What Is Gravity Die Casting and How to Leverage Its Advantages in Manufacturing?

Gravity die casting (also known as permanent mold casting) is a pivotal metal-forming process that relies on the natural force of gravity to fill mold cavities with molten metal. Unlike high-pressure die casting, it avoids complex pressure systems, making it a cost-effective and reliable choice for specific industrial scenarios—especially for thick-walled parts requiring heat treatment and structural stability. Однако, to maximize its value, manufacturers must understand its core principles, Ключевые преимущества, application boundaries, and technical innovations. This article systematically breaks down gravity die casting to help you solve practical problems like process selection, defect prevention, and efficiency improvement.

1. Основные принципы & Process Flow of Gravity Die Casting

To master gravity die casting, it’s essential to first grasp its working mechanism and standardized workflow. В этом разделе используется 总分 + linear 叙述 структура, with critical steps and parameters highlighted for clarity.

1.1 Fundamental Principle

Gravity die casting operates on a simple yet precise logic: molten metal flows into the mold cavity solely under its own weight, without external pressure (НАПРИМЕР., hydraulic or mechanical force). The mold—typically made of heat-resistant alloy steel (НАПРИМЕР., H13 or HT300)—is reusable and designed with a “сверху вниз” filling path. This natural flow minimizes turbulence, reducing the risk of air entrainment and ensuring uniform metal distribution in thick-walled areas (>8мм)—a key advantage over high-pressure die casting, which often traps gas in thick sections.

1.2 Standard Process Flow

The workflow of gravity die casting follows 6 sequential steps, each with strict operational requirements:

1. Подготовка плесени:

• Preheat the mold to 150-300°C (варьируется от сплава: 150-200°C для алюминия, 250-300°C for cast iron) to prevent molten metal from solidifying prematurely.
• Apply a thin layer of release agent (НАПРИМЕР., graphite-based or water-based) to the cavity surface—this reduces mold sticking and extends mold life by 20-30%.

2. Molten Metal Melting:

• Heat the metal (НАПРИМЕР., Алюминиевый сплав A356, cast iron HT250) to its liquid state: 670-720°C для алюминия, 1400-1450°C for cast iron.
• Degas the molten metal (для алюминия, use argon purging for 10-15 минуты) to reduce hydrogen content to <0.15ml/100g—this prevents porosity after solidification.

3. Controlled Pouring:

• Use a ladle to pour the molten metal into the mold’s sprue at a steady speed (0.5-1.0 L/min for aluminum). Avoid fast pouring, which causes splashing and oxide inclusions.
• Ensure the metal fills the cavity gradually, starting from the bottom and rising to the top—this pushes air out through dedicated vent channels (1-2мм шириной, 50-100мм длиной).

4. Natural Exhaust & Затвердевание:

• Rely on the mold’s vent channels and parting surface gaps for exhaust—no complex vacuum systems are needed.
• Let the metal solidify naturally: 5-30 минуты (в зависимости от толщины части: 5 minutes for 10mm walls, 30 minutes for 50mm walls). Slow solidification forms a uniform grain structure, supporting subsequent heat treatment.

5. Открытие формы & Удаление части:

• Once the metal is fully solidified (verified by temperature sensors: <200°C для алюминия), open the mold using hydraulic or manual actuators.
• Use ejector pins (spaced 50-80mm apart) to gently remove the part—avoid excessive force, which can cause deformation in thin-walled features.

6. Пост-обработка:

• Trim excess material (НАПРИМЕР., sprue, Шканеры) using a bandsaw or CNC router.
• For parts requiring high precision, perform machining (НАПРИМЕР., фрезерование, бурение) to achieve dimensional tolerance of ±0.1mm.
• Conduct heat treatment (НАПРИМЕР., T6 for aluminum: solution treatment at 530°C + aging at 120°C) to enhance mechanical properties—this step is impossible for most high-pressure die cast parts due to porosity.

2. Key Advantages of Gravity Die Casting: Why It’s Irreplaceable

Gravity die casting’s unique value stems from its ability to solve pain points that other processes struggle with—such as thick-walled part quality, heat treatment compatibility, и контроль затрат. В этом разделе используется problem-solution + specific 数字 structure to highlight its core benefits.

2.1 Superior Quality for Thick-Walled Parts

• Проблема: High-pressure die casting traps air in thick-walled areas (>8mm), leading to porosity and making parts unsuitable for pressure-bearing applications (НАПРИМЕР., блоки двигателя).
• Решение: Gravity die casting’s natural flow eliminates turbulence, reducing porosity to <1% (против. 5-10% in high-pressure die casting). Например, a 20mm-thick aluminum engine block produced via gravity die casting has a leakage rate of <1×10⁻⁶ mbar·L/s—meeting automotive hydraulic system standards.
• Поддержка данных: According to QYResearch, gravity die cast parts have a 60% lower defect rate than high-pressure die cast parts for components with wall thicknesses >15mm.

2.2 Compatibility with Heat Treatment

• Проблема: High-pressure die cast parts contain hidden pores, which expand during heat treatment and cause cracking or deformation.
• Решение: Gravity die casting’s low porosity enables full heat treatment. For aluminum alloy A356 parts:
• Tensile strength increases from 220MPa (Ассоциация) to 320MPa after T6 heat treatment.
• Elongation rises from 3% к 8%, improving toughness for high-load applications (НАПРИМЕР., heavy machinery brackets).
• Пример приложения: Volvo uses gravity die cast aluminum cylinder heads (heat-treated to T7) for its heavy-duty trucks—these heads withstand 300°C+ temperatures and 10MPa combustion pressure without failure.

2.3 Cost-Effectiveness for Medium Batches

• Проблема: High-pressure die casting requires expensive molds (\(50,000-\)500,000), making it uneconomical for small-to-medium batches (1,000-10,000 части/год).
• Решение: Gravity die casting molds cost 70-90% меньше (\(1,000-\)50,000) and have a lifespan of 10,000-50,000 выстрелы. For a 5,000-unit order of cast iron machine tool beds:
• Gravity die casting total cost: \(80,000 (форма: \)15,000 + стоимость за участие: $13).
• High-pressure die casting total cost: \(250,000 (форма: \)200,000 + стоимость за участие: $10).
• Ключевое понимание: Gravity die casting achieves the “сладкое пятно” between low upfront cost (кастинг песка) and high efficiency (high-pressure die casting).

2.4 Широкая совместимость материала

• Проблема: High-pressure die casting is limited to low-melting-point non-ferrous metals (алюминий, цинк, магний) and cannot process ferrous metals (чугун, сталь) or high-temperature alloys.
• Решение: Gravity die casting works with:
• Ferrous metals: Чугун (HT200, HT300), углеродистая сталь (Q235), and alloy steel (40Герметичный).
• High-temperature alloys: На основе никеля суперсплавы (Insonel 625) Для аэрокосмических компонентов.
• Приложение: GE uses gravity die casting to produce Inconel 625 turbine blades for gas turbines—these blades operate at 800°C and withstand 500MPa centrifugal force.

3. Gravity Die Casting vs. Other Casting Processes: A Comparative Guide

To help you select the right process for your project, the table below compares gravity die casting with high-pressure die casting and sand casting across 7 critical dimensions:

4. Сценарии приложения & Technical Innovations

Gravity die casting is not a “Один размер-все” solution—it excels in specific industries and is evolving with automation and new materials. В этом разделе используются приложение + инновации segmentation to provide practical guidance.

4.1 Key Application Industries

• Автомобиль (Тяжелый & Невз):
• Части: Блоки двигателя, головки цилиндров, ЭВ -аккумулятор (толстостенный, pressure-bearing).
• Пример: Daimler uses gravity die cast aluminum battery frames for its eActros electric trucks—these frames (20mm-thick walls) weigh 15% less than steel frames and withstand 200kN crash loads.
• Тяжелая техника:
• Части: Hydraulic valve bodies, gearbox housings (require heat treatment and low leakage).
• Данные: 70% of hydraulic valve bodies for excavators are produced via gravity die casting—due to its <1% porosity and dimensional accuracy of ±0.15mm.
• Аэрокосмическая (Low-Volume High-Performance):
• Части: Nickel-based superalloy combustion chambers, titanium alloy structural brackets (Высокотемпературное сопротивление).
• Преимущество: Gravity die casting avoids the high cost of forging for small aerospace batches (100-500 части/год).

4.2 Latest Technical Innovations

• Automation Upgrades:
• PLC-Controlled Pouring Robots: Replace manual ladling with automated systems (НАПРИМЕР., KUKA robots) to reduce pouring speed variation from ±20% to ±5%. This cuts oxide inclusion defects by 40%.
• Real-Time Temperature Monitoring: Embed thermocouples in the mold to maintain cavity temperature at ±10°C—ensuring consistent solidification and reducing part-to-part variation by 30%.
• New Material Compatibility:
• Low-Flow Aluminum Alloys: Developed alloys like AlSi10MgMn (low fluidity) perform well in gravity die casting—they reduce shrinkage by 25% compared to traditional ADC12, making them ideal for complex thick-walled parts.
• Composite Material Integration: Embed carbon fiber-reinforced polymer (CFRP) inserts in gravity die cast aluminum parts—this increases stiffness by 50% while keeping weight low (НАПРИМЕР., for aerospace seat frames).
• Рост рынка: According to QYResearch, the global gravity die casting market will grow at a 3.5% CAGR from 2024 к 2031, reaching $31.14 billion—driven by demand for lightweight, heat-treatable parts in automotive and aerospace.

5. Распространенные дефекты & Troubleshooting in Gravity Die Casting

Even with its advantages, gravity die casting can develop defects due to improper operation or mold design. The table below uses a defect-cause-solution structure to help you resolve issues quickly:

6. Yigu Technology’s Perspective on Gravity Die Casting

В Yigu Technology, we believe gravity die casting is a “strategic complementary process”—it fills the gap between high-pressure die casting (массовое производство) and sand casting (Маленькие партии) and is irreplaceable for thick-walled, heat-treatable parts. Many manufacturers underestimate its potential, focusing only on high-pressure die casting’s speed while ignoring gravity die casting’s cost and quality advantages for medium batches.

Мы рекомендуем process-material synergy approach: Например, use gravity die casting with AlSi10MgMn alloy for EV battery frames—this combination achieves 320MPa tensile strength (after T6) и 15% снижение веса, while keeping costs 40% lower than high-pressure die casting. We also advocate integrating automation (НАПРИМЕР., PLC-controlled pouring robots) to reduce cycle time by 30% без ущерба для качества.

Заглядывая в будущее, as new energy vehicles and aerospace demand more lightweight, Высокопроизводительные детали, gravity die casting—paired with new alloys and real-time monitoring—will play a larger role in high-end manufacturing.

7. Часто задаваемые вопросы: Common Questions About Gravity Die Casting

1 квартал: Can gravity die casting produce thin-walled parts (<8мм) like phone casings?

Технически да, Но это не экономически эффективно. Thin-walled parts require fast filling to avoid cold shuts, which gravity die casting struggles with (natural flow is too slow). Для <8ММ детали, high-pressure die casting is better—its 5-50 m/s injection speed ensures complete filling, и его низкая стоимость за деталь (\(0.5-\)5) компенсирует высокие затраты на пресс-формы для массового производства. Гравитационное литье больше подходит для деталей. >8мм где качество (не скорость) имеет решающее значение.

2 квартал: What is the maximum part size gravity die casting can handle?

Гравитационное литье под давлением не имеет строгих ограничений по размерам — можно изготавливать детали из небольших кронштейнов. (100глин) на большие станины станков (5,000кг+). Ключевым ограничением является конструкция пресс-формы и погрузочно-разгрузочное оборудование.: На запчасти >1,000кг, используйте разъемные формы (легко открыть/закрыть) и мостовые краны для перемещения пресс-форм. Например, Siemens uses gravity die casting to produce 3,000kg cast iron stator housings for wind turbines—these housings are 2m in diameter and 1.5m tall.

Q3: How to improve the surface finish of gravity die cast parts (Ra = 6.3-12.5 мкм)?

Three effective steps: 1. Polish the mold cavity to Ra = 0.8 мкм (use diamond grinding wheels) —this transfers a smoother surface to the part. 2. Use a water-based release agent (против. graphite-based) —it leaves less residue, reducing surface roughness by 30%. 3. Perform post-processing: Sandblast with 200# alumina powder (smoothens to Ra = 3.2 мкм) or conduct light machining (НАПРИМЕР., face milling) for critical surfaces (Ra = 1.6 мкм).