What Are Principle and Process of Die Casting and How to Ensure Quality?

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Die casting is a cornerstone of high-volume metal manufacturing, especially for aluminum alloys, enabling the production of precise, complex parts used in automotive, Электроника, and hardware industries. Yet many engineers and manufacturers still have questions: What’s the core mechanism behind die casting? How do key processes affect part quality? And what parameters need strict control? This article breaks down the fundamental principle, Пошаговый процесс, оптимизация параметров, and quality control strategies of die casting—helping you master this efficient manufacturing technology.

1. Core Principle of Die Casting: How Does It Work?

В его сердце, die casting relies on high pressure and high speed to shape molten metal into precise parts. Ниже приведен 总分 structure explaining its key mechanisms, power sources, and critical conditions:

1.1 Fundamental Mechanism

Die casting’s core logic is “force-driven filling + pressure-assisted solidification”:

  • High-Speed Injection: Расплавленный металл (НАПРИМЕР., aluminum alloy heated to 660~720°C) is injected into a precision metal mold cavity at speeds of 5~50 m/s. This ensures the metal flows quickly to fill even tiny mold details (НАПРИМЕР., 0.5mm-thin walls or embossed patterns) before solidifying.
  • High-Pressure Holding: After the cavity is filled, the die-casting machine maintains a pressure of 20~150 MPa for 1~10 seconds. This compresses the molten metal, eliminates internal pores, and improves part density—critical for parts needing high strength (НАПРИМЕР., automotive engine brackets).

1.2 Power Source: The “Driving Force” of Die Casting

А hydraulic system of the die-casting machine is the key power provider:

  • It drives the injection punch to push molten metal into the mold cavity (generating injection force).
  • It controls mold clamping force (to keep the mold closed during high-pressure injection, preventing metal leakage).
  • Для крупномасштабного производства, modern machines use servo-hydraulic systems—reducing energy consumption by 30% compared to traditional hydraulic systems while ensuring stable pressure output.

1.3 Critical Conditions: Parameters That Determine Quality

Four core parameters must be strictly controlled to avoid defects like cold shuts (unfused metal seams) or shrinkage holes:

Critical ParameterОпределениеТипичный диапазон (Алюминиевый сплав)Влияние на качество
Molten Metal TemperatureTemperature of the metal liquid before injection.660~720°CСлишком низко: Poor fluidity → incomplete cavity filling. Слишком высоко: Grain coarsening → reduced part strength.
Температура формыTemperature of the metal mold before injection.180~ 250 ° C.Слишком низко: Metal solidifies too fast → cold shuts. Слишком высоко: Extended cooling time → low production efficiency.
Давление впрыскаPressure applied to push molten metal into the mold.20~ 150 МПаСлишком низко: Internal pores → low part density. Слишком высоко: Mold damage or metal overflow → scrap parts.
Filling TimeTime for molten metal to fill the entire mold cavity.0.01~0.1 seconds (тонкие детали); 0.1~0.5 seconds (thick parts)Too long: Metal solidifies mid-flow → incomplete filling. Too short: Turbulence → air entrapment (пористость).

2. Step-by-Step Process of Die Casting: From Raw Material to Finished Part

The die casting process is a linear, sequential workflow—each step directly impacts the final part quality. Ниже приведен time-axis breakdown принадлежащий 6 Основные шаги, with key actions and quality checks:

2.1 Шаг 1: Подготовка сырья & Таяние

  • Выбор материала: Choose die-casting-specific alloys (НАПРИМЕР., aluminum alloy ADC12 for high fluidity, 6061 for high strength) that meet part performance needs.
  • Таяние: Heat the alloy in a crucible furnace to 660~720°C. Use a temperature sensor to monitor in real time—avoid overheating.
  • Дегазация & Переработка: Add scouring agents (НАПРИМЕР., hexachloroethane) to remove hydrogen (a major cause of porosity) и примеси (НАПРИМЕР., slag). Для высоких частей, использовать vacuum degassing—reducing hydrogen content by 80%.

Проверка качества: Use a metal sample analyzer to verify alloy composition (ensure no excess impurities like lead or cadmium).

2.2 Шаг 2: Подготовка плесени & Предварительная обработка

  • Mold Installation: Fix the pre-machined metal mold (made of H13 hot-work steel for wear resistance) to the die-casting machine’s fixed and moving platens. Align the mold carefully to avoid metal leakage.
  • Mold Preheating: Heat the mold to 180~250°C using electric heaters or hot oil circulation. Use thermocouples to ensure uniform temperature (±10°C variation is acceptable).
  • Распыление разделительного агента: Spray a water-based or oil-based release agent on the mold cavity surface. Этот: 1) Prevents metal from sticking to the mold; 2) Extends mold life (by reducing thermal shock); 3) Improves part surface finish.

Проверка качества: Inspect the mold cavity for scratches or residue—repair scratches >0.1mm deep to avoid part surface defects.

2.3 Шаг 3: High-Pressure Injection

  • Metal Feeding: Pour molten aluminum alloy into the machine’s pressure chamber.
  • Injection Execution: The hydraulic system drives the punch to push the metal into the mold cavity at 5~50 m/s. Для сложных частей (НАПРИМЕР., Электронные корпуса), использовать two-stage injection: Низкая скорость (5~15 m/s) for the initial filling (reducing turbulence) и высокая скорость (15~50 m/s) for the final filling (ensuring detail replication).

Проверка качества: Monitor injection pressure in real time—abnormal spikes may indicate mold blockages (stop immediately to avoid machine damage).

2.4 Шаг 4: Удержание давления & Охлаждение

  • Удержание давления: Maintain 20~150 MPa pressure for 1~10 seconds. This compresses the molten metal, eliminating shrinkage holes and improving density.
  • Охлаждение: Let the part solidify inside the mold. Cooling time depends on part thickness: 5~15 seconds for thin parts (НАПРИМЕР., 1mm-thick phone casings) and 15~60 seconds for thick parts (НАПРИМЕР., 10mm-thick automotive brackets).

Проверка качества: Use an infrared thermometer to confirm part temperature drops to 300~400°C (алюминиевый сплав) before mold opening—too high a temperature causes part deformation.

2.5 Шаг 5: Открытие формы & Удаление части

  • Открытие формы: The die-casting machine’s hydraulic system pulls the moving platen back, opening the mold.
  • Выброс: An ejection mechanism (pins or plates) pushes the part out of the mold cavity. Для хрупких частей (НАПРИМЕР., thin-walled electronics parts), использовать multiple small ejection pins (instead of a single large pin) to avoid part cracking.
  • Обрезка: Remove excess material (gate, riser, вспышка) using a trimming press or CNC router. Для высоких частей, use laser trimming—achieving a cutting accuracy of ±0.05mm.

Проверка качества: Inspect the part for surface defects (НАПРИМЕР., нормы, царапины)—burrs >0.03mm must be removed.

2.6 Шаг 6: После лечения

Post-treatment enhances part performance and aesthetics. Choose processes based on part needs:

Post-Treatment TypeЦельСценарии приложения
Термическая обработка– Отжиг: Eliminate internal stress (prevents part warping). – Старение: Improve strength (НАПРИМЕР., 6061 alloy strength increases by 40% after T6 aging).Parts needing high strength (automotive drive shafts, аэрокосмические компоненты).
Поверхностная обработка– Песчаная обработка: Create a matte finish (hides minor surface defects). – Полировка: Achieve a mirror finish (decorative parts like furniture hardware). – Анодирование: Form a protective alumina film (corrosion resistance for outdoor parts). – Гальванизация: Add metal layers (chrome for wear resistance, nickel for decoration).– Песчаная обработка: Промышленные детали (насосные корпусы). – Полировка: Декоративные детали (Кран ручки). – Анодирование: Открытые светильники (street lamp brackets). – Гальванизация: Автомобильная отделка (Дверные ручки).
Проверка качества: For anodized parts, test corrosion resistance via a salt spray test (must pass 48 hours without rust).

3. Распространенные дефекты & Поиск неисправностей: How to Fix Issues

Even with strict process control, defects may occur. Ниже приведен разрыв причинно-следственной цепочки из 3 common defects and their solutions:

Common DefectПервопричинаTroubleshooting Solution
Cold Shuts (unfused metal seams on part surface)1. Molten metal temperature too low. 2. Mold temperature too low. 3. Filling time too long (metal solidifies mid-flow).1. Increase molten metal temperature by 10~20°C. 2. Raise mold temperature by 20~30°C. 3. Shorten filling time by 0.01~0.05 seconds (increase injection speed).
Пористость (tiny holes inside the part)1. Inadequate degassing (high hydrogen content). 2. Injection speed too fast (turbulence traps air). 3. Holding pressure too low (no pore compression).1. Extend degassing time by 2~5 minutes or use vacuum degassing. 2. Reduce injection speed by 5~10 m/s (use two-stage injection). 3. Increase holding pressure by 10~20 MPa.
Shrinkage Holes (large holes in thick part sections)1. Holding time too short (metal shrinks without pressure). 2. Cooling time too short (part not fully solidified). 3. Mold cavity design flawed (thick sections with no risers).1. Extend holding time by 1~3 seconds. 2. Increase cooling time by 5~10 seconds. 3. Modify mold design: Add risers (metal reservoirs) to thick sections.

Yigu Technology’s Perspective on Die Casting Principle and Process

В Yigu Technology, Мы верим “principle mastery + process refinement” is the key to stable die casting quality. Many clients struggle with recurring defects (НАПРИМЕР., пористость) because they focus only on parameters, not the underlying principle (НАПРИМЕР., how hydrogen causes pores). We advocate a “3-layer approach”: 1) Train teams on die casting principles (НАПРИМЕР., pressure-assisted solidification) to help them understand почему parameters matter; 2) Use intelligent monitoring systems to track real-time parameters (molten metal temperature, давление впрыска) and alert for deviations; 3) Для пользовательских деталей, optimize mold design (НАПРИМЕР., adding risers to thick sections) based on the filling principle—reducing defect rates by 40% в среднем. We also prioritize eco-friendly processes (НАПРИМЕР., servo-hydraulic machines, water-based release agents) to meet sustainability goals.

Часто задаваемые вопросы (Часто задаваемые вопросы)

  1. Q.: Why is mold preheating necessary? Can I skip it to save time?

А: No—mold preheating is critical. Cold molds cause molten metal to solidify too fast, leading to cold shuts (unfused seams) and poor part strength. Skipping preheating may seem to save 5~10 minutes per mold, but it increases scrap rates by 20~30%—costing more in the long run.

  1. Q.: For aluminum alloy die casting, what’s the difference between ADC12 and 6061 сплавы? Which should I choose?

А: ADC12 has high fluidity (ideal for complex, thin-walled parts like electronics enclosures) but lower strength. 6061 has higher strength and corrosion resistance (suitable for load-bearing parts like automotive brackets) but lower fluidity. Choose ADC12 for complex shapes; выбирать 6061 for parts needing strength or outdoor use.

  1. Q.: How to confirm if a die-cast part has internal porosity? Can it be fixed after production?

А: Использовать X-ray inspection (for critical parts like aerospace components) или hydrostatic testing (for pressure-containing parts like pump housings) Чтобы обнаружить внутреннюю пористость. Small pores (≤0.1mm) can be fixed via impregnation (filling pores with resin or wax). Large pores (>0.1мм) usually require reworking or scrapping—better to prevent them by optimizing degassing and holding pressure during production.

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