Heat-treated structural frames
Thick 6061 or 6082 frames, platforms and machine bases that go through a solution furnace after welding so welds and plate share the same temper.
Filler metal guide
ER4643 / R4643 Aluminium Welding Wire
ER4643 is an aluminium-silicon-magnesium filler metal classified under AWS A5.10, made for 6xxx-series weldments that will be solution heat-treated and aged after welding. Its small magnesium addition lets the weld metal form Mg2Si and harden with the parent metal, which matters most in thick sections where the base metal adds too little magnesium to an ER4043 weld. Metline supplies ER4643 MIG wire on spools and R4643 TIG rod in straight lengths, with lot certificates, worldwide.
- Classification
- AWS A5.10 ER4643 / R4643
- Chemistry
- Al – 4.1 % Si – 0.2 % Mg
- Main use
- 6xxx welds that are heat-treated after welding
- Forms
- MIG spools · TIG straight rods
What is ER4643 filler metal?
ER4643 is best understood as a modified ER4043. The silicon content is cut from about 5 % to about 4 %, and 0.10 – 0.30 % magnesium is added. That combination was designed so that the weld metal behaves roughly like a mixture of four parts 4043 and one part 6061, which is the blend you would get naturally if enough base metal melted into the weld pool.
The reason this matters is heat treatment. A 6061 or 6082 structure is often welded in the T4 or T6 condition and then given a full solution heat treatment, quench and artificial ageing so the whole assembly, welds included, returns close to T6 strength. Weld metal can only respond to that treatment if it contains both silicon and magnesium. With ER4043, almost all of the magnesium has to come from dilution, that is, from parent metal melted into the pool.
In thin sheet and small fillets, dilution is high and ER4043 welds pick up enough magnesium. In heavy butt welds, typically above about 10 mm (3/8 in), the centre of the joint is mostly filler metal, so the weld stays soft after heat treatment even though the plate either side hardens. ER4643 supplies the missing magnesium from the wire itself, so the weld centre ages along with the parent metal.
ER4643 chemical composition (wt %)
Limits below follow the AWS A5.10 classification for ER4643 and R4643. The European and ISO equivalent is S Al 4643 (AlSi4Mg) under EN ISO 18273. Each Metline lot is supplied with a certificate reporting the actual analysis.
| Element | Limit | Purpose |
|---|---|---|
| Silicon (Si) | 3.6 – 4.6 | Fluidity, lower melting range, resistance to hot cracking |
| Magnesium (Mg) | 0.10 – 0.30 | Combines with Si to form Mg2Si so the weld responds to heat treatment |
| Iron (Fe) | 0.8 max | Impurity |
| Copper (Cu) | 0.10 max | Impurity; kept low for corrosion resistance |
| 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 welder health, as for all AWS A5.10 fillers |
| Others, each / total | 0.05 / 0.15 | |
| Aluminium (Al) | Remainder |
Some older supplier sheets show a higher beryllium figure. Current AWS A5.10 limits beryllium to 0.0003 % in all aluminium filler classifications, and that is the limit Metline supplies to.
Physical properties and weld behaviour
Typical physical data
- Melting range
- about 574 – 635 °C (1065 – 1175 °F)
- Density
- 2.68 g/cm³ (0.097 lb/in³)
- Hot-cracking sensitivity
- Low, similar to ER4043
- General corrosion rating
- Good; stress-corrosion resistance very good
- Colour after anodising
- Grey, so welds show against anodised 6xxx parent metal
- Ductility as welded
- Moderate; lower than 5xxx fillers
As-welded, an ER4643 joint in 6061-T6 is governed by the softened heat-affected zone, just as an ER4043 joint is, and design codes such as AWS D1.2 give the same reduced allowable strengths for both. The advantage only appears after a full post-weld solution heat treatment and ageing, when the weld centre can approach the strength of the parent metal instead of remaining a weak link.
Ageing alone (for example welding T4 material and then artificially ageing to T6) helps the heat-affected zone recover somewhat but does not fully harden the fusion zone. For predictable results the procedure should include solution treatment, rapid quench and ageing, qualified on test coupons before production.
Typical MIG and TIG settings for ER4643
These figures are starting points for flat-position welds with pure argon. Adjust for joint design, position, equipment and plate thickness, and fix the final values through procedure qualification. Argon-helium mixes increase heat input and penetration on thick sections.
| Wire diameter | Current (DCEP) | Arc voltage | Travel speed | Argon flow |
|---|---|---|---|---|
| 0.8 mm (0.030 in) | 60 – 175 A | 15 – 24 V | 0.6 – 1.1 m/min | 12 – 14 L/min |
| 0.9 mm (0.035 in) | 70 – 185 A | 15 – 27 V | 0.6 – 1.0 m/min | 14 – 17 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 |
| 2.4 mm (3/32 in) | 275 – 400 A | 26 – 31 V | 0.35 – 0.5 m/min | 28 – 35 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 |
TIG values assume AC with a pure or zirconiated tungsten and argon at about 10 – 12 L/min; inverter machines with balance control often need less current.
ER4643 sizes, spools and rod lengths
Supply range
- MIG wire diameters
- 0.8, 0.9, 1.0, 1.2, 1.6 mm (0.030, 0.035, 3/64, 1/16 in); 2.4 mm on request
- MIG packages
- 100 mm (4 in) and 200 mm (8 in) spools, 300 mm (12 in) spools, drums for robotic lines
- TIG rod diameters
- 1.6, 2.4, 3.2, 4.0, 4.8 mm (1/16 – 3/16 in); larger on request
- TIG rod length
- 914 mm (36 in) or 1000 mm straight lengths, end-stamped with the classification
- Packing
- Sealed plastic with desiccant, cartons on export pallets
- Documents
- Certificate of conformance to AWS A5.10 with lot chemistry; EN 10204 3.1 on request
ER4643 compared with ER4043, ER4943 and ER5356
| Point | ER4643 | ER4043 | ER4943 | ER5356 |
|---|---|---|---|---|
| Main alloying | 4 % Si + 0.2 % Mg | 5 % Si | 5.5 % Si + 0.4 % Mg | 5 % Mg |
| Responds to post-weld heat treatment | Yes, by design | Only through dilution | Yes | No (non-heat-treatable) |
| As-welded strength | Similar to 4043 | Lowest of the four | Higher than 4043 | Highest shear strength |
| Hot-cracking resistance on 6xxx | Very good | Very good | Very good | Good with correct dilution |
| Colour match after anodising | Grey | Dark grey | Grey | Good match |
| Service above 65 °C | Suitable | Suitable | Suitable | Not recommended |
| Typical choice for | Heavy 6xxx parts heat-treated after welding | General 6xxx and castings | As-welded 6xxx needing more strength | 5xxx structures, marine |
A simple rule: if the assembly goes through a solution heat-treatment furnace after welding, consider ER4643; if it stays as-welded and needs more strength than ER4043, look at ER4943; if the base metal is a 5xxx alloy, use ER5356 or ER5183.
Where ER4643 is used
Bicycle and sports frames
Many 6061 frames are welded in T4, then solution-treated and aged. ER4643 helps the joints harden fully along with the tubes.
Rail and vehicle structures
Selected 6xxx assemblies that are re-heat-treated, where the fusion zone must not limit fatigue or static strength.
Heavy-section repair
Rebuilding thick 6xxx parts that will be heat-treated afterwards, such as tooling plates and large fittings.
Castings to wrought alloys
Some A356 or 357 castings welded to 6xxx parts that are heat-treated as an assembly.
Pressure and process equipment
Where codes call for an Al-Si filler and heat treatment is specified in the procedure.
Storage, preparation and common mistakes
- Keep it dry: store spools sealed, at stable temperature, and return part-used spools to the bag. Hydrated oxide on wire is a common cause of porosity.
- Clean the joint: degrease first, then brush with a dedicated stainless brush just before welding.
- Use the right feed kit: U-groove drive rolls, a polymer liner and contact tips sized for aluminium; a push-pull or spool gun for soft small-diameter wire.
- Do not expect miracles as-welded: ER4643 only pays off when the procedure includes solution treatment and ageing.
- Qualify the full sequence: test coupons should go through the same weld, solution treatment, quench and ageing as the production part.
- Watch distortion: quenching welded assemblies can move them; plan fixtures or straightening.
How to order ER4643 from Metline
- SpecifyClassification (ER4643 wire or R4643 rod), standard (AWS A5.10 or EN ISO 18273), diameter, package and quantity.
- Describe the jobBase alloy and temper, thickness, process and the planned heat treatment, so we can confirm the filler fits.
- QuoteWe confirm availability, certification and delivery on EXW, FOB, CIF or DAP terms.
- ShipMoisture-protected packing with lot labels and certificate of conformance, by sea or air.
References and standards
- AWS A5.10/A5.10M – Welding Consumables: Wires and Rods for Aluminum and Aluminum-Alloys
- EN ISO 18273 – Welding consumables: wire electrodes, wires and rods for welding of aluminium and aluminium alloys
- AWS D1.2/D1.2M – Structural Welding Code: Aluminum
- ASM Alloy Digest Al-324 – Weld filler wire 4643 (silicon-magnesium)
- SAE AMS 4189 – Aluminum alloy welding wire 4643 (cancelled; superseded by AWS A5.10 ER4643)
ER4643 aluminium (aluminum) welding wire: FAQs
What is the difference between ER4643 and ER4043?
ER4643 has less silicon (3.6 – 4.6 % against 4.5 – 6.0 %) and adds 0.10 – 0.30 % magnesium. The magnesium lets the weld metal harden during post-weld solution treatment and ageing, even in thick joints where little base metal mixes into the weld.
Is ER4643 worth using if I do not heat-treat after welding?
Usually not. As-welded, joint strength is controlled by the heat-affected zone and ER4643 performs much like ER4043. Choose ER4943 if you need higher as-welded strength from a silicon-type filler.
Can ER4643 be used on 6061 and 6063?
Yes. It was developed for 6xxx alloys such as 6061, 6063, 6082 and 6351, especially heavy sections that are solution heat-treated and aged after welding.
Does AMS 4189 still apply?
AMS 4189 was cancelled and replaced by the AWS A5.10 ER4643 classification. Older drawings that cite AMS 4189 are normally satisfied by ER4643 certified to AWS A5.10; confirm with your customer or inspector.
What is the difference between ER4643 and R4643?
The chemistry is identical. ER4643 is spooled wire used as the electrode in MIG welding; R4643 is straight cut rod fed by hand in TIG welding.
Will ER4643 welds match anodised parts?
No. Like other silicon-bearing fillers, ER4643 welds turn grey when anodised. If colour match matters and the joint stays as-welded, a 5xxx filler is the usual choice.
Need ER4643 wire or rod?
Send the diameter, package, quantity, base alloy and destination. We reply with availability, certification and a delivered quote.
