This is the process of using a molten filler metal which is distributed between two or more base metals, leading to the formation of metallurgical bonds. The principle by which the filler material (alloy) is drawn through the joint to create the bond is called a capillary action. Brazing can be performed both manually and automatically. Compared to the traditional torch brazing, induction brazing is more localized, repeatable and easier to automate.
How to perform a successful induction brazing procedure?
Do it fast, safe and easy with UltraFlex`s induction heating systems!
Our team of engineers at UltraFlex is here to give you some essential tips that can help you achieve a precise induction brazing process. UltraFlex provides the heating in the brazing process.
What is brazing?
This is the process of using a molten filler metal which is distributed between two or more base metals, leading to the formation of metallurgical bonds. Brazing can be performed both manually and automatically. The principle by which the filler material (alloy) is drawn through the joint to create the bond is called a capillary action. The alloy always has a lower melting temperature than the base metal ( see Examples of Induction brazing with different metals).
IN A NUTSHELL
- The alloy is spread over the surface of the base metal;
- The base metal is heated by induction in a selected area until the alloy melts down;
- The base metal and the alloy react (mutual diffusion, formation of a new alloy);
- The new alloy in the place of the joint is cooled and crystalized
TIP: The area to be brazed should be preheated until the temperature of melting of the alloy is reached. Otherwise, the alloy will crystalize very quickly, and the process of diffusion will not be accomplished. If you fail to do that, you will end up with a weak joint.
When you want to braze two workpieces together, you should first consider their shape, metal type and surface. To choose a suitable alloy and flux, seek an advice from their manufacturer.
Induction brazing process criteria
- The service conditions and environment
- The parent materials to be joined
- The join design to be employed
- The dimensions of the joint gap
- The choice of a filler material
- Means of removing oxide films from the surfaces to be joined
- Design of fixture to be used to support components – Provided by UltraFlex
- Induction heating method – Provided by UltraFlex
- Level of complexity needed in the production equipment to satisfy the production requirement
STEPS of the brazing process:
- Clean the base metals properly
Any oil, grease, rust or scrap will form a barrier. Make sure to clean the workpieces properly. Oil and grease should be cleaned first. Then you can remove the rust. Cleaning can be done by using a wire brush, degreasing solvent, water, alkaline or steam. If the surfaces are oxidized, you can also clean them mechanically.
- Estimate the clearance
The usual clearance (distance) for most filler metals ranges between 0.001 to 0.005 inches (0.0254 mm to 0.127 mm). If the clearance is increased, the joint strength will decrease. The amount of alloy is determined by the clearance gap. It must be enough to fill the void with a very small amount of it left outside.
- Use a flux
When two details are heated up, the possibility of oxidation is increased. When flux is applied to the surfaces, it prevents oxidation. Fluxes come in different forms:
- As a powder or a paste – a brush is used to spread it over the desired area;
- As a flux coated alloy;
- As a liquid – by a dispenser
TIP: Choose a flux formulated for the specific metals, temperatures and conditions of your brazing application. Fluxes are extremely aggressive and should always be cleaned when you finish brazing. Otherwise, the metal will corrode. For successful brazing, the melted alloy should entirely wet the surface of the base metal. Flux also aids wetting of the base metal with alloy.
- Use an alloy
Different kinds of alloys can be used, depending on the shape of the joints:
- Thin Sheet
- Wire or rod
- Pre-made rings
- Paste with flux (alloy + flux)
- Position the joints
When your pieces are cleaned and fluxed, you should find the perfect alignment. To hold them together, UltraFlex offers specifically designed brazing fixtures.
- Brazе the joints
First, heat the assembly to a required brazing temperature. Second, spread the filler metal. The heated assembly will melt down the filler metal and it will be drawn instantly throughout the entire joint area by capillary action. Add flux to the end of the filler metal rod to improve the flow.
- Clean the new joint
After you have brazed the assembly, the new joint should be cleaned by removing the flux`s residue and any oxide scale formed during brazing. The flux can be removed with hot water, wire brush or a suitable acid after the filler metal has solidified completely. To get the best results, follow the directions given by the flux manufacturer!
- Safe process for the operator – serious physical damages are prevented
- Guaranteed repeatability
- Focused heating
- Reduced waste
- No need for special clothing and goggles
- Minimum amount of harmful fumes
- Minimized distortion and oxidation
PRODUCTS BY ULTRAFLEX
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