| Because of its high efficiency and excellent start-stop performance, supercritical unit are favored all over the world. Now it has become the future tendency of power technology for china to develop supercritical unit. The key to doing it is the properties of high temperature material. Cr-Mo-V steel has been used as HP/IP shaft material in supercritical unit for a long time abroad. And all Chinese manufacturers have also chosen Cr-Mo-V steel as the material for HP/IP shaft in the bid for the first China-made supercritical uints. but the experiment report about this material has not been published so far.Based on the experimental results, high temperature low-cycle fatigue behavior, creep behavior, fatigue-creep interaction behavior, and high temperature aging structure change were studies in this paper, as well as the analysis of the feasibility of using 30Cr1Mo1V shaft steel at 565℃. The low-cycle fatigue experiments were carried out at 540℃ and 565℃ and the feasibility of using 30Cr1Mo1V shaft steel at 565℃ is discussed from the view of low-cycle fatigue properties. Through interrupted experiments and Vicker's hardness measurement, the relationships between strain and life, which consider hardness modification, are established, and the validities are examined. The fatigue mechanisms at the temperatures are analyzed with the aid of optical microscope and scanning electron microscope, statistical analysis of fatigue crack density are performed. The results indicate that the fatigue failure lives of 30Cr1Mo1V reduced slightly as temperature increased from 540℃ to 565℃. Low-cycle fatigue properties of 30Cr1Mo1V at 565℃ are similar to those of 30Cr2Mo1V at 550℃. Therefore it is basically feasible to use 30 Cr1Mo1V as supercritical shaft material. Low cycle fatigue damage curves of 30Cr1Mo1V shaft steel are not linear, and the damage is relevant to the strain amplitude. Based on the experimental results, the low-cycle fatigue damage formula, life estimation formula and damage equations of 30 Cr1Mo1V at 540℃ and 565℃ are presented. The validity examination shows that hardness modification is valid only when the life fraction is less than 0.5.The creep tests of 30Cr1Mo1V were carried out at 540℃ and 565℃, and the experimental data are processed with projection concept. Norton damage formula in which the minimum creep speed was obtained from projection concept was used to study creep damage, therefore the full scale damage was considered. By comparing the Norton's damage with the Kachanov's damage, a new Kachanov's damage modified formula based on the creep harden theories is developed. Through interrupted experiment and Vicker's hardness measurement, the characteristic parameters of creep rupture were obtained and the validity was examined. The creep damage mechanisms under these two temperatures were analyzed through optical microscope and scanning electron microscope .The results show that creep rupture strength of 30Cr1Mo1V decreased greatly with the increase of temperature, but it is still greater at 565℃ than that of 30Cr2MoV at 550℃.. The validity examination of hardness-modified model shows that the modified value is consistent with the actual value only when Larson- Miller parameter is larger than 18000. The study on creep mechanism of 30 Cr1Mo1V shaft steels indicate that at 540℃ the crack propagation is of intergranular and transgranula mixt mode r. while at 565 ℃ the crack propagation is fundamentally intergranular. The number and the depth of the dint increased with the increase of temperature.The fatigue-creep interaction experiments of 30Cr1Mo1Vs shaft steel with strain holding from 10 to 60 seconds at 540℃ and 565℃ were performed. Stress relaxation phenomena during holding time were studied. Linear damage summation (LDS) method, frequency modification (FM) method, the strain range partitioning (SPR) method , strain energy partitioning (SEP) method and equivalent strain (ES) method were adapted to process these experimental d...
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