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pro tip, when dropping hardened steel to make chips fly off, safety glasses worn over your eyes instead of on top of your head will protect your eyes from small metal fragments, atleast the top of your head is safe!
I can see your point for the oil jar since oil have high boiling point. but generally, unless the hot knife touches the jar, the jar is insulated from the temperature extremes by the liquid medium. anything above the liquid's boiling point simply vaporize before heating up the jar itself.
@@nilebrixton8436 And when it comes to the nitrogen jar. It never experienced any other extremes of temperatures other than extreme cold. As you can see, even during the quencing process, the jar is covered in frost.
The 'file drawer problem' is an actual problem when doing scientific tests and studies. When testing a hypothesis, if the results do not support the tester's hypothesis, or does not show a major spread of results (usually an extreme of some sort) then the data goes no further than the tester's 'file drawer', which leads to publication bias. When you get results that are mundane or normal, that's boring and doesn't feel like it's worth publishing. You'd only want to publish something exciting, like getting results that are out of the ordinary. Basically, it's good to show your results and data even if the results are mundane, unimpressive or ordinary.
Besides the fact that if you dont fully submerge the entire blade at once the structural pattern of the blade will be different at different parts and will be extremely weak where the pattern changes. Its like day 1 of forging knives. If you cant fully quench your knife is screwed up and he screwed up every single one so this whole video is just a waste of time and stupid for misleading people when all data is worthless because he doesnt know how to properly quench a knife.
@@gooblaka not when your data is screwed because you cant properly quench a single knife. This is all worthless unless you think half quenching then quenching the rest 10 seconds later is the data you wanted but news flash itll probably break at the point where the quench es didnt match up. Thats not data thats fucking common sense so stop trying to glorify this failure of a video that never should have been posted by saying its all data. Yeah it is data. Data that everyone has known since the 1800s
Fun test. As a knife maker the biggest problem with rapid cooling (water, nitrogen) is stress cracks. A lot of times these won’t show until you sand the blade or during the tempering. Great video.
True it’s hard to rapidly cool evenly. The faster it cools the smaller the crystal formations you’ll get. Maybe if the blade were thinner and the liquid nitrogen spread evenly and immediately for a quench it might work.
I saw a friend of mine water quench a knife and it cracked so badly he was able to snap the knife in his hands. Took a bit of effort but less than I was expecting and it certainly would've stood up to even it's first use.
Part of being a scientist is both accepting your hypothesis being wrong as a good thing as you have learned from it. And considering on why your hypothesis is wrong and how that can lead to future tests or applications. Props for keeping these in your video :)
As a knifemaker who forges I can tell you that part of my process is to "normalize" my blades prior to heat treatment to minimize any unequal stresses imposed by the forging process. There are several ways to normalize but the key is get the blade up to critical temperature (the point at which it becomes non-magnetic for most non-stainless alloys) and then SLOWLY allow it to cool. One of the best ways I found to do this is to set the kiln to the appropriate critical temperature, allow it to reach that temp and soak for a while, and then just turn the kiln off and allow it to cool overnight. You can also do this in your forge, and although I certainly have less control over how quickly it cools, that seems to work just fine. You can also bring it up to heat in your kiln or forge and then stick the blade in a bucket full of vermiculite or lime ash which will allow it to cool more slowly. The key here is to have plenty of vermiculite or lime ash surrounding each blade. And for the record, I definitely HAVE had a knife shatter when I dropped it after quenching. I'm always really careful with just-quenched knives until I've had a chance to temper them.
annealing is allowing the steel to cool as slow as it gets, normalizing is usaully air cooling the blade or leaving it in the kiln overnight like you said
@@billhochella2555 maybe if it was being presented as advice and not the classic Grant-era TKOR "lmao what if we did _____" format. just cuz you're pissy and missed the point doesn't mean everyone else will be
It seems he was very disappointed that the nitrogen worked well. In fact there was no discussion what so ever. Hell they only quenched with water for a few thousand years. Its hard to believe that knife didn't explode and kill the whole planet, just shatter it completely.
@@negadoge he's right. I'm a material engineer and this video had a lot of things wrong, from the process control to the measurements, to the vague explanation of the phd dude. it was a train wreck, but for popular purposes it's fine :) people outside the field won't notice them, and it's fun
Thank GOD I found this channel! Loved your format on TKOR, and how you carried Grant's legacy there. That channel is just not the same. Their loss. Love your content, bro!
I remember a few years back when i worked at the mine as a welder, I was welding a ball hitch socket onto a trailer that way it could be pulled by the trucks on the site. After I was done, the guy that requested the job came buy to get it and it was still the process of air cooling. He asked how much longer it would take. I told him give it about 30 minutes and it should be good to go. He wasn't happy about that and walked over to the cooler, pulled out a bag of ice and set it on the welding site. He just looked at me and smirked like he had a big brain moment. I just shook my head, told him I'll see him in a little bit, and walked away... He came back about an hour later. Can anyone guess why? XD
@Daddy 1. You’re. If you are going to talk trash, at least have proper grammar. 2. I am neither a furry nor a fem boy. My avatar is not covered in fur, which is a requirement to be a furry. Don’t use terms you don’t know the meaning of. 3. Even if I was either of those thing, there are no rules saying you can’t be a furry or a femboy and working in the mine. A furry is a fetish that isn’t something that should be talked about in a workplace environment. And a femboy is just a personality type and not something that will bar you from seeking a place of employment. 4. Get over yourself.
As a blacksmith, most of the time when I've done a quench I've used water. Mainly because I haven't cared to get steel that uses an oil quench. However I want to point out that there are also projects that would require you to do a super quench to get it done properly. A super quench is salt water with soap added as well, and gets an even harder piece. Might make for an interesting follow up. There are a bunch of knife makers on you tube and they can teach you a lot about what we know of quenching.
when he mentioned that he was showing why you use oil over water to quench i was like "what do you mean??" people have been quenching blades with water for atleast 3000 years rather successfully. i know this because homers odyssey makes a mention of it. japanese sword makers also used water, and we know how good those are. speaking of, if you have never read how the japanese quenched their swords, do so, its ingenious as fk.
@Niki P it largely has to do with how quickly the heat leaves the metal. All solids have a crystalline structure, graphite, rubies, butter... metal is no exception. Temperature has a great effect on the crystalline structure of steel, not so much pure iron because carbon atoms are different sizes from iron ones they have difficulty fitting together nicely. This is actually where steel gets its strength mostly. Anyway as the steel cools the atoms try to align in the crystalline structure... all at once. However there's no higher command coordinating all of it so the atoms crystallizing in one area usually aren't aligned the same way as another. These Crystals grow until they run into their neighbors that aren't aligned exactly the same way, which is nearly impossible in 3 dimensional space. These form the grains in the steel metallurgists talk about. The slower the cooling the bigger the grains the softer the steel. The faster the cooling the smaller the grains, the harder and more brittle the steel. Most knife steels have carbon content that are at ideal hardness that balances edge retention and durability with an oil quench. I mean you don't want a knife that's chipping with every cut.
@@LanggerDangger Thanks Jaryn. So, if I've understood properly, what you want is a quenching agent that gives the right balance of hardness without making the metal too brittle and, on top of that you want a metal that retains its sharpness? I imagine that all those things factor into the cost and is why good knives are SO much dearer. Learned not to bother with cheap knives years back and was lucky to buy a reasonably good set at a garage sale from someone moving overseas. 10 years on they're still great and l think l've only had to sharpen them properly 2 or 3 times. One of those times was cos l chipped my favourite knife on the bone in a leg of lamb. It annoyed me so much that, l had to buy a whetstone and grind it down.
Hey Nate, you have to do a part 2 of this video. You've found the outside hardness, but there's an important step 2; Grain structure. The internal of the blade is what's most important during a quench, it'd be interesting to see the grain structure of the variations. I know it's simply snapping blades in half, but it goes a long way in teaching knife making/black smithing and why certain mediums are used to quench.
There is a crappy cardboard bailer at my work. I swear there will be some kind of metal snap eventually. The bailer is barely ok if the eject door is not over tightened. But it doesn't matter how many times we teach people, they are going to over tighten it and when I un-wheel-cog the door it pops so loud that I am covering my ears best I can. and yup the spiral cogger is bent slightly. I swear something is going to snap apart. More issues with this bailer, there was some kind of steel cable running looped through and it was getting pinched every time the upper smasher was lifted. more issues, it is just about impossible to fully fill the bail because they only welded one set of 4 hooks on the door that are not even big enough, so cardboard comes spilling out at 50%-75% of a full bail... so I am wasting my time at the end of the day by making 50% bails because the next crews don't know how, and females are no longer allowed to make a bail (for well reasons and events that repeatedly happened)... more issues with the machine, I have to walk about 30 feet away and still cover my ears waiting for the ejector to reset because the bang hurts my ears, I learned to not sweep the scraps to somewhat silence the bang but it still can hurt my ears 30 feet away.
True! This is why I would doubt the line about that quenching was the most important part in a heat treatment. It is strictly necessary. But the grain structure is usually ruined during the heating cycle, too long, too high, not long enough, not high enough, and these values change from alloy to alloy and even from batch to batch of the same alloy.
I worked in an industrial gear shop, and they always oil quenched the gears after machining. I always enjoyed watching the quenching process because of the flames they kicked up while being dipped into the oil.
The reason the water one may have broken off at the spot where it wasn't quenched was because when you hardened the blade, the hardened section grain boundary was pulling the softer section. The drop allowed the difference in the microstructure to come apart.
Couple of comments: Oil quench tanks normally have a lot of circulation to help with the heat transfer. The first quench in that steel tube was horrible and didn't get anywhere near its potential hardness. Second, you should always do a light surface grind or at least clean up the part with emery paper before hardness testing. You'll always get a bit of surface decarburization that will affect your test results. (even with a neutral atmosphere furnace) The nitrogen quench didn't work the way you expected because all it did was vaporize the nitrogen near the hot steel so in effect all you got was a frigid air quench with splashes of LN2. If you put it into a very fast stream of LN2 so that it could carry away the heat before it vaporized you might get the cooling you expect, but I doubt if the knife would survive intact.
I was thinking the same thing. Simple, basic but NOT the maximum quench in any of the fluids. Boiling the quenching fluid is BAD. Gases are inefficient compared to a liquid at removing heat. Sandwiching between metal plates, with each plate cooled by LN2 (or an even more effective refrigerant) could produce a quicker quench. However, the temperature shock resistance of the steel is likely MORE important than the quenching speed.
@@haroldhenderson2824 Actively cooled plates wouldn't produce a fast enough quench for an oil or water hardening steel, simply because the heat conduction through the plates is still less than the heat conduction submerged in a liquid. You actually would get a better heat transfer if you just used bigger plates for more mass (and/or switch to copper). They would be superb options for air hardening stainless steels that benefit from cryo treatments though, as you wouldn't have to split the quenching process into two separate events. Might even be able to pick up an extra point in hardness over convention cryo treatments if you could go straight into cryo during the plate quench. Whether the plates could handle the extreme temperature gradient or not is an unknown that I wish I could experiment with. I do agree that the quenching tests here were subpar in all regards, as well as the hardness testing protocol, but the heat treating and hardness testing process can accommodate a lot of variability along the way. I certainly wouldn't quench or test any of my knives in this manner, but that doesn't mean it won't harden the steel or give grossly erroneous readings either. It's good enough for a demonstration, just not good enough for a study or analysis.
Aye, true. Should keep the LN2 moving to have it work. Idk about the oil. Circulating that oil will increase the cooling, that is accelerate the heat pulled away from the knife, but if you're using oil, I'm not sure if that's desirable considering you want to cool slower, probably, if you're using oil.
@@eleithias You still want oil circulation to give you uniformity in cooling. Still oil will boil away from areas of the part with more mass to hold the heat just like his LN2, but to a lesser degree. While O1 steel wasn't common for customers to use when I worked in heat treating, we did see it once in a while. It's somewhat more crack prone than other machine steels so we'd quench in a tank that was heated to 180 degrees F and had a more gentle agitation than our larger tanks. One thing that wasn't mentioned in this video is polymer quenching. It's somewhere between oil and water for cooling rate and it's often used on parts with a larger cross section where oil doesn't cool fast enough but water is too prone to causing cracks. With almost all types of quench, you want to stop cooling it when it's in the 130-150 F temperature range. Also, the quench is never the end of the process. All parts are tempered after quenching to take some of the stress out of them and fine tune the final hardness. This can range from 300 degrees on case hardened parts that you want to keep at 60-64 RC to 800-900 degrees on machine steels that you want to be more malable. (like a set of forks on a forklift)
Been watching these types of videos a lot more now that they have a channel of their own, felt odd posting for someone else. Respect for all the time and effort you have put into everything.
amazing subject. I took on automotive chores welding in 2006. I keep my own unwritten book in my head about quenching. you don't know what you made, until a whole year has gone to meet the day you made it.
One thing that you didn't talk about was the microfractures you tend to get when quenching is a medium that is too harsh for that steel. That is really one of the biggest reasons you need to stay with the correct quenchant.
Well, the doctor did right at the end of the video. "If you cool slower, that leads to less chance of warping or distortion or size changes or cracking and so that's beneficial." Still, yeah, probably should have talked about that more in the video as it's a really important factor when dealing with steel.
@@LordSaliss yup, I quench knives in water because I was making knives with hamons and I don't like the look of oil hamons. A good way to remove warps is to put the knife immediately after quenching it into a straightener I used three c vices with two straight bar stocks to hold the knife straight and then temper it.
To expand on what Justin said here, when you snap a blade in half to check grain structure, you should notice a drastic difference in the texture of the cross-section. Something like a difference between coarse beach and and fine art or play sand. Sometimes even more fine like corn starch or baking powder. If you can see where the texture changes between inside and outside of the steel, that's an excellent indication that the quenching medium was not suited for that specific steel.
Why wouldn’t you get a container capable of submerging the entire knife? It would obviously cool faster if the entire knife is submerged. There are so many scientific channels on RU-vid. Why anyone would sit through this is baffling.
Actually you don’t typically even *want* the spine or the tang hardened, you want them quite resilient to hand stress and strain. Only the edge carrying elements need to be hardened.
Well done sir. I was about to start my day when I saw this video thumbnail and I clicked on it. then the video was interesting enough that I stayed through the entire thing even though I have a lot of stuff I want to get done and I am super excited for it. It’s kind of cool seeing somebody running an experiment using the stuff he has access to. This is how I learn stuff. not necessarily the most controlled environment but interesting results. I might look into the subject more later. makes me wonder if there are certain types of metals that need to be quenched with some thing super cold.
Timing is a huge factor. You'd have to test the surface and the core for hardness. It would be interesting to see a thermocouple embedded on the surface and another in the core to see how fast both the media and style of quenching does what it does.
Thanks for noting that as well. I picked up on that immediately between the oil cooled one and the water & nitro ones which were similar. The oil quenched one definitely had a higher (tighter) pitch. I was wondering if that relates to hardness domehow, as I know the faster it is cooled the more chance of stress cracks. I wonder if the oil one has a more thorough/durable "strength" than the others. I wish he could address that.
Now this is what An Experiment with Nate is all about. Brings me back to the Nate and Grant Duo days. I don’t comment on here much but you have come so far over the years my friend. Thank you for keeping this style of content alive. Cheers🎉
It's good to note that you also don't want blades too hardened, *Especially* if they are longer, thinner, or experience a lot of sudden kinetic trauma, notably because the give in the metal allows it to not crack, fracture, or snap under the load that you put it under, but at the same time it's important to make it hard enough so it isn't super pliable and deforming or blunting the blade with every cut.
You don't want retained austenite, not much anyways.. just temper or soak at a lower temp for less dissolved carbon for lower hardness. You probably don't want to not fully through harden your steel - Imagine how soft the center is if the surface isn't even fully hard.
Nate, I can’t help but feel that Grant would be very proud of this video! Keep up the great work brother! Really been enjoying your solo content and can’t wait to see how your channel grows!
@@soggyman3852 dude was one of the best people I ever watched on YT. I feel like the more Nate goes the more of that energy he brings that made me watch Grant. Totally here for it
@@joshbenoit2859 That makes no sense at all, plants and steel have nothing in common. That's why I use Apple juice to harden the metal since it's rich in Iron.
@@joshbenoit2859 brine solutions are popular for quenching since they are a bit less prone to forming vapor jackets, so Gatorade might genuinely be a good quenching medium.
I have a tool I made eons ago for the International Space Station that was made from Inconel 718. We used a cryo quench to help with ductility at low temps. It was basically a space version of a Stanley wonderbar.
I love how there was no build-up, no great speech or hook, he just dropped it right into the liquid nitrogen and my jaw dropped all the same. Subscribed.
A little bit of extra info. There are some steels that can aquire a specific structure if cooled down at the right speed/temprature. One thing that can be done is to cool it down inside another metal of lower melting point (such as aluminum) it is actually quite interesting how the temperature achieved, the cooling speed and the carbon (and other material contents) can highly change the outcome and give varied properties to the steel
@@insanitywolf5049Don’t worry He is averaging more views then TKOR now 😂 They really didn’t think about how removing the last piece of grants legacy would affect the channel
@@EternallyFrost 12M subs, 100k average views, this means channel is dead. 200k subs, and uhh... about the same average I guess, this one is doing very well.
I almost had to look away when he thrust the knife into the liquid nitrogen. He had gloves and glasses.. I feel like some kind of coat would have been appropriate.
@@jefflittle8913 I don't know much about his channel. But... This being my first video to experience watching it's dubious. Why the fuck was he slapping his durometer and openly stating the shit hadn't been calibrated. Weirdo
Correction, knives are quenched primarily in oil. Some steels can be quenched in water and this is the preferred method for traditional sword smiths in Japan. The water quench is part of what adds the curve.
Hey Nate. Glad your continuing the videos.. the reasons I loved the other RU-vid channel was because the guy was making stuff I always wanted to make and experiment with. And he done it at home. Which was even better. Making your own gun powder and liquid nitrogen was just amazing. Learning the stuff no one else can or will teach you was the greatest part of that show. It was the learning part. Learning the stuff I always wanted to know.. making the stuff I always wanted to make.. good job and good luck. I’m excited to see what curiosities you have.
I think the reason the water quenched knife broke is because there was a bunch of tension in that area. Hot expands, cold contracts. So that part was feeling the expansion from the heat and contraction from the cold all the way until it finally hit the same temperature as the rest. It's the same reason the layers of an ABS 3D print are weaker if you don't have an enclosure. Hot near the bed (and hot near the hot-end), cold everywhere else, you even get layers that snap apart mid print because the force is so strong.
Metallurgical engineer here, The reason that quenched steel breaks "easily" is because the internal crystalline structure is under high stress. The chemical composition can make different compounds, pearlite, cementite, martensite, austenite, ledeburite, etc. In general instances such as carbon steel, we are mainly talking about 2 transformations, during the heating process pearlite and cementite turn to austenite and ledeburite + cementite, and during the quenching austenite and ledeburite + cementite turn into martensite and retained austenite with some pearlite leftovers. Here the martensite is the important part, because is a very hard yet brittle phase (harder = more brittle) that isn't in equilibrium that forms only during rapid cooldown in very fine "needles", that means it will easily change yet again during tempering into very fine cementite crystals (but I digress). Martensite is the second hardest compound of carbon and iron, second only to Cementite. but finer crystals help distribute the energy more uniformly.
@@apollyon4578 It is interesting tho that it broke at where the quickly and slowly quenched areas met. I wonder if that's coincidence, stress or something to do with the grain structure.
@@HavocHounds1988 Indeed, the change from "out of equilibrium" martensite to stable finer cementite is done during tempering, but that is an even more complex phenomenon due to different factors like temperature, time, chemistry, and desired hardness. too long and the finer grains will very slightly fuse and act as almost one (this is also a process used extensively) too hot and you will return the steel back to its soft form.
@@Kenionatus That's a great question, all hardening and particularly differential hardening is very vulnerable to microfractures and chipping. these microfractures and chips create what are known as stress concentration zones. The smaller the volume, less thermal mass, thus faster cooling and higher chance of fractures in the case of the tip and in the case of the handle or grip, the difference in cooling speeds between sections make these vulnerabilities very likely. Also, O1 steel is a steel designed to be quenched in oil, not too fast, not too slow, quenching it in water is waaay too fast for it. There are different "codes" for different quenching mediums, like O1 is designed for Oil, W1 high speed tool steel is for Water and A2 steel is (you guessed it) Air Blast. Liquid nitrogen isn't as aggressive as a coolant because it forms a gas layer between the hot surface and itself, this effect is known as the Leidenfrost effect and because of that, it can be even less effective at cooling than the recommended quenching medium.
Some steel grades (for example H11 tool steel) can aquire so high internal stresses from water quenching that it can crack just from that. It actually happened to me once, i needed samples, i made then and then i left the lab for the weekend and when i got back, the block of steel i quench was in 4 pieces. Science behind steel is really beautifull and i think its a shame that other materials are much more popular in media. I will gladly spread knowledge if it means someone will get intrested and maybe even chose career in material science. AMA
Would have been fun to put the samples in a toughness tester to see the impact of quench speed on toughness rather than dropping on the floor. It was one of my favorite labs in materials science.
Always enjoyed your videos, Nate. Finding out your were a fellow knifemaker and you make videos about it was great. Getting Larrin on in one of your videos is quite the achievement. His book and website are excellent, plus he's made some very accessible and entertaining videos. I look forward to more from both of you.
This was very interesting, but it’s very important to mention that with a high grade steel the heat treat process does a LOT of things at the molecular level beyond just make the steel hard. Grain size, austenitization, distribution of carbon, various kinds of molecular alloying (depending on the steel), all kinds of things that neither a hardness test nor a drop test will show. The recommeded quench temp and medium isn't just pedantry, it optimizes a whole host of microscopic functions that give modern blade steels their extraordinary performance.
I think this is more of a editing issue than experiment issue (and I understand this may be a personal thing), but around the 6 min mark when he did the hardness testing, after he stating that he's doing a couple spots on the oil blade and then not doing so on the others, it took me a bit to realize what he did. At first, I thought why he just skipped the nitro blade, I think it was easy for me to mix that up because from that angle, I couldn't tell which blade he was using and there was no indication that he switched blades, it was just a edit cut.
Hearing the different sound frequency between the drop tests was informative. Are you aware of the ability for people to detect large temperature differences in liquids by their poured sound? The Food Theory channel did an interesting video on this. I would be curious to see & hear of any variation of this when experimenting with the sounds of metal using different cooling methods and environments. Metal glass is quite difficult to make because of how quickly it must be cooled, but I'd love to hear it :)
Metal does form different crystal structures inside when heat treated. That's what makes it harder or softer and tougher. So it's a good question! Do the different formations change the tone at all?
I would bet money that you'd be able to more accurately guess the hardness based on a set of 'standard' sounds. Get a bunch of known hardness coupons, and then 'drop' them in some standard way. Isolate the waveform via the microphone (contact or audio) and then plot the frequency/amplitude vs hardness. (Not a math major, just making guesses)
@@spokehedz Yes! This would be fascinating. You could potentially calibrate a microphone that accurately measures the structure and hardness of different metals (or even non-metals?). Maybe instead of dropping the material an impacting device could create a consistent sound.
Same in Electrical Engineering. I have worked with enough power supplies to know when the units have something wrong just from their sound. Since the hum gets higher or lower depending on current and voltage.
Hey Nate, it was definitely an interesting video, thanks for posting it. With liquid nitrogen; I'm guessing the knife was cooled in nitrogen gas rather than the liquid itself. The vaper barrier on something with extreme thermal difference has to last pretty long. I would think the fastest way to cool the metal, would be to quench it in moving salty ice water. This way the water can be well below freezing temperatures and stay liquid. I think -30°F mercury quench would be even more effective, but might render the blade useless because of mercury contamination. Mercury will still be liquid at -30°F and doesn't boil until 670°F. Not sure what safety measures would be needed to do such an extreme experiment.
The idea of boiling mercury seems fucking scary and fascinating lol. I kind of want to see if anyone has attempted using it as a quenching medium before
@@chefmarcos Mercury is toxic by itself. Wanna put it on the blade you're using to cook for your whole family? Unless you want to put an end to your annoying in-laws' days, that's a no-no.
@@chefmarcos Metalic atoms are pretty big and thus even in high temperature the diffusion into steel will be realy slow, in practice i would be suprised if you had more than couple nanometers of some mercury mixed with oxides on the surface, that would easily peel off. Quick google showed that attemps like that were made and there was basically no contamination seen, but the articles are from the 70'. High toxicity of mercury (and mercury vapor especialy) made people ban mercury thermometers so im pretty sure nobody would allow people to use it as quenching medium. But there are liquid metal baths used in industry, some heat treatment processes require keeping the material in temperatures like 400C (750f) for couple hours to achieve desired result. Liquid tin can be used for that because it makes it possible to reach this temperature by colling it fast enoug. It is not popular method, really expensive and used only for special parts. The contamination is negligable and after finishing grinding and polishing you have pretty much untoched material with no tin impurities.
Nice, the hardness of steel depends on the chimical composition not only on how you coolit down, you can see the FeC diagram and also the heat treatments diagram
Yes. Stainless steel being very low carbon might have had something to do with the results of the first batch, haven't looked into it for a while but i think austenite phase exists in stainless up to rather low temps
@@your-mom-irl Far removed from that myself as well, but I remember some alloys help getting a quench even with low carbon, but you're typically gonna hit more like 35-45 HRC than 50+. As I remember most quenching steels have between .25 and .45% carbon; at .50% you start to be on the brittle side, and more than that and you've got unquencheable iron up to 2.5%. O1, 1045 and 4140 were typical 20 years back as general purpose quenching steels, but I don't know what's common nowadays. There was some quenched stainless we were also using, but I can't recall its name, and it was around the low 40s HRC for thin sheets. Man do I sound like a boomer. XD
I am really surprised that there was no mention of the "sound" differences in each knife. The oil hardened one had a very distinctive higher pitch when dropped both flat and on the point, from the ones cooled in water & nitrogen. I wonder if THAT relates to hardness as well.
@@ludikonj8927 More precisely, lasting vibration means elasticity, not flexibility. It has to "flex" and then return to its prior shape - that is one "vibration".
What's interesting from what I've gleend from my own research of quenching and tempering is the grain structure of the steel and the formation of carbides in knife steels after buying a knife that said cryo on it.
A uniform grid of molecules produces the maximum strength of a material. I’ve seen good results of metal chilled in liquid nitrogen to the coldest temp then slowly allowed to warm at room temperature. This compresses the molecules be closer together then, when allowed to slowly warm, the molecules spread in a more uniform, even pattern. The handle broke in the drop test because it was cooled at a different rate. The molecule pattern was different which produced a weakness.
I had a friend (he passed away) named Daniel Watson that quenched in liquid nitrogen. The temper process was a little different. You bring your temp up for tempering slowly. It makes for the best blades starting with the right steel.
(5:05) Check out how much the liquid Nitrogen level goes down during that quench; how much evaporated off over the process of adding so much heat to it
Nate! There is actually a legitimate quenching method that uses liquid nitrogen and water, it's called Martfrost and was developed by a knife making company Mikov in 90's.
Awesome video! A topic near to my heart. Even having quenched many a piece o'steel muh-damn self, I learned several bits of new (to me) information, at least one of which I'll fo..sho be utilizing, probably on my very next, upcoming quench..
Best part of the video is the visualisation of the Leidenfrost-effect during the first nitrogen quenching. You can see that metal cools down slowlier despite the extreme cold nitrogen, because of this effect. The effect in short is that the difference in temperature is so high that the liquid immediately boils. Thus there constantly is a layer of nitrogen gas between the metal and the liquid nitrogen which acts as an thermal insulator, slowing down the cooling process. A really cool video, thanks!
I think the best way is to use oil, just because of the higher boiling point, to prevent the Leidenfrost effect. And if you noticed, at the beginning he uses a narrow metal column filled with oil, apparently in order for it to transfer heat from the oil to the atmosphere. And here something else is interesting: what if this oil column is placed in a container with liquid nitrogen for lower temperatures?
Generally, when you're dropping pieces of steel expecting chips to come flying off, it's a good idea to take the safety glasses that are on your head and put them over your eyeholes.
When i made a knife at school for a metal working project we used hot water. And then the knives spent 8-12 h in a oven at temperatures starting from like 4-500'c to 200'c, and then cooling down slowly to room temp. That way you get a hard enough blade, but it'll be easier to keep sharp and not be so brittle. Also theres a technique for quenching, if you want a straight blade you have to inject the blade VERY straight, just shoving it in at any angle at all will make the blade bend unpredictably due to cooling faster on one side.
The thing about quenching is that the more rapid the temperature change, the harder the metal gets. Water makes for a harsher quench, but it has lots of issues with oxidation, and sometimes you really just don’t want to harden the blade that much because every steel has a point where it’s too brittle to be useful, and if you harden it anymore past that point, you’re just gonna have to heat treat it back to the point of usability anyway.
@@billybifocals Great job! You’ve just ✨generalised✨ There’s no need to assume someone’s wrong. If you think they’re spreading misinformation, you could always disprove it
That's why tempering is every single bit as important as quenching. I was taught to do a figure 8 in the quenching medium so you're not just heating your medium immediately around your workpiece.
i m a mechanical engineer and i can confirm that fast quenching results more hard and brittle material like iron. i m not still an expert but the basic knowledge suggests that there are different atoms inside steel (iron and carbon) if you quench it fast there is no time for atoms to distribute homogeneously
Sound point, presumably harder blades/wrenches would vibrate at a higher frequency and more elastic ones would ring longer, which could give a more precise and overall measure of hardness and elasticity, does that ring true with your experience with wrenches?
Hardening using liquid nitrogen is quite actively used. High-quality cutters and drills are usually treated this way and cooled from about room temperature. Moreover, there are even several videos where people independently tested the performance of such heat treatment. So it all comes down to the fact that each hardening option is good only under certain conditions, otherwise it can be made even worse or at least more expensive. For example, axes are hardened by partial immersion in liquid, and the depth and time of immersion change depending on the heating temperature and liquid.
Once attended a metal working class and the quenching went as follows: First in water - then removing the coating so you could see the bare steel - then warming with a blow-torch until the steel turned blue - and then quenching in oil. Fahrenheit - please show temperature in C as well because this is the standard the rest of the world uses...
ladenfrost effect might be a factor for water and LN2 quenching, which would actually slow down the cooling process. That being said, there are heat treat methods that use water quenching, some use oil, some sand, etc ... and as you mentioned, different steels give better results with different quenching media.
So glad to have just learned the term for such an event as I posted an unnecessarily long comment trying to explain it.😑 Do you think that leidenfrost would cause the steel to cool slower in liquid nitrogen than water?
@@deep-freq nitrogen is colder. even the gas coming off of LN2 would be colder than the liquid H2O. heat transfer would be faster until you got near the boiling point of the water, where the leidenfrost effect would stop for water but continue on for LN2. youd get completely different cooling curves i think.
as it turns out, in old times they used different materials for quenching to get different hardness. i've read about them using animal pee for some swards... that gives more carbon to the edge of the steel. i would love to see nate try these crazy materials as well...
I would like to see you do a bend test on the 3 quenched knives to see if there's a difference in where they snap. The drop test, I dont believe , proved much. Thanks Nate!
as someone who has done some minor experiments with quenching all i can say is that, at least on a small scale, the quenching medium barely matters because small things have little mass and a lot of surface area, so they'll cool quickly enough regardless. on a large scale i feel the main advantage of oil is that it doesn't boil off as quickly, leaving you with the ability to keep using the same tub of oil for much longer.
1. I love that the liquid nitrogen was conspicuously absent from the first round of hardness testing 2. We got confirmation that it did, indeed, produce the hardest knife, despite being conspicuously excluded 3. We got an explanation as to why it would perform the best, because of how quickly it cooled the metal (to grossly oversimplify)
The LN knife was at 6:22. We showed two tests of the oil quench, then one with water, then one with LN. I did a poor job showing and saying which was which!
To stay true to the experiment it would have been nice to see the first 3 blades all undergo hardness testing in the same order. It seemed that because you got an unexpected result from the water quenching you just gave up on that part of the testing which was off-putting.
Typically the cooling rate of LN is way lower than the one of simple Water or brine (If I remeber correctly by< a factor of 10)... Yes it has a lower temperature but it does a really bad job at transfering the heat away. If one needs fast quenching (in the lab) tilting the oven and letting the sample fall into a bucket of water is perfect.
This is my understanding too. The key is the RATE of cooling. Cool too fast, and the atoms in the alloy don’t have sufficient time to find a low-energy-state lattice. Cool too slow, and the atoms will keep hopping out of the low-energy-state lattice. Quenching is a Goldilocks process.
Thats almost exactly what I did in the hardening shop in a controlled atmosphere. First heat to 1050 degree then cool with - 200 something then glowing it at 400 degree and cool again. Rinse and repeat.
Heat treatment of steel is about martensitic conversion of austenite. There are several factors at play. The hardening temperature, quenching temperature and quenching medium all depend on the steel type. Some steels are more forgiving than others. Research your material before attempting to heat treat it.
I loved the test, and I'd also love to see a round two with a brine quench. Not a knife maker, but I've read that brine cools the blade the fastest and hence gives it a higher Rockwell compared to oil, water, ect.
It also cools the steel more evenly than plain water which reduces the risk of cracking or warping compared to plain water despite being slightly faster.
This was cool to watch, because you can see how liquid nitrogen actually isn't great at cooling down very hot objects, because the nitrogen vaporizes and creates a film of hot gas around the hot item. It does the same thing if you pour it on your hands! Neat!
