Abstract: A method for butt welding two metal pieces which are difficult to weld, particularly pieces of medium or high carbon content steel with the use of laser beams is accomplished by forming a groove in at least a surface of one of the pieces to be welded to define a pair of longitudinal ribs having flat frontal surfaces. The flat surfaces are placed against the surface of the other piece in welding position and the two ribs are welded simultaneously by means of opposed laser beams moving along the zone of contact between the ribs and the surface of the other piece. An alternate method involves the use of a sheet of welding material having an aperture therein which is located between the two pieces to be welded. The two laser beams move along opposite surfaces of the apertured sheet to weld the two pieces together by means of the intermediate sheet.