4047
Near-eutectic Al-Si with the narrowest melting range (about 577 – 582 °C) and the highest fluidity. Fills wide or long joints and suits torch, induction and furnace brazing with flux.
Filler-metal and core strip
Non-Clad Aluminium Brazing Strip for Automotive Heat Exchangers
Non-clad brazing strip is a single-alloy strip, usually an aluminium-silicon filler alloy such as 4047, 4045, 4004 or 4104, used as a separate braze shim or preform where the parts being joined carry no cladding of their own. Bare 6951 strip is supplied alongside it as a heat-treatable core material for vacuum-brazed fins and plates. Metline supplies both in thin gauges and slit widths, worldwide.
- Alloys
- 4047, 4045, 4004, 4104, 6951
- Tempers
- O, H14, H16, H18, H24
- Thickness
- about 0.07 – 0.5 mm
- Width
- about 150 – 1000 mm, narrower on request
What is non-clad brazing strip used for?
Clad brazing sheet carries its filler metal bonded to the core. Non-clad strip separates the two: the filler alloy is supplied on its own as thin strip, and the brazer cuts or stamps it into shims, washers or preforms placed between bare parts before heating. When the furnace reaches temperature, the shim melts and fills the joint.
This approach suits joints where clad material is not practical: thick machined fittings and blocks brazed to tubes, bare extrusions joined to plates, repair and prototype work, and assemblies where only one or two joints need filler. It is also used in vacuum brazing of plate-fin exchangers, where bare fins or bars are combined with clad separator sheets or loose filler foil.
Alongside the filler alloys, bare 6951 strip is supplied as a core material. It contains magnesium, silicon and copper, braze-cycles without melting, and gains strength by ageing afterwards, so it is used for fins and plates that need more post-braze strength than 3003.
Composition of brazing strip alloys (wt %)
Registered limits for the main alloys. Note that bismuth belongs to 4104, not 4004: the two are otherwise almost identical, and some published tables reverse them.
| Alloy | Si | Fe max | Cu | Mn max | Mg | Zn max | Other |
|---|---|---|---|---|---|---|---|
| 4047 | 11.0 – 13.0 | 0.8 | ≤ 0.30 | 0.15 | ≤ 0.10 | 0.20 | — |
| 4045 | 9.0 – 11.0 | 0.8 | ≤ 0.30 | 0.05 | ≤ 0.05 | 0.10 | Ti ≤ 0.20 |
| 4004 | 9.0 – 10.5 | 0.8 | ≤ 0.25 | 0.10 | 1.0 – 2.0 | 0.20 | — |
| 4104 | 9.0 – 10.5 | 0.8 | ≤ 0.25 | 0.10 | 1.0 – 2.0 | 0.20 | Bi 0.02 – 0.20 |
| 6951 (core) | 0.20 – 0.50 | 0.8 | 0.15 – 0.40 | 0.10 | 0.40 – 0.80 | 0.20 | — |
Aluminium is the remainder in every case. Each lot ships with its actual analysis.
Which brazing strip alloy to choose
4045
About 10 % silicon, melting about 577 – 591 °C. A general-purpose CAB filler, often used as strip shims with fluoride flux.
4004
Al-Si with 1 – 2 % magnesium for vacuum brazing without flux. The magnesium evaporates and disrupts the oxide film.
4104
4004 with a small bismuth addition that improves wetting and fillet formation and makes vacuum brazing more tolerant of furnace conditions.
6951 (bare core)
Not a filler. A heat-treatable core strip for fins and plates; it survives the braze cycle and is then aged for strength. Typical O-temper values are about 110 MPa tensile and 40 MPa yield, rising markedly after ageing.
Supply range and tempers
| Alloy | Tempers | Typical thickness (mm) | Typical width (mm) |
|---|---|---|---|
| 4047 | O, H18 | 0.07, 0.10, 0.20, 0.50 | 150 – 1000 |
| 4045 | O, H18, H24 | 0.07, 0.10, 0.20, 0.50 | 150 – 1000 |
| 4004 | H16, H18 | 0.07, 0.10, 0.20, 0.50 | 150 – 1000 |
| 4104 | H16, H18 | 0.07, 0.10, 0.20, 0.50 | 150 – 1000 |
| 6951 | O, H18 | to order, commonly ≤ 0.3 for fins | 150 – 1000 |
Hard tempers (H16, H18) are preferred when strip is stamped into flat shims and washers, because they cut cleanly and do not distort. Soft O temper suits strip that is wrapped, formed into rings or bent around parts. Slitting to narrow widths for automatic shim feeders is available.
How to braze with non-clad strip
- PrepareClean and degrease all parts. Aluminium oxide must be removed or broken down by flux or vacuum for the filler to wet.
- Place the fillerCut or stamp shims slightly smaller than the joint face. Place them where capillary flow can draw filler through the whole joint.
- Flux (CAB, torch)With 4047 or 4045, apply fluoride flux to the joint area. With 4004 or 4104 in vacuum, no flux is used.
- HeatBring the assembly to roughly 590 – 610 °C, depending on filler, and hold only as long as needed for full flow.
- InspectCheck fillets visually; pressure- or helium-test sealed assemblies.
Keep the joint gap small, roughly 0.05 – 0.2 mm, for good capillary action, and support parts so that they do not sag as the core softens near brazing temperature.
Where non-clad brazing strip is used in vehicles
- Radiator and cooler fittings: joining machined inlet and outlet blocks to brazed cores
- Plate-fin oil and charge-air coolers: vacuum-brazed with 4004 or 4104 shims and 6951 fins
- EV thermal parts: manifolds and connectors on battery cold plates
- Air-conditioning components: header caps, brackets and connector blocks
- Prototype and repair work: furnace or torch brazing of one-off assemblies
Brazing strip is a heat-exchanger joining material. It is not used to weld car body panels, axles or suspension parts, and aluminium-silicon fillers cannot survive exhaust temperatures.
How to order brazing strip
- SpecifyAlloy and temper (e.g. 4047 H18), thickness, width, coil ID/OD and quantity.
- Confirm the standardAWS A5.8 classification, EN 573-3 composition or your own specification.
- QuoteWe confirm availability, tolerances, certification and delivery terms (EXW, FOB, CIF or DAP) for your plant or port.
- Process and inspectStrip is slit, checked for gauge, width and surface cleanliness, and packed in sealed, moisture-protected cases.
- Document and shipEach lot ships with an EN 10204 3.1 mill test certificate and packing list, in seaworthy export packing by sea or air; third-party inspection on request.
References and standards
- AWS A5.8 – Specification for Filler Metals for Brazing and Braze Welding
- The Aluminum Association – International Alloy Designations and Chemical Composition Limits (Teal Sheets)
- EN 573-3 – Aluminium and aluminium alloys: chemical composition and form of wrought products
- ISO 17672 – Brazing: filler metals
- ASM Handbook Vol. 6 – Welding, Brazing and Soldering (aluminium brazing)
Non-clad aluminium (aluminum) brazing strip: FAQ
What is the difference between clad and non-clad brazing strip?
Clad strip has the filler layer bonded to a core. Non-clad strip is the filler alloy alone, used as separate shims or preforms between bare parts.
Which alloy is best for vacuum brazing?
4004 or 4104. Their magnesium content breaks up the oxide film without flux; the bismuth in 4104 improves wetting further.
Does 4004 contain bismuth?
No. Bismuth (0.02 – 0.20 %) is the feature that distinguishes 4104 from 4004.
What is 6951 strip used for?
It is a heat-treatable core material for fins and plates in brazed exchangers. It does not melt during brazing and gains strength by ageing afterwards.
Which temper should I order for stamped shims?
A hard temper such as H18, which stamps cleanly into flat shapes.
Need brazing strip or shims?
Send the alloy, temper, gauge and width. We will reply with availability, certification and a delivered price.
