Most of those Lincoln Arc Welders especially the newer ones contain aluminum winding's instead of copper.
But if the lincoln arc welder you do have contains copper it most likely has only around 2 to 5 lbs of copper that could be removed for scrap.
Most of the weight in the welder is the metal that makes up the transformer and the welder case.
If it truly is scrap you'd be best off selling the welder as scrap as is for shred or removing the transformer and selling the transformer as is for scrap transformers.