Study On Preparation Technology,Microstructures And Properties Of Advanced Steam Turbine Blade Steels In Fushun Special Steel Shares Co.,LTD.

As the most important foundation for developing advanced power generation technology,the material of turbine blade has become the key factor that restricts the improvement of unit parameters.In recent years,with the introduction of foreign ultra-supercritical steam turbine technology and the continuous improvement of steam turbine parameters,the demand for high quality blade new materials in China's steam turbine industry is becoming more and more urgent.At the same time,higher requirements are put forward for cleanness,structure uniformity and products delivered in QT condition.By combining the industrial production practice of turbine blade steel of Fushun Special Steel Co.,Ltd.,this paper,represented by 10Cr11Co3B,1Cr12Ni3Mo2VN,X20Cr13 and other steel,aiming at the latest requirements for the technical indexes of blade steel for turbine enterprises,developing "the high-purity melting technology","research on uniformity of structure and properties" and "continuous quenching and tempering technology for flat blade steel" of steam turbine blade steel.The technical breakthrough and research results of this paper are as follows:1.Developing the high-purity melting technology 10r11Co3B ultra-supercritical blade steel.The composition of the electrode is designed according to the law of elemental burning loss.The realization of low-cost and stable production of this series of steels is achieved by a series of process measures such as high-purity melting of electrodes,argon-protected casting of electrodes and adding deoxidizer during ESR process.2.A comparative test of ESR process adopting ternary and quaternary slag system respectively was carried out on 1Cr12Ni3Mo2VN steel to study the changes of element burning loss,oxygen content and non-metallic inclusions in during ESR process.Through this experiment,it can be concluded that the products by ESR with quaternary slag system can achieve the sum of 9 items of non-metallic inclusions reaching ?2.0 level.3.By adopting low-carbon and low-nitrogen industrial pure iron melting technology and double vacuum melting technology,PH13-8Mo precipitation hardening stainless steel for last stage long-blade was developed.By optimizing the parameters of the melting process,the grain size of the forged material is 8 and the ferrite content is ?0.2%.The test results of mechanical properties meet the standard requirements.The quality level of the blade after forging is flush with the foreign level,which also lays a solid foundation for the localization of this material in future.4.The optimum homogenizing parameters of ESR ingots were determined through the study of the cast structure segregation of ESR ingot and the homogenization effect of alloy elements of 10Cr11Co3B.It solves the technical problem of hot work cracking and chain carbide due to the serious segregation of tungsten and molybdenum in the cast structure.5.The influence of the forging method on the "property isotropy" of the blade steel was systematically studied.Blade steels with uniform longitudinal and transverse properties were developed successfully by using innovative forging technology that combined the open die forging press(upsetting and drawing)and radial forging machine with variable frequency forging.The results show that for the 1Cr12 heat-resistant steel bar with ?-Fe ferrite content<0.2%,S content of 0.001%and high purity,when produced with open die forging press by four-time upsetting and four-time drawing,the ratio of the longitudinal and lateral impact energy of the forged steel bar reaches 1.17 to 1.20;when produced with combined process of open die forging press(upsetting and drawing)and radial forging machine,the ratio of the longitudinal and lateral impact energy of the forged bar is?1.05.6.the continuous quenching and tempering technology of turbine blade flat steel has been developed by using China's first off-line multi-functional continuous heat treatment line for alloy steel.The quenching equipment,using water air time controlled quenching technology.combined water immersion,mist cooling,blast cooling and so on,so that the cooling capacity can be transferred from strong to weak,and finally obtain the required structure and property.Several QT flat blade steels have been approved by American GE.French Alston.German SIEMENS.Italy Ansaldo and other internationally famous companies.