As a pivotal technique in the manufacturing process of grain-oriented silicon steel, magnetic domain refinement technology has demonstrated remarkable effectiveness in reducing core loss. This paper systematically reviewed the critical factors influencing core loss in grain-oriented silicon steel and elucidated the underlying mechanisms through which domain refinement achieves loss reduction. A comprehensive analysis was conducted on the current research progress of magnetic domain refinement technologies, encompassing both domestic and international advancements. Furthermore, the article provided insightful perspectives on future development trends, addressing technical challenges and potential innovations in this field.

The microstructure and texture evolution of 0.18 mm thickness medium temperature Cu-bearing grain oriented silicon steel during rolling stage were studied by optical microscope (OM) and Electron Back Scatter Diffraction (EBSD) technology. The results showed that the microstructure of the hot-rolled sheet exhibits significant inhomogeneity. The surface layer has the highest texture intensity of {110}〈112〉, while the center layer predominantly features α-texture and rotated cube texture, with a notable presence of Goss grains in the sub-surface layer. After the first cold rolling, the microstructure transforms into a rolling fiber structure with a dominant α-texture. Post-decarburization annealing leads to complete recrystallization, resulting in an average grain size of 12.43 μm, with γ-texture being predominant. The microstructure after the second cold rolling is similar to that after the first cold rolling, with prominent α-texture and γ-texture components.

Due to the high yield strength and high hardness of cold-rolled products with silicon content above 3.0 %, each stand is in a state of high rolling force during rolling, and the bad shape of the strip often occurs, and the strip after rolling presents edge waves or abnormal edge waves. The bad shape of strip with silicon content over 3.0 % in a tandem cold rolling mill of Shougang was analyzed. By adjusting the rolling load of each stand, the value of rolling shift and optimizing the use of rolls, the qualified rate of strip shape can reach over 98 % and the quality of strip shape can be improved.

The production pathway for cold-rolled silicon steel is relatively long, and the process control is complex. The production organization mode of conducting offline magnetic property testing during the final annealing stage of the finished product cannot meet the quality control requirements for correcting process deviations during intermediate stages to enhance product performance stability. In this paper, machine learning algorithms such as XGBoost, LightGBM, and Multi-Layer Perceptron (MLP) were utilized. By comparing the advantages and disadvantages of different algorithms, the magnetic property prediction models using XGBoost and LightGBM algorithms can meet the requirements for selective adoption and application in large-scale production conditions. These models support the prediction of the magnetic property levels of finished products during the production processes of various intermediate stages, thereby guiding process adjustments and ultimately stabilizing the magnetic properties of the final products.

The isolated DC transformer based on high- performance soft magnetic material (SMM) is the key equipment that supports DC collection boost of large-scale new energy, multi-voltage DC networking, and interconnection of DC transmission and distribution. The microstructures and grain orientations of 0.15 mm grain-oriented (GO) silicon steel, 0.10 mm ultra-thin (UT) silicon steel, and 0.025 mm amorphous alloy samples were studied by optical microscope (OM), electron back scatter diffraction (EBSD), and transmission electron microscope (TEM) techniques. The magnetic properties of the threee types of SMM at medium frequencies were researched using an arbitrary waveform magnetic field excitation measurement system. The modeling and simulation analysis of the medium-frequency isolation transformer (MFIT) core and winding in DC transformer were carried out using COMSOL finite element software. Physical models of the MFIT based on the threee types of SMM were built and experimental verification were completed. Results showed that, completely different microstructures of materials lead to different medium-frequency magnetic performance and magnetostrictive noise characteristics. The loss of 0.10 mm UT steel is higher than that of 0.15 mm GO steel at frequencies of 100 Hz~1 kHz. However, the no-load loss of the 0.10 mm UT steel MFIT model is 20.7 % lower than that of the 0.15 mm GO steel MFIT model under the rated condition of 400 Hz/35 kVA. The latter one has the advantage of low loss at frequencies of 100~200 Hz, minimizing noise as well as a large space for capacity expansion. Besides, the amorphous alloy MFIT model has the lowest no-load loss as well as the highest load loss and noise. Application prospects of the threee types of SMM in different scenarios and capacities of isolated DC transformers were discussed.

The causes of non-oriented silicon steel hot rolled edge warping defects are steelmaking protection slag, steelmaking oxide inclusion, casting billet angle crack, hot rolled iron oxide involvement, side guide clamping, etc. According to the causes of different edge warping defects, Al1 protection slag, small chamfering crystallizer and hot rolled side guide clamping without putting were adopted in test measures. The results showed that the incidence of edge warping defects of non-oriented silicon steel has been greatly improved.

To achieve the goal of reducing or eliminating edge trimming in silicon steel production processes and improving the overall yield across the entire production process, further advancements in wedge shape precision control technology during the hot rolling process are required. The core of non-oriented silicon steel wedge shape precision control technology lies in process optimization and parameter adjustment. This paper primarily focused on the research and application of wedge shape precision control technologies for the head, middle, and tail sections of the steel strip. By developing technologies such as pre-setting of roll gap at the start of rolling, stable temperature control during final rolling, load redistribution, and short-stroke guide plate control in finishing rolling, and combining these with the application of high-speed steel rolls, the wedge shape precision of non-oriented silicon steel in the hot rolling process has been improved to over 95.5 %, with the best performance reaching up to 98 %.

This article analyzed the microscopic characteristics and microstructure types of black lines through sampling and scanning electron microscopy. The results showed that the main cause of black lines is the uneven plastic flow of metal during the rolling process of coarse rolling vertical rollers. The main form of black line defects is hot-rolled iron oxide scale, mainly composed of Fe3O4 and Fe-Si spinel compounds. By standardizing the heating temperature, optimizing the distribution ratio of the vertical roll side pressure, optimizing the control of the hot rolling process, and increasing the final rolling temperature of the hot-rolled strip to reduce the rolling in the two-phase zone, the proportion of black line defects at the edge of hot-rolled non oriented silicon steel has been reduced.

This paper analyzed the mechanism and influencing factors of white wire defects on the surface of strip steel during the annealing process of non-oriented electrical steel annealing units. Combined with the structure of the annealing furnace and the actual production situation on site, the causes and locations of white wire defects were analyzed through comparative experiments, on-site investigation, electron microscopy composition analysis, on-site simulation experiments, etc., to accurately locate the location of white wire defects. And control and elimination measures were proposed for such defects, using furnace roller speed fluctuation detection and automatic adjustment methods to improve the accuracy of furnace roller operation, effectively reducing the occurrence rate and quality loss of white line defects.

Non-oriented silicon steel serves as the primary material for fabricating all kinds of motor core, and the insulating coating on its surface has the functions of insulation, corrosion prevention and rust prevention, which helps to improve the energy efficiency of the motor. Through the regulation of coating composition, coating and drying technology, the finished product with excellent surface properties can be obtained. The research progress, types and properties of insulating coatings on the surface of non-oriented silicon steel were introduced, and the coating equipment and drying technology were discussed. Finally, it was pointed out that the development of environmentally friendly and special functional coatings will be the focus of future research.