I just purchased some 52100. I've searched the threads for some time now. I will be using high temp salts for my heat treatment. Does anyone have info with temps and soak times for 52100. All of the threads indicate 52100 is particular about temps and thermal cycling. Since I'm high temps salts, I'm not sure I really need to triple quench if I can get the temps right the first time. Any thoughts or advice would be appreciate as I have never really used 52100. I'm reallly looking for a breakdown of the various temps for forging, annealling, quenching, tempering...etc... with soak time information as well.

Thanks ahead of time for any info!!!

David Rice
Ashland MO

Austenitize [and anneal ] from 1525-1550 hold 5-10 minutes.Quench in warm oil. Temper twice at 400F. It may benefit from cryo, -100F. If you do this it might be better to snap temper first at 300-350F for 1 hour , then cryo , then twice at 400F for two hours each time.

Mete, Thanks for the info. Would it be better to quench from high temp salts directly into low temp salts or stick with oil? If so at what temp should a maintain the low temp salts at for quench? I just received my low temp salts from Brownells and I've been excited about trying them out. I really trying to achieve consistent results and I figure what better way than salts to obtain consistency.

I've read quite a bit on the forums about cryo. Would a standard freezer get cold enough on 52100 to reach the martensite finish temp? I don't have whatever it is the stainless guys are using for the cryo.

One last question, do you know a site where I can look at the TTT for 52100. After two ABS classes at Arkansas and two years of reading about metallurgy I'm getting dangerously close to having a neanderthal understanding of metallurgy......I always face north and quench in live torso of my enemies to get the steel real hard.

Dave Rice
Ashland MO

I'd like to get a TTT diagram for 52100 too ! .....Just quench in oil [~140F] . The Ms is480F and Mf is 235F. It's not a matter of just getting below the Mf ,you'll still have some retained austenite. A freezer won't get much below 0F .While that would help some a proper freeze would be -100F, and deep cryo would be -300F......You can use the low temp salts for austempering [bainite] or for tempering.

During my search on 52100 I was reading about plate and lath martensite. I've been searching the forums to try to understand what is really going on in steels with above .6% carbon and plate martensite. How are all the extra carbides (is that just retained austenite) effecting the steel. So long as I keep the austenitizing temps below 1550 on 52100 with that ensure conversion to lath and not plate martensite? I guess I don't have a grasp on what all the extra carbides are doing after tempered martensite and how they benefit the steel. I know there are a lot of variables going on.
I posted this on swordforum as well hoping to get some responses from any metallurgists out there.

I'll answer it here too ! Whether you get lath or plate depends on carbon content no so much the austenitizing temp. Lath martensite is tough, plate martensite is not so tough .often you get a mixture. Carbides are good for wear resistance. :rolleyes: :rolleyes:

Just a note: I'm very much enjoying this thread. Great questions, great professional answers. I'm sitting in the background taking notes!

Your asking some questions I have been considering.

I do not have any answers to offer..just more questions :)

You mention the need or not need to triple quench 52100 as the high temp salts will be more accurate.........Maybe someone can answer this, but I understood that triple quenching was beneficial to 52100 (refining grain etc ), and has nothing to do with errors made in the first two quenches and getting it right the third time........I also understand that two quenches could also be performed during the forging process (and back in the heat to continue forging) which should give the same benefits (as multi quenching during the final ht phase)..........then finish off with just one quench for the final heat treatment process.............any comments?



Are you going to Austentize in high temp salts and and quench in oil...or are you going to quench in low temp salts for a holding temperature?.......if the latter, would you get a bainite transformation (if possible)?.......and if you did, what would this mean in terms of performance of a blade?

Here you go mete:

http://www.cashenblades.com/forum/52100.jpg

David, holding your steel at a particular temp within a range will allow a given amount of the carbon to be pulled into the austenite solution. If you soak at or above Acm for that steel you will get the maximum carbon in solution. If you hold at temps below this you will dissolve lesser degrees of the carbides. The point at wich grain growth occurs is when all of the carbides have been dissolved and the grains require more food to grow, it is then that they begin to devour each other and grow at a frightening rate, before this you are quite safe. By adjusting your temperature you can leave a certain amount of carbides suspended in a martensitic matrix of varing degrees of lathe or plate. I wished I could give you a magic set of numbers but every heat treat is unique due to its variables and you will need to work it out in your situation. One of the greatest variables is prior microstructure which leads me to the next topic- how many quenches?

If you control is tight (as in your salts) you have the ability to soak at any given temperature for any amount of time needed to get those carbides to where you want them. If all you have have is a forge or a torch, you do not have this luxury, so my hats off to the triple quenching forgers who figured out that if they austenitize at lower temps several times they can subsequently pull more and more carbon into solution to acheive their ends without the extended soaks. But much of the claims being made could indeed be achieved once with the equipment necesarry to do it right the first time. There has been some research done on the carbide refining benefits of quenching from a finer microstructure but one needs a steel that is capable of forming those carbides to begin with, so I believe the triple quenchers shoot themselves in the foot when they start making extraordinary claims about hypoeutectoids ;) . The largest problem I have found in this area is a number of people claiming they definately have the answers when they haven't even figured out the right questions yet. ;)

Ok so let me try to walk through this.....52100....I austenitize at 1550. So if I do not overheat am I just puting .6-.8 % carbon into solution prior to quenching or is all of the carbon being utilized? If only .6 to .8 % is being used isn't that lath martensite. If all of the carbon is being austenitized then it is plate martensite, right?

Mete, so the higher carbon is really the determining factor and not temp for lath versus plate martensite. So when a higher carbon steel is brought to the proper critical temp (and not hotter), is all of the carbon, regardless of the amount, being austenitized or just around .8%? What I'm really trying to understand is what is going on with all of the extra carbon in higher carbon steels? If too much carbon produces plate martensite, then why are so many people using steels such as 52100 and swear by them? I'm obviously just not understanding some metallurgy involved here. Can someone explain the higher carbon thing.

Another question...retained austenite is present after quenching and tempering as carbides which help in attributes like abrasion resistance and edge retention...is that right? So in a steel like 52100 or 1095 you will have large amount of extra carbides hanging around. What are the pros and cons of this versus a eutectic (or eutectoid can't remember which one) steel?

This all started by inquiring about the heat treatment of 52100. I would rather understand what is really going on in the steel versus blindly following a recipe. As far as the triple quench or quenching during the forging process, it is my understanding this only facilitates the austenitizing process. If I understand it right, the multiple quench converts some of the carbon to martensite. The next austenitizing cycle pulls more carbon into solution since martensite will convert very quickly into austenite for the quench. It seems the multiple quench is a way to make sure you are fully austenitized for martensite conversion. Keep in mind, I'm asking if this is right so someone jump in and school us. Again, however, single or multiple quench, what about all of the extra carbon (carbides)....and now don't we have plate martensite which is more brittle than lath martensite? As you can see, I'm confused on the matter......

Dave Rice

Kevin, Thanks for the TTT table also. I posted prior to seeing your last. So at say around 1550 with 52100 all of the carbon goes into solution right? Don't I then have plate martensite with 52100....and is that necessarily a bad thing? You probably saw my last post with questions about the extra carbon and what effects it has. I'm sure I'm just over complicating the matter but I really would like to understand what's going on and not just bake a cake (follow a recipe).

With the high temps salts I don't think a person should have to do multiple quenches and thanks for confirming that for me. Why not do it all the first time. The plate and lath martensite thing is new for me and I'm trying to figure it out. I guess there's a reason a euctoid steel is so popular (.8% carbon right?). Time to hit the library and start reading again.......

Dave Rice

Thanks Kevin. .....Let's not get too overcome by theory.A steel that has more than .8% C will have carbides in the final structure. So 52100 will have carbides .It would be best to have those carbides small and evenly distibuted.That is an advantage of Crucible's CPM steels. 52100 will also have retained austenite.We can austenitize from 1500-1550F.The higher the temp [and to a lesser degree the longer the time ] the more carbide will be dissolved and the more retained austenite there will be and the more chance for unwanted grain growth......David , you have some terms confused .When you austenitize you convert ferrite to austenite,that means forming new austenite grains .First they nucleate ,then form complete austenite grains, then[if you over do it, grains grow]. In the process the carbides in the steel dissolve completely or partially. If you quench the austenite with dissolved carbon that forms martensite......Hypereutectoid [above .80%C ]steels have carbides that help wear resistance .

Mete, thanks for the clarification. I understand it in my mind but mix the terminology on occasion. Not trying to get too complicated...I just want to understand what is happening and how to make a better blade that's all.