1. CONTINUOUSCASTING

2. SO,WHAT IS STEEL? Steel is an alloy of iron and other elements,including carbon. When carbon is the primaryalloying element, its content in the steel isbetween 0.002% and 2.1% by weight. Thefollowing elements are always present insteel: carbon, manganese, phosphorus,sulfur, silicon, and traces of oxygen, nitrogenand aluminum 3. CONTINUOUS CASTING Continuous casting, also called strand casting, isthe process whereby molten metal is solidified into asemifinished billet, bloom, or slab for subsequentrolling in the finishing mills. 4. Most basic metals are mass-produced using acontinuous casting process, including over 500million tons of steel, 20 million tons of aluminum, and1 million tons of copper, nickel, and other metals inthe world each year 5. The continuous casting has severalconfigurations to produce the steel as vertical,vertical with bending and curved type.. 6. Curved machines are used for the majority of steelcasting and require bending and / or unbending ofthe solidifying strand. 7. WHAT DO WE DO UNTIL CONTINUOUSCASTING ? Preparation the steel by adding some materialswithin the different furnaces such as BOF,EAF. 8. BOF(BASIC OXYGEN FURNACE)1.Molten pig iron from a blast furnace is poured intoa large refractory-lined container called a ladle2.The metal in the ladle is sent directly for basicoxygen steelmaking 9. 3.Filling the furnace with the ingredients is calledcharging. Molten iron from the ladle is added asrequired by the charge balance. A typical chemistryof hot metal charged into the BOS vessel is: 4% C,0.20.8% Si, 0.08%0.18% P, and 0.010.04% S.4.The vessel is then set upright and a water-cooledlance is lowered down into it. The lance blows 99%pure oxygen onto the steel and iron. This melts thescrap, lowers the carbon content of the molten ironand helps remove unwanted chemical elements5.Fluxes (burnt lime or dolomite) are fed into thevessel to form slag, which absorbs impurities of thesteelmaking process 10. 6.The BOF vessel is tiltedagain and the steel istapped into a giant ladle. 11. ELECTRIC ARC FURNACEArc furnaces differ from induction furnaces inthat the charge material is directly exposed toan electric arc, and the current in the furnaceterminals passes through the charged material. 12. SMELTING PROCESS OF ELECTRIC ARC FURNACE 13. AFTER FINISHSMELTING? 14. THE MORTEN STEEL IS NOW IN LADLEFURNACELADLE FURNACEThere is an important thing that should notbe forgotten!!!! Before the tapping from theEAF or BOF to the LF, the LF has to bepreheated.. 15. SO,WE ARE READY TO START TO THECONTINUOUS CASTING 16. THE BENEFITS OF CONTINUOUS CASTING Considerable energy savings Less scrap produced, i.e. improved yield Improved labor productivity Improved quality of steel Reduced pollution Reduced capital costs Increased use of purchased scrap whenoutput is maximized 17. 1) The liquid steel comes from the steel plant in a ladle2) From ladle it is tapped in a tundish 18. 3) Liquid Steel is flowed through the nozzle to mouldfrom tundish. The flow rate through the nozzle into themould can be controlled by a stopper in the tundish4) The mould is a rectangular copper box without a topand a bottom5) The outer shell is being grabbed by a driven roll justbeneath the mould, pulling a strand of steel out of themould.6) The core of the strand, as it exits, is still liquid;because of that, the strand proceeds through asecondary cooling section7) The strand is bent from the vertical plane tohorizontal plane using rolls 19. 8) At the end of the cooling section the cross-section ofthe strand is completely solidified, slabs are thencreated by cutting the strand9) These slabs are put in a tunnel furnace to let themhomogenize10) After a while the slabs come out of the furnace;subsequently they are rolled out, further cooled andfinally coiled 20. TUNDISH 21. The tundish holds enough metal to provide acontinuous flow to the mold, even during anexchange of ladles, which are suppliedperiodically from the steelmaking process 22. The shape of the tundish is typically rectangular, butdelta and "T" shapes are also common. Nozzles are located along its bottom to distributeliquid steel to the molds 23. The tundish also serves several other key functions!!! Enhances oxide inclusion separation Provides a continuous flow of liquid steel to the moldduring ladle exchanges Maintains a steady metal height above the nozzles tothe molds, thereby keeping steel flow constant Provides more stable stream patterns to the mold(s) 24. The tundish is a refractory-lined channel consistingof an inlet and outlet sections and sometimes hasflow control devices, such as dams and weirs or abaffle with holes, along its length.DAM BAFFLEWEIR 25. A tundish may have a refractory-lined lid, and hasbottom ports that are assembled with slide gates orstopper rods through which the melt is teemed intothe mold 26. TUNDISH OVERVIEW 27. THE USED DEVICES IN THETUNDISH IMPACT PADS: Designed to redirect steel upwardand outward for enhanced steel residence time in thetundish and prevent short circuiting to the closeststrand(s) Also used for optimized drainage and yieldenhancement for multiple radical grade changesequences 28. BAFFLES: While in the tundishes, impurities (called"inclusions") in the molten steel float to the top,forming a "slag" layer of impurities, and the pure,substantially "inclusion-free" metal exits from thebottom Depending on the size of the tundish, and the flowrate of molten steel, the molten steel may not alwayshave enough residence time in the tundish to permitthe impurities to float to the top.Therefore,the bafflesare used. 29. DAMS: This device helps to modifying the insidebottom surface of a tundish for continuous castingmolten steel to minimize turbulence thereby reducinggas bubble and slag entrainment during continuouscasting of steel, especially when initially filling of thetundish.DAM 30. Thermocouple: It reads the steel bath temperature inreal time at a fixed location inside the tundish. Diffusers: During operation the Tundish Gas Diffuserwill help reduce "dead" areas within the tundish andprovide a more stable steel temperature in the tundishbath 31. Stoppers: This is used to control the molten steelflow from the tundish to the mold 32. Slide Gates: Tundish gates are provided with 3plates in order to avoid the movement of thesubentry shroud in the mould during the flow controlby throttling. 33. Metering Nozzle: Key features of nozzle changersystems include:1) Improved casting operator safety2) Enables longer casting sequences3) Improved metallurgical quality4) Flexibility 34. Submerged Entry Nozzle: These refractories aresubjected to severe operating conditions such asthermal shock,molten steel erosion,and slag attack.Upper Nozzle 35. THE IMPORTANCE OF TUNDISH The melt remains in the tundish for a relatively shorttime, reflecting the continuous nature of tundishoperation Thus, the major refining reactions such as deoxidationand desulfurization are carried out in the ladle.The goals of a tundish are tominimize heat loss, deliver themelt evenly into molds, minimizethe formation of macro inclusions,andmaximize their removal. 36. INCLUSIONS AND DEFECTS Non-metallic inclusions are a significant problem incast steels The mechanical behavior of steel is controlled to alarge degree by the volume fraction, size,distribution, composition and morphology ofinclusions and precipitates, which act as stressraisers The inclusion size distribution is particularlyimportant, because large macro inclusions are themost harmful to mechanical properties. 37. The ductility and durability are significantly impairedby large-sized, non-metallic inclusions in steel.The samples of inclusions are shown above 38. Non-metallic inclusions in steel are of two kinds, andeach has its different mode of formation.1. one is indigenous oxide inclusions which form bydeoxidation of the steel melt.2. The other kind is exogenous inclusions, which formby reoxidation of deoxidized steel melt by air or bythe entrained slag into the melt during the melttransfer from ladle to mold.INDIGENOUS EXOGENOUS 39. DEFECTS IN STEEL PRODUCTSFlangeCracked CansSlag spots oncold rolledsheetLine defect oncold rolled sheet 40. THE FOLLOWING FACTORS NEED PARTICULARATTENTION IN MAKING A TUNDISH EFFECTIVEFOR REDUCING MACRO INCLUSIONS:#1. Steady state period of casting requires: Melt flow with less turbulence along the tundishflux/melt interface No short circuiting of melt flow from the inlet sectionto the exit (tundish nozzle) Minimal dead volume for the melt in the tundish Sufficient residence time for the melt to promoteflotation An argon gas shrouding pipe or long nozzle for ladlemelt discharge into the tundish Thermal insulation and protection against reoxidationby argon gas injection with lid or a tundish flux cover 41. #2. Non-steady state period of casting requires: Prevention of slag carry over by vortexing anddraining from the ladle to the tundish The above slag carry over issue also applies totundish to mold transfer Suppression of turbulence caused by impinging meltstream to the tundish at the ladle opening Sustaining an inert atmosphere at ladle opening andladle change Active compensation for temperature drop 42. TUNDISH DESIGN 43. The tundish can be designed according to thefollowing conditions: The amount of the production:The volumes of ladle,BOF,EAF The various of the production (bloom, billet, slab) The number of the strands The features should be placed to float the inclusionsfrom the morten steel to the slag( dams, baffles,weirs ) The control of melt temperature to an appropriate levelfor feeding into the mold The control of flow rates ( nozzle port(s), slide gates,stopper rods ) The adjustment chemical compositions 44. Various technologies such as a long nozzle or aninert gas shrouding pipe have been implemented toreduce air reoxidation and slag emulsification. Tundish thermal state during continuous casting asfunction of heat losses through the tundish shell,insulation of the steel bath and temperature. 45. TO INDICATE THE VOLUME AND THE NUMBER OFTHE STRANDS OF THE TUNDISH This exactly belongs to the amount and various offactory production The number of molds is usually 1 or 2 for a slabcaster, 2 to 4 for a bloom caster, and 4 to 8 for abillet casterBLOOM SLAB 46. 1) ANCHORING SYSTEM The anchoring system is done to be hold thepermanent lining slightly to the tundish. This anchors are assembledto the tundish walls at certaindistances by welding 47. 2) INSULATION MATERIAL The ceramic fiber panel is used due to its low thermalconductivity and low heat storing between the tundishwall and permanent lining. These may be showed according to the productionconditions and the volume of tundish 48. ANCHORINSULATIONMATERAL 49. THE PLACEMENT OF NOZZLES AND STOPPERS Before the permanent lining process is begun, thenozzles should be positioned to the outlet points atthe bottom of the tundish These devices are used to control the fluid flow fromthe tundish to the mold. The used of these may be showed differenceaccording to the various of production and theproduction conditions 50. 3) PERMANENT LINING The permanent refractory lining made of aluminous-siliceousrefractory concrete may be made ofrefractory bricks or may be a cast or rammedmonolithic lining or a combination of the two. The expected properties from the permanent liningare showed on following: Almostly zero cement should be The particule distribution of admixture should belower These may be lowest bonded cement according tothe production and the materials 51. The hot ratios of expansion of the componentsshould be close as material properties The high resistance against the high temperature,wear and impact The application of this lining should be easy 52. The permanent lining is generally made of highalmina refractory(%70-%93) and is the thickest partof the tundish lining. This lining has a low reactivitywith magnesia materials to form a surface workinglayer. Aluminous-siliceous refractory concretes proved thebest in the second layer. These are the materials that contain cement binderusually aluminate cement, which imparts hydraulicsetting properties when mixed with water The most common binder used in castables is HAC(high alumina cement) 53. Other binders that are often used include hydratablealuminas and colloidal silica When the working temperature is increased,theAl2O3 content should be increased.Because of this,the thermal conductivity and flexibilty. These monolithic castables should be dried, sintered,and preheated before being put in service to preventexplosion spalling 54. CAC in castables: The refractory concretes aredivided into 4 main groups:1) Conventional Cement Castables,CCC,high cementcontents(>20% CAC)2) Low Cement Castables,LCC (6-15%)3) Ultra Low Cement Castables (