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How to optimize the aluminum alloy motor housing process for new energy vehicles?

The global energy and environmental crisis has prompted the upgrading of international automotive technology, bringing major strategic opportunities to my country’s independent innovation in new energy, especially electric vehicles. As a key component of new energy vehicles, aluminum alloy motor housing have complex structures and high performance requirements.The material of the new energy vehicle aluminum alloy motor housing is ZL101A, which weighs 24kg. There are multiple bosses on the outside of the casting. The upper side wall is 27.5mm thick, the lower side wall is 32mm thick, and there is an 8.5mm wide spiral water channel in the middle side wall, such as As shown in Figure 1. The inner cavity, upper and lower end faces and boss end faces of the casting are all processed, and there must be no defects such as pores, shrinkage porosity, and slag inclusions. The air tightness requirement is ≥0.6MPa without air leakage.
EV motor housing
1.EV motor housing


Original process plan The upper and lower sides of the casting and the outer boss are thick-walled areas, which will produce hot spots during the solidification process of the casting, while the middle water channel is a thin-walled area. The wall thickness difference of castings is large, making it difficult to achieve sequential solidification and prone to defects such as shrinkage cavities and shrinkage porosity. The original plan is based on the structural characteristics of the casting, using low-pressure casting, using metal molds for the outer shape and inner cavity, using sand cores for the spiral water channel, four risers on the inner side, and a cross runner at the bottom, as shown in Figure 2.

custom design picture 2 Original process pouring system



Original plan simulationThe original plan is simulated, and the solidification process is shown in Figure 3. The casting begins to solidify at 22s and is completely solidified at 292s. During the solidification process, hot spots are formed in the thick-walled areas of the casting, and the feeding channels are interrupted at locations A, B, and C in the figure, forming closed liquid isolated areas. Castings do not achieve sequential solidification and tend to form shrinkage porosity.

casting process Figure 3 Solidification process of the original plan

2Problems in actual production After some castings are processed, shrinkage defects appear in the inner cavity and end face corresponding to the boss (see Figure 4 and Figure 5), and the scrap rate is high. And because the shrinkage of the risers on the four inner sides is blocked, it is difficult to demould the iron core during casting production, and the production efficiency is low.

4 Inner cavity defects

Figure 5 End face defects


Solution optimization The original casting is shown in Figure 6, with a large wall thickness difference. A, B, C, D, and E are five thick-walled areas. Among them, location A is not conducive to setting up riser feeding. The hot joints formed by the combination of locations B, C, D, and E with the riser exceed the feeding capacity of the riser, and the temperature gradient between the hot joints and the riser is not established. Castings Sequential solidification is difficult to achieve. Moreover, casting alloys have a critical wall thickness. When the wall thickness of the casting exceeds the critical wall thickness, the strength of the casting does not increase proportionally with the increase in wall thickness, but will decrease significantly. Therefore, with the consent of the user, the structure of the thick-walled area of ​​the casting was fine-tuned and the weight was reduced to reduce the hot spots during the solidification process of the casting. The optimized casting is shown in Figure 7.

EV motor housing

Figure 6 Original casting

EV motor housing

Figure 7 Optimized casting

According to the simulation results, in view of the interruption of the feeding channel at the intersection of B and C with the runner, the runner was moved upward and directly connected to B and C. This also reduced the distance between the runner and the upper end of the casting, shortening the Determine the distance that the riser needs to be fed. Since the hot joints at D and E are reduced after the weight of the casting is reduced, changing the four edge risers to have inflection allowances not only facilitates the top-down solidification sequence of the casting, but also reduces the volume of the gating system and shortens the solidification time. It is also conducive to demoulding and can greatly improve process yield and production efficiency. The optimized gating system is shown in Figure 8.

Figure 8 Optimized gating system




plan simulation The optimized scheme is simulated, and the solidification process is shown in Figure 9. During the solidification process, the casting forms a feeding channel through the subsidy, runner, and sprue, and the solidification expansion angle is always toward the direction of the runner, effectively establishing a temperature gradient between the hot section and the riser, and realizing sequential solidification. Figure 9 Optimized solution solidification process

2 Production verification

Judging from the production verification, the solidification time of the casting is reduced, demolding is easier than the original plan, and there are no casting defects after X-ray inspection. After the casting is processed, the structure of the processed surface is dense and defect-free, and the air tightness test is qualified. The original plan of castings with a gating system weighs 47kg, the process yield rate is 51%, and it takes an average of 20 minutes to produce one piece. The optimized plan has a casting with a gating system of 35kg, the process yield rate is 69%, and it takes an average of 15 minutes to produce one piece. For the same 1 ton aluminum alloy liquid, with a production time of 7 hours, the original plan can produce 21 pieces, and the optimized plan can produce 28 pieces. The optimization plan has greatly improved the process yield and production efficiency, and reduced production costs. The casting produced by the optimized plan is shown in Figure 10. completely EV motor housing Figure 10 Castings produced by the optimized solution



In conclusion ▶ By optimizing the casting structure and reducing the heat during the solidification process of the casting, it not only helps to improve the internal quality of the casting, but also reduces the material used and makes the product beautiful. ▶ By optimizing the process plan and using interruptions instead of side risers, it not only helps to achieve sequence probability for castings and improve product quality, but also improves process yield and production efficiency and reduces costs.