Method of making composite seamless tubing

Claim 1

IN A METHOD OF FORMING AN ELONGATED FLAT BLANK ADAPTED FOR EXPANSION INTO TUBING HAVING INTERIOR AND EXTERIOR SURFACES OF DIFFERENT METALS METALLURGICALLY BONDED TOGETHER, THE STEPS WHICH COMPRISE ASSEMBLY TWO PREFORMED TUBULAR MEMBERS OF DIFFERENT METALS WHICH ARE CAPABLE OF BEING METALLURGICALLY BONDED TOGETHER BY PLACING ONE OF SAID MEMBERS INSIDE THE OTHER OF SAID MEMGERS AND FORMING A UNIT IN WHICH THE INTERIOR SURFACE OF THE OUTER MEMBER AND THE EXTERIOR SURFACE OF THE INNER MEMBER ARE IN CONTACT; APPLYING A WELD-RESISTING MATERIAL TO THE INTERIOR SURFACE OF THE INNER MEMBER; COLLAPSING THE ASSEMBLED MEMBERS TO A FLATTENED CONDITION WITH OPPOSING PORTIONS OF THE INTERIOR SURFACE OF THE INNER MEMBER BEING IN CONTACT; METALLURGICALLY BONDING THE FLAT INTERIOR SURFACE OF THE OUTER MEMGER WITH THE FLAT EXTERIOR SURFACE OF THE INNER MEMBER BY ROLLING THE COLLAPSED UNIT IN A LENGTHWISE DIRECTION PARALLEL TO THE AXIS OF THE TUBULAR MEMBERS ANS SIMULTANEOUSLY ELONGATING THE COLLAPSED ASSEMBLY INTO A FLAT RIBBONLIKE STRIP OF REDUCED THICKNESS, SAID ROLLING VEING CARRID OUT WITHOUT BONDING THE CONTACTING PORTION OF THE INTERIOR SURFACE OF THE COLLASPED INNER TUBULAR MEMBER.