RU2344105C2 - Carbon-bearing fire-resistant material and method of production thereof - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention refers to production techniques of carbon-bearing fire-resistant products and can be used in chemical engineering, and in electrode and electrotechnical industry. Declared carbon-bearing fire-resistant product contains following components, wt %: thermoanthracite of fraction, mm: (-0.5+0), (-1.25+0) and (-2.50+1,25) - 40-55, graphite of fraction, mm: (-0.5+0) and -(-1.25+0) - 20-35, coal tar pitch 16-21, silicon carbide of fraction -0.071 mm - 8-15, metal silicon of fraction -0.071 mm - 5-8, powder aluminium oxide 0.8-1, powder iron 0.8-1. Bulk components in ratio and fraction size specified above are heated to 104-120°C, added with pitch heated to temperature 140-150°C and aggitated within 30-45 minutes. Then using extruder, mixture is moulded for blast-furnace blocks 600×600×3000 at pressure 50 kg/cm² and temperature 135°C. The blocks are thermally processed in gas box furnace at temperature in gas phase 1200-1300°C within 400-450 hours and then cooled in furnace within 6 days.

EFFECT: production of high-density microcellular carbon-base material, as well as lower energy intensity and time of material production process.

2 cl, 2 tbl

Description

The invention relates to a technology for the manufacture of carbon-containing refractory products and can be used in chemical engineering, as well as in the electrode and electrical industries.

A known method of manufacturing carbon products described in p. US No. 3219731, class. 264-29, op. 23.11.65.

The known method consists in mixing a carbon filler, for example, a mixture of carbon black and coke, with a binder — phenol formaldehyde resin and pitch, forming the resulting mixture and subjecting carbonization blanks to 1000 ° C and higher for 240-300 hours.

The disadvantage of this method is that the obtained carbon material has low strength characteristics due to the formation of pores in the carbon material due to the release of volatile substances formed during coking of the binder.

A known method of producing porous carbon products described in A. with. USSR No. 321078, class СВВ 31/04, з. 12/30/68.

The known method involves the introduction of a pore-forming agent - ammonium chloride (45-70 parts by weight) - in a carbon-containing filler - petroleum coke and soot - when mixed, adding a binder - coal tar pitch - when mixing, pressing from a mixture of billets and then firing them to 1000-1200 ° C for 440 hours.

Using this method, products with high porosity (65-73%), with insufficiently high strength at high energy consumption for their production due to the low heating rate during firing, are obtained. In addition, the use of ammonium chloride leads to the formation of nitrogen oxides that are harmful to the environment.

The closest in technical essence to the claimed are carbon-containing refractory material and the method for its preparation, described in RF patent No. 2214380, class. СВВ 35/32, 35/328, з. 02/18/02, op. 10/20/03.

Known carbon-containing material contains silicon carbide, metallic silicon, graphite, aluminum oxide, thermoanthracite and coal tar pitch in the following ratio, wt.%:

A disadvantage of the known material is the presence of very large pores and as a result of a not very dense structure, not sufficiently resistant to the penetration of aggressive media (molten metal).

A known method for producing a carbon-containing refractory material is that the components of the charge are weighed, the bulk components are mixed, the pitch is added and mixed for 60 minutes, then, using an extruder, molded at 600 kg / cm ² domain temperature blocks 600 × 600 × 3000, which are subjected to heat treatment in two stages, the first of which is carried out in a gas chamber furnace at a temperature of 900 ° C for 20 days, followed by cooling in a furnace for 6 days, and the second stage in electric chambers oh furnace at 1250 ° C in reducing atmosphere for 2 days followed by cooling in the furnace for 7 days.

The disadvantage of this method is its significant energy intensity and duration, due to two-stage heat treatment, and the second stage takes place at a very high temperature.

The task for the claimed technical solutions are:

- for carbon-containing refractory material - obtaining finely porous carbon material with high density;

- for a method for producing a carbon-containing refractory material - reducing the energy intensity and duration of the process with high quality material;

- for carbon-containing refractory material - obtaining finely porous carbon material with high density.

The tasks are solved in that:

- in a method for producing a carbon-containing refractory material, which consists in the use of thermoanthracite, graphite, coal tar pitch, silicon carbide, silicon metal, aluminum oxide as charge components, weighed them, mixed bulk components, added pitch and stirred for 30-45 min, then molded by an extruder at a pressure of 50 kg / cm ² at a temperature of 135 ° C domain blocks, they are subjected to heat treatment which is carried out in the gas chamber of the furnace, followed by cooling in an oven for 6 days, acc clearly the invention the charge is further added reduced iron, and the heat treatment is carried out at a temperature in the gas phase 1200-1300 ° C for 400-450 hours.

When metal particles — in this case, iron — are added as an initiator, according to studies described in the literature (see the book Silicon Carbide edited by G. Henish and R. Roy, M., Mir, 1972), decrease in the temperature of carbide formation onset. Already at 1200 ° C, the eutectic Fe-Si-C alloy dissolves, formed as a result of diffusion saturation of iron with silicon and carbon. The maximum growth rate of whiskers is observed in the temperature range 1250-1300 ° C. The use of silicon carbide and thermoanthracite with small particle sizes as a filler provides, with good porosity, a significantly greater erosion resistance in oxidizing media, and therefore increases the strength of the products. Conducting heat treatment in one stage for less time reduces the energy intensity of the process, its complexity and duration.

- in a carbon-containing refractory material, including thermoanthracite, part of which has fractions, mm:

- (-0.5 + 0) and (-1.25 + 0)

- graphite fraction, mm:

- (-0.5 + 0)

- (-1.25 + 0)

coal tar pitch in the form of a fluid viscous resin,

- silicon carbide fraction, mm (-0.071),

silicon metal fraction, mm (-0.071)

aluminum oxide (powder), according to the invention, additionally crushed iron is introduced in the following ratio of components, wt.%:

- thermoanthracite 40-55 when the size fraction of the carcass forming part equal to:

- (-2.5, 0 + 1.25) mm

- graphite 20-36

- coal tar pitch 16-21

- silicon carbide 8-15

- silicon metal 5-8

- aluminum oxide 0.8-1

- ground iron 0.8-1.

The introduction of crushed iron into the material during firing leads to the appearance of droplets of liquid metal - an intermediate phase through which the substance diffuses to the growing crystal. When heated in an atmosphere containing volatile silicon and carbon compounds, these elements dissolve in the metal melt, which initiates the growth of SiC whiskers, forming the so-called "whiskers", which overlap large pores, reducing the average pore size of the structure of carbon-containing refractory products and sealing it, which prevents the penetration of a metal melt into it.

A decrease in the size of the maximum grain of the carcass-forming part of the fractional composition of thermoanthracite leads to a decrease in pore sizes, for a material with a smaller maximum grain size, the average pore size is almost 2 times smaller. The use of an additive of alumina (aluminum oxide), which is a carrier of oxygen bridges, in an amount of 0.8-1% reduces the average pore size and increases the content of small pores in the material. Coal tar impregnation also reduces pore size.

Thermoanthracite is a filler, its grains serve as a framework for a carbon-containing refractory porous material. The above limits of its and graphite content are determined by the fact that if electrocalcined anthracite is used, then it is required more, and less graphite. When the content of thermoanthracite is less than 40%, the strength of the material decreases, its content of more than 55% does not significantly affect the strength. If gas-calcined thermoanthracite is used, then it is required less, and graphite - more. At the same time, graphite determines such operational properties as high thermal conductivity and low specific resistance, moreover, it has a large sorption capacity and is bake-intensive. The indicated graphite content limits (20-36%) provide the optimal named properties.

The pitch is a binder, its amount must be necessary and sufficient and is dictated by the general surface of the composition.

Silicon carbide serves as a center of crystal formation and is a barrier to the penetration of metal into pores. A content of less than 8% is not enough for the formation of crystals, and more than 15% does not make sense, because does not affect a further increase in the number of crystals.

Silicon should be sufficient for the growth of whiskers - less than 5% is not enough for growth, and more than 8% does not significantly affect the further increase in the number of crystals.

The use of alumina (alumina) additives in the material in an amount of 0.8-1% reduces the average pore size and increases the content of small pores in it.

Iron lowers the temperature at which whiskers begin to form and initiates their growth, as does alumina. A content of both less than 0.8% is not enough for the formation of a mustache, and a quantity of more than 1% does not significantly affect their growth.

The technical result for the method is to reduce the heat treatment time, for the material is to reduce the pore size and increase the number of smaller pores.

The inventive method for producing a carbon-containing refractory material has a novelty in comparison with the prototype, differing from it by such significant features as the use of a finer fraction in the frame forming part of the thermoanthracite, the introduction of crushed iron into the charge, heat treatment in one stage for another time, which together provide achievement of a given result.

The inventive carbon-containing refractory material has a novelty in comparison with the prototype, differing from it by such significant features as a slightly different percentage composition, another predominant fractional fraction of thermoanthracite and the introduction of crushed iron, ensuring the achievement of a given result.

The applicant is not aware of technical solutions possessing the indicated distinguishing features, which together provide the desired results, so he believes that the claimed technical solutions meet the criterion of "inventive step". The claimed technical solutions can find wide application in the electrode and electrical industries, therefore, meet the criterion of "industrial applicability".

The inventive method for producing a carbon-containing refractory material is as follows and is carried out in the manner described below.

As components of the charge take thermoanthracite, graphite, coal tar pitch, silicon carbide, silicon metal, aluminum oxide and crushed iron at the above ratio of components and size fractions. The components are weighed in the right amount, the bulk components are mixed, heated to 104-120 ° C, then the pitch is added, heated to a temperature of 140-150 ° C, and mixed for 30-45 minutes. Then using an extruder is molded from a mixture at a pressure of 50 kg / cm ² at a temperature of 135 ° C domain blocks 600 × 600 × 3000, which are subjected to heat treatment. Heat treatment is carried out in a gas chamber furnace at a temperature in the gas phase of 1200-1300 ° C for 400-450 hours, followed by cooling in the furnace for 6 days.

The inventive carbon-containing refractory material obtained by the claimed method contains the following components in the following ratio, wt.%, And the following fractional composition:

- thermoanthracite 40-55 fractions, mm:

- (-0.5 + 0), (-1.25 + 0) and (-2.5.0 + 1.25) (carcass forming part ≈ 40%);

- graphite 20-35 fractions, mm: (-0.5 + 0) and (-1.25 + 0);

- coal tar pitch 16-21

- silicon carbide 8-15 fractions, mm (-0.071)

- silicon metal 5-8 fractions, mm (-0.071)

- aluminum oxide 0.8-1 (powder)

- ground iron 0.8-1.

Physico-mechanical properties obtained by the claimed method of carbon-containing refractory material, depending on the iron content, initiating the formation of "whiskers", leading to a decrease in pore size, are given in table 1.

Table 1 Physical and mechanical properties The iron content,% 0.7 0.8 0.9 1,0 1,1 1. The apparent density, g / cm ³ 1.68 1.70 1.71 1.70 1.70 2. Total porosity,% 15.0 13.9 13.6 13.7 13.7 3. The pore content of less than 1 μm,% fifty 53 55 54 53 4. The pore content of less than 10 microns,% 80 90 92 91 91 5. The average pore size, microns 0.9 0.7 0.64 0.67 0.70

The effect of the remaining components is described above.

The possible content of the ingredients (100%) in the carbon-containing refractory material is given in table 2.

table 2 Ingredient Thermoanthracite Graphite Kamennoug. pitch Silicon carbide Silicon Alumina. Iron Contents the weight.% 45 22 17 8 6.2 0.9 0.9 Contents 43 24 16 10 5.2 0.9 0.9 Contents 46 21 eighteen 8.2 5,0 0.9 0.9

The effect of the individual components on the quality of the carbon material is described above.

Compared with the prototype, the carbon-containing refractory material is more finely porous and dense, and the method for its production is less durable and less energy intensive.

Claims (2)

1. A method of obtaining a carbon-containing refractory material, which consists in the following components being taken as a charge: thermoanthracite, part of which has fractions, mm: (-0.5 + 0) and (-1.25 + 0), graphite fractions, mm: (-0.5 + 0) and (-1.25 + 0), coal tar pitch as a fluid viscous resin, silicon carbide fraction, mm (-0.071), silicon metal fraction, mm (-0.071), oxide powder aluminum weigh them, mixed granular components pitch added and stirred for 30-45 minutes and then molded by an extruder at a pressure of 50 kg / cm ² at a temperature of 135 ° domain blocks, which are subjected to heat treatment which is carried out in the gas chamber of the furnace, followed by cooling in an oven for 6 days, characterized in that the charge is introduced additionally reduced iron at the following ratio, wt.%:
thermoanthracite 40-55 with a fraction of the carcass forming part equal to (-2.5 + 1.25) mm, graphite 20-36, coal tar pitch 16-21, silicon carbide 8-15, metallic silicon 5-8, aluminum oxide 0, 8-1, ground iron 0.8-1, and heat treatment is carried out at a temperature in the gas phase of 1200-1300 ° C for 400-450 hours 2. Carbon-containing refractory material made by the method according to claim 1 and comprising thermoanthracite, part of which has fractions, mm: (-0.5 + 0) and (-1.25 + 0), graphite fractions, mm: (-0, 5 + 0) and (-1.25 + 0), coal tar pitch in the form of a fluid viscous resin, silicon carbide fraction, mm (-0.071), silicon metal fraction, mm (-0.071), alumina powder, characterized in that it contains additionally crushed iron in the following ratio of components, wt.%:
thermoanthracite 40-55 with a fraction of the carcass forming part equal to (-2.5 + 1.25) mm, graphite 20-36, coal tar pitch 16-21, silicon carbide 8-15, metallic silicon 5-8, aluminum oxide 0, 8-1, ground iron 0.8-1.