The definitive O-1 heat treat thread

K

Kevin R. Cashen

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Sep 9, 2003
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It seems that the average is at least one thread every two weeks or so requesting how to heat treat O1. I have been in the process of overhauling my website but while the entirely new site is a ways off yet I have started work on a new set of information pages for steels so I though I would prematurely release the O1 page for this thread. Perhaps if we have just a fact based thread on all the little questions surrounding O1 heat treatment we could have a resource to refer to without retyping the same thread every couple of weeks.

Here is a link to my new page:

http://www.cashenblades.com/Info/Steel/O1.html

If anybody also has links to sound facts on O1 perhaps they would consider adding it here?
 
Great info. Makes me want to go make an O1 chef's knife. Any info on toughness at the different harnesses? It seams like it takes a dip around 59, which is a commonly used hardness for camp knives etc.

Thanks Kevin.

Nathan
 
Nathan the Machinist said:
Great info. Makes me want to go make an O1 chef's knife. Any info on toughness at the different harnesses? It seams like it takes a dip around 59, which is a commonly used hardness for camp knives etc.

Thanks Kevin.

Nathan
Click to expand...

i ll let you know how the O1 kitchen stuff im working on when i get feed back
the hardness will be between 60 and 62 I bumped the temp a bit on the 2nd run (forgot my kiln runs a hair cooler then the readout )

i have just tried to do a plate quench and ended up with .5 difference in hardness on tempered test blades (the stock was 3/32 thick)
i need to do a bit more testing on the plate quench on thin stock and can not recommend it on anything thicker then 3/32 inch thick
all other blades were quenched in parks 50

by my not so good counter i took the blade adn pressed it tween the Al plates not more then 10 sec and was cool to the touch by then
 
It's interesting that the little bit of V and W do require some more soaking time. You should put the composition on your website too.
 
Thanks for the info Kevin.

Since this is the "definative O1 heat treat thread", I have a question that perhaps Kevin or someone else can answer. Can O1 be successfully plate quenched? There's quite a bit of time (relatively speaking) to avoid the Pearlite nose, but can aluminum plates dissipate heat fast enough to do it?

By the way, I do have some info that might be helpful, but I've been castigated here a few times for posting it. Therefore, I will just post the links. If you choose to click on them it's your own choice. Link 1, Link 2
 
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Thanks, Kevin. A lot of newbies like me get confused because there are specifics that some vary such as triple quenching, tempering time and soak time.

I should have used 1095 on my first knife because I used a campfire to HT it, but it doesn't hold a very good edge.

added, could somebody please help me read one of those graphs such as Chris' second link?
 
Not to hijack the thread, but hey Kevin! Could you do this for most of the commonly used carbon and stainless steels!?! :D

Good reference......and then we hit "bookmark".....

--nathan
 
Holy crap 10 seconds to get past the pearlite nose!

Kevin it was fascinating to see the difference firsthand in your slides at Ashokan, between the long soaked O1 and the barely soaked O1, the difference was phenominal!
 
Kevin

Keith brought it up - I have been wondering for quite some time...


Heating to critical with proper soak and quenching i understand...

tempering multiple / 3 times i understand...

(heating to critical and quenching) all repeated 3 times....i just don't understand

Is there any value to it?. Some people seem very proud of it...
It seems to me that on the second heat, you have just undone the first heat and quench...only the last one counts and the others are just practice...
 
So Kevin, is it OK to use water to quench my O1? :)

Thanks for putting this together. I'd love to see more of these as well... Kind of a condensed version of the Atlas, with the added bonus of addressing the questions that come up over and over...

Josh
 
Steven Penner said:
Kevin

Keith brought it up - I have been wondering for quite some time...


Heating to critical with proper soak and quenching i understand...

tempering multiple / 3 times i understand...

(heating to critical and quenching) all repeated 3 times....i just don't understand

Is there any value to it?. Some people seem very proud of it...
It seems to me that on the second heat, you have just undone the first heat and quench...only the last one counts and the others are just practice...
Click to expand...

I believe the multiple normalizing heats, or thermal cycling, progressively refine the grain. You start by overheating the steel, allowing the grain to grow big--but evening them out. Then the second and third heats, progressively lower, get those big, even grains to be fine, even grains.

We stop at three because there is a diminishing return after that, and because getting the grain too fine reduces hardenability.

Josh
 
Josh,

While that type of thermal cycling is usually done as you're finishing up your forging work to refine the grain structure after multiple high heats and impacts during forging, I wonder if it still holds true in a spheroidized annealed bar stock that has been ground to shape.

I will stress relieve stock removal blades at 1250 and cool to room temperature prior to hardening, but I've never repeated the hardening process on a stock removal blade. It is my understanding that a piece of bar stock is usually delivered in a nice, uniform grain and doesn't really benefit from thermal cycling other than stress relieving.

--nathan
 
Steven Penner said:
Kevin

Keith brought it up - I have been wondering for quite some time...


Heating to critical with proper soak and quenching i understand...

tempering multiple / 3 times i understand...

(heating to critical and quenching) all repeated 3 times....i just don't understand

Is there any value to it?. Some people seem very proud of it...
It seems to me that on the second heat, you have just undone the first heat and quench...only the last one counts and the others are just practice...
Click to expand...

There seems to be great P.R. value to it;). However metallurgically there are a couple things it can do and whole lot it can't. The majority of the claims surrounding it are well buried under a whole lot of wishful speculation and convoluted doublespeak designed to keep you from sorting any grain from the chaff. To be honest it would be a serious thread hijack to get into it since discussions on the topic always result in the true believers who need no explanation flaming away at the skeptics who do.

A quick search on the topic will give you plenty of entertaining reading:).
 
silver_pilate said:
Not to hijack the thread, but hey Kevin! Could you do this for most of the commonly used carbon and stainless steels!?! :D

Good reference......and then we hit "bookmark".....

--nathan
Click to expand...

My plans are to only cover the worthwhile steels most commonly used by bladesmiths, if I get into the stainless and others I would be basically just rewriting the "ASM Heatreater's Guide". Which would be the place to go for such a comprehensive list.
 
Steven , while three normalizings make for smaller grain , O-1 has small amounts of V which retard grain growth. So to thriple normalize O-1 is not so beneficial.
 
Nathan,

I think it would depend on how well the steel was handled at the mill. If it was properly spheroidized, that's probably better than any thermal cycling I am able to do. Hot-rolled stuff would probably benefit from it more. I'm not sure about grinding stresses--how much stress does grinding really impart?

About the triple quench: From what I've read, the idea of hardening three times is nonsense. However, there is sometimes a benefit to triple quenching, or thermal cycling, which is just another way to refine the grain. You don't let the steel start to form martensite--just quench it to black, I believe. This is supposed to be slightly better than normalizing by cooling in still air. I think the stress of the quench is more effective in breaking down the larger grain structure.

Josh

silver_pilate said:
Josh,

While that type of thermal cycling is usually done as you're finishing up your forging work to refine the grain structure after multiple high heats and impacts during forging, I wonder if it still holds true in a spheroidized annealed bar stock that has been ground to shape.

I will stress relieve stock removal blades at 1250 and cool to room temperature prior to hardening, but I've never repeated the hardening process on a stock removal blade. It is my understanding that a piece of bar stock is usually delivered in a nice, uniform grain and doesn't really benefit from thermal cycling other than stress relieving.

--nathan
Click to expand...
 
Kevin R. Cashen said:
...I would be basically just rewriting the "ASM Heatreater's Guide"...
Click to expand...
What?! Did Kevin say he's going to rewrite the Heat Treaters Guide?! I guess pestering him to write a book has finally paid off.
laugh.gif




Mete, since you seem to be a big proponent of plate quenching, would you please tell me whether or not you think that O1 could be quenched with aluminum plates? Or is it just air hardening steels that can be plate quenched? Inquiring minds would like to know. Thanks.
 
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Why is it that I don't see Alberto VO5 anywhere on that page?

Boy am I hacked that I bought all that VO5.
 
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