ATS34 heat treating...

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I recently acquired some ATS34. Would someone be kind enough to post the hardening and tempering temperatures with approximate Rockwell C yields. Thanks.
 
Mike, there's no mention of cryoing. Do some makers HT and temper only, with no cryo? Is cryo just an added bonus to the process, that's not entirely necessary?
Robert
 
There are lots of people that heat treat without using the cryo step.
I don't believe they get as good a blade that way.

That step would take place, IIRC, after heat treat, and before tempering.
 
Foil wrap the steel.

Pre-heat slowly to 1400 F and hold until equalized. I usually hold for about 7 minutes at 1400 F.

Ramp quickly from pre-heat to 1950 F and soak there for 25 minutes.

Rapid air quench.

(if not cryogenically treating) After the steel becomes hand warm, temper immediately at about 450 F / 2 hours. Repeat at about 425 F / 2hours.

I am guessing about minimum 58, maximum 59 HRc.
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(if cryogenically treating) After quenching and the steel becomes hand warm, snap temper at 300 F / 1 hour. Cryo. Temper at 500 F / 2 hours. Repeat temper at 475 F / 2 hours. About 60 HRc.
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Cryogenic treatment converts retained austenite to UN-tempered martensite and that is all it does so far as I know, but doing that is plenty good enough.

RL
 
Thanks guys! BTW, I've been thinking about something. One of the big problems with HT'ing carbon steel is the trouble you have with the scale. The compound from Brownells is good, but why doesn't anyone that has an electric furnace (I have an old Lindberg) just put the blade in SS foil, with the little piece of paper for the O2 consumption, like the stainless steels are done. Wouldn't that help eleminate the scale, or would it still pick some up between the furnace and the oil? I never hear of anyone doing this, so there must be a reason why not to. :confused:
 
Quench times are too short for plain high-carbon steels, Robert. Can't get em cooled fast enough in the foil, and can't get em out fast enough to stop 'em from forming a bunch of Pearlite.
 
You can wrap oil quench steels in HT foil but you have to remove the blade from the foil prior to oil quenching. This is somewhat cumbersome and time consuming....at least for me......and you risk not getting a good quench if you have multiple blades to do. Most heat treat books I've read recommend not wrapping oil quench steels in HT foil due to the risk of improper quenching....and they say to never ever oil quench w/ the foil still on the blade. I suppose that is the beauty of air quench steels. Bill Bryson's book "Heat Treatment, Selection, and Application of Tool Steels" covers this on page 23 if can get your hands on a copy. Not long ago I had this same question. I was able to fairly quickly cut the foil and remove the 01 blade on several knives prior to quenching. However, if I'd have been HT'ing more than a few blades this way I believe I'd have run the risk of them cooling down too much prior to quench since it was taking a while to manipulate the blades out of the foil. It is tough working fast with gloves on and a very, very hot package!

Ed Barker
 
Ok Mike and Ed, I'm starting to see now. I keep wondering about quenching in the foil, :( it would be like quenching between plates in a way. With very little air in the foil, it seems the entire package and contents would qnench at almost the same rate, eliminating the necessity of handling the hot foil and removing the blade from it. Obviously, this has been tired before. If there was a way to produce a vacumn in the foil chamber, like those food freeze/bag gizmo's, the the steel inside the foil would for sure be touching the foil. I'll try some samples, I have a HT oven, use Brownells oil quench, and have a Rockwell hardness tester, so I'll give it a shot later on. Then again, the Brownells compound (PBS?, I forget, and it's at the shop) isn't hard to use at all (just be sure to get the steel to at least 500 before running the blade through it).
 
Medium and shallow hardening steels, those that are not air hardening, require quickness enough to quench that time taken to remove from foil misses the 'nose'. Shallow hardening (water hardening) and medium hardening (oil quenchables) should be atmosphered controlled by salt, gas, vacuum, or left large enough for grinding out scaling and decaruration. Most often these type steels are not soaked long enough (as stainless usually requires) to cause real deep decarburation. Stainless pits very deeply because of the relatively long soak periods required for it. Thankfully to plain chemistry these steels are deep hardening because of the elements added to help in that and that allows a tolorance, so to speak, in using such things as foil to atmosphere control the tool steel.

In short: Fitzo said it in less words.

If you are fortunate enough that Mete, our resident metallurgist, chimes in write what he says to you down and keep it as a reference.

RL
 
Yeah ! But at midnight I still have to repeat myself - I keep telling you guys to buy a vacuum furnace but you're too cheap !!!!! ...Unless you're dealing with an air hardening steel it gets a bit difficult to get that blade out of the pouch quickly enough to get a proper quench. Use one of the coatings to minimize decarb and scale. The other option would be hardening from a salt bath.
 
Mete, I of course have never once doubted your advise in getting the setup you have been recommending. The problem for me, at least, is financial. If it grows as I hope I will be able to follow your instruction in that, and the sooner the better so far I as desire.

RL
 
I don't know much about the salt heat treating, other than what I've seen on a couple of sites. Do you still oil quench after removing the steel from the salt solution?
My Lindberg HT furnace (bought at an auction many years ago, and only recently got it to working) came with a tube that has a ring seal, and I think was used for gas (argon? Nitrigen?). It has two fitting on the end. I wonder if possibly a vacumn pump could be attached to one of the fittings, and cause the tube to be under vacumn during the HT? I'd be happy to show a photo of it, but haven't studies how. I could send some pictures of my furnace to one of you guys.
 
Robert, most folks who use salt baths have two tanks. One uses high temp salts, and this tank is used for austenizing. The piece is then rapidly transfered to the low temp salt for quenching. Even though this lowtemp bath is essentially at tempering temps, it still as such great heat removal capacity it can successfully avoid Pearlite formation. From what I've read, there are some positive benefits in terms of Martensite transformation at the highest temp possible that avoids Pearlite formation.

As an aside to the pouches: my experience has usually been that the inclusion of a piece of sacrificial oxygen scavenger like a piece of brown paper or a cigaret butt will cause the envelope to expand a little from the carbon dioxide and water vapor formed, and that if the pouch is effectively sealed, it can't help but pooch out a bit. This creates a problem with optimizing heat transfer through the bag. That is why I personally went to the aluminum plates and now just put pouch and all between them, squeeze, and give a blast of cold compressor air. I know some don't like the plates, but I've had excellent results. Different strokes...., neh?

Hey, Mete, I'd love to have a vacuum furnace! I ran a small one almost daily at the carbide plant 30 years ago. I've never forgotten that little beauty of a beast! Using old analog controls, with that clock timer setting of on-and-off power, we could control temps to within 20F max as measured with a calibrated optical pyrometer. That unit would be a dream for knives. Vacuuum austenizing and then a blast of cold nitrogen to quench. Yum, yum! That said, it had to cost a bundle, and sucked power like no tomorrow. It was about three feet across and five feet tall, ran on 440 3-phase with a huge "hum", and was the very tiny sister to the production jobs that were two stories tall and about twenty feet in diameter!

Do you have any idea if small versions are available? And would there be anything usuable at home? Can't actually do it, but would be very interested in reading about them. Thanks!
 
rhrocker, Heat treating in an inert gas is another way of avoiding scale and your furnace is apparently set up for that. If you set that up to a vacuum pump you would probably ruin the pump.You would use argon but I have no idea how much gas would be needed. .....fitzo, last time I brought up the subject of a vacuum furnace someone found one used for sale on ebay - $25-30,000. To justify that you'd really have to be heat treating for others too !
 
Thanks again guys! I'm all straightened out now on the salts, etc! Appreciate the info. Mike, if you buy one of those $30,000 vac furnaces, you're more than welcome to keep it at my shop. I try to help out when I can :D
 
Robert, as long as you're next to a power plant and willing to pop for the 2" copper cable to bring the power in, it's a deal!

Now, all I gotta do is win the lottery.......... :)
 
Great! Let me know when you win it (arn't we related somehow?)! Back on the vacumn thing with my outfit (tube with fittings for inert gas), couldn't you vac the inert tube with a good air conditioner service type vac, close off the lines with a ball valve, then do the heat treat? This way the pump wouldn't be in the loop. I'm not trying to beat this thing to death here, but just wondering. Of course the simplest thing would be to put argon in the tube under a little pressure (very little).
 
Robert, if your furnace is anything like the standard knifemakers furnaces or the lab furnaces I'm familiar with, it would never hold any vacuum. You'd be sucking fresh air into it constantly.

As for the argon, it definitely works. Paragon actually sells an upgrade for their knifemaker furnaces to do this. Plain Ol Bill bought his with this. He did his first SS HT and left a trickle of argon through the entire cycle. It sucked up half a tank of argon if I remember right (no guarantees, CRS ya know!)!!!

What I would suggest is that if one were to try this, they wait until the temp gets a couple hundred degrees below austenizing temp, give it a good shot of argon for a minute, then slow it to a trickle. Since argon is alot denser than air, it'll displace it and should stay relatively stationary. For that reason, I've often wondered if one could do this vertically, install a tube in the muffle, and then stick a small probe in through a hole in the door to trickle in some Ar.

I'm gonna try and find the type of furnace you have on the web. Would you by chance be able to supply a model number or foto? Thanks.

BTW, my Pa was backwoods Missouri. The family tree seems to be branched in so many directions it's, shall we say, hard to tell who all I'm related to. :rolleyes: If you have any Stevens, Fitzgerald, Dane, or Sherrill in your background, we could well be cousins. :D I seem to have a lot more of em than anyone is really willing to admit to.... LOL. Some things were, well, "relaxed" back in them hills way back, is the way I'd put it. ;)
 
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