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What Is Furnace/Vacuum Brazing?

July 2nd, 2021

Explore the furnace brazing to see how you can create cost-effective, reproducible products from multiple metal components. Review the steps required to perform this semi-automated process and how you can improve your manufacturing capabilities. After following the steps of the process, you can see the benefits and common applications of this metallurgical technique.

Furnace/Vacuum Brazing

The furnace brazing process is used to join simple or complex metal components using a dissimilar filler metal. It’s used in a range of markets and applications for a firm, secure joint.

Choose brazing if you need a leak-free joint, lightweight assembly and cost-effective solution. Use the process for stainless steels, nickel-based alloys, carbon and alloy steels, titanium, copper or aluminum.

The Brazing Process

The process requires a braze material with a lower melting temperature than the components to be joined. First, the components need to be thoroughly cleaned to prepare for the process. Then the braze alloy needs to be applied between the components. The parent alloy parts need to fit closely and be fixtures into place to ensure an accurate process.

The parent alloys don’t need to be weldable, similar materials or even metallic. Brazing can be used to join a wide range of dissimilar or similar materials with a solid, void-free joint.

Next, the braze is heated between the components. There are different types of furnace brazing, but vacuum brazing is the most common. This process occurs in a vacuum furnace.

The entire assembly must be heated to around 450 degrees Celsius. The precise temperature varies depending on the braze and parent alloys. It must be hot enough to melt the braze alloy, but not the parent alloy.

Oxidation is a serious risk in other types of brazing, but vacuum brazing eliminates this risk. It also makes flux unnecessary for the process.

Capillary action creates a strong seal by completely filling the gaps between the two or more parent components. The result is a one-piece construction with uniform thermal conductivity and strength.

Benefits of Furnace Brazing

This popular furnace brazing process comes with many distinct benefits. Here are the benefits of this metallurgical technique:

  • Improved mechanical strength
  • Uniform thermal conductivity
  • Void-free joints
  • High proof pressure
  • Clean, consistent finish

Your component can withstand temperatures up to 350 degrees, proof pressures up to 800 psi and burst pressures up to 1,300. The high-strength joint prevents leaks and voids, even in inaccessible or complex joints.

You don’t have to worry about surface deterioration or excessive distortion when you use vacuum brazing. Compared to dip brazing, the process is extremely clean. The flux-free process means no corrosive flux needs to be cleaned from your parts.

The result is a highly affordable process that creates metal components with high levels of integrity. Engineers can use this joining solution for a single, basic joint or a complex design with multiple, hidden joints. It’s also usable in situations where the parent allows are unweldable or dissimilar.

Common Applications of Furnace/Vacuum Brazing

Virtually any application that requires a strong, void-free joint of similar or dissimilar materials can use furnace brazing. Here are the most common industries that use this process:

  • Aerospace
  • Electronics
  • Energy
  • Medical
  • Scientific
  • Automotive

While not limited to these industries, there are some areas where the features of brazing can give you the results you need. This metallurgical technique isn’t suited for every application, but it can be used to create simple or complex components that are durable and reliable.

Plate-fin heat exchangers, aluminum cold plates and other components are common applications of vacuum brazing. These thermal and structural assemblies need to be strong, uniform and withstand thermal changes without being affected by distortion.

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