The History of Iron and Steel

we take many things for granted these days but as a materials engineer I've always found it incredible how much we take materials for granted everything we build is dependent on these materials they are so significant that we've named entire periods of human history after them from the Stone Age to the Space Age they have all been made possible by the materials we have at our disposal and our mastery over their properties I've spoken about aluminium and silicon before but today we're going to talk about one of the most influential periods in human history the Iron Age some of the earliest evidence of iron being used as a material goes back as far as 3500 BC in Egypt where beads of iron taken from a meteor were found meteoric iron was a highly prized material due to its heavenly association Tutankhamun was buried with a dagger made of the material but meteoric iron was the only naturally-occurring source of iron at the time because iron reacts readily wood oxygen to form iron ore there is no oxygen in space so meteors deliver this material to earth in the form of humans could use without having the technology to extract it from its ore the Iron Age began at various points across the world as humans started to learn how to extract iron from its ore and its end date varies between regions - in Britain the rnh began in 800 BC and ended when the Romans invaded in 43 ad marking the start of the Roman Age if we continue to define human history but the materials being mastered at that time I would argue that the iron age lasted right up until a little over 150 years ago when steel was first mass-produced now wireless era is called the iron age the best materials at the time were made from steel they may not have known but iron and steel are mostly the same material before we go forward if you haven't seen my material properties 101 video the words in this section may confuse you a little if you haven't seen it yet and don't have a background in material science I highly suggest you pause and go watch that first so the main difference between iron and steel is the amount of carbon they contain anything with a carbon content above 2% is cast iron in general a higher carbon content results in a harder and less ductile material cast iron has a very high carbon content which makes it very hard but also very brittle as iron started to become more popular more and more of the early bronze continents were replaced with cast iron as it was cheap to manufacture and could be fired more often without being damaged but these material properties meant the cast iron cannons had a tendency to explode with no warning making them dangerous to operate cast iron is not suited for structural use either in fact it's use in bridges in the mid 19th century led to a series of bridge collapses later these bridges were rebuilt using wrought iron wrought iron contains less than 0.8 percent carbon which makes it a much better material for applications like this as it is ductile allowing it to bend under loads without breaking but it has a low carbon content which makes it a lot softer than cast iron steel is between the two with a carbon content between 0.8 and 2% giving it an ideal balance between hardness and ductility the history of iron is defined by our ability to control the carbon content art is the fourth most common metal on the surface of the earth just below aluminium but it reacts with oxygen readily to form iron oxide ores Ross is one form of iron oxide and preventing it as a constant struggle in structural maintenance the Eiffel Tower has been painted 17 times since its construction to protect it from the corrosion every seven years about 60 tons of paint is applied to the Eiffel Tower and the color of paint has changed over the years the tower was originally a Venetian red and has changed a few times from a more yellowish brown to a chestnut brown until the adoption of the current specially mixed Eiffel Tower Brown in 1968 because iron reacts still readily with oxygen to form iron oxide iron does not exist on the surface of the planet any usable form the first step to process iron is to remove that oxygen in the mid Bronze Age the first signs of production of iron are seen most of this early iron was smelted in these furnaces called Blue Mary's one of my favorite channels on YouTube primitive technology actually created a miniature version in one of his videos these blue Marie's heat the iron ore using charcoal as a heat source the burning of charcoal produces carbon monoxide which reacts with the iron oxide in the aura to form carbon dioxide and iron the bloomery is heated above the melting point of the impurities but below the melting point of iron and so as the fire rages material falls to the bottom of the bloomery and the heavier iron consolidates at the bottom while the impurities form a molten pool called slag which can be drained away and other great channel on YouTube how to make everything made a series about this process when the iron is removed it is in the form of this porous mixture of impurities in iron it needs to be worked with a hammer to consolidate the iron while the waste material is beaten off the material left over is wrought iron which as we discussed before has a very low carbon content these blue memories produce very small quantities of iron especially before the waterwheel was introduced to drive the bellows which allowed the bloomery to grow in size while keeping the temperature high enough despite the small quantities that produced the blurring revolutionized human life even beyond the obvious military advantages of iron weapons are nor is much more common than the copper and tin that spurred the Bronze Age allowing iron to be produced in many areas these communities can make their own tools and weapons without having to import the material from abroad iron plows are stronger and heavier allowing farmers to plateau their land quicker and thus grow more food a single farmer could feed more people allowing more people to dedicate their lives to different trades society was becoming more stratified and trade was increasing and things began to accelerate even more as we discovered better ways of extracting iron like the blast furnace blast furnaces increase the production of iron dramatically the blast furnace gets its name from the method that is used to heat it pre heated air at about 1,000 degrees Celsius is blasted into the furnace through nozzles near its base blast furnaces do heat the iron above its melting point along with flux materials the flux is a chemical that will combine with impurities allowing them to be extracted easily in this case the iron ore is mixed with limestone and coke coke is a refined form of coal with very little impurities and it works similar to the charcoal in the blue memories by producing carbon monoxide when burned which in turn reacts with the oxygen in the iron ore to remove it as shown before the heat from the process decomposes the limestone into calcium oxide and carbon dioxide the calcium oxide then reacts with the silicon impurities in the ore to form calcium silicate this along with other impurities form a liquid layer of slag that floats on top of the heavy molten iron which can be drained away while the heavier molten iron is tapped lower down this method allowed vast quantities of ore to be converted to iron quickly but it has a drawback but higher temperatures are in readily absorbs carbon so the iron created in blast furnaces had a very high carbon content may cast iron so an extra step is needed to decrease the carbon content this is called fining there were a number of ways of doing this one way was in a refinery where the cast iron is heated back up which oxidizes the carbon the material would then be beaten with a hammer to knock the oxidized carbon out of the material this process would be repeated until wrought iron was produced once again producing steel with this method would have required incredible skill but there were methods of producing it in small quantities all me demonstrated one of these when producing crucible steel which was produced by mixing wrought iron and cast iron in a sealed crucible which prevented carbon from the air from entering the material when mixed the low-carbon wrought iron and the high carbon cast iron would form steel the puddling furnace was another method of production that involved heating the cast iron in a furnace that separated the fuel and the iron the heat from the hearth would then radiate through the furnace and liquify the iron iron became molten a worker would then stir it to encourage the oxidation of impurities all of these methods of production were fueled and labor-intensive making the end product too expensive for general industrial use and the average life expectancy of a puddling furnace worker was just 30 years old due to the toxic fumes produced with the expansion of the railroads in the early 19th century the pressure to develop a faster and cheaper method was growing all our modern rail trucks are made from high-strength steel its superior hardness over wrought iron allows it to resist rare this is a difference between a worn steel rail and a new one this kind of wear happened so quickly with wrought iron that certain sections of popular lines needed to be replaced every six to eight weeks steel also has a superior strength over wrought iron allowing it to carry more load if you watch my last video you'll know why this shape helps the rail carry even more load so you can see why finding a method of mass production was so important and this is where the British metallurgist Sir Henry Bessemer came in Bessemer designed a converter that looked like this molten iron was poured in here from a blast furnace and hot air is passed through the bottom the oxygen in the air oxidizes the impurities in the iron the carbon reacts to form carbon monoxide which is expelled as a gas while the silicon and manganese oxidized to form a layer of slag this process was very fast in fact early on it was a victim of its own efficient as I removed too much carbon and left too much oxygen in the iron to combat this another ally that I am definitely about to pronounce wrong containing iron carbon and manganese called Spiegel Eisen was added ok the manganese would react with the oxygen to remove it and the caravan increased the carbon content as needed but it had another problem in the early days the process did not remove phosphorus from the iron and high concentrations of phosphorus make the steel brittle so initially the Basinger converter could only be used with aren't obtained from ores with low phosphorus concentrations which were scarce and expensive this problem was later solved by Welshman Sydney Gilchrist Thomas who discovered that adding a chemically basic material like limestone to the process would draw the phosphorus into the slag this availability of cheap steel caused an explosion and growth in the rail industry steel is so vital to our daily lives that it is often considered a measure of economic success of a country a high production of steel means a high demand for steel high demand for steel means your country is building infrastructure for example this is a graph showing Chinese steel production from the 1990s to present showing the rapid rise of China as a global superpower during their economic reform without steel our buildings could never have grown to the heights we see today and bridges like the famous Golden Gate Bridge would have never been possible there is even more to learn about Steel's fascinating history like how the expert blacksmiths of Japan managed to create the katana and they learned how to carefully control the crystalline structure of the steel to forge the perfect blade but we'll talk about that in another video thanks for watching this was my last video through 2016 and I wanted to end it by first thanking all of you for making this one of the most incredible years of my life I can't wait to show you what I have planned for 2017 I want to end this video with a message for a cause that's very close to my heart on this day two years ago one of my best friends died in a car crash in Malaysia and his family have set up a memorial fund in his name for the Nepal youth foundation Nepal is an incredibly beautiful country but there's a lot of problems it has one of the highest infant mortality rates in the world and due to problems with the internal conflicts the earthquake and just lack of social welfare and there's a lot of orphans in the country the Nepal Youth Foundation is dedicated to providing shelter food medical aid and a good education to the young people of Nepal I remember having this really deep conversation with Tom and some other friends on a little border town I wouldn't even call it a border town it was a horse on the border between Laos and Thailand and for whatever reason I I recorded this conversation just take a look with teaching English as a possibility because that I have this thing where I want what I do to have like a meaning in the world like I want to change things for the positive and I think teaching English I'd be to teach English because I think I'll be a good teacher and if I can go to some poor country and teach a group of kids [ __ ] good quality English they can go out into the world and then they look back 10 years time whenever right yeah I had a good teacher in English actually was his name was Tommy's he was pretty good like me then I would that's a better [ __ ] a brilliant thing to be able to give to a group of children right yeah yeah something I all want to be able I'd like the whole website thing is the whole point of it is engineering education it's difficult because I always think would get your anything started yeah get another thought something uneasy I've worked him to in this back in Hartman mmm my god I put up like just four kind of probing forward and I put up like a few videos on YouTube just basic kind of engineering education on and I'm like like ten fifteen thousand views over Tom never got to fulfill his ambitions but I did so I want to honor his life by donating to a cause he really cared about Tom volunteered in an orphanage in Nepal and he constantly spoke about how much he cared about the people of that country so I'm donating two thousand euro to the Nepal Youth Foundation I hope you can match that or donate whatever you can I really don't expect anyone to but it would mean the world to me if you did without Tom I'm not even sure I'd be standing here talking to you right now through all of our adventures together Tom always encouraged me to pursue my dreams and his positive attitude to life really rubbed off on me on when I really needed it and I definitely wouldn't have left my job to pursue this dream if it wasn't for the shock of his death making me realize that life is just too short to be doing something you're not passionate about so I hope we can have a positive impact on the young people of Nepal the way Tom had a positive impact on every single person he ever met in his life

Channel: Real Engineering

Views: 1,288,272

Rating: 4.9381065 out of 5

Keywords: iron, steel, bloomery, blast furnace, puddling furnace, refinery, bessemer converter, history, iron age, science

Id: 7E__zqy6xcw

Length: 13min 36sec (816 seconds)

Published: Wed Dec 21 2016

Reddit Comments

[u/TaytoCrisps]

Thanks for posting OP! Video was put up in a bit of a rush today for the charity message at the end. Hope ye like it. Feel free to ask me any questions here or over on: https://twitter.com/Fiosracht

[u/Nilbogtraf]

That was really well done, entertaining and educational.

[u/HortenWho229]

Ah good ol' space material