JPH0137839B2 - - Google Patents

Description

[Detailed description of the invention]

FIELD OF THE INVENTION The present invention relates to a unique method for manufacturing graphite electrodes for electric arc furnaces and to the unique electrodes obtained by implementing this method. Description of the Prior Art Premium petroleum coke is widely used in producing electrodes for arc furnace steelmaking. However, the price of this type of coke is rising very rapidly, and this is expected to have a major impact on the future use of arc furnaces and, therefore, on the development of the market for arc electrodes. Anthracite, bituminous coal, lignite, so-called
Inexpensive carbonaceous feedstocks such as No. 2 and No. 3 cokes have been tested for the production of arc furnace electrodes, but the properties of electrodes obtained from these materials are not as good as those made from premium petroleum coke. These electrodes were extremely poor and unsuitable for use in electric furnaces. Efforts to raise the properties of electrodes made from feedstocks other than whole petroleum coke as a carbonaceous feedstock to acceptable levels have been unsuccessful to date. The main object of the present invention is to provide a method for producing an electrode suitable for use in an electric arc furnace where the carbonaceous feedstock is not necessarily all premium grade petroleum coke. SUMMARY OF THE INVENTION The present invention provides a method for combining elemental boron or a boron compound, preferably boron carbide (B ₄ C), with a carbonaceous feedstock other than premium petroleum coke, preferably anthracite, in an otherwise conventional electrode manufacturing process.
The process consists in transforming the highly disordered structure of anthracite into a highly graphitic structure. DETAILED DESCRIPTION OF THE INVENTION In the practice of this invention, particles of a non-petroleum coke carbonaceous feedstock are mixed with conventional pitch binders and lubricants, and elemental boron or boron-containing compounds are added to the mixture. Suitable carbonaceous feedstocks other than anthracite are bituminous coal, lignite and No. 2 and No. 3 coke. Preferably, the boron feedstock does not release gaseous by-products when reacting with the carbonaceous feedstock during the graphitization step during the manufacturing process. Such boron raw materials include elemental boron, boron carbide (B ₄ C),
Silicon tetraboride ( _B4Si ) and iron boride (FeB)
It is. The boron material can also be combined with the carbonaceous feedstock during calcination, in which
The boron compound can be an oxide such as boric acid (H ₃ BO ₃ ) or boron oxide (B ₂ O ₃ ).
This is because the gaseous by-products generated in this case do not affect the structural integrity of the finished electrode. Example A coarse anthracite electrode with a diameter of 6 inches was prepared by extrusion. Anthracite is heated to 2200℃ prior to crushing and sizing.
I roasted it. B ₄ C additives for powdered coal, pitch, lubricants, and mixes are shown in the table below. The control mix contained no boron, while the mix of the boronated sample pieces was formulated to yield a finished product with about 3% boron by weight.

[Table] B ₄ C is Carborundum Company, technical grade 325/F, containing 72% boron,
The maximum particle size was 44 μm. The B ₄ C and powdered coal were blended in a ribbon blender for 1 hour before being mixed with other additives in a heated Sigma vane mixer. A mix temperature of 158°C was obtained. The mix was then cooled to 110°C and extruded at 105°C. Extrusion pressures ranged from 390-500 psi for controls and 400-800 psi for boronated mixes.
The high extrusion pressure of the boron-containing mix indicates that insufficient binder was present, which would likely be detrimental to the physical properties, especially strength. But nevertheless, as shown in the table, the borated electrode had much higher strength than the control electrode. Eight billets were formed from each mix, measuring 6 inches in diameter by 18 inches in length. These billets were packaged in a sugar bag with coke packing and heated at 2°C/hour up to 500°C.
It was then fired at 10°C/hour to 900°C and held at the latter temperature for about 10 hours. The fired billet was impregnated with Assuland 240 petroleum pitch. The impregnation process required preheating the billet in an autoclave to 225 DEG C. and then evacuating the chamber for one-half to one hour. Heat the pitch to 250℃ and introduce it.
The system was pressurized to 100 psi. Pack the impregnated billet in coke packing and
Refire to 750°C at 24°C/hour and to the latter temperature 24°C
Holds time. The graphitization process is carried out at a rate of 200℃/hour up to 2000℃,
Next, it was dielectrically heated to 3000°C at a rate of 400°C/hour. The holding time at 3000°C was 1 hour. During graphitization and cooling, stock oxidation was prevented by coke packing. The properties obtained for the control specimen and the borated anthracite specimen are shown in the table. All properties except CTE were measured on 1″ x 1″ x 6″ specimens cut in the extrusion direction (WG) and perpendicular to the extrusion direction (AG). These data are based on 9AG specimens. and an 11WG specimen.CTE data are essentially room temperature values, and these measurements are
Performed on 0.25″ x 0.75″ x 6″ bar.

[Table]

[Table]

Claims (1)

[Claims] 1 (a) Anthracite, bituminous coal, lignite, No. 2 and No. 3
(b) Calcining a carbonaceous material selected from the group consisting of coke; (c) extruding the mixture into the form of an electrode; and (c) extruding the mixture into an electrode. (d) A method for producing an arc furnace graphite electrode, comprising graphitizing the shape of the electrode to produce a graphite electrode. 2. The method according to claim 1, wherein the boron source is boron carbide. 3. The method of claim 1, wherein the boron content of the graphite electrode is about 3.0% by weight of the electrode.