Research On Normalizing Process Of High Magnetic Induction Grain-oriented Silicon Steel Produced By CSP Process

Manufacturing high magnetic induction grain-oriented silicon steel (Hi-B steel)produced by CSP is the primary emphasis on research in industry, currently, dues to itsshort production cycle, low energy consumption and simple processing method. Thenormalizing which is the key in Hi-B steel manufacturing has a significant impact onmicrostructure, texture and the precipitation of inhibitor. Investigating the normalizingof Hi-B steel basic on CSP has an important theoretical and practical significance onguiding industrial production.In this article, Hi-B steel plates were hot rolled using CSP and, then normalized indifferent process. TEM, OM, EBSD and XRD were applied to characterize the effectof precipitate, microstructure and texture on different normalizing process. The resultscan be concluded as:(1) The solution-precipitation and agglomeration of inhibitor in the process ofnormalizing are studied through the theory and calculation of solid solubility and thetheory of Ostwald ripening of secondary phase.Because of solid solubility of AlN andCu2S is larger in γ phase，The large-size inhibitor particles can dissolve hardly whennormalizing temperature is low nor normalizing time is short. On the contrary, whennormalizing temperature is high and normalizing time is long enough, small precipitatestart aggregating and growing up. After two-stage normalizing at1120℃for60s, thenkeeping warm at950℃for150s， the precipitate was obtained in minimum size (65.2nm) and maximum precipitate density (2.4×108per cm2). In this case, the precipitateprovided the highest resistance to impede the growth up of primary grain.(2) The recrystallization kinetics of hot rolled plate in the process of normalizingis studied by Arrhenius and Avrami recrystallization theory. With increasingnormalizing temperature and adding normalizing time, The substrate of hot rolled plateoccurs recrystallization gradually and the grains on the surface were morehomogeneous.It is beneficial for primary recrystallization. However, the microstructure on the cross-section occurs obvious recrystallization when the normalizing temperatureis higher than1200℃or the normalizing time is longer than120s at1120℃. It hadbad heterogeneity along the thickness direction of sample and It is disadvantageous forthe following secondary recrystallization. The sample is two-stage normalized at1120℃for60s which showed a relative homogeneous grain on surface, significantheterogeneity on the grain on the cross-section and enhance on secondaryrecrystallization.(3) The Goss textures was primarily distributed on the surface in hot rolledplates. Goss texture and γ texture are interconvertible in the process of normalizing.The {111} grain nucleate firstly and grow up gradually because Its higher storageenergy. The strength of Goss texture was decreasing. Then Goss grain began tonucleate and grow up with the normalizing temperature rising. The strength of Gosstexture increased and γ texture decreasd. There is a small amount of Goss grain innormalized plates and the γ texture showed highest strength after two-stagenormalizing at1120℃for60s in cold rolled steel plate. It benefits the followinggrowth up of Goss texture in this situation.