Abstract: Due to the characteristics of precision pulsed arc welding，such as compatibility，flexibility and the precise control of heat input，the welding experiments were carried out on K4169 alloy sheet with 0．2 mm in thickness．The results show that the microstructure is dendritic morphology with uniform and tiny strengthening precipitation．Furthermore，the welding defect is not free by X-ray inspection．Tensile properties of the joints at room temperature and 650 ℃ are equal to that of the base metal，but show lower hardness．The crack was repaired by precision pulsed arc welding and the result was qualified by the product quality inspection institutions．The conclusion proved precision pulsed arc welding can be applied to the crack repairing of casing．