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  1. #16
    Join Date
    Jul 2010
    Location
    Melbourne
    Posts
    9,088

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    Hi RC,

    Do you know that temp you getting to?
    My book says for 4140 you need 845C and then you will get 56Rc< there is a joke there some where RC.
    So if you're at 925C you're a little on the hot side for 4140 and I assume held the temp for way to long?

    As far as case depth goes. Could you treat a bar, let it cool in kiln, turn a taper along its length, reheat, quench, hardness test every 5mm along the taper?(havent done it, havent read it. just an idea).

    Great stuff, if you keep it up I might just get my finger out and try it lol.

    Stuart

  2. #17
    Join Date
    Aug 2008
    Location
    near Rockhampton
    Posts
    6,216

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    Case Hardening imparts carbon into the surface of the steel, I was thinking is a steel already has carbon, in it like 4140 I was wanting to see if more carbon can be put into it to make the surface even harder..

    This is obviously not the case with 4140 at least.

    The hotter you get the workpiece the more soluble carbon is in the steel.... One article I have here says at 920C carbon will migrate into steel at a rate of 0.01mm/minute.. I guess this is optimum results.. Carbon solubility in iron starts when the metal becomes a bit over 720C

    It is really hard to get my head around all the methods as they operate at different temperatures..... Case hardening using a metallic salt bath, operates at a lower temperature and achieves results in a shorter time frame.. I am starting to suspect the dedicated hardening shops keep a witchdoctor on hand to make sure the process is a success every time.
    Gold, the colour of choice for the discerning person.

  3. #18
    Join Date
    Feb 2010
    Location
    Cairns, QLD
    Posts
    1

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    I once read somewhere that back in the dark ages a good sword would be quenched in the urine of a boy. I thought that it was a joke but perhaps not after reading the comments about urine adding nitrogen. Although perhaps the part about the young boy is at least.

    This thread makes very interesting reading. Good work on the kiln RC.

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