An Experimental Study On Low-cycle-fatigue Behaviors Of 30Cr2MoV Steel

With the development of electric power industry in our country, life management and on-line monitoring are booming. The knowledge on the properties of using materials is urgently needed for reasonable life- prediction and life-distribution. As steam turbine is concerned, frequent starts-stops and great range changes in load usually cause rapid changes in temperature and tremendous thermal stress on rotor, which usually lead to low-cycle-fatigue (LCF) damages. But the experimental work of rotor material has not been done well in China. Nowadays, there is but no choice to use similar experimental data and experiential formula of other countries. Unfortunately, due to the difference in composition and processing techniques, this inevitably results in inaccuracy in life- prediction and life-management. This thesis presents the LCF experimental study of 3OCr2Mo V., an extensively used rotor shaft material in China-made 200MW steam turbine. The main work is as follows: 1. LCF experiments under strain-controlled cycling of 3OCr2MoV at room temperature and elevated temperature of 550 0C were carried out in a CSS-280 closed loop electric-hydraulic servo- controlled fatigue testing machine. A good number of experimental data were acquired and the data were processed and analyzed with statistic methods. 2. The comparisons of varied common used LCF life-prediction methods were made. Based on the experimental results and adopting the most common used method, the coefficient of cyclic properties and curve of fatigue life versus strain of LCF of 3OCr2MoV were drawn. Comparisons between experimental results and similar curves were made. 3. The fatigue mechanisms of 3OCr2MoV at room temperature and elevated temperature were studied.