Influence of local heating-cooling on welding residual stress of francis turbine runner

On basis of local heating-cooling method which is brought out to improve the distribution of welding residual stress in blade according to the property of weld formation, influence of local heating-cooling method on runner' s residual stress field is studied by numerical simulation technology.Moreover, the change process of welding stress in the blade dangerous area and the optimizing scheme of local heating are attained.The result shows that the method of local heating-cooling can decrease the residual tensile stress peak in dangerous area of the blade.The effect on decreasing residual stress is directly proportional to heating time, heating temperature and heating area.Moreover, with the augmentation of heating distance, the residual stress in dangerous area can decrease and with further the augmontation the residual stress will increase.