RU2353991C2 - Method of making current-conducting panels, raw mixture for making current conducting panels and current conducting filler them, based on crushed glass - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: proposed method of making current conducting panels involves mixing current conducting material - coal coke with particle size 0.2-1.5 mm with a binding component, moulding the products and subsequent thermal processing. The binding component used is a ground clay component. The current conducting material contains ground graphite, silicon carbide and current conducting filler in form of 0.1-1.0 mm granules, obtained from the following mixture, in wt %: chalk 1.0-5.5, graphite 7-9, silicon carbide 3-5, clay component 15-35, granular current conducting filler 4.5-10, coal coke with particle size 0.2-1.5 mm - the rest. Before moulding, the raw mixture is moistened to 4-7% moisture. Moulding is done using the semidry moulding method and thermal processing is carried out in a weak acid medium at 800-830°C temperature. The binding component used in the raw mixture is a clay component. The current conducting filler is granular with particle size 0.1-1.0 mm and contains the following components, in wt %: chalk - 1-5.5, 8-11% graphite 8-9.7, silicon carbide - 6.0-9.2, 8-12% aqueous solution of liquid glass - 1.0-2.6, and glass powder - 73.0-84.0.

EFFECT: wider assortment of equipment and raw material base for producing ecologically clean panel-type current conducting objects with a wide range of application properties.

3 cl, 2 tbl, 1 ex

Description

The invention relates to the electrical industry and can be used to obtain electric heating blocks and panels in housing and industry.

A known method of manufacturing conductive sheet products and raw material suspensions for their production, including, wt.%: Sodium metasilicate 28-30, graphite 11-15.5, alumina 3.5-3.7, iron oxide (III) 3.5 -3.7, strontium carbonate 3.5-3.7, potassium titanate 4.2-4.5, barium oxide 1.2-1.5, hydrochloric acid 4.9-5.1, water - the rest. The raw material suspension obtained by mixing the components is applied with a brush on the surface of the mica plates with a film 0.2-0.4 mm thick and calcined at a temperature of 300 ° C for 5-7 hours [RF patent No. 2277733, class. HB01 1/00, 2004].

The disadvantages of the method and the raw material suspension are low specific power and insufficient reliability of the film heating elements at high heat loads. These shortcomings worsen the technical and operational characteristics of film conductive products.

Closest to the proposed solution are a method of manufacturing conductive panels and a raw material charge, including, wt.%: Coal coke with a particle size of 0.2-1.5 mm 81 ... 94, epoxy resin 5.5 ... 16.5 and hardener 0, 5 ... 2.5. The method consists in mixing epoxy resin with a hardener and the subsequent introduction of crushed coke. Products are formed from the mixed mass, which are cured at a temperature of 80 ° C for 4-6 hours [USSR copyright certificate No. 355756, class. H05b 3/10, 1970].

The disadvantage of the prototype is that conductive panels of material on an organic basis have a low specific power and low operating temperature.

The present invention solves the problem of expanding the arsenal of technical means and raw materials for the production of environmentally friendly conductive panel-type products with an extended range of consumer properties: high operating temperature and specific power, as well as the absence of deformation during firing and operation due to low thermal shrinkage.

The technical result is achieved by the fact that in the method of manufacturing conductive panels, comprising mixing conductive material - coal coke with a particle size of 0.2-1.5 mm with a binder component, molding the products and their subsequent heat treatment, according to the proposed solution, ground is used as a binder component clay component, in the composition of the conductive material additionally use ground graphite, silicon carbide and conductive aggregate in the form of granules with a size of 0.1-1.0 mm, obtained and h mixture, wt.%: chalk 1.0-5.5, graphite 8.0-9.7, silicon carbide 6.0-9.2, 8-12% aqueous solution of water glass 1.0-2 6 and glass powder 73.0-84.0, in the following ratio of the charge components of the conductive material, wt.%: Graphite 1-9, silicon carbide 3-5, clay component 15-35, conductive aggregate in the form of granules 4,5 -10.5, coal coke with a particle size of 0.2-1.5 mm - the rest, while before molding the raw material mixture is moistened to a moisture content of 4-7%, molding is carried out by means of semi-dry pressing, and heat treatment is carried out in a slightly oxidizing gas medium e at a temperature of 800-830 ° C.

The technical result is achieved in that the raw material mixture for the manufacture of conductive panels, including conductive material - coal coke with a particle size of 0.2-1.5 mm and a binder component, according to the proposed solution as a binder component contains a ground clay component, the composition of the conductive material is additionally contains ground graphite, silicon carbide and a conductive filler in the form of granules with a size of 0.1-1.0 mm, consisting of a mixture, wt.%: chalk 1.0-5.5, graphite - 8.0-9.7, carbide silicon 6.0-9.2, 8-12% aqueous p a solution of liquid glass 1.0-2.6 and glass powder 73.0-84.0, in the following ratio of the components of the mixture, wt.%: graphite 1-9, silicon carbide 3-5, clay component 15-35, conductive filler in the form of granules 4.5-10.5, water 4-7, coal coke with a particle size of 0.2-1.5 mm - the rest.

The result is achieved using conductive filler for conductive panels in the form of granules with a size of 0.1-1.0 mm, consisting of components, wt.%: Chalk 1.0-5.5, graphite 8.0-9.7, silicon carbide 6.0-9.2, 8-12% aqueous solution of water glass 1.0-2.6 and glass powder 73.0-84.0.

The charge characteristics of the conductive material:

1. Coal coke in accordance with GOST 27044-86.

2. As a clay component used loam Shebekinsky deposits, Belgorod region. Refractoriness 1080 ... 1170 ° C. The main clay mineral is montmorillonite.

3. Graphite in accordance with GOST 5279.

4. Silicon carbide grade M 7 according to GOST 3647-80.

5. As a powder of glass used ground battle of green container glass, Voronezh.

6. Chalk technical dispersed MTD-2 according to TU - 21-020350-06-92, OJSC "Building Materials", Belgorod.

The chemical composition of the raw materials is given in table 1.

Table 1 The chemical composition of raw materials No. p / p Component The content of oxides, wt.% SiO ₂ Al ₂ About ₃ TiO ₂ Fe ₂ O ₃ CaO MgO R ₂ O SO ₃ P.p.p. one. Glass Fight 65,2 10.7 0.8 1,2 6.5 0.7 14.7 0.2 - 2. Loam Shebekinsky 58.9 7.6 0.4 1,2 10.1 2,8 3.4 0.4 15,2 3. Chalk Belgorod 1.3 0.7 0.1 0.1 54.7 0.3 - - 42.8

7. To obtain a conductive filler, the glass powder was dosed with chalk, graphite and silicon carbide by gravimetric method. The resulting mixture was loaded into a ball mill and grinding was performed until a specific surface of 300 ... 500 m ² / kg was reached. When granulating cullet powder, ground together with chalk, graphite and silicon carbide, on a plate granulator, an 8-12% aqueous solution of silicate glue (liquid glass) according to TU 2385-001-54824507-2000 was used as a binder.

Conductive material was prepared as follows.

Example. The pre-crushed coke with a particle size of 0.2-1.5 mm was weighed in an amount of 44 kg (44%, see Table 2, mixture 1), the following charge components were pre-ground and sieved through a sieve with a mesh size of 0.1 mm : graphite 8 kg (8%), silicon carbide 4 kg (4%), Shebekinsky loam 30 kg (30%), as well as 8 kg (8%) of aggregate in the form of granules obtained from 6.24 kg (78%) glass powder, ground together with 0.24 kg (3%) of chalk, 0.72 kg (9%) of graphite and 0.64 kg (8%) of silicon carbide granulated using 0.16 kg of a 10% liquid solution glass (2%) sifted through a sieve with ra mer diameter of 1.0 mm mesh sieve and remaining on the 0.1 mm, see. Table 2, mixture 1.

A mixture of dry components (coke, graphite, silicon carbide, loam and aggregate) was mixed until evenly distributed, moistened with water until the molding moisture (6 wt.%, See table 2, mixture 1). Samples of raw products from the resulting mixture were molded by semi-dry pressing

on the press at a pressure of 6 MPa, and then fired at a temperature of 820 ° C in a chamber-type furnace with a controlled composition of the gas medium with a content of 0.5 wt.% oxygen in the gas medium of the burning chamber. After cooling, product samples were tested for strength, and thermal shrinkage and electrical conductivity were determined.

Mixtures of compositions 2 and 3 (Table 2) were prepared in a similar way.

The mixture of composition 4 (Table 2) contained a conductive granular aggregate with a granule size of 0.06-0.08 mm, i.e. less than 0.1 mm. The mixture of composition 5 (Table 2) contained a conductive granular aggregate with a granule size of 1.2-1.6 mm, i.e. more than 1.0 mm. A mixture of composition 6 (table 2) was prepared without the use of conductive granular aggregate.

The known composition of the mass 7 (table 2) was made according to the prototype (USSR copyright certificate No. 355756, class H05b 3/10, 1970, table, composition 4).

Joint grinding of aggregate components (glass powder, chalk, graphite and silicon carbide) is preferably carried out in the ratios proposed by the authors until a specific surface area of 300 ... 500 m ² / kg is reached, while the size of its granules should be 0.1-1.0 mm.

The test results are shown in table.2.

Analysis of the data in Table 2 of the test results of samples of conductive panels shows the following.

1. Introduction to the composition of the conductive mass of granular aggregate in the form of a glass powder, ground together with chalk, graphite and silicon carbide, in the claimed quantities and grain sizes of 0.1 ... 1.0 mm, as well as subsequent firing at a temperature of 800-830 ° C in a slightly oxidizing environment they allow to obtain durable high-quality panels with good conductive characteristics.

2. To reduce the amount of conductive granular aggregate less than 4.5 wt.%, The amount of liquid glass in it is less than 1.0 wt.% And its concentration in water is less than 8%, graphite is less than 8.0 wt.%, Silicon carbide is less than 6, 0 wt.% (Table 2, mixture 2), the firing temperature is less than 800 ° C, while increasing the amount of glass powder over 84.0 wt.% Is impractical, because while the strength of the resulting conductive panels is reduced, the electrical resistivity is reduced; thermal shrinkage leads to the appearance of small cracks; therefore, this mixture composition and firing conditions are taken as boundary. A further decrease in these quantitative values (mixture 4) leads to a sharp deterioration in consumer properties, which is unacceptable in the manufacture of conductive panels.

3. Heat-treated conductive panels obtained from the raw material mixture 3 have a negative shrinkage, i.e. there is a uniform increase in linear and volume dimensions with acceptable surface defects of the fired panels in comparison with the sizes of the original raw products; panels from mixture 5 have cracks, which significantly reduces their strength and increases electrical resistance due to the violation of electrocontacting elements.

4. To increase the amount of conductive granular aggregate more than 10.5 wt.%, The amount of liquid glass in it more than 2.6 wt.% And its concentration in water more than 12%, graphite more than 9.7 wt.%, Silicon carbide more than 9, 2 wt.% (Table 2, mixture 3), the firing temperature of more than 830 ° C, while reducing the amount of glass powder less than 73 wt.% Is also impractical, because there is an increase in the electrical resistivity of the resulting panels due to the appearance of expansion cracks on the faces of the products, partial burning of conductive carbon-containing components, which also leads to a decrease in strength indicators, therefore this composition is also accepted as boundary.

The exclusion from the composition of the raw material mixture of conductive granular aggregate (mixture 6) does not allow to obtain conductive products, because After firing, large shrinkage phenomena are recorded, which lead to volumetric structural defects, up to the destruction of the panels themselves and the loss of their electrically conductive properties.

The inventive method for the manufacture of conductive panels allows you to get environmentally friendly electric heating products with a wide range of consumer properties that work reliably in a wide temperature range up to 650-700 ° C, they have a solid structure, reliable in operation.

The physicochemical nature of the technical solution to achieve the problem is as follows: the filler in the form of the inventive conductive granules contains in a powder state glass and chalk. It is known that when reaching 780 ... 790 ° C, the glass powder softens, and carbon dioxide is released from chalk during decarbonization, which porosizes the glass mass of the granule. This process creates a uniform bursting effect, which actively prevents the occurrence and development of fire shrinkage of conductive panels in the heat treatment process. When the temperature rises to 800-830 ° C, the glass passes into the liquid phase and actively interacts with all particles of the charge over the entire surface of the expanded granule, wetting and hardening the resulting composite electrically conductive material. The presence of loam of montmorillonite composition provides the formation of reinforcing crystalline structures in the product, which form a solid bulk crystalline structure. X-ray phase studies show that this structure is formed from wollastonite and anorthite crystals. A distinctive feature of the glass phase formed during the firing of the inventive conductive panels located on the walls of the formed bulk structures and consisting of a glass powder melt saturated with oxides that are part of the clay supplemented with conductive components is that the crystal structures formed in its environment have a predominantly prism-needle structure . The authors found that the increased density of the vitrified walls of the filler formed during firing of the product at a temperature of 800-830 ° C and the interaction of clay particles adjacent to the filler with molten glass phase from the granulate material and conductive components determines the high performance characteristics of the resulting conductive panels. When cooling the calcined product, these hardened areas, evenly distributed over the volume of the obtained conductive panels, prevent cracking, which explains the high strength of the products.

Providing a slightly oxidizing environment in the firing chamber during the heat treatment of raw products contributes to the complete preservation of carbon conductive components in the array of panels and surface burnup to a depth of 0.1-0.3 mm, depending on the mode of fuel combustion. Such a gas heat treatment mode allows you to adjust the electrical resistivity, specific power and further improve the consumer properties of the resulting heating panels.

The raw material mixture for producing conductive panels according to the prototype, including organic components as a binder - an epoxy resin and a hardener for it, does not allow to achieve a high result, implemented in the claimed method, because during their operation, gases harmful to humans are released, while, when destroyed, the panels degrade the conductive and strength characteristics.

Thus, the use of the proposed method, a raw material charge, including conductive aggregate, allows us to solve the problem of expanding the arsenal of technical means in the manufacture of durable conductive environmentally friendly panels, expand the raw material base by using natural materials as montmorillonite loams, previously for the manufacture of conductive panels, not used, and this technology is not demanding on the purity of the starting materials.

Claims (3)

1. A method of manufacturing a conductive panel, comprising mixing a conductive material - coal coke with a particle size of 0.2-1.5 mm with a binder component, molding products and their subsequent heat treatment, characterized in that the ground clay component is used as a binder component, the composition of the conductive material is additionally used ground graphite, silicon carbide and a conductive filler in the form of granules with a size of 0.1-1.0 mm, obtained from the mixture, wt.%: chalk - 1.0-5.5, graphite - 8.0- 9.7, silicon carbide - 6.0-9.2, 8-12% aqueous liquid glass solution - 1.0-2.6 and glass powder - 73.0-84.0; in the following ratio of the components of the charge of conductive material, wt.%:
graphite 7-9 silicon carbide 3-5 clay component 15-35 conductive granular aggregate 4,5-10,5 coal coke with a particle size of 0.2-1.5 mm rest,
in this case, before molding, the raw material mixture is moistened to a moisture content of 4-7%, molding is carried out by the method of semi-dry pressing, and heat treatment is carried out in a slightly oxidizing gas medium at a temperature of 800-830 ° C. 2. The raw material charge for the manufacture of conductive panels, including conductive material - coal coke with a particle size of 0.2-1.5 mm and a binder component, characterized in that the charge as a binder component contains a ground clay component, the composition of the conductive material further comprises ground graphite, silicon carbide and conductive aggregate in the form of granules with a size of 0.1-1.0 mm, consisting of a mixture, wt.%: chalk - 1.0-5.5, graphite - 8.0-9.7, carbide silicon - 6.0-9.2, 8-12% aqueous liquid glass solution - 1.0-2.6 and powder glass - 73.0-84.0, in the following ratio of the components of the mixture, wt.%:
graphite 7-9 silicon carbide 3-5 clay component 15-35 conductive granular aggregate 4,5-10,5 water 4-7 coal coke with a particle size of 0.2-1.5 mm rest 3. Conductive filler for the manufacture of conductive panels in the form of granules with a size of 0.1-1.0 mm, consisting of components, wt.%:
a piece of chalk 1.0-5.5 graphite 8.0-9.7 silicon carbide 6.0-9.2 8-12% aqueous solution of water glass 1.0-2.6 glass powder 73.0-84.0