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Views: 12 Author: Site Editor Publish Time: 2024-01-05 Origin: Site
There are two main materials for liquid cooling plates: copper and aluminum. Because copper is expensive, the weight is much larger than the same volume of aluminum, so in many places the preferred material is aluminum, and copper is the last choice.Aluminum alloy liquid cooled plates also come in various sizes and shapes and corresponding different manufacturing processes according to the use scenario, such as friction stir welding, brazing, laser welding and argon arc welding.
The promotion and use of liquid cooling technology has basically formed three modes of energy storage cold plate, namely, blown liquid cooling plate, brazed liquid cooling plate, and aluminum profile liquid cooling plate. Welding is a very important process in the processing of water-cooled plates. Nowadays, the welding process of water-cooled plate is mainly divided into three categories: electric diffusion bonding, vacuum brazing and friction stir welding. Because of the flexible design structure and high welding efficiency of vacuum brazing liquid cooled plate, it is widely used in the processing of some aluminum alloy products.
1, refers to the workpiece in the vacuum room heating welding, mainly used for high quality products and easily oxidized materials welding;
2, brazing is a solid phase connection, brazing base metal does not melt, due to the use of base metal melting temperature is lower than the base metal, heating temperature is lower than the base metal solid phase line and higher than the solder liquid phase of a connection method;
3. The connected parts and filler metal are heated until the filler metal is melted, and the connection between the parts is realized by wetting, spreading and mutual dissolution and diffusion of the liquid filler metal on the surface of the base metal and wetting, capillary flow in the gap between the base metal and mutual dissolution and diffusion of the base metal;
4, vacuum brazing is the use of vacuum environment and different mechanism of action to remove the oxide film, because the use of flux, significantly improve the corrosion resistance of the product;
5, the wettability and fluidity of the filler metal is good, it can weld more complex and narrow channels, has a high yield, and has good safety production conditions.
1, can be brazed multiple adjacent welds form the whole surface, welding can be stacked furnace, according to the capacity of the furnace, brazing multiple components with the furnace, improve welding efficiency.
2, the welded product can withstand high pressure without deformation.
3, the fixture is universal, one-time input cost, usually do not need to be specially designed for the product re-input.
4, the workpiece as a whole is heated evenly, the thermal stress is small, the deformation can be controlled to the minimum degree, and the small surplus can be smooth and easy to process.
5, the workpiece under vacuum conditions, there will be no oxidation, carburization, decarburization and pollution deterioration, brazing forming beautiful, difficult to corrosion.
6, the corresponding cold plate runner structure according to the parameters of arbitrary design of complex runner, can achieve product performance heat dissipation characteristics more superior, more stable.
1, the hardness of the material after high temperature welding is reduced, and the characteristics of the cold plate require re-heat treatment to improve the hardness and increase the cost.
2, welding operation process of high technical requirements, technical difficulty, high energy consumption, long time.
3, cleaning before welding, high cost of environmental protection.
Aluminum alloy with its light weight, good corrosion resistance, excellent thermal conductivity and other characteristics are widely used in aerospace, construction, electrical appliances, automobiles, ships and other departments, and the amount is increasing, has long been considered to be the production of heat exchangers, waveguides and many other complex structural materials.
The processing technology of aluminum alloy plays a very important role in the manufacture of its products, and one of the important methods is the vacuum brazing process without any flux.
Because it has many advantages: no need for complex cleaning work before and after welding, simplified operation, to avoid slag inclusion caused by flux, no residual flux in the structure to ensure its corrosion resistance, high productivity, from the present and future environmental protection concepts, aluminum alloy vacuum brazing will be more and more widely used.
There is a dense and very stable oxide film Al2O3 on the surface of aluminum alloy, which is the main obstacle to wetting the base metal by melting filler metal. It is difficult to remove the oxide film by relying solely on vacuum conditions, and some metal activators must be used at the same time, such as magnesium Mg, bismuth Bi, etc. Early on, some people believed that the purpose of membrane removal could be achieved through the action of Mg.
This is because on the one hand Mg reacts with residual O2 and H2O in the vacuum to eliminate their harmful effects on aluminum; On the other hand, it is also the most important, Mg and Al2O3 on the base metal surface reduction reaction to achieve the purpose of directly removing the oxide film.
However, a large number of subsequent studies have shown that the oxidation film of the base metal has not been completely removed, so a new idea on film removal has been proposed. Besides the effect of Mg on eliminating O2 and H2O in the environment, Mg vapor penetrates into the surface layer of the film and together with diffused Si, causes the surface layer to form Al-Si-Mg alloy with low melting point and melt. Thus, the bonding between the surface oxide film and the base material is destroyed, so that the molten filler metal can wet the base material, spread on the base material under the film, and float the surface film away.
Although a large number of studies and tests have made the vacuum brazing of aluminum alloy widely used in industry, it is impossible to give a reasonable explanation for many scrap brazing joints in actual production. Aluminum alloy vacuum brazing is very sensitive to subtle changes in parameters, and the brazing alloy coating layer prefabricated by different manufacturers often differs significantly from the brazing head, although the composition is within the specified range.
So far, due to the lack of real and accurate understanding of the vacuum brazing mechanism of aluminum alloy, the formulation of the ideal vacuum brazing process has been greatly limited, and is still largely based on the practical experience accumulated in the ordinary.
Most brazing alloys are based on Al-Si systems, where w(si) is generally between 7% and 12%. This series of brazing filler metal both in brazing, strength and base metal color consistency, plating and corrosion resistance are excellent, is a rare excellent solder, especially this kind of solder can be modified treatment, greatly increase the toughness and bending strength of brazing joint.
The Al-Si system with a w(si) of 11.7% is a eutectic system with a eutectic temperature of 577° C. The solder of this composition is the standard solder commonly used in production and is suitable for brazing a variety of aluminum alloys with relatively high melting points, such as 3A21. New brazing alloys can be prepared by adding Mg and other elements to Al-Si brazing alloy, but low boiling point elements such as Zn cannot be added to aluminum brazing alloy, otherwise, it will cause great pollution to vacuum brazing furnace.In addition, the brazed composite plate is also a commonly used method, that is, a layer of brazed alloy is coated on one or two sides of the structural parent metal.
Vacuum brazed composite panels are much more convenient to use than wire, strip or powder, and can be easily used to make complex parts. When the cladding metal on the brazed plate melts, it can directly wet the bonding base material and fill the gap immediately. The joint can be formed with only slight diffusion.
At present, although some low-melting vacuum brazing alloys available in the laboratory have been prepared, the solder alloys with certain corrosion resistance and good mechanical properties are still not suitable for industrial production, so the research of solder alloys is still a long way to go.
