Deep Dive into EV Battery Tray Manufacturing: The Trilemma of Safety, Precision, and Efficiency

In the three-electric system of new energy vehicles (NEVs), the battery tray is often the most overlooked yet safety-critical core component. As the “chassis backbone” carrying hundreds of kilograms of battery packs, it must not only meet multiple functional requirements such as crash protection, IP67/IP68 sealing, and thermal management, but also continuously “slim down” amid the lightweight trend — behind this lies a systematic interplay of materials science, welding processes, precision machining, and surface treatment technologies.

1. Material System Evolution: The Multi-Route Competition Dominated by Aluminum Alloys

Currently, battery tray materials have formed a landscape of “aluminum alloys as the mainstay, composite materials as supplements, and steel-aluminum hybrids as alternatives”. 6-series aluminum alloys (6061-T6, 6063) account for over 80% of market share, thanks to their yield strength above 300MPa, excellent corrosion resistance, and 100% recyclability.

Comparison of Mainstream Material Solutions:

Material Type	Representative Grade	Density (g/cm³)	Yield Strength (MPa)	Applicable Process	Cost Index
Wrought Aluminum Alloy	6061-T6	2.7	≥276	Extrusion + FSW	1.0
Die-Cast Aluminum Alloy	AlSi10MnMg	2.68	≥240	Integrated Die Casting	1.3
Long Glass Fiber Reinforced Plastic	LFT-PP/PA6	1.2-1.5	≥180	Compression Molding	0.8
Carbon Fiber Composite	CFRP	1.6	≥500	HP-RTM	3.5

Notably, integrated die-casting technology is penetrating the battery tray field. Tesla’s 4680 battery pack uses an integrated die-cast tray that reduces the number of components from 70+ to 2-3 and cuts welding length by over 60%, but equipment investment runs into hundreds of millions of yuan, and porosity and flatness control of large die-castings remain industry challenges.

2. Engineering Challenges of Three Major Manufacturing Process Routes

2.1 Extruded Profiles + Friction Stir Welding (FSW): Current Mainstream Solution

This is currently the most mature route for mass production, formed by splicing multiple extruded aluminum profiles and welding them with FSW. Its core advantages include:

Profile wall thickness accuracy can be controlled within ±0.2mm, meeting precision requirements for liquid cooling plate channels
FSW has a small heat-affected zone, with deformation controllable within 0.1mm
Relatively low equipment investment, suitable for multi-model mixed production lines

However, the pain points of this route are equally prominent: the total weld length of a single tray can reach 8-15 meters, and any false welding or pinhole may cause coolant leakage; flatness deviation exceeding 0.2mm after welding can lead to sealing failure, and subsequent CNC finishing requires significant material removal with a single-piece machining cycle of 15-20 minutes.

2.2 Stamping and Welding Route: Low-Cost Option for Steel Trays

Early LFP battery packs mostly used steel stamped trays, costing only 60% of aluminum trays but weighing over 30% more. As 800V high-voltage platforms increase lightweight requirements, steel trays are gradually exiting the passenger vehicle market, retaining applications only in commercial vehicles and energy storage.

2.3 Integrated Die-Casting Route: Future Trend with High Barriers

Using die-casting machines with clamping forces above 3500T for one-step forming reduces weld count by 90% and compresses production cycle to 2 minutes per piece. However, this process faces three major challenges:

Filling uniformity of large castings is difficult to guarantee, with distal porosity generally exceeding 5%
Deformation during heat treatment can reach 2-3mm, resulting in extremely high subsequent straightening costs
Mold costs exceed 20 million yuan, suitable only for blockbuster models with annual production above 100,000 units

3. The Overlooked Battlefield: Surface Treatment Determines Welding Yield

Throughout the entire battery tray manufacturing process, surface treatment is often the “invisible bottleneck” determining yield. The naturally formed 5-15μm oxide film (Al₂O₃) on aluminum surfaces has a melting point of 2072°C, far higher than the 660°C melting point of the aluminum substrate — if not thoroughly removed before welding, the oxide film will be entrained into the molten pool during welding, forming pores and slag inclusions, directly causing:

Surging weld porosity: Weld porosity on uncleaned surfaces is typically 5%-10%, far exceeding the 2% threshold required for IP68 sealing
Reduced joint strength: Oxide film inclusions reduce welded joint strength by 20%-30%, posing cracking risks under vibration conditions
False welding and missing welding risks: Oxide films cause unstable laser reflectivity and inconsistent penetration depth

Traditional surface treatment processes are facing increasingly severe challenges:

Chemical pickling: Although it removes oxide films, waste liquid treatment is costly with high environmental pressure, and it easily causes intergranular corrosion of aluminum alloys
Mechanical grinding: Manual grinding has poor consistency, complex rib positions and weld dead corners are difficult to reach, and it also causes abrasive embedding and surface scratches
Sandblasting: Impact deformation is large, which damages sealing surface flatness, and dust pollution is severe, making it unsuitable for precision components

More problematically, battery tray structures are becoming increasingly complex — dozens of accessories such as liquid cooling channels, mounting studs, sensor seats, and harness brackets are integrated on the tray, with dense ribs and numerous corners, creating more and more “blind spots” for traditional cleaning methods. Data from a leading battery manufacturer shows that welding defects caused by improper surface treatment account for over 35% of total defects, making it the number one yield killer during production ramp-up.

4. Technological Breakthrough: Laser Cleaning Redefines Surface Treatment Standards

As traditional processes become unsustainable under the triple pressures of precision, efficiency, and environmental protection, green surface treatment technologies represented by pulsed laser cleaning are rapidly penetrating battery tray manufacturing lines.

Compared with traditional cleaning methods, the technical advantages of laser cleaning precisely address the manufacturing pain points of battery trays:

1. Micron-level precision control, truly achieving “selective cleaning” High-power pulsed fiber lasers vaporize contaminants in milliseconds through photothermal effects, with the heat-affected zone controllable within 0.05mm — thoroughly removing oxide films, oil stains, and release agents in welding areas while completely retaining anodized layers or zinc coatings in non-welding areas, solving the contradictions of “over-cleaning” and “under-cleaning” in traditional processes.

Data shows that on laser-cleaned aluminum surfaces, laser welding porosity can be reduced from 5%-10% to below 2%, and joint tensile strength increased by over 20%, directly raising welding yield from 92% to the 99.5% level.

2. Non-contact processing, perfectly adapting to complex structures Laser cleaning can reach any geometric position through optical path guidance. Whether it’s weld seam cleaning after friction stir welding, precision degreasing of sealing surfaces, or dead corners such as bolt holes and reinforcing ribs, it achieves uniform cleaning results without tool wear or contact deformation issues associated with mechanical grinding.

3. Green and environmentally friendly, matching automated production line takt time Laser cleaning uses no consumables, produces no waste liquid or dust emissions, and can be directly integrated into welding robot production lines to achieve integrated “cleaning-welding” operations. Single-piece cleaning cycle is controlled at 60-90 seconds, fully meeting the mass production takt of 2-3 pieces per minute.

From engineering practice, 300W pulsed laser cleaning equipment has become the standard configuration for battery tray pre-weld treatment: for 6061/6063 aluminum alloys, it can stably remove 5-20μm thick natural oxide films, with post-cleaning surface roughness controlled at Ra1.6-3.2μm, exactly within the optimal process window for laser welding. Some leading manufacturers even combine laser cleaning with laser texturing, constructing micro-nano structured surfaces while removing oxide films, increasing structural adhesive bonding strength by over 30% and further optimizing the connection reliability of battery modules.

5. Conclusion: Manufacturing Competitiveness in the Details

The technological evolution of battery trays is essentially a microcosm of NEV manufacturing progressing from “functional” to “user-friendly” to “reliable”. While the industry generally focuses on visible indicators such as battery energy density and fast charging speed, what truly determines product reputation and safety bottom line are often these invisible details: 0.1mm flatness control on trays, 2% weld porosity adherence, and thorough removal of 5μm oxide films.

From material iteration to process innovation, from welding technology to surface treatment, every technological breakthrough in battery tray manufacturing ultimately points to the same goal: keeping hundreds of kilograms of power batteries safe throughout the vehicle’s entire lifecycle. The popularization of precision manufacturing technologies such as laser cleaning is helping China’s NEV industry chain build truly inimitable manufacturing competitiveness on these “invisible battlefields”.