Effect of Applying Pressure of High Pressure Diecasting Process Using Salt core

1. Overview:

• Title: Effect of Applying Pressure of High Pressure Diecasting Process Using Salt core
• Authors: Jun-Ho Lee, J. H. Moon, Dock-Young Lee
• Publication Year: 2008
• Journal/Conference: Journal of the Korean Foundrymen's Society, Vol. 28, No. 3 (한국주조공학회지, 제28권 제3호)
• Keywords: Salt core, Squeeze casting, High pressure die casting, Net-shape forming

2. Research Background:

• Social/Academic Context of Research Topic:
  • Increased application of pressure casting methods like die casting, low pressure casting, and squeeze casting in manufacturing aluminum and magnesium castings.
  • Pressure casting methods offer advantages in productivity, reduced defects, and improved dimensional accuracy compared to gravity casting.
  • Low temperature melting salt core composite casting technology is a core technology for lightweighting and modularizing integrated components.
• Limitations of Existing Research:
  • Conventional shell cores have weaknesses: fragility, damage during handling, resin odor, difficult recycling, and poor surface finish.
  • Shell cores are prone to melt penetration in high pressure casting, limiting their use in die casting and squeeze casting.
  • Previous research on high pressure solidification and squeeze casting mainly focused on the effects of pressure and pressure conditions on solidification structure and mechanical properties of aluminum and copper alloys.
  • Research on the effect of pressure on solidification phenomena is limited.
• Necessity of Research:
  • Increasing demand for casting technologies to manufacture high-quality integrated components with complex internal shapes.
  • Need to develop fusible core technology to overcome shell core limitations and be applicable to high pressure casting processes.
  • In-depth study needed on the effect of pressure during squeeze casting on solidification phenomena and core behavior.

3. Research Objectives and Research Questions:

• Research Objectives:
  • To evaluate the suitability of molten metal and fusible cores by applying low melting point cores in squeeze casting under varying pressures (gravity, 1000 kg/cm²).
  • To measure changes in heat transfer coefficient with increasing punch pressure.
  • To observe and analyze the microstructure of pressurized molten metal.
  • To develop high-performance fusible core materials and optimize alloy-core combinations through fusible core manufacturing and characterization.
• Core Research Questions:
  • What is the effect of pressure variation in squeeze casting on the interaction between low-temperature salt fusible cores and molten metal?
  • How does increased pressure alter the heat transfer characteristics at the molten metal-core interface?
  • Can fusible cores function as suitable core materials for realizing complex internal shapes under pressure conditions?
• Research Hypotheses:
  • Increased pressure will accelerate core melting by enhancing heat transfer at the molten metal-core interface, potentially increasing casting defects.
  • Low-temperature salt fusible cores can achieve complex shapes within a specific pressure range, and the optimal pressure depends on core material and process parameters.

4. Research Methodology:

• Research Design:
  • Experimental study using a 50-ton vertical hydraulic press for squeeze casting.
  • Experiments divided into gravity solidification and pressure solidification (1000 kg/cm²) conditions.
• Data Collection Methods:
  • Temperature measurement: Thermocouples placed in molten metal, core, and mold wall to record temperature changes using a Data Acquisition System.
  • Microstructure and Macrostructure Analysis: Specimens sectioned, polished, and etched. Microstructure observed using optical microscopy. Macrostructure visually inspected.
• Analysis Methods:
  • Cooling curve analysis: Analyzing temperature data to understand solidification behavior under different pressures.
  • Microstructure analysis: Examining grain size and phase distribution to assess the effect of pressure on solidification structure.
  • Macrostructure analysis: Observing core shape retention and surface quality to evaluate core performance under pressure.
• Research Subjects and Scope:
  • Alloy: Al-7 wt%Si alloy (A356 alloy). Chemical composition detailed in Table 2.
  • Core: Ceramic weight% 60% core (Ø20 mm diameter, 75 mm height) made of low melting point salt with ceramic particle addition.
  • Casting Equipment: 50 ton vertical hydraulic press (Squeeze casting device) shown in Figure 1.
  • Mold: SKD61 steel mold. Chemical composition detailed in Table 1.
  • Pressure Conditions: Gravity casting and pressure casting at 1000 kg/cm².
  • Experimental conditions summarized in Table 3.

5. Main Research Results:

• Key Findings:
  • Increased pressure led to faster cooling rates and shorter solidification times for the molten metal.
  • Chill zone formation was observed in pressure casting, indicating rapid initial solidification.
  • Increased pressure caused enhanced heat transfer, leading to melting of the core surface and increased surface roughness.
  • Fusible cores exhibited unstable behavior with increased pressure, making shape maintenance difficult.
  • Gravity casting with low-temperature salt cores resulted in good shape retention and sound casting specimens.
  • Core surface dissolution was observed at 1000 kg/cm² pressure.
  • Heat transfer coefficient at the molten metal-core interface was approximately 10 times higher in pressure casting compared to gravity casting.
  • Core temperature increased rapidly under pressure, reaching melting point temperatures quickly.
• Statistical/Qualitative Analysis Results:
  • Cooling curve analysis indicated significantly reduced solidification time under pressure casting compared to gravity casting (no specific numerical data provided).
  • Microstructure analysis showed a tendency for finer grain structures in pressure cast specimens (qualitative observation).
  • Macrostructure analysis revealed increased core surface roughness and shape defects with higher pressure (qualitative observation).
• Data Interpretation:
  • Increased pressure accelerates molten metal cooling and solidification but also enhances heat transfer to the core, potentially causing core melting.
  • Low-temperature salt fusible cores are effective for complex shapes in gravity casting but have limitations in high-pressure squeeze casting due to heat resistance and strength.
• Figure Name List:
  • Fig. 1. Squeeze casting device.
  • Fig. 2. Flow chart of experiment procedure.
  • Fig. 3. Cooling curve of A356 alloy.
  • Fig. 4. Microstructures of gravity cast specimen using fusible core added 60 wt% ceramic powder.
  • Fig. 5. Microstructures of squeeze cast specimen at a pressure of 1000 kg/cm² using fusible core added wt 60 wt% ceramic powder.
  • Fig. 6. Cooling curves of gravity cast specimen using fusible core added 60 wt% ceramic powder.
  • Fig. 7. Cooling curves of squeeze cast specimen at a pressure of 1000 kg/cm² using fusible core added 60 wt% ceramic powder.

6. Conclusion and Discussion:

• Summary of Main Results:
  • In squeeze casting with low-temperature salt fusible cores, increased pressure accelerates molten metal cooling but can induce core melting, degrading casting surface quality.
  • Low-temperature salt cores maintain shape and produce good castings under gravity conditions, but their heat resistance and strength are limited under pressure casting.
  • Rapid increase in heat transfer at the molten metal-core interface in pressure casting leads to rapid core temperature rise and melting.
• Academic Significance of Research:
  • Experimentally demonstrated the effect of pressure on low-temperature salt fusible cores in squeeze casting.
  • Provided fundamental data for process optimization by analyzing heat transfer characteristics at the molten metal-core interface under pressure.
  • Highlighted the applicability and limitations of low-temperature salt fusible cores in high-pressure casting processes.
• Practical Implications:
  • Emphasized the importance of pressure control when using low-temperature salt fusible cores in squeeze casting.
  • Suggested the need for technologies like core surface coating, pressure reduction, and core material improvement to maintain core surface quality in high-pressure casting.
  • Provided guidance for process design and core material development for manufacturing high-quality cast components with complex internal shapes.
• Limitations of Research:
  • Results are specific to Al-7wt%Si alloy and Ceramic weight% 60% core, limiting generalizability.
  • Experiments were limited to gravity and 1000 kg/cm² pressure conditions, lacking investigation of a wider pressure range.
  • In-depth analysis of core material's thermal and mechanical properties is limited.

7. Future Follow-up Research:

• Future Research Directions:
  • Expand squeeze casting experiments with various alloy and core material combinations.
  • Investigate core material composition and manufacturing process modifications to improve heat resistance and strength.
  • Develop and apply core surface coating technologies to control heat transfer and verify their effectiveness.
  • Study molten metal and core behavior under various pressure conditions and process parameters.
  • Evaluate thermal and mechanical properties of fusible cores and establish a comprehensive database.
• Areas Requiring Further Exploration:
  • Clarify the heat transfer mechanism between the core and mold during squeeze casting.
  • In-depth analysis of core melting behavior and casting defect formation mechanisms.
  • Simulation-based optimization of squeeze casting processes.
  • Development of environmentally friendly core materials and removal technologies.

8. References:

• [1] Fatih Cay, S. Can Kurnaz, Mater. & Design, "Hot tensile and fatigue behaviour of zinc-aluminum alloys produced by gravity and squeeze casting", 26 (2005) 479-485.
• [2] T. M. Yue, Jour. of Mater. Process. Tech., "Squeeze casting of high-strength aluminium wrought alloy AA7010", 66 (1997) 179-185.
• [3] Z.W. Chen, W.R. Thorpe, Mater Sci. and Eng. A, "The effect of squeeze casting pressure and iron content on the impact energy of Al-7Si-0.7Mg alloy", 221 (1996) 143-153.
• [4] M.A. Sava, S. Altintaş, Mater. Sci. and Eng. A, "Effects of squeeze casting on the wide freezing range binary alloys", 173 (1993) 227-231.
• [5] P.V. Evans, R. Keyte, R.A. Ricks, Mater. &Design, "Squeeze casting of aluminium alloys for near net shape manufacture", 14 (1993) 65-67.
• [6] A Bloyce, J.C Summers, Mater. Sci. and Eng. A, "Static and dynamic properties of squeeze-cast A357-SiC particulate Duralcan metal matrix composite", 135 (1991) 231-263.
• [7] M. R. Ghomashchi, K. N. Strafford, Jour. of Mater. Process. Tech., "Factors influencing the production of high integrity aluminium/silicon alloy components by die and squeeze casting processes", 38 (1993) 303-326.

9. Copyright:

• This material is based on the paper by [Jun-Ho Lee, J. H. Moon, Dock-Young Lee]: [Effect of Applying Pressure of High Pressure Diecasting Process Using Salt core].
• Paper Source: DOI information not available in the paper

This material is a summary based on the above paper, and unauthorized use for commercial purposes is prohibited.
Copyright © 2025 CASTMAN. All rights reserved.