what's the steps in heat treating

[cedar_fluteman]

Maybe this question should be in the newbe arena but this is the heat treating thread. Well I have never heat treated anything before. I have a gas forge on the way and I use 440-c a lot. So where do find a guide or starting point. Is 440-c a good steel for the gas forge or should I switch to another steel? I was thinking I would heat blade to a certain color and quench it in transmision fluid. If this is all wrong point me in the right direction. Sorry about being so dumb about this but I guess everybody starts somewhere.
Thanks

[mete]

440c is not for the beginner.You would do better starting with 5160 or 1080.The more complex steels ,especially stainless are much more critical as far as times and temperatures .Before you start read every tutorial about heat treating you can find.

[Don Robinson]

Stainless steels, such as 44C, require very precise temperature control and soak times. A highly accurate controller is required. Your gas forge probably isn't capable of that.

If you had a good electric furnace and programmable controller, you could heat treat stainless without problems, and i'd be happy to help you with recipes and instructions.

[Ed Caffrey]

I agree with the others. It takes some experience and skill to properly heat treat in a forge.
And even then 440 is not the place to start. As mentioned, start with simpler steel such as the 10XX series. Something like O-1 is a very good steel to learn heat treating with because it will allow you to try again should you make a mistake. The higher alloy and stainless steels (such as 52100 and 440) will give you only one chance. If it's not right, your done.

Some of the best information you can arm yourself with are the alloying elements in various steels, and how they react alone, and in combinations when heat treating, then apply that to the particular steel that you are attempting to heat treat.

In general, for non-stainless type steels, here are the steps you must take to properly heat treat a blade:

Normalize: This is done after forging, and again after rough grinding. This step relives the stresses you have built up in the steel, whether from forging or from grinding.

Annealling: Done after forging and normalizing. This step also relives any stresses, steps up the grain for hardening and tempering, and softens the steel to make grinding/sanding much easier

Hardening: This is quenching the steel to bring it to it's hardest possible form

Tempering: This is a controlled softening to relieve brittleness that comes along with hardness, and is necessary to create a usable cutting edge that is less likely to chip in service.

Those are the bare bones basics. Many of us have developed additional steps that improve the durability and edge retention in the steels we use. Make no mistake about it, the heat treatment throughout the entire process of making a blade is the soul of the finished knife.

[cedar_fluteman]

Well my goal was to be able to heat treat as to sending blades to have them done. Because of the cost and the amount of blades I have to make to get the best price. Then just afer I send a batch to have treated somebody wants something different. Being able to heat treat would solve that problem. But maybe I should have left well enough alone and scrap the idea of doing the heat treating myself. Sounds like it's rocket science to me.

[Ed Caffrey]

It's not really rocket science, it just takes very specific temps and times to correctly heat treat the majority of stainless steels. I do successfully heat treat S30V in the forge, but it took me about a dozen wrecked blades before I figured out the steps necessary for a method that would work.

I think it's well worth the time and effort expended to learn how to heat treat your own blades....but then again I'm pretty anal about sole authorship. There was a time that I sent blades out for heat treatment, but it always bothered me because I had no idea of what happened to those blades from the time they left my mailbox until they came back. My thought always was: "How do I know that these blades are the best they can be if I didn't do the heat treating?" And who knows what the company/person doing the heat treating did? Maybe they did a sloppy job, and if so, then my name is the one thats on the blade, and if it's not right, then I'm the one taking the hit for making a crappy knife. Just isn't worth the risk to me.

[cedar_fluteman]

A friend of mine heat treats 440-c in a forge and I watched him do it and it didn't look that hard. Maybe he isn't doing things right but he has been a knifemake for many years and he has an electric oven also but he uses the gas forge. He goes by color when heating then quenches in transmision fluid and tests the blades with a file for hardness. Then he reheats to temper and then checks with the file test again for hardness. I just thought he knew what he was doing but maybe not? Does this sound right or is he leading me down the wrong path?

[Jamey Saunders]

You can harden 440c that way, but to get the proper treatment (meaning it will be hard, tough, resilient, and hold an edge) it requires a 20 minute soak at 1800*. Too cold, and it won't harden correctly. Too hot, and it won't harden correctly. The difference may be something you'd never really notice in normal usage, but under stress or heavy usage, your blade will either fail or be useless because it won't hold an edge.

My suggestion would be to use a carbon steel like O1 or 1095. You can harden those exactly as you have described. In fact, that's the exact method, pretty much. Heat in the forge until a magnet won't stick to the blade, then quench in oil. Do your tempering in the oven, since the temp range needs to be pretty accurate. Most around here will tell you that you really can't judge by the color of the steel, since different lighting in different shops (or from a different time of day) can make the perceived color of the steel look different for the same temperature.

[Edited to say:] I used 440c exclusively for years, and then one day I decided to try some O1, and I love it. It's super-easy to work, compared to the stainless, and it gets scary-sharp. It will rust, but simple basic maintenance will keep that from happening. Also, it's cheaper than 440c, so if you're just learning, that'll cut down on the cost of education.

Oh, and welcome to the KN!

[/Edit]

[cactusforge]

Ed, would you mind shearing your procedure for heat treating S30V? I had read where you were experimenting with it and always wondered how successful you were. Thanks Gib

[cedar_fluteman]

I read where it sounded like o-1 and d-2 where about the same except the d-2 was a little easier to maintain as far as rust. Is that true?
Thanks for all the feedback. I know I have lots of questions but that's usually how I do things. I try to check things out bunches first so I don't waste to much time and money. I'm not out to reinvent the wheel.

[Jamey Saunders]

They're close, but D2 has a fair amount of chromium in it. The proper HT for D2 will also involve a soaking period, but it's possible that it won't be as bad to do the heat/quench like you'd do for O1 as it would be to do that with a pure stainless. D2's sort of a hybrid, a weird mix of carbon and stainless that puts it somewhere in between. It's also more expensive than O1, so again, if you're just starting, you might as well save on the cost of education by using a cheaper (and much more forgiving) steel. O1 is more forgiving in that if you really screw up the HT, you can just anneal and try again, no harm no foul.

[cedar_fluteman]

Thanks for all the information. I guess I was hoping to use what steel I had on hand which is 440-c and d-2. But most of all I don't want to make a crappy knife. I will order some 0-1 and start with that. With that figured out is there a good process to follow for using the gas forge to treat 0-1? With the gas forge do most go by color or do they use a temp gauge to judge the temp?

[Jamey Saunders]

Get yourself a speaker magnet and keep it close to the forge. Heat the blade until the magnet will no longer stick to the blade, then quench. Judging temp by eye (by color) is iffy. And do your tempering in the kitchen oven, or in a dedicated toaster oven.

[Don Robinson]

Originally Posted by Jamey Saunders

Get yourself a speaker magnet and keep it close to the forge. Heat the blade until the magnet will no longer stick to the blade, then quench. Judging temp by eye (by color) is iffy. And do your tempering in the kitchen oven, or in a dedicated toaster oven.

C_F, believe Jamey here, and I suggest you re-read Ed's message above. He told you the same thing.

[Ed Caffrey]

Gib,

It took me a while to figure out a forge method of heat treating S30V that would work for me...
Here's how I do it.

The blade is sanded to at least 600 grit (helps in finishing after hardening), then the blade is double wrapped in heat treating foil.
I dial the forge in to 1900F and let it stabilize. The the S30 (wrapped) in the heat treat foil goes in for a 30 min soak. (if you want to run the forge at 1950F you can, and let the blade soak for 20 mins) Once it's soaked, it comes out and goes directly between 2, 1" thick aluminum plates for the quench. I temper the blade immediately at 500-650F. (depending on the size of the blade) Then repeat the tempering two more times, allowing the blade to cool between tempers.

Eventhough I say that S30V is "the most acceptable" of the stainless steels I've tried, it is a flat out bear to finish after heat treating, and sharpening the stuff is a real adventure. Thats the reason that I don't advertise it as one of my steels. Ease of sharpening is one characteristic that I demand of my blades, and there just isn't anything easy about sharpening an S30V blade compared to a blade of 52100 or 5160.