Amorphous Steel Research Articles

Study of a 18-Pulse Transformer–Rectifier Unit with an Amorphous Steel Magnetic Core

This article discusses a study of transformer–rectifier units with a magnetic core made of amorphous steel. Transformers with various types of amorphous alloys have been analyzed, and the optimum amorphous alloy for transformers was determined. Thermal processes in transformers with magnetic core of amorphous steel have been simulated, and the maximum temperature under normal operating conditions has been determined. The simulation has demonstrated that no special transformer cooling system is required. An experimental transformer–rectifier unit has been designed and manufactured with a magnetic core of amorphous steel installed on an 18-pulse rectifier with a capacity of 10.5 kV A operating with a frequency of 400–800 Hz and voltage of 115/27 V. To verify the obtained data, experimental studies have been performed that confirmed the validity of the selected design procedure of a transformer engineering flowchart. It has been demonstrated that the thermal loads detected in the transformer during testing are in the range of allowable values.

Microstructure and Corrosion Behavior of Fe-15Mn-5Si-14Cr-0.2C Amorphous Steel

Microstructure and Corrosion Behavior of Fe-15Mn-5Si-14Cr-0.2C Amorphous Steel

Some Fundamental Issues of the Development of Electrical Steel Production Technology in Russia

This paper examines the key issues of modern industrial technology in the production of cold-rolled isotropic and anisotropic electrical steels, as well as amorphous steel for magnetic cores of electrical machines with high efficiency.

Influence of Amorphous and Silicon Steel on Performance of Permanent Magnet Synchronous Motors Used in Steering Pump of Electric Vehicles

Amorphous materials have the advantages of high permeability and low core losses. Their application in the motor can reduce the energy consumption and improve the efficiency. To investigate the advantage of amorphous materials on the performance of permanent magnet synchronous motors (PMSMs) at lower speed situation, three 1.5 kW motors used in steering pumps of electric vehicles are analyzed and compared. Two prototypes and the experimental platform are built. The experimental results indicate that the efficiency of the PMSM motor with amorphous materials increases by 1.4 % at 1200 rpm, which shows that amorphous materials can also improve the motor performance at lower speed. To further take advantage of amorphous materials, the particle swarm optimization algorithm is used to optimize the dimensions of amorphous motor and the efficiency is increased by 0.54 %.

Amorphous Steel Coatings Deposited by Cold-Gas Spraying

Cold-gas spray (CGS) deposition of amorphous steel coatings starting from a commercial feedstock powder containing boron, tungsten, and silicon was investigated. Microstructural characterization, carried out by X-ray diffraction (XRD), transmission electron microscopy, and backscattered electron diffraction (EBSD) analysis, confirmed the amorphous nature of deposited coatings. The amorphization phenomenon is related to high-strain/strain-rate deformation with shear instability caused by very high particle kinetic energy, with a mechanism that resembles the severe plastic deformation process. The CGS coatings were heat-treated at temperatures ranging from 650 to 850 °C to induce partial recrystallization. The effect of nanocrystal nucleation and growth on the hardness of the coatings was investigated, and the hardness of heat-treated samples was found to increase with respect to as-sprayed coatings, outperforming conventional high-velocity oxy-fuel (HVOF) deposits. Hardness was found to decrease after prolonged (<90 min) or higher temperature (>750 °C) exposures.

Electromagnetic Vibration and Noise Comparison of Amorphous Metal PMSMs and Silicon Steel PMSMs

This paper investigates the differences in the electromagnetic vibration and noise of an amorphous metal (AM) permanent magnet synchronous machines (PMSMs) and silicon steel (SS) PMSMs. The electromagnetic vibration and noise of an AM PMSM and an SS PMSM sharing the same structure and dimensions are calculated under different conditions: 1) only radial forces (RFs); 2) only magnetostriction (MS) effects; and 3) both RFs and MS effects, and the calculated results of the two machines are compared. The effects of Young's modulus parameters and the MS coefficients of stator cores on the electromagnetic vibration and noise are analyzed. The vibration and noise of the AM PMSM and SS PMSM prototypes are tested and compared with the corresponding calculated results to verify the accuracy of the calculated results.

Development and study of a dynamic model of single-phase amorphous steel core transformer

The use of amorphous ferromagnetic alloys in transformer construction allows reducing no-load losses by 4 times or more. At the same time, the magnetization curve of amorphous steel has a shape that is close to a rectangle, which significantly distorts the shape of the no-load current curve. This is accompanied by inrush current increases when a saturated transformer is turned on. However, there are no publications devoted to this issue in the periodicals. The purpose of this work is to develop a dynamic model and study the dynamics of an amorphous steel core single-phase transformer (TAS) operating at an arbitrary external load. The calculation of the electrical circuit was made by a one-step method based on a modified 2nd-order Rosenbrock formula, and the circuit parameters were calculated by the finite element method. We have developed dynamic models of the single-phase transformer based on the use of controlled current sources and EMF and implemented in the MatLab Simulink SimPowerSystem. These models allowed us to take into account the effect produced by the practically rectangular shape of the magnetization curve of the amorphous steel used to make the core on the operation of a saturated transformer. It has been established that the inrush current occurring when a saturated TAS is switched on can exceed the rated current tenfold. A significant distortion of the current curve has been detected in the first periods even when the transformer operates at nominal load. The developed models can be used to study the operation of a transformer at an arbitrary load. These models can be developed further. It has been found that a significant effect on the transformer operation is produced by the shape of the amorphous steel magnetization curve.

Analysis and Comparison of 2D Temperature between Amorphous Alloy and Silicon Steel Sheet of High-Speed Permanent Magnet Motor

Analysis and Comparison of 2D Temperature between Amorphous Alloy and Silicon Steel Sheet of High-Speed Permanent Magnet Motor

Obtaining of bulk amorphous steel with low carbon content using industrial ferroalloys

Abstract Bulk amorphous steels (BASs) are a novel class of Fe-based bulk metallic glasses (BMGs), which have an attractive physical, thermal and mechanical properties that make them suitable for lots of industrial applications [1-3]. BAS synthesis requires special preparation conditions such as vacuum or controlled atmosphere and high-purity raw materials. These obtaining conditions increase the cost of these alloys and thus limit the development of new industrial applications. Multicomponent BAS rods with a diameter of 3 mm and 40 mm in length have been obtained by water-cooled copper mold casting in an air atmosphere, using industrial ferroalloys as raw materials. The obtained samples were structurally characterized by X-ray diffraction (XRD) and differential scanning calorimetry (DSC), while the mechanical properties were investigated by hardness and compression tests. Resulting structural aspects and mechanical properties are reported.

Differences in dry sliding wear behavior between HVAF-sprayed amorphous steel and crystalline stainless steel coatings

Dry sliding wear behavior of amorphous steel coating (ASC) and crystalline stainless steel coating (SSC) manufactured by high-velocity-air-fuel-spraying was investigated. With increasing normal load, coefficient of friction (COF) of ASC decreases slightly from 0.78 to 0.69. COF of SSC presents a minor difference under various normal loads but increases with sliding time accompanied by relatively large fluctuation. Such a difference in friction behavior between such two coatings can be understood based upon the roles of shear stress and flash temperature. Wear rate of SSC is much higher than that of ASC, suggesting better wear resistance of ASC. The enhanced wear resistance is correlated with high hardness (H), reduced Young’s modulus (Er), and ratios of H/Er and H3/Er2. Detailed analyses on worn surfaces and sub-surfaces indicate that the wear mechanisms for ASC include delamination, abrasive and oxidation wear, whereas those for SSC are delamination and oxidation.

Magnetic Properties of Simultaneously Excited Amorphous and Silicon Steel Hybrid Cores for Higher Efficiency Distribution Transformers

We measured and calculated the distributions of the magnetic flux density and iron loss in a hybrid-configured core consisting of an amorphous wound core combined with a grain-oriented (GO) silicon steel stacked core with the goal of enabling the use of amorphous cores with lower iron loss in larger capacity distribution transformers. Excitation tests revealed that the GO core prevented over-saturation of the amorphous core. The hybrid configuration enabled the design to have an approximately 10% higher magnetic flux density than configurations with only an amorphous core. We then assembled a prototype 5 MVA single-phase hybrid-core transformer designed on the basis of our investigation results. Operation tests on the prototype demonstrated that its efficiency was higher than that of conventional silicon steel core transformers and its size was less than that of transformers with only amorphous cores.

Simulation of Thermal Field in Bulk Amorphous Steels

Bulk amorphous steels (BASs) have shown great potential for some structural applications due to very attractive physical, thermal and mechanical properties. This paper presents some results for numerical simulation of the thermal field developed during rapid cooling of Fe-Cr-Co-Mo-Y-C-B alloy, to obtain bulk amorphous steels. Rapid cooling technology gives the possibility to obtain bulk metallic alloys with an amorphous structure under conventional industrial conditions, using, for example, commercial-grade raw materials, low vacuum, conventional casting techniques, etc. Once the model being validate, it can be used to optimize the rapid cooling process and casting mold geometry to be able to investigate the possibility to obtain larger bulk amorphous steel components.

Effect of Magneto-Pulse Processing on the Microstructure and Magnetic Behavior of Amorphous Electrotechnical Steel

The effect of magneto-pulse processing on the microstructure and magnetic behavior of amorphous electrotechnical steel is studied. It is found that the directed ordering of Fe atoms helps to increase specific magnetization of saturation and the coefficient of the squareness of the hysteresis loop, and is related to ordering of the spin system.

Effect of Al and Mg Contents on Wettability and Reactivity of Molten Zn–Al–Mg Alloys on Steel Sheets Covered with MnO and SiO2 Layers

The reactive wetting behaviors of molten Zn–Al–Mg alloys on MnO- and amorphous (a-) SiO2-covered steel sheets were investigated by the sessile drop method, as a function of the Al and Mg contents in the alloys. The sessile drop tests were carried out at 460 °C and the variation in the contact angles (θc) of alloys containing 0.2–2.5 wt% Al and 0–3.0 wt% Mg was monitored for 20 s. For all the alloys, the MnO-covered steel substrate exhibited reactive wetting whereas the a-SiO2-covered steel exhibited nonreactive, nonwetting (θc > 90°) behavior. The MnO layer was rapidly removed by Al and Mg contained in the alloys. The wetting of the MnO-covered steel sheet significantly improved upon increasing the Mg content but decreased upon increasing the Al content, indicating that the surface tension of the alloy droplet is the main factor controlling its wettability. Although the reactions of Al and Mg in molten alloys with the a-SiO2 layer were found to be sluggish, the wettability of Zn–Al–Mg alloys on the a-SiO2 layer improved upon increasing the Al and Mg contents. These results suggest that the wetting of advanced high-strength steel sheets, the surface oxide layer of which consists of a mixture of MnO and SiO2, with Zn–Al–Mg alloys could be most effectively improved by increasing the Mg content of the alloys.

Composition-controlled active-passive transition and corrosion behavior of Fe-Cr(Mo)-Zr-B bulk amorphous steels

Various corrosive environments in daily life and industry have put forward high requirement on corrosion resistance of metals, especially steels. Unlike the strict demand in Cr content of crystalline stainless steels, amorphous steels (ASs) with lower Cr content can be endowed with outstanding corrosion resistance, while the intrinsic mechanism is not fully understood. Herein, we present a novel Fe92−x−y−zCrxMoyZr8Bz (6 ≤ x ≤ 40, 0 ≤ y ≤ 22, and 12 ≤ z ≤ 18) bulk amorphous steel (BAS) forming system and reveal the synergistic effect of Cr and Mo in determining the chemical stability of oxide films. It has been found the Fe92−x−zCrxZr8Bz BASs with 1 mm in diameter display a Cr-controlling active-passive transition at the Cr threshold of ∼25% in 1 M hydrochloric acid. When adding minor Mo into the BASs, the Cr threshold can be remarkably reduced by forming favorable hexavalent Mo oxides. The generation of Mo6+ is facilitated by atomic selective dissolution at the interface and can promote the passivation. In contrast, when the Cr content of the Mo-doped glasses exceeds 25%, few Mo6+ oxides would produce as the prior formation of protective passive films inhibits the further oxidation of Mo. Therefore, manipulating the active-passive transition properly is crucial to designing ASs with high stainlessness.

18-Pulse Transformer Rectifier Unit with an Amorphous Magnetic Core for Aircraft

This paper deals with a transformer-rectifier unit with a magnetic core made of amorphous steel. Transformers with various types of amorphous alloys have been compared. The most optimal amorphous alloy to use in a transformer is determined. The simulation of the electromagnetic and thermal processes occurring in transformers with a magnetic core made of amorphous steel was carried out, the amplitude and shape of the voltage and current were determined and the maximum temperature in nominal operating mode was defined. The dependencies of the specific losses in the studied samples of amorphous steel on the frequency of magnetization reversal, magnetic flux density and temperature were obtained. An experimental layout of a transformer rectifier unit with a magnetic core made of amorphous steel, loaded onto an 18-pulse rectifier with a power of 10.5 kVA and operating at a frequency of 400-800 Hz with a voltage of 115/27 V was designed and manufactured. An experimental study was carried out on the developed layout to verify the obtained data. The experimental studies confirmed the correctness of the chosen design methodology and of the design scheme of the transformer. It is important to note that the thermal loads detected on the transformer during its testing are within the permissible values.

Air Oxidation Behavior of (Fe41Cr15Mo14C12B9Co7Y2)97Ta3 Bulk Metallic Glass

The oxidation of (Fe41Cr15Mo14C12B9Co7Y2)97Ta3 bulk metallic glass (Fe8-BMG) was investigated in dry air at 500–625 °C. The results showed that the oxidation kinetics of the alloy obeyed the parabolic rate law at T ≥ 550 °C, while the mass gain at 500 °C was extremely small. The oxidation rates of Fe8-BMG increased progressively as the temperature rose, especially when having its value at 600 °C which was comparable to that of the commercial 304L stainless steel. The scales formed on the amorphous steel consisted of granular Cr2O3, and its grain size increased with increasing temperature.

Y-Ray Shielding Performance and Mechanical Properties of Mortar Strengthened by Amorphous Alloy Fibers

The γ-ray shielding performance of the mortar reinforced by zirconium-based amorphous alloy fibers was studied. Meanwhile, the mechanical properties of mortar blocks with two kinds of reinforcement addition phases, i.e. amorphous alloy fibers and steel fibers were tested. The results show that the linear attenuation coefficient to γ-ray increases and the thickness of half-value layer (HVL) decreases with the increasing of volume fraction of reinforcing fibers. The shielding results were simulated by Xcom software, and proven consistent with the experimental results. The compressive strength of mortar block reinforce with fibers of 0.4% volume fraction is 5% higher than that of pure mortar, the flexural strength of mortar block reinforced with fibers of 1.2% volume fraction is 57% higher than that of pure mortar, and 33.4% higher than that of mortar block added with steel fibers.

Обоснование целесообразности применения аморфной стали в магнитопроводах трансформаторно-выпрямительных устройств летательных аппаратов

Transformer-rectifier units with magnetic cores made of amorphous steel are investigated. The specific features pertinent to application of amorphous alloys are shown, and their comparative analysis is carried out. Experimentalsamplesoftwo types of transformer-rectifier unitswith the magnetic core made of different amorphous steels have been fabricated. The thermal processes occurring in transformer-rectifier units with the magnetic core made of amorphous steel are simulated on a computer. Specific losses in the magnetic core are experimentally investigated. The results obtained from the performed tests show that transformers with magnetic cores made of amorphous steel only slightly outperform the transformers with magnetic cores made of precision magnetically soft materials or electrical steels in terms of mass and dimensional indicators.

Experiments on Tensile and Shear Characteristics of Amorphous Micro Steel (AMS) Fibre-Reinforced Cementitious Composites

Amorphous micro-steel (AMS) fibre made by cooling of liquid pig iron is flexible, light and durable to corrosion, then to be compatible with high flowable and disperable states of mixing as well as high ductile post-cracked performances to apply in fibre-reinforced cementitious composites. In the current research, AMS fibre-reinforced cementitious composites based on cement and alkali-activated ground granulated blast furnace slag mortars were newly manufactured and evaluated for the strength and ductile characteristics mainly by direct tensile and shear transfer tests in the variation in the volume of AMS fibres with two different lengths of 15.0 and 30.0 mm. As a result, it was found that 1.0–1.25% fibre volume fractions were recommendable for AMS fibre-reinforced cementitious composites to maximize direct tensile strength, ductile tensile strain, and shear strength of the composites. However, a further fraction of AMS fibre lowered these mechanical characteristics. Simultaneously, it could be said that AMS fibre-reinforced cementitious composites exhibited up to about 3.7 times higher in direct tensile strength and up to 2.3 times higher in shear strength, compared to AMS fibre-free specimens.