Easy stainless steel for at home heat treating?

[mooseman645]

Hi folks, 

I know that 1080 and 1095 are able to be hardened and tempered at home without a fancy setup. I've done that with just the charcoal forge and the toaster oven, is there any stainless steels that can be similarly heat treated at home without a special kiln for tempering? Oddly enough I've got a pretty bad metal allergy and I instantly rust normal carbon steel knives i've made or owned. 

Thanks,

Corey

[Buzzkill]

That sounds like a simple question, but it's really not.  If you are asking if you can get a stainless knife steel to harden by heating it past critical and quenching the answer is yes. 

However, that will not get the most out of the steel.  High carbon stainless steels contain more elements in the alloys than simple carbon steels.  Those other elements need to go into solution in the steel before quenching in order to achieve the combination of hardness and toughness they were designed to provide. Corrosion resistance can also be affected if the correct heat treatment sequence is not followed properly. For those elements to go into solution both time and temperature are required.  That means holding a specific temperature within a fairly tight range for a specified amount of time.  In some cases there are several temperatures that must be attained and held so that the elements all go into solution in the correct order for maximum results. This is nearly impossible to do with a charcoal forge, and since quench temperatures for those steels also tend to be higher than those for simple carbon steels, carbon loss can be an issue.  That's why you often see stainless foil pouches used when preparing for quench.  It keeps the oxygen away from the steel which prevents the carbon from burning off.  A lot of the stainless steels benefit from a cryo-tempering cycle as well.

So, if you just want to harden a blade for your personal use you might get by with a simple heat treatment, but to me it would be fraudulent to sell a stainless steel knife that wasn't heat treated properly.  If you want to do it properly you will need some form of oven that can achieve high temperatures (1900-2000 degrees F is not uncommon for stainless knife steels) and hold those temps for a while.

[mooseman645]

Ok, thanks for the info, I was just talking about personal use not selling anything to anyone. 

[ThomasPowers]

There are places that will heat treat blades for you if you can specify what alloy it is.  Used to be ads for them in the back of the knife magazines. Not knowing which of the 100+ countries that participate in IFI on the World Wide Web, I can't make any suggestions of people to contact.

[Buster Bolster]

AEB-L and XHP can both be done in the open atmosphere, but the key to it is being able to get high heat very quickly, and very evenly and then quenching and taking what you can get out of it and that's it. 

I mention those two because I've made knives and tools out of them. I have a hardness tester and a metallurgical scope to look at the steel, though. the heat needs to be very high, very quick (like fraction of a minute to heat) and you need to do samples until you get something that's suitable. 

this is an XHP knife that I used to cut some sticks and then poplar when testing - it's a thin knife - only about a hundredth thick above the bevel, which was why I wanted to make it. Thinner than you can generally get near the edge with commercial knives. It's a little underhard - i'd have to guess 59/60, but good enough. I'm sure it's easy to write off a guess, but I've heat treated several hundred items and have a pretty good feel for what steel feels like on stones and belts. Stainless steels on an alumina stone really clue you in because if they have decent hardness between the carbides, they will be slick feeling on an alumina stone. if they are a touch soft, they will sharpen as easily as a carbon steel tool or knife that's hard and that's a red flag if you're  

I've had good luck with AEB/L hardness testing at 60.5 after a double 340F temper. I've made plane irons out of it and some number of knives and all seem to be fine. My first attempts with stainless were generally underhardened, and nothing good happens in the open atmosphere at both high temperature and some time elapsing. maybe it's my imagination, but I think chromium migrates and carbon definitely does. Thus the suggestion if you are in a pinch and need to do some, you need a very quick high temp. 

If I worked with these steels often rather than occasionally, i'd get a furnace (don't have one), or if someone was thinking of making a lot of knives or professionally, hiring out is also not a bad option. Even if I thought I could make an AEB-L knife that people would like (i could, there are a lot of variables that you can manipulate making one offs to make a 60/61 hardness AEB-L seem interesting), I wouldn't bother - it's easier to win a dispute with a buyer if you can tell them what you did.