Fillet welds
The higher silicon gives a harder deposit and higher shear strength in fillets than 4043, though still below 5356.
High-silicon filler metal
ER4047 Aluminium Welding Wire (AlSi12)
ER4047 is a 12 % silicon aluminium filler metal with a melting range of only about 5 °C, which gives the most fluid pool, the least shrinkage and the lowest hot-crack risk of any common aluminium filler. It is chosen for leak-tight heat-exchanger and refrigeration joints, thin-wall assemblies, casting repair and as a brazing filler. This guide explains when to use it, when not to, and how to specify it.
- Classification
- AWS A5.10 ER4047 / R4047
- ISO designation
- S Al 4047A (AlSi12)
- Silicon
- 11.0 – 13.0 %
- Melting range
- 577 – 582 °C
What makes ER4047 different?
ER4047 contains close to the eutectic amount of silicon for the aluminium-silicon system (about 12.6 %). At that composition the alloy melts and freezes almost at a single temperature rather than over a wide mushy range, so the weld pool goes from fully liquid to fully solid very quickly.
That behaviour has three practical effects. First, the pool is extremely fluid and wets joint faces readily, which helps seal fine gaps in tube-to-header and fitting joints. Second, solidification shrinkage is lower than with ER4043, so there is less distortion and fewer shrinkage cracks in thin parts and castings. Third, there is almost no time for a liquid film to sit between grains and tear, which is why 4047 is the filler with the lowest hot-crack sensitivity on crack-prone 6xxx and casting alloys.
The same silicon makes the deposit harder and less ductile than a 4043 weld and turns it very dark when anodised. 4047 is also the base composition of many aluminium brazing fillers (AWS A5.8 BAlSi-4), which is why the alloy appears in both welding and brazing catalogues. The filler is the same; the process and temperature differ.
ER4047 chemical composition (wt %)
Values are the AWS A5.10 limits for 4047. ISO 18273 lists the closely related S Al 4047A (AlSi12(A)); both are traded interchangeably for most work, but quote the exact designation your procedure names.
| Element | Limit (%) | Role |
|---|---|---|
| Silicon (Si) | 11.0 – 13.0 | Near-eutectic: narrow melting range, high fluidity, low shrinkage |
| Iron (Fe) | 0.80 max | Impurity |
| Copper (Cu) | 0.30 max | Impurity; kept low for corrosion resistance |
| Manganese (Mn) | 0.15 max | Impurity |
| Magnesium (Mg) | 0.10 max | Kept low |
| Zinc (Zn) | 0.20 max | Impurity |
| Beryllium (Be) | 0.0003 max | Restricted in all AWS aluminium fillers |
| Others, each / total | 0.05 / 0.15 | |
| Aluminium (Al) | Remainder |
Typical physical data
- Solidus / liquidus
- 577 °C / 582 °C (1070 °F / 1080 °F)
- Density
- About 2.66 g/cm³ (0.096 lb/in³)
- Related brazing designation
- AWS A5.8 BAlSi-4 (similar Si range, brazing filler)
- Aerospace brazing filler
- AMS 4185 covers 12 % Si aluminium brazing filler wire and rod
ER4047 or ER4043: how to choose
Both are aluminium-silicon fillers suited to 6xxx alloys and castings. The choice usually comes down to whether sealing and crack resistance outweigh ductility and cost.
| Property | ER4047 | ER4043 |
|---|---|---|
| Silicon | 11.0 – 13.0 % | 4.5 – 6.0 % |
| Melting range | 577 – 582 °C (about 5 °C) | 574 – 632 °C (about 58 °C) |
| Pool fluidity | Highest | High |
| Solidification shrinkage | Lowest | Moderate |
| Hot-crack resistance | Excellent | Very good |
| Fillet shear strength | Higher than 4043 | Lower |
| Ductility | Low | Moderate |
| Colour after anodising | Very dark grey | Dark grey |
| Brazing use | Yes, standard brazing filler | Rarely |
| Typical cost | Somewhat higher | Lower |
A practical rule many fabricators follow: use 4043 for general 6xxx structures and repairs, and switch to 4047 on parts that must hold refrigerant or pressure, on very thin walls where distortion matters, or where 4043 still shows cracking. Our ER4043 guide covers that filler in detail.
Which alloys suit ER4047?
| Parent alloys | Suitability | Comment |
|---|---|---|
| 1xxx: 1050, 1060, 1100 | Good | Common on refrigeration tube and fittings |
| 3xxx: 3003, 3102, 3005 | Very good | Standard HVAC and heat-exchanger alloys |
| 6xxx: 6061, 6063, 6082 | Very good | Lowest crack risk; lower ductility than 4043 |
| 5xxx with Mg ≤ about 2 %: 5005, 5050 | Acceptable | Qualify the procedure; check ductility |
| 5xxx with higher Mg: 5052 upward, 5083, 5086 | Avoid | Silicon and magnesium form brittle Mg2Si in the weld |
| Al-Si castings: A356, 413, 319 | Very good | Close match in silicon content and melting behaviour |
| 2xxx and 7xxx high strength | Not recommended | Not normally arc welded |
Suitability follows the general direction of AWS and Aluminum Association filler selection charts; confirm the exact pairing with the chart in your code (for example AWS D1.2) and a procedure qualification.
Strength and behaviour of ER4047 joints
As with any filler on heat-treatable alloys, the heat-affected zone governs the strength of a groove weld in 6xxx parent metal. AWS D1.2 and ASME IX set the same minimum as-welded tensile strength for 6061-T6 groove welds, 165 MPa (24 ksi), regardless of whether 4043 or 4047 is used; the filler mainly changes crack resistance, ductility and fillet capacity.
Ductility
Bend and elongation values are lower than 4043. Avoid 4047 on joints that must bend in service or pass tight guided-bend tests without qualification.
Elevated temperature
Like other Al-Si fillers, 4047 has no magnesium and is suitable for service above 65 °C, where high-Mg 5xxx fillers risk sensitisation.
Heat treatment
The deposit itself does not age-harden. Dilution with 6xxx parent metal gives a limited response; for joints that will be solution treated and aged, 4643 or 4943 is the more usual choice.
Corrosion
Good general corrosion resistance in air and fresh water, comparable with 4043.
Conductivity
Electrical and thermal conductivity are close to those of 4043, adequate for heat-exchanger joints.
ER4047 forms and sizes
| Format | Typical sizes | Packaging | Notes |
|---|---|---|---|
| MIG wire | 0.8, 0.9, 1.0, 1.2, 1.6 mm | 0.5 kg, 2 kg, 7 kg and 20 kg spools; drums | Layer wound for push-pull and robotic feeding |
| TIG rod | 1.6, 2.0, 2.4, 3.2, 4.0 mm | 1 m (36 in) straight lengths in sealed tubes or boxes | Manual GTAW and repair |
| Brazing rod and wire | 1.6 – 6.0 mm and other sizes | Rods, coils or cut lengths | Flame or induction brazing with separate flux |
| Flux-cored brazing wire | Agreed per order | Coils | Flux carried inside; for HVAC return bends and manifolds |
| Rings and preforms | To drawing | Bulk packed | For automated induction or furnace brazing |
Brazing products in 4047 chemistry, such as discs, rings, clad strip and coil, are covered on separate pages: brazing rings and preforms, 4047 brazing discs and 4047 coil and strip.
Welding and brazing tips for ER4047
- Prepare the jointDegrease, then brush with a dedicated stainless brush. On tube joints, keep fit-up tight: 4047 flows into small gaps but does not bridge large ones well.
- Set the gasPure argon for most MIG and TIG work; argon-helium mixes on thick sections or high-conductivity parts to improve penetration.
- Control heatBecause 4047 melts about 50 °C below 4043, use slightly less heat input and faster travel to avoid overheating thin walls.
- Mind the craterUse crater fill or a brief reverse at the stop. Even with 4047, crater cracks are the most common defect.
- For brazingHeat the parent metal, not the rod, to roughly 580 – 600 °C with suitable flux, and let capillary action draw the filler in. Parent alloys with low solidus temperatures, such as 6061, need careful temperature control.
- InspectLeak test (pressure decay or helium) on refrigeration parts; visual and dye-penetrant checks on structural welds.
Typical ER4047 applications
- HVAC and refrigeration: condenser and evaporator headers, return bends, accumulators and receiver-dryers in 3003 and 1xxx alloys
- Automotive heat exchangers: repair and assembly of radiators, charge-air coolers and oil coolers; 4047 is also the skin of most brazing sheet
- Casting repair: porosity and crack repair in A356 and 413 die and sand castings, wheels and housings
- Thin-wall tube and enclosure work: parts where distortion would spoil the fit
- Pressure-tight containers: small tanks and manifolds in 3xxx and 6xxx alloys that must pass leak testing
- Root passes: some procedures use 4047 for a crack-free root and a 5356 or 4943 cap where strength or colour matters
Specifying and ordering ER4047
State the classification (AWS A5.10 ER4047, ISO 18273 S Al 4047A, or a brazing designation such as BAlSi-4 or AMS 4185), the form and diameter, packaging, quantity and required documents. Metline supplies a certificate of conformance or heat-lot analysis with each consignment, packs spools in sealed moisture-barrier bags and ships worldwide on EXW, FOB, CIF or DAP terms.
References and standards
- AWS A5.10/A5.10M – Welding Consumables: Wires and Rods for Aluminum and Aluminum-Alloys
- AWS A5.8/A5.8M – Filler Metals for Brazing and Braze Welding (BAlSi-4)
- ISO 18273 – Wire electrodes, wires and rods for welding of aluminium and aluminium alloys
- SAE AMS 4185 – Aluminum Alloy Brazing Filler Metal, 12Si
- AWS D1.2/D1.2M – Structural Welding Code: Aluminum
ER4047 aluminium (aluminum) welding wire: FAQ
Is ER4047 a welding wire or a brazing filler?
Both. The 12 % silicon alloy is classified as a welding filler under AWS A5.10 (ER4047) and has a brazing counterpart under AWS A5.8 (BAlSi-4). For fusion welding the parent metal melts; for brazing only the filler melts at about 580 – 600 °C.
Can ER4047 be used on 5083 or 5086?
No. High-magnesium 5xxx alloys react with the silicon to form brittle Mg2Si. Use ER5183, ER5356 or ER5556 on those alloys.
Why is ER4047 preferred for refrigeration and HVAC joints?
Its near-eutectic composition gives a very fluid pool that wets and seals joint faces, with minimal shrinkage and very low crack risk. That combination produces leak-tight joints on thin 3003 and 1xxx tube and fittings.
Can the dark colour after anodising be avoided?
Not with 4047 itself, because the silicon stays in the anodic film. Options are to place welds out of sight, paint or powder coat after anodising, or cap a 4047 root with a 5356 pass.
Is ER4047 stronger than ER4043?
In fillet welds it usually gives higher shear strength. In 6061-T6 groove welds both reach the same code minimum of 165 MPa because the heat-affected zone controls strength. 4047 is less ductile.
How should 4047 wire be stored?
Keep spools sealed in their bags in a dry, heated store above the dew point, and reseal part-used spools. Moisture on the wire causes porosity.
Need ER4047 filler metal?
Tell us the form, diameter, packaging and quantity. We will confirm availability, certificates and delivered terms.
