Heat Treatment Process And Precipitation Control Of Twin-roll Strip Casting Fe-1.3%Si Steel

In this paper, the microstructure and precipitates of strip cast Fe-1.3%Si Non-oriented silicon steel were investigated. And then the effects of heat treatment processes on the precipitation behavior were also investigated. In addition, detailed studies of the microstructure, precipitates and magnetic properties were carried out under the different normalizing, cold rolling and annealing processes. The major work and inclusion are as follows:(1) The microstructure and precipitates of the strip cast were affected by material quality of cast roller and the inhomogeneous distributions were observed. Compared with the copper cast roller, the steel cast roller was easy to coarsening the microstructure and precipitates. Under the nozzle location (along the direction of width) and the central section (along rolling direction), the microstructure and precipitates of the as-cast strip were more coarsening, the average sizes of precipitates were210nm and270nm.(2) The effects of heat treatment processes on the size, volume fraction and ripening rate of precipitates were investigated. When the cast strip were holding heat treatment at the temperatures of1250℃and1300℃, the size of precipitates was increased while the volume fraction and ripening rate of precipitates were decreased. When the temperature was1380℃, the precipitates can solid solved completely, the volume fraction of precipitates decreased, the size increased firstly and then decreased.(3) The influence of normalizing processes on the precipitates and magnetic properties of final sheet were revealed. When the normalizing time was20min, at the temperature of1000℃, the massive precipitates would precipitate, at the temperature of1200℃,the size of precipitates would increase. When the normalizing temperature was1100℃, the volume fraction and the size of precipitates would both increase by increasing the normalizing time. The best normalizing process was1100℃20min,the iron loss of final sheet was4.15W/kg.(4) The effects of cold rolling and annealing processes on the microstructure, precipitates and magnetic properties of final sheet were explored. Heavy reduction rate was advantageous to decrease the iron loss of final sheet. The optimum annealing temperature was900℃, at this temperature, the recrystallized grain size can be ensuring and the size of precipitates can be coarsening at the same time. The rapid thermal annealing was adopted for the cold rolled sheet, when the heating rate was300℃/s, the precipitation behavior of precipitates would precede the recrystallization behavior of matrix. These precipitates would pin the grain boundary and inhibit the grain growth of recrystallization.