In induction brazing, the brazed portion of the part is placed in an alternating magnetic field, and the heating of the portion of the base material is achieved by the resistance heat of the induced current generated in the alternating magnetic field.
Introduction A welding method using 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 dismantled on the rocket.
Methods and Applications In induction brazing, the brazed portion of the part is placed in an alternating magnetic field, and the heating of this portion of the parent metal is achieved by the resistive heat of the induced current generated in the alternating magnetic field. The intensity of the induced current in the conductor is proportional to the frequency of the alternating current. As the frequency of the alternating current used increases, the induced current increases and the heating rate of the weldment increases. Based on this point, induction heating mostly uses high frequency alternating current. However, 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 magnetic permeability of the material. The larger the resistivity, the smaller the magnetic permeability and 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. Usually, 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 coil 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, filament, powder and paste brazing filler metal may be used, and the brazing material disposed should not form a closed loop, and the flux may be removed by using a flux and a gaseous medium. Induction brazing is widely used for brazing steel, copper and copper alloys, stainless steel "target=_blank> stainless steel, high temperature alloys, etc. with symmetrical shape welds, especially for pipe fittings, pipes and flanges, shafts and bushings Type 3 joints; for brazing of aluminum alloys, this method is not suitable because temperature is not easy to control.
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