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Brazing

Brazing

Magnetic assemblies overview

As you may be aware, the correct assembly technique is an important aspect in relation to the performance of any application. After a detailed look at the pros and cons of mechanical assembly, insert moulding, over moulding, gluing and ultrasonic welding, brazing is the next assembly technique up for discussion.

What is brazing?

Brazing is a metal-joining assembly process in which two or more metal items are joined together by melting and flowing a filler metal into the joint. The filler metal has a lower melting point than the adjoining metal. There are various filler alloys available, at Goudsmit UK we use a copper based alloy. Mainly because the copper based alloy improves wetting and molten metal flow characteristics, benefiting corrosion resistance.

During the brazing process, a filler metal is melted and distributed in between multiple solid metal components after they have been heated to the proper temperature. The filler metal must have a melting point that is above 840 degrees Fahrenheit, but below the melting point of the base metals.

Brazing Process

The brazing process

The brazing process is a simple process, consisting of six main steps:

  1. Ensure a perfect fit and clearance to allow capillary action to work most effectively.
  2. Clean the metal because if it is contaminated a barrier will form between the base metal surfaces and the brazing materials, impacting the flux of the magnet and the success of the overall assembly.
  3. Flux prior to brazing so that the surfaces are shielded from the air, preventing oxide formation.
  4. Ensure the fixture of the parts are accurate so that they remain in the correct alignment during the heating and cooling cycles.
  5. Braze the assembly.
  6. Clean the new joint.

Heat sources for brazing

  • Torch brazing is a heating source supplied by a fuel gas flame. Gases include acetylene, hydrogen or propane.
  • Induction brazing uses electric coils to heat the part and the brazing filler metal until the liquid metal flows via capillary action into the joint.
  • Continuous furnace involves conveyer belts transporting the pre-alloyed components through preheating, heating and post heating zones where the braze alloy reaches temperature, then re-solidifies during cooling.
  • Retort or batch furnaces can be refractory lined and heated by gas, oil or electricity.
  • Vacuum furnace is a furnace with electrically heated elements that surround the workload and heat the brazing filler metal to a liquid state, so flow and capillary attraction are achieved.

Applications using brazing

Brazing exists in industries where high there are demands for strength and fatigue, corrosion and oxidation resistance, such as:

  • ConstructionBrazing Application
  • Medical
  • Arts and Jewellery
  • Electrical and Electronic
  • Aerospace
  • Automotive

Benefits of brazing

Brazing provides an array of benefits to include:

  • Component distortion is minimised or eliminated.
  • Enables the joining of dissimilar materials.
  • Components may be batched processed.
  • Cost efficient assembly technique.
  • Process thermal cycles are predictable.
  • Base metal weakening is relatively low as brazing allows much tighter control over tolerances, producing a clean joint without the need for secondary finishing.

Disadvantages of brazing

Despite appearing hugely advantageous, brazing too has its limitations:

  • Brazed joints can be damaged under high service temperatures.
  • A high degree of base-metal cleanliness is required before brazing.
  • Some brazing applications require the use of adequate fluxing agents to control cleanliness.
  • The joint colour is often different from that of the base metal, which may be visually unappealing.

We have years of experience, so there is no other supplier that can provide better results. Contact us today for more information at dean@goudsmit.co.uk or speak to a member of our team on +44 (0) 2890 271 001.

For more information on assembly techniques visit our brochure.

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