Abstract: The present invention relates to an arc-welding device for securing studs on metallic elements underwater, and comprising a head containing a chamber and of which the welding bead is obtained by means of a dielectric refractory ring placed around the base of the stud, wherein an annular space is provided between the stud and the ring and neutral gas is blown into the chamber through said space, to drive the water out of the chamber and keep up therein a gaseous atmosphere to facilitate the welding of the studs; the refractory ring is produced from borosilicate glass, rich in silica.