EA014903B1 - Method for manufacturing graphite electrode - Google Patents

Abstract

The invention can be used in making graphite electrodes. A Method comprises mixing an aggregate, comprising a mixture of oilcoke, black coal or a mixture thereof and a binder as coal tar pitch, further compacting the obtained paste and forming thereof into a solid body, baking and graphitization thereof. During the aggregation fullerene carbon black. The amount of the binder comprises not more than 15% by weight. The inventive result in realizing said method is to increase the quality of the targeted product – graphite electrode concerning its life time and improving its operation qualities.

Description

The invention can be used for the manufacture of graphite electrodes, in particular, used in arc steelmaking and ore-thermal furnaces and other electrothermal installations for smelting high-quality alloyed and low-carbon steels, ferroalloys and special alloys, cast iron, non-ferrous metals, etc.

Graphite electrodes (EG) are traditionally made on the basis of petroleum coke and coal tar pitch (binder and impregnation pitch). The technology for their manufacture is currently well established and provides high quality products subject to very strict compliance with regulations, flexible consideration of the characteristics of incoming batches of raw coke and pitch. Among these technologies, we can mention the method according to the patent of the Russian Federation No. 2324646, in which the increase in the strength of graphite electrodes is achieved by adding carbon fibers to the mixture of coke (coal or mixtures thereof) and pitch binder, while the content of carbon fibers is from 4 to 10 wt. .% relative to all components of the mixture. The resulting electrodes have not only improved strength compared to conventional electrodes, there is also a decrease in the coefficient of longitudinal thermal expansion. The disadvantages of this method include the high temperature and duration of the graphitization process, which significantly complicates its commercial use. It should also be noted that both the described and many other known technologies for the manufacture of graphite electrodes are internally contradictory, since the pitch providing connectivity and density actually reduces the electrical conductivity and thermal conductivity, preventing the uniform distribution of the coefficient of linear thermal expansion.

The task underlying the creation of the claimed method of manufacturing a graphite electrode is to eliminate the main disadvantages of generally accepted technologies, namely, the complexity of technological operations, high costs to neutralize emissions, high porosity of the final product, which is inevitable when using a large amount of pitch and, in turn, causes reduction of the electrode lifetime, its electrical conductivity and thermal conductivity. The technical result obtained when solving the problem is to improve the quality of the final product - a graphite electrode in terms of increasing its service life and increasing operational properties.

To achieve the result, it is proposed in a method of manufacturing a graphite electrode, comprising mixing a filler in the form of petroleum coke, coal or mixtures thereof and a binder in the form of coal tar pitch, subsequent compacting of the obtained mass, its calcination and graphitization, when mixing to the filler, add fullerene soot in an amount from 1 to 4 wt.%, and the amount of binder used to limit no more than 15 wt.%.

Preferred, but not required process implementations include adding fullerene soot to the filler at the end of at least about 80% of the mixing cycle, as well as compacting by extrusion or extrusion at temperatures of 120-200 ° C.

The alleged invention may be based on a semi-dry method.

Schematic diagram of the production of graphite electrodes in accordance with the stated solution includes the following processes:

preparation of petroleum coke for production - calcination, grinding, sieving and fine grinding;

mixing the filler (fractions of coke, coal or mixtures thereof) with a binder - coal tar pitch in the required proportion, depending on the brand of the final product;

pressing from the obtained mass of preforms into a blank matrix or through the mouthpiece of a piercing press;

firing blanks at a temperature of 800-1200 ° C;

impregnation of billets with pitch in an autoclave;

re-firing blanks at a temperature of 800-1200 ° C;

graphitization of workpieces at a temperature of 2400-3000 ° C.

In general terms, depending on the purpose and required characteristics of the final product in the production process, various combinations of the above technological processes can be used. So, for example, petroleum coke can be used in a calcined or non-calcined form, the number of calcinations can vary from 1 to 5, the impregnation is carried out with coal tar pitch, salt solutions or pyrocarbon, etc.

The difference between the claimed solution and existing technologies is that fullerene carbon black is introduced into the filler at the mixing stage in an amount of 1 to 4 wt.%, And the amount of binder used is not more than 15 wt.%.

Below is an example implementation of the claimed method.

In accordance with such an example, preliminarily calcined to a temperature of 1300 ° C and ground petroleum coke in an amount of 73 wt.%, Coal - 12 wt.% And fullerene soot - 2.5 wt.% Are thoroughly mixed by dry method. Then the mixture of dry components is mixed with binding pitch in an amount of 12.5 wt.% Semi-dry method for 10 minutes The resulting mixture is compacted by pressing to form the body of the electrode, burned and graphitized at a temperature of 2700 ° C for 10 hours. The properties of the obtained electrode are shown in the following table.

- 1 014903

Bending strength MPa, not less Electrical resistivity, μOhm-m, no more Bulk density, g / cm ¹ , not less T temperature coefficient of linear expansion in the temperature range from 20 to 520 ° C, -10 ' ⁶ , K' ¹ , no more Porosity, %, no more eighteen 5 1.88 1,5 12

CLAIM

Claims (3)

CLAIM 1. A method of manufacturing a graphite electrode, comprising mixing a filler in the form of petroleum coke, coal or mixtures thereof and a binder in the form of coal tar pitch, subsequent compaction of the resulting mass, its calcination and graphitization, characterized in that when mixing, the amount of fullerene carbon black is added to the filler from 1 to 4 wt.%, and the amount of binder used is not more than 15 wt.%. 2. The method according to claim 1, characterized in that fullerene soot is added to the filler at the end of at least about 80% of the mixing cycle. 3. The method according to claim 1 or 2, characterized in that the compaction is carried out by pressing or extrusion at temperatures of 120-200 ° C. Eurasian Patent Organization, EAPO Russia, 109012, Moscow, Maly Cherkassky per., 2