Composition for producing of ceramic material

FIELD: powder metallurgy, in particular ceramic material composition.

SUBSTANCE: claimed composition contains (mass %) boron nitride 10-20; silicium carbide 73.5-82; titanium 3-7; silicium 0.1-1. Composition is obtained by blending and subsequent plasticizing with organic binder. Composition is useful as refractory materials for high temperature furnaces and chemical reactors. Articles from composition of invention are produced by hot pressing and have heat capacity of 577-601 J/kg0C at 250C, thermal conductance of 6.4-8.0 W/m.K at 4000C, thermal-shock resistance of 25-29 heating cycles up to 14000C followed by cooling with water at 200C.

EFFECT: materials with improved bending strength and hardness.

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The invention relates to the field of powder metallurgy and can be used in the manufacture of ceramic plates for high temperature furnaces and chemical apparatus, nozzles and various products, used as a refractory, electrically insulating, chemically resistant and wear-resistant parts used in metallurgy, power engineering and mechanical engineering.

Known composition for the manufacture of refractory material containing components, wt.%: BN 2-70; SiC 10-49; B4C 20-49, see A.C. SU # 349664, C 04 B 35/56, published in BI No. 26 from 04.09.72,

Ceramic material obtained from the composition can be used for lining metallurgical furnaces, chemical apparatus and various products, used as a refractory or insulating components. This material has the strength in compression (53-124,5) MPa. However, a ceramic material based on BN-SiC4With chemically unstable after prolonged use in the air with molten silicate materials, including basalt, because of the relatively high content in its composition of boron carbide, and also has poor resistance to thermal shock (quantity withstand cycles of heating to 1600°C and cooling water is 1-14).

Known composition for the manufacture of refractory material containing components, wt.%: BN - 31-32; SiC - sheet 18-5; In2About3- 3-6;4With the rest, see A.S. SU # 461918, 04 35/56, With 22 29/00, published in BI No. 8 of 28.02.75, Ceramic material obtained from this composition is resistant to thermal shock (number of heating cycles up to 1500°With subsequent cooling in water exceeds 40). It can be used in the manufacture of lining plates for metallurgical furnaces, chemical apparatus and fittings, used as a refractory and insulating parts in different devices. The disadvantage of this ceramic material is its poor chemical stability in contact with molten silicate materials, including basalt in the air, because of the content in its structure a large number of boron carbide.

Known composition for the manufacture of refractory and insulating material containing components, wt.%: BN - 19-27; SiC - 40-60; 20-35; see ALSO SU # 461084, 04 35/56, published in BI No. 7 from 01.04.75, Ceramic material obtained from the composition, resistant to thermal shock (can withstand more than 30 cycles of heating up to 1500°C and subsequent cooling water) and can be used in the manufacture of refractories for the lining of metallurgical furnaces or the manufacture of shaped products used as refractory insulating parts in a different condition is the hardware.

This ceramic has the same drawback as the previous example, low chemical stability in contact with molten silicate materials, including basalt, in the air because of the content in its structure a large number of boron.

Known composition for the manufacture of heat-resistant ceramic refractory insulating material with high resistance against oxidation containing components, wt.%: BN - 20; SiC - 80, see advertising sheet “New high-temperature insulating materials. Institute of materials science problems, USSR Academy of Sciences, Publishing house “Advertising”, Kiev, 1972

The ceramic material of this composition resistant to thermal shock (can withstand more than 25 cycles of heating up to 1500°C and subsequent cooling water), tensile strength at 20°C on the curve reaches 67 N/mm2the specific resistance at 20°C is 3·1010Ohm·cm, weight gain during oxidation in air at 1200°C for 6 hours does not exceed 14,8 mg/cm2maximum operating temperature reaches 2200°C. According to our data, the ceramic material has a hardness (HRB)=78, heat capacity at 25°C - 612 j/kg°C, thermal conductivity at 400°C to 6.75 W/m·To, in contact with the melt of basalt can be removed easily during cooling. All this allows to use this material in metallurgy as electroporation the CSOs and insulating material for the manufacture of devices continuous casting, transporting molten metals (particularly aluminium), molten salts, as well as the manufacture of nozzles, lining furnaces, baths, crucibles. The disadvantage of this ceramic material is a low strength when working in the environment with molten silicate materials including basalt and glass.

This composition, as the closest to the technical essence and the achieved technical result of the claimed composition, chosen as a prototype.

The present invention solves the problem of increasing strength during long work on the air with molten silicate materials, including molten glass and basalt, while maintaining a sufficiently high level of resistance to thermal shock, hardness (wear resistance) and chemical resistance of refractory ceramic material.

Technical result achieved with the use of the claimed composition the following table:

- obtained by hot pressing the mixture of SiC-BN-Ti-Si ceramic material has a homogeneous fine-grained structure with a grain size not exceeding the size of the grains of the starting components (<63 μm) with smooth contact interphase boundary;

- 6-6,5-hour exposure in air samples such ceramic material in molten basalt at temperatures (1350-1400)°C result is to stabilize the structure of the ceramic material. If this is not observed interaction of basalt ceramics, the latter is easily separated from the basalt after cooling. Cracks and other defects in the ceramic samples not detected;

- strength ceramics in three-point bending up (78-105) N/mm2for comparison, the prototype does not exceed 67 N/mm2;

- hardness of ceramics (HRB) has remained at the same level as that of the prototype (60-90);

the heat capacity of the ceramic material at 25°is (577-601)j/kg°and commensurate with the capacity of the prototype - 612 j/kg°C;

- thermal conductivity of the ceramic material at 400°attains values (6,4-8,0)W/m·and comparable with the conductivity of the prototype to 6.75 W/m·K.

The technical result is achieved by the fact that the known composition containing boron nitride and silicon carbide, according to the invention additionally contains titanium and silicon in the following ratio of components, mass %: BN 10,0-20,0; SiC 73,5-82,0; Ti 3,0-7,0; Si of 0.1 to 1.0.

The introduction of titanium in the composition of the charge allows you to thermoactivated the sintering process of ceramic material and get rid of free of boron present in small quantities in industrial powder of boron nitride, and a small quantity of free carbon present in industrial powder of silicon carbide, which leads to internal stress relieving, healing of microcracks in keramicheskom the material by increasing overall mobility system BN-SiC-Ti-Si compared with the system BN-SiC during hot pressing.

At the same time at a high temperature of hot pressing on the surface of the contacting grains of the original mixture are not only the processes of interaction of titanium with free boron and carbon, but also its interaction with the residual gases of air (nitrogen and oxygen). This surface interaction gives a ceramic material chemical resistance to further impact the environment. The introduction of titanium into a double composition of the prototype (SiC-BN) could be obtained by comparison with the prototype in the same conditions of hot pressing is less porous ceramic material.

The introduction of silicon in the composition of the mixture can improve the chemical stability of the ceramic material to the exposure to air at high temperatures due to the formation of a thin surface protective film of silicon dioxide.

All this together: adding to the composition prototype titanium and silicon and the selected ratio of the components is allowed to increase strength, maintain chemical resistance and wear resistance of the ceramic material after prolonged use with molten silicate materials, including molten basalt and glass in the air.

The proposed solution meets the criterion of “Novelty”, as it has ollicial the main characteristics of the prototype, namely: new features titanium and silicon and the new balance of ingredients.

When checking for compliance with the criterion of “Inventive step” is not found compounds that contain distinguishing features of the claimed invention: titanium and silicon in the specified quantities, so this solution meets the criterion of “Inventive step”.

The claimed composition is made by mixing in the mixer industrial powders of desired particle size and in the proper ratio. After stirring receive the charge with a uniform distribution of the components in its volume. Such a charge plastificator using an organic binder and an organic solvent, get plastic strip.

The obtained plastic strip is laid in a graphite mold and mode of hot pressing. Upon completion of the hot pressing mold is cooled and disassembled, then extracted the finished ceramic material.

To confirm the criterion "Industrial applicability" of the thus obtained ceramic material were fabricated samples for strength tests (tensile three-point bending), resistance to thermal shock (the number of cycles of heating up to 1400°and With subsequent cooling in water at 20° (C)for the study is the heat capacity, thermal conductivity, determination of hardness (HRB) and to assess in an air environment impact on the quality of the pottery of the time of its stay in molten basalt at temperatures (1350-1400)°C.

The porosity of a material is calculated based on the actual density of the obtained ceramics.

The experimental data given in the table. From the data (see table) shows that, compared with the prototype of the strength of ceramic bending the same porosity according to our data, has increased in 1,5 times and (78-105) N/mm2(prototype - 67 N/mm2), hardness (HRB) has remained at the same level and 60-90 units, heat capacity at 25°C reached values (577-601) j/kg°C, which is comparable with the prototype - 612 j/kg°C, thermal conductivity at 400°C is (6,4-8,0) W/m·and comparable with the conductivity of the prototype to 6.75 W/m·To, resistance to thermal shock remained at the same level as the prototype (withstands 25-29 cycles of heating up to 1400°and subsequent cooling water at 20°C).

The use of ceramic material obtained from the proposed application of the composition, can significantly extend the area of its use in industry and primarily in the production of basalt and glass fibers and fibers, as well as devices that operate at high temperatures in aggressive chemical environments.

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Table

Characteristics of the ceramic material
CeramicsThe composition of the ceramics. wt.%Bending strength N/mm2Porosity, %Hardness (HRB)The resistance, cycles 1400°C water at 20°CHeat capacity, j/kg°C, 25°CThermal conductivity W/m·K. at 400°CCharacterization of ceramics after 6,5 hours in molten basalt at (1350-1400)°C in the air
SiCBNTiSi
The placeholder8020--67-78256126,75No cracks, defects; easily separated from the basalt
Declare73,91970,17818,1-26--No cracks, defects: is easily separated from the basalt
Declare7620319214,280256,40No cracks, defects: is easily separated from the basalt
Declare73,51970,510112,560295778,00No cracks, defects; easily separated from the basalt
Declare82107110512,59027--No cracks, defects; easily separated from the basalt

Composition for the manufacture of ceramic material containing boron nitride and silicon carbide, characterized in that it additionally contains titanium and silicon in the following ratio, wt.%:

The boron nitride 10,0-20,0

Silicon carbide is 73.5-82,0

Titanium 3,0-7,0

The silicon of 0.1-1.0



 

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FIELD: powder metallurgy, in particular ceramic material composition.

SUBSTANCE: claimed composition contains (mass %) boron nitride 10-20; silicium carbide 73.5-82; titanium 3-7; silicium 0.1-1. Composition is obtained by blending and subsequent plasticizing with organic binder. Composition is useful as refractory materials for high temperature furnaces and chemical reactors. Articles from composition of invention are produced by hot pressing and have heat capacity of 577-601 J/kg0C at 250C, thermal conductance of 6.4-8.0 W/m.K at 4000C, thermal-shock resistance of 25-29 heating cycles up to 14000C followed by cooling with water at 200C.

EFFECT: materials with improved bending strength and hardness.

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