The Study Of New Reduced Activation Martensitic Steels

The structural materials of Fusion reactor is one of the keys for whether a fusion can be applied in the commercialization. The international community attached great importance and a good many countries are in the development of their unique materials. Low-activation ferritic / martensitic steel (Reduced Activation Ferritic / Martensitic steels referred to RAFM) was widely considered as the best choice of the structural materials for fusion demonstration reactor and fusion power reactor in the future, the most representative ones of which are F82H and Eurofer97 steels. Our country began the corresponding study in 2001 and our results are significant. We have developed CLAM steel that is used for the fusion with independent intellectual property rights.The main contents of this article are research the influence of heat treatment process to the tensile properties of two kinds of new RAFM steels which are melted by vacuum induction melting(VIM)+electroslag remelting (ESR), analysis the change of microstructures and properties.Firstly, this subject has studied out the effects of the heat treatment process on the new RAFM steels, such as quenching temperature, tempering temperature, tempering time, tempering cooling medium after tempering and a series of quenching and tempering on the tensile properties and microstructures of the steels. So to seek for the best heat treatment process, and fully enhance the strength and plastic, attain the optimized suitability of the strength and plastic. It was shown that the best heat treatment process was quenching in the water after 0.5 hour at 980℃, then tempering in the air after 2 hours at 760℃, and the properties of 9Cr-0.11V steel was better than 9Cr0.08V steel. The optimal comprehensive mechanical property indexes as the tensile strength 699MPa, elongate ratio31% and cut constriction ratio 69%.Secondly, evaluated the type and content of non-metallic inclusions of the new RAFM steel, analyzed the influence factors to structures and properties by optical microscopy, environmental scanning electron microscope, transmission electron microscopy. Obtained by electroslag remelting smelting, the new RAFM steel contains few non-metallic inclusions, and the distribution is uniform. After heat treatment, the microstructure of new RAFM steel is martensite, dislocations and carbon and nitrogen compounds are the main factors to enhance the mechanical properties, which mainly M23C6 type carbide, been to EDX analysis of that specific composition is (Cr_0.75Mn_0.02W_0.23)23C6, along with a small amount of hexagonal system of Cr₇C₃, Mn₇C₃ and tetragonal crystal system Fe3C, Mn3C, Cr3C2 carbides exist.