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Modern Steel Products (2014) - Ironmaking, Steelmaking: lecture 8

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so we had to wrapped up your
discussion of our standards in which started having a quick look
at the the liquid part of the
steelmaking because of the
number of things you should know about this in relation to come the qualities the internal quality of steels and and some basics like when do you alloyed steels unit with time exactly in and water so we had to do do was already make some headway but the number of things that idea added to the the original file that was on the the website for the class so let me go through them 1st and so as if you prepare for the quiz next on Thursday please look at the classic material because I I slightly changed despite its I added some material article in 1 material that might be relevant to the Furcal
just for your information on
that the blast furnace this is usually a separate entity from the UN steel plant wasn't so you then you basically carry the the liquid steel but from the the blast furnace 2 the steel plant wikis torpedo let labels or you also
have and charging ladles this style there's a which and both of them are usually mounted on the Reyes travel on rails through the plant 1 of the things so that it happens with these this do the IRA as you move it to the is there is a pretreatment analysts pretreatment is very important because that's the place where you were going to remove the sulfur that's so remember wait usually likes deals with very low sulfur content on last we want to make machine-readable steals yes the place where we removed this year due the sulfur to get very low sulfur levels it's actually the hot metal treatment care and that's storm which our culture and when museum "quotation mark will give you more details about you know would have to the culture as you added that basically you inject calcium and magnesia In the liquid metal and you also add why associated serial calcium oxide and so lucid equipment looks like this from Serie have a ladle the transport and and this is the injection station here and the calcium we usually use calcium carbide instead of pure metal calcium in this case but we do use magnesia concur you form the slag that then it and removed you have to remove dislike before he could still play but and this would you see here a forceful the reaction calcium carbide reacts with sulfur in In the metal to form calcium oxide this should be ready 2 types of carbon and of calcium sulfite Excuse me should be because please correct this error here calcium sulfide was 2 terms you don't have the slightest disengagement from the Cisco's himself and or direct uh reaction of calcium oxide with the sulfur to form calcium sulfite weren't so let me just make sure we got this right this is the 1st so the 1st reaction you you can form calcium sulfide lost 2 times carbon that's what it should be but you can also have calcium oxide from the line plus sulfur calcium himself lost oxygen this stance for oxygen in the In the Matter but that this is an area just because of and and you see that so as you add calcium carbide calcium oxide or this alloy of aluminum and calcium silicon and tells you you can reduce the amount of sulfur to very low levels and the time it takes about 20 2 30 minutes because of the time for the treatment to
dismantle as we said then is put in the basic oxygen steelmaking we already discussed what happened there just added this
light so you have maybe better visual picture of how the process actually happens the 1st you start by adding school this crap is added 2 of them for temperature control also to avoid damaging the were factories in Europe the furnace and here you poured a metal instead you blow 4 the blow you removed you taps the when when you when you don't win you you tap the metal fence you can venue make additions you make your 1st editions here following a difference many removed at the slack the about allying editions the
let's Francis look at manganese him so would depending on the steel grades of some steel rates don't need any manganese editions because we know we're happy with the attendance of a per cent of manganese them but if we want more work for constructional steals for higher manganese steel so the this is the moment during tapping where we were we add the manganese him the most Alinghi additions will occur at tapping no very often DE demands and the tolerances within which the steel is produced in vertical position of getting a very narrow nowadays and so we do what's called composition trimming so once you have measured D. the rough composition of U.S. Steel yes you do the Tremaine said this the exact the allying in this secondary metallurgical plant that's I won't do just basically the main subject of today will be to try to convey to you the importance of secondary mythology to make it still make some aspects that are relevant to just 2 products but in
this example here of course this secondary metallurgists you don't do anything in the do the U.S. you add when you do the tapping and needed the trimming in the secondary metal agenda and the secondary metal logy you'll see is usually carried out in some kind of legal ones and we have about some quite advanced techniques to add leading elements for instance protected editions for instance there is this the a method called composition adjustment by sealed Oregon bubbling combined with oxygen blowing so you work you put in vacuum the system in all 4 of the or protection system over EUR euros year metal and that's where you but you add the element here In controlled atmosphere or another method is to go to use of corridor wire to wire basically and the center you have you allocating a deferral following you want to add a new put it through a died into the liquid metal and other ensued it's protected against the environment students that get very accurate In addition the the many techniques many technologies for rugby U.S. we're not going to go into it nowadays most of the the U.S. are equipped with the top the oxygen plants and Balter stirring and it may also be some oxygen from the bottom of
we also discussed affected the BUX is basically a reactor where you remove a lot of elements mainly carbon Silicon manganese and also this is very important phosphorus we no that phosphorus is just like the sulfur in an element that we don't like to have in our steals it doesn't mean that there are almost no steel grades where we don't add phosphorus these exist but in general we will try to remove 2 phosphorus to very low levels of about 100 ppm and this is so that's actually going during the BUS during the late stages of the BUS when you've finished removing the carbon yes and you run the euro starting to oxidize your heart because that's that's when you get the right slag composition for the removal of phosphorus also note the fact that interview after you don't have to add any opt to any heat because the reaction the removal of carbon silicon manganese is very excellent Thermax so did the temperatures go up very high OK so there too elements that are of importance in the the U.S. that's the slant and the matter was and it is a very different phases will see to it the composition of the metal changes in the composition of the slack changes during the the blowing and so would we see that we see that toward the end of the blow you start to we have increasing the amount of Ethiopians flag and that's what's and this combined with the online editions it's very efficient for phosphorus removal of course there is some loss of of irony in this so How do I want you to think about it the dislikes like is basically an ionic solvents where else the metal steel is is a liquid alloys so what is of importance in the slide it 2 things 2 properties are of importance and its acidity or best sitting there and there it's oxidation potential so the acidity and of assistant is related to the ability of the slide to supply oxygen and iron for instance a basic slide readily supplies and I and to that's the case for why indeed the what the acidic /slash which is rich in I O 2 or P 2 0 0 5 years will do the reverse it will take away the I and oxygen and you have also neutral slabs of course which contained a both the life and soul of and oxidation reduction potential isn't all property that's related to the ability to transfer oxygen From the steel toed the slack all 4 4 from the selected to steal vial iron boxer think so In the liquid alloy we also have reactions but these are usually precipitation reactions and when do we have precipitation when when we when we have the temperature dependence solubility when we reach this temperature dependent on ability of the compound the compound will pursue but so far have manganese and sulfur in solution nothing will happen until I reach the solubility and when when it precipitates it forms a solid particles when the Coke carbon and oxygen when you Cross the solubility limit all form a gas OK right OK so so you don't need to To know this got all it in very great detail here at this probably covered in a course on melody but what I do want you to remember that the carbon is removed with oxygen yes yesterday that's I and we we have to remove large amounts of about 45 kilos per ton of steel and we eventually want to end at 500 ppm this were weak you can at 500 ppm of carbon take With plus or minus 100 ppm so you'll have 400 to 500 600 ppm of of carbon typically and the reactions of a reasonable and the first one is the main reaction is the formation of and under seal reacting to seal but the removal of the removal of carbon from the steel is from His by sea all reaction but the phosphorus again is removed in the but viable /slash I we need to oxidize and it's also very simple reaction the phosphors is a solution I oxidizer for appealed 2 in the presence of carbon yes it gets reduced again yeah that's why we cannot start removing phosphorus until the end of the blow when the the carbon content is low in and then it's also important to remove the P E 2 0 5 to the slack and that's being done this is for history and the total reaction here phosphorus CEO forms this compound in the slag plus 5 times carbon phosphorus temperature these are important 3 important parameters here and we'll see but that as I said we do reach high temperatures but the temperatures that but we need to have at at the exit of the steel plant are very well-defined also and so will will need methods to heat and cool the the liquid so we will need to make temperature adjustments in the steel plants right manganese silicon are easily removed to the to to the slag and sulfur as again as I said that's usually don't vise hot metal desulfurization I do want to say that removing phosphorus yes most about steelmakers removal in the but in the steel plant in the BUS there are some steelmakers in particular Japanese steelmakers which remove phosphorus In the hot metal yes that's another practice there was going to die let's concentrate on on the important things here but
and so let's talk about the oxidation so we've we've had blown a lot of oxygen on our metal that contains carbon and we have a very high temperature yes 1600 degrees 1 and so we that this again as I said we only need to consider seal because you too is it's not really relevant in the Nobuo efforts not formed so we need to look at equilibrium carbon and oxygen yes I have as a function of temperature and the pressure pressure the partial pressure of deceitful gaps so and in what we have is basically the solubility Co so when you know this all the little solubility Kurds if you plot you make a plot 6 directions carbon why direction the oxygen you get occur and this curse tells you that if you have a steel composition so that carbon and oxygen in solution in the steel that's in this yellow Range at 1600 deg C the carbon antioxidant will be in solution if we're above this yes c o will form you see gas will form so saying we have L a melt knows that contained I say here that this much carbon this much oxygen then the composition of the steel will move along the secure metric life to this point on the solubility curve and and this amount of oxygen will form C but the rest will stay in solution so I will be left for ends in this particular case with 500 ppm of oxygen and 500 ppm of carbon today and when the temperature drops this line will drop and I will form C O this cannot happen because state you take this deal with 500 ppm oxygen and 500 ppm carbon and you poor it ended in the mold yes that'll start cooling and then seal will for us because you will cross the solubility life and you're still will start to but yes so you you will be unable to cast that continuously you cannot do continuous casting because you material starts to be reset the materialist effervescence and bubbles the seal comes out so you need to to remove oxygen and carbon so you start by dioxin the oxidizing the Met you need to remove man OK and because this is the best you can do with carbon that's equilibrium right and of course what you do yes is there are 2 things you can do 1st of all you can say well let's see what is the effect of the pressure and so if we reduce the partial pressure of CO yes we can reduce the solubility so that's 1 of the things you can do we don't really use this will at this point in this after the steelmaking we don't use this that and you can see why it's why it's so difficult because if you say you you decrease the carbon you increase the oxygen content and vise versa if you decrease the oxygen content you increase the carbon content then you basically want to have both very low or at least control get ready L so we can do this now we can reduce the the pressure what we actually do will work in 2 steps will do 1st that the oxidation by adding elements that are very reactive for like 2 4 walks sites such as aluminum silicon and or manganese yes we can reduce it but when you reduce the amount of oxygen we're still left with carbon in solution and that will be taken care of in another step In vacuum treatment we did I'm very important here the the oxygen is removed by adding the oxidation a additions and aluminum silicon silicon and they the final reduction To get very low carbon contents we will use Turkey so let me 1st then talk about considered the oxidation right removing oxygen by adding aluminum and those of further at 1600 and 1 buyer of pressure the oxidation which sealed that's the solubility line that if I do if this is now is not carbonized assists and no or what it with a silicon carbon and aluminum also so now add silica you could see the solubility is slower this is carbon in the oxidation would comment at a new low vacuum can best but the best is of course you can see aluminum you could see how what the solubility is of aluminum yes it your mettle so that's why obviously that's the choice right we don't need vacuum which is tossed some alumina in forests and gone is the oxygen that could have reacted with the carbon to do To make my steel after vessel this process of adding aluminum to the European your liquid metal it's called killing kill you kill the steel so you and that you avoid making these bubbles that well that makes the material difficult or impossible to catch him it it's took so and that's why we very often speak talk about low-carbon aluminum killed state but that's almost nothing because most steel spire aluminum cans right well not really and some skills are also silicon deals but will talk about this animal or so so here and we pick up began with the the electric arc furnace where where we had to already introduced on Monday that get here in the in the steel plant and also have steelmaking unit which is the electric arc furnace and then a secondary mythology which was discussed in more detail and I think we had already the looked at a typical mass balance In and Out of the electric arc furnace and obviously it doesn't it comes as no surprise that In this case you introduce
about a ton of scrapping and you get about a ton of scrap out right you don't make new steel here in the electric have basically a scrap based route again I'm saying that it's only scrap that you can process in an electric arc furnace is not 100 per cent correct there is 1st of all a large variety of scraps on the markets you have what we call shred yes shredded is the highest quality scrap usually comes from carmakers it was when it comes it comes from recycling cars as very low carbon in general and we have Bush-Cheney yes that comes from car makers all the oldest steel that they don't use them because it cuts off parts that is not being used in the construction of automobiles but also very high-quality since then we have a plate and structural the fuel when you were when you scratch a boat for instance the ship known all these plates are our scrapped and go through 2 electric arc furnaces in bundles and then we have things that look more like the stuff we're used to but hope to break it IRA which is aspiring or plus editions of 1 to 2 per cent of carbon you have pallets balances also warned yes that's pelletised and form little balls that is that our free reduced direct reduction reduced IRA can be used for also think Irish soda you can feed into an electric arc furnace a material that comes out of a blast furnace and depending on the products you make yes there will be requirements for distract me and in particular the residuals and residuals are elements such as copper they're called cruel Molly 10 yes which depending on the applications have to be law and particularly if the applications are in the bowl to borrow automotive act applications you want very low no residuals but if you want to make for instance Reebok that deserted the reinforcement bars that you use when you are in connection to on cemented he has to make concrete for the construction of buildings there did the indeed the requirements are very much less in terms of residuals much of this is basically repeating some of the things that have been set up there so now L we we've had the hot metal production we've had this primary steelmaking either an electric arc furnace or In the BUS and we see that in the the listed all the reactions that occur there they're basically oxidation reaction you remove elements yes what we're going to talk about now is very important it's what we call secondary metallurgist secondary metal or secondary steelmaker also ladle metallurgist and you do a lot of things there yes and that's basically where you make the quality of its the steel the composition the internal the cleanliness of the steel is achieved there will see what that entails and then the temperature and the temperature is may not be so important for products but you'll see in a moment that it is but you need specific temperatures to achieve casting the or current so let's see so the secondary metal adjacent that that met the hot metal pretreatment B OF converted that's that's steelmaking yes so what comes after words between D b left converter and the continuous casting that's what we call a little melody or secondary melody or secondary steel and there are no steps processes In this secondary Meligeni argon stirring vacuum treatment he an inclusion modification he asserted that the most important steps you don't always have to applied there yes but this independence from product to product in this case will just go through you I could go through them as if the product needed to but this the argon stirring do it's used to homogenize the matter the liquid but then what do we homogenized while we homogenized temperatures and we homogenized composition but will also see that this argon stirring helps the removal of nonmetallic inclusions but also there has a cleansing effect the vacuum treatment is used to new carbon nitrogen hydrogen removal to very low levels to the ppm level then we can do adjustments of temperature In the heating part and then we modest we remove and modify inclusions nonmetallic inclusions in the the so-called inclusion modification steps and that's usually referred to as that calcium treatment OK and then when the metal has the right composition the right cleanliness and the right temperature it's ready for forecast after that you will not ever be able to remove nonmetallic expect you will never be able to change the composition anymore OK I this is it's very critical this is really critical part of the products of
these is the son of a label isn't that basically you know if you look it up in the dictionaries is basically a container right but it's at least containers the let labels are pretty complex In the In secondary metal orgy To date the look like this on the exterior so you have a the refractory lined container basically right with as that on which you can fit cover and the cover has openings for electrodes so you can do some heating you this openings for oxygen blowing this you can do Yang bye for instance why injection like we saw you can go out there and other elements of I'm bunker and shoot him Of course if there are gasses formed you can there a few could here and you can have also bubble In all gasses are gone for instance and you can have some powder that elements added in the form of power refractory linings of course yes and at the bottom we can do that and decide you can bubble and argon to stir the the metal so it's it's homogeneously and the temperature is homogeneous and the composition is and in addition you remove nonmetallic conclusion that you you have a sliding gate here it is used to pack to remove the the matter because this is view here let's have a this is what would you and put you have electrodes Yukon is also a place where you do a lot of sampling as this is the wife he drawled here this is shoots where you can do follow and you have censorious for temperature the etc. right Salesforce have a look at him what happens in for instance a vacuum of St vacuum mythology part of the secondary metallurgical so you this is not necessarily apply to all the steals as it's only applied to the steals where you want to have ultra-low carbon levels so so the there 2 types of vacuum the treatments ones uses this the vacuum d Gasser has so you put this can this vacuum chamber into the the melt him he has to pipes 1 pipe here and 1 pipe on the lower left and so you pump but that in fact with concurred With the and in 1 of the legs 1 of 2 tubes yes you be refractory so porous menu blowin articles here to the little argon bubbles so what happens is that when the density of this steel is lower then there's steel His and as a consequence of this works as a pump yes this deal goes up and it comes in the vacuum chamber and goes down this way that because you reduce the density of the distilled by just having small Oregon bubble the rights and this is called a snorkel this this this process called work so in the and in the vacuum of yes we have busily reduced vacuum so the reaction of sea the carbon a solution was options solution this Musial yes an icon of further removed the the carbon and I can use the additional oxygen here to reduce C O levels even further with oxygen to form sealed because you have nicely controlled atmosphere here you can also make a loading editions and at the same time right there and and you also have argon stirring and you can do aluminum killing at this stage as well but it would still like to point out is that the carbon levels can be as low as 10 ppm and the nitrogen levels usually on follow 20 ppm the other technique is a Tancredi gas here you you put the the ladle into a container In the vacuum container and and and that's where you punch the vacuum it's a little bit slower yes and as the conventional Tancredi gasses base leave a vacuum container yes and at the bottom you know you bubble Oregon 2 economics to steal you can also do a deeper decarbonization by doing oxygen blowing and this is what it looks like in but in practice because the process is lower usually people have that used to Tandy gasses in tandem with them this is useful or because it has lower investment costs in comparison to the if anyone that this this the
cancer is called Aurora style oracle R H D gas is very the industry
standards in this this is what it looks like in practice this is a standard part gasses and this is 1 where wouldn't oxygen levels Due to the bubbling is only in 1 of these elections but it wasn't as well as at the levels of the a carbon that you can achieve are typically 10 be with and R H and gasses and with attend Degussa about 20 ppm but that's already a very nice for many applications all right so we know we need to go back to b the process of the oxidation because of the width of the oxidation With the the aluminum we have created an issue and the issue is that of nonmetallic inclusions right where are
talking about the problem is the main the worries yes With the nonmetallic inclusions in steel products is are usually related to mn an e-mail to its 3 and why is that because if we don't do anything about the the tickler nonmetallic inclusions recalled nonmetallic because this is a sulfide and this is an oxide yes yes we for this these MMS In precipitates and the big him them at grain boundaries In my caste structure and in the cast structure I form L 2 3 dendrites intent when this material if we don't do anything and we're all this material this eminence we former very flat and long stringers in the Microsoft rupture yes and the yield to reforms small brokers Group the crystals the all with weak results in the Microsoft rupture and so what we will do what and you'll see animal and why we do this we want to change this this also you what is bad about these and failed to 3 particles and then I'll show you what we want so which will want to do is we want to modify them into rounded small rounded compounds in which we usually look like calcium eliminates With ring around of calcium sulfide ore and manganese sulfur why don't we like these the company seasonal momentum will 1st of all we don't like them because they gave us production problems production problem number 1 is clause as he bends submerged entry nozzles so submerge entry nozzle when you poor to Mattel Out of the the label In the Castor him as these and you go and intermediate liquid container here and then into the casting that there the cast has this stew here this is called it's a refractory tubes called the secondary isn't submerged entering also has and the metal has just to flow through it it turns out that if we have these conclusions these inclusions swell foreign deposits this is a nice too yes if we have deposits on this stew you can see here yes the Chu will gradually the the pinched off the clock yes entered the flow through the tube will be very unstable you and I and that'll give you very serious casting problems yes unstable of metal flow and an independent than so you want to avoid is the most skipped dislike because there is still 1 of the things that 8 these nonmetallic inclusions have is they have they can have a big impact on failure of the materials the steel model for instance this is the wire the steel wire yes and no and you can see it's a very small steel wire it's made it so that's why your and it's broken it's broken by fatigue and there is here editors there is the nonmetallic inclusions so forth wire products and in particular wire products that are use friends of tire cord or for valve springs for springs that are you know the dog in the fatigue testing operate in very harsh fatigue conditions and you want to avoid these nonmetallic inclusions because they will give you prematurity failure OK so that's any a reason to avoid them
but the just go obviously In particular you want to avoid the alumina base hard alumina inclusion and 1 of the things you do for these particular but wire raw products is instead of using aluminum killed materials you have you're going to use which calls send killed yes and there that you remove the oxygen not by adding alone but by adding silica silica them there so no clotting problems and the inclusions are liquid so that means that at the moment you casting yes you don't get solid particles that attach themselves to the nozzles once and former I don't think and clog the however this steel is set to be we we make dirty steel in the sense that show you next slide so if you look at the amount of oxygen in the steel as a function of the amount of aluminum basilica you see that fought for Silicon This is the Life and and for aluminum this is the light that means that even tho I had a very small amounts of aluminum I can get extremely low oxygen levels and that's typically if you I get an aluminum killed still you'll see there will always be story to 500 ppm of aluminum in your composition and that's the reason that's the dioxin that aluminum the oxidized as very low the PM's of you know the aluminum if you d oxidize with silica dust even if you add 1 per cent of silicon lopped more than this you still have 50 10 times as much oxygen in your state so that's why we these send me Khaled golden summer killed because it's not really fully killed as we call them also dirty steals because this dozens is not because it's just because of youngest more oxygen and but in many cases we will promote not sought in certain cases such as the valve springs tire cord yes we absolutely want to avoid is very hard alumina particles and that and we will use silicon kills steel grates good another example forming defects this isn't it can consider can but this is a cat it's been deep drawl still can do drawn and you can see here that the fracture the depend as fractured as and when we looked at the fracture is analyzed we see a nozzle clogging up issues inclusion in the car so inclusions are very important when they do this steel we use is either very has a very small thickness or small diameter because in 1 room particle can can destroy Indian this 1 alumina particle can destroy a wife because it's it's in the section war or aluminum particles can destroy give early fatigue fracture of a spring yes we did only to have many so that's what we I need to do something about these aluminum conclusions another thing and
that's related to the MMS yeah I 1 of the things we like to avoid Our is is a combination of 2 5 is a combination of abandoned might rastructure nose and Hi aspect ratio inclusions high as recreational clues these and this is typically eminence manganese sulfur because manganese sulfide it is a plastic compounds would be forgeries is when you roll material it gives you they very Long a high aspect ratio inclusion death and that can give rise to what's called Lamela cheering you have to imagine you have a plate With these the compounds like this and then you well this place yes you well display and and when you well this certainly did the plates are a thicker as you you can get very important shrinkage stresses yeah and and close to the heat affected so him and when you get the shrinkage stresses act as tiny internal cracks in and you can get very easily which called Lamela Lamela Teri and so the these inclusions will act as nuclear meekly Ifop for small cracks and of course you don't like that at all right so the sulfides the alumina particles we need to take care of themselves look at some
of but they're by no means the only about precipitates and they're in there and still business we talk about type a B and do inclusions nonmetallic inclusions of the type ace are sulfide tied these are oxides type C our silicates and the art globular writers basically all the rest if you want to know the a spot for all practical purposes it's it's basically Amaneser and they are plastic they will be formed classically in the matter for instance during a role type or oxides usually aluminum oxides and they're broken an ankle as because they knew they form the the larger particles which which were broken during the role at sea silicates particular many silicates of plastic and the make sure complex mixture of calcium aluminum and manganese magnesium oxides are blocking and and so these will be the tidy precipitous the kind of precipitates that are OK and Type C basilicas are also OK it's so the bad ones are Type a and Type B but 1 of the ways let me just go right and 1 of the ways we removed the inclusions is simply by argon stirring yes so In the metal it is in our legal we you remember we often inject this Our goal guests and the Argonne gas makes basically bubbles has ended so it's stirs the metal around so the particles can attach themselves to these bubbles or be carried by the flow and get into contact with the slack and then there the oxide is is captured by the inclusion is captured by the slack now it's very important is that when you have it small In his small diameter particle 25 micron nonmetallic inclusions in it's speed will be about a quarter of a centimeter per 2nd if you don't do anything it's so it'll take you it'll take about 20 minutes 2 go 3 meters yet so this tells you that if if you didn't use are gone yet I knew you just like to steal their stand there for 20 minutes a particle here alumina particle here of this size you would manage to get it it would float because it's it our oxides of the density Florida and that it would miss float too this lack but if it's a large particles yes at the time it goes fast but removing the tiny particles becomes critical and and that's the reason why the are gone and stirring helps In case of argon stirring that's 1 way of removing the exclusions the other thing we do this week we are going to modify these inclusion we're going to turn them into something else OK and that we do this by adding culture look at the this is the phase diagram both calcium oxide and aluminum yes and you see that at around 50 per cent of aluminum we have the Lowell temperature you tactic yes a low-temperature you tactic that is below the temperature of casting that means that this compounds here In the compounds here if we ate if I can get compounds with this composition they will be liquid when I cast so they will not form a solid particles that can attach themselves to the but in the the Jew yes and cause clogging so how is this Dong while it's simply instead of making having only aluminum we made aluminum and calcium compounds and they have names 68 to 1 yes basically C stands for calcium and a stands for aluminum prices here 1 means CA L 3 because of the Richard this compound littered the richer we can make the uh the modified oxide in calcium the lower its temperature and the 1 of the better the cast ability will be material however we have to watch out if we think if we add too much calcium then we will form calcium sulfite they counts himself was also bad news because it'll cost you brochure it will destroy did the refractory bye the abrasion and erosions of it and I'll create more pacific and Inc nonmetallic inclusions but recently was found out that but if these compounds in addition to containing the calcium also contains magnesium NGO the temperature the melt temperature is even lower so and you contributes to liquefaction but so these are the inclusions can be identified this as an example here this is a label exclude inclusion it contains it's basically spin out its Fangio to 3 it's it's not it's it's not been influenced by calcium and this is you can see that small particles here this is calcium sulfide that's also not God you don't want calcium sulfite because you can see it also creates these particles this is an inclusion here 4 of em and as this you can see along inclusion here continues there yes and you can very easily and this is a calcium felt this particle here is calcium eliminate you can see contains aluminum calcium right so I see this
as an example here of manganese sulfide very long years and because they're so long His these corners here act as cracked it yes just as an example here of the inclusion here you see that the center part of the inclusion here it is the Spinella said NGO field 2 or 3 years and that due to the aluminum additionally it's now coated with a the calcium sulfite later yes because this the reaction to the modification of this your aluminum August canal this is fire a solid-state reaction we're very often see these compounds oxide yeah I think this is an example here again spin out on this side and hear alumina on this side can look at so how how is this done in practice and what happens in practice what we basically Mattel metallic calcium to Wabasso is 1 this how we can put it but says it gives a very violent reactions and most of the calcium is evaporated and that is good very low densities of very low density metal so you really have to use special techniques to get it into the matter like a quarter wire for instance it is and in it it's very quickly evaporates remembered the metal is at 1600 the boiling point of calcium is less than 1500 right so it's it's going to be it's difficult to keep it in the industry right and it has a very low solubility and we did actually it's kind of difficult to measure and the different reports high or low OK so the the type of edition the way you can add it is is at it as a calcium carbide yes cobble and I tried that these companies have very low volatility citation because they're not matter and we use them when we do desulfurization of of the hot metal remember but in usually in steelmaking we use of binary your Ternary alloys of that contain calcium as a form of a wire or accord wire that this is poured into the into the liquid metal so Of the
calcium we inject yes we inject Astwood despite the most of it evaporates and most of his and some goes into the the matter and so what what happens there Kallstrom is very reactive yes and it's it's so what what happens when it will offer solid some of it will go into solution in and then it will react with sulfur and with oxygen 1st that's basically would have what happens for them and then these 2 compounds will react with the alumina or where to spend now to modify the considered will former coating around this Burnell a coating around this and ends and slowly modified these solid compounds In 2 calcium Rich compounds which which will have a low temperature consists of this is just down the street so you can see there why form calcium sulfite and calcium oxide very quickly because it's is livery stable and and also went when you add calcium to the melt instead of forming a asks you form calls himself I located just so it's also very efficient in terms of the GNU
removing the self and again I'm not going into I the details here I just want to make sure that you understand that this removal of nonmetallic inclusions is complex this and there you have to add just the right amount of calcium has so that you have urine in the Ternary you you liquefied you are the EU nonmetallic includes and and then you don't have any the nozzle clocking if you have if you composition is is very rich in calcium particularly counts himself and then you also have a problem that's because this did the count himself fired will cause very strong abrasion of you're not your your muscles and that will give you another type of inclusion OK and then the
we're it's also important to realize that when you add the calcium to the Mattel there's actually the 1st types of articles you for on tells himself and calcium oxide so and it's only after you know after the treatment has that after that do the the calcium oxide calls himself and have reacted with dioxin that you you you make you stop making the liquid nonmetallic inclusions so it it does need some time yes and this a very I think down for people that are in and still manages still a very active area of high temperature research because of the reaction is very complex yes so at the beginning we have Our particles calcium and oxygen will react with these particles to form Kallstrom illuminates his account eliminates well become richer and richer in calcium as time goes on as well eventually no become liquid the there is a secondary reaction where we form weakened form calcium sulfite solids as if from the calcium levels are too high for instance yes temperature
control of distilled that's pretty simple why do we want the temperature control because we want to have a stable casting conditions all right so what will affect the steel temperature low when you tap you when you go from the basic oxygen furnace to the ladle you lose temperature about 60 degrees but when you add a low heating elements the solid so in general that gives you temperature reduction not always necessarily reduction because there may be a heat of dissolution if it can be at Exeter might the dissolution but in general we have a temperature decrease when we add following elements and of course the natural heat losses just a few of them and the temperature drop is about half a degree per and finally and you also have argon public when you are bubble the Argonne who stirred a metal around and you lose temperature so that's as a parameter you always keep an eye on on the temperature so most modern supplants have models so they know what to heat loss is so during secondary steelmaking and they can take actions if the temperature is too low or if the temperature is too hot so let's have a look at what can they do to adjust the temperature well we can have arc furnace ladle arc furnaces it's basically on the label on which we can fix it the atop which has electrodes which will heed the the metal basically providing an electric arc in so we we can heed these are not very powerful system so you can increase the temperature 4 degrees 4 minutes 3 4 degrees men at full power you can do chemical heating yes and the trick is to add aluminum too and so you you inject it's the oxygen menu put in aluminum right so obviously this will heat and when the oxygen reacts with the ability to walk into steel obviously when you do that you introduce the alumina particles which you have to remove afterward visitors this is not the used very often there is prohibited when you make a very clean steal you can decrease the temperature obviously simple ways to do it Argonne bubbling in about half a degree minute you lose him when you just hold it and you can make scrap editions so you select high-quality scrap you know the composition of a new just put it added to your Mattel to reduce debt after France's cooling rate is set about a degree if you add 1 kilo of scrap to be about 200 tons of of steel kept so you can eat you can call it you do have to take the temperature into account right and then you're
ready to do the casting begin and will stop here and will continue on with continuous casting in Bonn on Thursday morning thank you
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Metadaten

Formale Metadaten

Titel Modern Steel Products (2014) - Ironmaking, Steelmaking: lecture 8
Serientitel Modern Steel Products
Teil 8 (2014)
Anzahl der Teile 31
Autor Cooman, Bruno C. de
Lizenz CC-Namensnennung 3.0 Unported:
Sie dürfen das Werk bzw. den Inhalt zu jedem legalen Zweck nutzen, verändern und in unveränderter oder veränderter Form vervielfältigen, verbreiten und öffentlich zugänglich machen, sofern Sie den Namen des Autors/Rechteinhabers in der von ihm festgelegten Weise nennen.
DOI 10.5446/18339
Herausgeber University of Cambridge
Erscheinungsjahr 2014
Sprache Englisch

Technische Metadaten

Dauer 1:15:13

Inhaltliche Metadaten

Fachgebiet Technik
Abstract Professor de Cooman talks about ironmaking and steelmaking. This is a part of a course of lectures by Professor Bruno de Cooman, of the Graduate Institute of Ferrous Technology, POSTECH, Republic of Korea.
Schlagwörter The Graduate Institute of Ferrous Technology (GIFT)

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