Furnace Brazing

Furnace brazing joins metal assemblies by heating in a controlled furnace with filler alloy, producing clean, repeatable joints across many parts at once.

Overview

Furnace brazing joins metal parts by heating the entire assembly in a controlled-atmosphere or vacuum furnace until a filler alloy melts and capillary action fills the joint. Because the heat is uniform and the cycle is programmable, it produces consistent joint quality across complex assemblies and large batch loads, with minimal oxidation and good cosmetic results.

Choose furnace brazing for repeatable production of multi-joint assemblies, tight gap-controlled lap joints, and parts that would distort under localized heating. It scales well for medium to high volumes and supports fixtured, simultaneous joining of many components.

Tradeoffs: you must design for brazing clearances, fixturing, and braze flow paths; joint strength depends heavily on overlap and cleanliness. Furnace size limits part envelope, and cycle time plus tooling cost can make one-off parts expensive. Post-braze cleanup is usually low, but any fluxless/vacuum process demands strict surface prep and compatible base/filler materials.

Common Materials

  • Stainless steel 304
  • Stainless steel 316
  • Low carbon steel
  • Inconel 625
  • Copper
  • Nickel alloys

Tolerances

±0.005"

Applications

  • Stainless steel heat exchangers
  • Carbide cutting tool brazed tips
  • Hydraulic valve blocks with brazed inserts
  • Aerospace honeycomb panel assemblies
  • Refrigeration tubing manifolds
  • Medical instrument subassemblies

When to Choose Furnace Brazing

Furnace brazing fits assemblies with multiple joints that need consistent quality and low oxidation across batches. It works best when joint gaps and overlap can be controlled with machining, forming, or fixturing, and when parts can tolerate a full-assembly thermal cycle. It’s a strong choice for production runs where repeatability and throughput matter more than fast one-off turnaround.

vs Torch Brazing

Choose furnace brazing when you need repeatability across many joints or many parts, and you want uniform heating to reduce local overheating and cosmetic oxidation. It’s better for production work where process control, atmosphere, and consistent braze flow outweigh the flexibility of hand heating.

vs Wave Soldering

Choose furnace brazing when joining structural metal assemblies or higher-temperature service parts where solder strength and melting point are inadequate. It also supports thicker sections and capillary lap joints rather than PCB-focused through-hole solder fillets.

vs Induction Brazing

Choose furnace brazing when the assembly has many joints or complex geometry that would require multiple induction coils or repositioning. Uniform, whole-part heating is also preferable when differential thermal gradients could warp thin features.

vs Dip Brazing

Choose furnace brazing when you need cleaner parts, better atmosphere control, or you want to avoid salt bath handling and residue removal. It’s also easier to run mixed geometries in fixtures without immersion-related buoyancy/float concerns.

Design Considerations

  • Design lap joints with controlled clearance and adequate overlap; specify target gap and allowable variation on the drawing
  • Add braze stop-off or features that prevent filler from wicking into bores, threads, and sealing surfaces
  • Provide escape paths for trapped air/volatiles and avoid blind pockets that can block braze flow
  • Specify surface prep requirements (oxide removal, plating if used) and avoid incompatible coatings in braze areas
  • Plan for fixturing: include locating features and ensure the assembly won’t shift during the thermal cycle
  • Call out acceptable braze fillet size and inspection method (visual, dye penetrant, leak test) to align quality expectations