ATS-34 HT Sample

Fitzo, yeah getting it out of packet is too late to do any rapid quenching. We are stuck in making our packets tight and quenching while in foil. Now, do you see what you are making me do? Now I have to do it all over again, just as before, and Rockwell test as quenched. I am confident though in my quench otherwise my results would not have tracked the data sheet and I wasn't even shooting for that. Hitting the data sheet so closely also indicates that the recommended 15 minute soak is fine too. I might add, the 25 minute soak that resulted in the 60 RHc of the blade that started this thread also hit the data sheet precisely at 60 RHc. Except that the data sheet specifies 1950 F. and I have been at 1965 F. (as per the Even Heat front panel).

Steve, I did. The steel - and all my steel - is placed in a cold oven and left there until time to quench. I believe in cryo for all knife and tooling steels regardless of the steel analysis.

RL
 
Sorry, Roger! Didn't really mean to cause ya extra work. But, yer getting good data, and the questions arise naturally. :) I never had as good a luck as I wanted with getting the packets tight enough, nor fast enough quench with them on, so I went through a lot of rigamarole to get them outta the bags as quickly as possible. The cigaret butt I'd toss in at the tang to create the anoxic atmosphere always seemed to gas off and blow up the bag some. So I tried to just put a hole in the bag, which trapped superheated oil next to the blade. that sucked even worse. I will stick with these aluminum plates from now on, they are easy and work great.

I am honestly far more interested in HT nowadays than in making many knives, so I find your work invigorating. I sincerely feel that "stainless" HT has not been well investigated in published work, especially as it pertains to knifemaking. We are using these steels for applications the steelmakers never intended, so their HT methodology was developed specifically for things like high-heat wear surfaces and such, like jet turbines, and has never been studied well for cutting edges. There is a lot an interested knifemaker can experiment with and learn. I plan on doing some investigating with 440C come winter, so hopefully I can get as good experimentation as you are doing, and share it here. I have a lot of reading to do first, though. I am finally getting a Dewar next week, tracked one down locally, a guy reselling em on ebay for the corpration i used to work for. That's about the only thing I miss from work; access to free dry ice and LN! :D

Thanks for sharing! I mean that..
 
Fitzo,

I just bought some aluminum plates, same size as yours btw. Looking forward to trying out.

--------------------------
Don't mean to confusing things on this thread, but I was looking at the Crucible sheet for S30V. For a cryo temp they used -112. It made quite a difference.

For example Sample #1 no cyro, #2 only -112 cryo
1950 Austeniting Temp

As quench
#1=62
#2=63

After 400 temper
#1=57.5
#2=60.5

After 600 temper
#1=59
#2=58.5

After 1000 temper
#1=59.5
#2=59

The whole thing is very strange. But does show even with only -112 S30V changes.


I wonder if -112 is enough for ats-34. Gee Roger didn't mean to make more work for you :D

Steve
 
Steve, it's not more work for me at all. You have an oven now and a dewar on the way ;) ;) . Steve, the Crucible data sheet which I have been referencing says this: "To completely transform any retained austenite, a freezing treatment with dry ice at -100 degrees F. is recommended either after the quench or in between the two tempers." Again, this is a sheet concerning their 154CM which was developed to compete with ATS-34 and is close enough in analysis to be practically interchangable. As for the freezing, I will continue to cryo stainless after quench (before any temper). It has been working for me and it has been recommended to me by Mr. Boss in a post here on this forum. For simple carbon steels I snap temper before cryo to help protect against thermal cracking. The stainless can better take it and it is important to quickly transform retained austenite. Regardless of temper type, heat or freezing, it is vital to do the first one very soon after quench.

The super steels that I have tried, and they only number two types so far, have been kind to me. To date my best stainless that I have tested well is the one I made for Chuck Leake. It is ATS-34 with a high end temper. Perhaps this is one reason I am reluctant to go too far down the temper scale for ATS-34. I am conservative in nature and if it works well I don't like taking large steps away from those specs that have performed. I am sold though on tempering all martensitic stainless steels at their mid to lower temperature range because of corrosion resistance. Going from 600 F. to 400 F. for ATS-34 will be a tuff sell for me though. What I really should do now is take one of those samples I did today and soak it in lemon juice over night. That may tell something of corrosion resistance at 600 degree tempering.

RL
 
Interesting :)
Roger I'd stay no less then 1950 just because you need the time from oven to quench
one thing you are doing that I don't is cryo after quench
I air quench at 15 min's in up to 1950 (put in when oven is up to temp)
then temper at a strong 425 deg
then cryo over night
My Lab Dewar with 8lb's LN will be empty in the morning so it
gets a slow warm up as the LN is dissipated and gone..
I then temper again at 425 deg.

now the ovens we have will act different as said.
and I have a ritual I go though

once My oven is up to temp I put my packet in
at this time I lose 100 deg's from the oven from the door being opened
( I have to be fast and this is all I lose)
now at 1850 I'm starting to count 15 mins
at 15 min's the/my oven
will hit 1950 again and it's time for me to get it out
((my target for the edge only will be 1950))
you may say oh no your steel hasn't fully come up to heat
in the packet yup? maybe.. but I don't care if the spine is up to heat or not ..
I use a soft fire brick with groves in it to hold the spine
with the edge up and it (the brick) will have been up to temp.
holding the temp better than the heat probe is telling me
the ovens at. sorta evening the heat in my even heat oven:D
I want just the edge up to heat anyway so that don't matter to me.:)
But every blade I do I'm on edge :D
to do it the same every time.:(
 
Steve,

From what I've read, unretained austenite converts regardless of temp, though it may take 100 years at room temp. It is a RATE dependent phenomenon, so temperature will affect the rate of conversion. Also, from what I've read, overnite at -112F will usually accomplish near complete conversion. The ultralow cryo performs the task more rapidly and also ostensibly affects the carbide type and dispersion. This presumably imparts better wear characteristics (cutting esge retention) than the "cold" -112F. Obviously this is a debatable point, based on commentary here on the forum.

You'll like the aluminum plates, I believe. I originally mounted mine in a wood vise, so the jaws were horizontal. It screwed shut, so took longer than I desired to close. Then I blew compressed air in the gap. Nonetheless, I get an as-quenched hardness on S30V of 63, not too shabby after years of tribulations with ATS. (440C gets much nicer quenches than ATS.) Now I am going to scout yard sales for one of those wood vises that have a trigger for "quick close". They're $200+ new in the MSC catalog; too much $$. I suppose I could use the drill press, and mount a rod in one plate to hold in the chuck. The guys I know using them are just taking the lo-tech approach, setting one on the floor, putting the blade-in-packet on it and laying the other plate on top with a weight. Unfortunately, I don't bend down or kneel anymore, so I have to work at bench height. :) They are sooo much easier than messing with the oil, and I think they help eliminate warpage. Lemme know how you like them, I'm curious to know.

One of you guys with too much money needs to go out and buy a metallograph and a spectrograph so we can study this a bit deeper... :D
 
Just for grins I put a piece of O1 I had heat treated without cryo a couple months ago in the LN yesterday for about 6 1/2 hours. I can't remember if I had double or triple tempered that piece but I tested it just before putting in cryo and it tests about one point higher now. Six and one half hours is not enough for my liking and I wouldn't make a steel tool with the cryo being the last step in HT but I was just playing around. RL
 
thinking back on what I said (the way I said it at least )
I don't want anyone thinking I negate any benefit of cryo tempering ,
it's just the reverse,, and anyone who has
seen my posts on the subject know that anyway, what I was saying was
simply put
the heat-treat (quench) is the foundation to build on
( with out it the rest can't be as good as you can get it)
the temper strengthens that foundation to last and to hold up.
and the Cryo adds to the whole package.
but you need that foundation first.

some say the benefit on different steels are not worth the bother
I don't agree
they've used LN on cast iron, plastic's and other things to toughen
for years so it works no dough
and the cost of LN is so low that it's hardly a factor anyway...

when I use it here I put files in even some of my razor blades..
Shihl uses it in their plastic top handles too I believe..
many of the High grade SS's were made/designed to be cryo'ed
anyway so it really needs to be done anyway to do what the steel was designed to do.

I will use it as a last temper for O1 I don't have a problem with that.
Roger thank you for the results you've come up with,
much food for thought for many I'm sure and very enjoyable.
keeping in mind this is all IMHO and what I feel and do in my shop..

my basic point was if you over time the SS at 1950 in my case 2 hr's it will take
a higher temper temp to get the Rockwell back down then if done for a shorter time
and I'm not sure just at what point in that time the grain grew. I'll have to test that out.. :D
 
Dan, I never thought you were discounting cryo. I understood that your thrust was on the significance of proper austenitizing. I, too, was not suggesting that cryo would make up for a otherwise faulty HT but rather greatly benefit a properly quenched steel.

Thanks. RL
 
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