This is probably a sacrilege

wmhammond

Well-Known Member
OK, Aldos 52100. This is how I heat treated it: Heated it to nonmagnetic and then tried to hold it there for 10 minutes then quenched it in Canola oil and then tempered it for 2 hours at 400. Testing it with a really fine, brand new file says it's hard, do you think it is and what will I turn out with using this process? Would love to know your thoughts.

Also about 52100: Can I Parkerize it or blue it or will the Chromium content make it act like stainless steel? Thanks guys,

Wallace
 
If you heated to nonmagnetic and held it there for 10 minutes, I would expect it to get hard. Maybe not the full 67 or 68 hard, but hard. 52100 is heat treated in different ways by different people. Ed Fowler likes to go to just above critical and edge quench, and then do this three times. He may not be getting the amount of carbon in solution that he wants on the first quench, because he goes just above critical, no soak, then quench. Do this three times, then he has the carbon he wants in solution. Kinda what you did...only you just did it once. Yeah, it got hard, but probably not max hard. To do it all in one quench requires a 10 minute hold at 1475F, assuming the steel was set up properly to harden.

For example, Aldo's 52100 used to come heavily spheroidized. Not sure if that is still the case. But in order to get that heavily spheroidized steel to harden properly to 67, a full normalizing was needed first. If you didn't do the normalizing, you would get max about 63HRC. I would assume that is where you are at......IF THAT. Non magnetic is only 1414F. If you quenched AT non magnetic, you don't have near enough carbon in solution for max hardness. Just enough to maybe skate a file.

The Cr content in 52100 in no way makes it act like stainless. It is still very much a carbon steel, and is prone to corrosion. Not as bad as O1 maybe, but still there. Blueing helps to some degree. Parkerize would probably be a neat option, but I don't like blade coatings myself.

Back to the 52100 heat treat. Done properly, 52100 excels! This is a heat treat recipe developed by Mr Kevin Cashen, the GURU on all things heat treat related, for Aldo's heavily spheroidized 52100.....
1650F, then air cool. This gets carbides in solution, homogenizes structure, but at expense of grain growth
1550F, then air cool. This further refines grain structure
1450F, then air cool or quench. This further refines grain structure
you can do some subcritical steps here if you like, as in 1375F, air cool or quench.
you can go right to hardening from here. 1475F for 10 or 15 minutes, quench in 130F oil, canola works well. temper
if you need to do more machining, after the 1450F quench, hold at 1200F for a few hours, then air cool. Or do a few subcritical cycles, either way, then quench

Point being, if the steel is supplied in coarse (heavy) spheroidized condition (I think it still is), to get most out of blade, you'll need to normalize at least.
 
I always assume I'm working with large grain structure and run heat cycles. I think its good practice.
 
you didn't say what kind of equipment you have for HT. 52100 needs several cycles at controlled temperature, at the very least, 1650F till heated thru, air cool to black, 1475F(800C) for 10 minutes(this is for thin, 1/8" or less) and quench.
 
Guys, thanks so much for the thoughtful responses. As it turned out, here's what happened. While I was tempering it the oven timer went off and the knife was just sitting in there cooling. My wife discovered it and when she took it out it was still a little warm and was slightly burning her hand so she ran cold water on it (we've been married 42 years so she got a pass). That put a serious bow in the blade. I took it out to the vice to try and straighten it - you guessed it - I snapped about one inch off the point. Sooooo, yesterday I started over. I had been doing a little reading since my last post so here is how I heat treated it:

First off, I don't have a heat treat oven. I do have a propane forge but I don't use it. What I do is clamp my knife in a pair of long vice grips and extend it edge down over a fire retardant soldering pad. Then using 1"x2"x5" soldering "bricks" I build a small confined space on the pad around the knife that just barely leaves room for the knife inside with the top open. Then I start heating the knife from the handle toward the tip. When the handle starts to turn red I cover the handle portion of the knife and then begin heating the blade portion of the knife. As it turns red I cover the point portion like the rear portion so now I have a little oven open at the front and partially open at the back and I can sorta control the temperature (color) up and down. Anyway, I heated this knife to red/orange and held it there for about 5 minutes and then let it cool all the way down to black. Then I heated it again to what I thought was slightly cooler than before and held it there for 10 minutes and then immediately quenched it in Canola oil. Tempered it at 400* for 2 hrs with my wife handcuffed to the bed :). Who knows what I've got but I'm gonna clean it up and blue it. Thanks again guys for your help,

Wallace
 
Wallace, you're telling us that running water over a warm blade (tempering temps) put a bow in it? Would you mind explaining that to us? You're wife is off the hook, bud. If the knife was "slightly burning her hand", and she ran water over it, there just really is no way for it to bend. If it was tempering in the oven (and you said it even cooled down some from tempering temps?), and your wife was able to hold on to it briefly, then water didn't do it. The bow was most likely in the blade previously, you just didn't notice it.

Here is what happens.....as you remove the steel from your quench oil, as the steel goes from 900F down to about 400F, that window of time (maybe 45 to 60 seconds), the knife is very buttery soft. You can VERY easily, with a gloved hand, move the blade and correct (or induce) a warp. Once the steel reaches the martensite start temp of around 400F, martensite begins to form. This is the hard brittle stuff (that doesn't bend). Once the steel has reached room temp, into the tempering oven it goes to help "soften" that matrix.

My guess is that out of the quench you looked at it, and it was straight. But between removing from the quench and the Ms temp of 400F or so, or maybe just as the martensite was starting to form, the bow manifested itself. You didn't realize it, tho. It went into the oven bent.

There just is no way that running water over a tempered blade will induce a curve. Now if you placed the blade into the tempering oven AT or above 400F, there may be something going on there, not too sure about that even.
 
I agree with Stuart, running water over a slightly hot blade didn't cause the warp. Beside, if you wife is willing to share her oven with you I'd cut her some slack on this anyway. You should have been watching you blade.

First of all double and maybe triple check that there is no warping in the blade before taking it in to temper. It is possible that the blade could warp while tempering. Either way, whether this happens before for during the temper the best way that I've found to correct the warp is get a piece of angle iron and clamp the blade to it with a shim under it to straighten or maybe even slightly counter bend the blade. One or two pennies will do for shims. Then run the blade through another tempering cycle. If that doesn't work then it back out to the forge, normalize once to relieve stress in the steel, austinize and quench.

One thing about your choice of steels. Yes, 52100 can be heat treated in basic (primitive) heat sources. No, it cannot be heat treated reliably that way. You don't have to go over the desired temperature for very long to get to trigger grain growth and going by the color of the steel you can really overshoot that mark without realizing it. It would even be easier to put to get the steel too hot and put too much carbon into solution and triggering the formation of too much retained austinite. It would be much better if you go to a simpler steel like 1084, 1080, or 80CrV2 and learn how to use your gas forge for heat treating.

Doug
 
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