1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Heat Treat Question

Discussion in 'Heat Treating' started by krash-bang, Jun 8, 2016.

  1. krash-bang

    krash-bang Active Member

    Likes Received:
    71
    Trophy Points:
    28
    I'm wondering if you put the blade in the kiln while it's warming up to temp or do you get the kiln to the right temp then put in the blades? Like frozen fries I guess.

    I've looked at a few vids but they never specify. I'm sure there is a difference in the end result. Could someone enlighten me please?
     
  2. dancom

    dancom Dust Maker Best Shop Tool

    Likes Received:
    921
    Trophy Points:
    113
    This is a good question and I couldn't find much info out there.

    For stainless, I put mine in about 860°C, soak for about 10 minutes. This is close to the stainless datasheet's "preheat" temperature. Then ramp up to 1060°C and hold.

    Dan
     
  3. John Noon

    John Noon Well-Known Member

    Likes Received:
    562
    Trophy Points:
    113
    I was putting the knives in the Kiln and hitting start, often with larger objects in the heat treating industry it is done this way. For smaller high volume items the kiln would be running and the part placed in a heated kiln then allowed to come up to temperature and soak for the recommended time.

    Not a yes or No answer but in the long run I do not believe one way or the other will make a difference. What matters most is the knives and kiln stabilize at the soaking temperature and remain there long enough, not much happens below 300-1200F range other than tempering or in the case of some stainless steels they become sensitized and prone to failure.
     
  4. Mythtaken

    Mythtaken Staff Member CKM Staff

    Likes Received:
    242
    Trophy Points:
    63
    I agree with John. The target temperature and soak time is what's important. It's not like baking cookies. Pre-heating the oven doesn't matter. (Damn. Now I want cookies.)

    I don't have any experience with stainless, but I don't think it makes a difference there either, providing you are heating the steel up to the target temperature. It might be different if you were to hold the steel at a lower temperature for some time before ramping up to critical, but I can't think of a good reason to do that.
     
  5. John Noon

    John Noon Well-Known Member

    Likes Received:
    562
    Trophy Points:
    113
    For AEB-L
    Heat Treating Information:
    Preheat:
    Heat to 1560° and equalize.

    1920°F Austenitize: Ramp to 1940°F and hold at temperature for 15 minutes. Oil or plate or air quench as quickly as possible.
    or
    1975°F Austenitize: Ramp to 1975°F and hold at temperature for 5 minutes. Oil or plate or air quench as quickly as possible.
     
    Mythtaken likes this.
  6. dancom

    dancom Dust Maker Best Shop Tool

    Likes Received:
    921
    Trophy Points:
    113
    I'll metricate that for us John.

    For AEB-L
    Heat Treating Information:
    Preheat:
    Heat to 849°C and equalize.

    1049°C Austenitize: Ramp to 1060°C and hold at temperature for 0.25 centons. Oil or plate or air quench as quickly as possible.
    or
    1079°C Austenitize: Ramp to 1079°C and hold at temperature for 0.083333 centons. Oil or plate or air quench as quickly as possible.

    I've heard anecdotally the slower you ramp up the less stressful it is on the steel. Not sure if there is any truth to that, but generally speaking things that happen quickly are stressful. Say, quenching, car accidents, hitting send on that rage email to your former boss that you shouldn't have sent. ;)

    Dan
     
  7. krash-bang

    krash-bang Active Member

    Likes Received:
    71
    Trophy Points:
    28
    When you say "Heat to 1560F/849C and equalize" what do you mean by equalize? Is this what you mean by "soak for about 10 minutes"?
     
  8. dancom

    dancom Dust Maker Best Shop Tool

    Likes Received:
    921
    Trophy Points:
    113
    krash-bang likes this.
  9. John Noon

    John Noon Well-Known Member

    Likes Received:
    562
    Trophy Points:
    113
    means the temperature has to stabilize within the steel through thickness. For a knife 10 minutes should be enough or fifteen if you like, should see a nice even color in the steel.

     
    krash-bang likes this.
  10. krash-bang

    krash-bang Active Member

    Likes Received:
    71
    Trophy Points:
    28
    Good article, thanks. If I understand correctly then, equalizing is beneficial to all types of steel. They refer to a minimum of 2 hours for equalizing but they are talking about fairly thick stuff. You mentioned 10 minutes, would longer be better or is it just pointless considering the thickness of the blades we make?
     
  11. krash-bang

    krash-bang Active Member

    Likes Received:
    71
    Trophy Points:
    28
    You answered my question as I was typing it. LOL
     
  12. John Noon

    John Noon Well-Known Member

    Likes Received:
    562
    Trophy Points:
    113
    that time is 1 hour per inch typically. so for a knife that is 1/4" thick 15 minutes is more than enough time for the heat to stabilize in the part.
    Industry standard is always to reference times as per inch as the median and calculate from there.
     
    krash-bang likes this.
  13. dancom

    dancom Dust Maker Best Shop Tool

    Likes Received:
    921
    Trophy Points:
    113
    I guess the footnote could read, if your knife is an inch thick, then more time is required. LOL
     
  14. krash-bang

    krash-bang Active Member

    Likes Received:
    71
    Trophy Points:
    28
    Thanks a lot for the info guys! Much appreciated. I'm gonna fire up the new kiln this weekend. I can't believe I waited so long to try it out. I guess I'm getting more patient as I age. Or maybe more careful. Yes, more careful, that must be it.
     
    dancom likes this.
  15. John Noon

    John Noon Well-Known Member

    Likes Received:
    562
    Trophy Points:
    113
    I have had the fun of making a couple of 1095 knives all done at the same time and one tested with the files at HRc 45. Guess the oil was to warm and it did not cool fast enough during the quench, lesson learned test hardness before buffing the blade and testing its edge retention.

    Now to patiently wait for the anti-scaling paint to show up so I can redo the heat treating, considering running it through a normalization cycle in foil before trying to harden again.
     
  16. Griff

    Griff Active Member

    Likes Received:
    119
    Trophy Points:
    43
    *BUMP*:D

    Unfortunately the link @dancom provided from SimplyToolSteel is no longer valid :(

    So I would like to ask again for my own clarification. I’ve been reading a lot of heat treat TDS recently and all of them say heat to *insert temp* and equalize...then increase to *insert temp* and soak X-length of time per inch of thickness.

    The latter I understand because I know how thick my knife is. What I don’t understand is the Equalize time. Simply because in most tech sheets ‘Equalize,’ is not followed by a recommended amount time per inch of thickness. So I’m not getting how you figure that out.

    I know ‘10 minutes,’ was not pulled out that place the sun doesn’t shine :p...but is it universal for all steels and thicknesses or not?
     
  17. dancom

    dancom Dust Maker Best Shop Tool

    Likes Received:
    921
    Trophy Points:
    113
    I'll see if I can explain this (the way I understand it).

    The reason that no one publishes equalization periods is that they don't know how fast or slow your oven can rise in temperature. 'Equalize' is a rest period to ensure the temperature is uniform throughout the piece. A thin piece of steel takes little if any time to equalize, even in a fast oven. A thick piece of steel in a fast oven will benefit from a rest period as the outside of the steel will be hotter than the inside of the steel. My oven is slow rising and with the thin steel I use, I don't equalize. If use thicker steel, I will give an equalization rest just to be sure the steel is heated uniformly. I hope that makes sense.

    Nice graphic by the way. Very cool!

    Dan
     
  18. John Noon

    John Noon Well-Known Member

    Likes Received:
    562
    Trophy Points:
    113
    For various coatings you only insert at the first temperature hold point above 600C or around the 1200F mark
    This should be a hold and stabilize step to uniformly heat the steel before going too austenising temperature and soaking
     
  19. Griff

    Griff Active Member

    Likes Received:
    119
    Trophy Points:
    43
    Let’s look at CruForgeV (Very easy by the look of things, 1084 easy)

    Hardening:

    Preheat: Heat to 1200-1250°F (650-675°C) Equalize.

    (A) I would put my knife in only when the kiln reached this temp?

    (B) Place my knife in at whatever the kilns standing ambient temp is and let the blade and the kiln raise to Equalizing temp together?

    Let the knife soak at this temp for how ever long because it doesn’t really matter as it not the critical temp for this steel...so let’s say 10 minutes...and then hit the program to raise to the Austentizing temp.

    Austenitize: Heat to 1500-1550°F (820-845°C) Equalize. (Soak for the manufacture recommended time per 1” of thickness)

    Quench in oil. (In my case Proquench 100 a versatile 9-13 sec oil)

    Hope I got that right, if not call me out as I won’t learn otherwise lol :D

    Thanks to everyone’s input, @John Noon and @dancom (and cheers for the kind words, the graphic is about all I can work on at the moment lol)

    :beer: Griff
     
    Last edited: Feb 9, 2019
    dancom and John Noon like this.
  20. dancom

    dancom Dust Maker Best Shop Tool

    Likes Received:
    921
    Trophy Points:
    113
    Last edited: Feb 10, 2019

Share This Page