Gamma Fiber Research Articles

Effect of deformation path on microstructure, microhardness and texture evolution of interstitial free steel fabricated by differential speed rolling

This paper reports the effect of the deformation path on the microstructure, microhardness, and texture evolution of interstitial free (IF) steel processed by differential speed rolling (DSR) method. For this purpose, total height reductions of 50% and 75% were imposed on the samples by a series of differential speed rolling operations with various height reductions per pass (deformation levels) ranging from 10 to 50% under a fixed roll speed ratio of 1:4 for the upper and lower rolls, respectively. Microstructural observations using transmission electron microscopy and electron backscattered diffraction measurements showed that the samples rolled at deformation level of 50% had the finest mean grain size (~0.5μm) compared to the other counterparts; also the samples rolled at deformation level of 50% showed a more uniform microstructure. Based on the microhardness measurements along the thickness direction of the deformed samples, gradual evolution of the microhardness value and its homogeneity was observed with the increase of the deformation level per pass. Texture analysis showed that, as the deformation level per pass increased, the fraction of alpha fiber and gamma fiber in the deformed samples increased. The textures obtained by the differential speed rolling process under the lubricated condition would be equivalent to those obtained by the conventional rolling.

Development of Ultra-Fine Grained Dual-Phase Steels: Mechanism of Grain Refinement during Inter-Critical Deformation

Heavy deformation of metastable austenite (below Ae3) or both austenite and ferrite in the two-phase region (between Ar3 and Ar1) has been found to develop ultra-fine ferrite grain structures with average grain sizes less than 3 μm. The sequence of different dynamic softening mechanisms involved in the grain refinement during heavy intercritical deformation, such as, dynamic recovery, dynamic recrystallization, and dynamic strain induced austenite→ferrite transformation, has been analyzed by considering strain partitioning between austenite and ferrite. Grain refinement is expected to be dictated by dynamic strain induced transformation (DSIT) at higher deformation temperatures (>1100°C) and pronounced dynamic recovery of ferrite at lower deformation temperatures (<1100°C). Evolution of crystallographic texture was dependent on the grain refinement mechanism and gamma fiber components (ND//<111>) and alpha fiber components (RD//<110>) dominated the texture at higher and lower deformation temperatures, respectively.

Magnetic properties and crystallographic textures of Fe 2.6% Si after 90% cold rolling plus different annealing

The effect of rolling and annealing on the crystallographic texture and the magnetic properties of Fe-2.6% Si non-oriented electric steel during 90% cold rolling and different annealing temperature at (600°C, 700°C, 900°C and 1100°C) for 60min and 20min was analyzed. The 97% hot rolled as received material shows development of alpha and gamma fiber texture affecting on the magnetic properties at rolling and transverse direction. 90% cold rolling with moderate annealing temperature (up to 700°C) and 60min annealing time leads to better textures and improved magnetic properties. Due to coarse grained microstructure after annealing, neutron diffractions is an efficient tool for the analysis of Bulk texture of polycrystalline materials, well known for sufficient grain statistics and bulk texture measurement.

Microstructure and Texture Development in Ti-5Al-5Mo-5V-3Cr Alloy during Cold Rolling and Annealing

This study focuses on the microstructure and texture evolution of a Ti-5Al-5Mo-5V-3Cr alloy during cold rolling and annealing treatments. Three samples with different initial microstructures were cold rolled to a 40% reduction in thickness. The starting microstructure of one sample was single β phase while two other specimens were α+β phases with different α particle sizes, distributed in β grains. For all three samples, the average size of primary β grains was 150 µm. The cold rolled specimens were then annealed at 860 °C (10 °C above the β transus temperature) for 5 minutes followed by water quenching. Microstructure development during cold rolling and recrystallization was studied by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) technique. Microstructure investigations showed that massive amount of shear bands occurred during the cold rolling of the single β phase sample while only a few shear bands were observed in the α+β cold rolled microstructures. The cold rolled texture of the sample comprised of a single β phase contains a gamma fibre (//ND) and a partial alpha fibre (//RD). Annealing treatment decreased the intensity of the cold rolled texture in the single β phase sample. Also, it was found that the presence of α precipitates changes the common annealing texture observed in the single β phase specimen.

Recrystallization Microstructure after Annealing inside Magnetic Field

Magnetic annealing at 17T, 800°C, for 15 minutes was conducted to evaluate the effect of the field on the recrystallized microstructure of Fe-3.25%Si samples. According to X-ray results, the main texture components were found not to be affected by the field. The volume fraction of eta fiber was slightly increased and the gamma fiber, an unfavorable texture component for materials with magnetic application, was not decreased when compared to samples annealed without magnetic field.

Thermomechanical treatment for enhancing gamma fiber component in recrystallization texture of copper-bearing bake hardening steel

► Steel for deep drawing is desired to have as high density of γ fiber as possible. ► A process has been developed to increase γ fiber density of CBBH steel sheets. ► The process comprises two first rolling–annealing processes. ► The first step process aims at seeding γ fiber grains. ► The second step process aims at the growth of the γ fiber seed grains. A two-step rolling–annealing process has been developed to increase the 〈1 1 1〉//ND (γ fiber) component in the recrystallization texture of a copper-bearing bake hardening steel. The two step process comprises the first rolling by a low reduction in thickness and subsequent annealing at 780 °C, followed by the second rolling by a high reduction and subsequent annealing at 780 °C. The first rolling process aims at seeding the γ fiber oriented grains, so that they can grow at the expense of differently oriented grains developed in the second rolling process. In this way the density of γ fiber component in the recrystallization texture of the bake hardening steel much increases compared with that in the conventional one-step rolling–annealing process.

Study of texture evolution in metastable β-Ti alloy as a function of strain path and its effect on α transformation texture

Texture evolution in a low cost beta titanium alloy was studied for different modes of rolling and heat treatments. The alloy was cold rolled by unidirectional and multi-step cross rolling. The cold rolled material was either aged directly or recrystallized and then aged. The evolution of texture in α and β phases were studied. The rolling texture of β phase that is characterized by the gamma fiber is stronger for MSCR than UDR; while the trend is reversed on recrystallization. The mode of rolling affects α transformation texture on aging with smaller α lath size and stronger α texture in UDR than in MSCR. The defect structure in β phase influences the evolution of α texture on aging. A stronger defect structure in β phase leads to variant selection with the rolled samples showing fewer variants than the recrystallized samples.

Efficacy of Magnetic Inductive Parameters for Annealing Characterization of Cold Rolled Low Carbon Steel

The evolution of magnetic inductive parameters during the annealing of a cold rolled low carbon steel is examined in order to analyze whether these hysteresis parameters can be useful to nondestructively characterize recovery and recrystallization processes. Unlike the induction values measured at 2500 A/m (B25) , the remanent induction (Br) values are useful to characterize the decrease in the dislocation density during recovery. As a consequence of recrystallization a weakening of alpha fiber texture and an enhancement of gamma fiber texture components take place. The effect of these textural changes on the magnetic magnetocrystalline energy is analyzed and the observed magnetic response is discussed in terms of this variation. Although Br and B25 can be used to monitor recrystallization in the studied steel, B25 values are more sensitive due to the significant effect that textural changes during recrystallization have at high induction values.

The effects of asymmetrical cold rolling on kinetics, grain size and texture in IF steels

Asymmetrical rolling is a promising way to achieve high rolling reductions and potentially grain refinement. However in steels the effect of asymmetrical rolling is not thoroughly quantified. In this paper the impact of cold asymmetrical rolling obtained by changing the roll velocity ratio (from 1.1 to 1.45) on the deformation and recrystallization features has been finely investigated by Electron Back-Scattering Diffraction in a Scanning Electron Microscope. In the investigated conditions (with low thickness reduction), it is found that asymmetrical rolling induces grain refinement and more homogeneous gamma fiber texture.

Evolução da textura cristalográfica de chapas de aço inoxidável ferrítico do tipo AISI 430 durante laminação a frio, recozimento e estampagem

A evolução da textura, nos estados "como recebido", laminado a frio, recozido e após a estampagem, e a estampabilidade de aços inoxidáveis ferríticos AISI 430, estabilizados ao nióbio, foram estudadas. Duas corridas de chapas com espessuras de 3,0 e 0,7 mm foram utilizadas. A de maior espessura foi relaminada a frio e recozida. A de menor espessura, de composição química semelhante à primeira, foi laminada a frio, na usina siderúrgica, e, posteriormente, submetida a estampagem. A textura foi avaliada usando DRX em todas as condições. O aço AISI 430, na condição "como recebido", apresentou forte textura {100}<110>, {100}<120> e a fibra g. Após a deformação, a intensidade da fibra g aumentou e apareceu a fibra a. O recozimento causou o desaparecimento da fibra a e o fortalecimento da fibra g, que é uma textura adequada para a estampagem. Embora o aço AISI 430, de espessura 0,7 mm, tivesse apresentado uma forte textura de fibra g, no estado inicial, as propriedades de estampagem não foram boas e o material trincou durante a conformação.

The Effects of Hot Band Annealing Temperature on the Texture of 1% an 2%Si Nonoriented Electrical Steels

The effects of hot band annealing temperature on the texture of the 1% and 2%Si nonoriented electrical steel were investigated. Slab was hot rolled and then hot band annealed in the temperature range of 900°C~1100°C. The magnetic flux density and the core loss were improved by the hot band annealing because of the texture improvement. As the hot band annealing temperature was increased, the magnetic properties were improved. The microstructure of the hot band was composed of a recrystallized structure at the surface and a deformed structure near the middle plane. These hot bands were completely recrystallized after annealing above 1000°C. The main texture of the hot band was rotated cube and gamma-fibre. After hot band annealing, rotated cube changed to cube texture and gamma-fibre intensity gradually decreased. In the case of specimen without hot band annealing, rotated cube in the middle plane was changed to near {111}<112>texture and Goss texture in the surface to gamma fibre after final annealing. In the case of the hot band annealed at 900°C, Goss texture and cube texture were developed. After final annealing, the {111} and {112} texture was dramatically decreased as the hot band annealing temperature was increased. Although the total {100} texture intensity was not changed, Cube texture, {100}<001>, was strengthened and rotated cube texture, {100}<011>, weakened for 2% Si steel. However, 1% Si steel was opposed to 2% Si steel. The {110} texture was strengthened irrespective of hot band annealing temperature. As the hot band annealing temperature was increased, the Goss texture was strengthened, and this makes the anisotropy of the magnetic flux density bigger.

The Influence of Hot Rolling Finishing Temperature on the Structure and Magnetic Properties of 2.0%Si Non-Oriented Silicon Steel

Rougher bar samples of 2.0%Si and 0.25%Al Non Oriented Grain with 25mm thickness were rolled to 2.3mm in a pilot reversible mill with temperatures ranging from 920 to 1120°C and processed until the final annealing to study the evolution of grain size and crystallographic orientation. The results showed that higher hot rolling finishing temperature results in larger hot band grain size, but the texture, composed mainly by alpha, gamma, {100} , and eta fibers suffers little effect. As a consequence, after final annealing, an increase of fraction of the grains with eta fiber orientation and a reduction of grains with gamma fiber orientation are observed, improving the magnetic induction. The final grain size decreases with hot rolling finishing temperatures above 1040°C in spite of increasing hot band grain size, deteriorating the core loss results. This was explained by the increasing of shear bands when the grain size prior to cold rolling increases. More shear bands generates more sites for nucleation on recrystallization, then smaller final grain size results. The Goss orientation is generated mainly in the sites inside shear bands. The increasing of prior grain size also increases the fraction of grains with Goss orientation after final annealing and its fraction increases suddenly when the hot rolling finishing temperature achieves 1040°C, supporting that affirmation.

The Effects of Hot Band Annealing Temperature on the Texture of 2%Si Nonoriented Electrical Steel

The effects of hot band annealing temperature on the texture of the 2%Si nonoriented electrical steel were investigated. Slab was hot rolled and then hot band annealed in the temperature range of 900°C~1100°C. The magnetic flux density and the core loss were improved by the hot band annealing because of the texture improvement. As the hot band annealing temperature was increased, the magnetic properties were improved. The microstructure of the hot band was composed of a recrystallized structure at the surface and a deformation structure near the middle plane. These hot bands were completely recrystallized after annealing above 1000°C. The main texture of the hot band was rotated cube and gamma-fibre. After hot band annealing, rotated cube changed to cube texture and gamma-fibre intensity gradually decreased. In the case of non-annealed hot band, rotated cube in the middle plane was changed to near {111}<112>texture and Goss texture in the surface to gamma fibre after final annealing. In the case of the hot band annealed at 900°C, rotated cube near the middle plane changed to Goss texture and Goss texture in the surface to rotated cube after final annealing. After final annealing, the {111} and {112} texture was dramatically decreased as the hot band annealing temperature was higher. The total {100} texture intensity was not changed. Cube texture {100}<001> increased and rotated cube texture {100}<011> decreased. The {110} texture increased after hot band annealing irrespective of temperature. As the hot band annealing temperature was higher, the Goss texture increased, and this increase of Goss texture causes the anisotropy of the magnetic flux density.

Evaluation of Annealing Texture in IF and EDD Steel Sheets

The textural and microstructural studies of cold-rolled-batch annealed (CRBA) interstitial free-Ti (IF-Ti) stabilized steel and extra deep drawing steel (EDD) produced at Tata Steel have been investigated. In the IF steels, α-fiber has been found to be strong even after batch annealing, which is not desirable for deep drawing applications. The presence of a stronger recrystallization texture in the surface region rather than in the central region accounts for the deformation and orientation path history of cold-rolling texture components and the texture inherited from hot band. The hot band of IF steel has been observed to have mixture of grain structure along with inhomogeneous texture throughout the thickness. While the inhomogeneity in EDD steel, pancake grain structure in the through-thickness direction, milder pancake grains in the transverse section, and polygonal grain structure in the longitudinal section have led to the inference that the undesirable α -fiber is present. This observation has been explained by the early precipitation of AlN during coiling. The results of all the steels have been explained with the help of the orientation distribution functions, volume fraction of alpha and gamma fiber along with their components, volume fraction ratio (γ /α), and the microstructure. The analysis of the present data suggests that the deep drawability of both steels can be improved by modifying the hot-rolling and annealing parameters.

Texture Evolution of Ferritic (AlSl 430) Stainless Steel Strips during Cold Rolling, Annealing and Drawing

The evolution of the crystallographic texture of ferritic stainless steels, starting from the as received (hot rolled) condition from the steel mill, going through cold rolling, annealing and final stamping is analyzed in this paper. Two ferritic stainless steels (Nb stabilized) having a thickness of 3.0 and 0.7mm, have been employed. The thicker one has been cold rolled to 40 and 73% thickness reduction, annealed at 750 and 850°C for 1 hour. The thinner one, with a similar composition, has been 77% cold rolled and annealed at 870°C at the steel plant and subsequently submitted to deep drawing in order to evaluate texture and drawability. Texture has been evaluated using DRX in the as received, cold rolled, annealed and after drawing conditions. Drawability has been evaluated using tensile testing in order to obtain the FLC curves. AISI 430 stainless steel, in the as received condition presented a strong {100} texture in the <110> and <120> directions and the gamma fiber. After cold rolling, the material presented stronger gamma and weaker alpha fibers. Annealing of the cold rolled samples conduced to the vanishing of the alpha and strengthening of the gamma fiber, adequate for deep drawing operations. In spite of the AISI 430 of 0.7mm having presented a strong gamma fiber, other deep drawing properties were not adequate and the material cracked during stamping.

Texture development during the production of high Si steel by hot dipping and diffusion annealing

The production of non-oriented high Si and Al electrical steel requires specific processing routes such as hot dipping followed by diffusion annealing. The evolution of texture during the different production steps is described. During the preheating and hot dipping the substrates recrystallize with a typical texture presenting an intense gamma fibre. A Fe 3 Si layer with cubic fibre texture is formed during the hot dipping. After hot dipping the substrate is further cold rolled with different levels of reduction and finally diffusion annealed delivering different final textures depending upon the Si content of the substrate and the thermomechanical processing.

The effect of wear and corrosion on internal crystalline texture of carbon steel and stainless steel

Wear and corrosion wear involve mechanical and chemical mechanisms and the combination of these mechanisms often results in significant mutual effects. In this research, wear performances, and texture changes of carbon steel AISI 1045 and stainless steel AISI 304 under simultaneous wear and corrosion were investigated and the results were compared with those obtained from dry wear tests. 3.5 wt.% NaCl solution was used as the corrosion agent and a pin-on-disk tribometer was employed to perform wear and corrosion wear tests. Wear tests of carbon steel and stainless steel samples have shown smaller weight losses and lower friction coefficients in the presence of corrosive environment. Texture investigations of the worn samples have shown texture changes after wear and corrosive wear tests. In worn carbon steel samples after dry wear test 〈0 1 1) 〈1 0 0〉 Goss texture and {1 1 1} gamma fiber component were developed in initially random oriented samples, whereas under corrosive wear conditions, {1 1 1} 〈 0 1 1 〉 fiber texture and {0 0 1} 〈 1 1 0 〉 cube texture were obtained. In stainless steel samples, {1 1 2} 〈 1 1 0 〉 texture component were observed under both dry and corrosive wear conditions, in initially random samples.

Evolution of Texture in Ferritically Hot Rolled Ti and Ti+Nb Alloyed ULC Steels during Cold Rolling and Annealing

The effect of chemical composition and ferritic hot rolling on the formation of texture in the hot rolled and coiled, cold rolled, and cold rolled and annealed ultra-low carbon steels was studied. One of the experimental steels was fully stabilized with respect to carbon, whereas two others were expected to have some carbon in solution under equilibrium conditions. The steels were processed to yield mainly gamma fiber texture intensities in the austenitically hot rolled condition. Three different thermomechanical treatments were applied, including rolling in the ferrite temperature region. After hot rolling and coiling, the steels were cold rolled and annealed. The crystallographic orientations for each condition were presented in the form of so-called skeleton plots along the RD-, TD- and ND-fibers. It was found that the resulting texture in the hot rolled and coiled as well as in the cold rolled and annealed steels was dependent on the degree of recrystallization of the ferritic substructure. A well-advanced state of recrystallization eliminated the detrimental rotated cube component, leaving behind texture with a complete gamma fiber. The average strain ratio, measured for the cold rolled and annealed steels, increased with advancing state of recrystallization and increasing intensity of the {111}‹110› texture component. It was also found that adding 100 ppm of Nb to the Ti alloyed ULC steel increased the average strain ratio by 15% at a given {111}‹110› texture intensity.

Effect of magnetic field applied during secondary annealing on texture and grain size of silicon steel

Temper cold rolled silicon steel samples were annealed with and without an applied magnetic field. The final grain size was the same for both annealing conditions. Application of a magnetic field affected texture development by increasing the strength of the Goss component and decreasing the intensity of the gamma fiber.

Approach to saturation in textured soft magnetic materials

A model has been developed for calculating the anisotropic magnetic properties of soft magnetic materials with the objective of accounting for variations in permeability in textured materials. The model in its current form takes account of the rotation of the magnetization direction in each domain of a textured polycrystal and, thus, is applicable to large applied fields. The magnetization direction is determined by minimizing the sum of the magnetocrystalline anisotropy energy and the energy of interaction between the applied field and local magnetization. Examples are given of the application to idealized textures, such as fiber textures, in which all grains share a common axis parallel to the sheet normal (ND). The cube fiber (〈100〉‖ND) has the highest permeability at any applied field, followed by a randomly oriented polycrystal, with the gamma fiber (〈111〉‖ND) having the lowest permeability. Two further examples are given of textured steel sheets, often referred to as “nonoriented electrical steels,” intended for use as laminations in rotating electrical machinery. In one case, the two samples show that a random texture is preferable to one in which the rolling texture is retained. The second example demonstrates the importance of a particular texture component, the Goss or 〈001〉{110}, for producing an anisotropic permeability.