Development history and technological progress of non-oriented electrical steel sheets at Baosteel

This paper briefly summarized the development history, product catalogue and magnetic properties of non- oriented electrical steel sheets at Baosteel, as well as the development and application of high-value-added steel grades. Recent advances in manufacturing electrical steel sheets were also introduced, including technologies for controlling inclusion,for producing high-grade steel strips by a tandem rolling mill and for controlling the transverse thickness difference of steel sheets, and the development of environmentally friendly coatings.

Effect of Boron Content on the Microstructure and Magnetic Properties of Non-oriented Electrical Steels

The effects of boron content in the range of 0-0.0082 wt%, on the inclusion type, microstructurc, texture and magnetic properties of non-oriented electrical steels have been studied. After final annealing, the addition of excess boron（w（B0〉0.004 1 wt%） led to the formation of Fe2B particles. As boron content increased, grain size increased and reached a maximum in steel with 0.004 1 wt% boron. Furthermore, steel containing 0.004 1 wt% boron had the strongest { 100} fiber texture, Goss texture and the weakest { 111 } fiber texture among the five tested steels. Flux density firstly rapidly increased and then suddenly decreased with increasing boron content and reached a maximum in steel with 0.004 1 wt% boron. Conversely, core loss first sharply decreased and then abruptly increased with the increase of boron content and reached a minimum in steel containing 0.004 1 wt% boron. Steel containing 0.004 1 wt% boron obtained the best magnetic properties, predominantly through the development of optimum grain size and favorable texture.

Fatigue Cracking Characterization of High Grade Non-oriented Electrical Steels

The fatigue behavior of 30 WGP1600 non-oriented electrical steel, which is generally used in the motors for electrical vehicles, was investigated. The detailed microstructure and dislocation configurations of the fatigue specimens were examined by OM, SEM, and TEM. The test results showed that fatigue cracks were commonly initiated from the surface grain boundaries, crystals plane, and inclusions. The rapid fatigue crack propagation was characterized by transgranular cleavage fracture, while most transient fracture exhibited ductile tearing characteristics. After cyclic deformation of the non-oriented electrical steels, various dislocation structures, such as short and thick lines, veins, persistent slip bands, cells, and labyrinth, were observed.

High temperature plastic deformation behavior of non-oriented electrical steel

High temperature plastic deformation behavior of non-orientated electrical steel was investigated by Gleeble 1500 thermo-mechanical simulator at strain rate of 0.01-10 s^-1 and high temperature of 500-1 200 ℃. The stress level factor （a）, stress exponent （n）, structural factor （A） and activation energy （Q） of high temperature plastic deformation process of non-orientated electrical steel in different temperature ranges were calculated by the Arrhenius model. The results show that, with dynamic elevation of deformation temperature, phase transformation from α-Fe to γ-Fe takes place simultaneously during plastic deformation, dynamic recovery and dynamic recrystallization process, leading to an irregular change of the steady flow stress. For high temperature plastic deformation between 500 and 800 ℃, the calculated values of a, n, A, and Q are 0.039 0 MPa 1, 7.93, 1.9× 10^18 s^-1, and 334.8 kJ/mol, respectively, and for high temperature plastic deformation between 1 050 and 1 200 ℃, the calculated values of a, n, A, and Q are 0.125 8 MPa1, 5.29, 1.0 × 10^28 s^-1, and 769.9 kJ/mol, respectively.

Efficiency of Model Induction Motor Using Various Non-Oriented Electrical Steels

The performance of a 3-phase 6-pole 400 W inverter-drive induction motor was investigated using a variety of non-oriented electrical steels for stator core at PWM inverter fundamental wave frequencies of 30 to 300 Hz. There existed an optimum Si content of the material depending on the tooth flux density. Both reduction of material thickness and stress-relief annealing of the stator core improved the motor efficiency. The influence of Si content on the efficiency was small at lower PWM frequencies, while at higher frequencies the motor efficiency increased with increasing Si content. The Cu loss WC increased and the Fe loss Wi counteractiveiy decreasedwith increasing Si content at lower frequencies; while at higher frequencies Wi had dominant effect on the efficiency. Newly developed materials RMA, having lower Fe losses after stress-relief annealing and higher flux densities with lower Si contents, showed motor efficiencies superior to conventional J1S grade materials with comparable Fe losses.

Characteristics and application of Baosteel's Cr-free ultrathick J coat for non-oriented silicon steel sheets

Baosteel＇ s Cr-free ultrathick J coat for non-oriented silicon steel sheets has excellent insulation performance and has been successfully applied to middle and large scale electric power trains and wind electric power devices, which have stricter requirements than typical for coat insulation. In this paper, the characteristics and application of this type of coating for non-oriented silicon steel sheets were described in detail.

A Physical Core-Loss Model for Laminated Magnetic Sheet Steels

A full-frequency instant core-loss equation built from the induction physical model of magnetic materials, where the iron loss, eddy loss, and hysteresis loss no longer have an integral term, and this new equation provides high simulation accuracy and performs dynamic core loss analysis on non-sinusoidal or pulse magnetic fields. The simulation examples use a high-grade electrical steel sheet 65CS400 by Epstein experimental data covering magnetic field 0.1 - 1.8 T and frequency 50 - 5000 Hz, and the average error of the simulated core loss is less than 4%. Since the simulation is converged by magnetic physical parameters, so the physical relevance of the similar laminated materials can be compared with the coefficient results. .

Effect of lanthanum on inclusions in non-oriented electrical steel slabs

The effect of lanthanum on the characteristics of inclusions in the slab of non-oriented electrical steels was investigated through industrial trials and thermodynamic analysis.The number,size,and chemical composition of inclusions in the surface,one-quarter of thickness and the center of slabs with and without lanthanum addition were statistically analyzed using an automatic inclusion analysis system.In the lanthanum-free slab,inclusions were predominately MgO.Al_(2)O_(3),MgO,and AlN as well as a small number of Al_(2)O_(3)-MgO-CaO and MgS.The number densities of oxide inclusions and AlN decreased from the surface to the center of the slab,which was ascribed to the difference in cooling intensity during the continuous casting.In the steel with lanthanum addition,inclusions were modified into LaAlO_(3) and La_(2)O_(2)S and gradually transformed into dual-phase MgO-La_(2)S3 with an increasing distance from the slab surface due to the reaction between the lanthanum-containing inclusion and the steel matrix.The uneven distribution of oxide inclusions along the thickness of the slab was eliminated in the lanthanum-bearing slab because the dissolved oxygen was remarkably decreased by lanthanum.Lanthanum-bearing inclusions were more likely to agglomerate AlN by inducing the heterogeneous nucleation of AlN on their surface,while small-size MgO.Al_(2)O_(3) inclusions hardly showed a coarsening effect on the size of AlN.

Effects of External Electric Field on AlN Precipitation and Recrystallization Texture of Deep-drawing 08Al Killed Steel Sheet

The effects of an electric field on AIN precipitation and recrystallization texture were investigated. Cold-rolled 08Al killed steel sheets were annealed at 550℃ according to the two-step processes, for various maintaining times, with and without applying an electric field. It was found that the electric field promotes the precipitation of the second phase （AlN particles）, strengthens the γ-fiber and weakens the α-fiber texture component in the recrystallized specimens. A possible explanation for the reinforcement of γ-fiber texture by the electric field is that the second phase AIN particle promotes the growth of γ-fiber at the expense of differently oriented grains.

Effect of lanthanum content on microstructure and magnetic properties of non-oriented electrical steels

The effect of lanthanum content in the range of 04）.01 1 wt.%, on the inclusion size distribution, microstructure, texture and magnetic properties of three non-oriented electrical steels was studied. After final annealing, lanthanum effectively inhibited the precipitation of MnS precipitates in steel, the formations of La2O2S and LaS inclusions not only acted as nuclei of AlN precipitates, but also combined with A1203 and formed composite inclusions with larger size. Grain size firstly increased and then decreased with lanthanum content increasing. Steel containing 0.0066 wt.% lanthanum obtained the largest grain size, the strongest { 110} 〈 110〉 texture and the weakest { 112}〈110〉 texture among all the tested steels. Magnetic flux density firstly increased and then decreased, core loss firstly dramatically decreased and then slightly decreased with lanthanum content increasing. Among the three tested steels, steel with 0.0066 wt.% lanthanum demonstrated the best comprehensive magnetic properties mainly through the development of favorable texture and appropriate final grain size.

Calculation of AlN and MnS Precipitation in Non-Oriented Electrical Steel Produced by CSP Process

Combining with the study of analogue experiments and test analysis, the kinetics of precipitation and growth of AlN and MnS in non-oriented electrical steel produced by the CSP process is calculated. The results show that the precipitate phase particles of AlN and MnS in typical non-oriented electrical steel grades produced by the CSP process have grown to some extent in the soaking stage, but the precipitation contents are less than 20% of the total contents of nitride and sulfide. The precipitate phase particles of AlN and MnS have precipitated almost after the hot rolling process. The precipitation contents are more than 80% of the total contents of nitride and sulfide, but it is very late for the precipitate phase particles to grow at the end of the hot rolling process.

Effect of Heating Rate on Microstructure Evolution and Magnetic Properties of Cold Rolled Non-Oriented Electrical Steel

The effects of heating rate （ranging from 50 to 300 ℃/s） during the final annealing process on microstructure evolution and magnetic properties of cold rolled non-oriented electrical steel were investigated. It was found that increasing heating rate increased the nucleation temperature and complete recrystallization temperature. At the same time, heating rate increasing could cause the substantially refined structures for the recrystallization grains and this grain refinement would decline when the heating rate was beyond 50 ℃/s. The recrystallization texture exhibited pronounced improvement with heating rate, such as the intensity decrease of 〈111〉//ND （normal direction） fiber and the intensity increase of { 110}%〈001〉 Goss texture component. The texture improvement and grain size refinement caused by heating rate increasing resulted in complicated variation of the magnetic properties. The magnetic induction （B50） keeps increasing while heating rate increases from 15 to 300 ℃/s which is due to the recrystallized texture optimization caused by rapid heating. The core losses （P1.5/50） decrease while heating rate increases from 15 to 100 ℃/s; however, the core losses would increase when heating rate is higher than 100 ℃/s, which is caused by the mean grain size refinement after rapid heating annealing. The results indicate that recrystallization texture and the magnetic properties of the non-oriented electrical steel can be improved definitely by rapid heating during the final annealing treatment.

AlN Precipitates and Microstructure in Non-oriented Electrical Steels Produced by Twin-roll Casting Process

Aluminum nitride （AIN） precipitates and microstructure of 4 wt.% （Si＋AI） non-oriented electrical steel were investigated. The 2.0 mm thick cast strips with three different silicon/aluminum （Si/AI） ratios were produced by twin-roll casting process, then the strips were reheated, warm rolled, cold rolled and annealed. The microstructure and AIN precipitates were characterized using optical microscopy, scanning electron microscopy and transmission electron microscopy. The results showed that with the increase of Si/AI ratio, on the one hand, the casting microstructure changed from columnar grains to equiaxed grains, and the uniformity of annealed microstructure was improved; On the other hand, the number of AIN precipitates in cast strips reduced meanwhile the distribution became dispersed. By the reheat treatment, the size and distribution of the AIN precipitates can be changed. Moreover, the grain size of the annealed strips is in the range of 20-50 #m, at the same time, many AIN precipitates were located at grain boundaries. Therefore, controlling the Si/AI ratio is a simple method to obtain desired microstructure. Then AIN precipitates in non-oriented electrical steel prepared by twin-roll casting process hinder markedly the recrystallized grains growth, A compatible reheat treatment can be an approach worth exploring to control the behavior of AIN precipitates.

Effect of normalization on texture evolution of 0.2-mm-thick thingauge non-oriented electrical steels with strong η-fiber textures

Thin-gauge non-oriented electrical steel sheets of 0.2 mm in thickness with high magnetic induction and low core loss were produced by a two-stage cold-rolling method with and without normalization annealing.The through-process texture evolutions of the two processes were compared and studied by means of X-ray diffractometer and electron backscattered diffraction.Results showed that excellent magnetic properties were attributed to strong η-fiber recrystallization texture in the final sheet.Coarse γ-fiber-oriented grains after intermediate annealing and medium cold-rolling reduction were considered key factors to obtain a strong γ-fiber texture given that a large number of shear bands within the γ-fiber deformed matrix provided dominant nucleation sites for η-fiber-oriented grains.The normalization annealing after hot rolling was favorable for the retention of cube texture,thereby decreasing the magnetic anisotropy of thin-gauge non-oriented electrical steels.

Evaluation of Microstructure and Magnetic Properties in Non-oriented Electrical Steel Strained by Tension

The effects of deformation on the microstructure and magnetic properties of non oriented electrical steels were investigated. Box annealed electrical steel sheets were deformed by tension at four different strains： 3%, 8%, 12 % and 25 % The internal grain misorientation caused by tensile deformation was measured by electron backscat- tering diffraction （EBSD） with grain orientation spread （GOS） as an indicator of the lattice distortion. The experi- mental results showed that the average GOS value increases with the strain. The microstructure and crystallographic texture of deformed samples did not show a significant change in samples strained below 25 %. However, the mag- netic properties were strongly affected： coercivity was directly proportional to the square root of the GOS value and energy losses increased as the strain level was increased.

Effect of pre-annealing prior to cold rolling on the precipitation,microstructure and magnetic properties of strip-cast non-oriented electrical steels

A novel processing route involving strip casting, pre-annealing treatment, cold rolling and recrystallization annealing was applied to a Fe-2.6%Si steel to improve the magnetic properties. The impact of as-cast strip pre-annealing on the microstructure, texture, precipitation and magnetic properties were investigated by electron probe micro-analysis, transmission electron microscopy, and X-ray diffraction analysis,etc. It was found that the precipitation of second-phase particles during strip casting was restrained by rapid solidification. The absence of pre-annealing led to the occurrence of a large amount of 20-50 nm Mn S precipitates in the final annealed sheets, which is responsible for fine grains and high core loss（4.01 W/kg） due to grain boundary pinning effect. Although the microstructure and texture of 900-1000？C pre-annealed samples were similar to those of as-cast strip, significant grain coarsening together with the strengthening of-fiber texture was observed in the 1100？C pre-annealed strips. In comparison with the case of as-cast strip, a higher amount of large-sized precipitates consisting of manganese sulfide and/or aluminum nitride occurred in matrix after pre-annealing. Correspondingly, in the final annealed sheets, the number density of precipitates with sizes smaller than 100 nm was substantially reduced, and100-200 nm and 200-500 nm sized particles became more dominant in samples subjected to 30-min and 120-min pre-annealing treatments respectively. In addition, the average grain size of final annealed sheets increased with the pre-annealing temperature and time because of the weakened pining effect of coarsen precipitates. Ultimately, the magnetic induction of samples subjected to pre-annealing was slightly increased and ranged from 1.73 T to 1.75 T owing to the enhancement of {100} recrystallization texture, and simultaneously the core loss significantly decreased until a minimum of 3.26 W/kg was reached. Nevertheless, large number of 200-500 nm particles presented during pre-annealing for 120 min could weaken the improvement in core loss which is likely associated with the pinning effect on magnetic domain wall.

基于Energetic和改进Jiles-Atherton-Sablik模型的电工钢片动态磁致伸缩特性模拟

准确模拟电工钢片的动态磁致伸缩特性是电工装备铁心振动和噪声分析的关键步骤。该文提出一种基于Energetic磁滞模型和改进Jiles-Atherton-Sablik(J-A-S)模型的电工钢片动态磁致伸缩特性模拟方法。首先,基于静态Energetic磁滞模型和损耗分离理论,考虑由励磁频率引起的动态损耗密度分量,并采用场分离技术建立动态Energetic磁滞模型。其次,将动态Energetic磁滞模型求解的动态磁场强度作为改进J-A-S模型的已知量,从而根据铁磁材料的非线性本构关系,建立以磁感应强度为输入量的动态磁致伸缩逆模型。在此基础上,设计电工钢片动态磁致伸缩曲线的模拟流程。最后,将所提方法的模拟结果与实测结果和现有方法模拟结果进行对比,可知所提方法的模拟结果与实测结果吻合更好,从而验证所提模拟方法的准确性。

Possible influence of sulfur content on magnetic aging behaviors of non-oriented electrical steels

Six non-oriented steel sheets of similar grade produced by different steel companies were used to analyze the magnetic aging behaviors after aging at 200~C for 48 h. It was observed that tiny S atoms, besides C and N, could also induce certain increase of core loss during aging. Thermodynamic calculation indicated that the nucleation driving force of FeS is much higher than those of Fe3C and Fe4N at low temperature, while S atoms, which tend to segregated around dislocations and boundaries, would diffuse rapidly along the crystalline defects while FeS particles would form. Therefore, higher content of tiny S atoms could increase core loss during service time of non-oriented steel sheets.

Formation of Edge Crack in 1.4%Si Non-oriented Electrical Steel during Hot Rolling

Microstructure evolution, dynamic recrystallization, high temperature oxidation and hot ductility of 1.4 % Si non-oriented electrical steel sheets were investigated to reduce edge cracking. The causes of cracking were found to be coarse as-cast microstructure, grain boundary oxidation in reheating furnace, lack of dynamic recrystallization during hot rolling and increase of temperature, resulting in reduced hot ductility in strip edge region. Countermeas- ures against the edge crack are proposed accordingly. Lowering reheating temperature and reducing holding time re- duced oxidation and decarburization. Hot charging temperature was increased to decrease reheating temperature. And using an edger can refine microstructure in strip edge region. Finally, edge heater can be added to increase edge re- gion formability by inducing dynamic reerystallization and ductility by increasing temperature.

一级能效电工钢片比总损耗的精确测量与仿真分析

针对国标爱泼斯坦方圈法测量新一级能效硅钢片比总损耗结果的不确定性问题,本文提出了一种工频下基于双爱泼斯坦方圈的新一级能效硅钢片比总损耗测量方法。通过双爱泼斯坦方圈法测量硅钢片的比总损耗,分析并修正了测量方法中的误差,实现了对爱泼斯坦方圈测量时接缝区和均匀区的损耗分离,并分析了接缝区比总损耗对爱泼斯坦方圈测量结果的影响机理。建立了爱泼斯坦方圈有限元模型,对其接缝区和均匀区的损耗进行研究,仿真结果与双方圈法测量结果吻合,验证了本文提出的新一级能效超低损耗薄硅钢片的比总损耗时测量方法的有效性和准确性。测量和仿真结果表明,基于双方圈法测量薄硅钢片比总损耗的结果比单方圈法测量的结果更精确。本文提出的测量和修正方法可用于一级能效薄硅钢片损耗特性的精确测量。