Wire harness pressure welding process introduction
The welding method is a welding method in which the welding parts are closely attached and kept under a certain temperature and pressure for a period of time, so that the atoms between the contact surfaces diffuse each other to form a connection. The main factors that affect the diffusion welding process and joint quality are temperature, pressure, diffusion time and surface roughness. The higher the welding temperature, the faster the atomic diffusion. The welding temperature is generally 0.5 to 0.8 times the melting point of the material. Depending on the type of material and the requirements for the quality of the joint, diffusion welding can be carried out under vacuum, protective gas or solvent, among which vacuum diffusion welding is the most widely used. In order to speed up the welding process, reduce the requirements for the roughness of the welding surface or prevent harmful structures in the joint, an intermediate interlayer material with a specific composition is often added between the welding surfaces, and its thickness is about 0.01 mm. The diffusion welding pressure is small, the workpiece does not produce macroscopic plastic deformation, and it is suitable for precision parts that will not be processed after welding. Diffusion welding can be combined with other thermal processing processes to form a combined process, such as heat loss-diffusion welding, powder sintering-diffusion welding, and superplastic forming-diffusion welding. These combined processes can not only greatly improve productivity, but also solve problems that cannot be solved by a single process. For example, various titanium alloy components on supersonic aircraft are made of superplastic forming-diffusion welding. The joint performance of diffusion welding can be the same as that of the base metal. It is especially suitable for welding dissimilar metal materials, non-metallic materials such as graphite and ceramics, and dispersion strengthening. high temperature alloys, metal matrix composites and porous sintered materials. Diffusion welding has been widely used in the manufacture of reactor fuel elements, honeycomb structural panels, electrostatic acceleration tubes, various blades, impellers, dies, filter tubes and electronic components.
Diffusion welding is to contact the welding surfaces of the substances to be welded with each other under a certain temperature and pressure, and expand the physical contact of the surfaces to be welded through microscopic plastic deformation or through the generation of a small amount of liquid phase on the welding surface, so that the distance between them is (1~5). ) within 10-8cm (in this way, the attraction between atoms can form a metal bond), and then after a long period of time, the atoms continue to diffuse and penetrate each other to achieve a welding method of metallurgical bonding.
Obviously, for the welding of ordinary wire harnesses, the cost of diffusion welding is too high.
High-frequency welding (high-frequency welding)
High-frequency welding uses solid resistance heat as energy. During welding, the resistance heat generated in the workpiece by the high-frequency current heats the surface layer of the workpiece welding area to a molten or close plastic state, and then applies (or does not apply) upsetting force to achieve metal bonding. Therefore it is a solid phase resistance welding method. High-frequency welding can be divided into contact high-frequency welding and induction high-frequency welding according to the way that high-frequency current generates heat in the workpiece. In contact high-frequency welding, high-frequency current is introduced into the workpiece through mechanical contact with the workpiece. During induction high-frequency welding, the high-frequency current generates an induced current in the workpiece through the coupling action of the induction coil outside the workpiece. High-frequency welding is a highly specialized welding method, and special equipment should be equipped according to the product. High productivity, welding speed up to 30m/min. It is mainly used for welding longitudinal seams or spiral seams when manufacturing pipes.
Obviously, high-frequency welding is not suitable for small wire harnesses.
cold pressure welding
Cold pressure welding, English is cold pressure welding
When pressurized and deformed, the oxide film on the contact surface of the workpiece is destroyed and extruded, which can purify the welded joint. The applied pressure is generally higher than the yield strength of the material to produce 60-90% deformation. The pressure method can be slow extrusion, rolling or impact force, or it can be pressed several times to achieve the required deformation.
Because cold-press welding requires no heating and no filler, the equipment is simple; the main process parameters of welding have been determined by the size of the mold, so it is easy to operate and automate, the welding quality is stable, the productivity is high, and the cost is low; no flux, the joint will not cause corrosion. ; The temperature of the joint does not increase during welding, and the crystalline state of the material remains unchanged, which is especially suitable for the welding of dissimilar metals and some metal materials and products that cannot be achieved by thermal welding. Cold-press welding has become one of the most important and limited welding methods in the electrical industry, aluminum product industry and space welding.
The working surfaces of cold-press welders and their dies may accumulate metal debris and must be removed regularly. Compressed air, if available, can be used to blow debris away. To remove the debris completely, take the mold out of the welder, disassemble the four modules of the mold, and use a magnifying glass to carefully examine each module to ensure that all traces of debris on the surface of the module are removed. Care must be taken when removing the mold, especially the small springs are easily lost. The surface of the mold is not clean, the wire will easily slip in the mold when wiring, and the welding will fail. Note that there must be no grease on the working surface of the mold after repair.
The equipment required for cold-pressing welding is simple, the process is simple, and the working conditions are good. However, the extrusion force required for cold-press welding is large, the equipment is relatively large when welding large-section workpieces, and the surface of the workpiece after lap welding has deep pressure pits, which limits its application range to a certain extent.
Therefore, cold pressure welding is not a perfect choice for wire harness welding.
