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Welding Experts of High Reflective Materials – Solving the Problems of Lithium Electric Welding

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Laser welding is to focus the laser beam on the surface of the workpiece through an optical lens, so that the material is rapidly melted to form a molten pool, and then rapidly cooled to form a welded joint. It has the characteristics of large aspect ratio, fast welding speed, and non-contact with the workpiece, which is easy to achieve Automated production, so this process has been widely used. However, due to the complex interaction between the laser heat source and the material during the laser welding process, as well as the special physical properties of aluminum alloys and copper alloys, high-reflection materials have high laser reflectivity during welding, unstable welding process, and easy to produce porosity defects, etc. problem. When using ordinary lasers to weld highly reflective materials such as aluminum and copper, the collapse of the keyhole will produce small holes and splashes. Due to the splashes, the weld metal will be reduced, resulting in pits and uneven surfaces; moreover, these materials have high laser reflectivity, The absorption rate is low, and most of the energy is reflected, resulting in poor fusion of the filler; at the same time, during the cooling process, due to the excessive cooling speed, the solubility of hydrogen and other gases in the molten pool is sharply reduced and it is too late to escape, resulting in pores. produce.

Mainstream welding methods to reduce spatter and porosity

How to reduce spatter, reduce porosity, and obtain a smooth weld is a major difficulty in welding high-reflection materials. Many domestic and foreign companies have also continued to explore this aspect and have launched their own products.

(1) Using the swing welding head The swing welding method can disperse the energy density, improve the uniformity of the weld temperature, and reduce the generation of spatter and pores to a certain extent. At present, mainstream laser head manufacturers (such as Jiaqiang, Wanshunxing, Kirin, etc.) have launched similar swing laser welding heads. But at the same time, there are some drawbacks. Since the energy density of the laser is reduced, the power has to be increased or the welding speed has to be slowed down.

(2) Use a dual-wavelength composite welding head to combine the fiber laser and the semiconductor laser with the dual-wavelength composite welding head, and overlap at the welding point. The fiber laser performs deep penetration welding. Minimize splashing. At present, laser head manufacturers such as Jiaqiang and Wanshunxing have also launched such welding heads. However, this welding method requires the use of two lasers, and the equipment combination is more complicated.

(3) Laser with special spot

The best cost-effective solution is on the laser side, changing the Gaussian distribution laser to ring + center light, the center light spot guarantees the depth of the molten pool, and the ring light spot plays the role of preheating and slow cooling, which is compared with the above-mentioned dual-wavelength composite welding principle. similar. Typical laser manufacturers have launched similar lasers, such as IPG’s AMB laser and Raycus’ ABP laser.

What is the FRM of GW Laser Tech

In response to the welding difficulties of the above-mentioned high-reflection materials, GW Laser has continuously explored on the road of technological development, and launched a high-reflection material welding expert – FRM (Flexible Ring Mode) dynamic spot output laser, which can effectively reduce the welding process of high-reflection materials. Splash and porosity generation.

The FRM laser couples two optical modules into the core layer and the ring core layer of the fiber through a customized coupler, couples the two laser beams into one beam, and then focuses it on the surface of the workpiece to form a composite spot. By adjusting the appropriate energy ratio, a relatively wide welding width and a low welding seam aspect ratio can be formed, which can effectively improve the stability of the keyhole, and can significantly reduce spatter and reduce stomatal sensitivity.

The FRM laser can arbitrarily control the power of the fiber core light and the ring core light. It can only turn on the central light or the ring light, or both can be turned on at the same time to form three modes of ordinary spot, annular spot, and compound spot; if turned on at the same time, it can The core and the ring core can make the center core power greater than the ring core power, or the center core power can be smaller than the ring core power, or the center core power is equal to the ring core power, and a total of five different spot shapes can be switched.

The diameter of the central spot is small and the energy density is high. The welding is based on the deep penetration welding mode, which will produce a keyhole and form a molten pool with a large aspect ratio. However, it has high requirements on the matching gap, and a large amount of high-pressure metal vapor is released when the keyhole is formed by deep penetration welding, which is prone to splashing and explosion points. The temperature of the molten pool is high and the internal flow is violent, and the fluctuation of the molten pool is obvious.

The diameter of the annular spot is large and the energy density is small. The welding is based on the heat conduction mode, which can form a wider molten pool. Since the thermal conduction welding does not form a key hole, the temperature of the molten pool is low during the welding process, and there is no obvious molten pool fluctuation. Spatter, the weld is flat and beautiful. However, due to the dispersed energy density, a large penetration depth cannot be obtained.

Combining the two together, by adjusting the appropriate energy ratio, while the central spot guarantees the depth of the molten pool, the annular spot increases the width and duration of the molten pool, on the one hand, improves the stability of the keyhole and reduces splashing On the other hand, the flow of the molten pool is more stable, the bubbles overflow for a long time, and the probability of porosity formation is reduced.

The FRM laser can provide a total output power of up to 20KW, and can flexibly adjust the parameters of the output light. The diameter of the central beam output fiber is 50μm/150μm, and the output power is up to 10KW; the diameter of the ring beam output fiber is 150μm/300μm, and the output power is up to 10KW. The center beam is a fiber laser with a wavelength of 1070nm, and the ring beam can be equipped with a 976nm semiconductor laser in addition to the 1070nm fiber laser to realize the compounding of dual-wavelength and dual-laser beams.

FRM excellent welding effect

In order to reflect the welding effect of FRM, the following uses FRM laser and ordinary laser to weld aluminum alloys and compare them.

A 1.5KW+1.5KW (50μm+150μm) FRM laser was used to weld 6061 aluminum alloy with a thickness of 3mm, and compared with a 3KW (100μm) ordinary laser. It can be clearly found that the spatter of FRM laser welding is significantly smaller than that of ordinary laser welding.

The welded samples were cut open for metallographic observation. Due to the effect of the annular spot, the weld obtained by the FRM laser has a wide top and bottom narrow shape, and the upper and lower surfaces are basically flat; while the weld width of the ordinary laser welding is basically flush at the top and bottom, and the top surface is collapsed and the bottom surface is convex.

The tensile strength of the welded seam after welding is tested, and the tensile strength of FRM welding is better than that of ordinary laser welding.

Important applications of FRM

China regards new energy vehicles as one of its seven strategic industries. Since the power lithium battery pack is a key core component of new energy vehicles, with the continuous development of new energy vehicles, it is also widely used and developed accordingly.

According to statistics from the China Research Institute of Puhua, the global demand for lithium batteries will continue to rise from 2017 to 2020, and the demand for lithium battery equipment will continue to grow in the next 3-5 years. The rapid development of the lithium battery industry has caused major companies to increase the construction of new factories and the expansion of production capacity.

The safety of the battery pack is very important. Once the relevant failure occurs, it will lead to very serious results and threaten people’s lives. Among them, the factor that plays a decisive role in the safety of electric vehicles is the welding of key parts of the power battery pack. The most important material in these positions is aluminum alloy, including explosion-proof valves, cell seals, tabs, bus bars, etc.; followed by Copper materials, such as poles, tabs, etc. The welding quality of these positions will directly affect the reliability of the quality of the battery pack.

For the welding of different parts of the power battery, the FRM laser using Guanghui Laser can effectively solve the welding problem, realize zero spatter in welding, no pores on the surface, stable penetration, smooth and beautiful welding seam, significantly improve the welding quality, and effectively ensure the stability of the power battery. Sex and safety.

The transformation of the global automobile market to electrification is the general trend, and under this general development trend, it is bound to put forward higher requirements for lithium-ion welding technology, and lithium-ion battery processing has become an important market for domestic laser companies. Guanghui Laser will continue to make efforts in the field of lithium battery welding. Through independent innovation, laser iterative upgrades will be carried out to help customers improve welding processes and enhance product safety and competitiveness.

About GW

We have a Dream: providing value-adding products for all customers. This belief brought enthusiasts with the same dream around the word to GW. We have been holding on this belief and entrepreneurial passion, and strive to become the most trusted laser enterprise for all customers. In this journey, we hope that the mission of “Laser As a Tool” will always guide the GW team.

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