Device for welding inside a tube of small diameter

Device for rotary welding inside a tube (3) of small diameter, in particular inside a steam generator tube crimped at one of its ends into a tube plate (2) of great thickness, comprising a welding head with a diameter smaller than the internal diameter of the tube comprising a carrier (25) to which a guiding component (29) and a radially directed electrode (30) are fastened, which is fastened to the end of a flexible tubing (16) and by means for moving (18, 21, 19, 57) the welding head in axial translation in the tube (3) and in rotation about the tube axis, wherein the driving means (57) for driving the welding head in rotation is arranged in a motor casing (18) inserted between a first section (16a) and a second section (16b) of the flexible tubing (16), said second section (16b) connecting the casing to a bush (26) in which the carrier (25) of the welding head is rotatably mounted and comprising a flexible member (35) for transmitting rotational motion between the driving means (57) and the carrier (25) of the welding head, and said first section (16a) being connected at one of its ends to the motor casing (18) and in engagement with a puller-pusher device (21) for moving the flexible tubing (16) and thereby the welding head (17) and the motor casing (18).