Numerical simulation of low pressure sand casting process for aluminum alloy moving coil skeleton

The electric vibration table can meet the simulation requirements under various vibration conditions, andHas been applied to the simulation test of typical vibration components in automotive, aerospace and other fieldsThe moving coil frame is the core component of the electric vibration table, mainly used for transmittingVibrating and load-bearing test pieces, so they require light weight, high stiffness, and high resonancefrequency characteristics.The moving coil skeleton is formed using traditional gravity casting technology,Low-pressure casting is a casting process that fills the mold under anti-gravity conditions and solidifies under certain pressure conditions.It is different from gravity casting in that it uses a low-pressure mold and a low-pressure filling system.Compared with force casting, its metal liquid filling is stable, and it is not easy to cause gas and slag entrainment, andSolidification under pressure is beneficial to the feeding of the metal liquid, reducing shrinkage cavities, porosity, etc.defects can significantly improve the mechanical properties of castings.By changing the pouring process and using low-pressure casting, we solved the problem of AC7ASlag inclusion and porosity problems in the aluminum-magnesium alloy moving coil skeleton;Su Dawei et al. used the ProCAST software to analyze multiple process options for a new aluminum alloy wheel hub productConduct simulation analysis, put the improved process plan into trial production, andThe sampling inspection results are basically consistent with the simulation results;numerical simulation is adoptedTechnology, research on the pouring temperature of alloy liquid and mold preheating in low pressure castingThe influence of temperature and filling time on porosity of castings, and the optimal lowThe parameters of the die casting process have been tested and the yield rate can reach 86% after trial production.The temperature and pressure during the solidification process of the low pressure casting of the caliper are simulated using numerical simulation.The degree of shrinkage and porosity were analyzed, and through optimizing the runner and adopting localInsulation, cooling, and other measures have been optimized to significantly eliminate casting defects.Defects such as shrinkage porosity and shrinkage cavity in the part.This study uses the ProCAST software to simulate the low-cycle fatigue behavior of aluminum alloy moving coil skeletons.Numerical simulation of the die casting process, analysis of pouring temperature, sand mold preheating temperatureThe influence of temperature and holding pressure on the production of moving coil skeletons is provided for reference.

1. Model establishment

The material of the moving coil skeleton is ZL302 alloy, and its chemical composition is shown in Table 1.The structure of the part is shown in Figure 1, and the overall dimensions are 320mm × 360mm ×The maximum wall thickness is 23mm, and the minimum wall thickness is only 8mm.According to the analysis of the low pressure casting process on the part structure, the surface of the part is provided withTo prevent the formation of holes, a 4mm machining allowance is set on the upper and lower surfaces.Three-dimensionalThe modeling software UG performs geometric modeling of the moving coil skeleton casting, as shown in the figure.

2 Low pressure casting process

In low pressure casting, the main parameters that affect the quality of the casting are the pouring temperature,temperature, sand mold preheating temperature, packing pressure, etc. For aluminum alloy moving coil skeletonsCasting, according to the principle of low pressure casting and production experience, using low pressure sandType casting.

3 Numerical simulation calculation

The numerical simulation was conducted using the ProCAST software.In the CAST model,The direction of gravity in the block is set to be opposite to the direction of filling the molten metal;virtual sand box materialThe material is Resin Bonded Sand, and it is set as a solid with a mechanical type ofLiner-elastic;casting material is ZL302, mechanical type is rigid;The heat transfer coefficient between the molten metal and the sand mold is h=500 W/(m2·K);The outer surface of the sand box is set to Air cooling, and the liquid pipe mouth is set to InletThe pressure parameter value should be higher than the pouring process parameter pressure value0.1 MPa);select LPDCFil in Simulation Parametersi n g to simulate.

4. Simulation Results

4.1 The influence of pouring temperature on the low pressure casting processSelect schemes 1-4 for numerical simulation analysis, as shown in Figure 2.It can be seen that the filling process of the castings under the four groups of schemes is relatively consistent, with the metal liquid flowing from theThe filling port is filled smoothly into the mold interior without air entrapment or splashing.The numerical simulation results show that with the pouring temperature rising from 690℃ toAt 750℃, the filling time of the casting decreases from 22s to 20s, indicating that as the pouring temperature increases, the filling efficiency of the casting increases and the filling time of the casting decreases.The main reason is that when the pouring temperature is low, the flowability of the molten metal becomes poor, making it difficult toFilling the cavity may lead to cold shut and insufficient pouring defects.Figure 3 shows the distribution of shrinkage porosity in castings at different pouring temperatures.It can be seen that the distribution of shrinkage and porosity under the four sets of schemes is relatively consistent, with the mainIt should be distributed at the junction of the rib plate and the base of the casting, where the wall thickness of the casting is relativelyThick, easy to form hot spots and produce independent liquid phase regions, making the casting stable during pressure maintaining and solidification.The solid-state pressure cannot make the molten metal shrink to the hot spot, resulting in shrinkage cavitiesPorosity defects.The shrinkage and porosity volumes of castings in schemes 1-4 are 0.224, 0.202, 0.128, and 0.140 cm3, respectively. Among them, scheme 3 (pouring temperature 730The shrinkage porosity volume at 100℃ is the smallest, indicating that appropriately increasing the pouring temperature can reduce the shrinkage porosity volume.Small shrinkage cavities and porosity.

4.2 The influence of sand mold preheating temperature on low pressure casting processTo investigate the influence of sand mold preheating temperature on the low-pressure casting process of moving coil skeleton, schemes 3 and 7 were selected for numerical simulation analysis. The results are shown in Figure 4.It can be seen that at different preheating temperatures of the sand mold, the filling process of the molten metal isKeep stable and no splashing.As the preheating temperature of the sand mold increases, the metal liquidThe filling time did not change significantly, indicating that at higher pouring temperatures, the sandThe preheating temperature of the mold has a small effect on the filling rate.Figure 5 shows the distribution of shrinkage and porosity in castings at different mold preheating temperatures.It can be seen that the distribution of shrinkage and porosity varies at different mold preheating temperatures.The position is basically the same, but when the sand mold preheating temperature reaches 100℃, the castingThe shrinkage and porosity volume generated inside the part is reduced.The main reason is that the shrinkage and porosity volume is reduced with the sand mold.When the preheating temperature rises, the temperature of the molten metal is high when the filling is completed, and during the packing stageThe metal liquid can improve the feeding effect on the hot part under the action of pressure.Therefore, in practical production, the preheating temperature of the sand mold can be appropriately increased to improve the quality of the casting.It is a liquid shrinkage effect.

4.3 The effect of packing pressure on the low pressure casting process

To investigate the influence of pouring temperature on the low pressure casting process of moving coil skeletonLaw, choose option 3, option 5, option 6 for numerical simulation analysis, resultsAs shown in the figure, it can be seen that the solid fraction is highest at the thin wall of the casting rib plate at the end of filling, and lowest near the ingate and thick parts at the top.From the castingThe distribution of solid fraction during solidification process shows that the overall solidification of the casting is over-complete.The process tends to solidify sequentially.The figure shows the distribution of shrinkage porosity in the castings after solidification.It can be seen that as the holding pressure increases, the volume of shrinkage porosity in the castings decreases fromSince the volume of the mold is reduced from 0.13cm3 to 0.11cm3, increasing the holding pressure appropriately can improve the casting quality.The quality of the piece.

5 Conclusion

(1) As the pouring temperature increases, the fluidity of the molten metal increases, and the filling timeThe shrinkage and porosity volume of the casting decreases firstly with the increase of pouring temperatureThe trend of increasing after a short period of time, appropriately increasing the pouring temperature can improve the casting defects.(2) The increase in the preheating temperature of the sand mold has a greater impact on the filling rate of the casting than the mold temperature.small, but when the preheating temperature of the sand mold is increased from 30°C to 100°C, the castingThe volume of shrinkage cavity and porosity is reduced accordingly.(3) During the pressure-holding solidification stage, as the pressure holding pressure increases, the flow of metal liquidThe dynamic performance is improved, the shrinkage performance is enhanced, and the shrinkage and porosity volume of the casting is reduced from 0.13As the volume of sand mold decreases from 3cm3 to 0.11cm3, increasing the packing pressure appropriately can improve the quality of the casting while ensuring the strength of the sand mold in practical production.

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