STAINLESS STEEL ... THE MIRACLE METAL

[Music] [Music] you and I have just been looking at the insides of three different kinds of alloys Steve magnifying about 1,000 times these are what the metallurgist calls micrograms and he reads them about the way you would read a menu in the restaurant in fact he not only knows what's going to be on the table for dinner but he can tell whether you've seasoned the soup properly or burned the dessert let's explore some of these metallurgical mysteries together and particularly as they relate to a story that is loaded with terrorists and excitement now in all five thousand years of recorded metallurgical history this is the finest banquet that has ever been served up stainless steel nobody ever supposed that such a thing could have been created if you had proposed it it would have been received about the same way as if you told somebody today you can levitate just like the law of gravity it has always been presumed to be a law that iron would rust you're used to seeing stainless steel in your kitchens and on the buses and trains but do you realize that this is also the foundation stone so to speak of the rocket missile satellite work nuclear reactors yes and many other things iron itself as I say has always gone back to rust in fact iron ore itself is nothing other than rust the metal word just goes out mines it puts it out of furnace heats it up to a tremendous temperature tears the oxygen away from the iron the iron trickles down they collect it freeze it Foreman put it into a bar or some other piece and then nature creeps in let lessly brings it back to rust or two or well we don't know everything that there is to know about the history of mankind we certainly are sure of ourselves to this extent that nothing has ever been found of iron from prehistoric times here for example is a pair of ribs from an extinct bison with a projectile point lodged probably in the exact position where it caused the death of this animal about 10 or more thousand years ago somewhere in the southwestern part of our country never a metal is left just rock and bones now if we come further ahead in history for example up to the Viking Age of a thousand years ago or so we do find some rather interesting accomplishments in the field of iron and steel for example here is a Viking ship which had been buried in Norway several miles from the sea along a river with the bow appointing a south toward the sea and in the cabin was buried a queen with a number of her effects some of these are extremely interesting for example this fine oaken chest lined with nails which are tin plated this is a remarkably early instance of tin being used to prevent or to slow up corrosion here is the restored oza bear this given as it is called now on display in the Museum of Oslo notice that the nails are still in place after 1100 years now they're not stainless but they had learned a few secrets themselves in fact in passing let me remind you that a copy of one of these boats was built and Julie sailed from Scandinavia to the Columbian Exposition in America in 1893 to show that the Vikings might have been here before Columbus but anyway let's take one of these nails cut it like the metallurgist does polish it Bechet and interestingly enough we find a structure which is not uniform but apparently has some interesting foresight and planning notice the dark limes here this is steel carbon has been added to the iron to make it strong and elastic but also note that these dark lines are inside the nail and the surface itself is light edging in other words that does not react readily with the etchant and we know now that this is iron relatively pure and relatively corrosion resistant yes they made their nails even so that they would stand a thousand years of course this is in the relatively dry and the definitely cold climate of Scandinavia the most remarkable piece of work that we have from the ancient times is the Damascus blade the Excalibur of King Arthur the legendary sword the beautiful watermark on this blade has always been a mystery to the mind of man but modern metallurgist has never solved completely the secrets of these ancient craftsmen about the only thing that we have in a way of a real historical record is that they quenched these blades by running of a new sword through the body of a slave and then they tested every blade by a decapitating if it could be done in one stroke without a nick it was fit for the emperor yes these were marvelous blades how were they made those were the days of alchemy secrecy closed gill nobody ever told anybody else how they were made so come with me back about 200 years and let us try to enter the mind of the metallurgy at that time thrilled as he was breaking away from alchemy and tearing apart from nature those secrets which we now know as science and particularly metallurgical science in those days there was a mystery that was the flying saucer talk of its day the meteorite iron from heaven apparently this wasn't quite so hard to swallow for the Egyptian of thousands of years ago because their hieroglyph actually means iron from heaven but in the french academy of science and believe this or not about 200 years ago they members actually stood up and took a vote that there was no such thing as iron that didn't come from this planet well they're cocksure us was short-lived because within a few years twenty thousand pieces came bursting in upon the land of normandy not far from paris and it wasn't long before these pieces were sectioned and studied and granted to be from heaven indeed now one of the first men to cut one of these in two and disclose the interesting inner structure was a bad nevada theme instead by name almost as bad as nothing but well let me show you over here more clearly and more interestingly an extremely historical piece this is a copy of the actual print that was made by leadmon stanton when he sectioned the meteorite and polished it and then rolled a printer roll over it to ink it and stamped it out to form his own lithograph in fact he called it a meteor Eisen autograph now for these purposes right here I want to point to the fine coarse on one hand structure that intrigue the metallurgist because he had in mind they similarly flying and beautiful structure of the dama CM sword could it be that this held the secret of Damascus steel well many of you have heard of stainless steel and usually when you hear about stainless you hear of it in terms of 18 8 the 18 refers to 18 percentage chromium and the eight to eight percentage nickel the chemists soon went to work on the meteorite and lo and behold they found that it contained about eight percent nickel in other words nature had made an alloy about two billion years ago give or take a billion but it was not a stainless steel because the Keystone element chromium was not in it at least not to this extent but she had made at the eighth of 18 8 and furthermore she put in the mind of these scientists the idea of adding nickel to make what we now call alloy steel yes here it was in the middle of the 1700s and a nature had tipped off the scientists of that time that there may be something exceedingly interesting found by alloying elements with iron not many elements were known in those days and if you will picture yourself for a moment back these 200 years you will realize that there was intense intellectual excitement over the discovery of elements which are common to us today we get excited about neptunium plutonium nobelium but in those days it was nickel manganese molybdenum tungsten and then finally the story of stainless steel opens the year is 1797 George Washington in the United States is just laying his gavel down from his second term our country is eight years old the Republic of France is six in Paris one of the famous chemists of the day bokmål Lange has been the dissolving and testing a mineral which he has obtained from mountains and Russia a new color can it be a new element yes the following year in 1798 it was his personal thrill to be able to present the world's first piece of chromium metal to the French Academy of Sciences incidentally it is very interesting today with regard to stainless steel to read in book Lola's presentation of this remark the metal resists acids surprisingly but the road was to be a much longer one than that there were hit and miss attempts to alloy chromium with iron along with these various other elements a classic occurred in 1821 again in France Bertier this time as the scientist he had a crucible on where the molten iron and steel and he dropped his chromium into it to make an alloy that had one or two percent chromium in it in fact he made a razor blade of remarkable quality and he recommended these chromium steel for cutlery and such things much as they're used today but he didn't have a stainless steel the thing that is particularly interesting to stainless technology is the second thing that he did had and that is ferrule chromium Bertier was apparently the first man who not only made Oh chromium but recommended its use has a master alloy for adding to iron and steel to make stainless steel yes Ferro chromium has a great deal of chromium in it but it is still set in a matrix of iron you can see how shiny the stuff is ferrule chromium like chromium does resist rust but stainless steel why this chunky brittle stuff who would want to build a bridge on this it's only good for melting down the alloys that can become stainless steel so 30a have never produced it and strangely enough nobody else did for nearly an entire century why didn't they let me give you a sneak preview wouldn't it be nice if we could go back 200 years knowing what I am about to tell you we would certainly be the famous ones of the day because there were three things that had to be discovered before stainless could come from the Bertier work let's see what this is now we know that the stainless steel is an alloy at least of chromium here is the first secret that chromium must be at least 11 or 12 percent Bertier put in one or two he didn't have a stainless steel him barely had a chromium steel on the other hand if you get more than about 30 percent chromium you're right back in the brittle Chucky's struffolis stuff which we can only use as a master alloy and making these Steel's so you see the first secret was to get it in leather a narrow range between about twelve and thirty percent the second secret every time these men have made their Steel's or even their pure chromium so-called they had carbon in it because there is a strange chemical relationship between carbon and chrome so that if one goes up the other one goes up in other words if you put chromium in your metal it drags carbon in with it if there is any around now remember that when I say an alloy steel I mean that the metal the alloying element must be dissolved in it like you'd put sugar into coffee excuse me for a minute while I let you go into the mental mysteries of some of the metallurgical work since you've already been baptized you remember the little gimmick that we use call a micrograph let's go back and see what some of these stainless steels look like when they start picking up carbon this is the second one that you and I were found looking at when this film opened a ferret ik stainless steel containing in this case about 26 27 percent chromium and only 1/10 of a percent or so of carbon and yet notice these little purple islands on here carbide wherever you see those carbon has robbed a chromium from the alloy and has isolated it in a useless island of carbide 1/10 or 2/10 of percent we never go beyond 1% today in stainless steels because even up just to 1% look at what happens almost 50% of the alloy is a mass of this purple carbide useful for wear resistance yes and by putting even more of it in we run right into the Steel's we call tool-and-die steels but they're not stainless the carbon has taken the chromium out of the solution and you have a steel but it's not a stainless steel where do they get all of this carp how come they could never make one without it well we can find that too and a little secret by going back and studying the crucible the means of making these alloys this is bertier's it's essentially the same that was used by both Malay Hassan frats any of the others in the early days here's a cutaway and with indications to show you that the crucible body itself was not only clay and sand a regular pairi but it usually had carbon in it in the form of a charcoal or a coke it was lined with what they called a brass a clay mixed with a charcoal and as a binder molasses or tar goodness gracious when that fighter Donner was loaded with carbon then he remember what I mentioned to you how the meddler just takes the ore and has to tear the oxygen away and let the iron or the chromium whatever it might be drip out how are you gonna do that carbon was the only means no one up until rather recently so they actually mixed carbon in with the ore and put it in with the flux and in short you had carbon every place the result you melted down a metal sure it's a medal its chromium or Farrell chromium but it's dosed with carbon up here is your slag look at the charcoal that came out of that molasses and tar so they always had karla and too much other so that they never had a stainless steel and there were two of the things that they didn't know about that you and I know about and it took them decades to this government to but there was a third one corrosion that was the third Joker it's an interesting thing man of the numerous solutions these early scientists could have used to test these steels such as acetic acid that you find in vinegar citric acid and the fruit juices water checking rusting or even nitric acid a powerful chemical they would have found that the steel was not harmed at all if they had ever made a stainless now instead of that they chose things like sulfuric acid and even today we don't reckon we don't recommend stainless steels for our service in sulfuric acid solutions without a great deal of care and forethought the same is true for hydrochloric acid it seems that they just persisted in choosing the wrong things and the result is that they ended up actually concluding chromium made the corrosion resistance worse and not better so for 10 years 20 30 40 50 yes up until the end of the 1800s they failed to get the chromium up high enough or if they got it up high enough instead of having the carbon just peeping over the edge here with a fraction of a percent they always had 3 or 4 or 5% in there the result is that they never had a stainless steel because they could never get pure chromium then in 1895 had happened a man by the name of Goldschmidt in Germany had cut this bond so to speak between chromium and carbon and from then on they had a pure carbon no longer bothered that this was a fantastic development let's see what happened it has to do of course with the means of preparing the chromium mass we recall in discussing bertier's crucible that carbon was always available well the first thing the Goldschmidt did of course was to get rid of the carbon he took a crucible that had no charcoal or coke or other carbon bearers in it he used a lining which was magnesia pure and carbon free and instead of mixing his or with a charcoal or a coke he mixed it with the newly discovered metal aluminum now I had explained to you how the metallurgist takes an ore which is an oxide of a metal and put something in there which likes the oxygen more than the metal does and the metal trickles down well aluminum likes the oxygen even better than the carbon in fact it likes it with such a terrific passion that they didn't even have to heat these crucibles up they merely placed a fuse in there let the fuse and then it was every man for himself this thing would be a bomb if a gas were produced but it happens that a gas is not produced in this particular action instead that the oxygen is torn away from the or a temperature of some six thousand degrees is produced this is the thermite reaction still use today in welding and the liquid metal trickled on down below now a pure chrome no carp this immediately opened up the possibilities on a worldwide scale for investigating chromium in all of its relationships with iron and steel and it didn't take long for a brilliant man to step up and do the job yes brilliant minds arose all over the world as soon as pure chromium was available for alloying many men tried it do ma in France in the land of the origin of these interesting metals followed by qui a about 1902 1904 then by a port of an up to 1909-10 but although these men actually made the stainless steels and held them in their own hands they never recognized what they had I guess it took an alchemist to have a dreamland high they had long aspired toward transmuting a base metal into a noble one they had fought in terms of lead in the gold but gold can only buy stainless steel these men actually produced a transmutation from rusting ordinary iron and steel into something that not only looks like platinum and resists attack chemically like gold but a square inch section can support a quarter of a million pounds now if anybody is to be given credit for discovery of the stainless to be a man who receives actually the least credit more Narns over in Germany Mon Arts dis covered and reported upon the phenomenon of stainless Ness and his paper still makes excellent reading today but the credit is commonly given to two other scientists in Germany who not only recognized that these were steels and that they were stainless but that they had commercial value the clouds of World War one were hanging over lay the country here from Germany to Britain over to America the military was pressing of metallurgy to develop the finest Steel's what they could and in Germany Strauss and Muller turned out the chromium nickel grade that today is the popular 18:8 now I color code these here let us get in mind that the martensitic the steel blue stainless steel the affair etic the silver gray and the austenitic the golden ones all of them actually handled in France but never discovered Mon Art's discovered stainless honest but never use the steel in Germany across the channel Prairie merely working with the cutlery graves discovered what we will call the martensitic stainless steels and finally amidst a great deal of confusion perhaps we could name of these men dance sisal and Becket in the United States as having discovered the theoretic so when the war was over around the entire world had spread a new class of alloys stainless steels now they had done so well these English and American and German investigators they had given the world something new to use at engineering the scientist knows easily enough what these are he uses very discreet definite terms the chemical symbols carbon chromium nickel get used to these you will see them again the FE for iron might confuse you just a bit but the Romans got here first their name iron was feral f/e now all have the stainless steels are alloys or combinations of these basic metals here others too but basically these there have been many terms used for these and that's very confusing and just in case you have heard of some of these terms I want to organize them and leave you and me with something definite to talk about English American German yes they've occasionally been used in reference to the respective rate martensitic yes the hard level ones of Brearley theoretic the non hardened noble ones and they have been called non hardenable and hardened above for these reasons and the austenitic well austenitic what is it hardened of or an unpardonable it doesn't use either of the mechanisms here but one of its own so some people call it work hardening but this is getting kind of confusing isn't it in fact both of these groups are sometimes referred to as the straight crows in contrast to crawl nickels and even where the engineers have given them definite type numbers they have listed that both of these groups under numbers that we call a 400 series as contrasted to the 300 series I think that I have made it clear that there are three major groups and let us learn how to lock all of these turns into something that we will simply call class one for anything that is called by any of these names class two for laforet ik the non hardened of all the straight chromes and so forth will describe these later and class three for the austenitic spaced usually upon chromium and nail classes one two and three in the great threefold family of stainless steel now we have taken you back hundreds of years under history believing that if you would follow the problems as they confronted the minds of the discoverers you would be better able to understand what it was that they discover a sort of stage the one principal fact that this miracle money is a know-how combination of iron with chromium and carbon and other elements such as nickel [Music]