Am I thinking correctly?

[mulie]

I was finishing up a knife last night and began thinking how hot I could the blade actually get before it began affecting the temper.  So here is my question.  If after I quench a knife and run it through three 350 degree (or whatever temperature used on a specific blade) temper cycles in the oven, wouldn't the blade temperature have to go above 350 degrees to really affect the temper?  It seems to make sense to me, but that really doesn't mean much.
Thanks for your imput.
Judd

[robtattoo]

As I understand it (& I'll admit, I'm a little out of touch on this stuff) your supposition is correct.

The blade would have to get above it's thermal-cycle temperature before it's molecules are affected in a negative way. However, if a constant heat is maintained, at any temperature above about 220º (IIRC) the grain structure will be affected. Think of it as a 'lower temperature thermal cycle' The degree that the steel will be affected wll be dependant on the type of steel & how it was treated from annealing through normalising, hardening & tempering.......


I think......

[Lin Rhea]

You are correct. Thus the basis for "losing your temper". Bad things happen when you get too hot.

[Kevin Evans]

I am far from being any kind of exspert ,but I think what you are asking what temp or color it will lose its temper?(get soft)
If it turns blue or gray you have diffitnatly lost it.Thats about 550 degrees to 650 degrees.
I try to get mine a gold color out of the oven on 5160. and maybe gold blochy looking on Damascus
If this is not correct believe me someone will come along shortly and correct me.

[mulie]

Lin,
The people in this area start losing their tempers when the temperature goes above 100 and there is no rain in the forecast.
Thanks,
Judd

[tippit]

That's why it's so important to watch your grinding heat after your quench/temper your blade.  If you get the tip too hot into the purple, you just lost it.  Only way to fix it is to start over with a re-quench/re-temper.

[Lin Rhea]

As Kevin and Jeff say, if it turns color while grinding, you have affected the temper. This is where developing good habits is so important. Always keep water close by and use it even if you dont think it's too hot. The edges are the vulnerable areas so dont think it is ok just because you are not feeling heat where you hold the blade. Grind a little and dip the blade in the water. New, sharp belts help too.