SHS welding technology

    Self-propagating high-temperature synthesis (SHS) is a new technology for synthetic materials, and SHS welding is a new application area of the process. SHS welding is a technique that uses the heat generated by the SHS reaction and its products to weld. Combustion synthesis technology is used to place the pressed powder between the materials to be welded, and the high-temperature reaction heat synthesized by powder body combustion and the synthesized product are used as filler materials to achieve the connection between the materials to be welded under pressure. This reaction process is similar to sintering, and the purpose of pressing is to obtain a highly dense welded joint.

    Generally speaking, SHS welding has three processes: ignition, pressurization, and insulation.

    1. There are many ignition methods, such as arc, electric spark, flame, high current, high temperature furnace, electron beam, laser, high temperature radiation and microwave, chemical furnace, etc.

    2. The pressure and time are the keys to the success of welding. If the SHS synthetic material is not pressurized, a large amount of pores will be caused due to the pores of the material and the gas generated during the reaction. Reactants are not allowed to remain in the weld and therefore must be densified. The usual method is to pressurize during the reaction.

    3. High density may not be obtained by simply pressing, and insulation should be performed at the same time.

    Compared with other welding methods, SHS welding has many advantages, mainly:

    1. Due to the exothermic reaction, the material need only be heated to a temperature several hundred degrees Celsius below its melting point, which can save energy.

    2. A reinforcing phase such as reinforcing particles, short fibers, and whiskers can be added to the solder to form a composite material.

    3. Local heat release during SHS welding can reduce the heat-affected zone, avoid damage to the microstructure of the heat-sensitive material, and maintain the material performance.

    4. Welding is a synthesizable gradient material, which is used as a solder to weld special-shaped materials to overcome the mismatch in chemical, mechanical and physical properties between the base materials.

    5. Because the green body can be pressed into any shape, SHS welding is easy to weld into products that are difficult to manufacture.

    6. SHS welding is suitable for surface treatment of materials.

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