SU895960A1 - Method of producing aluminium oxide ceramic articles with inner cavities - Google Patents

Description

(54) METHOD OF MANUFACTURING ALUMOOXIDE

CERAMIC EMISSIONS WITH INTERNAL The invention relates to ceramic production, in particular, to methods for the manufacture of ceramic products with closed cavities of any complex configuration that can be used as easily removable rods, for example, when drinking a bottle. models, die designs for isothermal molding, welding torches and other special purpose refractories, obtained from thermopastified powder compositions. Methods are known for the manufacture of ceramic articles with linear orifice openings, including blind holes, decorated with metaphysical lj and water-soluble 21 inserts and rods of thermoplastic powdered compositions, including a mineral base in the form of a powder composition and a thermoplastic organic plasticizer.

CAVITIES A disadvantage of the known methods is that they do not allow the fabrication of ceramic products with a complicated profile of the internal cavity, including a closed cavity. Using metal inserts, a cavity of a complex configuration in a ceramic product cannot be performed, since such an insert cannot be removed from the workpiece. Water-soluble inserts of any complex end can be removed from the workpiece, but at the pyrolysis of the plasticizer, the cavity must be filled with a bulk adsorbent and removed after firing. In the case of cavities, extended or labyrinth, it is almost impossible to fill them with adsorbent powder and remove it from there after firing. At the same time, the granulometric and intrinsic composition of the known powder compositions provides organic- at the pyrolysis stage. This plasticizer has a rather dense structure, a billet round that does not have the ability to transport decomposition products of the liner into the furnace space. Thus, if the insertion is not preliminarily removed, then such a structure prevents migration of decomposition products from it from the internal cavity of the ceramic product and to obtain a complex configuration in the product, and especially a closed cavity, is impossible. The closest to the proposed technical essence and the achieved result is a method of manufacturing ceramic articles of complex shape, in particular with complex profile strips of thermoplastic powder composition. The method consists in that the initial alumina powder is mixed with a thermoplastic bond, the blanks are molded by the method of hot injection under pressure into a mold with water-soluble inlays, made of technical urea, according to the configuration corresponding to the cavity profile, in the ceramic part. When cooling the melted thermoplastic (} the positioned composition hardens, the inserts from technical urea are removed by dissolving in water, and the cavity that forms the cavity, like the outer surface, is filled with an adsorbent to ensure the pyrolysis of the organic plasticizer at the calcining station 2. Used in The thermoplastic powder composition contains the following substances, wt. Monofractional powder mineral base with a specific surface of 2200-2500 cm / g Thermoplastic organic plasticizer based on paraffin with the addition of bees. The disadvantage of this method lies in the inability to make a ceramic product with a closed cavity. This is due to the fact that the powder composition used in this method of thermal paste is fine-grained and mono-fractional, therefore the structure of the product blank at the firing station is sufficiently dense The open porosity after pyrolysis of the plasticizer is. Such a structure almost does not have the capacity of 8959604 to transport into the furnace space you decomposition liner foriruyuschego inner cavity and the last prihodits removed from the workpiece before firing. The aim of the invention is to obtain ceramics with closed internal cavities. This goal is achieved in that according to the method of manufacturing alumina ceramic products with internal cavities, including preparing a slip on a thermoplastic binder, forming billets by hot-casting using technical urea inserts that make up the internal cavities of the preform, removing inserts and heat treatment in the filling of the adsorbent, the slip is prepared from powders of the following granulometric composition, weight.%: Fraksh1 10O-120 microns 45-5O Fraction 28-4O microns 28 DL Fraction 1-3 microns 22-25, the thermoplastic binder is administered in an amount of 9-11% by weight of the powder, and removal of the insert is carried out during the heat treatment step to remove the thermoplastic binder due to evaporation of urea through the pores due Delhi. Moreover, as the refractory compounds, oxides ACg 6z and additions of compounds, 7CaO-ZA) C2K) 2- are used. In practical implementation of the ---- method, thermoplasticized powder compositions of different compositions are prepared (the ratio of ingredients in which is given in the table. From each of the thermoplasticized composition, the billet is molded by hot-pouring it in the molten state at 60-85 ° C under pressure into the mold with the installed insert from technical urea, according to the configuration of the corresponding cavity profile, The insert in the mold cavity is fixed with metal rods, which are pulled out of the workpiece after it has hardened. The holes from the rods formed in the walls of the workpiece are closed with ceramic plugs from the same thermoplasticized powder composition, and the junction of the workpiece and the plugs are melted to form a solid flat surface. The ratio of the thickness of the insert to the wall thickness of the workpiece varies from O, O5

to 0.75. The blanks are placed in a loose adsorbent (alumina powder) and calcined in a furnace. At the same time, at the pyrolysis stage of the organic plasticizer and technical urea insert, the temperature rise is carried out at a rate ensuring that the profile of the closed cavity of the blank is preserved.

The determination of the open porosity after the preliminary calcination (pyrolysis of the plasticizer ia insert) by the known method confirms the positive effect achieved in the manufacture of products with a closed internal cavity by the proposed method. If in the manufacture of products in accordance with a known method, the porosity is open

is, in the manufacture of products by the proposed method, it is 24-34%, depending on the granulometry of the mineral base and the amount of injected organic plate (see table).

As a result of the post-fabrication inspection of products made from various thermoplasticized powder compositions with any applied ratio of the insert thickness to the wall thickness of the workpiece, they provide the required configuration of a closed internal cavity that corresponds to the insert configuration. The purity of the surface of the inner cavity of the product corresponds to the purity of the outer surface of the ceramic product.

Claims (2)

DETAILED DESCRIPTION OF THE INVENTION A method for producing alumina-oxide ceramics with internal cavities, including preparing a slip on a thermoplastic binder, forming blanks by hot-casting using technical urea inserts, forming the internal cavities of the blank, removing liners and heat treatment in backfill an adsorbent, characterized in that, in order to manufacture products with closed internal cavities, the slip is prepared from powders of the following particle size distribution a, wt.%: Fraction 1OO-120 µm 45-50 Fraction 28-4 O µm28-3 O Fraction 1-3 µm22-25 The thermoplastic binder is introduced in an amount of 9-11% by weight of the powders, and the liner is removed in the heat treatment process at the stage of removing the thermoplastic binder by evaporating the urea through the pore of the article. 78959608 Information sources,- 2. Sitnik N, P. and others. Manufacturing taken into account when examining ceramics of complex shapes, 1, Gribovsky P, O, Ceramic Glass and Ceramics, 1 6, 1975 ( solid schemes. M., Energie, 1971.Type).