Electric flash-butt welding machine and method of providing a welded joint between adjacent ends of rail sections

A method of flash-butt welding adjacent ends of successive rail sections of a rail of a track consisting of two rails fastened to successive ties with a mobile flash-butt welding machine, the machine comprising a machine frame, undercarriages supporting the machine frame on the track for mobility therealong in an operating direction, a drive for propelling the machine frame along the track, and the machine frame carrying a hydraulic fluid supply pump means, an electric current generator, motor means for operating the pump means and the generator, a longitudinally, transversely and vertically adjustable electric flash-butt welding head for selectively welding together the adjacent rail section ends of a respective one of the track rails, the welding head comprising two welding head halves movable towards and away from each other in a direction of the rail, hydraulic cylinders for moving the two welding head valves in said direction, a pair of clamping and welding jaws on each welding head half, and a hydraulic clamping cylinder connecting the jaws of each pair, a welding control connecting the pump means and generator to the hydraulic cylinders and jaws respectively, the control being programmed for hydraulically and electrically operating the clamping and welding jaws, and an apparatus for tensioning or longitudinally sliding a rail, which apparatus is associated with the welding head for encompassing the welding head in a horizontal plane passing through the rail and comprises two pairs of rail clamping jaw means and a hydraulic cylinder-piston arrangement extending in the direction of the rail and comprising respective operating cylinders connecting the pairs of rail clamping jaw means for operation thereof, which method comprises the steps of

• (a) clamping the successive rail section ends ahead and behind the adjacent ends with the two pairs of rail clamping jaw means by engaging the rail section ends immediately ahead of, and behind, the adjacent ends,
• (b) tensioning or longitudinally sliding at least one of the rail sections by operating the operating cylinders, and
• (c) flash-butt welding the two rail section ends together between the two pairs of rail clamping jaw means in an initial welding stage followed by a final compression impact welding stage.