RU2369476C1 - Mould for casting ceramic items out of water slurry - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: mould contains mould forming matrix consisting of zones or parts with different suction ability and of removable gypsum elements with easy deformed water-proof padding arranged on surface of removable elements. A frame out of transparent film with measuring points is installed on the matrix. Also a bottom part is made with low suction ability or passive.

EFFECT: moulding of ceramic items of various thickness by pouring method of water slurry casting in gypsum moulds; facilitating control of gain of wall thickness during process.

Description

The invention relates to techniques for molding ceramic products using the slip method of slip casting from aqueous suspensions in gypsum forms and can find application in the ceramic industry.

Known gypsum molds for molding ceramic products by the drain method of water slip casting, the inner surface of which is made according to the profile of the product, taking into account shrinkage during drying and firing. For forming complex products and facilitating the extraction of products from the mold, the latter performs detachable, and for forming the profile of the upper end of the product, an active or passive shell (frame) is used. Oversized forms can be equipped with a metal frame, clamps or rubber ties. / A.G.Dobrovolsky "Slip casting" ed. Metallurgy 1977, p. 240; Fine technical ceramics. Edited by H. Yanagida. Ed. Metallurgy, 1986, p.276 /.

The disadvantage of such forms is that they are applicable for thin-walled products with wall thicknesses up to 10 mm. In the manufacture of thick-walled products, even with the use of highly concentrated suspensions, an accelerated set of the bottom of the product occurs due to gravitational deposition of the solid phase of the slip, which significantly increases the thickness of the bottom of the products. So, when forming crucibles with a height of 200-300 mm from an aqueous suspension of quartz glass with technological parameters:

density - 1.86-1.91 g / cm,

viscosity - 20 - 40 s according to VZ-1,

pH - 4.0-7.0

Grain composition:

particles up to 5 microns - 20-30%

particles 63 - 500 microns - 4-10%

particles 5-63 microns - the rest,

when the wall thicknesses of the side surface are 5, 10, 15, 20, 25 mm, the bottom thickness will be 5-7, 12-15, 18-22, 25-30, 35-45 mm, respectively. In addition, due to the raster effect, the transition zone is accelerated at the junction of the side and bottom surfaces, which leads to a change in the profile of the inner surface of the product.

In some cases, when molding products with flat surfaces (boxes, trays, containers), it becomes necessary to obtain products with different thicknesses of the side walls. Known designs of gypsum molds for the drain molding method do not allow the molding of such products.

The closest technical solution is the mold for casting ceramic products by ed. St. USSR No. 662349, class B28B 1/26 dated 04/11/77, containing a mold-forming matrix mounted in the frame made of several zones with different porosity and suction capacity, and zones with increased suction capacity are located corresponding to the thickening of the product.

According to the prototype, the speed of a set of ceramic billets in a given area of the product is controlled by changing the porosity, the suction capacity of the matrix (shape) in this zone. The latter is achieved by the fact that an aqueous suspension of fused silica is introduced into the gypsum dough.

The disadvantage of the prototype is the limited capabilities of the form when receiving different thickness walls in one product. The manufacture of individual mold zones from a material based on gypsum of semi-aquatic and quartz filler does not significantly accelerate wall collection, the porosity of such zones is in the range of 40-70%, which is almost comparable with the porosity of ordinary gypsum molds (50-60%), and the increase in the set speed ceramic billet in these areas is negligible (no more than 20%). When molding containers of quartz ceramics in composite forms, in which two opposite walls are made of gypsum, and two of gypsum with quartz filler (according to the prototype recipe), the differences in wall thickness did not exceed 2-4 mm. The use of other non-gypsum porous mold elements, for example ceramic ones, with a higher suction capacity significantly complicates and increases the cost of production of molds and products. In addition, the prototype has not resolved the issue of reducing the speed of recruitment of the bottom of the product, where the collection of the workpiece is carried out not only due to capillary absorption of the liquid phase of the slip, but also due to gravitational deposition of slip particles.

The aim of the present invention is to obtain ceramics of different thicknesses by the drain method of water slip casting in gypsum molds, providing the ability to control and regulate the set of wall thickness of the ceramic billet during the set.

This goal is achieved by the fact that the proposed mold for casting ceramic products from water slips by the drain method of water slip casting, containing a forming matrix consisting of zones or parts with different suction capacity, characterized in that the matrix consists of removable gypsum elements made with the possibility of placement on the surface of removable elements of a waterproof, easily deformable gasket, and on the matrix there is a frame of transparent material with dimensional divisions. In this case, the bottom part of the form where the wall is set, including due to gravitational deposition, is made with low suction ability or passive. The frame from a transparent material with dimensional divisions simultaneously forms the height of the product and, together with the gypsum matrix, forms a cavity for the slip with an additional set of thick walls.

It was experimentally established that this form allows, in contrast to the prototype and analogues, to mold hollow ceramic products by the drain method of the following types:

- boxes, containers, baking sheets with different wall thicknesses in one product (from 5 to 30 mm) or more while maintaining the product profile and on the inner surface;

- crucibles, boxes, baking sheets with a thin bottom (5-10 mm) and a thick side wall (15-25 mm) while maintaining the profile of the product and on the inner surface;

- hollow ceramic products of various shapes of a given height and with a controlled thickness of the wall.

This is due to the fact that the mold matrix consists of removable elements that can be removed and replaced by others during molding, after a set workpiece thickness has been set, the raster effect has been reduced or eliminated through the use of active and passive matrix elements, and the possibility of combining capillary and gravitational components in the set the walls.

The form consists of interchangeable removable active and passive elements from gypsum, made according to one model, a passive frame made of plexiglas with dimensional divisions at each wall of the product. The frame with one flange is inserted into the cavity of the gypsum mold to a depth that determines the height of the product, and the other flange is laid on the upper end of the mold through a rubber gasket. Depending on the dimensions of the form, the fastening of the form elements and the frame is carried out using a metal frame, special clamps or rubber ties. In order to prevent destruction of the workpiece when removing the active forming elements and installing passive elements on the surface of the passive elements, an easily deformable material is laid, for example, foam polyethylene 0.5-2.0 mm thick. The selected material of the gaskets is waterproof, which eliminates the set of ceramic walls of the workpiece and the active gypsum element.

Caps for sensors for measuring the level of metal from quartz ceramics TU 1-596-195-84 with a bottom thickness of 5-10 mm and a thickness of the side surface of 15-20 mm were molded in a mold with a passive bottom part of the mold. In this case, the set of the bottom of the product is carried out only due to gravitational deposition of the solid phase. The products were molded from an aqueous silica glass slip with the parameters indicated earlier. Knowing the ratio of the capillary and gravitational components of the set on the horizontal wall for the slip, it is easy to choose the conditions and time of the set of the bottom of the product with a different thickness, for example, equal to the thickness of the side surface. Such products were molded by replacing the active bottom of the matrix with a passive or low suction capacity. The latter is achieved by coating the gypsum element with an alcoholic solution of shellac or other waterproof varnish. After the workpiece was set with a bottom thickness of 10 mm, the active bottom of the gypsum mold was replaced with the passive one and the workpiece was additionally formed to the wall thickness of the side surface of the required thicknesses.

For molding products with different thicknesses of the side walls, molds with replaceable active and passive side elements were used. After the workpiece was set to a thickness equal to the thickness of the thin part of the walls, the gypsum element forming this wall was removed from the mold, and instead a passive element or the same element with a non-porous gasket was installed and fixed and the workpiece was continued to set up to the next specified thickness on other walls. The thickness of the set was controlled using a transparent measuring frame. In order to accelerate the set of thick walls, the mold design allows you to install the mold on the side surface, and if necessary, add a slip to the cavity between the workpiece and the frame. After the workpiece has been set, the slip residue is poured through the frame, the frame is removed from the mold, and the mold with the blank in the open state is set for aging in room conditions for 1-3 hours until the workpiece is separated from the mold. Subsequently, the billet is fed to the basement, drying and firing.

The proposed mold for casting ceramic products from water slips allows molding hollow different thickness products by the slip method of slip casting with predetermined wall thicknesses in one product with a thickness of 5 to 30 mm or more. In contrast to the prototype, a relatively cheap material, gypsum, was used in the design of the mold. In addition, using active and passive elements, replacing them during the set, it is possible to obtain hollow ceramic products with a given profile of the inner surface by the drain method of water casting slip.

Information sources

1. A.G. Dobrovolsky. "Slip casting" ed. Metallurgy 1977, p. 240.

2. Fine technical ceramics. Edited by H. Yanagida Ed. Metallurgy, 1986, p.276.

3. A.S. USSR No. 662349, class B28B 1/26. Mold for casting ceramic products / K.K. Tikonovich - USSR /, Bull. No. 18, May 1979

Claims (2)

1. A mold for casting ceramic products from aqueous slips containing a forming matrix, consisting of zones or parts with different suction capacity, characterized in that the matrix consists of removable gypsum elements, made with the possibility of placing on the surface of the removable elements a waterproof easily formed gasket, and on the matrix has a frame made of transparent material with dimensional divisions. 2. The mold according to claim 1, characterized in that the bottom of the mold where the wall is set, including due to gravitational deposition, is made with low suction ability or passive.