RU2466965C1 - Method to produce items from quartz ceramics - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: method to produce items from quartz ceramics includes wet grinding of quartz stock, preparation of slurry, moulding of items in gypsum moulds, drying and annealing of items. Raw materials are ground unburnt wastes of quartz ceramics cleaned from gypsum traces, and slurry preparation is carried out by means of wet grinding in a ball mill at the ratio of "material: grinding bodies: water" equal to 1:(0.5-0.7):(0.13-0.15), for 2-6 hours with subsequent hydration of quartz glass grain for 10-30 hours while mixing the slurry. Annealing is carried out at the temperature of 1150-1200°C for 2-4 hours.

EFFECT: reduction of sintering temperature to produce strong and heat resistant items, high homogeneity of a material in items, elimination of underfilling and flaking, reduced scrap by cracks in production of large thin-walled items at the stage of moulding and annealing.

3 ex

Description

The invention relates to a technology for the production of products from quartz ceramics for various purposes by both drain and bulk methods. A known method of producing products from quartz ceramics (Y. E. Pivinsky, A. G. Romashin. Quartz ceramics. M .: Metallurgy, 1974), including wet grinding of quartz glass battle in ball mills and slurry preparation, molding products by water slip casting in plaster forms, drying and firing products. To obtain sophisticated thin-walled products, for example, shells of antenna fairings, to prevent crystallization of the material during firing, the glass is etched in an aqueous solution of hydrofluoric acid and cleaned of contamination, and the glass is ground and slurry prepared in ball mills lined with quartz glass using grinding bodies from quartz glass. The disadvantage of this method is the high cost of production, the presence of unused production waste.

A known method of molding products from quartz ceramics (RF patent No. 2153481, CL. SB 35/14, Bull. No. 21, 2000), according to which wet grinding of quartz glass battle is carried out in ball mills with the addition of 8-12% dry matter plum from centrifugal molding of products. Highly dispersed drainage improves the rheological and molding properties of casting slips. In addition, the proposed technical solution allows the use of waste products from quartz ceramics in the form of a drain.

The closest in purpose and technical solution is the method of manufacturing large-sized products from quartz ceramics described in the USSR author's certificate No. 1782970, Cl. C04B 35/14, Bull. No. 47, 1992. The invention is as follows. The quartz glass battle and the unburnt quartz ceramics battle were loaded into a ball mill, 13-14% water was added and wet grinding was carried out to a residue on sieve No. 0063 from 17.28 to 25.5% weight. The ratio of “material: grinding media: water” was in the range of 1: 1.25: 0.13-0.14. The finished suspension was poured into a gypsum mold for a set of ceramic billets. The products consisted of burner blocks measuring 250 × 250 × 400 mm and the shafts of glass-forming machines with a diameter of 85 mm and a length of 2700 mm. Then the products were dried and fired in electric ovens. The ratio of glass and unburnt waste of quartz ceramics was 1: 1 ÷ 0.4.

The disadvantage of the prototype is the unsuitability of the resulting slurry for forming thin-walled complex products with high density and strength of ceramic material. In addition, the large content of the coarse fraction in the cast slip even with a suspension density of 1.89-1.91 g / cm ³ causes the suspension to stratify according to the height of the molded products and a significant different density of the workpieces, which leads to a change in the physical and technical properties of the material in different product zones , degrades their performance. The significantly different strength and hardness of pieces of quartz glass and unbaked waste of quartz ceramics do not allow you to choose the grinding mode to obtain a slip with a predictable grain composition acceptable for high-quality castings.

The aim of the invention is to increase the manufacturability of the production of products from quartz ceramics by reducing the firing temperature, improving the quality of complex thin-walled products and the use of ceramic waste.

This goal is achieved in that the method for producing products from quartz ceramics, including wet grinding of quartz raw materials and slurry preparation, molding products in gypsum molds, drying and firing products, is characterized in that the raw material is fused from gypsum traces of unbaked quartz ceramic waste , the preparation of the slip is carried out by wet grinding in a ball mill with a ratio of "material: grinding bodies: water" in a ratio of 1: (0.5-0.7) :( 0.13-0.15) for 2-6 hours subsequent hydration of quartz grains Vågå glass for 10-30 hours while stirring the slurry, and firing is carried out at a temperature of 1150-1200 ° C for 2-4 hours.

The authors experimentally established that after removing the surface layer of the ceramic casting that is in contact with gypsum with an emery cloth and vacuum cleaner, unbaked quartz ceramic waste, when reused, does not crystallize during material firing to a temperature of 1200 ° C for up to 4 hours, and quartz ceramic obtained from such waste with additional hydration of fine particles of silica glass during the mixing of the slip, sintering more intensively than ceramic from the primary slip. A material with properties similar to those of NIASIT TU 1.596.195.84 quartz ceramics can be obtained at a firing temperature of 1150-1200 ° C. The molding properties of the slurry are also improved, the uniformity of the casting is increased, and crack rejects are reduced.

The conditions and modes of grinding unbaked waste of quartz ceramics for forming thin-walled complex products are selected. In contrast to the prototype, a scheme for processing waste using a reduced number of grinding media with a complete load of the mill with industrial waste is proposed. The ratio of "raw materials: grinding bodies" is taken in the ratio 1: (0.5-0.7), according to the prototype 1: 1.25. The grinding time is optimized, it is 2-6 hours depending on the density of the feedstock according to the grain composition of the molding slip. Distilled water in the amount of 13-17% of the weight of dry waste was introduced when loading the mill, but it is allowed to enter in portions (two to three times), then the grinding time is slightly reduced. After grinding, the suspension was separated from the grinding media and kept in a rotating state for 10-30 hours to improve the casting properties, then the slip was filtered through a 0.5 mm sieve and used to cast products.

Examples of the method

Example 1. In a ball mill TSA 115 with a capacity of 200 l, 64 kg of unbaked and sanded from the side of the gypsum battlefield defective quartz ceramic products, 32 kg of grinding bodies made of quartz glass, 8.3 liters of distilled water were loaded and milled for 2 hours. After separating the grinding media, the slip was additionally hydrated in the propeller stirrer for 10-30 hours.

Slip parameters: density - 1.87 g / cm ³ ;

viscosity - 30 "according to VZ-1;

pH 6.0;

grain composition: - particles up to 5 microns - 24%;

- particles 63-500 microns - 12%;

- particles 5-63 microns - the rest.

Crucibles were cast using the water method of slip slip casting in gypsum molds to melt precious metals and alloys up to 300 mm high. After drying, the products were fired in electric furnaces at a maximum temperature of 1150 ° C for a duration of 2-3 hours. The density of the material in the products is 1.96 g / cm ³ , the bending strength is 35-50 MPa. Different density along the height of the products did not exceed ± 0.01 g / cm ³ .

Example 2. Analogously to example 1, a slip was obtained from unbaked waste from the production of products from quartz ceramics by wet grinding in a TCA 115 ball mill when loading the battle of waste, grinding media and distilled water in a ratio of 75: 45: 11.2 kg. Grinding time 4 hours. After separating the balls, the slip was additionally hydrated by rolling in the same mill for 24 hours.

Slip parameters after filtering through a 0.5 mm sieve:

density - 1.88 g / cm ³ ;

viscosity - 23 "according to VZ-1;

pH 6.6;

grain composition: - particles up to 5 microns - 21%;

- particles 63-500 microns - 6.6%;

- particles 5-63 microns - the rest.

The casing of the devil was cast using the drain method of water slip casting in gypsum molds. OTI 1196.002 for monitoring the level of metal during steel melting with a wall thickness of 10-20 mm. After drying, the products were fired at a temperature of 1200 ° C for four hours. The average bending strength of the material in the products met the requirements of the NIASIT TU 1.596.195.84 material and amounted to 50 ± 10 MPa.

Example 3. Similarly to examples 1, 2, a slurry was prepared from unburnt waste of quartz ceramics by wet grinding in a TCA 115 ball mill with a load of 70: 49: 10.5 kg. After grinding for 6 hours, subsequent exposure in a mill without balls for 30 hours, a slip filtered through a 0.5 mm sieve had the following parameters:

density - 1.89 g / cm ³ ;

viscosity - 30 "according to VZ-1;

pH 6.2;

grain composition: - particles up to 5 microns - 20%;

- particles 63-500 microns - 10%;

- particles 5-63 microns - the rest.

From the obtained slurry, castings were cast in a plaster cast in a conical shape with a base diameter of 360 mm, a height of 700 mm, a wall thickness of 10-15 mm.

The dried products were fired in an electric oven at a maximum temperature of 1200 ° C for 2 hours.

On samples from the technological allowance of the products, the properties of ceramics were controlled. The values of the properties correspond to the requirements for the material NIASIT TU 1.596.195.84:

density - 1.96-1.99 g / cm ³ ;

bending strength - 35-65 MPa;

_{TECL 20-900 ° C} - (4.7) × 10 ^-7 / K;

the dielectric constant

at a frequency of 10 ¹⁰ Hz - 3.40 ± 0.02;

tangent of angular loss

at a frequency of 10 ¹⁰ Hz - (2-15) × 10 ^-4 .

The products obtained do not differ in properties from products manufactured by conventional technology using transparent quartz glass as the raw material — TU 11-87 ShchLO.027.252 quartz glass tube.

Shrinkage during firing products in all examples of the method was in the range of 0.5-1.2%.

The proposed method provides high-quality ceramic material based on quartz glass and products from it for various purposes, using ceramic waste. For molding the product, it is allowed to combine molding masses by mixing a water slip from production waste and a primary slip or introducing powdered as well as granular filler of silica glass or silica ceramics into it.

The advantages of this technical solution in addition to the use of production waste are also:

- improving manufacturability by reducing the firing temperature upon receipt of a durable and highly heat-resistant material and products;

- improving the quality of products (homogeneity of the material, elimination of underfilling, delamination in products, etc.);

- by reducing shrinkage during firing and warpage of the product, it becomes possible to reduce technological passes for machining and obtaining dimensionally stable products.

In addition, the method allows to reduce the marriage of cracks in the manufacture of large products by water slip casting.

Information sources

1. Yu.E. Pivinsky, A.G. Romashin. Quartz ceramics. M .: Metallurgy, 1974.

2. RF patent No. 2153481, Cl. C04B 35/14, Bull. No. 21, 2000

3. A.S. USSR No. 1782970, Cl. C04B 35/14, Bull. No47, 1992

Claims (1)

A method of obtaining products from quartz ceramics, including wet grinding of quartz raw materials and the preparation of slurry, molding of products in gypsum molds, drying and firing of products, characterized in that the raw materials are fused from gypsum traces of unbaked waste of quartz ceramics, the preparation of the slip is carried out by wet grinding in a ball mill with a ratio of material: grinding media: water in a ratio of 1: (0.5-0.7) :( 0.13-0.15) for 2-6 hours, followed by hydration of the silica glass grains for 10 -30 h with stirring ii slurry, and firing was carried out at a temperature of 1150-1200 ° C for 2-4 hours.