Can a Metallurgist Heat Treat with a Forge?
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- čas přidán 22. 09. 2021
- Written article that corresponds to this video with more details and full citations: knifesteelnerds.com/2021/09/2...
Previous video about how to set up steel properly after forging before the final steps of heat treating: • How to Thermal Cycle K...
Former gunsmith, blacksmith, knifemaker here... with machining and metallurgy schooling (but no degree)...
Just from an amateur guys perspective - you're right on. A furnace is better than forge. But, us hobbists can't often afford a furnace.
I got "OK" at forge heat treating. Not great... but OK. I know the camera distorts color, but from what could see, your forge was not an even temperature inside. Also you have that "hot spot" where the burner came in. My forge (back before I blew out my shoulder and couldn't swing a hammer any more...) I'd do forging for a few hours, then when the entire forge was preheated as evenly as I could, I'd do my heat treating. Getting the entire piece EVENLY heated was a challenge... I learned to stay AWAY from the burner, and heat my piece in the areas of the forge out of the direct blast from the radiant heat of the bricks, without touching them. That worked best for me.
I never had the inspection tools (after I finished my metallurgy class) to properly study my results, but, the blades I sacrificed with a vice and hammer, and files... I think I mostly got the hang of it.
All that said - I'm a nobody, and there are bladesmiths with FAR more skill than I ever had at forge heat treating. Most of the good ones would agree that a furnace is better... if you have one. They could heat treat in a forge better than I could with a furnace, though.
Came for the thumbnail, stayed for the knowledge dropping.
Hi, Larrin (I'm DW on the bladeforum post about knife steels) and have peppered you recently as I've been ironing out what I'm seeing from the forge. I ultimately resorted to torture testing chisels (which is what I'm making vs. knives) and breaking quenched samples to make sure they're finer grain than commercial files.
I think there's an important thing to in this case that I see a lot of folks don't have. A magnet is important to understand where steel goes nonmagnetic, but then the forge needs to be somewhere that the light situation is the same every time (no sunlight, doesn't need to be in the dark, but can't be with a bright light shining into the forge). More importantly, a hot source in a forge with the ability to move steel to get even color temperature is fairly critical. Forges that make a lot of heat with no ability to move steel back into the forge to a cooler area to even out the heat are problematic, and attendance while heating is important. So, that ends up being instead of having lots of burners, a burner toward the front of the forge and nothing in the back other than retained heat (so the back is cooler than the front - otherwise you have to pull the item being heated out of the forge and that's a problem for obvious reasons - it'll just cool quickly.)
refusing to buy parks and then trying to heat things like 1084 in canola is another thing I read a lot about. Any small problems that I was dealing with went away after switching from preheated soy oil to parks (26c3, 1084, 1095, etc.). Interestingly, you can heat XHP in a forge if you have a good enough heat source and just heat it *really* quickly and quench in soy oil and it seems fine. Any more than the shortest time in the heat and it ends up being chippy, though.
This is of particular interest to me because I know now why you said not to use a forge to heat treat, but I don't want to buy an oven. If you test samples for a fee, I'd love to send a few to find out what I'm really getting - with the steels mentioned above, I don't see any shorcomings. With 52100, since I'm not normalizing, but rather thermal cycling and then heating and quenching, I don't get quite as fine of grain, but it's still absurdly tough (for woodworking). It may not be tough enough for competition knives.
I test toughness coupons for free as long as they are ready to test and I don't have to machine them.
Dude, this video is fantastic. I already read your web-page about this particular topic of heat treating in a forge (among many others on your web page), but this is the first time I've watched your videos. Excellent content. So many "instructional" youtube videos are just filler crap with sprinkles of new or useful information. (So many youtube videos also have no new information as well.) Your entire video was pure information. Excellent work!
More content like this please. I would also love to see tests of tuff simple steels run higher in hardness and tested for edge retention (say 8670 or 5160) where the toughness at higher hardness is still equal to that of 01 or 1095 and see what the edge retention is.
That's one thing that jaw dropped me looking at his site.. most premade knives even in 1095 are tempted to.. like 58. 1080 at the same or harder would be even tougher.. and a better blade overall since there's no carbides coming into play here.
Thanks Larrin this is a real game changer for me. Now I can put out a quality knife and quit with the guessing. Wish I knew this years ago. Thanks again 👍
Absolutely great video and great summary on the topic! Thanks Larrin!
You are really fantastic at explaining! You make these pretty complicated facts very easy to understand.
Good job Larrin.
Really appreciate your content and insight from the scientific realm Larrin, thank you!
A lot depends on the kind of forge one uses.
A Venturi tube forge, especially with the burner mounted on top, would be very hard control precisely.
A blown ribbon burner forge with the burner on the side allows for a very good temp control through a wide spread of ranges, and a very good temperature consistency throughout the length of the forge, especially if baffles are used. A pyrometer can be used to really dial in the air and gas settings, so it’s a simple matter of selecting the right settings for the proper temperature.
Your videos are incredible, i really hope you keep creating content. For newbs like me, the information you provide is invaluable. If you ever have an inkling to do a video about quenching in motor oil ( i know..) Id love to see it. Keep up the great work, love your book!
Excellent! Thank you. Now to rewatch so I can get a better grasp of the graphs! :)
This is excellent content, looking forward to more.
Great work Larrin. Thx!
Thanks, man. I'm a big fan of your website, too. I'm hoping to build a heat treating oven one of these days, but it's been the forge for the last decade or so, and it does a passable job. Your video gave me some confidence that it can be made to work with some care, and also some reason for believing I'll get even better results when I build my oven.
Can't say I've tested this extensively, but I have the best luck keeping an even heat across the blade by heating in about 5 second increments and then pulling out of the forge to let the heat normalize across the blade. The thin sections and tip always get hot first, but if I do short increments like that, I can keep them from getting too much hotter than the rest of the blade. Check with a magnet often and dunk as soon as my whole cutting edge is non-magnetic (sometimes the spine is still sticking a bit at this point, but that's possibly even a good thing).
The ratio of views / information content is woefully small here - such a brilliant channel. Wish I could afford a furnace - don't even have 240v power in my garage for one.
With all your research and the fact I mostly heat treat with a forge AND use canola for quenching; I'm surprised my knives haven't been torn apart yet!
Great thumbnail, you are learning the ways of CZcams well young padawan!!!
"... it's more difficult to cook a brisket than it is to heat treat steel in furnace...so I would always..."
I thought you were going to finish the above phrase with "... choose the brisket"!
I'll use a muffle for my wood burning "forge" (hole in the ground) but I am happy to know that I can get good results!
I always had really mixed results with a forge, most stuff usually turned out ok but when I was first starting off there was also a level of anxiety about it that was also hard to manage seeing many hours of grinding and shaping turn into essentially 'knife shaped crap'. Would still use a forge (and thermocouple) on some simple carbon steels if I had to and my kiln was broken, but I still much prefer the precision of that machine even for the carbon steel knives I make.
You must have known that I was wearing my KSN shirt today!
Thanks for sharing 👍🏼 😊
Would have been best to do this same experiment with a choke as it is something easy for a beginner to add to their forge. First knife I heat treated was in a coal forge using a scrap piece of 2.5" iron pipe and a cap on one end. Much easier to keep temperatures even and prevent over heating.
Yeah this is pretty much a summary for my W2 heat treat. It’s a simple steel, hypereutectoid. I forge most of my knives so the very high heats dissolve any kinds of structures present in the factory annealed condition. Normalize twice just above non magnetic, do a simple sub-critical heat for stress relief... heat up to non-magnetic in my charcoal forge and into the brine. I’ve sent pieces to a friend who has a machine shop for hardness testing, and I’ve never had a piece test for less than 66rc like this.
I prefer my salt pots over my forge for any accurate heat treating. That being said, and this may be controversial, with your set up I would try a triple quench, quenching as soon as my coupon got to temperature to prevent over heating. Thanks for the great video.
I keep coming back to this video just to soak (no pun intended) everything 'til I know it by heart.
Thanks Larrin!
I don't have the price of a furnace so I use a forge and a muffler. You still have the issue of doing your best not to overheat and playing the blade in the flame or I should say in the hotspot but the temperature change is slowed down a bit so it's a lot more controllable especially if you got Square Tubing in there because the bottom of the square tubing is usually cooler thereby assisting in keeping the thin edge of the blade cooler than the back with your trying to heat up to the point where it's non-magnetic. By the way thank you for explaining the difference between normalizing and annealing. I knew normalizing was going to give me a finer grain structure and overheating was going to increase the green structure again and that annealing only needed to be brought up to the point where I was getting the proper color preferably in the 13 to 1400 degree window or more specifically to the proper color Like Straw
An oxy acetilene torch works for me. It gives me control of the flame. It takes skill but the consistency is better than that of a forge, but of course it is not a matter of applying heat with the instrument. A proper setup ir required. You need to move the blade and the torch; and direct the heat in the correct areas of the blade. You also need to have a way to surround the blade with heat refractors ( like bricks). You have to spend the same time on each face when heating the steel to prevent deformations.
So, oxy better than forge but of course inferior to a proper furnace. ( I know this video is old).
Man, heat treating in a forge is hard... I still mess it up. Different lighting alone can make it difficult. The power of your forge, I think, can also make it difficult since a more powerful forge will overshoot your temp faster. While I've had good success with the 1084 knives I've heat treated in the forge and tested; the variability with the forge still brings in a risk of sub optimal results. Different knife thicknesses can throw you off too; if you're used to say 1/8'' stock and HT-ing a 3/16'' knife. All of these "not knowing for sure" feelings is what influenced me to build a heat treating furnace. After watching your videos with the data presented, I'm happy I did! Cheers sir! 🙌
i find using a PSI gauge helps with forge heat treating especially with the Atlus mini forge. i upgraded to the larger gram forge. a thermal cupler(i am likely not spelling this right and it will which will get eaten up fast by the propane environment) or a temperature gun helps. my TG takes a few seconds to get an accurate read so i tend to have to go into the forge a few times but i still get my blades hard.
A trick for a forge. Table salt. Read up on it.
@@m4rvinmartian it melts at 1472F however like with a Tempilstik you do not know if you go over 1480F do to a moment of inatentiveness. the range of hardening steel is generally 1450-1480F for low alloy steels like 1075 or 1084. you can still over heat the steel a bit using the method. it also does not help with stainless steels like AEB-L which requires astinization at 1950F. as Kevin Cashin says in his official heat treatment video there is no foolproof method to heat treat steel (in a forge).
@@gundanium3126 If we are going to talk inattentiveness... this entire conversation collapses.
With proper Air control i can hold the temperature with a propane forge with in 10 degrees of fluctuation with a hold time. I also use a k-type thermocouple and a magnet together with a pipe. I do have a even heat oven now but I do miss heat treating in a propane forge for some reason lol.
I only have visual cues for a forge, but don't have a heat treat oven yet (and the thing that may flip me over to getting one is the fact that I could also kiln house made pencil leads in one - they're basically a ceramic). It's possible to get extremely fine grain and good toughness with a forge by eye, but I generally cycle steel just prior to the nonmagnetic transition to get it (it takes some repetition). My thermal cycling forge is literally a large exhaust pipe (like semi size) with two propane torches and refractory blanket - so that there are cool and hot spots in the forge to move the steel if it's heating unevenly. I have a "real" stainless forge with two vertical burners (propane), but it makes too much heat and it's harder to get a really even job.
Mill file from the factory (Generally very fine) - magnified about 50x.
i.imgur.com/CgnLghi.jpg
magnetic to nonmagnetic 1095 thermal cycling (three times)
i.imgur.com/CgnLghi.jpg
And the same process with 1095 by eye (and with a magnet) with a partial quench between heat cycles (three and then heat and quench)- but in this case, quenching just before it would generally (by color) lose magnetism. Heat then, as larrin says, nonmagnetic plus another step (but not long).
i.imgur.com/fAEI7Xk.jpg
Fine edge abuse testing with woodworking chisels shows correlation between fine grain and better fine edge holding (not much of a surprise). The second type sample can be brought back to look like the third with several cycles. The third sample also was forged prior to the thermal cycles, but forging and quench without the subcritical cycles doesn't do quite as well with fineness or fine edge holding.
The draw to doing this in propane is the subcritical cycling only takes a couple of minutes and it's engaging.
(Tried convincing the mrs. that we could kiln pottery in a knife forge, but she didn't go for it!!). Will eventually practice ask for forgiveness instead of permission.
Another great video. Have you ever considered doing a Q&A video? Soon I will have 2 PID controlled salt baths for heat treating. Any suggestions regarding the soak time needed? I ask because I assume that the mass of the hot salt would reduce the time it takes for the steel to come up to temperature. Thanks.
Recommended soak times are supposed to be for after the steel has heated up, so the decrease in heating time for the steel in the salt pot doesn't change things too much. You could experiment with shorter hold times but without toughness measurements it would be hard to know if you have made an improvement.
@@KnifeSteelNerds how about a Q&A VIDEO?
I really wish I could afford a furnace right now. I don't care very much about the simple forging steels, and have been fascinated with the applications of higher alloy tool steels in knives for a while.
I'm currently trying to make knives with a2, cpm d2, and cpm 10v with a forge to use for my heat treating. I have an infrared thermometer to use, but even with that, I know I'm just not going to be getting results like I would with a furnace. Still. It won't stop me from trying.
Larrin, thanks for all the knowledge you share. I do have a few questions that I believe you can answer. I really like 8670 steel. I noticed the HRC you heat treated it to was low in my opinion. I personally get 62+ HRC and still have a very tough blade. I quench at 1600 in parks 50. I believe that the edge retention goes up a lot with a 3 more HRC points. I also think that 8670 modified with .1 percent more carbon and a very small amount of vanadium would be the best forgeable steel with the best balance of edge retention and toughness. Any thoughts on this would be greatly appreciated. I like everything you do. Keep at it
I have a separate article on heat treating 8670: knifesteelnerds.com/2021/04/26/how-to-heat-treat-8670/
@@KnifeSteelNerds I've read it multiple times, I don't think you understand what I was saying and asking. Is there any way you can heat treat 8670 to above 62 HRC when you do your next edge retention test. Also you never answered what the effects would be on 8670 if you simply added just a very small amount of carbon and vanadium. I know you are pursuing the "perfect" carbon steel and have a some prototypes. Forget everything your PhD has taught you and try what I said earlier
Hey Larrin, thanks for all this great information! I may have missed this but did you normalize the steel in the forge as well? I saw that you recommend ten minutes at temp for the normalization process so I assume you did that in the furnace? Is it possible to get to a pearlite state with forge normalization? Thanks!
For normalizing in a forge I prefer to use a laser thermometer or a tempilstik and go ~50°F hotter because of the lack of hold time.
@@KnifeSteelNerds Awesome, thanks!
This guy is awesome
Hi Larrin
Thanks for taking the time and sharing your findings,can I ask why a second temper is necessary on most steels.
Reason I am asking I work with RWL-34 a lot and its a real nice steel to work with,I have got to a recipe for a 59hrc which is my target,but achieved by only one 2hr cycle.after many test cycles.
Regards
Davy Thomas
During tempering retained austenite can destabilize and transform to “fresh” untempered martensite upon cooling to room temperature. The second temper is is for that new martensite. Certain steel-temperature combinations even require 3 or even 4 tempers. For certain scenarios no RA will transform but a second temper is safer.
Thanks for sharing Larrin. Question if I may though, does the forging (hammering) add any value in grain refinement leading to a better product? Being older and remembering buying tools that were drop forged vs ground and heat treated for strength. That would lead to forging a knife first then heat treating in an oven for the best product.
Forging can lead to grain refinement, however with knives the temperatures are high enough and the reduction small enough (especially the "rate" of reduction), that grain refinement would be minimal. The high temperature is more likely to lead to grain growth than the forging to refine it. In industry when they want grain refinement through forging they perform "controlled rolling" with specific temperatures and degrees of reduction. Often with specific alloying elements like Nb to prevent recrystallization and grain growth.
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Alpha Knife Supply’s website says to heat 1095 to 1475 and quench, no soak time. Is that acceptable to you? Lots of people say to soak 5-10 minutes. Thanks for the help!
would you recommend using a square tube in a gas forge? would the temperature distribution be better as it does not directly blow fire on the blank? I cannot afford kiln hence the question
Can you try this with a muffle or pipe. I think the hobby population is mostly interested in getting the best heat treat technic using a forge. As we wouldn't be investing into a oven at any foreseeable point.
I used a tube on my charcoal forge and had pretty even, steady heat... I use a box blower so the rate of bellows equated specific temperature... Way too time consuming though and i have a kiln now for more control and efficiency... Quench oil question: does quench oil get worn out so to speak and become less effective over time and use?
Canola oil goes bad. Commercial oils last a long time.
A query from a fellow metallurgist with a heat treatment background:
Does the gap between the Curie point and critical temperature alter with alloying?
Yes, gamma is always nonmegnetic. But there is the region that alpha is still BCC but loses its ferromagnatism (where beta iron was though to be). I'd have though that relying on just a magnet would leave you at slightly too cold a temperature.
Perfectly happy being wrong though. It looks like you got decent enough results regardless.
(I am jealous of your set up. Smithing and knife making is something I'd love to get into myself when time and funds allow).
The curie temperature can change with alloying. As far as I know all high carbon low alloy tool steels transform to austenite at a lower temperature than the curie, assuming a slow heating rate.
@@cubee2006 That would explain the good results.
I've never really had to consider a steel's magnetic properties in detail so I've only learned about the curie point and 'beta' iron in relation to pure iron not steels.
Whilst this information is extremely beneficial and I certainly learned a lot.. It really doesn't benefit the forge heat-treater. The whole premise of this video is to show that soaking isn't needed to reach full hardness with a said steel. However manufacturers only sell blanks in an annealed state, not normalized. So, if I'm required to soak my annealed steel at an unknown temperature somewhere above non-magnetic in order to normalize, does this not put me straight back to square one, and negate the whole purpose of this demonstration? How did you normalise your steel for this particular video? I can only assume it was in a furnace. I'm not trying to be a hater. Your videos are extremely insightful and I've learnt more from a handful of your videos than I have with hundreds of hours worth of other videos and scrolling forums.
The normalization temperature doesn’t have to be exact like the final austenitization does. You can watch my thermal cycling video if you want to learn more
Isn’t the curie point lower than the austenizing temp?
Are you saying a "soak" time is not needed? Just get to non magnetic and get straight to the quench?
If it has a pearlite starting structure then it can be done without a soak
can you review about how blacksmith in 3rd countries heat treat leaf spring blades?, like when they make machete, kukris and such
I know this is probably a dumb question but I haven't been able to find an answer to my question. Say you take a production blade that's treated to 56 hrc, can that treated blade be heat treated again to a higher hrc? If I sent an m390 blade that's at 58 hrc to someone that does heat treats, could they redo it at 62? Or is it a one and done scenario
Has to be annealed first and then be HT again.
For some steels yes, though as Mountain Fisher said for something like M390 it would be best to anneal it before re-austenitizing/tempering.
As a new knife maker I originally started using 1084 steel. I then switched to 8670 steel because I was informed it did not need normalizing but rather just heat to 1550F and quench. Is it correct that 8670 steel does not need to be normalized? Also when heating 8670 for the quench cycle should it be heated only to non-magnetic then quenched or heated to 1500- 1550F then quenched? Thank you.
What is normalizing?
@@xlargetophat It is a heating and air cooling process you are supposed to go through at least once before heating and quenching for hardness. I was using 1084 steel which requires 1 normalizing cycle before heating and quenching. I changed to 8670 steel which has similar properties but no normalizing cycle is required according to my steel supplier....just heat and quench. Saves time and propane for me.
@@glenpaul3606 do you know if that's true? Skipping the normalizing on 8670? It doesn't seem true because it's a way to save a buck.. but I'm fairly new to this.
I think the common way for quenching is heat to 1600° let air cool, then heat to 1500 then quench. At least for the 1084
@@xlargetophat I spoke to Pops Knife supply and they confirmed 8670 does not need normalizing....that's why I switched from 1084. Made 25 knives with 8670 so far with no problems. I've only been making knives as a hobby for about 18 months...a lot to learn but I've done a lot of research too.
What about S7 tool steel?
"wait whaaat you can heat treat with fire like it has been done for 2000 years??"
"wjat do you mean it takes skill to manage the température of a fire, isn't it just typing a number on a screen?"
czcams.com/video/oboVGIDSf3E/video.html
Use pressure gauges and control your temperature.
The pressure was set to as low as the forge could go without having problems.
@@KnifeSteelNerds In our forge we used compressed air and propane and it was big enough to control the heat within 50 F. Used Tempil sticks at first then bought a thermocouple. A venturi setup gets too hot.
@@MountainFisher or just use a digitally controlled electric furnace BOOM!
@@FearNoSteel My brother owns a Blacksmith and sheetmetal shop in Calif. Initially he used a coke burning forge and I told him to build a forge, so he did, 8 inches in diameter with a 1/4 floor. It had two burners set to blow in a circular flow and was 24 inches deep. Doors on front and back. At first he used a simple venturi setup, but wanted more control as well as use less propane. Remember this was not a knife forge, but a Blacksmith forge for twisting and bending 4 inch square bar and even larger.
The heat treating knives came later and was my idea not his. Knifemaking is my hobby, he made a few, but mostly axes out of 4140 with a piece of 1/8" 15N20 forge welded into the center after folding the bit side of ax. How would you like an axe made out of the toughest steel there is at HRC 59/60? Toughness on the Charpy Notch test is 150 foot lbs at 59 hard, but drops to 80 lbs at 60 hard. S5 shock steel, an old high silicon tool steel.
The best advice I can give anyone heat treating with a forge is get a pyrometer. If you can't afford a heat treat kiln, controlling the temp on your forge is the next best thing. A high temp thermocouple and something to read it can be had for about $50. If you want to make good knives, it's a great investment that will vastly improve the quality of your heat treatment.
I'm still coming back to this video to figure out what I'm missing... My name is Can't Get Right after all... my 8670 steel isn't hardening properly. I can't even break it, it just bends (past 90 degrees). I tried hardness file testing and I think I'm just below 55 HRC as that's when scratches start showing up. What I can't figure out is if it's not hardening because I'm overheating it or underheating it. Sounds like a silly questions, but what does "non-magnetic" actually feel like? is it no magnetism across the entire piece? or is it no magnetism on the edge?
Non-magnetic across the entire piece
@@KnifeSteelNerds thanks Doc! You are too kind (also a legend forever)!
I think my favorite part of this video is the still picture showing you looking like a burglar or some criminal
So what are the basic steps with a slab of 1080 or 1084?
1. Heat to 1600 nonmagnetic. Let cool to room temperature.
2. Heat to 1500, dip in oil
3. Normalize in oven at 400° for 10 minutes?
Are these the basic steps?
Heating to exactly 1500 is exactly the difficulty with heat treating in a forge. Which is why I recommended quenching from nonmagnetic instead. The reheating to 400F is called tempering and you do it twice for 1-2 hours, cooling to room temperature in between.
You are making me like 5160 more and more… I want a damascus blade made from Vanax and 5160 or S7? would it be and good?
Not sure those would be compatible in heat treatment.
I wonder what super tough non stainless and what stainless high wear resistant, high rockwell steels would be compatible for Damascus
3v and aeb-l should work heat treat wise decently. 3v and z-tuff would make a super tough Damascus with decent wear resistance as well.
isn't 400F a bit hot for parks 50? i think the optimal temp for 50 is room temperature to 120F well parks aaa its120F
400F was the tempering temperature not the oil
Humans used coal and charcoal forges for heat treating for centuries , modern man .
"I wouldn't recommend using a forge to heat treat."
But in all honesty forges you can make yourself , they aren't expensive and I would rather have a newbie use a forge simply because it's more easily accessible .
I would love a furnace but $2000 isn’t in my budget.
Yeah...I "heat treated" 52100 bearing steel...over 1% carbon, quenched in peanut oil...sucks. I just use it for a steak knife. I'm going to be forging a canister with 52100 and 4800kc... we'll see how that goes
Great vid. It was over my head but as I see things explained the way you do and a little bit more sinks in. No one has gotten close to helping me understand as well as your vids. You should get together with RJ Martin. He speaks your language.Thanks
Ubiquitous comment for the algorithm.
Charcoal forge😢
First like :)
It's more difficult to afford an electric kiln.
You should take a harder stance against people “heat treating” knives out of a forge. In no other industry is eye balling it ok for a salable product.
Some of us can do certain steels as well as a furnace schedule. But it takes experimenting to know which ones.
@@daw162 You can’t “do” certain steels. You are just guessing, and selling people a substandard product, (probably at a high price).