Calculation of the mean path length of the Epstein frame under non-sinusoidal excitations using the double Epstein method

This paper discusses the effect of non-sinusoidal excitation on the mean path length of the Epstein frame. Two different steels, a non-oriented (NO) steel and a high-permeability grain-oriented (HGO) electrical steel have been tested under pure sinusoidal and non-sinusoidal excitations and the mean path length of the Epstein frame has been re-calculated. Results indicate that the actual mean path of the Epstein frame depends not only on the material permeability and anisotropy but also on the peak flux density and magnetising frequency. The amount of distortion of the excitation frequency also has an effect on the value of the actual mean path length of the Epstein frame.     

Effect of initial grain size on texture evolution and magnetic properties in nonoriented electrical steels

The magnetic properties of nonoriented electrical steels are influenced by the grain size and crystallographic texture. The technologies used to control the grain size in nonoriented electrical steels are approaching their limits. However, there is still some room for improvement of the magnetic properties through texture control. Hot-band annealing is known to be one of the most effective processing stages for texture modification. In this study, two types of initial grain sizes prior to cold rolling are obtained by different hot-band annealing. The effect of initial grain size on texture evolution and magnetic properties in nonoriented electrical steels containing 2% Si is examined. The specimens having different initial grain sizes have significantly different textures in the cold-rolled state and the annealed state. During the recrystallization stage, new grains formed in the coarse-grained specimens have stronger Goss but weaker γ-fibre texture than those in the fine-grained specimens. During the grain growth after complete recrystallization, the coarse-grained specimens still have weaker γ-fibre texture than the fine-grained specimens. The magnetic induction of the coarse-grained specimens is always higher at the same temperature than that of the fine-grained specimens. The core loss of the coarse-grained specimens is lower at the same temperature than that of fine-grained specimens. However, the improvement of the core loss becomes less pronounced as the annealing temperature increases.     

Effects of manganese and sulfur contents and slab reheating temperatures on the magnetic properties of non-oriented semi-processed electrical steel sheet

The effects of manganese and sulfur contents and slab reheating temperatures (SRTs) on the magnetic properties of non-oriented semi-processed electrical steel sheets were investigated. The core loss W15/50 of the steels increases with an increase of sulfur content in each steel with different manganese contents, while, the magnetic induction B50 hardly changed with an increase of the sulfur content at any manganese level. The SRTs affect the core loss in steels without hot band annealing, and in steels processed at an SRT of 1273 K showed the lowest core loss. Steels with higher sulfur content processed at an SRT of 1523 K showed deterioration of the core loss caused by the retardation of the grain growth at the recrystallization annealing by the fine MnS (ca.0.1 μm in diameter).     

The influence of compressive stress applied by hard coatings on the power loss of grain oriented electrical steel sheet

To reduce the core loss of electrical steel the vacuum arc ion plating technique has been used to deposit titanium nitride (TiN) layers on highly grain oriented electrical steel sheets. The layer thickness, the stresses of layers and coated sheets and the achieved reduction in core losses have been measured as functions of coating duration and applied bias voltage. Well adhered layers with high compressive stress up to 6.8 GPa have been produced. With increasing bias voltage the layer thickness decreases and the intrinsic stress of the layers increase. A further increase of bias voltage leads to a drop in stress due to thermal relaxation. In general, the tensile stress of the coated sheets rises with increasing layer thickness while the core loss of the coated material decreases with increasing tensile stress of the steel sheet and increasing bias voltage. The highest reduction of core loss has been found to be 28% (from P_1.7=0.86 W/kg for commercially coated HGO electrical steel sheet with glass film to 0.62 W/kg for TiN coated material) and is due to the reduction of excess loss only.     

Texture measurement of grain-oriented electrical steels after secondary recrystallization

The measurement of the final Goss texture sharpness in grain-oriented electrical steels is a challenging task due to the immense grain size ranging from millimeters to centimeters. Although, it is widely claimed in the literature that the orientation deviations from the ideal Goss orientation lie in the range of about 7° for conventional grain-oriented steel and in the range of about 3° for high permeability grades, no precise investigation with an appropriate statistical relevance is known to the authors.     

Magnetostriction measurements on the multidirectional magnetization performance of SiFe steel

By means of a 3-phase excited rotational single sheet tester in combination with three sets of strain gauges, multi-directional magnetostriction (MS) was studied for highly grain oriented (HGO) SiFe. Emphasis was put on a new type of material with hyper-stress coating based on titanium nitride. Experiments were performed for elliptical, Lozenge-type and circular magnetization. In all states that are relevant for practice, the new type showed lowest levels of MS, especially for the rolling direction and the normal direction. By means of a domain model, which is based on the results of MS, the superior behavior is explained by a suppression of oblique domains.     

Effect of annealing prior to cold rolling on magnetic and mechanical properties of low carbon non-oriented electrical steels

The effects of annealing prior to cold rolling on the microstructure, magnetic and mechanical properties of low-C grain non-oriented (GNO) electrical steels have been investigated. The grain structure of hot-rolled electrical steel strips is modified by annealing at temperatures between 700 and 1050 °C. Annealing at temperatures less than the ferrite to austenite+ferrite transformation temperature on heating (Ac₁) causes a marginal effect on the grain size. However, annealing in the intercritical region at temperatures between Ac₁ and Ac₃ (the ferrite+austenite to austenite transformation temperature on heating) causes rapid decarburization and development of large columnar ferrite grains free of carbide particles. This microstructure leads, after cold rolling and a fast annealing treatment, to carbide free, large ferrite grain microstructures with magnetic and mechanical properties superior to those observed typically in the same steel in the industrially fully processed condition. These results are attributed to the increment in grain size and to the {1 0 0} fiber texture developed during the final annealing at temperatures up to 850 °C. Annealing at higher temperatures, T>Ac₃, results in a strong {1 1 1} fiber texture and an increase of the quantity of second phase particles present in the microstructure, which lead to a negative effect on the final properties. The results suggest that annealing prior to cold rolling offers an attractive alternative processing route for the manufacture of fully processed low C GNO electrical steels strips.     

The influence of elastic deformation on the properties of the magnetoacoustic emission (MAE) signal for GO electrical steel

Magnetic properties of the grain oriented (GO) electrical steels are strongly affected by the stresses, both external and internal. The change is important even for the deformation resulting in stress level much lower than their yield limits. In this paper we present the results of investigation of the influence of compression and tension on the magnetoacoustic emission (MAE) signal properties. The experiment was performed with the help of bending machine in which the samples (0.3 mm thick, M140-30 S GO electrical steel) glued to the non-magnetic (austenitic steel) 8 mm thick bars were bent. The samples cut out in two directions (parallel and perpendicular to the rolling direction) were investigated. The elongation was measured directly with the help of tensometric bridge. Various parameters of the MAE signal, such as e.g. signal intensity and MAE peaks separation, have been examined.     

Optimisation of soft magnetic properties in Fe–Cu–X–Si13B9 (X=Cr,Mo, Zr) amorphous alloys

In the present paper a group of Fe–Cu–X–Si₁₃B₉ (X=Cr, Mo, Zr) amorphous alloys has been examined by applying different experimental techniques—magnetic permeability, magnetic after-effect, coercive force and electrical resistivity measurements. It has been shown that their soft magnetic properties can be optimised by 1-h thermal annealing at the temperature close to the crystallisation temperature. This leads to an increase of permeability and a decrease of coercive force, thermal instability (magnetic after-effect intensity) and electrical resistivity of the material. The optimisation effect is discussed in terms of different processes—(i) a formation of a nanocrystalline phase with the grain size much smaller than the ferromagnetic exchange length, (ii) an annealing out of microvoids formed during the fabrication process and also (iii) a decrease of the effective magnetostriction constant. The temperature of optimisation annealing treatment is always higher than the Curie temperatures of the materials and varies approximately linearly with the atomic radius of the alloying additions.     

Effects of sulfur content and slab reheating temperature on the magnetic properties of fully processed nonoriented electrical steels

The effects of sulfur content and slab reheating temperature on the magnetic properties of four fully processed nonoriented electrical steels have been investigated. Four slabs of nonoriented electrical steels with sulfur content in the range of 0.0006–0.0126 wt% were reheated to 1100, 1200, and 1300 °C, respectively. Then, they were hot rolled and annealed at 700 °C, cold rolled at the same condition and annealed at 820 °C in the salt bath furnace for 1 min to simulate continuous annealing. The ac core loss, dc hysteresis loss, and ac and dc permeability were measured at 15 kG inductions. It was found that the amount of inclusions in the hot-rolled bands increased with increasing slab reheating temperature and increasing sulfur content in steels. After final annealing, grain sizes of cold-rolled steel sheets decreased with increasing sulfur content and increasing slab reheating temperature. The main preferred orientations in the final annealed steel sheets were (0 1 1) 〈1 0 0〉 and (1 1 1) 〈u v w〉 γ fiber texture. Steel sheets containing 0.0032 and 0.0060 wt% sulfur developed a more stronger (0 1 1)〈1 0 0〉 texture than other steel sheets. However, steel sheets containing 0.0126 wt% sulfur had the weakest (1 1 1)〈u v w〉 texture during slab reheating at temperatures higher than 1200 °C. Both ac core loss and dc hysteresis loss increased with increasing slab reheating temperature and increasing sulfur content in steel sheets. Both ac and dc permeability decreased with increasing slab reheating temperature and increasing sulfur content in steel sheets. If sulfur content decreased from 0.0060 to 0.0032 wt%, there were great improvements in ac core loss, dc hysteresis loss, and ac and dc permeability. However, eddy current loss was almost independent of the sulfur content and slab reheating temperature.     

Precipitates in electrical steels

Precipitates heavily influence the magnetic properties of electrical steels, either as a key controlled requirement as part of the manufacturing process or as an unwanted harmful residual in the final product. In this current work copper-manganese sulphides precipitates are the primary inhibitor species in the conventional grain-oriented (CGO) steels examined and grain boundary pinning is effective at a mean precipitate size of 30–70 nm. The growth of CuMnS has been studied and the results show that a precipitate size above ∼100 nm allows the onset of secondary recrystallisation in the heating conditions applied.     

Magnetic properties of stainless steels at room and cryogenic temperatures

The magnetic properties of ten types of ferritic and martensitic stainless steels have been measured at room temperature and at 77 K. The steel samples studied were in the annealed state as received from the manufacturer. Our room temperature measurements indicate significantly harder magnetic properties than those quoted in the ASM International Handbook, which studied fully annealed stainless steel samples. Despite having harder magnetic properties than fully annealed steels some of the as-received steels still display soft magnetic properties adequate for magnetic applications. The carbon content of the steels was found to affect the permeability and coercive force, with lower-carbon steels displaying significantly higher permeability and lower coercive force. The decrease in coercive force with reduced carbon content is attributed to fewer carbide inclusions which inhibit domain wall motion. Cooling to 77 K resulted in harder magnetic properties. Averaged over the ten steels tested the maximum permeability decreased by 8%, the coercive force increased by 14%, and the residual and saturation flux densities increased by 4% and 3%, respectively. The change in coercive force when cooled is comparable to the theoretical prediction for iron, based on a model of domain wall motion inhibited by inclusions. The modest changes of the magnetic properties indicate that the stainless steels can still be used in magnetic applications at very low temperatures.     

高He通量注入条件下F/M和ODS钢中纳米微结构对He泡形核和长大的影响

利用LEAF装置提供的2 MeV的He离子,在500和600 °C分别对新型F/M钢-SIMP钢和ODS钢(MA956和Eurofer-ODS钢)注入1×1017 ions/cm2的高通量He离子,借助透射电子显微镜,表征了辐照后三种材料的肿胀行为,验证了各材料中纳米微结构(晶界,析出相和纳米氧化物)对辐照后He泡成核和长大的影响。结果表明,基于材料中晶界和析出相对He泡生长的抑制作用,温度为500 °C时,SIMP和Eurofer-ODS钢表现出较高的抗辐照肿胀性能,而MA956中纳米界面He泡成核和长大作用不明显,表现出较差的抗辐照肿胀性能;此外,温度为600 °C时,Eurofer-ODS钢由于其晶界和氧化物界面的较强作用,表现出较好的抗辐照肿胀性能。总体来说,在高He通量注入条件下,材料中纳米结构的存在会抑制He泡长大的过程,但不同材料中纳米结构对He影响作用不同。     

Effect of the rapid heating on the magnetic properties of non-oriented electrical steels

Measurements of the bulk magnetic properties for two non-oriented electrical steels after a rapid heating are reported. A deterioration of the magnetic properties was observed for the fully processed non-oriented grade and an improvement for the semi-processed non-oriented grade. This publication emphasizes the effects due to the competition between the increase of the grain size and the appearance of thermal stresses during the rapid heating on the magnetic properties of the steels.     

AC losses of YBa2Cu3O7−x high temperature superconductors

AC losses of randomly oriented and oriented grained YBa₂Cu₃O_7−x superconductors having different microstructures and silver content were studied at 77 K and frequency range between 0.5 Hz and 60 Hz. The measurements were made by an electrical technique applying an external sinusoidal magnetic field parallel to the longer axis of the specimen. In the randomly oriented samples, the results indicate that the addition of silver has no effect on the losses of the Y-123 superconductor. Unlike the behavior of the randomly oriented samples, the oriented material does not show grain decoupling and intergranular losses and its behavior is similar to that of conventional type II superconductors. The results also show that the oriented sample has a modest surface barrier against flux entry. In general, it is found that the critical state model can be used to describe the hysteretic dissipation of Y-123 superconductors, although some refinements need to be considered.     

Magnetic and electrical properties of (Ni0.8Cu0.2)1−x Cox Mn0.02Fe1.9O4 ferrites

The effect of Co substitution on the magnetic and electrical properties of iron-deficient nickel–copper mixed ferrites containing a small quantity of manganese oxide was investigated. The presence of Co enhances the specific magnetization although the saturation magnetization falls a little due to decrement of density. The initial permeability changes linearly with the average grain size of the materials and shows fairly good thermal stability for higher Co concentration. An appreciable increment in DC resistivity along with decrement in dielectric loss factor at 100 MHz can also be obtained for higher Co concentration.     

Investigation of energy losses in low-coercivity resin-bonded magnets in alternating magnetic fields

Energy losses during alternating remagnetization of low-coercitivity resin-bonded magnets and commercially produced electrical steels were studied experimentally. The studies were conducted on several samples of resin-bonded magnets with different manufacturing technologies and samples of electrical steel sheets of various thicknesses. The static and dynamic magnetic properties of the samples were measured on a vibration magnetometer and a specially designed apparatus, respectively. It was found that the studied samples of bonded magnets have a relatively high level of hysteresis losses associated with high coercivity, which reaches a value of 4–5 Oe. At the same time, the remagnetization losses due to the Foucault currents in the bonded magnets are considerably lower than in electrical steels. The measurement results show that bonded magnets at high frequencies of remagnetization, especially in high-rpm motors, can be competitive in comparison with electrical steels.     

Hydraulic permeability of (un)bounded fibrous media using the lattice boltzmann method

Several articles have been written regarding the hydraulic permeability of ordered and disordered fibrous media. Here, we explore wall effects on hydraulic permeabilities for ordered and disordered media using the lattice Boltzmann (LB) simulation method. Simulation results are found to be in excellent agreement with the semi analytic result of Sangani and Acrivos, and simulation results for disordered media are in good agreement with the results of Jackson and James and Higdon and Ford's fcc lattice. The macroscopic behavior, the hydraulic permeability, shows a distinct connection with the geometry of the system. This connection is explored and elucidated for ordered and disordered media. Finally, hydraulic permeabilities for bounded media at various wall separations are presented for both ordered and disordered media and results are compared with hydraulic permeabilities calculated for the unbounded media, and a phenomenological correlation is presented to facilitate rapid prediction of hydraulic permeabilities for both unbounded and bounded fibrous media.     

Low silicon non-grain-oriented electrical steel: Linking magnetic properties with metallurgical factors

Commercial supply, from several steel manufacturers, of low-silicon non-grain-oriented electrical steel was monitored over a span of several years. A total of 51 samples were selected—selected from many hundreds on the basis of large differences in magnetic properties, but absence of significant variations in chemistry (other than differences in silicon percentage). The selected samples were analyzed for crystallographic texture and for grain size.