There are many types of solder joint technology. When classified according to the phase formed during welding and joining, it can be classified into three types: a fusion bonding method, a liquid phase-solid phase reaction bonding method, and a solid phase bonding method. Each method can be further categorized into more methods. In addition, the welding and joining technology is closely related to various welding and joining equipment, simulation technology and inspection technology. Solder Joint Technology There are many types of solder joint technology. When classified according to the phase formed during welding and joining, it can be classified into three types: a fusion bonding method, a liquid phase-solid phase reaction bonding method, and a solid phase bonding method. Each method can be further categorized into more methods. In addition, the welding and joining technology is closely related to various welding and joining equipment, simulation technology and inspection technology.
Liquid-solid phase reaction bonding techniques and solid phase bonding techniques Liquid-solid phase reaction bonding processes are brazed and liquid phase diffusion bonded. The solid phase bonding process includes friction crimping, friction stir welding, normal temperature crimping, forging, explosive crimping, and ultrasonic crimping. This section introduces the development trend of liquid phase diffusion bonding and the ever-expanding friction stir joining in recent years.
The liquid phase diffusion bonding method is a method in which a workpiece is inserted into a joint surface, and the workpiece is joined in a state where the insert is melted and the base material is not melted. Liquid phase diffusion bonding is suitable for joining precision parts, complex shapes, special material parts, and dissimilar materials.
The liquid phase diffusion bonding method can be joined at a relatively low temperature, which has an advantage in that the adhesion of the joint surface is improved due to the action of the liquid phase. This method is suitable for the joining of some components in gas turbines and jet engines. The liquid phase diffusion bonding method is a very effective joining method for joining of dissimilar materials, and can be used for joining of Ti alloy and steel which are difficult to melt-weld. This combination of Datong's technology has been used in the manufacture of automotive turbine turbines.
The friction stir welding method is: when the cylindrical member as a tool is rotated, the joint portion is pressed into the joint portion, and the joint portion is softened by the generated friction heat and the heat of processing, and at the same time, the joint material is plastically flowed due to the rotation of the tool. Engage. The tool is usually made of tool steel. Due to the plastic flow, the joints are finer than the base material, and the mechanical properties are improved. In addition, since it is non-melt welding, the maximum heating temperature is relatively low, so the heat affected zone is small. This is a feature of this method. This method has been applied to low-melting materials such as Al alloys, and can be used in many fields such as railway vehicles and aerospace. In the automotive industry, cars with Al alloy girders have been replaced with improved friction stir joining-friction stir point bonding technology instead of resistance spot welding. Recent research reports indicate that improvements in tool materials can be improved, and friction stir welding can be used to join carbon steel, stainless steel "target=_blank> stainless steel, Ti and Ti alloys.
Surface modification technology In addition to surfacing (arc, plasma, laser) and vacuum coating (PVD, CVD), thermal spray technology is also being studied in changing surface materials. This section introduces surfacing technology and recent thermal spray technology.
In recent years, in order to be able to be used in a harsh environment, parts are required to have abrasion resistance, corrosion resistance, and heat resistance. Surfacing is a method that can meet these requirements inexpensively. At the same time, surfacing is an indispensable welding method for repairing component damage. The surfacing welding process includes: arc welding surfacing, powder plasma arc surfacing, powder laser surfacing and the like. Arc welding surfacing is used for the repair of soil sanding parts and metal molds. Powder plasma arc surfacing, because it can produce a variety of functional powders, can be used in many aspects besides powder plasma arc surfacing for engine valve surfacing and petroleum refining cracker tubes. Powder laser surfacing, because of the laser as a heat source, is suitable for surfacing in small parts, and is expected to be used in many aspects such as precision product mold repair and jet engine repair.
Surface modification techniques include techniques such as nitriding and carburizing to change the structure and properties of the surface of the component itself, and techniques such as plating and ion plating to attach other high-performance materials to the surface of the component. The thermal spraying method belongs to the second technique and is suitable for improving the corrosion resistance of the boiler pipe fittings and improving the wear resistance of the rolls and the cold working die. Recently, according to the requirement of improving the fuel utilization rate of automobile lightweighting, the method of using thermal spraying technology instead of pressing the casting cylinder sleeve into the engine cylinder has attracted people's attention.
The thermal spraying method is a technique in which a thermal spray material (filament, powder, or bar) such as a metal or ceramic in a molten or semi-molten state is impacted on a base material at a high speed by an energy source (heat source) to deposit a film on the base material ( See Figure 2). The energy sources for thermal spraying are: chemical energy generated by fuel combustion or explosion, spark discharge, and electrical energy generated by plasma. In addition, recently, cold spray technology that uses only particle motion to form a film has attracted attention. The characteristics of the thermal spraying method are: (1) a wide selection range of thermal spraying materials; (2) no limitation on the material and size of the base material; (3) rapid film formation; (4) thick film formation; (5) A porous film is produced; (6) construction can be carried out on site.
Related techniques for welding Generally, various evaluation experiments after welding are performed on the welding materials. Mainly include: microstructure observation, hardness test, tensile test, Charpy impact test, welding crack test and so on. In addition, evaluation and analysis during the welding process play an important role in the development of welding materials in the future. Here, an introduction to the analysis technique of the welding arc phenomenon is given.
Taking a picture of the welding arc phenomenon with a high-speed camera can not only judge the movement pattern of the welding droplet, but also accurately understand the arc shape and the welding pool generated during the welding process. The development of higher precision welding materials and welding techniques is made possible by the analysis of these images. Datong Company has developed a unique analysis technique for welding arc phenomenon, which can quickly and quickly determine the vibration of the front end of the wire, the size of the droplet, the length of the arc, the angle of the front end of the wire when the droplet is detached, the wire feeding speed, the number of splashes, etc. And can perform high-precision analysis work.
It can be expected that the analytical results obtained by the technique are fed back to the welding process, and welding with higher quality and higher precision can be realized.
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