Effect of Different Welded Structures on Mechanical Properties of TA2 Tube-to-Tubesheet Joints

Four types of TA2 welded tube-to-tubesheet joints prepared by manual tungsten arc argon-shielded welding technique are studied in this paper. The pull-out tests and low cycle fatigue tests were performed to optimize welded structures of tube and tubesheet. The results show that fractures of welded TA2 tube and tubesheet samples occur at weld zone of TA2 steel tube for the pull-out tests and low cycle fatigue tests. The extension-tubesheet welded joints have the maximum pull-out forces and the best fatigue resistance, and the internal-bore welded joint with 45 deg bevel occupies second place. Fractures are both initiated from weld toe of the outside of tube for the pull-out tests and low cycle fatigue tests. Crack propagates along the direction of 45 deg for the pull-out test. However, crack propagates perpendicularly to the direction of the applied load for low cycle fatigue test, and then fractures immediately parallel to the direction of the applied load. Fatigue striations with a spacing of about 10 μm can be observed on the fatigue crack propagation zone. However, hemispheroidal dimples exist on instant rupture zone.