SU1731401A1 - Mixture for making casting patterns - Google Patents

Abstract

Essence: the mixture contains, wt%: liquid glass 11-13; anion-active surfactant class 0.18-0.22; 20-25% aqueous solution of caustic soda 1.8-2.2; refractory filler based on silica the rest.

Description

The invention relates to a foundry, in particular, to a mixture for making casting models used in vacuum molding.

It is known that during vacuum forming the model is wrapped around a heated film. For better film wrapping, holes are usually drilled in the model, the grooves are cut or special vents are inserted for better air suction.

Known model of gas-permeable material. Epoxy powder and water glass are used as a release coating. Curing occurs when flushing with carbon dioxide.

A known gas permeable model for vacuum forming, made from sand and 3% synthetic resin. After compaction in a wooden or gypsum-modeled box, the mixture is cured with acid or by heating. It is also proposed to manufacture a gas-permeable model of silicate metal powder.

The known mixtures have a number of disadvantages: metal powder and synthetic resin are more expensive, scarce materials are used, the powder sintering process requires high temperature and special equipment, low gas permeability. Synthetic resins and curing agents usually have a detrimental effect on the environment.

The closest on the proposed composition and the technical essence and the achieved effect is a mixture of the Japanese company Shinto Kogyo and Takada Tudzos. The model is made directly in a flask equipped with a vacuum system, curing a mixture of granular material and a binder. The model is made from a mixture of quartz sand with 8-10% liquid glass. The liquid-glass mixture is cured with carbon dioxide gas.

The disadvantage of this mixture as applied to the manufacture of models for vacuum molding is low gas permeability and strength.

with

with

ai

The purpose of the invention is to obtain a durable and gas-permeable mixture for the manufacture of casting models.

To achieve this goal, a liquid-glass mixture containing a refractory silica-based filler, liquid glass, anion-type surfactant and a 20-25% aqueous solution of caustic soda is offered in the following ratio, wt.%:

Liquid glass11.0-13.0

Surface active

anionic substance

class 0,18-0,22

20-25% water

NaOH1.8-2.2 solution

Refractory filler

dioxide based

flint rest

The invention is illustrated by the compositions of the mixtures and their properties, which are listed in Tables 1 and 2.

Composition 1 has a liquid glass content below the permissible value, and Composition 5 has a liquid glass content above the upper permissible limit.

As can be seen from table 2, composition 1 has a reduced strength, and composition 5 has a reduced gas permeability, Therefore, the optimal composition 2-4.

With a decrease in the content of the surfactant of the anion-active class below the lower limit, the fluidity of the mixture and the filling ability of the model decrease, and with an increase in the content of the surfactant of the anion-active class above the upper limit, its introduction is not practical.

By reducing the content of caustic soda below the lower limit, the strength of the material decreases, while increasing above the upper limit the hygroscopicity of the material increases.

In tab. 3 shows the dependence of the strength of the mixture on the concentration of caustic soda solution.

From Table 3 it can be seen that with a decrease in the content of caustic soda below the lower limit, the strength of the mixture decreases, and with an increase above the upper limit, the hygroscopicity of the mixture increases. The optimum concentration of caustic soda solution is 20-25%.

The proposed composition of the mixture has a higher gas permeability due to the content of surfactant in it.

substances - anion-active class and heat-drying at 200 ° C for 2-4 hours.

It is known that with an increase in the content of the surfactant of the anionic class, the gas permeability of the mixture increases.

It is also known that the increase and full restoration of the gas permeability of liquid mixtures occurs when they are heated to 140-150 ° C.

The increased content of liquid glass and the hardening of the proposed mixture by heat drying ensures high strength of the model and an increase in its service. The making of models for vacuum forming of the glass-liquid mixture is as follows.

First, a solution of the liquid components is prepared in a paddle mixer, then a filler and a liquid composition are loaded into a batch mixer for batch operation and mixed for 5 minutes.

The resulting mixture is poured into a metal model, fixing pins and fixing fittings are installed, the model with the mixture poured is dried at 473 K for 2-4 hours, depending on the dimensions of the mass of the model. The mixture according to the invention can be used in the manufacture of models for vacuum forming. Castings made according to the models of the proposed mixture have a clean surface.

Claims (1)

Invention Formula The mixture for the manufacture of casting models, mainly for vacuum forming, includes a refractory filler based on silicon dioxide and liquid glass, which in order to increase the strength of the mixture, reduce hygroscopicity and increase its gas permeability, it also contains an anionically active surfactant and 20-25% aqueous solution of caustic soda in the following ratio of ingredients, wt.% Liquid ste cl o11-13 Surface active anionic substance class 0,18-0,22 20-25% water caustic soda solution 1,8-2,2 Refractory filler dioxide based flint rest Table 1 table 2 Table 3