Good work. The heat treat conclusion is correct. However, you are misinterpreting what you are observing. You are not looking at the grain structure. You are looking at different types of failure modes. In a brittle fracture, a crack forms and cleaves through the material, leaving a smooth finish. In a ductile fracture, the material distorts and "necks down". This simultaneously creates a rougher looking surface and simultaneously the effective cross-section is reduced. Eventually, the cross section is reduced enough that tensile strength is exceeded. When that occurs crack forms, the crack quickly propagates through the material and the knife breaks. Part of the fractured surface will be rough and a part will be smooth. You can tell all about your heat treat process by simply looking at the fractured surface and estimating the ratio of ductile to the brittle fractured surface. As a side note, the ideal condition would be for the cutting edge to be hard (but not "brittle") and for the back to be more ductile. That would create a knife that would both hold an edge and not snap under heavy loading. To observe the grain structure, you would need to cut polish the surface until it was mirror-like. You would also need a microscope. Sometimes you need polarized light and an etchant to cause the boundaries to "pop" out. In any case, good job.
Ductile definitely isn't the word you meant. Also, you wouldn't necessarily want a brittle edge. It doesn't matter too much how tough it is, but a higher toughness means you can repair it more easily. Brittle or tough, the priority should be making the edge strong and hard
@@goodguykonrad3701 You are correct. I did not think this lay audience would be interested in the technical definition of toughness: The area under the stress strain-curve or the ability to absorb energy before fracture. I simplified the description to a ductile-brittle analogy. For a specific heat-treated steel, the more ductile heat treat is almost always tougher than the more brittle heat treat. I just came across this. It is a better explanation than mine. www.materials.unsw.edu.au/tutorials/online-tutorials/2-cup-and-cone-fracture#img - Any idea on how to succinctly explain toughness to this audience?
Kinda. I mean, lots of valuable effort, I love that he did this, I agree on that part. But plenty of research students all over the world are expected to put similar effort into their respective fields of study to earn whatever degree their aspiring to get. The difference is, he did this out of pure interest, which makes it even cooler. If he continues he might get enough data out of this to write a scientific paper.
Also the idea that this is far beyond what any normal human could ever be expected to do I feel is a terrible statement and reinforces the reduction of work ethic for quality we see. What we expect these days sure. I do love though that he dov down into trying to figure out what was happening.
@@ruolbu Not really. In material science, the things that he has looked at are pretty much common knowledge. My respect towards him putting in the effort but nothing he has done is new or groundbreaking. If he knew where to search, he could have read this in some very old books (or of course more modern literature).
@@shawnpitman876 OK Shawn the irony of your statement is my 10/10 was my support in a positive light . While your poo-pooing , reflects in your 5 subs and zero , yes that's right zero content , yet you feel the need to poo-poo others , telling us just how little i strive for with your zero content channel .
I heat treat 1095 at 1485 in my evenheat oven. I put blades in cool and let them heat with the oven. Once they hit 1475 I start the timer and soak for 10 min. and quench in 5 gallons of parks 50. When I do multiple blades I make sure each blade comes back up to 1485 before quenching. Remember when you open that door temp drops quickly. I have not noticed any grain change between 8 and 15 min soak time as long as I allow each subsequent blade to get back to 1485. I usually heat treat 6 blades at a time. I also keep the blade vertical in the quench and do not swish it side to side only up and down. I notice less warpage also I hang them from a hook to cool to room temp before temper. don't lay a warm blade on a bench or piece of metal I have noticed this warp a blade. I have not put a cold blade into an already hot oven not sure if that has an affect
Dear Outdoors55, I love your investigative nature and believe that you are following the right tests to ensure the quality of your knives! I'm from Germany and am currently in my second semester of my "Ausbildung" (sort of a vocational training) that specializes in metallography, so eesentially the analysis of grain structures, impurities and the likes in metals. Now I'm by far not an expert yet, nor will I be for a long time but it is channels like yours and other creators that pushed me to pursue this career and it has been nothing but rewarding! I've talked about heat treatment with one of my teachers, since I'm so fanatical about knives, and according to her about two or three normalizing cycles at about 30-50°C (I think thats about 90°F to about 120°F) under quenching temperature, followed my multiple quenches (without tempering in between!) ensures a really fine grain structure and positively affects toughness whilst not affecting the final hardness after tempering. Also driving the temperature differential up is really beneficial (cryogenic treatment after the last quench), as that temperature difference allows for a stronger setting in the crystalline lattice and by thermal compression allows for 'clearer' boundaries. Then after all that and tempering you should be rewarded by a really great performing knive. Thanks a lot for your content and greetings from Germany ! edit : sorry for the long comment ;)
Multiple quenching is something that has been done in knife making for a long time. I forget who was the first to really put it into practice. From the knife research ive done it seems to be the best way to get a very fine grain. It will definitely something ill do in the future. Maybe a follow up to this video. Thanks for the input!! It definitely intrigues me more😂 im also wondering if more normalization cycles slightly under quenching temperature would refine grain even further without multiple quenching. Seems some people swear by it. Thanks again 👍👍
@@OUTDOORS55 I think you can refine the grain a lot but don't forget that if you go to far on the refining it gets harder and harder to fully harden the steel.
@@evias9943 Der Beruf heißt Technischer Assistent für Metallographie und Werkstoffanalyse und wird nur in Berlin und Solingen angeboten, meine mache ich im Lette Verein Berlin
I love you don't mind destroying things you made to make sure they are up to snuff. No one should have any reservations buying any knife you make. Great channel. Keep it up.
Do not beat yourself up over testing mistakes. You are doing things that help the rest of us and identifying your mistakes. This is the proper method. Keep it up. Informative and enjoyable
I am not even a beginner. I've never made a knife. I'm finding your videos informative (as much as I can understand). I assume this test proves that a very fine even grain is desirable. Even though you never really came right out and said that. I want to make a FOREVER knife for bush craft. I don't know what steel to use, how to treat that steel - heat treatment, quenching, annealing etc. or even the order in which to do this. I'm 65 years old and retired so my definition of a Forever knife is a knife my grandson can have and use once I'm gone. About all I do know is I want it to be a full tang and the back side of the blade should take a little bit of a beating from a hatchet maybe 3/16 inch wide. While splitting small kindling. I want it to be about 8 inches of usable blade (probably more like 10 inches long with enough left over to go the full length of the knife handle. I want it to take an edge I can shave with and hold that edge for a reasonable amount of time. I'm learning sharpening and stropping and general care for a knife in the meanwhile but no where near the skill level to produce what I want. For me your videos might be a little to far advanced but if you spoke like you were talking to an idiot it would make it easier for me. I don't really expect you to do that because I think you'd lose a lot of your viewers. Lol. Can you direct me (or any of your other viewers as well) towards any of your videos that would help me. I like your style of making videos and prefer if I could stay with you. Does anyone think I'm crazy? Is this a knife I can make - or is it like a Holy Grail. I definitely don't want to buy a knife like this I want to make it. I have access to most every type of tool I think I would need and am even considering purchasing what I need if I don't already have it. For instance a 2" wide belt sander (I presently have a 4 inch wide) Would a 1" wide work? What's better one inch or 2 inch - do I need both? Thanks for reading this tome of a comment and I gratefully thank any help anyone can provide. I live in Allen County, Ohio if there is anyone near me with these skills who would allow me to have lunch with them and shoot the breeze let me know. Even better a chance to see your shop and set up. Lunch is on me.
Just a thought from having a Kiln and modifying it. I used to put in my blades into cold kiln and fire it up with them in the whole time up to 1475. Then I would get lots of decarb. Then I would let it get up to temp (1475) put it the blade let it rebound and time it from the time it got back up to 1475. Now since I slit a hole in my front door I let it get to temp wait 10 minutes then slide them in the slit for 5 minutes.From what I have seen in my testing is the first way is bad because I was putting it the whole time while the kiln was getting hot while the coils are set to max heat or as fast as possible on my kiln which I think is hotter than 1475 that causes grain growth. The second way was not as good because the rebound time can be long and cause grain growth. The last way seems the best with the finest grain I think because when I stick it through the slit without opening the door temp drops a tiny bit and rebounds in almost no time. Check out my last video to see what I mean about the kiln mod. The sweet spot seems to be 5 minute soak time from my testing. I hope you understand my ramblings lol. Also I use parks 50 but with a 7 gallon tank and I have not noticed a difference with oil temp.
Thats interesting info! I was thinking that the ramping up to temp might have something to do with it but wasn't sure. I loose about 50 degrees (if im fast) each time to door opens. And it takes about 5 minutes to ramp back up. I suppose that could have caused the last blade to over heat. I've even thought about over heating the oven 50 degrees over temperature so that when the blade goes in it drops back down to where it's supposed to be. Thanks for the info 👍
Actually putting it in cold is the best way, but if you're concerned about the coils affecting the blade, put it in a tube to shield it so the tube is absorbing the temperature fluctuation.
Nice job showing what diligent knife makers go through to understand the steels they decide to work with. Tested my share, still do, just to make the processes are still valid.
I think there may be a difference between soaking and bringing up to temp. Longer periods of time at the same temp would allow the steel to adjust to the current temp. Maybe try a test where you let one piece slowly get up to 1550 and then the other heat up in about half the time and let set at 1550. Say, If you can control your forge, piece one allow it take 10 mins to get up to 1550, quench. Piece to allow 5 mins to get up to 1550, soak for an additional 5 mins, quench.
The 800 is for 1095 the austenite phase transformation limit, generally you should soak up to 30 minutes for the steel to fully transform to austenite at that temp. This transformation is not fast at all. But huge chunky austenite does not imply huge chuncky martensite, as the quenching is a powerful phase transformation that restructures the whole steel.. I think you are not getting full austenite in your piece and that results in less martensite transformation and more of those nice chuncky grains of perlite (maybe). Going up with temp would ensure full austenite transformation and thus a full quench and less chunkiness. As to why 5 minutes soak making smaller grains is that again you are having some austenite transformation but mainly pearlite which keeps growing until austenitisation. So with time you get bigger grains of pearlite back, but less of total. Anyway do a 30 minute soak and you should get the best result.
When you open the oven the temp drops, just like a crockpot or household oven. Try recording sample temps with a pyrometer as you pull parts out and see how much the temperature drops from the first sample to the last.
I used to work for a stress relief company. Heat Treating different types of Steel, we used to start at an ambient temperature and then slowly heat the product to whatever temperature that particular Steel calls for, then there is a soak time again different for each type of Steel. After that we would slowly bring down the temperature over an extended period Of time . very technical and each type of Steel requires completely different heat treating but it always starts from an ambient temperature and slowly Works its way to asoke temperature and then slowly Works its way back down to ambient temperature. All types of Steel , if you want them perfect they require this type of heat treatment.
#1: Every knife should meet it's user's needs. Not all needs are the same. Rigidity is great when rigidity is needed, but leads to unwanted breaks. Flex is great for most knives and will fill the "sharp piece of metal" role that general use knives need. But they take plastic deformation. A flaw, but not a broken knife. #2: Cut, polish and etch if you want to view grain structure bro! Thanks for video!
Awesome info!! Now I’m going to have to do a bunch of testing myself. I’ve done destructive tests on knives and it always makes me cringe to put all that work in just to break the thing in half but i think its a very important step for anyone wanting to ensure quality. Thanks again this video was the most informative heat treating I’ve seen on youtube particularly of interest to me because i use a lot of 1095.
@@OUTDOORS55 Were do you get your stainless steel foil for keeping the O2 out of the "Quenching"? Think it will work with a atmosphere propane forge or and forced air propane forge? I can run them rich so that I greatly reduce the O2 but was thinking that adding the foil might save me even more addition Carbon content. Thoughts?
Hmm Have you thought about the temperature of the oil you are quenching in ? Each time you quench a piece of steel in that same oil you are raising it's temperature and each peace that follows is quenched in hotter and hotter oil. Oil that's lets say 90 degrees Celsius will quench steel quicker than same oil at room temperature of 25 degrees even thou its hotter. Have a think about that ;)
Yeah, just a bunch of BS. Maybe if you want consistent metal work, use consistent procedures across the entire build cycle including the oil temp you are quenching at.
Kudo's for going the extra mile to improve your craft/product. However, why not invest in an inexpensive microscope and polarized light source to see what the grain actually looks like? I think you might find it informative, and you can rest assured that your current method isn't actually leading you astray. Also, it would benefit your 'research' if your method of stressing the steel to failure was more uniform.
@@TheGunz0001 Actually, a 30X or 60X Jewelers Loupe would work just fine. They're not very expensive and it's handy to have around the garage anyway. In most cases you don't even need the polarized light source, just taking the time to file the broken edge flat and etching with a clear acid will reveal detail in the grain.
@@namzarf polarizing filters are also quite cheap and can be used with most small light sources, flashlight included so the polarized light also isn't a problem
Have you considered that (concerning the three initial blades) that the third was quenched after 2 rapid succession "openings" of your H.T. oven. I wonder if you may have significantly dropped the temp off the third knife from heat loss due to the openings/exposure to ambient temperature. Possibly your thermocouple is placed in a bad spot to get accurate temps. I would suggest possibly doing a test of temp loss or general atmospheric condition changes in your oven due to opening it.
Wow, I remember a couple yrs. ago telling you that you would be a great knife maker,with your knowledge of knives and your enthusiasm. That was a understatement !!! Ive gotta go back and review what Ive missed. 👍
Great dedication to the craft. However, you're not actually looking at grain size. You're looking at fracture surfaces, which generally occur along grain boundaries. To look at grain size, you must polish the sample, apply an etchant, and view under a microscope. Also, a factor that's missing here is the hardness. It's very likely the pieces that were not soaked 5 minutes or more did not reach full hardness capability, which defeats the purpose of a high carbon steel knife. If you're not soaking it adequately to achieve the steel's potential, grain size doesn't really matter. there's a point of diminishing return where ultra fine grain becomes a problem as you lose hardness. I got on the grain size merry go round a while ago too but then I got off after I learned a little more... :)
Theres a lot of factors missing here that i cant necessarily test with my limited equipment. All of the pieces however were saoked minimum of 5 minutes. Theres still a possibility that full hardness wasnt reached. I dont have a hardness tester so i dont know for sure. Thanks for the comment 👍
Great video Alex, I'm glad you talk about this subject because heat treatment is what makes a knife good imo. I studied metallurgy last year and what you say is true. Soaking time increases grain size for simple carbon steels. Alloyed steels can sometimes reduce their grains with soaking time. And the higher you go beyond the critical temperature, the bigger the grain. What I would love to see is the grain structure difference between a forged blade and a stock removal blade. I have no idea about the result...😅
The seriousness take, and the clarity of steps throughout makes this a fantastic work. Well don, on looking at every aspect you could, and showing the results.
Great video. Im subbed because you explain things very well and cover all the things that need covered. The fact you picked up on your time issues at the end of the video just reinforces how serious you are about covering all your bases. Easy sub. Highly recommended.
Remember your phase and TTT charts, specific to 1095. 1095 is a hypereutectoid steel, meaning the carbon above 0.80 (nominal) will not go into solution with the ferrite (austenize). The extra carbon hangs out to form carbides. Carbides are hard, and probably bigger than your martensite grains. Temp and temp over time does promote grain growth, as experienced by your long soak @1475. The 1550, higher temp, allowed for carbide formation, and probably better carbide control and better solution balance, in your hypereutectoid steel. If you repeated your test with a 1075 or 1080 steel, the results of grain growth, you were expecting would probably become more evident. The comment on quench oil temp, being 120, is more about nucleation (bubble formation) at the knife surface. 120 is better than colder, but if you can beat the "nose" on the 1095 TTT curve, your goodto go.
I have seen issues when quenching multiple blades in a small 1 gallon container. The oil temperature increases dramatically from blade to blade. A thermocouple in the oil would add another data point. On bladeforums, it was recommended that a 1 gallon can of oil might be too small for a blade larger than 7-8" and for multiple blades back to back. At least 2 gallons - 5 gallons was recommended.
I really liked this video you showed that you take real pride in your work a few books on metals and heat treating would have helped you but what you did is impressive and educational
Wow that's clear as mud. However; my brother and nephew normalize for about as long as it takes to get to tempature, for three cycles and then quench. I'm sure your conclusions are correct about over temp and soak times. Thanks I your videos are a great source of info.
A lot of 1095 shows inconsistent results when comparing it to the data sheets because a lot of 1095 has minute amounts of alloying elements, such as nickel. I have had consistent results when ordering steel from the same company, but some slight variations with others (Amazon was a steel ordering platform for a while). I do not have a temp monitored oven for quenching so I only have results based on "feel". 1095 cools very rapidly so its possible when you are pulling the blades out one at a time to quench, there is a drop and rise in temp for the others. I would be interested to see one blade at a time. In my experience I have not had issues soaking for too long, but I honestly can't think if I have soaked at around critical for longer than 10 minutes, again "feel" sadly I never had a watch near me. Tldr Try the soak time test one piece in the oven at a time, might look different.
Yeah not all 1095 is the sam. This specific batch is only 0.9 carbon. Thats the minimum needed for it to be called 1095. Ill have to look to see what other elements are in this batch. I think thats why alot of custom makers seem to stay away from it and use a steel thats more consistent like o1 or cpm steels that give you specific info on heat treating.
I’m about to heat treat a O1 dagger/chopper and this information is actually really helpful. I was getting a little stressed trying to find a good soak time lol
Question: heating the oil with every quenching doesn't change the result? Shouldn't you use a different "can" of oil at the same temperature every time?
if you want the grain structure to show up better on camera, keep using your good lighting, but in video processing, turn up contrast, and down brightness. great video!
You could make standardized cross sections of the test pieces for future tests and use a cheater bar that has a notch in a specific place along its length in which you could place a spring scale. Do so could allow you to gather some more data out of each test you make.
by reading the book, I have to say a big tank is required and when you quench the knife, shake it. the reason is the effect of quench is the rate of temperature getting down, a proper rate is the key. and small tank would cause the rate down below the best range.
Very cool! I've broken and tested a few of my knives too and just recently started to use an electric forge. The results I get are satisfying. My oven ramps up very slowly and I put the knives in when the forge is still cold, let them soak fo 5 min at desired temp before quench. I wonder how much the ramp speed affects the grain.
Very informative video, thanks for opening my eyes to the Variations that can occur! the first thing I'll do now once I get my own forge going is to go through different steel samples and try to find the optimal heat treatment cycle for my work!
I'm a machinist and have done a fair amount of heat treating of various metals for various reasons. I think what Dan Pedersen said was correct, but wanted to add a couple suggestions to help you fine tune your process. Get a hardness tester, and perhaps something to measure torque as you are bending those knives to failure for more accurate diagnosis of what's going on. Unfortunately, my experience is with tooling steels and oddball alloys, so I really don't feel qualified to add specific insight into normal carbon steel. In my personal experience I haven't seen longer soak times lead to bad results. For me, I have found the tempering to be more critical but again, different materials and substantially different thicknesses.
I like your reasoning and scientific approach. I took metallurgy to earn my associates of science for welding technology but remember very little except different boundaries and phases and they analyzed failures (yours being vise angular leverage failure) like you did with your pieces - to see what caused the failure . What I gathered from your experiment was that no matter your soak time or temp - NORMALIZING (CORRECTLY NORMALIZING, and soaking at critical temperature for 5 minutes is the B diggity G) is Mucho Grande Importante! You did great! but the camera to me showed a better grain the farther you went to the left - maybe cutting the pieces would show the grain structure better because breaking the pieces tends to disrupt the grain pattern/structure as it elongates and deforms the end pieces. Great Job and great lesson on the importance of normalizing 1095 and I am sure 1080 would bear similar results. Also testing metals you haven't used before and finding normalizing procedures and critical temps for each new material you use - of course writing down these notes in a knifemakers logbook for future use and less re-googling (is that regurgitation). You are an inspiration on the path to the knife making grotto! I have never made a knife but I should be qualified son with all the different videos I have watched - KEEP Making them!! I copied your pattern on my laptop screen enlarged - maybe I will be ordering 1080 next.
Here are some reasons for your test inconsistencies: 1. Steel is cooking with variable temperature and variable time. 2. Water temperature varies between quenches. What this means is, you don't know if it is the cooking time, the cooking temperature, or the quenching temperatures because water temperature rises and falls between quenches. There are three factors here that need to be addressed and each might compound the other. Proposed approach: 1. Cook each piece of steel separately for the same amount of time. 2. Check water temp before and after quenching. Use the same water temp for each quench. 3. Check results for grain growth. Repeat with minor adjustments to cook time, cook temp, and quench temp. Change only one factor between tests. Then you'll know which causes the most grain growth.
Excellent practice to record as much data as possible for times like this. Especially something like heat treatment with so many variables. I think a recall is in order, to be on the safe side ;)
I would love to get as involved into knife making as you are now. At the moment I just make a blade, heat treat until it gets to the color I think it should be and then I quench immediately lol. My edge retention is impressive in my opinion considering I've dulled store bought knives a lot faster than my own. I've also never broke one of my own blade (on accident). Hopefully some day I can get a set up similar to yours! Great video as always
Yeah this is going in depth (at least for me). Any of these pieces or knives would have made great blades for the most part. They just wouldn't be as good as they could be🙂 Thanks my friend!
just some passing observations: the opening and closing of the oven door could play a factor. also, iv seen a number of comments about the oil temperature going up with each quench and that does sound like a potential issue. the last thing would be sample size. just using 1piecee of steel to test each variable leaves a lot of room for error. still, its a super cool video :-D
scrolled down to see if anyone said this. In the first test there is some thermal cycling going on each time the door is opened, In the last test no thermal cycling is occurring.
Mech E here, though not MSE so it’s not my particular expertise. Some thoughts: Normalization would likely refine the starting grain structure and help prevent grain growth despite extra soak and temp. Perhaps try the temp test on non-normalized samples to find out. This might be a lesson in normalization prior to heat treatment for consistent safe results. Also, the thing your looking at isn’t actually the grains (would need a scope to see those) but the fracture mark size. Regardless the interpretation of the visual gives the intended result. You want a single consistent failure across the material, not random low stress failures that increasingly weaken the material. Also: oil temp inconsistency may play a factor, though I wouldn’t expect it on such small samples unless the average oil temp rose 200+ °F... But maybe it did?
Very interesting. Thanks for sharing this information Alex. I hope the channel doesn’t change too much. I kinda like it the way it is. Keep up the great work my friend. 👍🏼
I'm not sure but I think you need to reach austenite temps before the grains can grow. I think you can keep steel at below critical temp for a long time and not see much or any grain growth.
Other advice I got was to get the oven to soak temperature first and run it for 20mins or so, then open door put blade in, close door. Start timer clock once temp has come back up to soak temperature.
Grain structure and shepherd grain baby! This is why it's important for all companies heat treating steel products in general to check surface hardness and do break tests
Really surprised I haven't seen any knife makers on here do any cryogenic hardening. I just forge welded 30 layers of 15n20 and 1090 with a core of 1.25% high carbon steel. Def running heat treat retaining some austenite, slowly dropping temp of said heat treated blade down to -300F and holding will boost martensite and eta carbide formation significantly.
check out he oil temps, soak time seems as important as quench temp. room temp oil cools the steel faster than oil that has temp raised after several quick succession quenches.
Only thing that I could think of would possibly be your oil. If you are quenching piece after piece in the same oil then the oil would be significantly hotter than it was when the first piece went in. I'm no expert but I've heart that having your oil to hot can have adverse effects.... Hope this helps in some way.
i once unknowingly compleatly overheated a O1 blade and soaked for 30 min. it snapped lilke a twig and the grain were in the 100 µm scale, visible with the naked eye.
I made a small knife using 1084 steel. When it was time to heat treat I made a fire bc i dont have a oven yet. I threw the knife under the fire and let it stay there. It was in the fire for a great deal of time but it didn't turn orange , but I decided to quench any way. I quenched it in a water cup with water, mom wasn't to happy about the cup. But any way I put it in a vice to finish up wen the blade simply broke off. It did have a large warp in it but I noticed the blade was extremely grainy inside. Huge grains wish I could show u. Not quite shure how this has happened
I know for aluminum there’s a peak temperature and peak time that’s best for hardening. As you get away from that time/temp, more or less, it won’t harden as good. Interesting video!
The only mistake I can see is in your last test you didn't start at 1200 and go up to 1575, as you did in the prior two tests. Otherwise, very well done. I think your conclusions are spot on, and the added info from Lucas Kramer below is important as well. As for the heat treating multiple items: industry does it all the time. They just make sure that their ovens can handle the mass of steel present, and hold the temps. As long as your setups can do it, I can't see how multiple items (unless you stuff a few dozen in there) would be a problem. Once again, fantastic video. Thank you. Subscribed.
Hi Alex. Maybe the problem could be secondary recristallisation. I'm a maschine engineering student and we talked about this in our material science class. As far as i understood, secondary recristallisation is the growth of some grains at the cost of others. This can occur on small wall thickness, sharp textures and fine contaminations inside the metal. This is all just from looking in one of my books and there will be a lot more behind this (probably temperature in heat treatment)! Maybe you can find some more info on this toppic. Greetings from switzerland
Yes i don't believe i have the ability to figure this out based on what i have available to me. There are some other theories some other people have left as well. It's difficult to make a determination. Thanks for the comment 👍👍
If you leave them in the oven too long you can get segregatiom of the impurities at the grain boundaries due to the high diffusion rate which can cause drastic changes in the material properties of the metal
I think like this guy. I tested in my wood shop the most common ways to assemble a ply wood box for a cabinet, and knocked them apart with an ax. It was clear: glue or rabbets or brads are not nearly as strong as properly drilled wood crews.
Also, for the 10 series, from about 1050-1090, I've always been under the impression you always should quench at the lowest transformation possible to prevent martensite formation. The other big thing, is the temperature of the quenching medium, which might be playing a factor here. During your tests, were you maintaining a set temp of your quench oil? Itll have a massive affect on crystalline structure.
It's been a while since I've read up on it, but martensite, to my knowledge, is a larger grained, unrefined extremely brittle grain structure that can add inconsistencies in the temper.
0:58 does anyone know what song that is? Shazam says it is Spirited Away by Bernstein but I can't find the specific part of the song he used in this video :( EDIT: Found it!!!! IT is called ALLA HJÄRTANS SWAG
For a layman like me, oh, 3 good knives had been wasted! But I understand also the need to investigate more for ensuring the high standards of what you make. I'm just thinking what sort of practical use of the knife that would require such abuse. It's like expecting a car to perform like a cargo truck. For my intended use of the knife, the 1st one you broke will already make me a satisfied customer. The other 2 maybe good enough already for fighting swords like a Katana. Good job you did.... I am more educated now than before about knife making. Thank you!
here's my guess toward why you found what you did toward the end. im a welder (well was) and back when had to do my cert test my teacher taught me to always air cool the plates. why because the grains are more solid and longer this way. so my best guess is leaving the metal overheated for 15 mins allowed the grains to have a similar effect as air cooling. though this is a just a blind guess and i haven't checked my metallurgy books in yeats
It shouldn't grow the grain for a 10 minute soak, maybe lower your temp by 25 degrees and try this test again? (quench @ 1450). I actually do heat treat 1095 in my forge, I am quenching in Parks 50, but I can cut through nails with it. I know it isn't 100% optimal, but it still has excellent results.
and you are right, in a forge, temperatures are hard to tell just by color, a good rule of thumb for me has been heat treat when it is pitch black, and when the steel reaches nonmagnetic (1414 F), and then go a shade brighter. (about 75 F more) and then quench.
also, normalizing can help keep grain growth small as well, even when overheated for a short time, that may be why when you quenched the test piece at 1525 F and it was still fine grain, but not so in the 1st batch of testing.
“I put my ENTIRE 150lbs on them” 🤣🤣 Great video man. I am really enjoying your strength test videos. Being a total amateur knife maker, JUST getting in to the hobby, these have been very helpful.
More time in the heat does enlarge the grain,and increses decarb....I would even leave them litle bit harder(less tempering) but that depens on the useage of a knife....
try cooling the metal in 900dg lead, this might give the metal more time to organize. also try running a little dc through the molten lead to help organize the structure. just some odd thoughts. careful with the lead, it can mess you up
Great vid man very informative. I’ve been making knives for only a year now more for hobby. I know the heat treat process is important, but who is actually going to pound on metal and try to cut logs with a knife? My question how much effort should I put into the heat treat if I want to start selling knives?
it depends on what you want to sell? top knotch knifes at a premium price or just nice knifes for a reasonable price but not as good as the first. Also depends on what kind of knife you make, a thick sturdy knife like 4mm or so probably has not that much to fear of a less than ideal heat treat, but if you want smaller knifes bending and breaking becomes much more of a thing to consider. in my opinion one should always try to get the best results, or at least with the options given to you to produce the quality you want. Everyone can buy some chinesium steel and make knifes. Good knifemakers make knifes that cut through chinesium knifes.
I don't use 1095 because minute differences between manufacturers makes it so picky. It is supposed to be taken up to 1500, 1500 is supposedly 1095's sweet spot. Then I've also read 1475, but I have always gotten differences so I never use it. I use O1 and it heat treats very consistently and I make certain I always get the O1 with the 0.2%* vanadium which at that small amount doesn't make carbides, but GREATLY restricts grain growth. Plus O1's sweet spot is 1475 for 13-15 minutes to get the half a percent of chrome and tungsten into solution. O1 also benefits from deep cryo if you already have it sitting around, makes it tougher. *some is 0.1%, it still works. Another one of the reasons I only use O1 tool steel for non-stainless knives is after quench for about two to three minutes you can straighten the knives by gloved hand in the vise. It is the only steel I know you can do this with. My O1 knives I grind the main bevel all the way down to about 1 mm, little less because they are so easy to check and straighten. I also only do 4 knives at once because quench oil gets hot and the soak time doesn't go past 15 minutes. O1 needs a 12-15 minute soak time at 1475. The 12 minute soak is for 3/32 thick knives, 3/16 can go 17, but I rarely use a steel that thick. I know the book says 10 minutes for O1, but that's for O1 without vanadium, just FYI. During your ht cycles with so many knives did your quench oil rise very much in temperature? I use canola oil because it's cheap and Parks 50 is a little too fast for O1. I start at 120 degrees and stop at 135 degrees (4 knives) or else my HT suffers, the knives don't harden as hard. Plus there are other issues too complicated to get into about martensitic to austenite processes etc etc. Suffice to say that you try and HT to get the best you can and you want every parameter to be where its supposed to be. Like don't leave your 1095 knives in past their proper soak time unless you're raising the temperature. About myself, knife making is a hobby I've done since 1992, but I was a heat treater in a machine shop for several years as a young engineer working towards my masters in biology. I also do leather work since my knives needed sheaths. I found I like leather working more than knife making and will make a belt to match my sheath. I have been retired for 10 years.
Maybe the grain size is increased if the metal is soaked in the same temperature for long time, but the change in temperature causes the process to reset. In other words, maybe the atoms are aligned unfavorably if the material is heated longer at the same temperature, while changing the temperature cases them to realign
i think the temperature of the oil may have something to do with it as well. by the time you get the second and third pieces of steel in the oil will be nice and hot compared to how it was with the first blade.
crystal growth temp and smelting temp of the steel might be the reason of the inconsition you see. im thinking just like salt and bismuth the temp makes crystals at lower heat then the smelting point and if you quench both salt and bismuth wont make crystals as they normaly do, in other words you probaly just hit the minimum heat for your iron to remelt.
by not quenching in the same temperature oil for each piece you change two of your variables to know it is the soak time the oil needs to be the same temp for each piece
Been going through some heat treating science at work. Our engineers have found for aeronautical use, direct radiation is causing issues when tempering. Suddenly, all our furnaces are bad.
Were you using the same quenching bucket? If so then the oil will have increased temperature with each quenching, thus reducing the cooling effect for each piece.Thus, last steel receiving the least effect of the quenching. Just a thought.... Also grind the surface of the specimens fine, acid etch and view under a microscope for grain structure...
From the beginning I thought the test was flawed because you weren't using the same temperature oil every time, the oil tape is going to rise each time you quench something else into it so you would need an oil quench sample for each test subject to keep your control group the same
Very interesting. I had a knife in chinesium that looked just like that when it broke. I would assume that the metal itself was not high grade, but also that when mass produced the blades just go through one heat treatment and causes the metal to be grainy overall.
G'Day,,After watching you Film,,I Have had problems with parent metals not being the same all the way through,First hurdle,,The other thing is quench liquid temp, now depending on the original steel,,different Heat treatments are recommended,have seen a full furnace go to scrap because of over heating,,maybe 50 ton of high quality scrap,, for example when making steel grinding balls,,they air cool and then quench,,but quenching water is at 50 c,these balls come hard and tough, Now in the rod mill,,the quenching process is highly adjustable,,have seen rod from mill go through the tying machine and turn to dust under 40 ton pressure ,wrong cooling schedule, it may be to your advantage to test each piece before manufacture of blade,, Sorry for the long winded comment,,and late viewing,,But i do like the way you went for it,
I think a statement you put in text on the screen near the end sums it up best. Don't do more than 1 blade at a time. Not saying I know anything. I know I do the best job on 1 thing. Rather than more than one thing. Might be the same for the forge. Is this metal all from the same purchase? From the same company? Just thinking not consistent metal through out. Or even just a bad batch of metal. That would be saying the problem wasn't your fault. I just end with more questions than final thoughts. Still a really great video. I did enjoy the experiment you did. You explained it well. Sometimes in doing something their isn't an answer. You might repeat that and get a different outcome. Your work is great. Keep up the great work. 👍😁
Good work. The heat treat conclusion is correct. However, you are misinterpreting what you are observing. You are not looking at the grain structure. You are looking at different types of failure modes. In a brittle fracture, a crack forms and cleaves through the material, leaving a smooth finish. In a ductile fracture, the material distorts and "necks down". This simultaneously creates a rougher looking surface and simultaneously the effective cross-section is reduced. Eventually, the cross section is reduced enough that tensile strength is exceeded. When that occurs crack forms, the crack quickly propagates through the material and the knife breaks. Part of the fractured surface will be rough and a part will be smooth.
You can tell all about your heat treat process by simply looking at the fractured surface and estimating the ratio of ductile to the brittle fractured surface.
As a side note, the ideal condition would be for the cutting edge to be hard (but not "brittle") and for the back to be more ductile. That would create a knife that would both hold an edge and not snap under heavy loading.
To observe the grain structure, you would need to cut polish the surface until it was mirror-like. You would also need a microscope. Sometimes you need polarized light and an etchant to cause the boundaries to "pop" out.
In any case, good job.
This guy forges
Do you teach? 😅
@@gamer.004 No, I did research in fracture mechanics.
Ductile definitely isn't the word you meant. Also, you wouldn't necessarily want a brittle edge. It doesn't matter too much how tough it is, but a higher toughness means you can repair it more easily. Brittle or tough, the priority should be making the edge strong and hard
@@goodguykonrad3701 You are correct. I did not think this lay audience would be interested in the technical definition of toughness: The area under the stress strain-curve or the ability to absorb energy before fracture. I simplified the description to a ductile-brittle analogy. For a specific heat-treated steel, the more ductile heat treat is almost always tougher than the more brittle heat treat.
I just came across this. It is a better explanation than mine. www.materials.unsw.edu.au/tutorials/online-tutorials/2-cup-and-cone-fracture#img
- Any idea on how to succinctly explain toughness to this audience?
Oil temp is probably playing a role here. If you want to know for sure, do the same test and use 5 different buckets of oil.
this was my first thought also
or different types of oils because on this depends how quick will metal cool off, thats why we dont use water all time for this
Can you use lard instead?
The warming the oil, the more malleable the blade.
The colder the oil, the harder the blade, but also more brittle.
Oil temp is probably not making a difference
10/10 for going over and above what any normal human could ever be expected to do , so it's a gold star from me .
Kinda. I mean, lots of valuable effort, I love that he did this, I agree on that part.
But plenty of research students all over the world are expected to put similar effort into their respective fields of study to earn whatever degree their aspiring to get. The difference is, he did this out of pure interest, which makes it even cooler. If he continues he might get enough data out of this to write a scientific paper.
Also the idea that this is far beyond what any normal human could ever be expected to do I feel is a terrible statement and reinforces the reduction of work ethic for quality we see. What we expect these days sure. I do love though that he dov down into trying to figure out what was happening.
@@ruolbu Not really. In material science, the things that he has looked at are pretty much common knowledge. My respect towards him putting in the effort but nothing he has done is new or groundbreaking. If he knew where to search, he could have read this in some very old books (or of course more modern literature).
The fact that you believe this is so far above what a human could ever be expected to do just shows how little you strive for.
@@shawnpitman876 OK Shawn the irony of your statement is my 10/10 was my support in a positive light . While your poo-pooing , reflects in your 5 subs and zero , yes that's right zero content , yet you feel the need to poo-poo others , telling us just how little i strive for with your zero content channel .
I heat treat 1095 at 1485 in my evenheat oven. I put blades in cool and let them heat with the oven. Once they hit 1475 I start the timer and soak for 10 min. and quench in 5 gallons of parks 50. When I do multiple blades I make sure each blade comes back up to 1485 before quenching. Remember when you open that door temp drops quickly. I have not noticed any grain change between 8 and 15 min soak time as long as I allow each subsequent blade to get back to 1485. I usually heat treat 6 blades at a time. I also keep the blade vertical in the quench and do not swish it side to side only up and down. I notice less warpage also I hang them from a hook to cool to room temp before temper. don't lay a warm blade on a bench or piece of metal I have noticed this warp a blade. I have not put a cold blade into an already hot oven not sure if that has an affect
This is functionally identical to my process. Do we know if he is quenching in parks or is he using canola?
even car makers crash their cars. this is common sense
Even Samurais who live by the sword, die by the sword. Oh wait, that's Seppuku.
Weaboo
xD
@@blackflamelvl2007 u wrote sudoku wrong
What about dildo makers?
Dear Outdoors55,
I love your investigative nature and believe that you are following the right tests to ensure the quality of your knives!
I'm from Germany and am currently in my second semester of my "Ausbildung" (sort of a vocational training) that specializes in metallography, so eesentially the analysis of grain structures, impurities and the likes in metals. Now I'm by far not an expert yet, nor will I be for a long time but it is channels like yours and other creators that pushed me to pursue this career and it has been nothing but rewarding!
I've talked about heat treatment with one of my teachers, since I'm so fanatical about knives, and according to her about two or three normalizing cycles at about 30-50°C (I think thats about 90°F to about 120°F) under quenching temperature, followed my multiple quenches (without tempering in between!) ensures a really fine grain structure and positively affects toughness whilst not affecting the final hardness after tempering. Also driving the temperature differential up is really beneficial (cryogenic treatment after the last quench), as that temperature difference allows for a stronger setting in the crystalline lattice and by thermal compression allows for 'clearer' boundaries.
Then after all that and tempering you should be rewarded by a really great performing knive.
Thanks a lot for your content and greetings from Germany !
edit : sorry for the long comment ;)
Multiple quenching is something that has been done in knife making for a long time. I forget who was the first to really put it into practice. From the knife research ive done it seems to be the best way to get a very fine grain. It will definitely something ill do in the future. Maybe a follow up to this video. Thanks for the input!! It definitely intrigues me more😂 im also wondering if more normalization cycles slightly under quenching temperature would refine grain even further without multiple quenching. Seems some people swear by it. Thanks again 👍👍
@@OUTDOORS55 I think you can refine the grain a lot but don't forget that if you go to far on the refining it gets harder and harder to fully harden the steel.
Hallo in welchem Beruf machst du deine Ausbildung?
@@evias9943 Der Beruf heißt Technischer Assistent für Metallographie und Werkstoffanalyse und wird nur in Berlin und Solingen angeboten, meine mache ich im Lette Verein Berlin
magst du meine messer härten? :D
I love you don't mind destroying things you made to make sure they are up to snuff. No one should have any reservations buying any knife you make. Great channel. Keep it up.
Question. Would the elevating oil temp throughout the process of quenching cause the steel to cool slower and allow for larger grain size?
Curtis Barkes I was thinking the same thing I’m sure it could play a fairly large role in the results
No, oil temperatures were monitored throughout the testing. 110 for the low and 155 for the high👍
@@OUTDOORS55 right on
if anything, hotter oil would be more fluid and cause the steel to cool faster.
@@Jiminycroquet never heard that.
Do not beat yourself up over testing mistakes. You are doing things that help the rest of us and identifying your mistakes. This is the proper method. Keep it up. Informative and enjoyable
I am not even a beginner. I've never made a knife. I'm finding your videos informative (as much as I can understand). I assume this test proves that a very fine even grain is desirable. Even though you never really came right out and said that. I want to make a FOREVER knife for bush craft. I don't know what steel to use, how to treat that steel - heat treatment, quenching, annealing etc. or even the order in which to do this. I'm 65 years old and retired so my definition of a Forever knife is a knife my grandson can have and use once I'm gone. About all I do know is I want it to be a full tang and the back side of the blade should take a little bit of a beating from a hatchet maybe 3/16 inch wide. While splitting small kindling. I want it to be about 8 inches of usable blade (probably more like 10 inches long with enough left over to go the full length of the knife handle. I want it to take an edge I can shave with and hold that edge for a reasonable amount of time. I'm learning sharpening and stropping and general care for a knife in the meanwhile but no where near the skill level to produce what I want. For me your videos might be a little to far advanced but if you spoke like you were talking to an idiot it would make it easier for me. I don't really expect you to do that because I think you'd lose a lot of your viewers. Lol. Can you direct me (or any of your other viewers as well) towards any of your videos that would help me. I like your style of making videos and prefer if I could stay with you. Does anyone think I'm crazy? Is this a knife I can make - or is it like a Holy Grail. I definitely don't want to buy a knife like this I want to make it. I have access to most every type of tool I think I would need and am even considering purchasing what I need if I don't already have it. For instance a 2" wide belt sander (I presently have a 4 inch wide) Would a 1" wide work? What's better one inch or 2 inch - do I need both? Thanks for reading this tome of a comment and I gratefully thank any help anyone can provide. I live in Allen County, Ohio if there is anyone near me with these skills who would allow me to have lunch with them and shoot the breeze let me know. Even better a chance to see your shop and set up. Lunch is on me.
Just a thought from having a Kiln and modifying it. I used to put in my blades into cold kiln and fire it up with them in the whole time up to 1475. Then I would get lots of decarb. Then I would let it get up to temp (1475) put it the blade let it rebound and time it from the time it got back up to 1475. Now since I slit a hole in my front door I let it get to temp wait 10 minutes then slide them in the slit for 5 minutes.From what I have seen in my testing is the first way is bad because I was putting it the whole time while the kiln was getting hot while the coils are set to max heat or as fast as possible on my kiln which I think is hotter than 1475 that causes grain growth. The second way was not as good because the rebound time can be long and cause grain growth. The last way seems the best with the finest grain I think because when I stick it through the slit without opening the door temp drops a tiny bit and rebounds in almost no time. Check out my last video to see what I mean about the kiln mod. The sweet spot seems to be 5 minute soak time from my testing. I hope you understand my ramblings lol. Also I use parks 50 but with a 7 gallon tank and I have not noticed a difference with oil temp.
Thats interesting info! I was thinking that the ramping up to temp might have something to do with it but wasn't sure. I loose about 50 degrees (if im fast) each time to door opens. And it takes about 5 minutes to ramp back up. I suppose that could have caused the last blade to over heat. I've even thought about over heating the oven 50 degrees over temperature so that when the blade goes in it drops back down to where it's supposed to be. Thanks for the info 👍
Actually putting it in cold is the best way, but if you're concerned about the coils affecting the blade, put it in a tube to shield it so the tube is absorbing the temperature fluctuation.
Nice job showing what diligent knife makers go through to understand the steels they decide to work with. Tested my share, still do, just to make the processes are still valid.
I think there may be a difference between soaking and bringing up to temp. Longer periods of time at the same temp would allow the steel to adjust to the current temp. Maybe try a test where you let one piece slowly get up to 1550 and then the other heat up in about half the time and let set at 1550. Say, If you can control your forge, piece one allow it take 10 mins to get up to 1550, quench. Piece to allow 5 mins to get up to 1550, soak for an additional 5 mins, quench.
The 800 is for 1095 the austenite phase transformation limit, generally you should soak up to 30 minutes for the steel to fully transform to austenite at that temp. This transformation is not fast at all. But huge chunky austenite does not imply huge chuncky martensite, as the quenching is a powerful phase transformation that restructures the whole steel.. I think you are not getting full austenite in your piece and that results in less martensite transformation and more of those nice chuncky grains of perlite (maybe). Going up with temp would ensure full austenite transformation and thus a full quench and less chunkiness.
As to why 5 minutes soak making smaller grains is that again you are having some austenite transformation but mainly pearlite which keeps growing until austenitisation. So with time you get bigger grains of pearlite back, but less of total.
Anyway do a 30 minute soak and you should get the best result.
When you open the oven the temp drops, just like a crockpot or household oven. Try recording sample temps with a pyrometer as you pull parts out and see how much the temperature drops from the first sample to the last.
I used to work for a stress relief company. Heat Treating different types of Steel, we used to start at an ambient temperature and then slowly heat the product to whatever temperature that particular Steel calls for, then there is a soak time again different for each type of Steel. After that we would slowly bring down the temperature over an extended period Of time . very technical and each type of Steel requires completely different heat treating but it always starts from an ambient temperature and slowly Works its way to asoke temperature and then slowly Works its way back down to ambient temperature. All types of Steel , if you want them perfect they require this type of heat treatment.
This is not that.
#1: Every knife should meet it's user's needs. Not all needs are the same. Rigidity is great when rigidity is needed, but leads to unwanted breaks. Flex is great for most knives and will fill the "sharp piece of metal" role that general use knives need. But they take plastic deformation. A flaw, but not a broken knife.
#2: Cut, polish and etch if you want to view grain structure bro!
Thanks for video!
Awesome info!! Now I’m going to have to do a bunch of testing myself. I’ve done destructive tests on knives and it always makes me cringe to put all that work in just to break the thing in half but i think its a very important step for anyone wanting to ensure quality. Thanks again this video was the most informative heat treating I’ve seen on youtube particularly of interest to me because i use a lot of 1095.
Thanks my friend! I agree its a necessary evil. 👍
@@OUTDOORS55 Were do you get your stainless steel foil for keeping the O2 out of the "Quenching"? Think it will work with a atmosphere propane forge or and forced air propane forge? I can run them rich so that I greatly reduce the O2 but was thinking that adding the foil might save me even more addition Carbon content. Thoughts?
Hmm Have you thought about the temperature of the oil you are quenching in ? Each time you quench a piece of steel in that same oil you are raising it's temperature and each peace that follows is quenched in hotter and hotter oil. Oil that's lets say 90 degrees Celsius will quench steel quicker than same oil at room temperature of 25 degrees even thou its hotter. Have a think about that ;)
Yeah, just a bunch of BS. Maybe if you want consistent metal work, use consistent procedures across the entire build cycle including the oil temp you are quenching at.
Thats what i was thinking... evertime he opens the door he will loose some heat aswell...
Kudo's for going the extra mile to improve your craft/product.
However, why not invest in an inexpensive microscope and polarized light source to see what the grain actually looks like? I think you might find it informative, and you can rest assured that your current method isn't actually leading you astray.
Also, it would benefit your 'research' if your method of stressing the steel to failure was more uniform.
idk where you're from but here it's much cheaper to borrow from a local college/ university than to own 1.
@@TheGunz0001 Actually, a 30X or 60X Jewelers Loupe would work just fine. They're not very expensive and it's handy to have around the garage anyway. In most cases you don't even need the polarized light source, just taking the time to file the broken edge flat and etching with a clear acid will reveal detail in the grain.
@@namzarf polarizing filters are also quite cheap and can be used with most small light sources, flashlight included so the polarized light also isn't a problem
Have you considered that (concerning the three initial blades) that the third was quenched after 2 rapid succession "openings" of your H.T. oven. I wonder if you may have significantly dropped the temp off the third knife from heat loss due to the openings/exposure to ambient temperature. Possibly your thermocouple is placed in a bad spot to get accurate temps. I would suggest possibly doing a test of temp loss or general atmospheric condition changes in your oven due to opening it.
Test the oil temp? You quenched sequentially for the first test, which increases the oil's temp, right?
He replied to another comment saying he monitored the temp. 110 low and 155 for the high.
Wow, I remember a couple yrs. ago telling you that you would be a great knife maker,with your knowledge of knives and your enthusiasm. That was a understatement !!! Ive gotta go back and review what Ive missed. 👍
Haha thanks! Im learning for sure!
@@OUTDOORS55 I'm totally impressed, you've made some really good knives !!!
Great dedication to the craft. However, you're not actually looking at grain size. You're looking at fracture surfaces, which generally occur along grain boundaries. To look at grain size, you must polish the sample, apply an etchant, and view under a microscope. Also, a factor that's missing here is the hardness. It's very likely the pieces that were not soaked 5 minutes or more did not reach full hardness capability, which defeats the purpose of a high carbon steel knife. If you're not soaking it adequately to achieve the steel's potential, grain size doesn't really matter. there's a point of diminishing return where ultra fine grain becomes a problem as you lose hardness. I got on the grain size merry go round a while ago too but then I got off after I learned a little more... :)
Theres a lot of factors missing here that i cant necessarily test with my limited equipment. All of the pieces however were saoked minimum of 5 minutes. Theres still a possibility that full hardness wasnt reached. I dont have a hardness tester so i dont know for sure. Thanks for the comment 👍
Thank you for making these videos. Your hard work and explanation on this subject matter is much appreciated. Thanks again
Great video Alex, I'm glad you talk about this subject because heat treatment is what makes a knife good imo.
I studied metallurgy last year and what you say is true. Soaking time increases grain size for simple carbon steels. Alloyed steels can sometimes reduce their grains with soaking time. And the higher you go beyond the critical temperature, the bigger the grain.
What I would love to see is the grain structure difference between a forged blade and a stock removal blade. I have no idea about the result...😅
The seriousness take, and the clarity of steps throughout makes this a fantastic work.
Well don, on looking at every aspect you could, and showing the results.
Great video.
Im subbed because you explain things very well and cover all the things that need covered.
The fact you picked up on your time issues at the end of the video just reinforces how serious you are about covering all your bases.
Easy sub.
Highly recommended.
Thanks for the sub my friend🙏
Remember your phase and TTT charts, specific to 1095. 1095 is a hypereutectoid steel, meaning the carbon above 0.80 (nominal) will not go into solution with the ferrite (austenize). The extra carbon hangs out to form carbides. Carbides are hard, and probably bigger than your martensite grains. Temp and temp over time does promote grain growth, as experienced by your long soak @1475. The 1550, higher temp, allowed for carbide formation, and probably better carbide control and better solution balance, in your hypereutectoid steel. If you repeated your test with a 1075 or 1080 steel, the results of grain growth, you were expecting would probably become more evident. The comment on quench oil temp, being 120, is more about nucleation (bubble formation) at the knife surface. 120 is better than colder, but if you can beat the "nose" on the 1095 TTT curve, your goodto go.
That pearlite nose can be a real bastard thats for sure ...as far as ive noticed about 1500 is the sweet spot for 1095
I have seen issues when quenching multiple blades in a small 1 gallon container. The oil temperature increases dramatically from blade to blade. A thermocouple in the oil would add another data point. On bladeforums, it was recommended that a 1 gallon can of oil might be too small for a blade larger than 7-8" and for multiple blades back to back. At least 2 gallons - 5 gallons was recommended.
I really liked this video you showed that you take real pride in your work
a few books on metals and heat treating would have helped you
but what you did is impressive and educational
it was very cool to be able to SEE what everyone is always TALKING about. awesome!
Wow that's clear as mud. However; my brother and nephew normalize for about as long as it takes to get to tempature, for three cycles and then quench. I'm sure your conclusions are correct about over temp and soak times. Thanks I your videos are a great source of info.
A lot of 1095 shows inconsistent results when comparing it to the data sheets because a lot of 1095 has minute amounts of alloying elements, such as nickel. I have had consistent results when ordering steel from the same company, but some slight variations with others (Amazon was a steel ordering platform for a while). I do not have a temp monitored oven for quenching so I only have results based on "feel". 1095 cools very rapidly so its possible when you are pulling the blades out one at a time to quench, there is a drop and rise in temp for the others. I would be interested to see one blade at a time. In my experience I have not had issues soaking for too long, but I honestly can't think if I have soaked at around critical for longer than 10 minutes, again "feel" sadly I never had a watch near me.
Tldr
Try the soak time test one piece in the oven at a time, might look different.
Yeah not all 1095 is the sam. This specific batch is only 0.9 carbon. Thats the minimum needed for it to be called 1095. Ill have to look to see what other elements are in this batch. I think thats why alot of custom makers seem to stay away from it and use a steel thats more consistent like o1 or cpm steels that give you specific info on heat treating.
Ecspecially like his recommendation of the one at a time soak test
I’m about to heat treat a O1 dagger/chopper and this information is actually really helpful. I was getting a little stressed trying to find a good soak time lol
O1 will de different than 1095. O1 is more resilient to soaking issues.
Love your channel. I’ve learned so much from you. I’m compiling a list of materials to start my first blade.
I just wanted to thank you for taking the time to do all this and sharing it. It was a very informative video!
Thanks! It was a necessary evil so I might as well film it🤷♂️ Thanks for watching my friend!
I'd say the key take-away here is to experiment with HT on small sample pieces before taking the time to cut and grind full-size blades.
fascinating, this is why I love youtube, getting recommended very interesting channels.
Question: heating the oil with every quenching doesn't change the result?
Shouldn't you use a different "can" of oil at the same temperature every time?
@@WaterfieldForge and what oil temperature is better for quenching?
if you want the grain structure to show up better on camera, keep using your good lighting, but in video processing, turn up contrast, and down brightness. great video!
I am very impressed. I love the extra you go to to improve your own knowledge in knife making. Keep up the excellent work man. You are doing great!
I've never made a knife before nor do I intend to. I'm not sure why I'm here but I'm glad I am.
You could make standardized cross sections of the test pieces for future tests and use a cheater bar that has a notch in a specific place along its length in which you could place a spring scale. Do so could allow you to gather some more data out of each test you make.
by reading the book, I have to say a big tank is required and when you quench the knife, shake it. the reason is the effect of quench is the rate of temperature getting down, a proper rate is the key. and small tank would cause the rate down below the best range.
Wow! Lots of time and expense went into this! Thanks for sharing! Can't wait to hear about the "big news" for your channel.
Very cool! I've broken and tested a few of my knives too and just recently started to use an electric forge. The results I get are satisfying. My oven ramps up very slowly and I put the knives in when the forge is still cold, let them soak fo 5 min at desired temp before quench. I wonder how much the ramp speed affects the grain.
I dont know, thats my thought as well.
Very informative video, thanks for opening my eyes to the Variations that can occur! the first thing I'll do now once I get my own forge going is to go through different steel samples and try to find the optimal heat treatment cycle for my work!
I'm a machinist and have done a fair amount of heat treating of various metals for various reasons. I think what Dan Pedersen said was correct, but wanted to add a couple suggestions to help you fine tune your process. Get a hardness tester, and perhaps something to measure torque as you are bending those knives to failure for more accurate diagnosis of what's going on. Unfortunately, my experience is with tooling steels and oddball alloys, so I really don't feel qualified to add specific insight into normal carbon steel. In my personal experience I haven't seen longer soak times lead to bad results. For me, I have found the tempering to be more critical but again, different materials and substantially different thicknesses.
I like your reasoning and scientific approach. I took metallurgy to earn my associates of science for welding technology but remember very little except different boundaries and phases and they analyzed failures (yours being vise angular leverage failure) like you did with your pieces - to see what caused the failure . What I gathered from your experiment was that no matter your soak time or temp - NORMALIZING (CORRECTLY NORMALIZING, and soaking at critical temperature for 5 minutes is the B diggity G) is Mucho Grande Importante! You did great! but the camera to me showed a better grain the farther you went to the left - maybe cutting the pieces would show the grain structure better because breaking the pieces tends to disrupt the grain pattern/structure as it elongates and deforms the end pieces. Great Job and great lesson on the importance of normalizing 1095 and I am sure 1080 would bear similar results. Also testing metals you haven't used before and finding normalizing procedures and critical temps for each new material you use - of course writing down these notes in a knifemakers logbook for future use and less re-googling (is that regurgitation). You are an inspiration on the path to the knife making grotto! I have never made a knife but I should be qualified son with all the different videos I have watched - KEEP Making them!! I copied your pattern on my laptop screen enlarged - maybe I will be ordering 1080 next.
Here are some reasons for your test inconsistencies:
1. Steel is cooking with variable temperature and variable time.
2. Water temperature varies between quenches.
What this means is, you don't know if it is the cooking time, the cooking temperature, or the quenching temperatures because water temperature rises and falls between quenches. There are three factors here that need to be addressed and each might compound the other.
Proposed approach:
1. Cook each piece of steel separately for the same amount of time.
2. Check water temp before and after quenching. Use the same water temp for each quench.
3. Check results for grain growth.
Repeat with minor adjustments to cook time, cook temp, and quench temp. Change only one factor between tests. Then you'll know which causes the most grain growth.
Excellent practice to record as much data as possible for times like this. Especially something like heat treatment with so many variables.
I think a recall is in order, to be on the safe side ;)
I would love to get as involved into knife making as you are now. At the moment I just make a blade, heat treat until it gets to the color I think it should be and then I quench immediately lol. My edge retention is impressive in my opinion considering I've dulled store bought knives a lot faster than my own. I've also never broke one of my own blade (on accident). Hopefully some day I can get a set up similar to yours! Great video as always
Yeah this is going in depth (at least for me). Any of these pieces or knives would have made great blades for the most part. They just wouldn't be as good as they could be🙂 Thanks my friend!
What about getting a pocket microscope? Its about 20$ and u can magnify up to 100x. U really see the grainstructure with it :)
just some passing observations: the opening and closing of the oven door could play a factor. also, iv seen a number of comments about the oil temperature going up with each quench and that does sound like a potential issue.
the last thing would be sample size. just using 1piecee of steel to test each variable leaves a lot of room for error.
still, its a super cool video :-D
scrolled down to see if anyone said this. In the first test there is some thermal cycling going on each time the door is opened, In the last test no thermal cycling is occurring.
Mech E here, though not MSE so it’s not my particular expertise.
Some thoughts:
Normalization would likely refine the starting grain structure and help prevent grain growth despite extra soak and temp. Perhaps try the temp test on non-normalized samples to find out. This might be a lesson in normalization prior to heat treatment for consistent safe results. Also, the thing your looking at isn’t actually the grains (would need a scope to see those) but the fracture mark size. Regardless the interpretation of the visual gives the intended result. You want a single consistent failure across the material, not random low stress failures that increasingly weaken the material.
Also: oil temp inconsistency may play a factor, though I wouldn’t expect it on such small samples unless the average oil temp rose 200+ °F... But maybe it did?
And they say you dont know what you are doing. Well done and very informative!
Very interesting. Thanks for sharing this information Alex. I hope the channel doesn’t change too much. I kinda like it the way it is. Keep up the great work my friend. 👍🏼
Maybe some new faces and a new location 🙂
I'm not sure but I think you need to reach austenite temps before the grains can grow. I think you can keep steel at below critical temp for a long time and not see much or any grain growth.
Other advice I got was to get the oven to soak temperature first and run it for 20mins or so, then open door put blade in, close door. Start timer clock once temp has come back up to soak temperature.
Big science in a little shop, BRILLIANT. Thanks, and I’m in.
Grain structure and shepherd grain baby! This is why it's important for all companies heat treating steel products in general to check surface hardness and do break tests
Really surprised I haven't seen any knife makers on here do any cryogenic hardening.
I just forge welded 30 layers of 15n20 and 1090 with a core of 1.25% high carbon steel. Def running heat treat retaining some austenite, slowly dropping temp of said heat treated blade down to -300F and holding will boost martensite and eta carbide formation significantly.
check out he oil temps, soak time seems as important as quench temp. room temp oil cools the steel faster than oil that has temp raised after several quick succession quenches.
Only thing that I could think of would possibly be your oil. If you are quenching piece after piece in the same oil then the oil would be significantly hotter than it was when the first piece went in. I'm no expert but I've heart that having your oil to hot can have adverse effects.... Hope this helps in some way.
I love how methodical you were.
i once unknowingly compleatly overheated a O1 blade and soaked for 30 min. it snapped lilke a twig and the grain were in the 100 µm scale, visible with the naked eye.
I made a small knife using 1084 steel. When it was time to heat treat I made a fire bc i dont have a oven yet. I threw the knife under the fire and let it stay there. It was in the fire for a great deal of time but it didn't turn orange , but I decided to quench any way. I quenched it in a water cup with water, mom wasn't to happy about the cup. But any way I put it in a vice to finish up wen the blade simply broke off. It did have a large warp in it but I noticed the blade was extremely grainy inside. Huge grains wish I could show u. Not quite shure how this has happened
I know for aluminum there’s a peak temperature and peak time that’s best for hardening. As you get away from that time/temp, more or less, it won’t harden as good. Interesting video!
Thanks! I dont know much about aluminum but I believe it's quite a bit different than steel in that regard. 😀 Thanks again my friend 👍
The only mistake I can see is in your last test you didn't start at 1200 and go up to 1575, as you did in the prior two tests. Otherwise, very well done. I think your conclusions are spot on, and the added info from Lucas Kramer below is important as well.
As for the heat treating multiple items: industry does it all the time. They just make sure that their ovens can handle the mass of steel present, and hold the temps. As long as your setups can do it, I can't see how multiple items (unless you stuff a few dozen in there) would be a problem.
Once again, fantastic video. Thank you. Subscribed.
You cannot see grain structure with the naked eye. Grain size is measured in grains per micron. What you are seeing is conchoidal fracture.
Hi Alex.
Maybe the problem could be secondary recristallisation. I'm a maschine engineering student and we talked about this in our material science class. As far as i understood, secondary recristallisation is the growth of some grains at the cost of others. This can occur on small wall thickness, sharp textures and fine contaminations inside the metal. This is all just from looking in one of my books and there will be a lot more behind this (probably temperature in heat treatment)!
Maybe you can find some more info on this toppic.
Greetings from switzerland
Yes i don't believe i have the ability to figure this out based on what i have available to me. There are some other theories some other people have left as well. It's difficult to make a determination. Thanks for the comment 👍👍
If you leave them in the oven too long you can get segregatiom of the impurities at the grain boundaries due to the high diffusion rate which can cause drastic changes in the material properties of the metal
I think like this guy. I tested in my wood shop the most common ways to assemble a ply wood box for a cabinet, and knocked them apart with an ax. It was clear: glue or rabbets or brads are not nearly as strong as properly drilled wood crews.
Also, for the 10 series, from about 1050-1090, I've always been under the impression you always should quench at the lowest transformation possible to prevent martensite formation. The other big thing, is the temperature of the quenching medium, which might be playing a factor here.
During your tests, were you maintaining a set temp of your quench oil? Itll have a massive affect on crystalline structure.
It's been a while since I've read up on it, but martensite, to my knowledge, is a larger grained, unrefined extremely brittle grain structure that can add inconsistencies in the temper.
0:58 does anyone know what song that is? Shazam says it is Spirited Away by Bernstein but I can't find the specific part of the song he used in this video :( EDIT: Found it!!!! IT is called ALLA HJÄRTANS SWAG
You may consider smoothing, polishing, and etching the broken surface to get a good view of the grain structure.
It is generally difficult to actually see the etched grain structure with any level of accuracy without a metallurgical microscope.
For a layman like me, oh, 3 good knives had been wasted! But I understand also the need to investigate more for ensuring the high standards of what you make. I'm just thinking what sort of practical use of the knife that would require such abuse. It's like expecting a car to perform like a cargo truck. For my intended use of the knife, the 1st one you broke will already make me a satisfied customer. The other 2 maybe good enough already for fighting swords like a Katana. Good job you did.... I am more educated now than before about knife making. Thank you!
here's my guess toward why you found what you did toward the end. im a welder (well was) and back when had to do my cert test my teacher taught me to always air cool the plates. why because the grains are more solid and longer this way. so my best guess is leaving the metal overheated for 15 mins allowed the grains to have a similar effect as air cooling. though this is a just a blind guess and i haven't checked my metallurgy books in yeats
It shouldn't grow the grain for a 10 minute soak, maybe lower your temp by 25 degrees and try this test again? (quench @ 1450). I actually do heat treat 1095 in my forge, I am quenching in Parks 50, but I can cut through nails with it. I know it isn't 100% optimal, but it still has excellent results.
and you are right, in a forge, temperatures are hard to tell just by color, a good rule of thumb for me has been heat treat when it is pitch black, and when the steel reaches nonmagnetic (1414 F), and then go a shade brighter. (about 75 F more) and then quench.
also, normalizing can help keep grain growth small as well, even when overheated for a short time, that may be why when you quenched the test piece at 1525 F and it was still fine grain, but not so in the 1st batch of testing.
I recently made my first knife and it cracked on the heat treat , but I think I have learned a lot from it and I'm now attempting my second knife
ive only had one blade crack during quenching. Guess ive been lucky😂Thanks for watching my friend!
12:05 - 1425° to 1475° has 50 degrees between them but then, (12:16) at 1550°F you have added 75 degrees, doesn't that skew the results a bit?
Good video, the art of forging. Murray Carter also explains this well in one of his videos.
“I put my ENTIRE 150lbs on them” 🤣🤣 Great video man. I am really enjoying your strength test videos. Being a total amateur knife maker, JUST getting in to the hobby, these have been very helpful.
More time in the heat does enlarge the grain,and increses decarb....I would even leave them litle bit harder(less tempering) but that depens on the useage of a knife....
try cooling the metal in 900dg lead, this might give the metal more time to organize. also try running a little dc through the molten lead to help organize the structure. just some odd thoughts. careful with the lead, it can mess you up
Great vid man very informative. I’ve been making knives for only a year now more for hobby. I know the heat treat process is important, but who is actually going to pound on metal and try to cut logs with a knife? My question how much effort should I put into the heat treat if I want to start selling knives?
it depends on what you want to sell? top knotch knifes at a premium price or just nice knifes for a reasonable price but not as good as the first. Also depends on what kind of knife you make, a thick sturdy knife like 4mm or so probably has not that much to fear of a less than ideal heat treat, but if you want smaller knifes bending and breaking becomes much more of a thing to consider. in my opinion one should always try to get the best results, or at least with the options given to you to produce the quality you want. Everyone can buy some chinesium steel and make knifes. Good knifemakers make knifes that cut through chinesium knifes.
I don't use 1095 because minute differences between manufacturers makes it so picky. It is supposed to be taken up to 1500, 1500 is supposedly 1095's sweet spot. Then I've also read 1475, but I have always gotten differences so I never use it. I use O1 and it heat treats very consistently and I make certain I always get the O1 with the 0.2%* vanadium which at that small amount doesn't make carbides, but GREATLY restricts grain growth. Plus O1's sweet spot is 1475 for 13-15 minutes to get the half a percent of chrome and tungsten into solution. O1 also benefits from deep cryo if you already have it sitting around, makes it tougher. *some is 0.1%, it still works.
Another one of the reasons I only use O1 tool steel for non-stainless knives is after quench for about two to three minutes you can straighten the knives by gloved hand in the vise. It is the only steel I know you can do this with. My O1 knives I grind the main bevel all the way down to about 1 mm, little less because they are so easy to check and straighten. I also only do 4 knives at once because quench oil gets hot and the soak time doesn't go past 15 minutes. O1 needs a 12-15 minute soak time at 1475. The 12 minute soak is for 3/32 thick knives, 3/16 can go 17, but I rarely use a steel that thick. I know the book says 10 minutes for O1, but that's for O1 without vanadium, just FYI.
During your ht cycles with so many knives did your quench oil rise very much in temperature? I use canola oil because it's cheap and Parks 50 is a little too fast for O1. I start at 120 degrees and stop at 135 degrees (4 knives) or else my HT suffers, the knives don't harden as hard. Plus there are other issues too complicated to get into about martensitic to austenite processes etc etc. Suffice to say that you try and HT to get the best you can and you want every parameter to be where its supposed to be. Like don't leave your 1095 knives in past their proper soak time unless you're raising the temperature.
About myself, knife making is a hobby I've done since 1992, but I was a heat treater in a machine shop for several years as a young engineer working towards my masters in biology. I also do leather work since my knives needed sheaths. I found I like leather working more than knife making and will make a belt to match my sheath. I have been retired for 10 years.
You should run this test with 1080 and see how it affects Perlite formation.
Maybe the grain size is increased if the metal is soaked in the same temperature for long time, but the change in temperature causes the process to reset. In other words, maybe the atoms are aligned unfavorably if the material is heated longer at the same temperature, while changing the temperature cases them to realign
i think the temperature of the oil may have something to do with it as well. by the time you get the second and third pieces of steel in the oil will be nice and hot compared to how it was with the first blade.
crystal growth temp and smelting temp of the steel might be the reason of the inconsition you see. im thinking just like salt and bismuth the temp makes crystals at lower heat then the smelting point and if you quench both salt and bismuth wont make crystals as they normaly do, in other words you probaly just hit the minimum heat for your iron to remelt.
Try the difference between an as sending and a dessending heat for your quench .
I thought about that exactly. It's definitely something im looking into👍
by not quenching in the same temperature oil for each piece you change two of your variables to know it is the soak time the oil needs to be the same temp for each piece
Been going through some heat treating science at work. Our engineers have found for aeronautical use, direct radiation is causing issues when tempering. Suddenly, all our furnaces are bad.
Direct radiation from tempering?? What kind of temperatures are you dealing with?
Were you using the same quenching bucket? If so then the oil will have increased temperature with each quenching, thus reducing the cooling effect for each piece.Thus, last steel receiving the least effect of the quenching. Just a thought....
Also grind the surface of the specimens fine, acid etch and view under a microscope for grain structure...
From the beginning I thought the test was flawed because you weren't using the same temperature oil every time, the oil tape is going to rise each time you quench something else into it so you would need an oil quench sample for each test subject to keep your control group the same
Very interesting. I had a knife in chinesium that looked just like that when it broke. I would assume that the metal itself was not high grade, but also that when mass produced the blades just go through one heat treatment and causes the metal to be grainy overall.
G'Day,,After watching you Film,,I Have had problems with parent metals not being the same all the way through,First hurdle,,The other thing is quench liquid temp,
now depending on the original steel,,different Heat treatments are recommended,have seen a full furnace go to scrap because of over heating,,maybe 50 ton of high quality scrap,,
for example when making steel grinding balls,,they air cool and then quench,,but quenching water is at 50 c,these balls come hard and tough,
Now in the rod mill,,the quenching process is highly adjustable,,have seen rod from mill go through the tying machine and turn to dust under 40 ton pressure ,wrong cooling schedule,
it may be to your advantage to test each piece before manufacture of blade,,
Sorry for the long winded comment,,and late viewing,,But i do like the way you went for it,
I think a statement you put in text on the screen near the end sums it up best. Don't do more than 1 blade at a time. Not saying I know anything. I know I do the best job on 1 thing. Rather than more than one thing. Might be the same for the forge. Is this metal all from the same purchase? From the same company? Just thinking not consistent metal through out. Or even just a bad batch of metal. That would be saying the problem wasn't your fault. I just end with more questions than final thoughts. Still a really great video. I did enjoy the experiment you did. You explained it well. Sometimes in doing something their isn't an answer. You might repeat that and get a different outcome. Your work is great. Keep up the great work. 👍😁