Brazing FAQ

Answers to the questions we hear most often about contract brazing. For the terminology behind these answers, see our brazing glossary.

What is brazing and how does it work?

Brazing is a thermal joining process that permanently connects two or more metal parts using a filler metal with a lower melting point than the base materials, without melting the base materials themselves. A liquid phase forms by melting the filler metal, or through diffusion at the joint interface, and is drawn into the joint gap by capillary action. Unlike welding, this means dissimilar metals can be joined reliably in the same operation.

Why choose brazing over welding or other joining methods?

Brazing produces reliable joints across a wide range of material combinations, with good dimensional tolerance, comparatively low heat input into the surrounding material, good electrical conductivity across the joint, and consistently high joint quality — which is why it’s standard across industries like tooling, refrigeration and air conditioning, transport and electronics wherever stable, long-lasting metal-to-metal connections are needed.

How strong is a brazed joint?

With a well-designed joint and the right silver braze alloy, we typically achieve tensile strengths of around 350 MPa on S235 steel and around 430 MPa on E295 steel. Special alloys such as hardmetal or high-temperature filler metals can achieve different figures, so always check the technical datasheet for the specific alloy in question — or ask us for guidance on your application.

What brazing processes does Armin Hain use?

We work with several processes depending on the part, material and volume: induction brazing (including under protective atmosphere for oxide-free, flux-free joints), flame brazing for prototypes, small batches and awkward geometries, and specialised processes for PCD, CBN and PCBN tooling. See our services overview for the full picture.

Do I need my own brazing equipment?

No — that’s the point of working with a contract brazing partner. We produce on our own induction and flame brazing equipment, so you don’t need to invest in machinery, tooling or process development for a single component or a limited production run. See brazing outsourcing & series production for how this typically works.

Why is flux used in brazing?

Flux removes oxides already present on the joint surfaces and prevents new oxides from forming while the joint is heated. Without it, the filler metal generally can’t wet and bond to an oxidised surface. We supply matching flux alongside our braze alloys and solders, selected for your base metal, filler metal and process.

Can brazing be done without flux?

Yes, but only under a controlled atmosphere — typically vacuum brazing or brazing under protective (inert or reducing) gas. We offer induction brazing under protective atmosphere for exactly this: clean, oxide-free, flux-free joints with no post-braze cleaning needed.

Is brazing flux hazardous to work with?

Most brazing fluxes contain boron compounds and fluorides, and should not be inhaled or allowed to contact the skin. As a contract brazing partner, we handle flux selection, application and extraction in-house under controlled conditions, so this is one less thing you need to manage yourself.

How is flux residue removed after brazing?

Flux residue is removed by washing, pickling, or mechanical cleaning, depending on the flux type and the part’s surface requirements. Where a component needs to stay completely flux-free, brazing under protective atmosphere removes the need for post-braze cleaning entirely.

Which flux or filler metal is right for my application?

That depends on your base metal, joint design, working temperature and any applicable standards. Rather than a one-size-fits-all recommendation, we assess this per application — see brazing materials & filler metals or simply send us your requirements and we’ll help you find the right combination.

What’s the difference between brazing and soldering?

Both use a filler metal with a lower melting point than the base material, but the dividing line is 450°C: brazing (also called hard soldering) uses filler metals with a liquidus temperature above 450°C, typically silver-copper-zinc alloys, and produces stronger, more heat-resistant joints. Soldering (soft soldering) uses filler metals below 450°C, such as tin-copper or tin-silver alloys, and is common in plumbing and electronics. Our services are all in the brazing (hard soldering) range.

Is brazing required by code for certain applications?

In some industries, yes — for example, joints in gas-carrying pipework are often required by applicable technical standards to be brazed rather than soldered, because of the higher joint strength and temperature resistance brazing provides. If you’re unsure which standard applies to your application, get in touch and we can help you think it through.

Didn’t find your question here? Contact us and we’ll be happy to help.