Fe-3 Pct Si Research Articles

Effect of Cold Rolling Reduction Rate on Secondary Recrystallized Texture in 3 Pct Si-Fe Steel

The phenomenon of secondary recrystallization in 3 pct Si-Fe electrical steel subjected to relatively high cold rolling reduction rates has been investigated. The texture of the secondary recrystallized sample that has a cold rolling reduction rate of 97.2 pct consists mainly of {110}〈112〉 component, which is quite different from the ideal Goss ({110}〈001〉) texture obtained after lower cold rolling reduction rates. The grain boundary character distribution (GBCD) analysis on the primary recrystallized sample with a cold rolling reduction rate of 97.2 pct indicates that the {110}〈112〉 component has the highest frequency of high energy (HE) boundary with a misorientation angle between 20 and 45 deg, whereas the Goss component in the sample subjected to lower cold rolling reduction rates has the highest frequency of HE boundary. These results indicate that the component with the highest frequency of HE boundary surrounding it after primary recrystallization has the privilege to outgrow other components during secondary recrystallization. However, the GBCD analysis for coincidence site lattice (CSL) boundary points out that the Goss component has the highest frequency of CSL boundaries in the primary recrystallized texture irrespective of the cold rolling reduction applied. These results suggest that the HE model can predict the orientation relationship between the primary and secondary recrystallized textures better than the CSL model.

Electropulsing Induced Texture Evolution in the Recrystallization of Fe-3 Pct Si Alloy Strip

Electropulsing induced texture evolution in the primary recrystallization of a Fe-3 pct Si alloy strip was studied using the electron backscattered diffraction technique. The results revealed that the electropulsing strengthened considerably the recrystallization of a cold-rolled Fe-3Si alloy strip. Various textures with high-energy storages, such as α (100)〈110〉, γ (111)〈110〉, γ (111)〈112〉, and G-texture (110)〈001〉, formed after several seconds of electropulsing treatment (EPT), depending on the intensity of electropulsing. The athermal effect of electropulsing is 319 times stronger than the thermal effect of electropulsing for the formation of the G texture. The mechanism of electopulsing induced texture evolution is discussed from the point of view of Gibbs free energy and dislocation dynamics.

Retention of the Twinning Σ3 Misorientation in the Process of Lattice Transformation during Cold Rolling of a Fe3 Pct Si Single Crystal

The article investigates the twinning evolution of two active systems during cold rolling of a (110)[001]-oriented Fe3 pct Si single crystal. An intriguing fact is revealed that for both twinning systems the Σ3 misorientation is retained, regardless of the fundamental difference in their transformation in the course of the matrix crystal lattice reorientation. One of the twinning systems retains the regular habit plane position, while the other acquires an irregular one. A model is proposed that describes the mechanism of such transformations.

Preannealing, Annealing Atmosphere, and Surface-Energy-Induced Selective Growth in 0.1 Pct Mn–Added 3 Pct Si-Fe Alloy Containing 95 ppm Sulfur

The total number of {110} grains after final annealing increased with preannealing and was greater in a hydrogen atmosphere than under a high vacuum. Magnetic induction decreased with increasing total number of the {110} grains. This is attributed to the increase in {110} grain size, the decrease in a range for the selective growth of {100} or {111} grains, and thus the increase in number of {110} grains that show a deviation angle between the \( \langle 001\rangle \) crystal and the rolling directions.

Model of {110}〈001〉 Texture Formation in Shear Bands during Cold Rolling of Fe-3 Pct Si Alloy

A shear band formation model during the cold rolling of Fe-3 Pct Si alloy is advanced. The model assumes a two-stage mechanism based on abnormal twinning according to the {114}〈221〉 system and secondary twinning in two standard {112}〈111〉 systems. As a result, the transformed shear band consists of nearly Goss orientated {11 11 1}〈1 1 22〉 and {111}〈112〉 being symmetrical to initially {111}〈112〉 orientated areas. This model provides an explanation for available experimental data.

Formation Mechanism for the Orientation Relationship between {110}〈001〉 and {111}〈112〉 Grains during Twinning in Fe-3 Pct Si Alloy

A hypothesis is advanced about the origin of areas having close to Goss orientation as a result of secondary twinning in the Fe-3 pct Si alloy. This hypothesis does not contradict available experimental data for single and polycrystals of the Fe-3 pct Si alloy.

Atmosphere change of vacuum to hydrogen and sharpness of {110}〈001〉 texture in thin-gaged 3 Pct Si-Fe alloy strips

Heating in vacuum finally resulted in a main {100}〈uvw〉 texture and a trace of {111}〈uvw〉 texture. However, the texture was changed to the {110}〈001〉 texture when the strip was heated in hydrogen or when the vaccuum was changed to hydrogen at a temperature Tc. As Tc increased, the sharpness of the {110}〈001〉 texture increased, resulting in the high magnetic induction. This can be understood in the light of surface segregation kinetics of sulfur.

Annealing atmosphere, magnetic induction, and the number of {110} grains in inhibitor-free 3 pct Si-Fe alloys

Under flowing hydrogen of a lower flow rate or a vacuum, a high magnetic induction, which arises from the decrease in the number of {110}〈uvw〉≠〈001〉 grains, was obtained from annealed strips. This is due to the surface segregation profile of sulfur that is broadened to the longer annealing time range.

Observation of cold-rolling texture and partially recrystallized texture in polycrystalline 3 pct Si-Fe by high-resolution electron backscattered diffraction

Cold-rolling texture and partially recrystallized texture of polycrystalline 3 pct Si-Fe were investigated using high-resolution electron backscattered diffraction (EBSD) method. From the measurement on a deformed grain with {211}〈011〉∼{111}〈011〉 orientations, deformation bands with {12 4 1}〈014〉 orientation were found. It turned out that the orientation rotation relationship between deformation bands and surrounding deformed grain can be explained by the activation of the slip system, which has a common slip plane with an adjacent grain. Oriented nucleation of recrystallized grains with {12 4 1}〈014〉 orientation was observed in a deformed grain with {211}〈011〉∼{111}〈011〉 orientation. Exactly the same orientation relationship that was observed between deformed grain and the deformation bands was also observed between the deformed grain and the recrystallized grain. A hypothesis that recrystallization nuclei are generated directly from the deformation bands formed by an activation of the slip system that has a common slip plane of neighboring deformed grains was proposed from the present experimental results.

Effect of silicon content and carbon addition on primary recrystallization of Fe-3 pct si

A study was made on the effect of the increase of silicon content and the addition of carbon on the primary recrystallization of silicon steel sheet containing MnS and AlN as inhibitors. The increase of silicon content led to the reduction of the size of primary grains and the intensity of {110} that is considered to represent the amount of {110}〈001〉-oriented nuclei, to the gain of the size of precipitates, and to the coarse dispersion of the precipitates. The carbon addition promoted primary recrystallization and decreased the size of primary grains. From the points mentioned earlier, the increase of silicon content is considered disadvantageous, and the carbon addition is advantageous to the secondary recrystallization of the {110}〈001〉 texture.

The kinetics and micromechanics of hydrogen assisted cracking in Fe-3 pct Si single crystals

The kinetic and micromechanical behavior of hydrogen-assisted cracking (HAC) was evaluated on Fe-3 wt pct Si single crystals with {001} and {00l} orientations. This was accomplished by sustained load tests in gaseous hydrogen under various temperatures and in humid air at ambient temperature. Severe plastic deformation was observed to accompany the hydrogenassisted sustained load slow crack growth. The crack growth proceeded by a tunneling behavior in both orientations, indicating that plane strain conditions promoted the kinetic process. Microscopically, the crack propagated discontinuously with a 1-μm size instability along (1l0) directions, as revealed by fractographic and acoustic emission (AE) results. The crack growth rate was found to exhibit a plateau region with regard to the applied stress intensity. In this stage II regime, the growth rate increased with temperature in the lower temperature Arrhenius rate regime, with an apparent activation energy of 25 kJ/mol. After reaching its maximum at about 100 °C, the growth rate dropped down rapidly, and no slow crack growth was observed above 160 °C. The experimental observations were analyzed to show that the kinetics of HAC were controlled by hydrogen availability rather than by plasticity. Based on this, a transient kinetic model was applied to fit the data. The present interpretation of the crack tip stress field and the HAC nucleation site strongly implies that long-range diffusion of hydrogen over distances ranging from one to several microns is required. The kinetic aspects of this study are presented here with the underlying micromechanics being considered in terms of a decohesion mechanism

The mechanism of hydrogen induced cleavage in Fe-3 pct Si alloy

Hydrogen promotes the cleavage fracture of Fe-3 pct Si alloy. Hydrogen atmospheres moving alone with a dislocation will reduce the strain energy of the dislocation, resulting in decreasing the exte nal stress necessary to operate the Frank-Read source. Thus, hydrogen can promote dislocation mul tiplication, which has been verified using a dislocation decoration technique. Fractography and mechanics analysis indicate that a set of the [001] sessile dislocations on the [001] plane is just a cleavage microcrack. Hydrogen carried by the gliding dislocations will enter into the microcrack and the hydrogen pressure will augment the external stress and reduce the critical numbern necessary to form a stable cleavage crack and the numberm of the piled-up dislocations. This indicates that hydrogen promotes the formation of the stable cleavage crack before the other slip systems operate

The study of desulfurization kinetics in grain oriented 3 percent silicon iron

The desulfurization kinetics in grain oriented 3 Pct Si-Fe have been studied by using the model proposed by Swiftet al.1 The model assumes the desulfurization is diffusion controlled and the sulfur is present as dispersed sulfide particles. Desulfurization experiments were conducted at temperatures ranging from 899 °C to 1171 °C in a dry hydrogen atmosphere with the thickness of sample ranging from 0.138 mm to 0.325 mm. There are wide variations among the published sulfur solubility data in 3 Pct Si-Fe, but theoretical calculations showed good agreement with the experimental results only when the sulfur solubility data published by Brown were used. The effect of MgO coating on desulfurization has also been studied.

New information on texture development in regular and high-permeability grain-oriented silicon steels

The formation of the Goss texture in Fe-3 Pct Si has been studied using crystallite orientation distribution function (ODF) analysis. Textural and microstructural changes through various stages of processing have been investigated for silicon steel with MnS (regular) as well as for steel with a combination of MnS and A1N (high permeability) as grain-growth inhibitor. In both cases the genesis of the final sharp cube-on-edge texture seems to lie in the grains already present in the Goss position in the surface layers of the hot-rolled strip. The major difference in the mechanism of Goss texture formation in the two types of steels is with respect to the relationship between the strengths of the {011}〈100〉 and {111}〈112〉 components through successive processing operations.

High temperature grain growth during slab reheating of oriented 3 pct Si-Fe made using continuous casting

Studies were made into the process behind the excessive grain growth which is observed in continuous cast slabs of both regular and high permeability oriented 3 Pct Si-Fe during reheating from 1230 °C to 1400 °C. These large grains are undesirable because of the greater difficulty incurred in obtaining the suitably uniform and fine primary grain size desired prior to the final high temperature anneal during which the (110) [001] texture is developed. It was found that the driving force for the growth is the subgrain structure which develops due to the strains of solidification and cooling during continuous casting; however, the temperature at which growth initiates is related to the austenite-ferrite phase relationship. The grain growth begins when the austenite which forms during slab reheating decomposes to form highly perfect ferrite which then grows by consuming the strained preexisting (as-cast) ferrite matrix. Data summarizing studies into the energy storage and recrystallization processes which occur with the use of slab breakdown (or prerolling) prior to reheating from 1230° to 1400 °C are also discussed.

A grain boundary etching method for the analysis of intergranular P-segregation in iron-based alloys

The effectiveness of a grain boundary etching method for the non-destructive analysis of intergranular segregation of P in iron-based alloys was examined by using a saturated aqueous solution of picric acid containing sodium tridecylbenzene sulfonate. Among all the alloys examined only those doped with P suffered selective etching attack against grain boundaries. The degree of the etching attack in a P-doped NiCr steel was found to have a linear relation with the concentration of grain boundary P as measured by Auger electron spectroscopy. From these evidences, the grain boundary etching method was concluded to be useful as a technique analyzing the grain boundary concentration of P in NiCr steels. The application of the method was successfully made to CrMo and C-free NiCr steels which are hard to exhibit perfect intergranular fracture. The application was not successful to Fe-40 pct Ni and Fe-3 pct Si alloys whose surfaces were unstable electrochemically compared with those of NiCr and CrMo steels.

The influence of subgrain boundaries on the rate controlling creep processes in Fe-3 Pct Si

The influence of subgrain boundaries on the kinetics of high temperature creep is studied by comparing the creep properties of textured Fe-3 pct Si with the properties of randomly oriented polycrystalline samples of the same composition. The steady state creep properties of the two materials are very nearly the same even though the randomly oriented polycrystalline samples exhibit subgrain formation while the textured samples do not. The transient creep properties of these materials are widely different indicating that the presence of subgrain structure can affect the transient creep behavior without affecting the steady state properties. We find that long creep delays produced by stress reductions during creep are associated with the presence of subgrain boundaries. The textured samples which have no subgrains do not show these transients. It is suggested that the creep transients for the randomly oriented polycrystalline samples are more sluggish than those for the textured samples because recovery involving subgrain boundary movement is slower than that for homogeneous dislocation rearrangement.

Adsorption surface energy and crystal growth in lron-3 pct silicon

The effect of surface energy and sulfur adsorption on secondary recrystallization and texture development in thin sheets of Fe-3 pct Si has been delineated. In the absence of adsorbed sulfur, a {110} secondary recrystallization texture develops. The influence of sulfur on the surface energy hierarchy of the {100} and {110} planes was determined by observing grain boundary motion in thin bicrystals exposed to controlled gaseous environments. High temperature sulfur adsorption isotherms were obtained from a radioactive tracer study and it was found that sulfur adsorbs preferentially on the {100} plane. The Gibbs adsorption equation was used to analyze this preferential adsorption, demonstrating a reversal in the surface energy hierarchy with the {100} becoming the minimum energy plane. Under these conditions a {100} secondary texture develops.

Slip sources in the surface layers of polycrystalline Fe-3 pct Si in the early stages of deformation

Results of a systematic etch-pit study of the distribution of slip sources in successive layers of silicon-iron in its early stages of deformation are presented. These indicate that slip initiates at sources associated with grain boundaries that emerge at the surface and that grain boundary sources lying at progressively greater depths are activated as the applied stress is increased. A simple model is proposed which adequately explains the observed characteristics of slip traces which are nucleated at applied stresses insufficient to propagate them across the grain. Contradictory observations on the nature of slip sources made by other workers on polycrystalline copper are also discussed.

High temperature creep in Fe-3 pct Si

The kinetics and structure dependence of the high temperature-low stress creep of Fe-3 pct Si has been studied and compared with the predictions of current creep theories. It is shown that the steady state creep rate is diffusion controlled and exhibits a power law stress dependence in the temperature range 1393 to 1678 K and stress range 6.9×104 to 1.03×106 Pa. In this same range of experimental conditions the dislocation density present during steady state creep is essentially stress independent. It is shown that current creep theories are incompatible with the experimental results.