Heat Treating Carbon Steel - Heat Treating101

G"day everyone,
In this video I will be attempting to do two things, make a spoo.. I mean knife, and attempt to explain the theory behind basic heat treatment of carbon steel. Heat treating is on the face a very straightforward subject (especially with carbon steel) but there is a lot more in the theory that is at least worth knowing.
In this first video of a three part series I will go over the basic theory behind the heat treating of plain carbon steel, which is the steel I heat treat the most often. I will go over the reasoning behind why I choose to either oil or watch quench my parts and the expected results that one would expect from doing so. I will also go over the expected results that one would expect from tempering the steel at various temperates - looking at the expected hardness and toughness.
And through all of that I will attempt to make a single bevel Japanese style chef knife, although the real focus of the video is the heat treating aspect. This is not a knife making channel and I doubt you will ever see me make a knife again.
I will be light on some of the details however, a lot of he heat treating characteristics of low carbon steel are glossed over, as well as describing pearlite (I tried to but I was not very good at visualizing and describing it when I tried to edit it in) and I skipped over the TTT diagram (the bane of my existence in my materials course). Don't worry, a lot of these details will be filled in in part 2, along with alloy steel. But at over 26 minutes, I think there is enough detail for basic home heat treatment.
I hope you enjoy the video.
#heattreatment
Timestamps
0:00 - Intro
1:10 - Carbon Steel
2:56 - Mild Steel, Work Hardening and Normalizing
7:57 - Knifeing
10:18 - Case Hardening and Annealing
16:41 - Water vs Oil Quenching
20:04 - Final Hardness and Tempering
20:28 - Knifinging

[@artisanmakes]

This is a part 1 of a 3 video series I am hoping to make, with the other videos coving alloy steel and non ferrous metals. Some information I have glossed over or left out in this video should be covered in the follow up videos. Cheers

[@unperrier5998]

Why is it written WOOD ONLY on your hand saw?

[@NightsReign]

​​@@unperrier5998 The Artisan Makes community has a running joke around his refusal to replace his manual hacksaw with an automated option, bandsaw or chop saw. So, in this video, we got the addition of a coping saw and pull saw to his hand saw collection. (Oh right, also a slitting saw.) 🙃 The WOOD ONLY warning was purely for our benefit.

[@Nobe_Oddy]

you REALLY CAN stop saying "Rockwell - C" .... just say "C" - there aren't any other hardness scales that use "C" aside from Rockwell, so everyone knows you are referring to the Rockwell scale... heck you don't even have to say "C" TBH ... if you start the video and mention hardness at "Rockwell C" at first, then just say "C" a couple of times, then you don't have to mention which scale you're using because you already stated it in the beginning of the video..... it just feels like you have said "Rockwell C" more times in this video than I have heard it previously throughout my entire life LOL :) But you don't have to change... it doesn't make a difference... I just noticed how many times you've said it in this video and ITS A LOT!!! lol :D

[@scottpageusmc]

That "you call that a knife" remark was just what I needed this morning. That's such a great movie!

[@LiviuGelea]

I only realized the reference when reading your comment :)

[@JoshuaDavidson]

That was a lot of effort for a double reference joke. Love it.

[@drstrangefart]

MAN you did a great job explaining heat treating. I've rarely heard it broken down that cleanly.

[@oscartattoo3910]

Man i really felt that "sigh" when the coping saw blade got loose. Must be hard coping with that... (Ba-dum-tsss)

[@JoshuaDavidson]

Nice

[@orangetruckman]

I’m a little back and forth with this joke 😬

[@oscartattoo3910]

@@orangetruckman You saw it, that's what matters.

[@cheztaylor8]

Yeah, but not something to fret over...

[@JoshuaDavidson]

Something you can sink your teeth into.

[@Bob_Adkins]

Excellent class on heat treating/carburizing! As a supervisor of 3 heat treating labs in a Fortune 500 machining facility, I can say with some authority that you were spot-on! Carburizing/case hardening takes a lot of time, so your case was probably thin enough to risk straightening the blade. But I get it, why risk it for a slightly warped blade? I make my knife handles the same way as you, I have never seen that method anywhere else.

[@cornebistouille]

0,15 mm = 150 microns ;) anyway you're forgiven : I love your vidéos so much :) they remind me when before becoming an enginer, I took machining courses, and I learn and did all the machining and treating you make... that ws fifty years ago, if only we have done all the cool stuff you make a this time :) :) keep going ! :)

[@tijnstarr]

I have been a mechanical engineer for over 10 years and I find that he imparts good knowledge every time, so that I learn something every time, despite the fact that I am professionally involved in mechanical engineering.

[@johnhege6502]

Enjoyed your talk. I've been bladesmithing for 20 years and I always like to hear another take on this subject. I've listened to many lectures on this subject and I've noticed that if you put ten smiths in the same lecture and then ask them what they took away from it, you'll get ten different answers.

[@joeofloath]

I make knives from scrap steel. I mostly play with old blunt files, which you can get in huge quantities for free if you know maker types, but I've also used scrap 40x1mm bandsaw blade and garden shears. It takes some experimentation (and some quality time with the belt grinder) but I do all my heat treating in a charcoal/coal fired rocket stove with forced air. I like making useful stuff from scrap, and my day to day pocket knife is one I made myself which is pretty cool to show off.

[@Kolokotrones]

Knifey spooney got me right in the childhood Hollow grinds on knives like that typically need larger radius wheels to work and to actually be noticable.

[@vx-iidu]

I think he could have used a face mill or fly cutter tilted very slightly as well

[@artisanmakes]

Probably but I don’t have a larger radius belt grinder so I make do with what I have on hand

[@Kolokotrones]

@@artisanmakes time for a new project and video series 😲

[@artisanmakes]

Maybe but I’m not that interested in knife making. I knew I’d do it at least once but that’s about it. So I don’t see a real need for changing up the belt grinder

[@NightsReign]

This video had me checking whether the channel was renamed *This Old Aussie* when I wasn't looking. I appreciate the WOOD ONLY warning on the pull saw, I assume specifically for our benefit. Kinda expected the other side to be labeled SUBSCRIBE, though.

[@RomainGineys]

I know that many people doubt that quenching does not alter "flexibility." For some clarification, the "flexibility" of a material is defined by its Young's modulus. This constant dictates the "deformation" (or more precisely, the relative elongation or strain) under a certain stress. The Young's modulus remains unchanged or varies negligibly after quenching. On the other hand, the elastic modulus (not the Young's modulus), that defines the maximum allowable stress before plastic deformation (or irreversible deformation) can be linked with “Hardness”. This modulus depends on the crystalline structure of the material and can therefore be altered. The structure can be mechanically deformed, such as through cold rolling or hammering (work hardening), or it can undergo a heat treatment such as quenching for steels, or the addition of certain atoms for other materials like aluminum or copper. If this elastic modulus becomes sufficiently high and exceeds the "maximum resistance" of the material, it will enter the brittle fracture domain; in other words, it will break before plastically deforming, giving the impression that the material's flexibility has been reduced. In practice, the metal will deform or "flex" less before braking, but according to its definition, the flexibility (or in another words, the strain under a certain stress) will remain constant.

[@TheDistur]

Interesting!

[@andromedajacobson2520]

Regarding hardening mild steel, look up 'super quench'. Blacksmiths use it to harden mild steel for tools. Mild steel quenched in super quench aren't knife hard, but they make good anvils, springs, and other hard objects. It makes mild steel a little harder than it normally is and it makes it more rigid. Look it up!

[@leslieaustin151]

Really enjoyed it, thanks. And plenty of baiting of bandsaw owners too! Nearly every saw in the box out there, and no problem with any of them… there was even a slitting saw! Thanks, will be looking for the other episodes on this topic then. Les in UK 🇬🇧

[@t0mn8r35]

This was very interesting.

[@cornebistouille]

to show the transformation of steel i remember we cut a treated piece transversally, and polish (up to 1200) the surface and then see it in microscope witha polarzed light. theer youcan see the martensite (little pins) cementiteite or even bainite (which i think you obtained with the process in which you are adding carbon and quinching it the temper..)

[@grandpasbarn2806]

Good video for basic DIY or home workshop heat treating. If you make additional vids on this topic, you might consider some tips on design for parts that'll be heat treated. For example, sharp corners are an area where stress risers and cracks can develop during the heat treating process, e.g, where your milled tang met the blade portion. Keep up the inspiring videos, I admire that you make many items that many would not even consider possible.

[@theangelshomestead4132]

Thank you very much for the vid!

[@mundaryus]

Good video. Thanks!

[@TheDistur]

Congrats on the knife!

[@rjung_ch]

Nice one, thank you. 👍💪✌

[@TheChillieboo]

Awesome!

[@MCsCreations]

Fantastic work, dude! Really well done! 😃 I live in Brazil around half a mile from the sea... And here everything rusts pretty easily... 😕 So I searched about hardening stainless steel and damn... That's really difficult! Anyway, stay safe there with your family! 🖖😊

[@robertwalker7457]

Very nice.

[@TalRohan]

interesting process with the case hardening, People look at me oddly when I handle knives the way you did, and I don't know why cause there's nothing wrong with it. I quite like seeing the tang on one side and not the other...easthetics really I suppose Great share thankyou

[@msmith2961]

24:50 So glad you marked that saw as 'wood only'. I'd hate to see you struggle trying to cut through cold rolled steel bar with it 😆

[@todd-fc9ft]

i love all your vidios but that intro has to be the best its one of my favorite clasic simpsons jokes and thank you for all the cool vidios

[@MyLittleWorkshop631]

As someone who forges knifes by hand, i hated seiing you just cut and grind out the shape haha but it looks nice !

[@neoasura]

Hey there's an easy way and hard way, enjoy doing things the hard way.

[@MyLittleWorkshop631]

@@neoasura wtf did i just read

[@Adler983]

Great! The more interesting cutting test is tomatoe, but you got a decent result obviousl! Nice work man, keep it up

[@lucasandri5462]

It turned out pretty good, I've made 3 knives up to date and my favourite one is a small one with 11cm blade. I've cheated a bit as i made the blade from a broken planer blade which is hss (18%Co) so it was a pain to grind but the cutting edge lasts for decades and it doesn't rust also.

[@bigmotter001]

Great explanation of hardening steel. That knife will probably outlast us all in productivity. Soon AI will be making them for us to use and we will be a little more dumbed down as a species! Thanks for posting and take care!

[@lukas187]

Bro really needs a Jigsaw 😅

[@crazynthree]

Man if he got a cheap jigsaw and tried to make it into a homemade tiny bandsaw that would be amazing.

[@MrThorBor]

Every time I see you use a hacksaw I hope that you one day feel the awesomeness of using a metal band saw.

[@dragonwing4ever]

small correction mate 1055 is definitely not a knifemaking steel be good for hammers or tooling but not a blade. that being said if you ever find yourself in wa come over and we can show you how to make a knife

[@artisanmakes]

Interesting. I remember watching an Alec Steele video where he uses a 1055 blank to make a knife. Granted it was more a hunting knife style, rather than a chefs knife

[@dragonwing4ever]

@@artisanmakes can't say I've seen that video, may work for hunting knives in a pinch but far from idea. that o1 you have would be good to use if you don't feel like buying specific steel to make a knife

[@archloy]

For wrapping, I saw a video about old technique (1700 or 1800) to help unwrapp hardened steel. It's a small "pickaxe" (more or less, visually it is ;)) which you hit gently the blade with, it deform a little bit and play with steel stress to make the job. If you're interested, I can search for it, but it will be in french I guess

[@rogervickery9376]

Hey, you should make yourself a proper 72 inch belt grinder and do a video! you won't believe how useful it is! Love the content, keep it up bud! Roger from Calgary.

[@artisanmakes]

I would but I don’t have the space in the workshop for it

[@browntown52]

Next episode idea, build a better (sturdier) stand for that sander.

[@clintchapman4319]

Using a heat treating oven will give you more consistent results, and that will give you your best chance of successfully hardening. Nothing against torch heating, but the oven is the best way to go if you can afford it.

[@artisanmakes]

Well yes but they do cost several thousands of dollars to buy compared to $200-$300 for a basic lpg furnace. That’s why everyone chooses a furnace

[@RectalRooter]

Our hearts goes out to the Australian people living under the Emu Yoke

[@jjcc8379]

Knife and spoony 🤣

[@UncleKennysPlace]

Called "case hardening" because only the outside skin ("case") of the part is affected. Thus the part can have a harder surface but not be as brittle as a through-hardened part.

[@beanieweenie9543]

Umm yeah that’s exactly what he said.

[@artian11]

@@beanieweenie9543 Like UncleKennysPlace I thought he was saying it was because it was in a case of carbon in a steel box, so now I had to go back and replay it, and yeah, he actually has it right as you heard it. Strange, our miss-hearing might be because of accent/inflexion/local phrasing.

[@TheCreat]

Very nice project and demonstration. Unrelated: As usual, your patience for using hackssaws and manual saws in general is still blowing my mind.

[@mlmmt]

That belt sander looks awfully familiar, I have one too, though in the old dark blue colors instead of that neon color... I hate that neon color so much..

[@jrk1666]

The thing with the japanese geometry is that if you use too coarse a stone you destroy the back geometry that is hard to make, only use a coarse stone on the Shinogi the inclined side

[@stevengunter3457]

@WillStelterbladesmith would be impressed you used mild steel to make a knife

[@sdspivey]

Why not use an emulsifier to get oil and water to mix? Would this give you a better cool rate vs. hardness than either water or oil alone?

[@artisanmakes]

I don’t know the rate of cooling that it would give you but there is a maximum harness that metals can achieve and we can get that with out water quench (for carbon steel)

[@LiviuGelea]

you need to protect your air intake not your eyes when cutting onions. That being said, this mith of protection glasses is useful so our chefs don't mouth-breathe over our food

[@heronguarezi6501]

That is 150 micron. 15 micron is 0.015mm. Just trying to help. Love your vids

[@artisanmakes]

Yeah I think I missed the decimal point on the shim :)

[@untamedhacker]

I'm not sure if we should be concerned that your woodsaw says "wood only" on it, do you have a different one for cutting flesh?

[@artisanmakes]

I used to have I’ve for cutting up large sheets of abs and acrylic. Tended to gum up the teeth so we kept them separate

[@HaveAGoAlan]

Only used my furnace for melting down metal to cast lathe parts. Could be interesting to try making a knife this way... (hammering for hours to do this does not appeal to me.)

[@blazunlimited]

Hello Alan! It’s good to see you are watching the right channels when not making your own content. I am watching your Gingery lathe build with great interest. I hope your channel really takes off soon.

[@honeycuttracing]

Try preheating your oil, seen lots of knife makers, heat up a large chuck of some scrap piece of metal and put it in oil to preheat oil🔥 so not such a thermal shock ⚡️

[@jesperwall839]

I’m wondering what your not supposed to cut with the handsaw marked wood only 🤔😀

[@artisanmakes]

Engineering Plastics

[@SergeiPetrov]

You should have heated the oil to 230 degrees Celsius and thrown the part into that hot oil for a couple of hours. The steel had to be carbon. You would end up with lower bainite. At a hardness of 50 hrc, the knife is more likely to bend than break.

[@clinthansen469]

That intro was a masterpiece...and the gag will be wasted on anyone under 25

[@fyghetr]

well if you want to check for sharpness use the tomato, or a newspaper or see if it can shave hair...

[@xelaxander]

Seems like a small band saw would really upgrade your shop.

[@mrcpu9999]

I think I'd of just glued it to something and milled it out, everytime I see the hacksaw or the coping saw come out, I cringe, because I know I'll never make whatever it is if it requires those tools. :)

[@noviceartisan]

As you didn't mention it, water = leidenfrost effect super duper easy... Oil = not so much, well used high carbon used motor oil = infinitely less than water.. So dumping it in water is not good :)

[@noviceartisan]

Play back your videos of water quenching, obseve the effect, then observe the effect in oil, you should instantly see the differences in teh effect

[@artisanmakes]

I talk about in the water quench section I just don’t call it by name. I don’t really remember it off the top of my head. That’s why I use a salt brine quench some of the times or just move the part In the water. That’s fine enough for parts that aren’t hugely complex. Cheers

[@noviceartisan]

@@artisanmakes Yeah, I played it back again and noticed you do talk about it. It's why oils with high boiling temps are used, salt water increases it a bit but not by much. Used motor oil has so much shit in it that the temps really quite high to boil it fully, usually *much closer to the red temp of quenching. I guess peanut oil mixed with graphite powder would function better, but not played with this side of stuff myself as of yet, just research. Going by what you mentioned about cold rolled mild steel early in the video, I'm temped to whack my stock of it in the kiln for 10 hours (i have a lot and a big kiln) at 600C then let it cool down controlled over 12 hours so all the stresses get relieved, should mean less distortion when i'm cutting my small parts that I need precise.

[@JohnChuprun]

You said 15 micron shim, but don't you mean 150 micron? I'm still in the imperial system so what do I know.

[@Fetch049]

Yes, but can it julienne fries?

[@blazunlimited]

Did I just flash back to a Ronco commercial?

[@ErikBongers]

I think you meant 0.10mm and .15mm, not 10 and 15 micron. 100 and 150 micron.

[@artisanmakes]

Bugger yes of course. Can’t even read these days.

[@joepjongen3784]

First

[@Nobe_Oddy]

I always prefer the TOMATO cutting test as the TRUE TEST of a knife's cutting ability... it's NOT JUST ABOUT SHARPNESS.... the tomato cut also test how smooth the steel is.... if it's not very smooth it will cut into the tomato but catch and crush it a bit - depending oh just how smooth you've made it...... everyone worries JUST about sharpness, and that is about 80% of it... but you also need to worry about the shape too.... if it's not very smooth and the shape of the sharpen part is too acute, it wont push the cut part tomato away and crush it even further.... MIND YOU, this is all JUST MY OPINION and I could be completely wrong about the smoothness and shape of the blade... and it could have been a dull knife that I THOUGHT was sharp... but I really don't think this is the case.... this is why there are about 25 different types of knives in Japan JUST FOR CUTTING UP TUNA!!! lol (and every other type of thing to cut) I really don't know if the number is 25, but there are quite a few different knives just for the different parts of the fish... they really ARE the masters of craftmanship IMO

[@shanent5793]

The metric system strikes again!

[@whittysworkshop982]

That feeler is 150 microns lad, easy mistake to make tho 😁

[@clintchapman4319]

Why don't these guys ever use quench oil instead of all these other oils?

[@artisanmakes]

Like I said in the video, if you are oil quenching carbon steel in a home workshop the difference in results between a vegetable oil and a quench oil are not going to be very apparent. Not worth the extra price you pay for them

[@iamnoone.]

Oh man. Where's the Tylenol

[@WoodfulProjects]

Great educative video, as usual. One question though. Does the carbon % decrease every time you quench the metal for hardening? Had some tools that had their hardening ruined (blued) and trying to harden them back. They are nowhere near their previous hardness and I’m wondering if it is because the carbon rate has decreased. Thanks

[@artisanmakes]

decarburization is a thing that can happen but not through quenching. It can happen if the part is left in the furnace too long, its effectively the opposite of the carburization/case hardening process I showed. I obviously cannot know for certain but if you are having issues rehardening tools, it wouldn't surprise me if they are made of an alloy/tool steel. For a lot of the alloy steels you need to heat them up to specific temperatures and soak them for specified periods of time before quenching to effectively reset the internal microstructure. Unlike carbon steel the soak times and temperatures can be very important and less forgiving and if you don't correctly do it it can result in a reduced hardness. That would be my best guess

[@WoodfulProjects]

@@artisanmakes thanks for the additional infos. Might be due to the fact that I’ve left the pieces a bit too long in the forge. Cheers and keep up the excellent work

[@grandpasbarn2806]

@@artisanmakes Excellent point! The internet (not just KZbin) is a great source of information for heat treating specific materials. That information is key for proper and successful treating of materials such as O1, W1, A2, D2, S7 and so on.