Effect Of Pulsed Magnetic Field On Microstructure And Texture Of Grain-oriented Silicon Steel During Primary Recrystallization Process

Magnetic field, as a significant physical field, has been widely applied to controlmaterial structure increasingly. Combined with the traditional process, it can be usedto prepare advanced material and develop new technology, manufacturebetter-performing products consequently. Magnetic heating treatment is one of thefrontier hotspots which has broad space and excellent prospect in innovation andapplication. The wide application of steady high-intensity magnetic field in industrycannot be realized because of its complicated infrastructure and high maintenancecosts, while the pulsed magnetic field used in this article has a prospect of wideindustry application because of its simple equipment, high-energy density andlow-running costs. Grain-oriented silicon steel is an important soft magnetic materialmainly be used in production of various kinds of iron core. Silicon steel plays a veryimportant role in power electronics, national defense and livelihoods. The control ofrecrystallization microstructure and texture, as core technology of oriented siliconsteel production, deserves our in-depth exploration and researching.Cold plates for commercial common grain-oriented silicon steel (CGO) and highmagnetic-induction grain-oriented silicon steel (Hi-B) were chosen as experimentalmaterial. The existing high-voltage pulsed magnetic field device and self-madeheating treatment furnace were used to carry out comparative experiments with andwithout pulsed magnetic field in different heating treatment conditions.Microstructure, crystal orientation and grain boundary structure of silicon steel wereanalyzed using electron back scattering diffraction (EBSD). The effect of pulsedmagnetic field on primary recrystallization microstructure and texture of orientedsilicon steel in different heating treatment conditions was studied. Experimentalresults show that pulsed magnetic field annealing can affect the primary recrystallization grain size and distribution, texture and grain boundary structure. Themagnetic field effects is different under different conditions. Based on the magneticorder and anisotropy energy of silicon steel grain during magnetic annealing, ahypothesis about magnetic field action mechanism is proposed, which is fairlysupported by almost all of the experimental results in this work.When cold rolled Hi-B specimens were annealed at730℃for different timewithout and with1T magnetic field parallel to rolling direction of specimens, grainsize of magnetic annealing specimens is bigger than that of the non-magneticannealing for the annealing time less than80min, while a opposite result is obtainedwhen the annealing time more than80min. The magnetic annealing specimens havemischcrystal structure because of magnetic ordering in nucleation. Magneticannealing inhibits {111}<110>,{001}<110> texture and facilitates {111}<112>,{001}<120> texture. Magnetic annealing reduces low-angle grain boundary and CSLgrain boundary and, at the same time increases high-energy grain boundary in all ofthe grains,especially in the case of shorter time annealing. Magnetic annealingreduces low-angle grain boundary and increases high-energy grain boundary aroundGoss texture, which might possess the Goss grains a priority in grain growth duringsecondary recrystallization.Whencold rolled CGO specimens were annealed at different temperature for60min without and with1T pulsed magnetic field in rolling direction, the averagegrain size of magnetic annealing specimens is bigger than non-magnetic annealingones, the effect is weakened with the annealing temperature rises. The magneticannealing specimens have mischcrystal structure. Magnetic annealing restrains{111}<110> texture and facilitates {111}<112> texture a little, meanwhile, restrains{001}<110> texture and facilitates {001}<120> texture strongly. Magnetic annealingreduces low-angle grain boundary and CSL grain boundary，meanwhile increaseshigh-energy grain boundary in all of the grains and the impact is more pronounced inlower annealing temperature. Magnetic annealing reduces low-angle grain boundarymeanwhile increases high-energy grain boundary and CSL grain boundary aroundGoss texture, making Goss texture has advantage in grain growth during secondaryrecrystallization.When cold rolled CGO specimens were annealed at20℃/h from700℃to different temperature without and with2T rolling direction magnetic field, magneticannealing increases average grain size, and the grain size increases with the increasingannealing time and temperature. The most obvious effect of increasing grain sizeappears at760℃and780℃. The magnetic annealing specimens have mischcrystalstructure. Magnetic annealing restrains {111}<110> texture and {001}<110> texture,meanwhile facilitates {111}<112> texture and {001}<120> texture and Goss texturealong with the increasing annealing time and temperature. The magnetic promotioneffect of {111}<112> is stable and the magnetic inhibition effect of {111}<110> isunstable relatively. Magnetic annealing reduces low-angle grain boundary，meanwhileincreases high-energy grain boundary in all of grains and the impact is morepronounced at760℃and780℃. Magnetic annealing decreases CSL grain boundaryat lower temperature and increases CSL grain boundary at higher temperature in all ofgrains. Magnetic annealing reduces low-angle grain boundary and increaseshigh-energy grain boundary around Goss texture, but the effect is not obvious.When CGO was annealed in magnetic field along different directions withrespect to the sample coordinate system, magnetic field has different effects onrecrystallization texture of silicon steel because it changes the free energy of maintextures. Magnetic field along rolling direction facilitates {001}<120> texture and{111}<112> nucleation and grain growth, meanwhile restrains {111}<110> textureand {001}<110> texture. Magnetic field along transverse direction facilitates{001}<120> texture and {111}<110> nucleation and grain growth, meanwhilerestrains {111}<112> texture,{001}<110> texture and Goss texture. Magnetic fieldalong normal direction facilitates {001}<120> texture,{001}<110> texture and{001}<100> texture, meanwhile restrains γ texture strongly. The2T magnetic field ismore efficient than1T magnetic field.