The reason of harmonic wave in the magnetic flux density was analyzed according to the magnetic circuit characteristic, distribution of magnetic flux density, magnetic properties of silicon steel sheet and connection mode of excitation winding. Using the spectrum analysis results of magnetic flux density in the frame of the core as the measurement condition, the service properties of GO silicon steel sheet applied to 3D wound core transformer were measured. The basis of the measurement method was proposed by analyzing the magnetic properties of different size GO silicon steel sheets and their application status in 3D wound core. The type selection suggestions was proposed by the test results of different size silicon steel sheets.

The adhesion of insulation coating is an important index to measure the surface quality and applicability of grain oriented silicon steel, and low adhesion will reduce the qualified rate and applicability of products. In this paper, the typical phase and structure characteristics of the surface layer were examined by SEM and EDS, and the influencing factors of insulation coating adhesion was analyzed to provide theoretical basis for improving the adhesion. The results showed that the adhesion level is corelated with the structure of glass layer, and the surface layer of high adhesion samples is mainly composed of continuous layer structure (insulating layer and glass layer) with a total thickness of about 3 μm and spinel particles of 0.5~4 μm.Besides, the glass layer with continuous and uniformly distribution in the matrix and fine embedded spinel particles can improve the adhesion.

The effects of hotrolled coiled temperature on microstructure, texture and magnetic properties of 0.9 % Si  nonoriented electrical steels were investigated based on conventional process. The study found that the coiled microstructure at 650 ℃ was mainly characterized by fine deformed grains, causing the fine and heterogeneous recrystallized annealed grains. Nevertheless, coarse and homogeneous coiled microstructures were obtained at 700 ℃ and 750 ℃, resulting in homogeneous microstructure in final annealed sheets. After coiling, the γfiber texture significantly weakened and λfiber texture increased in the final annealed sheets. The magnetic induction significantly improved with the coiling temperature increasing. Compared to that without coiling, the average magnetic induction (B50) increased by 0.013 T when coiling at 750 ℃. It indicated that the coiling temperature was one of the key factors that affect the magnetic properties.

The 0.1 mm thick Fe3.2%Si0.7%Al ultrathin nonoriented silicon steel were successfully produced by strip casting. The microstructure, texture evolution throughout the whole processing and effect of onestage and twostage cold rolling methods on magnetic properties were investigated in detail. The results showed that the microstructure of cast strip was characterized by typical columnar grains. Equiaxed ferrite grains were obtained after onestage cold rolling and annealing, and the associated texture was dominated by α*fiber and γfiber texture. The magnetic induction B50 of final annealed sheets was 1.681 T, which was much higher than that of ST100 in Japanese. The higher iron loss might be related to the lower purity of steel under laboratory conditions. Therefore, the magnetic induction of nonoriented silicon steels produced by strip casting significantly improved. Compared with the onestage cold rolling method, the grain size of final annealed sheets produced by the twostage cold rolling method was larger, and the unfavorable γfiber texture weakened, resulting in the iron loss obviously reduced and magnetic induction B50 increased from 1.681 T to 1.734 T.

In order to find the reasons for the fluctuation of magnetic properties in the head and tail during the industrial production of nonoriented silicon steel，the microstructure and texture were analyzed by OM, XRD and EBSD techniques. The results showed that: (1)because of the temperature fluctuation, the closer to the tail, the banded structure was more serious, and the banded structure still existed in the core at 25 m from the tail; (2) the average grain size of the head and tail of the strip steel was smaller than that of the middle 7~10 μm, which is the direct cause of the reduction in iron core loss of the head and tail; (3) compared to the middle of the strip steel, the unfavorable texture {111}〈112〉 of the head specimen was reduced by 2.8 %, but the favorable texture {100}〈010〉 was also reduced by 1 %,which resulted in a small difference in magnetic flux density. 

The standard of GB 18613 is an important mandatory national standard in the small and mediumsized motor industry.The development process of the standard was briefly described in this paper, and the changes of the newly issued national standard GB 18613-2020, the impact on the small and mediumsized motor industry and the demand for electrical steel were also introduced. 

During the 13th fiveyear plan period, electrical steel has made important contributions to the modernization construction and people's living needs. The electrical steel industry of China during the period of the 13th fiveyear plan was reviewed from the aspects of production scale, variety and technological progress, patent technology, import and export quantity and industrial shortage. At the same time, some suggestions on the development of electrical steel in China during the  14th fiveyear plan were put forward, which can guide the sustainable and healthy development of electrical steel in our country, guide the correct investment of enterprises, plan the strategy of electrical steel, restrain the structural surplus of electrical steel and avoid the new surplus production capacity.

According to the current development status of new energy vehicles, the effective patent technologies of Nippon Steel Corporation in the field of silicon steel for new energy vehicles were analyzed in the past ten years, and the characteristics of the patent technologies and core patents were also researched.