Ferrite Components Research Articles

Laves Phases in Ferrite-Martensite EC-181 Steel

The microstructure and phase composition of EC-181 ferrite-martensite steel were studied in dependence on their heat treatment (temperature and aging time after quenching from 1080°C). It was established that Laves phases are formed only at the boundaries of ferrite grains, whereas Me23C6 and V2C carbides are formed in the ferrite and martensite components of the structure.

Calcium Lanthanum Permanent Magnetic Ferrite Coupled with Soft Magnetic Ferrite

This paper introduces the production method of calcium lanthanum permanent magnetic ferrite coupled with soft magnetic ferrite components. This type of calcium lanthanum permanent magnetic ferrite has excellent magnetic properties. Soft magnetic ferrite components (CoFe2O4) can be coupled effectively with permanent magnetic ferrite (the main ingredients: Ca0.548Sr0.120La0.542Fe12O19) by adding the additives (SrB2Si0.67O5.34 and CaSiO3), which can promote the sintering of the liquid permanent magnetic ferrite. This calcium lanthanum permanent magnetic ferrite can be significantly improved in the microstructure, density, magnetic properties.

Corrosion-electrochemical properties of α-Fe + Fe3C + TiC nanocomposites in acidic sulfate solutions

Corrosion-electrochemical properties of model α-Fe + Fe3C + TiC three-phase nanocrystalline composites in acidic sulfate solutions are studied. Anodic processes on α-Fe + Fe3C + TiC composites are determined chiefly by the oxidation of ferrite and cementite components. The passivation of nanocomposites takes place due to the formation of γ-Fe2O3 · nH2O surface hydroxides with a high water content n = 0.7–2.2 and low protective properties. The high activity of α-Fe + Fe3C + TiC composites with respect to hydrogen evolution is determined by the cementite component and increases with an increase in the dispersion of Fe3C inclusions. Under the effect of cathodic hydrogen, titanium carbide decomposes to produce free carbon.

Effect of Microstructure and Texture on the Edge Formability of Light Gauge Strip Steel

Twin roll casting (TRC) of low-carbon ultra-thin cast strip (UCS) steel has the potential to deliver significant economic advantages over steels made by conventional processes. Novel microstructures containing intragranularly nucleated acicular ferrite may be produced in UCS products manufactured by the CASTRIP®* process, however, their mechanical property performance has yet to be fully evaluated. This study compared the mechanical properties and edge formability of UCS steel produced by the CASTRIP process to steel produced by conventional hot rolled (HR) and cold rolled and continuously annealed (CR & CA) process routes. The results revealed an apparent paradox, where recent UCS steel produced by the CASTRIP process was shown to have lower total tensile elongation values, yet higher edge formability than products manufactured by the conventional process routes. The discrepancy was largely attributable to the influence of acicular ferrite microstructure on steel plasticity. Acicular ferrite decreased macro-plasticity by reducing the contribution of yield point elongation (lower volume fraction of pro-eutectoid ferrite) and post uniform elongation (strain localisation to softer pro-eutectoid ferrite) components of the total tensile elongation value. Conversely, the high homogeneity of the acicular ferrite microstructure enhanced micro-plasticity of the UCS steel produced by improving resistance to void initiation and propagation during forming. This study also showed that plastic anisotropy can significantly influence the edge formability of low-carbon sheet steel, with failure occurring along the direction where the resistance to through thickness thinning was the least.* CASTRIP is a registered trademark of Castrip LLC

Structural features of the behavior of a high-carbon pearlitic steel upon cyclic loading

The structural evolution upon high-cycle fatigue (tension with the magnitude of stress in a cycle below the macroscopic yield stress) of the hypereutectoid steel U10 (1.03 wt % C), in which pearlite of different morphology (fine-lamellar, coarse-lamellar, and partially spheroidized pearlite) was formed, has been investigated by scanning and transmission electron microscopy. Based on the fractographic analysis, features of fracture of these structural states have been considered. At a significant distance (10 mm) from the fatigue fracture, features of structural transformations caused by cyclic loading have been revealed. It has been shown that upon high-cycle fatigue in the steel U10 with structures of lamellar and partially spheroidized pearlite, substantial structural changes occur, namely, fragmentation and partial dissolution of cementite plates, and in fine pearlite, additionally, spheroidizing of cementite and polygonization of the ferritic component are observed. A dependence of the character of fracture on the type of structure formed upon fatigue loading has been established. In the steel with a nonequilibrium structure of unannealed fine pearlite, an enhanced elasticity modulus, as compared to other more stable structures (coarse-lamellar, annealed fine, and spheroidized pearlite), and a reduction in the magnitude of the elasticity modulus under the action of cyclic loading have been found. It has been established that the structural changes in fine pearlite of laboratory specimens of the steel U10 upon cyclic tension are qualitatively similar to those in a railroad wheel of the steel 65G under the service conditions.

Determination of Electric and Magnetic Properties of Commercial LTCC Soft Ferrite Material

This paper offers an effective, accurate, and simple method for permittivity and permeability determination of an LTCC (low temperature cofired ceramic) ferrite sample. The presented research can be of importance in the fields of ferrite component design and application, as well as for RF and microwave engineering. The characterization sample is a stack of LTCC tapes forming a toroid. Commercially available ferrite tape ESL 40012 was used and standard LTCC processing was applied for the sample fabrication. For the first time, the electrical properties of a ferrite toroid sample of ESL 40012 LTCC ferrite tape is presented at various frequencies. The electrical properties of LTCC ferrite materials, permittivity and specific resistivity, are shown in a frequency range from 10 kHz to 1 MHz using the capacitive method. The hysteresis properties of this material are also determined. B-H hysteresis loops were measured applying a maximum excitation of 2 kA/m and frequencies of 50 Hz, 500 Hz, and 1000 Hz. Permeability is determined in the frequency range from 10 kHz to 1 GHz and a characterization procedure is divided in two segments, for low and high frequencies. Low frequency measurements (from 10 kHz to 1 MHz) are performed using LCZ meter and discrete turns of wire, while a short coaxial sample holder and vector network analyzer were used for the higher frequency range (from 300 kHz to 1 GHz). In addition, another important factor required for the practical design of devices is presented, the temperature variation of the permeability dispersion parameters.

Synthesis and hyperthermia property of hydroxyapatite–ferrite hybrid particles by ultrasonic spray pyrolysis

Biocompatible hybrid particles composed of hydroxyapatite (Ca10(PO4)6(OH)2, HAp) and ferrite (γ-Fe2O3 and Fe3O4) were synthesized using a two-step procedure. First, the ferrite particles were synthesized by co-precipitation. Second, the suspension, which was composed of ferrite particles by a co-precipitation method, Ca(NO3)2, and H3PO4 aqueous solution with surfactant, was nebulized into mist ultrasonically. Then the mist was pyrolyzed at 1000°C to synthesize HAp–ferrite hybrid particles. The molar ratio of Fe ion and HAp was (Fe2+ and Fe3+)/HAp=6. The synthesized hybrid particle was round and dimpled, and the average diameter of a secondary particle was 740nm. The cross section of the synthesized hybrid particles revealed two phases: HAp and ferrite. The ferrite was coated with HAp. The synthesized hybrid particles show a saturation magnetization of 11.8emu/g. The net saturation magnetization of the ferrite component was calculated as 32.5emu/g. The temperature increase in the AC-magnetic field (370kHz, 1.77kA/m) was 9°C with 3.4g (the ferrite component was 1.0g). These results show that synthesized hybrid particles are biocompatible and might be useful for magnetic transport and hyperthermia studies.

Evaluation by the Double Loop Electrochemical Potentiokinetic Reactivation Test of Aged Ferritic Stainless Steel Intergranular Corrosion Susceptibility

An experimental design method was used to determine the effect of factors that significantly affect the response of the double loop–electrochemical potentiokinetic reactivation (DL-EPR) test in controlling the susceptibility to intergranular corrosion (IGC) of UNS S43000 (AISI 430) ferritic stainless steel. The test response is expressed in terms of the reactivation/activation current ratio (Ir/Ia pct). Test results analysed by the analysis of variance (ANOVA) method show that the molarity of the H2SO4 electrolyte and the potential scanning rate have a more significant effect on the DL-EPR test response than the temperature and the depassivator agent concentration. On the basis of these results, a study was conducted in order to determine the optimal operating conditions of the test as a nondestructive technique for evaluating IGC resistance of ferritic stainless steel components. Three different heat treatments are considered in this study: solution annealing (nonsensitized), aging during 3 hours at 773 K (500 °C) (slightly sensitized), and aging during 2 hours at 873 K (600 °C) (highly sensitized). The aim is to find the operating conditions that simultaneously ensure the selectivity of the attack (intergranular and chromium depleted zone) and are able to detect the effect of low dechromization. It is found that a potential scanning rate of 2.5 mV/s in an electrolyte composed of H2SO4 3 M solution without depassivator, at a temperature around 293 K (20 °C), is the optimal operating condition for the DL-EPR test. Using this condition, it is possible to assess the degree of sensitization (DOS) to the IGC of products manufactured in ferritic stainless steels rapidly, reliably, and quantitatively. A time–temperature–start of sensitization (TTS) diagram for the UNS S43000 (France Inox, Villepinte, France) stainless steel was obtained with acceptable accuracy by this method when the IGC sensitization criterion was set to Ir/Ia > 1 pct. This diagram is in good agreement with the time–temperature–start of precipitation (TTP) diagram that delineates the domain of low dechromization consecutive to chromium carbide precipitation.

Properties of MnZn ferrites prepared by powder injection molding technology

Abstract In this work, manganese zinc ferrite components were manufactured by powder injection molding—PIM technology. A fine powder consisting of Mn 1− x Zn x Fe 2 O 4 with small addition of hematite α-Fe 2 O 3 as used in mass ferrite production was mixed with an organic binder (Solvent System) to form ferrite feedstock for powder injection molding—PIM technology. Excess of Fe 2 O 3 was present in the starting powder in order to suppress conversion of Fe 3+ to Fe 2+ ions which would lower the permeability. The ferrite feedstock was injected in a mold with a cavity shaped like a small cylinder with a hole on the main axis. Injection molded samples were then solvent and thermally debinded and sintered in different atmospheres: air, argon and nitrogen. The starting powder, injected green samples and sintered samples were characterized using X-ray diffractometry, scanning electron microscopy, thermogravimetry, differential thermal analysis as well as by magnetic measurements. Rietveld refinement of measured X-ray patterns was done to detect possible phase transformations of Fe 2 O 3 to other iron oxides through reduction by binder residues (carbon) at elevated temperatures during thermal debinding and sintering. Finally, the magnetic properties were measured by hysteresis graph and mutually compared for the injected samples that were sintered in air, argon and nitrogen. The obtained magnetic characteristics where found to be comparable with commercial samples prepared by traditional sintering technology.

Fracture assessment of ferritic steel components under dynamic loading

This paper summarizes recent studies on application of the Weibull stress model to predict cleavage fracture of structural components under dynamic loading. Two pressure vessel steels, the strongly rate-sensitive A515-70 steel and the moderately rate-sensitive Euro material (22NiMoCr37), are considered in the investigation. The results, based on independent calibrations at different loading rates, demonstrate that the Weibull modulus ( m) is invariant of loading rate for both materials. While m remains a constant for each material, σ u decreases and σ w–min increases with higher loading rates. The studies also show that dynamic loading reduces constraint loss, i.e., it drives the response towards the small-scale yielding configuration, and this rate effect tends to saturate at higher loading rate. The demonstrated loading rate invariance of m, when combined with the Master Curve for dynamic loading, can provide a practical approach which simplifies the process to estimate σ u as a function of loading rate.

Fatigue life prediction of components made of spheroidal graphite cast iron

In many cast metals fatigue crack initiates from a defect. The lower bound of the fatigue life in cast components can be estimated based on the maximum defect size which is present in a component. In this research the distribution of defects in a ferritic spheroidal graphite cast iron component was determined. Then, Gumbel distribution was used to estimate the maximum sizes of defects in cylindrical fatigue specimens with different dimensions. Based on estimated maximum defect size, the fracture mechanics approach was used to determine the lower bound of the fatigue life for fatigue specimens with different dimensions and the geometrical size effect was modeled.

Behavior of pearlite of various morphologies during cyclic tension

The structural evolution of hypereutectoid U10 steel with a pearlitic structure of various types (fine lamellar or partly spheroidized pearlite) is studied during fatigue loading. The fracture of these structures is considered using fractography data. The specific features of the structural transformations and the changes in the dislocation structure of the U10 steel are revealed during cyclic tension in the high-cycle fatigue region at a significant distance (10 mm) from a fatigue fracture surface. Substantial structural changes are shown to occur in U10 steel with various pearlitic structures during high-cycle fatigue tests (tension at a stress amplitude in a cycle lower than the macroscopic yield strength). These are the fragmentation, partial dissolution, and spheroidization of cementite lamellae and the polygonization of the ferrite component. The relationship between the type of fracture surface and the type of structure formed upon fatigue loading is found.

Ferromagnetic metamaterial with tunable negative index of refraction

We investigate the index of refraction of the ferromagnetic metamaterial, which consists of periodic layered ferrite and semiconductor or metallic mesh. We find that the metamaterial has the negative index; the frequency range and magnitude of the negative index are tunable in applied magnetic fields. The frequency range of the negative index shifts to higher frequencies as the applied magnetic fields increase. The permeability and permittivity of the ferrite and other component materials, as well as their thickness ratios, influence the tunable range of the negative index. It is demonstrated that ferrite-mesh structure has a much lower loss than that of a ferrite-semiconductor structure.

Preparation of hydroxyapatite–ferrite composite particles by ultrasonic spray pyrolysis

Abstract Bio-compatible composite particles composed of hydroxyapatite (Ca10(PO4)6(OH)2, HAp) and ferrite (maghemite (γ-Fe2O3) or magnetite (Fe3O4)) were synthesized by two-step synthesis. In this work, co-precipitation method using aqueous solution of FeSO4 and FeCl3 was employed to synthesize γ-Fe2O3 and Fe3O4 particles. It was found that the resultant phase was changed by the molar ratio of FeSO4 and FeCl3, and optimal molar ratio to suppress the coexistence of α-FeOOH was FeSO4/FeCl3 = 2. The suspension composed of crushed ferrite particles, Ca(NO3)2 and H3PO4 aqueous solution with surfactant ultrasonically nebulized into mist and the mist was pyrolyzed at 500 °C to synthesize HAp–ferrite composite particles. The shape of the synthesized composite particle was round with dimple, and the particle size was around 0.5–3 μm in diameter. The composite particle showed saturation magnetization of 0.833 emu/g. Net saturation magnetization of the ferrite component was calculated to be 46.4 or 48.0 emu/g under the assumption that the ferrite was composed of γ-Fe2O3 or Fe3O4, respectively.

Prediction of residual stresses in a dissimilar metal welded pipe with considering cladding, buttering and post weld heat treatment

Dissimilar metal weld joints are widely used in the nuclear power plants to connect the ferritic steel components and the austenitic steel piping systems. Because the manufacturing processes are considerably complicated, it is difficult to accurately predict residual stresses in dissimilar metal weld joints by numerical simulation technology. In this study, a simplification methodology has been developed to compute residual stresses in a dissimilar metal pipe joint with considering cladding, buttering, post weld heat treatment (heat treatment after cladding and buttering) and multi-pass welding using a united fashion. The computational procedure based on thermal elastic plastic finite element method is used to simulate the thermo-mechanical behaviors. With using this computational procedure, the variations of stress status at each manufacturing stage are investigated and the influences of cladding, buttering and post weld heat treatment on the final residual stresses after welding are also clarified. In addition, the simulation results are compared with the measured data and the usefulness of present method is verified.

Helical Ferrite Devices for Non-Reciprocal Applications

This paper introduces the use of Viscous Plastic Processing (VPP) for the production of microwave ferrite materials and components. Conventional ceramic processing methods produce bulk ferrite materials restricted to relatively simple shapes and that can possess significant micro-structural defects resulting in poor mechanical properties. Using VPP the microstructures and physical strength of ferrite materials can be substantially enhanced and entirely new and unique device geometries produced, such as those based on ferrite helices. Ferrite Materials produced by VPP, such as lithium based ferrites, will be compared to those produced by standard methods of production such as powder pressing.

A New Method to Study the Effect of Cooling Rate on the Decomposition of Austenite in Advanced High Strength Sheet Steels

Abstract A new modified Jominy holder and specimen were developed to study the effect of chemical composition, intercritical annealing temperature, and cooling rates on the transformation behavior of a series of dual-phase sheet steels. Correlations between temperature, time, and the distance from the water quenched end were developed using a laboratory view data acquisition program. In addition, the hardness and microstructure along the length of the sheet steel sample were determined as a function of cooling rate from the intercritical annealing temperature. Special chemical regents were used to reveal new ferrite, bainite, and other microstructural components, which were also evaluated by optical, scanning, and transmission electron microscopy. Critical cooling rate equations, based on steel composition, volume fraction of austenite and intercritical annealing temperatures, were developed to avoid or minimize the formation of new ferrite and bainite. The results of this work show that the modified Jominy test is an effective and efficient way to evaluate the hardenability of sheet steels.

Enhanced mangnetoelectric voltage in multiferroic particulate Ni0.83Co0.15Cu0.02Fe1.9O4−δ/PbZr0.52Ti0.48O3 composites – dielectric, piezoelectric and magnetic properties

Multiferroic particulate composites of Ni0.83Co0.15Cu0.02Fe1.9O4−δ– NCCF and lead zirconate titanate (PZT) were prepared conventional ceramic method. The generic formulae x NCCF + (1−x) PZT where x=0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 mole fractions. The presence of two phases in multiferroic was confirmed with XRD technique. The dielectric constant and loss tangent were studied as a function of frequency (100Hz to 1M Hz) and temperature (30–500°C). The piezoelectric coefficient d33 were also studied on these particulate composites. The hysteresis behaviour was studied to understand the magnetic properties such as saturation magnetization (Ms) and magnetic moment (μB). The static magnetoelectric (ME) voltage coefficient was measured as a function of dc magnetic bias field. A high value of ME output (3151mV/Oe.cm) was obtained in the composite containing 50% highly magnetostrictive ferrite component NCCF – 50% highly piezoelectric ferroelectric component PZT. These multiferroic particulate composites are used as phase shifters, magnetic sensors, cables etc.

Hearing aid with a magnetic field-controlled switch, and operating method therefore

In a hearing aid with a magnetic field-controlled switch and a method for operating such a hearing aid, the magnetic field sensor for automatically switching the hearing aid is miniaturized and made more cost-effective by the use of a ferrite component as the magnetic field sensor. This component can be evaluated by a Wheatstone bridge circuit which is fed by an oscillator. In this context, a measuring amplifier with a threshold value detector supplies a corresponding switching signal for the hearing aid.

The occurrence of magnesioferrite-rich spinels in a trachyandesite from NE China

Magnesioferrite-rich spinels were found in the Cretaceous Jianguo trachyandesite in northeastern China. The trachyandesite is comprised of augite, plagioclase, K-feldspar, spinel, phlogopite, apatite, zircon, and pseudo- morphed phenocrysts, which are interpreted as former olivine and/or orthopyroxene crystals and now consist of a mixture of chrysotile, antigorite and chlorite. Texturally, four stages of spinel growth are observed: magnesioferrite- rich spinel-I occurs within the pseudomorphs and magne- sioferrite-rich spinel-II occurs in the matrix of the trachyandesite. Magnetite-rich spinel-III occurs either as rim around spinel-II or as distinct magnetite grains, whereas worm—like magnetite—rich spinel-IV occurs within the pseudomorphs. Chemically, spinel-I contains 51 to 82 mol.% magnesioferrite component, spinel-II contains a magnesio- ferrite component ranging from 60 to 79 mol% and spinel-III contains less than 15 mol.% magnesioferrite component. In contrast to spinel II, spinel-I is poor in TiO2 but rich in Cr2O3, MnO and NiO. Two-feldspar thermometry yields temperatures of 880-1000°C for the formation of the trachyandesite matrix assemblage. In the absence of olivine and/or orthopyroxene, Schreinemakers analysis of T-fO2 model phase relations indicate that magnesioferrite-rich spinels-I, and II are stable at high T and high fO2. Magnetite-rich spinel-III formed under more reducing conditions, while spinel-IV most likely formed during subsolidus late-stage alteration of olivine and/or magnesio- ferrite phenocrysts. Semi quantitative fO2 calculations using the oxygen barometer of Ballhaus et al. (1991) yielded fO2 >7 log units above QFM, which excludes a mantle origin of these magnesioferrites. Thus oxidation of these trachyandesites most likely occurred at some stage during melt ascent, or in a differentiating magma chamber or even after emplacement of these still hot magmas at near surface conditions.