| Zirconium alloys are widely used in nuclear power reactors,nuclear-powered submarines and atomic energy due to their excellent nuclear properties.Zirconium alloy has excellent corrosion resistance in high pressure water and steam,and its thermal neutron absorption cross section is very small,and its compatibility with nuclear fuel is good.Therefore,zirconium alloy is often used as the core structure material of nuclear reactors.Nuclear-grade zirconium is an indispensable key structural material in the manufacture of nuclear reactor fuel assembly,and it is also a common consumption material in the operation of nuclear power plant.Zirconium alloy strip is the main material for manufacturing grid in nuclear fuel assembly.Zirconium alloy strip is used as positioning frame,which can not only hold the fuel rod in hold,keep the necessary spacing,but also allow the fuel rod to slide in the axial direction.That is to say,the fuel rod can expand freely in the axial direction to prevent the bending of the rod due to the thermal expansion.The environment of zirconium alloy is very harsh,and the processing technology of zirconium alloy strip can provide stable and reliable products.Among them,the corrosion resistance of zirconium alloy strip is the most important one,which is related to the safety and stability of reactor operation.In order to meet the requirement of good corrosion resistance of the finished zirconium alloy strip,the processing technology of zirconium alloy strip was studied,the reasonable process route was selected,and the related technological parameters were formulated.In this study,zirconium-tin-niobium and zirconium-niobium alloys were used as experimental objects.The corrosion properties of zirconium-tin-niobium and zirconium-niobium alloys were studied by hot-cold processing and heat treatment in steam at 400 ℃,10.3 ±0.7Mpa for 72 h.The production process of zirconium alloy strip was optimized by studying different solid solution treatment,annealing process and deformation process.The microstructure and particle size distribution of zirconium alloy strip during machining were studied.The cumulative annealing parameters were calculated and the factors affecting the microstructure and corrosion properties of zirconium alloy strip were investigated.The microstructure and second phase structure of Zr-1.0Sn-1.0Nb-0.3Fe alloy and Zr-1.5Sn-0.2Fe-0.1Cr alloy were observed by Leica optical microscope and Hitachi scanning electron microscope.The corrosion resistance of the autoclave was studied and the following conclusions were drawn:The processing technology of Zr-1.0Sn-1.0Nb-0.3Fe alloy strip: the number of the second phase with slow quenching and cooling rate in β quenching process is less and the size becomes larger;The number of second phase precipitated at a faster cooling rate is large,and the size of precipitated second phase particles is generally smaller.After hot rolling and cold rolling with the same deformation,it can be concluded that the fine second phase particles are uniformly dispersed in the crystal and at the grain boundary.When the samples are hot rolled and heat treated below 610 ℃,the second phase particles are small,and the second phase particles are larger and the corrosion weight gain is slightly larger when the second phase particles are hot rolled and heat treated above 610 ℃.The processing technology of Zr-1.5Sn-0.2Fe-0.1Cr alloy strip: β phase quenching makes the alloy elements fully solid solution,and the solid solution effect of thick slab quenching is better than that of thin slab.The second phase particle size of 0.5mm strip processed in 110 mm thick slab quenching process is larger than that of 40 mm slab quenching process,and the uniform corrosion resistance is better.With the increase of annealing temperature of 0.5mm strip,the particle size of the second phase is increased,and the uniform corrosion resistance is optimized.With the increase of cumulative annealing parameters,the size of the second phase particles will also increase,and the uniform corrosion resistance will also be improved. |
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