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Analysis of generator rotor material Xiang Dong S Liu Zengliang 2 Quan Jin 3 (. Department of Materials Science and Engineering, Shandong Institute of Architecture and Engineering, Jinan, Shandong 25 (1) 142. Department of Mathematics and Physics, Shandong Institute of Architecture and Engineering, Jinan, Shandong 2500143. Shandong Graduate School of Architecture and Engineering, Jinan, Shandong 25 (1) 14) Its different roles and applications in turbo generators. After quenching and tempering with different quenching and high temperature tempering, CrMo series steel (such as 34CrMo1A) has poor hardenability, but the comprehensive mechanical properties of such materials can meet the application of N-CrM for rotor materials of medium and small generator sets. -V series steel (such as 26NiCrMoV115) has large grain refining and tempering resistance, high strength and toughness, and is often used for large generator rotor materials with large loads.
1:A With the development of society, electricity has become the pillar industry of the current national economy, and it has received more and more attention. The generators used in China are mainly steam turbine generators. At present, most of the rotors used in the world are high-toughness Ni-CrMo-V steel, which combines the characteristics of high- and medium-pressure rotor C-Mo-V materials and low-pressure rotor Ni-Ci-V materials to make them very good. Greatly improved, and CrMo steel has good toughness and creep strength and is a commonly used material.
1Rotor steel requirements Steam turbine rotor has high working temperature and rotor forging volume is large; when rotating at high speed (3000 ~ 3600 rpm), it needs to bear large centrifugal force and additional stress; instantaneous shock and vibration caused by starting, stopping, etc. Stress; often withstands large torsional moments due to overcoming the magnetic field; thermal stress due to temperature gradients. This requires good normal temperature comprehensive mechanical properties, high high temperature tensile strength, good plasticity, toughness, high creep strength, low toughness and brittle transition temperature and high magnetic permeability.
2 Rotor material heat treatment process analysis Compared with the surface layer of the large generator rotor, the axial part is inferior in steel ingot quality, forging and heat treatment, and mechanical properties. Various defects are easily concentrated here, so this time.
Table 1 After the hardness and quenching treatment of the material, the microstructures of S and 8 are obtained, wherein S has good comprehensive mechanical properties, good toughness, hardness and wear resistance, and good properties such as low notch sensitivity and brittle transition temperature. . It ensures that the rotor will not be subjected to stress and fracture due to uneven organization and poor performance when rotating at high speed, and it can also improve fracture toughness. At present, China still uses mechanical performance requirements as the main acceptance criteria. However, the brittle transition temperature commonly used in the world has not been included and needs to be improved.
4.1 The measured mechanical properties are compared with the standard requirements. The measured index of 34CrMo1A steel is generally improved by 13%, while the 26NiCrMoV115 steel does not decrease the plasticity and toughness index on the basis of maintaining high strength index.
4.2 Comparison of the two materials The composition and structure of the two materials are quite different. The structure of 26NiCrMoV115 is coarser, but due to the higher content of alloying elements, the dispersion strengthening effect is obvious. It can be seen from Table 1 that it is better than 34CrMo1A steel in strength and hardness. And the plasticity is similar.
The overall performance of 26NiCiMoV115 is significantly better than that of 34CMo1A ​​steel.
5 Conclusion In summary, CrMo series steel has poor hardenability, and it is difficult to implement ordinary quenching process to achieve higher performance requirements during heat treatment. It can be improved by intermediate critical quenching process. The comprehensive mechanical properties of such materials are inferior to those of Ni-CrMo-V steel, but they are widely used in medium and small generator sets because of their low price and convenient manufacturing. Ni-CrMo-V series steel can refine grains, improve tempering resistance and reduce brittle transition temperature. The strength and toughness of vines are often used in large generator rotor materials.
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