Patent EP-2193872-A1 (EP)
Title: Method of manufacturing a welded rotor for a gas turbine engine with heat treatment of the weld seam and its heat affected zone with different temperatures
Inventor: SCHREIBER KARL
IPC: B23K15/00
Filed: 2009-11-05
Abstract: The method comprises connecting two or more rotor discs (1) to each other by conventional welding process through welding seam (3) running radial to rotor axis. The welding seam area is subsequently subjected to a heat treatment at a temperature for reducing internal tensile stress as a result of relaxation. The heat treatment of the welding seam is adjusted on a clearly lower temperature level causing no relaxation as heat influence zone (2) adjacent to the welding seam. The method comprises connecting two or more rotor discs (1) to each other by conventional welding process through welding seam (3) running radial to rotor axis. The welding seam area is subsequently subjected to a heat treatment at a temperature for reducing internal tensile stress as a result of relaxation. The heat treatment of the welding seam is adjusted on a clearly lower temperature level causing no relaxation as heat influence zone (2) adjacent to the welding seam. The internal tensile stress strongly reduced based on high temperature gradient is impressed up to internal pressure stresses in the welding seam. The total area of the heat influence zone and the welding seam is heat treated at a temperature causing the reduction of the internal tensile stress and subsequently mutually shielded heat influence zone is further treated by heat at same temperature during the welding seam is cooled at lower temperature level. The cooling of the welding seam and pre-heating of the area adjacent to the welding seam are carried out by a coolant stream and a heat stream that are shielded to the respective adjoining areas. The coolant stream and the heat stream move itself continuously along the welding seam area. The coolant stream and the heat stream are positioned staggered to each other. The coolant stream is produced by compressed air and heat stream with a gas flame. Rotor (5) is transferred during the duration of the heat treatment in a continuous rotation movement. The rotational speed of the rotors lies in an area producing a homogeneous circumference temperature field. The total area of the heat influencing zone and the welding seam is heat-treated at a temperature causing the reduction of the internal tensile stress and the welding seam is subsequently cooled at the low temperature level. The cooling of the welding seam is carried out by coolant stream moving continuously along the welding seam. The rotor is rotated during cooling treatment by a rotating speed that guarantees a uniform temperature in the circumference direction of the welding seam. The cooling stream is produced by compressed air. The heating is carried out with the point energy of welding stream continuously moving relative to the rotor. The temperature gradient of internal pressure stresses and strongly reduced internal tensile stress is impressed in the welding seam. The rotor guides a continuous rotation around its longitudinal axis during heating with the welding stream. The welding stream is electron stream. The rotor discs to be welded to each other consist of nickel or titanium based forge materials. The heat treatment temperature corresponding to the respective internal stress profile is 700-800[deg] C and the temperature of the welding seam to be cooled is adjusted for producing the thermal gradients of 150[deg] C. The rotor discs are connected to each other by electron beam welding.