Fast Measurement of Magnetostriction Coefficients for Silicon Steel Strips Using Magnetostriction-Based EMAT.

Strain gauges and optical methods are commonly used to measure the magnetostriction coefficient of a sample. All these methods require a specific size sample and can only realize offline measurement, which is time-consuming. Therefore, we propose a new method using a magnetostriction-based electromagnetic acoustic transducer (EMAT) to measure the magnetostriction coefficient. The amplitude of the ultrasonic waves generated by the EMAT is applied to characterize the magnetostriction coefficient of a sample. A nonlinear magnetostriction finite element model is established, and the simulation results show that the amplitude of the ultrasonic wave generated by the magnetostriction-based EMAT is proportional to the magnetostriction coefficient of the material. Experiments are carried out on silicon steel strips with different silicon contents. The results show that the method can effectively measure their relative magnetostriction coefficients. Furthermore, the structure of the magnetostriction-based EMAT is optimized to maximize efficiency. The excitation and receiving transducers reach their maximum efficiency when the static magnetic flux densities are 3.5 mT and 6.8 mT, respectively. Moreover, the relative error caused by the vibration reaches the minimal size when the lift-off of the receiving coil is set to 3 mm around. This method is fast and can be applied to online measurement.

Texture-Differentiated Grain Growth in Silicon Steel: Experiments and Modeling.

Grain growth for various texture components in silicon steel was investigated via experiments and modeling. It was found that the clustered spatial arrangement of grains with specific orientations significantly altered the local environment for grain growth and consequently resulted in texture-differentiated grain size distribution (GSD) evolution. A novel local-field model was proposed to describe grain growth driven by continuous changing orientation and size distribution of adjacent grains. The modelling results show that the texture-differentiated grain growth in microstructure with grain clusters can produce a GSD with increased proportion in small-sized range and large-sized range by more than two-times, accompanied with an evident change in area fractions of various texture components. The effect of clustered spatial arrangement on grain growth can be precisely predicted, which is valuable to design and control the texture-differentiated GSD as well as the global GSD.

Study on the Performance of a High-Speed Motor, Considering the Effect of Temperature on the Properties of High-Strength Non-Oriented Silicon Steel.

Considering the high-speed and high power density technical specifications of new energy vehicle motors, there is a growing demand for rotor strength as motor peak speeds reach 20,000 r/min and beyond. The utilization of non-oriented silicon steel with a high yield strength in rotors has emerged as a promising approach to increase motor speed. However, the magnetic and mechanical properties of high-strength silicon steel under variable temperature conditions have not been fully explored, particularly in regards to their impact on motor torque, efficiency, and speed. This manuscript investigates the behavior of high-strength silicon steel before and after annealing and at different temperatures, analyzing its influence on high-speed motor performance. The validity and feasibility of this study are confirmed through prototype testing, providing a comprehensive reference for engineering design.

Harmonic and DC Bias Hysteresis Characteristics Simulation Based on an Improved Preisach Model.

Transformers, reactors and other electrical equipment often work under harmonics and DC-bias working conditions. It is necessary to quickly and accurately simulate the hysteresis characteristics of soft magnetic materials under various excitation conditions in order to achieve accurate calculations of core loss and the optimal design of electrical equipment. Based on Preisach hysteresis model, a parameter identification method for asymmetric hysteresis loop simulation is designed and applied to the simulation of hysteresis characteristics under bias conditions of oriented silicon steel sheets. In this paper, the limiting hysteresis loops of oriented silicon steel sheets are obtained through experiments under different working conditions. The first-order reversal curves(FORCs) with asymmetric characteristics is generated numerically, and then the Everett function is established under different DC bias conditions. The hysteresis characteristics of the oriented silicon steel sheets under harmonics and DC bias are simulated by improving FORCs identification method of the Preisach model. By comparing the results of simulation and experiment, the effectiveness of the proposed method is verified, so as to provide an important reference for material production and application.

Process Parameter Optimization for Laser Powder Bed Fusion of Fe-Si Alloy Considering Surface Morphology and Track Width of Single Scan Track.

A laser power bed fusion (L-PBF) manufacturing process was optimized by analyzing the surface morphology and track width w of single scan tracks (SSTs) on Fe-3.4wt.%Si. An SST was evaluated under process conditions of laser power P, scan speed V, and energy density E = P/V. The SST surface shape was mainly affected by E; desirable thin and regular tracks were obtained at E = 0.3 and 0.4 J/mm. An L-PBF process window was proposed considering the optimal w of SST, and the appropriate range of E for the alloy was identified to be 0.24 J/mm to 0.49 J/mm. w showed a strong relationship with E and V, and an analytic model was suggested. To verify the process window derived from the appropriate w of SST, cubic samples were manufactured with the estimated optimal process conditions. Most samples produced had a high density with a porosity of <1%, and the process window derived from SST w data had high reliability. This study presents a comprehensive approach to enhancing additive manufacturing for Fe-3.4Si alloy, offering valuable insights for achieving high-quality samples without the need for time-intensive procedures.

Evolutions of Cube ({001}<100>) and {115}<161> Orientations in Cold-Rolled Ultra-Thin Non-Oriented Silicon Steel.

In this study, the evolutions of Cube and {115}<161> orientations of a cold-rolled ultra-thin non-oriented silicon steel were investigated using a combination of experimental investigation and the crystal plasticity finite element method (CPFEM). The results show that Cube orientations remain relatively stable when their initial deviation angles from the ideal Cube orientation are less than 12°, even after a 60% cold rolling reduction. However, larger deviations occur due to higher strain near grain boundaries. Furthermore, the {115}<161> orientations, with an initial deviation of ~18° from the ideal Cube orientation, become separated into different orientation regions during cold rolling. Some regions gradually approach the ideal Cube orientation as cold rolling progresses and reach ~12.5° deviation from the ideal Cube at a 40% reduction. This study demonstrates good agreement between simulation and experimental results, highlights the micro-deformation mechanisms during rolling, and offers insights for optimizing the ultra-thin strip rolling process.

Study of High-Silicon Steel as Interior Rotor for High-Speed Motor Considering the Influence of Multi-Physical Field Coupling and Slotting Process.

Currently, high-speed motors usually adopt rotor structures with surface-mounted permanent magnets, but their sheaths will deteriorate performance significantly. The motor with interior rotor structure has the advantages of high power density and efficiency. At the same time, high silicon steel has low loss and high mechanical strength, which is extremely suitable for high-speed motor rotor core material. Therefore, in this paper, the feasibility of using high silicon steel as the material of an interior rotor high-speed motor is investigated. Firstly, the magnetic properties of high silicon steel under multi-physical fields were tested and analyzed in comparison with conventional silicon steel. Meanwhile, an interior rotor structure of high-speed motor using high silicon steel as the rotor core is proposed, and its electromagnetic, mechanical, and thermal properties are simulated and evaluated. Then, the experimental comparative analysis was carried out in terms of the slotting process of the core, and the machining of the high silicon steel rotor core was successfully completed. Finally, the feasibility of the research idea was verified by the above theoretical analysis and experimental characterization.

Micro Characterization of Hot-Rolled Plate of Nb-Bearing Grain-Oriented Silicon Steel.

In this study, niobium was added into grain-oriented silicon steels, four Nb-bearing hot-rolled bands with Nb content range from 0-0.025 wt% were prepared and a detailed study of the micro characterization (microstructure, texture and precipitates) of hot-rolled bands was carried out by various analysis methods, such as EBSD and TEM. The results indicate that the precipitates in Nb-free steel are MnS and AlN; however, in the Nb-bearing steel they are MnS, AlN and Nb(C, N). The precipitates are finer and more dispersed in Nb-bearing steel, and a stronger pining force was obtained, which contributes to the finer microstructure and less recrystallization fractions of the hot-rolled bands. A larger volume fraction and stronger intensity of Goss texture is presented in steel with 0.025 wt% Nb due to the effective inhibiting effect. However, it has little effect on the changes of microstructure and texture when the Nb content is more than 0.009 wt%.

Characterization and Calculation of the Dynamic Recrystallization Texture in Fe-3.0 Wt.% Si Alloy.

High-temperature plane-strain compression tests were performed on Fe-3.0 wt.% Si alloy from 900 °C to 1150 °C at strain rates of 5 s-1 to 1 s-1, and the texture development from different initial textures was investigated by means of electron backscattered diffraction. Dynamic recrystallization occurs by strain-induced boundary migration, and the evolutions of the microstructure and different texture components vary with the initial texture. The critical orientation boundary separating the weakened and enhanced texture components moves with the initial texture, and a quantitative relationship is established to represent the dependence of the critical Taylor factor on the instantaneous texture. A model is proposed to describe the dynamic recrystallization texture by incorporating the oriented nucleation probability with a variable critical Taylor factor. The present work could improve the accuracy of hot deformation texture prediction based on strain-induced boundary migration.

Transient Magnetic Properties of Non-Grain Oriented Silicon Steel under Multi-Physics Field.

High-speed, high-efficiency and high-power density are the main development trends of high-performance motors in the future. At present, the design accuracy of traditional electric machines is already high enough; however, for the future demand of high performance and utilization in special environments (such as aviation and aerospace fields), more thorough research of materials' performance under multi-physics field (MPF) conditions is still needed. In this paper, a test system that combined temperature, stress and electromagnetic fields along with other fields, at the same time, is built. It can accurately simulate the actual complex working conditions of the motor and explore the dynamic characteristics of non-grain oriented (NGO) silicon steel. The rationality of this method is verified by checking the test result of the prototype, and the calculation accuracy of the motor model is improved.

Effects of High-Temperature Annealing Atmosphere on the Secondary Recrystallization Behavior and Magnetic Properties of Fe-3.2%Si-0.055%Nb Grain-Oriented Silicon Steel.

High-temperature annealing is a key step for the secondary recrystallization of grain-oriented silicon steel, which has an important effect on the final sharp Goss texture. In this work, the effects of three different annealing atmospheres during high-temperature annealing (100%H2, 25%N2 + 75%H2 and 50%N2 + 50%H2) on the secondary recrystallization microstructure and texture of Fe-3.2%Si-0.055%Nb low temperature grain-oriented silicon steel were analyzed by optical microscopy (OM) and electron back-scattered diffraction (EBSD) techniques, and the magnetic properties of the samples were compared. The results show that when the high-temperature annealing atmosphere is 100%H2, the texture of the grains with secondary recrystallization is mainly <110>//ND orientation, but the grains without secondary recrystallization have a disordered orientation. When the high-temperature annealing atmosphere is 50%H2 + 50%N2, the secondary recrystallization grains present a Goss texture and brass texture. After high-temperature annealing in the 25%N2 + 75%H2 atmosphere, the sample can be fully recrystallized to obtain secondary recrystallization grains; the grain size is relatively uniform and the texture is mainly a Goss texture with a sharp edge. The content of this reaches 93.1%, the magnetic induction B800 is the highest, reaching 1.89 T, and the iron loss P1.7/50 is the lowest, reaching 1.33 W/kg.

Investigation and Application of Magnetic Properties of Ultra-Thin Grain-Oriented Silicon Steel Sheets under Multi-Physical Field Coupling.

Nowadays, energy shortages and environmental pollution have received a lot of attention, which makes the electrification of transportation systems an inevitable trend. As the core part of an electrical driving system, the electrical machine faces the extreme challenge of keeping high power density and high efficiency output under complex workin g conditions. The development and research of new soft magnetic materials has an important impact to solve the current bottleneck problems of electrical machines. In this paper, the variation trend of magnetic properties of ultra-thin grain-oriented silicon steel electrical steel (GOES) under thermal-mechanical-electric-magnetic fields is studied, and the possibility of its application in motors is explored. The magnetic properties of grain-oriented silicon steel samples under different conditions were measured by the Epstein frame method and self-built multi-physical field device. It is verified that the magnetic properties of grain-oriented silicon steel selected within 30° magnetization deviation angle are better than non-grain-oriented silicon steel. The magnetic properties of the same ultra-thin grain-oriented silicon steel as ordinary non-oriented silicon steel deteriorate with the increase in frequency. Different from conventional non-grain-oriented silicon steel, its magnetic properties will deteriorate with the increase in temperature. Under the stress of 30 Mpa, the magnetic properties of the grain-oriented silicon steel are the best; under the coupling of multiple physical fields, the change trend of magnetic properties of grain-oriented silicon steel is similar to that of single physical field, but the specific quantitative values are different. Furthermore, the application of grain-oriented silicon steel in interior permanent magnet synchronous motor (IPM) for electric vehicles is explored. Through a precise oriented silicon steel motor model, it is proved that the magnetic flux density of stator teeth increases by 2.2%, the electromagnetic torque of motor increases by 2.18%, and the peak efficiency increases by 1% after using grain-oriented silicon steel. In this paper, through the investigation of the characteristics of grain-oriented silicon steel, it is preliminarily verified that grain-oriented silicon steel has a great application prospect in the drive motor (IPM) of electric vehicles, and it is an effective means to break the bottleneck of current motor design.

Effect of Different Austempering Heat Treatments on Corrosion Properties of High Silicon Steel.

A novel high silicon austempered (AHS) steel has been studied in this work. The effect of different austenitizing temperatures, in full austenitic and biphasic regime, on the final microstructure was investigated. Specimens were austenitized at 780 °C, 830 °C, 850 °C and 900 °C for 30 min and held isothermally at 350 °C for 30 min. A second heat treatment route was performed which consisted of austenitizing at 900 °C for 30 min and austempering at 300 °C, 350 °C and 400 °C for 30 min. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) have been used to evaluate the microstructural evolution. These techniques revealed that the microstructures were composed of carbide-free bainite, ferrite, martensite and retained austenite (RA) in different volume fractions (Vγ). An aqueous borate buffer solution with 0.3 M H3BO3 and 0.075 M Na2B4O7∂10H2O (pH = 8.4) was used for corrosion tests in order to evaluate the influence of the different volume fractions of retained austenite on the corrosion properties of the specimens. The results showed that when increasing the austenitization temperatures, the volume fractions of retained austenite reached a maximum value at 850 °C, and decrease at higher temperatures. The corrosion properties were investigated after 30 min and 24 h immersion by means of potentiodynamic polarization (after 30 min) and electrochemical impedance spectroscopy (after both 30 min and 24 h) tests. The corrosion resistance of the samples increased with increases in the volume fraction of retained austenite due to lower amounts of residual stresses.

Finite Element Analysis and Experimental Investigation of Cut Surface Formation of Magnetic Silicon Steel in Shear Cutting.

Shear cutting allows for shaping materials with any length of cutting line with high efficiency and without negative thermal effects, but it causes stresses and deformations in the cutting zone of the material. This has a negative effect on the magnetic properties of the sheet in the areas of the cut edge. The main problem on production lines is to ensure appropriate control of the process so as to obtain the appropriate technological quality of the cut edge, free of not only defects in the form of burrs and shape deviations, but also the minimum deformed zone. This task is difficult due to the large number of control variables, the influence of which on the shaping of the material and the formation of the cut edge is not fully understood. The article attempts to determine the course of the cutting process and to examine the influence of control variables on the formation of the cut edge in the shear-slitting process in which the tools perform a rotary motion. For this purpose, FEM modeling, vision techniques and experimental studies were used. A 3D model of the process was developed, which enables a detailed analysis of the states of stresses, strains, displacements and fracture mechanisms of the material. The simulation results were verified using vision techniques, which were used in the work to observe the flow and cracking mechanisms of the material. Parametric analyses were performed for the process control variables. The research showed a significant influence of the cutting velocity and the clearance between the tools on the formation of the cut edge. The most homogeneous surface of the cut edge with the minimum burr height was obtained for the following parameters: rake angle α = 15-30°, horizontal clearance hc = 0.03 mm and slitting velocity v2 = 15 m/min. The developed results can be useful for controlling the cutting process on production lines in terms of maximum process efficiency while maintaining the appropriate technological quality of the cut edge.

Effect of Grain Size on the Corrosion Behavior of Fe-3wt.%Si-1wt.%Al Electrical Steels in Pure Water Saturated with CO2.

The corrosion behavior of two silicon steels with the same chemical composition but different grains sizes (i.e., average grain area of 115.6 and 4265.9 µm2) was investigated by metallographic microscope, gravimetric, electrochemical and surface analysis techniques. The gravimetric and electrochemical results showed that the corrosion rate increased with decreasing the grain size. The scanning electron microscopy/energy dispersive x-ray spectroscopy and X-ray photoelectron spectroscopyanalyses revealed formation of a more homogeneous and compact corrosion product layer on the coarse-grained steel compared to fine-grained material. The Volta potential analysis, carried out on both steels, revealed formation of micro-galvanic sites at the grain boundaries and triple junctions. The results indicated that the decrease in corrosion resistance in the fine-grained steel could be attributed to the higher density of grain boundaries (e.g., a higher number of active sites and defects) brought by the refinement. The higher density of active sites at grain boundaries promote the metal dissolution of the and decreased the stability of the corrosion product layerformed on the metal surface.

Evolution of the Shear Band in Cold-Rolling of Strip-Cast Fe-1.3% Si Non-Oriented Silicon Steel.

Cube texture and microstructural evolution of as-cast non-oriented silicon steel (1.3% Si) during cold rolling and annealing were studied. The results showed that the as-cast microstructure with grain size in the range of 100-500 µm had a weak texture. The strong orientation was mainly located at {100} and {110} planes. A significant content of shear-deformed grains oriented with {110}<110> were obtained by cold-rolling, and many regions oriented with Cube texture were distributed in the shear bands. During cold-rolling, the orientation of the shear-deformed microstructure tilted towards the {111}<112> orientation, while the matrix orientation retained {110}<110>. On further cold-rolling, the residual part of {110}<110> experienced shear deformation, forming more shear bands, strengthening the Cube orientation. During annealing, Cube orientation grains nucleated in the shear bands leading to strong Cube texture, and corresponding B50 was 1.83T/1.79T.

Influence of Nb Content on Precipitation, Grain Microstructure, Texture and Magnetic Properties of Grain-Oriented Silicon Steel.

The effects of Nb content on precipitation, microstructure, texture and magnetic properties of primary recrystallized grain-oriented silicon steel were investigated by various methods. The results show that the precipitates in primary recrystallized sheets are mainly MnS, Nb(C,N), composite precipitates of MnS and AlN, and composite precipitates of Nb(C,N) and AlN. Adding niobium could refine the primary recrystallized microstructure. The steel with 0.009 wt% Nb possesses the finest and the most dispersed precipitates, which contributes to the finest primary recrystallized microstructure due to the strong pinning force. Adding niobium is beneficial to obtain large volume fraction favorable texture for grain-oriented silicon steel, and the effect of Nb addition is not obvious when the content is higher than 0.009 wt%. After final annealing, the steel with 0.009 wt% Nb shows the best magnetic properties, B800 = 1.872 T, P1.7/50 = 1.25 W/kg.

Effect of Shear Bands Induced by Asymmetric Rolling on Microstructure and Texture Evolution of Non-Oriented 3.3% Si Steel.

In the present work, the microstructure and texture of non-oriented 3.3% Si steel processed by asymmetric rolling (ASR) and subsequent annealing at different temperatures were compared with those obtained when using traditional symmetric rolling (SR). This work aims to reveal the effect of shear bands introduced by the ASR on the microstructure and texture evolution. The ASR sample reaches a recrystallization fraction of 62% at an annealing temperature of 650 °C, which is 32% higher than that of the SR sample annealed at the same temperature. This can be attributed to the abundant shear bands introduced by the ASR, which serve as the heterogeneous nucleation sites for the recrystallized grains. When increasing the annealing temperature to 750 °C, complete recrystallization could be observed in both asymmetric- and symmetric-rolled samples. When using an annealing temperature of 650 °C, the γ-oriented grains were dominant in the surface layer, while strong Goss-oriented grains could be observed in the center in the ASR sample. This is due to the fragmented small subgrains with different orientations in the surface layer inhibiting the nucleation of Goss- and cube-oriented grains during the annealing. In contrast, numerous Goss- and cube-oriented grains were formed in the surface layer after complete recrystallization when the ASR sample was annealed at a temperature of 750 °C. This may be related to the higher thermal energy, which benefits the nucleation of the Goss- and cube-oriented grains. In addition, ASR significantly increased the strength of η-fiber after complete recrystallization when compared with SR. This work might be helpful to design the rolling and the subsequent annealing processes.

Magnetostrictive Properties of the Grain-Oriented Silicon Steel Sheet under DC-Biased and Multisinusoidal Magnetizations.

As an intrinsic property, elasticity of soft material is affected significantly by the externally applied alternating magnetic field. Magnetostrictive properties of the grain-oriented (GO) silicon steel under DC-biased and multisinusoidal magnetizations are measured by using a laser-based measuring system. Magnetostriction curves of the GO silicon steel sheet under different magnetizations are obtained and the influence of frequency and DC bias on the magnetostrictive property is observed and analyzed based on the measured data. In addition, the spectrum of magnetostriction under harmonic magnetization is obtained, and the acoustic noise level of the GO silicon steel sheet represented by the A-weighted decibel value caused by magnetostriction is measured under DC-biased and multisinusoidal magnetizations. The measurement results are applied to the simulation of the three-limb laminated core model, and the effects of DC bias and harmonics on magnetic flux density and displacement are analyzed.

Low-cost Sensors Based on the GMI Effect in Recycled Transformer Cores.

Sensors based on the giant magnetoimpedance (GMI) effect in silicon steelswere constructed. Strips of silicon steels (0.500 mm-thick, 35.0 mm-long) with widthsranging from 0.122 to 1.064 mm were cut from recycled transformer cores. Since amaximum GMI ratio of 300% and a maximum field sensitivity of 1.5%/Oe were observedin a 1.064 mm-wide sample at 200 kHz, the 1.064 mm-wide strips were chosen as sensingelements in a slot key switch, angular velocity sensor, current sensor and force sensor. Thesensing elements were integrated into electronic circuits and the changes in impedancewere monitored. Variations in voltage due to these changes were typically small and musttherefore be amplified by the electronic circuits. For the current sensor and force sensor,the variation in the voltage drop across the GMI sensing element had non-linear variationswith either current or force and a conversion formula from a computer program wastherefore needed. The performance of the systems was tested. These sensing systems werestable, highly sensitive, hysteresis-free and could be produced on a mass scale. Based ontheir GMI effect, the silicon steels are versatile alternative low-cost sensors.