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Heat Treat Question

Discussion in 'Heat Treating' started by jeff, Feb 4, 2016.

  1. jeff

    jeff New Member

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    I am heat treating 1095 steel at 1500 f for ten minutes problem is within that ten minutes temperature rose to 1600 then down to 1400 managed to get it at 1500 at the end of the ten minutes then i quenched in chevron 70 oil at 130 f extremly difficult to keep a constant temperature using my forge put knife in pipe then in forge what do you guys think file seems to skate across hardened areas i used clay to make a hamon line knife is in oven tempering now 350 for 2 hours times 2 tell me what you think
     
  2. John Noon

    John Noon Well-Known Member

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  3. dancom

    dancom Dust Maker Best Shop Tool

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    I suspect at that drawing temperature the blade could be on the chippy side. The 350°F tempering should put you around HRC63 if everything else went good. Okay for a Japanese chef's knife. You can always draw the hardness down. 500°F should get you down to the HRC 59-60 range. You cannot however increase the hardness again without re-hardening.

    My go to site: Kevin Cashen's pages on Heat Treatment

    Dan
     
  4. jeff

    jeff New Member

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    does it matter how many times i heat treat knife will that affect it at all
     
  5. Grayzer86

    Grayzer86 Active Member

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    You may have some grain growth from the overheating but it will depend by how much and for how long. You likely still achieved good, although not ideal hardness. Heat treating at a higher temperature can blow grain boundaries and cause a course grain, which can weaken the steel, or cause it to take a less perfect fine edge.
     
    Last edited: Feb 4, 2016
  6. Grayzer86

    Grayzer86 Active Member

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    If you plan to re do the heat treat I would run the knife through a few normalizing cycles to try to bring the grain size back down, and reduce stresses, and then redo the hardening.
     
  7. jeff

    jeff New Member

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    i was thinking of trying it again and normalizing a few times but just cant seem to keep a constant temp in my forge is it just me or is it next to impossible to keep a constant temp in a forge
     
  8. dancom

    dancom Dust Maker Best Shop Tool

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    After two or three times cycles the difference in refinement/conversion becomes unnoticeable. But additional tempering cycles at higher temperatures can be used to draw down the hardness.
    I've tempered six times when straightening a stainless blade. Hardness wasn't affected as I never went above the original tempering temperature.

    Dan
     
  9. dancom

    dancom Dust Maker Best Shop Tool

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    Maybe John was thinking 350°C not F?
     
  10. Grayzer86

    Grayzer86 Active Member

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    A forge can be quite difficult to control which is why many guys choose PID control for them. Using the steel pipe muffle helps, and the thicker the pipe the better as it helps keep the heat inside the tube regulated. Perhaps a better option is to very carefully watch the steel and cycle it in and out of the forge to keep from overheating. When the temp climbs too high pull it out momentarily then replace, before it cools too much. It's not ideal but it may be easier than trying to dial the forge in to an exact temp

    That could very well be Dan. I was thinking based on the link that the suggestion was on hardening temp but you are most likely correct.
     
  11. jeff

    jeff New Member

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    whats pid control
     
  12. dancom

    dancom Dust Maker Best Shop Tool

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    We're metric right?
     
  13. jeff

    jeff New Member

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    whats metric lol
     
  14. dancom

    dancom Dust Maker Best Shop Tool

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    PID is a method of adjusting the process (heat or gas) to target in on a temperature, like a smart thermostat. Similar to the way you step on the gas to speed up, but as you approach the speed limit you reduce the gas so you don't go over. PID (proportional integral derivative) controllers do this with electronics. The controller reads the thermocouple and controls the gas to lock on the target temperature.

    That's as simple as I could make it!

    Doh!
     
  15. jeff

    jeff New Member

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    the pid must be also able to control the amount of air from the blower or it is assumed it is set at a constant blast or no air at all
     
  16. dancom

    dancom Dust Maker Best Shop Tool

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    Yes, you are correct if using a blower. Adjusting the LPG will need a corresponding adjustment to the air in order to maintain the mixture.

    I use Venturi burners thus no need to adjust the air. The air is sucked in by the fuel and more fuel sucks more air (to an extent).

    Dan
     
    Last edited: Feb 4, 2016
  17. John Noon

    John Noon Well-Known Member

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    I use temperatures interchangeably so never much thought given they are just numbers. first post was deg F so went with it.
     

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