52100 HT Question. Yikes!

carbonsteel928

carbonsteel928

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Feb 15, 2010
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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.
 
Great google-fu, I remember seeing that but could not find it now matter how the heck I searched for it. Thank you Willie.
 
This wasn't the one where the soak time specific to Aldo's 52100. I seem to remember a 30min soak.
 
If its Aldo's 52100 it needs thermal cycling. It is highly Spheroidized and that needs to be cycled to set it up for the quench. Here is how I do it.
1. Heat to 1650, equalize, soak for 5-10 min., & air cool to black.
2. Heat to 1550, equalize, soak for 5-10 min., & air cool to black.
3. Heat to 1450, equalize, soak for 5-10 min., & air cool to black.
4. Heat to 1475-1480, soak for 10-15 min., & quench. The med. speed oil will do fine.
5. Temper 2 hours, 2 times, with water quenches after each temper. I suggest starting your temper @ 375 and working up to the hardness that works best for your application.
This process consistently gives me HRC 66-67 out of the quench. I usually draw it to HRC 59-63 depending on the application. You can do the thermal cycling in foil to reduce decarb. then use some type of coating like ATP or PBC for hardening and you'll have a nice clean blade when finished. Hope this helps.
 
Thank you Darrin, I was actually going to give you a call but I had lost your number and for whatever reason, it didn't dawn on me that your number was in your signature line. :)
 
The following is recommended by one of the best 52100 gurus arounhd, and it worked wonders for me using Aldo's 52100.

For normalizing and grain refining.... 1650 for 5 minutes, cool to black, quench if you like
1350 cool to black, quench if you like
1250 cool to black, quench if you like
Austenize......... 1475 for 10 minutes, quench in med speed oil.

Temper......... I do 420 for 2 hours twice.
 
I have been testing 52100 HT's this week and haven't got the results that I've been chasing. I'll try your HT next. Thanks!
 
I use something similar to Sanders process. It pretty much will give ya as much as you can get from this stuff (Aldo's steel).

I had some issues when I first started with this steel with warpage until I started doing my thermal cycles and used a much slower oil. I actually use canola oil now (slightly warm). I have used water and parks 50 before, the water didnt get it as hard I dont think and both of these caused alot of warping. The canola oil not only got the steel very hard but also reduced the warping to zero or very minimal. The normalizations are highly recommended though. After doing all this the grain structure in this stuff is fantastic.
 
Thanks for all the info!
I had the same thing, unwisely started with a fairly long blade and could not control the warpage- it took three tries to get it to harden and be straight.
 
I'm the furthest thing from an expert on this subject, but I spoke with Aldo about it a few weeks back when I placed an order that included some 52100. He didn't seem to believe in doing anything crazy. I wrote down what he recommended back at home, but of the top of my head it was:

Coat the blade in anti-scale or place some charcoal in the kiln to prevent decarb
35-45 minute soak at 1550F
Air cool to ambient
10 minute soak at 1475F
Quench in medium speed
Temper twice for 2 hours

I coated the blade in ATP and quenched in Parks AAA, tempered at 375 (kitchen knife). Only did one blade in 52100 so far and it's not yet complete, so I can't really comment on performance too much, but my as-quenched hardness was right at 66-67rc. I'll definitely be testing some of these other methods in the future when I have the opportunity, but for now that seemed to have worked nice enough.
 
While I'm probably even LESS knowledgable than Weebus on this subject than he is, I really don't think that the soak time needs to be quite that long. If we were talking about a very large blade, thick, maybe the longer soak time would be warranted. I'm making knives that are rarely larger than 5" blade, never over 1/8" thick, and I try to concentrate on geometry and bring that steel down thin as I dare before the heat treat. So my soak time is rarely over 10 minutes, closer to 5 really (I probably should be doing 10 minutes), during the normalizing and austenizing. I do get great results, edge seems to be EXTREMELY hard after quench. I really, really, really like this steel!

With that said, most 52100 HT recipes do indeed call for longer soak times, but I think that might be for larger cross section pieces in industrial applications.
 
Stuart, soaking has very little or nothing to do with stock thickness. Its about getting all the carbon and other alloys into solution before the quench. Its basically the same thing with epoxy. Some brands of epoxy require 4 minutes of stirring. The epoxy is actually homogenous after 10-15 seconds of stirring but it takes the full 4 minutes before the reaction actually takes place. Its not about getting the steel the same temp. all the way through its about allowing the steel to have time for everything to go into solution so it will be properly dispersed for the quench.
I hope all that made sense.
 
Derrin, makes perfect sense. I see what you're saying, and totally understand. Soak time, especially with 52100 is something I must say I don't really understand. Maybe it just boils down to what one guy has figured out that works for him.....and maybe that is a 30 minute soak. So why, if 52100 really requires a 30 minute soak, do other well informed bladesmiths recommend no more than 10 minutes soak? Soak time in 52100 is probably my biggest question right now, and I sure didn't intend to sound like I've got it all figured out. As a matter of fact, the intital normalization temperature is all over the place, depending on who you talk to. 1650, 1550, 1515. I've researched this steel's HT recipe till my fingers bleed, and every one is different. There are even 52100 recipes out there that do not even call for the higher normalizing temps, just a 10 minute soak at 1475. I don't buy that at all, though.

I say that it makes perfect sense and that I understand. But maybe I don't. Am I wrong on this? Take a piece of steel 1" x 6" x .065" and place it in the forge at the same time as a piece 2" x 6" x .5". Will not that smaller piece come to a complete even temp faster than the larger piece? It would seem to me that the larger piece has more mass to heat (at the same rate) so would take longer. I place a little bitty piece of steel in the forge and quickly it is red hot. Not so with a knife blank. It takes a while to get red hot. That was my thinking with soak times and small vs large blades. Hey, I'm a sponge......fill me with the right info!
 
I think it is related to the annealed state of Aldo's steel needing longer soaks to get everything into solution. If it was not in this state, less soak would be required.
 
Sounds right Willie. As per Mr. Cashen's posts, Aldo's 52100 is 95-98% spheroidized which makes it very machinable but leaves it in a poor state for heat treating as all the carbon is locked up. Here is Mr. Cashen's post regarding it.

Mr. Cashen @ Knifedogs.com:

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.
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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.
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No matter which steel you ask about you will get several "recipes". Thats why I just use any info. I get as a base to start my own testing and work up what I know what works on MY equipment. I completely understand what you're saying about having it all figured out. The more I learn about this stuff the more I realize how much I still don't know or completely understand.
You are correct about mass effecting the time it takes to heat a piece of steel. It took me a while to realize this too but soak times are for a piece of steel that is ALREADY at the soak temp.. In other words you should allow the steel to equalize at the desired temp. before you start timing the soak. Does that make sense?
 
I feel like I'm hijacking this thread....and my sincerest apology to carbonsteel928. Yeah, that sure makes sense Darrin about soak time after equalization. However, in Mr Cashen's post above, he didn't mention a 30 minutes soak. I asked Mr Cashen about a certain HT recipe for 52100 on another forum, and our conclusion was what I had posted above in this thread. While our conversation was more towards the initial normalizing temp of 1650F, he did not indicate that a 30 minute soak was necessary for Aldo's 98% spherodized steel. Originally, this recipe I had seen called for quenching after each normalizing heat, right out of the heat into the oil. We quickly dispelled with that notion, but decided that quenching once it is black is certainly not going to hurt anything. If we can get away with 10 minutes instead of 30 and get 100% out of our steel, hey, I'm all for it!
 
samuraistuart said:
I feel like I'm hijacking this thread....and my sincerest apology to carbonsteel928. Yeah, that sure makes sense Darrin about soak time after equalization. However, in Mr Cashen's post above, he didn't mention a 30 minutes soak. I asked Mr Cashen about a certain HT recipe for 52100 on another forum, and our conclusion was what I had posted above in this thread. While our conversation was more towards the initial normalizing temp of 1650F, he did not indicate that a 30 minute soak was necessary for Aldo's 98% spherodized steel. Originally, this recipe I had seen called for quenching after each normalizing heat, right out of the heat into the oil. We quickly dispelled with that notion, but decided that quenching once it is black is certainly not going to hurt anything. If we can get away with 10 minutes instead of 30 and get 100% out of our steel, hey, I'm all for it!
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No worries Stuart, we all get something out of Q&A so long as the thread doesn't turn into the typical 52100 mess. :)

In regards to the long soak, I'm with you and favor Darrin's posted protocol as it seems to make the most sense. Now, this shouldn't be read as me saying that one is better than the other as I'm a big believer in that folks should do what fits their views.
 
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