Texture Evolution And Magnetic Properties Of Thin-Gauge Non-oriented Silicon Steel Based On Strip Casting

When the motor is operating in high frequency,the core will produce huge eddy current loss and iron loss.In order to reduce the loss,the thin-gauge non-oriented silicon steel sheets are widely used in high-frequency equipment.The high-frequency iron loss is extremely sensitive to the thickness since the eddy current loss which is dominant in the high-frequency is proportional to the square of the thickness.The thinner of the thickness produce the lower iron loss.The research on thin-gauge non-oriented silicon steel is few,which is based on twin roll strip casting is fewer.While,some texture evolution mechanism is not clear.Based on the twin roll strip casting,the mechanism of nucleation and growth process of grains in different orientation as well as the effect of cold rolling reduction and annealing temperature on the microstructure,texture and magnetic properties in thin-gauge(H<0.30mm)and ultra-thin-gauge(H<0.15mm)non-oriented silicon steel were investigated in this paper.The main research contents are as follows:(1)The orientation evolution of recrystallization nucleation and growth process was investigated.α’ orientation({311}<136>,{411}<148>)mainly recrystallizes in the vicinity of the{112}<110>deformed grain boundary.Large amount of {112}<110>deformed grains formed in the cold rolling process,α’ orientation has the advantage of nucleation in the partly recrystallization.{111}<112>orientation pinning can be detected in the grain growth process,which is attributed to sharp α’ orientation by consuming fine {111}<112>grains.When the thickness is reduced to ultra-thin gauge(H≤0.14mm),α’ orientation can nucleate in the vicinity of the surface of sheets.Generally,the mechanisms of y texture being reduced by the selective growth and surface energy inducing grain growth of α’ grain contribute to optimizing magnetic induction intensity.(2)The effect of cold rolling reduction on microstructure,texture and magnetic properties was investigated.When the cold-rolling reduction increases,deformed texture gradually rotates to α orientation line.Besides,nucleation rate of recrystallization rises rapidly during annealing,which results in gain size getting finer.When the thickness is reduced to ultra-thin gauge(H≤0.14mm),1～3 layers of grains,due to the surface energy,are generated in recrystallization microstructure along the thickness direction.That makes the grain size pick up.(3)The effect of annealing temperature on microstructure,texture and magnetic properties was investigated.The average grain size gets larger and more uniform with the increase of annealing temperature,which contributes to lower iron loss.Magnetic induction’s varying with cold rolling reduction is different from iron loss.H>0.25mm,ηtexture can rapidly nucleate in shear band.High temperature as 1100℃ can effectively improve the speed of nucleation and grain growth.The favorable η texture can be enhanced,which optimizes magnetic induction intensity.While H≤0.20mm,there is few shear band in the cold-rolling deformed matrix.And the nuclei of η texture is greatly reduced.The {111｝<112>orientation grains can consume the deformed matrix rapidly at higher annealing temperature which makes the magnetic induction get deteriorated.In a word,magnetic induction of thick sheets(H>0.25mm)is better at 1100℃.And the conclusion is opposite at thin sheets(H≤0.20mm).