole and the pole, but also require the weld to be smooth and beautiful.

3, the battery pole with spot welding

The materials used in the battery electrode strip include pure aluminum strip, nickel strip, aluminum-nickel composite strip and a small amount of copper strip. Pulsed welding machine is generally used in the welding of battery pole band. With the emergence of IPG QCW quasi-continuous laser, it has also been widely used in the welding of battery pole band. At the same time, due to its good beam quality and small welding spot, It has unique advantages in the welding of aluminum and copper strips with high reflectivity, as well as narrowband battery electrode strips (electrode width of less than 1.5mm).

4, power battery shell and cover plate sealing welding

The shell material of the power battery is aluminum alloy and stainless steel, of which the most aluminum alloy is used, generally 3003 aluminum alloy, and a few are pure aluminum. Stainless steel is the best material for laser weldability, whether pulsed or continuous laser can obtain a good appearance and performance of the weld. Using continuous lasers to weld thin-shell lithium batteries, the efficiency can be increased by 5 to 10 times, and the appearance and sealing are better. Therefore, there is a trend to gradually replace pulsed lasers in this application field.

5. Power battery module and pack welding

The series and parallel between the power battery is generally completed by the welding of the connecting sheet and the single battery, the positive and negative electrode materials are different, generally copper and aluminum 2 kinds of materials, due to the formation of brittle compounds between copper and aluminum after laser welding, can not meet the requirements of use, usually using ultrasonic welding, copper and copper, aluminum and aluminum are generally laser welding. At the same time, because the heat transfer of copper and aluminum is very fast, and the reflectivity of the laser is very high, the thickness of the connecting sheet is relatively large, so it is necessary to use a higher power laser to achieve welding.