Low Pressure Casting Technology for Aluminum Alloy Cylinder Heads

Lightweight design has become a core direction in passenger car engine development.   

Reducing vehicle weight directly improves fuel efficiency and lowers emissions.   

Among structural components, the engine cylinder head plays a critical role in thermal management and combustion efficiency.   

As a result, aluminum alloy cylinder heads have become the standard solution in modern passenger car engines.

Importance of Low Pressure Casting for Cylinder Heads

Aluminum alloy cylinder heads can be produced by several casting methods.   

Metal mold gravity casting and low pressure casting are the two mainstream technologies used worldwide.   

Compared with gravity casting, low pressure casting allows molten aluminum to fill the mold under controlled pressure.   

This significantly improves internal density, reduces porosity, and enhances mechanical properties.

Low pressure casting is widely adopted in high-performance engine applications due to its stable quality and high yield.   

This process is especially suitable for complex cylinder head structures with multiple internal channels and thin-wall sections.

Advantages Over Gravity Metal Mold Casting

The main advantage of low pressure casting lies in pressure-assisted filling and directional solidification.   

Molten aluminum rises smoothly from the bottom of the mold, minimizing turbulence and oxide inclusion.   

Solidification under pressure improves feeding efficiency and reduces shrinkage defects.

For automotive manufacturers and parts suppliers, these advantages translate into higher consistency and reduced rework rates.   

This makes low pressure casting a preferred technology for mass production of aluminum alloy cylinder heads.

Key Process Design of Low Pressure Casting

Gating System Design

The gating system of an aluminum alloy cylinder head typically adopts a riser tube with multiple gates.   

This multi-gate configuration ensures balanced filling and uniform temperature distribution.   

For four-cylinder heads, two-gate and four-gate systems are commonly used depending on mold layout.

Proper gate positioning near the combustion chamber area helps control solidification order.   

This reduces hot spots and improves feeding efficiency in critical sections.

Alloy Selection and Melt Treatment

Common aluminum alloys for cylinder heads include Al-Si-Cu series such as ZL105 and ZL107.   

When higher elongation and corrosion resistance are required, ZL101 or ZL104 can be selected.   

Melt quality directly determines casting performance and final properties.

Standard refining operations include argon gas rotary degassing, strontium modification, and Al-Ti-B grain refinement.   

These treatments improve fluidity, reduce hydrogen content, and refine the microstructure.

Pouring Process Control

Mold Maintenance and Surface Coating

Regular mold maintenance is essential for stable production and extended mold life.   

Cleaning is typically performed after every 500 to 700 castings.   

This prevents coating buildup, aluminum adhesion, and vent blockage.

Before pouring, molds are preheated to around 200℃ and coated evenly.   

General coating thickness is controlled between 0.1 and 0.2 mm.   

High-precision areas such as combustion chambers require thinner coatings for surface accuracy.

Filtration and Temperature Control

Filters installed in the riser tube prevent oxide inclusions from entering the cavity.   

Simple galvanized metal mesh filters are widely used due to their low cost and effectiveness.

Molten aluminum temperature is typically controlled between 680℃ and 730℃.   

Temperature deviation during production should be kept within ±20℃.   

Stable temperature control is critical to prevent internal defects and surface imperfections.

Cooling Strategy and Solidification Control

Directional solidification is a key feature of low pressure casting.   

Cooling channels are arranged in the upper and side molds to control temperature gradients.   

Both water cooling and air cooling systems are used, with independent channel control.

Indirect cooling is preferred to protect mold life.   Direct cooling is applied only in thick sections where rapid heat extraction is required.   

Temperature-controlled cooling using thermocouples provides higher accuracy than time-based control.

Pressurization and Mold Release Parameters

Pressurization Time and Pressure Curve

Pressurization time refers to the period from filling to gate solidification.   

It is usually controlled between 2 and 8 minutes depending on cylinder head weight and temperature.   

Optimized pressurization improves feeding and internal quality.

The pressurizing pressure directly affects molten metal flow behavior.   

Excessive pressure can cause coating damage and sand core penetration.   

Therefore, precise pressure curve control is essential for defect-free castings.

Mold Release Timing

Mold release time is typically set to about one third of the pressurization time.  

 If released too early, the casting may deform.   

If released too late, sticking and surface damage may occur.

A staged mold opening sequence improves cooling efficiency and reduces deformation risk.

Quality Control and Industrial Value

Low pressure casting technology offers high production efficiency and excellent internal quality for aluminum alloy cylinder heads.   

Advanced process simulation and parameter optimization further enhance consistency.   

saivs supports automotive manufacturers with reliable aluminum casting solutions tailored for engine applications.

By combining optimized alloy selection, precise pressure control, and intelligent cooling systems, manufacturers can achieve stable mass production.   

This provides strong support for high-efficiency, low-emission passenger car engines.