52100 heat treatment in a gas forge

[Doug Lester]

So, if I read you right, no sub-critical annealing or not annealing period.

Doug

[Kevin R. Cashen]

You may need annealing to do much working of this alloy, it just shouldn't be heavy annealing like what the mill did. There are spheroidizing procedures that involve long kiln ramps, these are the type that build large spheroids. Shorter procedures that simply ball the carbides into fine spheres are more responsive to heat treatment. Even the ramp cycles will work if you don't over do it with the low temp cycles beforehand. I have locked up my O-1/L6 Damascus the same way (63 HRC max) by getting crazy about cycling everything down as fine as possible and then a long ramp anneal. It required the same fix as the 52100.

So it really is not the fault of the steel, it is all the goofy things that bladesmiths do to it. I have a saying that I use often- there are no bad steels, there are only bad application choices and bad heat treatments (or perhaps, bad heat treaters). I really think that sometimes bladesmiths get so hung up on making the "ultimate" knife that they don't take the time to simply make a good knife. Ultra uber superdooper fine grain, .0001% retained austenite etc.. when in the end it is just a knife, and you need a laboratory just to detect these differences. Don't get me wrong, the pursuit of that last 1% is what drives us to get better, and I am the worst about it, but sometimes it results in serious mission drift and we forget what it is we are trying to make.

[jimmontg]

O1/L6 Damascus? Any differential problems because of the higher Carbon content of the O1? I know it's only 0.20 difference, but I've read it can cause problems and undue stresses.

[samuraistuart]

Yep, Aldo's 52100 is a great, great steel, no doubt about it. The mill he receives it from does an excellent job annealing it, that's for sure! It is butter soft to work, and I bet guys using CNC really like the fact that it is so heavily spheroidized. I myself wish it wasn't so coarse spheroidized, but it's not a big deal to normalize and cycle it.

And about going crazy with cycling, I hear you. I hear all kinds of stuff about cycling on the forums. Claims that "you HAVE to do sub critical cycling to get the most out of it" and stuff like that.

I only do 3 cycles after normalizing, and never below 1425f.

[Michael Grieb]

Thanks for the info. I will probably order a thermocouple and pid controller today and get back to you when I have done my first heat treat on a sample chunk. What is the HRC required for a file to skate, so I have a reference point?

[jimmontg]

But a good modern file will skate across a 63-64 RC hardness blade. I've been running into some newer files including Nicholson that are not as hard as the older ones though. I can cut a little with a 40+ year old Black Diamond into a small 6" Nicholson I bought last year. But if a file skates against the blade you should be fine.

I have some Nicholson Swiss needle files in a set that are just as good as they ever were and a few mill files as well. A flat mill file tested at RC 66.+ when I had access to a Harness tester I tested it just to see. All from the 70's.

I looked into the changes in files just a while ago. All those files from the 70's were basically high carbon like 1.5% or higher. If you have an old Black Diamond or a Grobet and the file skates you're probably 64+ hard. I use my half round to check hardness and use the round side. It's a Nicholson as most of my files are, I have a couple of Grobet files too and they held up pretty well too when I was a welder. I wore the heck out of files on the edges of laser cut steel and the Grobet and Nicholson files held up the best, had some Heller files that didn't last nearly as long.
Now you know more than you wanted to know about files.

[Michael Grieb]

😂. No. Thanks for that! Can never have too much info on files. So realistically speaking, if I got 51200 austenitized and quenched correctly, I could get a kitchen knife that would have a file skate after tempering?

[Kevin R. Cashen]

Originally Posted by jimmontg

O1/L6 Damascus? Any differential problems because of the higher Carbon content of the O1? I know it's only 0.20 difference, but I've read it can cause problems and undue stresses.

There will be no differential, after a few heats in the welding process the carbon content will be the same in both steels. The alloying has them in the same window for heat treatment so they actually play very well together. There are other things that makes the entire mix touchy to weld up but the steels are as well matched as they come.

[jimmontg]

Originally Posted by Michael Grieb

😂. No. Thanks for that! Can never have too much info on files. So realistically speaking, if I got 51200 austenitized and quenched correctly, I could get a kitchen knife that would have a file skate after tempering?

Michael the file test is for checking how hard the steel is right after quench, but usually not after temper. A file as made, has a specific temper cycle and good files like the Grobet are very high carbon like 1.7 and higher and are like RC 68+ as quenched and are tempered back to 65 or so. 52100 only has 1.0 or 1.05 and a file skates over or tends too at RC 62, but if its a good file some pressure should dig into the edge some. I presume after tempering 60-62 is the hardness you're shooting for? So keep that in mind, if it digs in easy it probably isn't above 60. Using files of unknown hardness isn't the best way to determine hardness.

52100 is used a lot by makers because it forges well and holds an edge well thanks to the chromium carbides that it forms. If edge holding or abrasion/wear resistance is your target, 52100 is a good forging steel. I tend to make my carbon steel knives right at 60 hardness, but I've reached the point where I only use O1 unless I'm making Damascus, in which case I use 1084 and 15N20. After reading Mr Cashen's answer if I can get access to a forge I may try the O1/L6 combo.

There is also a steel made for forging called CruForgeV and it has 0.75 vanadium in it which will form vanadium carbides (harder than chrome carbide) and it will hold an edge even if it is tempered back a little too much. Only place I know who still sells it is Alpha Knife Supply, it's inexpensive and only comes in .250" thickness. It is very similar to 52100 except a little less chrome and of course the vanadium. It is also easy to forge as that is specifically what it was developed for. For instance my S30V knives are high Vanadium (4%) and a file tends to skate over them even though they are RC 60 hard. Vanadium adds a lot of wear resistance. Needs a diamond hone to sharpen it in a timely manner though.

By the way Ed Caffrey told me that some files are only case hardened and would be useless if made into a knife. Said even some Nicholson rasps were made like that.

Please pardon my long answers, I'm in the hospital and have time on my hands.

[Michael Grieb]

Thanks for the detailed response. The major reason I picked it up had to do with what I heard about its edge retention and because I assumed the heat treat was far easier than it is.

[jimmontg]

When I first started making knives in the early 90's I used O1 exclusively because that is what a certain knife store sold. I heat treated it in a forge, charcoal forge. The knives were quite hard, but not optimal. Without a temperature controlled oven you won't get optimal performance from any steel, but you can get good results nevertheless.

Please keep that in mind, plus you picked a picky steel to start with. You will get good results by following the advice of other posters here and I am not an expert at 52100 as I rarely used it except in an industrial situation. I was a heat treater at a machine shop and was put into that position simply because I had a lot of metallurgy experience from being a TIG welder and one of the best if I may be so bold. Also I made knives so they figured I knew all there is about HT. LOL
I wish you good luck in your new endeavor.

[Doug Lester]

This conversation makes me realize that what a well known knife makers said about 52100 making a better forged knife that a stock removal knife might have a kernel of truth to it, even though I originally doubted it. The forging temperatures get the carbon from the carbides into solution where a stock removal maker may not get the temperature at heat treating high enough to do the same thing.

Doug

[Kevin R. Cashen]

Originally Posted by Doug Lester

This conversation makes me realize that what a well known knife makers said about 52100 making a better forged knife that a stock removal knife might have a kernel of truth to it, even though I originally doubted it. The forging temperatures get the carbon from the carbides into solution where a stock removal maker may not get the temperature at heat treating high enough to do the same thing.

Doug

I have thought the same thing as far as the irony of it. When industry started the heavy spheroidization in the last few years, I said to myself, "well darn, those forged blade fantasies are finally coming true, if the stock removers don't normalize this stuff." But we need to also remind ourselves that a lot of outlandish things were said long before industry started spheroidizing the snot out of steel.

[Michael Grieb]

Hey people! Dredging up this thread again. I found a possible solution on youtube for heat treating 52100 accurately in a gas forge. I am going to try putting a piece of stainless angle in my forge between the burner and the part of the forge with the blade and the thermometer. This way i should be able to keep a consistent temp under the angle. Is there any fundamental flaw with this plan that i am not seeing?

[Andrew Garrett]

Very interesting and informative. Thanks.
I have recently started using Aldo's 52100 myself and chose to heat treat the way Ed Fowler does--sort of (modified for an annealed foundry steel).
Ed does massive reduction forging on his steels and does three annealing cycles (he does many things in threes come to think of it).
I do not anneal. I do not quench 3 times (tried it once), and I do not put my blades in the home freezer as he does since every bit of advice gleaned from this network in the 13 years I've been here indicates that this has little or no scientific merit (not to discount Ed's considerable success in high performance blades-just a choice on my part).
Ed uses Texaco type A quenchant. I use peanut oil at *130
He uses a gas forge, magnet, and color to determine critical temp. He also does what he calls a 'flash normalizing' three times. These are the processes I borrowed from his published instructions. I've had good results.
It is entirely possible that I'm just 'Forrest Gumping' my way through this.
http://www.knivesby.com/Ed-Fowlers-heat-treat.html