Brazing by induction heating.
Induction brazing is will need welding metal artifacts (mostly in the general copper) is placed within the induction coil, high frequency alternating current, induced electromagnetic field, on the workpiece surface coupling induction electromotive force, form induced eddy current in the metal surface, on the metal surface to produce eddy current heating, in welding parts will be coated with solder powder, when a workpiece to solder melting temperature when welding, induction brazing is currently the world's most clean environmental protection heat welding way.
Welding using high frequency, medium frequency or power frequency induced current as heat source. High frequency heating is suitable for welding thin wall pipe fittings. The use of coaxial cable and split-type induction coil can be away from the power source of the site for brazing, especially suitable for some large components, such as rocket on the need to remove the welding of pipe joints.
In induction brazing, the brazing part of a part is placed in an alternating magnetic field, and the heating of this denominator is realized by the resistance heat of the induced current generated in the alternating magnetic field. The higher the frequency is, the smaller the penetration depth of current is. Although the surface layer is heated rapidly, the thickness of heating is thinner. The internal part can only be heated by the heat conduction from the surface layer to the inside, which is the so-called skin effect. Therefore, it is not advantageous to choose too high ac frequency. Generally, the frequency around 500kHz is more appropriate. In addition, the skin effect is also related to the material's resistivity and permeability. The larger the resistivity is, the smaller the permeability is, and the weaker the skin effect is; otherwise, the more significant the skin effect is. Induction coil is an important component of induction brazing equipment. The basic principle of correct design and selection of induction coil is to ensure rapid, uniform and high efficiency during welding. Generally, the induction coil is made of pure copper tube, which is cooled by water when working. The thickness of the tube wall should be less than the penetration depth of current, generally ranging from 1 mm to 1.5mm. The gap between the induction coil and the welding part should be kept to avoid short circuit, but in order to improve the heating efficiency, the gap between the induction coil and the welding part should be reduced as far as possible. Induction brazing often requires some auxiliary tools to clamp and position the welding parts. When designing the fixture, it should be noted that the fixture parts adjacent to the induction ring should not use metal to avoid induction heating. In induction brazing, foil, wire, powder and paste filler metal can be used. The filler metal installed should not form a closed ring, but the brazing agent and gas medium can be used to remove the film. Induction brazing is widely used for brazing steel, copper and copper alloy, stainless steel, high temperature alloy and other welding pieces with symmetrical shape, especially suitable for pipe socket, pipe and flange, shaft and shaft sleeve, turning tool blade serrated piece welding; For brazing aluminum alloy, induction brazing can also be used, but the temperature control requirements are relatively high.