Importance and control method of wax shrinkage in precision dewaxing casting

Importance and control method of wax shrinkage in precision dewaxing casting.

With the continuous development of industrial level, people's demand for products is gradually increasing. The ability of precision dewaxing casting process to solve the complex structure of products has been recognized by the industry. Common precision dewaxing casting processes include water glass process, silica sol process, composite process, etc. Among them, due to the casting quality and processing rate of silica sol process, it stands out in many processes. Because of its high density, it is widely used in small and medium-sized, special small and other casting products.

According to the above official WeChat account, the silicon sol dewaxing casting process steps are divided into:

Wax (wax mold) - wax mold repair - wax mold inspection - tree (wax mold tree) - shell (first mud, sand, then mud, and the mold shell is dry) - dewaxing (steam dewaxing) - mold baking - chemical analysis - casting (pouring molten steel in the mold shell) - vibrating shell - cutting and separation of castings and pouring rods - mouth grinding - shot blasting cleaning.

It can be seen that half of the processes are related to wax models. As the precision tolerance of silicon sol dewaxing casting can be guaranteed to CT6, the small tolerance precision is only plus or minus 20 wires, and the process requires high shrinkage of wax mold. In all steps, the shrinkage of wax pattern is not only related to the size of the later products, but also the quality of wax pattern is one of the important factors that directly affect the quality of casting products. The size of the wax pattern directly determines the size of the finished product after casting the mold shell. Therefore, in the process of silicon sol dewaxing and casting, more stable green medium temperature wax is usually used. White low temperature wax with high cost advantage is generally used in water glass and composite dewaxing casting process.

In this paper, the stability control method of Besay casting medium temperature wax will be described in detail.

After a long period of high temperature use, some components of wax will be oxidized and deteriorated. In addition, metal ions will enter the wax, making the wax worse and more impurities. The shrinkage of the wax is very different from that of the new wax. Because it is different from solid impurities, it is difficult to completely solve the problem by sedimentation, dehydration or filtration alone. The factory must regularly discharge some old wax and replenish new materials to ensure the overall stability of wax performance. When the shrinkage rate fluctuates greatly, it is necessary to isolate some wax, increase the investment proportion of new wax, neutralize the recovered wax, and stabilize the shrinkage rate of wax. At present, there are professional medium temperature wax manufacturers that can recycle waste wax. As there is a special miscellaneous removal process in the process, the ash in the recovered wax can be lower than the original new wax, and other properties can be adjusted at will. Generally speaking, competent companies will also equip their own manufacturers with systematic medium temperature wax quality and water removal devices, greatly stabilizing the shrinkage rate of medium temperature wax. Therefore, the shrinkage rate of wax will be different with different treatment methods in different factories. Therefore, in order to save money, replace the supplier directly. We must first test the sample to confirm whether the final product size meets the drawing requirements. In a few cases, due to the different shrinkage of wax, it is necessary to modify the size of some molds.

In order to strictly and stably control the shrinkage rate of the medium temperature wax, the quality of the medium temperature wax is very important. Control the wax from the source, reduce the impurity content, pay attention to the wax treatment and use process, do not use high temperature treatment, and extend the service life of the wax. In order to control the shrinkage rate of medium temperature wax in real time, the factory will customize the wax size measurement mold, set the designated waxing machine, and operate in strict accordance with the specified parameter settings. The expert will measure the wax film every day, record the data, compare the near end time data, and confirm whether the current operation needs to be adjusted.

In addition to the above control and supervision, in daily production, in order to control the size of wax film finished products, it is necessary to set the setting parameters of the wax injection machine in strict accordance with the values given by the Technology Department. Due to the high injection temperature of medium temperature wax, it will shrink slightly after cooling and molding, and the size will change slightly. If the temperature, pressure and time of wax are inconsistent, the wax size will be out of control directly.

Besay Foundry is not only committed to providing customers with forward-looking casting solutions, but also to providing customers with stable commodity quality. The latter is the purpose that we pay attention to each process control, including wax shrinkage in this paper.