Shell preparation method for investment casting

Abstract

The invention relates to a shell preparation method for investment casting. The shell preparation method comprises the steps of stiffener determining, reinforced investment pattern module preparation,shell preparation, stiffener removal, investment pattern removal and shell roasting. According to a casting piece structure, the investment pattern stress situation and mold filling solidification process computer simulation, the position of a stiffener is determined, and the investment pattern and the shell are prevented from deformation advantageously and are supported. By removing the stiffener, a hole channel and a demolding opening are formed in the investment pattern, the shell can be separated from the investment pattern without being turned over, and the surface quality of an inner cavity of the shell is improved.

Description

technical field [0001] The invention relates to a method for preparing a mold shell for investment casting with high dimensional accuracy and complex structure, which can be applied to the fields of investment casting and lost foam casting. Background technique [0002] Investment casting is the main method for industrial manufacturing of products with high dimensional accuracy and complex structures, and has been widely used in the manufacture of components in petroleum, electronics, chemical, automotive and aerospace industries. The investment casting process is mainly to use fusible materials to make a fusible model (investment mold), which is coated with several layers of special refractory coatings (adding sand), and then dried and chemically hardened to form a whole module. The hollow shell is obtained by melting the molten mold from the mold group, and then the shell is fired at a high temperature to make a shell for pouring, and finally the molten metal is poured int...

AI Technical Summary

Problems solved by technology

For investment patterns with large volume, large wall thickness or complex internal structure, the demoulding time of the shell is long, the production cost is high, and the phenomenon of incomplete demoulding is prone to occur, making the residual investment pattern a foreign object in the later use of the shell. thing

If it is necessary to demould by tilting the shell or flipping the shell multiple times, the shell will be damaged, and micro-cracks will be formed on the surface of the inner cavity of the shell, which will affect the surface quality of the casting

At the same time, long-term demolding will affect the shell with fillers or coatings inside, causing problems such as thermal oxidation of fillers and coatings, thermal expansion, deformation, and cracking of the shell. For example, by coating on the surface of the investment mold, Furthermore, the coating formed on the inner surface of the shell will cause composition changes and cracking problems in the coating due to the long demoulding time, which will affect the quality of later products

[0004] The Japanese invention patent with the publication number JP S63194842A provides a demoulding method in investment casting. This method adds a metal core in the investment mold, and the metal core plays the role of hanging and assisting the later mold shell flipping. It can be used for small investment casting The preparation of castings, but for large-scale investment casting shells, the surface quality of the inner cavity of the shell will be affected by repeated flipping and demolding

[0005] The Chinese invention patent with the publication number CN201310741021.4 provides a demoulding method. In the process of preparing the mold shell, the amount of demoulding can be reduced by using a metal core method, but this method does not mention that the mold shell turnover process can be avoided. , and the setting method of the metal core fails to consider the impact on the investment pattern and the dimensional accuracy of the casting mold