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edge master
11-13-2011, 06:54 PM
Crucible's data sheet for CPM S30V recommends that when using an oil quench, an interrupt quench should be used to about 1000 degF. and then air cooled to below 125 degF. Can anyone tell me how to determine when the metal reaches 1000 degF?

Knifemaker.ca
11-13-2011, 07:34 PM
That would be pretty much cool to "black" - all heat colour gone. Why would you choose oil quench for S30V? Its doable - but so darn messy and so much extra cleanup after heat treat as compared to plates.

Just curious.

Rob!

edge master
11-13-2011, 08:05 PM
Are there any down sides to the plates? Seems that there would be very little contact surface with the ground blade to actually conduct the heat away. I know the practice is used pretty extensively. I'm new to heat treating and want to get off on the right foot. Would be very frustrating to spend hours grinding and filing away on a blade only to end up with a poor heat treatment process.

Knifemaker.ca
11-13-2011, 10:38 PM
I guess there are downsides to everything. In the case of the plates, some people get issues with the foil sticking. We get it too on maybe 1 in 100 blades. As for contact, it doesn't seem to be an issue - even with tapered tang. We did a test a couple years ago making a "stepped" "Blade". I don't remember the exact numbers, but parallel surfaces are required for rockwell testing. We took a bar - probably about 3/16 thick and ground a section down to 1/8 and another to 3/32 thick. Obviously, only the full thickness section had contact with the plates. The hardness was the same (+/- .5) on all three sections, suggesting to us that the cooling was plenty fast enough for good hardening. Heck, these steels will quench in still air if necessary, so any plate contact just accelerates that big time. Warping is rare with plate quench, but by the time you know about it, it's too late. The blade is already too brittle to straighten without re-heating.

Plate quenching is widely used because of the results. Many makers send us blades at 1000g finish or more and when they get them back, they can often finish the blade with just the buffer.

The rest of this is just opinion - and of course, it relates just to air quench steels.

If I had $30,000 to spare, I'd probably use vacuum heat treat
I don't so I use plate quench, which I consider about equal, but way more work
Salt bath turns out a fine product, but from what I've heard, also lots of pitting and clean-up.
Oil, also ok, but messy as heck, with lots of clean-up and anti-scale required. Cutting hot blade out of envelope risks warping.
Still air (or fan - positive pressure) works, but doesn't get all the potential of the steel
I don't know anyone who has been truly happy with inert gas.
We have oil here for carbon or tool steel blades - and we can keep the uglies to a minimum, but I can't imagine using it on air quench steels. Hope that helps some.

Rob!

edge master
11-14-2011, 04:08 PM
Thanks Rob. You've made my decision easier, and the cleanup too. Plate quench it is. Really appreciate the time you put into your response.

badgerknives
11-15-2011, 10:40 AM
wait what is a a plate quench i all ears?

Knifemaker.ca
11-15-2011, 10:30 PM
Fair question badgerknives. Plate quenching essentially is another way of quenching steels that will quench in still or blown air. Examples would be all (I think) of the CPM blade steels - common stainless steels like ATS34, 154CM, 440C, 19C27, Elmax.... the are many dozens. When the blade comes out of the kiln (or well controlled forge) after it's soak in a tightly sealed foil envelope, we used to take the blade out of the foil to cool in air, or in front of a fan. People are now leaving it in the foil and placing the packet between thick plates - usually aluminum. This cools the blade quicker - even with minimum contact, but very importantly, it ensures the hot blade never sees oxygen - so it stays relatively clean and shiny. Generally, a point more hardness can be acheived compared to air quench as well. Cheap - Easy - Now widely accepted - and it saves a whole load of clean-up after heat treat. Anyone who can heat treat air quench steels can do it easily.

Dwane Oliver
01-29-2012, 09:44 AM
Fair question badgerknives. Plate quenching essentially is another way of quenching steels that will quench in still or blown air. Examples would be all (I think) of the CPM blade steels - common stainless steels like ATS34, 154CM, 440C, 19C27, Elmax.... the are many dozens. When the blade comes out of the kiln (or well controlled forge) after it's soak in a tightly sealed foil envelope, we used to take the blade out of the foil to cool in air, or in front of a fan. People are now leaving it in the foil and placing the packet between thick plates - usually aluminum. This cools the blade quicker - even with minimum contact, but very importantly, it ensures the hot blade never sees oxygen - so it stays relatively clean and shiny. Generally, a point more hardness can be acheived compared to air quench as well. Cheap - Easy - Now widely accepted - and it saves a whole load of clean-up after heat treat. Anyone who can heat treat air quench steels can do it easily.

This is all good stuff.
One more question : Do you quench one blade at a time? Or can you quench a stack of blades , say 1" thick ( 4 blades )?
Thanks for the answers.

Knifemaker.ca
01-29-2012, 02:22 PM
I put up to six blades in the kiln at a time - in six envelopes - take all six out and transfer to the plates - add the top plate and quench. I have big plates 12 x 24 x 1 each. I have not tried stacking blades, but I'm guessing you'd lose many of the advantages of quick cooling - less warping - and the envelopes would be tough to manage without the blades sliding around.

Doesn't mean it won't work, but I'm not gonna try it. ;-)

rhinoknives
01-29-2012, 11:56 PM
I've oil quenched damascus, 1080 & 1095 Steels.
I mostly use all CPM Stainless & Tools steel now except for 440C.
I send all of these to Bos Heat treating at Buck knives. They have at least $500.000 in the equipment from what I have gather and do the Liquid Nitrogen second hardening.
The man that's there now,also named Paul, Continues the Paul Bos tradition of excellence and being at the for front of Stainless and Tool Steel heat treatment.

I have almost 40 blades ground and near ready to go! If you like, Your welcome to send your blade to me and I will batch it with mine. We can work it out. it will be around $15-20?? with shipping.
Let me now if you're interested?

Laurence

www.rhinoknives.com/

Dwane Oliver
01-30-2012, 10:23 AM
Thanks for the quick reply , I was thinking the same thing too , but wanted to ask.

Laurence : thanks for the offer buddy , but I havent even profiled the blade yet.