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.

Structure Evolution and Solidification Behavior of Austenitic Stainless Steel in Pulsed Magnetic Field

To understand the solidification behavior of austenitic stainless steel in pulsed magnetic field, the solidification process is investigated by means of the self-made high voltage pulse power source and the solidification tester. The results show that the solidification structure of austenitic stainless steel can be remarkably refined in pulsed magnetic field, yet the grains become coarse again when the magnetic intensity is exceedingly large, indicating that an optimal intensity range existed for structure refinement. The solidification temperature can be enhanced with an increase in the magnetic intensity. The solidification time is shortened obviously, but the shortening degree is reduced with the increase of the magnetic intensity.

Effect of Magnetic Field on the Friction and Wear of Polyamide Sliding against Steel

The present work discusses the friction and wear of polyamide sliding against steel in the presence of magnetic field. Tests were carried out at dry and oil lubricated steel surfaces. Paraffin and vegetable oils such as almond, castor, corn, glycerine, jasmine, olive and sun flower oils were used as lubricants. The friction coefficient and wear were investigated using pin on disc wear tester. Based on the experimental results, it was found that application of magnetic field on the contact area affected both friction coefficient and wear of polyamide sliding against steel at dry and oil lubricated conditions. Magnetic field decreased friction coefficient. Lubricating the sliding surface by paraffin oil as well as almond, castor, corn, glycerine, jasmine, olive and sun flower oils significantly decreased friction coefficient. Generally, friction coefficient increased with increasing applied load. Dry sliding of polyamide against steel surface showed increased wear with increasing load. The lowest wear values at no magnetic field were displayed by jasmine oil followed by sun flower, almond, olive, castor, corn, glycerine and paraffin oils. Under the application of magnetic field, the lowest wear values were displayed by sun flower oil followed by jasmine, castor, glycerine, olive, paraffin, almond and corn oils. It can be concluded that friction and wear decrease observed at dry sliding can be explained on the basis that presence of magnetic field around the contact area decreased the adherence and transfer of polyamide into the steel surface. For oil lubricated sliding, the polar molecules of the tested lubricating oils were much affected by the magnetic field, where they oriented themselves to the polar end directed towards the sliding surface making a close packed multi-molecular layered surface film that could protect the sliding surfaces from excessive wear.

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.

Effect of annealing parameter on microstructure and magnetic properties of cold rolled non-oriented electrical steel

The microstructure and magnetic properties of cold rolled non-oriented electrical steel,annealed at 200-1 000 ℃ for 0-240 min with different heating rates,were investigated by optical microscopy,scanning electron microscopy,Epstein frame,and transmission electron microscopy. The results show that the magnetic properties of cold rolled non-oriented electrical steel can be improved by controlling the annealing process to obtain uniform coarse grains with critical sizes after the recovery,recrystallization and growth of grains. Additionally,the annealing temperature influences the magnetic properties more significantly than annealing time,and with the increase of heating-up rate during the annealing process,the magnetic properties of the cold rolled non-oriented electrical steel increase.

Interactions of Sn and S and their effects on the magnetic properties of non-oriented silicon steel sheets

The interactions of Sn and S and their effects on the magnetic properties of non-oriented silicon steel sheets were discussed in reference to industrial production. Results show that minor amounts of Sn can improve magnetic induction sharply but have little effect on core loss when the S content is below 10 × 10 ^-4%. The precipitation of AlN can be restrained effectively by Sn. Sn, as the nucleus, can remove some of the inclusions with a size of 0.5μm or larger, but has little effect on inclusions smaller than 0.5 μm,which is the key factor affecting core loss. Sn improves the magnetic induction of finished steel sheets mainly through the change of the steel texture. The relationship between the magnetic induction and Sn and S content can be regressed as B50 = 1.69 -4.37 ws ＋0.30 Ws,. From the regression formulation,the magnetic induction can be improved by 0.03 T when 0.01% Sn is added under relatively low S content conditions.

Effect of plastic strain and forming temperature on magnetic properties of low-carbon steel

Claw poles are a key component of automobile generators.The output power performance of the generator is very dependent on the magnetic properties of its claw poles.Plastic deformation is known to significantly change the magnetic behavior of ferromagnetic materials in claw poles.In this paper,changes in the magnetic properties of low-carbon steel,used for claw pole components due to their plastic deformation,were investigated for different strains and temperatures.Ring-shaped material samples were prepared by machining and their magnetic properties were measured.The surface roughness was first evaluated and a machining process with an arithmetic average of roughness Ra 1.6μm was selected as enabling the lowest measurement error.Hysteresis loops at different applied magnetic fields of the material were obtained for different plastic strains and forming temperatures.The magnetic parameters of magnetic flux density,coercivity,and remanence were obtained and compared with magnetic flux density as the primary focus.Results showed that machining,cold forming,and hot forming all led to lower magnetic flux density,larger coercivity,and smaller remanence.Magnetic flux density showed a sharp decrease at the start of plastic deformation,but as the strain increased,the decreasing trend gradually reached a constant value.The decrease was much larger for cold forming than for hot forming.For example,at 500 A/m,the degradation of magnetic flux density with a reduction percentage of 5%at room temperature was about 50%,while that of hot forming at 1200°C was about 10%.Results of this research may provide a reference for the future process design of hot-forged claw poles.

Study on precipitation and transition mechanisms from the magnetic properties of silicon steel during annealing

Precipitates play an important role in determining the mechanical and magnetic properties of silicon steel. This paper aims to investigate the growth kinetics of precipitates in commercial silicon steel by analyzing its magnetic properties during isothermal annealing at 200℃. The growth of precipitates was studied by optical microscopy, scanning electron microscopy, transmission electron microscopy, and magnetic measurements. In combination with the coercive field and initial susceptibility, this technique offers the advantage of being non-destructive and providing quantitative information about the number, mean radius of precipitates, and fraction of transformation. An ob- served decrease in the number of precipitated particles indicates that the transformation starts from particles of appreciable initial size.

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.

EFFECTS OF Sn AND Sb ON STRUCTURE AND MAGNETIC PROPERTIES OF HIGH INDUCTION ORIENTED SILICON STEEL

Effects of Sn and Sb on the structure and magnetic properties of high induction oriented silicon steel have been investigated.The heats with Sn or Sb possess rather fine primary and secondary gram sizes.Sn or Sb promotes the finer AlN particles,increases the amount of pre- cipitated AlN after normalizing and strengthens the ability of inhibition.After decarburizing annealing,the texture components of{110}〈115〉and〈110〉〈001〉tend to increase and form more secondary grain nuclei.

Effect of Stable Magnetic Field on the Phase Transformation of Sr3 Steel

The experimental equipment designed by the author was used to carry out quenching treatments on Sr3 steel, with and without magnet it field in different quenching mediums. The effect of steady magnetic field on the phase transformation of Sr3 steel was studied by metallographic microscope and scanning electron microscope. The result shows: the application of magnetic field can obviously increase the volume fraction of ferrite during the austenite to ferrite transformation of Sr3 steel, promote the ferrite grains refining and homogenization, and get the pearlite beam much homogeneously and much compact, when Sr3 steel is quenched in the water.

MAGNETIC PROPERTY CHANGE IN AN AUSTENITIC STAINLESS STEEL SUBJECTED TO DAMAGE AT ELEVATED TEMPERATURE-MICROSTRUCTURE RESPONSIBLE FOR MAGNETIC PROPERTY

It has been found that magnetic property changes in austenitic stainless steel subjected to creep at high temperature. The change of magnetic property is mainly due to decrease the chromium concentration in the vicinity of grain boundary and transform into martensite in the area. However this result is for short-term creep. It is necessary to evaluate the long-term creep in order to develop non-destructive technique for plants. Moreover it is important to evaluate the fatigue. The change of magnetic property for those damages at high temperatures is investigated. The transformation into martensite is observed for both the long-term creep and fatigue. The magnetic regions are observed in sever deformed area and near crack. Then the formation of magnetic phases is related to the damage. The damage at high temperature can be universally evaluated.

A Dynamics Study of a Magnetic Flux Leakage(MFL) Signal and its Application to Defect Location Discrimination in Steel Pipes MFL Testing Equipment

Difference processing was used to the direct current magnetic flux leakage （DC-MFL） signal, emanating from the defects machined artificially on the internal and external surfaces of a steel pipe. Consequently, the loea-tion discriminating index 8 was provided to identify the defect whether it is on the internal surface or the external one. Three characteristics, shape, depth and orientation of the defect, were discussed through a series of experiments on the artificial defects, such as transverse notches, oblique notches and pits on the steel pipe. The approach has been verified effective to address the defect location identifying problem, albeit the limits on the accuracy assessment to those natural defects on steel pipes in service.

Primary Recrystallization of Grain Oriented Silicon Steel Strip Rolled by CSR and Annealed in Magnetic Field

The magnetic properties and textures of grain oriented silicon steel with different thickness rolled by cross shear rolling （CSR） of different mismatched speed ratio （MSR） and annealed in magnetic field under hydrogen were presented.Effects of the factors such as thickness and mismatched speed ratio on the magnetic properties and recrystallization texture were analyzed and the recrystallization principles in magnetic field annealing were discussed. The study would provide a new route for mass production of high quality ultra-thin grain oriented silicon steel strip.

Effect of an upward magnetic field on nanosized sulfide precipitation in ultra-low carbon steel

An induction levitation melting （ILM） refining process is performed to remove most microsized inclusions in ultra-low carbon steel （UCS）. Nanosized, spheroid shaped sulfide precipitates remain dispersed in the UCS. During the ILM process, the UCS is molten and is rotated under an upward magnetic field. With the addition of Ti additives, the spinning molten steel under the upward magnetic field ejects particles because of resultant centrifugal, floating, and magnetic forces. Magnetic force plays a key role in removing sub-micrometer-sized particles, composed of porous aluminum titanate enwrapping alumina nuclei. Consequently, sulfide precipitates with sizes less than 50 nan remain dispersed in the steel matrix. These findings open a path to the fabrication of clean steel or steel bearing only a nanosized strengthen- ing phase.

Effects of calcium treatment on non-metallic inclusions and magnetic properties of non-oriented silicon steel sheets

Based on the industrial production of non-oriented silicon steel,calcium treatment by CaSi wire feeding during the RH refining process was studied. The thermodynamics of CaS inclusion formation was analyzed, and the morphology and the size distribution were observed. Furthermore, the change in inclusion characteristics after calcium treatment and the effect of calcium treatment on magnetic properties were discussed. The results show that the formation of MnS and A1N inclusions were restrained, and the aggregating, floating and removing of microinclusions after calcium treatment were effectively promoted. The cleanliness of liquid steel was obviously increased. The main type of inclusions was single phase of CaO, with some complex inclusions composed of CaO, SiO2 and MgO. No CaS inclusion was observed after an appropriate calcium treatment. The size of all inclusions was distributed in the range of 2 - 20 μm, and the number was about 1.8 × 10^5/mm3. In addition, as an increasing amount of calcium was added,the core loss gradually decreased to a stable level, and the magnetic induction decreased quickly after a slow increase. The optimal calcium treatment mode depends on the chemical composition of steel.

Effects of tin and sulphur on magnetism and its interaction in effecient non-oritened silicon steel

Based on the manufacture of efficient non-oriented silicon steel grade,the effects of tin and sulphur on magnetism and its interaction was discussed.The results showed that for present work,minor tin could improve magnetic induction sharply and had little effect on core loss when the sulphur content below 10×10^(-4)%.The precipitation of AlN could be prohibitted by tin,remarkably.As the nucleus,tin could removal any inclusions which size was 0.5μm or above,and had little effect on inclusions which size was below 0.5μm as a key factor for core loss.For final sample,the magnetic induction was improved through the change of steel texture by tin.The relationship between magnetic induction and tin,sulphur content could be regressed:B = 1.69 - 4.37S + 0.30Sn.From the regression formulation,magnetic induction could be improved for 0.03 T when 0.01%tin was added under the condition of relatively low sulphur content.

MAGNETIC ACOUSTIC EMISSION CHARACTERISTICS OF HYDROGEN ATTACKED LOW CARBON STEEL

Hydrogen attack occurred in low carbon steel and steel 25CrMo which had been exposed in hydrogen under 18MPa at 450 and 500℃ for 240,480 and 720 h.The methane bubbles and microcracks grow along grain boundaries.The degree of hydrogen attack increases with increasing exposure time and temperature.Magnetic acoustic emission(MAE) was used to detect the degree of hydrogen attack.The results show that the characteristics of MAE for samples of low carbon steel and steel 15CrMo with hydrogen attack have changed obviously comparing to the samples without hydrogen attack,and the MAE signals was sensitive to the degree of hydrogen attack at the last stage of hydrogen attack.The magnetic detection way,as a new method of nonrestrictive testing of hydrogen attack,can be used to detect the hydrogen attack in practice.

脉冲磁场对GCr15轴承钢网状碳化物的影响

在GCr15轴承钢的球化退火过程中施加脉冲磁场,研究脉冲磁场对其组织形貌和力学性能的影响,探讨脉冲磁场作用下网状碳化物溶解的热力学和动力学机理。结果表明:随着施加脉冲磁场时间的延长,GCr15轴承钢中沿晶界分布的碳化物由封闭网转变为半网,当施加脉冲磁场时间为20 min,晶界处的网状碳化物消失。这主要是由于施加脉冲磁场后,在热力学方面网状碳化物溶解的势垒降低,动力学方面原子扩散系数增大,这都促进了网状碳化物的溶解。随着施加脉冲磁场时间的延长,GCr15轴承钢的抗拉强度(R_(m))和屈服强度(R_(p0.2))基本保持不变,伸长率(A)提高了18%(从5 min的33%提高到20 min的39%),断面收缩率(Z)提高了13%(从5 min的61%提高到20 min的69%)。

磁场与应力耦合作用下电工钢磁畴动态观测与磁滞特性模拟

电工钢等磁性材料是构成电力变压器、中高频变压器等电气设备磁路的关键材料,其磁滞特性决定着设备损耗,磁滞特性的本质体现为磁化过程中电工钢内部磁畴畴壁的移动和磁畴的翻转,而外应力的引入会改变电工钢磁畴结构。该文针对磁场和应力耦合作用下取向电工钢磁滞特性的模拟问题,借助应力磁光克尔显微镜观测了应力影响下磁畴动态磁化规律,揭示电工钢内部磁畴动态演变机理。在此基础上,利用图像处理技术获取了耦合外作用下畴壁移动的位移、速度以及加速度等特征量,并以磁畴能量最小化为理论基础,以畴壁移动加速度作为特征量构建表征模型用以模拟电工钢的磁滞特性。结果表明:提取的特征量可直观地了解电工钢内部磁畴在不同应力下的演变过程,基于畴壁移动加速度特征量的磁滞模型能够有效描述电工钢在不同应力下的磁滞特性。研究成果建立了磁畴磁化特征量与材料宏观磁滞特性的映射关系,为磁性材料改性研究提供一定理论支撑。