52100 Steel - Differential heat treating of double edged blades?

Joss

Joss

Joined
Nov 20, 2001
Messages
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Hi,

I have a couple clip point fighters (or bowie) made out of 52100. I want to heat treat them, and would like to know the best way to do it. What I'm currently thinking of doing is clay coat what I don't want hardened, and then go at it (3 times per Mr. Fowler's excellent book.) What do people think?

Thanks,

JD
 
...doesn't sound too promising. On another forum, someone told me that "52100 allows much more time [than other C steels] to cool to form martensite, so the clay can't hold out the cooling long enough to keep the back from getting hard."

Comments and suggestions would be much appreciated... :D Right now I'm at a loss. :confused:

Thanks,

JD
 
The average quence time for 52100 is about 2 seconds. Plenty quick to differential heat treat with clay.
About an 1/8" of clay is needed to prevent the blade from getting to the critical and if it did, prevent it from cooling fast enough to harden.
I would let the clay dry first, then heat to critical and quench. I prefer to use very hot transmission fluid (300 deg.) to cool the blade with and then leave it in the fluid for an hour. Just watch the steel and check with a magnet to see when to quench. If you use the tip to check the heat (it will get hot faster), then look for that color and quench. This is basically what I use when hardening 52100.
 
Hey Ray,

Thanks so much for the info - I've been trying to get a good answer on that forever. Quick follow up for you are:

On your differentially HT 52100 blades, do you get a "hamon" (aka temperline)?

And how do you heat up your quench fluid?

Thanks again,

JD
 
Hey Joss, how do you heat your blades for heat treating? Do you use the Ed Fowler super jet torch method? That's my most used method but I sometimes use my coal forge if it's a large blade. For a differential heat treat of a double edged blade you have your work cut out for you. At least if I understand your question. If that's what you're trying to do, here's how I do it.

Using a rosebud torch tip with oxy/propane fuel, I heat just the areas I want to quench. In your case it will be the primary edge and the false or clip edge. Heat the blade up slowly and evenly on both sides to keep it from warping. As the centerline of the blade starts to turn blue you're getting close. Switch to the edges with the torch keeping the torch moving constantly. Actually, I clamp my torch with the flame pointing up in my chop saw clamp and run the edge over the flame instead of running the torch over the edge if that makes any sense. I find that much easier and more precise for some reason. Hey, I live in Arkansas where the sun don't always come up or go down in the same place. He he.

Anyway, you have to be really quick in order to get it right. And I mean REALLY quick! As soon as both edges are at non magnetic and the centerline is still relatively dark, plunge the entire blade point first into your quench medium, preheated of course. I always preheat mine by heating up a big chunk of 1/2" leaf spring with the torch and quenching it repeatedly until I get the temp I want. If you did the quench right you will have beautiful quench lines that are very symmetrical following the grind line all the way around the edge. It's really impressive on a dagger blade. A side note here for Ed's enjoyment. I've only achieved the three division lines on a blade separating all the differential zones one time and that was by accident! But I'm sneaking up on it with each successive heat treatment I do.

I don't work with 52100 much but when I do I always do the triple/triple/triple full meal deal on it. Triple normalize and anneal, triple quench and triple temper. That stuff is alot of work. But it sure is excellent steel when you get the heat treat right. Hope this helps and don't get you all twisted up. Somebody jump in here and put me in my place if I've led Joss astray. This is just how I do it so it isn't necessarily the correct or best method. Good luck.
 
I appreciate all the help I got so far. Because 52100 is so finicky (check out Howard Clark's page about salt temps for his opinion on the HT of it: http://www.mvforge.com/salt pot info.html), I think I'll do the HT using an oven - I'm lucky enough to have access to one.

JD
 
Joss, I get a temper line with the 52100 and I heat my
Dextron II with an electric skillet for the smaller blades.
An acid etch will show the hard and soft steel. I have to use a larger tank and I heat mine with a torch for longer blades. I
use a digital thermometer (to 392 deg. F) to keep a check the temp.

With a heat treat oven, I set the temp at 1550 and as soon as it gets
there, remove and quench quickly. Leave it in the oil for
about an hour at the 300 deg. This is what I do and others do
things a little different. The main thing is to not get the steel
close to the 1700 deg. temp. because of grain growth and to cool it
quickly. An 1/8" of clay will prevent the blade from reaching the critical temp. and if it should happen to soak at 1550 long enough, it should keep it from cooling fast enough to form martinsite.

I am assuming that you have normalized the steel at least twice and annealed it prior to the hardening and tempering phase of heat treat.

Ray Kirk
 
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