I just stumbled across this post. I see no one has responded. Ouch!
The procedure would be qualified just like any other procedure except you would not employ a filler metal. That being the case, you may have to machine the plates to provide extra material that can be consumed during the welding operation or you may have to machine the face and root surfaces to get to sound metal for the purpose of performing the guided bend tests and reduced section tensile tests.
Best regards - Al