What quenching and tempering does to SWORDS 

As a professional bladesmith, I'd like to say THANK YOU!!!!! for doing some solid research and presenting factual information on this topic. I can't tell you how much people misunderstand most of this so I greatly appreciate you using your very popular channel to dispel a lot of wrong headed thinking when it comes to sword.

Shadiversity: Helping me to study Steel constructions and entertaining me with swords at the same time

Shad, as a Mechanical Engineering student, who had to pass a pretty heavy Materials exam where this subject was pretty much 1/3rd of a 900 pages book... I must applaud you. It would be easier to explain with a Fe-C phase diagram (Alpha Iron, Beta Iron, Alpha Carbon, what happens if a dash of Chrome or Cobalt is put in...), but this is really an outstanding work, expecially with the real-world applications in sword-making.

I can only think of how _insanely_ interesting this is compared to the typical Hollywood depiction of making swords, which usually involved pouring molten metal into some stone mold (yeah, good luck with that). Imagine a scene between a master and apprentice, but done with historical accuracy in mind. We see the forging of a sword from beginning to end, with the master explaining everything in fine detail. He may not understand the mechanics or physics behind what's happening, but he still knows the process.

And languages caused a lot of headaches for Spanish speakers having access to English sources because lots of people confuses tempering with templado. Quenching = Templado Tempering = Revenido

Brought back all of the stuff I learned in my material science class as part of my mechanical engineering curiculum, I probably would have paid closer attention if they would have applied to to swords.

I could listen to you talk about swords for ages. The amount of enthusiasm you show for swords and castles and stuff is wonderful. If I ever see you, I'll buy you a pint.

Thank you Shad, you have *quenched* my thirst for a sword video!

This was a fantastically well constructed video shad. What truly blows my mind is that people in medieval times may not have understood what was happening at an atomic level but they knew enough to develop incredibly advanced weaponry techniques

Maaaan ... one of the best videos I've seen. I mean ... I'm a physicist and I've seen my fair share of lectures about atomic crystalline structures, but I never really looked into this ... and I've always wanted to ... For me as a sword enthusiast it was great, but the pure pleasure I just recieved as a sword enthusiast AND someone who understands the physical contexts ... woooow Swords are even more beautiful now. Keep it up with this kind of great stuff! Cheers!

A quick correction: ductility is a measure of how much a material will deform until breaking when subjected to tensile stress (pulling away on both sides). Malleability is the same for compressive stress (pushing in from both sides). The flexibility of a material is better described with the word "elasticity", the tendency of a material to return to its original shape once deformed (or "plasticity", the tendency of a material to remain deformed rather than return to its original shape). In other words: the traditional katana trends more plastic, spring steel trends more elastic. Great video, regardless.

Very nicely and clearly explained. Great work... Just one tiny correction. If you get to the blue during tempering on a blade, you already went too far and made it too soft. Blue is only desirable for springs. For blades (even longer ones), a traditional blacksmith looked for straw or light brown over the fire. A modern one sets the oven at 400-500ºF for 2 hours...

As someone that does metallurgy testing, I will say that was well done. Most people don't go into the detail that you did in tempering and quenching. Bravo sir.

This is mostly old basic stuff, for me ...except that, for once, I hear terms like pearlite and martensite, and have them _clearly and simply explained._ Now I know what those things are, and how/why they form! Thanks for that :)

"If you're beating it when it's cool" ~ Shad, 2017

Shout out to 'Man at Arms' and the boss that is Ilya

It's fun to point out that iron is the only element capable of shifting phases from BCC to FCC, and back to normal. It's dependent entirely on the heat applied and for how long.

I must applaud you in your research, I'm a professional blacksmith myself and wanted to inform you on a few thing's I've discovered. I have to say you don't temper swords to a "Blue" oxidation level on the edge because it looses too much hardness and rigidity. I generally temper my swords to a dark straw or red color. I'd like to bring up, I generally harden my swords with a slightly (when I say slightly I mean by color difference of one, so generally cherry red to low orange glowing heat) differing color from tang to tip. I have the tip a slight bit harder but a slight bit more tempered (So I'd temper the closest part of the blade a straw because it's not as hard, but temper the tip a dark straw or even red oxidation level) meaning it's still harder on the tip, but it's also a little bit more springy. For clarification you DO temper the spine a blue or purple color (depending on steel, hardness, sword, etc.) On a second note you don't always loose your hardness if you heat it up over and over and quench it over and over. I did a test on this and it showed a smaller grain size meaning sharper edge, and a stronger structure as it took about 300lbs of force to break it compared to the once quench 50lbs of force. (same piece of metal and the thickness was extremely thin, don't remember the measurements) Or rather, in short, if you quench a piece of high carbon steel over and over again it generally holds and edge better (and longer) than a single quench. Though it's extremely dangerous as you can introduce stress fractures into it. Again I must say excellent work on your research and that is all.

this is the best explanation of quenching i have ever seen.

I have Mech Eng deg, been a weld inspector, and a non destructive inspector for 20 years. Spot on and well done.

Interesting; the cooling of carbon steel and freezing salt water are rather similar on a molecular level.

Such a complicated process to be explained in a clear and illustrative manner...nobody does it better than Shad.

It's bring back good old memories of Katana series... Best ever

I love how you always grab your glasses. its very... teachery

The best way to combine my two favourite classes: History and science. You're great.

The heating up and cooling down of metals, and the effects it has on them is fascinating. Ferrous metals, such as iron (steel), and nickel when heated and quenched as said in the video, are hardened, but do the same thing to copper, silver or gold, which are all non-ferrous metals and they’ll soften. I make videos of myself hand forging jewellery, and annealing is something I have to do to keep the metal pliable. So I heat and quench the silver and it stays soft.

Hmmmmm... he’s talking about swords BUT WHAT ABOUT DRAGONS

As a technical designer I knew most of the things you said but there were still some things I didn't know or forgot over time. Good video as always xD

hi chad. nice in dept video, really liked it. but there are two things you mentioned that might make people get it wrong. first of all, the way you talked about katana's was like there was no tempering done to the blade at all. the truth however is that katana's do get tempered, but at way way lower temperatures than spring steel swords. if you would not temper a katana at all, it could be so brittle that you can chip it using it on a tatami mat. secondly, somewhere around the 5-6 minute mark you were talking about work hardening and that it was not that useful on steel swords, only on bronze because the steel gets normalized anyway. yes, all of this is true, but also not entirely. a well forged sword is never heated up beyond the orange color when forging it in the last stages. by forging it at this temperature the grain of the steel becomes smaller and that improves the quality of the blade. note, this is not just a sword thing, but mayor steel industries use this fact when rolling steel. but again, really nice video. it is rare to come across video's about this subject that only get this little wrong. keep it up.

Informations was not new for me (coz metallurgy was part of my education) but it is quite rare to see it in such interresting and informative video, really good and precise work from you, Shad.

Shad - I love the way you can explain insanely complex concepts in a clear and concise way.

I did know a lot of this, but I definetly learned a lot more today. Thanks Shad for combining education with entertainment in such a great way!

exactly the stuff we learn in our first year as students of materials science. great video, gonna share it with my fellow students.

Very good, Shad. Other than mixing the words iron and steel a time or two, this is very accurate. I study mechanical engineering and even I got something out of this(mostly the english words for a few of these things). I ought to show this to my first year teachers, maybe they can use it as teaching material.

This is fantastic! I really enjoy going more in depth to the process involved in the process of making things. Processeption.

Well done, Shad! That was basically half a year of material science in 20 minutes, much more entertaining and very accurate. If you add 5 minutes of math and 2 about common alloy types you can teach a mechanical engineer 99% of what he needs to know about steel in 27 minutes. Awesome! =D

9:30 Hold up. Tool steels are quite a bit more complicated than that. The different types of tool steels get their various properties from a combination of carbon content, alloying elements, and their heat treating. For instance, those drills you showed would be made of high speed steel, which is a high carbon steel that's either going to be alloyed with tungsten or molybdenum (alongside a whole bunch of other stuff) and heat treated at very high temperatures. But aside from that, pretty spot on. A lot of these same concepts are used in industrial settings for heat treating steel parts. Actually it's almost identical, except that in a lot of cases you'll want to temper parts in an oven instead of an open flame for better temperature control.

This blacksmith approves

As an engineer i love the technical level and accuracy that this video goes into. but I'd also like to add that in the good old days, these processes were still used to make things like the beds of industrial milling and turning equipment. These days, to make things cheaper they dont do it any more. this means that second hand metal working machines hold their value because even if they were made in the 1950s they can still be more accurate than something made 2 years ago because they've not done any of the stress relieving to any of the precisely ground surfaces, which eventually start to buckle.

Wow, one of the most informative and simple to understand videos I have ever seen! You're great at explaining stuff Shad. And thanks for another great series!

Man, Shad gives out a lot of hearts.

THIS IS WHAT I CAME HERE FOR! SWOOOOOOOOOOOOOOOOORDS!

Great video Shad. Amazing how many different topics you branched off into for an 18 minute video this time. We start with the 2 fundamental topics of your channel, history and HEMA, then add in metallurgy, physics, and geology, and you've got this video. Great job Shad. You're explanation of how the crystal structures form in steel depending on if or how it's quenched is spot on, and matches well with what I've learned in some Geology classes I took in College a while back on how rocks form. Same principal at work, cool minerals fast, and you get crystals of very small size and evenly distributed, cool it slowly, and the minerals have a chance to form big crystals and separate themselves out more, and you get a more uneven distribution. Anyone wants to see the difference in what Shad's talking about in a visual way, do an image search on granite, then do another on rhyolite. Compare the 2 rocks. Both will look completely different, but if you study what minerals make each up, you'll see they're made up of the exact same minerals, the only difference is the granite cooled very slowly underground (over millions of years), whereas the rhyolite cooled more quickly above ground (over a few weeks-years).

I have been thirsting for this video!

I studied this on university and you made visualize some things in a really cool way. Great video.

Chemistry and the like are usually my Achilles' Heel, this stuff just doesn't easily enter the brain box, however the way you explain stuff makes this go down simpler - undeniably helped by your clear love for swords and the such. Thanks Shad

Just a little correction: Heat treatment (tempering and quenching) is not anywhere close to the last step in the manufacture of a sword. It still has to be brought to its final form, polished, hilted, sharpened, and have a scabbard fitted to it. If anything, I would consider heat treatment to be the halfway point.

History can be very interesting if taught right! wish i had such passionate teachers once i was going to school, not just less than interested boring zombies :(

15:59 _"Hardness does not determine how sharp a sword can get."_ Technically true, but when you get into some of the more exotic steels (albeit not sword steel), hardness and steel composition do dictate how sharp you can get it. For instance, with steels like ZDP-189, CPM-S20V, ect. - you run into issues with *_edge stability._* And with steels that are extremely hard like ZDP-189 with a high HRC or steels like CPM-S20V, S30V/S35VN, ect. with carbides not normally found like vanadium carbides (which are... absurdly tough, don't quote me on this, but IIRC vanadium carbides would be measured in the hundreds or perhaps thousands in HRC if you were to to measure and convert it). So what happens if you don't sharpen something that is harder than the carbides (like diamond), you're not actually _sharpening_ the steel, but ripping/tear/fracturing the carbides out. Meaning that you can't get it as sharp as a steel that does not have those carbides/hardness.

I get excited when I hear the theme music. Love this channel!

Amazing video and likely my favourite so far. You've made what could be very complicated into something very simple. THANK YOU!

I learned this in university but you were by far WAAAAY easier to understand. I saw it too late to help with the course but I like this topic anyway so thanks for clearing it all up X3

Having the practical aspects of the design of the sword really helps to understand the metallurgy behind it. Thanks .

Hi Shad! This video is very well made I think, you just clearly explained a complex topic... going quite deep, in my opinion. Thanks, I'm very interested in steel, forging, blacksmithing, blades etc, and this kind of videos help me a lot to understand this complex world. Greetings from Italy!

Amazing video. You're right, Shad, swords really are awesome.

The process of normalizing is called thermo-cycling. This was the best explanation of iron/steel quenching and tempering I've ever seen.

Wooo Iliya! AWE me does weird weapons. Still great blacksmithing

so many hearted comments, XD! shad youre a madman! Also, you make quite useful videos. keep up the amazing work!

I love this. It has all the detail needed to understand what's going on without diving into the why and muddling the message.

YES! THANK YOU SO MUCH! I needed to watch this video. this fills in so many gaps of knowledge I had!

I highly appreciate you made this video, I am a blacksmith's apprentice from the Netherlands and I learned quite a bit from your video. it's good to see how much research you've actually done to make this video because most people I know don't even know what quenching and tempering is for. I've also met people who claimed that quenching in oil is much better than quenching in water due to oil not being as cold as water. Although, when I tested it (without tempering) it seemed like they both had the same result (using low carbon steel)

Very interesting video, just like the folding steel video...

This is the only side of chemistry I will ever find interesting

Quenching and tempering is sweet, but WHAT ABOUT DRAGONS?

Thanks Shad for finally bringing the RU-vid HEMA community a good video about heat treatment! Even with my nitpicking mind, I could only find two minors points to correct you on: first, and probably the most significant, is that Curie temperature, where a ferro-magnetic material rapidly lose its magnetic property, is not the same as the austenitizing temperature, and sometimes it can be quite off. A variation from 0% to 2.1% of the carbon content in the iron won't significantly change the Curie temperature of the material, and it will roughly stay around 770°C, while in the same time A3 and Am (complete austenitization temperature respectively for hypoeutectoid and hypereutectoid steels) will somewhat "yoyo" from 912°C, to 727°C, back to 1145°C (to which you can practically add a good 50°C, if not 100°, to be absolutely sure you pass austenitization). So the Curie temperature is only a mildly relevant practical indicator, and it's physically completely unrelated. The second minor point, but more minor, is the tempering temperature: there is no rule. It's true with carbon steels there is a temperature range you don't want to be into too long, because secondary carbides (i.e. cementite) tend to precipitate at joint boundaries and it makes the steel brittle (that's precisely why it's called "temper embrittlement"), and bellow blue is always a safe bet, but in historical times tempering methods might have varied. Especially during the napoleonic era, we know from a fact (a reference book left by the one who precisely supervised sabers production during that era, the General Gassendi) that French sabers were tempered at the verge of glowing, so over 600°C. This may sound somewhat surprising, but blades were not kept at that temperature (for a long time), just brought there and left to cool, which is somewhat similar to nowadays "flash temper", though certainly not as accurate as with modern methods. I don't exactly know why they opted for this method, but as the effect of tempering are also a function of time, not just temperature, maybe they could more reliably control that a whole blade would be starting to glow once, rather than make sure it would stay at 200-250°C for one hour. With a saber blade, you rather want to be too soft than too brittle, while it's not nearly as much of a trouble on a knife (because it's short) or axe (because it's compact). But I'm only speculating here, and this would be really nerdy fringe archeometallurgy to exactly study this question. Maybe your next video will be about the Iron-Carbon diagram and how it's to be read and interpreted? Just kidding! But you'll have to face the Behemoth one day...

a very good video just very little things 1. it is also quenching if you expose the iron to "room tempered" air the best method depends on steel and form 2. on 6:25 you probably mean toughness and not ductility and and at least i learned to always use the term "pure iron" or "technical pure iron" to avoid confusion with cast iron all in all great video with no real mistakes (one can always go deeper into the matter and nitpick about the heterogeneity of austenit microstructures but not in an introduction level video)

Absolutely THE BEST description I’ve ever seen. Thank you

Now, watching these smith vids on YT will make even more fun because I know what and why they are doing.

WOW!! Seeing the Katana bending whilst cooling blew my mind!

Your personality is a great asset in explaining this stuff, the way you say it makes it sound like something I wanna know about, on the cusp of comedy.

This is basically part of what I'm learning as part of my forensic science program at university. Nice video.

This is genuinely a really fascinating process, and I always feel like I can't get enough information on it. Imagine a material that behaved similarly to this, but in different conditions - Like the mechanism of change was light, or sound, or something of that ilk. Manaforged blade? This is great inspiration, even though I already felt I knew a lot about the process. Thanks for the video, Shad!

it's amazing how much i've learned about metal, quenching and atom like stuff today throughout this few hours being online

**sees man at arms in the thumbnail** immediately worth viewing

Love your channel, as a machinist/metallurgist, this is a great primer on steel. Nit picking: during the tempering stage the metal does not "glow" this is a color change to the polished surface similar to what you see on motorcycle chrome pipes, it indicates oxidation to the surface and leads to bluing which is ferrous oxide (but lets not go there) from ancient time the color changes that a surface goes through has been an indication of heat which you noted on your color band slide.I think you're selling Europe short on iron and steel development, consider the Halstatt sword, which though it is labeled as iron is actually low grade steel, also consider Swedish watered steel and Iberian Celt steel. Most stack up well against Wootz steel. In the case off Halstatt (600 BCE) the Goths and the Scandr were well ahead of the game..Be Well and my Best, KW

Additional note, you should be proud the professionals are lauding your work, the next time I teach I'm going to reference this video, well done and huzzah

This is a 4 year old video, but I think it's quite well worth the comment. My Grandad survived the Great Depression, and one story my Dad likes to tell is he'd make his pickaxes for mining coal out of springs from old junk cars. They last forever because of the kind of steel but also exactly what you're talking about! Very neat stuff to learn!

hey shad, drill bit maker here. at our company, who supplies tools for the likes of boeing and ford, we actually use a tungsten-carbide drill bits that are good at going through carbon steel.

Shad: Historian, author and scientist. What an intellectual.

Very interesting. I am a farrier and only work with mild steel to make horseshoes so quenching and tempering is something I never needed to learn. Forging blades is something I would love to learn about.

awesome video.You dropped the comedy Your video's have only gotten better out standing.

Great video, this semester I learned all about this, metals and termic treatments, one of my fav classes

I wanted to find out more information about tempering steel. Well put together information. I now know why drill bits and files can cut through steel, but can easily snap or be shattered.

So I make various blades, etc. both forged and stock removal, and read a lot of metallurgy. you did a pretty good job of laying this out. Bladesmith approved!

ha ha I love it, I was just thinking about this today! Thanks Shad! You're the best! And I love how you make this stuff fun and interesting

am a materials engineering student. was looking for some fun after studying heat treatment found this video. wow. having fun while reinforcing my knowledge u the best

When I was doing my undergrad for mechanical engineering, I learned all this in my intro materials science class, in fact I kept the textbook...somewhere in the basement. But putting this knowledge in context of sword making was refreshing and a lot of fun. Thanks Shad and Happy New Year!

Without a doubt, this is one of the best explanations I have ever seen. I hope you don't mind I shared it to my blacksmithing page. It's excellent!

I enjoyed watching this...it reminds me of pouring epoxy resin. You want it to be liquid enough to be able to push bubbles out and self level. But you also want it to dry quickly so no more bubbles form or any stuff gets in it while its wet. So you add a hardener to the resin to make this happen. The hardener is essentially tempering the resin...which would otherwise be soft and full of impurities.

Amazing video as always. Keep up the great work, Shad.

This is a great video for clearing up misconceptions and myths while being VERY informative and enjoyable (at least to people like me who are interested in metallurgy and chemistry). Good job Shad.

As a moulder I only touched on heat treatment but thank you for reminding me of a lot of what i learnt at tafe.

It's ok, Shad. We were taught about those phases and constituents that you were talking about (ferrite, austenite, cementite) for a whole semester in Univesrity. A bit of studerring is fine and your explanation is correct. So, great video!

You explained this so well! As a chemist I'm gonna use your video to show others!!

I thought quenching and tempering were the same thing too, I learned a lot from this video! I knew about the differential hardening of traditional katanas and always wondered "but if the cutting edge is brittle won't it still chip?" I never got how a softer back would prevent that, like many people inaccurately claimed. Though it's not as good as spring steel, I love the creativity the Japanese employed to try and find a balance of strength and resiliency, not to mention the beauty in the resulting blade.

Man, I am an engineer (technically NA) even I didn't study this much metallurgy. Great video Shad, very informative and well researched videos. Thanks!

there is so much misinformation/bad/half ass explanations for all of this on the internet. For someone with an educated point of wiew, who also had an interest in trying to learn this before i got any good explanations in school i had a lot of misconceptions because of other "informative videos". THIS video on the other hand is marvelously informative in a good explanatory way which will easily educate people. I have not seen anyone go into such depth with such ease, good damn work there!!! :) :)

Thank you for not only being very informative, but also entertaining as well. :)

This reminds me of one of my favorite quests in Kingdom Come: Deliverance. One blacksmith hires Henry to investigate a blacksmith from another town, he does this because he has heard that the other blacksmith is a sorcerer who is casting spells on his steel to make it indestructible and he wants to know what the spell is so he can recite it over his own material as well. When you investigate the other blacksmith one of the first things you likely notice when you come upon him is that he is always singing. As you ask him questions about how he makes his swords (Henry's father was a blacksmith, and so Henry is able to get him to open up about it to some extent) and why he is singing he tells you that one time after finishing the blade for a sword he got distracted and left it sitting right by the fire of the forge and when he finished that sword he realized that it was much tougher than his other blades. He had no idea why it happened, but he realized that when he partially heated up the blade again after quenching it became more flexible while retaining the hardness of steel. He then proceeds to tell your character that the song he sings is a way of timing how long he lets the steel re-heat by the fire before he removes it in order to get the most durable steel. He essentially learned how to properly temper steel without having any idea what was happening.

The chemistry behind iron and steel is very interesting. I have learnt a few things in my training.