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As the global new energy vehicle (NEV) industry enters the large-scale development phase, demand for core housing components in electric drive systems and power battery packs is growing rapidly. Motor housings and battery pack housingsare critical structural parts of NEV powertrains; their quality directly impacts vehicle safety, reliability, and service life. For procurement professionals in the new energy sector, establishing a systematic procurement checklist for low-Pressure Castings is fundamental to ensuring supply chain quality and cost control.

I. Why Low-Pressure Casting Is the Preferred Process for NEV Housings

In the manufacturing of motor and battery housings, process selection directly determines internal casting quality and service performance. Low-pressure casting (LPC)works by introducing dry compressed air (typically maintained at 20–100 kPa) into a sealed crucible, pushing molten metal upward through a riser tube and gating system to fill the mold cavity smoothly, followed by solidification under pressure. Compared to high-Pressure Die Casting, LPC features extremely stable mold filling with minimal turbulence and drastically reduced gas entrapment, resulting in far lower internal porosity than gravity castings.

NEV motor housings feature complex structures with average wall thicknesses of 4–5 mm, 6–7 mm spiral water-cooling channels in sidewalls, and embedded steel bearing bushings at the base. These complex castings integrating water cooling and structural load-bearing demand exceptional internal density and airtightness. LPC’s stable filling and pressure-solidification characteristics effectively eliminate shrinkage cavities and gas porosity, ensuring watertight performance under high pressure. For battery pack housings, large thin-walled structures (3–5 mm) also rely on LPC for complete filling and overall sealing integrity.

II. Core Procurement Elements: Material Specifications

Aluminum alloy selection is the primary technical decision in the procurement checklist. In NEV motor and battery housing applications, A356 (AlSi7Mg) alloy is the most widely used grade. With approximately 7% silicon content, it improves casting fluidity via eutectic phase formation, while magnesium provides precipitation strengthening (forming Mg₂Al₃ phases) to significantly enhance strength.

When defining material specifications, procurement teams must focus on the following alloy composition controls:

• · Silicon (Si): Maintain 6–12% for optimal filling and reduced shrinkage; >13% causes network silicon formation and reduced toughness
• · Magnesium (Mg): Recommended 0.25–3%; excess increases oxide film formation and porosity risks
• · Copper (Cu): Strictly control 0.5–3.2%; excess reduces fluidity and increases hot cracking tendency
• · Impurities: Zinc (Zn) <0.5%; total lead (Pb) + tin (Sn) ≤0.05%

For high-demand applications, A356-T6 Heat Treatment is the standard delivery condition. After T6 treatment (solution treatment at 535±5°C for 6–12 hours + artificial aging at 155°C for 3–6 hours), ZAlSi7MgA tensile strength increases from 200 MPa to 280 MPa. A356-T6 typically requires tensile strength ≥310 MPa.

III. Core Procurement Elements: Dimensional Accuracy & Tolerances

Dimensional accuracy is a key metric for evaluating low-pressure casting suppliers. Per GB/T 6414, critical mounting surfaces of NEV motor housings require CT6–CT8 precision, meaning minimal dimensional deviations on key mating surfaces to ensure assembly accuracy and NVH performance.

The procurement checklist must explicitly specify tolerance requirements for critical dimensions, particularly bearing mounting holes, end-face mating surfaces, and water-cooling channel interfaces. For wall thickness, premium housing castings require critical location tolerances within ±0.3 mm.

IV. Core Procurement Elements: Internal Quality & Mechanical Properties

Internal casting quality is a non-negotiable core acceptance metric. Per industry standards, premium low-pressure castings require internal porosity <2%. For high-pressure critical components (e.g., motor housing water channels), internal gas pore diameter ≤0.5 mm, with ≤1 pore per cm².

For mechanical properties, the checklist must specify tensile strength, yield strength, and elongation requirements. For test bars cast with the production or body sampling, A356.2 aluminum alloy after T6 treatment typically requires:

• · Tensile strength ≥275 MPa
• · Elongation ≥2%
• · Hardness ≥HBW 90

V. Core Procurement Elements: Airtightness Requirements

Airtightness is one of the most critical service performance indicators for NEV motor and battery housings. Motor housing water channels require absolute leak-proofing under operating pressure, typically tested at 600 kPa air pressure with 10-minute hold time and zero bubble leakage. Battery pack housings demand strict airtightness standards, usually passing 0.3–0.5 MPa air or water pressure tests.

The procurement checklist must define test methods, pressure values, hold times, and maximum allowable leakage rates. Example: Operating pressure 0.3–0.6 MPa, 5-minute hold, leakage ≤0.05 mL/min.

VI. Supplier Evaluation Criteria

When screening low-pressure casting suppliers, procurement teams should conduct systematic evaluations across the following dimensions:

1. Process Capability Matching

Verify suppliers possess mature, stable low-pressure casting expertise, not just proficiency in high-pressure die casting or gravity casting. LPC requires specialized technical capabilities in filling pressure control, riser tube design, and mold temperature management.

2. Quality System Certification

IATF 16949 certification is the basic entry requirement for mainstream NEV supply chains, demonstrating systematic capabilities in process control, continuous improvement, and defect prevention.

3. Full-Process Quality Control

Evaluate end-to-end inspection capabilities from raw material (e.g., national standard aluminum ingots) receipt to final shipment, including spectral analysis, X-ray inspection, and coordinate measuring machine (CMM) testing.

4. Mold Development & Maintenance

Molds are foundational to casting quality. Assess suppliers’ mold design, machining, and lifecycle management capabilities. For complex water-cooled motor housings, mold core-pulling structures and cooling system design directly determine forming quality and production efficiency.

5. Mass Production Experience & Delivery Track Record

Successful mass production experience in NEV motor or battery housings is a critical reliability indicator. Direct supply records with mainstream automakers or top-tier suppliers in the past three years effectively reduce procurement risks.

VII. Typical Procurement Project Reference

In practical procurement, typical specifications for NEV electric drive system aluminum castings include:

• · Motor Housing: ~8.6 kg, dimensions 240×186×184 mm
• · Reducer Housing: ~5.6 kg, dimensions 292×258×150 mm
• · Inverter Housing: ~2.0 kg, dimensions 331×289×59 mm

Annual procurement volume for single-model motor housings typically reaches 50,000–100,000 units.

Standard requirements include fluid tightness, porosity ≤5%, cleanliness ≤5 mg (per ZFN1132/ZFN1136), high-precision mating holes/surfaces, impregnation processing, concentricity control, and compliance with ELV and hazardous substance regulations. Suppliers must hold IATF 16949 certification and possess English communication capabilities.

VIII. Conclusion

Procuring low-pressure castings for NEV motor and battery housings is a technology-intensive task spanning materials science, casting processes, and quality inspection. A comprehensive procurement checklist must not only define technical parameters (material grades, dimensional tolerances, mechanical properties, airtightness) but also establish a scientific supplier evaluation framework covering process capability, quality systems, process control, mold development, and mass production experience.

As the NEV industry continues to evolve, low-pressure casting will see broader application in housing component manufacturing. Procurement professionals’ depth of understanding of relevant technical specifications and industry standards directly determines supply chain quality and cost competitiveness.

Media Contact
Company Name: Yongkang Hantai Industry & Trade Co., Ltd.
Email: Send Email
Country: China
Website: https://www.htprecisioncast.com/