52100 Heat treatment question

spend the $40 and get a thermocouple and display. put the thermocouple next to center of the blade. when thermocouple says temperature you want, start timing. 1/16 takes about 2 minutes to heat thru, 1/8 about 4 or 5. trying to rely on color? or get a magnet into a 1500*F furnace? try and simplify. heat to 1650-1700*F. air cool. for 3/32" material like you have, into 1475*F furnace, when thermocouple next to blade says 1475*, 6 to 8 minutes, then quench till you can touch. wipe off oil. ice water or dry ice and alcohol. temper for 1 hour at 350F, cold water quench, 1 hour at 325F.
52100/L2 has been around forever, how come none of the texts even mention multiple heats before final hardening? are you doing a spheroidize anneal? might be easier to shop and find a supplier that sells properly annealed material
 
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scott.livesey said:
spend the $40 and get a thermocouple and display. put the thermocouple next to center of the blade. when thermocouple says temperature you want, start timing. 1/16 takes about 2 minutes to heat thru, 1/8 about 4 or 5. trying to rely on color? or get a magnet into a 1500*F furnace? try and simplify. heat to 1650-1700*F. air cool. for 3/32" material like you have, into 1475*F furnace, when thermocouple next to blade says 1475*, 6 to 8 minutes, then quench till you can touch. wipe off oil. ice water or dry ice and alcohol. temper for 1 hour at 350F, cold water quench, 1 hour at 325F.
52100/L2 has been around forever, how come none of the texts even mention multiple heats before final hardening? are you doing a spheroidize anneal? might be easier to shop and find a supplier that sells properly annealed material
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Texts are assuming he steel is in a heat treat ready condition. This batch of 52100 was so heavily spheroidized that longer soaks didn’t break apart the carbides resulting in a carbon depleted solution. My experiments with this are in the stickies. Kevin Cashen came up with the recipe listed above to get the steel in optimum condition for blades. Industry heat treat is optimized for bearings.

Edit: link to sticky thread: https://www.bladeforums.com/threads/52100-aldos-alternate-heat-treat-epic-fail.1169466/
 
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Recalescence is not a colour, it is an event that will happen, without fail, when the internal structure begins to transform. I was just pointing out the most reliable method for determining that transformation is taking place.
 
I've been messing with 52100 heat treat with a propane forge, using a torch to play around with small samples, and I feel like I still don't understand what needs to happen to get this stuff to harden. I have a blade I did a few weeks ago that ground out (no forging) and did a single quench from non-magnetic and tempered for an hour at 400F. It's hard to file, sparks well on the grinder, and when I try to scratch it with steel that I know is hard (O-1 and S30V) it will barely scratch or not scratch at all. It just doesn't seem to hold an edge as well as O-1 or 1095, however, so I'm a little confused.

Last night I took some small piece and heated it up non magnetic with a torch and quenched it just like I did that blade. The file didn't want to cut into it but it also didn't skate across like it does with O-1. Next I took another piece and heated it to non-magnetic, quenched, heated to non-magnetic and also watching closely for the decalescence, and quenched again. The file definitely didn't bite into that and when I tried halfheartedly to break it with a hammer to see the grain it just bent at the boundary where the steel had hardened.

What I was trying to imitate with all that was the cycling you all are doing in ovens prior to the final quench but I know I'm not anywhere near as specific with the temperatures. Now, put your Ed Fowler filters on and follow along with me for a minute. Ed says he does his heat treat with an oxy/acetylene torch along the edge and does it three time. If I remember correctly he also says he does three two hour tempers and puts the blade in the freezer between tempers. I get many old timer, if Ed falls into that category, have their superstitions and habits that they claim make a difference and that his heat treat method might be exactly that. His results, however, are pretty definite and something he does has to work to get him to that point.

Thoughts?
 
"Thoughts?"

Yes... many but I will hold back... lol.

You are not doing 52100 any favours, heating it with a torch. You will never see decalescence with a torch... some folks won't recognize it with a forge in a dark room. It needs to be crept up on, so-to-speak. Heating to non-magnetic is not good enough for most steels, aside from 1084, which I still wouldn't recommend at such a low heat. 52100 will not respond well to that heat treatment, as you have experienced. I respect that you are experimenting with 52100 but others have already done it with proper equipment and practices. You are essentially trying to plaster a wall with a butter knife and wondering why you can't get it nice and even.

52100 has some alloying and is hypereutectoid. Both, need to be addressed with time and temperature. A standard propane forge can barely hold temperature to pull the potential from 52100. IMO, opinion a torch is useless. Some may disagree.

I have had my fill of discussing, Ed Fowler. Is his book out yet?
 
Ben_M said:
I've been messing with 52100 heat treat with a propane forge, using a torch to play around with small samples, and I feel like I still don't understand what needs to happen to get this stuff to harden. I have a blade I did a few weeks ago that ground out (no forging) and did a single quench from non-magnetic and tempered for an hour at 400F. It's hard to file, sparks well on the grinder, and when I try to scratch it with steel that I know is hard (O-1 and S30V) it will barely scratch or not scratch at all. It just doesn't seem to hold an edge as well as O-1 or 1095, however, so I'm a little confused.

Last night I took some small piece and heated it up non magnetic with a torch and quenched it just like I did that blade. The file didn't want to cut into it but it also didn't skate across like it does with O-1. Next I took another piece and heated it to non-magnetic, quenched, heated to non-magnetic and also watching closely for the decalescence, and quenched again. The file definitely didn't bite into that and when I tried halfheartedly to break it with a hammer to see the grain it just bent at the boundary where the steel had hardened.

What I was trying to imitate with all that was the cycling you all are doing in ovens prior to the final quench but I know I'm not anywhere near as specific with the temperatures. Now, put your Ed Fowler filters on and follow along with me for a minute. Ed says he does his heat treat with an oxy/acetylene torch along the edge and does it three time. If I remember correctly he also says he does three two hour tempers and puts the blade in the freezer between tempers. I get many old timer, if Ed falls into that category, have their superstitions and habits that they claim make a difference and that his heat treat method might be exactly that. His results, however, are pretty definite and something he does has to work to get him to that point.

Thoughts?
Click to expand...

Follow the process listed above in this thread, and you will get consistent, high performing results.

Do it the Ed Fowler way, and keep coming here to ask why your blade doesn’t perform well. (What was Ed’s source of 52100? Was it heavily spheroidized?)

You choose.
 
So essentially trying to heat treat 52100 to its potential without a digitally controlled oven is going to be an exercise in futility and frustration. I bought a bar of it because it was reasonably cheap and I wanted to give it a try. I had heard it was similar to 5160 but better performance but didn't realize the extra control required for hear treat until after I got it. I figured I'd try it anyway since I had it; I wasn't attempting to rewrite the book on heat treating 52100. Thanks for taking the time to respond.

I might look into sending some blades out for heat treating since I have a good bit left.
 
That is not to say you can't make a good knife with 52100 in a forge. You just have to be realistic with your expectations and not assume you are squeezing every bit of performance out of it.

It is more important to have fun with this craft.

You want a simple backyard HT for 52100? here is my suggestion.

Heat to bright red/orange, cool to magnetic
Heat to cherry red, cool to magnetic
Heat to medium red, quench in warm oil.
Heat to dull red(still magnetic) 2-3 times
Grind Drill or File
Heat to red or a shade brighter than non-magnetic, quench in warm oil.
Temper in an oven between 400-425 depending on what you need
 
Ben_M said:
So essentially trying to heat treat 52100 to its potential without a digitally controlled oven is going to be an exercise in futility and frustration. I bought a bar of it because it was reasonably cheap and I wanted to give it a try. I had heard it was similar to 5160 but better performance but didn't realize the extra control required for hear treat until after I got it. I figured I'd try it anyway since I had it; I wasn't attempting to rewrite the book on heat treating 52100. Thanks for taking the time to respond.

I might look into sending some blades out for heat treating since I have a good bit left.
Click to expand...

There are a number of ways to get 52100 to it's potential without a digitally controlled oven, it's just that none of them are a torch by eye. I would encourage you to send them out for heat treating if an oven or a drum forge or a PID controlled forge or even a plain old forge with a muffle isn't on your to do list, as finishing your blades with a quality heat treat is likely going to be more satisfying than saying you did it all yourself but the heat treat is kinda sketchy.
 
Ben_M said:
So essentially trying to heat treat 52100 to its potential without a digitally controlled oven is going to be an exercise in futility and frustration. I bought a bar of it because it was reasonably cheap and I wanted to give it a try. I had heard it was similar to 5160 but better performance but didn't realize the extra control required for hear treat until after I got it. I figured I'd try it anyway since I had it; I wasn't attempting to rewrite the book on heat treating 52100. Thanks for taking the time to respond.

I might look into sending some blades out for heat treating since I have a good bit left.
Click to expand...

The only source I know of that comes rèady to heat treat is AKS. Chuck makes sure all of his steel is in ready to heat treat condition. You can skip all of the normalizing and cycling steps. Nailing the soak at 1475 for 10 minutes would be the only challenge in a forge then.
 
Rick Marchand said:
Decalescence is the single most reliable way to determine that steel is at the critical temperature. Learn how to recognize it. Open the door(slightly) and see if the shadows are flickering along the blade. When they stop, start your timer. I desperately want to install a viewing window in my kiln.
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What about this furnace
 
samuraistuart said:
Robert, that's exactly what I am doing now. I do heat up the oil. 130°F. Good luck!

Just to add: If you're doing any machining after the normalizing/cycling, then to a subcritical anneal: On the last thermal cycle of 1450F (or whatever temp you're using), quench. Then into the oven at 1200F for 2 hours. You'll now have a fine spheroidized structure ready for machining and hardening. I usually prefer hardening from pearlite over spheroidite, tho.
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Any reason why? I find if I'm wanting to forge to final dimensions I can do so without getting distortions in quench by straightening @ 1260F and then quenching from fine spheroidite.
-Trey
 
If you're grinding after forging, you may induce stresses in the steel, especially if the grind is uneven. A subcritical anneal will help with that. It's a step that I normally don't do, tho, but recommend if you have problems with warps in quenches (if it's not due to bad quench technique).

Out of curiosity, what exactly are you doing after forging?
 
samuraistuart said:
If you're grinding after forging, you may induce stresses in the steel, especially if the grind is uneven. A subcritical anneal will help with that. It's a step that I normally don't do, tho, but recommend if you have problems with warps in quenches (if it's not due to bad quench technique).

Out of curiosity, what exactly are you doing after forging?
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I forge to shape, forge distal taper and start bevels. I forge very thin..
I normalize @ 1650
Thermal cycle 1500
1475
1450 quench
1250 2 hours
I then profile, clean off all scale, check for straightened. If I need to straighten I heat to 1250 and lightly tap straight on anvil, back in and cool to black. Once blade is straight and clean I put on a coat of ATP, soak at 1475 for 12 minutes and quench in room temp McMaster Carr 11 second oil. No distortions in quench using this method. Temper 350-380 twice @ 2 hours for high hardness kitchen knives. Lowest ive had one test is 62.5 after temper.
Aside from profiling all grinding is done post HT
IXZWaDC.jpg

6EJjn4z.jpg

I forge .187" or .156" stock down to 2.4-2mm my the middle of the blade and usually hold till tip and grind wide bevels.
-Trey
 
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