Comparison and Advantages of Low-Pressure Casting and High-Pressure Die Casting Processes [SMM Aluminum Industry Conference]

On April 16, at the AICE 2025 SMM (20th) Aluminum Industry Conference and Aluminum Industry Expo — Aluminum Die Casting Industry Development Forum, co-organized by SMM Information & Technology Co., Ltd., SMM Metal Trading Center, and Shandong Aisi Information Technology Co., Ltd., and co-sponsored by Zhongyifeng Jinyi (Suzhou) Technology Co., Ltd. and Lezhi County Qianrun Investment Service Co., Ltd., Wenping Zhu, Eaton (China) Investment Co., Ltd.'s global aluminum alloy casting expert, special expert/director, and senior die casting engineer qualification certification training lecturer, shared a comparison of low-pressure casting and high-pressure die casting processes, as well as their advantages and disadvantages.

**Differences in Process Principles**

**Low-Pressure Casting**
Pressure range: 0.01-0.1 MPa (low pressure).
Principle: Compressed air is used to slowly press molten metal from a sealed holding furnace into the mold through a riser tube. The metal fills the cavity from top to bottom under low pressure and solidifies under pressure.
Characteristics: Smooth filling, good metal fluidity, fewer pores and inclusions.

**High-Pressure Die Casting**
Pressure range: 10-200 MPa (extremely high pressure).
Principle: Molten metal is injected at high speed into a steel mold under high pressure (provided by the injection cylinder), rapidly filling the mold and solidifying under high pressure.
Characteristics: Fast filling speed (millisecond level), suitable for complex thin-walled parts, but prone to gas entrapment.

Low-pressure casting and high-pressure die casting are two common metal casting processes, mainly used for forming non-ferrous metals such as aluminum alloys and magnesium alloys. They have significant differences in principles, application scenarios, and product characteristics.

**Comparison of Process Characteristics**

**Low-Pressure Casting**
Advantages: Good casting density, high mechanical properties, fewer pore defects, capable of producing larger parts.
Disadvantages: Long cycle time, higher mold cost, not suitable for ultra-thin-walled parts. Higher production cost, wall thickness must be >3.5 mm, preferably over 4 mm.

**High-Pressure Die Casting**
Advantages: High production efficiency (multiple parts can be produced per minute), suitable for complex thin-walled parts, high surface precision. High dimensional accuracy, small machining allowance.
Disadvantages: Internal pores are common in castings, usually not heat-treatable (pores may expand), extremely high mold cost. Wall thickness greater than 2 mm is sufficient.

Low-pressure casting can design closed beams of any diameter, and its advantages in torsional stiffness of closed beams were introduced. High precision dimensions and ultra-thin wall thickness are significant advantages of die casting. Additionally, magnesium alloy high-pressure die castings were introduced.

**Breakthroughs and Development Directions for Low-Pressure Casting**
1. Material Innovation: Breakthroughs in high-performance aluminum alloys
• Development of high-strength and high-toughness alloys: To meet the needs of new energy vehicles and aerospace, develop new-type aluminum alloys (such as high-silicon aluminum, aluminum-lithium alloys) to improve the specific strength and high-temperature performance of castings. Tensile strength breakthrough of 380 MPa for A356.
• Application of composite materials: Breakthroughs in casting technology for aluminum matrix composites (such as SiC particle-reinforced aluminum) to achieve higher stiffness and wear resistance, used for chassis and powertrain components.
2. Process Upgrade: Intelligence and efficiency improvement
• Development of low-pressure casting methods with efficient cycles,
• Riser tube casting technology,
• Electromagnetic pump casting technology
• AI algorithm optimization to improve yield and cycle time.
• 3D printed sand molds/metal molds

**Breakthroughs and Development Directions for High-Pressure Die Casting**
Technological breakthroughs: Enhancing performance and process limits, mainly focusing on defect elimination
• 1. Ultra-large integrated die casting
Breakthroughs needed in mold material heat resistance, press tonnage (over 12,000 mt), and vacuum technology.
• 2. Popularization of vacuum high-pressure die casting (VHPDC)
Reducing pores through vacuum (porosity <1%), enabling castings to be heat-treated and welded, broadening application scenarios (such as structural safety parts).
• 3. Semi-solid high-pressure die casting (SSM-HPDC)
1. Principle: Pressing semi-solid slurry (solid phase rate 30%-50%) into the mold to reduce turbulence and pores.
2. Advantages: Mechanical properties close to forging, better surface quality, used for high-strength motor housings, suspension components.
• New high-pressure material innovation: High-strength, high-toughness, multifunctional alloys
1. Development of new high-strength aluminum alloys
Goal: Tensile strength breakthrough of 400 MPa (such as Al-Si-Mg-Cu series alloys), replacing some steel parts.
2. High-temperature resistant aluminum alloys
Demand: Adapting to near-heat source conditions of motor housings (such as electric drive system temperatures >150℃).
3. Efficient application of secondary aluminum
Trend: Improving the purity of secondary aluminum through refining technology (Fe content <0.15%), reducing costs and carbon emissions.
• The application scenarios and development of magnesium alloy high-pressure die casting and semi-solid die casting, as well as the development and research of magnesium alloy raw materials suitable for die casting, were also elaborated.

**Breakthroughs and Development Directions for Both Casting Processes**
• Green Manufacturing: Low-carbon and circular economy
1. Energy-saving equipment upgrade: Servo motor-driven die casting machines (energy consumption reduced by 40%), waste heat recovery systems.
2. Environmental protection release agents and coatings: Trend of replacing oil-based agents with water-based release agents, chromium-free passivation treatment.
3. Closed-loop recycling system: Model of OEMs collaborating with aluminum companies to establish scrap recycling networks.
• Low-carbon, energy-saving, and environmentally friendly equipment and technologies
Analysis of multi-barrel injection technology and micro-precision spraying technology.
• Intelligence and Digitization: Precise process control
1. AI-driven process optimization
Real-time monitoring. xx launched intelligent die casting machines, improving yield by 15%.
2. Digital twins and virtual trial molds
Integration of AI algorithms in simulation platforms such as MAGMA and ProCAST.
3. Blockchain traceability system
Function: Recording the process parameters and material sources of each casting, meeting the quality traceability needs of the automotive industry.
• Expansion of Application Scenarios: From automotive to multiple fields
1. Aerospace and robotics
Drone frames. Robotic arm joints.
2. Consumer electronics: Mobile phone/computer frames
3. Commercial vehicles, general equipment fields.
• Peripheral, post-processing automation
Online, intelligent detection, automatic feedback, and automatic parameter adjustment.
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