A method for manufacturing a rotor by welding a plurality of elements together is described. The elements have a body with cavities and surfaces to be welded to surfaces of adjacent elements. According to the method, the elements are vertically stacked one above the other to form a pile with facing surfaces to be welded together defining slots. The cavities of adjacent elements define bores that extend within the pile. Then, adjacent elements are welded together within the slots. The bore is purged with an inert gas or mixture during welding. The slots are welded at an upper part of the bore before the slots at a lower part of the bore, and a slot at the upper part of the bore is welded last.