Study Of Twin-roll Strip Casting1.2%Si Non-oriented Electrical Steel

Eliminating the continuous casting and hot rolling processes in the traditional technology for producing non-oriented silicon steels, the twin-roll strip casting which can supply a silicon steel strip directly with the same thickness as those of hot-rolled strip for use in cold rolling is a new advanced and energy-efficient technology.The microstructure, texture and magnetic properties of non-oriented1.2%silicon steel processed by the twin-roll strip casting was investigated in this work, especially under the different cold rolling and annealing conditions.A number of micrographs, EBSD and X-RD results about the cast strips show that (1) the microstructure with the maximum value of approx350μm and the average value of approx280μm in grain size can be obtained by cooling in air. The αâ†'γâ†'α phase transformation occurred during cooling will lead to the refinement of some grains and the wider range of grain sizes. The maximum and average grain size can respectively be up to approx400μm and330μm during cooling in an incubator filled with asbestos.(2) A nearly random, diffuse, homogeneous texture is formed through the strip thickness, and it has a very weak intensity.After hot leveling and normalizing which were identical for all the cast strips, the following different experimental routes were carried out to provide sets of different sample states:(1) After pickling, the cast strips were cold rolled to0.5mm in thickness;(2) The cast strips were firstly hot leveling, then pickling and cold rolled to0.5mm and0.35mm;(3) The cast strips were processed by normalizing and pickling, then cold rolled to0.5mm.The final magnetic properties were measured by annealing these three kinds of samples at different temperatures, and relatively low core loss and high magnetic induction were obtained. E.g., the minimum values of core loss of these three samples were respectively5.16W/Kg4.35W/Kg, and4.33W/Kg at1.5T and50Hz (P15/50).The magnetic inductions were measured at5000A/m (B50) corresponding to the minimum core losses were1.83T,1.78T and1.84T respectively. The main conclusions have been summarized as follows.(1) The grain sizes of the final annealed samples are up to40-60μm, which reaches the level of the traditional production mode;(2)Although the final microstructure is still characterized by a comparatively diffuse and weak texture, the relatively strong η fiber component and weak y fiber component can be observed, which is thought to be associated with the high B50values;(3) The inclusion sizes in final annealed samples are mostly in30-60nm, suggesting that the inclusions have no much effect on inhibiting the grain growth, which is very benefit for producing non-oriented silicon steels.