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1080 heat treat process?

Discussion in 'Shop Talk - BladeSmith Questions and Answers' started by wolf5391, Dec 23, 2011.

  1. wolf5391


    Sep 23, 2010
    hey guys just got some 1080 to work with and was looking for a good heat treat process for 1080.

    The tools i have are as follows:

    1) Whisper momma forge (maintains forge welding heat only, at 2300' F)
    2) canola oil or used motor oil
    3) kitchen oven for tempering
    4) My piece of 1080
    5) Magnet

    Let me know what you guys think is the best heat treatment for my set up.
  2. SShepherd


    Nov 23, 2003

    1080 is eutectoid steel - It has the simplest HT. You need to heat it evenly ( avoid overheating the edge) to 1500F and quench as soon as the blade is at that temperature. No need to soak ( hold at austinitization temp) for any length of time. Quench in fast oil, like parks #50,. Water or brine will work, but blades can crack or warp much more likely. Temper twice at 450F. This will give you a hard and tough blade.

    Read Kevin Cashen's post at the top of the page "Working with three steels". The entire process is explained.

    My advise would be to avoid blends of old motor oil and ATF. It will work for many steels, but for shallow hardening steels, it may be less than optimal. Buying a gallon or two of proper quench oil will be a good investment.
    1080,1084,1095, W1, W2 all need fast quench oil.
    1070 and below often need water or brine to quench them.
    O-1, L-6, 5160, S7, and other high alloy steels need a medium speed oil quench.
    A-2. D-2,and stainless steels are air quenched, often using quench plates to avoid warping.

    You will hear and read a lot of conflicting info about HT procedures. One advantage of 1080/1084 is that most all of those procedures will work for it. The one critical step is the quench. Assuming the steel is about the right temperature, the quench is where the austinite ( what forms above non-magnetic) converts into martensite ( what we want for a knife blade). Cooled too fast...it cracks or warps, cooled too slow...the blade is too soft or only partially hardened. Most blade steels between 1080 and W2 ( from .80% to 1.00% carbon) have only about one second to lower the steel temperature from 1500F to below 900F. That is what the words "fast", "medium", and "slow" mean in quench oil ratings.

    As to using a magnet to determine the blade temperature....it is a good system. At about 1300F the steel changes from one structure to another. It looks the same, but the new structure is not magnetic. Checking the steel by using a magnet ( the cheap telescopic pick-up magnets work well) as the blade heats up will tell you when this change occurs. At this point it is not ready to quench ( even though many will tell you to quench then). It has to heat up about 150-200 degrees more. You observe the color at non-magnetic, and heat it up a shade or two brighter. That should put you in the ball park. The things you want to do are keep the blade moving and turning, so the thicker spine and the thinner edge are as near the same temperature as possible. Avoid overheating the edge...that the part you are going to use in cutting.

    Once the blade is at the austinitization temperature, quench in a smooth and even plunge into a gallon or more of the proper quenchant. Quench straight in, point first. Only move the blade up and down, or in a cutting motion from spine to edge. Avoid moving it from side to side or it may warp. After about 7-10 seconds, pull the blade out and check it for warps. If it has some warp or twist, immediately straighten them with gloved hands or on a 2X6 with a wooden mallet. You have until the blade cools to 400F to do any straightening. At 400F the steel converts into martensite, and will become very hard and very brittle. Do not attempt to straighten any more. Allow to cool to room temperature, wash off the oil, and as soon as possible , place in the oven at 400-450F to temper for one to two hours. Take out and let cool to room temp and put back in the oven for a second temper cycle. Now your blade is hard and tough.

    There is a lot more to HT than this, but that is a basic starter procedure. Again, reading Kevin's posts will provide a lot more detail.

  3. Remyrw


    Jun 17, 2010
    Wow, that's gonna be fast.
    First, get another piece of 1080 to test with, at 2300 you're gonna run a real risk of overheating by a mile.

    I'd get your quench oil up to temp at the same time you turn on the forge, no point waiting on it. I'm not super picky about the quench temp, basically I get it warm enough it's hot to the touch but not too hot to touch. Since I've got a rather large tank of it the temp changes slowly and it's easy to stop it in the right range. I use the heat escaping out the back of my forge to heat the quench (it's in a nitrogen gas cylinder with the top cut off) so when it's ready I just slide it a bit further from the heat and it's fine.

    Put the blade in the forge, edge down, and I wouldn't let go of it with the tongues since it's not going to be in there long. Try to move it around enough to keep the heat even as it comes up to temp. As it starts to get warm enough to glow a bit be extra careful about evening up that heat. When it's a bright orange check with the magnet, continue to check along the blade as the color shows increasing heat until you get a feel for where it's going non magnetic. Don't worry about the tang, but the whole blade plus ricasso area should be non magnetic. Then go just a touch hotter than that. If that's a light orange in your lighting conditions, go dark yellow, for example. It's easier to see than explain in words. Luckily 1080's pretty forgiving, as long as you're past magnetic and not way past then it'll be fine.

    Once up to temp and evenly heated, quickly go from the forge into the quench. Straight in, with no sideways motion. You want it almost as if you were trying to slice into or stab the quench. Avoid any and all sideways motion or you multiply your chances of a bent blade since it's fairly plastic at this point. Keep it in there, agitate a bit, give it at least 30 seconds to a minute. Longer won't hurt with 1080, you just give up the option to straighten it if it bent, you'd do that later during tempering in that case. For starting out that's how I'd go, safer for your hands and harder to screw up. (eta - as mentioned in the first reply, the first few seconds are doing the real work. I leave it in longer simply to reduce the time delay between quench and temper. I let the canola soak up more of the heat before I take it out. As a newbie, and for a newbie, judging the initial quench accurately enough and then straightening right then is too much to juggle reliably when there's a slower but effective method.)

    Wipe it off, check for any cracks or major warping. The scale will make it tough to see tiny cracks but as long as it looks ok it's time to move on. Take a needle file or even a regular file and make sure it skates on the hardened portion. I use the spine of my knives not the edge, less damage if I screwed up :) and in 1080 and 1084 if the spine is hard it's essentially foolproof for the edge area. You don't want to bang the knife around at this point, don't drop it or smack it with the file, it's brittle and will break.

    If it skates, get it into the tempering oven (preheated) at 400-425. You want the oven already at temp and settled, use the middle rack position. Let it soak for at least an hour. Most folks suggest 90 minutes to 2 hours. When it is done with that temper, running water to cool it off, check for straightness since this next cycle is when you'll fix that. Assuming it's straight, back in for another 2 hours. I don't turn off the oven, it's usually only a couple minutes between temper cycles with this method.

    Once out of the tempering oven, cool it off again and put it in a container of vinegar to deal with the scale. I use a throw away oven pan, those foil like things, just enough in the bottom to cover the steel. Let it soak, swish it around a bit now and then, turn it over... a few hours to soften up that scale makes life easier afterward. Just wear gloves or be ready to have black hands afterward, it's messy. I use paper towels to do the wipe down afterward and then it's on to the grinder or sandpaper for finishing.
    Last edited: Dec 23, 2011
  4. xmtgx


    May 11, 2007
    2300* is far to high no matter what.
    Warm your oil to around 130. Heat the blade evenly in the forge to above non magnetic then just a little more and quench. I get the blade around 1480-1500 for 1080.I temper around 415-435 but start lower and test to find what works for you.
  5. Remyrw


    Jun 17, 2010
    Yeah, that's my concern. It'll be really tough to get the whole blade and ricasso up to temp without seriously overheating thinner parts. I'm thinking it'll have to get taken out of the heat a few times to even out. The edge will give up the heat faster than the thicker sections, bringing it more into balance. It'll be a balancing act, that's for sure.
  6. xmtgx


    May 11, 2007
    Thats what he will have to to. Heat it once a area reaches temp, remove and let cool to deep red or black then back in. It will take some time but if you can't hold around 1500 or so its really the only way.
  7. mgysgthath


    Dec 15, 2009
    Would a muffle help more evenly distribute the heat? He'd still have to pull out and let it equalize but that might take the edge of the more drastic heat.
  8. wolf5391


    Sep 23, 2010
    thanks to everyone who has posted a response, i greatly appreciate your help. I have heat treated plenty of knives before, just wanted to make sure i had the 1080 process down. ive heat treated alot of steels and just recently i got into 1080 and figured id ask before i screwed it up :D It seems this steel will be quite a walk in the park compared to others.

    Thanks again everyone.
  9. Stacy E. Apelt - Bladesmith

    Stacy E. Apelt - Bladesmith ilmarinen - MODERATOR Moderator Knifemaker / Craftsman / Service Provider

    Aug 20, 2004
    Per-heat the forge by running for about ten minutes. Then, back off the pressure on the regulator slowly. It will hold around 1500-1600°F when the pressure is around 2-3 PSIG. If the flame backs up into the burners, and makes a loud squeal, shut off the main valve at the manifold,raise the regularor pressure, and then re-open the valve. The chamber heat should re-ignite the flame immediately. Raise the pressure until it maintains the flame without flashback.
    Last edited: Dec 24, 2011
  10. SBuzek

    SBuzek KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Dec 7, 2006
    Another little trick,take piece of kaowool blanket and cut a piece about 2"X3" stick the point into the wool about 2".Start heating the blade and as the thick parts start to get slight red glow remove the wool and finish heating.
  11. LRB


    Feb 28, 2006
    "As to using a magnet to determine the blade temperature....it is a good system. At about 1300F the steel changes from one structure to another. It looks the same, but the new structure is not magnetic."

    Just a clarification, but non-magnetic is not in the 1300° range. It is a consistant 1414° F for all iron or steels.
  12. Brian Ayres

    Brian Ayres

    Feb 4, 2011
    Glad you caught that Wick, 1414 is non-magnetic. You only want to take the steel 61-86 degrees higher as said.

    It's hard to judge and get right but try putting salt on the blade at just above non-magnetic. Salt melts at 1475. It will have to be outside the forge.

    Use canola if you must. I have a friend who was using motor oil, I loaned him 5 gallons of Parks 50 and he was amazed at the difference visible to the eye in the steel structure when he did side by side destruction tests. McMaster Car sells quench by the gallon. Cheap for what you get.

    A highly respected Bladesmith I know taught me a simple trick He has a big round magnet attached to his stand under his forge. Just pull the blade with the tongs. Touch the magnet and back in the forge if it's not there yet. Never 100% trust your eyes.

    Good luck!
  13. Stacy E. Apelt - Bladesmith

    Stacy E. Apelt - Bladesmith ilmarinen - MODERATOR Moderator Knifemaker / Craftsman / Service Provider

    Aug 20, 2004
    I place a welding magnet on the side of the forge and do the same thing. Works well.
  14. Kentucky


    Dec 13, 2008
    might I also suggest a muffle..Simply a piece of pipe running thru the forge or at least the length of it..The blade will be heated more evenly inside the muffle..
  15. wolf5391


    Sep 23, 2010
    hey guys just finished heat treating most of my 1080 steel knives, and have to say this steel is very nice to work with. and its durable as hell with this heat treatment ( i used the 400' F temper at two 1 hour cycles)i love the results. Just hammered the knife through some mild steel round stock with no edge damage at all and it seems to hold that edge for a long time through card board.

    Thanks, Ryan
  16. LRB


    Feb 28, 2006
    Excellent. Good for you! You succeeded in spite of all our advice.:D
  17. PaMtnBkr


    Dec 31, 2009
    Cool little trick there with the salt! Gotta remember that one!
  18. Remyrw


    Jun 17, 2010
    That's the beauty of 1080 and 1084. They're never going to be as hard as the fancy stuff, nor hold an edge as long as some others, but they're in that sweet spot for it all and are incredibly tough.

    I gave a little tanto I made from Aldo's 1084 to a friend who's very very hard on knives. I told him to use it however he wants, just no intentional destruction, then let me know when and how it has a problem or fails. I know he'll eventually manage it, he'll keep pushing the envelope until he breaks or at least bends it badly, but so far all he's done is dull up the edge a little cutting things like CAT5 cable, opening boxes and his usual day to day stuff at work. I'm waiting to get a phone call that it does not survive being used as a pry bar right after being dropped in a liquid nitrogen bottle.
  19. Danbo

    Danbo Platinum Member Platinum Member

    Nov 28, 1999
    Curious as to what you quenched the 1080 in. Canola, or the used motor oil? Not that there's anything wrong with using the Canola oil(do a search; there's plenty of arguments for and against it already). Just that my 1080/1084 blades quenched into prewarmed Parks 50 and then tempered at only 400 end up pretty dang hard(like, 62 Rockwell). Probably a bit too hard to be hammering through mild steel bars. Blades quenched in the Canola oil must not get quite as hard as the ones quenched in Parks 50. I find that I have to temper at closer to 450 to get around 60 Rockwell.
  20. Jason Fry

    Jason Fry KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Jun 5, 2008
    I was thinking the same thing. When I quench 1080 in vet grade mineral oil, I temper at 425 to get to 61. If I use Maxim's 10 second oil, I have to temper at 450 to get to 61. Whatever he's quenching in is working, but he's not getting full conversion.

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