Modern Steel Products (2014) - Overview of Tandem Mill Designs (Cold- Strip Mill): lecture 13

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Modern Steel Products (2014) - Overview of Tandem Mill Designs (Cold- Strip Mill): lecture 13
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13 (2014)
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Professor de Cooman talks about the cold rolling of steels to achieve the right thickness, shape profile and surface condition, after which the strip may be coated. 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)
Rolling (metalworking) Rolling (metalworking) Mail (armour) Titan Saturn System Mission
Coating European Train Control System Coating Galvanotechnik Galvanotechnik Singing Titan Saturn System Mission Separation process Rail transport operations Rolling (metalworking) Lubrication Lubrication Ship of the line Flatcar Material Sheet metal
Ammunition Hot working Rolling (metalworking) Kickstand Wear Bauxitbergbau Jig (tool) Ship of the line Rail transport operations
Drum brake Coal Kickstand Cord (unit) Kümpeln Kesselflicker Page layout Reel Raft Titan Saturn System Mission
Typesetting Coal Kickstand Kickstand Drill Cord (unit) Stationery Page layout Reel Titan Saturn System Mission Drum brake Gentleman Rolling (metalworking) Cartridge (firearms) Single-cylinder engine Engine Single-cylinder engine Kümpeln Außenbordmotor
Friction Hot working Kickstand Kickstand Scouting Cord (unit) Hot isostatic pressing Reel Scouting Space suit Cartridge (firearms) Spare part Caliber Single-cylinder engine Rail profile Mail (armour) Sheet metal Van
Tin can Kickstand Verzinnen Kickstand Food packaging Ink Cord (unit) Reel Weapon Titan Saturn System Mission Rolling (metalworking) Tram Commodore MAX Machine Rolling (metalworking) Mail (armour) Photographic plate
Hydraulische Maschine Kickstand Automatic watch Transmission (mechanics) Titan Saturn System Mission Scrap Volumetric flow rate Mechanical watch Wear Jack (device) Commodore MAX Machine Mint-made errors Engine Hose coupling Firearm Mail (armour) Sheet metal Cylinder head Truck Wägezelle Hydraulische Maschine Kickstand Gas compressor Titan Saturn System Mission Wood Rolling (metalworking) Crown (headgear) Fahrgeschwindigkeit Cartridge (firearms) Ground effect vehicle Screw Mint-made errors Gate valve Engine De Havilland Venom
Friction Hot working Reamer Barrel Fahrgeschwindigkeit Lubrication Commodore MAX Machine Rolling (metalworking) Plane (tool) Mail (armour) Material Sheet metal Typesetting Hydraulische Maschine Kickstand Drive shaft Towing Texturizing Weapon Titan Saturn System Mission Rolling (metalworking) Fahrgeschwindigkeit Lubrication Pottery Ship of the line Friction Programmable logic device
Friction Chemical substance Hot working Ship breaking Kickstand Carriage Suitcase Casting defect Laserschweißen Compound engine Separation process Mechanical watch Wear Lubrication Gentleman Tank Posamentenmacher Kümpeln Firearm Station wagon Water vapor Automobile Clothing sizes Separation process Gas compressor Chemical substance Weapon Laserschweißen Sizing Petroleum engineering Cartridge (firearms) Lubrication Spare part Pottery Fluid bearing Water vapor Friction Last RWE Dea AG
Mechanic Mechanismus <Maschinendynamik> Gas compressor Weapon Rolling (metalworking) Continuous track Lubrication Gentleman Lubrication Water vapor Kümpeln Material Mail (armour) Water vapor Friction Trimaran
Friction Typesetting Typesetting Hot working Separation process Gas compressor Turning Roots-type supercharger Rolling (metalworking) Cartridge (firearms) Fahrgeschwindigkeit Lubrication Lubrication Pottery Book design Remotely operated underwater vehicle Fluid bearing Firearm
Friction Widerstandsschweißen Steel Hot working Key (engineering) Spaceflight Überschallstaustrahltriebwerk Fahrgeschwindigkeit Compound engine Tissue paper Lubrication Gentleman Commodore MAX Machine Rolling (metalworking) Kümpeln Firearm Water vapor Snips Typesetting Widerstandsschweißen Ampoule Gas compressor Weapon Fahrgeschwindigkeit Cartridge (firearms) Lubrication Pottery Fluid bearing Ship of the line Water vapor Kümpeln Flatcar Strapping
Typesetting Rolling (metalworking) Cartridge (firearms) Fiber Rolling (metalworking) Plane (tool) Plane (tool) Cord (unit) Mail (armour) Material Texturizing
Blast furnace Rolling (metalworking) Rolling (metalworking) Ship of the line Guard rail Material
Blast furnace Tin can Fiat 500 (2007) Volumetric flow rate Rolling (metalworking) Packaging and labeling Scouting Electric locomotive Book cover Blast furnace
Tin can Fiat 500 (2007) Ship class Gemstone Enigma machine Blast furnace
we so today we will be
discussing topics related to young cold rolling mill this the cold mail usually also involves really In terms of the deal production associated with the annealing and as we concentrate on stretch for the technology the description in this course will we're talking about batch kneeling and continuous annealing and here but there is also it temporarily the for coated products be the route is slightly different I many will allow will discuss stepped in separate from lecture OK select some let's get started here so what do we get
out of but we produce in the cold strip mill of nuclear industry that's a has the right to exit thickness and the right shape flatness and profile and it was the defect free and after the Cold strip mill the deposed as this it will be annealed yield for continuous annealed or they can go 2 a separate coating line all of which is usually a separate entity To be Elektra galvanized hot dipped galvanized etc the material the weights would on the market Will will be temporal this means it's a it's given a final cold rolling step after the coating for after annealing 2 achieved a number of stripped characteristics in particular there a particular roughness on did applies to secure office on the surface of distress and the as I said In addition to being electoral galvanized the balkanized the the stricken can indeed dish then go through additional coating the process whereby a paint layer is applied and I loved and this may involve actually to paint layers of primary and a topical again these are usually separate production plants this it will be talking about a different technologies and designs for the use the Colstrip males as and will also I talk a little bit more detail about lubrication in the Colstrip milk it's really very important
good so basically in the cost the rolling we get the strip with the right to exit the thickness and the material is heavily called deformed so it's cannot be used in practice so you need to emulate In a continuous annealing line about smelling like ass said that after this annealing the material can be lecturer galvanized or you can do both the annealing and the galvanizing in the hot the galvanizing this these lines that HTG Alliance you actually make we recruit sliced the steel and you the new galvanized steel and eventually you get a cold rolled Delta galvanized coil the
Colstrip mill traditionally I will consist of the Correla the number of stance and the 2 the according the unit nowadays as if you remember I from discussions a presentation on the pickling lines nowadays but there is a new units are usually built so that you have continuous operation which involves the pickling line and the cold rolling with the exit of the the pickling line goes straight into the culturally
usually usually modern Colstrip males are very highly automated and there it really not much to see in the exterior of this this of the line it's usually do do the mill stands are not visible and and what you see here are deep in the work roles at the ready for the to replace the worn-out work worlds but if so this an
example here in nowadays you get lots of 6 high standards he has to get perfect strips control 2 profile control it's a few words about this and when will have a separate lecture on it also so these are these stance and then we usually have to quotas and these are With recalled exit tension reels or likes attention corners so that means you can apply attention on the I would accept the structure of the new remember why we do this because it has a big impact on the diffraction peak in the enrolling Tinker right so
these callers so why do we have to Coila debts because of you can uh while you are coiling 1 it using 1 of the quarters to coil you have the other coal is being unloaded and there you there may also be a sheer 2 1 2 cut the this trip to the right length I these
scholars is offensive presented here have are separate units you also have the corners which where you have a drum a big drop With 2 man drills and you have 1 Mandrell is in a position to 4 coiling and the other Mandrell is in a position for unloading there are different
ways in which this can be note you do not or you don't always have attendance coal rolling you can have a single stand cold rolling units Our in particular if you visit stainless steel mills very often they will have a single stands reversing males for the cold rolling this is an example here Of the 6 high Gold Medal single stand With a and eggs at contention real so you can apply tension on the exit but it's only got a payoff for you so payoff will assist gave the year you are unknown wrapped the the strip here and there is no tension this this unit could not apply any tension so In this particular case these this type of set is for situations where the coils are loaded into their world once toiled on the other side and then removed and this is a non reversing situation that's when you only the ones In the past
what you but you don't see the smoke more often with would you often see far single stand cold rolling males where you have to be reversing mail and so did the stripes passes through this same the mail back and forth a few times as many times as you need to achieve a final thickness and it does this this turns In the following year so you have a payoff real that allows you to load this trip until the the male yes standing once you have but this district on 1 of the tension rails then you pass it through and you attach it to a an entry pension we'll also so this stress passes through the mood of the mail with forward and backward tension has OK so how does this work so you start here on the on the right-hand side years so you you rife with too hot the rolled coils yes anything you have to call Oilers here the 1st College Corner is a payoff rail so this year just you just unwrapped the at the heart of the hot rolled the pickled coral and new passes through the the Mel and then you you pick it up here and on this tension real right now this trend here will eventually come off come the at the Mandarin right and you don't want it to flap around and you want it to there should be some tension on this trip so you have a strip press yes that will keep give you some attention by friction yes and also prevents the stripped from moving around us and most of this district is now here yes and this and party here is now put on the tension real here yes he was here when you start rolling in so this is this is the 1st pass this is the 2nd pass so you can do even number of passes or an even number of passes so if you do and uh an even number of passes 1 too the coil ends up here you have to unloaded from here or if you do and even of a number of passes the coil will be here yes now remember but when you go back and forth yes you always keep the end parts the end parts here of district on demand dropped so they never get role content so if they don't get rolled their remain thick yes so you have to get rid Of these ends yes they didn't get to roll in so what would you do here is you cut it friends in this case you can see here you you will take out of this the coil so you you come here yeah you cut the end and then you go back and you roll up what's left there's so here you get a small piece of coil In a small piece of coral that is has the that's off thickness there can you call this a popcorn yes and on this side of course the central part Of the coil will be off which will not have the right thickness of so this this this odd number of passes which you see is most common to get off set the gage sector sections for remain inside and the outside off gage section makes a public course and these are a public
chorus are the small coils that are offstage and this is a puppy it's the same part of this means it's because there's pop calls like you call them particles because they're small and cute like dog OK so
and that's very common views on reversing males and you produce about but "quotation mark you then you sell the public also to smaller companies that can do something with them but would you also have mill stands where you don't have 1 uh standard you have to step against and so for here you have a situation where you have 4 Hi the stands you have 2 of them and you have to tension real so that means you can do twice the number of reductions protests so it has a higher productivity but it's basically by reversing mail also you can just do more you can produce a fast and of course because you have to stance it's going to be a more expensive mail there are also
a double gold rolling mills like but that are different as and they're not reversing males and they're used to but make 10 players and 10 plates it is a product with with which you make it's packaging yes and these the non reversing so you only go you past ones through the through this a mail so you have you only need to pay off real no tension has an attention real where you wrap up the district after the rolling and so they're usually you have to to stance you have a reduction stand and then surface conditioning staff but basically gives the right surface roughness to the strip this is the same the situation here you have the reductions stand on this surface treatment standard in succession here too and it's for as I said on the tin plate production we
said a few things about by gage control In when we discussed the the hot strip mill yes I just want to say a few things that this point at this juncture about the tandem male so in attend a mail you have to strap goes from 1 stand into the other yes then indeed when you have to I do In order to have stable rolling you have to have that constant mass flow through the mail that means what does that mean it means that these whatever the mass that comes in as to go out yes exactly the same value otherwise if the value that comes out is higher than what comes then there will be rupture or if the value that comes out is lower then what you put in you will have a couple of years have so would does that means constant Maslow said the product of the velocity of the strip out times the thickness of the strip it should be equal to the velocity and and the thickness in Of the next Of the next step so far have the speed exit after the exit speed after all the 1st a mail milled 1st stand excuse me is the 1 and thickness speech 1 in the mass flow out of the 1 but out of the year the 1st stand is the 1 H 1 the 2 each to after the 2nd 1 etc. The 5 H 5 so the constant mass flow the requirements means that the 1 H 1 should be to feed 5 times each fight and of cost it H 1 is the and thickness N H 5 if the required exit thickness of the thickness like the actual gage this week needed so the mass slaughter the volume flow the head of each stand as a product of the gage yes at times to strip out of each step so if if there is an error yes of gage here yes it will always propagate through the Mets through the mail so if we have a constant the mass flow Out of the 1 . 2 4 1 to stand 1 and say it we have an exit gage error we can exit here and we can do corrected by changing the speed yes because if this differences between the source or if you have to correct for H yes you can do this by changing the velocities yes and so this brings In the new concept of Gates control In the cold strip mail and that is the control woods vise speed incentives based on basically this year so the way to control at the the thickness is With
speak right so again here just as in the case of the hot strip mill the gates control yes is achieved by actuators and we have mechanical screwed down actuators and hydraulic capsules and we know we already discussed this mechanical screwed down the slow response to the hydraulics are fast responders yes I guess so but how does it work that you you remember that hydraulic gap control is Don but controlling the pressure In the hydraulic capsules has right and you put the pressure on the a backup role truck 4 it can be electromechanical screwed up and that means that then you have a motor yes and invite the mole and assorted gearbox and crew and not geometry you can apply pressure has an increase of decrease the the gap by applying pressure on the backup role truck In most as I had done said to in most of the modern males yes we will also have the possibility 2 improved this trip profile that's the cross-sectional remembers the cross-sectional shape of the strip and that is known for instance in this case by bending by roll bending capsules new for instance you have kept that means that you have a little hydraulic capsules here that can bend the role so you achieved a right role profile 10 but this year In
addition to this you can also have lateral roll shifting that's the Musée du the roles your ass symmetric and and it allows you to do some additional types of bending which which will discuss in more detail His or daily to achieve the right stripped profile that's the cross-sectional shape of distress and you can have a electoral roll shifting or you can even have Cross barrels yes all these things are
very common in modern called the rolling mills In addition because we're working at low temperature we knew a lot more In line measurements on the Strip we can so standard the Gold rolling as it will have a thickness gages which can be X-ray gages or isotope gages or even contacted ages I although the contact gages are only suitable when you have no strips speeds you have tension control there can it also is also available and of course you you measure the force with load cells and you also have stripped velocity measurements you can get will talk about this in more detail later wrong when we are when we talk about the profile let's not go back to so data about the cold rolling mill whatever typical cold rolling mill parameters well if you In terms look in terms of the reduction yes these the the Colstrip mail will typically produce material that's less than 2 millimeters thick and so you can see here if the reduction if the strip is about . 8 mm depending on the type of steel you're processing the DQ meaning deep drawing quality drawing quality that will be Bachand meal that will be continuous Neil the carbon manganese structural steel value will it of the reductions are technically of the order of 75 per cent 4 of which here of 12 15 the number of male stance is 4 2 5 nowadays can be different can be more like 5 or 6 perhaps they need thickness that cold rolling mill can take any it's typically maximum as a maximum around 5 to 6 mm yes and the thickness out you can say about . 2 mm yes minimum so the maximum reductions that we can give our 80 per cent 90 per cent these a very high reduction usually usually called strip mill will operate at 70 75 the very high reductions are given to stretch where we want to achieve texture control very strong texture control and is also usually strip tension get to remember that's but when we did the discussed the rolling fundamentals we saw that I would is very important in rolling is friction and we also the described the fact that In the role the gap these there was a considerable flattening Of the brawl so you have be elastic deformation of the role surface and it's flattened it was strongly flat and again there's forward slept and you have the shearing Of the surface in the role gap and remember this a lot here shows that if we decrease diffraction we can decrease the rolling yes now in the hot strip mill that was difficult to achieve this reduction of friction through lubrication but you can achieve it very easily in but cold strip mill yes
and so we're going to take some time to discuss lubrication in the Colstrip Mont what all the functions of the lubrication well number 1 of course is most important is the reduction of friction that because then you have a direct economic advantage and technical advantages you reduce you have considerable reduction of rolling forces and because of that you also have a higher-quality strip surface and better control of the strip profile and a reduced work will wear so very important To have lubricants whenever you can indeed the additional benefit of the the lubrication is cooling you because you use you use last the forces less slowed you will have less heating also you have less heating of the role because there's less friction I was in his opinion the heating is caused by friction by deformation we know I now 1 of the things we could be using this water yes because water is a very good coolant has so we could use water but water is a very poor has a very poor lubricants and so we will not be using water air or not only water in the lubricants for the Colstrip we use emulsions dispersion all stabilized dispersion human emotion but is it the product that typically contains a few per cent of surfactant will see that would that would it is in a moment which limits the the breaking up of the oil particles and into separate layers on and that means we don't need to agitate makes the emulsion the water oil mixture continuously to achieve to make our lubricant a dispersion here we have added surfactants which forms a protective colloidal layer on the surface of oil particles again the reason why we do this is to eliminate coalescence of the oil field In dispersion so what's the big difference between its dispersion and emotion the robber similar is the fact that you the distribution of particles to control of the particle oil particle size is isn't much narrower than the case of animals yes and In the dispersion of the oil layer will tend to Split off has and so you need to keep the a dispersion of well dispersed yes bye keeping it's there by agitating it by mixing it basically and then you have stabilized aspersions which are newer system with some something between emulsions and dispersion but they don't need agitation note these are the fact that you reduce friction and you reduce and and you out the lubricants also works as a school and is positive there is a negative about lubricants lubricants are basically organic products and they will but because of the very high pressures in the role gap make it they are the sensitive to the breakdown and so lubrication Will King will call carbon deposits there's uh which you will need to be removed you can't and of course you will also need to remove residues of lubricants on your stress from can it so let's have a look at you know the basic some basics off the oil Water mixtures that we call emulsions and so wait and oil and emulsifiers and emulsifier is basically a molecule which has a hydrophone fell like and and Lippo filling air and so the Lippo feel like and is oil soluble and water soluble or hydrophobic and is is water soluble and so these molecules will orient themselves this way yes and this will stabilize our emulsion the now V so if you ever work later in the hot strip mill the of providers of lubricants are very specialized companies usually tend to be it's a side product of petrochemical industry so for instance Texaco shall I and others are big suppliers of lubricants it's a site product of the petroleum industry he is a very complex chemistry yes so don't try to by all by yourself tried to improve the chemistry or whatever but it's pretty complex where many chemicals going into and and whatever I'm going to tell you here is just the tip of the iceberg but typically Of these lubricants can easily can't contain you know 15 the chemical In their compositions the major constituents are mineral salts would call mineral oil investors or mineral their major constituents and today is the basis lubricants and they are important in what we call the last hydrodynamic lubrication so the HD is an idea the absorbed and into it's not included here but UHT as with the last hydrodynamic lubrication drool dynamic lubrication I don't live in the stands were with them but then you have additional important compounds you have fatty acids yes they are important in boundary lubrication boundary lubrication is when 2 surfaces the strip surface and the role surface France's In physical contact and strong physical called you also have and tight oxidants that will protect the lubricant from oxidation polymer Asian and in other words degradation over time but we have emulsifiers of course to the view that we aren't so we can mix the oil and water mixtures and then we also have phosphorus and sulfur containing additives and those are not In all organic molecules they tend to there added to form a very strong films yes at the surface since and the phosphorus containing additives for films that can easily noses very thin films that can easily be shared yes and the sulfur containing additives very resistant to hide pressures yes and they prevent welding called welding is and going with this and see where the call welding workers so let's
have a look at but to surfaces technical offices to technical services of all kinds Our never atomic police moved against their work that they have a certain roughness and waving practices at the surface so but let's have a look now like metal to metal contact the real estate is no oil right now so we called this dry lubrication this there's no lubricant is just right and so this kind of lubrication is also called boundary lubrication when there is little or no lubricant what happens if I bring these 2 surfaces together well I do the hell's the the the beaded tops Of the surface profile as well may contact us and if I oppressed them together yes but these the top-seeded ' s parities will be squeezed and if I squeeze hard enough I may even cold weld them to each other and in the case I have a little bit of lubricant yes there will be pockets of lubricants yeah pockets of soaked in what we call the boundary lubrication as I have tiny pockets of lubricants and then I have disparities that are flattened and there may be cold welding all these surfaces so what kind of
situations do we have now if the 2 surfaces move relative to each other as well if we have sigh so hard asperity In a hard topic for we have a hard surface like a roll surfaces are hard and we can we have a soft struck surface as we can get scratching clawing of the soft surface by a hard asperity in or we can have a balding they can become Coldwell and then when the surface is a move away from each other you can have breakage of that that bombed us that process these 2 1st processes and gave rise to what we call Byron fights Byron finds this are typically found almost all in gold the foreign products and a very fine Byron particles they come from these processes if we have yes it and while felt in between these processes can be avoided because now the deformation is which we recalled this viscous track and this is basically 1 1 2 2 the surfaces move with respect to each other and we are not the making of balding were not plowing the surfaces but we're just shearing shearing this lubricant fell 2 so let's have a look at this shearing process hence the shearing process the shearing process of and of oil is determined by its viscosity and the viscosity is equal to this year's divided by the she right 2 so if they have a high high viscosity the material prices custody oil I will need a high shear stress 2 achieved the same shear right yes now said the viscosity instead important parameter is the main parameters the lubricants and and from mechanical point of view and it's very much pressure and temperature dependence what we are all familiar with the temperature dependence we know that if you have an oil yes and you warm it up it will become standard it will lose its viscosity so the viscosity decreases with increasing temperature what we usually do not know from experience is the fact that which pressure the this custody increases right and of course why is this so important is so important because rolling we have a very high pressures OK now let's have a
look at the pressure influence the infamous of pressure on viscosity so let's look at water 1st and we increased the pressure None so here from point 1 major Pascal 2 1 digger Pascal you see that water the viscosity doesn't change very much was from 1 2 at less 2 but by the way that the discussed incentives and send the poor instead since it's Mick Pascal's times Securites and but with mineral oils yes course we start with them at the end of a lubricant that's that's a lot more viscous than water but as you increase you get a dramatic huge increases in the viscosity but just a little bit not just doubling but you know very very large increases in the world viscosity 10 so in the mail the viscosity much much higher than the 1 you feel with your fingers of because of these very high pressure
Clinton alright no with lubrication while there are many parameters let's just look at the process of rolling when we know that locally there will be a pressure yes we also know that there will be a relative velocity yes this trip it is never at the same velocity yes as the roll surface and so there is a relative and then the lubricant has a certain this custody yes so how is it possible 2 talk in this simple manner about lubrication taking into account all these parameters on what yes it just turns out that you can plot the master for a lubricant has where are you get theirs us on the Y axis you get the coefficient of friction new which is the shares stressed divided by Russia so you know what fraction answers if you if you have 2 surfaces and there on the new the new pressure right they friction coefficient is to is the ratio this year's stress to deploy the apply pressure then you want to lose so when a lubricant works well yes the friction coefficient will be locked because the shares for us to get the thing moving will be of so there were also in the Y axis you do Speed dial viscosity divided by depression and this is this this parameter yes allows you to draw up a single curve 4 these friction coefficient and it looks like them this is what it looks like so when this parameter has a low value I have a high friction when this brother has a high value I have no friction so let's 1st look at pressure so if I have a high pressure yes the velocity and the lubricated the lubricant viscosity being the same as an increasing PE means that I'm on this side of the wimpy increases I'm on the so I have high friction conditions if I have velocity Inc yes then I'm going this way I will get a reduction in friction all other things being the same the viscosity of my lubricant and the pressure of being the same why is it that this happens well the reason is very simple it's because something happens to the lubricant failed thickness the lubricant film thickness goes like this so and what happens well at shown here yes when this parameter here yes layaway discourteous called the stream that curve has but it's also when when this parameter small you have metal to metal contacts and you have dried lubrication conditions a high friction conditions and typically they friction coefficient is then between . 1 to what as this parameter increases because you increase the viscosity or you increasing the speed for you decreasing the pressure you have you creating lubricant pockets lubricant book you concede that the thickness of the film increases and you get a situation is called mixed lubrication the minimum is reached when we have alas still hydrodynamic lubrication is where you have the a large number of lubricant pockets and then the hydrodynamic lubrication is the case a year when you when you the thickness of the film is such that the surfaces are separated separated us and the friction is then a function of the the properties of the lubricant only 2 but so
when when are we going In the rights of working conditions so we know we we like to avoid boundary type lubrication and we'd like to have the last of hydrodynamic lubrication with low friction so but what the situation will depend on the the roughness of the combined roughness is reviewed your Europe surfaces which in the case of rolling is the role surface and the strip surface and the lubricant film thickness so when we have earned the role rolling situation we have a work-rule roughness and is stripped roughness yes and the combined roughness is taken as the square root of the roughness of the work rolled squared times to strip roughness square the lubricant film thickness we called so when H it is about the same as the Sigma we have boundary lubrication if the the film thickness is 1 2 3 times the combined roughness then we are in mixed condition and we have the right the electoral the physically last 0 hydrodynamic this is a title here the HTC Billesø hydrodynamic lubrication if the thickness is about 3 times they the combined roughness this
is kind of a picture here so you have an idea of what happened so at end let here yes but we have they need the oil is and trapped yes between the work crawl and the strap and so in this contact area we have lubricant pockets and we may have places where the surface it is in contact yes where the touched touching so in In the case of boundary lubrication I have a very small these pockets of very small as in the case of the the last 2 hydrodynamic lubrication I have a lot moral brick and between the 2 surfaces and you get In in areas many areas you get total separation the surfaces now having said that but it's also important to realize that at the surface here yes I because there is a relative movement between the surfaces but this these contacts places don't remain like this and in particular these lubricant the pockets will become UN deeper and they will flatten out yes and also the surface will be stretched like this that's a bit mission the shape doesn't stay like this so we get past parities of the crushed and there is I plastic shear deformation at the surface and the process here of these asperity is being there for them being sheared off leads to carbon finance and it also these extreme mechanical conditions here will also lead to the composition of these the mineral oils and will form the carbon residues which again both of these things need to be reduced but in the it role gap itself but the the film thickness is pretty pretty flat because you know the role gap is actually very far because of a role flattening is very flat at the beginning of course we get the ball at start the entry you have to do the Oilers is taken into the role gap and at the exit you get an interesting phenomenon is that the the thickness of the oil is decreasing and we can't we get a pressure p which is called the corrosive each pressure appealed and the reasons why we have this precious is because when the straps that leaves the role gap there is an elastic the the role surface is now free yes it's free and so it will elastically the bounce back yes it's been flat and very much is going to bounce back and so it will likely squeeze the oil fell a little better and that his this pressure so I'm very important this UHT the last 100 anemic lubrication and it's lubrication by lubricant film for lubricant film In condition of elastic contact and high pressure To this high-pressure results in a very flat contact area because of this high pressures your oil is very very biscuits yes and there where you have no contact between the 2 of you have what we call the a Galanga like the conditions in which you you've basically shear the oil but it is have a look now at a velocity the impact of the velocity what happens With the velocity so you can already see here yes Dad when I keep the this custody of the oil the same I keep the pressure the same I just increase the velocity that means might oilfield will increase in thickness then and you can measure does so a rather complicated way the task to do this but it's possible to I measured the film the oil film thickness as a function of the velocity and you can do this for me too oils or you can do this for emotion when when I you talk about neat oils that means you not mixing it with water we just used a pure oil as as such as In case you can use the need oil or water plus oil emulsion and so you see that as you increase the velocity you get that the thickness of the failed increases and you can see here so what type of thicknesses we're talking about 10 nanometers 100 enemy is very thin film and you also see the effect of the temperature so the temperature increases that means the lubrication lubrication and there if your viscosity decreases and so there is and a shift of this lying to the right it's basically you basically get with decrease in film thickness I think so quite they
complex thing happens when you know but then trapped the lubricant film In the role gas so so in the role gap the In oil on the lubricant this sucked into the rolled down and and you get me what's called a phase inversion of the oil-water emulsion what actually happens is this oil-water emulsion turns into a lot of oil emulsion get it In version of listing here the other thing that happens years instead if we b speeds to watch yes there will not be enough did you need to so did the dollar goes through the all you do the role Gathright right so you will you need to suck in the lubricant at the entry tissue role too fast you turn to fast not going to be enough oil supplied at the entry and then you can get what's called oil starvation yes where there's not enough oil being supplied at the entry yes and you get a collapse of the oil fell yes In age decreases suddenly as and when aged decreases of course we're going into boundary lubrication situation situation has now these things can happen yes and then suddenly you find yourself with very little lubricant yes and you start making contacts between the 2 metal surfaces very high pressure contacts and there's going to be sheer forces sheer just so that's why we added these sulfur and phosphorus compounds 2 prevents welding in at the surface so when we have when you happen to have a boundary lubrication the problems Sears and you will have those for instance when for some reason or another you have to go and work into low-speed conditions or higher temperatures for some reason or higher roughness yes is surfaces happens to be higher efficiency and it then we luckily have In the compounds of the lubricant formulations you have boundary films phosphates and the sulfites the oxides and sulfides at the surface and soak them so you're boundary failed very close to the steel surface is In organic yes the Oriole it is on top of that that's how you good picture here so when the oil film collapses these 2 inorganic compounds will that the play a role 2 because you did dear to the steel surface so they can easily sheer yes and they have very high resistance against being squeezed out and Avery fracture resistance and because they're there they also make a difference difficult for the 2 surfaces to Caldwell to each other so that's why we have phosphates and sold so well you know you did the situation where D the the conditions become bad in during rolling happens for instance when you have to reduce the velocity yes for instance you rolling and then you have to stop rolling because you knew you finished the strip strip comes out of the melded so that you have to stick that reduced the the velocity so when you were starting to roll yes you don't you're not suddenly at very high rolling speed you build up right so you start at low velocity and so in these cases you can you can be in In in high friction condition OK and this is 1 of 2 the reasons why I'm working continuously is so important so if you are asking yourself why do we has the why do we put our pickling line this and put it right into the the Caldwell that's because the cold mill and can work all the time yes you can just attached the coils after the other in the cold mill never stops you never have these big speed variations that's it makes economic sense because you put things together and some equipment disappearance but but it also makes sense From the products point of view to work in constant and continuous conditions but
this let's get back to our of gold mail here when we start we have events of carbon steel we have Our grains here against you pass-through through the cold rolling mill and you basically have a plane strain defamation which leads to a pronounced preferred orientations of all these great so you get these grains and all pancaked as highly deformed the formations can be as I said 75 per cent 80 per cent so all walked more a lot larger than the defamation you give for instance in a tensile test and and as a consequence the orientation crystallographic orientation distribution changes us and in the case of carbon steels and what we want to have in our product is what's called a very strong Gamma we want to have all these little crystals we wanted to have the 1 1 1 orientation parallel to the 1 1 direction parallel to the normal direction all of the sheep yeah and this is
achieved by a combination of Levels of the formation and we re crystallization annealing so the cold-rolled material has a very high level of crystallographic preferred orientation but you cannot do anything with that because it's the 4 heavily deformed has no residual plasticity so you need to do 2 meal this yes and during the annealing process you recreate no defect density gradients His enter the highly textured Mike rastructure with 1 1 1 parallel to normal direction being the preferred orientation for the grains and this situation gives you a high our value of Hi plasticity and a very playing I myself refusal of Dr value doesn't change much as a function of the direction in which tested now that the
process of going from this to this yes yes but kind Maddox process it depends on time it depends on temperature it also depends on the amount of defamation you forgive such typically if you do if your deformation near the amount of information is of less than 50 per cent is going to take a long time to request and that's why In cold rolling in cold deformation we like to give large amounts of information because that will speed up the re crystallization why is that will because the dislocation density here is the driving force for the recruits lies Asian the more I have deformed the material the hired a driving force the faster it it will be crystal content so there are 2
ways 2 recruits lies the a steel products you can do it by Bachchan knee-length yes you basically take you coral cold-rolled material you put it in a furnace for a long time yes any letters re crystallized this is a tough 1 of these furnaces it's being open you can't see the corals to close are inside this this this is due here that's where the furnaces and this year is a continuous annealing for their you instead of annealing the coil you meal this trip and so you uncoiled the stress and you pass this straight through the furnace this please see here this trip 1 of I guess coming out of local going into the furnace I can't out of the furnaces here and this is the accumulator where you store storm some through hundreds of meters above and corralled struck let's start with the batch annealing furnace so in this furnace let's have a look at
it is this what they look like Indian terrier we stack the that the court's hands and we and we said Let's Dance flow through this uh the difference and we let OK and its protective gas it's hydrogen nitrogen mixture and it's a protective atmosphere so where due do to heating you do do heating on the outside of this furnace so there is this here this where you have burners yes and so that will speed up the interior walls of this the furnace and this radiation heat will then he ducked your appeal courts let's see here can
this this is what you see here this is indeed the the coils are inside this this furnace and this is a cover yes to cover which contains the burners so you can have this you know the amount of wait did you can anneal here as friends of the order of 100 and 15 so that means it's quite a few coils can go be put in there on top of each other heights and 5 meters and annealing capacity 2 . 7 tons per hour that's not very high so because the process is very slow you need many of these furnaces in parallel so if you visit Abacha kneeling a section of a cold rolling mill you will not see 1 for its you'll see many furnaces you for instance 47 furnaces and there may be even more basis has bases already that these places on which you can put a furnace yes b Why are they much which more basis then you have a kneeling goods because you have to heat you only need there the Hudson yes when when you he yes when you cool down you just don't need this discover so capacity 80 thousand tons per year surface cleanliness exceed the carbon residue that I talked about and the gas in for this particular picture he was hydrogen but in general it's hydrogen plus nitrogen and I'll say something about the the house the use of hydrogen and the heating itself is done by LPG or by electricity I'm seeing on
overtime here so I will let alone .period at this point and will continue I guess
will continue next week because Thursday in 1st of they this and I think we don't have money USA will reconvene a week from now yeah what is next I don't know is isn't it numbered is an official post at their haven't heard about them Is it official perspective tell it's written then I'm not going to say anything about that right so so will we
will need to perhaps
have the makeup classes or something the but so well then we need we meet next week on and on Thursday 2 don't forget that that there will be a 2nd request


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