What Are the Key Precautions for Die-Casting Processing of Aluminum Parts?

Aluminum die casting is widely used in automotive, eletrônica, and aerospace industries due to its lightweight, alta resistência, e custo-efetividade. No entanto, the process involves multiple complex links—from material selection to post-treatment—and any oversight can lead to defects like porosity, rachaduras, or undercasting. To ensure stable production and high-quality aluminum parts, manufacturers must master critical precautions throughout the workflow. This article systematically breaks down key considerations in each stage, providing actionable guidance to avoid common pitfalls.

1. Seleção de material: Match Alloy to Part Function

Choosing the right aluminum alloy is the foundation of successful die casting. Different alloys have unique properties, and mismatching alloy to part function can cause premature failure or performance issues. Abaixo está um comparative table of commonly used aluminum alloys and their application precautions:

Core Tip: For parts with mixed requirements (Por exemplo, Resistência ao calor + resistência), conduct small-batch trials first. Por exemplo, an EV battery frame may need A356 for heat resistance but require adjusting copper content to enhance strength—test 50-100 samples to verify performance.

2. Design de molde & Fabricação: Avoid Structural Hidden Dangers

Mold design directly affects part quality and production efficiency. Poor mold structure often leads to defects like flash, encolhimento, or difficult ejection. The following are key precautions organized by mold component:

2.1 Shrinkage Compensation: Ensure Dimensional Accuracy

Aluminum alloys shrink during solidification—ignoring this leads to undersized parts. Siga estas regras:

• General Compensation: Apply an average shrinkage rate of 1.6%-1.8% for most aluminum parts. Por exemplo, a part with a designed length of 100mm should have a mold cavity length of 101.6-101.8mm.
• Zonal Compensation: For complex structures (Por exemplo, costelas, bosses), adjust compensation rates:
• Adicionar 0.2milímetros to rib thickness (Por exemplo, 3mm rib → 3.2mm mold cavity) to prevent shrinkage-induced thinning.
• Reduce compensation to 1.2%-1.4% Para áreas de paredes finas (<2milímetros) to avoid overfilling.

2.2 Gating & Sistemas de escape: Prevent Porosity and Undercasting

• Gating System:
• The cross-sectional area of the main runner should be 15%-20% maior than the gate sleeve entrance to reduce flow resistance. Por exemplo, if the gate sleeve entrance is 20mm², the main runner should be 23-24mm².
• Inner gate thickness = 40%-60% of part wall thickness (typical 3-5mm). A 5mm thick part needs an inner gate of 2-3mm—too thin causes premature solidification; too thick leads to excess material.
• Exhaust System:
• For deep-cavity parts (depth >50mm), usar three-stage exhaust (main exhaust groove + auxiliary exhaust needle + vacuum valve) to fully remove trapped air.
• Total exhaust cross-sectional area ≥ 1/3 of inner gate area. If the inner gate is 30mm², exhaust area should be ≥10mm² to avoid air entrainment.

2.3 Mecanismo de ejeção: Protect Part Integrity

• Ejector Pin Spacing: ≤Φ8mm for general parts; ≤Φ5mm for thin-walled parts (<1.5milímetros) to prevent deformation. For a 100mm×100mm thin-walled cover, arrange at least 9 pinos ejetores (3×3 grid).
• Ejection Force Calculation: Conta expansion pressure (aluminum expands 2-3% Quando aquecido) e coeficiente de atrito (0.15-0.2 for aluminum-mold contact). Use a fórmula: Força de ejeção (KN) = Part weight (kg) × 8-10 (fator de segurança).

3. Process Parameter Control: Stabilize Production Quality

Aluminum die casting is sensitive to process parameters—small deviations can cause major defects. Focus on the following critical parameters with specific control ranges:

3.1 Controle de temperatura: Balance Fluidity and Solidification

3.2 Injeção & Pressurization: Avoid Turbulence and Shrinkage

• Injection Speed: 0.5-1.2EM. Para peças complexas (Por exemplo, 5G filter cavities with narrow grooves), usar stepped speed increase (0.5m/s → 0.8m/s → 1.0m/s) to prevent splashing.
• Pressurization Build-Up Time: 3-8 segundos. Extend to 10 segundos for stress-bearing parts (Por exemplo, automotive suspension brackets) to ensure full compaction.
• Processos especiais:
• Elenco de matriz de vácuo: Cavity vacuum >90kPa reduces porosity to <1%—suitable for pressure-resistant parts (Por exemplo, Cilindros hidráulicos).
• Fundição sob pressão oxigenada: Inject pure oxygen into the cavity to reduce inclusions by 70%—ideal for parts requiring high surface quality (Por exemplo, quadros de smartphone).

3.3 Contenção & Resfriamento: Ensure Dimensional Stability

• Tempo de espera: 10-25 segundos. Adicionar 2 seconds for every 1mm increase in gate thickness. A 5mm gate needs 18-20 seconds of holding time to compensate for shrinkage.
• Tempo de resfriamento: 8-20 segundos. Use cooling inserts (Por exemplo, copper inserts with water channels) to shorten cooling time by 30% para peças de paredes grossas, melhorando a eficiência da produção.

4. Defect Prevention & Response: Troubleshoot Common Issues

Mesmo com controle rigoroso, defects may occur. The table below lists typical defects, their causes, and immediate solutions:

5. Pós-tratamento & Controle de qualidade: Ensure Final Performance

Post-treatment and inspection are the last lines of defense against defective parts. Follow these precautions:

5.1 Post-Treatment Processes

• Usinagem de precisão:
• CNC milling allowance: 0.3-0.5mm per side (0.8mm for complex surfaces with curved shapes).
• Usar PCD (polycrystalline diamond) inserts to improve tool life by 3-5 times compared to carbide inserts—critical for high-volume production.
• Surface Strengthening:
• Micro-arc Oxidation: Achieve film thickness of 15-25μm; ensure salt spray test >2000 hours for corrosion-resistant parts (Por exemplo, componentes marinhos).
• Composite Coating (Ni-P/PTFE): Apply double coating for parts requiring wear resistance (Por exemplo, rolamentos deslizantes) to reduce friction coefficient by 40%.
• Defect Repair:
• Argon arc welding: Current ≤90A, interlayer temperature <150°C to avoid thermal cracks.
• Metal penetrant impregnation: Use low-viscosity impregnants for small pores (<0.1milímetros) to ensure leak tightness.

5.2 Quality Inspection Standards

• Inspeção dimensional: Use CMM (Máquina de medição de coordenadas) for key dimensions (CTQ, Critical to Quality) with tolerance ≤±0.15mm.
• Desempenho mecânico: Tensile test requires σb≥320MPa, δ≥2% for structural parts.
• Leak Detection: Helium mass spectrometry ensures leakage rate <1×10⁻⁶mbar·L/s for pressure-bearing parts (Por exemplo, EV water-cooled plates).
• Defeitos Internos: X-ray real-time imaging meets ASTM E446 Nível B to detect internal porosity and inclusions.

6. Yigu Technology’s Perspective on Aluminum Die-Casting Precautions

Na tecnologia Yigu, we believe that aluminum die-casting success lies in “controle preciso + systematic prevention.” Many manufacturers focus only on process parameters but ignore early-stage DFM (Design para fabricação) reviews—for example, designing parts with sharp corners that inevitably cause cracks. We recommend establishing a cross-departmental DFM team (incluindo design, mofo, and process engineers) to identify manufacturability issues before mold production.

Para produção em massa, we advocate Spc (Controle de processo estatístico) to monitor key parameters (temperatura do molde, velocidade de injeção, tempo de resfriamento) in real time—this reduces defect rates by 40-50% compared to manual monitoring. Adicionalmente, for high-end parts like aerospace servo valve housings, combining vacuum die-casting with selective laser cladding (for local reinforcement) balances precision and performance. By integrating these precautions into every stage, manufacturers can achieve a yield rate of over 98% for aluminum die-cast parts.

7. Perguntas frequentes: Common Questions About Aluminum Die-Casting Precautions

1º trimestre: Can I reuse aluminum scrap from die casting, and what precautions should I take?

Sim, but the proportion of return material should be controlled within 30% to avoid increasing impurity content. Before reuse, remove surface oxides and oil stains by shot blasting; preheat scrap to 150-200°C to eliminate moisture. Mixing return material with new ingots in a 3:7 ratio maintains alloy performance stability.

2º trimestre: How to prevent mold sticking during aluminum die casting?

Primeiro, ensure mold preheating temperature is ≥180°C (cold molds increase adhesion). Segundo, use high-temperature resistant release agents (Por exemplo, à base de grafite) and apply a uniform film (espessura 5-10μm) to the cavity. Terceiro, polish the mold cavity to Ra≤0.8μm—rough surfaces increase friction and sticking risk.

3º trimestre: What are the precautions for packaging and transporting aluminum die-cast parts?

• Anti-Rust Protection: Impregnate with LZ-301 anti-rust oil (oil film thickness 3-5μm) to prevent oxidation during storage.
• Physical Protection: Use pearl cotton for corner protection and EPE foam padding between layers to avoid collision scratches.
• Environmental Control: Maintain relative humidity ≤60% and temperature -20~45°C during transportation—avoid extreme temperatures that cause thermal deformation.