In the last three decades new stronger modified 9%Cr steels have been introduced in new power plants with steam parameters up to 300 bar(1 bar =10~5 Pa) and 600℃. In order to further increase the steam parameters of ...In the last three decades new stronger modified 9%Cr steels have been introduced in new power plants with steam parameters up to 300 bar(1 bar =10~5 Pa) and 600℃. In order to further increase the steam parameters of steel based power plants up to a target value of 650℃/ 325 bar it is necessary to double the creep strength compared with todays strongest 9%Cr steels,and at the same time the resistance against steam oxidation must be improved by adding 12%Cr to the steel. However,so far all attempts to make stronger 12%Cr steels have been unsuccessful because the high chromium content introduced severe microstructure instabilities in the tested steels.Recently,it was found that the microstructure instabilities in 11%- 12%Cr steels can be explained by the precipitation of coarse Cr(V,Nb)N Z-phases, which dissolve fine(V,Nb)N nitrides. A new possibility to use the Z-phase for strengthening of 12%Cr steels has been identified,and the development of stable strong martensitic 12%Cr steels based on this concept is expected to allow the construction of 325 bar/ 650℃steam power plants all based on steel.展开更多
文摘In the last three decades new stronger modified 9%Cr steels have been introduced in new power plants with steam parameters up to 300 bar(1 bar =10~5 Pa) and 600℃. In order to further increase the steam parameters of steel based power plants up to a target value of 650℃/ 325 bar it is necessary to double the creep strength compared with todays strongest 9%Cr steels,and at the same time the resistance against steam oxidation must be improved by adding 12%Cr to the steel. However,so far all attempts to make stronger 12%Cr steels have been unsuccessful because the high chromium content introduced severe microstructure instabilities in the tested steels.Recently,it was found that the microstructure instabilities in 11%- 12%Cr steels can be explained by the precipitation of coarse Cr(V,Nb)N Z-phases, which dissolve fine(V,Nb)N nitrides. A new possibility to use the Z-phase for strengthening of 12%Cr steels has been identified,and the development of stable strong martensitic 12%Cr steels based on this concept is expected to allow the construction of 325 bar/ 650℃steam power plants all based on steel.
