Automotive and EV structures
6xxx extrusions and castings in subframes, battery trays and brackets, where stronger welds help meet fatigue and crash targets.
Filler metal guide
ER4943 / R4943 Aluminium Welding Wire
ER4943 is an aluminium-silicon filler with 0.30 – 0.50 % magnesium, classified under AWS A5.10, that welds like ER4043 but gives noticeably stronger welds without relying on dilution from the base metal. Manufacturer test data show roughly 25 % higher tensile and up to 50 % higher yield strength than ER4043 as welded. Metline supplies ER4943 MIG wire and R4943 TIG rod with lot certificates to fabricators worldwide.
- Classification
- AWS A5.10 ER4943 / R4943
- Chemistry
- Al – 5.5 % Si – 0.4 % Mg
- As-welded UTS
- ≈ 240 MPa (35 ksi) typical
- Forms
- MIG spools · TIG straight rods
What is ER4943 and why was it developed?
For decades fabricators welding 6xxx alloys chose between two fillers. ER4043 flows well, resists cracking and suits heat-treatable alloys, but its welds are relatively weak, especially when little base metal mixes into the pool. ER5356 is stronger, yet it is more sensitive to cracking on some 6xxx joints and is unsuitable for service above about 65 °C. ER4943 was developed to close that gap.
The alloy keeps the 5 – 6 % silicon of ER4043, so puddle fluidity, wetting and crack resistance stay much the same. A controlled 0.30 – 0.50 % magnesium addition then forms Mg2Si in the weld metal. Because the strengthening element comes from the wire, the deposit is strong even in multipass welds and heavy fillets where dilution is low, which is where ER4043 is at its weakest.
ER4943 was added to AWS A5.10 in the 2010s and carries the same ASME Section IX F-number (F-23) as ER4043. In many shops that means existing ER4043 procedures can be requalified for ER4943 with modest effort, though any change of filler classification still needs to be handled under the governing code.
ER4943 chemical composition (wt %)
Values follow the AWS A5.10 limits for ER4943 and R4943. A lot certificate with the actual analysis accompanies every Metline supply.
| Element | Limit | Purpose |
|---|---|---|
| Silicon (Si) | 5.0 – 6.0 | Fluidity, wetting and resistance to hot cracking |
| Magnesium (Mg) | 0.30 – 0.50 | Forms Mg2Si; raises weld strength without relying on dilution |
| Iron (Fe) | 0.40 max | Impurity, kept lower than in ER4043 |
| Copper (Cu) | 0.10 max | Impurity |
| Manganese (Mn) | 0.05 max | Impurity |
| Zinc (Zn) | 0.10 max | Impurity |
| Titanium (Ti) | 0.15 max | Grain refinement |
| Beryllium (Be) | 0.0003 max | Restricted for health reasons |
| Others, each / total | 0.05 / 0.15 | |
| Aluminium (Al) | Remainder |
Physical and mechanical properties
Typical data
- Solidus / liquidus
- about 574 / 632 °C (1065 / 1170 °F)
- Density
- 2.68 g/cm³ (0.097 lb/in³)
- All-weld-metal tensile strength, as welded
- about 240 MPa (35 ksi) typical
- Compared with ER4043
- about 20 – 25 % higher tensile and 40 – 50 % higher yield as welded (manufacturer test data)
- Fillet shear strength
- about 20 % higher than ER4043 in reported tests
- Electrical conductivity
- about 41 % IACS
- Ductility and toughness
- Similar to ER4043 (moderate)
- Colour after anodising
- Grey
The strength figures describe weld metal. In a butt joint on 6061-T6, the heat-affected zone still softens to roughly T4-level strength, so the joint efficiency improves less than the weld-metal numbers suggest unless the assembly is heat-treated afterwards. Where ER4943 shines is fillet welds, where failure often runs through the throat of the weld itself: a stronger deposit means smaller fillets or higher allowable loads.
Design to the allowable values in your code (for example AWS D1.2 or Eurocode 9) and treat manufacturer data as typical rather than guaranteed.
Typical MIG and TIG settings
ER4943 runs on the same equipment and broadly the same settings as ER4043. Values below are starting points with pure argon in the flat position; confirm with trial welds and procedure qualification.
| Wire diameter | Current (DCEP) | Arc voltage | Travel speed | Argon flow |
|---|---|---|---|---|
| 0.9 mm (0.035 in) | 70 – 185 A | 15 – 27 V | 0.6 – 1.0 m/min | 14 – 17 L/min |
| 1.0 mm | 90 – 200 A | 17 – 27 V | 0.6 – 1.0 m/min | 15 – 18 L/min |
| 1.2 mm (3/64 in) | 125 – 260 A | 20 – 29 V | 0.6 – 0.9 m/min | 17 – 21 L/min |
| 1.6 mm (1/16 in) | 170 – 300 A | 24 – 30 V | 0.7 – 1.0 m/min | 21 – 26 L/min |
| TIG rod size | Tungsten | Current (AC) | Typical base thickness |
|---|---|---|---|
| 1.6 mm (1/16 in) | 1.6 mm | 60 – 80 A | 1.6 mm |
| 2.4 mm (3/32 in) | 2.4 mm | 125 – 160 A | 3.2 mm |
| 3.2 mm (1/8 in) | 3.2 mm | 190 – 220 A | 4.8 mm |
| 4.0 mm (5/32 in) | 4.0 mm | 200 – 300 A | 6.4 mm |
| 4.8 mm (3/16 in) | 4.8 mm | 330 – 380 A | 9.5 mm |
Use argon or argon-helium shielding. Helium additions raise heat input for thick sections and faster travel.
ER4943 diameters and packages
Supply range
- MIG wire
- 0.8, 0.9, 1.0, 1.2 and 1.6 mm (0.030 – 1/16 in)
- MIG packages
- 100 mm (4 in), 200 mm (8 in) and 300 mm (12 in) spools; drums for robots
- TIG rod
- 1.6 – 4.8 mm (1/16 – 3/16 in) in 914 mm (36 in) or 1000 mm lengths
- Packing
- Sealed bags with desiccant in cartons, palletised for export
- Documents
- Certificate of conformance to AWS A5.10 / ASME SFA-5.10 with lot chemistry
ER4943 compared with ER4043 and ER5356
| Point | ER4043 | ER4943 | ER5356 |
|---|---|---|---|
| Alloy type | Al-5Si | Al-5.5Si-0.4Mg | Al-5Mg |
| As-welded weld-metal strength | Lower | Medium-high | High |
| Hot-cracking resistance on 6xxx | Very good | Very good | Good |
| Fluidity and bead appearance | Excellent | Excellent | Good, more spatter-prone |
| Feedability (MIG) | Fair (softer wire) | Fair–good | Good (stiffer wire) |
| Service above 65 °C | Yes | Yes | No |
| Colour match after anodising | Poor (grey) | Poor (grey) | Good |
| Responds to post-weld heat treatment | Partly (dilution) | Yes | No |
| Suits 5xxx base metal | Not over about 2.5 % Mg | Not over about 2.5 % Mg | Yes |
Do not choose a filler on one strength figure. Base alloy, joint type, service temperature, finishing and the code all matter. For 5xxx hull plate, ER5356 or ER5183 remain the normal choice; for heavy 6xxx sections heat-treated after welding, compare ER4943 with ER4643.
Where ER4943 is used
Bicycles and sports equipment
6061 frames, trailers and recreational products, often aged or heat-treated after welding.
Trailers and truck bodies
Fillet-welded 6061 and 6063 extrusion frames where higher throat strength reduces weld size.
Marine fittings
6xxx extrusions in railings, ladders and superstructure details; 5xxx hull plate still uses Al-Mg fillers.
Elevated-temperature parts
Heat exchanger housings and equipment above 65 °C where Al-Mg fillers are not advised.
Architectural and general fabrication
Frames, guards and handrails in 6xxx where bead appearance and crack resistance matter.
Handling tips and common mistakes
- Store wire sealed and dry; moisture on the wire surface causes porosity.
- Remove oil first, then the oxide film with a clean stainless brush, just before welding.
- Use U-groove rolls, a polymer liner and the correct contact tip; a push-pull gun helps with 0.9 mm wire.
- Requalify procedures when changing from ER4043, even though the F-number is the same.
- Do not use ER4943 on high-magnesium 5xxx alloys such as 5083 or 5086; Mg2Si formation makes the weld brittle.
- Expect grey welds after anodising; plan finishing accordingly.
How to order ER4943
- SpecifyER4943 wire or R4943 rod, AWS A5.10 / ASME SFA-5.10, diameter, package type and quantity.
- Share the jobBase alloy, thickness, process and any approvals or test documents your programme requires.
- QuoteWe confirm availability, documentation and delivery terms (EXW, FOB, CIF or DAP).
- ShipMoisture-protected, labelled by lot, with certificate of conformance.
References and standards
- AWS A5.10/A5.10M – Welding Consumables: Wires and Rods for Aluminum and Aluminum-Alloys
- ASME Boiler and Pressure Vessel Code, Section II Part C – SFA-5.10
- AWS D1.2/D1.2M – Structural Welding Code: Aluminum
- Hobart Maxal 4943 product data sheet
- Fabricating & Metalworking – Aluminum filler metals approved for wrought commercial applications (2014)
ER4943 aluminium (aluminum) welding wire: FAQs
How does ER4943 differ from ER4043?
ER4943 adds 0.30 – 0.50 % magnesium to a similar silicon level. The weld metal forms Mg2Si, giving about 20 – 25 % higher tensile and 40 – 50 % higher yield strength as welded in manufacturer tests, while flow and crack resistance stay similar.
Can I use my ER4043 welding procedure with ER4943?
Both share ASME F-number 23 and similar settings, so procedures transfer easily, but a change of filler classification still needs review or requalification under your code.
Is ER4943 good for welding 5083 or other 5xxx alloys?
No. On high-magnesium 5xxx base metals, silicon fillers form brittle Mg2Si. Use ER5356 or ER5183 for 5083, 5086 and 5456.
Can ER4943 welds be heat-treated?
Yes. Because the wire contains magnesium, the deposit responds to ageing and to full solution treatment and ageing.
Is ER4943 available for TIG and MIG?
Yes. ER4943 is the spooled MIG wire and R4943 the straight TIG rod, with identical chemistry.
What do you need for a quotation?
Classification, standard, diameter, spool size or rod length, quantity and destination. Base alloy and process details help us confirm the filler suits the job.
Need ER4943 filler metal?
Send the diameter, package, quantity and destination. We reply with availability, documentation and a delivered quote.
