Heat treating W2 with P50 question.

[SBranson]

I was just reading Patrice Lemée's thread about his broken blade:
http://www.bladeforums.com/forums/showthread.php?t=796368
and was struck by this comment from Kevin Cashen:
"...the heavy smoking are explained by your photo of the end grain (far too coarse). The blade was probably overheated. In a proper full quench Parks #50 or any oil should not smoke at all, upon removal from the oil in an interrupted attempt at marquenching there should be light wisps of smoke from the blade. Overheating the blade will lead to flashing the oil or the heavy smoke you describe. "

I recently added a thermocouple to my forge and just heat treated a blade of Aldo's W2 following Don Hanson's advice:

"... Heat to 1450f, hold for a couple minutes, or until a good even heat. Quench in a very fast oil, (Parks 50 is the fastest)..."

Well, I'm not sure how many minutes it was held. I set the forge to 1450°'ish and put in the clayed blade. I'm not sure how to tell when the blade is at temp. Temperature control is pretty iffy in my set up as the forge runs hot so I vary it by allowing heat to escape out the back door. I have to run it with the front door open too to keep the temperature anywhere near 1450°.

So, I had a nice even heat, quenched the blade in Parks 50 at about 125°.
I got a big plume of smoke and when I interrupted after a good count of 7 the thing burst into flames.
I guess it was too hot?

Just when I thought I was making progress..

 

[John White]

Stuart,

W-2's heating range for quenching is 1425-1475F. Don's been doing this for a long time. For the rest of us, holding a blade within a 50 degree range needs a heating source more constantly controlled than "1450ish"

Parks 50's working range is 50-120 degrees F. Pre-heating P-50 oil to more than 60 or 70 degrees F is likely to send the oil beyond it's high end with one blade. Pre-heating it to 125....

The blade perhaps was overheated, and the oil the same, leading to the flaming and problematic hardening, but even if the blade went in at 1450, with the oil already at or beyond it's high end working range...

I've sent you a PM with some photos. Give me a call if you like.

John

 

[A C Richards]

Your clay was causing the flame up. I would not recommend the interrupted quench with the clay back. Though it does not really hurt the HT it does cause a flare up. Also you might be putting way too much clay on your blades. I have gone to putting less than .125 on each side. Getting good results and no flare.

 

[SBranson]

Thanks Chuck. I had a good talk with John and I think it was a combination of doing almost everything wrong.
Steel too hot, oil too hot, uneven temperature in my forge, improper pre-heat treatment...

First thing I have to do is really figure out how to get a controlled temperature. Once I've got that then the rest is easy. Ha Ha....

 

[A C Richards]

Control is important. I have a salt pot and my forge will hold +- 5 deg. I have had the flare also but I know I was not overheated. It happened when I pulled the blade out too early and the clay was way over flash point. That said, you cannot do much better than speaking with John White. He is very knowledgeable and can teach you a lot.