A method for preparing surface shells that can effectively improve small-sized concave surface casts

Abstract

The invention relates to the field of shell mold preparation of investment casting, in particular to a surface shell mold preparation method that can effectively improve small-sized concave surface casting nodules, comprising the following steps: coating preparation: preparing the first coating: parts by weight Prepare 1 part of silica sol, 0.5 to 1 part of water, 2.5 to 3.5 parts of aggregate, 0.001 to 0.005 parts of wetting agent, and add them to the first batching tank in turn, stir evenly to form the first coating; prepare the second coating: press Prepare 1 part of silica sol and 2.5 to 3.5 parts of aggregate in parts by weight, and add them into the second batching bucket in turn, stir evenly to form the second coating; pre-coat the wax model; and make the shell. By using the first paint with low viscosity and low surface tension to pre-coat the wax pattern, a wet pre-coat layer is formed between the top coat and the wax pattern, avoiding direct contact between the top coat and the wax pattern, and can Avoiding the accumulation of air bubbles on the small-sized concave surface of the wax mold caused by excessive surface tension of the surface coating, effectively reducing casting nodules.

Description

technical field [0001] The invention relates to the field of shell mold preparation of investment precision casting, in particular to a surface shell mold preparation method which can effectively improve small-sized concave surface cast nodules. Background technique [0002] Investment casting, also known as "lost wax casting", is widely used in the production of aero-engine precision castings due to its high precision and less inclusions. With the continuous improvement of engine performance requirements, the dimensional design of some parts is more complex, which puts forward higher requirements for the precision of castings. In investment casting, the key factors affecting the molding accuracy of castings are mainly affected by the shell making process, except for the dimensional accuracy of the wax mold itself. In recent years, silica sol has been widely favored in the field of shell-making binders for investment precision casting, and has gradually replaced ethyl silic...

AI Technical Summary

Problems solved by technology

[0003] However, the surface coating prepared with silica sol as a binder, due to its high density, increases the viscosity of the coating and the surface tension increases sharply, which seriously reduces the wettability of the coating to the wax model. The surface of the mold, especially the surface of the wax mold with small concave surface, is particularly obvious; and when coating the wax mold with small concave surface, the surface tension of the surface coating is also easy to cause air bubbles on the small concave surface. As a result, the shell mold cannot accurately replicate the small-sized concave surface, resulting in the casting of the casting at this position, which in turn leads to the scrapping of the casting, reducing production efficiency and increasing production costs