SU856647A1 - Method of calcining casting ceramic moulds made with use of investment patterns - Google Patents

Description

one

The invention relates to the foundry industry, in particular, to get into molds made on melted models.

There is a known method of calcining ceramic casting molds, which are creeped on melted models by means of them in furnaces, in which they create an oxidizing atmosphere fl).

However, with this method, the cycle of time is long, since the cavities of the mold are not venous, the removal of organic residues is difficult.

 Close to the proposed essence and the achieved result is a method of roasting ceramic molds produced by melted models in furnaces with an oxidizing medium, in which hot oxidizing gas is blown into the cavity of the ceramic mold during the entire period of annealing 2.

However, the known method of calcination reduces the strength of ceramic forms as a result of the occurrence of the temperature difference between the external and external surfaces that does not disappear until the end of the calcination.

the inner surfaces of the ceramic form, the difference in temperature, and the blower and oxidant.

The goal of the invention is to increase the strength of the hardening of the molds. . In order to achieve the set goal of the Slava method, Wku {{heating ceramics baking pan in an oxidative qwfle with hot octall gas into the mold cavity, feeding a hot sweetener with a thermal tube of 300–700 ° C during the initial period of puncture; makes up 15-40% of the total time of the npOKajmaaan forms.

The drawing shows a graph, built on the results (.

Experimental calcination of casting molds to cmsheaded forms is carried out in heals with an oxidizer layer having a different temperature in the range of 300-700 ° C, into the internal cavity of ceramic forms. The flow rate of the blown (iron 6.5 m / h. The furnace temperature is 1050 ° C.

The graph shows curve 1, characterizing the dependence of the temperature of the outer on (the surface of the ceramic mold on the calcination time). Curve 2 characterizes the dependence of the temperature of the inner surface of the ceramic mold on the calcination time of the oxidant at 700 ° C during the entire calcination period (according to the well-known method 1) Curve 3 characterizes the dependence of the temperature of the inner surface of the ceramic form on the calcination time when the oxidant is injected with a temperature of 300 ° C during the whole the calcination period, which corresponds to the conditions according to method 2. Curve 4 characterizes the dependence of the temperature of the internal surface of the mold on the calcination time when the oxidant is supplied with a temperature of 700 ° C until the internal surface of the form reaches 700 ° C. This moment corresponds to the flow blowing for 40% on the total duration of calcination. Curve 5 characterizes the dependence of the temperature of the BHJTTne surface of the mold on the calcination time of an oxidizer with a temperature of 300 ° C until reaching the internal i surface of the mold 300 ° C. This moment occurs when applying blowing for 15% of the total duration of calcination. The total calcination time for the forms with four five layers of the coating according to the proposed method is 15-20 ms

As can be seen from the graph, when the oxidizing agent is fed into the internal cavity of ceramic forms according to a known method 2, a temperature difference of 150 ° C for the blow temperature of 700 ° C and 190 ° C for the blow temperature does not disappear between the external and internal surfaces of the mold. 300 ° C. If the oxidant is supplied only in the initial period, which is 15-40% of the total calcination time, the temperature difference gradually disappears. After the termination of the hot blow, the inner surface of the molds 1 heats up due to the heat conduction from its noninflated surface and the temperature difference between them disappears.

The oxidizing time of 15–40% of the total calcination time corresponds to a blowing temperature of 300–700 ° C. Blowing with a temperature of less than 300 ° C is ineffective, and more than 700 ° C is practically difficult and requires additional costs.

The results of measuring the strength of ceramic samples calcined according to the proposed method, in comparison with the known method 2 are shown in the table.

As follows from the table, the strength of the ceramic molds calcined by the proposed method is more than doubled, and the crack on mold cracking is reduced by 20%.

The expected economic effect from the implementation of the invention is 120 pj per ton bw.

Form l. and invention

The method of calcining casting ceramic molds obtained from above models by heating them in a furnace with an oxidizing medium and feeding a hot oxidizing gas into the cavity of the mold, characterized in that, in order to increase the strength of the calcined ceramic forms on a silica-containing filler and: This silicate, the supply of hot oxidant with a temperature of 300-700 ° C, is produced in the initial period of calcination, which is 15-40% of the total calcination time of the molds.

Sources of information taken into account in the examination

1.Shpindler S.S. et al. Calcination of casting molds by melted models in gas-fired methodical furnaces, Foundry, 1972, N 2.

2. USSR author's certificate number 199356, cl. B 22 C 9/04, 1966,

Claims (1)

Claim The method of calcining cast ceramic molds obtained by investment casting, heating them in a furnace with an oxidizing medium and supplying hot oxidizing gas to the cavity of the casting mold, characterized in that, in order to increase the strength of the calcined ceramic molds on a silica-containing filler and ethyl silicate, the supply of hot oxidizing agent with a temperature of 300-700 ° C are produced in the initial period of calcination, which is 15-40% of the total calcination time of the forms.