RU2746607C2 - Method for making facing ceramic articles - Google Patents

Abstract

FIELD: production of construction ceramics.SUBSTANCE: invention can be used in making facing ceramic articles: tiles, slabs, bricks and blocks for internal and external finishing walls of buildings. Said technical result is achieved by using stiff clay as the main component, and cryolite as the main component, with the following ratio of components, wt %: stiff clay 97.5–99.0; cryolite—1.0–2.5. Samples of ceramics were obtained at moisture content of the crude mixture of 8 wt %, pressing pressure of 15 MPa and firing temperature of 1050 °C. For said stiff clay containing 10.75 wt % Al2O3, introduction of 1 to 2.5 wt % cryolite is most effective.EFFECT: technical result of invention is higher strength and low water absorption of ceramic articles.1 cl, 1 tbl, 4 ex

Description

The method relates to the production of building ceramics and can be used in the manufacture of facing ceramic products: tiles, slabs, bricks and blocks for interior and exterior walls of buildings.

Known ceramic mass for the manufacture of facing tiles [1], containing (in wt.%): Loess-like loam - 50.0-54.0; kaolinite clay - 33.0-36.0; pegmatite - 9.0-11.0; alumina - 2.0-3.5; cryolite - 0.5-1.0. The disadvantages of this ceramic mass are low strength of the resulting products (about 10 MPa), multicomponent composition, high energy consumption of production (pressing pressure 30 MPa and firing temperature 1100-1180 ° C) and the need to apply a layer of glaze on the surface of the fired tiles.

Known ceramic mass for the manufacture of tiles [2], containing (in wt.%): Kaolin 84.0-86.0; bentonite 3.0-5.0; loess 3.0-5.0; tile fight 0.1-0.5; cryolite 0.5-1.0; alumina 5.0-7.0. The disadvantages of this ceramic mass are low strength of the resulting products (12-15 MPa), multicomponent composition, high energy consumption of production (firing temperature 1100-1150 ° C) and the need to apply a layer of glaze on the tile surface before firing.

Known raw mixture for the manufacture of facing tiles [3], including (in wt.%): Coal enrichment rock, heat-treated at 570-600 ° C, clay, and in the quality of flux - the sludge part of the waste of iron ore, the chemical composition of which, wt.% : SiO ₂ - 42.45; Al ₂ O ₃ - 14.54; CaO - 14.88; MgO 4.52; FeO 8.06; Fe ₂ O ₃ - 9.46; SO ₃ 0.98; R ₂ O - 3.25; MnO 0.49; TiO ₂ - 0.73; P ₂ O ₅ - 0.64%, with the following ratio of components, wt.%: Coal enrichment rock, heat treated at 570-600 ° C, 90-70, clay 5-20, sludge part of iron ore dressing wastes 5-10. Products based on this raw mixture, despite the presence of flux, also differ in low compressive strength (15-18 MPa) and high water absorption (10.1-11.5%) with high energy consumption of production (pressing pressure 25-25 MPa) and the need for glazing.

Closest to the proposed solution is a ceramic mass used for the method of production of fired building materials [4] and containing 50 wt.h. refractory and difficult to sinter clay, incl. low plastic, as the main component and 50 wt.h. fired cryolite-containing additive as flux. The cryolite-containing additive is obtained by mixing 200 kg of crushed clay, 100 kg of crushed cryolite, preferably if it is fired at a temperature of 600 to 700 ° C, 10 kg of iron oxide and 400 kg of water. The resulting mixture is mixed with clay in a proportion of 10 kg of the mixture per 1000 kg of clay, blocks are formed from it, which are fired at a temperature of 800 ° C, and then crushed to obtain a fired cryolite-containing additive. The advantages of the ceramic mass from the known method are the low firing temperature when obtaining the final products (900 ° C) and low shrinkage, which allows drying, firing and cooling immediately after molding in a relatively short time equal to eight hours. The disadvantages of this ceramic mass are the labor intensity and the total duration of the technological process associated with the preparation of the fired cryolite-containing additive.

The technical problems to be solved by the invention are to reduce water absorption and increase the strength of ceramic products.

The most effective tasks are solved by firing at a temperature of 1050 ° C, using low-plastic clay with an Al ₂ O ₃ content = 10.75 wt.%, Replacing the fired cryolite-containing additive with cryolite with the following ratio of the components of the raw mixture (in wt.%) :

Low plastic clay with Al ₂ O ₃ content = 10.75 wt.% 97.5-99.0 Cryolite 1.0-2.5

This invention provides for the use of clay from the Suvorot deposit of the Vladimir region, containing in its composition the following compounds (in wt.%): SiO ₂ = 67.5; Al ₂ O ₃ = 10.75; Fe ₂ O ₃ = 5.85; CaO = 2.8; MgO = 1.7; K ₂ O = 2.4; Na ₂ O = 0.7. This clay has a plasticity number of 5.2 and belongs to low plasticity (according to GOST 9169-75).

As a flux of at least 1.7 (GOST 10561-80) with cryolite module in the raw material mixture used artificial cryolite technical grade SC premium, which in pure form melts at temperatures of about 1010 ° C and in conjunction with Al ₂ O ₃ forms system, the melting point of which depends on the quantitative ratio of cryolite and Al ₂ O ₃ .

Considering the amount of Al ₂ O ₃ contained in the clay according to the invention and the amount of cryolite introduced, systems with melting points of about 945-950 ° C are obtained. In this case, the cryolite melt is able to dissolve Al ₂ O ₃ , and the resulting solution will fill the pores and voids in the material, leading to its compaction and at the same time act as a binder between the ceramic particles. Once cooled, this will increase strength and reduce water absorption.

In this case, for the specified low-plasticity clay, containing in its composition 10.75 wt.% Al ₂ O ₃ , the most effective will be the introduction of 1 to 2.5 wt.% Cryolite. When cryolite is introduced in an amount of less than 1 wt%, there is no significant change in the properties of the resulting ceramics, which is explained by the insufficient amount of the cryolite melt formed. With the introduction of cryolite in an amount of more than 2.5 wt% after interaction with Al ₂ O ₃ contained in the clay, an excess of melt remains, part of which is released in the form of volatile fluorine and fluoride compounds, which leads to warping of products, and when cryolite is introduced into in an amount of more than 5 wt%, the resulting internal stresses lead to significant deformations and rupture of products.

Implementation of the claimed invention is preferable according to the following technology:

Low-plastic clay is pre-crushed to a fraction with a particle size of less than 0.63 mm and dried, and then mixed with cryolite in the required ratio. Then the mixture is moistened to obtain a molding mass with a moisture content of 8 wt.%, From which a raw material is obtained at a pressure of 15 MPa. Then the raw material is fired without drying at a temperature of 1050 ° C.

The validity and advantages of the claimed invention are based on the measurement of physical, mechanical and operational parameters of ceramics based on a charge with a cryolite content of 1 to 2.5 wt.% And are illustrated by the following examples:

1. To 99 wt.% Low-plastic clay add 1 wt.% Cryolite, mix and get the material according to the specified technology;

2. To 98.5 wt.% Of low-plasticity clay add 1.5 wt.% Cryolite, mix and get the material according to the specified technology;

3. To 98 wt.% Of low-plasticity clay add 2 wt.% Cryolite, mix and get the material according to the specified technology;

4. To 97.5 wt.% Of low-plasticity clay add 2.5 wt.% Cryolite, mix and get the material according to the specified technology.

The properties of materials obtained using the known [3] and proposed compositions of the ceramic mass are shown in Table 1.

Information sources

1. Patent for invention No. 2439026, cl. С04В 33/13, 2012.

2. Patent for invention No. 2420479, cl. С04В 33/13, 2011.

3. Patent for invention №2258684, cl. С04В 33/00, 2005.

4. Patent US No. 1,664,815, cl. C04B 33/02, 1928.

Claims (2)

A method for the manufacture of facing ceramic products based on a mixture consisting of clay and flux, which consists in preliminary grinding and drying of clay, mixing clay with flux, moistening the mixture to obtain a molding mass, pressing the raw material and firing without drying, characterized in that the firing is carried out when temperature of 1050 ° C, as the main component, low-plastic clay with an Al ₂ O ₃ content = 10.75 wt.% is used, and cryolite is used as a flux with the following ratio of components, wt.%: Low plastic clay with Al ₂ O ₃ content = 10.75 wt.% 97.5-99.0 Cryolite 1.0-2.5