Experimental and Theoretical Studies on the Effect of Die Temperature on the Quality of the Products in High-Pressure Die-Casting Process

This document summarizes the research paper "Experimental and Theoretical Studies on the Effect of Die Temperature on the Quality of the Products in High-Pressure Die-Casting Process."

1. Overview:

  • Title: Experimental and Theoretical Studies on the Effect of Die Temperature on the Quality of the Products in High-Pressure Die-Casting Process
  • Authors: Mohammad Sadeghi, Jafar Mahmoudi
  • Year: 2012
  • Published in: Advances in Materials Science and Engineering
  • Keywords:
    • Die temperature
    • High-pressure die-casting (HPDC)
    • A380 alloy
    • Numerical simulation
    • Experimental observation
    • ProCAST software
    • Ladder frame

2. Research Background:

  • Social/Academic Context:
    • High-pressure die-casting (HPDC) process has been widely used to manufacture a large variety of products with high dimensional accuracy and productivities.
    • It has a much faster production rate in comparison to other methods and it is an economical and efficient method for producing components with low surface roughness and high-dimensional accuracy.
    • All major aluminum automotive components can be processed with this technology [1-7].
    • Although HPDC has a considerably higher speed than other metal forming processes, due to complexity of the process and the number of variables, optimization of the process is essential.
    • In particular, there are issues related to control of:
      • Die temperature
      • Solidification of the components
      • Quality control of the castings
      • Development or use of a coherent and integrated system
    • The mechanical properties of a die-cast product are principally related to:
      • Die temperature
      • Metal velocity at the gate
      • Applied casting pressure [4]
    • Combination of:
      • Die temperature
      • Fluidity of the molten metal
      • Geometrical complexity of the parts
      • Cooling rate during die casting
        affect the integrity of a cast component.
    • Thermal profile of the die during operation is another important factor in the production of high-quality components.
    • Too high temperature of the die will lead to longer solidification which consequently prolongs the cycle time.
    • A cold die will contribute to a number of surface defects [3, 8, 9].
  • Limitations of Existing Research:
    • In many of these works, the geometry of the part is simple and there are few researches on very complex part in industry.
  • Necessity of Research:
    • The aim of this work is optimization of process parameters in die casting of a complex automotive component named ladder frame by simulation.

3. Research Objectives and Research Questions:

  • Research Objective:
    • Die temperature in high-pressure die casting of A380 alloy is optimized by experimental observation and numerical simulation.
  • Core Research Question:
    • What is the effect of die temperature on the quality of the products in high-pressure die-casting process?
    • What is the proper die temperature for this alloy?
  • Research Hypothesis:
    • It is shown that the proper die temperature for this alloy is above 200°C.

4. Research Methodology:

  • Research Design:
    • Combined experimental observation and numerical simulation.
    • Experimental measurements of die temperature and melt temperature.
    • Numerical simulation using ProCAST software.
    • Verification of simulation results by experimental measurements.
  • Data Collection Method:
    • Experimental Data:
      • Die temperatures at the initial step and the final filling positions were measured.
      • The difference between these values was calculated.
      • Melt temperature was measured by thermocouple and Laser pyrometer (model chy 110) at the die surface.
      • Experiments were conducted at die temperatures of "150°C, 200°C, and 250°C".
    • Simulation Data:
      • ProCAST software was used to simulate the fluid flow and solidification step of the part.
      • Material properties of the alloy were extracted from the software database and are shown in Table 1.
      • Initial and boundary conditions used in the simulation are given in Table 2.
  • Analysis Method:
    • Numerical Simulation:
      • Governing equations for mass balance, momentum balance, and energy balance (enthalpy formulation) were solved using ProCAST software.
      • Free surface modeling is achieved with a scalar variable, Φ.
      • Two deferent mesh sizes were used and simulation results were compared at these two mesh sizes to ensure mesh independency of the results.
    • Experimental Verification:
      • The results were verified by experimental measurements.
  • Research Subject and Scope:
    • Material: A380 material.
    • Part Geometry: Ladder frame (one part of the new motor EF7) with a very complicated geometry (Figure 1).
    • Process: High-pressure die casting (HPDC).
    • Die Temperatures: "150°C, 200°C, and 250°C".
    • Melt Temperature: Initial melt temperature of "680°C", shot sleeve speed of "3 m/s", and speed melt in gate of "55 m/s" for the ladder frame were assumed.
    • Machine: IDRA1600 die-cast machine.

5. Main Research Results:

  • Core Research Results:
    • It is shown that the proper die temperature for this alloy is above 200°C.
    • Cold flow surface defects occur at final filling positions predicted by the software at die temperature of "150°C" (Figure 5).
    • Shrinkage defects occurred at the final solidification positions are shown in Figure 12, which were predicted by the software.
    • The verified model interestingly represented the correct location of the porosity defects in the castings.
  • Statistical/Qualitative Analysis Results:
    • Melt Temperature Variation:
      • The results show that the die temperature varies from "150 to 250°C", while the melt temperature varies between "660°C and 680°C" (Figure 2).
      • Table 3 shows melt temperature at outset injection in shot sleeve and at end injection final filling position.
      • At die temperature "150°C", Melt temperature °C at outset injection was "670, 669, 671" and Melt temperature °C at end injection was "650, 649, 652".
      • At die temperature "200°C", Melt temperature °C at outset injection was "675, 676, 674" and Melt temperature °C at end injection was "664, 666, 663".
      • At die temperature "250°C", Melt temperature °C at outset injection was "679, 680, 679" and Melt temperature °C at end injection was "671, 670, 668".
    • Melt Temperature Reduction:
      • The difference of two melt temperature curves at the initial and end of the process at "250°C, 200°C, and 150°C are 9.5°C, 10°C, and 19.5°C, respectively" (Figure 3).
    • Defect Observation:
      • Figure 5 shows typical examples of cold flow surface defects in pieces produced in a die with temperature of "150°C".
      • Gas porosities caused by entrapped air during metal injection are illustrated in Figure 7.
      • Shrinkage defects occurred at the final solidification positions are shown in Figure 12.
  • Data Interpretation:
    • There is a break point in the curve of end injection at die temperature of "200°C".
    • Defects are more probable at die temperatures less than "200°C".
    • With regard to this break point, it can be seen that the normal die temperature for this alloy is "200°C".
    • Maximum temperature depends on the die cooling system and optimized cycle time for production of a specific part.
    • Comparison of the experimental and simulation results indicates that defects in the pieces are placed at the predicted places by simulation.
  • Figure Name List:
    • FIGURE 1: Geometry of ladder frame product.
    • FIGURE 2: Melt temperatures at die entrance and start injection versus die temperatures.
    • FIGURE 3: Melt temperatures at the end of the die and end injection versus die temperatures.
    • FIGURE 4: Reduction of melt temperature at various die temperatures at the initial and the end of injection.
    • FIGURE 5: Cold flow surface defects at final filling positions.
    • FIGURE 6: positions of added overflows to the mold.
    • FIGURE 7: Some porosity defects.
    • FIGURE 8: Velocity vectors of the melt at the three holes in the front of the gate.
    • FIGURE 9: Steps filled die by the melt and show End points.
    • FIGURE 10: Flow pattern of melt with die temperature (a) 150°C and (b) 250°C in same time. Time al = b1, a2 = b2, and a3 = b3.
    • FIGURE 11: Hot spots at the end of solidification step, which are susceptible to casting defects.
    • FIGURE 12: Defects occurred in final solidification positions.
Figure 7: Some porosity defects.
Figure 7: Some porosity defects.
Figure 12: Defects occurred in final solidification positions.
Figure 12: Defects occurred in final solidification positions.

6. Conclusion and Discussion:

  • Summary of Main Results:
    • Comparison of the experimental and simulation results indicates that defects in the pieces are placed at the predicted places by simulation.
    • Optimum die temperature for A380 alloy for H13 die material is around "200°C".
    • If the die temperature is reduced from the optimum temperature range, probability of cold flow defects and air porosities increase.
    • Determination of optimized places of overflows by simulation led to decrease of some casting defects such as cold shots and air porosities.
  • Academic Significance:
    • This study experimentally and theoretically determined the optimal die temperature for high-pressure die casting of A380 alloy.
    • The research highlights the importance of die temperature control in achieving high-quality die-cast products.
    • The use of numerical simulation (ProCAST software) is validated as an effective tool for optimizing die casting processes and predicting defect locations.
  • Practical Implications:
    • For manufacturing components using A380 alloy and H13 die material in HPDC, maintaining a die temperature of around "200°C" is recommended to minimize defects and ensure product quality.
    • The findings suggest that die casters should carefully control and monitor die temperature to avoid cold flow defects and air porosities, especially when using die temperatures below 200°C.
    • Numerical simulation can be used to optimize die design and process parameters, particularly in determining effective locations for overflows to mitigate defects.
  • Limitations of Research:
    • The study focused on a specific alloy (A380) and part geometry (ladder frame).
    • The optimal die temperature may vary for different alloys, die materials, and component designs.
    • Further research may be needed to investigate the influence of other process parameters and die cooling system designs.

7. Future Research:

  • Future Research Directions:
    • Further research is recommended to investigate the effect of die temperature on other aluminum alloys and different component geometries in HPDC.
    • Optimization of die cooling systems to maintain a uniform die temperature and improve cycle time could be explored.
    • Further studies could investigate the influence of other process parameters such as injection speed and pressure in conjunction with die temperature.
  • Areas for Further Exploration:
    • Investigating the effect of different die materials on the optimal die temperature.
    • Exploring advanced simulation techniques to predict and mitigate other types of casting defects.
    • Conducting economic analysis to determine the optimal balance between die temperature, cycle time, and product quality in HPDC.

8. References:

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9. Copyright:

  • This material is based on the paper by Mohammad Sadeghi and Jafar Mahmoudi: Experimental and Theoretical Studies on the Effect of Die Temperature on the Quality of the Products in High-Pressure Die-Casting Process.
  • Paper Source: https://doi.org/10.1155/2012/434605

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Tags: A380; ,aluminum alloy; ,aluminum alloys; ,Applications; ,CAD; ,Die casting; ,High pressure die casting; ,Quality Control; ,STEP