Investment Casting Process Development in China

Investment casting is based on the ancient wax mold casting. As an ancient civilization, China was one of the early adopters of this technology. As far back as BC, hundreds of years ago, the ancient Chinese working people created this lost wax casting technique, which was used to cast various fine patterns and characters. Zhong Ding and utensils and other products, such as the Zeng Houyi tomb in the Spring and Autumn Period. The base of Zenghouyi's tomb is a pair of intertwined dragons. They are connected at the end and are staggered up and down to form a multi-layered cloud pattern in the middle. These patterns are difficult to manufacture by ordinary casting process, but are cast by lost wax method. The process can take advantage of the fact that the paraffin has no strength and is easy to engrave. With ordinary tools, it can engrave the paraffin-like handicrafts like the Zenghouyi tomb, and then add the pouring system, paint, dewaxing and pouring. You can get the exquisite Zenghou Yi tomb.
The practical application of moderninvestment casting methods in industrial production was in the 1940s. At that time, the development of aviation jet engines required the manufacture of heat-resistant alloy parts such as blades, impellers, nozzles, and the like, which were complex in shape, size, and smooth in surface. Since the heat-resistant alloy material is difficult to be machined, the shape of the part is so complicated that it cannot be or is difficult to manufacture by other methods. Therefore, it is necessary to find a new precision molding process, so that the lost wax casting which has been handed down from ancient times is passed through the materials and processes. The improvement of the modern investment casting method has achieved important development on the basis of ancient techniques. Therefore, the development of the aviation industry has promoted the application of investment casting, and the continuous improvement and improvement of investment casting has also created favorable conditions for the aviation industry to further improve its performance. In the 1950s and 1960s, China began to apply investment casting to industrial production. Since then, this advanced casting process has been greatly developed and has been widely used in the manufacturing industries of aviation, automobiles, machine tools, ships, internal combustion engines, gas turbines, telecommunications equipment, weapons, medical equipment and cutting tools, as well as in the process. The manufacture of art.
The so-called investment casting process, simply by using a fusible material (such as wax or plastic) to make a fusible model (referred to as investment or model), coated with several layers of special refractory coating, dried and hardened After forming a monolithic shell, the model is melted from the shell by steam or hot water, and then the shell is placed in a sand box, and the dry sand is filled around the mold, and then the mold is placed in a roaster at a high temperature. Calcination (for example, when a high-strength type shell is used, the demolded shell can be directly fired without styling), and the mold or shell is fired, and molten metal is poured therein to obtain a cast piece.
Investment castings have high dimensional accuracy, generally up to CT4-6 (sand casting is CT10~13, die casting is CT5~7). Of course, due to the complicated process of investment casting, there are many factors affecting the dimensional accuracy of castings, such as mold. The shrinkage of the material, the deformation of the investment mold, the change in the amount of the shell during heating and cooling, the shrinkage of the alloy, and the deformation of the casting during solidification, etc., so the dimensional accuracy of ordinary investment castings is high, but Consistency still needs to be improved (the dimensional uniformity of castings using medium and high temperature waxes is much higher).