Stainless quench methods!

[luc]

Hey all!
I did a search for this but did'nt come up with much!
I'm getting ready to take the plunge and try HTing some stainless, But I have a few questions about the diferent quenching methods used for air hardening steels.

Basicaly I'm wondering what the most practical/effective set up is.
I have read about, quench plates, hanging in front of a fan, using a rack with a blower underneath, and also oil quenching.

The main thing that I am worried about is not getting the blades to cool fast enough.
I will be using a Even Heat oven with a throat of 10x8 and was hoping to be able to do at least 4 blades at a time to conserve energy.

If I were to use a wire rack/grate combination over a blower, would I have enough time
open the oven and remove all 4 knives and set them over the blower.
Also with this method would I be able to leave them in the foil during quenching?

warping is the next question, if use the blower method, should I place the blades in the rack edge up or down, I also know that some guys grind after HT and with stainless this seems like it might work very well.

I figure most of the knives that I will be doing in stainless will be 1/8 or 3/16 and probably 6 to 12 inches maybe some 1/4 inch as well.

Oh! and the steel I will be using is ATS-34.

Any thoughts on this would be greatly appreciated.
Sorry about being so long winded.
Lucas

[SteveS]

Me be quench plate fan. (Everyone has a method and most will defend to the death. I can only say what I've settled on - which is what I think you are asking. BTW you have to get a hardness tester, well I think so.)

I have 2 aluminum plates, 6x12x1".

I heat the blades edge up.

Pull out of the oven.

Set on one plate.

Put another on top

press down with one hand

Shoot compress air all around for 15 or 30 seconds or so (I don't really know).

Open the packet and Remove the blade(s), still too hot to touch without gloves. Almost burning leather.

The blades are still pliable for a minute or 2. I straighten by hand or in the vice as needed.

That's it. Nothing to preheat or clean up (oil).

As far as batches the largest I've done was 3 packets with 2 knives each.

Hope that helps,

Steve

[RJ Martin]

Lucas: Quench plates are the preferred way to go, for the following reasons:
1) You can put several blades in a package, provided they are all the same thickness.
2) Warpage is minimized
3) You can leave the blades in the foil during the quench. You may want to remove them after they have cooled some, as Sando points out, to check for warpage. But, you aren't handling red hot blades at this time.
4) Quench plates give you the fastest, most even quench, with the least amount of scale.

Just make sure your plates are FLAT.

[luc]

Thanks for the quick response guys!
With the Quench plates would it be better to just profile before HT and grind after?
It seems like any part of the blade that was'nt touching the plate might be prone to warping. Or is it not that big of a problem?

when you press down on the top plate are you applying much pressure?

About how much time do I have to get the packets to the plates?

Do the blades tend to warp into the bottom plate before you set the top?

Can you think of anything else I should know about using quench plates?

Thanks again!
You guys rock!

[SteveS]

Originally Posted by luc

Thanks for the quick response guys!
With the Quench plates would it be better to just profile before HT and grind after?

It seems like any part of the blade that was'nt touching the plate might be prone to warping. Or is it not that big of a problem?

I thought the same thing. Doesn't seem to be an issue. Steels like ATS-34 give a long time to harden (hence air hardening). The plates suck out the heat plenty fast, even if there isn't contact all over. I've been told I don't even need the compressed air, but I like it. Compressor noise and all that.

Originally Posted by luc

when you press down on the top plate are you applying much pressure?

No I just lean on it while I'm blowing the air.

Originally Posted by luc

About how much time do I have to get the packets to the plates?

Oh a lot. I've fumbled around trying to remove from the packet just to try it, then gave up 15 seconds later and quenched the whole thing. Came out fine.

Originally Posted by luc

Do the blades tend to warp into the bottom plate before you set the top?

Not all blades warp. Heck, there's lots of people that air harden on a rack. The flatness is an issue because they are going to harden in line with the pressure you put on them. Other warping is probable due to stress from grinding.

Originally Posted by luc

Can you think of anything else I should know about using quench plates?

If you can afford it buy copper. I hear it's even faster. Well then again aluminum sure works fine. Quenching air hardening steels is a whole lot easier than oil/water steels. I've only had one small crack and that was near a pin hole.

If you want something to worry about, worry about an accurate oven temp. THAT makes a difference.

Steve

[luc]

Thanks Steve!
A couple more!

Do you ever stress relieve after grinding to minimize warping?

How do you keep track of your ovens accuracy?

I can't wait to try this. I love high carbon steels, But I could do without coming into the house smelling like a firefighting mechanic, holding a warped knife, and tracking oil 10 feet onto the carpet.

[SteveS]

Stress Relieve: Yes I do that, doesn't always help, but seems to reduce the warping.

Oven's accuracy: I have one of those volt meters with a type K thermocoupler (harbor freight has them for about $40). But even better is a hardness tester. You can tell a drop of 25 degrees pretty darned easy. Besides, hardness is more important than the oven temp.

Steve