The effect of temperature on corrosion behavior of 316L stainless steel (316L SS) in 3.5% NaCl solution was studied by potentiodynamic polarization and electrochemical impedance，the semiconductor properties of the passivated film were analyzed by Mott⁃Schottky curve. The surface morphology of 316L SS after corrosion was observed by metallographic microscope.The results show that in the NaCl solution with a mass fraction of 3.5%, the open circuit potential and corrosion potential of 316L SS gradually decrease with the gradual increase of temperature, and the self⁃corrosion current density increases gradually.And the pitting potential is also gradually reduced. The results of surface corrosion morphology observation showed that the number and diameter of corrosion pits on the surface of 316L SS increased as the temperature increased.This is mainly because the temperature decreased the density of the passivation film and increased the dissolution rate of the passivation film, and decreases the corrosion resistance.

The theoretical analysis of the stress concentration factor K of three types of tubes with three different types of unfused defects is very complicated. In this paper, the finite element numerical analysis software is used to be established the finite element model of the three⁃way pipe with defects under the action of internal pressure. After calculation, the stress concentration factor K and its variation law under the four influencing factors are obtained. The results show that the stress concentration factor K of the three⁃way tube with three different unfused defects is relatively large in the shoulder and collar region, and the stress concentration is serious. The stress concentration factor K increased slowly with the increase of the axial length and depth of the defect, and decreased rapidly with the increase of the circumferential length of the defect.