Study On Secondary Recrystallization Annealing Of Cu-bearing Hi-B Steel Produced By Stimulated CSP Process

In the global environment of energy-saving and emission-reduction,the CSP process has become the major trend of steel production because it does not need double heating.Therefore,the production of Hi-B steel by CSP process has become one of the hot research topics.In this study,the Cu-bearing Hi-B steel produced by stimulated CSP process was used as the experimental substrate.The microstucure was observed by optical microscope,the data of EBSD was collected by scanning electron microscope,and the analysis of precipitates was conducted by transmission electron microscope.Thus,the evolution of the microstructure and inhibitor during the process of nitriding at different temperatures and the subsequent secondary recrystallization annealing were studied.The results show that,the inhibitors are mainly?Al,Si,Mn?N and composite precipitation of Cu₂S and AlN after nitriding annealing at 550?,whereas the inhibitors are mainly AlN and a small part of composite precipitation of Cu₂S and AlN after nitriding annealing at 900?.In the secondary recrystallization annealing under the two nitriding temperatures,the inhibitors are mainly AlN,the average size of inhibitors increases with the increasing of annealing temperature,and the volume fraction and Zener factor gradually decrease with the increasing of annealing temperature.Goss grains grow abnormally at 1040?in the secondary recrystallization annealing of nitriding at 900?,while Goss grains grow abnormally at 1000?in the secondary recrystallization annealing of nitriding at 550?.During the abnormal grain growth of Goss grains,the{111}<112>and the{411}<148>texture transform to Goss texture.The misorientation between the grains with{111}<112>and{411}<148>orientation and the surrounding grains mainly distributes at 20-45°and tends to concentrate toward20-45°,while the misorientation between the Goss grains and the surrounding grains mainly distributes at 20-45°and tends to distribute toward both ends.The final annealing microstructure of nitriding at 900?is better than the microstructure of nitriding at 550?.