History and Properties of 52100

Thanks for the history lesson! Good, solid, factual info on 52100, thanks!
It seems that this steel is plagued by more misinformation and general “woo-ery” than most!
 
Thanks for posting another good article, Larrin. A point or two about the heat treatment...

"Many knifemakers use 1475°F and 400°F, which would lead to about 59.5 Rc. I’m not exactly sure why they use 1475°F, perhaps it comes from copying recommended heat treatments from 1095."

Those of us who use the 1475F austenitizing temperature for 52100 aren't copying the recommended heat treatment for 1095. We are copying Kevin Cashen's recommended heat treatment for 52100, truth be told!!! Perhaps the heat treating numbers cited in the article ("This is why the recommended hardening/austenitizing temperatures of 52100 is higher than 1095, usually 1550°F rather than 1475°F") are for 52100 in the annealed (spheroidized) condition, and I am almost certain that is the case. Why we choose the 1475F+soak for 52100 is heavily dependent upon what the carbide condition was prior to hardening. If the 52100 was in the spheroidized condition (especially a heavily spheroidized condition), the 1550F austenitizing temperature would be necessary (and maybe not hot enough!). But after normalizing to break the carbide bond and free up carbon for solution (and then thermal cycling to deal with any possible enlarged aus grain issues), the 1475F, soak, quench gives maximum hardness post quench, 66-67HRC, and 400F tempers result in ~62-63HRC.

"The peak in hardness comes from an austenitizing temperature of about 1650°F". That may be the case when hardening/quenching from a heavily spheroidized condition, but when hardening/quenching from pearlite (after normalizing/cycling), the peak hardness falls in that 1475F-1500F range.

I once spoke with Kevin and asked him specifically about the industry standard recommended 1550F (after normalizing/cycling and quenching from pearlite or even martensite) for 52100. His reply was it works good for ball bearings, but not so much for a fine cutting edge for at least 3 reasons.....a lower "as quenched" hardness, higher % RA, and higher % plate martensite.
 
samuraistuart said:
Thanks for posting another good article, Larrin. A point or two about the heat treatment...

"Many knifemakers use 1475°F and 400°F, which would lead to about 59.5 Rc. I’m not exactly sure why they use 1475°F, perhaps it comes from copying recommended heat treatments from 1095."

Those of us who use the 1475F austenitizing temperature for 52100 aren't copying the recommended heat treatment for 1095. We are copying Kevin Cashen's recommended heat treatment for 52100, truth be told!!!
Click to expand...
Well I'm not naming names in the article, though Kevin isn't the only one recommending 1475°F.
Perhaps the heat treating numbers cited in the article ("This is why the recommended hardening/austenitizing temperatures of 52100 is higher than 1095, usually 1550°F rather than 1475°F") are for 52100 in the annealed (spheroidized) condition, and I am almost certain that is the case. Why we choose the 1475F+soak for 52100 is heavily dependent upon what the carbide condition was prior to hardening. If the 52100 was in the spheroidized condition (especially a heavily spheroidized condition), the 1550F austenitizing temperature would be necessary (and maybe not hot enough!). But after normalizing to break the carbide bond and free up carbon for solution (and then thermal cycling to deal with any possible enlarged aus grain issues), the 1475F, soak, quench gives maximum hardness post quench, 66-67HRC, and 400F tempers result in ~62-63HRC.

"The peak in hardness comes from an austenitizing temperature of about 1650°F". That may be the case when hardening/quenching from a heavily spheroidized condition, but when hardening/quenching from pearlite (after normalizing/cycling), the peak hardness falls in that 1475F-1500F range.

I once spoke with Kevin and asked him specifically about the industry standard recommended 1550F (after normalizing/cycling and quenching from pearlite or even martensite) for 52100. His reply was it works good for ball bearings, but not so much for a fine cutting edge for at least 3 reasons.....a lower "as quenched" hardness, higher % RA, and higher % plate martensite.
Click to expand...
The article that I cited for hardness and austenitizing/tempering information used multiple starting microstructures, including pearlitic and spheroidized. I can send you the article if you are interested. Thermodynamically, 52100 requires higher temperatures than 1095; thermodynamics is not affected by starting microstructure. That doesn't mean that 1475°F doesn't work, I'm sure it works fine. You can also heat treat 1095 using 1425°F and that will also work just fine. It also doesn't mean that those using 1550°F are doing it wrong, which I see somewhat frequently stated.
 
samuraistuart said:
Thanks for posting another good article, Larrin. A point or two about the heat treatment...

"Many knifemakers use 1475°F and 400°F, which would lead to about 59.5 Rc. I’m not exactly sure why they use 1475°F, perhaps it comes from copying recommended heat treatments from 1095."

Those of us who use the 1475F austenitizing temperature for 52100 aren't copying the recommended heat treatment for 1095. We are copying Kevin Cashen's recommended heat treatment for 52100, truth be told!!! Perhaps the heat treating numbers cited in the article ("This is why the recommended hardening/austenitizing temperatures of 52100 is higher than 1095, usually 1550°F rather than 1475°F") are for 52100 in the annealed (spheroidized) condition, and I am almost certain that is the case. Why we choose the 1475F+soak for 52100 is heavily dependent upon what the carbide condition was prior to hardening. If the 52100 was in the spheroidized condition (especially a heavily spheroidized condition), the 1550F austenitizing temperature would be necessary (and maybe not hot enough!). But after normalizing to break the carbide bond and free up carbon for solution (and then thermal cycling to deal with any possible enlarged aus grain issues), the 1475F, soak, quench gives maximum hardness post quench, 66-67HRC, and 400F tempers result in ~62-63HRC.

"The peak in hardness comes from an austenitizing temperature of about 1650°F". That may be the case when hardening/quenching from a heavily spheroidized condition, but when hardening/quenching from pearlite (after normalizing/cycling), the peak hardness falls in that 1475F-1500F range.

I once spoke with Kevin and asked him specifically about the industry standard recommended 1550F (after normalizing/cycling and quenching from pearlite or even martensite) for 52100. His reply was it works good for ball bearings, but not so much for a fine cutting edge for at least 3 reasons.....a lower "as quenched" hardness, higher % RA, and higher % plate martensite.
Click to expand...

From my experience a 1525-1550 aust on 52100 leaves little to no RA since only .7-.8% C is in solution. I would suggest cryo for RA if temp is around 1575-1650. 1475 aust makes a fantastic heat treat for an edc or sword though on 52100.
-Trey
 
I have to admit I was puzzled by the temp ranges in the article too. When I did coupons a few years back, I found as quenched hardness dropped when I got to temps over 1500f, much like temps over 1470f with W2 (1460f ideal in my shop for W2.) I was under the impression that heat treating 52100 at 1475f put 0.8%C in solution, but your numbers are much lower. I get Rc66/67 out of quench with 52100 at 1475f. I’m not sure I could get Rc66/67 with less than 0.7%C in solution.

This article is making me think a lot.
 
When I finally get some oil and 52100 I can do some heat treatments myself and see. Too many different potential projects.
 
Larrin said:
When I finally get some oil and 52100 I can do some heat treatments myself and see. Too many different potential projects.
Click to expand...

I’m going to get some more too. I’ll redo my coupons from 1460f to 1600f and check hardness. For the charpy tests, I did use 1550f for one condition, but used cryo to minimize potential RA.
 
Willie71 said:
I have to admit I was puzzled by the temp ranges in the article too. When I did coupons a few years back, I found as quenched hardness dropped when I got to temps over 1500f, much like temps over 1470f with W2 (1460f ideal in my shop for W2.) I was under the impression that heat treating 52100 at 1475f put 0.8%C in solution, but your numbers are much lower. I get Rc66/67 out of quench with 52100 at 1475f. I’m not sure I could get Rc66/67 with less than 0.7%C in solution.

This article is making me think a lot.
Click to expand...

I tested 1475 on 52100 for almost a year and could not get it to quench over 65 unless i quenched in parks50.
In my shop 52100 gets aust 1525 into parks or 1545 into mcmastercarr 11 oil.
This is regardless of normalizing or thermal cycles. 1650, 1475x3, aust 1475 with 10 minute soak into parks 50 with 2 hour temper at 325° tested 61.5Hrc average of 3 tests.
I use 1475 with 1095 and hit 67 regularly though.
-Trey
 
comet_sharp said:
I tested 1475 on 52100 for almost a year and could not get it to quench over 65 unless i quenched in parks50.
In my shop 52100 gets aust 1525 into parks or 1545 into mcmastercarr 11 oil.
This is regardless of normalizing or thermal cycles. 1650, 1475x3, aust 1475 with 10 minute soak into parks 50 with 2 hour temper at 325° tested 61.5Hrc average of 3 tests.
I use 1475 with 1095 and hit 67 regularly though.
-Trey
Click to expand...

Yes, I use DT-48. When using lower aust temp, 52100 benefits from faster quenches. One of the datasheets I researched said to water quench at the low end of the range. More questions and tests coming up.....
 
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Willie71 said:
Yes, I use DT-48. When using liweraust temp, 52100 benefits from faster quenches. One of the datasheets I researched said to water quench at the low end of the range. More questions and tests coming up.....
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Yes, 52100 aust at 1475 into the standard medium oil yields a blade in the 58rc range after a good 350° temper.
-Trey
 
I talked with Mr. Cashen about this a while back. Another thing that he did say was that the ideal HT that he found for his 52100 was 1475F in salt then into medium speed oil, not his normal low temp salt, for the quench. That is different than his normal recipe for O1 and L6. That would appear to confirm what Warren is saying about the "faster" quench for 52100.
 
Willie71 said:
I have to admit I was puzzled by the temp ranges in the article too. When I did coupons a few years back, I found as quenched hardness dropped when I got to temps over 1500f, much like temps over 1470f with W2 (1460f ideal in my shop for W2.) I was under the impression that heat treating 52100 at 1475f put 0.8%C in solution, but your numbers are much lower. I get Rc66/67 out of quench with 52100 at 1475f. I’m not sure I could get Rc66/67 with less than 0.7%C in solution.

This article is making me think a lot.
Click to expand...


I thought of one possibility... maybe the scholarly work on this (and the temps they used) are normalized / standardized for sea level?? (or not), and that could be the reason for the differences?
 
Thanks Larrin, as a 52100 fan, I look forward into digging into your article....I assume a few readings and note taking will be required. Thanks again!
 
Willie71 said:
I have to admit I was puzzled by the temp ranges in the article too. When I did coupons a few years back, I found as quenched hardness dropped when I got to temps over 1500f, much like temps over 1470f with W2 (1460f ideal in my shop for W2.) I was under the impression that heat treating 52100 at 1475f put 0.8%C in solution, but your numbers are much lower. I get Rc66/67 out of quench with 52100 at 1475f. I’m not sure I could get Rc66/67 with less than 0.7%C in solution.
Click to expand...

Maybe what you have is 1095 and not 52100?
I've never worked with 52100 as I have a bunch of O1. If I get my hands on some 52100 I would test it also. But currently my oven is down.
 
I can see how the lower austenization temperatures are what has been recommended given knifemakers have been aiming for ~59 rc. However there is a recent trend toward thinner, more acute edges and higher hardnesses to maximize edge stability and edge retention. Thus if one is aiming for 63+ rc, then one should aim for max hardness at the quench of 66-67 rc. And those temps seem to be higher than what anyone expected. Cryo is probably required due to retained austenite.
 
cotdt said:
Maybe what you have is 1095 and not 52100?
I've never worked with 52100 as I have a bunch of O1. If I get my hands on some 52100 I would test it also. But currently my oven is down.
Click to expand...

Nope, definitely 52100.
 
cotdt said:
I can see how the lower austenization temperatures are what has been recommended given knifemakers have been aiming for ~59 rc. However there is a recent trend toward thinner, more acute edges and higher hardnesses to maximize edge stability and edge retention. Thus if one is aiming for 63+ rc, then one should aim for max hardness at the quench of 66-67 rc. And those temps seem to be higher than what anyone expected. Cryo is probably required due to retained austenite.
Click to expand...
No. Using 1475f and a good 10-15 minute soak, quenching in parks 50, gives me as quenched 66+, and 400f tempers is still 62-63. I’ve never tempered a knife wanting 59. All of that after normalizing and cycling.

I’ve been using that heat treatment for 52100 after extensive talks with Kevin. One thing I appreciated about his help was he talked me through “why” and not just “how”. Giving recipes is not his style. He teaches you through it. Or at least “did”. His online presence has taken a back seat to some serious knife/sword making and metallurgical research. Not to mention his DVDs. The next DVD is supposed to be about 52100, and I can’t wait for it (although he had been very free with his help on 52100).

I can think of another maker, big time maker, who uses the 1475f hardening temp for his Uber expensive 52100 kitchen knives. Of course that doesn’t make it right, but it works.

The whole point of using 1475f is that is where the maximum as quenched hardness seems to lie, with the lowest amount of RA and lowest amount of plate martensite. These are properties you would want for any blade.

When I first started 52100 I did the “industry standard” 1550f. It was soaked for 10 minutes but quenched in 130f canola (no sub zero quench). That knife never held an edge worth squat. It compared almost exactly like a 1095 blade I had sent to Peters who used 1575f (fifteen seventy five) plus cryo. That edge, like the high temp 52100, wouldn’t hold worth squat.

Quench speed and soak time may play an extremely vital role with this alloy. The pearlite nose is only 3 seconds. 52100, although it has 1.5%Cr only has 0.3% Mn. Compare to O1 that has a 10 second PN, if memory serves.
 
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