Abstract: A process for automatic fusion welding of rails by a combination of submerged arc welding and electroslag welding, comprising a root run for welding a rail base by submerged arc welding and, without interruption of the welding, subsequent runs for welding the rail base and welding a region from a rail web to a rail head by electroslag welding; wherein, during all of the runs, a metal mold is mounted on an upper surface of the rail base and a metal shoe is mounted on the metal mold to prevent an outflow of molten slag and molten metal and, during all of the runs, welding is performed by using a DC welding transformer having constant potential characterisitcs, a filler-wire having a diameter of from 1.2 to 2.0 mm, and a fused-type flux. The inventive process avoids the use of different fluxes and an alteration of welding machine conditions during the whole sequence of welding from the rail base through to the rail head.