With the rapid development of aerospace technology, its impact on the internal and external surface quality and internal structure of aluminum alloy castings At the same time, higher requirements are put forward for the integration and lightweight of aluminum alloy castings For these complex aluminum alloy castings, during the development stage of the casting process, low-cost and fast The importance of rapid casting technology is increasing. This article designs a casting process for a gear pump housing through research on rapid casting technology The production process plan not only shortens the product development cycle, but also improves the quality of castings.
Development background of castings
The shell structure is complex, with interlaced internal oil paths, scattered and numerous thermal nodes, and large local wall thickness variations, which require strict design requirements. The shell can only be formed using metal forming to meet design requirements, but the development cycle of the shell is tight, and there are many problems such as the possibility of structural changes in the shell after the first batch of trial production of the blank. If this casting is produced using traditional production methods, firstly, it is necessary to process the mold, which requires a minimum cycle of 45 days. Secondly, from shell core blowing, mold scribing to casting production and delivery, it takes a maximum of 14 days, with a total time of about 60 days. The cycle cannot meet the requirements of scientific research and production tasks. After the first batch of trial production, if the shell structure changes greatly, it may lead to the scrapping of both the metal mold and the shell core mold due to unrepairable damage, which poses a high risk. This article simplifies the shape structure of the developed casting, and the casting shape is formed by additional processing. The inner cavity uses 3D printing sand cores, which can quickly and flexibly adjust the process plan, saving mold manufacturing and casting development cycles and costs.
Foundry process design
The outline dimensions of the gear pump housing are 485 mm×386 mm×329 mm, and the blank weight is 26.8 kg. The casting has a smooth inner cavity and a complex outer surface shape, with evenly distributed reinforcing ribs and concave-convex structures. The thinnest wall thickness is 8 mm and the thickest is 26 mm. The average wall thickness of the casting is 12 mm. After processing, it must undergo airtight and hydraulic inspections, so defects such as porosity, slag inclusion, shrinkage porosity, and cracks are not allowed in the casting cavity. The casting material is ZL101A.
(1) Oil circuit in the casting cavity. Based on the shape of the oil circuit in the casting cavity, add allowance to the machined parts and maintain the shape of the oil circuit in the non-machined parts. Finally, complete the design of the sand core shape and positioning core head.
(2) Simplify the shape of the casting. According to the shape of the casting, maximize the containment of the casting shape, with a minimum machining allowance of 5 mm. Select the casting pouring process and method, and then increase the wall thickness from bottom to top according to the direction of shrinkage compensation (by increasing the allowance through the shape), simplifying the casting to achieve mold opening through two-part molds, and finally simplifying the casting diagram.
(3) Design of casting process plan. Add risers based on the subsidized casting shape.
(4) Simplify the design of metal molds. After simplifying the structure of the casting, the mold can be simplified to a two-part design with upper and lower sections.
(5) 3D printing sand core. The shell is a metal-type tilting pouring, and the sand core is 3D printed. Due to the suspended oil circuit, the post-processing after printing is required
It is easy to deform. It is necessary to increase support and improve the deformation situation.
6) Meet the accuracy requirements of castings.
Casting process simulation
The metal mold tilting casting process [6] is used, and the AnyCasting software is used for simulation analysis of the filling and solidification processes. The pouring temperature is set at 720-730 ℃, and the metal mold temperature is 280-320 ℃. Through simulation analysis, it can be seen that the residual melt is located at the position of the casting’s open or closed risers. There is no isolated molten pool in the hot spot of the casting, and the overall solidification is good, without shrinkage porosity defects, indicating that this process plan can be implemented. However, after calculation, the yield of this casting is low. The casting weight is 8 kg, and the riser mass reaches 6 kg, with a yield of about 57%. This is a rapid development of the first batch of castings. After using an insulating riser in the later stage, it can not only improve the efficiency of riser shrinkage, but also improve the yield of castings.
Conclusion
The development cycle of newly developed products is relatively short, which requires exploring a fast and low-cost development route. Firstly, by simplifying the shape of the casting, this technical solution not only reduces the design difficulty of the casting process plan, but also reduces the difficulty of mold design and processing. Secondly, the inner cavity sand core of aluminum alloy castings was rapidly manufactured through 3D printing, which not only saved the mold development cycle but also improved production efficiency. Thirdly, machining has supplemented the simplified position of the casting’s appearance, and through surface sandblasting treatment, the appearance quality meets the requirements. The mechanical properties and internal quality of the final produced castings can meet the design requirements, and this method can be applied to the development process of new products in other fields.