Effect Of Processing Technology On Microstructure And Properties Of Zr-1Nb Alloy Fuel Cladding Tubing

With the rapid development of the global economy,the energy supply system is constructed in the direction of clean,economic and stable.Nuclear power,as a clean energy source,has been greatly developed in recent decades,which fuel core mainly uses the zirconium alloy as the fuel cladding material to play the role of the first safety barrier of nuclear reactor.The Zr-1Nb alloy studied in this paper is the third generation of zirconium alloy independently developed in China.The effects of quenching,cold rolling deformation and heat treatment process parameters on Microstructure and second phase particles were investgatied.The microstructure and properties were analyzed.The main conclusions are as follows:(1)Through the study of the effect of aging on the quenching microsturcture after no pre-deformation and pre-deformation,it is shown that the heat treatment time below the peritectoid reaction temperature of Zr-1Nb alloy is harmful to the precipitation and growth of the second phase particles.When the temperature is above 650 ℃,too long heat treatment time will lead to the local growth of the second phase particles and the poor distribution uniformity.After aging,the microstructure of Zr-1Nb alloy with pre-deformation is more uniform and fine than that of the microstructure without pre deformation.(2)Simulation was used to study the influence of cold rolling by pilger on the microstructure of pipes and observed microstructure morphology of pipes in cold forming process.It was demonstrated that cold rolling by pilger can improve the degree of equiaxed recrystallization of pipes and the degree of homogenization of their microstructure.When the pipe is cold rolled by pilger,the reduction of the wall should be greater than the reduction of the diameter,that is,when the Q value is greater than 1,the texture of the pipe is radial texture,and the index of the hydride orientation factor characterized by it meets the design requirements.(3)By observing the precipitation,distribution and morphology of the second phase in the rolled and annealed state of the cold-rolled tube with the deformation increased from 55%to 99.6%,the second phase particles changed from band distribution to point distribution.Intermediate annealing is beneficial to the precipitation and dispersion distribution of the second phase particles.The final heat treatment of the finished product determines the morphology,distribution and size of the second phase particles.(4)The mechanical properties of the finished tube were obtained by the heat treatment experiment of 440 ℃ ～ 580 ℃ / 1h and argon filled cooling.The heat treatment under the condition of the 83% deformation of the finished tube was determined to be recrystallization annealing 510 ℃ / 5h and stress relief annealing 470 ℃ / 8h,respectively.The fuel cladding tube which physical and chemical properties meet the design requirements could be obtained,and its long-term corrosion resistance is equivalent to the third generation of commercial zirconium alloy.(5)The processing technology of Zr-1Nb fuel pipe was established,which can be determined as 4-pass cold rolling deformation in 1050 ℃ ± 20 ℃ range 630 ℃extrusion 99.6% total deformation finished product heat treatment system,respectively recrystallization annealing 510 ℃ / 5h argon filled cooling mode and stress relief annealing 470 ℃ / 8h argon filled cooling mode,and obtained the processing technology window in industrial production.