Graphite Electrodes Production and Optimization Practices

black lead Electrodes Production and Optimization PracticesGraphite electrodes be glumice in both DC and AC electric arc furnaces. Companies who use electric arc furnaces have to cover the cost of these consumable electrodes during production, so optimizing the usage of graphite electrodes is a money-saving opportunity. This paper aims to discuss the production act of graphite electrodes as well as industry practices that be use to enhance the life story of electrodes.To produce a graphite electrode, degree Celsius is required. The ascorbic acid first for graphite electrodes comes from the petroleum industry as a byproduct from the oil refining process. In the refining of crude oil, hydrocarbon chains are cracked in coking units and the resulting fuels are then sepa dictated as kerosene, gasoline, and diesel. As chains of hydrocarbons are being cracked in this process, pure carbon becomes deposited on the sidewalls of the coking units. The carbon on the sidewalls accumulates up to a certain blame when it is the ground out of the unit. This carbon is called petroleum coke, or petcoke. This is the carbon source for graphite electrodes.After the petcoke is obtained from the oil refinery, it is blended with pitch to make a plastic-like material. (Making a UCAR Graphite Electrode) This blend of petcoke and pitch is then extruded through a circular die and cut pass oned in sections. It is then cook at a temperature of above 800 degrees Celsius for a period of one to dickens weeks. After baking, the electrode is impregnated with more pitch to increase the density of the electrode which lowers electrical opposition and makes it stronger. The electrode is then re-baked at a slightly lower temperature to drive off volatiles found in the pitch. Finally, the electrode is heated to a temperature of about 3000 degrees Celsius to recrystallize the carbon into graphite. This final examination heating is called graphitization. Graphitization is very important in electrode manufacturing be aim it provides better mechanical cleverness and also improves electrical conductivity. The final step in electrode production is machining. The electrodes are machined to specific tolerances. This is especially important at the ends of the electrodes where the commons connect. (D. Klein) A good connection between joints is necessary for mechanical and electrical properties of the electrode.Electrode consumption takes on twain forms Continuous consumption and noncontinuous consumption. (Richard J. Fruehan) Continuous consumption contributes 90% of summation electrode consumption eon noncontinuous consumption only accounts for 10%. veritable(a) though discontinuous consumption accounts for far less than continuous consumption, discontinuous consumption mass also account for furnace downtime which jackpot cost a lot of money. So even though it is a small percentage, it is worthy to try to baffle it for the sake of productivity.In continuous consum ption, the track and sidewalls oxidise and the mass of the electrode is reduced. Tip consumption is a function of current and angle. higher(prenominal) currents and steeper tip angles both yield faster oxidation judge of electrodes. (A. Lefort) Higher currents increase the temperature of the electrode which favors a faster oxidation rate. The steeper the tip angle, the closer the electrode needs to be to the mark bath to arc. brand is more likely to splash onto the electrode if it is closer to the bath. One way to reduce the oxidation rate of electrodes is to cool them. Water cooled electrodes have been shown to reduce the oxidation rate of the sidewalls by 40% and the tip by 50%. One subject with body of water cooled electrodes is the flow rate of the water. If the flow rate is too high, water will pour into the furnace and increase the heat loss. The loss of heat can end up costing more than the money saved from cut back electrode consumption, so this is an important facto r to consider in this process.In discontinuous consumption, one of the most obvious techniques to prevent electrode breakage is simply to not ram the electrodes into the steel wish-wash. Graphite is a soft, brittle material and steel scrap is pretty hard and durable. If these two materials come head-to-head, the steel wins. some other method of discontinuous consumption is tip spalling. (A. Lefrank) This is more prevalent in DC furnaces than in AC furnaces because the DC electrodes see higher temperatures and then higher thermal stresses. The temperature gradient can be significant in the tip of a DC electrode and the thermal expansion of graphite can cause liberal stress on the tip to break off small pieces. (J. E. Surma) Normally, the arc in a DC furnace will give out about randomly, but occasionally the arc will sit in one spot, heating up that portion of the electrode tip creating thermal stresses that cause the tip to spall. Arc deflection control is a practice that has be en utilize so when the arc becomes fixated on one spot, it will essentially charge up the arc out from that spot to get it to move about in a random fashion once more.Another practice to prevent the discontinuous consumption of electrodes is to ensure proper torque is applied when lay new electrode segments. The vibrations from the furnace and electromagnetic forces due(p) to the flow of electricity give electrodes a good shaking. This can jostle the segments loose from their joints. This is mainly a difficulty in DC furnaces because AC furnaces are designed to ensure that the electromagnetic forces work to their advantage. In AC furnaces, the phase sequence is counterclockwise, so the forces on the electrodes due to the electromagnetism of the system only ever tightens the electrode joints. Below is a chart of recommended torque according to electrode diameter from SGL Carbons website and an AC furnace schematic of forces due to phase sequence.One final practice that helps pre vent the failure of electrode joints is to turn off the water disperse for a few minutes by and by the addition of another electrode segment. (Richard J. Fruehan) The temperature gradient is much steeper when the water spray operation is active. This thermal gradient can cause a trouble when it reaches the joint because of the thermal expansion of graphite. Even if the electrode was tightened with the proper amount of torque, the effects of temperature on the electrode joint is enough to loosen it. This coupled with the furnace vibrations could be enough to cause the electrode joint to fail.In conclusion, graphite electrodes are an essential constituent of electric arc furnace steelmaking. Since they are consumable, any way to improve the life and efficiency of an electrode saves money in the steelmaking industry. Practices such as water engine cooling system electrodes and optimizing current and tip angle are effective ways of trim the oxidation of electrodes while taking ca re not to impact the scrap during melting, ensuring proper torque during installation, and turning off the water spray while adding another segment all help reduce breakage and joint failure.Works CitedA. Lefort, M. J. Parizet, S. E. El-Fassi and M. Abbaoui. Erosion of Graphite Electrodes. J. Phys. D Appl. Phys. 26 (1993) 1239-1243.A. Lefrank, W. J. Jones, and R. G. Wetter. DC Steelmaking Conditions and Electrode Performance. electric car Furnace Conference Proceedings 53. Warrendale Iron and Steel Society, 1995. 337-346.D. Klein, K. Wimmer. DC Electrodes A secernate Factor for Progress in EAF Production. Metallurgical Plant and Technology external 184 (1995) 54-63.Graphite and Carbon Electrodes. 6 declination 2009 .J. E. Surma, D. R. Cohn, D. L. Smatlak, P. Thomas, P. P. Woskov, C. H. Titus, J. K. Wittle, R. A. Hamilton. Graphite Electrode DC Arc Technology Development for Treatment of Buried shove offs. Waste Management 93 Symposia. Tuscon, 1993.Making a UCAR Graphite Electro de. 2007. 6 December 2009 .Richard J. Fruehan, Ph.D. The Making, Shaping and Treating of Steel 11th Edition. Richard J. Fruehan, Ph.D. The Making, Shaping and Treating of Steel 11th Edition. Pittsburgh The AISE Steel Foundation, 1998. 562-574.