Determination of properties of domestic 690TT alloy U-shaped pipe in elbow area

Wall thickness measurement, metallographic examination, intergranular corrosion, stress corrosion and residual stress test were carried out on the elbow area of 690TT alloy U-shaped pipe of domestic steam generator, and the performance was compared with that of straight pipe section. The results show that the outer wall thickness of elbow area of 690TT alloy U-shaped pipe of domestic steam generator was thinned by 7.8%, the microstructure, grain size and intergranular corrosion rate of the elbow area were equivalent to those of the straight pipe area. After bending, the surface residual stress of the inner side of the elbow area was tensile stress and the surface residual stress of the outer side was compressive stress, after stress relieving heat treatment, the absolute value of residual stress in the elbow area decreased and the stress corrosion was not easy to occur. The properties of the elbow area of domestic 690TT alloy U-shaped pipe could meet the application requirements by using bend and stress relief heat treatment.