Go-Mai

K

KenH

Well-Known Member
I've always been impressed with the copper line in the blade. I did this one with a .070" of 26C3 core, a .030" layer of copper on each side, with a 3/16" of 1075 on each side. After forging and shaping I got this skinner. It's still a bit rough in the ricasso area. It seems the tong hole is popular so I added a bit of paracord with mammoth ivory button.
Copper-Skinner.jpg
 
It's forged around 1850F to stay below the melting point of copper. The copper acts as a bonding (soldering?) agent between the two layers of steel.

Purpose? Solely for looks, as well as to show off a different skill. I've made a couple of small kitchen knives for the wife with the copper layer (she LOVES copper).
 
Really looks great Ken. I hope to try forging some CuMai in the next few months.
 
Ken how do you keep billet together at first for the "FORGE WELD" (I guess?)
 
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You're right, I think the proper name is CuMai. I couldn't think of it when I posted - thanks.

The billet for that knife was pretty thick with 2 layers of 3/16", a .070", and 2 layers of .030". Knowing it would have to be drawn out I seal welded all the way around, just like San Mai with SS cladding. I did the work in the forge while trying to hold temp around the 1850°F range to prevent melting the copper.

The next I did was with a thinner billet, .040" core of 26C3, .010" copper on each side, and .062" of 410 SS cladding.This I wrapped in SS foil and heated in oven at 1850°F. I figured the oven would help hold the temp more accurately than I could in the forge. Using a 4" flat die in the 16 ton press I just squeezed the foil packet. The first billet done this way I used the drawing dies to to get the billet thinner for kitchen knife, trying to .090 or less. It looked like I did a bit too much pressing and the thin copper didn't like that.
CuMai-2.jpg

So, next billet I just pressed with 16 tons using only full flat die. This blade is the result. After squeezing I expect the core and copper might only be in the .050" thick range, I used the SGA to grind the SS so the final thickness is in the .090" range for the final blade. Still a tad thicker than I like for small kitchen knives, but they work pretty good - and the wife LOVES her some copper :) At .090" with a .050" core/copper thickness that only .020" on each side causing more of the 26C3 core to be exposed than I wished. Especially on this side.
CuMai-3a.jpg

and more copper than I wished on this side:
CuMai-3b.jpg

I think my next attempt will use the drawing die, but gently so it doesn't squeeze quiet so much, but still give a wavy line to the copper.

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Copper doesn't really affect anything. Heat to 1500°F and quench. I'm told that the cladding, be it mild steel, high carbon, or SS doesn't really affect the core metal when hardening.
 
Have you done any destructive testing with it? I’ve seen this method used quite a bit lately, and often wondered what would happen if it was severely bent. Because there shouldn’t be carbon migration, one should be able to use a very thin center core. It’s a pretty interesting technique, and could have a lot of potential.
I recall back in the 90’s I made a billet using steel cable that I fluxed and melted copper into. Never made anything with it, it was just an experiment, but it looked pretty cool ground flat and cold blued.
 
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