Hot Deformation Behavior And Heat Treatment Parameter Of 12Cr13 Steel For Nuclear Power Unit

The driving rod is the key component of nuclear power unit.Its performance directly affects the safety production of nuclear power unit.The drive rod components of domestic units mainly rely on foreign imports.,although scholars have conducted research on its molding process and performance,there is still a big gap in performance compared with foreign products.Foreign products also have the disadvantage that the processing process is too long and does not conform to the concept of green manufacturing industry.Therefore,this article takes the forged 12Cr13 martensitic stainless steel as the research object,and adopts the direct hot extrusion process to produce nuclear power drive rod pipes,so as to realize the domestic manufacturing of the pipes with short process and green manufacturing.Using Gleeble thermal simulator combined with DEFORM-2D finite element simulation,the hot deformation behavior and extrusion characteristics of 12Cr13 martensitic stainless steel were studied,a reasonable hot extrusion process was developed and trial production was carried out.The results show that the rheological characteristics of the experimental steel are dominated by dynamic recovery type,which only appears as dynamic recrystallization type at high temperature and low strain.When the extrusion ratio is 19.8,the extrusion temperature is determined to be 1150 ?and the extrusion speed is 100 ?200 mm/s,and the tube blank was successfully trialproduced through the extrusion line,which differed by 8.8% from the finite element prediction error value.The internal friction method is used to study the dissolution of carbides in steel at different quenching temperatures,and the microstructure and grain size of different quenching processes are analyzed by SEM.Studies have shown that: when the quenching temperature reaches 950?,the SKK peak value tends to be the highest,and the carbides in the experimental steel have basically dissolved.The quenched martensite is distributed in the original austenite grains in different orientations of lath.As the quenching temperature rises,the grain size gradually increases.When the quenching temperature is higher than 950 ?,the grain growth speed becomes faster.Combined with the technical requirements of nuclear power steel,the quenching temperature process window is determined to be 950?980 ?.According to the changes in the structure and mechanical properties of different tempering processes,the P-parameter method is used to establish the tempering kinetic equation to predict the performance of the experimental steel after quenching and tempering,and to determine the optimal tempering process window.The results show that there is a phenomenon of temper embrittlement at 450?500?,the activation energy of tempering at 580?700? is 94.83KJ/mol,which is similar to the activation energy of carbon atoms in ? ferrite,the transformation process is controlled by the carbon atom diffusion mechanism.The parameter range that meets the performance requirements calculated by the P parameter method is 1.688?P?1.92,and the appropriate tempering window is determined according to the performance requirements as 610±10?,and the heat preservation is 1.12?1.67 h.