Low-pressure die casting and gravity die casting are two foundational metal-forming processes, each built on distinct mechanical principles. While both shape molten metal into finished parts using molds, their approaches to filling cavities—one driven by controlled pressure, the other by natural gravity—create stark differences in quality, эффективность, и стоимость. Для производителей, choosing between them means balancing needs like part strength, объем производства, и бюджет. But what exactly sets their workflows apart? How do these differences impact end-product performance? And which process is right for your specific application? This article answers these questions with detailed comparisons and actionable guidance.
1. Основные принципы: The Fundamental Contrast in Filling Mechanisms
The biggest divide between the two processes lies in how molten metal is delivered to the mold cavity—a difference that shapes every other aspect of their operation.
А. Малочное кастинг с низким давлением
- Driving Force: Использование dry compressed air or inert gas (НАПРИМЕР., азот) to apply controlled pressure (typically 0.02–0.15MPa) to a sealed crucible holding molten metal.
- Filling Process: Pressure forces metal up a vertical liquid lift tube and into the mold cavity from the bottom up. This creates a slow, steady “laminar flow” (no turbulent splashing), ensuring the cavity fills completely without trapping air.
- Затвердевание: The pressure is maintained during cooling (pressure-holding crystallization). This pushes remaining molten metal into shrinkage gaps, eliminating defects like pores or voids.
Беременный. Гравитация литья
- Driving Force: Relies solely on metal’s own weight (гравитация)—no external pressure is applied.
- Filling Process: Molten metal is poured into a sprue (funnel-shaped inlet) at the top of the mold. It flows downward through runners and gates into the cavity via “natural flow”—filling speed depends on the mold’s design and metal’s fluidity.
- Затвердевание: Cooling happens passively, with no pressure to counteract shrinkage. This means thicker sections may develop small shrinkage pores, though the slow filling reduces gas entrainment compared to high-pressure methods.
2. Side-by-Side Process Comparison: Key Operational Differences
To understand how these processes perform in practice, let’s break down their workflows, параметры, and constraints in a clear, data-driven table:
| Process Aspect | Малочное кастинг с низким давлением | Гравитация литья |
| Filling Mode | Bottom-up laminar flow; pressure-controlled (0.02–0.15MPa). | Top-down gravity flow; no external pressure. |
| Filling Speed | Медленный, униформа (typically 5–15cm/s); adjustable via pressure. | Переменная (depends on mold design); faster than low-pressure but slower than high-pressure die casting. |
| Metal Fluidity Requirement | От низкого до среднего; works with most non-ferrous alloys (алюминий, магний). | Высокий; requires alloys with good flowability (НАПРИМЕР., алюминий, медь) to fill cavities via gravity alone. |
| Mold Design Complexity | Высокий; needs sealed crucibles, liquid lift tubes, and pressure ports. | Низкий; simple sprue-runner-gate systems (no pressure-related components). |
| Время цикла | Дольше (60–120 seconds per part); includes pressure ramp-up and holding. | Умеренный (45–90 seconds per part); faster than low-pressure but slower than high-pressure die casting. |
| Waste Rate | Низкий (5–8%); no need for risers (extra metal to feed shrinkage). | Выше (10–15%); may require risers for thick-walled parts, increasing material waste. |
3. Производительность & Качество: Which Delivers Better Results?
The filling mechanism directly impacts part quality, механические свойства, and defect rates. Below is a detailed comparison of key performance metrics:
| Показатель производительности | Малочное кастинг с низким давлением | Гравитация литья |
| Плотность части | Высокий (≥99.5% theoretical density); pressure eliminates shrinkage pores. | Умеренный (98–99%); small pores may form in thick sections. |
| Предел прочности | Начальство (НАПРИМЕР., 280–320MPa for aluminum alloys); dense structure boosts strength. | Хороший (НАПРИМЕР., 240–280MPa for aluminum alloys); slightly lower due to minor porosity. |
| Поверхностная отделка | Отличный (Ra 1.6–3.2μm); smooth filling avoids surface defects like cold shuts. | Умеренный (Ra 3.2–6.3μm); may have minor surface irregularities from uneven flow. |
| Скорость дефекта | Низкий (2–5% scrap rate); minimal oxidation or gas defects. | Умеренный (5–10% scrap rate); risks include cold shuts (from slow flow) or shrinkage pores. |
| Совместимость с термообработкой | Отличный; uniform structure resists deformation during heat treatment (НАПРИМЕР., T6). | Хороший; can be heat-treated but may require pre-inspection to avoid pore expansion. |
4. Приложения: Matching Process to Part Needs
Each process excels in specific scenarios, based on part design, материал, и требования к производительности. The table below maps processes to ideal use cases:
| Part Requirement | Prefer Low-Pressure Die Casting | Prefer Gravity Die Casting |
| Высокая сила, Критически важные для безопасности детали | Automotive wheels, engine blocks/covers (need density and strength to withstand loads). | None—safety parts require the higher density of low-pressure casting. |
| Large Thin-Walled Components | Missile housings, Структурные детали самолетов (laminar flow prevents thin-section voids). | Not suitable—gravity flow can’t fill thin walls (≤3 мм) uniformly. |
| Thick-Walled, Простые формы | None—overkill for low-performance thick parts. | Rail transit accessories (НАПРИМЕР., bogie brackets), robot structural parts, ship propeller hubs (толстые секции, низкая сложность). |
| Чувствительный к стоимости, Medium-Volume Parts | None—higher equipment costs make it uneconomical for low-margin parts. | Потребительские товары (НАПРИМЕР., large cookware), промышленные клапаны (Простой дизайн, средний объем). |
| Non-Ferrous Alloy Parts | Ideal for aluminum, магний, and copper alloys (controllable flow suits these materials). | Best for aluminum and copper alloys (Хорошая поток); less suitable for low-fluidity alloys. |
5. Cost Analysis: Upfront Investment vs. Долгосрочная экономия
Cost is a critical factor for manufacturers. Below is a breakdown of equipment, форма, and per-part costs (based on aluminum alloy parts, 10,000-part batch):
| Категория затрат | Малочное кастинг с низким давлением | Гравитация литья |
| Equipment Investment | Высокий (\(150,000- )300,000); includes sealed crucibles, pressure control systems, and lift tubes. | Низкий (\(50,000- )100,000); simple melting furnaces and open molds. |
| Стоимость плесени | Высокий (\(15,000- )40,000); complex designs with sealed cavities and lift tubes. | Низкий (\(5,000- )15,000); простой, open designs with minimal features. |
| Per-Part Material Cost | Низкий (\(0.4- )0.6/кг); no risers reduce waste. | Умеренный (\(0.5- )0.7/кг); risers increase material usage. |
| Labor Cost | Умеренный; requires trained operators to monitor pressure (1–2 operators/line). | Низкий; simple process needs minimal supervision (1 operator/2 lines). |
| Total Batch Cost | ~ (30,000- )60,000 | ~ (15,000- )30,000 |
6. Yigu Technology’s Perspective on the Two Processes
В Yigu Technology, we see low-pressure and gravity die casting as complementary tools—each solving unique manufacturing challenges. For automotive clients needing high-strength wheels, our low-pressure casting lines (equipped with real-time pressure monitoring) deliver parts with 99.8% density and <3% scrap rates, meeting IATF 16949 стандарты. For rail transit clients, our gravity casting solutions cut upfront costs by 50% while producing durable brackets that pass 100,000-cycle load tests.
We’re optimizing both processes: 1) Adding AI to low-pressure systems to auto-adjust pressure for different part thicknesses (reducing cycle time by 15%); 2) Developing modular gravity molds that switch between part designs in 30 минуты (ideal for small-batch production). Our goal is to tailor each process to the client’s “pain points”—whether it’s quality, расходы, or flexibility—instead of forcing a one-size-fits-all solution.
Часто задаваемые вопросы
- Can gravity die casting be used for thin-walled parts (НАПРИМЕР., 2мм толщиной)?
No—gravity-driven flow can’t fill thin walls uniformly, leading to voids or incomplete filling. Тонкостенные детали (≤3 мм) require low-pressure die casting, which uses controlled pressure to push metal into narrow cavities without gaps.
- Is low-pressure die casting worth the higher upfront cost for medium-volume production (НАПРИМЕР., 5,000 части/год)?
It depends on part value: Для дорогостоящих запчастей (НАПРИМЕР., Автомобильные колеса, where defects cost $100+/part), yes—lower scrap rates and better quality offset equipment costs. For low-value parts (НАПРИМЕР., Простые скобки), gravity casting is more economical, even with higher material waste.
- Which process is better for magnesium alloys—low-pressure or gravity die casting?
Low-pressure casting is better. Magnesium is prone to oxidation, and low-pressure’s sealed crucible and inert gas protection reduce oxidation by 80% compared to gravity casting (which exposes molten magnesium to air during pouring). This ensures magnesium parts meet corrosion-resistance standards (НАПРИМЕР., ASTM B94).