Hollow sections or pipes are manufactured on a tube mill using high frequency induction welding techniques. The flat strip is seam welded while it is round in shape and then gradually brought to the desired section in the sizing mill. The welded seam undergoes a great amount of cold working while being sized. This is a very severe test of the weld quality of each length of hollow section. The pipes are produced in round, rectangular, square and L Z sections conforming to high leading international standards.