RU2213713C2 - Blend for manufacturing chamotte refractory materials - Google Patents

Abstract

FIELD: refractory materials. SUBSTANCE: blend contains 30% refractory clay, 30-50% chamotte with grain size 3-0.5 mm, and 20-40% topaz-containing component with grain size below 0.088 mm and content of topaz at least 70%. Preparation: laminated coarse-grained (3-0.5 mm) chamotte thinning agent is moistened with ceramic slurry to moisture content 6-8% and then mixed with fine composition of topaz-containing component and clay binder. Formation of products is accomplished by semidry molding technique at pressure 60-80 MPa depending on thinning agent content. Products are fired at 1320-1350 C. EFFECT: increased mechanical strength, temperature resistance and refractoriness of products and lowered firing temperature due to increased intensity of caking of clay-chamotte compositions and increased yield of needle mullite. 3 tbl, 1 ex

Description

 The invention relates to the production of refractory materials of aluminosilicate composition and can be used for the manufacture of, for example, fireclay refractories.

 Known mass for fireclay refractories, including a cleaner and clay. The disadvantage of this mass is the increased firing temperature of the products and low strength due to the incompleteness of the sintering process of the clay / Vakalova T.V., Luzin A.V., Pachin V.N., Vereshchagin V.I. Improving the quality of chamotte products from Troshkovskiy clays using intensive dispersion methods. Complex use of mineral raw materials, 1986, 11, p. 81-83 /.

Chamotte masses for normal and ladle refractories are known, the disadvantages of which are low compressive strength due to the insufficient degree of sintering of the clay bond at the applicable firing temperatures (1320-1350 ^o C). The introduction of soda additives to intensify sintering adversely affects the thermomechanical properties of products / Popov A.D. Chamotte products from clays of the Troshkovsky deposit. Proceedings of the Eastern Institute of Refractories. Metallurgy, 1966, issue 6, p. 22-36 /.

 It is known that the control of the binder sintering ability, as well as of such important operational properties of chamotte products as slag resistance and heat resistance, is possible by affecting the properties of the synthesized structure, mainly on the forming density, due to variations in the amount of chamotte and its grain composition, as well as methods for its preparation and introduction to the composition of the mass. In multi-chamotte masses with a low binder content (15-20%), special attention is paid to the fraction content of less than 0.088 mm for a number of reasons. Firstly, it is this fraction that most actively affects the degree of sintering of the material. Secondly, clay is found in such products in quantities sufficient only for the formation, together with the smallest chamotte fraction (smaller than 88 microns) of thin films, cementing larger chamotte grains. In this regard, the high heat resistance of multi-chamotte products is ensured by the presence of more mobile (due to the low clay content) inter-chamotte interlayers, which determine the low modulus of elasticity of these products / Mamykin P. S. Refractory products. Gos. publishing house on ferrous and non-ferrous metallurgy. Sverdlov. Dep., Sverdlovsk, 1955, p. 308-321 /.

Known mass for producing fireclay refractories, which includes components, wt.%:
Clay - 13.5
Refractory clay fireclay - 86.5
including fraction of 5-0 mm - 55
fraction less than 0.088 mm - 31.5
moreover, the clay binder and the finely divided fraction of the detergent are a mixture of co-grinding in a ball mill with a fraction of less than 0.088 mm more than 85-90% / Popov A.D., Schetnikova I.L. et al. Regulation of the process of sintering and production of chamotte products from Troshkov clays. Proceedings of the Eastern Institute of Refractories. Metallurgy, 1969, no. 9, p.31-42 /.

The disadvantage of this mass is that it consumes a large amount of artificial finely dispersed scrubber obtained by intensive grinding high-burnt (at temperatures not lower than 1400 ^o С) chamotte in ball or tube mills, which greatly complicates and increases the cost of production. In addition, to ensure the necessary thermomechanical properties of the products require higher firing temperatures (1400 ^o C).

Closest to the proposed is a mixture for the manufacture of capsule stocks, including, wt.%:
Clay - 16-22
Unburnt Alumina - 12-15
Hydrolyzed Ethyl Silicate - 11-14
Chamotte fraction 3-1 mm - 26-59
Synthetic Topaz (FR. 0.03-0.05 mm) - 2-23
The disadvantage of this mass is the need to use high firing temperatures (1500 ^o C) for the synthesis of thermal degradation products of ethyl silicate and technical alumina of secondary mullite, as well as sintering of products.

 The objective of the invention is to increase the mechanical strength and refractoriness of the products while reducing the firing temperature due to the intensification of the sintering of clay binder and increase the yield of needle mullite, which is achieved by adding finely dispersed topaz-containing component to the non-plastic part of the mass.

The proposed refractory mixture for the manufacture of fireclay refractories contains in its composition, wt.%:
Refractory clay - 30
Fireclay with a grain size (3-0.5) mm - 30-50
and additionally:
Topaz-containing component (with a topaz content of at least 70%) with a grain size of less than 0.088 mm - 23.1-40
A decrease in the amount of the fine-dispersed additive of the topaz-containing component introduced less than 23% is insufficient to ensure optimal particle packing during mass compaction, which necessitates an increase in the firing temperature to intensify the sintering process in order to control the macrostructure and properties of the products. An increase in the content of additives of the topaz-containing component by more than 40% slows down the sintering process and, accordingly, reduces the operational properties of refractory products due to a decrease in the packing density of particles at the pressing stage due to the excess of fine fractions and an increase in the amount of gaseous fluorine compounds released during thermal decomposition, loosening the forming ceramic structure .

An example of the manufacture of fireclay refractories
Preparation of raw materials is carried out in a separate way. Clay on a bunch, for example Troshkovskaya, is crushed in a disintegrator or in runners before passing through a 0.5 mm sieve of at least 70%. A purifier from the same clay with water absorption of not more than 3% is prepared in the traditional way by grinding in the necessary equipment, followed by isolation of the required coarse fraction with a size of (3-0.5) mm. The topaz-containing component can be represented by a topaz rock with a topaz content of at least 70% or a topaz concentrate, which is a finely dispersed flotation product of poorer topaz rocks with a particle size of less than 0.088 mm. The chemical composition of the raw materials is given in table 1.

To prepare the mass, the coarse coarse chamotte clarifier with a fraction of (3-0.5) mm - 30-50% is moistened to a moisture content of 6-8% with a clay slip, with a density of 1.25 g / cm ³ , which is a mixture of the composition,%: clay - 35, calcium lignosulfonate (PRS) - 10 (per dry matter), water - 55.

Then, the resulting mixture of moistened detergent is mixed with a finely divided composition of a topaz-containing component, a fraction of less than 0.088 mm — 23.1-40%, and prepared clay binding. This creates a close contact between the grains of the filler and the bunch. Component compositions of chamotte masses with the proposed filler are given in table.2. After homogenization from the charge by known technological methods, a semi-finished product is pressed at a pressure of at least 60-80 MPa (depending on the degree of refinement). Firing is carried out at 1320-1350 ^o With a shutter speed of at least 2 hours. Lowering the firing temperature less than 1320 ^o C does not ensure the completeness of the sintering process and the formation of the structure of the refractory, firing at temperatures above 1350 ^o C is impractical for economic reasons due to the increase in energy costs. The properties of the calcined products are given in table.3.

 The improvement of the thermomechanical properties of chamotte products when a finely dispersed topaz-containing component with a topaz content of at least 70% is introduced into the non-plastic part is determined by the action of topaz itself on the sintering and phase formation processes in clay-base compositions. Firstly, gaseous fluorine released during thermal dissociation of topaz is an anionic type active mineralizer that promotes the activation of primary mullite formation in clay binding. Secondly, this fluorine is partially absorbed by the formed silicate melt and affects its rheological and reaction properties, creating favorable conditions for dissolution of the primary mullite and recrystallization of the secondary, lowering the temperature of its synthesis, increasing the yield and improving the structure. Thirdly, the thermal decomposition of topaz itself is accompanied by the formation of a specific needle-shaped mullite mullite, thus ensuring an increase in the total content of needle-shaped mullite, which reinforces the structure and contributes to the improvement of strength properties and fire resistance.

Claims (1)

A mixture for the manufacture of chamotte refractories, including clay, chamotte and a topaz-containing component, characterized in that it contains a topaz-containing component with a topaz content of at least 70% and a grain size of less than 0.088 mm and chamotte with a grain size of 3-0.5 mm in the following the ratio of the components of the mixture, wt.%:
Refractory clay - 30
Fireclay with a grain size of 3-0.5 mm - 30-50
The specified topaz-containing component is 20-40r

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