Temperature before tempering

A

alexmin

Joined
Nov 16, 2005
Messages
513
I quenched my O-1 full integral blade in ToughQuench oil but didn't let it cool to 130F(my blade was too hot to hold it by bare hand for more than 2-3 sec.) before putting in boiling water(to remove PBC) and when while it was still hot after boiling I put it into 350F tempering oven.

Is it important to let blade cool to 130F before tempering?
 
I believe so. I like to allow my blades to achieve hand warm in still air before placing in pre-heated boiling water. I then allow to acheive hand warm after PBC removal before placing in pre-heated temper. It does not hurt to repeat a heat treat if you think one of the steps was conducted in error so long as the integrity of steel has not been compromised (no pings please).

rlinger
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I guess it would depend on what the steel is. A complex steel (any stainless or high alloy steel) retains austenite after quench as a function of how cold it was quenched. So you tempered any martensite you had formed, but upon subsequent cooling some retained austenite would have converted yet be untempered. So you should cool and temper again.

It is my understanding that austenite that sits around long enough, due to temperature too high to form martensite, yet too low to allow austenite, will eventually form bainite. Not real common though.

So long as your quench was fast enough to "get under the nose" of your steel, you shouldn't have any pearlite, which is what you're probably trying to avoid. So I expect you're fine.
 
Most steels are cooled to warm oil temperature and a good number of steels should not be cooled lower than that before temper.
 
To temper the martensite you have to let it form first. For most simple knife steels,the Ms is a little above 400F, and the Mf is around 200F (these are just basic numbers for the point of this discussion). If you put it in boiling water it got to 212F so it should have transformed virtually all of the austenite into martensite. Now, the reason you temper twice (sometimes three times) is that each time the temperature falls to room temp (or below the Mf). ,some more retained austenite transforms into martensite. This is now Un-tempered martensite ,and needs to be tempered to remove the brittleness. After two temper cycles, most all of the austenite is gone, and there is little gain from further temper cycles on most steels. The reason for cryo is that some high alloy steels don't transform until around -100F.
Stacy
 
I quench my blades in oil and leave there til I get my oven down before I put back in to temper the steel. Cooling the steel at 125F to 130F in oil is a good temperature before tempering the steels. I like the Gold look in my steel when it comes out of the tempering. I alway look for that in my treatment. And I never quench in water or let air cool before I temper the steel. I do that later on slow. 1095 - 1084 - 52100 steels. ----------:thumbup:
 
alexmin said:
Where can I see the "nose" chart for O-1 steel?
Click to expand...

Alex,

Here are the pages on O1 from my copy of the Heat Treater's Guide. Hopefully, they are what you were looking for.


HTG-p-278_O1.jpg


HTG-p-278a_O1.jpg


HTG-p-279_O1.jpg


HTG-p-279a_O1.jpg


HTG-p-280_O1.jpg



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