Aluminum-magnesium alloy component connection new technology

Friction Stir Welding (FSW) is a solid-state joining method proposed by The Welding Institute (TWI) in 1991. This technical principle is simple, less control parameters, and easy to automate, which can reduce the human factors in the welding process to a lower level. The friction stir welding process parameters mainly include the welding speed of the stirring finger, the rotation speed of the stirring finger, and the pressing force. These parameters determine the heat generated around the finger during the welding process and directly affect the microstructure and properties of the weld. Friction stir welding technology has many advantages compared to traditional fusion welding, and therefore has a wide range of industrial application prospects and development potential. Friction stir welding technology is a solid phase connection technology in the history of welding technology development in the world. It has a short span of time from invention to industrial application and has developed rapidly. It has been successfully applied in aerospace, aviation, vehicles, shipbuilding, construction and other industries.

The use of friction stir welding instead of fusion welding to achieve the manufacture of light alloy structures is another leap in the development of modern welding technology. It can be said to be a revolutionary progress. With the improvement of friction stir welding technology, it is expected that in the near future, the connection of light metal materials such as aluminum alloys, magnesium alloys, zinc alloys, and titanium alloys will be mainly performed by friction stir welding, especially in carrier rockets and high-speed aluminum. Alloy trains, aluminum alloy high-speed boats, all-aluminum cars will occupy a dominant position in the project.

China established the China Friction Stir Welding Center in April 2002, marking the official start of friction stir welding in China and a milestone in the history of China's welding technology development.

Spot friction welding is a new type of linear friction stir welding process technology, with the potential to form strong joints between the same or dissimilar metal sheet, especially for low-melting soft metals, such as aluminum, magnesium alloys. At present, point-friction welding has been successfully applied to the connection of aluminum alloy sheet parts, and it is a promising connection method for connection of aluminum alloy parts for light locomotives.

More recently, Ford Motor Company of America, Oak Tree National Laboratory and Dearborn University of Michigan, USA are researching and developing connections for magnesium alloy components. During the welding process, the continuously rotating mold traverses the interface of the connecting plate under pressure, so that the plates are connected. The heat generated by the rotation of the mold (frictional heat) causes the interface and the connecting zone to produce a softened zone. The material in the thermal softening zone is in the probe. Nearby was forced to rotate and gather. The joint is formed when the probe is retracted. For aluminum alloys and magnesium alloys, friction stir welding improves joint quality over ordinary welding. Friction stir welding does not require the melting of the base metal, the strength of the joint is close to that of the substrate, the energy output is relatively low, the heat affected zone is relatively small, and the residual stress of the weld is negligible. The difference between point and linear friction welding is that point friction welding cannot move laterally. After the mold reaches a predetermined load or insertion depth, it evacuates the plate. The friction and force caused by the rotation of the mold generate heat and deformation, and heat and deformation are generated. Mixing area. In the process of cooling to room temperature, spot welds are formed at the plate interface.

As we all know, magnesium alloy has the advantage of better weight reduction than iron and aluminum, and has received great attention from the global automotive industry. Magnesium has a density of one-quarter of that of iron and two-thirds of that of aluminum. It is used in the automotive industry. The structural material has a lower density, but has a higher specific strength and a modulus higher than that of ordinary engineering plastics and glass fiber strong polymers. At present, magnesium alloy materials are applied to the engine from the dashboard frame to the engine, and the automotive body and chassis components are also beginning to use these magnesium alloy materials. However, there is a problem of poor molding. At the same time, attention has not been paid to the connection technology of magnesium alloy components.

The connection of many magnesium alloy components is focused on the welding of cast magnesium alloys, such as gas shielded welding, gas tungsten electrode welding, resistance welding, laser welding, and electron beam welding. All of these techniques can be used for magnesium alloy plate joining, but often brittle interruptions in the welds are likely to occur, resulting in reduced strength. Adhesive and bolting require additional process steps, increase assembly costs, and the bolted magnesium alloy plate is Sensitive riveting can also be applied but rarely successful.

The point-friction welding process technology can overcome the deficiencies of the above-mentioned welding process technology and is therefore a connection technology with great potential. The working temperature is 412 degrees Celsius, which is a typical low-temperature solid state process connection technology with a long tool life and high reliability. Sex and a better working environment.