SU799889A1 - Suspension for producing casting moulds made with use of investment patterns - Google Patents

Description

FIELD OF THE INVENTION The invention relates to foundry production, namely, to obtaining in molds - molded by melted models.

A known suspension for the manufacture of molds, containing a refractory filler, ethyl silicate, ethyl alcohol, inorganic acid, water, cryolite i,

The closest in technical essence and the achieved result is suspension 2, containing refractory filler, ethyl silicate, alcohol, organic acid, water, cryolite, fluoroflogopite and bertolette salt (KCtOj).

The presence in the suspension of fluoroflogopite and bertoleth salt as an oxidizing agent allows reducing the temperature and time of calcining the forms, (Prodal can be produced up to 1.51, 8 hours).

Removing models from molds made from such a suspension is in hot water, while the residual content of the model composition in the shell is 2-10%. When using the model udgshin process in a model melt, the carbon content in the form increases to 5.2- 5.5%

The purpose of the invention is to increase the combustion of residues of the model composition from molds previously melted in the model melt during the proxy process.

This is achieved by the fact that, as an oxidizing agent, the suspension contains potassium nitrate or sodium nitrate in the following ratio of ingredients, weight. %:

11.0-13.0

Ethyl silicate

14.0-16.0

Alcohol

1.0-2.0

Water

Inorganic acid

0.6-1.5

Potassium nitrate or ni0.5-1.0 sodium waste

Refractory filler Rest

Sodium nitrate in the course of heating308 C decomposes in the reaction above, 1 2NaN02 02 with the separation of 2 NaNO.

atomic oxygen. Sodium nitrite also decomposes with the release of atomic oxygen.

Potassium nitrate is decomposed by heating in the process of heating.

2X05-2 KfJ02 + 02.t. Potassium nitrate KNOj also decomposes with the release of atomic oxygen. In order for C4ST to start decomposing sodium nitrate first, and then starting to release oxygen, potassium nitrate provides for the distribution of oxygen over time. Oxygen, excretion of ex: gy, with decomposition of nitrates, promotes intensive oxidation (burning of residues of the model composition). The combustion process of the model composition, with the presence of atomic oxygen, occurs at higher rates than its evaporation process. The combustion temperature of residues of the model composition in the presence of atomic oxygen is significantly lower than the evaporation temperature of the model composition. This allows reducing the temperature and duration of calcining of the ceramic forms, ensuring complete removal of the model composition. With the gradual introduction of oxygen, the remnants of the model mass are more completely burned out, not the cause of the destruction of the shape of animib by gases (combustion products), since they will also be introduced gradually. The amount of sodium nitrate in the suspension should not exceed 0.9% by weight of the entire suspension, since its solubility in water at 2 ° C does not exceed 4 by weight of water, and the maximum amount of water in the suspension is 2% by weight of the suspension. Thus, it is impossible to dissolve more than 0.9 weight of sodium nitrate in the water used to prepare the suspension. The amount of potassium nitrate should not exceed 0.6% of the suspension, since this is the limiting amount of potassium nitrate that can be dissolved in 2% of the water in the suspension (the solubility of potassium nitrate in water is 31.6 wt.% Pr) . The total amount of nitrates should not exceed 1% by weight of the suspension, which is connected with the limiting solubility of nitrate. In addition, the increase in the total amount of nitrates above 1 wt.% Leads to softening of the ceramic shell and casting as a result of its destruction. With an increase in the total amount of cBbEue nitrate of 1 wt.%, The depth of the decarburized casting layer increases due to the excess amount of oxygen in the mold cavity. . With the introduction of nitrates of less than 0.01 wt.% Each, the effect of accelerating the combustion of residues of the model mass is practically not. The optimal process for slurry preparation is as follows. Sodium and potassium nitrates are dissolved in distilled water, then water and solvent are added to the hydrolyzed ethyl silicate during slurry preparation. After melting the model composition from the ceramic shell in hot water and drying the ceramic shell, it is calcined. Calcination is carried out for 1.5-2 hours. The fine suspension was tested in the manufacture of molds, cast low-alloy gnomes and carbonaceous steels. In the manufacture of a hydrolyzed solution of ethyl silicate, which is a binder in the process of preparing a suspension, an inorganic acid is used as a catalyst. To eliminate the possibility of chemical interaction of the acid with the added oxidant during the period of their mixing in the hydrolyzer and the premature release of the active acidic acid, it is preferable to use potassium and sodium nitrates when used as the oxidizing agent and nitric acid as the catalyst. Mixing them in one container does not entail chemical reactions and the hydrolysis of ethyl silicate takes place without premature release of active oxygen, which is necessary only during the calcination of the shells in the furnace. Otherwise, the preparation of a suspension is generally accepted. In tab. 1 shows the composition of the proposed suspensions, in table. 2 their properties. ", Table 1

table 2

The number of gaseous products after calcination, 0.890.34 The strength of the ceramic shell for bending at 700 ° C, kg / cm 28.31 28.5-30 Depth of the dehumid 0, 3400.30 of the bore layer, The temperature of the calcining to remove the model composition, € 750-800750 -800 5,41,5-2 Calcination time, H 4694 Yield,%

The data table. 2 show that the introduction of an insufficient amount of nitrates (suspension 1 causes an increase in the amount of gas (0.89 cm- / m) in the ceramic shell, despite the fact that the duration of calcination is increased (5.4 hours). The yield of the effective yield is reduced with an insufficient amount of indicates a complete burnout of the model composition. The introduction of nitrates in a total amount of 1.1 wt.% (suspension 6) leads to a decrease in the strength of the shell (24–26 kg / cm) and an increase in the thickness of the decarbonized layer to 0.53 mm.

Thus, it was found that the introduction of nitrates in a given amount contributes to a more complete combustion of the residue of the model composition from the forms during their calcination, from which the models were previously removed in the same model melt, and the forms were calcined at 700-800 s for 1, 5-2 hours

The economic effect according to the preliminary calculation will be 30 thousand rubles. in year,

Claims (2)

1. Author's certificate of the USSR 512852, cl. In 22 C 1/00, 1974. 2. The author's testimony about the USSR to Lo II II 2679263 / 22-02, Cl. B 22 C 1/02 dated 07/12/78. 0,250,220,240,25 27-3029-3129-3024-26 0,3150,3000,320,53 750-8UO750-800750-800750-800 1,5-2,51,5-22-2,52 96989862