A method for repairing cracks in water turbine blades

Abstract

The invention discloses a method for restoring a crack of a blade of a hydraulic turbine. The method mainly comprises a preparation stage, a self-melting welding stage, a filling welding stage and an aftertreatment stage. At the preparation stage, the blade to be restored is cleaned and detected; at the self-melting welding stage, an inclined convergent laser beam with a negative defocusing amount is adopted for carrying out scanning in the extending direction of the crack, a V-shaped melting pool is formed, and molten metal liquid sinks to the bottom of the melting pool under the action of gravity, and is solidified to form a self-melting weld joint; at the filling welding stage, a material identical to a body of the blade is adopted as a welding wire for surface layer bead welding; at the aftertreatment stage, distressing tempering and blade surface finishing machining are carried out after welding is completed. In the restoring process, based on self-melting of the material of the body of the blade, the blade is filled with a few materials identical to the body of the blade, the material of the weld joint is identical to that of the blade, the material and the blade are combined well, a weld joint defect is not likely to be generated, and the combining strength of the weld joint is improved. In the self-welding welding and filling welding processes, molten metal in the melting pool is vibrated through ultrasonic waves generated by an ultrasonic generator on the back face of the blade to remove gas, and the defects of weld porosity and the like are reduced.

Description

Technical field [0001] The invention relates to the technical field of repairing metal parts, in particular to a repairing process of a water turbine blade. Background technique [0002] The blades of equipment such as steam turbines or water turbines are impacted by the fluid working medium during operation, and long-term operation will cause fatigue cracks on the surface of the blades. If not repaired in time, the blades will break. The blade repair often adopts methods such as surfacing welding and cladding. [0003] For example, the Chinese invention patent with application number 201310054557. 9 discloses a method for repairing damage to aero-engine blades. The method performs segmentation processing according to the size and shape characteristics of the blade surface to be repaired, and sets the pulse plasma heat input parameters and pulse transmission Wire control parameters and perform plasma welding repair in sections. Another example is the Chinese Invention Patent Appl...

AI Technical Summary

Problems solved by technology

[0004] Conventional repair method (i.e. filling welding) due to the difference between the filling material and the blade body material, the material composition and structure at the welding joint interface are complex, and welding defects are prone to occur at the bottom of the weld, which affects the joint strength of the weld and reduces the service life of the blade after repair

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