Abstract:The microstructures of X42 expandable convoluted tube was studied by optical microscopy and scanning electron spectroscopy after cold rolling and annealing, respectively. It was found that the microstructures of cross- and longitudinal- sections have not obvious differences, and those in different parts even have not obvious differences, while banded structure of outer part of weld seam was eliminated the most evidently, considering as one factor inducing the bent of expandable convoluted tube. The results provide basis for further revealing the mechanism of the bent and controlling the shape stability.