Investment Precision Casting

Lost wax casting, now known as investment precision casting, is a casting process with less cutting or no cutting. It is an excellent technology in the casting industry, and its application is very wide. It is not only suitable for casting of various types and various alloys, but also produces castings with higher dimensional accuracy and surface quality than other casting methods, and even complex, high temperature resistant, not easy to process castings that are difficult to cast by other casting methods can be cast by investment precision casting.

Investment precision casting is developed on the basis of ancient wax casting. As an ancient civilization, China is one of the earliest countries to use this technology. As far back as hundreds of BC, Chinese ancient working people created this kind of lost wax casting technology, which was used to cast Zhong Ding and vessels with various fine patterns and characters, such as the tomb of Marquis Yi Zeng in the Spring and Autumn Period. The pedestal of the tomb of Marquis Yi Zeng consists of several intertwined dragons, which are connected end to end and interleaved up and down, forming a multi-layer moire pattern with hollow in the middle. These patterns are difficult to be made by ordinary casting process, but the lost wax casting process can take advantage of the lack of strength and easy carving of paraffin. Ordinary tools can be used to carve handicrafts with the same paraffin material as the desired tomb plate of Marquis Yi. Then, with the addition of pouring system, coating, dewaxing and pouring, the exquisite tomb plate of Marquis Yi can be obtained.

It was in the 1940s that modern investment casting method was applied in industrial production. The development of jet engines at that time required the manufacture of heat-resistant alloy parts with complex shapes, precise dimensions and smooth surfaces, such as blades, impellers and nozzles. Because heat-resistant alloy materials are difficult to be machined and the shape of the parts is complex, it is impossible or difficult to be manufactured by other methods. Therefore, a new precision forming process needs to be found. Therefore, the lost wax casting passed down from ancient times is learned from, and through the improvement of materials and technology, the modern investment casting method has achieved important development on the basis of ancient technology. Therefore, the development of aviation industry promotes the application of investment casting, and the continuous improvement and perfection of investment casting also creates favorable conditions for the further improvement of performance in aviation industry.

Our country began to apply investment casting to industrial production in 50 and 60 years. Subsequently, this advanced casting process has been greatly developed, and has been widely used in aviation, automobile, machine tool, ship, internal combustion engine, gas turbine, telecommunication instruments, weapons, medical instruments and cutting tools and other manufacturing industries, but also used in the manufacture of arts and crafts.

The so-called investment casting process is simply to use fusible materials (such as wax or plastic) to make a fusible model (investment mold or model for short), coated with several layers of special refractory coating, after drying and hardening to form a whole shell, then use steam or hot water to melt the model from the shell, and then the shell is placed in a sand box, and filled with dry sand around it. Finally, the cast is placed in a roaster and roasted at high temperature (if high strength shell is used, the mold can be fired directly without molding). The cast or shell is roasted and the molten metal is poured into it to get the casting.