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Heat Treating 440C Stainless

Discussion in 'Shop Talk - BladeSmith Questions and Answers' started by J.D., Mar 24, 2007.

  1. J.D.


    Feb 12, 2006
    I tried the search function, but no luck. I want to try a knife made from 440C or ATS34, I have been using O1 and 1095. I bought an Evenheat oven a year ago so I could do stainless steels later on, I think I am ready to try it. What I need to know first, is 440C an oil quench or air quench? Jantz supply says oil quench and on the Evenheat web page, they say it is air quench:confused: . Also is ATS 34 air or oil quench? Any help would be appreciated. Thanks in advance to all who respond.
  2. mete

    mete Gold Member Gold Member

    Jun 10, 2003
    First you have to use stainless foil packets to prevent scale and oxidation at the high hardening temperatures. Makers then use 'plate quenching' [with blade still in the foil] which works very well .Lots of info on plate quenching in this forum.
  3. Barkes Knife Shop

    Barkes Knife Shop

    Jan 2, 2006
    440C Stainless

    Preheat thoroughly at 1400/1500ºF and hold for 30 minutes.

    Raise heat to 1950º F and hold for one hour.

    Air quench at room temperature. Subzero freeze at 200º below 0.

    Tempering: Temper at 400ºF for one hour, two times
    ATS-34 Stainless

    Preheat thoroughly at 1400º/1500ºF and hold for 30 minutes.

    Raise heat to 1950º/1975ºF and hold for one hour.

    Air quench at room temperature. Subzero freeze at 200º below 0.

    Tempering: Temper at 950ºF for one hour, two times

    I hope this was of help to you. And have a great day. -------------:thumbup:
  4. Rob!


    Feb 9, 2000
    The answer to you oil / air quench question for both steels is "yes". Both can be either oil or air quenched but why in heavens name would you choose the mess of the oil? :rolleyes:

    Both can be air quenched just fine. Plate quenching between thick heavy plates of (preferably) aluminum will yeild straighter blades and some say a bit extra hardness. Not necessary but nice.

    You'll get as many different heat treat answers as there are makers on this board.

    Somehow, you have to exclude most of the oxygen from your hot blades. We double wrap in high temp stainless foil envelopes with a bit of paper inside to eat up what oxygen is in there to start. Some use Turco or PBC compounds.

    I do 440C at 1900 for 30 minutes.

    I do ATS34 or 154CM at 1950 for one hour

    Both get plate quenched, still in the envelopes till hand cool. If there are no obvious stress points, they go straight in to the liquid nitrogen over night. The liquid nitro soak is also optional but yeilds measurably better results enough to make it worth the extra.

    440C gets double tempered at 350 twice for 2 hours each
    ATS34 gets double tempered at 500 twice for 2 hours each

  5. Larrin


    Jan 17, 2004
    IMO, 1950F is a little bit high for 440C, from what I've read, you might be getting grain growth at that temperature (though a short hold time would minimize this). Personally, I wouldn't go higher than 1900F.
  6. Allan Molstad

    Allan Molstad Banned by Moderators

    Feb 1, 2007
    I could not get it to work for a search of "440 steel" too.
    However this morning I did a search of "440 steel" and got lots of links to look at.
    Im not sure why it seems to work fine , then not at all?
  7. J.D.


    Feb 12, 2006
    Thanks guys for the help. I was going to just air quench, but now I will make quench plates and use them. I found some aluminum angle 1/2 inch thick x 4" x6". at a local scrap buyer. I have enough to double the thickness if need be. What do you guys think? Is 1/2" enough, or should it be thicker? I will only do one or two blades at a time. Thanks again
  8. mlovett


    Oct 22, 2004
    1950 for 440-c is too high. It will promote grain growth. Double temper at 350, to 475 depending on the Rc, you want. one hour at heat-1850 to 1900 is also too long. And will also cause grain growth, and decarb. Many make this mistake. It is taken straight from the heat treat manuals. Sound right, but is wrong. The books all say 1 hour per inch of thickness. Ever seen a 1 inch thick cutting edge? Didn't Think so. The one hour is to allow the thick steel to come up to heat. The thickness we use in knives will come up to heat very quickly. A very thin hollow ground blade will take less time than a large flat or convex ground chopper. As little as 10 minutes can work just fine for a thin hunter. 15 us usually just fine for a larger Bowie type blade. You will have troubles with plate quenching deep hollow ground and tapered tang blade's. You will quench the recasso just fine. But be insulating the edge. A bad thing. Do not just Air quench. The specs call for 2 bar forced cool air. If I'm not mistaken, this is a minimum of 28 lbs of forced air. Not a problem with shop air at all. Also, you never know if the blade, or edge could have become warped during heat-treat. Leaving the blade in the wrap, and plate quenching, prevents you from being able to check for this while the blade is still in a heat range where it can be safely straightened, with out the possibility of cracking. Mike
  9. J.D.


    Feb 12, 2006
    Thanks to all for your help. mlovett, you mention problems with plate quench with tapered tangs and deep hollow grinds. I don't do tapered tangs, need to work on that, but I do hollow grind some blades. Mostly 1/8" and 5/32" thick stock ground down to 1/16" at the edge, before heat treat. would this be a problem and not get the edge quenched? And if so could I blow compressed air between the plates on the edge side, to speed cooling of the edge?
    Thanks again, this forum is great. Dale
  10. mlovett


    Oct 22, 2004
    Thanks Sir! And yes you can. Just take the blade out of the foil pack first. But if you use compressed air to cool the blade while holding in thongs, you can watch the edge. I like to know exactly what is going on with the blade. Mike

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