• Bryn Davies
    Hi all,
    Starting to lose my confidence in my heat treating of my standard O1 tool steel. Done a bunch of blades that turned out just fine, big and small, but the last 3 attempts on bushcrafters have come out the quench soft.

    I'm heating to 820°C and holding for around 10 minutes, then quenching into warm peanut oil. Files skated on everything done previously to this, but not the three blades I've done since then. Todays attempts probably soaked for a fair bit longer than normal (because I forgot to pre heat my oil in time) , so I'm wondering if it's a layer of decarb that's the problem? I tried to drill through the handles, and the drill gave up after the surface fraction of a mm, so I'm not giving up on them just yet.
  • eeny
    Do you slowly heat to around 400°C first? Also, maybe drop the austenising heat down to nearer 800°C for a 15-20 minutes soak, if might be you are too hot and putting too much carbon into solution = retained austenite? It sounds like the quench isn't ideal either, pre heat the oil to about 50°C. This is not from experience I will add! But from what I've gleaned in trying to get skilled up for my own pending O1 heat treats.
  • Bryn Davies
    I usually pre heat to 500, then ramp up slowly. My kiln is old as heck, so I upped the temp a bit to compensate for leakage. I think the retained austinite might be a good shout though, probably in combination with the decarb. I tried filing a "sharpening" notch into the edge to test it. Got maybe 0.5 mm in and it's hard as hell. A touch up on the grinder might do the trick.
  • JR Knifemaker

    For what it’s worth, here’s my recipe I learnt from a dab hand and it’s never failed me yet!

    Ramp to 520 hold for 10
    Then ramp to 815 hold for 12
    Oil quench
  • Bryn Davies
    Thanks mate. That's not far off what I would normally do. This time I think I just forgot to pre heat, and left it at temp for too long. I took it to the grinder, kinda ruined my really nice grind and plunge lines, but (I think) got through a layer of decarb into some good hard steel. Now just need to see if I can clean it all up and make it pretty again.
  • JR Knifemaker

    It’s made me realise that the 52100 debacle I had a couple of weeks ago may have been similar story.

    Slight off topic: do you think if I quench the blade, but with the handle suspended by the tongs and out of the oil, you’d in effect have differential gardening and the tang would be substantially softer??
  • Bryn Davies
    Should work as long as the blade is submerged long enough to prevent any heat from the handle creeping up and auto tempering the blade. I know folk partially submerge 52100 for a differential quench, leaving it in until the colour goes out of the spine, then quenching the spine while it's sub critical so it's softer than the edge. Basically what you're looking for I think. Check out Stuart Smith from South Africa, he did a video about it a good while back.
  • Smith Knifeworks
    It's probably decarb. I've gotten discouraged before on a file test. I typically test on a sharp corner of the steel so the file cuts quickly. Generally, I'll think it's soft, make a couple more swipes with the file and it suddenly stops cutting and starts skating. This is not with tool steel, but with 1095. I would think the idea carries over, though.
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