Modern Steel Products (2014) - Continuous Casting: lecture 9

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Modern Steel Products (2014) - Continuous Casting: lecture 9
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9 (2014)
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Professor de Cooman talks about the continuous casting of steel. This is a part of a course of lectures given at the Graduate Institute of Ferrous Technology, POSTECH, Republic of Korea.
Keywords The Graduate Institute of Ferrous Technology (GIFT)
Ladle (foundry) Semi-finished casting products European Train Control System Ladle (foundry) Steel Eisengießerei Scouting Bending (metalworking) Spray painting Überschallstaustrahltriebwerk Roll forming Game Speise <Technik> Cartridge (firearms) Packaging and labeling Institut für Raumfahrtsysteme Continuous casting Molding (process) Molding (process) Water vapor Material Water vapor
Ladle (foundry) Lint (software) Blow torch Eisengießerei Scouting Bending (metalworking) Watch Volumetric flow rate Packaging and labeling Gentleman Commodore MAX Machine Surface mining Molding (process) Firearm Material Distributor Van Typesetting Mat Semi-finished casting products Ladle (foundry) Cut (gems) Steel Hüttenindustrie Intermediate bulk container Eisengießerei Bending (metalworking) Speise <Technik> Locher Casting defect Ammunition Saw Sizing Speise <Technik> Diving suit Gate valve Molding (process) Water vapor Gun
Nut (hardware) Eisengießerei Scouting Buoy tender Alcohol proof Packaging and labeling Gentleman Forging Molding (process) Material Melting Water vapor Typesetting Tin can Truck Semi-finished casting products Steel Eisengießerei Captain's gig Machine Locher Casting defect Mine flail Bloomery Gas compressor Wood Powder metallurgy Food storage
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Ship breaking Unterseeboot Semi-finished casting products Steel Steel Eisengießerei Casting defect Suitcase Pen Scouting Last Saw Volumetric flow rate Cartridge (firearms) Fahrgeschwindigkeit Dashboard Gentleman Molding (process) Molding (process)
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Semi-finished casting products Semi-finished casting products Steel Hot working Steel Automobile Eisengießerei Eisengießerei Vehicle Captain's gig Ford Transit Clothing sizes Finger protocol Kutter Sizing Lace Cartridge (firearms) McDonnell F-101 Voodoo Blow torch Surface mining Rail profile Material Mail (armour) Clock face
Semi-finished casting products Semi-finished casting products Steel Eisengießerei Scouting Bloomery Wire Wire Bloomery Scouting Rolling (metalworking) Surface mining Dashboard Gentleman Klassifikationsgesellschaft Guard rail Rail profile Semi-trailer truck Material Flatcar
Semi-finished casting products Semi-finished casting products Steel Surface mining Klassifikationsgesellschaft Semi-trailer truck Bloomery Sheet metal Scouting Flatcar Bloomery
Semi-finished casting products Semi-finished casting products Steel Scouting Clothing sizes Bloomery Blanking and piercing Bloomery Scouting Surface mining Cartridge (firearms) Gentleman Cartridge (firearms) Klassifikationsgesellschaft Surface mining Saddle blanket Flatcar Sheet metal Last
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Typesetting Ship breaking Semi-finished casting products Semi-finished casting products Eisengießerei Machine gun Bloomery Scouting Bloomery Surface mining Gentleman Screw Klassifikationsgesellschaft Remotely operated underwater vehicle Ship of the line Molding (process) Semi-trailer truck Material Sheet metal
Semi-finished casting products Sharpening Semi-finished casting products Mountain Dashboard Cartridge (firearms) Forging Backpack Casting defect Rail transport operations Clock face Van
Semi-finished casting products Stagecoach Semi-finished casting products Ford Focus Steel Stagecoach Mixing (process engineering) Brush Rolling (metalworking) Surface mining Gentleman Cannon Rolling (metalworking) Blow torch Musical ensemble Material
it it looks like everybody's got son and Land the to it started with the lecture so we we had arrived at the point where In the process the still chemistry is that the the temperatures said the melt this homogeneous in terms of temperature and composition so you basically coming out of the secondary very important secondary metal achieved and your ladle is now ready 2 delivered the steel to the casting most of the casting nowadays it is by continuous casting sold you you will produce a continuous and endless In stripped or the amount of material I continuously the IRS big advantages to working this way it is in terms the cleanliness of the steel and general properties In terms of segregation so you compositional and Mike rastructure all on which a native of the material is much better in case of continuous casting you still do all want out it In good casting but those are usually in the area of use in the area of for checks to make forgery so it's not a very large amount of 2 production of steel production that goes into In got castings and will focus on continuous casting because 95 form or more Percent of 2 steals are actually made by continues cast this is a I'm a schematic of of what we call a slab caster so you you have a rectangular section I and II and you can see where we start up there in the label label and has an opening at the bottom and it's poured into the tonnage and the the the role of the determined is basically to distribute the the liquid steel in the cast of the Castor itself is the water cooled oscillating copper mold and it's a bottomless mold has no bottom out and that's which you poor Wilson will see what happens with the material partially solidifies yes and you can just bacon is basically being pulled out of the of the Decosta by D. oscillating movement of of the castle the Picasa goes down the material moves down yes this game left in the uh which you should support is solidified so when the Decosta goes up it's the it's retained by these roles and so on slowly the material advances out of this small we don't have in general the bending zone so you cast vertically thank you you're material comes out horizontally so you are going to have to do some change of direction here so that's done in the bending the rules and you have support roles and bending roles in this in this and in between the roles you will need to cool the material you need to pull it out because it's not solidify partially solidified but to the cooling is with water sprays between the roles of course you will lose heat to thermal radiation role contact cooling etc. and then at the end you do do cutting of the this
friendless I strip of material with torch cutting and in which you get out isn't called slack let's have a look at some some indifference different types of of Casarez nowadays and the types that you would use the most our fold curved Costas yes but but they're all casters which would be the 1 is you have a vertical yes there you cast In the material and you solidified it In the vertical direction and some and then you have special construction here that that will flippant horizontally you can have casters which very long straight segment was and then bending many of these pastors the slab is banned In once it solidified and you have a similar broadcasters with a shorter vertical section they Will the half of the the bending the solidification will happen during bending 2 1 you're different sizes of contract as but in the end the curved Castres you always have solidification during the bending so why are people interested in what way did you decide how do you decide which 1 to get obviously there is a matter of cost vertical cancers are more expensive watches leave because they're much taller against but however there are some advantages 2 the use of daily these casters because there no bending and unbending there's no bending and bending of the material right so when you when you bend the material here is basically means that you bend it and then you have to unbanned rights of there's deformation of the slap so this is just and you not going to have to use this type of Stratus and then I don't metallurgical center what we call the metallurgical center that's where the the solidification ends nest it is well defined as in the center of the of the of the of the cast of material is in the air when you have it curved Castor the metallurgical center and a geometrical center of Europe obvious Labree ability for your blue they don't match office and and you have of course bending stress so In general you will see that but for higher and products where stresses etc. are important as surface quality home which innately etc. But you'll see this kind of vertical Costas but in general most of the time you see basically a curved cast their yes that operates on 2 floors about 10 to 12 meters high and this is this is typical view here this is the view of the casting Hall so you see here on 1 floor you have the casting Florian have the the ladle here little here a little here you you notice there mounted on a target so you can continuously poor material so when this label is emptying ubiquitous label in position yes and of course there is liquid metal in the dish so you can continue pouring but while you are replacing the legal and so so the material that you don't see here Kurds that see had slap coming out of and if we look a little bit closer this is the label is a Tunbridge Wells which is basically like a reservoir for the the metal and distributor of the public with metal and here it is played here played like thing is is the oscillating malls current let's have the look in more
detail at the 1st default the this time there's no the suits the tonnage this is where you live liquid metal goes into 1st doesn't go right into the oscillating all right so it's an intermediate container and it's also at the container distributes the liquid so why do we need this intermediate container because we like to cast continuously so when you when 1 the the label is Empty Nest and you need to remove it changed to another label so that needs to be intermediate and the reservoir of liquid steel L so suicide has a special construction inside because you want to avoid turbulence as you want to have a very stable the flow of metal so you for turbulence you can still use the the opportunity to remove nonmetallic inclusions because you need to protect the surface of the metal it has large surface of metal that exposed to 2 air right you need to protect that so there will be some slack a use here OK and then the but then new poor through these nozzles nozzle openings here now are usually the the schematic here shows for different types yes so usually there's 1 type theirs so but here the schematic show 1 type was called a metering nozzle which is basically a hole yes the bottom of the then you have which is more the common are there not nozzles which yes which have to give you the opportunity to open and closed the uh the flow of the steel so here you have a sliding gate or you have stop stoppers which Will prevented the liquid metal from flowing so and then and what is also important to the middle flows in these 3 last systems in the at you which recalled the a submerged entering also also against submerged and we the do words submerged the refers to the fact that this stew is into the liquid Mattel in the mold of it's under the surface now you have metal flowing through the system you want to avoid oxidation and you want to avoid pick-up of a nitrogen knows but you want to avoid resell for isolation has so we have we use grants tryout is basically you flow are gone Darcy around all the critical openings yes in this system of for instance here where the label is connecting to the attendants where the condition is connected to the casting and so you have and is very important you basically flow of argon that will prevent the cup of nitrogen and oxygen hydrogen at such Q systems important
things so now the next thing is to look into the casting the itself DeCosta is basically an open mold of bottomless most of this is here the at the edge of this mold its copper yes and it's it's uh cool its water-cooled considers this water flowing through it and this here just you here the entry Nelson submerged entering also and the metal flows through it it through anything comes out of the on 2 sides holes made on the site of the stew so it flows to the last year and to the left today against this bird the metal yes needs to be protected against re oxidation and we have what's called flux for casting Parker yes to this there is no very special type of powder that will protect the material this distilled from oxidizing from picking up hydrogen or nitrogen and it will also act as a lubricant so that it can it can it can slide against the the malls you have to imagine that when the steel touches the mold it solidifies so it shrinks and uh you slide it along the wall and there is a liquid flux and which is performed at the surface of the system so that you form of skin cancer skin on the on the sly and in a slap at the surface of the metal units which solidifies gradually but by the time you you leave the mold yes this the steel is by no means fully solidified just a lot of liquid sink inside yes but that they could steal insights me and and so but in between this support roles yes and the bending rules that the which the Pharaohs static pressure will deform the surface of the material so you'll have some bulging him the incident between Aswat in between you use a lot of cooling to accelerate the the Kulik can so interesting and so the due the complete the this casting powder yes we open in order to 2 make this Fluxus is is very rich vein so you oxides and fury compacts and so on and so very often that you are uh also very often you may have you may encounter in practice some problems the surface problems In the product and 1 of the ways in which you can recognize that In inclusion a surface defect is related to the casting yes His by identification of the composition of the Of these inclusions and so this is the only place in the process necessary for you use this type of this type of slack compositions so high sodium and high fluorine content so if you ever come across surface problems and you find high amounts of soldiers don't think it's sodium chloride has on or a corrosion problem it may be a a casting crack casting related trucks and of course there will stress will see a risk of that making surface defects it is very hot and you can imagine this is but inside is 1500 this has to be hiding in the woods the melting temperature right we talking depending on the grades etc. of 1500 to 1600 degrees In terms of casting an eye the strength of this on high temperature the film is very low yes so we were talking about less than 50 major Pascal of strength here from 10 took the risk is that you're going to produce surface defects is very hot and very often when you visit steel plants you know it all looks like a very powerful big machines etc but do to steel itself under the heavy machinery and that's all because it's very heavy yes but the steel itself in terms of strength is actually very soft you can easily damage to surface and so it's very important to never to forget that because very often surface defects that you create and during hot the formation and casting will remain in the material till the very end but this is an
example here on where are you looking at they are as a strand Castor so instead of having 1 0 1 single slab you get strands of blooms or ability coming out of the customer so for instance here are you see the label DUE here is the tenders and this is the 1 the Castres so now we have 1 2 3 4 the separate Customs so this is the the top of the molds and to see the mold entry now the cast is basically visibility yes can it's not a big slap its ability and you cast as this 1 entry nozzle for each ability and and if you look down this Castor Is it says because it actually looks more comfy much more complex than just a piece of Cup water-cooled copper incident of this this year is which is see if you look on the side of what you have is this this construction here that I will be moving up and down necessity entry than we have here the attachment which is called and he amassed system that's electro magnetic stirrer electromagnetic store talk about the smoke and then and the already attached to the the mold yes section is you have the exit cooling of distress to distract comes out goes through an electromagnetic stirred and then right into the district cooling so am I.
very important here the 2 it is not so critical things are the way you want to have the shroud here yes the do clubbing I was there mentioning on Monday this is where it appears that this is this is where it appears in the the submerged tween also and you can see here that of course if you have a large deposits of a of a solid on this tube and the flow the amount of of of of steel that comes out will be influenced right and so on you'll you'll have an unstable casting but the wreck it then as a case of 1st of all about it there's this bobbing here remember what I said on Monday we we calcium 2 modified alumina inclusions you form calcium eliminates and these are liquid so if the liquid they don't they want you stick to this wall noticed flow out I if you've added too much calcium is you can have problems with calcium sulfite yes and and did that can also give you clogging or abrasion and then the abrasion is again in this stew begin when the Lakewood moves out this a goes it with take high-velocity sideways it's like like shown here right now we don't like to do this yes we don't like to have this kind of strong flows whenever you cast him and that and that's 1 of the reasons why we add these electromagnetic storage the EMS system to control what is left of inside material can and we we will act these electromagnetic starters at different positions
1st of all let's have a look at what 2 functions are of these electromagnetic starters yes segregation you can influence segregation you can improve inclusion removal you can decrease temperature loss Oregon homogeneity and the the minimized a very pronounced solidification might restrict soap and because the the MSS put can be put in different places in during the casting when we put them up high yes yes In the past it's like when we put
in EMS for instance the
excuse me mean to you look at all
like in this case the effect of the EMS is
is to work as a break what a break what you do get a pen here but by having an
that that basically you have inducted In inducted you're right His services basically an inductive a coil that you pulled the the at will provide it Forest electromagnetic force they were goes in 2 in this direction so that breaks the flow Of the the outgoing flow of the look into the matter OK so you basically avoid very high velocities here you can also also put an EMS later yes there it will makes the metal it'll keep the metal moving so that you don't have compositional gradients consider look at that and so why and why is this important to minimize compositional gratings gradients or to minimize Mike rastructure microscope structural features well if we have you probably know this from from undergraduate studies is when when a Mattel will solidify like steel solidifies our the UPU you form when the cooling rates are not too high you form large crystals this March crystals which we called dendrites that dressed as an during the solidification of these dendrites we get partitioning certain elements will and rich in the solid all the elements will partition to delinquent and so we get to thanks and we get then Microsoft arches and we get compositional differences the center here doesn't have the same composition as there on the side so but by mixing the liquids that while it solidifies we can minimized I right at this this is actually but continuously cast of Microsoft rupture it's an example of a 40 39 the stainless steel and so on the microscope should that it doesn't go through transformations like regular carbon steels also that extinguished soda MicroStrategy you get In the slab is actually due the high temperature structure so you can see that a close to the wall of the Of the other copper mold you get very quick solidification yes as we get small grains that's good but inside this cooling rates dropped dramatically and then you get these dendritic Mike rastructure so that's why we will not I had these In
Starace and so this is an example here it's ability yes the square ability while the slab square ability and this 1 is passed without any MS and you can see that this patterning here which of dendrites was enlarged and if you but I haven't you Mass In I don't find you can minimize the growth of the Eastern Drive and you can also see that the centerline segregation is much lower so you get your your your abilities more homogeneous market no a lot of this equipment's and attachment to align depends on uh your investments possibilities that you have an on you know how how worried you are about quality issues of it so you have Costas whichever the EMS everywhere yes and you have Casas who have not yet so it's not it's not always there as the rule depends pretty much from company to company all right
so again when you look at the casting him as it looks like there's nothing much to it to worry about it it works very smoothly nothing happening right about that the many issues that are of importance to steel products and in particular related to the defects which which we generally called tracts and attracts is a very young surface cracks in casting it's a big bag of many things that I 1 of them there which is important for steel products is the at the Perry tactics steals a Parry tactics steel is defined as as is a steel would were you when you go the solidified the goes to the Perry tactic reaction so this is the only time that I focus on another part of the iron carbon diagram in this course and that's at high temperatures and high temperatures New iron carbon diagram you have the Perry tactic reaction units and if you have steel compositions this less than 2 . 2 per cent of carbon and those of many steel compositions that you will go rule tool contractions steps there to clinched during solidification contraption that is the 1st contraction the reactions shown here when the liquid so you you look here in the woods and this in this zone here the 1st when you solidified the liquid goes to liquid plus delta and so there is a solid defecation here the contraction during solidification and then there is a 2nd contraction when you go through the protected reaction here at the protecting and it is the liquids becomes gamma make of gamma plus delta and you can measure these thermal contraction if you do the mystic casting In this zone here knows depending on what temperature of look right you do the the solidification here so this big contruction and if you do do solidification of lower temperature it becomes even bigger so that what does that mean you have a surface it contracts the center doesn't contracted right so you got stresses this is material at between 1415 and deg C I just told you the strength of this material is very very low so cracks can develop at the surface this small cracks so of the when people measure the book currents of surface cracks in the observer always observed a very large maximum on the surface cracks at . 1 2 . 2 per cent of carbon what people also measure is Francis the depths of the of what we call oscillation marks do you remember that I said to the the casting unit most up with certain frequencies and so it moved up and down about about the lives of of the URA centimeter there's up-and-down with certain frequencies and L every time he goes up and down you will have stresses because when was up move moving down its together with the slab moving up new stresses the and this motion is oscillating motion leaves also surfaced marks which we call oscillation marks and Castres and still makes in general don't like baked oscillation work but you can see that the debt of the oscillation marks and are very large in the case of terror tactics OK so very tactics feels very careful that's just see less sensitive to surface cracks because of their composition and way solidified you can get all the crux In developing in the material you remember that when you cast the slap you you also In in many of these equipment you yes so if you actually put defamation on the material OK so what happened well you can get cracks developed this is an example where it was really bad examined a good example of a best level it's a big cracks In this the EU calling the material right and I we know that you in our composition we for instance added NI albeit or vanadium because we want to pursue some precipitation hardening yes and so what these compounds to they precipitous while we cooling the slab and casting and because we calling very slowly know they tend to form precipitates at grain boundaries yes and they weaken the grain boundary strength at the very high temperatures right it's not a problem at room temperature because you control the distribution of these precipitous but at high temperature they form where they want and they're very costs so we observe a doctor lady gaps and so if you the measure the the longer a share of the material in conditions of continuous casting a very important so very slow strains at very high temperatures and and you make sure the reduction of sections of the the reviews the the plastic deformation of where you get a fracture was so if something is very plastic the reduction before fracture is very large and 100 per cent and what high-temperature that's what you measure thousand degrees here measure very high Dr. lady but if you go to in the range of 800 to 900 degrees you it just drops to 30 % the image of study and Britain that's due to the east precipitated and then at a lower temperature deductibility comes back but these kind of temperatures you will this last it is is exposed to know for instance that at the surface and so this can also give cracks and if anything really bad cases of the cracking can be it can even be inside to slap so hot practice because this is what comes
out here then the slab looks nice and straight don't forget it's been banned once and twice spending unbending and and that it may have cracks at the surface usually for slaps you looking at 20 5 centimeters of thickness they're lying it is about 10 meters can be longer 12 meters but that's typical length and the with depends on the slab here at the width of the cast yes and the weather doesn't change very much and so the cast and and actually also this dimension of the case's also defines the way the maximum weight of for instance those she products that you manufacture so if you have cast that can only do a 1 . 2 meters you will not be able to provide material to customers that need 1 . 6 meters for instance automotive constructors construction needs 1 . 6 3 ,comma rights to you you knew the Casa will be should be able to provide this material so right and that it was a slab is made calls its market you remove burgers and and the new stacked the material because this process is an endless process in a you basically have to produce the same thing all the time right behind you make different compositions so you want to have a a low-carbon steel and other the time you want to have it in a microbiologist right so I didn't as well you have to make transitions slaps yeah you have to basically that if you want to make it change in steel chemistry you will have to waste material you'll have to cast slabs that go from the previous chemistry to do next Chemistry yes I'm sold so you can you know depending how good you are yes and and and of course what product it as you know you can have to scrap a few slabs or a few meters of materials by end of a few meters that made mean that quite a few tons of steel kind them so it's expensive so when as a young researcher you go to steel plants you know you cannot ask them to make something for you right because it doesn't work that way because they cannot make something for you in a steel plant just like this somebody on this needs to be organized young because normal production is all program and that's also always worried so challenging to introduce new products in big companies like this because you have these of the plans are designed for continuous production so there is no not much space there is no space to do experiments against over a little and so the introduction of new products means a big organizational task group has to be organized to 2 students right a typical of things here the exit temperatures slapped thicknesses again as I said typically 25 cm lengths 10 to 12 meters and take end there did the width of the slab as you know as big impact because obviously it is the 1 meter Europe the equipment that comes next the hot hot strip mill which know has to be able to a role this material right so it was everything the the hot strip mill dimension and has to be in In In agreements with the weights that it is provided and the final which requirements it
is 1 thing and just just for your information that is sometimes used in this this call the P-I W it's North America's means pounds per inch of weather of your I of your Slattery of coils news and that day the reason why it's users because gives you an idea of you know that your your mail size cast size his nose and would basically is a very simple concept is is you know when you when you have differences have a slab here and the slab is turned into a the strip here that's rolled and then into its cold-rolled strips yes that's coiled and on the amount of material yes in terms of weight that you so if you could often hear 1 millimeter of material from the slapped hands or 1 millimeter from this intermediate the product or 1 millimeter from this coral it's what they all have the same way but it gives you know this gives you an idea of the kind of productivity young male can achieve so it's is Macy's specific coiled white minister weight and on the way per inch of whether or per millimeter of which so as to what is it is how'd calculators the length times the thickness times 12 times the density and you can if you want there to use the metric PI W this is so that's basically kilograms per mm canons of weather it's the American the P-I W. divided by 50 or so what typically a modern the production units are around 20 kilos per mm so if you take a strip of coral you cut it off it gives you the 21 To be 20 kilos per mm Anderson example here yeah France is a thousand pounds per inch with PI W. Coyle here as you can recalculate this that this is 21 and a half kilos of specific way this is give you an idea of coils sizes slap sizes that are routinely
uses used in the in India still production unit you would you visiting France's but that's not bad it's a it's always interesting to to spend some time talking about nomenclature is so Acosta but will produce slaps and blooms and billets and so what are these and and what's the difference
well In and and also it's important to realize these products slab blooms and ability are also products that is steel plant will sell to customers so we call these products that would give the following so In with steel company producers are what we call Sammy's semi-finished products and finished products so for instance what is this semi-finished products the semi-finished products are slab rooms and build up so semi-finished means that half answer it still needs processing is not a finished product What is a finished product of the things we discussed previously for instance sections bars wire rails or flat products plates hot-rolled strip cold-rolled but so slab looms ability so what comes out of it continues cast
uh of Oval Office still steel plant basically in Our semi-finished products and they will be processed further in other companies they can be processed inside the company that produced these cast brother goal they can be sold to outside products and so you can already
see the these days the 2 products where there's always a lot of confusion about what's the difference was once so so of a bloom counter looks like this inability looks like that's right well what where do we make the difference where Woodward were does definition between the bloom and billet change well In other words was difference between ability and blue while anything that's larger than 7 by 7 yes is called the Blue and when it's smaller than this 7 by 7 inch this about 17 and have limited call ability that would be simple this is a simple
definition but not ability and blooms come in different sizes and they're not always square they're not always square on it can be round they can be rectangular depending on the application so what we have usually on alternatively here's consistency the socially blue Council will will produce rules that will that can be square but they usually rectangular or they can be round and they can also have a shape yes In in this case we don't call them the rooms we called him being blacks has been blankets and they can be used to make this being less can be used to make beans but also rails but and publicly again around and around 20 centimeters last week anything that smaller than 20 centimeters we call ballots and you have billet Costas they will produce square sections and round sections which are typically less than 200 mm in the dimensions of dynamic died at the diameter of the small and and 20 2 centimeters 4 around sections and again also if you let the blooms be right the rectangular what's met with the difference between a a slap and a blue yes because they're both rectangular while a slab caster Of course makes products that will be used to make flat products strip yes there with it is usually more than 60 CM and the the ratio of which 2 thickness it is Florida this kind of away 2 make 2 different source or choose your
words well get so this example here right now some of blooms said that blooms with this he comes out of it the bloom caster and in an in steel plant was of this 1 is 13 by 13 has and and this 1 is 250 bite of it so here hereabouts stance this would be the day the difference between them billets and rooms yes but nobody's going to be upset at you if you if you call them all let's yes and these are ever being blanks and here you see that some of you you basically poured a steel in the shape I wish to shape cast the and and this
is what you have get to see In plants that make this so slab casters the produce lapse you're cancers can have many parallel strips for instance this 1 here is it a double strand slab caster and so that will be the weather here is 1400 has and of course the Moss trends you have the more capacity you have been so a double stranded Castor which the casting speeds by the way it's kind of interesting to know what typical casting speeds are it's about a meter perspective minutes it's to really slow way what a high casting speeds on 5 maybe 6 and what's the world record may 7 to 8 so for much of their materials this is 20 this is 23 mm state yes and so if you if you have a been strapped yes and you can only go 5 times of faster in casting your production rates will be much lower so compact compacts strip casting which will talk about later I have usually much lower production productivity look at and this is the slabs being cut strips these analysts the strips being cut this is an image here
where you have to read strands at 1 strand its research and then around you can see the section here round billets literacy well it's to the I guess increase should call the blooms yes according to my hair and definition of so you can see here in the Brown and again you have produced a in parallel but casting a slightly higher with the billets in about 2 meters per minute and here you
see therefore the strands and new ceded these billets are square so that's that's basically the shape of the the cast directions 1 of the the
important things people do after the the slanted abilities of the blooms are producers is to have a look at the surface quality because you have cracks many types of cracks longitudinal transfers of segregation can give can center lines to the open it means that the insider material there is actually a solidification ferocity against the center you of course have oscillation marks due to the oscillating mold you can have it he checks from Scarface that may be a little bit mysterious sometimes the surface quality of a slab is not very good and you will be burned off yes burn off these defects which the there's a by hand or with a machine gun that is you basically melt material that you melt away the material and that's schools scot-free slaps coffee so there may be defects related surface defects related to this thing which would call he checks scarfing scat curve is this surface damage you to scarfing handling damage of course and he checks from ripping bonds that servants lateral actually break In a brittle fashion and in the end it's well known that friends high silicon
slabs are very sensitive to 1 to this problem some pictures here now as using these oscillation marks Association March you know the oscillation March because their periodic knows that you see an edge crack and here you have a centerline crack and of course inclusions are all can always be a big problem so that's a big headache of course these these cracks and In practice you can use to get a lot of attention and certainly if if the cracks are major and they
can be major sometimes the cracks are not very visible on for instance you can have a crack at the surface of a slab theirs this and that and oxidation and removal of scale will round the the sharp edges Nos and deepen its but when you start rolling these are the surface defects they will tend to have to be closed by the rolling process and so you get things like I rolled in oxides units they did not really visible anymore but you have to imagine these are not very huge cracks in it and small surface cracks and you basically the the cracks and these oxides disappear under the surface and then they will reappear 1 you for instance do indeed drawing operation you'll get these really bad surface defects and you have to figure out you know where they come from and certainly if it's affecting a lot of the production look and these
are the very serious cracks here that again will often not appear very clearly in the slab but will give you a major problems when you start rolling the material this is for instance a this this slab that was that fractured during hot rolling during the rough world stage To get so when we are
reconvene on Tuesday will be talking about the next step what what happens to the cast steel that we made and will focus In the becoming lecture on the hot rolling and I will see how the material yes and will focus 1st on slabs slab materials for production and how this material is reheated and goes through roughing milk goes through it finishing mill runout table to cool it and then is being corralled yes In the process the material then there a Yugo From about 250 mm to an intermediate thickness of 20 to 30 millimetres cannons does the material at this stage here His called above Sullivan as this deal student you should definitely no there are bars and that there are bars bars where you enjoy drink and is also the transfer but this is a transfer of our forces at brush rolled slack end of the this bodice transfer is then further reduced 1 and a half to 12 mm thickness typically 5 to 6 mm before you got so in the process many things happened and Mike rastructure involves the temperature drops we get phase transformations etc. so we'll be talking about this on Tuesday start to talk about this on Tuesday will 1st focus on our already because I don't know what your knowledge is about them the rolling process I will 1st introduce a few concept about rolling process that you need to know if you know about if you want to understand what happens in the hot rolling mill to thank you very much and I'll see you Tuesday


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