O (annealed)
Soft rod for further drawing to fine welding wire, and for coiling straight-length TIG rod with no spring-back.
Filler metal guide
4043 and 4047 Aluminium Wire Rod for Welding (O, H12, H14, H18)
4043 (about 5 % silicon) and 4047 (about 12 % silicon) are the two main aluminium-silicon filler alloys. Both give a fluid weld pool and strong resistance to hot cracking; 4047 flows even more freely and is also a brazing alloy. They are supplied as finished MIG and TIG wire, and as wire rod in O, H12, H14 or H18 temper for further drawing or straight-length filler. This guide explains the difference and how to choose.
- Alloys
- ER4043 · ER4047
- Tempers
- O, H12, H14, H18
- Diameter
- about 0.8 – 15 mm
- Standards
- AWS A5.10 · ISO 18273
What silicon does in a filler alloy
Silicon lowers the melting point of aluminium and narrows its freezing range. In a weld, that means a more fluid pool that wets the joint well and, critically, liquid metal that can feed shrinkage as the weld solidifies, preventing solidification cracks.
Many base alloys, especially the heat-treatable 6xxx series, are crack-sensitive if welded without filler or with a filler of similar chemistry. Diluting the weld with 4043 or 4047 moves the weld metal out of the crack-sensitive composition range. That is why 4043 is among the most widely used aluminium fillers in the world, alongside the magnesium-bearing 5356.
4047 takes the effect further. At 11 – 13 % silicon it is close to the aluminium-silicon eutectic (about 12.6 % Si), so it melts over a narrow range of about 577 – 582 °C. It flows into tight joints, gives minimal shrinkage and is used both as a welding filler (ER4047) and as a brazing filler (BAlSi-4).
4043 and 4047 composition (wt %)
Limits below follow AWS A5.10 for bare welding electrodes and rods. ISO 18273 uses S Al 4043A (AlSi5(A)) and S Al 4047A (AlSi12(A)), with very similar limits.
| Element | ER4043 | ER4047 |
|---|---|---|
| Silicon (Si) | 4.5 – 6.0 | 11.0 – 13.0 |
| Iron (Fe) | ≤ 0.8 | ≤ 0.8 |
| Copper (Cu) | ≤ 0.30 | ≤ 0.30 |
| Manganese (Mn) | ≤ 0.05 | ≤ 0.15 |
| Magnesium (Mg) | ≤ 0.05 | ≤ 0.10 |
| Zinc (Zn) | ≤ 0.10 | ≤ 0.20 |
| Titanium (Ti) | ≤ 0.20 | — |
| Beryllium (Be) | ≤ 0.0003 | ≤ 0.0003 |
| Others each / total | 0.05 / 0.15 | 0.05 / 0.15 |
| Aluminium | Remainder | Remainder |
The beryllium limit applies to welding filler because of fume exposure. Wire rod intended for welding wire must meet the filler standard, not just the general wrought-alloy registration.
4043 compared with 4047
| Property | 4043 | 4047 |
|---|---|---|
| Melting range | about 573 – 632 °C | about 577 – 582 °C |
| Fluidity | Very good | Excellent |
| Hot-crack resistance | Very good | Excellent |
| Weld shrinkage and distortion | Low | Lowest |
| Shear strength of fillet welds | Lower than 5356 | Slightly higher than 4043 |
| Colour after anodising | Grey | Dark grey to black |
| Typical use | General welding of 6xxx, 3xxx and castings | Leak-tight joints, castings, brazing, heat exchangers |
| Brazing filler | No | Yes (BAlSi-4) |
Neither 4xxx filler should be used on 5xxx base metals with more than about 2.5 % magnesium (such as 5083 or 5456): the weld forms brittle magnesium silicide. Use 5356 or 5183 for those. And because 4xxx welds are not heat-treatable in the way 6xxx base metal is, an as-welded 6061-T6 joint is designed to a reduced strength, about 165 MPa (24 ksi) minimum tensile in AWS D1.2.
Wire rod tempers and what they are used for
H12 / H14
Partly work-hardened rod for straight-length TIG filler and for cutting into brazing rings and preforms.
H18 (full hard)
The temper of finished MIG wire: stiff enough to push through liners and contact tips without kinking.
Spooled MIG wire
Usually 0.8, 1.0, 1.2 and 1.6 mm on 0.5 – 7 kg spools or larger drums for robots.
Straight TIG rod
Typically 1.6 – 5.0 mm diameter in about 1 m lengths, marked with the alloy.
Larger rod
Up to about 15 mm for further processing, feedstock and specialised filler.
Quick filler selection by base metal
| Base metal | Preferred filler | Alternative | Comment |
|---|---|---|---|
| 1xxx | 1100 / 1188 | 4043 | 4043 if cracking is an issue |
| 3003, 3004 | 4043 | 1100, 5356 (3004) | 4043 is the common choice |
| 5052, 5005 (Mg ≤ 2.5 %) | 5356 | 4043 | 4043 acceptable for low-Mg alloys |
| 5083, 5086, 5456 | 5183 / 5356 | — | Never 4xxx |
| 6061, 6063, 6082 | 4043 or 5356 | 4047 | 4043 for crack resistance and post-weld heat treatment; 5356 for strength and anodise match |
| Castings A356, A357, 413 | 4043 / 4047 | 4643 | 4047 for high-Si castings |
| Brazing 3003 / 6063 assemblies | 4047 | 4045 / 4343 clad | Flame or furnace brazing with flux |
Diameter tolerance, surface and cleanliness
Typical requirements
- Diameter tolerance (finished wire)
- AWS A5.10 limits, about +0.01 / −0.04 mm on MIG sizes; wire rod to the agreed grade
- Surface
- Free of cracks, laps, burrs, die marks, oxide, lubricant residue and inclusions
- Cast and helix (spooled wire)
- Controlled so wire feeds straight and the arc stays stable
- Hydrogen sources
- Minimal surface oil and hydrated oxide; these cause weld porosity
- Packaging
- Sealed bags with desiccant; open spools should be used promptly
- Certification
- Certificate of conformity to AWS A5.10 / ISO 18273, plus EN 10204 3.1 chemistry
Porosity in aluminium welds is almost always caused by hydrogen, and the filler surface is a major source. Store wire in a dry, warm area, keep spools in their bags until use and never leave a spool on a machine in a humid shop overnight without cover.
Where 4043 and 4047 are used
- Structural and general fabrication: 6061 and 6063 frames, trailers, railings and bicycle frames (4043)
- Automotive: radiators, condensers, intake manifolds and repairs to cast wheels and housings
- Heat exchangers and HVAC: torch and furnace brazing of tube-to-header joints (4047)
- Electronics and power: heat sinks, cold plates and housings where low distortion matters
- Casting repair: filling defects in silicon-bearing castings
- Pressure-tight assemblies: tanks and housings where fluidity helps achieve leak-tight seams
References and standards
- AWS A5.10/A5.10M – Welding Consumables: Wire Electrodes, Wires and Rods for Welding of Aluminum and Aluminum Alloys
- ISO 18273 – Welding consumables: wire electrodes, wires and rods for welding of aluminium and aluminium alloys
- AWS D1.2 – Structural Welding Code: Aluminum
- AWS A5.8 – Filler Metals for Brazing and Braze Welding
- The Aluminum Association – Welding Aluminum: Theory and Practice
4043 and 4047 welding wire: frequently asked questions
What is the difference between 4043 and 4047?
4043 has about 5 % silicon and is a general-purpose filler. 4047 has about 12 % silicon, melts at a lower, narrower range, flows more freely and is also used as a brazing alloy.
Can I weld 6061 with 4043?
Yes. 4043 is one of the two standard fillers for 6061 and is preferred when crack resistance or post-weld heat treatment matters. 5356 gives higher shear strength and a better colour match after anodising.
Can 4043 or 4047 be used on 5083?
No. On 5xxx alloys with more than about 2.5 % magnesium the weld forms brittle Mg2Si. Use 5183 or 5356.
Why is MIG wire supplied in H18 temper?
Full-hard wire is stiff enough to feed through the gun liner without buckling. Softer tempers are used for drawing stock and straight TIG rods.
Will 4043 welds match the colour of anodised parts?
No. Silicon-rich welds turn grey (4043) or dark grey (4047) when anodised. Use 5356 where appearance after anodising matters.
What causes porosity with aluminium wire?
Hydrogen from moisture, oil or hydrated oxide on the wire or base metal. Keep wire dry and sealed and clean the joint before welding.
Need 4043 or 4047 filler?
Send the alloy, temper, diameter, form and quantity. We will confirm the standard, certification and delivery.
