Forge welding questions- copper, 15n20, and Nickle

R

running bird

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I have a lot of copper, like a whole lot.
I'm planning on using some of it for a mokume-gane billet but the sheet I Have is rather thin. How easily dose copper forge weld to itself? I was thinking I could make some thicker billets of copper by stacking some smaller sheets together and forge welding them to my desired thickness.
I was looking to do a copper and Nickle design, I have some good sized peices of Nickle but I also have a lot of some 15n20 that I use for Damascus, will copper forge weld to 15n20? I know copper can forge weld to Nickle but I wasn't sure if it would work with 15n20 because it is steel, has anyone tried this?

The copper sheet I have is about 6ft by 3ft and roughly 1mm thick, the 15n20 and the Nickle I have are both 1/16th of an inch thick so I want to make my copper close enough to the same thickness so that the mokume-gane billet will have a more even design.

Thanks for helping,
Kevin
 
Copper is difficult to forgeweld. It so quickly oxidises at heat its nigh on impossible.
Maybe some guys managed...
But its fairly easy to melt. Casting to thicker profiles or use as a fluxed brazing upon steel.
 
You can't forge weld copper to copper .... actually, I don't think it forge welds to anything very well. It is usually joined by diffusion welding of brazing.
 
The OP asked about forge welding coper to copper for making mokume - which won't work. Copper has to be kept oxide free to even braze together. I regularly have to re-pickle a copper fitting half a dozen times when brazing the parts together, as it stops flowing as soon as the oxide starts. As far as using a forge to work copper welds, the forge atmosphere will be a huge problem. Electric kilns are far better. While there are folks who make mokume in a forge ( especially quarter mokume), it is usually either a fairly primitive mokume, or has a high failure rate.

If all things are done right in a mosaic billet, like the lime cutter shows, it is possible. But I suspect it will not be an easy weld to make ..... and surely not a beginner skill.



In making mokume gane, the weld is either by diffusion bonding or eutectic alloying ( eutectic bond).

In eutectic fusing, the two dissimilar metals ( say copper and silver) are under moderately high pressure ( in a torque plate) and temperature. With the temperature just right, the two form a eutectic alloy at the surface junction with a lower melting point than either parent metal. They "melt" together enough to become a fused solid. The eutectic depth of the weld is sufficient for strength, but leaves the two metals showing as different layers. If the temperature is too high, or the timing is off, the two completely alloy into the eutectic metal and the whole thing melts. More than one person has opened his kiln to a puddle of metal while learning to make mokume. The weld layer is increased in thickness by the setting process, where it is gently hammered while still hot. The hammer blows add energy to the junctions and locally decrease the eutectic melting point. This fuses the billet more. After that, the billet is worked down only in the annealed state, and should not be worked above 1000F. Regular annealing is required, as the copper work hardens rapidly. Because the two metals and the eutectic layer all have different properties, care must be taken in forging down and any manipulation to avoid shearing them apart.

In diffusion welding, the metals are places together under very high pressure and held for a long time at a certain temperature. The temperature and pressure must be exact. The two surfaces are in such close contact that the electrons from the atoms cross the boundary and the metals fuse. Melting is not an issue unless the temperature is off. This isn't usually an easy home method. Depending on the parameters, the bond may be weak or strong. What is used in diffusion bonding is basically a high pressure screw press with the jaws holding the billet inside an electric kiln. Think of a hydraulic press with the ram and anvil post going through the top and bottom of a pottery kiln and meeting in the middle. IIRC, the pressure needed is many tons
 
Thanks so much for explaining it for me Stacy, I set up a rig with some quarters layered inside and I'm setting upset up another rig with some of my copper sheets and Nickle sheets in it. I saw a video explaining how to make mokume with quarters and thought I would try that out along with the sheets. I'll use the processes you explained and hopefully I can get it to work out in a cuppel tries.

Also while I was working on another project in my forge I tossed two small peices of copper sheet in and heated them up. I kept them in there for maybe 20seconds at the most then took them out and tapped the corner a little. I did successfully get the copper to weld together. After I cleaned it up a little to check the weld it seemed like a very solid weld. I tried as hard as I could to pull the two peices apart but they were welded good. So now that I know that worked I might try making mokume that way after I do it with my rigs.

Pictures of the copper weld: https://imgur.com/a/4jqgx

Thanks again for the help, I'll check back in after I go back to my forge later to try out the mokume-gane.
 
Sounds good. Keep us posted, as many things seem difficult in theory, but prove easier in reality.
Steve Midget's book on mokume-gane is fantastic. It has charts and tables for bonding nearly every metal possible.
 
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