EP0109839B1 - Method of making graphite electrodes - Google Patents
Method of making graphite electrodes Download PDFInfo
- Publication number
- EP0109839B1 EP0109839B1 EP19830307051 EP83307051A EP0109839B1 EP 0109839 B1 EP0109839 B1 EP 0109839B1 EP 19830307051 EP19830307051 EP 19830307051 EP 83307051 A EP83307051 A EP 83307051A EP 0109839 B1 EP0109839 B1 EP 0109839B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- electrode
- boron
- percent
- anthracite coal
- electric arc
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims description 12
- 238000004519 manufacturing process Methods 0.000 title claims description 12
- 229910002804 graphite Inorganic materials 0.000 title claims description 9
- 239000010439 graphite Substances 0.000 title claims description 9
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims description 23
- 229910052796 boron Inorganic materials 0.000 claims description 23
- 239000003245 coal Substances 0.000 claims description 22
- RHZUVFJBSILHOK-UHFFFAOYSA-N anthracen-1-ylmethanolate Chemical compound C1=CC=C2C=C3C(C[O-])=CC=CC3=CC2=C1 RHZUVFJBSILHOK-UHFFFAOYSA-N 0.000 claims description 20
- 239000003830 anthracite Substances 0.000 claims description 20
- 239000000203 mixture Substances 0.000 claims description 13
- 238000010891 electric arc Methods 0.000 claims description 12
- INAHAJYZKVIDIZ-UHFFFAOYSA-N boron carbide Chemical compound B12B3B4C32B41 INAHAJYZKVIDIZ-UHFFFAOYSA-N 0.000 claims description 10
- 239000003575 carbonaceous material Substances 0.000 claims description 9
- 239000000571 coke Substances 0.000 claims description 9
- 229910052580 B4C Inorganic materials 0.000 claims description 8
- 238000005087 graphitization Methods 0.000 claims description 7
- 238000000034 method Methods 0.000 claims description 7
- 239000000314 lubricant Substances 0.000 claims description 6
- 239000011295 pitch Substances 0.000 claims description 6
- 238000002156 mixing Methods 0.000 claims description 5
- 239000002245 particle Substances 0.000 claims description 5
- 239000002802 bituminous coal Substances 0.000 claims description 3
- ZDVYABSQRRRIOJ-UHFFFAOYSA-N boron;iron Chemical compound [Fe]#B ZDVYABSQRRRIOJ-UHFFFAOYSA-N 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 claims description 3
- NUSDCJCJVURPFV-UHFFFAOYSA-N silicon tetraboride Chemical compound B12B3B4[Si]32B41 NUSDCJCJVURPFV-UHFFFAOYSA-N 0.000 claims description 3
- 229910000831 Steel Inorganic materials 0.000 claims description 2
- 238000001354 calcination Methods 0.000 claims description 2
- 238000002844 melting Methods 0.000 claims description 2
- 230000008018 melting Effects 0.000 claims description 2
- 239000010959 steel Substances 0.000 claims description 2
- 239000002006 petroleum coke Substances 0.000 description 10
- 239000000463 material Substances 0.000 description 9
- 229910052799 carbon Inorganic materials 0.000 description 5
- 238000001125 extrusion Methods 0.000 description 5
- 239000012535 impurity Substances 0.000 description 4
- 230000003647 oxidation Effects 0.000 description 4
- 238000007254 oxidation reaction Methods 0.000 description 4
- 238000007792 addition Methods 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 238000012856 packing Methods 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 238000009834 vaporization Methods 0.000 description 2
- 230000008016 vaporization Effects 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 239000004411 aluminium Substances 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 235000013312 flour Nutrition 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 239000011301 petroleum pitch Substances 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 229910010271 silicon carbide Inorganic materials 0.000 description 1
- 238000004513 sizing Methods 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B7/00—Heating by electric discharge
- H05B7/02—Details
- H05B7/06—Electrodes
- H05B7/08—Electrodes non-consumable
- H05B7/085—Electrodes non-consumable mainly consisting of carbon
Definitions
- the invention relates to a unique process for manufacturing graphite electrodes for electric arc furnace applications and the unique electrodes resulting from the practice of the process.
- an electric arc furnace graphite electrode which comprises calcining a carbonaceous material selected from anthracite coal, bituminous coal, lignites, and No. 2 coke, mixing the calcined carbonaceous material with the pitch, a lubricant, and a boron source selected from elemental boron, boron carbide, silicon tetraboride and iron boride, in an amount such that the boron content is from 0.1 to 5.0 perent by weight of the graphite electrode; extruding said mixture into an electrode form; and graphitizing said electrode form.
- No. 2 coke ordinary or regular coke which is well known to be more or less amorphous and has a dark, spongy appearance, breaking into lumps of irregular shape.
- the boron content of the graphite electrode is preferably substantially 3 per cent by weight of the electrode.
- This invention resides in subjecting a carbonaceous source material, other than premium petroleum coke, and preferably anthracite coal, to the action of particular sources of boron, preferably boron carbide (B 4 C), whereby the highly disordered structure of the carbonaceous material (preferably anthracite coal is transformed into one that is very graphitic in an otherwise conventional electrode manufacturing process.
- a carbonaceous source material other than premium petroleum coke, and preferably anthracite coal
- an electrode suitable for use in an electric arc steel melting furnace which comprises hot mixing calcined anthracite coat particles, pitch, lubricants and boron carbide, such that boron is present in the amount of substantially 3 weight percent of the electrode, extruding said mix into an electrode form and heating said shaped electrode to graphitization temperatures.
- particles of the defined calcined non-petroleum coke carbonaceous material are mixed together with the conventional pitch binder and lubricant, and to this mixture is added the defined boron source.
- the boron source is one which does not release a gaseous byproduct when it is to be reacted with the carbonaceous material at the graphitization step in the manufacturing process and, as defined above, is selected from elemental boron, boron carbide (B 4 C), silicon tetraboride (B 4 Si) and iron boride (FeB).
- the B 4 C was Carborundum Company Technical Grade 325/F, containing seventy-two percent boron and a maximum particle size of 44 um.
- the B 4 C and flour were blended in a ribbon blender for one hour prior to mixing with the other additions in a sigma-bladed heated mixer. A mix tempertaure of 158°C was achieved. The mix was then cooled to 110°C and extruded at 105°C. Extrusion pressures varied between 2689 and 3447 kPa (390 and 500 psi) for the control and between 2758 and 5576 kPa (100 and 800 psi) for the boronated mix.
- the billets were packed with coke packing in saggers and baked at 2°C/hour to 500°C, at 10°C/hour to 900°C and held for approximately ten hours at the latter temperature.
- Baked billets were then impregnated with Ashland 240 petroleum pitch.
- the procedure entailed preheating the billets in an autoclave to 225°C and evacuating the chamber thereafter one-half to one hour.
- the pitch was heated to 250°C and introduced and the system pressurized ton 698 kPa (100 psi).
- the impregnated billets were packed in coke packaging and rebaked at 10°C/hour to 750°C and held for twenty hours at the latter temperature.
- the graphitization process consisted of heating inductively at a rate of 200°C/hour to 2000°C and at 400°C/hour to the final temperature of 3000°C. Hold time at 3000°C was one hour. During graphitization and cooling the stock is protected from oxidation by coke packing.
- an electrode made with boronated anthracite coal exhibits exceptional resistance to oxidation. This is an important characteristic for electrodes which must perform satisfactorily in the exacting environment of an electric arc furnace.
- the principal impurities in anthracite coal are compounds of iron, silicon, aluminium, and titanium, and they equate to approximately ten percent ash.
- Most naturally occurring carbonaceous materials have as impurities similar kinds of elements in varying levels. The vaporization of these materials during graphitization results in lower density, poorer structure and properties. The presence of boron has been observed to prevent their vaporization. Impurities in the boronated carbonaceous stock provide excellent protection against oxidation. This phenomenon is clearly shown as explained below in the single Figure of the drawing.
- the single Figure of the drawing is a graph illustrating the improvement in oxidation resistance of electrodes employing in their manufacture boronated anthracite coal as compared to electrodes employing non-boronated anthracite coal.
- the data illustrated in this graph was generated as follows: 2.54 cm (one-inch) cubes of the control and boronated anthracite coal stock were heated four hours in still air at temperatures between 800° and 1600°C. Material (carbon + ash) was weighed at the end of this time and the results are expressed as percent remaining in the Figure.
- the oxide coating developed in the coal specimens is a very small percentage (2-5 percent) of the remaining mass. Even at 1600°C, a substantial portion of the remaining material is carbon.
- the range of the amount of boron content to be added to the carbonaceous mix to be extruded into the finished electrode is between 0.1 and 5 percent by weight of the graphitized product, with about three percent being the preferred level of boron addition.
- the properties of the electrodes of the invention compare very favourably with those that are available from conventional processing using premium petroleum coke.
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- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Plasma & Fusion (AREA)
- Ceramic Products (AREA)
- Vertical, Hearth, Or Arc Furnaces (AREA)
- Furnace Details (AREA)
- Discharge Heating (AREA)
- Carbon And Carbon Compounds (AREA)
- Electrodes For Compound Or Non-Metal Manufacture (AREA)
Description
- The invention relates to a unique process for manufacturing graphite electrodes for electric arc furnace applications and the unique electrodes resulting from the practice of the process.
- Premium petroleum cokes are used extensively in the manufacture of electrodes for steelmaking with electric arc furnaces. The cost of such cokes is increasing very rapidly, however, and this could markedly affect the future growth of the use of electric arc furnaces and thus the market for electric arc electrodes. Less costly carbonaceous materials, such as anthracite coal, bituminous coal, lignites, so-called No. 2 coke, etc., have been tested in the production of electrodes intended for use in electric arc furnaces but the properties of the resulting electrodes are sufficiently inferior when compared to electrodes made from premium petroleum coke that they have been unacceptable for use in electric furnaces. Efforts to upgrade the properties of electrodes made from other than wholly petroleum coke as the carbonaceous source material to acceptable levels have been unsuccessful to date.
- It has now been found possible to provide a method for manufacturing electrodes acceptable for use in electric arc furnaces in which the starting carbonaceous souce material is not premium grade petroleum coke.
- According to the present invention there is provided a method of making an electric arc furnace graphite electrode which comprises calcining a carbonaceous material selected from anthracite coal, bituminous coal, lignites, and No. 2 coke, mixing the calcined carbonaceous material with the pitch, a lubricant, and a boron source selected from elemental boron, boron carbide, silicon tetraboride and iron boride, in an amount such that the boron content is from 0.1 to 5.0 perent by weight of the graphite electrode; extruding said mixture into an electrode form; and graphitizing said electrode form.
- By "No. 2 coke" is meant ordinary or regular coke which is well known to be more or less amorphous and has a dark, spongy appearance, breaking into lumps of irregular shape.
- The boron content of the graphite electrode is preferably substantially 3 per cent by weight of the electrode.
- This invention resides in subjecting a carbonaceous source material, other than premium petroleum coke, and preferably anthracite coal, to the action of particular sources of boron, preferably boron carbide (B4C), whereby the highly disordered structure of the carbonaceous material (preferably anthracite coal is transformed into one that is very graphitic in an otherwise conventional electrode manufacturing process.
- By a preferred embodiment of the present invention there is provided a method of making an electrode suitable for use in an electric arc steel melting furnace which comprises hot mixing calcined anthracite coat particles, pitch, lubricants and boron carbide, such that boron is present in the amount of substantially 3 weight percent of the electrode, extruding said mix into an electrode form and heating said shaped electrode to graphitization temperatures.
- In the practice of the present invention particles of the defined calcined non-petroleum coke carbonaceous material are mixed together with the conventional pitch binder and lubricant, and to this mixture is added the defined boron source. The boron source is one which does not release a gaseous byproduct when it is to be reacted with the carbonaceous material at the graphitization step in the manufacturing process and, as defined above, is selected from elemental boron, boron carbide (B4C), silicon tetraboride (B4Si) and iron boride (FeB).
- 15.24 cm (six-inch) diameter coarse-grain anthracite coal electrodes were formed by extrusion. The anthracite coal was calcined at 2200°C prior to crushing and sizing. The coal particles, pitch, lubricants, and B4C additions to the mixes are indicated in Table I. The control mix had no boron, whereas the mix for the boronated stock was formulated to produce a finished product having approximately three weight percent boron.
-
- The B4C was Carborundum Company Technical Grade 325/F, containing seventy-two percent boron and a maximum particle size of 44 um. The B4C and flour were blended in a ribbon blender for one hour prior to mixing with the other additions in a sigma-bladed heated mixer. A mix tempertaure of 158°C was achieved. The mix was then cooled to 110°C and extruded at 105°C. Extrusion pressures varied between 2689 and 3447 kPa (390 and 500 psi) for the control and between 2758 and 5576 kPa (100 and 800 psi) for the boronated mix. The higher extrusion pressure for the boron-containing mix indicates that insufficient binder was present, which should probably be detrimental to physical properties, especially strength. However, in spite of this, as shown in Table II, the boronated electrode had significantly higher strength than the control electrode. Eight billets measuring 15.24 cm (six inches) diameter by 45.72 cm (eighteen inches) long were formed from each mix.
- The billets were packed with coke packing in saggers and baked at 2°C/hour to 500°C, at 10°C/hour to 900°C and held for approximately ten hours at the latter temperature.
- Baked billets were then impregnated with Ashland 240 petroleum pitch. The procedure entailed preheating the billets in an autoclave to 225°C and evacuating the chamber thereafter one-half to one hour. The pitch was heated to 250°C and introduced and the system pressurized ton 698 kPa (100 psi). The impregnated billets were packed in coke packaging and rebaked at 10°C/hour to 750°C and held for twenty hours at the latter temperature.
- The graphitization process consisted of heating inductively at a rate of 200°C/hour to 2000°C and at 400°C/hour to the final temperature of 3000°C. Hold time at 3000°C was one hour. During graphitization and cooling the stock is protected from oxidation by coke packing.
- Properties obtained on the control and boronated anthracite coal specimens are shown in Table II. With the exception of the CTE, all properties were measured on 2.54 cm x 2.54 cm x 15.24 cm (1" x 1" x 6") specimens cut in the extrusion direction (WG) and normal to the extrusion direction (AG). The data are averages of nine AG and eleven WG specimens. The CTE data are essentially room temperature values and these measurements were made on 0.635 cm x 1.905 cm x 15.24 cm (0.25" x 0.75" x 6") bars.
- The data in Table II indicate the boronated material has properties superior to those for the control in both billet directions. The WG CTE and WG resistivity for the boronated coal are significant improvements.
- In addition to the foregoing advantages imparted by the employment of boronated anthracite coal over nonboronated anthracite coal, an electrode made with boronated anthracite coal exhibits exceptional resistance to oxidation. This is an important characteristic for electrodes which must perform satisfactorily in the exacting environment of an electric arc furnace.
- It appears that, uniquely, boron causes the anthracite coal or other carbonaceous stock to retain its impurities; even after graphitization.
- The principal impurities in anthracite coal are compounds of iron, silicon, aluminium, and titanium, and they equate to approximately ten percent ash. Most naturally occurring carbonaceous materials have as impurities similar kinds of elements in varying levels. The vaporization of these materials during graphitization results in lower density, poorer structure and properties. The presence of boron has been observed to prevent their vaporization. Impurities in the boronated carbonaceous stock provide excellent protection against oxidation. This phenomenon is clearly shown as explained below in the single Figure of the drawing.
- The single Figure of the drawing is a graph illustrating the improvement in oxidation resistance of electrodes employing in their manufacture boronated anthracite coal as compared to electrodes employing non-boronated anthracite coal. The data illustrated in this graph was generated as follows: 2.54 cm (one-inch) cubes of the control and boronated anthracite coal stock were heated four hours in still air at temperatures between 800° and 1600°C. Material (carbon + ash) was weighed at the end of this time and the results are expressed as percent remaining in the Figure. The oxide coating developed in the coal specimens is a very small percentage (2-5 percent) of the remaining mass. Even at 1600°C, a substantial portion of the remaining material is carbon. At 1200°C, the control is almost completely oxidized, whereas approximately sixty percent carbon is retained in the boronated specimen. Accordingly, consumption will be much less for a boronated anthracite coal electrode exposed to electric arc furnace conditions than it would be for the unboronated counterpart.
- The range of the amount of boron content to be added to the carbonaceous mix to be extruded into the finished electrode is between 0.1 and 5 percent by weight of the graphitized product, with about three percent being the preferred level of boron addition.
- The properties of the boronated anthracite coal stock of the above example when compared to a graphite electrode made from premium petroleum coke are shown below in Table III.
- As will be appreciated the properties of the electrodes of the invention compare very favourably with those that are available from conventional processing using premium petroleum coke.
- Finally, it should also be appreciated that new, and lower cost electrodes suitable for use in electrical arc furnaces will also be achieved in those instances where the non-petroleum coke carbonaceous stock material which has been subjected to boronation replaces only a portion of the petroleum coke stock material rather than replacing it entirely.
Claims (4)
1. A method of making an electric arc furnace graphite electrode which comprises calcining a carbonaceous material selected from anthracite coal, bituminous coal, lignites, and No. 2 coke, mixing the calcined carbonaceous material with pitch, a lubricant, and a boron source selected from elemental boron, boron carbide, silicon tetraboride and iron boride, in an amount such that the boron content is from 0.1 ton 5.0 percent weight of the graphite electrode;. extruding said mixture into an electrode form; and graphitizing said electrode form.
2. A method according to claim 1, wherein the boron source is boron carbide.
3. A method according to claim 1 or 2, wherein the boron content of the graphite electrode is substantially 3 percent by weight of the electrode.
4. A method of making an electrode suitable for use in an electric arc steel melting furnace which comprises hot mixing calcined anthracite coal particles, pitch, lubricants and boron carbide, such that boron is present in the amount of substantially 3 weight percent of the electrode, extruding said mix into an electrode form and heating said shaped electrode to graphitization temperatures.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US44309882A | 1982-11-19 | 1982-11-19 | |
| US443098 | 1982-11-19 |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| EP0109839A2 EP0109839A2 (en) | 1984-05-30 |
| EP0109839A3 EP0109839A3 (en) | 1985-06-19 |
| EP0109839B1 true EP0109839B1 (en) | 1989-09-06 |
Family
ID=23759400
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP19830307051 Expired EP0109839B1 (en) | 1982-11-19 | 1983-11-18 | Method of making graphite electrodes |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0109839B1 (en) |
| JP (1) | JPS59108294A (en) |
| DE (1) | DE3380551D1 (en) |
| ES (1) | ES8407284A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102015221853A1 (en) | 2015-11-06 | 2017-05-11 | Technische Universität Bergakademie Freiberg | Process for the preparation of carbonaceous ceramic components |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| IT1396948B1 (en) * | 2009-12-16 | 2012-12-20 | Italghisa S P A | ELECTRODIC PASTE FOR GRAPHITE ELECTRODES WITHOUT "BINDER" WITH HYDROCARBURIC BASIS |
| CN105025602A (en) * | 2015-07-13 | 2015-11-04 | 河北联冠电极股份有限公司 | Carbon nanometer ultramicro material large carbon electrode and preparation method thereof |
| JP6482442B2 (en) * | 2015-09-30 | 2019-03-13 | クアーズテック株式会社 | Carbon electrode for melting quartz glass |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1285559A (en) * | 1961-03-15 | 1962-02-23 | Union Carbide Corp | Production of artificial graphite |
| DE1904408A1 (en) * | 1969-01-30 | 1970-08-06 | Conradty Fa C | High performance electrode with stabilized arc |
| CH545249A (en) * | 1971-04-15 | 1973-12-15 | Lonza Ag | Process for making an isotropic graphite material |
| DE3116258A1 (en) * | 1981-04-23 | 1982-11-11 | C. Conradty Nürnberg GmbH & Co KG, 8505 Röthenbach | ELECTRODE FOR ARC OVENS AND METHOD FOR USE THEREOF |
-
1983
- 1983-11-18 EP EP19830307051 patent/EP0109839B1/en not_active Expired
- 1983-11-18 ES ES527373A patent/ES8407284A1/en not_active Expired
- 1983-11-18 JP JP58217623A patent/JPS59108294A/en active Granted
- 1983-11-18 DE DE8383307051T patent/DE3380551D1/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102015221853A1 (en) | 2015-11-06 | 2017-05-11 | Technische Universität Bergakademie Freiberg | Process for the preparation of carbonaceous ceramic components |
Also Published As
| Publication number | Publication date |
|---|---|
| ES527373A0 (en) | 1984-08-16 |
| EP0109839A3 (en) | 1985-06-19 |
| JPS59108294A (en) | 1984-06-22 |
| JPH0137839B2 (en) | 1989-08-09 |
| EP0109839A2 (en) | 1984-05-30 |
| ES8407284A1 (en) | 1984-08-16 |
| DE3380551D1 (en) | 1989-10-12 |
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