Modern Steel Products (2014) - Fe-C phase diagram: lecture 3


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Modern Steel Products (2014) - Fe-C phase diagram: lecture 3
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3 (2014)
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Cooman, Bruno C. de
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A lecture about the iron-carbon equilibrium phase diagram. This is a part of a course of lectures by Professor Bruno de Cooman, of the Graduate Institute of Ferrous Technology, POSTECH, Republic of Korea. This comprehensive course leads the audience through a large variety of metallurgical aspects that influence steel products.
The Graduate Institute of Ferrous Technology (GIFT)
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OK so let us start personal and went to remind you that on Thursday there will be questioned and so his quest every Thursday from now on and and that's basically where are In you can get your great struck all right so and the course is I remind you that yes and no things just because you have to go through with you use them now hearing from me In the last few lectures and you know you should be fine with the Midbury all I've given to you registers and the trick questions OK so wanted to on that is the question of ovaries straightforward and you will see also that and in the E-Class get lots of material because because it's a technology costs and you know it I want to make sure that someone will graduate and work in the industry say industry of you know you can go back to this course and you know get information from it at some in some way useful to you In Europe in Europe activities at that time so good so let's start again and continue with which we had started namely the introduction of the euro familiar I get I assume would the phase diagrams Oliver useful will love will use the number of diagrams quite often suggest phase diagrams and so would we use or is the result we we use them as tools right in our costs we were not going in to calculate how you calculate and what what it means in terms of thermodynamics I soon you know these things and will will use them as a tool in this course and so what would be the does it tell us His at any point on this diagram yes but who has a the the temperature and the composition for instance carbon content here and I think there's also information about the the face is involved in the MicroStrategy at that time in this particular case will have gamma phase and Symantec's if I have to .period say 2 per cent of them so I will not only have the information about the number of faces the type of phase also the composition of each until tell me that at this temperature the Austinite contains this March 1 . 2 that 1 would like to be Percent of carbon and that indeed some entirely contains 6 . 7 per cent of carbon bank so I will also the US and a number of points of the of interest here uh this structure it did my crystal tree I get here is a very well known Lamela Mike restriction that we call the new toyed yes and we Will so if we add the information here on the ground I uh want to tell you that when we look at steals we typically defined them as Our and carbon alloys With less than 2 per cent of but carbon and you can see where this .period where this information comes from its it's Due to the maximum solubility of carbon in Austin area in and around the temperature close to 1200 deg C and many steals that's what we're dealing with is cause I do not have this level of carbon was a matter of fact the most seals will have a look up to 1 per cent carbon atoms then you have all your close to 99 per cent of the steals that by you will encounter on so will go up to 9 edition read about a Percent of carbon unit I'm and all wild of steels are produced with even alas what about . 5 per cent of course so of all this huge make complex phase diagram the most important part of it is this little piece here Is this piece went from 0 to a half a per cent of carbon and so no wonder that's a lot of research is being done on you know what would going would goes on here it is pretty simple in terms of the you know the defaced diagram itself but let's move on OK that this is a binary phase diagram so any time we talk about steals a few remember last the lecture were wasn't there but today I hope you listened to the video of the year we talk about silicone manganese and chrome etc. so I we have to have a multi component system steals a multi component Allen and so these this displays and doesn't look like this anymore because it's not a pure binary carbon and uh In particular you will have this this Austin 98 this region here we call the Austinite stability range yes this range here will be influence will be it will become larger or smaller depending on the ILO yet is 1 of the things it by which you can described the effect of a lawyer elements is by looking at this you take Tory temperature and what happens when you add elements to the the uh the Austinite here yes this will 1st of all you tuck toyed composition yes you take to it composition that is this composition here goes from . 8 yes to a lower value so that means you take to it composition moves to lower carbon ,comma and this is independent of whether or not but the Alliene element you add is also might stabilize or a thorough stabilizes you could see your nickel and Austinite stabilizer has this effect and you also these however the EU text toyed temperature yes you take your temperature it is moves in a very specific direction if the element so you can see here I have if this is the Utrecht or temperature yes this is the temperature here it's around 7 20 degrees seeing as if I add the verite stabilizing element of right stabilize them at this point will move up the mean temperature if I Austinite stabilizing elements of nickel and manganese it will move and that is in line with the increases in the stability range of the Austin good so far In this
diagram that number of things but because still research you should know and does so In the pillar you should know that the reserve in the system there is a new tactic here and not again is not really important when you're dealing with steel yes but that's 1100 and 48 degrees this important here at this point here at all .period 77 Percent of carbon that's the Utech toyed the composition and you tech toys temperature is 7 27 degrees C in in the system as the other thing you should know is that carbon content of the semen Titus about 6 . 7 percent of carbon unit and that we call all this steals would carbon contents less then you take toyed composition we called them Hi Paul as you tech toys and the ones that are above this week all the hype Utrecht on what's and we'll see what the big difference as you can so if we are In steel compositions very close to at this point very Byron rich the composition then we see fairer than many
act many steals actually looked like testimony carbon steels apartments it looks like there's nothing much to see small grains acquiesced grains and its Varitek and there may be lots going on but the microscope to the pretty there are so good now once we add carbon yes will start seeing things happen in particular there will be some reactions us and again we will focus on this part of the diagram in this lecture so let's see what happens at high temperature we have the Austinite and at low temperature we have verite we know if it's pure irony that in the case of a the uncovered we have verite and summoned tied at would that be so what happens well if we have the composition is you take to it composition we know that the Austinite transforms into variety and Simone tied in alarming fashion but and and this happens this 720 but for many steals were actually dealing with part of the dying and that you can't actually see here and so I blow this up and this part up and this is what I see I see of course the far-right stability range as of 2 900 and 10 degrees C above this pure irony is stable and then as I add carbon the Austinite stability range increases as of this temperature here decreases so this is this temperature here is called the aid Read temperature it is the the 8th that many of these lines here because they're used so often that they had we don't which is called them by name we will enable them to do so so this is the year the DAB temperature East E stands for equilibrium and so this is this line here it's like this is sweet like this line here the you check torrid air temperature this horizontal line here is the 8 you want temperature and while we're at it the name of this line it sea see online for the precipitation of cement and when it has a little heat it means the equilibrium temperature the Soviet he means its equilibrium temperature why do we specified s because when down when we heat steals weeks cool steals the temperature at which these transformations transformation reaction have or not exactly 83 when you heat up the transformation tends to the at a higher temperature and when you cool down the temperature this transformation tends to be at a lower temperature so I'll be give them all the names when we he we called them a c 3 lines and when we call and we cool down we call them the arts we and the the CND art come from the EU also comes around you because Akiba equilibrium they see Customs show flashes meaning heating this year so far as Arkansas mover the smell which means cooling in French 10 and the same for 81 you have there are a lot of you haven't they it should be in a C 1 and B R 1 temperature get and those thanks to you generally measure and are of importance to you if you running 8 of the deindustrialise that involves he treatments because that's the temperature at which the transformations will happen but let's have a look
at some of the structures here so if if you have the EU tech toy composition the Midas touch of this and just might rastructure you know is called perlite and its alternating layers of far-right and cement entice if you've never seen perlite the number of people that did do research on paralytic steals it publishes when it publishes it makes a very nice and silvery shy and people call it looks like Pearl services and so that's where the name comes from it's not somebody's name or was it just looks like and this nice gray Nice gray surface all right to say no that just a few words about what happened
what these compositions above this 2 per cent or do we use these alloys yes we do we use impact actually quite a lot of from and we call them cast Ourense years and again very different metal Agee's yes and and a and uh Mike rastructure controls will not talk about cast tyrants in the course of a lecture this is an example here where you can see 1 of the big differences that you can have in cast Arabs this is a would call a great cast Arab and instead of having seaman tight a we see in the MicroStrategy we have graphite yes and in the end in this particular cast iron this the graphite is modular forms little nodules now let's go back to
our steals in steals instance steals we knew we don't see graphite which summoned tights and carbide and the end and so so what happens now if you
have you go back here if you have compositions which are Hypo you technology and hyper you tacked on how do they compare In my
Christopher will you can see it here yes so had the composition is very close to point of 7 but a little bit less then so the year the carbon is a lesson and all .period the 77 pursuant and he had the carbon is larger than 0 . 77 per cent as so what you get is you see you still see the perlite and mother structure and yet here you see the perlite also but in this case you have fair rights he's very grains that surround these perlite islands and here you see this whites to wreak here the White Street is actually seem entirely and this is called primary Simone tight and in this case we have primary far-right admits only transformed the Austinite 2 Simone tied 1st you form Hypo you take toyed compositions steals and you for primary Stephen tight in the hyper .period this situation so this is just illustrate again let's let's say you have a point to Percent of carbon so it when you cool this material to room temperature like this the 1st phase to form from the Austinite will be far-right when you come in this region here fair plus Austinite and so the 1st phase 2 4 Is this body's primary yes primary far-right grains as you know that at this temperature you will have 2 phases 1 will be the very low-carbon far-right that would be this grain here right then you will have this high-carbon Austin this is the user to 2 phases and as you cool down the composition of the Austinite will move to this and the composition of the far-right will move to this eventually you reach 727 degrees and the remaining Austinite transforms too Price and this is what you see here is this used to be this year's this also denied that transform yes 10 2 course if I very little it less carbon I will have more fair right into my prescription and as increased to carbon as I get more and more perlite and when I have a composition that's friends and 1 . 2 per cent of carbon what happens here when when I'm cool let's say in this region here but at this point here I will start forming seem tight at these grain boundaries yes the composition of the Austinite will move along this still it hits this point and there the remaining Austinite transfer of super so let me just go
back to remind you of
right so In this particular case for instance yet
yes a little too deliberately to
remind you of that but that's just
suggests there's a so what
would you have have for instance if you if you go from say
. 1 2 about . 77 per cent of carbon against you get the amount of far-right decreases yes and the amount of perlite increases but about 80 .period 77 per cent of cup of common structure is fully we say fully earlier today so How do we How
do we know How much of each phase we have well we used the what's called the lateral so France's if at this temperature and carbon content . 2 per cent of carbon I want to know how much I know I How far with this composition this gamma With this composition yes I want to know what's the phase fraction well I measured this piece of land and a college and major this please and I call this season and so then the phase fractions of Alpha is equal a divided by C-plus yes In the face fraction of them divided by its seedless so I can always also from the phase diagram determined the phase fractions to expect so
here the princess for life the I see sir right there's and cement sold the different want to know what is defaced fraction of each
phase in this case well I have it's for Alonso's states about points 77 what faces 2 I have all I have verite Persimmon tied the semen Titus here let's get rid of this year
and if what is the amount of as of far-right and Simonton well this and this select here from here To here I call then the there from here To here insert called so the fraction of verite for instance is equal to divided by the simplest thing and I can just can measure does because see plays a is 6 . 6 years and 8 is 6 . 6 9 9 miners 0 . 7 7 yen if you calculate this you will find their face version of 10 good thank Joe now 1 of the
things very interested in in no when we make steals when we processed it is we want to know what happens when we process steals in conditions which are not equilibrium yes because when you heat up uh you steal you cool it down you deformity at high temperature you use a certain heating rate certain cooling rate and the information you have from the equilibrium phase diagram is of limited use so we need to have information about the transformations yes and their dependence on the under cooling most of the time so we'll see what happens will 1st read it Gold through this analysis of the effective date cooling rate of the under cooling 1st and we look at the ISA thermal you tech toy transformations so what we do here is we go From Austinite with . 7 7 per cent carbon and we cool down 2 the low 727 we do this ad different temperatures and so I go without this we say I go suddenly To this temperature wanted this Pritchard and I keep the temperature Comstock so I do the transformation I thermally active the temperature constant and I do it at a certain amount of under cooling fans the 1st year that the under calling being the temperature below the 8 E 1 temperature OK so let's see what what we have content perhaps it would we years instead the the speed of the kind that text of the transfer of very sensitive to the under cooler heads so since if you measured the the amount of pride formed as a front Jack it doesn't go like this right there is no instantaneous transformation yes this does not occur yes but the transformation is not instantaneous the way why is it not instant Asia's because the perlite needs to grow From the Austinite him so and this requires that the carbon the it distributed yes In addition to the face transformation so you need to form variety they also need to redistribute the far-right between the semen tied and the variety reflects what what so what what happens actually has so if we I have a smile on cooling for instance which closed to Close to the 81 temperature that's what we see instead if we plot the transformation in the log diagram in a log With log timescale we see it S-shaped curve if we increase the under cooling yes we make we go lower and lower we see that the transformation actually goes faster they want to .period about that the undergraduate years very often people say all this dish this curve especially the shape of diff curve depends very much on the what you use sp expects its if if I were to what this on a on the regular linear time what you wouldn't see much of this special this is a log diagram so so at 600 deg C you can you say the transformation is faster actually really much faster that's because here it takes maybe 5 seconds to be fully done here it takes 20 at 100 seconds this is probably 500 sector yet so this is not a faster it's it's much much faster it's very sensitive but when you plot a lot of time scale it's kind of you expand you know the 1 who did the short timescale so big the right so now what White House does this curve halved this shape what and and so why isn't is this the transformation of formation of perlite instantaneous well it's because of this particular transformation many transformations and we're dealing with in high temperatures transformations are the result of nuclear nation grow so I have to do in this S-curve here in the region where nothing seems nothing much seems to happen here's what you actually if Opel urine the nuclear nations state so we make small nuclei yeah that becomes larger and larger ones this nuclear nation rate this is important we uh we see that the nuclear nation is high when Delta T it is larger so you get more nuclear nation has when the Monday under cooling is larger and the reason this but because you have a hydro higher driving force for the transformations I and if you want to have it in terms of thermodynamics the free energy change is larger so not lots of nuclei right now in the grows stage yes In the Is he Dead of the particle or whatever the polite silence His in order to grow you have to have diffusion yes and long-range diffusion and so the growth rate as the rate of
growth is higher at high temperatures the small Delta Two and we use is simply because at higher temperature In diffusion yes so In the nuclear nation states we have the free energy that plays a big role in Greenwich and differences in the gross stage we have the diffusion is important and why does the curve not continue like this yes but goes like this and you see this as shape doesn't go like this that's because as that these islands of perlite starts to the grow and they will start impinging on each other hands and it will prevent each other's growth in certain directions where to touch each other said and that gives me this lowering Of the kind antics at the later stages of OK you can solicited bids let's you this process of but nuclear nations and growth and it's important for you to realize that nuclear nation and growth are not separate stages not that they're happening at the same time so if you have from the very beginning that you have and depletion rate at a certain temperature at and you have a growth doesn't appear so if I started D 0 there's nothing and delta T I have to particles so what is my the a nuclear rate this is a unit volume so my nuclear nation rate is 2 particles per unit time per unit volume right so that means that after 2 Delta T 3 delta T every time I will see To and new I will I can't be yes but of course there is also growth that means these nuclei will grow at a certain rate so the change in their radius per unit time yes but is a certain value Soviet therefore insist there 1 9 9 0 meter in size here there 2 nanometers inside that such incidents growth rate it is and and you see that you get at same time to good growth and depletion and sentences it did not separate stages is not like a stage where are you form nuclei and and then that stops and then you have a gross stage of the taps at the same time 10 so so let's go back now to would have to perlite so we have send a new creations stage we would we still talk about the nuclear nation states it is because the rate of the nuclear nation is higher we have Of course there is nothing so the main thing that happens says nuclear nation up and we have a lot of kids and do have already told that if you do the formation of perlite at lower tensions lots of driving force free energy difference so far we will have a higher depletion that in the growth process what is important there is diffuser the diffusion of atoms Towards the growing phase yes and that is higher at high tea or at small under cool so if we look now at 2 this Per lights situation To have Boston and I look at the perlite islands off recall the colony's the backs of parallel Lamela these the temperatures just below the you tactile attended in depletion rate will be lower than the growth rate will be high so I get few were large colonies if the temperature is very far below T E yes I did behind nuclear nation range but these new TI's don't roll very large that's because the few sedatives floor and in between as I have an intermediate nuclear fission rate and an intermediate growth so the track the change different ways to do this and that this transformation friends as we look at the transformation at 6 75 so witnesses we retract the sent sentence transformed as a function of the log of the time and we measure where the transformation starts where its 50 percent transforming where it reaches 100 per cent and we use this data we put it on a diagram of temperature versus the same time this and of course at 1 temperature I a 1 .period 4 the start of the transformation 50 % transformed at 100 % transport and I can do this at different times yes To me at different temperatures of different sizes and I will get these is typical the curves which are at a time characteristics various direct characteristic of depletion and growth transformations then in the following compared to what we see is that at very close to 727 I do like you know it takes a very long time for that the perlite reaction to start because I have very little depletion rate is very little driving force for the the formation of Pearl but then as they reduce the temperature it In around 550 the kind very high it takes you seconds for the transformation to be complete Nazir continue reducing the temperature that the tactics that are slower again "quotation mark and so if if we would look at it picture early parts of at this point here from from all this region here Austin migraines are stable and and then they just start transform perlite and then at the red the bike research transfer OK
this that's what happens is another thing that happens is that found as we increase the yeah the other cooling the area you can refine the perlite you can make it final the reason is that at Lord amp should diffusion is slower perlite is finer and the colony's are small so you can refine the Microsoft truck truck by choosing the temperatures you get the slain phases pretty much the same composition but the MicroStrategy is refined and this is a track that is very often used 2 I didn't do it transformations at lower temperatures to refine the and 1 of the reason why you would we find them restricted is to make it more homogeneous and if you concerned about mechanical properties you also the refined might restore and will see widened as has a higher strength it's an at higher temperature we have faster diffuser costs a perlite and larger colonies and again the reason is because nuclear fission rates Association good but sigh we're
doing this transformation we reform perlite and what happens if we continue dropping the temperature will know this we get finer and finer and progressively finer my Cristiano as you reduce the temperature yeah you get into situations where the diffusion becomes very almost impossible at what temperature is that what would be 550 5 50 to 500 degrees C that you can assume that the diffusion substitution all solutes so elements such as that manganese silicon Molly chrome it's a truck in steals substitution of is finished and not be any the movement of these species anymore you up what about interstitial such as carbon they could still move over long distances and that has an impact on the transfer may be due to the low the 552 600 temperature range as you stop making her life and you make another the company which call a decomposition products and that's Bay nights and in what's what specific about the day-night is that do the growth is a combination laughter diffusion processes diffusion control processes so how can something be at same time the fusion was an and diffusion control but there is no diffusion of substitution elements and there is the fusion of interstitials that's basically what the definition me at such low temperatures if you look at the MicroStrategy you don't get the slim Allison work which you get this Bay Knight this is a very fine much finer
Mike restricted as you can see here also a few more words about this as we go along right the I'm so you
have that made either perlite or of a nite but you have a structure yes and it's a lump Lamela and that is that the the equilibrium structure that the material world will have what we if you if you would say I'll I'll just continue holding on at this temperature was just 600 I'll wait for a long time for hours and hours the same thing would be I see that the structure Will continually evolve and you'll end up having which calls Ferro .period screwed up died there b instead of a lamellar Mike rastructure you get these Simone tied nodules so why why does this happen his white waited for the dentist is that there's simply because in perlite you have Le malice alternating far-right and Symantec and so you have lots of interfaces yes lots of interfaces and they contribute energy into facial energy and it's very high in the perlite so In comparison this the situation where you have this spherical the same entitled not this as a much lower surface energy and so OK term 7 tide will tend to become spherical and forms stereotype and this is not a packet of academic interest only those pharaoh died sterilizations is very common on it in certain products steel products very many in particular why here products and go through this stage of sterilization in order to make them very soft OK considers an
example here of this sterilization and called his globular retirement course
you've all heard about Martin side and in the case of Martin side there the the transformations fully infusion list so there's no substitution of the few no interstitial diffusion and of depending on the carbon content in Europe your lattice UBC lets can be distorted as you can have different types of Martin side this From last March side too plate marked inside yes
what is this interested about the Martin transformation is in its 8th in low-carbon steels is its 8 thermal a thermal means it's not time dependence so if you so you as you know there is a mess start temperature and so if you go to certain under cooling you will get a certain amount of Martin and if you keep it there nothing will happen nothing nothing that's the definition of thermal so if you want to make more market you have to decrease the temperature if MS is below room temperature it's not going to transform to Martin's unless you cool it below room temperature that important about a thermal transformations and not time-dependent their by under Kulik the 1 more might decide you have to go below what have 100 percent mark you have to go below the amassed temperature and that averages of the temperature at which the
transformation is stopped and this is actually a very common a form of site which call Latham Arkansas sorry complex MicroStrategy calls a really much about them unless you look into this microscope weight SAA at at Seattle media Mike rastructure it it's very difficult to have unless you working with they unite and Martin inside for your research very difficult to tell them apart yes but this this is the the very common form of Martin cited you get in low-carbon steels so the many and so would all engineering steels steals we and builds machines with having this Microsoft rupture but if you
have high carbon market site because this is the MicroStrategy the very different than we do and so actually there 2 phases here all these feathers are Martin side and you can see this still white is white background that's Austinite that has not transformed this is also the merits of some these feathers here right Our hope Martin side usually of which we sell for prime it's here is is called is is also its is also hasn't transfer so why would then why would that happen to have captain you have these 2 phases whatever there was very simple this is a temperature and this is the time and say this is room temperature room temperature and you transformation so this is the MS temperature and the CMF temperature and you cool down to room then the amount of translation will be such that it's not fully transform is not fully transferred because a mass is below room temperature the transformation is only partial and it stays like this so that's an interesting thing to do 2 yes to control the range of a math and amassed yes because that allows you to keep Austinite yes stable at room temperature you have to realize friends in this still the the temperature the thing to equilibrium diagram yes the temperature at which the Austinite should transform is about 700 deg C this is at room temperature yes you got Austinite yes it's stable at room temperature not for 5 minutes but forever you because a transformation that thermal so very interesting properties and so you could you could you can actually by doing some clever things in steels which is you know you can have been of high-temperature phases at room temperature for stable at room temperature and of course the presence of this game offers its you cannot I it's not going to give them and find this on a phase diagram right because the phase diagram tells me at this temperature the stable phases Our variety instrument today spread and did so
this this the democracy transferees had it's as I said it's not diffusion transformation it's it's it's called the sheer transformation which basically means that the Austinite is transformed to by very specific ship as so all the atoms before and after the transformation have a specific position this that's not the case when you have a diffusion and the history of the policeman growth process the the position of the Adams after the transformation are due to render diffusional jumps yes so for instance here I believe you can see that the this specific Shearer here this is the Austinite piece of the Austinite Microsoft you can see here shown a 1 1 1 plane yes and you can see here is nice hexagonal shape of the 1 1 1 planes when we Shearer in this specific direction what exactly this amount is this the state phase this turned into a 1 1 0 face of 8 of PCC or or Martin site To get very
different shapes of modern science so here again this was this what we call lenticular this this smokin side here is called lenticular and because its
form the shape is like lands the reason why it's form is is because of strain energy associated with translation
but you can have plate here you have the market sides of or plates is so here .period babies what we call epsilon site and and this here is just as Austin take me and since played tight market size very commonly Byron manganese alloy so studying this translation to mark the sites important and we I have different ways to to look at this transformation start inside with 1 of the things that is important in connection with Martin size and certainly for engineering steel is the idea that skull Hardin ability concepts on ability ,comma so in engineering steels natural people don't talk much about Hardin abilities because they don't very often make Martin cite this as a microscope to the people that make up motor parts for instance uses Lycra structure this marked inside so they want to know how easy can I make Martin side can I make this high condemning the special Microsoft trucked in and in particular they want to know because they make parts which have a certain section as they want to know if I cool down at a certain cooling rate how easy is it to get the full democracy take much structure the 1st of all there's only need to know why are these people interested in the socialite will market size the for engineering steel ball for a simple reason is because Martin side would call Ferris Martin sites can have very high strength these the typical various markets I can give you 1 . 5 digit Pascal To figure Pascal In UTS ultimate tensile stress that's very high and that's mostly achieved through carbon carbon salute solution so you insolvent in solid solution In solid solution did you remember I said that the solubility of far-right of combination inference almost nothing has In order to keep the common in salt solution but I need to make Martin In fact Martin side is this is what you get as a result of a transformation by adding carbon in such solution I make it very hard transformation product that is interesting for injured many engineering applications very important here when we when we talk about Martin side or Mark acidic transformation the result the product does not have to be hard that's the Martin site is very common in the world of Material Sciences this you any and material system that has transformation you can probably make Martin inside ceramics other alloys semiconductors no it's not something that's all steel right Martins and do the results of the market site instead is the result of a military sheer transformation that's what's Martin's so it's not necessarily hard and strong and brittle like you may sign the reason why it's hard and strong and brittle In the case of fares marked is because we have carbon and solid solution yeah that makes it hard and brittle In fact there are steals some of the highest strength steels available which called Maher aging steals we have a very soft Martinson pretty soft markets so you can actually make Martin side and the shape parts with the steel and then after that you do heat treatment to make it very hard for this the markers I does not have to be hard Brit right so they want this phase yes and I'm going to simplify things temperature and time so what do you do 2 To make Martin
side you need to just this these are references for instance perlite or the United so far log t and then make lofty and outside in a moment while use locked 2 years if you half the thin sheet of material and you put it and to quenching medium which continues which can be boiled special quenching oils or other Water for instance that if I put this down here yes I will have a will achieve a certain quenching rate yes and so on so France's effect from thousand degrees C I will the able to the best yes this this looks like a curved yes it's because its analog diagram as if I actually making a linear take it's a lie but because it's logarithmic it's looks like her so but if I have a part for instance debts the crankshaft now like this the production which has a certain section yes at the surface I will be able to achieve this but not in the center yes not Anderson and surrounded this so in reforming something else before I make my Arkansas years so in this case if this is the transformation behavior of this particular steel which I say this is not a very hard enables steel I can only harden it if I increased the cooling rates somehow cooling cooling rates must be higher so that a medal the cooling rate is such Disney in the middle and submit to serve for the other thing I can do it is I will add alloy impairments I will not following element cultures use another steel which has this transformation behavior so then with the schooling rate I can still make it 100 percent mark side and I want achieve for the market acidic Mike rastructure with this cooling rate so so did different ways in which we study in practice these days this concept of Hardin ability and so we have the the so-called charmingly test and the other 1 is the quench test so the Johnny tests would do we do we have we taken bar of this material is since and we quench it now we quench it is you picture here this is the bar you can see it's not this is not paint it's just but In the Austin enticing temperatures it's red and of course the end here is being cooled by this water so it looks dark right and and as this schools yes you know this he conceded that the the part getting darker and darker and 1 seconds for items five-second became so I so you do this at at this end here of course this and this quenched very quickly but the cooling rates here and here and here and here because progressively less and so in general if you don't measured the hardness and you see that you only have these very high hardness is very close to the quench and in the decreases you can never you can do this kind of that's all you can do the quench test where you basically again take a bar yes and now you cool it from the side and you budget for the new measure the hardness profile the more Martin site you have the higher the hardness is and you see here the hardness drops at the center where the cooling rate is the lowest you have the softest material this is this profile here you have to realize is a function of the steals Hardin ability and what is that that's basically the composition so you have steals that will give you this hardness profile right this 1 is it is very hard Annabel steel or you will have steals it will give you the same still would then give you this harnessed before yes this is a very hard OK and it's hard ability is as a said function of the composition no In other words
if you have if you have added allocating elements which influence the Skynet Texas by influencing the stability of these phases of the arrived on or influence the kind that takes of the transformation and then I you know that's the way you engineered a hard ability to get so let's have a look a little bit more than an hour which certain cases that let's have a look at a point for carbon 6 . 4 is very common engineering students has to make parts for instance motor parts all but so well let's have 1st we start the this steel called thousand 40 it has this is very we'll talk about standards after this introductory the production class here man this 40 here the result of the media backtrack here this as a the standard which is in the eye as I S A E Standard North American and very ,comma very commonly used in it said you have . 4 percent of cars in the last 2 digits give you the carbon content and said so it doesn't have much of outlawing the elements so this is what you measure as a function of the quashed and please see very quickly drop off of the hardness as a function of him no I haven't allowing elements here in this case half a per cent Croat and . 2 per cent of Molly as you can see now the hardness is here I can continue adding the following elements Crowley and 1 . 8 percent of mining and now the Steelers extremely hard so From this harness I can and you get to know what is the uh that the hardness here that corresponds to they did the amount of mom's side that corresponds to this hard so if I have here that state 45 Rockwell hardness of 45 years so when they show here is the hardness as a function of the carbon content yes for different amounts of Martin sites in the margins of the more modest side at half the hard news the more carbon I have in this same amount of Of the amount of Mark inside the higher diamonds so senses this is 100 percent close to 100 % Martin the more Martin said more carbon I add in the mark inside the harder it gets so rights is at this point is important 45 a Rockwell C because this corresponds to so I know in this particular steel I have . 4 per cent of carbon the . 4 % I have this hardness yes so how much Martin side by half 50 % In this in this deal Mike rastructure but so forces in this case yes where do I have 50 per cent of Martin side here right this very very close to the it's already 50 % not 100 percent fit now at this carbon content where once the hardness for 100 % everything is turned into market I would it's that corresponds to disappoint them this point should cost corresponds to what well that's what we have at the surface look at the surface I have just for measuring the hardness and using this diagram here I know that I have 100 Percent of Martin side and the Marcos icons . 4 the scent of course so it's From this carbon content from this diagram I cannot have 65 hardness because that would require 100 percent of market yes but a lot more card OK this this is the maximum I can get right so now the question is How do I have to I work with this in practice the guy Germany test we have a flat and and we cool this and that but then not many parts that we treat this way yes we usually what we have bars for you know something that cylindrical and then you know we you need to have something to because most of the producers of Steel's steel companies they but they will give you this kind of tests test results in so you want to be able to know OK I have a BA which is certainly the diameter you where can I expect how much diameter should the Barbie the book and Barbie Circle sold to make sure we still have 50 per cent of Martin site in the center of we alright well will answer this question on on Thursday to take a little bit too long and this has gotta have you understood well so will love break here and we'll talk about the the parameters that come into play In in particular of the coolant as you will see that comes into play In that
"quotation mark all right so again for those who were not here this morning no the this quest


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