Induction BRAZING does not involve any melting or plastic state of the base metal. Brazing comprises a group of joining processes in which coalescence is produced by heating to suitable temperatures above 450 °C (840 °F) and by using a ferrous and/or nonferrous filler metal that must have a liquidus temperature above 450 °C and below the solidus temperature(s) of the base metal(s). The filler metal is distributed between the closely fitted surfaces of the joint by capillary attraction. Induction Brazing is distinguished from soldering in that soldering employs a filler metal having a liquidus below 450 °C.
Induction Brazing has four distinct characteristics:
- The coalescence, joining, or uniting of an assembly of two or more parts into one structure is achieved by heating the assembly or the region of the parts to be joined to a temperature of 450 °C or above.
- Assembled parts and filler metal are heated to a temperature high enough to melt the filler metal but not the parts.
- The molten filler metal spreads into the joint and must wet the base-metal surfaces.
- The parts are cooled to freeze the filler metal, which is held in the joint by capillary attraction and anchors the part together.
There are very specific reasons to use induction heating for industrial brazing. These include selective heating, better joint quality, reduced oxidation and acid cleaning, faster heating cycles and more consistent results.
Induction heating can be targeted to provide heat to very small areas within tight production tolerances. Only those areas of the part within close proximity to the joint are heated; the rest of the part is not affected. The life of the fixturing is substantially increased because problems due to repeated exposure to heat are eliminated. This advantage becomes particularly important with high-temperature brazing processes.
With efficient inductor design, careful fixturing and consistent part placement, it is possible to simultaneously provide heat in different areas of the same part.
Induction Brazing Produces Better Quality Joints
Induction heat produces clean, leakproof joints by preventing the filler from flowing in areas that it shouldn't. The ability to create clean and controllable joints is one of the reasons that induction brazing is being used extensively for high-precision applications.
Reduced Oxidation And Cleaning
Induction Brazing greatly reduces both oxidation and costly cleaning requirements, especially when a rapid cool-down cycle is used.
Fast Heating Cycles
The Induction heating cycle is very short in comparison to flame brazing, therefore more parts can be processed in the same amount of time, and less heat is released to the surrounding environment.
Induction brazing is a very repeatable process because variables such as time, temperature, alloy, fixturing, and part positioning are very controllable. Temperature control can be accomplished with pyrometers, visual temperature sensors or thermocouples.
For processes which involve medium to high production runs of the same parts, an automated part handling system is can be utilized to maximize productivity.For the most part, induction brazing and soldering is done in an open-air environment but it can also be done in a controlled atmosphere when necessary to keep the parts completely clean and free of oxidation.
For the most part, induction brazing and soldering is done in an open-air environment but it can also be done in a controlled atmosphere when necessary to keep the parts completely clean and free of oxidation.
Induction brazing generally works best with two pieces of similar metal. Dissimilar metals can also be joined by induction brazing but they require special attention and techniques. This is due to differences in the materials' resistivity, relative magnetic permeability and coefficients of thermal expansion.
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