Graphite electrode transport
1,Graphite electrode should be covered with rainproof cloth during long distance transportation.
2, with lifting machinery unloading wooden box packaging electrode, you must use the wire rope, not directly touch the electrode steel packaging belt for hanging unloading.
3, for the protection of the electrode surface and the thread, not directly with the hook hook electrode hole Diaoyun electrode.
4, loading and unloading joints, boxes should be handled with care, in case of damage to the thread.
Graphite electrode storage
1, the electrode should be stored in a clean, dry place; temporarily do not use the electrode and connector, do not remove the packaging, to prevent dust, debris onto the thread or electrode hole, affecting the accuracy of product docking.
2, The electrodes open space piled up, must use the rainproof cover peng.
3, the electrode storage in the warehouse should be placed neatly, the two sides of the electrode pad should be good to pad.
4, the bulk electrode stacking height usually not more than 2.8 meters, box electrode height should not exceed 4 layers.
5, the storage site temperature should not be too high, in case the asphalt joint plug melting.
Connection operation of graphite electrode
1, wet electrode, use before drying.
2. Remove the foam protection cap on the spare electrode hole and check the integrity of the thread inside the electrode hole.
3, compressed air oil and water cleaning standby electrode surface and the internal threads of the hole; avoid using steel wire group or metal brush cleaning cloth.
4. Carefully turn the connector into one of the electrodes in the spare electrode (not recommended to be mounted directly on the furnace to replace the electrode) and shall not impact the thread.
5. The electrode sling (graphite spreader is recommended) is screwed into the electrode hole at the other end of the standby electrode.
6, lifting the electrode, the electrode to the standby pad fluffer joint end, to prevent the ground damage joints; rings with a hook into the spreader after lifting, lifting the electrode to smooth, prevent the electrode from B and other loose or fixed device collision.
7, the electrode to be connected to standby hanging above the electrode, electrode alignment hole slowly after falling; rotating standby electrode, the spiral hook electrode together with rotation in two decline; the electrode surface is 10-20mm, again with the compressed air cleaning electrode two and exposed part of the joint end; at last completely decentralized electrode. Not too hard, otherwise because of violent collision, will cause the thread electrode hole and joint damage.
8. Use the torque wrench to reserve the electrode until the ends of the two electrodes are in close contact (the gap between the electrode and the joint is less than 0.05mm).
Precautions for graphite electrode in use
1,the electrode holder should be clamped outside the warning line of the top electrode, otherwise it will cause the electrode to break. The contact surfaces of the holder and the electrode shall be cleaned regularly to keep in good contact with the electrode and the jacket shall be protected against leakage.
2, the electrode joint found cracks exist, must find out the reason, eliminate the connection gap can be used.
3. In connection electrode, it is found that when the joint bolt falls off, the joint bolt should be filled and then connected.
4, the electrode should be used vertically, avoid tilting operation, especially not to connect a set of electrodes horizontally, so as not to break.
5, to charge into the furnace, should be installed near the furnace bottom at the bulk material, in order to reduce the burden of the large collapse impact electrode.
6, when smelting, should avoid insulation block a large number of piles in the electrode just below, so as not to affect the electrode use, and even the electrode broken.
7, the electrode in the rise or fall, should avoid rubbing the furnace cover, resulting in electrode damage.
8, in the smelting site, to avoid steel slag splash to the site of the electrode or joint of the thread buckle, damage thread precision.
Questions & Answers
1. What are the factors that affect the consumption of electrode in EAF steelmaking ?
Factors affecting the consumption of electrode mainly include:
1) charge amount and the feeding way,
2) feeding time and outage time,
3) Tap-to-tap time,
4) emissions and dust removal system,
5) electrode adjustment,
6) high current, large amount of slag,
7) improper oxygen injection,
8) electrode connection and joint,
9) body quality and the processing precision of electrode,
10) nipple strength.
2. How to avoid the electrode from breakage and tripping in the process of steelmaking?
Taking the following measures can effectively avoid electrode from breakage and tripping in steelmaking process:
1) the phase sequence is correct, that is anticlockwise.
2) steel scrap uniform distributed in the furnace and try to put large pieces of steel scrap at the bottom of the furnace.
3) avoid non-conductive material in scrap.
4) electrode column and the top hole alignment, and parallel to the electrode column. The top hole wall should clean up frequently to avoid accumulation of residual steel slag to force electrode to break.
5) to keep the electric furnace tilting system in good condition, and keep the electric furnace tilting steady.
6) the electrode holder should not be placed in the joint and sockets.
7) choose to use high strength, high machining accuracy and high quality nipples.
8) torque should be appropriate for electrode connection.
9) to prevent the mechanical damage of electrode socket thread and nipple thread in and before the process of jointing.
10) steel slag or foreign material shall prevent from embedding the socket and nipple which may affect screwing.
3. What shall be noted when steel mills lifting electrodes by crane？
No matter use a forklift or crane to transport electrodes requires for elaborate operation. In the process of electrode lifting, any electrode end or thread damage can cause serious problems for the use of the electrode, especially to protect the threaded hole and the nipple thread. Pads should be used when ascending electrodes , so as not to damage the electrode end face and the nipple thread.
4. How to join electrode correctly?
When joining electrodes, compressed air should be used to blow off the socket, electrode surface and nipple. Dust and foreign objects embed should be prevented. Joint should keep clean and smooth. When electrode is screwed to a certain extent (1-2 cm gap between the two electrodes), compressed air should be used again to blow off the dust and then use a torque wrench to tight the electrode in proper torque.
5、About the correct clamping position of electrode holder.
Electrode holder can't clip in the joint of electrode and thread parts, but between the two safe lines. Meanwhile, the electrode surface and holder should be blew off by compressed air before clamp a electrode to ensure that current and heat flow between the electrodes and gripper conduction is good, and prevent holder damaged by electric arc, so as to extend the use of the holder.
6. What are the measures to reduce the consumption of electrode oxidation in EAF furnace steelmaking process?
Reducing measures mainly include:
1) to reduce the oxidation consumption of electrode perimeter, strengthen the sealing of the furnace, and reduce air intrude into the furnace; to minimize the exposure time of overheated electrodes outside the furnace, and standardize oxygen blowing operation.
2) if conditions permit, adopting spray cooling technology to effectively reduce the electrode side oxygen consumption in EAF furnace.
3) steel mills could spray antioxidant substances on electrode surface, or the electrode manufacture can take antioxidants impregnation treatment technology before delivery to improve the oxidation resistance of electrode ontology.
7. What are the impacts of electrode phase sequence on the use of electrode?
In EAF furnace steelmaking process, the phase sequence of the electrode has a great influence on electrode loosen and breakage. If the sequence is clockwise, electrode will get loose after powered on and used for a period of time, which will easily cause electrode loose or nipple breakage. The correct phase sequence is anti-clockwise. In that way, electrode joint will be more and more tight in use. For the sequence of the electrode measurement, Nantong Jiangdong carbon co., LTD can provide free measurement if required by the users.
8. Why the electrodes columns need to be parallel and align with the top hole of furnace cover?
Electrode column shall be centered with the top hole of furnace cover and electrode column should avoid friction with the furnace cover. Otherwise, the lifting and lowering friction can make the furnace cover force to break electrodes. For AC furnace, three phase electrode columns should try to keep parallel.
9. How to exert torque when screwing electrode?
Torque should be proper when screwing electrode and operation should be spoiled. Too small torque will cause nipple heat loose and too big torque will result in socket cracks. Special screw electrode tool shall be used in screwing and please do not twist too tight or too loose.
10. Why we say graphite lifting appliance is better than metal one?
Though metal hook is durable and not easy to be damaged, thermal expansion of the metal hook could easily burst electrode socket when heated. Meanwhile, it is easy to damage the electrode thread when carrying and cause massive scraping which makes electrodes easy to loose. On the contrary, graphite lifting appliance have same thermal expansion property and hardness as the electrode, which will not happen the above poor situations. But the use of graphite lifting appliance period is short, and easy to be damaged. If found serious damage, it should be changed in time.
11. How to correctly choose electrode for arc furnace steelmaking?
According to the design characteristics of electric arc furnace to choose proper and most cost-effective electrode which is suitable for arc furnace production. It is very necessary to choose proper electrodes for each furnace. The special properties of the steel furnace, charging mode, maximum current intensity, the length of the electrode column under the holder, and the distance between the electrode circle and so on are the factors which must be considered in choosing electrodes for arc furnace.
12. What are the effects of specific resistance of the graphite electrode to electrode usage in steelmaking.
The specific resistance of graphite electrode is a sign of physical and chemical index of electrode conductivity state which is related to its manufacturing process. Generally, when steel mills choose a certain specifications of electrodes, they must choose those whose resistance is within the national metallurgical standard range. High resistance will make electrodes red and hot after energized, that will increase electrode oxidation consumption.
13. What are the effects of bulk density of the graphite electrode to electrode usage in steelmaking?
Graphite electrode bulk density reflects the solid state of electrode, which is related to the manufacturing process of the electrode. Our country has different specified value for different specifications of graphite electrode. The low bulk density products shows that the overall structure of porosity is higher, which will make electrode oxidation speed faster under high temperature. Then it will easily cause electrode consumption increase. In general, steel mills shall choose larger bulk density electrodes but within the specified value. However, it does not mean the higher of bulk density the better. Because some electrodes with too high bulk density are sometimes not good at thermal shock resistance, which easily lead to electrode surface spalling, butt loss and crack that affects steel making. The bulk density of electrode is closely related to the manufacturing process.
14. Why domestic UHP electrode production must use imported needle coke?
UHP graphite electrode production must choose high quality needle coke. Due to domestic research and development of needle coke is so slow that the production of needle coke quality cannot achieve the quality requirement of producing high quality UHP electrode, and most of them are only used to product normal electrodes or HP electrodes. Therefore, raw materials of UHP electrode production have to rely on imports of needle coke.
15. What are the features of the needle coke used for UHP electrode production?
Needle coke is a high-quality carbon raw material, which mainly come through thermal cracking residue of petroleum refining. It’s surface have obvious strip lines and form elongated needle fragments if crushed, and fibrous structure could be observed under the microscope lens, so it is called needle coke. Needle coke is easy to be graphitized above 2000 degrees of high temperature. If we use needle coke to produce graphite electrodes, the electrodes will have low resistance, high bulk density, and small thermal expansion coefficient. So, it’s a must material in producing UHP electrode. Needle coke is more expensive than ordinary coke.
16. What is the distribution and price of the needle coke in current world?
Currently, there are mainly 9 enterprises around the world who produce needle coke (one company in America shut down in 2005). The needle coke annual output decreased from 900000 tons in Y2004 to 800000 tons ，Annual output of 1.1 million tons by 2018，which is far from enough to meet the needs of carbon industry in the world. The world needle coke prices are rising rapidly from $540 per ton in 2004 up to 2005 the $920 per ton (rose 70%), By the end of 2018, it had reached $3200-4000 per ton，The prices will continue to rise in the future，and resources will be in great tense. It will make a great impact on domestic production of the UHP electrode, and the total production amount of UHP electrode will not improve under the influence.
17. How to avoid electrode consumption increase in steel making?
The following items should be noted to avoid electrode consumption increasing:
1) maintain good state of power supply, and energize within the current range according to the requirements of electric furnace design.
2) prevent the arc starting point immerse in the molten pool.
3) prevent electrode immerse into molten steel to refrain from add carbon.
4) If conditions permit,spray cooling technology shall be used.
5)set up the correct exhaust system.
6)adopt right oxygen blowing system.
18. What are the procedures of UHP graphite electrode production? How long does it take for the whole production cycle?
A batch of UHP graphite electrode production process and corresponding time is as follows: extrusion (3 days) - baking (25 days) - impregnation (4 days) - re-baking (15 days) - graphitization (15 days), machining, quality inspection (2 days), finished product packaging (1 day). Thus from feeding materials to end-product requires 65 days without stop. Normally, the production cycle is about 90 days. Because the nipple production requires three more procedures, its production cycle is much longer.
19. What aspect of LWG furnace products is better than Acheson furnace?
The development direction of graphitization furnace is LWG, and the reason is its products quality is better than that of Acheson furnace in homogeneity. It’s more suitable for the electric arc furnace steelmaking production requirements.
20. Why the quality of nipples is very important in EAF steelmaking?
Nipple plays a key role in electrode connection and it is directly related to the electrode usage in electric furnace steelmaking. No matter how good quality the electrodes have, problems will happen without reasonable collocation of good nipples during steelmaking. According to relevant data which shows that in electric furnace steelmaking, more than 80% of the electrode using accident is caused by nipple fracture and tripping. Therefore, high quality nipples are the guarantee of EAF steelmaking normal use.
21. Which properties of graphite electrode(nipple) have influence on electric furnace steelmaking?
2)nipple bulk density, specific resistance, strength, elastic modulus and coefficient of thermal expansion etc. 3)machining precision of electrodes and nipples. Without good machining precision, the using effects will not be good even with high quality of electrodes and nipples.
4)the quality of internal structure of electrode and nipple. No cracks is allowed inside electrode and nipple which may cause problems.
22. What will happen if the electrode surface at the top of the holder were severe oxidized in EAF steelmaking? How to prevent?
When making steel in EAF, blowing oxygen into furnace will make the flame higher than the electrode end surface at the top of holder during combustion scrap steel. Sever oxidation may turn the electrode end surface from flat to slope. If connect a new electrode on its top end, the deformation of end surface could not well matched with the new electrode. A big electrode gap will easily cause the inner nipple oxidation and broken. Under the condition of no changing condition of steelmaking, the best preventive measure is to add a shield on the surface of the electrode end face at the top of the holder, to protect electrode end face by blocking fire and air.
23. Whether the dust collection system on EAF will influence the electrode consumption?
When the fan of dust collection system is working, it forms negative pressure, which will speed up the air flowing around the hot electrodes during making steel. In that case, it increases electrode oxidation consumption. In steelmaking, a good dust collection system adjustment could not only maintain a good working environment, but also stabilize electrode consumption.
24. The quality of Nanjing Su-sino Supply Chain Management Co., Ltd. export graphite electrodes.
The factories cooperated with Nanjing Su-sino Supply Chain Management Co., Ltd. are the first-class large-scale graphite electrode manufacturers in China mainland, which ensures the excellent quality and stable supply quantity of graphite electrodes.
Since we company set up. Based on years of practice, with our users carrying cooperate together to reduce electrode consumption in steel-making. Good effect has been obtained for the past several years. In order to let users better use of electrodes, we inductive analyzed the common abnormal problems that occur in the process of using electrodes for your reference.
Example 1:One company used RP and HP φ 300 mm electrode on a 70 mt LF furnace, and found the electrodes turns red and thin and can no longer use.
The problem is that the above electrode cannot bear 26 KA current
Example 2: The effect of AC Furnace phase sequence to electrode loose.
AC Furnace phase sequence has a great effect on electrode loose, which is happened on users from home and abroad.Among the15 units of domestic electric furnace that we measured: 10 of them need to change the phase sequence. 5 of them no longer get loose after take our advise to change their phase sequence. 1 of them don’t want to change, and 1 of them doesn’t change because the operator can not read English, and the electrode loose situation still the same; 3 of them is going to change. Recently, there are another plant who also face such problem. After our introduction, they are going to measure the sequence.
Example 3: One factory reflected electrode loose. According to our investigation: in addition to the phase sequence should change, only 4 teeth inside of the electrode upper hole are in good condition, other teeth have different degree of damage.There was one T3 iron lifting plug found mix-used to carry T4 electrodes on the spot. After corrected phase sequence and removed the T3 lifting plug, no loose were found till now.
Example 4: One plant’s electrodes always got broken, result from the large blocks of steel slag collapse or non-conductive factors. According to the statistics from their engineering department, 78% of electrodes breakage are caused by above reasons.
Example 5: Due to electrode hole wall on furnace cover slagging, electrodes were broken for many times handled by one team on LF furnace. After slag removal and keep the distance between electrode and wall of hole, no such breakage happened again.
Example 6: One factory used TOKAI φ 700 electrodes and happened more than 20 times of breakage. The manufacture came and checked their operation and found they connected the electrodes so tight that over the triangle mark. After justified, the breakage phenomenon eliminated.
Example 7: Every team of one factory has breakages on LF furnace. The reasons are: 1) one foot screw of the column was broken and one loosen among the four screws;2) The column verticality is 14 times larger than required. After adjustment, no more breakage.
Example 8: 16 pcs of nipples were broken in a factory. After check, we found they all broke at the point of pin. Pin hole φ 28mm, and deep（ 30 ～ 50mm ）× 2. We suggest them not to use pin.
Example 9:One plant reflect electrode breakage. We found that was caused by molten steel ladle-to-ladle, large temperature drop, and slag layer hardness increase, which not only often forced electrodes to breakage but also destroyed clamps causes electrode consumption increase.
Example 10: Electrode consumption increased when used in one plant’s LF furnace. After we compared the data of before, we found the electrode consumption rose 77.9%, power consumption rose by 15.8%, and 17.5% growth on production cycle. Then through calculation, there would be 170MT electrodes consumption increasing amount and their lost is about 5 million RMB. Through field investigation,we knew that in order to improve the environmental protection, the factory increased the height of small furnace cover about 1 meter; At the same time, suction dust removing valve from opening 45 ° to 90 °, that caused electrodes oxidation and heat dissipation increased. We wrote a report according to our findings and sent to the relevant leader of that factory and they approved.
Example 11: One factory reflected that their electrodes consumption has increased from 0.42kg /t to 0.52kg /t on LF furnace . The reason is VD ratio grew from 42.76% to 73%.
According to the memory of the leader in that factory, what they knew was same as our analysis.
Example 12: A plant said their electrodes have tripping phenomenon. Through on-the-spot investigation, we found that they used electrodes from several manufactures, and no loose will happen when they use separately but join two electrodes from different manufactures. This is mainly due to different manufacturers have different electrode machining tolerance and we recommend the user to reduce the changing times of electrodes from different manufactures to avoid mixing.
The above are some excerpts of electrode using problems we encountered and put forward suggestions of improvement through years of experience. Because the continuous and discontinuous consumption of electrodes involves the design of the electrode manufacture and design, equipment, raw materials, process, operation, and many other aspects, both sides and internal shall work together to find out the real reason as soon as possible when an exception occurs. The above instances are examples of honest fellowship solves practical problems. We are very appreciate the great help, cooperation and support from our customers during our investigation.We have a professional after-sales service team, and once you encounter electrodes use question, we will provide you with solutions in the first time.
Graphite electrodes are packed in wooden cages, joints are packed in wooden boxes, or joints are packed in conjunction with electrodes according to user's requirements. The graphite electrodes are lined with waterproof and dust-proof plastic cloth, and the steel strips for external use are firm and beautiful. They are suitable for land and sea transportation.
The packing method is as follows：
1 、Separate Packaging Type
The electrode and the connector are separately packaged and transported.
2 、Pre-packaging Type
One end of the electrode is connected with the connector, both ends of the electrode are installed with protective caps, and then the electrode is packaged and transported.
The main action of the packaging is to protect the electrode and the connector from being damaged in storage and transportation, particularly protect threads from being damaged.