Longitudinal seam
It is the oldest manufacturing process, which starts from a sheet of sheet metal (which is obtained by winding a steel coil until the desired thickness is achieved) cut according to the width that corresponds to the size of the tube that will be produced. This sheet is folded by rollers to join the ends longitudinally to obtain the shape of the tube. Depending on the separation of the rollers, different curves and therefore different tube diameters are obtained. Welding seals this joint straight to close the cylinder in a chemically neutral environment.

Helical welding (or spiral)
This tube manufacturing process follows the same methodology as that of the longitudinally welded tube, with the difference that the weld spirals the entire length of the tube diameter as if it were threaded, instead of straight in the longitudinal joint of the sheet.

To hide the weld, a hot treatment process can be applied to the welded tube to forge it, and then pass through lathes to polish the seam and make it almost impossible to perceive with the naked eye. Keep in mind that welding is the weakest part of the tube, and will mark the maximum stress it can withstand.

The cost of sewn pipes is usually lower than that of the seamless tube, since less stretching and tempering is needed, and the manufacturing time, therefore, is also usually less.