stainless steel treating

[logan]

does anyone know if you can heat treat stainless steel with a torch this may be a dumb question but im lost thx

[GANNMADE]

most stainless needs a soak time at critical and temper.
most makers have blades sent off for heattreating for
best results and exact hardness and temper. ss's are more complex than carbon might lead you to a head ach most use
electric heattreat oven that can be dialed in to the right heat.
that my2 cents

[wrathlord]

hello, ,thats my fight buddy,I'm 1 of the few that belive you can,But to a degree,I belive it is possible to harden the bevel portion closest to the edge with a torch ,even on SS blades.Now wether or not that is worth the trouble is the question.SS needs to be fully treated in order for the steel to be "optimal",for the "stainless" qualities to benefit the steel.I have been experimenting with this,I used 1/16" ATS-34,ground the bevels,put a magnate on the bevel,painted the bevel with the torch untill the mag fell off,then drawn in a kiln.Then went to a friends buisness and was able to freeze it in dry ice overnight.The edge is very hard,but orange peely in appearence,the grain flow is visible and flowing nicely,but the edge is very skatey,hard to get bite out of it.As far as staining or discoloration,none so far,but that may take some time and use.But for all it's worth,spend the few bucks and wait the few day's on a profesional service and do the whole thing.Because chances are you'll grind a decent blade,and after doing so,you'd want it to be treated as well as you had ground it.Paul Bos,Texas knifemakers Supply are 2 of a growing list that offer it.

[Robert Sox]

This is a controversial area, but I've seen it done. I took a 'basic knife making' class at Trinidad State Junior College several years ago. We used 3/16 440C for blade stock. The instructor hardened everyone's blades with a torch. The best part was, if you acid etched the blades you got a pretty decent hamon for your efforts. I tried it in class and can make it work. I don't have the confidence to do it on a production basis, so I send my blades out. I still have that knife, and I can tell you the blade is hard -- pretty sure it would rockwell at 59 or so. One of these days I'm going to spend the time to learn the control necessary to be consistent and repeatable... Then I'm going to sell 440C blades with a homon.

I can provide more information if you're interested.

[Wildman]

Robert
what did you quench in?
How hot and how long on the temper?

Enquiring minds want to know


mick

[Robert Sox]

The quench was oil. The instructor had a five gallon bucket of a commercial quench product that he uses. We did warm it up to ~120F before quenching. I have the name of the product in my notes, but I don't think that particular product was essential to success. I should check my notes for particulars, but we used an 'interrupted' quench -- process was like 10 seconds in oil, 30 seconds in air, and back in the oil till cool.

We did not have access to an oven, so the draws were done with a torch. We cleaned up the surface of the blades w/ 400 grit, then gently heated the splines and watched the colors. When the edge got to light straw we quenched.

We also cyro treated the blades w/ dry ice and isopropyl alcohol.

When using the torch for HT, we started at the ricasso with light torch action to slowly heat up the blade. Constantly turn the blade from side to side so it heats evenly. Slowly enlarge the area you heating, working towards the tip, so the entire blade becomes hot -- there is no color showing yet at this point. When the blade is hot, begin to concentrate on the edge. Run the torch along the edge and turn the blade over to do the other side -- only heat the edge. Keep repeating until the proper color is achieved. Here's the catch -- I can't tell you what that color is. The instructor was standing right beside us to coach us through it, so he always said 'now' and then we quenched.

I'm not a forger, so I have never worked with color, before or since. I do believe that it was quite a bit hotter than non-magnetic would appear with carbon steel -- almost bright orange to my eye, but we were in a very dark room. Keeping the entire edge at the proper temp required very rapid torch motion from tip to plunge. My perception was that we attempted to hold the color for a couple of seconds before quench.

I also believe there is a limit to the blade size that you could effectively do this way. I watched the instructor HT a bowie blade of mine that I took to class. Steel was OF (old file). Length was about 7 inches and he wasn't sure he could do it. It turned out beautifully!

I don't have a place to host pics yet, but I have three blades we HTd this way and could provide digital images if there is interest and someone could post them. Interested?

Does that help?

[Ray Rogers]

I think it would be great to find out stainless could be done that way but I doubt it. I'm sure the blade got hard but I'm guessing the grain structure sux big time. Before you decide to sell a knife made that way, I would strongly suggest some serious testing, especially destructive testing. A flex test could turn out to be very enlightening if that edge were to break loose right along that hamon. We all know stainless steel doesn't flex a lot anyway but the expectation would be that an torch hardened blade should flex much better than an oven hardened blade if the grain structures are equal. So, I'm not saying a torch hardened 440C blade should be able to bend 90 degrees like a 5160 blade might, but I would like to know if it will bend more than an identical stainless blade treated in an oven without cracking the edge ....