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Modern Steel Products (2014) - Introduction: lecture 1

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Modern Steel Products (2014) - Introduction: lecture 1
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A course of lectures by Professor Bruno de Cooman, of the Graduate Institute of Ferrous Technology, POSTECH, Republic of Korea. This comprehensive course leads the audience through a large variety of metallurgical aspects that influence steel products.
Keywords The Graduate Institute of Ferrous Technology (GIFT)
Paper Clock Steel Committee Ship class Winterreifen Computer animation Ship class Rutschung Book design Ship of the line Thorns, spines, and prickles Material
Widerstandsschweißen Optics Steel Hot working Vehicle Hüttenindustrie Screwdriver Reisezugwagen Alcohol proof Ship class Tire balance Engine Hose coupling Material Transport Pelzware Typesetting Tin can Truck Steel Automobile Stagecoach Train Railroad car Computer animation Moving walkway Screw Mode of transport Material
Paper Chemical substance Tertiäre Erdölförderung Vehicle Bessemer process Transmission (mechanics) Mitsubishi Colt Blanking and piercing Roots-type supercharger Separation process Roll forming Matrix (printing) Rolling (metalworking) Institut für Raumfahrtsysteme Spring (device) Spare part Ship of the line Engine Powertrain Truck Material Gate valve Truck Steel Mechanic Hüttenindustrie Eisengießerei Galvanotechnik Food packaging Railroad car Wire Finger protocol Laserschweißen Sizing Melting Computer animation Surface mining Cartridge (firearms) Forging Steering Material Flatcar Coin
Computer animation Steel Ship class Steering Railroad car Material Material Eraser
Steel Eisengießerei Vehicle Die casting Railroad car Hot isostatic pressing Multiple birth Spant Sheet metal Computer animation Kraftfahrzeugzulieferindustrie Lawn mower Work hardening Spant Photographic processing Porsche, Ferdinand Spare part Internal combustion engine Negation Backpack Material Material Electric motor Engine control unit
European Train Control System Ford Focus Bottle Steel Handwagen Fahrzeugrahmen Intermediate bulk container Camshaft Vehicle Railroad car Hot isostatic pressing Wood drying Spant Roll forming Computer animation Wood Lawn mower Spare part Backpack Engine Material Material Backpack
Steel Furniture Piping Furniture Distribution board Intermediate bulk container Food packaging Bridge (nautical) Food packaging Bridge (nautical) Computer animation Ducted fan Grubenbewetterung Ducted fan Material Gun
Steel Machine Electric locomotive Railroad car Aircraft carrier Seeschiff Rigging Computer animation Cartridge (firearms) Tanker (ship) Engine Schiffbau Electric motor Material Schiffbau
Vertical stabilizer Optics Optics Steel Piping Hüttenindustrie Machine Commode Railroad car Seeschiff Wood drying Computer animation Transport Material
Truck Steel Steel Train Texturizing Wire Missile Computer animation Plane (tool) Single-cylinder engine Plane (tool) Stream bed Ship of the line Material Flatcar
Steel Steel Ford Transit Hot isostatic pressing Wire Pattern (sewing) Sizing Turning Roll forming Computer animation Alcohol proof Cartridge (firearms) Thrust reversal Spare part Surface mining Firearm Material Mail (armour) International Space Station
Typesetting Vertical stabilizer Steel Sizing Computer animation Cartridge (firearms) Drill Book design Clothing sizes Material International Space Station
Computer animation Ship class Spare part
the committee hearing clearly so before we start and like to have your your name on the paper so we can have a look at it afterward so just put your name on it and your affiliation so if you're wrong From GST right until Schiffer for material science or any other department right and the average and please use nice nice script so I can read what's your name this the rate of so did number of things the material will be on the E-Class site yes there's nothing today so don't look for it has yet to come the it's 1 thing the other thing is that did that Of course is being taped right so if you want to look at it again some you miss something or or you missed a class that you can always have a look at it and and so please refrain from you know using the mobile phone or something so the 2 classes this is also a nice and easy and to watch without disturbances but let me have refused number of other EU as we start if you want to won't have a textbook that goes with 2 course there is a book called Fundamentals of steel products physical analogy it's available from IST . org and you can order it on this site and the price is 50 dollars it's a softcover His mother material from the course in there but not everything but that's a good thing book to have if you would want a textbook for this course you don't need to buy at all the material would discuss will be in the slides that will be on the site the class of right then some organizational points we meet here twice a week at 11 o clock here on Tuesday and on Thursday and then we started 11 we finish at 12 15 years room for 1 I don't have time for my courses I don't use exams or matter we do want quiz every week so on Thursday morning we take 10 which is really took 15 minutes for a short quiz about the material from the 2 previous classes so you don't need to just need to keep up with the material so that gives you also due the entire the semester you will have about 100 to 150 questions that you will have answered and that is plenty of and I also use In order to foil having it language bias yes the answer the questions are either multiple-choice or yes-or-no questions right or it's very simple calculations there is there is very little language bias To date the tests also it's just if you worried about the number of quizzes rage you can miss 1 or to quizzes them because you sick or United have to go conference or you have is an experiment you have to do out of town so I will understand that yes if you missed more than 2 quizzes you're in trouble .period that's the idea ideas of that
you you take courses alright would would is the essence of the course when I designed to cause was the big idea so most of you for all of you either in materials science or in steel research yet and so would this course offers you is the big picture about steel products Seoul on most of you are either a master's degree students the PhD students you're involved actively involved in research but research tend to be very focused by its nature so you will be working all partitioning of molybdenum you know 2 car by in a heat-resistant steels that this very tiny little it also science Europe Uribe's working on this and some of you may be doing this study of this partitioning my motherland the The course offers you the opportunity to see you know where your research for From Italy steel products point of view that's because we easily talk about steals but there are many steals the very many applications and steals a very different yes so what's the big picture but so although this is not the traditional materials science courses we tried to use this materials science well-known materials science Trudy drawn yes where there is a balance between looking at Mike rastructure of the material looking at how the Microsoft rupture involves Ariz created during the process sees such as for instance here in the forging and in looking at the properties over Steele's years and also looking at the engineering performance In service for instance when we talk about the chemical properties of steels for automotive crash resistance is the being application the performance parameter to will try to To also incorporate this view this holistic view in and of course but said at this for the
start here the 1st couple of lectures will just we heard saying just to make sure everybody has the concepts knows the concept in the world will be talking about the fundamentals for the the 1st classes so will talk about it Kompas things like compositions of steel steel crystal structure Microsoft rupture strength from a very general point of view so and as and and this will allow us to set the stage for the relationship between properties and Mike rastructure ruptures and also how the MicroStrategy is generated In but mainly thermal cycles and thermal cycles which it is vault involved mainly what we call the decomposition of Austin right and also also show you through examples that's a you know what how it how you go about getting these properties in practice where I am so this course is not a basic core introductory level course interview looking for a basic introductory level courses is not that I assume that you already have a considerable amount of you know knowledge and you feel familiar with no material science concepts such as diffusion of I'm not going to have explain to you what diffusion as I assume you know what it is and what controls because this is not a course about fundamentals wrecked so at the beginning I just want to stressed the discuss rather than from the an aspect of of steel is like why is it that the the two-day hearing problem we are like a whole institute devoted to still science and training in those 2 as you know what makes me no steel so you know special that you know you have steel institutes across the world working on this material as well 1st of all I want to do to show you how How big the material errors but and this is for instance is a graph here where I show you distill production and millions of tons per year as a function of the time here and up to say a 1970 she's about 4 years ago Levels of steel production had reached around 600 million tons a year and a nowadays we are will probably reach 3 times that amount thousand 800 His million tons is a 1 . 8 billion Thomas a year of steel production that is incredible forceful travel increase yes but at the inn the growth rate in steel production but it's also you know a few at a massive amount of materials so steal still is the material that we not only make most of in terms of weight but also in terms of volume and a lot of it is driven by economic growth of course we would know steals gets gets produced because its use yes you never forget that yes what do you do still research and you the work and steel plants because somebody else also there users of this material and needs and an example for instance are the automotive industry has "quotation mark of industry and you can see how the the trends in the number of cars produced every year but in the world that follows very closely the steel production units and so it's very important you to realize that this it's not that car production follows this steel production it's the steel production who follows the growth in the car the man OK and it's very important here that's the driver is economic growth and jobs how many cars do we produced per year in the world 17 2 million cars per year 17 million cars a year against hazardous a huge number and it's growing goes up and down of course this is for instance doesn't that here is the recent financial crisis this time but you can see the numbers are back up has and will continue to grow this is only cars this a passenger car doesn't the doesn't include light trucks it doesn't include trucks a dozen accrued all the all the other transportation means of transportation we use it's just basically your regular type of passenger cars here right so but when we
talk about steel to stop so we talk about mostly carbon steel and that's going to be they core of the costs that will be talking about carbon steel and carbon steel families family has a little brother for this In this stainless steels that in comparison it's only the size of the the stainless steel production is only a few per cent so few persons Of the the amount of the amount of steels produced every year from the list deals are steals which have very different physical metallurgist units the produce In a similar but different ways and carbon steel we will not talk about stainless steels in this course if you want to here and learn about stainless steel there is a separate quarters on stainless steels acheived it so you can't you can take that course and and hear about these products and their physical mental agenda production yes and usually but it's not always the case stainless steels are produced in plants separately from carbon steel but again as I said it's not always the case you have smaller companies that will produce commercial grades notice using electric arc furnace roots and it will produce both carbon steels and certain of the new very well no 1 stainless steel for which there is demand OK so altered the application areas for stainless steels and carbon steels are deference so date basically served other industries so if you look in the carbon steels Our close to 70 per cent about 70 per cent of the currencies are using enough transport as I said instance automotive trucks industry Watson to steel goes in there and there is and the building industry structures civil engineering structures buildings etc. 22 % so these are 2 very big clients and well-defined clients of the steel industry carbon carbon steel industry in the case of stainless steel the processing industry and the agricultural and fooled products industry uses 40 per cent of the very different clients they make use of the fact that stainless steels are resistant to corrosion and so for instance in food production yes it's extremely important that your view of the materials that come into contact with food are not contaminated in any way or form so for instance if you visit a milk processing plant for instance has everything is made out of stainless steel yes there's no carbon steel being used so different clients different metallurgists and so we will not be taught will be talking about these and carbon steels in the cost of
the lectures now and again let's have a look at numbers here yes so you get an idea of what it means to produce 1 . 8 billion tons of steel for years In an integrated steel company that's a company like Paul school 1 year plan yes In the steel plants will produce steel treatment of the IRA In In process that's called the oxygen uh the BUX is the basic oxygen furnace process In this process you know depending on the steel plant in the technology 250 Thomas to 400 Tong about every half an hour yes 24 hours per day 200 attribute 365 days per year yes In 1 furnace yes there are many furnaces blessed with basic oxygen furnaces in integrated plants but if these in plant like Bohon works and we produce flat flat products in such as coils yes these 250 to 400 tons are translated into 10 coils of 250 tons or 11 coils of 36 tons as 36 dollars being big coiled so the length of these coils varies 27 thousand meters so if you uncoiled theirs you have 27 kilometers of yes or 40 thousand square meters of material that is being produced 30 minutes so we're talking about you which amounts of material that's 1 of the strengths of the steel as a material is that it's available because obviously we would talk about hung about the many companies like this in China japan Western Europe North America that produce at this same right so we produced huge amounts of steel soda consumption is very high and if you plot the consumption of steel as a function of the children's consumption of materials and as a function of the price you also see that steel it has very low price yes it's a very available material and it's also very low-cost materials yeah and just so you you can see here Steel is a top here then you have a plastics of aluminum structural plastic composites magnesium epoxy composites hi tania that we use I'm very many the materials and steals I but the whenever we do this yes In many applications the the advantage of the low cost and the availability of the the material is very important to him so for instance the car industry today use steel still make very many parts In a powertrain parts the year spring for suspension Springs Fla the engines Of course mechanical parts for transmissions the motor here we'll exhaust systems etc. the the main part of the the use of
steel His body in white about 40 per cent of the car's weight is in steel and this for the body but of the many in the car many other materials are being used to make car yes even what we call the steel car now contains many other materials bentsen
particularly if you out if you look at the materials that are being used To make a traditional that for instance this yield which is produced in Korea today then a you know we make this is was the body of the car as with the steals show in in this graph and his graph shows the properties of these different steals totally long-duration as tensile strength you know from your materials science the classes that whenever you have high-strength materials tend to have low Dr. Lydia it doesn't have to be this way there are materials humorous deals that don't for which this general rule does not apply but but does apply in the case of of the steel spheres and and you can see this is a crime that demanded the properties of the steals that use of very different you have very soft steals about 300 mega Pascal in tensile strength a new very hard up to to 1600 mega Pascal strength and in these steals can have a softer ones a very high plasticity reductive if you make a tensile specimen in tested 40 45 per cent of the the harder materials much less plasticity have much less plastics but you can them
replaced steel when other materials the car industry again the car industry doesn't use steel because this because the steel industry tells it to yes the car industry there's nothing to do with steel industry yes they just use materials to make cars so there I have alternative materials are available 2 of the car industry do to do their material selection it can use aluminum alloys that Itanium alloys if the use malaise they do use polymer making use of very strong carbon fiber reinforced composites has and they do they but we show you for instance here the city's aluminum alloy well are used 2 to use the different ways I don't know if you familiar with is that the different ways in which you can make cars you can make cars into the model cop concept where you have to do the body of the car is also the structure of the car yesterday or you can have a space frame concept where you 1st built a frame and then you put then that's going to be to the structure of the the structural backbone of the car and then you put external parts on the on the on off body parts on this frame yes so there are different to alloys that they're being used different materials that areas that have been used yes of course if you make Monica lock you have sheet aluminum sheet if you have space frame you will use die castings and extrusions used to make the space for it so use aluminum alloys that you would say we you know that the density is much lower than that of steel so it would be obvious change to make certainly because you can see the properties are very close to this in the properties of the steals we already use yesterday but that masks the number of things you know you're probably familiar with aluminum you know there's nothing wrong with the little Missouri plastic UCD nation very high so what's no 1 on Tuesday I'm not well there some tension challenges 1 of them is that this strain hardening is also issued you you take in the aluminum and deformable that it doesn't harden as much as steel so you body is aware yes and the strain rate sensitivity it is negatives what does that mean that means that it's harder to make high-quality presents and yes and the material I will give you more difficulties In during press forming and that's that's how you make body parts is my press forming wooded dies and so this lowered so there are manufacturing challenges when you use aluminum that do not exist this Wikinews state it's a few more words about this minimal but I want to stress that to you the fact that so but the steel is not used because the steel industry forces everybody to use its its use because it's in the match you people needed for public and in particular while we're talking about Karzai I want you to know that but the still this this competition between materials has always existed in its very often you know on people presented this as if I this materials competition is something new and dangerous and you know the challenge that the steel industry has never faced but you know for instance and there's some really interesting things for instance of the over 100 years ago yes I went out and people started building cars and user is a series of cars from Nona Portia cars loan arresting me company and Portia is the designer it's the same portion of that Ferdinand Porsche from the racing cars says the same person this is these other cars he decided early in his career there is no steel being used here Kassirer and some and unwanted mainly yes and is also no internal combustion engine user electrical cars all 3 of them you may use to win all the races yes and no without using a drop of gasoline that's 100 years ago that's actually how to steal the car industry started electrical cars and no steel yes In the island AP and and I'm
only elected to internal combustion engine that was invented and developed and it was very clear that the performance of the internal combustion engine could not be matched by electrical motors so this whole early electrical motors vehicle development was pretty much stopped but about a
hoops and steel was used
in the fifties differences this car here yes is fading French carmaker that doesn't exist anymore "quotation mark bottle on a slow but they used to produce cars aluminum carts there's nothing special about this my by the when I was a kid I used to go and do my own uncle had a car like that so very well but to disguise a very very common you know this is not a luxury car is a very common brand in France other in the fifties also there were companies start ups by I'm making electrical vehicles )right parenthesis whose car called the Henny kilowatt yes what they made very few of them because nobody bought yes but you know let cars announced steal vehicles it's always have always been around as all alternatives and nowadays there is a little new materials yes for being tested and as you know carbon reinforced the polymers composites used for instance to make the frame of the I 3 BMW 3 BMW in the car that has some song as the batteries yes and uh STL is an American company that manufactures automotive carbon fiber reinforced composites and it has an aluminum chassis guess yesterday the strength and to carry the batteries on this car it is very lightweight tests despite the very heavy 230 kilograms of battery pack is 1250 kilos In total so a waste actually very similar similar weight and had no small still the and so competition and this is steel in automotive industry in other fields there is competition too so that is not new then what is the driving here 1 very often the driving force is Mass containment yes because steel has a density of 7 . 8 as grams per pupil centimeters and you Titaniums you can have this Bloomberg even lasts magnesium not even 2 grams per square peculiar centimeter and plastics are even lighter Of course however engineers don't make materials not make materials wood density of smaller property it has an effect on the mass but you stiffness is important for structures strength is important and then if you want to make something out of the form ability of a material is also important to that if you look at France the modulus to have an idea of the stiffness still has modulus of typically 200 10 but Titaniums is already half that amount uh aluminum a 3rd of that amount magnesium a fast and plastics have no stiffness whatsoever so if you want to make something suspect and those magnesium it will have to be more voluminous right so the advantage of having a lower density is not really 100 percent because you need to use more that was you need to have a look at your your part will have to have a larger cross-section you just have to get the stiffness right this strength is of course also important now he would have to be careful because there are many different steals it in a very soft ones in very hard ones I you can have many different I Tanium alloys aluminum alloys itself so In and particularly when you look at Tania Itanium properties covered very much those of steels With the advantage of a it's so bad but you can see here that if you want those very high strengths 1500 may get a part with 1500 maker Pascal of so all 14 hundred megabytes low-yield stringers focus against I'm it's going to be impossible 2 to get this with a plastic magnesium you will have a hard time finding that material etc. that doesn't exist basically the same thing with aluminum etc. so when it conceded very high strength you have a problem with this this you don't you did not many alternative materials but and it now and I do have to say here I didn't put envy carbon reinforced composites and they do have higher no highest-ranked season and then you have the form ability and because in general but you know if you want to bake parts you 1 of the easier ways and with high productivity the 2 forms nice parts is press for me it's very little time to make a lot of them so and you can see here also that I didn't do that the range of along basins you get with steel products is very much larger than the longest instead you can achieve with alternative materials such as aluminum Indonesian etc OK so we have some strength
aspects of sees as a consequence we still know still see that in very many applications steel is the material of choice at a construction applications definitely you familiar with reinforcement bars structural steels bridge cables yes all of them made of carbon steels the roof
tile panels interior of the the building's ventilation and air conditioning ducts roofs stainless steel in this application but
packaging furniture very often we have of steel products being used we look around this this office is a lecturer room we don't see the steel yes but it's there for instance of this this most of this desk is actually still you're so when we spend but you look at it you don't you don't think steel bread that actually most of it is still and again in all these if we would remove the paneling yes uh everything you would see behind the paneling would be still just mostly steel pipes the structural steals etc 2 that of course young
consumer appliances are made of steel very often we already discussed the automotive applications there are certain applications where and even if yeah you know you we would start to use posits a room to make cars you would not be able to replace that easily in the power and energy applications for instance that's the case electrical steels yes so stiff that are used to make the electrical motors very tiny ones to do very big ones they're all made of steel yes made of steals because of the electrical properties of status and the magnetic properties of states as you know so lecturer motorists transformers all are an entire energy grid depends on a very high quality of power transformers they're all made out of steel and then you cannot just replace it with an alternative materials 2 can end
all industries and shipbuilding related to the oil industry Oleg gas industry rigs like these offshore rigs this uh tanker here In gas for gas transport this carrier here all of all of these are made 100 % carbon steel and to very and
this is the oil industry and to not only the structures but all these pipes that go into making and transportation and into I'm getting the oil and gas out of the ground and transporting it all of this is that all of these is made
of steel market so we have a material that has a very very Hi demand it's got the right in terms of price it's not the excessively high prices and there is a lot of it available yes there is another a big strength that still has yes it said the price stability yeah I many uh materials are very sensitive to what called speculative price changes so where people buy material just for financial reasons to speculate on price changes aluminum many the pytania zinc Nicole 1 the prices vary fluctuate a lot more then for steel and the reason is because people by and so nickel just to buy and sell it to make money on the transactions they're not interested in using it it in any way is just interested in I'm not making money on that commodity this is something that is totally absent in 4 steel the price is determined almost exclusively by demand yes and supply so and this is 1 of the thing is really important because if you're going to if you're a big car makers what Toyota all GM you don't buy 20 tons of steel you buy huge amounts of steel and so you make big contracts which steel companies over long terms and so it's very important that the price remains the same that's because of the prices fluctuate this is going to be and the additional costs because you will have to take an insurance yes To protect you against very big changes in the price they if the price will double yes all you have to have insurance that will take care Of this change and yes so you have to get 2 hedge you are In yourself you protect yourself against these fluctuations that things become more costly yes right God so so much for the general introduction we will now start with them admittedly reviewing the basics and 2 0 0 4 the year physical malady of steel and as you can see here in these micro grass 1 of the important things to do this too To look at Mike rastructure insisted and but when you talk about Mike rastructure of structure steels it's important to us we realize that there are many scales of Mike rastructure for instance there is democracy would call the macro scale than Mesa skill on the at 2 Potomac sticks scale has obviously you know the macro scale that's no uterus something you can capture with a camera it's something you can see massive scale it's what you need an optical microscope for years if you want to go down to atomic-scale you will need an electron microscope high-resolution machine yes and all these things are important for instance it may be that you observed a crack in your material visually the material is this season's crack of this crack may be due grain boundaries yet the cohesion of grain boundaries because of grain for some reason there is grain loss of grain boundary strength you would be able to see is the cohesion at the massive scale and the optimistic scale would allow you to you could see that this is the cohesion is related to segregation of sulfur phosphorus at grain boundaries for instance as such what and this all is MicroStrategy just like rastructure spans many scale so will talk about this
Microsoft truck train will begin with a very simple things cost you familiar with that is when we look at it steel This is for instance a steel it's a mark citic steel it looks like a baby what does it look like the looks like you know it's a very complex yes I'm about what you're actually looking at is a polycrystalline materials and what these things are here this long things with call last we refer to this structure was Latham Arkansas and although it doesn't look like it if we would have and be able to us look at the crystal structure here it would be as ordered yes as crystal line as the single Pollack crystal all this magnesium oxide all the crystals you familiar with in the courts Chris same it's a crystallize it's that agglomeration of Chris stops and so there is a crystal structure to to steal
and we know that of crystal structures this is 1 of the crystal structures of Steelers we have translational symmetry you have symmetry axis Madrid planes and other cemeteries in any way which we will be using the courses unit-cell here yes and so if you translate if you repeated this unit cell in 3 dimensions you can we create the atomic structure of 1 of these flats this of course you know that and we know that there are 2 important for steals important but Crystal Graphics variants that's the the CC variant and the FCC vary from which we the call respectively right and Austinite respected this is the BCC this units sell for Arab yes In our Pollack result it basically means that the we have this unit cell this orientation is different from grain to grain and that's why I wear these 2 grains meats but there is a mismatch small large mismatch in the orientation and that's why you can't match these action these boundaries yes and make the the missile scale visible the orientation relative orientation of these units cells can be random or can be texture if its stature it means that the difference in orientations between these unit sales from grain to grain is not very large so there is a problem with goal of preferred orientation or a crystallographic texture and care certain products such as should the products wire products Have you can have very pronounced texture directions OK again you're
familiar with the crystal structures that you don't exist for Ireland for pure Al-Faran which has been BCC This is the units BCC unit-cell you know this from introduction to material science courses you've had as an undergraduate at short and you have the SEC structure which we called gamma or Austin here very different unit and this phenomenon called polymorphism I you see here that the unit itself dimensions are very well known what but . 2 8 9 nanometres for Alpha parent and its larger gamma are now is there 1 important thing 2 not to forget said although the gamma iron what this parameter is larger this is the phase if you compare the density of between Alpha and gamma this has a higher density because here I have more atoms 4 units sell then he area to act as Brazilian itself here have year after letters a year for atoms for units Account so the higher density is this way so when I go from their right to Allston nite there is decreases In size and dimensions on increase in just to make sure I need you know confused so few if I have a piece of steel and I it's far right at room temperature NI heated up to a temperature where the transforming face transformation occurs and then this sample this smaller it's it's reduced in other words I have more atoms pop closer to the the patterns of closer together to get a higher density and so the density goes up this the same number of atoms right it also means that if I go from here to here yes from high temperature To I have an expansion this winter still here in this direction have contraction His direction and expansion so that means that With the transformation there will be there may always but there always stresses involved here because when you when you go if you cool down something the temperature is not the same everywhere but can be slightly cooler in 1 area than the other ones so the transformation will not be homogeneous yes and so you may have internal stresses as a consequence so polymorphism the C C R and S E C R SEC irony is a higher density so there's
change in From high-temperature SEC to know temperature BCC In carbon steels workers at around 900 and 12 degrees C for pure computer that no In steals Nos and in any other material that undergoes a phase transformation in the face transformation itself is a function of the temperature at which you do this this transformation and it will also be time-dependent phase transformation can be very quick In this stress this from here to here can be very quick look can be very slow considers a time dependence and there is a temperature dependence so presses this this this is here and stood the reverse if I go from Austinite I cool down too far right so I know as I said material will expand I think this is at 9 and 12 degrees C yes but I can do this transformation at the different temperature yes I don't have to do it I can know France transformation at 800 deg C and the transformation will not be suddenly not you know instantaneously the material will not instantaneously transformed From Austinite affair there will be a kind antics in so you have to face transformation kind that takes are involved in the polymorphic transition from gamma iron to Alpha come on and we presented a spin and diagrams which will discuss repeat a little bit in the In the coming the coming of for instance but it holds these transformation temperature time diagrams are applied to steals Dakhla France's this example here where you have runout table that's a part of the strip mail where after you've deformed the material hot deformed material you cool it down 2 clearly was the 1st ever In the temperature time the diagram you have a fast cooling rate To the Correla and once the material is Escorial these temperature change as a function time is much slower you have a much slower calling him and this is a transformation from damage to Alpha in this particular case these are the kind that takes it starts at this temperature yes if so well below the would go equilibrium temperature at which the transformation should start against and then it there is a certain kind attics here and I will see what the transformation to provide the impetus of 2 transformation to perlite is as we go along Of course steals and not pure irony their alloys the alloyed yes and as the name says it already carbon steels is no 1 of this the elements that is present in these in the steel will be caught and it is carbon may or may not play an important role for instance in wire products yes commonplace and very big world because we use a lot of carbon in wire products very soft steals there are used for demanding form ability applications we use extremely low carbon ,comma so that could affect and impact of current is minimal and so it pretty much depends on the application the toxic but we all these deals we called and carbon steel even the department range can in be very wide and the impact of carbon can or cannot be imported so steels are not pure iron their iron alloys and we have interstitial solutions that means that we
have small interstitial carbon atoms and to a lesser extent nitrogen atoms we have interstitial these interstitials in particular carbon and nitrogen and yes no will be interstitial is located in the latter's and it that we know from our own studies over many years that did the favorite position of the carbon madam is in the Oct taking droll positions this book book both in the far-right and in the Austin area and so this is desired the optic he drove In and the many this is 1 of the officers many different options Dr. he and this is the optic in the Austin yes but now I want you to its important for you to realize that this size the size of the October he drawn yesterday the size the space available here yeah and the space available here is a very different units so the diameter Of the October the drill space With just before I go on you have to realize that because I To make the crystal structure clear very often we draw the unit-cell like this when we do this we make the fiery items very small yes the iron atoms are there are much bigger than that actually they touch each other In in this direction yes In this out and this sentiment is out of touch each other so but if I would do this if I would draw them size you wouldn't be able to see the crystal structure very clearly so we make them smaller but that was actually much bigger and it particularly along along this these diagonal touch each other so that that this is the space he Antioch he space is small and the diameter of this is this time a point 0 3 8 nanometers and its 2 ends much larger in the case of 8 Austin attic that he drove into assistants this has a very big there implications carbon is not soluble In the a right and it's very soluble in Austin this is a very important thing you have to remember and then verite and it's too density prospects and the other thing is that In steals where you have carbon carbon is soluble In Austinite it is not soluble In Sara at room temperature but then you will oscillate ways attended you know when I was an undergraduate they told me about fire and in price and why are you drawing it here if it's not soluble in which the point point is is that that's the equilibrium situation carbon cannot be is not soluble in fairer at room temperature but when you process steals when you make sales you are rarely in equilibrium situations so you you process materials quickly you have very high calling and you can keep elements that are not supposed to be in solution you can keep them in Super saturation yes it also means that if you give the material they need the material a chance to get out of the latter's yes it will do so very quickly In the case of carbon you know you may not know that the common will very quickly make a Carbide called semen time as soon as it gets the opportunity OK so and so what happens basically and uh when the carbon is kept in solution it will do this is to set this to he drowned in the sea see it will distort artistic doctor he drove us and so this elastic energy is is a relatively large and constitutes a driving force for the precipitation or formation of Carter writes
but but when we I didn't think of Steele's we not only think of at the carbon and solid solution but we also have a lawyer elements in uh solution Seoul for instance elements such as manganese silicon crew Our common allocating elements 2 steals and and so they can be in solution in this deal with that and then they are substitution also solutes their replaces iron atoms has on the Irish lactose some of these items may have Estrada the size similar to that of Ireland in they can be larger or they can be smaller for if you have Cro-Magnon needs and Molly the larger atoms yes so around these items they will be it's a lattice expansion plans all the atoms can give rise to let this contraction in silica aluminum will contract would make the latter deed when you and allocating elements whether it's carbon guide to Germany manganese etc. You will also change the thermodynamic stability of the alpha phase and the gamma phase since this and other important for him From Linux excessively and so on as a consequence you may favor the formation of Austinite relative to you know the saying that Alinghi elements have is they influence the it's kind Maddox Of the transformation told you that gamma transforms the Austinite demarches was referring to in it will do that with certain kind if you allied also denied the kind that ticks may change why would do kind that exchange well take for instance carbon yes when you making verite from Austin I the carbon doesn't want to stay in the far right endit there is a process called partitions and it's partitions To the Austinite that's transforming this process yes this process has an impact on the kind that the following elements have an impact on the kinetics and the relative stability of the Faces Inc yeah actor we
close to finishing in because the part I have to talking about it takes more than 1 minute to start will stop here so as I said my earlier on we have 1 quiz at the week because we just started with the introduction to that is no quiz on Thursday July the quiz next week and yes and that's basically it and I will I will put the the lectures on the year the class for you too look at two-day thank you very much