Heizvorrichtung fuer eine Turbinenschaufel und ein Verfahren zum Schweissen

WO 2009098106 A1 UPAB: 20090824 NOVELTY - The heating loop (41) used in the new turbine blade heating unit is seen to be generally U-shaped, with intentional additional curvatures. Its arrangement is such that a temperature gradient is produced in the fin section of the turbine blade (406). The loop (41) is run close to the blade, above and below the blade platform (403). Above the platform (403) the loop is run near the blade and is curved to correspond with the blade curvature. The loop is curved below the blade platform, especially in correspondence with the turbine blade curvature above the blade platform. DETAILED DESCRIPTION - Only a single heating loop is used. It is led near the blade platform. It is passed near the turbine blade or the blade root. The heating loop is arranged on the suction- and/or pressure side of the blade. The heating unit forms part of welding equipment for a turbine blade. In the new method of welding, the heating unit is used in conjunction with welding equipment (49), especially a laser, to produce a weld seam. Welding is carried out on the side of the turbine blade where the heating loop runs below the blade platform. The weld seam is intentionally allowed to harden to a DS- or SX-orientated structure. The transition region between turbine blade and platform is welded. In the region to be heated, a powder is coated-on. This is a magnetic powder, especially a magnetic and dielectric powder. An INDEPENDENT CLAIM is included for the corresponding welding method. USE - A heating unit used when e.g. welding cracks in turbine blades or removing material from them. ADVANTAGE - Turbine blade welding e.g. re-melts and fuses cracks together, or removes material. Pre-heating precedes welding, to reduce thermally-induced stressing. In prior art, the desired temperature or temperature distribution is not achieved. The new equipment and measures described are used to overcome this problem. Use of only a single heating loop is preferred, since it represents an easily-reproducible arrangement. The magnetic and dielectric powder acts as a concentrator for the heating loop, during the heating operation. Its use masks selectively against welding. The blade is used in e.g. an aviation- or power generation gas turbine, a steam turbine or a compressor. Suitable alloys and structure are also discussed in the disclosure.