Aluminum laser welding defect control technology

Under the action of high-power laser, the main defects of deep fusion welding seam are porosity, surface collapse and biting edge defects, the use of laser wire filler welding or laser arc composite welding can improve the surface collapse and biting edge defects, but the control of weld porosity defects is more difficult.

Existing research results show that there are two kinds of characteristic porosity in aluminum alloy laser deep fusion welding.battery pilot line One type is metallurgical porosity, which, like arc fusion welding, is hydrogen porosity caused by material contamination or air intrusion during the welding process. The other type is process porosity, which is caused by unstable fluctuations of small holes inherent in the laser deep-melt welding process.

In the laser deep-melt welding process, due to the viscous effect of the liquid metal, the movement of the small hole often lags behind the movement of the beam, under the action of the plasma/metal vapor, the diameter and depth of the small hole fluctuates with the movement of the beam and the flow of the molten pool of metal,laser welding machine for lithium ion batteries and the flow of molten pool of metal makes bubbles appear at the tip of the small hole. The bubbles move and roll with the flow of liquid metal, either escaping from the surface of the molten pool or being pushed back into a small hole.

Obviously, metallurgical porosity is mainly controlled by pre-welding surface treatment and reasonable gas protection during welding, while the key to process porosity is to ensure the stability of small holes in laser deep-melt welding.ESS lithium battery machine According to the research of laser welding technology, aluminum alloy laser deep fusion welding porosity control should be comprehensively considered before welding, welding, welding, post-welding aspects, summarized in the following several new processes, new technologies.

1. Pre-welding treatment method

Pre-welding surface treatment is an effective way to control the aluminum alloy laser weld metallurgical porosity, usually the surface information processing methods and methods of physical mechanical cleaning, chemical cleaning, in recent years there has also been a laser impact cleaning, which will need to further improve the degree of automation of laser welding professional.

2. Parameter stability optimization control

Aluminum alloy laser welding process parameters usually include laser power, the amount of focus, welding speed, protective gas composition and flow, etc.. These parameters not only affect the protection effect of the welding area, but also affect the stability of the laser deep fusion welding process, thus affecting the weld porosity. Through the laser deep-melt welding of aluminum alloy thin plate, it is found that the stability of small hole melting affects the stability of the molten pool, which in turn affects the weld shaping, resulting in weld porosity defects, and the stability of the laser deep-melt welding is related to the matching of the laser power density and the amount of wire, so determining the reasonable process parameters is an effective measure to stabilize the weld shaping.

The results show that the ratio of back width to surface width (back width ratio) can be used to evaluate the weld seam forming and stability of aluminum alloy thin plate. Reasonable matching of laser power density and line energy of thin plate laser welding can ensure the weld backwidth ratio and effectively control the weld porosity.

3.Double spot laser welding

Double spot laser welding refers to the welding process in which two focused laser beams act on the same molten pool at the same time. In the laser deep fusion welding process, the instantaneous closure of the molten pool of small holes in the gas closure is one of the main reasons for the formation of weld porosity. When using double-point laser welding, due to the role of two light sources, the opening of the small hole is larger, which is conducive to the escape of the internal metal vapor and the stabilization of the small hole, thus reducing weld porosity. Studies have shown that double-point laser welding can significantly reduce weld porosity.

4. Laser arc composite welding

Laser arc composite welding is the laser and arc action in the same pool of welding technology. Generally laser as the main heat source through the use of laser and arc of the mutual promotion of the role of the laser welding depth and welding speed, reduce the precision of welding assembly. The use of data filler wire regulates the organizational and structural properties of the welded joints, the use of the arc's auxiliary therapeutic role to continuously improve the stability of the laser welding of small holes, thus more conducive to reducing weld porosity.

In the laser-arc composite welding process, the effect of the arc on the laser-induced metal vapor/plasma cloud is conducive to the absorption of laser energy and the stabilization of porosity. Aluminum alloy laser - arc composite welding research results also confirmed its effect.

5. Fiber laser welding

The small hole effect in the laser deep fusion welding process originates from the intense vaporization of the metal under the action of the laser. The vapor force of metal vaporization is closely related to the laser power density and beam quality, which not only affects the melting depth of laser welding, but also affects the stability of small holes. Qingzhi. et al. The study of SUS304 stainless steel high-power fiber laser showed that the molten pool was elongated during high-speed welding, spattering was suppressed, pinhole fluctuations were smooth, and there were no bubbles at the tip of the pinhole. When the fiber laser is used for high-speed welding of titanium alloy and aluminum alloy, a weld without porosity can also be obtained.Allen's research on the shielding gas control technology in fiber laser welding of titanium alloys shows that by controlling the position of the welding shielding gas, it can prevent the gas from being entrapped, reduce the time for the pinhole to close, stabilize the weld pinhole, and change the solidification behavior of the molten pool, thus reducing the weld porosity.

6. Pulsed laser welding

Compared with continuous laser welding, pulsed laser output can make the molten pool periodic stable flow, conducive to bubble escape, reduce weld porosity. Research on the YAG laser welding laser power output mode, studied the output mode of SUS 304L stainless steel and Inconel 690 high temperature alloy weld porosity and performance of the impact of the basic power of 1700W, weld porosity with the pulse amplitude of ΔP increase and reduce the porosity of stainless steel from 2.1% to 0.5%, the high temperature alloy porosity from 7.1% to 0.5%. The porosity of stainless steel is reduced from 2.1% to 0.5%, and that of high temperature alloy from 7.1% to 0.5%.

7. Post-weld composite processing technology

In practical engineering applications, even if the welding before the strict surface treatment, the welding process is stable, laser welding of aluminum alloys will inevitably produce weld porosity, so the use of post-weld treatment to eliminate porosity is very important. At present this method is mainly decorative welding. Hot isostatic pressing technology is one of the methods to eliminate porosity and shrinkage inside aluminum alloy castings. It is combined with the stress heat treatment after laser welding of aluminum alloy to form a composite process of hot isostatic pressing and heat treatment of aluminum alloy laser welded components, which eliminates weld porosity and improves joint performance.

Due to the characteristics of aluminum alloys, high-power laser welding technology application there are still many social problems ability to be further in-depth analysis and research, its main problem is mainly through the control of weld porosity defects, to improve the quality of their welding work. Aluminum alloy laser weld porosity engineering control should be comprehensively considered before welding, welding production process, post-welding treatment of all important aspects, so that can improve the welding process has stability. This has been derived from a lot of new technologies and new processes, such as pre-welding laser cleaning, welding process design parameters back width ratio control system optimization, dual beam laser welding, laser arc composite welding, pulsed laser welding and fiber laser welding.

high-power laser cell aluminum alloy welding.battery

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