Studies Of Mechanical Property And Transformation Plasticity Of Low-Pressure Rotor Steel

As the most modernized power resource, electric power is critical energy for modern technology, residential life and new sector development. Approximate 80% electrical energy is produced by steam-turbine generator with fuel including fossil and nuclear, which is a demonstration of an overwhelming position of steam-turbine generator in energy industry. As an important part of generator, rotor is a typical heavy forging. With the development of power industry, rotor is becoming larger and higher-performance, which are two main challenges for research and production.In the first part of this dissertation heavy forging, steam-turbine generator and low-pressure rotor steel 30Cr2Ni4MoV are briefly introduced. After which, in the second part mechanical properties, transformation dynamics and transformation plasticity of martensite and bainite are interpreted. The following two parts are experiment and discussions in detail. In the first experiment, the mechanical testing has been performed to investigate the mechanical properties of different microstructures in low-pressure rotor steel 30Cr2Ni4MoV at different temperatures by Gleeble 3500 thermal simulator. The Young's modulus, yield strength and plastic modulus of martensite, bainite and austenite have been obtained and fit, respectively. The analysis and discussion on the mechanism of mechanical properties variation has been presented according to their relationships with temperature, providing important basis for numerical simulation of heat treatment process and its optimization. In the next experiment, transformation plasticity of 30Cr2Ni4MoV is investigated also by Gleeble 3500 thermal simulator. Strain-temperature curve of martensite at different tensile and compression stresses and strain-time curve of bainite at different stresses and temperatures are obtained, the effects of stress to transformation dynamics and transformation plasticity of martensite and bainite are discussed after transformation plasticity is separated from the whole strain.