Abstract: In the welding of tubes with bevelled ends without heels or root-faces, all the weldings beads are made from the outside of the tubes with the tubes being in contact with local gap not exceeding 2 mm. The first and second welding beads are made both by the up-hill method and the down-hill method with the axis of the welding torches at the same inclination to the normal or the radius of the pipe and the accuracy of welding is improved by the use of mechanical guiding means for the welding means comprising at least one roller which bears on the bevelled ends of the tubes adjacent the welding zone.