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Quick Question

Discussion in 'Heat Treating' started by EzraM, Jul 13, 2018.

  1. EzraM

    EzraM New Member

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    What're your thoughts on 01 steel that's been HT + tempered then tested and has results ranging up to 52 rockwell hardness? Too soft?
     
  2. ToddR

    ToddR Putterer, Tinkerer, Waster of Time Staff Member

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    If it passes the file test it should still be useable for something. I don't know that I'd baton pieces of ebony with it. (I don't know why I'd baton ebony though - or baton anything for that matter) . Indoor use maybe?
     
  3. dancom

    dancom Dust Maker Best Shop Tool

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    Easy to sharpen. Depending on the (ab)use you will be sharpening it more or less.
     
  4. EzraM

    EzraM New Member

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    Exactly. I think I tempered at too high a temperature for too long.
     
  5. EzraM

    EzraM New Member

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    Shoot I totally forgot the file test. Still, at twice the hardness of most structural fasteners the knife is quite hard. I'll be sharpening it more often, but I don't mind that. I think I tempered for too long at too high a temperature. Next time I lower temp to 300 degrees and only for a half hour.
     
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  6. Mythtaken

    Mythtaken Staff Member CKM Staff

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    Yes, you likely drew it back too far. For O1, I tend to use 2 tempers, 1 hr at 400F. I've never done a hardness test but blades seem to hold an edge pretty well.
     
  7. dancom

    dancom Dust Maker Best Shop Tool

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    Have you put a handle on it yet? If not, you can try a re-harden and temper it again. A little extra work, but you may be sweetly rewarded for the effort.

    I am not certain how much the duration of tempering cycle affects the hardness. I have blown the temper in a blade edge is less than a second when grinding the cutting edge. My understanding is that if it's gone bluish you've made that area into spring steel. If everything went well in the hardening phase, 200°C (~400°F) is good for tempering O1. Also you may want to check your tempering oven against a thermometer (or two) if you have. Sometimes the thermostat controlling the elements can be off. I had one toaster oven off by 50°F from the what the dial said. Maybe not a make or break difference but good to know for repeatably.
     
  8. John Noon

    John Noon Well-Known Member

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    Tempering is time and temperature critical
    You have to get above the Martensite finish temperature on the TTT diagram for the particular steel.

    Then you must hold that temperature for an hour or more often two hours as the process of tempering is very slow.

    If you are using a toaster oven then you run into a temperature swing of 50 to 150 degrees as the elements cycle on. It helps to have the knife in a tube or something that smooths out the temperature swings or a oven tamer that provides better temperature control.
    In a pinch you could place the blade on a bar of steel or better yet a thick chunk of aluminum then wrap that with tin foil to form a chamber.
     
  9. cuatroXcuatro

    cuatroXcuatro Active Member

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    I've got a large piece of mild steel flat bar in my toaster oven, I preheat until the bar reaches the right temp and it smooths out the temp fluctuations, I first confirm the bar temp with a temp gun and have a digital temp readout/probe setup to monitor for any temp changes. Seems to work pretty well.
     
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