Non-oriented Grain Research Articles

Effect of Hot Band Annealing on Microstructure of Semi-Processed Non-Oriented Low Carbon Electrical Steels

ABSTRACTEffects of hot band annealing on the final microstructure and magnetic properties of cold rolled and annealed non-oriented grain Si-Al electrical steel strips are investigated. Microstructures are characterized using optical and scanning electron microscopy and magnetic properties are determined using a vibrating sample magnetometer. It is shown that annealing of hot rolled bands at temperatures between 800 and 850 °C causes rapid decarburization and development of a microstructure consisting of large columnar ferrite grains free of secondary particles. This microstructure leads, after cold rolling and a fast annealing treatment, to large grain microstructures similar to those observed in production scale, fully processed strips. It is observed that the final grain size increases with the final annealing temperature, leading to a significant improvement of the magnetic properties. Therefore, hot band annealing technology can be an attractive alternative processing route for the manufacture of non-oriented grain low carbon Si-Al processed electrical steel strips.

Influence of grain size and additions of Al and Mn on the magnetic properties of non-oriented electrical steels with 3 wt. (%) Si

The influence of hot-band grain size and additions of aluminum and manganese on the magnetic properties of non-oriented grain (NOG) low-carbon electrical steel with about 3 wt. (%) Si were investigated using optical microscopy and X ray diffraction. The addition of manganese resulted in larger grains after final annealing. Coarse grains in the hot-band and addition of Mn led to a Goss orientation component after final annealing, which resulted in an increase in the magnetic permeability.

Processing, adhesion and electrical properties of silicon steel having non-oriented grains coated with silica and alumina sol–gel

Silicon steels having non-oriented grains are usually coated with a series of inorganic or organic films to be used in electrical applications. However, the commercially available coatings have several disadvantages that include poor adhesion to the substrates, low values of electrical resistance and degradation at higher temperatures. In this work, silica and alumina sol–gel films were deposited onto silicon steel in order to evaluate the possibility of replacing the commercially available coatings by these sol–gel derived materials. Silica and alumina sol–gel coatings were prepared by dipping silicon steel samples into hydrolyzed silicon or aluminum alkoxides. Samples coated with sol–gel films were studied by scanning electron microscopy, energy dispersive spectroscopy and infrared spectroscopy. Adhesion between silicon steel and sol–gel films was measured by using several standard adhesion tests. Electrical properties were evaluated by the Franklin method. Results showed that homogeneous sol–gel films can be deposited onto silicon steel. Thicknesses of the films could be easily managed by altering the speed of deposition. The structure of the films could also be tailored by introducing additives, such as nitric acid and N, N-dimethyl formamide. Adhesion tests revealed a high level of adhesion between coatings and metal. The Franklin test showed that sol–gel films can produce coated samples with electrical resistances suitable for electrical applications. Electrical properties of the coated samples could also be manipulated by altering the structure of the sol–gel films or by changing the thickness of them.

Evolution of Non-Oriented Silicon Steel Texture on Recrystallization and Grain Growth

The evolution of annealing texture of non-oriented grain silicon steel as a function of annealing temperature was investigated from hot rolled samples taken from industrial production. Hot band samples were annealed at 900°C, cold rolled to final thickness of 0.5mm in a single stage cold rolling process or in two stages with intermediate annealing at 900°C, and final annealed in the temperature range from 540°C to 980°C. The results show that the [001]||RD fibre is an important recrystallization texture component, but it may be consumed by further grain growth and become a minor component. The effect of grain growth in the temperature range investigated seems to be that of strengthening the main components at the expenses of the others. The results suggest that to avoid the reduction of the [001]||RD fibre on grain growth a volume fraction ratio between the texture components (111)[112] and (110)[001] close to unity is necessary after recrystallization. This can be obtained under conditions that enhance [001]||RD fibre on recrystallization, such as: strong [111]ND fibre in the deformation texture, large initial grain size and enhanced grain boundary mobility, by proper composition and purity.

A comparative study of Preisach scalar hysteresis models

In this paper different Preisach-relays-based models are taken into account for the modeling of scalar hysteresis. The main features of such models are presented and discussed, and identification procedures are illustrated, either using complete numerical approaches, or using mixed analytical–numerical approaches. The results obtained for a non-oriented grain steel suggest that the mathematical models of scalar hysteresis taken into account have comparable predictive capabilities and accuracy.

Remarks about preisach function approximation using lorentzian function and its identification for nonoriented steels

In this paper, we will discuss the use of the Lorentzian function as a possible candidate for the accurate approximation of the Preisach function in the modeling of scalar hysteresis for nonoriented grain steels. In particular we discuss here the identification procedure of the parameters of the function from measured data.

Investigation of magnetic and magnetomechanical hysteresis properties of Fe–Si alloys with classical and mechanical Barkhausen effects and magnetoacoustic emission

Grain oriented Fe 3.5% Si sheet samples with a Goss (GO) microstructure and Fe 3.5% samples with nonoriented (NO) grains were tested using two Barkhausen effects, the classical Barkhausen effect (HBE) and the mechanical Barkhausen effect (MBE), as well as the magnetoacoustic emission (MAE). The aim of the work was to present further evidence that the B(H) hysteresis with effects like HBE and MAE, and magnetomechanical hysteresis with MBE are correlated via internal stress barriers pinning domain walls (DWs). In the case of a GO alloy, the long axis of the sample was parallel to the [100], [110], and [111] directions with respect to the rolling direction. The HBE and MAE were measured using a C-core electromagnet supplied with a triangular wave form of current intensity. The MBE intensity was recorded during a monotonous increase of shear stress using a torque machine. The maxima of MBE intensity for the “first load” mode for a NO sample and for three GO samples indicate an internal stress distribution pinning 90° DWs. The MAE plots reveal at least two maxima which are well correlated with H strength values where creation and annihilation of magnetic domains appears. Since the MBE and MAE are associated with abrupt jumps of 90° DW, the existence of MBE and MAE reinforces the fact that such DWs are present in the tested samples. These walls belong mainly to the secondary closure domains at GO alloys and to closure domains at NO alloy.

Microstructure of NiCu multilayers electrodeposited from a citrate electrolyte

Multilayered nickel-copper deposits were produced on rotating cylinder electrodes from a citrate electrolyte. The modulation was 20 nm and 10 nm for nickel and copper sublayers, respectively. Multilayer deposits of the same modulation were prepared using two different current densities for deposition of the copper sublayer, corresponding to kinetic control or to mixed mass transport and kinetic control of the electrode reaction. The microstructure of the NiCu multilayer deposit was determined using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Depending on the applied current density for copper deposition a columnar structure of large grains, oriented in the [110] direction, or an equiaxed structure comprised of small non-oriented grains were observed. The results show that by modifying the deposition conditions for copper it is possible to alter the grain size of the multilayered alloy without changing the modulation.

Relationship between Thermoelectric Properties and Microstructure on n-Type (Bi<sub>2</sub>Te<sub>3</sub>)<sub>0.95</sub>(Bi<sub>2</sub>Se<sub>3</sub>)<sub>0.05</sub> Ceramics Prepared from Mixed

The n-type (Bi2Te3)0.95(Bi2Se3)0.05 was synthesized by modified pulverized and intermixed sintering elements (PIES) method and its figure of merit was evaluated to be 1.8×10-3/K (25°C). The milling mechanism obeyed to the Kick's law and Tanaka's equation. No anisotropy of electrical transport phenomena in thermoelectric properties was observed, because the microstructure consisted of non-oriented grains due to use the milling powders of Bi, Te, and Se as starting materials. Thermal conductivity was smaller than that of single crystal by the large phonon scattering due to small grain, and Seebeck coefficient and resistivity were smaller than that of single crystal due to imcompletely formate solid solution and oxides of sintered body.

Fretting Behavior of Titanium Alloys

Fretting wear tests were performed on three titanium alloys, α + β-Ti-6Al-4V, α-Ti-15V-3Al-3Cr-3Sn, and β-Ti-15V-3Al-3Cr-3Sn, in air. Friction conditions were chosen in order to get gross slip at the interface. The tangential load was recorded during each cycle of the test. Optical and scanning electron microscopy, grazing incidence X-ray diffraction, energy dispersive X-ray analysis and transmission electron microscopy (TEM) were used to characterize the superficial surface layers of the specimens after the fretting test. Particle detachment was observed in every case and the friction coefficient was always very high. A hard tribologically transformed structure (TTS) was detected in some areas of the superficial layers. TEM revealed that TTS was formed of ultra fine non-oriented grains of alpha-titanium. No beta phase was detected. The wear debris particles were produced from the transformed areas of the contact zone and were then quickly oxidized in the interface. The formation of the TTS is interpreted...

Reflectance anisotropy of Carboniferous coals in the Appalachian Foreland Basin, Pennsylvania, U.S.A.

Vitrinite in coal is optically anisotropic in reflected light, because of a preferred orientation of its component aromatic lamellae. This molecular fabric is interpreted to have formed in response to differential stresses ambient during coalification, with maximum reflectance developing incrementally in the minimum compressive stress direction, and minimum reflectance developing incrementally in the maximum compressive stress direction. As a consequence of this interrelationship, coal reflectance fabrics can, under some circumstances, provide a record of stress and strain events occurring during coal metamorphism. Patterns of vitrinite reflectance anisotropy in coal are represented by a three-dimensional graphical form resembling an ellipsoid, termed the vitrinite reflectance indicating surface (VRI), which is analogous in some respects to the finite strain ellipsoid. VRI shapes are measured by estimating the magnitudes of the three principal reflectances, R max, R int, R min, either on oriented blocks or non-oriented grain mounts (Levine and Davis, 1989a). Spatial orientations of the principal axes are determined by reflectance measurements on oriented polished cores. Standard deviations of the principal reflectance axes, measured on oriented cores, average around 0.09% in magnitude and 5° in orientation. Measurements are highly reproducible between pairs of oriented cores. Estimates of the principal reflectance magnitudes, as measured on oriented vs. non-oriented samples, agree on average to within 0.04% for R max, 0.08% for R int, and 0.20% for R min. VRI shapes are graphically depicted on axial ratio diagrams, which plot R max/ R int on the vertical axis and R int/ R min on the horizontal axis. Axial ratio diagrams are also used to depict the progressive change in shape of VRIs during coalification and structural deformation. VRIs of coals from the central Appalachian basin, Pennsylvania, range in shape from biaxial negative to biaxial positive, depending on their coalification history and tectonic setting (Levine and Davis, 1989b). Coal-bearing strata in the North-Central fields (medium-volatile bituminous to semianthracite) in northern Pennsylvania exhibit structural evidence of only mild tectonic deformation. Coals from this region have biaxial negative reflectance, with R min axes roughly perpendicular to bedding, and are only slightly anisotropic in the bedding plane. This VRI geometry is indicative of coalification in a predominantly burial-strain environment with only mild tectonic deformation. With increasing rank toward the southeast, VRIs for this suite of coals plot along a straight-line coalification pathway on the axial ratio diagram. This pathway comes from near the origin and extends through the biaxial negative deformation field, close to the horizontal axis. Maximum reflectance orientations for North-Central field coals are polymodal and aligned with polymodal Alleghanian fold axes (Levine and Davis, 1989b). Low-volatile bituminous coals from the Broad Top field, in the more intensely deformed Valley and Ridge Province, south central Pennsylvania, exhibit much stronger tectonic reflectance fabrics than rank-equivalent coals from the North-Central fields. VRIs are substantially elongated parallel to the fold axes, and some are prolate rather than oblate in shape. Broad Top samples also bear evidence of two superimposed reflectance fabrics, one predating the folding and a stronger one postdating the folding, which indicates that the final rank was attained only after folding was complete in this part of the fold-and-thrust belt. VRIs of coals from the intensely folded Western Middle anthracite field exhibit a wide range of shapes and orientations, which reflects their more complex textonic history. R max axes of sporinite are aligned parallel to bedding, suggesting that the strata were still flat-lying, and not subject to tectonic forces when the coals passed through the first and second coalification “jumps”. In their present-day orientation, vitrinite R min axes of Western Middle field coals are scattered about a great circle distribution, the pole to which is precisely coincident with regional fold axes. When beds are unfolded to a flat-lying orientation they become significantly less scattered, indicating that most coalification here proceded the final phase of Alleghanian folding. A suite of 7 coal samples from the Pioneer Tunnel (underground) coal mine in the Western Middle field ( R mean approximately 4.3%) provides additional constraints used in reconstructing the coalification history. Coal rank increases very slightly down section, but R min decreases down section, opposite to the expected trend. Pioneer mine coals probably attained anthracite rank prior to the principal phase of Alleghanian folding, but at least come coalification continued after folding, as suggested by reconstructed coalification pathways on the axial ratio diagram. During this final phase, the stratigraphically upper beds were coalified more than the lower beds, possibly reflecting thermal re-equilibration of the strata. This latter, syn- to post-tectonic phase of coalification, in the presence of a tectonic stress field, produced elongation of the R max and R min axes, causing the stratigraphically upper beds to attain a prolate space geometry while the stratigraphically lower beds retained their original oblate form.

Differential resistance and critical-current distribution in YBa2Cu3O7-x ceramics.

V-I curves of several Y-Ba-Cu-O samples have been measured in the temperature range 77--91 K in weak magnetic fields (H150 Oe). For the well prepared low-resistivity samples ${\mathit{R}}_{\mathit{f}}$==dV/dI reaches a value of about 0.1${\mathit{R}}_{\mathit{n}}$ (${\mathit{R}}_{\mathit{n}}$ is the normal resistance just above transition) in the linear V-I regime. This is consistent with a picture of decoupled superconducting grains and does not yield any direct information about the flux-flow effects. Because of self-field effects, critical-current density (${\mathit{J}}_{\mathit{c}}$) obtained from transport (and magnetization) measurements does not provide clear insight on the nature of intergrain coupling. Information on the distribution of critical currents, obtained from ${\mathit{d}}^{2}$V/${\mathit{dI}}^{2}$, supports the tunneling and/or proximity-effect coupling between the grains and seems to rule out large enhancements of ${\mathit{J}}_{\mathit{c}}$ in sintered samples with nonoriented grains.

Reflectance anisotropy of Upper Carboniferous coals in the Appalachian foreland basin, Pennsylvania, U.S.A.

Patterns of vitrinite reflectance anisotropy in coal are represented by a three-dimensional graphical form resembling an ellipsoid, termed the vitrinite reflectance indicating surface (VRI). Naturally occurring VRIs from the Northern Appalachian basin, Pennsylvania, range in shape from biaxial negative to biaxial positive depending on their coalification history and tectonic setting. VRI shapes are measured by estimating the magnitudes of the three principal reflectances, R max, R int, and R min, either on oriented blocks or non-oriented grain mounts. Spatial orientations of the principal axes are determined by reflectance measurements on oriented polished cores. The various VRI shapes are portrayed on axial ratio diagrams, i.e. plots of R max R int on the vertical axis and R int R min on the horizontal axis. Axial ratio diagrams are also used to depict the progressive change in VRI shape with coalification. Standard deviations of the principal reflectance axes, as measured on oriented cores, average around 0.09% in magnitude and 5° in orientation. Measurements are highly reproducible between pairs of oriented cores. Estimates of the principal reflectance magnitudes, as measured on oriented vs. non-oriented samples, agree on average to within 0.04% for R max, 0.08% for R int, and 0.20% for R int. Coal-bearing strata in the North-Central coal fields (medium-volatile bituminous coal to semianthracite), in northern Pennsylvania were diagenetically altered in a predominantly burial-strain environment and exhibit structural evidence of only mild tectonic deformation. VRIs from this suite of coals are biaxial negative with R min axes roughly perpendicular to bedding. With increasing rank toward the southeast, these VRIs plot along a straight line pathway on the axial ratio diagram, emanating from near the origin and extending through the biaxial negative deformation field. VRIs of coals from the Western Middle anthracite field exhibit a wide range of shapes and orientations, which is indicative of a more complex tectonic history. In their present-day orientation, R min axes are scattered about a great circle distribution, the pole to which is precisely coincident with regional fold axes. When beds are unfolded to a flat-lying orientation they become significantly less scattered, indicating that most coalification here preceded the final phase of Alleghanian folding. R max axes of sporinite grains are alwayas aligned parallel to bedding, which suggests that the strata were still flat-lying, and not subject to tectonic forces, when the coals passed through the 1st and 2nd “coalification jumps”.

Geotechnical sampling and testing of gas-charged marine sediments atin situ pressures

Gas-charged marine sediments were sampled using a pressure core barrel and a new technique involving standard wireline sampling procedures. Pressure core barrel sampling provides sediments atin situ pressures with no degassing. Analysis of gas content, geotechnical properties and microfabric were performed for samples atin situ pressures and compared with degassed results. Methane concentrations ranged from 3,450 to 137,140 ppm for pressurized samples. Microfabric analyses reveal highly nonoriented clay particles and grains in degassed samples. Degassing of these methane-rich sediments increases porosities and compression indices, while reducing undrained shear strengths and computed preconsolidation pressures.

Topotactical reactions with ferrimagnetic oxides having hexagonal crystal structures—I

A new method is described for the preparation of polycrystalline materials with oriented crystals by reaction of the oriented grains of a strongly anisotropic ferrimagnetic with non-oriented grains of usually non-magnetic components. Using this type of reaction, for which the name “topotactical (or “topotaxial”) reaction” is proposed, oriented samples of Ba 3Co δZn 2−δFe 24O 41, BaCo δZn 2−δFe 16O 27, Ba 2Zn 2Fe 12O 22 and BaCo δTi δFe 12−2δO 19, which have related hexagonal crystal structures, have been prepared as well as some ferrites having the cubic spinel structures.