Abstract: Method for manufacturing a large-sized, cylindrical, metal casing by welding successive cylindrical sections, characterized in that metal in the form of a strip is unwound continuously and at a uniform speed from a coil (6) and in that, as the strip (16) is fed through, crushing (15) or breaking of the fibre, pulling (13), polishing (17) and measuring of the length are continuously performed, in that at the same time the strip (30) thus unwound is continuously arranged on turntable (2) comprising a rotating table (26) the speed of rotation of which corresponds to the feeding speed of the strip at the radius of the cylindrical section being made, and then in that, when the length corresponding to the spread-out form of the cylindrical section has been obtained, unwinding of the strip is stopped, the cylindrical section (30) is cut off from the remainder of the strip (16) and is wound onto the turntable, in that the structure being assembled is then brought into position above this cylindrical section (30) and