Research On Recrystallization Kinetics Of Hot-rolled Sheets Of Ferritic Stainless Steel

With the increasing price of nickel, the costs of traditional austinetic stainless steels containing nickel are increasing year by year. Therefore, ferritic stainless steel with none or little nickel are being used widely. Because of the excellent overall performance, high-pure and ultra-pure ferritic stainless steel with low carbon and nitrogen become one of the most important development subject. The mechanical properties of ferritic stainless steels are greatly influenced by microstructures and precipitates, while microstructures and precipitates are influenced by annealing process.In this paper, based on the effect of recrystallization microstructures on the formability of hot-rolled sheets, the annealing recrystallization process of ferritic stainless steel was studied by annealing experiment. By using inclusion analysis method, scanning electron microscope, transmission electron microscope, the effects of niobium and titanium in steel during recrystallization process were discussed, and the recrystallization kinetics model of hot-rolled sheets was established. The conclusions were as follows:(1) With the increase of holding time at 950?,.all of the steels completed the transition from fibrous tissue to recrystallization completely in 7min?9min except No.9 and No.10. No.9 steel completed recrystallization in 5min, while No.10 did not complete even after 25min. The recrystallized grain size of No.9 was the biggest, about 38?m, while No.10 was the smallest, because of the different content of niobium and titanium, the grain size changed.(2)NbC?TiC?TiN and NbN were precipitated in the solidification of molten steel and annealing process under the experimental conditions.(3) When the content of titanium was constant, with the increase of niobium, the small size precipitates were precipitated in steel, which can pinning the grain boundaries, restrain recrystallization and refine grain.(4) When the content of niobium was constant, the increase of titanium is benifical to the recrystallization process but harmful to the grain refinement.(5) When the ratio of niobium and titanium in high pure ferritic stainless steel was constant, simply increasing the content of niobium and titanium can not exert the grain refinement effect of niobium. The effect of titanium on recrystallization is greater than the effect of niobium under the condition.(6) The recrystallization kinetic model of hot-rolled sheets at 950 ? was established based on Avrami Equation using annealing experimental results of ferritic stainless steel.