01 - how much time do I have from quench to temper?

That's the best way , Roger . My flippant response really meant you have just enough time to quickly clean off the oil , then temper !
 
fitzo said:
It sounds good to me, Fred. I misunderstood what you were saying regarding the freezer.

How much chilling a blade affects it will depend on the specific martensite finish for that blade. With stainless, and I suspect most air-hardening steels, that temp is way below ambient. One thing I've never run across is data that actually graph the sub-ambient conversion of retained austenite versus time and temp. I have asked the question several times and never gotten a good answer: is it an absolute temp thing, or is it a rate phenomenon, such that a longer time at a higher temp achieves the same thing? This is getting into minutae of HT that are beyond my meager knowledge. If anyone has a source, I'd enjoy reading it.
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My knowledge in this area is slight and , like you, would lke to understand this better. Fred
 
As always I default to and bow to what Mete advises. Always, all here, default to Mete's advice if you be wise.

Thanks Mete for that vote. You helped teach me that and maybe a bunch more:) . - FOR SURE!

RL
 
Fred, as you go through the cooling from Ms to Mf you continue to convert to more martensite and on some of the TTT diagrams there are lines showing M10, M50, M90 lines etc.[that is 10% conversion, 50% conversion etc] However it's more complex than that .Assume the more complex the alloy the more retained austenite no matter what you do with it. Also some of the tool steels show a marked difference in retained austenite vs austenitizing temperature .Too high an austenitizing temperature and you could end up with maybe 15% RA !! Freezing will convert some of the RA but don't expect to correct poor heat treating with cryo !!! It's all very dependant on composition and the details of heat treating .BTW some RA is beneficial in some cases and of course double tempering stabilizes remaining RA so it won't convert !
 
Protactical said:
I've had O1 blades kicking around for days before I put them in the oven. They were all stock removal pieces, and did fine. I find O1 is pretty forgiving.

You can increase the performance of your torch with a brick, just look up "brick forge". I suspect that is more effective than MAPP.
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If your doing stock removal, the steel isn't put through the same stresses that are introduced during forging. It's a lot different when you beat a blade out on an anvil. Or at least thats what I think....I could be wrong and if I am someone will set me straight.
 
mete said:
Fred, as you go through the cooling from Ms to Mf you continue to convert to more martensite and on some of the TTT diagrams there are lines showing M10, M50, M90 lines etc.[that is 10% conversion, 50% conversion etc] However it's more complex than that .Assume the more complex the alloy the more retained austenite no matter what you do with it. Also some of the tool steels show a marked difference in retained austenite vs austenitizing temperature .Too high an austenitizing temperature and you could end up with maybe 15% RA !! Freezing will convert some of the RA but don't expect to correct poor heat treating with cryo !!! It's all very dependant on composition and the details of heat treating .BTW some RA is beneficial in some cases and of course double tempering stabilizes remaining RA so it won't convert !
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Hi Mete, Assuming you performed all the austenitizing work properly; correct temperature, soak time per specified steel, use of the right quenchant at correct temp. does it then make sence to continue the cooling, after hardening, into the sub ambient temp[cryo] before you temper. Or would this increase the odds of the blade cracking or distorting under the retained stress of hardening. Does this come under the heading of a trade off? you can't have it all. If the double tempering stabilizes the RA so it will not convert to martensite what is the purpose of cryo after tempering or the freezer treatment between tempering cycles? Thanks Fred
 
kricket said:
If your doing stock removal, the steel isn't put through the same stresses that are introduced during forging. It's a lot different when you beat a blade out on an anvil. Or at least thats what I think....I could be wrong and if I am someone will set me straight.
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correct Kricket:thumbup:
 
Wow, thanks for all the input everyone!! I don't know what I'd do without this forum. It sure must have been a lot harder getting into knifemaking before the net :)

I'm going to try to find some fire brick and make a one brick forge using my propane torch. Just have to find some fire brick supplier - hopefully I can find some in Edmonton. After that, maybe I'll see if I can find a local welder to make me up a small pipe forge I can line with refractory cement or something... see how it goes.
 
Yes Fred there are trade-offs. Those steels that are more prone to cracking should be tempered the minute the blade gets to quenchant temperature ....Looking at a more complex steel such as the S30V, 154CM etc - we quench, maybe snap temper for safety [300-350F] ,freeze, double temper. The freezing converts more of the RA to martensite , the double temper then stabilizes the remaining RA so it won't transform over time.....The snap temper temperature is such that it doesn't stabilize the RA. If we raise that temperature to 400F , it will stabilize the RA !!...It's all logical -the right times, temperatures and sequence get the results !
 
Funny topic as I was trying my hand at some 01 heat treating just this past Sunday. According to my Crucible Tool and High Speed Steel Selector orange book, Roger Linger is on the money. Crucible says that for 01 it should go IMMEDIATELY from hand warm quench to tempering oven. I noticed that someone above commented about tempering at 350 degrees. According to the Crucible book, 350 will yield RC62-64 which might be a little brittle. 400 degrees will yield RC61-63 and 450 degrees will yoeld RC60-62 with 500 degree temper cycles yielding RC58-60.

I'm no expert by any stretch, just posting what the book says.
 
mete said:
Yes Fred there are trade-offs. Those steels that are more prone to cracking should be tempered the minute the blade gets to quenchant temperature ....Looking at a more complex steel such as the S30V, 154CM etc - we quench, maybe snap temper for safety [300-350F] ,freeze, double temper. The freezing converts more of the RA to martensite , the double temper then stabilizes the remaining RA so it won't transform over time.....The snap temper temperature is such that it doesn't stabilize the RA. If we raise that temperature to 400F , it will stabilize the RA !!...It's all logical -the right times, temperatures and sequence get the results !
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That shines some light on it for me. Thanks for the clarification Mete. :thumbup: Fred
 
Kricket - It should make no difference how the blade was shaped.If the blade is normalized before quench there is no stress to deal with.After quench the temper is to stabilize the martensite,and that is identical ,regardless of how the blade was made.
 
Thanks for the acknowleagment. Again, I owe what little I might know to Mete for kicking me in the ass. He helped make me understand data sheets and the 'whys' about them. Always STRIVE to temper NO less than approximately 400 F for at least the first temper unless you decide to do a snap temper before hand and if snap tempering take care not to lag long before the 'primary' temper of approximately 400 F. An example of snap temper might be for a preliminary cryogenic treatment or a delay because of time constraint.

RL
 
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