A device for joining metallic well tubulars to be lowered into a wellbore, which comprise a first well tubular in a substantially vertical position suspended in the wellbore, with an upper end of the first well tubular outside of the wellbore, in particular in a position corresponding to a rig floor, and a second well tubular in a position substantially vertical and axially aligned above the first well tubular, with a lower end surface of the second well tubular set against an upper end surface of the first well tubular, where the device comprises: - a welding arrangement for forming a circumferential weld bead at said upper and lower end surfaces (6a, 7a) of the first and second well tubulars (6, 7); the device being characterized in that it comprises a control arrangement (CU, UI), and in that the welding arrangement comprises a welding assembly, which includes at least one laser welding head and at least one induction-heating device (14 1, 14 2), the at least one laser welding head is configured for directing a laser beam towards a circumferential working zone, which includes an upper end portion of the first well tubular and a lower end portion of the second well tubular, the at least one induction-heating device (14 1, 14 2) is prearranged for supplying heat by induction to a corresponding part (EW 1, EW 2) of the circumferential working zone that includes respective parts of said upper and lower end portions of the first and second well tubulars (6, 7), the welding arrangement further comprises a driving system (15, 16), controllable for displacing the welding assembly around the circumferential working zone according to a respective trajectory of revolution, the at least one induction-heating device (14 1, 14 2) is arranged in the welding assembly upstream, respectively downstream, of the at least one laser welding head, with reference to the direction of revolution of the welding assembly, and the control arrangement (CU, UI) is configured for controlling the welding assembly and the driving system (15, 16) in such a way that, during revolution of the welding assembly, - the laser beam emitted by the at least one laser welding head progressively forms the circumferential weld bead; and - the at least one induction-heating device (14 1, 14 2) supplies heat to said corresponding part (PH 1, PH 2) of the circumferential working zone before the laser beam reaches said corresponding part (PH 1, PH 2), respectively after the laser beam has reached said corresponding part (PH 1, PH 2). - a welding arrangement for forming a circumferential weld bead at said upper and lower end surfaces (6a, 7a) of the first and second well tubulars (6, 7); the device being characterized in that it comprises a control arrangement (CU, UI), and in that the welding arrangement comprises a welding assembly, which includes at least one laser welding head and at least one induction-heating device (14 1, 14 2), the at least one laser welding head is configured for directing a laser beam towards a circumferential working zone, which includes an upper end portion of the first well tubular and a lower end portion of the second well tubular, the at least one induction-heating device (14 1, 14 2) is prearranged for supplying heat by induction to a corresponding part (EW 1, EW 2) of the circumferential working zone that includes respective parts of said upper and lower end portions of the first and second well tubulars (6, 7), the welding arrangement further comprises a driving system (15, 16), controllable for displacing the welding assembly around the circumferential working zone according to a respective trajectory of revolution, the at least one induction-heating device (14 1, 14 2) is arranged in the welding assembly upstream, respectively downstream, of the at least one laser welding head, with reference to the direction of revolution of the welding assembly, and the control arrangement (CU, UI) is configured for controlling the welding assembly and the driving system (15, 16) in such a way that, during revolution of the welding assembly, - the laser beam emitted by the at least one laser welding head progressively forms the circumferential weld bead; and - the at least one induction-heating device (14 1, 14 2) supplies heat to said corresponding part (PH 1, PH 2) of the circumferential working zone before the laser beam reaches said corresponding part (PH 1, PH 2), respectively after the laser beam has reached said corresponding part (PH 1, PH 2).