HU185496B - Process for producing one piece, high strength, graphitic shaped bodys and stamping masses of coke base and metal-carbide and metal boride scelet - Google Patents

Abstract

According to the present invention, the electrical and strength properties of the electrically conductive, usually carbon-based, body masses and ramming masses can be further improved if the binder binds the particles through the intermediate product of furfuryl alcohol boronic acid to the thermal decomposition boron carbide and pyrene bridges. -1-

Description

The present invention relates to a process for the production of graphite-containing and / or coke-based and / or tetracarbide and / or metal boride-based shaped bodies and rams.

In the metallurgical and chemical industries, many equipment is known which is lined with ramming material made of carbon or graphite or with pre-fired bodies. Carbon or graphite-based electrodes are used in large quantities in melt electrolysis cells and arc furnaces.

A. High chemical strength, good electrical conductivity, low porosity, and high resistance to oxidation corrosion at high temperatures in oxidizing atmospheres are important requirements for carbon or graphite shaped bodies used in the chemical industry and metallurgy.

The higher strength carbon or graphite shaped bodies are more resistant to various mechanical forces.

. Carbon materials in high temperature equipment are subjected to high tensile forces due to thermal expansion, but the infiltration of certain melt components into the carbon fabric also causes tensile force. They cause such a swelling effect e.g. in aluminum production, the Na and Na compounds in the carbon and graphite fabric structure. In many cases, carbon and graphite materials may contain materials such as carbon. They incorporate metals that have a much higher coefficient of thermal expansion than carbon materials, which also causes harmful tensile forces.

The disadvantages of carbon and graphite shaped bodies, most of which have extremely favorable physical and chemical properties, are that they oxidize above 600 ° C in the presence of air and that this process is accelerated with increasing temperature.

Some carbon-based lining materials are used to form graphite and / or pitch coke-based ramming masses in which the binder is usually resinous. They have the disadvantage that they can only be rammed when heated to 140-180 ° C. Their vapors are harmful. The heating conditions affect the composition of the mass, which significantly affects the quality of the post-firing carbon web structure. The porosity of the spent material is greater than is permissible.

As is known, carbon black and, more recently, various synthetic resins, such as carbon black, have been traditionally used as binders in the manufacture of carbon and graphite shaped bodies. furan or phenol-formaldehyde resins are also used.

It is already known that boron and its compounds, boron carbide, reduce the oxidation of carbon materials at high temperatures. Therefore, boron compounds are used for surface treatment of carbon bodies or for impregnation of carbon pores. Most of the ramming masses used to form special carbon liners can be hot rammed at 140-180 ° C. Recently, lower temperature masses at 30-60 ° C are known, but they contain narrow softening point additives. Their disadvantage is that they still require less heating and the porosity is high after the additive burns out.

It is known that furl'urol or furfuryl alcohol as binder for the production of artificial carbons is also known recently, with the use of an acid or other catalyst. Such procedures are described in U.S. Pat. No. 901,848. No. 994,146. s. English and 229,844 Ij. s. Austrian patents. These descriptions utilize the property of the resin binder to form ordered pyrosene bridges upon firing that provide the bond. Their disadvantage is that their bond strength does not exceed that of conventional pitch binders.

No. 3,284,373. According to U.S. Pat. No. 5,2-2% boric acid is added to the pitch binder in the manufacture of carbon electrodes. This process introduces boric acid or B ₂ O ₃ into the carbonaceous structure of the carbon electrodes without chemical conversion, thereby causing no significant change in tissue structure.

No. 1,256,138. According to German Patent Specification, coke or coke. to form metal carbides in graphite skeleton by addition of metal halides. The process is expensive and complicated for the starting compounds. Because of the volatility of most metal halides, the so-called volatility reducing agents are stabilizing compounds should also be added. The resulting HCI also complicates the technology and the equipment is demanding. Therefore, its application is not widespread.

A 3.458341. s. In the process of U.S. Pat. No. 3, a metal carbide and graphite-containing coating is formed on the surface of graphite starting from metal halide, methane and a metal boride-graphite coating starting from metal halide, boron halide and methane compounds. The process is suitable for forming surface coatings.

No. 155,954. Hungarian Patent Specification No. 4,121,125 describes a method for bonding carbon and graphite bodies using an adhesive that provides high strength and good electrical conductivity. However, the present invention does not provide a solution and method for making carbon and graphite shaped bodies or for manufacturing carbon and graphite ramming compounds.

According to Hungarian Patent No. 158,712, boron carbide protective coatings are formed on pores of carbon and graphite shaped bodies by impregnation of organic boron compound and subsequent heat treatment. This patent process provides a solution for improving the properties of already manufactured carbon and graphite shaped bodies for subsequent use.

It is an object of the present invention to provide a novel process which, when manufactured, can provide sufficient results in terms of both mechanical strength and oxidation corrosion.

The object of the present invention is to recognize that the conventional tissue structure of carbon and / or graphite-based and / or metal carbide-based and / or metal boride-containing cores is reinforced by the in situ formed quasi-crystalline skeletal structure of boron carbide pyrosene from organic boron compounds.

Surprisingly, it has been found that the mechanical strength of the conventional carbon structure is increased approximately threefold by the process of the present invention, and

185,496 can also be multiplied by the oxidation inhibitory effect of boron trioxide if it is not incorporated neatly into the carbon mass but is incorporated into the ordered structure resulting from the polymerization. The final boron carbide-pyrosene skeleton structure is formed during combustion.

The object of the present invention is achieved by using the known furfuryl alcohol resin binder instead of the conventional pitch binder, but simultaneously adding B ₂ O and / or boric acid to the furfuryl alcohol, and forming the boron carboxylic bonds via the organically boron formed temporarily. provided. Boron trioxide or boric acid reacts with furfuryl alcohol to form furfurylborate. Upon exposure to heat, furfuryl alcohol and furfurylborate are polymerized in the presence of an acid catalyst. At higher temperatures, large organic molecules are cracked to form B ₄ C and pyrosene, which is a strong bond between the carbon, graphite, metal carbide and metal boride particles used as filler. A further advantage of the present invention is that boron carbide formation takes place up to 1000 ° C, although otherwise much higher temperatures are required.

In the process according to the invention, a dry matter mixture of known fractions is mixed with 1 to 15% by weight of boron trioxide and / or boric acid, followed by addition of up to 20% by weight of fresh furfuryl alcohol resin, further blending until uniform wetting and in several steps.

An advantageous feature of the shaped bodies and ramming masses produced according to the invention is that the so-called green mass can be extruded or rammed at room temperature. The boron carbide-pyrosene bonds produced by the process of the present invention achieve very high strengths in the products of 100-120 MN / m ² - and the desired strength and specific electrical resistance can be easily selected.

Another very advantageous feature is that the carbon dioxide bodies of the present invention have a very high resistance to oxidation corrosion. The reduction in oxidation corrosion is 50-100% of the weight of the sponge.

It is also significant that the resin is a binder

5 to 10 weight percent less than conventional pitch binder is required, resulting in lower porosity, denser carbon materials.

The process according to the invention is carried out as follows:

Furfuryl alcohol resin is used as a binder in the manufacture of carbon and / or graphite and / or metal carbide and / or metal boride rubbing compounds: In the manufacture of the resin, a small amount of phosphoric acid is added to the furfuryl alcohol under constant stirring, left. The fresh resin thus obtained is directly used for mixing the solids.

"Dry Material"

- Two types of particle size fractions are used for graphite, pitch coke, metal carbides and metal borides:

C, 1 to 1 mm in a weight ratio of 45%

C, less than 1 mm, 55% by weight

To the graphite and / or pitch coke is added B ₂ O ₃ or H ₃ BQ ₃ . TiB ₂ and / or TiC and / or ZrC and / or B ₄ C and / or SiC may also be added as an additive or a substitute for dry matter. The dry matter is uniformly mixed and the freshly prepared weighed furfuryl alcohol resin is evenly mixed with the dry matter.

The resin blended material can be well rammed at room temperature. The kneaded material is heated to 200 ° C to polymerize furfuryl alcohol and furfurylborate. it becomes very strong. Thereafter, in a programmed firing of up to 1000 ° C under an inert atmosphere, the polymerized binder is cracked to form boron carbide and pyrosene, which provide a high strength bond.

To form the mold, press the "green mass" mixed with the resin at room temperature into the desired shape. The molded body is preheated uniformly to 200 ° C, and then the solidified body is programmed to be fired at 1000 ° C, sealed from oxygen.

The main uses of the invention are:

For arc furnaces with graphite and carbon electrodes, and for finishing water and melt electrolysis cells. It can be advantageously used in the cathode formation of aluminum electrolyzing cells and in the production of block cathodes.

EXAMPLE 1 At room temperature, 5% (v / v) concentrated phosphoric acid (85%) was added to 95% (v / v) technical grade furfuryl alcohol in small portions under constant stirring, keeping the liquid temperature not above 30 ° C. The dry matter fraction of graphite and pitch coke is formed so that the fraction with a particle size of 0.1 to 1 mm is 45% by weight and the fraction under 0.1 mm is 55% by weight in both types of material.

39 grams of tar coke, 38% by weight of graphite, 8% by weight of B ₂ O ₃ were weighed into a mixing vessel and mixed well. Then, 15% by weight of fresh furfuryl alcohol resin is added in small portions under constant stirring until the resin moistenes evenly the dry matter particles.

The so-called "green paste" mixture can be crushed or molded into the desired shape at room temperature.

The heat treatment is carried out in two stages. Depending on the size of the mold, it is gradually heated to 200 ° C for 3 to 8 hours while the material solidifies. In the second stage, the programmed incremental heating up to 1000 ° C is used to burn the rammed masonry or oxygen in a sealed manner. the format body.

185,496

Example 2

All of the procedures described in Example 1 were followed except that 8% by weight of boric acid was added in place of boron trioxide.

Example 3

It differs from the procedure described in Example 1 in that the furfuryl alcohol resin is composed of 97% by volume of furfuryl alcohol and 3% by volume of phosphoric acid.

Example 4

A variation of the process of Examples 1 and 3, wherein the dry matter composition is as follows:

pitch coke 35s% graphite 35s%

B ₂ O ₃ 15 s%

Example 5

A variation of the method of Examples 1 and 3 wherein the dry matter composition is modified to:

pitch coke 35 s% graphite 40 s%

TiB, 5 s%

B ₂ O ₃ 5 s%

Example 6

A variation of the process of Examples 1 and 3, wherein the dry matter composition is as follows:

pitch coke 25s% graphite 40s% B ₂ O ₃ 10s% Type ₂ 10s% Example 7 1 and 3 version of the procedure published in the arias, wherein the dry matter composition is as follows amended as follows: graphite 65s% b ₂ o ₃ 10s% Type ₂ 10s%

Example 8

It differs from the procedure of Examples 1 and 3 in that the dry matter composition is as follows:

pitch coke 77%

B ₂ O ₃ 8 s%

This mass can be used for ramming.

Example 9

A variation of the process of Examples 1 and 3, wherein the dry matter composition is as follows:

pitch coke 70%

B ₂ O ₃ 15 s%

Example 10

It differs from the process described in Examples 1 and 3 in that SiC is used as the dry matter instead of graphite and pitch coke with the same grain composition as follows:

SiC 77 s%

B ₂ O ₃ 8 s%

Example 11

A variation of the method of Example 10 wherein the dry matter is modified as follows:

SiC 70 s%

B ₂ O ₃ 17 s%

Example 12

It differs from the procedure described in Examples 1 and 3 in that TiC is used as a dry substance as follows:

TiC 70 s%

B ₂ O ₃ 15 s%

Example 13

It differs from the procedure described in Examples 1 and 3 in that B ₄ C is used as a dry substance as follows:

B ₄ C 70 s%

B ₂ O ₃ __ 15 s%

Example 14

4-13. It differs from the procedures described in Examples _{1 to 4 in} that H ₃ BO ₄ is used instead of B ₂ O ₃ .

The following table compares the most important properties of the products of the invention with conventional resin impregnated products.

Compressive strength MN / m ² oxidation corrosion Original carbon weight %-in, same circumstances ones next to Charcoal is traditional 35 90 It has boron on carbon 35 75 Moonshine resin 60 60 The product of Examples 1-3 of the present invention 100 20 Graphite profile 25 80 Graphite profile with boroxide 25 65 Graphite profile resin Graphite profile invention 7. Ex. by 40 80 40 Titanium carbide fitting, 12. eg. by min. 120 - Silicon carbide frame fitting 11. eg. by min. 120 -

185,496

Claims (1)

A patent claim Process for the production of solid graphite and / or coke base and / or metal carbide and / or metal boride shaped bodies and / or ramming masses in known manner from fractions of graphite and / or pitch coke and / or metal carbide preferably silicon carbide and / or metal boride preferably titanium boride characterized by mixing the dry components and the binder and heat treating the pulp, wherein the dry matter mixture contains from 1 to 15% by weight of boron trioxide 5 and / or boric acid, up to 20% by weight of fresh furfuryl alcohol resin is added to the mixture and stirred until uniformly moistened.