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Issues forge welding


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I have been able to weld steel together in the past for Damascus. but recently i tried to make a San Mai billet out of 1084 and 15n20 and the welds didn't stick. I thought this was a fluke so it tried again and the second billet failed as well.  I then switched to a coke forge to see if it was the forge that was the issue and it failed yet again. The billet when ground clean appears to be welded but you can still see slight indications of where the layers are and when i tried to forge a blade it came apart. The pieces were ground clean and mig welded on the corners prior to each attempt. If anyone has any input as to why they failed it would be greatly appreciated. 

-Jacob

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Need more information.  If it met the three criteria for a weld to stick (clean/oxide free, close contact, and enough heat to make up the difference) it should have stuck.  A highly polished surface in a vacuum will actually weld at room temperature.  So, either you're not getting hot enough, you're oxidizing the steel, or the pieces aren't in close enough contact.  

 

Are you using flux? Is the smoke/goop from the MIG welder getting in between the layers?

 

Finally, how hard are you hitting it to set the weld?  If you're using flux and smacking it really hard to get the flux out, you may be blowing the weld apart on impact.  Gentle taps until you know it's solid.

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Alan, thank you for the advice. The steel that I used has claimed to be flat (it is from alpha knife supply) and I ran it over my grinder immediately before welding. I used a 4 lb hammer with a medium blow to set the welds, then I took a few more welding heats before I began to draw it out. I would assume that I hit it too hard. 
-Jacob

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My guess would be by hand hammering it's separating between layers especially if the outer layers were say 3/16 or less.  I don't think it would take much to get some oxidation in there. I weld my San mai all the way around but I think at least adding a weld in the middle would increase your success. 

Edited by Gilbert McCann
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I use a 1.5 lb hammer for most welding, and gentle taps.  I think too much enthusiasm is the problem. ;)

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One technique I find really helps, is using clamps to tightly bind the stack before tack-welding, so there really is no chance for gaps. When I forget to do this, I get layers bowing out, and additional oxides forming despite all my other mitigations.

Especially for a thin billet of san mai, running tacks every inch or two, under clamped pressure, should seal the whole thing up well enough to reduce the chances of intrusive oxygen.

Also, old trick Tai Goo taught, was toss a chunk of dense wood in your gas forge when you're doing this... it will scavenge whatever loose oxygen might be flying around, improving your reducing atmosphere. YMMV, and the only side effect is soot if things aren't hot enough to burn it off.

The Tidewater Forge

Christopher Price, Bladesmith

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What about de-greasing?

You didn't mention it, so I ask.

 

Before grinding, did you wipe/soak in acetone or something to remove any oils?

 

If not, you may have actually ground them into the steel, contaminated the belt.

 

Just a thought.

Edited by Welsh joel
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Thank you to all that have responded, I tried all of these suggestions and it worked. I will post pictures when it is finished. I started by cutting the steel then i ground it flat and clean on my grinder. i then decreased it and put it in a drill press vice to weld with bits of paper in between the layers to consume oxygen. the billet was then welded completely around and a handle was welded on. i heated it up and set the weld with a 1 lb ball peen and then reduced the thickness. A while before i fired up the forge I also gave it another coat of metrikote Ir reflector.

 

-Jacob

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Clean with acetone BEFORE grinding or sanding. You can actually- possibly push oils deeper into the metal by grinding it. I take a tray, fill it with enough acetone to cover my steels. Then I soak them in it, wipe down with a paper towel while in acetone to disturb the surface.

 

Then I'll take a piece at a time- sand the surface, and if cool enough, return it to the acetone bath. 

 

Paper between the layers? No... I've never heard of this, and from my viewpoint- by clamping it in the vise and welding this way- you'd trap the paper in a place so tight... it might not burn out completely, and leave residue between your steels.

 

I've heard of people doing so in a canister style damascus... but never in welded layers.

 

I've certainly never done it, and probably wouldn't. 

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