Cold rolled non-oriented electrical steel with high reduction rate

Microstructure and texture are important factors affecting the properties of non-oriented electrical steel. In order to improve the product properties, the effects of cold rolling reduction rate (71.7%~87.0%) on the microstructure, texture, magnetic properties and mechanical properties of high grade non-oriented electrical steel were studied. The results show that the average grain size decreases first and then increases with the increase of cold rolling reduction rate. The Gaussian and cubic textures weaken, γ fibers strengthen, α fibers change into stronger α*({h, 1, 1} < 1/h, 1, 2 >) texture, and strengthen with the increase of cold rolling reduction rate, and its peak value gradually moves towards the {111} plane. Power frequency iron loss P1.5/50, high frequency iron loss P1.0/400 and magnetic polarization strength J5000 decreased at the same time, the yield strength changed little, and the surface hardness gradually increased. When the reduction rate of cold rolling is increased from 84.7% to 87.0% and the thickness is reduced to 0.30mm, the decrease of high frequency iron loss is 11 times that of power frequency iron loss, and the increase of surface hardness is larger. The above research results provide a good guide for the optimization of texture and structure of electrical steel after thinning.

Problems such as exhaust pollution and oil safety have prompted new energy vehicles to become the mainstream of future motor vehicles, and high-grade non-oriented electrical steel, as an important soft magnetic material, is widely used in high-end home appliances, new energy vehicle drive motors and efficient industrial motors and other fields. Benefiting from the stable development of the power industry, the implementation and promotion of frequency conversion technology in the home appliance industry, the rise of the new energy automobile industry and the development of motor energy saving and high efficiency, the domestic demand for high-grade non-oriented electrical steel will continue to rise significantly. In the past 10 years, due to the rapid promotion of new energy vehicles, high grade non-oriented electrical steel is required to have higher magnetic induction, lower iron loss and thinner thickness. Improving the magnetic properties of non-oriented electrical steel has always been the focus of research in the field of electrical steel. Due to cost and efficiency, most enterprises tend to use the cold rolling method when producing non-oriented electrical steel. The content of alloying elements, the quantity and distribution of inclusions, the structure, texture, plate thickness and surface quality all have significant effects on the magnetic properties of non-oriented electrical steel. Texture and grain size are the two most important factors affecting magnetic properties and mechanical properties of non-oriented electrical steel under the condition of constant composition and plate thickness. In actual industrial production, in order to meet the different needs of the market, electrical steel needs to prepare a variety of thickness specifications, and the thinner the specifications, the greater the cold rolling reduction rate. Changing the reduction rate of cold rolling will affect the deformation microstructure and texture, and thus affect the formation and development of recrystallization texture. Many scholars have focused on the influence of thickness reduction on product structure, texture and magnetic properties. The number of recrystallization nucleation increases, the average grain size decreases, and the grain size distribution becomes uniform with the increase of cold rolling reduction rate of high grade unoriented electrical steel. When the cold rolling pressure is increased to 87.0% and the thickness is reduced to 0.30mm, the heating rate of the steel plate during annealing is accelerated, the average grain size increases, and the grain size distribution is uneven again.

The power frequency iron loss P1.5/50, high frequency iron loss P1.0/400 and magnetic polarization strength J5000 decrease with the increase of cold rolling reduction rate. The decrease of high frequency iron loss P1.0/400 is higher than that of power frequency iron loss P1.5/50. When the reduction rate of cold rolling increased from 84.7% to 87.0% and the thickness decreased to 0.30mm, the decrease of power frequency iron loss slowed down, and the decrease of high frequency iron loss increased, and the decrease of high frequency iron loss was 11 times that of power frequency iron loss.

 

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