Roll Your Own...S30V

G

Gene Ingram

Joined
May 29, 2001
Messages
198
I have been heat treating S30V for quite some time now, and every now and then I have a problem with the stainless foil sticking to the blade. Anybody else have this happen? More importantly; figured out how to stop it?
Mete?, Roger?
 
Are you using the high-temp foil, Gene? There are two temp-ranges of foils out there, and if the lower-range one is used, more sticking will occur.
 
Gene,

I like when that happens. It helps provide for a quicker and more uniform quench. I wish I could learn to prepeat it with each wrap. My guess is that a tiny air port exists in the wrap. If I find time I'd like pocking a pin hole at the tang area of wrap and see what happens.

Fitzo, I am guessing what Gene means to say is the wrap sucks up around the blade, as if under a vacuum.

RL
 
I think the in-pouch vacuum is critical to a good quench, but when I say "sticking", I mean just that...Welded. So Fitz may have the answer.

There are two types of wrap listed in my MSC book...309 High Temp and 321 high titanium. I am using 321 which is supposed to be good to 2000 degrees and I'm going over that a few degrees.

Anybody tried purging oxygen with heavy gas?
 
Actually, Gene, I think purging the oxygen from the envelope will create a better weld, like the purpose of using a gas shield in MIG welding instead of fluxcore. In this case, a little bit of blade oxide may be a good thing. Perhaps something like a little lampblack on the foil or something else that may inhibit the fusion?

I know a couple makers who use the argon purge on their furnaces and no foil, and while very gas consumptive for them, it has produced good results.
 
In that case, sounds like the problem is not with the foil but the temperature you austenitize S30V. Why are you going past 2000 F for this steel, I wonder.

RL
 
Roger...Crucible provides 3 austenitizing temperatures in there data sheet dated 10/02. They are 1900, 1950, and 2000. The most complete transformation occurs with a 2000 degree 15 minute hold. I am getting a 63-63.5 Rc on 3/32 to 5/32" thicknesses. Which schedule are you using and what is your Rc?
 
A little off-topic, but out of curiosity, do you guys have a TTT for S30V?
 
Your foil should be fine at 2000 F. I thought you mentioned you go over 2000 F.

I austenitize S30V at about 1950 - 1960 F. and temper to achieve 59 to 60 HRc about 59.5 being my target. I do not like austenitizing steels at there high end. I wonder about grain growth at 2000, however you are only soaking for 15 minutes. I usually soak at 1950 to 1960 for 23 minutes.

RL
 
fitzo said:
A little off-topic, but out of curiosity, do you guys have a TTT for S30V?
Click to expand...

Mike, I sent an email request to Crucible's tech help once a year or so ago asking for a TTT diagram and have never heard back.

I harden it at the low side of 2000°F and use quench plates with the wrap on. I get the same results as I used to with an interrupted oil quench, but don't have to mess with getting the foil off super-fast. I always end up at HRC 60 with a 400° snap temper and two 400° tempers following cryo.

I have not had the foil weld to the S30V, but I also wrap a sheet of paper around the blade under the foil.
 
Thanks, Steve, I wish they'd be forthcoming with a TTT, but if not, oh, well.

I went to the quench plates too, after 20 years of using oil, and have had good success. Thanks for the input.
 
Try dusting the part with talcum powder. It's inert material that will prevent parts from welding to the tool wrap when heat treating at high temperature.

Jamie
 
Polarbear,

That is very interesting and unique, in that I have not yet seen such a recommendation. A suggestion worth experimenting with. The fact remains though, if staying within specifications no such problems should arise.

RL
 
The two things that bother me about using regular foil and this temp range are:

A small difference in foil manufacture could lower max temp specs and they usually don't expect their product to be used at so close to the upper limit, and,

The standard +/- for a thermocouple is something like 3%. That could easily mean that a 1950F setting is over the max temp for both the austenizing AND a 2000F foil. I don't trust thermocouples despite relying on them. Two of them placed side-by-side will rarely read the same, and there is no way to know if they are still accurate with age unless they totally puke. It's not in their manuals, but both Paragon and Evenheat will tell you to periodically replace the thermocouples.
 
Fitzo,

Very good and sound advise to take note of. However, it does not explain away Gene mentioning that he goes over 2000 F for S30V. Not that this means much but I have taken the 2000 F foil I use (that sold by Enco) to 2050 F on several occassions austenitizing S90V. So far I experience no welds at that temp with that steel and the foil was uncompromised, but on the very edge of being (extemely brittle). On another note, using the very same foil, I have on an occasion or two had the foil weld to other type blade steel at oven temp. of about 1950 or so. When this has happened, and on a time or two, the foil packet has been very tight all about the blade - as if a partial vacuum had been pulled. Go figure(?). Other times I have experienced the foil packet resembling a vacumm pull with no noticable welding. I like it when it goes that way.

RL
 
When I set my Evenheat for 2000, it wanders around between 1995 and 2005, so a few degrees should not be misconstrewed as out of spec. I use this schedule only after much dicussion with Crucible Tech, and extensive field testing. I am getting the very most from S30V hardness capability, with a very small reduction in it's toughness potential. In small blades, as most of mine are, my philosophy is wear resistance is most important when toughness is still higher than many other commonly used blade steels.
I am possibly pushing the foil a bit too hard as the problem does not occur everytime. There have been some good ideas come from the discussion, and I think I'll first try the paper wrap technique until the Ticronic arrives. I have been using a toothpick.
 
Gene Ingram said:
I think I'll first try the paper wrap technique until the Ticronic arrives. I have been using a toothpick.
Click to expand...

interesting
I have used some paper but not much, I fear that
when it blows up with the expansion of the gasses, once it starts to cool
on the quench
it will/may allow O2 in and doing just what you don't want it to do anyway.

normally I don't use anything in the pouch
and I've had no weldings but I don't go above 1950 with 154 CM either. :)

CO2 is cheap and will work as a gas but it's not good for your electric elements :(
 
Gene Ingram said:
When I set my Evenheat for 2000, it wanders around between 1995 and 2005, so a few degrees should not be misconstrewed as out of spec. .
Click to expand...

If I remember correctly, the swing in temp around the setpoint is called "hysteresis", and +/- 5F around a 2000F setpoint is only a 0.5% range, a heckuva good value. Evenheat makes a pretty danged good product, considering a very expensive controller couldn't do any better!

Theoretical discussion only: Another problem that can occur in a furnace is that the thermocouple placement doesn't reflect the actual temperature at the spot you place your blades. This happened with the earliest Paragons; it was about 50F hotter at the bottom than up top in a corner where they put the thermocouple right by the door. After I found this out, I changed the placement of the themocouple and it was much better. Thus, when I bought a second furnace, an Evenheat, I drilled several holes in it to insert a thermocouple and monitored temp close to where the blades go. I am happy to report that Evenheats seem to read essentially the same on the meter as on the external probe. Good engineering!

Gene, since you use quench plates and don't have to worry about the bag expanding since you'll squish it back down, you may consider putting a cigaret filter in the envelope instead of paper (if you smoke, that is. Scrounging butts may not look so good and draw some odd looks!LOL). It makes quite a bit of gas. It's an old trick used by some to expand the bag so the blade can be removed readily for oil quenching.

Because I don't trust thermocouples so much, I personally use the mid-point on the austenizing schedule and allow a little more time. But, that's just me. Running at 2000F, I don't think that small hysteresis is a concern for the quality of the blade, especially considering you get the good Rc's. One of the good things, though, about these high alloys is that some of the alloying elements do a good job of restricting grain growth. I keep two old blades around that I broke, an ATS34 and a 440C HT'd by Paul Bos 20 years ago, and use them for magnified visual comparison of the grain on testing a new HT schedule. If I can get that look or better, I'm happy.

Something else just occurred to me: Gene, how are you prepping the blades prior to putting them in the envelope? Any possibility of any residue that could turn acidic at high temp and act as a flux to induce welding?

This is a real good thread. I hope you can get the sticking problem fixed, Gene! The biggest PITA problematic skill involved in knifemaking doesn't need any additional problems like the blade sticking to the bag!
 
I just bought a new thermocoupler for my oven, so the topic is near and dear to me right now.

The Orton book says their type K is good for 20 to 50 firings. They should be replaced before they break. Before mine broke the themocoupler was reading 50 degrees too high! Yup, that makes a big difference. (I bought a pyrometer to double check the oven's meter.)

So, (like already stated) you have to set your oven to whatever temperature gets the results you need. I had to set my oven 50 degree over. In other words, if I wanted 1950, the oven had to be set to 2000.

Also, the temperature is not even while ramping up. My thermocoupler is near the top. While ramping up the temp at the blades was another 50 degrees cooler than the top of the oven. (Because of the worn thermocoupler it actually read 100 degrees higher than it was.) Once the oven was at temp for awhile things evened out.

So, just because your oven says 1950 at the thermocoupler, doesn't mean the spot where your blades are is 1950 (especially while ramping). Plus, just because you were getting good results 6 months ago with the oven at 1950, doesn't mean you'll get the same thing today at 1950.

FWIW, omega sells standard thermocouplers just like what I had (by looks). They also have Nextel Ceramic thermocouplers that are designed for continous use. They look very different. Mine broke at the tip with has a little bead weld. These Omega XC series look different. And they are flexible, so I can bend it down to the level of the blades.
http://www.omega.com/ppt/pptsc.asp?ref=XC&Nav=temb05
Hope it works, I sure paid enough for it!

Steve
 
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