Modern Steel Products (2014) - Batch Processing: lecture 14

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Modern Steel Products (2014) - Batch Processing: lecture 14
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14 (2014)
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Professor de Cooman builds on the previous lectures in the sequence, this time dealing with the batch processing of rolled steel sheet, and consequences on properties. 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)
Blast furnace Fiat 500 (2007) Cartridge (firearms) Sewing needle Tram Stationery Surface mining Material Texturizing Blast furnace
Typesetting Tertiäre Erdölförderung Hot working Steel Automobile Stationery Texturizing Casting defect Sheet metal Spant Angle of attack Roll forming Rolling (metalworking) Cartridge (firearms) Rolling (metalworking) Fiber Rutschung Surface mining Remotely operated underwater vehicle Shipwreck Ship of the line Material Transport Stock (firearms)
Fiat 500 (2007) Textile European Train Control System Automobile Texturizing Blast furnace Angle of attack Rigging Roll forming Alcohol proof Gentleman Rolling (metalworking) Kohlenstoffarmer Stahl Surface mining Material
Blast furnace Roll forming Automobile Surface mining Cartridge (firearms) Surface mining Ship of the line Blast furnace
Blast furnace Rohrpost Truck Blow torch Distribution board Vehicle Printing Blast furnace Kette <Zugmittel> Sheet metal Volumetric flow rate Surface mining Cartridge (firearms) Spare part Caliber Surface mining Ship of the line Hose coupling Material
Airbus A300 Scouting Cylinder head Blast furnace Laserschweißen Alcohol proof Photographic processing Gentleman Rutschung Surface mining Ship of the line Kümpeln Semi-trailer truck Carburetor Blast furnace Steel Stagecoach Texturizing Scouting Laserschweißen Cartridge (firearms) Work hardening Lubrication Photographic processing Sedan (automobile) Caliber Vacuum pump Ship of the line
Friction Airbus A300 Hot working Scouting Wasserstrahlschneiden Roll forming Alcohol proof Tire balance Rolling (metalworking) Surface mining Mail (armour) Material Water vapor Sheet metal Blast furnace Typesetting Tin can Fiat 500 (2007) Truck Steel Furniture Coating Kickstand Cord (unit) Galvanotechnik Railroad car Texturizing Titan Saturn System Mission Seeschiff Austin Motor Company Cartridge (firearms) Matrix (printing) Spare part Photographic processing Screw Tanning Steering Ship of the line Water vapor Flatcar Friction Last
Sheet metal Hot working Roll forming Turning Steel Surface mining Slip (ceramics) Striking clock
Friction Abrasive blasting Lugger Hot working Suitcase Game Deep drawing Lubrication Spare part Forging Surface mining Rail transport operations Material Melting Sheet metal Reference work Typesetting Tin can Tool Steel Vacuum pump Electric locomotive Machine Hot isostatic pressing Texturizing Sheet metal Pattern (sewing) Rolling (metalworking) Surface mining Roll forming Lubrication Spare part Material Disc brake
Friction Stoneware Hot working Key (engineering) Distribution board Printing press Cord (unit) Hot isostatic pressing Bridge (nautical) Texturizing Überschallstaustrahltriebwerk Roll forming Rail transport operations Rolling (metalworking) Volumetric flow rate Surface mining Cartridge (firearms) Spare part Surface mining Piston ring Friction
Coating Steel Mitsubishi Colt Key (engineering) Automobile Hull (watercraft) Coating Cord (unit) Railroad car Surgical suture Towing Kopfstütze Game Rail transport operations Kraftfahrzeugzulieferindustrie Surface mining Hochseeschlepper Cartridge (firearms) Spare part Negation Engine Firearm
Coating Typesetting Widerstandsschweißen Typesetting Steel Vehicle Distribution board Coating Galvanotechnik Yarn Railroad car Roll forming Rolling (metalworking) Cartridge (firearms) Spare part Primer (paint) Material Sheet metal
Typesetting Coating Widerstandsschweißen Steel Automobile Coating Coach (bus) Galvanotechnik Roll forming Cartridge (firearms) Gentleman Institut für Raumfahrtsysteme Spare part Primer (paint) Water vapor
Widerstandsschweißen Ship class Gentleman Coating Captain's gig
where we left off last week mainly with the kneeling so just to remind you that after cold rolling your material it is cold before it's very hard a very culturally use but in most applications so you need to read crystallizes on when you do director slice station you have 2 options you betcha kneeling or you can do it if I continuous annealing In the case of batch annealing you have a very slow process very slow process that you can see here that too the needle corals that stacked in the batch annealing furnace you need about 24 hours at about the same amount of time to but to get to cooling to during this time Re crystallization annealing so there's no transformation going on and on and you out you basically lies material he also developed texture in the strip material and and this can be very
beneficial to close you the texture we obtained a form cold-rolled low-carbon steels as defined by the parameters are yes the former ability as defined by the parameter or is a very strong function of the amount of 1 1 1 of fiber orientation you have and the material In the case so
and and this is what I have to imagine this you have the grains here in the In your sheet material which is which basically want to have this unit cell in each frame the Orient in such a way that the one-on-one access points upward but that's the main thing but you know there are some preferred orientations within this fiber inferences the 1 shown here were in addition to having the one-on-one orientation perpendicular to the sheets you have 2 1 1 orientation parallel to the rolling direction OK and this kind of orientation gives you high our values and low values of the planar anisotropy that's not the on the way you achieve this high texture I have a high volume fraction of favorable texture and is In the case of factional strip material due to very special phenomena which in which the precipitation aluminum nite tries during week crystallization has an impact on the texture so in order to understand this you have to look at the 2 temperature as a function of time yes and the consider the wreck crystallization stock temperature line and precipitation of aluminum light so when you when we precipitately have a precipitate formation dance wait it's characterized by kind that Texas so at the temperature below the solubility temperature of aluminum nitrite yes as a function of time yes I will have a certain amount of aluminum tried In precipitated so I can for instance and you look at this as saying while the amount of aluminum president as aluminum were sold the total amount of aluminum that you you have will be of the order of 3 sites 300 ppm yes and if I'm below the solubility temperature as a function of time I will form aluminum nitrate and it may not be this aluminum that's tied up as aluminum nitrate doesn't need to be on the entire 300 ppm as a function of the other so you can also see the notice at different temperatures and then you get the temperature versus time diagrams which we call the transportation the temperature time diagram the PPP's presentations shouldn't interpret PTT precipitation time temperature diagram and it it's basically a seeker of like this and the precipitation of course can only start as when you below the solubility temperature basically tells me that at this temperature here I very fast precipitation of aluminum nitrite that starts at this moment that OK so and then there is another curve curve for the work week slide station the process of re crystallization has a very simple In time dependence if I do a recapitalization of high-temperature it doesn't take long for the regionalization to start that if I do direct flights Asian at lower temperature there exists isolation is more sluggish typically we crystallization starting curve we crystallization start curve looks like that's so in the case of batch kneeling of low-carbon steels we have precipitation curves for aluminum nite tried and we have a we crystallization curve for it the steel yes new seeing no matter what the depending Bond the heating rate the heating right I can have different situations for instance if a heat up In this way I will start to read crystallization and then have later on Have the precipitation of aluminum nitrite if I make a slightly longer here point clear if I a heat at this heating rate I will start recruits still lies and start precipitating aluminum nitrite before the re crystallization endit if go this way I can see that both re crystallization and aluminum nitrite precipitation will occur at the same time and there will be the opportunity for the aluminum nite tried to I have an impact on the re crystallization and in particular what happens is this selection although the texture variance that become prominent so that's why the optimal heating rate has to be chosen and it turns out that this optimal heating rate is a slow heating rates yes this slow heating rate
that it's very much the
heating rate that you have in batch annealing so in that yes this slow heating rate is not necessarily and
negative points as a matter of fact it allows you to
make very formidable steals that's because this slow heating rate is optimal heating rate to get the good texture related to
form ability of course yes In order to have aluminum nite tried in precipitating during batch nearly you must have aluminum nitrite in solution yes and how is this achieve well to the aluminum nitrite must be in solution and how is this achieved while you do this by controlling indeed coiling temperature in they hot strip mill thank you the so this is shown here but this is the coiling temperature and we change the clothing temperature here from a very high quality and temperature to local and 600 10 so what you see is indeed cold-rolled and meal the material yes you measure the art value when the ah values high it means you have the right texture because but this effect the the influence of the aluminum nitrate precipitation on the Re crystallization detection for major new see if I'd call oil at low temperatures 600 degrees in law have achieve a high power failure if I call you at a high temperature In 700 etc and hired to me I get a much lower our value the reason areas when I clearly at a low temperature quarreling temperature the 600 I get I didn't aluminum nitrite stays in solution if I coil a boss uh 650 aluminum nitrate precipitates In the coil In the coiled to strip and so and that means you don't get our values that are so this means power value will be higher this means far value will be lost and you can also see that because the the you have an impact of D the precipitation of aluminum nitrite on the selection of the for the year texture components grains which certain texture components that will grow that will be favored during the grow you can see that in this the picture here and you have a high our value you get these typically these pancaked grains whereas if you had used a high calling temperature Ukraine's of very equally axed yes and and the texture is much more random
but that a very important the L the rate of the heating and cooling this however such an issue the slow rates of heating and cooling on the issue In but in many cases while well because company doesn't always make Hi form ability strip some of don't they don't need these very high highs are values so and then having this slow heating rates and slow cooling rates has an impact on productivity and infected so and that's why some of them but simulating the lines do not use or will use instead of beach annexed so that's a mixture of hydrogen and nitrogen in the atmosphere of the furnace they will use pure hydrogen and Puget hydrogen because it's a much better heat conductor yes will reduce the process duration and will also have an impact on this the cleanliness of the surface so if you compare here and each annex the thermal cycle only you can see here that surface temperature and the core temperature takes about 80 hours in this particular example if you replaces would hydrogen a little bit over half that amount of time to do as much faster and so productivity has improved then if you look at the removal of carbon carbon residues from the surface you see that you have about 5 or more milligrams of carbon the residues per square meter after and that's reduced to about 1 milligrams per meter infuse pure hydrogen so there are advantages to using
hydrogen the alternative to using batch annealing is so continuous annealing and what could be the reason but folded and use of continuous annealing furnaces rather than batch annealing furnace what you can
see it here you see there is a very large the range of heating rates yes between the surface of year sheet ended clear or you and and sheet at the 4 Of the course yes you can see it and and so what does this mean it means it's very hard to engineer the MicroStrategy of deep With batch annealing I it's very hard so but it's not
a problem with 80 continuous annealing furnace with a continuous annealing furnace you have the possibility to engineer the Microsoft truck and the properties in a much more flexible manner yet and the reason is because you UN role trip and you apply exactly the same but process to the thermal cycle rather to every part of the strip so in there and so as a consequence you don't have in homogeneity in the length of the strip in terms of properties and then you can engineer to Mike rastructure you can still generate a lot more Mike restrictions than in the case of a Bachand link so what you have you have the furnaces this new conceded assisting the continuous annealing furnace seen from the media outside you can do this to the strip basically unwound at the entrance it's welded to deploy the end of the previous and so there is a continuous flow of the material through the furnace at temperatures that don't change yes and so you can apply this exactly the same thermal cycle to as the entire stretch from the start to the year again in a typical the continuous annealing thermal cycle will look like this there are many different thermal cycles as it's possible that if you work in a job company that this thermal cycle will not apply will talk about this in a moment but this is a typical continuous annealing thermal cycle which original designed by buying the bonds deal for the production of the low-carbon formidable steals Prince for automotive panels and so what you do is you you if you reheat to much higher temperatures you can already see here over 800 at a much faster rate than you cool down slow cooling than a fast cooling then there is a a plateau you can keep the temperature flat here will see in a moment why we would do this and then you colder write to this particular unit here is a continuous annealing process in that line often referred to as C A P L couple wine couple lines in the industry it has radiant tube furnaces so so again you don't expose destruct surface 2 flame burner flames but 2 radiant tubes so that means that you have chills into tubes there are burners knows that heats up these tubes has and it's the radiant heat from the stew that will heat up the destruction and the gas atmosphere and the height of the strip period the strip moves up and down yes and so the height of the strips typically about 20 meters and the furnace this of course filled with a I protective gas so it doesn't oxidize and it's filled with nitrogen and about 5 per cent of hydrogen
so they have an entry in section in consisting of the core Oilers share welding and then decreasing decreasing involves removing of Byron fines and carbon and that's being don't by alkaline decreasing alkaline solutions will remove the the lubricant the leftovers and you will also have electrolytic decreasing which allows you to remove small particles from the surface and there's also can also be brushing involved in the process of decreasing and then used his you go through it accumulated there are accumulators In these lines at the front and the back the reason why we accumulate some strict In the Line is to make sure that the line speed the speed of the strip inside the process you know is concept yes and that's essential because if you want to have every point of the US trip go through the same thermal cycle you need to have constant strips speed that's why you have these accumulated I write so so how does this look like you have a heating section soaking section of 1st cooling and over aging typically as we just saw it is the thermal cycle in the previous slide and then you have a 2nd coolant typical temperatures here can be varied and the temperatures you can also be very so you have flexibility in these licenses the soaking is typically 700 250 and and this overreaching typically 350 to 450 OK so that's very
important difference here when we do this is a system that the this is here on top is a tyrant carbon phase diagram the Byron rich signed this year is the the most cycle for a batch annealing furnace where you have heating rates .period all 1 degrees per 2nd hand and cooling rates are even slower you can yield up to maximum 700 deg sees and a typical process duration will be 2 days as and when you heat and you call yes the carbon content Of the steal of the far-right will follow exactly the equilibrium carbon content like yes because we you heat up and you cool down so slowly so you end up with very low carbon in solid solution after the batch annealing In the case of the continuous annealing right to look at this scale here this is 72 hours this is 500 and the so 400 and something minutes it's easy to be seconds so we we're talking about an overall process duration it's less than 10 minutes and so the heating razors less than 10 degrees was 2nd the cooling rates between 10 and 100 degrees the 2nd at most the annealing temperatures of 700 or higher 702 15 and the constant in the process duration of 2 500 seconds maximums of less all less than 10 minutes it's all finished right in comparison to 2 days so as a consequence we don't achieve equilibrium carbon distribution in fact hour when we do the cooling here yes Our far-right is oversaturated in Cobb too much carbon and that is the reason why we have this plateau here any of the thermal cycle because let's see what happens during the thermal cycle 1 week the process strip so 1st the strip cold work so you 1st get recovery that around 400 450 degrees seized at 600 the re crystallization will be Starting in and by the time we reached 800 degrees C we get grain growth and texture development plans OK then we decrease but the temperature so what we get there isn't super saturation of carbon in Feira and so we need to make sure that this carbon precipitates out as soon OK and so this is done in this With recalled over Beijing stage at the beginning Simon tighten nuclear haves and it's slowly grows and so I get a decrease of the carbon content In solution as I go through the overreaching section and then you fight you to the final call now some lines yes again some lines process mostly interstitial free steel-gray the steel grades are all we all go through a process of vacuum the gassing yes the Steelers also alloyed with small amounts of Titaniums In other words In these deals because I only have 20 ppm of carbon and because I add we to 400 ppm of pending 2 to 400 ppm of Titaniums I form Karbala there is no need to do all 4 aging right so lines that process mainly so-called Titaniums stabilized I have steals these lines will not need these very large this very long over aging stages he there you can just do recovery re crystallization grain growth and 1 1 1 5 protection development and then just cool down does in this case the process is finished it 256 so you you basically talking about less than 5 minutes you process this trip but so I
but you can also do other things with the continuous annealing line if you have if it if you have the appropriate cooling sections or reheating sections example for instance is you can make very very hard Martin said greats yes How would you do this well strip goes into a furnace furnaces now at relatively high temperatures at 9 at this temperature we for we can transform the sting in this case we're not the only interested in texture development we're interested in Microsoft truck Terrel development so we make fully Austinite take annealing at 50 instance here and then we cool we cool for instance 1st slowly with the water jet and then very quickly With fast cooling and giving this gives you a water quench but the fast cooling water .period gives you fast cool yet and said Here you cooled below the MS temperature and as a consequence you for you go from gamma to after that you can't just give a small reheating to district so that you temper the strip that's a receding at 200 degrees C began 1 or 2 minutes and here in less than 10 minutes you have process just strip yes when you have now the home which seniors last Martin side very hard steel strip just it's very homogeneous properties Avery are independent from the position in the strip yes and the strengths of very hot you can play around With this kind of concept and 1 of the things you can do is instead of fully Boston enticing distract you can into a critically and distress and when you into critically Neil distress I just want you to remind you what into critical meeting so if I look at the Byron carbon phase diagrams Clinton dismissed this is to gamma radiation doses of openers Simon time this call for region if do an annealing In this temperature range for instance this much carbon steel I go to this temperature I will form 2 phases I will have verite and also Monday so my mike rastructure will look will have far-right and Austin Tex OK that's this into critical annealing as France's at 8 16 this might Mike rastructure Will for instance but it depends on the carbon content here that say will contain about 25 per cent of it will be Austinite when I do the cooling here I can't do the cooling such that this Austinite transforms to Martin site yes so this phase there's no change to my In my form now at room temperature a steel that contains the far-right matrix and small particles small grains of Martin side dispersed throughout the microscope In other words I have produced what is called a will face steel yes you'll find steals are very formidable very high strength steel and they are multifarious to face so big advantages
In the use of continuous annealing and that's the future for annealing because not only do we get homogeneous properties but to weaken gets a huge variety in steel like rastructure and and and properties as a consequence look at now when you have but Rick crystallized you don't every crystallization annealing I hope you will do something that but were at 1st worlds look very silly you will do but the formation you will deform here and this deformations called the skin pass the temper rolling yes and I am so so that's included and the animal you do DNA knee-length on the hop that galvanizing will talk about this moment and then the 1st thing you do is you into the skin fasteners that and why do you do this well you do this for 3 reasons you may have to remove a yield .period because they're still some carbon and solid solution you made you will also use it to apply a surface texture now this is not a crystal of graphic texture it relates to the way of the surface and the roughness of the surface I knew may also have to improve the flatness Of the ship that's the reason why you apply the 3 reasons why we applied a skin past and it's a very small reduction introduce it's not like 10 per cent it's about 1 to 2 per cent at the at most and it's being that special mail because you have a very long contact length between the brawl and the sheep I'm so you have a very large work role and it's usually the domain of dry uh rolling dry friction conditions and the defamation it is not homogeneous because we have these very low amounts of information defamation is not homogeneous oval come back to that in a moment that this and it's a small reduction so the amount of elastic strain the demand of plastic deformation you give is almost the same as the amount of elastic deformation of the it's a very very a small amount of information you can usually it looks like this but you can have a stand-alone skim past Mills where you bring in all the this trip and you uncorrelated and then you pass it through the strip mill and a new coil again as a single stand up in what could in what situations would you have this kind of investment well if the material has been Abacha because in batch annealing you cannot do in-line skating bats In the case of the continuous annealing you can have the skin passed in life OK so this is 1 of the things that is compelled to middle dust them if you steal after annealing gives you a still yield .period along long-duration you can remove it was this is the material without skin passengers this is apt to skimp on so why would you we want to remove it because this when win when you have this Lueders balance against the defamation it is localized Yoshida union to foreign material it's not homogeneously forming it's a deforming locally and that gives you surface defects and in many applications the surface defects are unacceptable thank you cannot use it for me to make a steel furniture you cannot make it to make steel cabinets you cannot use it to make cars that so you really need to remove this but the steel itself the strength it has no impact on the strength you the steel industry it's just surface effect is the quality surface quality visual appearance effect which and Andy's marks a call structure strings so removing them is so what happens when you remove this you .period yes you see that the yield .period the yield strength decreases as to the effectiveness of this past mill it's related to decrease in the yield strength work of his suggested this would be a skin past mailed schematic a new unwind you rewind use some strains typical strains a few per cent as as an example electrical steels electrical steels we do give them relatively high strains but that's because that will improve the magnetic properties and the usually get thermally treated later rock and that's this is the reason why we have this and so so what happens if you look at the yield strength as a function of strange you see that in steels that have I yield .period elongation there is a drop in the yields and then an increase as the the defamation will also give you work hard if you deform a lot you get work hard and hasn't minutes it's not good so the amount of defamation you want to give this typically at the minimum .period here and the minimum is less than 2 % typically around 1 per cent of the location of specific thus reduction yes and disorders is number of of graves and this is this some more
data here perhaps the more precise but you get the same idea here just as foreign aluminum killed by them drawing quality steel so you see that the yield .period decreases to a minimum value of at around . 7 per cent of the longer Asian wonderful motion and then as if I do too much information it will increase here is the behavior that In the question is not do we always applies confessed yes we do right we always do it because it's not only important to get rid of the yield .period you also want to have a surface roughness on your sheet and you also want to make sure that you sheet is nice and flat has so you always do it even for steals that do not have yield points the White steals don't have yield points :colon well I already talked to you about steals that do not contain any carbon to meet not only do you know of free carbon because the carbon the very low carbon content is stabilized with Titaniums BIS feels so when you skin past role and I are still you will not see a minimum obviously because there never was a deal .period along nation so there you only see work hardening this of Mori deform and I are still the higher strike duo face deals do also don't have yield points either so the deals because of the presence of Martin said so when you on the form them in the best they also only show work hard so you really need to have steals witches which have yielded ports and and those ones will be steals with about a new low-carbon steels where there is carbon in solid solution carbon or nitrogen solids OK right and so
this this is an example to you can you can not only look at the yield strength but you can also look at the yield .period along gations itself Booker and the more you deformed smaller the yield .period along duration becomes and you can see here the effect usually as I said a few per
cent less than 2 per cent and of the location is typically place that this deformation in this investment is not homogeneous and so on I. because the deformation the amount of defamation you yes only a part of the volume will actually go through will actually plastic lead to 4 yeah so this disk temper also stressed this in schematic will contain gray regions which is not the forum and the black regions which are the 4 yes and and that is the reason why we get they the the yield .period along donation the deal .period disappear because I at many points in the strip these black regions here I can easily initiate yielding there is a higher dislocation density has and and and there is no pending of the dislocations by carbon atoms and so I the initiation of defamation in these distributed .period news pointed of distributed all across the street look at skin past is also you used to for that to apply in this what we call a surface texture or surface roughness and so the white wine do we want this to be over specific Russians on the strip so well we wanted because we can by controlling the roughness on the trip we can control the deep drawing behavior of the strip in the press as it controls the friction it controls the distribution of the lubricant during forming has a controls the straw the transport of the lubricant to the defamation zones that's 1 reason and the other reason is because roughness on the surface of the strip that also has a big impact of the appearance the visual appearance of the part after painting yes so in that is so friends with you when you do it a press forming operation you will have your sheet and it will have a certain roughness OK so here are just want just so you know this roughness here we're talking about my crops OK not so not mm microbes is very very small reference very very small topography rather and and this is the tool for instance stamping tool this and there is a lubricant applied when you do this so soaked the the roughness here will have a big influence on the distribution of this lubricant and on the friction properties of stripped them to conventional roughness the lubricant distribution will for instance the very and homogeneous whereas if we controlled the roughness we can control the distribution of the lubricant and have lubricant pockets distributed all over the surface In a non-random when in a controlled manner can
so I and then the control of the the roughness is Don by texture rain applying as a specific roughness on the work role Of the skin past smell so is a picture Of the where not not distract the work role of stripped of confessed and this is a controlled but random texture and which has been of the obtained by electoral discharged capturing and this is a non-random texture obtained by electron-beam texture and of the role surface so with which you have here is a role skim past but work crawl yes and these so-called EDT or electric discharge capturing units that generate this specific roughness on the role surfaced this isn't EBT picturing machine electron-beam tech shrink machine where you see this is the role here and the manner in which you make these little the craters on the role surface is by an electron beam yes then let's have a look at these and how this what the the ways we make roughness on a roll yes there are basically 4 methods yes well you can do shot blast texture and where you basically use special shot the and you blast that on the surface we do have a get a specific the roughness and demanded the roughness is created when a particle Of this blast material hits the role surface yes it makes an impression as in the case of lasertec shoring we have a laser being pursued to laser other laser type of laser as we chopped this being so it goes up on and off on and off yes and we focus it on the surface of the role so where the laser beams hats we form a little crater and the the steel Is checked out of molten and ejected out of this crater and you get the solidified edge and little bets at the surface of laser treachery electron-beam shoring is similar except we have electrons that hits the surface of the role again you melt the steel surface you eject some of them at the molten material away and you end up with a little craters on the surface and you can do electoral discharging where you actually have a disk and electrical discharge and that will cause the you will sputter away some of the material and create roughness this way but the
EDT role texture and is becoming popular used quite widely because simple and robust structuring their methods so here you see that your work role this is the text ring units it basically consists of the phosphor bronze electrodes heads that will face the coral has and then there is some dielectric fluid between these these electrodes here and the role so you make you you apply a field between the still has their little metallic particles In this summer the dielectric so that the the particles will lying and former branch yes this bridge will calls the the spark yes this spots and you will also form bubbles studio form the liquid droplets here in the trader RAM and will form a little bubble yes and then you end up with the surface will little crater has and the whole process can start all over again OK so so this is so for
instance in the parts that are there that our have to undergo an important amount of deformation of the tribal diffraction behavior at press forming is very important and you want to have a little friction coefficient and that is achieved with the specific surface roughness isn't very often certainly in automotive industry these these textures are our discussed with the customer so that they have high yield and high productivity in their forming presses what's also important is that these panels here horizontal panels and vertical panels the the visible yes there that surfaced the painted surface appearances very important so you want to have things like a high peak count in your roughness you want to have a home which she distribution want ever-lower roughness of controlled way Venus in this year so that you get In improved paint flow and that of of improved paint appearance and also good paint a deviation In the case of stone chipping on the exterior panels very important quality issues arises now we've come to the idea end of the year Colstrip male and what comes with the Colstrip we already talks about the fact that a lot of district cold-rolled strip is actually coated and so that means that we need to introduced the
subject of coating
technologies 1 of the
year the interesting thing is
that related to steel
products it is and I'm sure you've heard this as you are when you were getting undergraduate education in materials science is when when when you presented a and when there is talk about steals 1 of the the big negatives of that is mentioned is the fact that steel rusts and the interesting thing is that in practice there rusting steel is is actually not an important engineering problem In many cases because not because it doesn't occur it's because we have engineering solutions 2 the issue this whether it's for cars or 4 buildings or for oil rigs as we know how to take care of so in in this sense it's the it's an arm problem and 1 of the big successes of the steel sheet is defined as the fact that in the past whereas in the past the automotive vehicles would be sensitive very sensitive to to roster yes I am nowadays and when you want to purchase a car you can be sure that there will be there with the car will probably show only very minimal rust 20 years from now this some companies actually guarantee easily get will guarantee you are of you more than 10 years without any rest so I'm the young and the reason why that is is because of a lot of parts of automotive parts are provided with the a coterie that will work suppressed this corrosion and a key part to this this coating is is the application of sink by galvanizing the application of saying by galvanized is not the only reason why of the have no corrosion issues anymore system of of a car will consists not only of saying but also of the the application of a phosphate later than fostered player and then so-called Elektra Ferretti primary and top colts 1 or 2 cops of and it is this system escorting system which has been very efficient in suppressing them corrosion but it's let's let's talk a little bit
about this In there very many applications where steel is going to not only Automotive a division what you see of automotive products but also parts such as exhaust systems consumer products also are coated and and the constructional steel products are also very often in coated that when that
happens we know what happens when it's not coated all the coating is inadequate um and in particular when there is no sing coating you get a very special types of corrosion such as filler form corrosion on cold-rolled steel that is painted or you can get and this this kind of corrosion here is called the area a cosmetic corrosion just visually very ugly to see but all dangerous what's more dangerous are perforation corrosion situations where you basically lose the material yes and that can be of course very dangerous and if these are structural parts when you see this in old cars you you you can see this this perforation corrosion the problem now know usually we cast fault corrosion performance by taking panels of a material applying it in a coding system and ends basically destroying the the coding system because if you don't do that it's takes forever to test and then you apply the South protest and this is the example of the recent example of results that you get when you apply it is protest on painted panels yeah cold-rolled steel on which you have applied and automotive paint system that consists of a phosphate layer and Electra frantic primer and the topical but the base coat and talk any would you see is that you get a while a red rust and also paint under creep the the corrosion goes under the if you use a hot dipped galvanized panel instead you see that there is very little red rust With except maybe in the scratch here and then you it's replaced by this White Rocks coming from the zinc corrosion products and now if you use instead of using a galvanized the material purists Inc coated steel use and alloy layer France in this particular the case zinc iron alloy a layer you see that the amount of corrosion is much less and that you also get excellent paint a decent so In the
absence of zinc yes the they the IRA will oxidize and the problem is that these oxidation products are you have a very large specific volume and so they will calls the listing lifting off of any any need them part of this deal that is protected or should be protected by uh paint system this shown here so and you get what's called Catolica that this Borland flock the reactions if all the the topic reduction of dissolved oxygen so oxygen and water yes are present everywhere in this system also where you have thanks because paints are the the oxygen and water can diffuse troop paint layers so for instance here you have oxygen and water reacting to form hydroxy and ions at the surface and picking up electrons and he's electrons come from the irony that goes into something and that's the and reaction that can occur at a surface defect for instance you get the formation of these oxides and that will lift off dioxin the auditory action is always saying yes so you you basically reduce the oxygen this form O H and ions us and so and and usually the type of oxides you form Our Oxy hydroxide it's just like for instance you tyrant voyage to New and that this going then further evolve into the formation of magnetite ore hematite at the surface in the scratches and that's would basically gives you disparate In the
case of the the zinc you see here you have this is a scratches you have scratch here this is the same player here it this is a primer and this is a filler on the door Of course it is also the name of a paint layer here and use and there is a phosphate later here you can see that the corrosion this an entirely limited to to the zinc yes he received corrosion products in Navesink layer it's actually a zinc iron layer and that's where the corrosion from this and you can even see it on this image here where you see the zinc layer White and all these products are zinc corrosion problem OK so you the presence of the same makes it possible to have no to suppress all the corrosion of the the IRA even if you have a badly scratched painter layer in which included scratching the uh the galvanized but later To achieve this the level of protection against aren't you need very little the SEC yes in fact but there the 2 ways by way with which we apply zinc is by electrical doing collective galvanizing or by halted it galvanized so I think when you electro coach stretch you typically have 2 . 5 to 15 microns per side yes for 20 to 100 and 5 grams per square meters obsolete we talk about again microcircuits electric coatings are usually applied on the consumer products yes and they tend to be on the lower end of this thickness scale public coatings are used In constructional applications of constructional steals and automotive steel and so in constructional steals very often and we want long-term corrosion resistance In the in situations where there there may not be a painter later applied and so we need to take a coldness coat the coating thicknesses so 700 grams per square meter which which makes it about 50 micron 1st that state but in automotive seals we always have a pretty complex coding system so I will have the GI galvanize coatings will go from 6 to 20 microns beside energy 80 this Galvin yield or zinc Byron coatings they'll go from 6 to 11 microns was so very thin layers in the will continue this next tomorrow experiences next week but
will do this tomorrow and terms and for those who haven't received the e-mail tomorrow we have to make up to make of classes


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