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Abnormal Electrode Usage Cases Analysis

HP Graphite Co., Ltd. has more than 15 years of experiences in graphite industry. We have summarized the "Graphite Electrodes Usage Instructions" according to many years of hands-on experiences and peer-related literature, for customers reference during installation and usage, and meanwhile, based on the exchanges with customers over years, we have summed up and analyzed the common abnormal problems during graphite electrodes usage, to form this manual of abnormal cases analysis in graphite electrodes use, for customers reference. 

Main Solutions of Abnormal Cases

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

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

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

In October 2006, we were invited to attend the LF furnace analysis meeting held by this factory. We were required to make a speech on the meeting, and we spoke in our suggestions: "Using UHP φ450 electrode instead of UHP φ350 electrode can make the equipments matching, thereby achieving the purpose of heating up and heat preservation." Through investigation, in September 2007, this factory finally decided to change the electrode to UHP graphite electrode φ450 after comparative survey.

In 2006, a 70t LF (electric arc furnace) furnace was equipped with RP graphite electrode and impregnated graphite electrode φ 300mm by a factory, resulting in redness and thinning of the electrode, which can not be reused.

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, which occurs in users at home and abroad. Among the 15 domestic electric furnaces measured by us, 10 needed to change the phase sequence, and 5 of them were no longer loose after changing the phase sequence according to our suggestion; One was not willing to change, and one electric furnace was not changed because the installers didn’t understand the foreign language and the electrode was still loose; Three users were ready to change. Recently, there was another factory. Recently, the electrode of another factory has been always loosened after starting up. After listening to the introduction, they also prepared to measure the phases sequence. 

In May 2008, a factory reflected the electrode loosening. Upon 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 hanging head in the lifting of T4 products. After the phase sequence was changed and T3 hanging head was removed, the electrode has not loosened again.

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

In 2008, the electrodes of LF furnace in a shift of a factory was broken for eight times. Upon investigation: the electrode wall was scraped and broken due to slagging on the electrode hole wall of the furnace cover. After slag cleaning and keeping a certain distance between the electrode and the hole wall, the electrodes had not been broken again.

In 2000, a factory used φ700 electrodes of Tokai Carbon were broken more than 20 times in one moth. The manufacturer came to see the operation: 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 electrodes of LF furnace in a factory were broken in every shift. Upon investigation: ① in the screws of four feet of column, one broken and one loose; ② the verticality of the column was 14 times larger than the requirement. 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 was broken. 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 increased. Upon investigation: the electrode consumption increased by 77.9%, the power consumption increased by 15.8%, and the period prolonged by 17.5%, compared with that before and after April. Through 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 one meter 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 increasing 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 large 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 among many manufacturers, and there was no tripping when these products were used separately. 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 to prevent mix.

Abnormal Problems Summarization

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 support, cooperation and help during our investigation. HP Graphite Co., Ltd. has a professional technical service & after-sales team. If you encounter problems during the use of graphite electrode, you can directly contact us, we will provide you with the first time solution.

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