3 Main Types of Vacuum Casting and Their Advantages

Vacuum casting can generally be divided into three main types: vacuum suction casting, vacuum low-pressure casting, and vacuum differential pressure casting. Each process uses vacuum or pressure difference to improve metal filling, reduce defects, and produce castings with better density and mechanical performance. These methods are especially useful for precision castings, thin-wall parts, and components with high quality requirements.

1. Vacuum Suction Casting

Vacuum suction casting places the mold inside a sealed container and removes the air from the mold to create negative pressure. This pressure difference causes the molten metal to be drawn into the mold cavity. After the inner runner solidifies, the negative pressure is released, and the unsolidified molten metal in the sprue flows back into the melt pool.

This process improves the filling ability of molten metal and helps produce small precision castings with fine detail. It is especially suitable for cast steel parts, including stainless steel components.

Advantages of Vacuum Suction Casting

• Helps remove gas from the mold and reduces turbulence during filling
• Improves molten metal flow and filling performance
• Reduces defects such as gas porosity and slag inclusion
• Allows lower pouring temperatures, usually 20°C to 30°C lower than gravity casting
• Suitable for castings with thin walls, thick sections, and high quality requirements
• Can achieve smoother filling by controlling vacuum level and metal entry speed

2. Vacuum Low-Pressure Casting

Vacuum low-pressure casting applies vacuum to the mold during the pressurized filling process. After filling is complete, the casting is allowed to crystallize and solidify under constant pressure, helping the molten metal fill the cavity completely and produce a dense internal structure.

This method is commonly used for precision casting of aluminum and magnesium alloy parts. It improves both casting density and mechanical properties while maintaining relatively stable filling conditions.

Advantages of Vacuum Low-Pressure Casting

• Negative pressure helps compact the mold sand and increase mold strength
• Moderate vacuum shortens filling time and improves filling stability
• Improves aluminum alloy flowability at lower temperatures
• Helps reduce pinhole defects caused by high-temperature casting
• Produces castings with clear contours and smooth surfaces
• Suitable for large thin-wall castings and precision parts
• Produces dense cast structures with improved mechanical properties
• Usually does not require risers, so metal yield can be greatly improved, often up to 90%
• Provides a better working environment and supports mechanization and automation

3. Vacuum Differential Pressure Casting

Vacuum differential pressure casting seals both the resistance holding furnace and the mold. Compressed air is introduced into the sealed chamber so that pressure inside the mold and crucible remains equal at first. Then additional pressure is applied to the molten metal surface, causing the molten metal to rise and fill the cavity.

This process is particularly suitable for complex thin-wall castings with demanding structural and mechanical requirements. However, the equipment is larger and the operation is more complicated, so it is usually used only when special casting performance is required.

Advantages of Vacuum Differential Pressure Casting

• Provides very good filling ability for complex and thin-wall castings
• Can successfully fill sections as thin as 1 mm
• Produces castings with dense crystal structure and improved mechanical properties
• Strength is typically about 20% to 25% higher than vacuum suction casting and gravity casting
• Elongation can increase by approximately 50%
• Can effectively reduce porosity in castings
• Can improve casting density by more than 1%

Conclusion

Vacuum suction casting, vacuum low-pressure casting, and vacuum differential pressure casting each offer distinct advantages depending on the casting material, part geometry, and performance requirements. By selecting the appropriate vacuum casting method, manufacturers can improve filling quality, reduce casting defects, and produce more precise and reliable metal components.