View Full Version : 52100 and salt pots
son of liberty
02-21-2011, 07:43 PM
I need a start point, dose someone have a recipe? If you would explain all the steps from fresh bar to temper in high temp , low temp pots?
02-21-2011, 08:39 PM
I guess my question is...how much experience do you have working with 52100? Unless you,re well versed with that steel, I would recommend starting with only using the high temp salts, dialed in at 1550F. No soak, then temper in the conventional manner. That will establish a baseline for you, and you can experiment from there. I personally do not use low temp salts unless I am seeking to "Marquench".
52100 is not a steel to use unless you are intimately familiar with less critical steels (such as 5160). 52100 has some unique forging characteristics, and in my opinion a forged blade including all the heating/cooling cycles associated, creates a far superior blade of 52100 than a stock removal blade without those associated heating/cooling cycles.
son of liberty
02-21-2011, 09:27 PM
Im not as familiar as i would like to be..lol. Can I temper in the low temp salts rather then a kiln?
I have been reading allot about how the salt pots can be used to marquench and wanted to give it a try. It dose sound like i should stick with what i know though and work out from there. Branching in to other possibilities with the pots as i become more familiar with the steel and pots.
I forge most of my blades but dont have much time with 52100 under the hammer, its been very particular so far. The 5160 seems to be a better steel to play with on the anvil anyway but I have a bunch of 52100 bar, I guess ill save it and get some other steels to play with that are less difficult to play with.
Im in proses of serious upgrades that I hope will help me refine my processes even more, Temperature controlled forge, salt pots , and a few other little things that I hope will give me more control and consistency.
02-21-2011, 10:21 PM
52100 is a wierd steel. It retains carbides mixed in with the austinite until you get up to really hot temps. I start forging at a pretty bright orange and stop before it looses color. What you could do is austemper the blades at about 500 degrees for an hour in low temperature salts to form bainite. That should put you somewhere around an HRC of 58. If you want to get it a little harder you could quench in oil or another salt pot at about 475 for a few seconds and then immediately up quench it at 500 degrees.
Kevin R. Cashen
02-22-2011, 08:34 AM
I do all of my tempering in low temp salts, the thermal conduction is many times faster than an oven and the heat is completely uniform. I do most of my "walking in tempers" to determine my desired HRC for 30 minutes, which would be impossible with any type of oven, and then my long soaks. After studying 52100 inside and out, most only guess from the outside, I am convinced that most of the fantastic performance gains many makers have gotten from it with oddball heat treatments is a matter of contrast and elation at overcoming all the issues that you can get with that steel if you are not very careful. I have often joked that 52100 scares me that there could be some element in it that burns out and gets into a smiths brain because it seems that whenever I hear of some of the strangest and convoluted heat treating practices 52100 is most often involved somehow.
But joking aside 52100 is just steel but like all modern steels it has its own unique chemistry and heat treating parameters based on its application. It was designed and meant for bearings, so not only do you have to realize its unique heat treating requirements, but you need to adjust what industry gives you to make a cutting tool out of it, not so for something like say O-1 which was designed for may cutting and slitting type applications. For bearings compressive strength is very important and abrasion resistance is a close second, heat treating for such deals with retained austenite a little differently than what we do and 52100, for a simple steel, is very prone to retained austenite. As Ed mentioned the heating cycles in forging can disperse and refine the carbides (not the magic hammer mind you, but the heat cycles). Avoiding slow cools from above critical, such as many of the traditional bladesmithing anneals is essential. When heating the book will tell you 1550F, but that is under the assumption that you are making bearings and will have different approaches for dealing with retained austenite. If you keep your austenitizing temp below 1500F you can expect to reach as much as 67 HRC as you reduce the amount of RA.
02-22-2011, 04:13 PM
Good post Kevin! I had thought about mentioning heating it below critical, but thought I would muddy the waters if I did. Now that you brought it up, I can blame it on you! :) Just kidding.
When I use the salt tank to heat treat 52100, I run it through at 1450F for a 5-6 min soak. Spectrographs have shown that Kevin is 100% dead on about the RA.
son of liberty
02-26-2011, 09:09 PM
So I need to avoid annealing or other delayed cooling methods?
Forge starting at a high heat and keep reducing the heat with every heating to help refine the grain?
then normalize? at what temp?
Then run it through the salt pot at 1450 for 5-6 minutes before quenching?
Im trying like crazy to wrap my head around kevins knowledge but its hard for me, im a back woods KY redneck. I am reading constantly so I am making an effort to learn , its just slow and difficult.
So in theory, could I grind out a 52100 blade and then run it through a series of heats in the salt pot to refine the grain, then normalize in the salt pot?
Again thank you guys very much for all the effort you put in to answering my questions, i know its not an easy thing to constantly do topped by several people constantly asking the same questions.
Kevin R. Cashen
02-26-2011, 10:28 PM
Why all the concern about grain refinement, have you had an issue or problem from the forging process with large grains? Just forge your blade using the logical steps of going hot when forging thick stuff and working cooler when working the thin stuff. Normalize three or so times to fix the uneven issues from forging and then spheroidize or subcritical anneal. Don't get caught up in the grain size mania you will read too much about in the magazines by guys more concerned about making the finest grain than they are about making knives. Fine grain is indeed nice, and fortunately steel has a lot of built in mechanisms to keep it in a reasonable size range so long as we stay out of its way with our actions, and careful normalizing can do wonders.
02-26-2011, 11:39 PM
To go along with what Kevin said, I don't get all that caught up in forging heats except for working ranges for a particular steel which I usually find out from people who have experience working with it. I normalize three times just before quenching. I've broken probably more than my share of blades straightening or testing the edge and all of them have had very fine grain. Some of the alloys will inhibit the growth of grain.
Kevin R. Cashen
02-27-2011, 08:19 AM
... Some of the alloys will inhibit the growth of grain.
Perspective can really contrast this, work with homemade bloomery steel for a while and you will get a whole new appreciation for the grain size retention of modern steel. That old stuff had nothing but iron carbide and the skill of the smith to control grain size and both are a pretty fine line.
son of liberty
02-27-2011, 11:04 AM
Thank you guys , I think that what I needed to hear. I was drinking the kool aid so to speak. I have a tendency to read so much that I start second guessing and loosing my mind about my process.
02-27-2011, 06:25 PM
Don't feel bad. I was just fortunant enough to run across a discussion on grain growth and correction on another board when I was starting out and the advice there stuck. There are plenty of people who think that you have to avoid grain growth at almost all costs like it cannot be corrected. Where you do have to watch the heat a bit is when you are normalizing before quenching. If you get your heat too high for too long you will defeat your efforts at to decrease grain size. As stated above, some steels are worse on grain growth than others and some need to be austinized a bit hotter for a bit longer to get carbides to go back into solution so that the carbon from them can disolve into the austinite. It all depends on the alloy that you're using. But trying to figure it out is just about enough to make your head spin. That's where people like Kevin and Howard are indispensible.
03-02-2011, 03:06 PM
I wanna throw one in here...
not to hijack, but from what I am reading, the idea of forging from a much larger bar doesnt do much, its the thermal cycling of the steel that gives the results we are all looking for?
I "think" that is what i am reading...
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