The principle of ultrasonic metal welding and its common applications
As another emerging ultrasonic welding method after ultrasonic plastic welding-ultrasonic metal welding technology, it has advantages that other welding methods can't match in the welding of the same and dissimilar metals. Ultrasonic metal welding does not require flux and external heating source, does not deform due to heat, has no residual stress, and does not require high pre-weld treatment on the surface of the weldment. It can not only weld the same kind of metal, but also can complete higher welding requirements for dissimilar metals, and can weld thin sheets or thin wires on thick plates. Ultrasonic welding of good conductors consumes much less energy than current welding. Ultrasonic bonding is a low-power application of ultrasonic metal welding and is often used for welding transistors or integrated circuit leads. When used for sealing welding of medicines and explosive materials, it can avoid the pollution of medicines caused by dissolved substances in the general welding method, and will not cause an explosion due to heat or sparks. Ultrasonic metal welding has many advantages such as fast speed, energy saving, high bonding strength, good electrical conductivity, no sparks, and solid state processing.
Ultrasonic metal welding was discovered by accident in the 1830s. At that time, during the current spot welding electrode plus ultrasonic vibration test, it was found that it could be welded without current, so the ultrasonic metal cold welding technology was developed.
Principle of Ultrasonic Metal Welding:
The ultrasonic metal welding process is mainly for the high-frequency mechanical vibration between the interface of the workpiece to be welded under the action of welding pressure, which generates shear force, and generates heat during the friction process, which induces plastic deformation, so that the workpiece achieves a solid phase connection. state. The principle of ultrasonic metal welding is shown in Figure 1. The ultrasonic generator converts the 50Hz power frequency current into a 16-80 kHz resonant current, transfers the resonant current to the ultrasonic transducer through the inverse piezoelectric effect, converts it into elastic mechanical energy, and then amplifies the amplitude through the horn, and finally The elastic vibration energy is transferred from the upper sonotrode to the workpiece. The acoustic system is a whole composed of transducer, horn, upper sonotrode and clamping mechanism. When the system is working, the frequency of the oscillating current in the generator is consistent with the natural frequency of the acoustic system, and the entire system is in resonance. While applying pressure to the workpiece, it also transmits elastic vibration energy, which is finally converted into friction work, deformation energy and thermal energy between the upper and lower workpieces, which can make it reach the welding state in a short time.
Advantages of ultrasonic metal welding:
Ultrasonic metal welding is a brand-new technology, and its research and application are still in the development stage, but there is no doubt that it is superior to traditional welding technology in many aspects, specifically as follows.
1. Low pressure and low energy consumption
The biggest advantage of ultrasonic metal welding different from traditional welding is its low pressure and low energy consumption, which saves energy costs to a large extent, and it can also weld different kinds of metal materials together, breaking through the original technical limitations. The bottleneck of dissimilar metal welding cannot be realized. In addition, in the process of rapid prototyping of metal parts, some functional devices can be embedded to realize smart metal matrix composite materials, which cannot be achieved by traditional welding technology.
2. Fast speed and high stability
Ultrasonic metal welding can ensure the increase of welding speed by using spot welding and continuous welding. It can not only weld materials with different physical properties, but also apply to the large difference in thickness and thickness that cannot be achieved by other technologies and between multilayer metal sheets. Welding. Due to its very high solder joint strength, it has good stability.
3. Simple procedure and high precision
Ultrasonic metal welding technology can guarantee the quality of the welded product with a simple procedure during the welding process. The simplicity of the procedure is reflected in the following points: First, it does not need to use water cooling and gas protection, and eliminates the need for welding finished products. De-heat treatment process; secondly, no welding rod is used, and the welded metal is not directly heated, reducing energy loss and avoiding heating troubles; finally, no need to add flux, eliminating the need for later cleaning and environmental protection of the finished product. Ultrasonic metal welding also uses a power electronic circuit, which can achieve high-density welding through electrical control.
Application of ultrasonic metal welding:
At present, ultrasonic metal welding has four main applications: spot welding, seam welding, wire harness and tube sealing, which are widely used in various fields such as automobiles, refrigeration, solar energy, batteries, and electronics.
At present, the specific applications of ultrasonic metal welding mainly include:
1. Welding of multi-layer positive and negative electrodes of power battery; welding of nickel mesh and nickel sheet of nickel-hydrogen battery;
2. Welding of copper foil and nickel sheet of lithium battery and polymer battery; welding of aluminum foil and aluminum sheet; welding of aluminum sheet and nickel sheet;
3. Automobile wiring harness; wire forming; wire mutual welding; multiple wires are mutually welded to form a wire knot; copper and aluminum wire conversion wires, cables and various electronic components, contacts, connectors, and terminals are welded;
4. Solar cells, flat solar heat-absorbing panels, aluminum-plastic composite pipe roll welding, copper and aluminum plate splicing;
5. Welding of high-current contacts, contacts, and dissimilar metal sheets such as electromagnetic switches and non-fuse switches;
6. Sealing of copper pipes in refrigerators, air conditioners and other industries; welding of copper and aluminum pipes for vacuum devices, etc.
Ultrasonic metal welding is an emerging special processing technology, it is superior to traditional welding technology in many aspects, and has a wide range of applications in various fields. This advanced welding technology is not only an important manifestation of scientific and technological progress, but also a major contribution to the development of human society.