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Induction brazing similar dissimilar metal welding method

Introduction to induction brazing

Induction brazing is a welding method that uses high frequency, intermediate frequency or power frequency induced current as a heat source. High frequency heating is suitable for welding thin walled pipe fittings. Coaxial cable and split-type induction coils can be used for brazing on the ground away from the power supply, especially for some large components, such as the welding of pipe joints that need to be disassembled on the rocket.

It is also commonly used in the pin welding of the electronics industry to simultaneously heat the solder joints in the area, and send the tin wire to the solder joint through the tin feeding mechanism to complete the soldering. The metal workpiece to be welded (mostly copper) is placed in the induction coil, and the high-frequency alternating current is generated to generate an induced electromagnetic field. The induced electromotive force is coupled on the surface of the workpiece to form an induced eddy current on the metal surface, and the eddy current generated on the metal surface is heated. Solder powder is usually applied to the welded parts. When the workpiece reaches the melting temperature of the solder, it can be welded. Induction brazing is the cleanest and most environmentally friendly heating welding method in the world.


Induction brazing component

Induction welding systems usually include: high frequency generator, (high frequency induction heating machine high frequency welding machine) induction head, automatic tin feeding system, tin wire, circulating water cooling system, smoke purification system.

Induction brazing method

In induction brazing, the brazed portion of the part is placed in an alternating magnetic field, and the heating of this portion of the base material is achieved by the resistance heat of the induced current generated in the alternating magnetic field. The higher the frequency, the smaller the current penetration depth. Although the surface layer is heated rapidly, the thickness of the heating is thinner, and the inside of the part can only be heated by the heat conduction of the surface layer to the inside. This is the so-called skin effect. It can be seen that it is not advantageous to select an excessively high AC frequency, and a frequency of about 500 kHz is generally suitable. In addition, the skin effect is also related to the resistivity and permeability of the material. The larger the resistivity, the smaller the magnetic permeability, the weaker the skin effect, and the more significant the skin effect.
 

The induction coil is an important component of induction brazing equipment. The basic principle of correctly designing and selecting the induction coil is to ensure that the welding year is heated quickly, evenly and efficiently. Generally, the induction coils are made of pure copper tubes. When working, the tubes are cooled by water, and the wall thickness should be less than the current penetration depth, generally 1~1.5mm. A gap should be maintained between the induction ring and the weldment to avoid short circuit, but in order to improve the heating efficiency, the gap between the induction coil and the weldment should be minimized. Induction brazing often requires some auxiliary tools to clamp and position the weldment. When designing the fixture, it should be noted that the clamp parts adjacent to the induction coil should not use metal to avoid induction heating. In the case of induction brazing, foil-like, filament-like, powder-like and paste-like brazing filler metals may be used, and the brazing filler metal is not suitable for forming a closed loop, and the flux may be removed by using a flux and a gaseous medium.



Induction brazing application

Induction brazing is widely used for brazing steel, copper and copper alloys, stainless steel, high temperature alloys and other symmetrical shaped weldments, especially for pipe fittings, pipes and flanges, shafts and bushings, turning heads Sheet welding; for brazing of aluminum alloys, induction brazing can also be used, but temperature control requirements are improved.

 ※ Hardware industry: welding accessories, precision mold parts, metal handles, egg beaters, drill bits, alloy steel and steel, steel and copper, copper and copper equivalent metal or dissimilar metal welding;

※ Tool industry: welding of diamond tools, carbide turning tools, tungsten steel knives, milling cutters, reamers, planing knives, etc.;

※ Home appliance industry: welding of composite pot bottom, welding of electric hotplates such as electric kettles and coffee pots, brazing between stainless steel flat bottoms, aluminum sheets and various shapes of electric heating tubes;

※ Plumbing industry: welding of faucets, water pipes, etc.;

※ Refrigeration industry: welding of air conditioner shunt, air conditioner sight glass, air conditioner condenser, air conditioning tube, copper tube, etc.;

※ Medical industry: welding of needles, detectors, scalpels, etc.;

※ Welding of mining tools, such as “one” word bit, column tooth bit, dovetail coal bit, riveting bit, various miner picks, and welding of various roadhead picks.
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