Brazing is a metal-joining process in which a filler metal — with a melting point above 450 ℃ (842 ℉) but below the melting point of the base metals — is melted and flows into the gap between closely fitted parts by capillary action.
The base metal is never melted. Because the parts are not fused, brazing can join dissimilar metals (aluminium to copper, copper to brass, steel to carbide), thin sections and complex assemblies with minimal distortion — making it the process of choice across Automobile, Air-Conditioning, Refrigeration, Defense, Heavy Engineering and Radiator industries.
In short, welding is a technique that joins metals by melting the base metal and causing fusion, while brazing joins metals by melting and flowing a filler metal into the joint. In both brazing and welding, fabricators add a filler metal into the joint — but in brazing, fabricators don't melt the base metal.
Common features of welding, soldering and brazing — all join metals, all use heat, all may use a filler metal and produce permanent joints. Here is how they differ:
| Parameter | Welding | Brazing | Soldering |
|---|---|---|---|
| Base metal melted? | Yes — fusion of base metals | No | No |
| Working temperature | Above melting point of base metal | Above 450 ℃, below base metal MP | Below 450 ℃ |
| Filler metal | Optional (may or may not be used) | Always — flows by capillary action | Always — soft alloys (tin/lead based) |
| Joint strength | Highest | Intermediate — strong with good joint design | Lowest |
| Dissimilar metals | Difficult | Easily joined | Possible |
| Heat distortion | High | Minimal | Minimal |
| Flux needed? | Rarely | Mostly yes (BCuP self-fluxes on copper) | Usually yes |
| Typical uses | Structural fabrication | AC & refrigeration, radiators, heat exchangers, tubing | Electronics, electrical connections |
Brazing 🔶 Brazed joints are far stronger than soldered joints — high-temperature filler alloys and capillary flow into tight, closely fitted gaps produce a much more robust bond.
Welding 🔷 Welded joints are typically the strongest because the base metals themselves are fused together. Soldered joints are the weakest of the three processes.
Lower temperature means minimal distortion, it joins dissimilar metals and thin sections easily, delivers clean, neat joints with little finishing, and is faster & more economical for mass production.
Brazing is used wherever strong, leak-tight, clean joints are needed — especially in Automobile, Air-Conditioning, Refrigeration, Defense, Heavy Engineering and Radiator industries. Typical uses include joining copper tube and fittings, aluminium heat-exchanger assemblies, HVAC pipework, electrical conductors, brazed joints in fire-protection systems, and repairing cast iron or joining dissimilar metals like aluminium to copper.
In absolute terms, welded joints are usually stronger because the base metals are fused together. However, a properly designed brazed joint — correct gap, good fit-up, right filler alloy — is strong enough for the vast majority of applications, and in shear loading a well-made brazed joint can rival the strength of the base metal itself. Brazing also wins where welding cannot easily work: dissimilar metals, thin walls and delicate assemblies.
The main limitations are: joints lose strength at very high service temperatures (close to the filler's melting point); flux residues can be corrosive and must be cleaned off; filler/base-metal colour mismatch may need finishing; joints rely on good fit-up and capillary gaps; and for very heavy structural sections, welding remains the better choice.
Not really — brazing is generally easier to learn than welding because you never melt the base metal. The key skills are keeping the joint gap correct (typically 0.05–0.15 mm), applying the right temperature so the filler flows by capillary action, and using the correct flux. With the right filler metal, flux and a little practice, operators become productive quickly — which also makes brazing ideal for automated production.
The essentials are: a heat source (torch, induction coil or furnace), the correct filler metal (rod, wire, ring or paste — e.g. BCup, BAg, SKA/SU series), suitable flux (powder, paste or pre-injected flux-cored), cleaning tools (wire brush, hot-water soak), fixtures to hold alignment, and safety gear — goggles, gloves and ventilation. For production work, an automatic wire-feeding machine is used with SU-series wires.
For most metals — yes. Flux prevents oxidation during heating and helps the filler wet and flow. One important exception: BCup alloys are self-fluxing on copper-to-copper joints, so no flux is required there. Flux is always needed when brazing brass or bronze with BCup, and for aluminium brazing our SKA/SU series wires have non-corrosive flux pre-injected inside — no separate flux needed.
Common choices are air-acetylene torches for light work, propane / MAP-Pro (with or without oxygen) for general copper-tube brazing, and oxy-acetylene for larger or thicker assemblies needing concentrated heat. Tip size should match the joint area so the flame heats both parts evenly. For mass production, induction heating and furnace brazing replace the torch entirely.
1. Prevents oxidation — heating metal in air forms oxides; flux shields the joint area so a clean bond can form.
2. Removes existing oxides — flux dissolves oxide films already on the surface, allowing the filler to wet the metal.
3. Improves flow & wetting — with a clean surface the filler spreads by capillary action through the whole joint, producing a strong, leak-tight connection.
Brazing takes place above 450 ℃ (842 ℉) — the defining line between brazing and soldering — but always below the melting point of the base metal. In practice, ranges depend on the alloy: aluminium brazing ≈ 450–590 ℃, BCup copper-phosphorus alloys ≈ 700–846 ℃, BAg silver alloys ≈ 618–982 ℃. See our Copper Brazing page for full composition and temperature tables.
Brazing paste is a blend of finely powdered filler metal (sometimes with flux mixed in) carried in a binder, applied to the joint before heating. It's used where wires or rings can't be used — aluminium sheets, dissimilar metal sheets, complicated brazing points — or where the flux amount should be minimised. Pastes are also the standard choice for furnace brazing. See our Aluminium Brazing page for our paste range.
Brazing offers: joining of dissimilar metals (aluminium-to-copper, copper-to-brass, steel-to-carbide); minimal heat distortion — perfect for thin walls and finished assemblies; cleaner, neater joints needing little finishing; faster, lower-skill, lower-cost production; and the ability to braze multiple joints in one pass. That's why heat exchangers, radiators and AC/refrigeration systems are brazed, not welded.
All three processes: join two or more metals permanently, use heat, may use a filler metal, and depend heavily on clean surface preparation for joint quality. The key differences are the temperature used and whether the base metal melts — see the comparison table above.
❓ No questions in this category.