SA-02-2(114) ASSESSMENT OF RESIDUAL CREEP LIFE OF Cr-Mo-V STEEL(Life Assessment of Thermal Power Plant 2)

概要

論文の詳細を見る
High temperature components of thermal power plants undergo deformation under service condition. Thus there is degradation of mechanical as well as creep properties along with change in microstructures. Therefore the assessment of residual creep life is very important particularly from safety point of view. Keeping this in view steels exposed for 15yrs and 24 yrs in thermal power plant were subjected to accelerated creep tests in laboratory at stresses 90-180MPa and temperatures 525-600℃. It was observed that rupture data for 15 yrs exposed steel falls in the scatter band of stress and L-M parameter plot while data for 24yrs fall below the lower band. The results also reveal that yield strength and ultimate tensile strength of 15 yrs exposed steel were higher than the new as well as 24 yrs exposed steel, however the elongations of exposed steels were reduced as compared to new steel. This simply confirms that during service exposure the steel components are first hardened followed by softening. The hardening is associated with the formation of dislocations and sub cells while softening is caused due to stress relaxation. The micro structural studies were also carried out with optical, scanning and transmission electron microscopes. The microstructure showed fine precipitates in the grains while lump precipitates at the grain boundaries.
2001-06-03