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Help needed: burned edge

Discussion in 'Shop Talk - BladeSmith Questions and Answers' started by Revolverrodger, Apr 17, 2018 at 12:38 PM.

  1. Revolverrodger

    Revolverrodger Gold Member Gold Member

    Jul 23, 2007
    While I was grinding the bevels of my knife (nitro v steel) I unfortunately overheated the edge and it changed color (burned)

    What can I do to fix that?
    Can I directly heat to 1900 and plate quench or do I need to add prior steps

    Thanks for the help
     
  2. Grayzer86

    Grayzer86

    Jan 15, 2012
    Is this before or after heat treat?
     
    Revolverrodger likes this.
  3. Revolverrodger

    Revolverrodger Gold Member Gold Member

    Jul 23, 2007
    Before HT
    Thanks
     
  4. joedhiggins

    joedhiggins

    149
    May 31, 2016
    If it never got past a dull red in color, you did not do anything that needs fixing (I haven't looked into/used nitro-v, but unless it is wildly abnormal this is true). Burning steel, in the proper sense of the term, happens well into the 2000s F range. What you are properly refering to is overheating/overtempering the blade, and refers to a reduction in hardness to a hardened blade that would hapen from overheating a section past your intended temper temperature.

    If you had already heat treated the blade, such an error may require heat treating the blade again, grinding the overheated section out, etc. That all being said, I have tested this on a couple coupons of steel, and while I can't give precise HRC reductions, I can say that in the case where the steel was heated momentarily to a temp sufficient to create a blue area on the edge, I couldn't observe a reduction in hardness. Tempering is a temp vs. time process, and while temperature is the larger factor, I imagine that tiny area of the edge only held that temp for half a second at the longest. This may be the reason. I did the test on 1084, where a blue color should have equated to an HRC in the low 50s. A file should have chewed right through it and did not. Either way, I am not precisely sure why it didn't lose as much hardness as it should have. It could have been errors in my testing methodology, and as I used files for the test, it likely did lose a cople points of HRC in that area.

    No matter my results, in this case, since it was prior to HT, you are OK.
     
    Revolverrodger likes this.
  5. john april

    john april KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Feb 27, 2006
    yup, prior is ok. its good training to avoid the "blues" after HT.
     
    Revolverrodger likes this.
  6. Revolverrodger

    Revolverrodger Gold Member Gold Member

    Jul 23, 2007
    The over heated section of metal is straw / brown color

    Will that disappear after HT ?
     
  7. JTknives

    JTknives ABS Apprentice Knifemaker / Craftsman / Service Provider

    Jun 11, 2006
    that color is just a very thin oxide layer on the surface. comes right off with sand paper
     
  8. Revolverrodger

    Revolverrodger Gold Member Gold Member

    Jul 23, 2007
    Ok looks deeper but I may be wrong
     

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