How to perform a successful induction brazing procedure?

Do it fast, safely and easily with UltraFlex induction heating systems!

Our team of engineers at UltraFlex is here to give you essential tips that can help you achieve a precise induction brazing process. UltraFlex provides the heating in the brazing process.

Automated Induction brazing of copper pipes in refrigerator assembly for in-place brazing

     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 crystallized.

TIP: The area to be brazed should be preheated until the temperature of melting of the alloy is reached. Otherwise, the alloy will crystallize very quickly, and the process of diffusion will not be accomplished. If you don`t do that, you will end up with a weak joint.

How-to

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 advice from the 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 for brazing – Provided by UltraFlex
  • Level of complexity needed in the production equipment to satisfy the production requirement

STEPS of the brazing process:

1. 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 or steam. If the surfaces are oxidized, you can also clean them mechanically.

2. 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.

3. Use 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.

4. 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)

5. 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.

6. Braze the joints

First, heat the assembly to the 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.

7. Clean the new joint

After you have brazed the assembly, the new joint should be cleaned by removing the flux residue and any oxide scale formed during brazing. The flux can be removed with hot water a 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!

ADVANTAGES

  • Safe process for the operator – serious physical damage is prevented
  • Guaranteed repeatability
  • Focused heating
  • Reduced waste
  • No need for special clothing and goggles
  • Minimum amount of harmful fumes
  • Minimized distortion and oxidation

application evaluation