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Analysis on abnormal case in using electrode

HP GRAPHITE has more than 15 years of experiences in graphite industry. We have summarized the "Use Instructions of Graphite Electrodes" according to many years of hands-on experiences and peer-related literature, for the reference of our customers during installation and use, and meanwhile, we have summarized the exchange with the customers over the years and have summed up and analyzed the common abnormal problems during the use of graphite electrodes, to form this manual of analysis on abnormal cases in using graphite electrodes, for user's reference. 

In 2003, a factory introduced 150 t second-hand LF (electric arc furnace). Equipped with 25MVA, 43KA transformer, this furnace can overload 20%. UHP φ350 electrode was selected. Although it is limited to 36KA current, the electrodes at home and abroad are often broken during the use, and it was also difficult to heat up technically. 

Through the careful calculation and comparison, we suggested the Technology Section of this factory to use UHP φ450 electrode in March 2004.

In October 2005, this factory claimed that: it prepares to use UHP φ400 electrode. 

In October 2006, we were invited to participate in the analysis meeting of LF furnace held by this factory. We were required to make a speech on the meeting, and we spoke in our suggestions that: "the equipment matching would be realized by using UHP φ450 electrode instead of UHP φ350 electrode, thereby achieving the purpose of heating up and heat preservation." Through investigation, in September 2007, this factory finally decided to change the electrode to the ultra-high power graphite electrode φ450 after the comparative survey.

In 2016,  a factory used regular power graphite electrode and impregnated graphite electrode φ 300mm on 70t LF (electric arc furnace) furnace, which caused that the electrode was reddened and thinned, and could not be used. 

Upon investigation: the reason was that the above electrode could not bear 26KA current. 

The phase sequence of AC electric arc furnace has a great effect on the electrode loosening, and the users at home and abroad have such phenomenon. In 15 electric furnaces detected by us: 10 electric furnaces were needed to change their phase sequences, among which, 5 electric furnaces were not loosened after changing their phase sequences according to our suggestions; the manufacturer of one electric furnace refused to change, and one electric furnace was not changed because the installation personnel failed to understand the foreign language, and was still loosened; and the users of three electric furnaces prepared to change their phase sequences. Recently, the electrode of another factory has been always loosened after starting up, and it was used after hitting its pin. According to the introduction of this factory, we also prepared to measure the phases sequence. 

In May 2008, a factory reflected the electrode loosening. Upon the investigation: in addition to changing the phase sequence, all teeth in the upper hole of electrode had different degrees of damage, except that four teeth were intact. We found on the site that, it was caused by mixing one T3 iron handing head in the lifting of T4 product. After the phase sequence was changed and T3 hanging head was removed, the electrode has not loosened so far. 

In 2006, since a factory had big lumpiness of slag steel, the electrode was broken due to material collapse or failure to conduct. According to the statistics of Technology Section of this factory, this phenomenon accounted for 78% of broken electrodes.

In 2008, the electrode of LF furnace in a shift of a factory was broken for eight times. Upon investigation: the slagging of hole wall of electrode on the furnace cover caused the friction between the electrode and wall to break. Through the slag removal, the electrode has not been broken after keeping a certain distance between the electrode and hole wall.

In 2000, a factory used φ700 electrode of Tokai Carbon, which was broken for more than 20 times in one moth. The manufacturer sent the person to see the situation: the cause was that the triangular mark was too tight when connecting the electrode. There was no fracture after change as required.

In 2003, the electrode of LF furnace in a factory was broken in each shift. Upon investigation: ① in the screws of four feet of column, one was broken and one was loosened; and ② the perpendicularity of the column was 14 times larger than that required. After alignment, there had no break.

In 2003, the nipple of a factory was broken. Upon investigation, 16 broken nipples were located at the pinholes of the nipples. The depth that the pinhole φ28mm was hit into the nipple was (30~50mm) ×2. We required that the pinhole was not hit into the nipple. 

In January 2002, a factory reflected the electrode break. Upon investigation: we found the molten steel reladling, fast temperature drop and increase in hardness of slag cover, causing the break of electrode, damage of holder, as well as increase of electrode consumption.

In July 2002, a factory reflected that the electrode consumption of LF furnace was raised. Upon investigation: the electrode consumption was raised by 77.9%, the power consumption was raised by 15.8%, and the period was prolonged by 17.5%, compared with that before and after April. Through the calculation, 170t electrode would be additionally consumed, with a loss of RMB 5,000,000. Through the field investigation, this factory heightened the small furnace cover of 1m to improve the environmental protection; and meanwhile, the air suction and dedusting valves were opened from 45° to 90°, which was caused by the increase in electrode oxidation and heat dissipation. We made the findings into a report, and sent it to the relevant leaders of this factory. Its leader agreed with our findings.

In September 2000, a factory reflected that, the electrode consumption of LF furnace was raised from 0.42kg/t to 0.52kg/t. Upon investigation: it was caused by increase of VD ratio from 42.76% to 73%. In August 2004, when its leader recalled, he fully agreed with our analysis at that time.

In May 2002, φ300mm RP electrodes were used on three 8t electric furnaces of a factory, and in April-May, the electrode consumption was raised to above 5kg/t from 4.6~4.8kg/t. Upon investigation: it was caused by start-up of its big electric furnace and drop in hot metal supply of small electric furnace. We have reached a consensus regarding this truth. But, at that time, it could not be understood by the competent leader. 

In 2012, a factory reflected the electrode tripping. Through our field investigation, this factory used the products of many manufacturers, and there was no tripping when these products were used separately, and the tripping only occurred while the connection of the two manufacturers' electrodes, which was mainly caused by the difference in machining tolerances of electrodes of different manufacturers. We suggested the users to reduce the frequency of change when using different manufacturers' electrodes, so as to mix.

The above problems are encountered by us during the use of electrodes for years. We simply describe several solutions proposed. The graphite electrode has continuous consumption and discontinuous consumption during the use, and from manufacturing to the complete use of the electrode, it involves user operation, quality of raw material, production process and many other problems, besides its manufacturing design, therefore, for the problems during the use of graphite electrode, the user shall solve them by negotiating with the manufacturer, so as to eliminate the barriers as soon as possible, and normally put into operation as early as possible. Meanwhile, the exchange with the peers is also an important way to solve the problems. The above cases are typical cases to solve the actual problems through collaboration. Thanks the users for supporting, cooperating with and helping our work during our investigation. HP GRAPHITE has a professional technical service & after-sales team. When you meet the problems during the use of graphite electrode, you can directly contact us, and we will provide the solution for you in the first time.