Aluminum Welding Wire for EV Battery Trays & Enclosures
EV battery trays and lower battery enclosures are mostly welded into a frame from 6xxx aluminum extrusions, with some 5xxx plate, where the seams must both carry load and keep out water and dust while preventing coolant leakage. TGM keeps the common grades — ER4043, ER5356 and others — in stock, with wire offering smooth payoff, stable feeding and good batch-to-batch consistency, supporting dense, low-porosity seams and a steady cycle in high-volume continuous welding, with reliable lead times and continuous supply.
Common base metals and welds
The battery tray is the structural part carrying the battery modules — usually a frame built from extrusions, then welded to the base plate, cross-members and mounting brackets. It is both a load-bearing structure and a sealed enclosure: the seams must be leak-tight to achieve the water- and dust-protection rating and to prevent coolant leakage. The base-metal and service combinations most commonly seen on the floor are as follows:
- 6xxx-series extrusions (e.g. 6061, 6082): widely used for the tray frame, cross-members and floor profiles — adequate strength, heat-treatable, and the most common base metal for the tray frame, where the welds are mostly long straight seams and sealing seams.
- 5xxx-series plate (e.g. 5083, 5754): used on more heavily loaded areas or base-plate panels, with good strength retention after welding, often forming mixed joints with 6xxx extrusions.
- Sealing and density requirement: tray seams must be leak-tight, dense and low in porosity — pores or lack of fusion create leak paths that directly compromise the battery's water-, dust- and leak-protection, the core quality concern in tray welding.
- High volume and distortion control: trays are mostly high-volume repeat welding of similar joints, demanding a steady cycle; meanwhile the seams are concentrated and thermal distortion accumulates readily, so distortion must be controlled to maintain enclosure flatness and downstream assembly dimensions.
Which grade to use
Selecting the wire requires considering the alloy series of the base metal, the sealing and density requirement of the seam, and the loading on the joint. For battery trays, the choice usually comes down to the first two grades below, with ER5183 and ER4047 covering specific joints:
ER4043
An Al-Si wire with good weld-pool fluidity and low cracking tendency, suited to the many straight seams and sealing seams on 6xxx-extrusion trays — dense welds that readily form continuous, leak-free sealing beads, the primary grade for battery trays.
View datasheet → Alternate · load-bearing / 5xxxER5356
An Al-Mg wire with higher weld strength, suited to load-bearing areas of the tray and to welding 5xxx-series plate. Choose this grade where the joint has a higher strength requirement, or where the base metal is 5xxx plate.
View datasheet → Higher strength · 5083 plateER5183
An Al-Mg-Mn wire that gives higher as-welded strength than ER5356 when welded to 5083; the advantage comes from its higher manganese, not from more magnesium. Choose it where a tray design uses 5083 plate and the joint must match the as-welded strength of 5083, including 6xxx-to-5083 joints where the 5083 strength governs.
View datasheet → Alternative · Al-Si cast partsER4047
An Al-Si wire with about 12% Si, used as an alternative to ER4043 when better fluidity and a lower cracking or shrinkage tendency are wanted, and a common choice for welding Al-Si castings. Where a tray design welds a cast part such as A356 into a larger assembly, casting guidance lists ER4047 as the alternative to ER4043. There is no published guidance naming it as a standard filler for tray seams.
View datasheet →Selection approach: for the many straight seams and sealing seams on 6xxx-extrusion trays, ER4043 is the primary choice for its fluidity, low cracking tendency and dense welds; for load-bearing areas or 5xxx plate, ER5356 is the alternate for its higher weld strength. The final choice should also account for the specific base-metal combination, the welding procedure specification (WPS) and the drawing requirements — for assistance, you are welcome to share the details with our technical team to confirm the selection.
Three further points apply to mixed-alloy trays. First, where one side of the joint is a 5xxx alloy with more than about 2.5% Mg, such as 5083, use an Al-Mg filler (ER5356, or ER5183 where the 5083 strength governs) rather than an Al-Si filler such as ER4043: too much Mg2Si in an Al-Si weld reduces ductility and increases crack sensitivity. 5754, at about 2.6–3.6% Mg, sits above that threshold and is normally welded with ER5356. Second, ER5356's strength advantage matters most in fillet and lap welds loaded in shear, which usually fail in the weld metal; in 6061-T6 butt welds the softened heat-affected zone, not the filler, sets the joint strength. Third, for a cast Al-Si-Mg part such as A356 welded into a larger assembly, the usual guidance is an Al-Si filler, ER4043 first and ER4047 as the alternative; high-pressure die castings also need low gas content to be weldable (see below).
Practical welding notes
- Ensure sealing and weld density: sealing seams should be continuous, free of arc breaks and lack of fusion, with crater fill at the stop to avoid leak paths. The air-tightness and density of the seam directly determine the battery's water-, dust- and leak-protection — the core requirement in tray welding.
- Stable feeding for a continuous cycle: trays are mostly high-volume repeat welding, where feeding stability directly affects the continuous-welding cycle. TGM wire has a clean surface and uniform diameter, giving low feed resistance and a stable arc, reducing feed stoppages and helping high-volume continuous welding run steadily.
- Control distortion for assembly fit: tray seams are concentrated and thermal distortion accumulates readily. Plan the welding sequence sensibly, apply symmetrical and back-step welding, control heat input and interpass temperature, and use rigid fixturing to maintain enclosure flatness and assembly dimensions.
- Clean before welding, shield well: before welding, thoroughly remove the oxide film, oil and moisture, and shield with pure argon or an argon-helium mixture to reduce porosity and improve weld density — the fewer the pores, the more reliable the sealing seam, so this step must be carried out rigorously.
Leak-tight welds and the leak test
Battery housings must keep out moisture, and many packs are specified to IP67, meaning no harmful water entry at 1 m depth for 30 minutes. Production packs are commonly screened by air pressure decay, with helium leak testing where higher sensitivity is needed. Both methods look for the same thing: a continuous path through the seam. In an arc-welded seam, porosity or incomplete fusion can create that path, for example where a bead restarts, where beads meet or at the root. A seam with incomplete fusion may also hold at a light test pressure and open later, so weld soundness has to be built in rather than inspected in.
Porosity in aluminum comes mainly from hydrogen, which dissolves readily in the molten pool but much less in solid aluminum, so it forms pores as the weld solidifies. Its sources are moisture, hydrocarbons (oil, grease, lubricant) and hydrated oxide on the base metal or wire, so most controls sit before the arc is struck:
- Cleaning order: degrease with solvent first, then brush with a stainless-steel brush kept for aluminum only, and weld soon after cleaning.
- Wire condition: store filler wire clean and dry, including opened spools.
- Gas coverage: keep the gas supply dry and leak-free; TWI recommends a dew point preferably below −50 °C at the torch.
- Starts, stops and craters: overlap each restart onto sound weld metal, avoid placing stops at seam intersections, and fill every crater.
For a full checklist, see the guide to aluminum weld porosity.
Mixed joining on one tray: MIG, FSW and cast parts
A single tray often combines several joining methods. Friction stir welding (FSW) is widely used for the long, leak-tight seams between extruded floor profiles; it is a solid-state process and uses no filler wire. MIG, including pulsed MIG, is used on frames and more complex joints, and TIG is commonly used for short seams and repairs, as in general aluminum fabrication. Some designs also combine extruded profiles with die-cast components. High-pressure die castings are a special case for arc welding: gas trapped during casting can cause porosity or blow-outs when the arc reaches it, so weldable castings need low gas content, for example from vacuum die casting, and a qualified procedure.
Two effects apply to every process. Welding heat softens the heat-affected zone of heat-treated 6xxx extrusions, and transverse butt welds typically fail there regardless of filler. For 6061-T6, typical tensile strength is about 310 MPa before welding, against an AWS D1.2 as-welded minimum of about 165 MPa; that figure applies to 6061-T6 only. FSW also leaves a softened zone. Low heat input limits the loss, and only a full post-weld heat treatment recovers a substantial part of it. Distortion is the second effect: aluminum expands about twice as much as steel and shrinks about 6% by volume on solidification, and even FSW can distort long seams. Alongside sequencing and fixturing, avoid over-welding and preset parts.
Symptom, cause and corrective action
The table below covers defects that commonly arise in the arc-welded seams of a tray. It is a starting point for investigation; the qualified WPS and the drawing remain the reference.
| Symptom | Likely cause | Corrective action |
|---|---|---|
| Porosity in the seam, often worst at starts and stops | Hydrogen from moisture, oil or hydrated oxide on the joint or wire; damp or leaking gas supply; disturbed gas coverage | Degrease, then stainless-brush the joint; keep wire clean and dry; check that the gas line is dry and leak-free; see the porosity guide for the full check sequence |
| Leak found where seams cross or meet | Incomplete fusion or porosity at a restart, a bead overlap or a stop placed on the intersection | Plan the sequence so stops fall away from intersections; overlap restarts onto sound weld metal; fill the crater |
| Crater crack at the end of a bead | Shrinkage at the termination on crack-sensitive 6xxx weld chemistry, with too little filler added | Fill the crater; on 6xxx joints ER4043 is less prone to crater cracking than ER5356 |
| Tray out of flatness after welding | Heat accumulated along long seams; aluminum's high expansion and solidification shrinkage; oversized welds | Weld to drawing size without over-welding; use lower heat input such as pulsed MIG; balanced and back-step sequences; preset and clamp the parts |
| Cracking or blow-outs at a casting-to-extrusion joint | Filler not matched to the Al-Si casting, or gas trapped in a high-pressure die casting | Use an Al-Si filler, ER4043 first or ER4047 as the alternative; specify castings with low gas content; qualify the procedure on representative parts |
Need help with selection?
Our selection guide matches you to the appropriate TGM grade by alloy series, the seam's sealing and density requirements, and joint loading. For a specific battery-tray project, you are welcome to contact our technical team directly — we can provide grade recommendations, help determine the WPS direction, and arrange on-site welding technical sessions as needed.
Further reading: for the troubleshooting sequence when porosity appears, pre-weld cleaning practice and shielding-gas checks, see the guide to aluminum weld porosity.
Frequently asked questions
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