Modern Steel Products (2014) - Hardenability: lecture 4

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Modern Steel Products (2014) - Hardenability: lecture 4
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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 particular lecture deals with the principles of hardenability with respect to martensite, including considerable detail about heat treatments. 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)
Nut (hardware) Saw Gemstone Stem (ship) Last
Saw Gentleman Commodore MAX Machine Captain's gig Crowbar (tool) Glass
Steel Vehicle Hovercraft Cylinder (geometry) Separation process Alcohol proof Gentleman Spare part Forging Engine Semi-trailer truck Firearm Material Water vapor Reference work Unterseeboot IKEA Steel Ballpoint pen Crowbar (tool) Weapon Ammunition Saw Cartridge (firearms) Ship of the line Water vapor Flatcar Kurbelwelle
Typesetting European Train Control System Steel Hot working Rapid transit Steel Baler Ink Camel (cigarette) Clothing sizes Separation process Rigging Sizing Roll forming Cartridge (firearms) Gentleman Wärmebehandlung Engine Ship of the line Water vapor Material Kurbelwelle Water vapor
Tin can Airbus A300 Fiat 500 (2007) Steel Lugger Steel Lawn mower Clothing sizes Bill of materials Cardboard (paper product) Zementation <Metallurgie> Cartridge (firearms) Gentleman Photographic processing Spare part Bow (ship) Steering Jig (tool) Book design Ship of the line Firearm
Typesetting Blast furnace Jet (lignite) Lader <Verdichter> Steel Narrow gauge railway Bauxitbergbau Bending (metalworking) Rubber stamp Bill of materials Wasserstrahlschneiden Spray painting Seeschiff Ammunition Saw Outsourcing Surface mining Narrow gauge railway Spare part Coining (metalworking) Surface mining Piston ring Ship of the line Material
Blast furnace Steel Mockup Steel Bauxitbergbau Machining Electric locomotive Polishing Machine Railroad car Roll forming Cartridge (firearms) Photographic processing Screw Spare part Wärmebehandlung Engine Material Kurbelwelle
Turbine Turbine Steel Axle Arbeitszylinder Cartridge (firearms) Forging Spare part Surface mining Wärmebehandlung Firearm Bleisatz Kurbelwelle Forge
Typesetting Nut (hardware) Turbine Steel Ballpoint pen Steel Ballpoint pen Beschaufelung Machine Schiffsdampfturbine Connecting rod Wire Seeschiff Turning Alcohol proof Spare part Wärmebehandlung Material
Steel Ballpoint pen Automobile Alcohol proof Cartridge (firearms) Spring (device) Bauxitbergbau Wärmebehandlung Presspassung Mixing (process engineering)
Turning Automobile Coining (metalworking) Ford Transit Material Mixing (process engineering)
Steel Karabiner Automobile Captain's gig Material Mixing (process engineering)
Steel Automobile Commodore MAX Machine Narrow gauge railway Firearm Sail Mixing (process engineering)
Tin can Nut (hardware) Steel Mechanic Camshaft Clothing sizes Ammunition Becherwerk Rigging Sizing Cartridge (firearms) Nuclear fission Gentleman Ground effect vehicle Commodore MAX Machine Photographic processing Firearm Material Lumber Van
Ammunition Typesetting Fender (vehicle) Gentleman Phase transition Plough Commodore MAX Machine Spring (device) Gun
the last question Justice and there are some diagrams here this year the summer still compositions you have to compilations what you have to do is simply this goes here and this corresponds to that because nothing more this year's sparrows no English needed at the time time of the
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you think you have to you in the it was at home the problem is that you have to be in the interest of of you and the yield on the so body .period it was not alone the next year parents who was not we need more time no nobody needs more time to protect certain from new bring it here collected the picture you name is on it make sure your name is on right good so let's backtrack a little bit so we were talking about the concept of Hotan ability steals and it's very important enough for engineering steels and because Cotton ability depends very much on composition and that some old will Willows what we want I'm going to explain to you why white composition comes into the picture and and how this thing is approached technologically so take a piece of steel in the hardened ability test you Austin ties it and then you can either quench at 1 end this or quench a bar certain diameter than you can measure the hardness from the quenched and you can measure the hardness when you make it to the cross section of sample from the edge quenched the surface the middle and back then you get a hardness profile and obviously a material that's very hard the ball as will have a very flat harness profile In both cases so what causes this drop here In the end the hardness is basically the smaller cooling rates from some material that can easily Hardin that is because Martin site at low cooling rates is said to be very hard in the ball or have a hard hard nobility yes
so an already illustrate that this that so carbon is important because it could determines that the hardness of your material that's 1 thing the 2 other allying elements of are important because they change the kind that takes of the markets that the transformation so that's how they come into the picture Of the Hardin ability but to let's let's have a look at have we had we already discussed this August would quickly if you have the material like that with . 4 Percent of carbon yes you have a version without much allying elements in version weight some manganese half-percent of chrome and . 2 percent of molybdenum This is the hardest profile you get them and if you have it but even more elements in Europe steel like 1 . 8 % manganese chrome and Molly you have a very flat harness profile as a function of the distance from the quenched and right so super 1 of the things we're interested in is in the technological reasons as will say Is the 50 percent of road Martin site microscope trip Nos and the the 100 % MicroStrategy for hard ability very often but the young the 2 critical diameters etc. that will talk about a of 50 per cent of the market citing the MicroStrategy so we need some information about the the amount of so what went to me when we measure the certain hardness for its steel with a certain carbon content How much Marcus site the Microsoft we have this very convenient that reference diagram for you the carbon content here you have the hottest news and so we see that this is the line for 50 per cent of Martin signed this OK so this gives me the hardness for a 50 percent mark inside at . 4 percent of carbon so this tells me that if that I will have 50 percent of at about half an inch long that's that's about a little less than 1 . 5 centimeters away from the quenched and you see that the fall for this highly alloyed steels it's much much deeper below the surface so well rights so that if I use this CIA aside the 86 14 not out 50 still great so I will have 50 per cent of Mercosur at a distance slightly more than half an inch the way from the water quenched and of my time in the park and so what can I do With this information time now I In In in practice and this is a very simple test but it is a little bit inconvenient what you get S information because of the parts you you're interested in hardening look like this for instance of the crankshaft for a motor that you want to know well you know and you know how much Martin side will I have when I'm heat treating this part and and this part yes so you need information about typically cylindrical bars theirs and so on I have for it's able and I'm using this particular steel here against them by 50 % at a distance slightly more than this half an inch here for the Germany but what does this correspond to four-cylinder began there we have again reference diagrams units that are provided for instance by date steel many of the people that make the steals for instance company like Tim makes this kind of engineering steels for automotive applications and so they will it will give you this data right so you have to look at that this half L the let's it's Ikea larger than half an inch distance this distance from the quench and and here this is related to the diameter of a yes the problem is you can see the many lines I can use what are these lights while they're related to what we call the quench severity when we're conch you do Johnny test you basically use tap water yes 2 start around 20 degrees just quenched disband right so you it's a very Hi clinching rate yes "quotation mark but full bars that you use in practice and I you can use water you can use circulating water you can use Stillwater you can use oils it also can be circulating the oil can be sale what is the the diameter obviously if I have a very still effective 5 heat removal yes I have I will have a large diameter so this is the distance from the questioned could corresponds to France's 3 and a half inch bar will have the fully it will have a 50 per cent mark the site at the center if I have what's called an ideal quench Watson ideal quench ideal quench is such that the temperature at the the surface is equal to the temperature Of the cooler yes if you keep the coolant flowing yes yes you you will have a situation like that if you will if your coolant is the stationary obviously the you will have less than ideal the removal of heat and and you'll have this much smaller diameter that you can have it 50 per cent of Martin site in the center let's say have a look here comes at City with same week I'm we didn't we couldn't when know we can't afford this material because it's highly alloyed so we're looking at the unalloyed steels can we can we I make this uh this material here so this is the Getty year the 50 cent Martin signed and so you have a 50 percent mark said only very very close to the surface now 10 no I look here that would this corresponds to In this craft has you see that I have very very tiny diameters yes and that's where the ideal cooling has so you can imagine if I cool with oil I will I will not be able 2 To achieve any hardening of 4 inches apart like a crankshaft partly because the diameter of the bar is too small so his diameter that we find here which ideal cooling is called the D of the Act and it's a very important parameter in for engineering steels D I knew the ideal diameter the idea that there would be the the diameter where you will get 50 per cent of Martin site in the center of the bar if you
do it ideal quite Ch the New quenches surface of 2 metal is the same as the temperature after the cooler so we the so talent how does this work yes so we have our but it is very important when you get into our if you would get ever get into 2 discussions of pardon ability of engineering steels for your research or form for your work is the some of the people define hard ability as 90 per cent 100 per cent of Martin site in the center of the bar incident and doesn't have to be doesn't have to be deregistered different definitions of the 50 percent Martin site in the commonly used for engineering student but right so let's let us look here at this example here so this is a the is a maximum diameter where you have a 50 percent of March the center of the the bar in ideal conditions since look at how do we calculate this so we can help we can calculate this and of course it will depend on the large number of factors it will depend upon the uh the uh the factors which are grouped into this 1st parameter here the so-called critical diameter critical data the and is it it's tabulated this isn't tabulated value would be based on carbon content Austinite grain size and the severity of the cooler so every type of cooling has a number assigned to it called H shares and each is in the case of an ideal cooling age is infinite and if you have a still oil cooling ages .period 25 the much lower In a how does this work will 1st Ken and you have the we determined the the critical diameter the intent behind it said you you you have to start with the conditions and say we have a steel you wake up a certain composition so you know the composition 5 . 3 carbon 1 % manganese .period for silicon . for chrome . 3 Molly Bloom and that is the grain size of size and sex which corresponds to graze 40 microns in right so that we use this 1st graf here we selected the grain size 6 here in this line and we select the carbon content and this gives me the the C or D. C by value which is 40 mm and I need to multiply this way factors related to the composition which we called Hardin ability factors the larger the factor is foreign element the larger the impact on the ability so not surprisingly we see molybdenum Kroll yes as having a high multiplying factor but said looks here and our composition we have 1 per cent of manganese so we go to L. a content 1 per cent of manganese ore factor is 2 . 2 years it's just 14 mm we multiplied by 2 and we multiplied with the factor for silicone and chrome and manganese etc so when we fight and alas and number 67 mm as this is the D value of Europe your steel yes that's that the diameter you would get in ideal conditions as above of schooling so this bar that this me in the eye of 67 yes past 50 % manganese yes at the center Of the baht after an ideal coolness in the ideal quench but in actuality you never use water 2 the Heat Treat except you of your student and you want really fast cooling rates use water but in general you we don't quench the engineering steels rapidly because otherwise we may get surface cracks and and we may get distortions so we actually do relatively we we use a lot of oil to to do quenched but so far we have not ideal quenches and the factor for oil this is typically . 3 . 5 rotten and so did the actual ideal diameter about 30 mm those of you want to understand is that so instead of having an ideal diameter here which would be 67 yes when we have oil cooling yes it gets reduced to close to 3 centimeters so that means that of an engineering steels when they're produced the composition all that is required from the manufacturer Mayor In include requirements related to DEI value yes which is composition dependence because and have this it for what kind of products this is happy it doesn't happen for she products because they didn't know if you want to eat 3 cheap products that's very easy answer of the only mm sec but above all bar products I think you make the crankshafts waits for instance that's important to have the composition that gives you the right D I value so you should that the material are you made Hastie the correct amount of Martin cited the MicroStrategy after heating and heat treatment but this method is called the Grossman methods yes but the original Grossman methods users to do that the plots that I showed you nowadays we have facilities where weekend do very rapid thermal treatments In terms of heating and cooling and aunt we use for instance leader alloys to get same properties so there are all the parameters involved and do it and the the Grossman matter has invoked falls and their are friends now you can get in data that allows you to look at Hahn ability of steals with much lower carbon contents less than point to this this is the year multiplying factor graph for for carbon where you go below 0 . 2 per cent yes and as people are learning more all have learned more about the hard ability also the the relative Hahn ability scale for different elements has also changed we on France's out here you can see this is a more modern data than the original data we go back if you look at the original approach
this when you see that the
multiplying factor for molybdenum very high yes if it's perfect ability element as if we look at the more recent data there's a more recent the evaluation of the effect of the molybdenum you see that actually manganese has the hard bills almost equivalent to that of molybdenum and people like me are very aware of this this phenomena witches which has not been used enough in steel design as the incredible part ability potency of manganese so that's it led to lots of developments where people have used expenses following editions of molybdenum allying additions whereas you know they could have done very well with our most of them manganese instead right OK let's another thing that's important instead of their are interactions certain parameters I'm very sensitive To the presence of other elements and 1 of them is the they've been impactful carbon for instance on the board you know that boron is extremely efficient pardon ability element and it will allow you to do make mark site bye basically suppressing far-right nuclear nation however if you have a high amounts of carbon this high amounts of carbon you see that this means the multiplying factor for boron decreases yes and that if you are close to viii reaction yes the boron effect this isn't nonexistent yes why is that well when you add carbon carbon has a tendency to also go to grain boundaries yes and there is a competition between boron and carbon certainly at high carbon levels whereby the the carbon-based we places a boron on the Austinite grain boundaries and as a consequence you have lowering or no Hardin ability when you add but when you look at higher carbon-containing steel To don't add boron in very high carbon steels it's it's not going to have any hardening In fact that's the message the director less now the Oscars cells which would we know can we already designed steals Our with the the level of sophistication we have reached in our knowledge Is there anything useful we can make for instance well but you'd be surprised that that's indeed the case so I remember we looked to at of the aura of steel here focused on you check toyed composition because that's given me is simple diagram would that seek to so-called seekers here for perlite higher temperature for Bay nite at lower temperature remember that reforms pharaoh died if we deal very long times then we have our markets aside the thermal transformation lines here but the locked a bitter let's say look at this in a way this is called cycle of cycle what excuse there was a little bit too fast cycle 1 What happens if I do a thermal simple thermal cycle cool through from Austinite which audits 350 and hold it for 400 thousand seconds before cooling to room temperature and so if we do this To this temperature 50 hold it there for then thousand circuit Excuse me yes and so what do we get we get 100 per cent the nice this To because once it's transformed to be knighted it doesn't matter whether you call the better through M S M F temperature range it's already transformed so nothing happens collects another 1 the cool to 250 this time we keep it 100 seconds no we cool to room temperature this would look like this constant too nice Call it very quickly the fast school indeed keep it there for the 100 seconds and Quentin during this whole here nothing happens since there is no the nite transfers no MarketSite transformation really have to go through the MS MS temperature range to form 100 per cent of and there may be some retained Austinite and Mike rastructure right so let's do that's something with more complicated tweak that another cycle we call to 360 people 10 seconds and we will to 400 C and then hold it there for thousand seconds and then cool to room temperature would we get so we go from here to here we transform to about 50 per cent a perlite as you know Mike restricted and we cool down from here to year has now we have 0 per cent of a nite and the transformation the fastest thousand 2nd is but you need to do what hadn't transformed after the politicos who is now transformed to Bain active so when I quench nothing happens again when I go on that's through DMS MF temperature range and end up with a 50 per cent of the perlite 50 % so I can make more complex Mike restrictions always the same
:colon stood aside while you probably think this with these alleged baby thanks yes that's it would not that's not being used industrially this kind of know stepped thermal and this simple isothermal casts there just for academic and that's not directly the case out of it as 1 of the structure material that is being processed but this way there in isothermal steps to To make them objects he will give a few examples and in a moment rights so if these lines assistant an example of a line like this dozens of different segments and it will talk about them and what does what what comes in bodies coils yes is narrow coils of strip material so if you uncoiled and you get a long long strips of of steel and make them demand they going to this the line like dozens of us have a look at with this furnace basically looks like so and it's used the commonly used to do the treatment of narrow strip and 1 of the things you can do it like this is going to Al Stamper a steel and what is our stamp ring in very simple we already discussed as you go you Austin ties the material and then you do an isothermal quench to debate a nite transformation range and you turn the material into a relatively strong and tough take the MicroStrategy so so how does it work you uncoiled at the strip here you go through an Austin enticing furnace Of the quenching here is done by a liquid metal can before instance led we equivalent liquid led me leveling their furnaces the is so good that the temperature is whole marginalized OK and then you do tempering furnace was where you kept you keep this this strip at the B'nai transformation temperature before calling it with this just calling Park and new you roll the strip Becker so what's happened we beef between the the start and the end here you have a very simple soft steel here you have a very hard tough steel you can rearrange this furnace knows what to make of the types of Microsoft options for instance you can make of their narrow stretch that is Mark tempered so the word mark tempering the was the 1st part Mark tunes said Martin site and the 2nd part temporary to basically make tempered Martin site Mike rastructure you you uncoiled you strip period goes into of course proselytizing furnace you cool the uh the stripped rapidly from Austin I to mark site and then you go the increase the temperature In this leveling furnace and keep its I saw thermally tell you tampering time is finished and the new quenched again and the role of the strip this allows you to but turned this relatively soft starting material and extremely hard the strip after this process the so what what would you
do it and what would you do instance way when you produce loss never won source come from want to that's how you make to you make he treated narrow strips and with the composition and the the right composition the right he treatment you can you can achieve very high and very hard materials to cut this is another example here of clench and tampering because maybe the Quentin tempering you want to do is not on a on the straight and narrow strip but perhaps on the bottom an and here you see how the news of the day the yellow thing here it goes here is he Bob steel bars and the the units you see here the red units here are in doctors In doctors today you you heat the bar by induction goes very rapidly and it's a non-contact heating bills and then and so you you induction heated the bar you see the bar here and the body of enters this box here this where you have a coin ship this is the way the quenching is carried out is you see here is circular loops water jets yes let cool the on the surface of the bar yes quench it and then you go through again induction heating yes you reheat the bar so it tempers and it gains and loses some of its hardness but it regains some toughness and you can see the bar being him because of severe what you're looking inside the the quenching unit here the desire
for methods it used a very of very very commonly this Mark acidic transformation and then the temporary Of but obviously there are challenges when you do complex heat treatments because I miss you when you are when you hit something up years of that will cost money is because you need to have a furnace either you I have to pay for electricity or for natural gas as I and when you pull down to when you cool down very quickly you are you will need a large amounts of coolant yes and no it adds to the production costs so materials development is also certainly wanted related to steals but there's a lot of an effort and simplifying thermal treatments as and so on as much as we love these complex he treatments yes but we have to look at what are the final properties the notes of giving an example where you can actually but the way With very complex he treatments and replacing the simple wants us and example where this happened is that In hot in 4 drinks so originally on the list of the people who still use this you you hop fortune material and you use Austin at ties at you if you want to have a mock acidic microsecond Austin said you temporary to regain your use of summer toughness and then you straightened the the part because when you do declined there's usually thermal distortions usually once you straighten the material the way you straighten this is by applying stresses the forming of a material and then you need to In many applicants distress relief you low-temperature stress relief that the treatment of cancer so it's complicated and costly but you can get similar properties this is so ended the 1st MicroStrategy get is basically tempered Martin site the 2nd approach is very much simpler you hop forged a material and right after the hot forging you just let it cool down slowly to slow the and the structure you get at the end here this is basically not Martin site but it's just I was polish and would gives you this but is very high strength yes it is small additions of vanadium the vanadium forums for Nadia it's horrible nitrites yeah precipitations In the MicroStrategy this and you get a very strong very pronounced precipitation hardening effect yes the properties are equivalent to date the ones you get after the Top heat treatment yes and then you can imagine that the costs the cost of the additional small additions of vanadium are compensated by the the simply the simplification of the of the thermal treatment general this is an
example here so what I Wikinews this form Francis for this crankshafts here you can you can basically used this approach to make corrections and would produce millions and millions of dollars so it's very important that to have her use simple and reliable heat treatment so this is an example here there you have a carbon contents . 4 typical engineering steels 1 to one-and-a-half send many of silicone low sulfur and he had this is the important part yes is the the vanadium additions and you can see that the of vanadium additions are technically in the range of . 1 2 Highveld high values .period we a very low amounts the strengthening is due to the Canadian car when I tried to the sulfur here I just want to know mentioned is Hi then normal usually you in in many applications you like to have no sulfur yes as little as possible a few ppm if at all possible it for engineering steels in many cases that rule doesn't hold because you want to it able to machine these parts there's an inability to to make them easily machine a bowl you can't sulfur and when you get there manganese sulfides which are which make a chip production chip during the year machining easier that's why we had so far in this
case so I don't think so we would like to give you an example of a a strip that is being done he treated if you an examples of of bars that have been heat-treated and a cracked crankshaft but there are some huge pots steel parts of the but being To take for instance here are very large forgings part are commonly he treated so this is princess we used in Gotz the cylindrical in God's here then you know these things going to open forgers ended here on the right here you have just gigantic computer controlled are there takes this very hot metal into Diaz 14 equipment here conceded again here another part of the forging a new conceit slowly this this piece getting some shape here and then you do he treatments to the surface you machine at and then you basically take this all stood ties Huge foster ties cylinder and you put it in a quenching back to give it to the heat treatment that you want and here you see at the end result it's or it's a role that will be used to In a rolling mill dancers another example here the persistent looks in all sorry this is not the missus AT the
forging debt is actually used to make turbine Texas axle so here that this part
here is an machines lots of it lots and lots of material is removed and you you left with these these parts here where the turbine blades will be fitted on eventually looks like this the turbine blades of fitted on you put it in the and the turbines body and this is this is where this large forging ends up 2 right good so the
DPP general aspects of the heat treatments are are well known then as now some simple things let's let's look at a situation that is no flood of interest to us when we think about the steel products and and then let's have a look at the time a very important no part of any piece of machinery and as a bearings the there is a slim important we manufacturer huge amounts of this year's and and is basically what the different types of bearings as Bartlett's that's just simply of the ball bearing here and I'm the made of steel the men of high carbon steels and out of the way the baby originally the original still looks like it's wire rod not all wire rod you see on the roads in Paul all are used to make ball bearings but don't important part of it is theirs so In the steals His we typically have is of very high carbon content steals the wire products are a steel products that have some of the highest carbon contents and that you can think of them we we use them to make cables and we also use them to make nuts and bolts we used to make ball bearings yes many of the things will discuss it in more detail which of interest to us now is how can we see the impact of the heat treatment and so on viii Mike rastructure of this kind of direct so so when you you want to predict the uh my constructed that you did you get that you basically need 3 basic diagrams 1st of all you need to have 80 the thermal treatment diagram which tells you OK I'm going to do this as a function of time going to heat up keep at 10 minutes at a thousand degrees and then cooler down at 1 ship Oregon to isothermal transformations but then that you need to know what the system the alloy systems but with yellow assistants equilibrium the situation years from Fallujah basically have to have a nice carbon diagram yes again we're not interested in the entire island covered with just interested in the island rich part of it yes that's why we only see this low-temperature iron-rich segment years and we've indicated on this diagram also the MS M F temperature again the MS MS temperatures on not equilibrium temperatures but it's interesting to have them there yes because these it yet because the M S & M F temperature or carbon dependent has an eye for all the steals below 1 % one-and-a-half percentage you see if you cool down quick enough yes you can turn all the steals into Martin's it is so it's interesting to have this information on your face and ended 3rd diagram we have is D is basically a transformation diagram and there we like to use C C T diagrams if you don't have CCT diagrams you could use T T T diagrams OK right so this is a city diagram and so will let's have a look at 1 the 1st situation here we have 1 per cent of carbon and we're going to do the median of than here and we're
going to do this heat treatment we going to do so to cool down this cool down and then go through the perlite transformation like this right and that what earned M I going to To see when I hear a cool down and I go true I'm going to see you around a little bit below 700 years I'm good and doing the transformation when 10
all cancers such issues with this this is just a general thing and and assistant it in more detail cases so we do 1st cycle that we foster ties then we quench yes "quotation mark so that means you go from this temperature very quickly we quench so where do I see if we find can do it fast enough yes I should get Martin site alright quench fast quenching fast enough 50 degrees for 2nd it's a little bit it's like at you would need to have a springs to get that cooling but it's it's it's not very difficult to get his so this is what you get to switch you get and uh so so it it looks like something you've seen before you can CDs is Martin sites units here yes we get Martin side again but if I look more carefully this is here you can see this you have these these Winkleigh things here in the MicroStrategy and that is not Martin site but that's so where does the seem tight from France Quebec well reasonable when I go from here to here yes 1 the stood phase diagram tell me well you can form Symantec's so apparently you know I cool down very quickly I did make some Simone tied in with Mike rastructure that's 1 thing that was not obvious from this and the other thing here is that when I cool down here when a cool down to yes this time at high temperature was enough to I
have temporary In we call this out to temporary and how do I know that democracyThe distemper because when we look at high magnification you see the Martin side has all these little boxes in it and that's basically it's seamen ties or perhaps low-temperature transition Carbide's adopt precipitated into my and these and in these tell me that the carbon is not fully in solution US and has precipitated out of solution 1 would something like this happen a few coins so rapidly well when you clench there is a face transformation the Austinite changes too yeah are we already know that there are dimensional changes expansions but there's another thing I have the heat of transformation is released there is there is a material during the transformation there is in the heat of transformation that's really stood the material gets warmer and so and that causes the material to I to temper the heat is enough to get but it did material to temper democracy that's something that very often happens this out to tampering if you get a 2nd
cycle here and now we are thousand 15 years and then we go to 7 70 keep that keep it there and then we will Wilkinson so now we go from here to here so where above this temperature here under this temperature right away and remember this is the 81 temperature and we're above this so what should I get when making this temperature here the 1st always their transformation while it this is it no there's no transformation going and make pro-life basically to what should I get well well I should form seaman died there's an Austinite In this range and then when I cool I will perhaps it if I call very rapidly as is shown here whatever is not transformed to seamen tide will form perlite but to we believe that because of its seat on
the direction what we get scandal but so now wait stuff looks pretty much the same thing I've get there so with something that looks the McMartin site it's also tempered I see all these little carbines and Martin said and that this when Titus Grain Boundary seamen died yes this year you don't get much grain boundary human tide of course why don't you get much grain boundary seamen died because the action remember Persimmon tight 53 seeing fractions is equal to what is equal to the length of this segment yes divided by the length of this segment right OK so it's a very small volume fraction that you made and the
fast cooling that I did afterward and turned everything into the and and Indian transformed Austinite at high temperature into Martin side of course OK so but still something different now we we go and sit right at 7 30 years which is this very close to 83 yes so here we have to look at the surface which may be slightly cooler than the interior of the material let's see what we would we get at the at the center of the material yes I see basically my pro you tech toyed Seaman tight this human time and then Martin side at the surface the temperatures slightly cooler yes so there we 4 Mark admitted to me perlite you can see some perlite nodules here yes OK but not in the interior the reason as because of this small temperature difference
the so but even as really unexpected To me
there is very big difference you can get very
big difference in the MicroStrategy within a very narrow temperature ranges can In now
let's do what typically do in industrial situation you will go from 1 thousand 52 615 yes and keep the temperature constant adhere we we should see political MicroStrategy basically let's see what we get and that is
true right now Microsoft looks very different and you actually have to look into the SCM to see these alternating layers Seaman tight and far-right In your microscope test and that's totally fully Portland or so so we already
discussed this Florida
ideas compositions of the the last 2 the dancers who
would what we've seen is that even even with you know when you know the basic principles of of transformation the trail we can already generate very many different Mike rastructure with different problems and England have different properties 1 of the things and I want to continue a little bit but about this is that the things that we know we can do In now development of steel products as we don't only have to heat and cool In we can heat strained material deformity To get properties that's the thing that happens walked actually In particular in when you we make she products wait thermal treatments and mechanical treatments at the same time so 1st I need to say before I could go into detail on this I it's a few things about grains the effect of grain size on transformations In particular the effect of the he also migraines size on diffusional transformation it's 1 of the things I and II yeah people sometimes forget is that when you take a fate and not physical transformation diagram whether it's CCT diagram or TGT diagram but I think it's it applies general universally actually it doesn't it only applies if or the particularly grain size for which the diagram was made if you change the grain size of the Austinite yes you will have a very different transformation behavior but why would that be because it's the same transformation right at the same nuclear nation and growth well let's just look at her very big Austin migraines and let's look at a very tiny Austinite grades I knew soon that nuclear fission rates and the growth rates of the same year so so you when you will form a variety it forms in nuclear dates on grain boundaries so will yes this but this is a unique you volume units the same volume unit here and there and we got we make 2 precipitates every unit of time is so at the time T 1 we we make yes to unity 2 nuclei units in each case and there a time of yes I make 2 more units Clinton said and what's important here is that when I have large brains these guys don't look like these there are no nuclear fission this is not nothing is happening here if the grain size here is small and a and I do at the same distance I have the same unit I will also have a grain in this unit and this 1 will also transform this the same 2 units not more advanced no there's no magic it's just this 1 doesn't do anything that's where as he is here so In other words the depletion rates yes the being the same I still get faster kinetics yes because of the grave sites if you have a seeker seekers floor 8 particular steel at a particular grain size yes when you reduce the grain size yeah you will enhance so this is 1 grain size this is a smaller grain size yes and there is more or less but are you know role in the future if you have 1 grain size as you can calculate where this there will be for smaller grain size differences like this if if you have the 1st Boston I grain sizes smaller than this the 2nd Austin migrants than the ratios yes the ratios of the Times needed for a certain amount of transformation Our are such that the ratios of these 2 times are the same as the ratios of the grain diameters it's to 2 2 you want or divide by teacher is equal to the 1 over the 2 so that allows you to and of course if but the 1 is smaller than the 2 yes it means that T 1 will always be smaller than teachers bunch of justice to this basically your transformation curse moved to the left that's very important in what we will see next Monday thank you for your attention if yeah
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