The so-called investment casting process, simply put, involves making a fusible model from easily meltable material, coating it with several layers of specially formulated refractory coating, drying and hardening to form an integral shell, then melting out the model from the shell using steam or hot water, placing the shell in a molding box filled with dry sand, and finally placing the mold in a firing furnace for high-temperature firing (when using high-strength shells, the demolded shell can be fired directly without molding). After firing, molten metal is poured into the mold or shell to obtain the casting. Investment castings have high dimensional accuracy, generally reaching CT4-6 (sand casting is CT10-13, die casting is CT5-7). Of course, because the investment casting process is complex with many factors affecting dimensional accuracy, such as pattern material shrinkage, pattern deformation, linear changes of the shell during heating and cooling, alloy shrinkage rate, and casting deformation during solidification, ordinary investment castings, despite their relatively high dimensional accuracy, still need improvement in consistency (castings using medium to high-temperature wax have much better dimensional consistency). When pressing the pattern, a die with a high surface finish is used, so the pattern also has a high surface finish. Additionally, the shell is made of refractory coating formulated from high-temperature special binders and refractory materials coated on the pattern, and the inner surface of the mold cavity in direct contact with the molten metal has high surface finish. Therefore, the surface finish of investment castings is higher than that of ordinary castings, generally reaching Ra1.6-3.2μm. The greatest advantage of investment casting is that due to the high dimensional accuracy and surface finish of investment castings, machining work can be reduced, leaving only a small machining allowance on parts requiring higher precision, or even just grinding and polishing allowances without machining. This shows that the investment casting method can save machine tools and machining time, and significantly conserve metal raw materials. Another advantage of investment casting is that it can produce complex castings of various alloys, especially high-temperature alloy castings. For example, jet engine blades, with their streamlined outer contour and internal cooling cavities, are almost impossible to form by machining. Investment casting not only enables batch production, ensuring casting consistency, but also avoids stress concentration from residual tool marks after machining.