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  1. #1
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    N690 heat treat, ramp soak

    Hi,
    I finished to build my kiln, any suggestion about ramp soak of blade 3mm and 5mm thickness?

    Thanks in advance

    Rocco

  2. #2
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    Re: N690 heat treat, ramp soak

    Hi Rocco,

    N690 is very popular as a knife steel here in South Africa. Most of the guys don't ramp during heat treating. They put the blade in the kiln at the recommended temperature for 7 minutes for 3mm and 10 minutes for 5mm, quench in oil, straighten (if needed) and that's it.

    Given the high chrome content of 20% you could cryo as well.

    Really forgiving steel.

    The heat treatment sheets can be found on Bohlers website.

  3. #3
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    Re: N690 heat treat, ramp soak

    @ ant topps

    Thanks for your info,
    what do you think to quench between two alloy plates?

    Here how Sandwick heat treat his steel:

    http://smt.sandvik.com/en/products/s...ing-procedure/
    Last edited by rockblades; 13-04-17 at 11:20 AM.

  4. #4
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    Re: N690 heat treat, ramp soak

    I use the n690 alternative supplied by ground flat stock , I asked about the HT on another forum and was given this answer

    Pre-heat to 400 degrees and hold for approx 1 minute per mm cross section (so if 3mm hold for 3 minutes)

    Heat to 650 degrees and hold for approx 1 minute per mm cross section

    Austenise between 1000 to 1040 holding for approx 15 minutes.

    You can oil quench. It needs two tempers at an hour per time between 240 and 300 degrees for 55 to 58 HRC.

    That's what Lohmann's advise! I'm not sure why they don't publish in more detail on the data sheet but I'll get it put on the website.




    Hope that helps
    Warren
    http://bushbabyknives.blogspot.com/
    My Knives so far
    everything i make is for sale pm me if you see anything you like
    thanx
    warren

  5. #5
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    Re: N690 heat treat, ramp soak

    We quench N690 in quenching oil (genheat22) and then clamp between steel plates to keep it all straight.

    I've used alu plates for the air hardening steels like AEBL and K110. Oil can be used for both, but AEBL like to warp.

  6. #6
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    Re: N690 heat treat, ramp soak

    Here is one heat treatment spec sheet from Bohler. http://www.bohlerperu.com/files/n690.pdf Sandivick makes great steel, but nothing equivalent to N690 last time I checked. Best to use the above and do you own testing vs your application.

  7. #7
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    Re: N690 heat treat, ramp soak

    I would have thought that gradually increasing temperature would be kinder to any grade of steel?
    Although after quenching and tempering, how much difference does it make to obtaining a good, long lasting cutting tool?

    I dunno, only doing it both ways then testing the knives back to back may show a difference??

  8. #8
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    Re: N690 heat treat, ramp soak

    Think the main difference would be for the guys who forge and if you initially heavily shape the blade. Both increase the internal stresses, which would need to be relieved prior to your final hardening. Not many people forge N690 as its stainless. But due to its high chromium content a pre-soak could help ensure your getting all the correct carbides to from in the right amounts???

 

 

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