Yikes, 52100 Question!

Mike Martinez

Mike Martinez

Well-Known Member
So, I'm trying my hand at heat treating 52100 tonight and would like some advice on a heat treating schedule. I have LN2, Paragon HT Oven, ATP 641 and Maxim's Medium speed oil (the name escapes me). I'm trying to get the max out of the steel for a run of straight razors that need to be done ASAP (I've got some headed to Peter's but they won't meet my deadline). Any BS-free, no nonsense approach is welcome. Thank you guys.
 
Mike928 said:
... Any BS-free, no nonsense approach is welcome. Thank you guys.
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Well that is typically right up my alley. 52100 is not a very forgiving steel to HT, 1% carbon makes for a lot of extra carbide that you have to deal with so that it doesn’t give you problems, and to make it machinable it typically comes with that carbide very well spheroidized so that you need serious soaking or temperatures to get it free- these two considerations are in opposition to each other. It is little things like this that is the reason you see so many eclectic or unusual practices adopted by folks who heat treat this steel without equipment capable of meeting its demands.

What was your source for the 52100? Some is more spheroidized than others.

If you already have the razors ground to a close to finish dimension it could be a problem, since unlocking the needed carbon from the spheroidal carbide will require heating before you move onto hardening.

If the carbon is ready to go, in fine structures- pearlite, very fine spheroids etc… Heat to 1475F for 10 minutes and quench in any light oil. If available, Houghton, Parks AAA, McMaster-Carr, Brownells Tough Quench etc… are ideal oils for this steel, if not almost any vegetable oil will do for 52100 chrome levels.
For a straight razor I would go from 375F to 400F for two hours with the temper.

The nitrogen should not be necessary if you did everything correctly, if you see noticeable increases in hardness from cold treatment with a steel this simple, you overheated it and it is that simple. If all is done correctly you may still get around 6% retained austenite and squeezing more out of less than 6% should not be very perceptible on the Rockwell scale, I mean freezing a 66-67HRC blade doesn’t give you much more room for improvement.

Now for the down side- if your steel is heavily spheroidized the best way to free the carbon for hardening is to heat it to 1650F and let it air cool, and then proceed with the heat treatment, but if you are already shaped like a razor this can make a mess of it. In which case you may be left with some of the hokey pokey ("BS") dances that many do, in order to keep decarb and scaling down, but there will be increased distortion issues. I would rough out, profile or drill anything that has to be machined and then normalize before the final edge grind to avoid this.

With the carbon freed up, you can expect around a 66HRC as quenched, with it still locked in carbide you can expect around 63HRC as quenched.
 
Thank you Mr. Cashen for your response. I appreciate that you take the time out of your undoubtedly busy schedule to address questions at this "level."

My source for 52100 is Aldo and the blades have been ground but have been left very thick... around .050 or so. Hopefully this leaves some room in which to move around.
 
Great info thank you both!

Kevin,
If you were trying to hit 57-59 range using the temps and times you listed above; what tempering temp would you recommend?

Thanks in advance,
Tom
 
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Mike928 said:
Thank you Mr. Cashen for your response. I appreciate that you take the time out of your undoubtedly busy schedule to address questions at this "level."

My source for 52100 is Aldo and the blades have been ground but have been left very thick... around .050 or so. Hopefully this leaves some room in which to move around.
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Yes Mike928, your rough dimensions should give you some wiggle room. If you 52100 is Aldo’s then you are going to need it. I am very familiar with that steel, it was I that analyzed the issues for Aldo and developed the heat treating sequence to get the desired hardness. It is very good steel, some of the most consistent that I have worked with but the makers want it to be machineable so it comes between 95% and 98% spheroidized, and that requires that that carbon be unlocked and put back into play. The soak at 1650F will peal the needed carbon off from those spheres and hopefully deposit it into easily dissolved fine pearlite. Lower subsequent thermal treatments will then help distribute the carbon evenly and refine the grain. Just avoid going too low or you will can start to ball or bunch things up again.
 
TASelf said:
Great info thank you both!

Kevin,
If you were trying to hit 57-59 range using the temps and times you listed above; what tempering temp would you recommend?

Thanks in advance,
Tom
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Tom, tempering temperatures for specific Rockwell is one of the most elusive unicorns to chase. I rarely if ever venture to offer them because it is an excellent way to be proven quite wrong. You see, final HRC for a given tempering temperature is VERY heavily dependent on the effectiveness of the hardening soak. If you fall short of the needed solution your post tempering Rockwell will drop significantly. On the other hand if you put too much carbon into solution (easy to do with 52100) things will get really crazy in the tempering as the lower readings from the retained austenite can go either way over time and with temperature shifts. If you nail the right range of carbon in solution, as indicated by seriously high as-quenched Rockwell numbers then the hardness can be very stubborn in lowering from tempering.

In the initial stages of tempering you can expect to see the most dramatic Rockwell drop, as much as 3 points, as the shift to more stable body centered martensite is achieved. After that the struggle should be more for every point. Because of all of these factors, I never simply punch in a tempering temperature to go straight to a desired hardness, but instead start low and walk in every tempering hardness. The only steel that I can get pretty good at predicting to a fairly precise level is my O-1/L6 damascus, but I still walk that in for my own piece of mind.

If I may suggest however, the range you are seeking will be a bit below the ideal properties range for a steel like 52100, and you may be better off going with another steel that will peak in hardness/toughness closer to the 57-59 range.
 
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Thanks Kevin!
I'm more interested in learning about 52100 than I am in hitting that 57-59 range. Is there an RC value that I could target for peak hardness/toughness in 52100?
I read that O1's peak was around 62 would you agree? I'd also like to know the peak for 1084 as well.
Is there a way to calculate or predict peak hardness and toughness values in other types of steel based on composition?
Do manufacturers list this info in their data sheets and I'm just missing it?


Sorry to go on, thanks for taking the time to teach me.
Tom
 
Mike I ht aldos just as Kevin has stated but I do foil wrap the blade while soaking at 1650* I add a small piece of paper in with the blade and double wrap it. Leave it wrapped till the third Normalizing cycle is over then I sprinkle on some pbc go back to 1475 for 10 after it equalizes and quench. Count to 7 and check the blade with an IRL and generally about 425* and if there is any warpage , usaually very very slight, I will straighten it then and let coot to room temp before tempering. Minimal decarb and seems to be working for me very well. Till I get some salts this is the best way I have found for me to avoid all the warpage and excessive decarb.
 
TASelf said:
Thanks Kevin!
I'm more interested in learning about 52100 than I am in hitting that 57-59 range. Is there an RC value that I could target for peak hardness/toughness in 52100?
I read that O1's peak was around 62 would you agree? I'd also like to know the peak for 1084 as well.
Is there a way to calculate or predict peak hardness and toughness values in other types of steel based on composition?
Do manufacturers list this info in their data sheets and I'm just missing it?


Sorry to go on, thanks for taking the time to teach me.
Tom
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This is actually a major part of a chapter in the book I hope to finish someday, with some excerpts and ideas from it included in lectures I have done for the ABS on steel selection. Think of steel selection parameters in the terms of a couple of major criteria one of which is desired properties for application. These applications will fit into the type of cuts done; some having abrasion resistance as a priority and the other having toughness as a priority. To achieve these properties one needs simply to look at the chemistry of the steel, I divide the chemistry into two major components, carbon content and all the other alloying additions. In carbon content alone you have natural propensities for either strength/abrasion resistance or toughness based on the levels present. Steels with less than .8% carbon will naturally be tougher before you even consider heat treatments, while steels above .8% carbon will naturally have properties leaning more to strength and abrasion resistance, and the farther above .8% the greater this will be.

Alloying does its part with carbide formers above .3% giving a boost to abrasion resistance while things like silicon and nickel swing things toward toughness. Chrome, depending on amounts and other alloying, can swing somewhat either way but most often toward abrasion resistance due to carbide. So in the case of a 52100 I would go with it for blades I wanted to have above 60HRC but would opt for its little sister 5160 for blades I wanted to go below 60HRC, they are just natural fits for these ranges.

Yes, I would agree that taking O-1 below 61HRC is an unfortunate waste of the steels strength/abrasion resistant potential, and many steels that work better below 61HRC are also much less expensive. You also bring up a good point regarding 1084, it is right on the line so it can be easily heat treated to perform well in either category.

So while you can compare a lot of hardness to toughness charts it is also easer just to think of the chemistry considerations. Part of my canned lecture is how ideally bladesmiths would not even need names, numbers or designations, but could simply look that the chemistry to determine what it would work best for and even how to heat treat it. The info is all there, and often the names of alloys sort of get in the way to reading it.
 
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I posted a link in the Knife Steel Reference thread on O1 that has Crucible's Charpy test data where you can find hardness/toughness information. If I am reading the numbers right, going from Rc62 to Rc55 will only give you a 10% increase in toughness. Finding that data for 52100 may be a little harder, as 52100 was formulated for ball bearings not blades.
here is a link that explains Charpy testing http://www.csun.edu/~bavarian/Courses/MSE 227/Labs/2 - Charpy_Impact.pdf
the old sailor
 
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Thank you again Mr. Cashen. Following your advice and Darrin's yielded better results. Without addressing the issue of its spheroidized state the blades were coming out of the quench "soft." I took my first blade and broke it and it deformed quite a bit before breaking and had visible grain. Using your information, the blades came out hard and broke with ease and the broken area smooth like plastic. Though this isn't very scientific proof, I am happy with my perceived improvements. I'm running out monday to have the HRC tested and with any luck put under a magnification.
 
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