Research on the Principle and Development of Ultrasonic Welding


The outstanding advantages of ultrasonic welding, such as energy saving, environmental protection, solid welding, convenient and simple operation, are attracting more and more attention. Ultrasonic welding technology has been widely used in many fields.

In 1950, ultrasonic welding technology was invented by an American. As a special link technology, this technology has been reused in the field of industrial production. In addition, it has also been widely used in various fields, such as electronic industry, electrical appliance manufacturing, new materials and equipment, automobile parts manufacturing, toy manufacturing, aerospace and nuclear energy industries, food packaging boxes, cosmetics tailing, Sealing technology of advanced snacks, etc.


The main advantages of ultrasonic welding are energy saving, environmental protection, solid welding and simple operation. This technology plays a huge role in promoting the construction of a resource saving and environment-friendly society in China.

[Principle of ultrasonic welding]


As a special welding method, ultrasonic welding usually uses the mechanical vibration energy with ultrasonic frequency of 20 khz (15 khz) to connect the same or different metals, semiconductors, plastics and cermets. When metal is welded by ultrasonic, on the one hand, it is not necessary to transmit current to the workpiece, on the other hand, high temperature heat source is not introduced into the workpiece. During the welding process, under the action of static pressure, elastic vibration energy is transformed into friction work, deformation energy, and limited temperature rise between workpieces. Under the condition that the base metal does not melt, the metallurgical bonding between joints is realized. Therefore, ultrasonic welding belongs to solid state welding.

Under the action of the ultrasonic generator, the power frequency current is further transformed into an oscillating current of ultrasonic frequency (15~20 khz). Through the magnetostriction reaction, the transducer converts electromagnetic energy into elastic mechanical vibration energy. The function of the amplifier is to amplify the amplitude, and to couple with the parallel operation by means of the coupling rod and the upper sound pole. If the natural frequencies of the transducer, amplifier, coupling rod and elevator are consistent with each other, in this case, the system will generate resonance, thus transferring the elastic vibration energy to the workpiece under static pressure. Two kinds of thin materials are bonded together through this energy conversion.

[Characteristics of ultrasonic welding]未标题-1-恢复的-恢复的-恢复的-恢复的.jpg

(1) The range of weldable materials is wide, which can be used for welding the same metal materials, especially the materials with high conductivity and high thermal conductivity (such as gold, silver, copper, aluminum, etc.) and some refractory metals, as well as the dissimilar metal materials with widely different properties (such as heat conduction, hardness, melting point, etc.), metal and non-metal, plastic and other materials, as well as the welding of special structures such as multilayer foils with widely different thicknesses.

(2) The weldment is not electrified, does not need external heat source, does not have macro porosity and other defects in the joint, does not generate brittle intermetallic compounds, and does not have problems such as the splash of molten metal that is easy to occur during resistance welding.

(3) The physical and mechanical properties of the weld metal do not change macroscopically. The static load strength and fatigue strength of the welded joint are higher than those of the resistance welded joint, and the stability is good.

(4) The oxide film or coating on the surface of the metal to be welded has little influence on the welding quality, and the surface preparation of the welding butt weldment is relatively simple.

(5) The electric energy required to form the joint is only 5% of the resistance welding, and the weldment is not easy to deform.

(6) It does not need to apply any screws, adhesives, glue, etc. It has the advantages of simple operation, firm welding, high welding efficiency, fast welding speed, no environmental pollution, time-saving and labor saving. The main disadvantage of ultrasonic welding is that it is limited by the power of existing equipment, so the thickness of the weldment in contact with the upper acoustic electrode cannot be too thick. The joint form can only be lap joint, and the butt joint cannot be used.

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