Need help heat treatiing 52100

Tom Lewis

Tom Lewis

Joined
Feb 24, 2000
Messages
1,952
Yesterday I got some flat bars of 52100 steel from Aldo. Today I ground out a blade, (stock removal) and in my Paragon oven heated it up to 1650 for ten minutes, , took out and let it turn black, heated it up to 1550 for ten minutes, took out and let it turn black, heated it up to 1450 for ten minutes, took out and let it turn black. Then heated up to 1475 for ten minutes and edge quenched in 130 degree Texaco type A oil .
The Blade did not harden. A file easily cut it.

I Reheated to 1475 for ten minutes and quenched it in 130 degree Brownells Tough Quench . It did not harden, a file easily cut it.

I reheated to 1475 for ten minutes and quenched it in room temperature Parks 50. It did not harden.

I reheated to 1475 for ten minutes and quenched it in water. It did not harden.

After the Water quench, I cleaned up the blade and checked it on my RC hardness tester. It tested a RC of 52. I checked my tester with a CPM 154cm blade that I got back from Paul Bos heat treating and the 154 blade tested a RC of 60, which is what it should be. I think my RC tester is accurate.

So, I can think of a couple of reasons. 1. Maybe my Paragon oven is reading wrong and I need to try heating to maybe 1500 on my oven instead of the 1475. 2. Maybe I don't have 52100. I really doubt that, I have gotten lots of steel from Aldo and it has always been labeled right.

Maybe There is something else I need to try.
 
I'd try a bit closer to 1500 and a longer soak of about 20-30 minutes... it should get so hard the file shouldn't touch it. The Parks 50 should be plenty fast as far as oil goes.
 
DFK is correct.
But after the thorough regimen you run the steel i'd think you should have started with a microstructure more ready to austenitize, 10 minutes should have brought you further

...more, 1475 is not too distant from 1500 and i wouldn't expect your results anyway...i can't forsee any radical improvement from 1475 to 1500 given the premises.

Have you got any way to ascertain your temperature measurements? If not i would try boosting the temperature at least to 1600 (by your current TC reading) with a 15 min soak on a coupon and see what happens.

Another tought: Did you protect anyway the steel surface during HT? Could it be a decarb layer you are hrc reading ?
 
I would grind the blade a bit and see if you have a thick decarb layer. That was a lot of time in the oven.
 
Thanks for the help. The steel was not protected during the heat treat, but I did grind the decarb off the blade and the RC test was on clean metal.
What quenching medium would you recommend?
 
I would highly suspect decarb as well. It can be deep with those soaks. 52100 has a PN of 3 seconds. I use P50 and 130F canola with 52100 with excellent results. Pretty much using your same HT, although I will do a quick spher anneal after normalizing and cycling. Well....it isn't really "quick". Takes a few hours.

If all the temps are good, the steel is really 52100, and decarb was sanded thru, should be at 66-67. Do you have a bar left over with color code on it?
 
The decarb was ground off before I did the RC test. I bought six bars, and they had 52100 written on them. The ends appear to have a light yellow color on them.
I have a round bar of 52100. I just forged it into a bar. I will grind a blade of it and try the same heat treatment and see what happens. Also I got the 52100 from Aldo in two different sizes. I will grind a blade out of a different size and see if that makes a difference.
Also next time I have the steel in the oven at 1475, I will check with a magnet to see if it is non-magnetic.
I have a feeling that my Paragon oven is not reading right.
Thanks for the suggestions, I'll post my results when I get them.
 
Tom, what you're describing is nearly the exact experience I had a few weeks ago, with my first time using 52100. I had three blanks made from Aldo's 52100 and each time after HT they'd be in the high 40s - low 50s HRC. My recipe was basically the same as yours except my first cycling temp was 1625°F, I used antiscale, and quenched in P50. After three tries and three fails I was getting pretty frustrated.

I did a little more reading and came to the conclusion that "under soaking" was my problem. 1475° is right at the point below which that will occur, according to an old Cashen post I read here on BF. So if your oven is off a little you may not be getting the steel hot enough. Metallurgically I think I know the problem this would create but I'm not sure, so won't try to guess. In any case, I upped my temp to 1490 and it solved the problem. The fact that you were able to quench in water and heard no "ping" might support this theory, but again, I have no idea.

The other possibility is you may not be grinding off all the decarb. All those heats adds up to a lot of time for a piece of steel to go unprotected at those high temps. Maybe try grinding off a few more thousandths. Maybe there's additional slightly affected steel beneath the obvious blotchy-textured decarb layer.

Good luck. I'll be interested to see how it all shakes out.

-Mike
 
Aldo's 52100 is 99% spheroidized....yes 99%. That bundles things up in nice balls and rods. They have to be unbundled, and evenly distributed to get things ready for hardening. A 10 minute long soak at 1650F, followed by reducedtemperature soaks and cooling help get it all redistributed. If you have a concern about grain, an oil quench at 1450F will help refine any large grain. Once it is in proper shape, it will harden in fast/medium oil at 1475-1500F with a 15 minute soak. Some sort of oxygen protection is a good idea or you will have a good layer of scale and decarb to remove. Scale can be removed by an overnight soak in sodium bisulfite ( Ph Down), but decarb needs to be ground away.

Here is Darren sanders procedure:
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.
 
A big THANKS! to all who made suggestions. I tried it again today and Mike, I used 1490 degrees like you suggested and then quenched in Parks 50. It RC tested at 65.
Stacy, thanks for the procedure you gave, I followed it except I went to 1490 degrees before quenching.
Thanks again to everyone for your help.
 
Man, I love this forum. I have a HT process that works great for 52100, but having this to put in my notebook just in case is priceless.
 
Tom, after you posted the thread and the problems, seriously...I've been thinking about you the whole time. I'm GLAD you got the problem squared away! Going from 1475F to 1490F solved it, huh? Amazing that 15 degrees made that much of a difference. 65 is not too shabby, but 67 can be pushed out of it, as I'm sure you're aware.

Quite a few cycles that that knife saw. Eight total including the last one, if I counted right. I think the theory goes that with that many cycles, and seeing 5 quenches, grain size should be very small, thus necessitating a faster quench than usual.
 
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I ran the original blade through all the cycles and quenched at 1490. I also ran two new blades through the same cycle. They all RC at 65. To get 67, I may need to go to 1500 before the quench. Now, 1500 on my paragon is not necessarily 1500 degrees on someone else's oven.
The original blade has some interesting features. When I finish I will post a picture.
Thanks again to everyone for your help.
 
Tom, that's great news. Sounds like you may have been dealing with the same issue I was. I think my oven TC may be a little off, or at least the temp in the middle of the oven (where the blades sit) may be a little cooler than where the TC is. I'm going to get another TC to stick through the "peep hole" in the door and run some tests.

RE getting to 67HRC. If I remember the Cashen thread correctly, he said that the HRC value was inversely related to the temp; i.e, he got consistently higher HRC values the lower the austenitizing temp was, and that 1475 was the lowest temp that worked and gave the highest HRC value. I should probably just find the thread. Okay, got it. In his words: "I have done soak temperature experiments that show Rockwell hardness climbing steadily with every 20F less from the upper range until you drop below 1475F and then undersoaking occurs. I have managed to get 67HRC from 52100 but the strain and embrittlement becomes a problem." Here's the thread:http://www.bladeforums.com/forums/showthread.php/598363-on-a-no-BS-52100-heat-treat

I assume that with my oven, I program for a soak at 1475 but what I really get is a soak that hovers between 1460-1470 (or thereabouts?). So I program for 1490, which probably gives me an actual soak closer to 1475, which is the temp I want. If you want to hit 67HRC (assuming you were having the same issue), I'd go down rather than up. Maybe try 1485 or even 1480.

Great to hear things are going well and I'm looking forward to a pic of that blade!

-Mike
 
Mike, thanks, I just read the Cashen thread and am glad to get that information. Thanks for the help. I think you saved me a lot of trouble.
 
I tried taking some pictures of the 52100 blade that went through cycles of 1650, 1550, 1450, then at 1475 was quenched in Texaco type A, Brownells tough quench, Parks 50, water. Then recycled through 1650,1550, 1450, and at 1490 was quenched in Parks 50. This blade appears to have surface fractures. I hope the pictures show this.
 

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