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

Aluminum die casting is widely used in automotive, Электроника, and aerospace industries due to its lightweight, Высокая сила, и экономическая эффективность. Однако, the process involves multiple complex links—from material selection to post-treatment—and any oversight can lead to defects like porosity, трещины, 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. Выбор материала: 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. Ниже приведен comparative table of commonly used aluminum alloys and their application precautions:

Core Tip: For parts with mixed requirements (НАПРИМЕР., теплостойкость + стойкость), conduct small-batch trials first. Например, 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. Дизайн плесени & Производство: Avoid Structural Hidden Dangers

Mold design directly affects part quality and production efficiency. Poor mold structure often leads to defects like flash, усадка, 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. Следуйте этим правилам:

• General Compensation: Apply an average shrinkage rate of 1.6%-1.8% for most aluminum parts. Например, a part with a designed length of 100mm should have a mold cavity length of 101.6-101.8mm.
• Zonal Compensation: For complex structures (НАПРИМЕР., ребра, bosses), adjust compensation rates:
• Добавлять 0.2мм to rib thickness (НАПРИМЕР., 3mm rib → 3.2mm mold cavity) to prevent shrinkage-induced thinning.
• Reduce compensation to 1.2%-1.4% для тонкостенных помещений (<2мм) to avoid overfilling.

2.2 Gating & Выхлопные системы: Prevent Porosity and Undercasting

• Gating System:
• The cross-sectional area of the main runner should be 15%-20% более крупный than the gate sleeve entrance to reduce flow resistance. Например, 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), использовать 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 Механизм выброса: Protect Part Integrity

• Ejector Pin Spacing: ≤Φ8mm for general parts; ≤Φ5mm for thin-walled parts (<1.5мм) to prevent deformation. For a 100mm×100mm thin-walled cover, arrange at least 9 выбросы (3×3 grid).
• Ejection Force Calculation: Счет для expansion pressure (aluminum expands 2-3% При нагревании) и friction coefficient (0.15-0.2 for aluminum-mold contact). Use the formula: Сила выброса (кН) = Part weight (кг) × 8-10 (safety factor).

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 Контроль температуры: Balance Fluidity and Solidification

3.2 Инъекция & Pressurization: Avoid Turbulence and Shrinkage

• Injection Speed: 0.5-1.2РС. Для сложных частей (НАПРИМЕР., 5G filter cavities with narrow grooves), использовать stepped speed increase (0.5m/s → 0.8m/s → 1.0m/s) to prevent splashing.
• Pressurization Build-Up Time: 3-8 секунды. Extend to 10 секунды for stress-bearing parts (НАПРИМЕР., automotive suspension brackets) to ensure full compaction.
• Специальные процессы:
• Вакуумный кастинг: Cavity vacuum >90kPa reduces porosity to <1%—suitable for pressure-resistant parts (НАПРИМЕР., Гидравлические цилиндры).
• Oxygenated Die Casting: Inject pure oxygen into the cavity to reduce inclusions by 70%—ideal for parts requiring high surface quality (НАПРИМЕР., Рамки смартфонов).

3.3 Держащий & Охлаждение: Ensure Dimensional Stability

• Время выдержки: 10-25 секунды. Добавлять 2 seconds for every 1mm increase in gate thickness. A 5mm gate needs 18-20 seconds of holding time to compensate for shrinkage.
• Время охлаждения: 8-20 секунды. Use cooling inserts (НАПРИМЕР., copper inserts with water channels) to shorten cooling time by 30% Для толстостенных частей, Повышение эффективности производства.

4. Defect Prevention & Response: Troubleshoot Common Issues

Даже при строгом контроле, defects may occur. The table below lists typical defects, their causes, and immediate solutions:

5. После лечения & Контроль качества: Ensure Final Performance

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

5.1 Post-Treatment Processes

• Точная обработка:
• CNC milling allowance: 0.3-0.5mm per side (0.8mm for complex surfaces with curved shapes).
• Использовать ПКД (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 (НАПРИМЕР., Морские компоненты).
• Composite Coating (Ni-P/PTFE): Apply double coating for parts requiring wear resistance (НАПРИМЕР., sliding bearings) 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 (<0.1мм) to ensure leak tightness.

5.2 Quality Inspection Standards

• Проверка размерных: Use CMM (Координировать измерительную машину) for key dimensions (CTQ, Critical to Quality) with tolerance ≤±0.15mm.
• Механические характеристики: 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 (НАПРИМЕР., EV water-cooled plates).
• Internal Defects: X-ray real-time imaging meets ASTM E446 Level B to detect internal porosity and inclusions.

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

В Yigu Technology, we believe that aluminum die-casting success lies in “Точный контроль + systematic prevention.” Many manufacturers focus only on process parameters but ignore early-stage DFM (Дизайн для производства) reviews—for example, designing parts with sharp corners that inevitably cause cracks. We recommend establishing a cross-departmental DFM team (в том числе дизайн, форма, and process engineers) to identify manufacturability issues before mold production.

Для массового производства, we advocate Спк (Статистический управление процессом) to monitor key parameters (температура формы, скорость впрыска, время охлаждения) in real time—this reduces defect rates by 40-50% compared to manual monitoring. Кроме того, 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. Часто задаваемые вопросы: Common Questions About Aluminum Die-Casting Precautions

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

Да, 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.

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

Первый, ensure mold preheating temperature is ≥180°C (cold molds increase adhesion). Второй, use high-temperature resistant release agents (НАПРИМЕР., graphite-based) and apply a uniform film (thickness 5-10μm) to the cavity. Третий, polish the mold cavity to Ra≤0.8μm—rough surfaces increase friction and sticking risk.

Q3: 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.