SU996058A1 - Method of producing two-layer ceramic moulds - Google Patents

Description

(54G METHOD OF MAKING THE TWO-LAYER CASTING FORMS OF CERAMIC

1 - The conversion of ogosits to the pygeic proizvodsgvu, in chasmosgah to histvovlekvyu ceramic liguyh forms. There is a known method for two-layer molds in which two models are used, one of which is precisely the color of the casting being made in configuration and size, and the other has a somewhat larger frame (s). According to the model with large sizes, the mold is made of chemically solid mixtures. This form is then installed on a model with smaller dimensions, the surface of which is tightly pressed due to the vacuum created by a synthetic film in its cavity. The gap formed between the mold and the synthetic film is filled with a dry filler, after which the mold is sealed with a second sheet of synthetic film and evacuated with f IJ. The closest to the invention in technical; The essence and the achieved result is a method of making a two-layer ceramic mold, including prior art making the first support layer of the form, applying a separating lubricant to the model, making the second facing layer by pressing the ceramic mixture into the gap between the model and supporting the layer of the form, hardening the ceramic mixture and separating the form from equipment With the disadvantage of this method with the low quality of the surface of the form due to the formation of shells of various sizes on it. The reasons for the occurrence of sinks are backed by both local air accumulations, and the use of high pressure, which causes coagulation of the ceramic paste and reduces its fluidity. The use of a gap of 5–2 mm in the known method of the gap between the model and the tooling, 1, leads to: the consumption of an expensive ceramic mixture. The clearance of the gap in the well-known method is impossible in the middle of the appearance of a larger number of crayfish. The purpose of the invention is to improve the quality of the surface of the ceramic layer and reduce the consumption of the ceramic mixture. The aim is achieved according to the method of manufacturing two-layer ceramic molds, including preliminary production of the first support layer of the mold, installation on the model of the mold, application of separation lubricant to the model, placement inside the mold of the support layer molds with a flammable gap between the model and a support layer, making the second facing layer by pressing in the ceramic the gap between the model and the support layer of the mold, the curing of the ceramic mixture and the separation of the mold from the tooling, before pressing the ceramic mixture with the support layer, cover the top with a synthetic film with an opening, and press the ceramic mixture through the hole in the film at a pressure of 3-6 kg / cm and at the same time carry out the evacuation of the mold at a dilution of ICH-10 mm Hg. St ... Example, On a sub-model slab with openings of 01 mm, a rough model is installed, enlarged relative to finishing one by 1-3 and a flask. The base layer is made of a two-layer form from a mixture by a CO2 process possessing the necessary gas permeability (tabl, I After the mixture from the top of the mixture, the flask is mounted on a finishing model with a pre-applied release lubricant, between which and the supporting part there is a small gap (1-3 mm). The bottom of the flask adjacent to the sub-model plate is sealed with a rubber cord and vacuum grease. From above, the mold is covered with a plastic film with a hole for pressing the ceramic mixture, To the bottom. the submodel plate is hermetically connected vacuum chamber around the perimeter of the mold with the pump. For complete volumetric evacuation of the shape of the hole in the inner part of the submodel slab, a grid of 0.5 mm depths are interconnected, and a hole of 05 mm is made in the center of the model in the slab. The pump is turned on before pressing in the ceramic suspension of the gap between the model and the supporting part of the mold. The vacuuming is stopped after filling the gap with the mixture to form the facing layer. The pressing is carried out on a mechanical press of small capacity. The use of low pressure on the ceramic slurry (3-6 kg / cm) in the method allows several times to reduce the filling time (from 2-8 s depending on the complexity of the surface and the size of the covered area) of the gap between the model and the reference layer of the form io compared to free fill (or 3012O with and more). Therefore, capillary absorption significantly less influences the rheological properties of the suspension, and practically with fast filling (2 sec) of the gap, these properties do not change (the gap between the model and the support part of the form is ten times the thickness of the capillary liquid chamotte mixture; a relatively small (2–8 s) time interval (and the gap is filled with a ceramic suspension; the capillaries do not have time to absorb the liquid component of the ceramics). When ceramics are coated with more developed and complex surfaces, when the time of filling the gap increases, it is envisaged that a hydrophobic material is applied to the support part, which significantly reduces the capillary forces of absorption. In addition, during the time of filling the gap, the pressure of the suspension in the glass under the piston does not exceed the capillary pressure. However, the first is changed from the minimum at the beginning of filling | clearance to a maximum (3-6 kg / cm) at the end. At the same time, the flow rate with the full filling of the gap is minimal, and the pressure is maximum, which entails an accelerated coagulation of the liquid suspension and its transition from the plastic to the elastic-plastic state for a short period of time (5 - 10 sec) after filling the gap and the suspension under the indicated pressure. Applying the same vacuum in the form before pressing in the suspension and during filling its gap and holding it under low pressure helps to eliminate air plugs and high-quality filling of the gap. The composition of the ceramic mixture is given in table 2, the rheological properties of the mixture are given in table 3, the results of the comparison of the known method 2 and the proposed method are given in table. 4. After removing the model, the mold is sent to be dried with a gas flame. As follows from Table 4, the use of the proposed method allows to reduce the consumption of the ceramic mixture - -, - - B 3.5-4 times (example 6) and improves the surface quality of the ceramic layer (examples I and 5). The proposed invention allows G} | arolizavavny solution

(After the introduction of the coagulum, with

Without coagul torus

15

thirty

60

120

24O

48О

Note. The viscosity of the suspension was measured on a VZ-4 viscometer; pre-shift shear stress v according to metoiki 1EZ "

Table I

Table2

T. a b p and c a 3

Viscosity (), s

Limiting soda xenia shift -10, N / m

0.06 0.04 0.07 0.14 0.26 0.54 1.12 8 ". It doesn’t improve the surface quality of Keiia. layer, reduce the consumption of ceramic mixture - 3.5–4 times, which, when casting weighing up to 10O kg, will give an economic effect of 7–10 rubles per mold.

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YU

6 Formula of the invention Method of making; two-layer ceramic molds including preliminary manufacture of the first support layer of the mold, installation on the flask model, application of a release agent onto the model, grinding of the support layer inside the flask with the formation of a gap between the model and the support layer, making the second facing layer by pressing the ceramic mixture and the gap between the model and the support layer of the mold, the curing of the ceramic mixture and the separation of the mold from the tooling, characterized in that, in order to improve the quality over the nosg of the ceramic layer and voltage flow ceramic mixture by reducing the gap between the model and

l and c a 4

1.58 Gas sinks are missing. Non-filling ceramics. O-OD5% of the surface of the form is supported with a supporting layer of the form, before pressing with the ceramic mixture, the ceramic mixture is covered with a plastic film with a hole on top, and the ceramic mixture is pressed through the hole in the film at a pressure of 36 kg / cm and at the same time vacuuming of the mold is carried out under vacuum. - Yum mer, art. Sources of information taken into account in the examination 1. Japan Patent N 53-.11486, cl. In 2 C 9/02, 1978. 2. Matusevich I. S. Ceramic forms and rods. - Foundry, NI, 1972, p. 3. 3. Voyuiky-C. C. The course of colloid chemistry. M., Himi, 1975, p. 334335.

Claims (1)

Claim A method of manufacturing 'double-layer, ceramic molds _> comprising 30 pre-fabricating the first mold support layer, installing the mold on the model, applying release agent to the model, placing the mold support layer inside the mold with the formation of a gap between the model and the support layer, performing the second facing layer by pressing ceramic mixture and the gap between the model and the • supporting layer of the mold, curing the ceramic mixture and separating the mold from the tool, characterized in that, in order to improve the quality of the ceramic layer and reducing the consumption of the ceramic mixture by reducing the gap between the model and I with the support layer of the mold, the flask together with the support layer is covered with a synthetic film with a hole on top of the ceramic mixture, and the ceramic mixture is pressed through the hole in the film at a pressure of 36 kg / cm ^ · and the form is evacuated at a pressure of 10 “* 1. - 10? mm rg. Art.