Modern Steel Products (2015) - lecture 4

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Modern Steel Products (2015) - lecture 4
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4 (2015)
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Cooman, Bruno C. de
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A series of lectures on steels, given by Professor Bruno de Cooman, Graduate Institute of Ferrous Technology (GIFT), POSTECH, Republic of Korea
The Graduate Institute of Ferrous Technology (GIFT)
Stagecoach Ballpoint pen Wire Finishing (textiles) Connecting rod Playground slide Pattern (sewing) Turning Computer animation Alcohol proof Cartridge (firearms) Ship class Remotely operated underwater vehicle Steel Wire Wärmebehandlung Ship of the line Steel Material Stahldraht
Saw Sonic boom Computer animation Alcohol proof Spare part Tannin Bus Steel
Ammunition Computer animation Automobile Steel Kopfstütze
Computer animation Ship of the line Material
Game Lugger Computer animation Ship class Institut für Raumfahrtsysteme Optics Steel Wood drying
Lugger Ink Printer (publishing) Game Turning Brickyard Typesetting Institut für Raumfahrtsysteme Spare part Material Typesetting Vertical stabilizer Blast furnace Ballpoint pen Key (engineering) Casting defect Paper Kopfstütze Playground slide Finger protocol Ammunition Sizing Computer animation Crown (headgear) Cartridge (firearms) Ship of the line Steel Miner
Stock (firearms) Machining Machine Chemical substance Scrap Compound engine Outsourcing Computer animation Cartridge (firearms) Wolframdraht Spare part Tool Steel Tool Wire Steel Miner Material International Space Station
Chemical substance Mechanical fan Folland Gnat Vertical stabilizer Ink Boeing 777 Gedeckter Güterwagen Compound engine Silvering Turning Automobile Typesetting Spare part Steel Material International Space Station Vertical stabilizer Typesetting Pen Reel Ammunition Game Computer animation Cartridge (firearms) Thrust reversal Steel Ship of the line Paddle steamer
Vertical stabilizer Fiat 500 (2007) Airbus A300 Fender (vehicle) Ink Playground slide Zementation <Metallurgie> Sizing Computer animation Cartridge (firearms) Automobile McDonnell F-101 Voodoo Typesetting Spare part Steel Ship of the line Stool (seat) Steel Ship of the line Holzfaserplatte
Computer animation Avro Canada CF-105 Arrow Bending (metalworking) Steel Clothing sizes Steel Lumber
good because from now on we have the
same and routine every week this is the time for questions you get so if you came to class but you had a look at the slides all we should be OK OK that we would which is going through a number of examples where I was trying to sh the show to you didn't know how a 100 basically go about changing Mike rastructure by the doing a of thermal treatments and and eventually you don't you that a very large and very large forgings or or heat-treated routinely this another example here where we are for instance look at Barry the the wire rods used in wire rod Michael structure of wire rod and wire rod this on the news used to make a ball bearings for instance not to ferment make many other things but 1 of the USA system called out and I went when you making ball bearings the the wire rod makers is a high-carbon wire rope that percent or so of cop very high amount of carbon now of usually it's it's not produced the ball bearing is said when its use is up to the very heart of material it's it's it's heat-treated to make markets side but that's not the way you produce it we produce it is it is to make the prolific Mike rastructure cancer let's let's have a look at the way you would die but you you would look at this stage so that 1st of all I so you always have to consider the In the Heat Treatment the temperature versus time cycle that you consider but then you have to be a phase diagram phase diagram for that particular Steele said that as you can see it doesn't look like the face diagram of a regular on carbon steel because it's that particular wider Raul composition contains a toluene elements and others and then you have it the transformation diagram this time the transformation diagram which is shown here right and I'm you don't have the use of the sea currents here because it's it's not the t diagram into CCT diagrams where 1 where you have is the 1 that is obtained by doing continue schooling this is the 1 type of and you want to use if you continues so let's have a look at summer things here and right so that you can do it different things you can do and and will last have a look at the hours so you can see this is a steal that when you cool down here the primary faced that you form will assume and tight In the end and the Austinite of also denied transforms that remains transforms at this temperature here so we will look at the 1st a transformation here so we we cool down the from farm the letter from the distemper due from the high temperature has and then we hold it so this is a linear linear the temperature time curve right so when you put this in a logarithmic scale yes but you use instead of having a straight line you get curved line OK but it's basically the same cooling pattern as as in both cases so I cool down from high-temperature relatively fast and then I hold for a longer time and so if I look at the transformation diagram here I can see when I do this while nothing happens for a while and then after about the 10th and 20 30 seconds the transformation starts and the diagram he tells me I'm going to make perlite this there are so let's have a look at end a bit more the tale the 1st we we will do 1 of the 1st act we go from this temperature thousand 50 and we cool down quickly to room temperature so what would wouldn't we expecting him in normal conditions so well we 1st of all we always look at our phase diagram here so it's thousand 50 is somewhere here you can see I'm in home which used Austin at the Grange man when a cool down quickly I'm not going to make any transformations except the MarketSite transformation and demand-side transformation will start at the so-called Marcus I start temperature which is around 200 here has an effect continued to cool down to room temperature I can see now that I have and I'm not leaving his gray back so the transformation will be partial was because I've been crossed the finish of temperature and then you know that the democracyThe transformation in steals is not time-dependent it's temperatures so I and I said and crossed the master MF temperature I'm going to have a partially and transform microscope there but now is this is this true yes this is only true if I can show that for this cooling rate of 50 degrees the 2nd 2 years In my transformation diagram I don't cross any of the transformation of curves so this is 50 degrees of the 2nd again it's a curved line because it's a logarithmic scale here and you see that at this time of cooling rates I don't cross perlite and the nite transformation ranges so I get Martin said microphone so let's have a look at at
this my structure are so along with it and Mike rastructure that's very much that's Martin said it is very difficult to see much in the optical microscope and this is what the optical microscope shows you and this is so you get a better view of what's happening in the the In the Asean region and what you see as you see some of this white stuff here and then is in between here you see what looks like Martin site has inside and in between democracyThe there's some space here that's because we have fun transform Austinite and if you notice also if you look carefully they like white dots everywhere yes and why adults it's not because I knew over etched a sampler or something it tells you that these white dots tells you that there are Carbide's state so that means you know that when you for Martin certainly 1 per cent of carbon is very high carbon markets I in the solubility of carbon and varieties 0 almost at room temperature you have a very high super saturation of carbon and during the cooling even during the cooling the carbon will have a tendency to leave the at the higher temperatures to leave the DeMarcus IG Markets that starts to former at 200 degrees C that's already high enough to a Allred temper that means that the MarketSite tempers itself that means what does it mean it means Carbide's precipitate out of the market site during the cold and and very fine and that you can see it everywhere and and of course if you look carefully on the mayor it's everywhere these suspects are everywhere except in this region here the black region is no suspects no no little dots and the reason is very simple the carbon is highly soluble in the Austinite so the high carbon content of the Austinite part of the doesn't lead to precipitation Of course
let's let's do the an numbers so another cycle we just debates 5 minutes now we stopped right above him in this zone here this long we cool down and we keep it at this temperature so what do I do we basically and I cool down quickly there's a quench so what you expect that would happen here well meanwhile according to the diagram here should make some seem tight and that the temperature I should have Austinite stable yes nothing much should happens and then when I cool down and I basically should make Martin yes let's have a look and that's
indeed what you see is basically looks this saying now as I think of some of its protectorate Semin tied at at the grain boundaries and the rest of the microscopic is basically the market society with a little bit of With the tried precipitous OK so now I'm
going to have go to go lower than to go lower and going to and the a transformation diagram here predicts that as I do this I'm going to start forming for life for all this cycle number 3 let's have a look what happens here
and you can see that is again against the disease black lines of the white lines here and the SEM picture but those on this is the primary phase this human tide for always 7 times and if I look carefully at the the center of the material ah I basically don't really see perlite it's it's at a surface that I see perlite and the reason is that is
because the temperature was set at exactly the EU take temperature nothing much should have happened however at the surface it's slightly cooler so there rights the transformation but I don't see much year the seven-time that is intended to provide this transformation is
partial but now I go 2 at a temperature that's really nicely lower than the you tech toy temperature where I have the perlite transformation of society for and this is what I get again the optical microscope dozens of pictures doesn't show very much but if you look in the SEM you can see the very fine Lamela structure of of life so you
always need if you want to know something or predict Mike rastructure as you need to know I will 1st of all you need to have an exact thermal cycle then you need to have the equilibrium of phase diagram for that particular composition and then you also need to have a baby I do t t t diagram for the season CCT continues cooling temperature died and yet this is a slight it's only in the class it's not very important it's just a just want to make sure that everybody knew this I said so in the end In the IRA
carbon Phase I got we we basically only interested in this part Of the diagram really was on this and and there are very characteristic their number characteristic temperatures this and that 81 and 83 temperature to the A-1 temperature is EU tech toyed temperature and the 8th temperature it is the the temperature of the transformation here where you take of variety for this boundary between the Austinite region and the Boston I was there I with the these temperatures are In this particular phase diagram are equilibrium temperature yes so those are the ones that you will observe for the transformation To perlite and attributed the formation of created new tech toys variety and if you do very slow processing In practice that never happens you always have a cooling rate or the heating rate has had so that's why we make a difference between 83 we are free and they see story yes when I'm when I cooled down quickly yes the temperature at which the transformation starts Austinite starts to decompose into far-right was also it is is not here is not here but is here is at a lower temperature so we that the temperature at that we observe yes this call the aid arteries 3 temperature has insisted that you do the the temperature with the transformation started during cooler yes at a certain cooling rain and if I made up the same thing the the Austinite will this is what will follow will form a fully Ostojic Mike rastructure not at this temperature but at a slightly higher temperature so this you get an overshoot hasn't worked OK so that that's called the A C 3 temperature and so there is a DA 3 temperature is not equal to the agency that it's in and are 3 temperatures the sea comes from the city of shuffle eyes which is French for heating and power comes from rough or the small which is French for cooling that don't get it confused because obviously the city here isn't this C 4 it's the on it's to this is the French C 4 0 heating and that similarly the 81 temperature and this line here at these temperatures here has this aid c and temperature that's C and stands for Seaman tied in with temperature at which Seaman tights precipitates out of Austin ideas yes you do you have heating and cooling of temperatures where this line of well if we have an 81 and in 83 temperature do we have a 0 and an aide to temperature tests these also exist but these are the sort of magnetic transformation so there is a magnetic transformation in Simone tight that's a 0 temperature and the aid to a temperature we should probably also never have heard about but that's the magnetic transformation temperature for far-right yes this is the Curie temperature was securing the temperature magnetic long magnetic transformation in the rest is dependent on composition in steals yes that's that's what you call the the 2 temperature but also just for those who do not familiar with the phrase diagrams or if you have forgotten how to use it as something like that lever which allows you to calculate how much and of each phase is present and what composition is of each face of France's which just discussed this 1 per cent the ball bearing steel yes I think so I think liberal and no it's it's it looks like there's a lot of perlite and this thing yes so what the what's the phase fraction which the actual amount at the end of the Seaman tight in this might rastructure so so in order to find this out you you draw a line vertical leaps through the composition and then you draw a line at the temperature that's of interest to you which in our case would be room temperature the rules so you draw horizontal lines and and so what with this vertical line will cut the horizontal line into segments on this segment in this segment here is a blank you can show the cost of the fraction of a seaman type is proportional to this length and the fraction of far-right is proportional to the size and you can also see what it would've compositions are as the carbon content of the far-right is here it's 0 yes and the carbon content of the statement ideas here 6 . 6 7 so How do I calculate the the 1st phase fraction of of 7 tied what is basically the ratio of this length the length of this segment over the length of this segment this is the 2nd this segment is 1 because it's 1 weight Percent of carbon and the this year is the composition of semen Titus 6 . 6 7 so if you make this ratio 15 . 58 and for far-right it's the the ratio of this length of the horizontal lines divided by the total length of horizontal lines so that's that's a unified and of course to some of these 2 was we 1 so you see that although I you know you do have lots of carbon in the volume fraction of persimmon Titus this is not the personal future it's about the only 15 per cent if you
get a very carefully the Microsoft dropped a as we've seen can be made 100 per cent per letter yes but to face fraction of Seaman tide is only 15 per cent so this this slide area uploaded just before here I oppose the revised plan a version of the course material to interest printer that proclaim victory so let's say fewer before we start talking about the effect of of some key elements geology and elements on face stability and on kinetics of transformation let's just say a few things about allying elements insisted on it when you if you're not familiar with steals and you while you get the compositions of steals yes 1st time you while I was confronted with the conversation that the people and the plant would give me a little sheets of paper with 30 to 40 elements yes analyzed and done and so my 1st feeling was like Oh my God this is this is incredible material you know that you've got to on alloy like 40 elements and you know what's the logic behind all of this but 1 of the reasons you get so many elements when you ask them from people and foreign steel plant is because they analyzed for these elements it doesn't mean that all these elements are actually following elements many of these elements are just there because there in the and end up in the In the oral and in the and the basic starting materials and end up being in your steel as a consequence and some elements must be tracked because even tho they're not added and the concentration is very low they may have a negative impact on the properties so they're all their measure you track as the way to control the quality of your this the soap but so let's now look at from the point of view of the designing its deal you know the we do we really need the entire day the table of Mandela to to understand steals it and in it as a matter fact not there actually what the relatively few elements that we play well when we make students come from and this is what I'm going to try to explain to you to this that Table of Elements is a siren various central place here yes and these are the if I if you really look at what's important for steals this is these are the elements that that are of importance to us to steal and end and sits in in this set of elements there some basic what I would call basic following elements that have carbon aluminum silicon manganese and culture is these are elements that are in this deal because we tend to control their we tend to want to have a certain level all carbon content aluminum content silicon manganese and calcium for diverse reasons for instance calcium but ends up in the steel because not because of the properties of the steel is because we want to do it come from the calcium treatments we calcium treatment to give the inclusions oxide inclusions in the steel certain properties so we add the Kallstrom for that reason aluminum saying thing is added in many styles not as an ally element but as an element for the D oxidation of your steel so you know that you produce steel by In many cases by if if you worked through the yard the blast furnace as you are you go the from the blast furnace you go into the oxygen making and you blow a lot of of pure oxygen on your steal to get rid of the very high low levels of carbon has been so you need after that you need to be oxidized be removed the oxygen that's in solution yet you did this with aluminum that's why the aluminum is the newest manganese silicon are elements that are always part of the Constitution of your uh of your boss the minerals that you where the steals come from so when you're you're reducing IRA you also reducing partially reducing the silicates yes the manganese oxide cigar in the or you always end up with princess manganese about the tent . 1 2 . 2 per cent of manganese and so they're always there but these elements also have will see an impact on the strength of the US so they're very commonly used as editions strengthening conditions due to the steal the very basic knowledge and of course the carbon comes both from the reduction of the steel asks it it
can also be used very effectively asked in element to strengthen the steel we will discuss it but so there are also other elements in the steel which we call program elements have elements that end up in the steel because they are in the minerals we makes deals with all they are in the scrap that we used to make steel if that's or that their picked up in from the atmosphere there's so examples hydrogen and hydrogen can come very many sources what a favor oxygen of course nitrogen from air units and then we have elements such as copper phosphorus sulfur 10 anti-money led this with these elements are they are very common for instance copper is very much used in all kinds of wiring yes so if by chance you have some wiring has not been removed from your scrap material it will end up in years and I just to tried and element you don't you don't really want them but they tend to have a very negative impact on your properties you if you have had a materials science courses in the past you probably know that sulfur is very In many applications it has a negative impact on the toughness of steel so we don't like this elements saying for phosphorus so these are trampled you really wouldn't want them but that you have to where would delight come from from batteries for instance In the scrap and scrap metal order than then you but at and that we come to elements that we had 2 steals because we're interested in controlling the transformation yes the TGT died that's basically what we want to have these elements of boron we already talked about borrowing nickel Kroll Molly and manganese that they will allow us we'll see in a moment how what they would for instance crewmen Molly due yes but it will allow us to get some Mike rastructure is that would be very difficult to make or to obtain if these elements were not at there are many reasons why certain elements are added as for instance if fighting I go back you so France's let's just focus here just for a 2nd on chromium has grown them is an element that I will add to control transformation but with immediate transformation is the transformation of of Gannett to Alpha the decomposition reactions on to banal but I see here at special underlying additions to see us as chrome again here is what is the meaning of the safe I add a a little bit of Kroll likened the crew will have an impact on the transformation behave if I had a few percents of Kroll was then Chrome will start forming Carbide's very hot Carbide's and so we use these Carbide's of Molly Crowley tungsten yes because a very hot Carbide's it's much harder than Seaman tied and we will use this To make tool steels tools deals with very hot carbide particles which makes that which makes them wearer system I will see it is 1 of the coming elections that Titaniums Canadian Idaho really are very often added to high-strength steels because they gave me I'm very small precipitates very small precipitates an economy also gave me a large volume fraction of very small so that they can the amounts we have to add to get this precipitation is not very large should we call these Michael Allen additions cobalt copper Copper is for instance added 2 precipitation hardening additions this I led and sulfur which I had just said to you or elements we pursued tramp elements in certain cases but they are added 2 facilitate machining and in particular sulfide compounds are used to that of the situation where you add a lot of sulfur yes and there's nothing wrong with that actually it improves matter during machining parts stocks and of phosphorus again very often will hear people say Well you know you don't want any false for us because it's and Breitling edition but there are cases where we do add quite a substantial amount of forces because it has a very high strengthening effect you in general also and the left of the irony here is that these compounds here continue and my Our Carbide forming elements enter there
are certain steals but I where complex still special steels where we add very expensive following elements such as cobalt and wants more aging steals or such elements that's because we want to control the and mask temperature basically and and allow us to do Mark acidic aging of Mark acidic steals in a special conditions to call but what happens if we add a lot of chromium not half a per cent of 4 5 per cent when we add 10 per cent and more yes we make stainless steels and then there's and stainless steel we're not really interested in the game the transformation we're not really involved although it has an effect of course were not really interested in formations that we I don't want Carbide's but we're interested in corrosion protection against saying what molybdenum in stainless steels were basically interested in corrosion protection probably heard about chrome nickel stainless steels on is added and nitrogen is not adequate for corrosion resistance the reasons but to stabilize Boston I to use our Austin in fixing the you use the nickel and then again there are always special steels there's a woman called steals where you will have certain element that is very important Silicon is 1 of those there is an electrical steels are critically dependent on the the high silicon content and it's very interesting because when will see this later when you add very high amounts of silicon to steal it tends to unbridled steel a lot of this so very low toughness tests but ended in particular case if you want to do that when you want to make transformers for motorists I this loss of toughness is not really that important the electrical properties are most important and you ask yourself why why do we absolute could we add silicon In order to control resistive fatigue in these materials it's basically do not really for the magnetic properties which the electrical electrical properties of that silicon confers to look at so now let's say let's look at them a handful of important elements I am manganese chrome Molly silicone let's 1st start with manganese so see 2 things of all we're always interested in what US but at the compound due to the stability of a phase Alpha programmer and what does it what's the effect on the transformation kinetics because that's what and again interested in the irony rich side of the face diagram so if this is the the top line here is the the Irish carbon phase diagram so you can see as I add 1 per cent 2 per cent manganese this temperature goes down the you take temperature goes down in other words the Austinite stability phase the region expands we will call this element the Austinite stabilizer OK so now let's have a look at the transformations with what was the effect Of the transformation in . 9 percent of carbon so . 9 per cent this year I'm so that would be the steel that is almost entirely political and so you get in the TD TE curves you get the see yes this but like transformation behavior for you can see however that as you add manganese the 8 remember what this temperature what is called this 81 temperature decreases in and so on but the 81 temperature is is here you can see me that has an increased the manganese content 81 temperature decreases the temperature at which the transformation to perlite starts is decreased so manganese there's stabilize gamma and what is more important also when you add manganese to see you can do the prolific transformation at lower temperatures that this is something we often use when we want to process steals and we want to refine the mike rastructure we got we want to do it at lower temperatures as we want to do it at lower temperatures this by adding manganese 2nd lowered the temperature and have the paralytic transformation at a lower temperature at lower temperature we know that the new creation rates are higher the high depletion rates means a lot of small places where things start growth rates are not phenomenal but you get and as a consequence you get a very much we find Mike so far so this is what manganese does but that silicon silicon is another 1 of these elements and that would like to work with I it's it's strengthens my skills yes it has also in effect all the phase diagram it increases it because it's a fair right stabilizer it increases these so the 81 temperature increases as I add silicon so the reverse of what the manganese dozens and the other thing is so that this would be for instance that day and the Seeger 4 the prolific steel without selected or with very little silver and now at 2 per cent of silica 1st the transformation starts at a higher temperature then the knows this is a list from from here to here so the Silicon will and accelerate you can see here accelerate the transformation of because it accelerates the verite formation g accelerates its during a political instrument but also whenever you for pro you take torrid affair that's a little bit in the manganese dust this is the reverse basically of what manganese dust Silicon has also another important and
aspect which which we can use also in the a when we we do steal decide then Silicon increases the EC carbon activity in in Boston thank yeah so and you can see the the effect here so manganese nickel not much effect silicon increase connectivity and what was this important when I'm sorry I'm Montserrat which is good appears this should be variety of there the government should be held just noticed right so how does this serve what why is this important when you when you have diffusion dance the diffusion usually go you know we think about diffusion as a result of the atomic motions in a concentration gradient so the princess's carbon carbon content and this position 1 and hear the carbon content in position number 2 so if I show you this you'll say Well they'll be at this this is the case Delaware flocks of patents from here to here which is proportional to the the diffuse years and then at times Times this distance suspects for Delta X instead of Delta City over Delta effects on the specifics it is actually not correct the the diffusion is is the the result of atomic motion in the free energy gradient listed it's actually what is important is the free energy of carbon In position want and in position to and does and this free energy as a function of the activities of cars 10 the notice from this former newest near-zero this part of the island activity consistent with the free energy that actually important so the Georgia presence what is what the effect of increasing the activity of carbon of St. Francis I make Simone talked this the when I make a particle of Simone tight carbon has to move for this particle to grow as the carbon has to move it has to be carbon flux yes 2 of the disarm tied particles yes the type particle then the article can grow right now said I make Simone ties when I make Seaman tights does not dissolved silica so sickened gets expelled Out of the region where seem tied is growing this region near Silicon gets expelled so what happens I have a gradients of carbon concentration gradient that looks like this is what 1 is a drop next to the president table because it comin ' built into the precipitate taken away from solution right here the silicon however goes like this White because the silicon is expelled out of the carbide but it's so it next to the growing particle carbide particles have a high silicon culture yes end the result is that the carbon activity here yes the common activity but the carbon content increases yes and you get the reduced gradient free energy graded or activity courageous and as a consequence and so did the sodium content of the so-called content is high enough you can surprise formation and growth of semen died yes because continued the selected can be used to suppress Seaman tight formations in conditions where you'd expect Seaman tied to 4 this and this is used can be used to good effect for instance to make certain types of Benedict Mike rastructure look at what about the chromium content well let's have a look 1st at what the chromium does To the bayern carbon face agony conceded only iron rich side there's not much happening but we conceded when we increase the chromium content there is a tendency for the 81 temperature to increase for the you take toys composition to go this way upward and then to the left so it's an element that is generally considered to be the far-right stabilizer OK let's have an inch from from from looking at this phase diagram yet let's have a look at what it does to the transformation kind and so let's
have a look at but this particular transformation diagram it said that the T diagrams CCT diagrams but those you can see at high temperatures have far-right and polite transformation this is the composition of the steel this because steal it has .period for carbon 1 . 5 manganese years so we don't chromium we get these dashed line and and and mass temperatures indicated the c throwing temperature indicate an C 1 temperatures so let's not have a look at what happens if we add "quotation mark 77 mass Percent of cruel and as you can see here that the the far-right Her lights transformation is pushed back and the bay I transformation is brought forward so you get an expansion of the bay nite transformation range another thing that is important with what before I decides that the 1st discussed the molybdenum and I'll come back to this of molybdenum in general will be laying diffusional transformation that means perlite transformation and it will have an then at the beginning back on the bay 9 transformation particularly will expand the Bay 9 transformation range that's a year you can see an example here of calculated DTT diagram 4 . 55 carbon steel with . 8 Molly and with 2 per cent more than you can see that very nite transformation is knows this promoted the far-right and the perlite transformation is suppressed so let's have an example you with this tete-a-tete diagram on the next slide the 1st
which is seen as being the irony .period for carbon steel again the seemed PAC-3 3 that they see 1 b temperatures so now we have a look at what happens when we had . 3 percent of Molly you see the transformation of variety and the perlite is very much surprised him and this allows you to easily make a Benedict Mike rastructure so but let me now go back to another thing I wanted to say yeah well elements such as manganese and chrome along and Molly yes are elements that you can replace irony in Seaman tied it when the concentration is not too high the chromium and Molly a very strong carbide performers but if the content is small the it's like half a per cent 1 per cent they will they will also tend whenever Carbide's therefore to be part of the semen tight lattice for instance here we have we we look at the DTT diagram for the irony carbon 1 . 4 % cross steel endit you know that when you form perlite obviously you for you you have Carbide's as it in lines but when you fought when you make big nite you also form small copyrights and you can see you can analyze the content of the Carbide's yes you can see this is here this is what we call the partition coefficient you look at the ratio of how much carbon this injury the carbon is come chrome isn't it the by relative to chrome in the indeed fairer and if a if there is more chrome in the perlite in the cement tight there is being partitioning or enrichment of that Allen element in the similar to what you see Is that as you In the pro-life as you increase the transformation temperature the amount the door of the petitioning of chrome true the ceiling tile increases a lot when you look at the Bay nite transformation there is no and Richmond and the reason is during the B'nai transformation substitution all elements do not the fumes so they can also not rich in the carbide OK so and think this is what would you often observers said the only thing Molly the chrome manganese ore also partially present in the car elements of boron this is the effect of or on the phase diagram you can see that even very tiny amounts of boron have that will reduce the size of the Austinite stability Rangel it's a verite stabilizer the reason why we added boron is because at very very small amounts of boron the borrower will go and sits at grain boundaries indeed Austinite and when you cool down for this steel here which points 16 % apartment you would expect in normal cases when born free that the Austinite grain boundaries would be the place where varieties is formed In the case of boron editions nothing it's so you can suppress very effectively suppressed far-right formation In a pro you Tech to its steals by the addition of board because it is it's the suppresses variety creation and you can see this
here also on the PTT diagram you see this as a T diagram here for steel that I point at 2 % carbon as the top 1 does not contain more of the bottom 1 has a small amount of boron and you can see that only the far-right transformation is delayed 10 but so will continue on this topic of composition effective composition on a micro structure and only a text Monday UK but the we think


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