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.

Formation and Control of Sharp {100}<021> Texture in Electrical Steel

The formation and control of sharp {100}〈021〉 texture in electrical steels were experimentally investigated and the main influencing factors were discussed. The steels of a base composition of Fe-3.2%Si with a certain amount of carbon and manganese were employed to obtain {100}〈021〉 texture through one stage cold rolling and annealing. The results indicated that by careful control of the amount of alloying elements and the annealing temperature, a relatively sharp {100}〈021〉 texture in fairly thick sheets is obtained. After primary recrystallization, a weak component of {100}〈021〉 and strong component of （447） 〈18114〉 texture, which constitute ∑9 coincidence site lattice boundaries with a common 〈011〉 axis for 39° difference, are presented. This special grain boundary promotes the growth of {100}〈021〉 grains in addition to the lower surface energy of （100） grains during secondary recrystallization.

Improved cold rolling workability of warm rolled Fe?6.5wt%Si electrical steel with columnar grains by annealing

The effects of annealing temperature（with the annealing time being constant at 1 h） on the microstructure, ordering, residual stress, mechanical properties, and subsequent cold rolling workability of Fe-6.5wt%Si electrical steel with columnar grains were investigated, where the steel was warm rolled at 500℃ with a reduction of 95%. The results show that recrystallization began to occur in the sample annealed at 575℃ and that full recrystallization occurred in the sample annealed at 625℃. When the annealing temperature was 500℃ or greater, the extent of reordering in the sample was high, which reduced the room-temperature plasticity. However, annealing at temperatures below 300℃ did not significantly reduce the residual tensile stress on the edge of the warm rolled samples. Considering the comprehensive effects of annealing temperature on the recrystallization, reordering, residual stress, and mechanical properties of the warm rolled Fe-6.5wt%Si electrical steel with columnar grains, the appropriate annealing temperature range is 300℃-400℃. Unlike the serious edge cracks that appeared in the sample after direct cold rolling, the annealed samples could be cold rolled to a total reduction of more than 71.4% without the formation of obvious edge cracks, and bright-surface Fe-6.5wt%Si electrical steel strips with a thickness less than 0.1 mm could be fabricated by cold rolling.

Effect of Ball Scribing on Iron Loss of CGO and HGO Electrical Steel

The effect of ball scribing on iron loss of conventional grain-oriented ( CGO) and high-permeability grain-oriented ( HGO) electrical steel was investigated. In this paper,ball scribing was achieved by self- designed ball scribing instrument and a computer-controlled system capable of providing high accuracy and automatic measurements was developed for the magnetisation and measurement at high and low flux densities. The results showed that after ball scribing,iron loss of two types of steel ( C711 and H668 ) apparently decreases ( 5. 5% and 8. 2% respectively after 16mm scribing at 1. 2T) ,and at high and low flux densities, CGO and HGO electrical steel performs differently. Through the formation and development of free magnetic poles and secondary magnetic domains due to compressive stress,primary magnetic domain spacing of grain- oriented electrical steel becomes smaller,which reflects as a reduction of iron loss in the macroscopic magnetic properties. Through iron loss formula derivation,the effect of domain refinement on grain-oriented electrical steel was also interpreted.

Hard magnetization direction and its relation with magnetic permeability of highly grain-oriented electrical steel

The magnetic properties of highly grain-oriented electrical steel vary along different directions. In order to investigate these properties, standard Epstein samples were cut at different angles to the rolling direction. The hard magnetization direction was found at an angle of 60° to the rolling direction. To compare the measured and fitting curves, when the magnetic field intensity is higher than 7000 A/m, it is appropriate to simulate the relation of magnetic permeability and magnetization angle using the conventional elliptical model. When the magnetic field intensity is less than 3000 A/m, parabolic fitting models should be used; but when the magnetic field intensity is between 3000 and 7000 A/m, hybrid models with high accuracy, as proposed in this paper, should be applied. Piecewise relation models of magnetic permeability and magnetization angle are significant for improving the accuracy of electromagnetic engineering calculations of electrical steel, and these new models could be applied in further industrial applications.

Model Transformer Evaluation of High-Permeability Grain-Oriented Electrical Steels

The dependence of transformer performance on the material properties was investigated using two laboratory-processed 0.23 mm thick grain-oriented electrical steels domain-refined with elec-trolytically etched grooves having different magnetic properties. The iron loss at 1.7 T, 50 Hz and the flux density at 800 A/m of material A were 0.73 W/kg and 1.89 T, respectively; and those of material B, 0.83 W/kg and 1.88 T. Model stacked and wound transformer core experiments using the tested materials exhibited performance well reflecting the material characteristics. In a three-phase stacked core with step-lap joints excited to 1.7 T, 50 Hz, the core loss, the exciting current and the noise level were 0.86 W/kg, 0.74 A and 52 dB, respectively, with material A; and 0.97 W/kg, 1.0 A and 54 dB with material B. The building factors for the core losses of the two materials were almost the same in both core configurations. The effect of higher harmonics on transformer performance was also investigated.

Effect of Cutting Techniques on the Structure and Magnetic Properties of a High-grade Non-oriented Electrical Steel

The high grade non-oriented electrical steel sheets containing 3.0%Si were manufacturing processed using different cutting techniques, then they were stress relief annealed（SRA）, the profiles and textures of the cutting edges were compared before and after annealing, and the magnetic properties of these specimens were tested and compared. The experimental results show that the iron loss of the specimen by water jet cutting is the lowest, but the magnetic induction under the low magnetic field is the highest, the iron loss of the specimen by laser cutting is the highest, but the magnetic induction under the low magnetic field is the lowest. It is necessary to adopt suitable production conditions and minimize the deterioration involved, and the magnetic property can be recovered by SRA effectively.

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.

Effect of Typical Elements on the Heredity of Hot-rolled and Annealed Texture in Non-oriented Electrical Steel

Macroscopic texture and microscopic orientation in hot-rolled and annealed sheets of nonoriented electrical steel were studied by XRD and EBSD techniques. The microstructure of hot-rolled and annealed samples was studied by OM. Experimental results indicate that a strong heredity is observed in texture evolution between hot-rolled texture and annealed texture. Typical elements have a large effect on the recrystallization microstructure and texture distribution. The texture distribution through thickness is highly affected by recrystallization in hot rolled sheets. The recrystallization is boosted by Si and Al. Goss grains originate from cracked initial 〈100〉 columnar grains. {110}〈112〉, {112}〈111〉 and {111}〈112〉 grains are related to Goss grains. In subsurface lay of hot rolled sheets, Al can strengthen Goss texture and weaken copper-type texture. {112}〈111〉 texture and {110}〈112〉 texture are strengthened by Si. In the central layers, {100}〈001〉 texture and {111}〈121〉 texture are weakened by Al. {100}〈011〉 texture is increased by Al. Si can increase the proportion of γ-fiber texture and decrease that of {100}〈011〉 texture. In annealed texture, {100}〈001〉 texture and Goss texture are decreased by Al and Si. γ-fiber texture is increased by Si and {111}〈121〉 texture is preferentially increased by Al. The recrystallized grain size is increased and iron loss of annealed sheets is reduced by Al and Si, which means that the magnetic properties are optimized by the Al and Si content.

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.

Low-loss B18R065 and B20R070 grain oriented electrical steels for grade 1 energy efficiency distribution transformers

To reduce distribution transformer losses and carbon dioxide emissions, in recent years, the major countries in the world have issued mandatory standards for high-energy efficiency in distribution transformers. In 2013,China has carried out a new standard GB 20052-2013. To meet the update of the standard and energy efficiency,it is important to enhance the magnetic properties of core materials. The new products B18R065 and B20R070 which are developed by Baosteel, are successfully used for grade 1 energy efficiency distribution transformers. And Baosteel becomes one of the companies which can supply both the 0.20 mm and the 0.18 mm gauge grain oriented electrical steels （GOES） in the world. The development principle, material properties, and transformer performance of B18R065 and B20R070 were introduced,which were expected to be a useful reference for materials selection by transformer manufacturers.

Recent progress of high silicon electrical steels

This paper summarized recent progress of high silicon grain-oriented and non-oriented electrical steels. Technical development in composition adjustment, inclusion control and process optimization was introduced, and future development trend was explored. In addition, a brief introduction was provided to technical progress of high silicon thingauge strips with a Si content of 6.5%.

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.

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 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.

Analysis of Micro-texture during Secondary Recrystallization in a Hi-B Electrical Steel

The understanding of Goss texture in Hi-B electrical steels possesses significant industrial and academic value, thus attracts worldwide attention. The prevailing models for sharp Goss texture formation during secondary recrystallization are CSL （coincident site lattice） boundary theory and HE （high energy） boundary theory. These theories stress the key factor of preferred growth and the difference between them only lies in the specific selection manner. This work examined the texture gradient in primarily recrystallized sheet and demonstrated its possible influence on the formation of secondary grains, and then determined the micro- texture during different stages of secondary recrystallization using EI3SD （electron back-scattered diffraction） technique, finally analyzed a special type of secondary grains with near Brass orientation, which were detected in the later stage of secondary recrystallization, and discussed its origin and effect in terms of surface energy effect. The results indicate that texture gradient in primarily recrystallized sheet will lead to a multi-stage formation of Goss texture, namely, early stage of secondary grains with various orientations in subsurface region, intermediate stage of preferred growth of Goss grains into center layer and re-grow back to the surface and the final stage of Goss grain growth by swallowing slowly the island grains with the help of H2 atmosphere.

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.

Development of Continuous Casting Technology of Electrical Steel and New Products

The development of continuous casting technology of electrical steel was analyzed. The technologies and products characteristics of conventional continuous casting, thin slab continuous casting and rolling, middle thin slab continuous casting and rolling and twin-roll thin strip were compared. Conventional continuous casting technology was widely adopted in producing electrical steel, thin slab continuous casting and rolling and middle thin slab contin- uous casting and roiling technology industrialized electrical steel~ and study of twin-roll thin strip casting technology was focused on fundamental experiments.

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.