torch hardening 440c stainless

F

fetz

Joined
Dec 30, 2003
Messages
88
any help on sucessfully torch hardening 440c? when i do it the blade
does not seem to harden. i know you are suppose to use a kiln for a
couple of hours but i dont have that luxury. thank!
 
It won't harden properly. Stainless steels are complex alloys, and require some skill, and the proper ovens in their heat treat.
http://www.admiralsteel.com/reference/sstltech.html

Edited to add;

The only thing I can suggest is to either send them to a knifemaker that can do it, or send it to a company that performs these services.
TKS is one, and they do small lots.
http://www.texasknife.com/

The heat treat is what determines the quality of the knife, at least as far as holding an edge, resistance to fracture etc.
 
Isn't there a maker that swears by oil quenching stainless. I'm thinking Matt Shade for some reason.I may be wrong:(

Mark
 
There are posts here about oil quenching 440C, believe he does a triple quench(searched for it about a week back, as interested in doing 440C at home if I can). Don't have the threads bookmarked here at work though
 
Stainless steels have specific temp. and soak times in order for them to be properly heat treated. Contact a heat treater that does stainless. Paul Boss for one.

Michael
 
rlinger does his own ATS-34, but I don't know about 440C..
 
You CAN do stainless steels at home, and oil quench it. Then you need cryo, as there will be retained austenite. I (PERSONALLY) feel you need an electric furnace to get the heats (soaks) right, but others will debate that. I have HT'd my own plain carbon, ATS34, 440C, and D2 for years, successfully, at home. I have a furnace and I Rockwell at each and every step to insure my goals are met. Recently I have done S30V successfully, too. For years I cryo'd with dry ice and acetone. It will get the hardness to max (per factory spec at a given temp), but there is enough conjecture that there are carbide changes at ultralow temps that I recently popped for a Dewar for liquid nitrogen. I also have switched to aluminum quench plates and an air blast; I get better initial hardness as compared to oil.

That is not to take away from Paul. He's the best, IMO, but I wanted to do one knife at a time, and I desired sole authorship.
 
Because of the amount of chrome and other alloys in the stainless it is adviseable to use an electric furnace to do the heat treat. It takes considerably longer for the carbon to go into solution in a stainless where as it is almost instantanious in a carbon steel when the proper temp is reached.
 
OK, I'm gonna catch hell for this I'm sure...

The only stainless I use it 440C because I can quench it at home with my torch, plus I grew up with 440C. I picked this tip up from Ed Fowler right here on the forums. You can do a triple oil quench on 440C. That triple quench seems to have the same effect on 440C as the long soak (which was my original question on the subject). On mine I do a triple oil quench keeping the oil at about 155 degrees. I wait 24 hrs. between each quench. Then I triple temper the blades at 375 degrees in an oven, again waiting 24 hrs. between the 2 & 3rd temper. I go right from the 3rd quench to the 1st temper. After the last temper I stick the blades in the kitchen freezer overnight (another tip from Ed, I believe). I've been doing this method with 440C for over a year and a half with excellent results. I've tried it with a few other stainless steels without getting good results but, with 440C, it works and works very well.

I'd strongly suggest sending blades your uncertain of heat-treating to a pro until you experiment for awhile. It took me a bit to get this just right. I'm just too hard headed to send my stuff off the mountain. If I can help at all, drop me a note.
 
THATS FUNNY, I AM ALSO VERY HARD HEADED AND WILL GO TO GREAT LENGTHS
TO AVOID SOMEONE ELSE MESSING WITH MY STUFF!!!! ANY MORE DETAILED
INFO ON THE TRIPLE QUENCH? I WOULD LIKE TO TRY IT!! THANKS!
 
Fetz, if you want, send me an e-mail or give me a call and we'll go through it. I'll be gone on the 1st but, back on the 2nd.
 
Originally posted by Gouge
Isn't there a maker that swears by oil quenching stainless. I'm thinking Matt Shade for some reason.I may be wrong:(

Mark
Click to expand...

WOW! Somebody knows I'm alive! haha. Yeah I'm one of a couple guys here that refuses to listen to the metalugists. I do my own heat treat on 440C. You need something capable of some serious heat, but its not hard to do.
I've done it with a torch and pile of firebricks, but I'm currently using a homemade burner (modification of a reil type)with fire bricks in a sort of forge.
Its pretty simple.
I grind to about 85% to avoid warping which is a problem with thinner stuff.
Do the normalizing stuff. I generally just put a few blades in the forge for about 10 minutes and then cut out the burner and let them cool off with the forge. Probably not as good as vermiculite but I haven't had anything crack at all, and only warped a dagger blade that was paper thin.
For the actual heat treat I bring it up to a good orange color (this is subjective, you'll have to experiment on your own) A little past red, but not really really bright. Hold at that temperature for 10-15 minutes. Bigger blades get a little longer, you have to give the carbon time to dissolve.
While its heating I use a heat gun and warm the oil up to about 110 degrees. I use a gallon can full of 10W40 motor oil (used, but I don't think that matters).
To quench, I do a full quench tip first. Haven't tried any differential hardening. Leave it in the oil a few minutes until they're about the same temperature.
Test with a file. It will skate like its on a peice of glass. Make sure you always use the same file for your experimenting. You can see, I'm far from scientific but that is one important thing you want to be consistent with.

Ed Fowler originally started all this, and he did a triple quench. It seems to give more consistent hardness over the whole blade, but scaling can be a problem. You'll have to decide for yourself, just repeat the steps above, minus the normalizing.

Temper around 400 degrees for 3-2hour periods in your oven. This will also take experimenting becuase all ovens are a little different. I've settled on 390 deg for my own.
I've taken very thin edged knives and chopped peices of (cured) hard maple and black cherry without damaging the edge. Can also cut brass. Flexibility is as good as I would expect from an 1/8" thick 3" long blade. I haven't broken any yet but they will bend to at least 45 degrees.


I've tried the commerical heat treat route with other steels and was very happy with the results, but I can do this at home and get results I like. It saves a little money and I get to say I took it from barstock to blade doing it all myself.
 
These are just questions that I have out of pure curiosity. I am not here to argue your methods, but to understand, hopefully to learn something from other peoples' work. I developed my methods "by the book", but realize it is not necessarily the only way.

J.: How are you checking for the proper hardening temp? With a magnet or just how? (BTW, I don't think you catch any flak if your method produces a good blade. After all, that is the only important parameter.) Are you getting the whole blade to the same teemp, and are you full or edge quenching?

Matt: How are you contolling the forge temp at just the point you need so that the steel will rise to a temp at which a soak is achievable without overshooting because the forge is too hot? Is this also by a color? Know anyone with a temp probe that could tell us what that is? Also, just how much scaling is there? Blades protected in an inert atmosphere or in an envelope tend to discolor, but not much more. I've never done a 440C blade unwrapped in the furnace to see what happens (guess I better, just to see!).

Have either of you guys ever gotten any Rockwell hardness numbers on the hardened blade and post tempering?

Heat treat is an amazing mix of science and backyard experimentation, and only by trying to understand other peoples' work with an open mind can we come to improved understanding of the process. Thanks for any answers, guys!

Happy New year to all, and may health, happiness, and prosperity be yours in 2004!.
 
Fitzo: I use a magnet to check the temp. just the same way as my carbon steel blades. Get it up to nan-magnetic al around and then just go a tad higher and even things out. You have to keep nice even passes with the torch on both sides, back and forth. Also, just to be clear, I have a rosebud tip on my oxy/acet. set-up. As opposed to the high carbons I edge quench, I do heat/harden the entire blade when it's 440C. Do it three times waiting 24 hrs. between each and then right after the third hardening cycle, clean off the blade and put it in the oven (I do 375 in mine but, like Matt says, they all vary). Do the tempering cycle twice more (3 total) waiting 24 hrs. between each. Then the freezer if you like.
:D
 
thanks, J.! I guess after 20+ years of HT'ing my own SS with a furnace, it's just about time to try one with a torch and see if I can get it to come out decent once I get it worked out! I'll try your method.

Happy New Year to you....
 
For temperature I go for a constant color. It just happens that if I leave one end of the forge halfway open and run the burner at about 3 psi, it seems to max out at the right temperature. I keep an eye on it and adjust the opening as necessary. Seems to be OK if it gets a little too hot during the soak as long as its at the right temp when you quench.

For scaling, I get a black coat on the blade. About 2 passes on a 60 grit wheel will take it all off (provided I did a good job grinding and don't have lots of dips and stuff:footinmou )I think it has more to do with the oil than the forge, there really isn't much pitting or anything as long as your heating it evenly and have the burner running clean.

I haven't personally gotten anything rockwell tested. If you do a search on 440C triple quench there are a lot of old threads. One in particular, is a few pages long and has alot of information. Roger (rlinger) did an experiment for us and rockwell tested the peices. 440C in small blade sized peices will harden without the real long soak time. I think he did 5 minutes at temperature, using an oven.

Its pretty hazy directions I know,but it works for me. I'm sure anyone else that tries can get similar results if they put a little work into it. And I'm not saying in any way that this is superior to a HT following manufacturers specs, or done by someone like Paul Bos. It just gets me good results, and is something I can do myself.
 
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