Precision castings are divided into: investment casting, ceramic mold casting, metal mold casting, pressure casting, and lost foam casting. It is the casting obtained by lost wax casting, lost foam, silica gel and other casting methods. This type of casting has high dimensional accuracy, high surface finish, few defects, clear and perfect outline, and generally you don't need to use mechanical processing.
The casting method of obtaining precision castings with precision casting is called precision casting. Precision casting is also called lost wax casting. Its products are precise, complex, and close to the final shape of the part, and can be used directly without processing or with little processing. Therefore, investment casting is an advanced technology with near net shape.
Compared with traditional casting processes, precision castings can obtain relatively accurate shapes and higher casting accuracy. The so-called precision casting process is simply to use fusible materials to make a fusible model, apply several layers of special refractory coatings on it, dry and harden to form an integral shell, and then use steam or hot water to remove Melt the model in the mold shell, then place the mold shell in the sand box, fill it with dry sand around it, and finally put the mold into the roasting furnace for high-temperature roasting, and then pour the mold or shell into it after roasting Molten metal to obtain castings.
At present, there are two kinds of technology for precision casting: lost wax precision casting and pressure regulating precision casting technology.
Lost-wax precision casting is now called investment casting. It is a precision casting process with little or no cutting. It is an excellent process technology in the precision casting industry and has a wide range of applications. It is not only suitable for precision casting of various types and alloys, but also produces castings with higher dimensional accuracy and surface quality than other precision casting methods, and even other precision casting methods are difficult to cast, high temperature resistant, and difficult to process. All castings can be cast by investment casting.
Surge forming precision casting technology is a new casting technology invented mainly for the casting production problems of large complex thin-walled parts. Using this technology to produce large and complex thin-walled castings can obtain better filling capacity and feeding capacity, so that the crystal grains of the castings are refined, the density is improved, and the performance is significantly improved. With the continuous research and development of this technology, the application effect and scope of application of this technology have been continuously strengthened and broadened. At present, the pressure-regulated forming precision casting technology has been engineered in the production of large and complex thin-walled aluminum alloy castings of a certain aviation category, and the technical benefits are very obvious.
More and more mechanical products adopt precision casting, which is mainly inseparable from the two advantages of precision castings:
1. Precision casting makes complex castings of various alloys, especially high-temperature alloy castings. For example, the blade of a jet engine, its streamlined outline and cooling cavity, can hardly be formed by machining technology. Production with precision casting technology can not only achieve mass production, ensure the consistency of castings, but also avoid the stress concentration of residual knife marks after machining.
2. Precision casting. Because investment castings have high dimensional accuracy and surface finish, machining work can be reduced, just leave a little machining allowance on the parts with higher requirements, and even some castings only need to be polished, Polishing allowance can be used without machining. It can be seen that the use of precision casting methods can greatly save machine tool equipment and processing man-hours, and greatly save metal raw materials.