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General question on tempering


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I've read through the stickies and guides but can't seem to find an answer to a question I have about tempering a blade. I get the whole concept of quenching to get max hardness then tempering to remove brittleness while keeping edge holding ability. What I'm not sure of, is after soaking the blade at tempering temperature for however long, do you then quench (rapid cool) to lock in the temper? If so, does this second lower temp quench need to be in the same media (preheated oil if used for initial quench) or can it be a water quench.

I realize there are way too many variables for a one size fits all answer, but I'm trying to understand the general principle.

Thanks in advance for sharing your wisdom.

 

John

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it is often a good idea to quench after tempering color is reached.  When using an oven to temper it is really not necessary though.  If you run the colors  and desire a differential temper (blade spine softer for instance) then it will be important to quench quickly to halt the color run at the right point!  Water quench is normally sufficient for this type quenching as you are NOT at a heat that could harden the metal... you just need to cool the metal and only little at that.

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Not trying to hijack John's thread here, but if you are tempering with the heat running and need to quench it rapidly, does quenching in water adversely affect steels that are hardened with an oil quench?  An oil quench to stop heat run in tempering takes a bit longer than water.

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No the temperature shock of going from 450 degF to ambient is nowhere near as radical as the temperature shouck going from 1500 deg F to ambient.

 

You quench so as to not overshoot the temp and to make it easier to handle.  Now a subzero quench to help lower retained austinite is another kettle of quenchant...

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