Design Project - Electric Furnace for Steel Making
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Design Project - Electric Furnace for Steel Making

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  • Christopher (2007) focuses on the method of making steel using in an electric arc furnace out of so many furnaces. From the result of his research, he managed to come up with an invention to make steel at substantially reduced costs. Christopher (2007) identified that by charging and melting the scrap in the furnace, a source of lime will be generated. It will be compacted to form a conglomeration of compacts; charged to the furnace in the shortest period of time to avoid energy loss, and at the same time adding extra fluxing agents and additives to produce refined molten steel. As the research of Christopher (2007) focused on the provision of lime to the electric arc furnace as quick as possible, he did not go about explaining how different kinds of steel, like stainless steel, are made directly from the electric arc furnace. Rather, he placed importance on the continuous supply of lime to the furnace. Despite this, we would be able to determine the ideal design, through our results of our research, as to how stainless steel can be made using the electric arc furnace.
  • Christopher (2007) focuses on the method of making steel using in an electric arc furnace out of so many furnaces. From the result of his research, he managed to come up with an invention to make steel at substantially reduced costs. Christopher (2007) identified that by charging and melting the scrap in the furnace, a source of lime will be generated. It will be compacted to form a conglomeration of compacts; charged to the furnace in the shortest period of time to avoid energy loss, and at the same time adding extra fluxing agents and additives to produce refined molten steel. As the research of Christopher (2007) focused on the provision of lime to the electric arc furnace as quick as possible, he did not go about explaining how different kinds of steel, like stainless steel, are made directly from the electric arc furnace. Rather, he placed importance on the continuous supply of lime to the furnace. Despite this, we would be able to determine the ideal design, through our results of our research, as to how stainless steel can be made using the electric arc furnace.
  • Clifford (1971) patented a design which allowed them to produce stainless steel without using an electric arc furnace. A channel furnace is employed to mix chromium containing and chromium-free hot metal, producing a converter feed metal of desired temperature and chemical composition. Clifford (1971) also ensured that the weighted charges of such feed metal are blown in the converter, and helps in the saving of time and electricity, which yields cost savings. However, in the article, Clifford(1971) made use of 2 furnaces to carry out the steel making process. In our design, we would be aiming to resolve the issue. Not through the use of another furnace, but through re-designing the current electric arc furnace to make stainless steel using one furnace only
  • Arturo (1991) put forward a patented invention which involved the production of stainless steels in an electric arc furnace. His invention identified the problems of using an added oxygen process to obtain good reducing conditions. The problems were that good reducing conditions were still present even though it was more economically favourable, and also the maintenance of desired temperature in the melt. Arturo(1991)’s invention involved the installation of a charging door stopper device, bottom gas injection devices, and an oxygen by lance system. The motive of Arturo(1991) in doing that is to introduce oxygen to remove the excess carbon via an electrode at the top of the roof to decarburize the carbon, and the charging door stopper device is to prevent any melt from flowing out. Also, the bottom gas injection is to homogenize the melt. Arturo (1991)’s invention did not exactly look into reducing the loss of chromium. The introduction of gas through the bottom of the furnace cannot rule out the possibility of the melt flowing down the pipe at the bottom of the furnace. Arturo(1991)’s invention neglected the importance of maintaining the temperature, which he explained only by adjusting the arc to control the tapping temperature. Our design would look into the area of minimizing the loss of chromium, as well as achieving the ability of homogenizing the melt in the electric arc furnace.
  • Corrosion resistance Lower alloyed grades resist corrosion in atmospheric and pure water environments, while high-alloyed grades can resist corrosion in most acids, alkaline solutions, and chlorine bearing environments, properties which are utilized in process plants. Fire & Heat ResistanceSpecial high chromium and nickel-alloyed grades resist scaling and retain strength at high temperatures. HygieneThe easy cleaning ability of stainless makes it the first choice for strict hygiene conditions, such as hospitals, kitchens, abattoirs and other food processing plants. Aesthetic appearanceThe bright, easily maintained surface of stainless steel provides a modern and attractive appearance.  5. Strength-to-weight advantageThe work-hardening property of austenitic grades, that results in a significant strengthening of the material from cold-working alone, and the high strength duplex grades, allow reduced material thickness over conventional grades, therefore cost savings.   6. Ease of fabrication Modern steel-making techniques mean that stainless can be cut, welded, formed, machined, and fabricated as readily as traditional steels.  7. Impact ResistanceThe austenitic microstructure of the 300 series provides high toughness, from elevated temperatures to far below freezing, making these steels particularly suited to cryogenic applications.  8. Long term valueWhen the total life cycle costs are considered, stainless is often the least expensive material option.
  • 4.2.1 400 Series Martensitic (Typical Grade: 410)Consists of Straight Chromium (12-18%), magnetic can be hardened by heat treatment. Typical use: Fasteners and pump shafts. 4.2.2 400 Series Ferritic (Typical Grade: 430)Consist of Straight Chromium (12-18%), “low carbon”, magnetic but not heat treatable. Typical use: Appliance trim, cooking utensils. 4.2.3 200/300 Series Austenitic – Typical Grade: 304Consist of Chromium (17-25%)/ Nickel (8-25%), non magnetic, not heat treatable and develops high strength by cold work. Addition of molybdenum (up to 7%) increases corrosion resistance. Typical use: Food equipments, chemical equipments, architectural applications. 4.2.4 Precipitation Hardening – Typical Grade: 17-14Consist of Chromium (17-25%)/ Nickel (3-9%), either martensitic or austenitic and develops strength by precipitation hardening reaction during heat treatment. Typical use: Valves, gears, petrochemical equipments. 4.2.5 Duplex – Typical Grade: 2205Consist of Chromium (18-25%)/ Nickel (4-7%) and up to 4% molybdenum. Has a higher resistance to stress corrosion cracking than austenitic, yet tougher than fully ferritic alloys. Typical use: Pipelines, pressure vessels, shafting. 4.3 Benefits of Stainless SteelStainless steel is a class of metal alloy with many unique properties and values making it a powerful candidate in materials selection. Engineers, Specifiers and designers often under estimate or overlook these values because of what it is viewed as the higher initial cost. However, over the total life of a project, stainless steel is often the best value option.
  • There is another concern which is over stirring of the molten melt. When this happens, the molten metal might be ejected causing fire hazards.
  • So, our proposed solution would be: Electromagnetic stirringAs mentioned by Kenvin earlier, it is a process already used in continuous casting.The advantages of Electromagnetic stirring is that itEliminates the need for an external body to be physically be in contact with the molten metal. It is also allows the user to vary the stirring strength by adjusting the power supply and the flow patterns can actually be customized accordingly. It also simplifies the entire furnace system.
  • Let me now explain the working principle of Electromagnetic stirring.An inductor is placed close to the molten melt with a 3 phase power supply connected to it.A magnetic field would be generated which causes an induction current to flow through the molten metal.The electromagnetic force that is created would then cause the molten metal to move in the direction of the magnetic field, creating the flow required to stir the molten melt.
  • For our project, we have 2 options to position the electromagnetic stirrers, either at the top or at the side of the furnace. Our group prefer to have the stirrer positioned at the top as it very much simplify the design of the furnace.
  • To position the stirrer at the top of the furnace, 3 inductors would be connected to the 3 phase alternating power supply.Considering the scenario where the current supplied at point X to be higher than that at points Y and Z.This would cause current to flow from point A to C and A to B, creating 2 close loop currents. However, there would be no current flowing through points BC and ZY.The 2 close loop currents will then reinforce each other and create a magnetic field under the furnace lid. As the phases of the power supply changes, the magnetic field would rotate, stirring the molten melt.
  • This a diagram of the predicted flow lines generated by 2 magnetic stirrers.
  • However, after reviewing the stir patterns created, our team felt that the stirring pattern might not sufficiently stir the molten metal.The stirring strength might also be too weak as it relies on a single electrode.Therefore, we decided try installing the magnetic stirrers at the side of the furnace instead.
  • With the magnetic stirrers installed at the side of the furnace, the stirring strength could be increased by simply adding more transducers.The stirring pattern would also be altered and the new “Donut shaped” stirring pattern generated would be much more effective.
  • To conclude, the electromagnetic stirrers would be installed at the side of the furnace so as to ensure sufficient stirring strength.The speed of stirring can also be easily varied and through proper positioning of the magnetic inductors, the flow patterns can be customized to suit the shape of the furnace. By doing so, we hope to optimize the stirring strength and speed of the furnace system.
  • Installation of Heat Exchanger systemTo improve energy efficiency and reduce energy consumptionHeat loss due to cooling of molten melt, can be ‘captured’ and recycled by a heat exchanger systemImprovements in Refractory MaterialIncur cost due to periodic replacement of the refractory material lining which will be damaged after several production cycles. Overall effectiveness of the arc furnace is compromised Frequent replacement of the refractory lining = …A more suitable refractory material can also be proposed to further improve overall effectiveness. Refractory Cooling SystemProlong the refractory material production life - prevent the lining from being heated to excessive levels. To control the temperature of the refractory material, a cooling system can be integrated into the arc-furnace design. To achieve optimum results, this cooling system should have some sort of feedback loop to monitor the temperature conditions at various parts of the furnace and take corrective action accordingly. The type and method of the cooling system to employ would be an ideal area to work on for future work.

Design Project - Electric Furnace for Steel Making Presentation Transcript

  • 1. DESIGN OF AN ELECTRIC FURNACE FOR MAKING STEEL BY GROUP 23 : EUGENE TEO GUO SHUN 061933G07 KENVIN TEO SHI YU 061932E07 JOELTEE HAN YUN 060420D07 FIZH TO CHUN YU 060324H07
  • 2. MS 3005 DESIGN PROJECT List of Contents  1. INTRODUCTION  2. MOTIVATION  3. SCOPE  4. CURRENT OPERATION OF MAKING STEEL  5. LITERATURE REVIEW  6. WHY STAINLESS STEEL?  7. MATERIALS SELECTION  8. DISCUSSIONS  9. RECOMMENDATIONS  10. REVIEW  11. QUESTIONS AND ANSWERS
  • 3. MS 3005 DESIGN PROJECT Introduction  Steel making can be separated into two categories- primary and secondary  Current trend – using of electric arc furnace (EAF)  Advantages  400 tons of steel in 60 minutes  Mass production= low price  Flexible in stopping according to demand  Disadvantages  Environmental and efficiency  Cost
  • 4. MS 3005 DESIGN PROJECT Motivation & Scope  The growing Steel processing industry  The gist of making stainless steel lies in the decarburization process.  2 types of decarburization processes  Vacuum oxygen decarburization (VOD)  Argon oxygen decarburization (AOD)  hassle of transferring to another ladle  focus on improving and redesigning two aspects of the existing electric arc furnace  1. The process of vacuum decarburization  2. The stirring of the molten steel to obtain a homogenous melt.
  • 5. MS 3005 DESIGN PROJECT Current Operation of Making Steel Video
  • 6. MS 3005 DESIGN PROJECT Literature Review  DESIGN OF AN ELECTRIC FURNACE FOR MAKING STEEL Our group is going to focus on improving the design and manufacturing stainless steel using the Electric Arc Furnace
  • 7. MS 3005 DESIGN PROJECT Literature Review Methods of making steel (Christopher 2007)  Hits  Focuses on the method of making steel using an electric arc furnace  Manage to come out with an invention make steel at a reduced cost  Generation of source of lime compacted to form a conglomeration of compacts; charged to the furnace in the shortest period of time to avoid energy loss  Misses  Did not explain how different kinds of steel, like stainless steel, are made directly from the electric arc furnace
  • 8. MS 3005 DESIGN PROJECT Literature Review Making of stainless steel without using electric arc furnace (Clifford 1971)  Hits  patented a design which allowed them to produce stainless steel without the use of an Electric Arc Furnace  Misses  Uses 2 channel furnaces  A channel furnace is employed to mix chromium containing and chromium-free hot metal, producing a converter feed metal of desired temperature and chemical composition.
  • 9. MS 3005 DESIGN PROJECT Literature Review  Making of stainless steel with an electric arc furnace without using secondary processes (Arturo 1991)  Hits  identified the problems and enhanced the added oxygen process to obtain good reducing conditions  Installation of devices + lance system to introduce oxygen to improve efficiency  Misses  Never looked into reducing the loss of chromium + homogenization of melt
  • 10. MS 3005 DESIGN PROJECT Literature Review  Electromagnetic Stirring  Commonly used in continuous casting of metals  Prevents the creation of inhomogeneous steel  It agitates the molten core  Balances the temperature gradient between the outer shell and inner core of casted metal  Feasible in homogenizing the stainless steel melt in the steel making process
  • 11. MS 3005 DESIGN PROJECT Why Stainless Steel?  WHAT is Stainless Steel?  Low carbon steel alloy, 10 wt% of chromium by mass, chromium oxide layer Advantages  1. Corrosion resistance  2. Fire & Heat Resistance  3. Hygiene  4. Aesthetic appearance  5. Strength-to-weight advantage  6. Ease of fabrication  7. Impact Resistance  8. Long term value
  • 12. MS 3005 DESIGN PROJECT Materials Selection  Stainless Steel chosen for the roof of electric arc furnace typically Properties considered  1. Melting point - high  2. Fracture Toughness - high  3. Specific Heat Capacity - high  4. Thermal Expansion coefficient - high  5. Thermal Conductivity – high  Total number of decisions = N(N-1)/2 = 5(4)/2 = 10 decisions  Weighting factors method  Gathered data from CES software located at MSE computer lab  Scaled data according to criterion  Calculate Performance index
  • 13. MS 3005 DESIGN PROJECT Materials Selection Table 1 Application of Digital Logic Method Property Decision Number 1 2 3 4 5 6 7 8 9 10 Melting Point 1 1 1 1 Fracture 0 0 1 0 Toughness Specific Heat 1 1 0 0 Capacity Thermal Expansion 1 0 1 0 Coefficient Thermal 0 1 0 0 Conductivity
  • 14. MS 3005 DESIGN PROJECT Materials Selection Table 2 Weighting Factors Property Positive Decisions Weighting Factors Melting Point 4 0.4 Fracture Toughness 1 0.1 Specific Heat Capacity 2 0.2 Thermal Expansion Coefficient 2 0.2 Thermal Conductivity 1 0.1 Total 10 1
  • 15. MS 3005 DESIGN PROJECT Materials Selection Table 3 Property of Candidate Materials for EAF Fracture Specific Heat Thermal Expansion Thermal Material Melting Point °F Toughness Capacity Coefficient µ Conductivity ksi.in^1/2 BTU/lb.F strain/°F BTU.ft/h.ft^2.F Wrought 418 Martensite Stainless Steel, tempered at 2597 24.57 0.1075 5.00E+00 13.29 260degC Wrought 403 Ferritic Stainless 2597 47.32 0.1075 5.56E+00 13.29 Steel, intermediate temper Wrought 202 Austenitic Stainless 2552 61.88 0.117 9.17E+00 8.667 Steel, annealed Wrought 301 Austenitic Stainless 2552 61.88 0.1149 9.00E+00 9.013 Steel Wrought 301 Precipitation 2552 61.88 0.1149 9.00E+00 9.013 Hardening Stainless Steel Cast Duplex Stainless Steel CD- 2660 46.41 0.1075 5.56E+00 8.667 4CU
  • 16. MS 3005 DESIGN PROJECT Materials Selection  As stainless steels are chosen commonly as roof material for the typical electric arc furnace, 5 classes of stainless steels are chosen to be analyzed. Table 4 Scaled Values of properties and performance index Performance Scaled (1) Scaled (2) Scaled (3) Scaled (4) Scaled(5) Wrought 418 Martensite Stainless 39.05 3.97 20 10.91 10 83.93 Steel, tempered at 260degC Wrought 403 Ferritic Stainless Steel, 39.05 7.65 20 12.12 10 88.82 intermediate temper Wrought 202 Austenitic Stainless 38.38 10 21.77 20 6.52 96.66 Steel, annealed Wrought 301 Austenitic Stainless 38.38 10 21.38 19.64 6.78 96.17 Steel Wrought 301 Precipitation Hardening 38.38 10 21.38 19.64 6.78 96.17 Stainless Steel Cast Duplex Stainless Steel CD-4CU 40 7.5 20 12.12 6.52 86.14  Wrought 202 Austenitic Stainless Steel, annealed, should be chosen to be made as the roof of electric arc furnace.
  • 17. MS 3005 DESIGN PROJECT Discussions - Vacuum Oxygen Decarburization Concept  To produce large steel ingots, rails, ball bearings and other high quality steels.
  • 18. MS 3005 DESIGN PROJECT Discussions - Vacuum Oxygen Decarburization Concept  The oxidation of liquid steel components under the influence of vacuum would result in the oxygen being used up mainly by the reaction [C] + [O] = {CO}  Use of Ellingham diagram
  • 19. MS 3005 DESIGN PROJECT Discussions - Vacuum Oxygen Decarburization Concept  A plot of Gibbs Free Energy ΔG against temperature.  The Ellingham diagram shown is for metals which react with oxygen to form oxides.  The position of the line for a given reaction on the Ellingham diagram shows the stability of the oxide as a function of temperature.
  • 20. MS 3005 DESIGN PROJECT Discussions - Vacuum Oxygen Decarburization
  • 21. MS 3005 DESIGN PROJECT Discussions - Vacuum Oxygen Decarburization Concept  Carbon unusually useful as a reducing agent.  Ellingham Diagram  This process helps to decarburize the steel with minimum chromium losses.  Complete deoxidizers  then desulfurizing slag  Problem?
  • 22. MS 3005 DESIGN PROJECT Discussions - Vacuum Oxygen Decarburization Design of the Furnace in incorporating an extensible roof with vacuum  Combine step of Vacuum Oxygen Decarburization
  • 23. MS 3005 DESIGN PROJECT Discussions - Vacuum Oxygen Decarburization Design of the Furnace in incorporating an extensible roof with vacuum  2 roofs which are interchangeable  Simultaneous addition of oxygen  Use of Vacuum  Eliminates the need for another furnace
  • 24. MS 3005 DESIGN PROJECT Discussions - Electromagnetic Stirring Importance of Stirring the Molten Melt  Homogenizing of molten melt  Improving heat and mass transfer rates  Reduce processing times  Metallurgical restrictions
  • 25. MS 3005 DESIGN PROJECT Discussions - Electromagnetic Stirring Current Practice: Gas Stirring  Use of Inert gases Vacuum  2 commonly used methods: Pump Outlet Ladle Lid  gas valve  semi permeable refractory material Safety Height Molten Steel Refractory Material and Ladle Wall Porous Plug Gas Injection or valve for System gas injection
  • 26. MS 3005 DESIGN PROJECT Discussions - Electromagnetic Stirring Disadvantages of Gas Stirring  Additional processing step  Cost  Inability to cut off gas flow  Violent turbulence  Dangerous ejection of the melt
  • 27. MS 3005 DESIGN PROJECT Discussions - Electromagnetic Stirring Proposed solution: Electromagnetic stirring  Applied in continuous casting processes  Non-invasive  Adjustable stirring strength  Simplifies furnace process  Variable stirring pattern
  • 28. MS 3005 DESIGN PROJECT Discussions - Electromagnetic Stirring Electromagnetic stirring: Working principle Three Phase Power Supply
  • 29. MS 3005 DESIGN PROJECT Discussions - Electromagnetic Stirring Electromagnetic stirring: 2 proposed solutions  Installation of stirrers at top of furnace  Installation of stirrers at side of furnace
  • 30. MS 3005 DESIGN PROJECT Discussions - Electromagnetic Stirring Proposed solution 1: Installation of Inductor at top of furnace Top Ring Furnace Lid Energizing (toroid) coils Molten Melt X Bottom Refractory Ring Material and Ladle Wall X Top View of Furnace Lid
  • 31. MS 3005 DESIGN PROJECT Discussions - Electromagnetic Stirring Proposed solution 1: Installation of stirrers at top of furnace Predicted Flow lines Electromagnetic transducer
  • 32. MS 3005 DESIGN PROJECT Discussions - Electromagnetic Stirring Proposed solution 1: Installation of stirrers at top of furnace Verdict: Unsuitable  Inefficient Stirring pattern generated  Inadequate Stirring strength  Stirring strength will have to rely on a single electrode  Distance of electrode to melt Solution: Installation of stirrers at side of furnace
  • 33. MS 3005 DESIGN PROJECT Discussions - Electromagnetic Stirring Proposed solution 2: Installation of stirrers at side of furnace Slag Molten Metal H ν F Electromagnetic transducers Electromagnetic transducers
  • 34. MS 3005 DESIGN PROJECT Discussions - Electromagnetic Stirring Proposed solution 2: Installation of stirrers at side of furnace  Final Solution  Installation of transducer at side of furnace Summary  Placement and number of magnetic stirrers  Ability to control flow strength  Predetermined stirring patterns for optimum performance  Workable idea
  • 35. MS 3005 DESIGN PROJECT Recommendations  Installation of Heat Exchanger system  Improvements in Refractory Material  Refractory Cooling System
  • 36. MS 3005 DESIGN PROJECT Review  Summary of the current electric furnace operation present  Literature review  Why stainless steel is chosen  Materials selection of the roof for the EAF (group design)  Ellingham diagram and Vacuum Oxidation Decarburization  Design of the Furnace in incorporating an extensible roof with vacuum  Design of the Furnace by implementing and installing magnetic stirrers – side of furnace versus top of furnace  Recommendations for future work  Last but not least . . .
  • 37. MS 3005 DESIGN PROJECT Questions & Answers  “Now… who ever said that steel making was a process that is hard to understand...”  “perhaps if your presenter was that informative, more students will be interested to venture into the steelmaking industry!”  Thank you. . .  Questions and Answers