Abstract: For the S-Zorb regenerator, which has been in use for nearly 2 years and operating at over temperature, the deterioration of its main material 14Cr1MoR(H) is studied through mechanical property test, metallurgical structure analysis and simulated postweld heat treatment tests, and the welding repair process was developed. The results show that the yield strength and elongation after fracture of the base metal decreased by 40% and 15% respectively at normal temperature, and the impact toughness in the heataffected zone of the weld decreased by about 30%. There was a certain degree of material deterioration, but the metallographic structure of the material was normal and the ductilebrittle transition temperature was still far lower than the minimum metal design temperature of the equipment. After holding at (690±14) ℃ for 20 h and 4 h, the maximum decrease in the normal temperature tensile strength and high temperature yield strength of the base material was 15% and 21% respectively, and the impact toughness decreased by 55%. The maximum decrease in the normal temperature tensile strength and high temperature yield strength of the weld was 11% and 4.7% respectively, and the impact toughness decreased by 31%. In the metallographic structure, the carbide precipitates increased obviously and the particles became coarser. However, the yield strength and plasticity of the base metal at normal temperature were restored to a certain extent. The ductilebrittle transition temperature had little change. The material properties still met the technical requirements of the equipment. On this basis, the welding repair process was developed and applied to the regenerator. The equipment was put into operation for one cycle (3 years) and was in normal operation.

Key words: S-Zorb regenerator, 14Cr1MoR(H), over-temperature operation, material degradation, welding repair