Thread: Work Hardened Steel Is No Bueno

Just a quick post to celebrate what has been my vexing bane for the last couple days....

I forged out a bit of San Mai - High carbon core (1095) with stainless cladding. (Which by the way I have become quite good at, if anyone would like to know my method, let me know and I'll do up a full picture thread of my step by step process in a couple weeks when I run some new billets through the forge) Anywhoo - back to the celebration at hand!

So, I forged out this San Mai billet. Now, this time round I thought it would be fun to go thicker on the stainless, thinking that I could grind down to a more exact spine thickness. Like some gents, I overestimated the size... of the stainless stock. Came out of the forge and press darn near 1/2" thick. Much grinding would be needed.

Now, I have no idea how much stainless fun you folks have had, but there are some interesting properties to stainless. It is extremely hard on your abrasives (which is why it makes for a great cladding. Hone wear is minimal on the spine) and damn does it ever get hot while you work it.

I anneal my billets after forging, however, when taking off that much stainless as I had to, I apparently heated up that high carbon core pretty well. During the grinding, as it got hot I quenched it and kept going. After finally getting the razor shape cut in and fully flattened, twas time to drill the pin hole. I choose a traditional 1/16" for this. And that was when my trouble started...

Turns out, just the heat created in the grinding of the stainless and quenching to cool hardened that core. Really. Hardened. The. Core.

I ended up killing five drill bits on the press. Got so fed up I threw it back in the kiln, and re-annealed it. Presto! #6 drill bit finally got the job done!

I'm honestly shocked that the grinding could have heated up that 1095 enough to harden it. But, at least now I know once this piece goes through heat treat that blade edge will harder than drill bits...

The temperature required to austenitize 1095 is much hotter than can be safely held in the hand even with big gloves on. I doubt it was the heat from grinding.

Depending on the type of drill bits/alloys they could have work hardened just the hole. Good sharp cobalt or carbide is kind of where we all evolve to after years of trying various things on the cheap.

What kind of stainless? That it forges is interesting.

It's also possible that the two materials are different enough that your annealing ritual for 1095 isn't enough for the stainless slabs.

Originally Posted by Mike Blue

The temperature required to austenitize 1095 is much hotter than can be safely held in the hand even with big gloves on. I doubt it was the heat from grinding.

Depending on the type of drill bits/alloys they could have work hardened just the hole. Good sharp cobalt or carbide is kind of where we all evolve to after years of trying various things on the cheap.

What kind of stainless? That it forges is interesting.

It's also possible that the two materials are different enough that your annealing ritual for 1095 isn't enough for the stainless slabs.

100% correct - but I didn't grind it holding with gloves. I had to use a 200Lb (strength) hand held magnet. That was enough to get past the stainless and magnetically pull the high carbon steel enough to keep it sticking to the magnet. I use that, because very much hate burning my hands during pre-heat treat grinding. I figure that heat is not really a problem until after temper. That's when the gloves come off and I grind bare handed, to make sure I don't get things so hot they lose temper. Prior to that? I'll grind until flames shoot out! (lol!)

The stainless is a 403. I picked that, as it forges pretty darn well. It won't harden when I heat treat the blade. I'll be hardening to the 1095, and won't be getting the steel hot enough to harden the 403.

Annealing is done in a kiln with pyrometer - taken to 1575, then slow cooled for the next 12 hours. I had a few billets in with it - I'll see how those cut later this week and if they hardened, that that will be the culprit!

I'm thinking though, that perhaps the initial drill may have hardened just the hold. That bit was a cobalt and I was wrenching on it. Kept having to add cutting oil as I was drilling, until that bad boy snapped. The other four bits are cheapo backup bits I keep around for when I kill a cobalt to have something on hand as I wait for the replacement. It's a good possibility I did it to myself in just the drilling...

Just finished the initial rough grind of the razor at 36 grit - You can see how hot I get the core steel before temper here. You can see there the 1095 is darkening, and the stainless has not discolored.

I think I'm leaning towards perhaps the initial drilling hardened it. Even with the magnet, I just could not imagine the steel getting hot enough to austenitize. That thought was blowing my mind, for sure.

If the steel austenitized, it would be non magnetic. I'm thinking that some big carbides formed at the 1095/stainless interface.

Originally Posted by bluesman7

If the steel austenitized, it would be non magnetic. I'm thinking that some big carbides formed at the 1095/stainless interface.

Hmmm... Now there is a thought too. I have not run across this in the past, but I also have not used such a thick stainless before.

Yeah, all that chromium just loves to form carbides. It's so common for the hole to work harden though. From your description of drill bit performance that's what I'd think too. Stick with the simplest solution.

Holding with a magnet will work, until the steel becomes non magnetic, and it should have took off across the room when it let go. That'd be hot enough to quench to hard. Doesn't sound like that happened though.

It looks like you got a great weld, pretty stuff for sure.

Nothing to add, but would love to see your "tutorial " on how you forge weld the two. We always love to see stuff like that.

Originally Posted by ScottGoodman

Nothing to add, but would love to see your "tutorial " on how you forge weld the two. We always love to see stuff like that.

Sounds good! I'll put that together in the next couple of weeks when I do my next round of stainless San Mai and post in this sub forum. Easy peasy!

One of these days I'll get an electric oven so I can mess with stainless, I've always worked off gas.

Also as mike said: good brand name cobalt drill bits.