The definitive O-1 heat treat thread

Josh, Ok...I see. You're not actually cooling past 400 and thus starting the martensite formation, just cooling to black heat and repeating as you would while finishing up the forging process, except quenching to get the temp down faster.


--nathan
 
Butch explains it well. Al plate quench works for O-1 for MAX 3/32" thick blade. Both hardenability and thickness play a part. I seem to remember someone else doing a test on O-1 but with a thicker blade and it didn't work. If you want a thicker blade then switch to A-2 for plate quench.
 
the things that really worried me when i did the plate quench test.

one that i would get past 1000 fast enough.

now maybe a bit more scary is the fact that i can pick the blade up bare handed after only 10 sec total or so. i have to wander if im adding extra stress by speeding down to 200f or less . the parks blade zip down past 1000f fast but seem to slow on the way to 400f

thoughts
 
silver_pilate said:
Josh, Ok...I see. You're not actually cooling past 400 and thus starting the martensite formation, just cooling to black heat and repeating as you would while finishing up the forging process, except quenching to get the temp down faster.


--nathan
Click to expand...

That's correct, at least as I understand it. However, I just do a single normalize after forging, then do a triple-normalizing after I rough grind right before the heat-treat. I figure that way I'm getting rid of any leftover forging ugliness and the grinder stress in one shot... :)

Josh
 
Slightly off subject, but since Kevin started the thread I have been compiling my own database of sorts. I have a lot of free time at work, so I have been creating word docs with all sorts of info that I can dig up from old threads. Anything that looks like I could use the information, it gets cut and pasted so I have access to that stuff down the line when I need it instead of searching on here all the time (which I can't do anymore...). I started with threads over a year old and just scan for anything that catches my eye.
 
Thanks Mete,

I have the aluminum plates and lots of O1 (but not as thin as you mentioned), so I just wanted to know whether it would work. I guess I'll just save the plates for when I get around to trying to HT stainless on my own. Of course, then I'll have to buy a dewar and some liquid nitrogen...
 
save the plates
remember that the 3/32 had no bevels ground on them so that i could get all the contact with the plates that i could
 
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...


Nathan I had a few other things that I wanted to add to the page, but everything you see there is based on other material and redone by me in Photoshop to avoid copyright issues, thus things can get labor intensive and the toughness curves are a bit harder to extrapolate in a creative way. I could perhaps just post the numbers.
 
JoshEarl said:
That's correct, at least as I understand it. However, I just do a single normalize after forging, then do a triple-normalizing after I rough grind right before the heat-treat. I figure that way I'm getting rid of any leftover forging ugliness and the grinder stress in one shot... :)

Josh
Click to expand...

I am finding it shocking how much stress machining operations can cause. I now believe that forging will result in less final distortion than heavy milling or uneven grinding. So of either of the latter are involved I would support the idea of a good normalizing or stress relieving operation before final hardening.

I personally do all my normalizing (serious normalizing in the traditional sense) after the forging and then spheroidize to leave the effects intact. I have found that very even grinding with careful avoidance of turning the steel blue will safely get me through the hardening. It is amazing how much scribing good center lines and accruately grinding to them will keep things stright later on. If I have my doubts I will use a stress relief before the quench.
 
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...

Folks who are afraid of heat in forging may need really good normalizing to undo the segregating effects of low temperature cycling. I used to think that the steel was perhaps the best it could be straight from the mill, however I am disturbed at the ammount of banding and segregation I am seeing in steel off the shelf. This condition makes that which I have always claimed to be bunk quite possible- that proper forging could indeed improve the steel:eek:. If we are careful to forge enough at the higher end to produce multiple heavy normalizing effects, it could have a homogenizing effect. However the love affair too many bladesmiths have with low temperature forging will only increase the segregated condition. It may even be possible to say that pattern welding may significantly affect these conditions. The very high heat can really move things around and the lengthwise folding would greatly narrow and elongate any permanent deviations in the structure. Relax, I have not taken leave of all my senses however since it has to realized that this would not be a total improvement but instead an increase in anisotropic properties in a direction that is slightly to our advantage, one still has to remember all the crud introduced with every weld zone;).
 
BTW, on the subject of normalizing O1...

O1 has that 10 second lag in forming pearlite so it may be trickier to refine the grain than say 1095. If one can get it to cool very slowly around 1100F and make pearlite they can then go right back to heating and imediately make finer austenite grains. If however the air cooling gets things below 1000F too quickly, reheating too soon will only be working with the same austenite grains and no gains will be made. If one has doubts it may be better to cool to room temp and then reheat. The best way to check this is with the magnet (it is a hell of a lot more usefull here than in heating for hardening). When the magnet starts sticking really well again you have converted a reasonable percentage into another phase and can reheat with confindence that you will accomplish your goals.

L6 is an even better example of this quirk. Any grain refinement with that steel must come from cooling to 800F or below and using upper bainite as your platform for recrystalization.
 
Yes any grinding or machining can induce stress !In the bearing factory we used to adjust grinding to induce favorable stresses in the bearing races ! For the most critical parts start out with stress relieved material , machine , then stress relieve again .
 
mete said:
Yes any grinding or machining can induce stress !In the bearing factory we used to adjust grinding to induce favorable stresses in the bearing races ! For the most critical parts start out with stress relieved material , machine , then stress relieve again .
Click to expand...

Oh, I knew it induced stress, I just am surprised how much! I have seen some pretty impressive displays of stored energy in heavily machined parts.
 
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