Cycling pre spheroidized steel harmful or beneficial? 26C3 samples compared.

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Londinium Armoury

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Okay so I was going to ask a question, but I decided to do my own test first and then ask the question after I have something to go on myself.
So here is a picture showing 2 cross sections of quenched 26C3 white steel. (Probably at 67-68 HRC)
Cycling vs not cycling
https://imgur.com/a/kwRL5Fv
One piece was thermal cycled by myself 3 times by eye, using colour change, first it was heated to orange, cooled then heated to bright red, cooled then heated to dull red and cooled.
The other piece was not cycled, just heated to bright red bordering orange held for 4-5 mins then quenched.
So is this pointless, and am I wasting my time cycling? or am I actually damaging an already very refined steel and messing it up slightly, or at least partially degrading the quality?
I honestly can't see any difference, they seem the same to me when sharpening them on stones, they act the same, can't see any difference.

The pieces of steel were starting to rust, that is the dark spots forming, it was damp outside while I was busying making another knife.
 
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Tom Lewis said:
Very good question. I don't have an answer but appreciate you doing the testing.
Click to expand...
My pleasure Tom, I still don't know for sure, but I'm guessing this stuff is okay to just quench without cycling, as long as you aren't repeatedly heating and forging it, should be good to go leaving stress relief out of it, for say stock removal etc.
No problems so far,
Regards Aaron.
 
Londinium Armoury said:
Okay so I was going to ask a question, but I decided to do my own test first and then ask the question after I have something to go on myself.
So here is a picture showing 2 cross sections of quenched 26C3 white steel. (Probably at 67-68 HRC)
Cycling vs not cycling
https://imgur.com/a/kwRL5Fv
One piece was thermal cycled by myself 3 times by eye, using colour change, first it was heated to orange, cooled then heated to bright red, cooled then heated to dull red and cooled.
The other piece was not cycled, just heated to bright red bordering orange held for 4-5 mins then quenched.
So is this pointless, and am I wasting my time cycling? or am I actually damaging an already very refined steel and messing it up slightly, or at least partially degrading the quality?
I honestly can't see any difference, they seem the same to me when sharpening them on stones, they act the same, can't see any difference.

The pieces of steel were starting to rust, that is the dark spots forming, it was damp outside while I was busying making another knife.
Click to expand...
Larrin Larrin made some good videos and articles about this topic
 
DeadboxHero said:
Larrin Larrin made some good videos and articles about this topic
Click to expand...
Could you point me in the right direction? I don't want to sound lazy but I am juggling like 4 pots of different quench oil at different temps on the stoves haha. I'm about to quench some knives and Try out what Stacy suggested, with interupted water quench then oil quench right after.
I did try searching this topic and read a few threads on bladeforums about it, but there didn't seem to be a unified consensus more like guess work.
I'd appreciate the knifesteelnerds link if you have it handy.
 
Those two samples, to my eye, look very similar to each other, and good. I am looking at one place in particular, as the shear on both samples is not (rarely is) perfect. The little area directly below the index fingernail on the top sample, and directly underneath that on the bottom sample. I don't recall if you said you do forging or not. If you are hardening from the as received fine spheroidized condition, I don't think you're going to get much finer grain by doing cycles. A 10 minute hold at 1475°F quenched in P50 is really all you need to do to this steel in the as received condition to have a very fine grain structure. The only time that I perform thermal cycles on a steel is if I had to normalize the steel for whatever reason. In my shop, a forged blade gets normalized. New Jersey Steel Baron's carbon steels (all of them) get normalized. Their 52100 at 1700°F. Their W2 at 1900°F. And the Ultra Blue from Europe I normalize at 1900°F. I actually do thermal cycle all those after normalizing, but I don't cycle precision ground O1, nor any of the carbon steels from AKS. I know that the finer the grain structure a steel has, the better the toughness. At what point does the human eye not detect what is fine enough, I don't know. But the idea is to have a fractured specimen look like gray velvet with no discernible texture to it (and the shearing effect can cause problems reading that grain structure). It may be that the human eye cannot detect a grain structure finer than 12 (I am just guessing), but if I can get the steel to say, 16 by doing a few cycles, I think it's worth it in my shop. And it may be that having a grain size of, let's just say 12, is just as good as far as real world toughness goes as a fracture grain size of 16.
 
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samuraistuart said:
Those two samples, to my eye, look very similar to each other, and good. I am looking at one place in particular, as the shear on both samples is not (rarely is) perfect. The little area directly below the index fingernail on the top sample, and directly underneath that on the bottom sample. I don't recall if you said you do forging or not. If you are hardening from the as received fine spheroidized condition, I don't think you're going to get much finer grain by doing cycles. A 10 minute hold at 1475°F quenched in P50 is really all you need to do to this steel in the as received condition to have a very fine grain structure. The only time that I perform thermal cycles on a steel is if I had to normalize the steel for whatever reason. In my shop, a forged blade gets normalized. New Jersey Steel Baron's carbon steels (all of them) get normalized. Their 52100 at 1700°F. Their W2 at 1900°F. And the Ultra Blue from Europe I normalize at 1900°F. I actually do thermal cycle all those after normalizing, but I don't cycle precision ground O1, nor any of the carbon steels from AKS. I know that the finer the grain structure a steel has, the better the toughness. At what point does the human eye not detect what is fine enough, I don't know. But the idea is to have a fractured specimen look like gray velvet with no discernible texture to it (and the shearing effect can cause problems reading that grain structure). It may be that the human eye cannot detect a grain structure finer than 12 (I am just guessing), but if I can get the steel to say, 16 by doing a few cycles, I think it's worth it in my shop. And it may be that having a grain size of, let's just say 12, is just as good as far as real world toughness goes as a fracture grain size of 16.
Click to expand...

You basically got it spot on, that is actually why I needed to do the comparison, because some blades I forge distil taper into and some blades I don't It all depends on length of knife. So if I'm making anything long I forge some taper into the upper half. So I need to cycle those blades because I ruined the fine grain from the mill or factory it came from just by forging it.
Anything small like a single bevel petty, I don't bother with distil taper so I don't forge them just 100% stock removal, so I don't mess around with cycling those as I probably can't get it better than the mills with their better equipment.
So those just get ground, clayed up and quenched.
I kind of miss Precision ground O1 that was my main steel before I moved to UHB26C3, the 26C3 loves warping, the O1 was so stable in the quench, even 1.5mm stock ground asymmetrical zero ground, still comes out perfectly straight, I love O1 whatever is in the O1 maybe trace vanadium that makes it stable in the quench, the 26C3 needs a dash of that I say, to stop this warping.
I had to make a special knife torture device out of a vice that will fit inside my oven, to straighten out all the warps during second temper cycle.
My first temper cycle is basically tempering a bunch of bananas.
 
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