大型タービン軸実体の機械的性質について

Abstract

To investigate the relation of the test piece positions and directions to the mechanical properties of a large sized steam turbine rotor shaft, the authors examined the impact transition temperature and the creep rupture properties of the 1Cr-11/4Mo-1/4V steel high pressure turbine rotor shaft for a 125, 000kW generator with varied positions of test pieces.As to the test piece positions, the impact transition temperature rises gradually from the outer part to the center, and the creep-rupture strength at the central portion is higher than that of the outer part because of slower cooling rate; this is in good agreement with other reports. Both the elongation and the reduction of area are higher at the outer portion than those of the central.As to the test piece directions, the impact transition temperature of the test piece of radial direction is 10° to 15°C higher than those of longitudinal and tangential direction at each position; however, these transition temperature values, even if at the central portion, satisfy mostly the A. S. T. M. standard value. The creep-rupture strength of the radial or the tangential test piece is lower than that of the longitudinal, the difference between them, however, being comparatively small, with the decrement under 10%.Finally comparing the notched specimens with the unnotihed, the former shows a higher creep rupture strength in the short time rupture test, and on the contrary a lower value in the long time rupture test, than the latter.