Differentially HTd S30V

[Andrew Garrett]

I'm sitting here at work flipping through an old (March/April 2004) issue of Handgunner magazine.

Way back in the spotlight section (sort of like classifieds) I found an add highlighting the accomplishments of Canadian knifemaker Tom Haslinger. In short, he differentially heat treated S30V and got a hamon. The add directs you to his website for more details, so I went.

The website gives some facts but then directs you to the February '04 issue of Blade for the real details.

Anybody still have that issue? I'd like to hear about the process.

[Larrin]

The issue says nothing about the process.

[Andrew Garrett]

Thanks for checking. Now I'm even more curious.

[AUBE]

Its hard to tell from the pics how he did it but there are a few ways I have toyed with on ats34 to get hamon lines that worked. They were nothing near what you can get on something like a 10xx steel but you could see temper zones and sometimes a bit of activity. He could be doing it completely different than this though.

Method 1 Heat treat the whole blade then resting the edge in water (so it doesn't heat) apply heat to the spine tempering it back. It will etch differently than the edge but no activity.

Method 2 Heat just the edge with a torch so when you oil quench it the spine stays soft. About the same results as with one but without the benefits of a soak time (unless you are good enough to sit there with a torch soaking it at proper temp, I'm not)

Method 3 Coat the spine with a very thick layer of clay, heat entire blade, quench the edge in oil. The very thick layer keeps the spine hot so it stays soft when quenched. The most noticeable/active results I have gotten were from that method but also the most amount of cracked edges.

Method 4 Heat the entire blade, quench the edge in oil while applying heat to the spine with a torch. I tried this with some clay down the middle of the blade too. I didn't get as good of results as with 3 and it was harder to do (pat head, rub tummy)

For the time being I gave up playing around with it. Steel is expensive, college is expensive....had to pick which to waste money on. Hamons are better suited for carbon steels so thats what I do them on.

[Andrew Garrett]

It seems like I posted a thread about differentially heat treating stainless a while back. I did a search, but can't find it now.

I was shot down pretty convincingly then, so maybe the person who did that can do it again in response to this question:

If you did a heavy clay coat on, say..., CPM154 and placed it in the furnace for the regular times, etc. then air quenched in inert gas or by whatever air-quenching method would work best, wouldn't the spine stay considerably softer, to a degree that gave performace advantages?

[mknife]

I believe that with these very expensive stainless, who buy them search a knife with excellent blade quality.
Trying to get the hamon on CPM, however, satisfied the aesthetic side but not that functional.

[AUBE]

I haven't tried that yet Andy so I'm not sure. I would be concerned that the clay would retain enough heat where it would keep trying to radiate down to the edge as the edge air cools....heating it up and not allowing it to harden thoroughly. It might be hard to get the right combination of clay thickness, distance from the edge, and air flow. If you are looking for purely performance, method #1 I tried did give some extra performance. In stress tests the edge cracked before the spine did and I was able to bend the knife farther than a regularly heat treated ats34 blade. Not much in the way of a hamon-looking line though. Its been awhile now so I don't recall how many degrees it bent (I need to start video taping everything or at least keep a log) but it did not make it 90degrees.

I agree with what Mknife said. I love hamons so I was trying to make a stainless knife that displayed one but I think the potential problems (hidden stress cracks, not fully hardened edge, etc) outweighed the aesthetic gain in my experiments. Plus since the temper lines are pretty boring compared to a straight carbon steel the aesthetic gain wasn't much.