Cleanliness And Mechanical Properties Of Low Activation Steel With Ti,Zr And Y

Low-activated ferrite/Martensitic（RAFM）steel has low activation performance and good tissue stability which is considered to be one of the preferred structural materials for the first wall cladding of the fusion reactor.In order to further improve the cleanliness and comprehensive mechanical properties of low activation martensite steel-CLAM steel which with our independent intellectual property rights,CLAM steel with Ti,Zr and Y were prepared by vacuum induction smelting and vacuum induction smelting+electric slag remelting.The influence of alloying sequence,slag remelting and heat treatment process on the microstructure and mechanical properties of low activation steel are studied.The main conclusions are as follows:（1）The effect of alloying sequence on cleanliness,microstructure and mechanical properties of VIM steel is studied.In Vacuum induction melting experimental steels with Ti,Zr and Y,the inclusions are mainly Y-O-S,Y-Ti-O-S、Y-Zr-O-S and Y-Zr-Ti-O-S,and there are a small amount of large-sized Zr-rich inclusions.The VA steel（V:Vacuum Induction Melting）with Ti and Zr First and then Y has finer inclusions.The average grain size of VA steel is smaller,after heat treatment of 1050℃×30 min+750℃×90 min.The precipitates in two steels are MX and M₂₃C₆.The precipitates density of MX phase in VA Steel is higher and the average size of M₂₃C₆ phase is smaller.VA Steel has higher yield strength,tensile strength,impact work at room temperature and hardness.The yield strength,tensile strength,impact power and hardness of VA steel are 9 MPa,17 MPa,18J and 5 HV higher than VB Steel respectively.（2）The effect of ESR on cleanliness,microstructure and mechanical properties of experimental steel is studied.After electroslag remelting,the kinds of inclusions in the steel did not change,and no large-size Zr-rich inclusions were found.Compared with VIM Steel,Y,Ti and Zr of EA and EB Steel（E:Electro Slag Remelting）have smaller mass fraction,smaller average size of inclusions,and higher microstructure and mechanical properties.The yield strength,tensile strength,impact power and hardness of EA Steel are 79 MPa,68 MPa,89 J and 10 HV higher than VA Steel respectively.The yield strength,tensile strength,impact power and hardness of EB Steel are 84 MPa,68MPa,99 J and 13 HV higher than VB Steel respectively.（3）The effect of pre-tempering on microstructure and mechanical properties of ESR Steel is studied.In the pre-tempering process,the residual stress in the experimental steel decreases gradually,the austenite grain size decreases gradually,and the mechanical properties increase gradually,with the increase of the low-medium temperature pre-tempering temperature.The mechanical properties of EA6 and EB6 pretempered with500℃were optimized.The yield strength,tensile strength,impact work and hardness of EA6 steel are 665 MPa,756 MPa,307 J and 269 HV respectively.The yield strength,tensile strength,impact work and hardness of EB6 steel are 659 MPa,749 MPa,301 J and 267 HV respectively.（4）The effect of double normalizing and double tempering on the microstructure and mechanical properties of ESR Steel is studied.Double normalizing and double tempering process can improve the microstructure and mechanical properties obviously of the experimental steel.The MX was further precipitated by secondary normalizing,the C in the matrix was consumed,and the M₂₃C₆ was refined.EA9 and EB9 steels with 950℃double normalizing have the best comprehensive mechanical properties,The yield strength,tensile strength,impact work and hardness of EA9 steel are 693 MPa,765 MPa,331 J and 285 HV respectively.The yield strength,tensile strength,impact work and hardness of EB9 steel are 688 MPa,760 MPa,324 J and 287 HV respectively.