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Doug Humbarger
05-25-2011, 07:42 PM
We hardened & tempered my bowie blade (ATS 34). Tempered once
at 375 for 2 hrs. then air cool. It now rockwells at 60. Data sheet called for another draw, 275 degrees for another 2 hours. Is this needed? How much lower will that second draw pull the rockwell down?

Doug Lester
05-25-2011, 09:31 PM
It is not so much to reduce the hardness, actually with a lower heat the second time I would not expect to see that happen, especially at 275 degrees which I doubt would allow all that much carbon migration. You would be doing is to help cause retained austinite to convert to martensite and then temper it. Retained austinite is unstable at normal temperature and it can convert to untempered martensite during use and increase brittleness.

A cryoquench is another method of reducing the retained austinite by forcing the steel past the Mf point, which can be well below freezing in the higher alloys. A second tempering is easier and cheaper and a third cycle at 275 might be good insurance.

Doug

Doug Humbarger
05-26-2011, 10:24 AM
Thanks Doug I appreciate the info. So in simple terms it retards work hardening.

Doug Lester
05-26-2011, 01:22 PM
No, work hardening does not come into play here. Work hardening is the result of impact on the steel distorting the bonds between the iron atoms in the body centered crystals in the steel. In the process of austinite converting to untempered martinsite under cold conditions a stresser, such as a shock from chopping with the blade, causes the unstable retained austinite, a face centered crystal, convert to a body centered crystal. Because there is not any heat involved the carbon within the face centered austinite cannot migrate out of the crystal and it is trapped within it forming untempered martinsite. Further stresses on the untempered martinsite in use can trigger cracks that can result in the blade breaking.

Doug

Doug Humbarger
05-26-2011, 03:06 PM
Thanks Doug. I think I understand now.

McClellan Made Blades
06-07-2011, 03:34 PM
"A cryoquench is another method of reducing the retained austinite by forcing the steel past the Mf point, which can be well below freezing in the higher alloys. A second tempering is easier and cheaper and a third cycle at 275 might be good insurance."

Doug


Doug,
I was under the assumption or belief based on reading the HT requirements that the Sub Zero quench was required, can ATS-34 be used with out doing a sub zero quench? I aquired some a long time ago, been chomping at the bit to give it a try, BUT thinking it needed the Nitrogen, I've resisted the temptation to give it a go. If it is possible to use it with out the LN, I may go ahead and make some kitchen knives for the wife, and Mom and Mom-N-Law!!! Heck of a Christmas gift!!! Thanks Bud, Rex

Doug Lester
06-07-2011, 05:07 PM
Yes, the ATS-34 can be used without cryoquenching. Multiple tempering cycles can also cause the retained austinite to convert to other products. However, because I don't use that steel or anything like it, I cannot comment on other aspects of the heat treating reqirements such as any preheating required, soak times, austinization temperature, and the like. I also don't know what the actual Mf point is that steel is so I don't know if you really need liquid nitrogen to cryoquench or if dry ice in a bath of acetone or alcohol would do. It might be one of those cases where it is really worth the money to send it out for heat treatment.

Doug

James Terrio
06-07-2011, 06:41 PM
If you're only doing a couple, I'm told it will help to at least use dry ice and alcohol to complete the quench. If you're doing a whole bunch it comes out cheaper to send them to Peter's and they'll do the full LN cryo and double temper.

Knifemaker.ca
06-08-2011, 08:15 AM
If you look at the 154CM Datasheet (http://www.crucible.com/PDFs/DataSheets2010/ds154cmv12010.pdf)(same alloy), the heat treat response chart tells the story of response to cryo. Even after double temper, there is a marked difference in hardness between freeze and no freeze. You know there has to be some conversion going on with cryo that just doesn't happen without.

In answer to your question though, the chart also tells that story. Sure you can use it without cryo. The results are different, but it makes a fine knife.

Rob!

McClellan Made Blades
06-08-2011, 10:43 AM
Doug, Rob & James,

Thanks Guys,
I have been holding this steel for over 2 years, I did inventory last night and found that not only do I have a 2' bar I also have 1 that is about 10"! With the idea of useing this to make Christmas presents, I think I'll stay on a the safe side and send them to Peter's HT, I want these to be the BEST they can possibly be, and since I'm not quite ready to commit to the higher end steels, I'll send it to Peter's. I met them at BLADE last year and they are wonderful people. If I was ready to start using it on a regular basis, I would go ahead and buy the Dewar, and everything else needed to be able to HT it myself. I feel like it's important to control all aspects of the process, if something were to go wrong, then I would have a better chance of figuring out what went wrong.

I'm not sure at this point if I will ever use the CPM's or the other high end steels.
I LOVE Aldo's 1084, I want to be able to master 1084, to the degree that I know as much as can be known about that one steel, it is cheap (OK, affordable) enough, that when (NOT IF) I make a mistake, it doesn't break the bank AND with a little extra attention it makes an incredible blade. Strong, sharp, tough, whatelse do we need a steel to do? I have seen many 1084 blades do everything required fo rthe ABS Journeyman test.

The only reason I can see and one of the reasons I bought the
ATS-34, is to be able to offer a Stainless Steel to those customers that have to have Stainless steel, not to mention, some knives should be made with Stainless, because some folks will not take care of a knife......., until they really PAY for one!

I lucked up on this steel, another knifemaker I know was cleaning out his stock, and had these 2 pieces, I was buying some horn material from him and he threw the ATS-34 in and gave me a price on the lot, he picked it up from an estate sale of a Knifemaker that passed away. So he got it really cheap and basically gave it to me to sweeten the pot.

I don't normally make several knives that are the same pattern at the same time, with these being for the most important women in my life, I decided these will be a Santoku pattern, that I basically drew up myself, I've made one so far, and it turned out very well, it was the thinnest steel I've ever used, and the edge on it was INCREDIBLE!!!! Scary sharpest knife I ever made, and it was made with the 1st steel I ever bought, it came from Admiral, <note the shame in voice>, I got this before I knew better, but it did turn out better than fine. Whe I was testing the edge, I started by cutting notebook paper, then went to newspaper, then got a little crazier and picked up some cigarette paper, never thought I'd be buying that, much less for testing and edge, it cut curls on it as well! The customer actually told me it was too sharp!<?>!

OK I'm on a tangent, I'll get back to y'all when I get them done, I'm going to attempt to do it secretly, my wife will know her Mom and my Mom will be getting one, but not her, she'll just think I didn't have enough steel for her one, sneaky joker that I am!

Thanks guys for the help, I didn't think about the dry ice, cold treatment, and seriously thought it HAD to be Cryo'd, I'm understanding it will not reach it's full potential if it isn't Cryo'd, which I think is what y'all are saying, for it to reach it's maximum abilities the Cryo is a neccesity, it'll still make a fine blade without it, just better with it, Got It! Thanks again, Rex
BTW, can it be put in the dishwasher? My high carbon blades are not dishwasher safe, I was curious if these are a no no, too. I would say not, but I'm not sure, Thanks! 1 more time, Rex

Doug Lester
06-08-2011, 01:38 PM
Thanks for the data sheet, Rob. Looking at it really shows that 154CM is a steel that requires a heat treating oven, even though the long soak times may be a little off for something with the dimentions of a knife blade. It does strike me that they say to avoid tempering between 800-1100 degrees F but then goes ahead and displays a graph of HRC values for just those temperatures. Actually, one should be aware of the increased brittleness caused by the formation of native carbides in secondary hardenig and decide if that is the way they want to go.

Rex, I think that you see why there are knife makers who avoid complex steels like this. Everything in knife making has trade-offs but using a complex steel like 154CM comes at a cost. It's harder to work with and you get less toughness in the bade. It also takes cryotreatment to really drive the steel across the Mf point to convert as much austinite as possible.

Doug

Knifemaker.ca
06-08-2011, 02:04 PM
You're right about conflicting data Doug - and that doesn't necessarily mean any of it is wrong. Paul Bos uses the seconday hardening range for ATS34 and 154CM and I'm sure not about to challenge his judgment. The charts also refer to oil or oil/freeze with footnote reference to positive air or salts. No mention at all about plate quenching which is now widely accepted, and who the heck oil quenches stainless blades these days? The nice thing is that knife makers have pushed the limits of knowledge and technique (usually forward). :3:

I've learned not to discount anything just because it "shouldn't work".

James Terrio
06-08-2011, 02:08 PM
I'm only guessing but I suspect the oil quenching info isn't really directed at knives, but bigger more complex parts that you couldn't put between plates and might take too long in air. Don't they make turbine blades and stuff out of 154CM?

James Terrio
06-08-2011, 02:11 PM
I think I'll stay on a the safe side and send them to Peter's HT, I want these to be the BEST they can possibly be, and since I'm not quite ready to commit to the higher end steels, I'll send it to Peter's. I met them at BLADE last year and they are wonderful people.

You won't be dissapointed. Brad at Peters' HT has done dozens of blades for me in several different alloys (including many in CPM-154) and I am totally happy with his work. I hear Rob does a fine job too :)

McClellan Made Blades
06-08-2011, 03:24 PM
You won't be dissapointed. Brad at Peters' HT has done dozens of blades for me in several different alloys (including many in CPM-154) and I am totally happy with his work. I hear Rob does a fine job too :)


Thanks James,
I met Brad last year, super nice guy and extremely knowledgeable and willing to share, especially for a knuckleheaded newb like ME!
If I remember correctly, ATS-34 is the Japanese version of CPM-154, or is it the other way around? Isn't it made by Hitachi? I know they make some incredible knife steels, I think ZDP-189 is one of them, I have to say 'think' all the time because my memory is CRAP! I don't normally exclaim something unless I KNOW FOR A FACT, and that will be because I have done it many times....recently, with large amount of repetition!

Will the ATS-34 make an exceptional kitchen knife? Santoku type blade? I know it's supposed to be stainless, or it is stainless, which does stain, I wish they would have called it rustless, or at best rust resistant, calling stainless steel, stainless is very misleading.

BTW, James, are you going to make BLADE? We will be there Saturday. Sunday, I'm taking the family to the Georgia Aquarium, I got out voted for a return to the SHOW! Since they put up with all of my sh...err, I mean stuff, I have to give in sometimes!!
Let me know, I would like to meet you in person someday, Rex