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.

STUDY ON REDUCING THE CORE LOSS OF GRAIN ORIENTED SILICON STEEL AND IMPROVING ITS AGING PROPERTY BY LASER NITRIDING TECHNIQUE IN ATMOSPHERIC AMBIENT

CW-CO2 laser nitriding technique was applied to improve the properties （such as aging property and the core loss） of grain oriented silicon steel. The samples were nitrided with regular space. Laser power density and scanning speed were chosen as 7.8×10^5W·cm^-2 and 100mm·min^-1. By some laser irradiation, Fe4N and Fe3N were formed in the nitrided zone. The nitrided samples were annealed at the temperatures ranged from 100 to 90℃. The core loss of some interested samples was tested. The results show that the core loss of the nitrided samples with different thickness of 0.23 and 0.30mm decreased by 14.9% and 9.4% respectively, and the aging property were improved up to 800℃. The mechanism of laser nitriding to improve the properties of grain oriented silicon steel is discussed.

Effect of Ball Scribing on Power Loss Separation of Fe-3%Si Grain-oriented Silicon Steel

Power loss of Fe-3%Sigrain-oriented silicon steelwas measured after ballscribing with different spacing using a self-designed tool.Three different sections of power loss,including hysteresis loss,abnormalloss,and eddy current loss,were measured and calculated,respectively.The loss variation and ratio were analyzed based on the experimentaldata.At 1.0 T,hysteresis loss of tested steelwith scribing spacing of 8 mm descends by 8.2% compared to samples without scribing,which is similar to the totalloss variation,and abnormalloss descends by 16.8%.At 1.0 T,hysteresis loss ratio of the steelwith scribing spacing of 16 mm ascends from 55.7% to 57.9%,and eddy current loss increases from 17.4% to 24.1%,while abnormalloss descends from 26.9% to 23.7%.The experimentalresults show that the reduction of power loss after scribing is mainly due to decreasing of hysteresis loss and abnormalloss.

Effects of Primary Annealing Condition on Recrystallization Texture in a Grain Oriented Silicon Steel

The recrystallization texture in grain oriented silicon steel sheets, which were annealed at different primary annealingtemperatures with and without an electric field, was investigated. An automated electron backscattered diffraction(EBSD) technique was used to analyze the recrystallization texture. It was found that recovery and application ofelectric field in primary annealing lead to an increase of {001} component and a decrease of {111} component afterannealing at 900℃. The development of recrystallization texture can be explained in terms of the effects of electricfield and primary annealing temperature on recovery.

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.

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.

Development of top high-grade non-grain-oriented silicon steels at Baosteel

The development, production and application of top high-grade non-grain-oriented （NGO） silicon steels at Baosteel were introduced in this paper. Top high grades refer to the highest grades in the intemational silicon steel product standard and above. B35A230 and B50A250 were developed at Baosteel in 2009 and have been used in inverter compressors for air-conditioners, small transformers and big hydropower generators in the Three Gorges project. Small- batch production of B35A210 and B50A230, which exceed the highest grades listed in the intemational silicon steel product standard,began in 2010. That was a breakthrough in the silicon steel making history in China. Presently,Baosteel＇ s high- grade NGO products have passed the strict qualifications of the three major electric power equipment manufacturers in China and the leading international power equipment suppliers like ALSTOM, GE, SIEMENS, VESTAS, etc. These products are characterized by low iron loss, low anisotropy, good punchability and a high lamination factor. They have been used in the 770 MW hydropower generator at Xiluodu Power Station in the three gorges area, 1 000 MW thermal power generators and 2.5 MW wind power generators.

热轧加热对无取向硅钢中AlN和MnS析出相的影响

AlN和MnS等析出相对无取向硅钢的磁性能有重要影响,受热轧加热工艺影响,无取向硅钢中的析出相与免常化工艺实现的效果紧密相关。以1.5%Si-0.3%Al无取向硅钢锻造坯为研究对象,利用热力学软件计算钢中可能的析出相,使用箱式电阻炉在不同温度和保温时间下对实验钢进行热轧加热实验,利用光学显微镜(OM)、扫描电子显微镜(SEM)表征分析析出相的形貌、尺寸及样品晶粒尺寸,研究热轧加热温度和保温时间对实验钢中AlN和MnS析出相的影响。结果表明:实验钢中夹杂物主要为AlN和MnS,当加热温度为1050℃时,保温时间由1h延长至3 h,细小的AlN和MnS析出相(直径小于1μm)占比由33%降至19%,平均晶粒尺寸从100.0μm增加到149.7μm;保温时间为1h时,加热温度由1050℃提高至1150℃,细小的AlN和MnS析出相占比由33%降至7%,平均晶粒尺寸从100.0μm增加到124.3μm。不改变其他实验条件,热轧加热温度的提高与保温时间的延长都会使实验钢中AlN和MnS析出相与晶粒尺寸变大,有利于绿色低碳的无取向硅钢免常化生产工艺的实现。

取向硅钢细化磁畴技术研究进展

细化磁畴技术是取向硅钢生产过程中重要的技术手段之一,可有效降低带材损耗。介绍了取向硅钢损耗的影响因素、细化磁畴降低铁损的原理,同时对两种类型细化磁畴技术的原理和研究现状进行了综述。非耐热型细化磁畴技术相对成熟稳定,已实现工业应用。耐热型细化磁畴技术目前被少数企业所垄断,国内仅宝钢掌握大功率激光刻痕细化磁畴技术,而其他耐热型细化磁畴技术更多处于实验室研发阶段,无法应用于工业生产。在能源结构调整、电工装备要求不断提升的背景下,对耐热型取向硅钢提出了更多的需求,未来耐热型细化磁畴技术将成为取向硅钢细化磁畴技术的一个重点研究方向。

激光刻痕降低取向硅钢铁损的研究现状

激光刻痕是降低取向硅钢铁损的有效手段,也是目前唯一在工业生产中得到广泛应用的刻痕技术。本文列举了细化取向硅钢磁畴的各种技术及其优缺点,综述了激光刻痕系统的种类和特点及其研究现状,并对激光刻痕技术的发展进行了展望。

硅溶胶粒径对取向硅钢绝缘涂层性能的影响

为了探究不同粒径硅溶胶对取向硅钢绝缘涂层性能的影响,分别对使用至少一种粒径硅溶胶的绝缘涂液及涂层性能进行研究。实验表明:使用小粒径硅溶胶的涂液更稳定,并且能提升涂层与底层的结合程度,具有较大的硬度和较小的铁损;使用大粒径硅溶胶能提升涂液的润湿性能,并能有效提升涂层光泽度,使涂层更容易结晶,按照一定比例混合时还能略微提升涂层的耐腐蚀性能。

Inhomogeneous Distribution of Second Phase Particles in Grain Oriented Electrical Steels

The second phase particles were observed during the whole manufacturing process of conventional grain oriented electrical steels, exhibiting that the areal density of particles in the center was obviously higher than that on the surface at each manufacturing stage. After hot rolling, the approximately equiaxed grains formed upon recrystallization were present on the sheet surface while the deformation structures were retained in the central part. Thus, the dislocation density on the surface was evidently lower than that in the center and this trend became more noticeable after the first cold rolling. Since new precipitates were mainly nucleated at dislocations during both hot rolling and annealing following cold deformation, the difference in dislocation density resulted in the inhomogeneous distribution of particles through the thickness of sheet. According to this, Goss grains, which were usually found near the surface, tended to grow up more easily during the secondary recrystallization treatment.

Correlation between Primary and Secondary Recrystallization Texture Components in Low-temperature Reheated Grain-oriented Silicon Steel

Low-temperature slab-reheated grain-oriented silicon steel is characterized by a sharp {411}〈148〉 primary recrystallization texture. To date, the influence of this texture on secondary recrystallization is not clear. Microtextures in primary and secondary reerystallized sheets of low-temperature reheated grain-oriented silicon steel were examined using electron backscatter diffraction. By comparing the textures and microstructures of specific primary reerystallized grains neighboring secondary grains with those of other primary grains, the influences of primary re- crystallization textures and microstructures on the orientations of secondary grains were investigated. Results show that for low-temperature reheated graiworiented silicon steel, the primary recrystallization sheet comprises { 411 } 〈148〉, {111}〈112〉, and {001}〈120〉 texture componems. During secondary recrystallization, the {111}〈112〉 primary recrystallized grains were easily consumed by abnormally grown Goss, deviated Goss, Brass, or {210}〈001〉grains ;the { 411 }〈148〉 primary recrystallized grains were more resistant to being swallowed; and the {001} 〈120 grains were the most resistant to being consumed. For a particular primary grain, the distribution of its surrounding grain boundaries determined how easily it is consumed during secondary recrystallization. Primary grains surrounded by 20°- 45° grain boundaries were consumed much earlier than those having grain boundaries above 45°, which is in accordance with high-energy grain boundary theory. In addition, special ∑9 boundaries between {411}〈148〉 and Goss grains move more slowly than ∑9 boundaries between {111 }〈112〉 and Goss grains, which is attributed to the different positions of 〈110〉 rotation axis with respect to the normals of grain boundaries.

Effect of Initial Goss Texture Sharpness on Texture Evolution and Magnetic Properties of Ultra-thin Grain-oriented Electrical Steel

In this study, high- and low-grade grain-oriented electrical steels were used as the initial materials to produce 0.08-mm-thick sheet with one-step cold-rolling method. Electron backscattering diffraction analysis technique and X-ray diffraction texture analysis technique were adopted to investigate the effect of initial Goss texture sharpness on texture evolution and magnetic properties of ultra-thin grain-oriented electrical steel. The results showed that primary recrystal- lization and secondary recrystallization were the main processes that occurred during annealing. The induced factors for secondary recrystallization of two grades samples were not Consistent. The high-grade samples presented texture induction mechanism, while the low-grade samples revealed strong surface-energy induction mechanism. The initial Goss texture sharpness had a great impact on texture evolution and magnetic properties of ultra-thin grain-oriented electrical steel. The Goss texture component formed after primary recrystallization was stronger, and better magnetic properties were obtained at low frequencies. For low-grade samples, secondary recrystallization enhanced the intensity of Goss texture, and both grain size and texture contributed to better high-frequency magnetic properties after secondary recrystallization. By controlling the annealing process, the magnetic properties of low-grade products could be significantly improved, thus achieving conversion from low-grade to high-grade products.

Abnormal Growth of Goss Grains in Grain-oriented Electrical Steels

With the help of electron back scattering diffraction techniques and field emission microscope, the misorienta- tion and the precipitation environment of Goss grains in conventional grain-oriented steel were observed and investigated at the initial stage of secondary recrystallization. It reveals that the abnormal Goss grains have a high fraction of high angle boundaries ranging from 25 to 40 deg. The most important observation is that some of {110}〈001〉 grains in matrix indicated higher particle density than their neighbor grains during final annealing at 875℃ before secondary recrystallization, which could create a favorable environment for their abnormal grain growth. Based on misorientation and precipitation results, the abnormal growth mechanism of Goss grains was sketched.

Effect of Ball Scribing on Magnetic Barkhausen Noise of Grain-oriented Electrical Steel

Effect of ball scribing on magnetic Barkhausen noise （MBN） of conventional grain-oriented （CGO） and high- permeability grain-oriented （HGO） electrical steel was investigated. The results showed that after ball scribing, root mean square of MBN （MBNrms） of CGO electrical steel increased 9.8% with 4 mm scribing spacing at 1.2 T, and that of HGO electrical steel apparently decreased 17.3% with 16 mm scribing spacing at 1.2 T. Through the formation and development of free magnetic poles and secondary magnetic domains due to compressive stress, primary magnetic domain space of grain-oriented electrical steel becomes smaller, which reflects as a variation of MBN in the macroscopic magnetic properties. Through correlation formula derivation of MBNrms and equilibrium distance between domain walls, effect of domain refinement on grain-oriented electrical steel was also interpreted, and optimum equilibrium distance between domain walls was determined.

Efect of Ball Scribing on Relative Permeability of Grain-oriented Electrical Steel

Efect of ball scribing on relative permeability of conventional grain-oriented（CGO） and high permeability grain-oriented（HGO） electrical steel was investigated. The samples were scribed with spacing of 2 mm, 4 mm, 8 mm and 16 mm. The results show that after ball scribing with 16 mm width at 1.0 T, relative permeability of both℃GO and HGO steels was increased by 109% and 80%, respectively. Relative permeability rises as the scribing space increases, with the movement of the peak value of relative permeability to a higher flux density. Relational models describing relative permeability and flux density were constructed with high accuracy based on experimental data. The experimental data curves were analyzed during the magnetizing process.

Characteristics of LDPE and Oriented Montmorillonite Nanocomposites Produced by Electric Field-inducement

In order to make montmorillonite (MMT) nanosheets disperse in low-density polyethylene (LDPE) with highly homogeneous orientation, alternating voltage is applied to molten LDPE with MMT nanosheets. The effect of electric field on the dispersion of MMT in the solidified LDPE is studied. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses suggest that the MMT nano- sheets are aligned with high anisotropy to the electric field direction, which is perpendicular to the LDPE film plane. Differential scanning calorimetry (DSC) results reveal that the crystallization degree of the oriented LDPE/MMT composite increases. Moreover, through a broadband dielectric spectroscopy analyzer, it is found that MMT manifests a significantly influence in the dielectric property of the oriented composite: the dielectric constant and loss tangent of the composite both become larger. Analysis shows that the electric field-induced torque caused by the polarization of MMT flakes is the main force inducing the orientation of the MMT flakes.

激光刻痕工艺对取向硅钢铁损降幅影响规律研究

以0.27 mm规格高磁感取向硅钢为研究对象,研究了激光刻痕功率、刻痕频率、刻痕速度及刻痕间距等参数对取向硅钢铁损降幅及磁畴结构的影响。结果表明,不同工艺刻线形貌及磁畴结构存在差异性,其中低刻痕功率、高刻痕频率和刻痕速度下,刻线呈现浅轻形貌,磁畴呈不均匀散乱分布。该牌号优化刻痕工艺参数为:刻痕功率30%、刻痕频率50 kHz、刻痕速度500 mm/s、刻痕间距5 mm,磁畴细化效果好,相应铁损降幅达9.47%。此外,在激光刻痕参数交互作用下,铁损降幅随激光能量密度增大而显著增加,但激光能量过大会加剧破坏取向硅钢应力涂层,不利于磁畴细化和提高铁损降幅。

考虑各向异性和模型参数应力依赖关系的改进Sablik-Jiles-Atherton磁滞模型

机械应力会显著改变取向电工钢片的磁滞特性。Sablik-Jiles-Atherton(S-J-A)磁滞模型由于计算简单、物理含义明确,被广泛用于模拟机械应力作用下的磁滞特性,然而此模型存在模拟精度低的问题。为此,该文在现有S-J-A磁滞模型的基础上,考虑取向电工钢片本身的各向异性和由机械应力引起的各向异性,实现对无磁滞磁化强度表达式的修正;在此基础上,根据机械应力对取向电工钢片磁畴排列模式的影响,引入无磁滞磁化强度形状系数和钉扎系数对机械应力的依赖关系,提出一种改进的S-J-A磁滞模型;最后,以30QG120型取向电工钢片为例,应用所提改进模型模拟了不同机械应力下的磁滞回线,通过与实验测量和现有模型进行对比,验证了所提改进模型的准确性。