HT question

SDS

SDS

Joined
Oct 22, 2007
Messages
1,389
Is there any reason you cannot or should not temper a blade with it still wrapped in the HT foil? I have read posts where people say that as long as the air quench (D2 and ATS34) is quick enough you can leave them in the foil.

I was just wondering if I can just quench them, and then place them back in for the temper while still wrapped or if this is detrimental somehow.

Thanks,
SDS
 
The foil would not help or hinder the temper in any way. If you are tempering at say 450 for a couple hours there is really no reason to leave the foil on
 
I haven't had any issues at 450. However at 950 I have had some carbon or scale buildup. It isn't a huge issue. It just takes more time to clean them up before finishing. I figured that if I left the wrap on during the high temperature temper it might help prevent the buildup.

Thanks,
SDS
 
Mike, I'm tempering ATS34 at 975 (I thought it was 950 from memory but checked). I got that tempering temperature from Terry Davis' chapter of "How to make multi-blade folding knives."

He says to temper at either 400 or 975 but that 975 "results in a tougher, more flexible blade." He recommends 975 twice for two hours each.

I'm open to suggestions or opinions on what others think is better.

SDS
 
The 975F temper doesn't make it more flexible, it makes it more wear resistant through carbide precipitation and increased hardness. The 400F temper will give you greater toughness, edge stability, and corrosion resistance.
 
Just when I thought I had this figured out.

So which does everyone recommend?

SDS
 
My problem is that most of the advice I have read comes with pretty good justification for what they are doing. Guess I'll just have to decide which is best for me.

On a side note, is there any reason not to re-use the foil wrap after a knife is finished? Assuming it isn't torn or mangled it seems like it would still perform the function of preventing oxygen from getting to the blade.

Thanks,
SDS
 
SDS said:
On a side note, is there any reason not to re-use the foil wrap after a knife is finished? Assuming it isn't torn or mangled it seems like it would still perform the function of preventing oxygen from getting to the blade.
Thanks,
SDS
Click to expand...

SDS, I throw all my foil envelopes that I use on my airquench steels into a bucket for later use. I use them for different thermal cycle process' that I do on my forged blades (which, because of more precise temp control, I feel more comfortable doing in my evenheat over my forge). I use the old envelopes for everything short of austinitizing or grain size reduction where a quench might be called for. Obviously the envelope isn't practical in those cases.

But yes, I re-use my old envelopes all the time :thumbup: :thumbup:

And, fwiw, I also use the lower tempering temperature when working with ATS34 (2 hrs @ 400*F x 2)
 
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Thanks. I don't think of myself as a cheapskate, well, at least not most of the time, but it seems like a waste to toss them if I can use them again.

And thanks for the input on the tempering temps. It seems like the lower temp is the more popular choice.

Thanks,
SDS
 
The foil is reuseable for some thins however I would not use it on a blade for the first heattreat, as it will get small pinholes and cracks that will let oxygen in. the foil is cheap enought on a per blade cost that I would not take the chance. Also on ATS-34 420 F. 2 X 2hrs.
 
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I presume you are plate quenching, because I would not recommend air quenching in the envelope. Holds the heat in too long.

I don't re-use foil. Mostly becuase the bulk of the blades I do are for others - and I'm not going to risk their blades. As a matter of fact, I double wrap - both envelopes with new foil.

I have tried leaving blades in the envelopes for tempering. The problem comes in cryo, where the envelopes are hard to hang. Then, when you take them out of the Liquid Nitrogen. the nitrogen (which will surely leak into the envelope) boils almost immediately - and blows the envelope up like a ballon - wrecking the envelope and spitting Nitro all over the place.

As for the tempering range for ATS34, 154CM is considered the same alloy - just cleaner - and crucible recommends avoiding the higher tempering ranges because it leads to lower corrosion resistance and lower toughness. Add me to the list of those using the lower tempering range.

Rob!

Disclaimer. I am occaisonally not entirely right. Someone told me Paul Bos uses the high range. I have no idea what his justification is - or if that is even true.
 
Rob! said:
Disclaimer. I am occasionally not entirely right. Someone told me Paul Bos uses the high range. I have no idea what his justification is - or if that is even true.
Click to expand...

I believe that Mr. Bos will use which ever temp you want. I sent him a blade made from CPM154CM and told him I intended to use it for fishing. He then selected the lower hardening temp, stating that it provides better corrosion resistance. If you send him some steel and aren't sure which temp to use, just tell him what you are trying to accomplish and he will take care of the rest.

(By the way, I was very pleased with the service I got from Mr. Bos.)
 
SBuzek said:
The foil is reuseable for some thins however I would not use it on a blade for the first heattreat, as it will get small pinholes and cracks that will let oxygen in. the foil is cheap enought on a per blade cost that I would not take the chance. Also on ATS-34 420 F. 2 X 2hrs.
Click to expand...

Agreed :thumbup: Thats why I only use the old foil envelopes for thermal cycles on my forged blades. All air quench stock gets a new wrap.
 
I hate to ask what is surely going to be a stupid question but, since I don't forge (yet) can someone explain what a thermal cycle is??

Thanks,
SDS
 
SDS said:
I hate to ask what is surely going to be a stupid question but, since I don't forge (yet) can someone explain what a thermal cycle is??

Thanks,
SDS
Click to expand...

Annealing, stress relieving, normalizing, Spheroidizing or Spheroid annealing are all different types of "thermal cycles". Tempering ? I'm not sure, but I think I would consider that a type of thermal cycle too. And I don't think you necessarily have to forge to benefit or use certain types of thermal cycles. Stock removal only knifemakers often use thermal cycles too. For the most part, bar stock that is purchased from the supplier for stock removal knives should already be in the proper condition to mill, drill, grind, etc. and ready to harden & temper when you're to that point. Certain stock removal knives can benefit from a stress relieving cycle (or 2). For instance an integral with complex geometry that might tend to move or warp when going directly from the mill or grinder to the kiln for hardening.

Some of the cycles can be lengthy, and at high heats (just below, at, or above austinitizing temperatures) causing pitting, scaling etc. Rather than using PBC or similar products to protect the surface of my forged blade while in the kiln I use my old envelopes like I had mentioned in an earlier post. If I have a forged blade in an old envelope with a pin hole in it that I missed and it ends up with pitting, the blades usually have enough meat left on them at this point that I can still clean them up. The old foil envelopes just save me a little potential grief "just in case" the meat isn't there. So far I've been lucky and the old envelopes have done there job well. But, like SBuzek said, the potential for pinholes, etc. exists.

Sorry if I confused you about how I re-use the foil envelopes SDS. For austinitizing my air harden steels I always use a new foil pack. I usually have a considerable amount of time into them and don't want to risk using an old, bad envelope. For austinitizing my forged blades I use either PBC or Satanite (when doing Hamon) for protection. IMHO, foil envelopes are not practical during austinitizing of oil or water quench steels due to time required to remove the knife from the foil before quenching.

And I might get thrashed for my technique here. Re-using the old envelopes is just one of my ways of being frugal, trying to eliminate problems during thermal cycling.

Basically, the only thing I use my forge for is for shaping my blades. All other "thermal cycles" are done in my kiln, at precise temps, with what I believe to be, plenty long enough soaks. I've become down right anal about trying my best to insure my steel is in the perfect condition before austinitizing and quenching (blame it on Cashen). That's how, (and why) I re-use my old foil, and how I do it. OMMV ;) Some guys are masters at controlling everything in their forge. I'm not to that point yet :o
 
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David, thanks for taking the time to answer. That makes plenty of sense. I guess if I had thought about the actual words "thermal" "cycle" it might have been a little clearer was being talked about.

I feel like I'm just a little bit away from having a pretty good grasp on most of this. There is so much to learn about this stuff. I'm just glad it's fun or I'd give up on trying to figure all of this out.

Thanks to everyone for having patience with me.

SDS
 
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