I bought a roll of dead soft copper wire from Rio Grande it works great I can pull it without any trouble through my wire draw plate. It good for teaching students. J.J.
what is source of your wire?
I was given 50m of .5mm "copper" wire once, that turned out to be copper placed steel wire.
if it was ordered, and not given/found, then I'm not sure what the issue might be. wrapping it up in about a 2-4cm diameter coil, and heating it till it all relaxes and lays flat should soften it up to be ready for inlay.
heat the wire till a dull red color. once it gets to room temperature, the fire scale (oxidation) must be removed. pickling will work-- fast-- fine sandpaper-- slow-- will also work.
To anneal copper without the need to pickle or sand the wire:
Evenly heat the copper wire coil to a dull red colour and quench immediately in methylated spirits. It will be dead soft and perfectly free of oxides!