Study on the composite process of investment casting and sand casting for impeller

The core pulling molding sand casting technology commonly used in the production of cast impeller and the assembly and welding technology commonly used in the preparation of complex investment mold divide the large and complex cast impeller into two parts: complex blade and simple hub and spoke. For the complex blade part, the wax mold of a single blade is pressed by pressing, the single blade is assembled and welded into the investment mold of the blade part with the help of the designed tooling, and the mold shell of the casting impeller blade part is prepared through coating, dewaxing and roasting. For the hub and spoke parts with simple shape, the water glass mold of this part is manufactured according to the shape and size of the cast impeller body, the upper and lower shapes of the hub and the blade shell.

The two parts of the melt mold shell and the water glass mold are combined to form an investment sand mold composite mold for the whole casting impeller. Through melting and pouring in induction furnace, the required impeller castings are obtained. Finally, the rationality, feasibility and scientificity of the composite mold process are proved through the appearance quality inspection, hardness test, tensile test, metallographic microstructure test and analysis of key parts, and combined with the practical application of production.

(1) The designed welding equipment for cast impeller blade assembly solves the problems of assembly welding, positioning and coating of blade part, and provides a reference for the design of welding equipment for other types of castings.

(2) Using ethyl silicate water glass composite shell coating process is a simple and practical process with low cost, high production efficiency and good surface quality.

(3) The composite casting process of investment casting sand casting combines the advantages of investment casting and sand casting, overcomes the shortcomings of single investment casting and sand casting process, and realizes the casting of this kind of large and complex integral impeller.

(4) During the production of zg1cr18ni9ti impeller castings, the composition of furnace charge shall be strictly controlled, and the medium frequency induction alkaline electric furnace shall be used for rapid melting. The melting time of 300kg molten steel shall be controlled within 60min, and the pouring temperature shall be controlled at about 1580 ℃.

(5) The large and complex stainless steel impeller castings produced by the above process method have a single weight of 202kg, dimensional accuracy of cT4 ~ CT5 and surface roughness of RA3 2~1.6; After the test of a pharmaceutical enterprise in Baoji, the entrusted unit of the project, the product quality has reached the level of imported parts, which can be replaced completely. A total of 10 castings of the impeller were produced at one time, creating an economic benefit of more than 100000 yuan.

The investment casting sand casting composite mold process has certain particularity and pertinence for the casting research of large and complex impeller castings, but there is no further research and Discussion on other types of impeller casting, and the research work in this field needs to be further carried out.