Evolution On The Microstructure And Texture Of The4.5%Si Non-oriented Silicon Steels Prepared By Twin-Roll Casting Process

As general high silicon steel,6.5%Si-Fe alloyed sheet is the most suitable material for making high speed and high frequency motors and transformers. But with the silicon content in high silicon steel increasing, there might be structural ordering and the material would be too brittle to be cold formed. Therefore, it is significant to keep high frequency electromagnetic property while reducing the silicon content. In this paper,4.5%Si non-oriented silicon steel with self-designed chemical component is used as experimental material, and2mm cast strip is made by means of two roll casting. The structure, texture and precipitates in different sections are studied by means of OM, TEM, EPMA, EBSD, XRD. Results are as follows:(1) By increasing Cr and decreasing Si, the brittle rupture of cast strip in cold rolling period was greatly improved, with the help of lubrication, the sheet can be rolled to0.18mm.(2) Precipitates in the cast strip are mainly AlN with typical polygon shape. The way of second cooling have an influence on the size of precipitates, air-cooled is much larger than water-cooled, and the size is3～5times larger in air-cooled strip than water-cooled; after900℃×5min normalization, the size of the precipitates in cast strip was developed, the side length of hexagon AlN was developed to more than800nm from600nm, some can even reach1μm.(3)’With cold rolling reduction more than75%, typical textures like{112}<110>、{111}<110>>{111}<112> and rotated cubic begin to exist. The overall strength of cold rolling texture increased with the cold reduction increasing. After1050℃×5min normalization, with the cold reduction increasing, textures develop from{001}<120>、{111}<112> to {114}<481>、{554}<225> respectively.(4) High temperature annealing is good for improving magnetic property. With the increasing of annealing temperature, the density of y texture becomes weaker and weaker, and {111}<112> gradually turns to{554}<225>.(5) By doing semi-annealing experiment, we discovered that plenty of (110) and (100) recrystallized grains appeared at deformation bands and shear bands inside the grains. Those recrystallized grains gradually grew up with the temperature increasing, there were more and more (100) grains which led to strong cubic textures in the structure; the main mechanism of forming recrystallization textures is oriented nucleation theory.