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A medium-Mn steel (Fe–0.3C–4Mn–1.82Al–0.6Si wt-%) was produced by a novel processing route involving twin-roll strip casting, hot rolling and intercritical annealing (IA). Macrosegregation was abse...

A new method for producing high permeability thin-gauge non-oriented electrical steels with 2.3 mm thick Fe-3.2% Si steel as-cast strip was studied. The evolution of microstructure and texture was characterized during the entire processing route. Furthermore, the effects of cold-rolling with large reduction and intermediate annealing process on magnetic properties were studied. The results indicated that the as-cast strip with coarse grains exhibited strong λ-fiber. Coarse equiaxed grains with Cube texture were obtained after first-stage cold-rolling with a reduction of 71.74% and intermediate annealing at 900 °C, which promoted the formation of λ-fiber and α-fiber components in the final cold-rolled sheets. {100}⟨0vw⟩ texture was partially retained from the intermediate annealed grains, and new Cube and Goss components were nucleated within {110}〈110〉 shear bands. The magnetic properties of 0.2 mm final sheets were greatly improved by strengthening λ-fiber component with two-stage rolling process, and best magnetic properties were B50 = 1.758 T, P15/50 = 2.065 W/kg, P10/400 = 15.173 W/kg, P10/1k = 59.48 W/kg.

Grain-oriented silicon steel was produced by strip casting route. The effect of different annealing temperature on primary annealing and secondary annealing was investigated. The result showed that the average grain diameter increased and the grain uniformity was gradually destroyed with the increasing annealing temperature. Regardless of annealing temperature, the primary texture consisted of strong γ-fiber and weak λ-fiber. With the increase of annealing temperature, the γ-fiber intensity increased. In addition, the Goss component was not shown at 780-880 °C but appeared at 980 °C. After secondary annealing, complete abnormal grain growth occurred in all samples and the average grain diameter increased with the primary annealing temperature. The Goss sharpness of secondary grains firstly increased and then decreased with a peak value obtained at 830 °C. This result was explained in terms of the combination of the inhibiting force, primary grain diameter and primary texture.

We elucidate here the significance of cold rolling reduction on Luders band formation and mechanical behavior in cold-rolled intercritically annealed medium-Mn steel. The study indicated that Luders strain can be decreased by decreasing cold rolling reduction. Moreover, inactive recovery and recrystallization of ferrite consisting of a high dislocation density was responsible for the presence of low Luders strain.

The present study focuses on improving the magnetic properties and decreasing the anisotropy in non-oriented electrical steel by optimizing {1 0 0} recrystallization texture. As-cast Fe-1.3%Si strip with {1 0 0} texture produced by strip casting was subjected to hot rolling in the ferrite region, cold rolling, and recrystallization annealing. Magnetic properties and texture evolution after different stages of processing were studied. Annealed sample without hot rolling exhibited pronounced Cube and Goss texture, which led to high permeability but induced a large difference (∼0.15 T) in magnetic induction B50 between the maximum at 0° and minimum at 45° to the rolling direction. The introduction of hot rolling with 17–40% reduction weakened the intensity of recrystallization texture and had small influence on the nature of texture and magnetic induction. However, relatively complete {1 0 0} recrystallization texture was developed in the sample with hot rolling of 55% reduction. On the other hand, the average grain size of annealed sheets gradually increased with the increased hot rolling reduction. As a result, the magnetic induction and the core loss was optimized together with the improvement of anisotropy. The development of recrystallization texture is discussed on the basis of the deformed microstructure and nucleation mechanism, while the magnetic properties are correlated to the magnetic quality of the texture.

The primary annealed sheets of strip-cast grain-oriented silicon steel were isothermally secondary annealed for 15 min under 100% H2 atmosphere. The microstructure and crystallographic orientation at different annealing temperatures were characterized and the secondary recrystallization behavior was elucidated. It was observed that relatively complete abnormal grain growth occurred at 1025 °C. Incomplete abnormal grain growth developed when the temperature was lower than 1025 °C, and normal grain growth occurred when the temperature was higher than 1025 °C. During the abnormal grain growth, both of the Goss and {110}⟨227⟩ grains developed because of the rapid decrease of the inhibiting force and the limited annealing time. Considering the high energy boundary (HE), coincidence site lattice boundary (CSL) and solid-state wetting (SSW) models for abnormal grain growth, the first one explained the development of the Goss and {110}⟨227⟩ grains. Another result was that several matrix grain colonies were observed in the interior or at the boundaries of secondary grains after abnormal grain growth. The grains at the periphery of these colonies showed a large fraction of high energy boundaries (20–45° misorientation) with the surrounding secondary grain and similar grain size with the unconsumed matrix grains. Therefore, these colonies were expected to be consumed by prolonging the annealing time and thus the limited annealing time was responsible for their occurrence. A possible explanation for the dominated high energy boundaries instead of low energy boundaries at the periphery of these colonies was proposed. All of these behaviors promoted the understanding of abnormal grain growth.

A 3.1 mm thick non-oriented Fe-1.0% Si steel as-cast strip was produced by twin-roll strip casting. Samples with/without strip annealing were cold rolled to 0.5 mm and then annealed. The development of microstructure, precipitate and texture was characterized along the entire processing route. It was found that annealing after strip casting had a minor influence on the average grain size and texture of the as-cast strip. A large number of particles precipitated and coarsened during the strip annealing process. Meanwhile, precipitates hindered dislocation slip and crystal rotation such that more significant in-grain shear bands were formed in cold rolled sheets. During recrystallization annealing process, the newly formed fine precipitates in directly cold-rolled sheets consumed stored strain energy and also hindered grain growth. But the initial precipitates in the annealed strip grew further and the effect of pinning of dislocations and grain boundary was lost. Therefore, annealed sheets with strip annealing process showed homogeneous equiaxed grains and the recrystallization texture was characterized by strong λ-fiber texture, which led to high permeability.

High-grade non-oriented electrical steel was successfully processed by controlling texture using strip casting technology. Remarkable abnormal grain growth of {100} grains occurred in the as-cast strip after isothermal annealing. This phenomenon is considered to be the synergistic effect involving the size advantage of coarse columnar grains and surface energy, where the normal grain growth was inhibited by thermal grooving in the surface layer. Special rotation path was identified during the cold rolling process and metastable {118} 〈110〉–{113} 〈110〉 texture dominated the deformation texture. The final annealed sheet exhibited strong Cube texture together with significantly superior magnetic properties.

Thin-gauge non-oriented silicon steel with high strength was successfully processed using strip casting. Texture evolution and strengthening mechanism via nanoscale Cu-rich precipitates were studied to fundamentally understand the balanced combination of magnetic properties and mechanical properties. Coarse equiaxed grains with average size of ∼190 μm and relatively random texture were formed in the as-cast strip, which contributed to the inhomogeneous deformation, resulting in high density of shear bands. Exact Cube was retained from the initial Cube texture and new Goss was formed during the heavy rolling process in the 0.20 mm cold rolled sheet, which promoted relatively strong Cube and Goss texture after recrystallization annealing. The 0.20 mm annealed sheet exhibited high magnetic induction of 1.709 T, which corresponds to the high texture factor of 0.5. The total iron losses were significantly reduced with decrease in thickness, and the P1.5/50, P1.0/400, and P1.0/1000 in 0.20 mm sheet were as low as 2.63, 15.17 and 55.63 W/kg, respectively, which showed a good match between magnetic induction and iron loss. During the aging process, both the magnetic induction and total iron loss exhibited relatively good stability. With increase in aging time, the yield strength first rapidly increased and then slightly decreased. In 0.20 mm sheet, peak yield strength of ∼630 MPa was obtained on aging at 550 °C for 90–120 min. The key mechanism of precipitation strengthening was attributed to the difference in modulus and coherency strain associated with high density of nanoscale precipitates of ∼5 nm. The study revealed that the nanoscale Cu-rich precipitates can be adopted as effective approach to increase the yield strength over ∼100 MPa without deteriorating iron loss in thin-gauge non-oriented silicon steel by strip casting, which guaranteed the balance of magnetic properties and mechanical properties to meet the requirements of high-speed motor.

Ultra-thin grain-oriented silicon steels were processed via the conventional process and strip casting process, and the mechanisms of texture inheritance and inhibitor induced secondary recrystallization were comparatively studied in detail. In the conventional route with commercial grain-oriented silicon steel as the starting material, exact {1 1 1} 〈1 1 2〉 dominated the deformation texture after cold rolling with ~ 63% reduction, and strong Goss texture was formed in 0.08–0.10 mm thin-gauge primary recrystallized sheet. Meanwhile, weak {2 1 0} 〈0 0 1〉 and {h11} textures were also observed because of the inhomogeneous deformation with initial deviated Goss texture. After high temperature annealing, the sheet experienced incomplete secondary recrystallization with abnormal growth of Goss grains accompanied by normal growth of {2 1 0} 〈0 0 1〉 and {4 1 1} 〈1 4 8〉 grains, considering the absence of pinning force on grain boundary migration. In the strip casting process, the intensity of γ-fiber texture was increased, while grain size decreased from ~ 13.3 to ~11.4 μm and the area fraction of Goss grains decreased from 2.8% to 0.6% in the primary recrystallized sheet with decrease of thickness from 0.15 to 0.08 mm. During high temperature annealing process, MnS, (Nb,V)N and AlN provided continuous and sufficient inhibition force for normal grain growth, which guaranteed the formation of complete secondary recrystallization of exact Goss grains. Superior magnetic induction B8 was up to 1.97 T in the strip casting process, which was 0.09 T higher than the conventional route. Meanwhile, the iron losses P1.7/50 and P1.0/1000 were as low as 0.85 and 20.7 W/kg, respectively, which were comparable to the reported ultra-thin grain-oriented silicon steels. The present study provided a novel method to produce high efficiency ultra-thin grain-oriented silicon steel, which may significantly contribute to energy saving in high-frequency electrical devices.

The short communication presents a welding behavior of a dual-phase Mg alloy under different friction stir processes. Growing weld speed obtained different microstructures and ripple spacing of weld joint, and with which the mechanical properties of weld joint generally decreased. Butt-welding joint was more tenacious than lap-welding one.

We elucidate here the impact of niobium in ultra-low carbon grain oriented electrical steel (GOES) in terms of microstructure, texture, precipitation and magnetic properties that was processed by twin roll strip casting. Coarse and complex MnS + NbN precipitates, and fine NbN were nucleated at the grain boundaries and in the interior of the grain in the as-cast strip, which contributed to a small degree of grain refinement together with relatively random texture, and AlN precipitation was suppressed during the strip casting process. NbN continuously precipitated during the entire process and exhibited high stability during the reheating cycle, which provided stronger inhibiting force in comparison to AlN precipitates. As a consequence, fine and homogeneous inhibitors were obtained in the primary annealed sheet in the presence of Nb under cold rolling and annealing parameters used in the present study. On considering the effect of NbN particles or Nb in solution on the deformation and recrystallization behavior, the primary annealed Nb-containing sheet exhibited significantly more homogeneous microstructure in relation to Nb-free GOES, with grain size in the range of ∼8–12 μm, and was characterized by relatively more pronounced γ-fiber and weak Goss texture, beneficial for the abnormal growth of Goss grains. Furthermore, Nb-containing GOES experienced complete abnormal growth during secondary recrystallization annealing, such that the enhanced magnetic induction (B 8 as high as 1.88 T) was obtained. In summary, the present study underscores that NbN can be used as an effective inhibitor in ultra-low carbon grain oriented electrical steel using strip casting technology.

In the present study, a hot-rolled and heat-treated TRIP steel (Fe-0.25C-1.23Si-2.09Mn-2.92Al wt%) was successfully produced by a simple process that involved intercritical heat treatment (IHT) followed by direct quenching without bainite reaction step. The microstructure of the as-cast ingot, as-hot-rolled sheet and heat-treated sheet was studied and related to mechanical properties of the heat-treated sheet. It was observed that δ-ferrite was retained from the solidification stage and remained as a stable phase during different stages of processing because of the alloy design that included ~ 3 wt% Al. Banded structure was obtained in both as-hot-rolled sheet and heat-treated sheet. The microstructure of 770–820 °C heat-treated sheet consisted of δ-ferrite, retained austenite (RA), α-ferrite and martensite. Based on the alloy design and direct quenching process, ~ 20–30% volume fraction of RA was obtained in the heat-treated sheet. The 780 °C heat-treated sheet exhibited an excellent combination of tensile strength and total elongation of 880 MPa and 28%, respectively.

High silicon steel was fabricated by twin-roll strip casting. The cracks on the surfaces of the processed strips were obtained and analyzed by digital camera after series of surface treatment. Optical microscopy (OM) and scanning electron microscopy (SEM) were used to observe and characterize the microstructure nearby crack and fracture surface along the normal direction, respectively, and the crack formation mechanism was further analyzed in conjunction with processing parameters utilized during twin-roll strip casting process. The results indicated that morelongitudinal cracks along the rolling direction were observed in comparison with transverse cracks along the transverse direction on the strip surfaces. Trans granular and intergranular fracture modes both worked during the formations of longitudinal and transverse cracks on the processed strips. The dominant factor causing the formation of crack on the surface of the processed strips was the inhomogeneous transfer of heat during casting and rolling. The inhomogeneous transfer of heat induced by gas gap during casting resulted in variations of dendrite length and secondary dendrite spacing (SDAS). Meanwhile, the casting velocity influenced the formation of gas gap, which further influenced the thermal contraction. So the control of velocity of casting above a certain level proved beneficial to enhancing the performance of strip casting and to improving the quality of strip products.

Grain-oriented 6.5%Si steel was produced by strip-casting, followed hot rolling, cold rolling, primary annealing and secondary annealing. Microstructural and textural evolution was studied with particular focus on the effect of solidified microstructure on the ultimate microstructure and texture. The study indicated that solidified microstructure of the as-cast strip was determined by melt superheat. The relatively low melt superheat resulted in fine equiaxed grains with random texture, whereas large melt superheat led to coarse grains with moderate λ-fiber texture. After cold rolling, the fine-grained steel showed narrow pancake grain structure in comparison to the coarse-grained steel, which was similar to the microstructure of the initial as-cast strip. After primary annealing, fine equiaxed microstructure with favorable {111}⟨112⟩ texture was obtained in the fine-grained steel. While inhomogeneous microstructure with strong α-fiber and moderate γ-fiber texture was obtained in the coarse-grained steel. The desirable microstructure and texture in the fine-grained steel led to abnormal grain growth with B8 = 1.65 T after secondary annealing. By comparison, normal grain growth occurred in the coarse-grained sample with B8 = 1.37 T. Another observation was high frequency core losses of grain-oriented 6.5%Si steel sheet with adequate secondary grains was significantly lower than non-oriented 6.5%Si steel and grain-oriented 3.0%Si steel. The study suggests that the strip-casting is a suitable route to fabricate grain-oriented 6.5%Si steel, and the initial fine grain size with random texture is preferred to obtain adequate abnormal grain growth.

In order to improve the mechanical properties of Inconel 718 alloy produced by sub-rapid solidification, the yttrium (Y) element was added during casting. One alloy with 0.1% weight Y content (0.1Y) and a reference alloy without Y addition (0Y) were produced, which involved homogenization, cold rolling, intermediate annealing, and aging treatment. The influences of Y addition on the microstructure and mechanical properties of Inconel 718 alloy were examined. Due to the precipitation of Ni3Y and Ni17Y2 particles, 0.1Y alloy exhibited a refined grain size and a lower recrystallization fraction. The average grain size of 0Y homogenized sample and 0.1Y homogenized sample were about 50.8 μm and 29.5 μm, respectively. Besides, a higher fraction of δ phase precipitated in the 0.1Y annealed sample, including a large amount of granular or short-rod shape δ phases and a small amount of needle-like δ phases. The area fraction of δ phase in the 0.1Y annealed sample was ~10.45%. However, the area fraction of δ phase in the 0Y annealed sample was lower (~7.93%), and needle-like δ phase was hardly observed under this condition. Compared with 0Y alloy, 0.1Y alloy showed better tensile properties. The 0.1Y alloy after aging treatment exhibited an excellent combination of ultimate tensile strength (~1400 MPa), and total elongation (~20%) when deformed at room temperature.

Low mismatch and low energy interface between precipitates and ferrite matrix was adopted to promote the precipitation of high density of uniformly dispersed coherent NiAl phase in the silicon steel, aiming to improve strength to meet the requirement of drive motor. The precipitation mechanism of NiAl and its influence on magnetic and mechanical properties of silicon steel were studied. The theoretical lattice mismatch between precipitation and matrix was 0.72%, and a new high strength non-oriented silicon steel reinforced by B2 structure NiAl precipitation with a volume content of 1.73% and an average size of 15 nm was prepared. The uniformity of precipitation size and minimization of interface energy remarkably reduced the driving force for NiAl precipitation and hindered the Ostwald ripening. The texture of annealed silicon steel was characterized by strong α* fiber with a peak at {411} and a moderate γ fiber texture with a peak at {111} . With increase in aging time (from 0 h to 16 h), the strength of silicon steel increased to peak values then decreased and the magnetic properties decreased slightly. The nano-scale NiAl precipitation had little effect on coercivity and hysteresis loss of silicon steel while improving the strength of silicon steel, P10/400 and P10/1000, of silicon steel was as low as 21.7 W/kg and 93.3 W/kg, respectively in the peak-aged condition (at 550 °C for 4 h), and the yield strength was 802 MPa. Thus, it is underscored that using NiAl precipitation as strengthening phase improves the mechanical properties of silicon steel without excessively deteriorating the magnetic properties.

A novel high magnetic induction Fe-6.5%Si alloy with B800 that reached up to 1.77 Telsa was prepared by twin-roll strip casting. Electron backscattered diffraction (EBSD) investigations demonstrated that Σ3 grain boundaries formed in the body-centered cubic (BCC) metal solidified microstructure without phase transition where the ratio of grain boundaries was greater than 20%. Transmission electron microscopy (TEM) revealed that the partial Σ3 grain boundaries are BCC structured twinning. A certain amount of Σ3 boundaries were inherited from the process of warm rolling, cold rolling and annealing, which acted to stabilize the matrix grain boundaries, resulting in the formation of a perfect Goss microstructure with excellent magnetic properties.

An unconventional cold rolling scheme (inclined rolling at 0°, 30°, 45°, 90° during second-stage cold rolling process) was adopted to process grain-oriented silicon steel based on strip casting process. The influences of inclination angles on microstructure, texture, inhibitor and magnetic properties were studied by a combination of EBSD, XRD and TEM. It was found that the α-fiber texture was weakened and γ-fiber was strengthened in cold rolled sheet with increase in inclination angle. The primary recrystallization sheet exhibited more homogeneous microstructure with relatively strong γ-fiber, medium α-fiber texture, weak λ-fiber texture and Goss component at high inclination angles. Fine and homogeneous inhibitors were obtained after primary annealing with increase in inclination angle from 0° to 90° because of more uniform deformation after inclined rolling. The grain-oriented silicon steel experienced completely secondary recrystallization at various inclination angles after final annealing process, with superior magnetic properties at 0° and 90°. Furthermore, Goss nuclei capable of final secondary recrystallization in strip casting process newly formed both in-grain shear bands and grain boundaries region during second-stage cold rolling and subsequent annealing process, which is different from the well-accepted results that Goss texture originated from the subsurface layer of the hot rolled sheet or during intermediate annealing process. In addition, the Goss texture that nucleated in-grain shear bands was weaker but more accurate as compared to that in grain boundaries region.

A novel ultra-low carbon grain oriented silicon steel was successfully produced by strip casting and two-stage cold rolling method. The microstructure, texture and precipitate evolution under different first cold rolling reduction were investigated. It was shown that the as-cast strip was mainly composed of equiaxed grains and characterized by very weak Goss texture ({110} ) and λ-fiber ( //ND). The coarse sulfides of size ~100 nm were precipitated at grain boundaries during strip casting, while nitrides remained in solution in the as-cast strip and the fine AlN particles of size ~20–50 nm, which were used as grain growth inhibitors, were formed in intermediate annealed sheet after first cold rolling. In addition, the suitable Goss nuclei for secondary recrystallization were also formed during intermediate annealing, which is totally different from the conventional process that the Goss nuclei originated in the subsurface layer of the hot rolled sheet. Furthermore, the number of AlN inhibitors and the intensity of desirable Goss texture increased with increasing first cold rolling reduction. After secondary recrystallization annealing, very large grains of size ~10–40 mm were formed and the final magnetic induction, B 8 , was as high as 1.9 T.

An ultra-low carbon grain-oriented silicon steel as-cast strip is produced by twin-roll strip casting process, and subsequently subjected to one-pass hot rolling, one-stage cold rolling, primary annealing, and secondary annealing. The effect of hot rolling process on microstructure, texture, and inhibitor evolution is studied. It is shown that the precipitation behavior of AlN particles is significantly affected by the hot rolling temperature and the optimal precipitation temperature is ≈1100 °C. On the other hand, the intensity of Goss texture in hot-rolled sheets is determined by hot rolling reduction, which is limited in the strip casting process and the hot-rolled Goss texture is relatively weak compared to the conventional process. The primary annealed Goss texture can originate from the cold rolling process and this texture is homogeneous through the thickness, besides the inherited hot-rolled Goss texture mainly presented in the subsurface layer. Thus, relatively strong Goss texture in primary annealed sheets is obtained. The results indicate that the hot rolling process is an efficient way to optimize the texture and precipitation in strip-cast silicon steel, and relatively good magnetic properties can be obtained by the strip casting process.

A 0.23 mm grain-oriented 4.5 wt% Si steel sheet was prepared by strip casting, hot rolling, one-stage warm rolling, primary annealing and secondary annealing. A detailed study of microstructure, texture and precipitate was carried out by methods of OM, EBSD, XRD and TEM. It was found that the as-cast strip exhibited equaxied microstructure with random orientation, enabling the fine and homogeneous primary microstructure to be obtained after one-stage warm rolling. After hot rolling, weak Goss texture was observed, which could not act as Goss seed. In contrast, the Goss seed was found to originate within the shear bands in {111}〈112〉 grains during warm rolling. Another finding was that the precipitates was suppressed during strip casting due to the rapid solidification and subsequent cooling rate, and mainly precipitated during hot rolling. After secondary annealing, abnormal Goss grains evolved sufficiently, and showed prominent properties. The B 8 was 1.73 T, which was similar to 1.85 T for grain-oriented 3.0 wt% Si steel, and the core losses were low than the grain-oriented 3.0 wt% Si steel and non-oriented high silicon steel.

A Fe-1.3% Si non-oriented silicon steel strip was produced by twin-roll strip casting process, and subsequently treated with cold rolling and annealing. The effect of heating rates on the recrystallization and precipitation behavior of second phase particles (AlN and MnS) was investigated by MMS-200 thermal mechanical simulator. It was found that the recrystallization area fraction decreased obviously with the increase of heating rate. At the heating rate of 5 °C/s, the recrystallization rate gradually decreased with the extension of holding time, but it increased at the rapid heating rates. The particle’s sizes mainly concentrated in 50~200 nm at the heating rate of 5 °C/s during annealing. The number of particles under 50nm increased gradually and the number of precipitates between 50~400 nm reduced significantly when the heating rate was increased to 50~300 °C/s. The results indicated that the rapid heating rate could refine the size of precipitates and decrease the number of particles above 50nm.

A Fe-3wt% Si strip was produced using a vertical type twin-roll casting process. Sub-grains with an inhomogeneous distribution through the thickness direction were firstly observed in the as-cast strip. It was found that the surface layer was characterized by columnar grains containing lineage sub-grains, the subsurface layer was dominated by numerous polygonal sub-grains inside columnar grains or fine equiaxed grains, and the center layer was composed of coarse equiaxed grains without sub-grains. In addition, the sub-grain boundaries provided additional nucleation sites for precipitates and the nanoscale MnS particles were successfully obtained. Moreover, the average size of MnS precipitates in the surface layer was smaller than that in the subsurface layer. The inhomogeneous distributions of sub-grains and precipitates can be attributed to the large temperature gradient through the thickness direction during the strip casting process.

Grain-oriented 6.5% Si steel was produced by strip casting and the effect of warm rolling and cold rolling at the latter stage of rolling was investigated. The result showed the rolling method had a minor influence on the rolling microstructure but significant on the rolling texture. Compared to the cold-rolled sheet, the warm-rolled steel showed strong α -fiber and γ -fiber texture at the surface but weak α -fiber and γ -fiber texture in the center layer. After primary annealing, the warm-rolled sheet showed inhomogeneous microstructure and strong { 2 2 3 } 〈 1 1 0 〉 texture together with weak γ -fiber texture. By comparison, the cold-rolled sheet showed fine equiaxed grain with favorable { 1 1 1 } 〈 1 1 2 〉 texture component. During secondary annealing, the warm-rolled sample displayed significantly normal grain growth at the initial stage and abnormal grain growth at ~1150 °C. The final microstructure was characterized by coarse matrix grains and abnormal Goss grain. In contrast, the cold-rolled sheet showed complete abnormal grain growth. The different secondary annealing behavior was attributed to different grain structure and texture.

This paper proposes the influence factors of coupling effects of shearing flow and vibration on diffusion coefficient and critical nucleation energy during metal solidification. Based on this proposal, a metal solidification–nucleation–rate model under coupling effects of shearing flow and vibration is established. Verification experiment using Al–7Si alloy is carried out. When vibration frequency and melt flow velocity are zero, the results calculated by the above model agree with that calculated by Turnbull’s theory. The results calculated by the above model under coupling effects of shearing flow and vibration agree with the experimental results, with the error within 0·2–14·3%. So the established model can calculate and explain the nucleation rate of melt under coupling effects of shearing flow and vibration.

The mechanism responsible for secondary recrystallization is still disputed in grain oriented silicon steel. This is mainly related to the complexly of itself. In this work, the occurrence of {2 1 0} texture through secondary recrystallization was observed in the grain oriented silicon steel with Cu 2 S as main inhibitor. In order to elucidate the abnormal growth of {2 1 0} grain, texture evolutions in Fe–3% Si–0.5% Cu steel were investigated using micro-texture analysis. In addition, the {2 1 0} texture was used to validate the current mechanisms of secondary recrystallization. The result indicates that the surface energy plays a significant role in the selection of secondary recrystallization besides the characteristics boundaries which are linked to high mobility.

An ultra-low carbon Fe–3%Si grain oriented electrical steel strip was produced by a twin roll strip casting process. Next, the strip with or without annealing was cold rolled and subsequently annealed. The effect of annealing after strip casting on the texture development was studied using macro-/micro texture analysis. Due to the rapid solidification, the precipitation behavior of second phase particles was suppressed and very few particles were observed in the as-cast strip. The direct cold rolled texture was characterized by strong α ( //RD) and weak γ ({111}//ND) fibers. While, in the annealed strip, a large number of particles were precipitated during the annealing of the cast strip and these particles hindered the crystal rotation during cold rolling such that part of the initial solidification texture remained in the cold rolled sheet. In the case of the direct cold rolling process, the precipitation occurred before recrystallization during primary annealing. These fine particles had a significant pinning effect on dislocations and further retarded the recrystallization behavior, leading to relatively strong α-fiber in the primary annealed sheet. On the other hand, compared with the fine and dispersed particles precipitated during the strip annealing process, the distribution of particles precipitated during primary annealing were inhomogeneous. Therefore, there was no secondary recrystallization during secondary annealing, which was distinct from the strip annealing process where abnormal growth of Goss grains were observed and the magnetic properties were significantly improved.

Non-oriented electrical steel as-cast strip was produced by twin roll strip casting process, and subsequently cold rolled and annealed at heating rates in the range of 3–450 °C/s with the aim to elucidate the effect of heating rate on the evolution of recrystallized microstructure and texture. The average grain size was rapidly increased when the heating rate was increased from 3 to 25 °C/s, and decreased when the heating rate was greater than 25 °C/s. The average grain size did not increase linearly with heating rate, which was related to different degree of nucleation and growth rate. The recrystallization texture exhibited pronounced improvement during rapid annealing. At high heating rate, the Goss and Cube had a higher probability of nucleation of shear bands with high stored energy, while the intensity of the γ-fiber texture was significantly reduced. The highest B50 value attained was 1.803 T at a heating rate of 300 °C/s. The study indicates that rapid heating has strong effect on the recrystallization behavior in non-oriented electrical steels, which facilitates optimization of microstructure and texture, especially in the coarse-grained structure.

Grain oriented silicon steel was produced by strip casting and two-stage cold rolling processes. The development of microstructure and texture was investigated by using optical microscopy, X-ray diffraction and electron backscattered diffraction. It is shown that the microstructure and texture evolutions of strip casting grain oriented silicon steel are significantly distinct from those in the conventional processing route. The as-cast strip is composed of coarse solidification grains and characterized by pronounced 〈001〉//ND texture together with very weak Goss texture. The initial coarse microstructure enhances {111} shear bands formation during the first cold rolling and then leads to the homogeneously distributed Goss grains through the thickness of intermediate annealed sheet. After the secondary cold rolling and primary annealing, strong γ fiber texture with a peak at {111}〈112〉 dominates the primary recrystallization texture, which is beneficial to the abnormal growth of Goss grain during the subsequent high temperature annealing. Therefore, the secondary recrystallization of Goss orientation evolves completely after the high temperature annealing and the grain oriented silicon steel with a good magnetic properties ( B 8 =1.94 T, P 1.7/50 =1.3 W/kg) can be prepared.

Texture evolution in Fe-1.3%Si steels with ultra-high magnetic induction produced by strip casting, cold rolling and annealing was investigated using macro-/micro-texture analysis. A new and strong {1 1 0} fiber has been founded in thin as-cast sheets. The in-grain shear bands with the Cube orientation can be observed in deformed {1 1 0}〈1 1 0〉 grains after cold rolling. The new Cube grains are mainly nucleated and grow within those shear bands at the beginning of recrystallization and consequently determine the overall annealing texture.

In this work, the evolution of microstructure, texture and magnetic properties of non-oriented 1.3% silicon steel processed using the twin-roll strip casting was investigated, especially under different solidification structures. A number of microstructures about the as-cast strips show that the initial solidification structure of casting a strip can be controlled by the melt superheats. The microstructures with the average grain size of ∼100–400 μm can be obtained in strips when the melt superheats are from 20 to 60 °C. A nearly random, diffuse, homogeneous texture under a low melt superheat, but comparatively developed {100} oriented grains are formed under a high melt superheat through the cast strip thickness. The relatively low core loss and high magnetic induction can be obtained in the cold rolled and annealed sheets when increasing the initial grain size of cast-strip. The textures in annealed sheets with coarse initial grain size are characterized by the relatively strong Goss component and {001} fiber but weak γ-fiber component, which lead to the high permeability.

The simulation studies were carried out on the oriented silicon steel produced by thin slab casting and rolling (TSCR) and twin-roll strip casting in the laboratory. The precipitation of inhibiter, formation of microstructure and texture were investigated before cold rolling. The inhomogeneous microstructure and texture gradient were observed in the 7-pass hot-rolled strip（2mm）for TSCR process, and texture gradient was not changed after normalizing, and the twin-roll strip casting directly supplied a strip with approx 2mm of thickness being same as that of hot-rolled strip by TSCR. The microstructure of twin-rolling casting strip was almost composed of all equiaxed grains which similar to the normalizing microstructure in TSCR process, but the random texture was obtained by twin-rolling strip casting. The dispersed and clustered precipitates were presented in hot-rolled strip when the ingots were soaked at 1200°C and 1150°C respectively for the TSCR process. And disperse and acicular precipitates were observed by TEM for air-cooling cast strips for process twin-rolling casting.

Grain-oriented 4.5%Si steel is processed by strip casting and two-stage rolling with second rolling reduction varied from 53.3 to 82.7%. The microstructure and texture evolution are studied with emphasis on the effect of second rolling reduction on secondary recrystallization. After secondary annealing, significant abnormal grain growth occurs for all reductions in the range of 53.3–82.7%. The underlying reason is the strong inhibiting force induced by additional Nb, and the grain diameter of the secondary grains increase with increased rolling reduction. Additionally, the sharpness of secondary grains to ideal Goss orientation increase with increase in second rolling reduction. This is attributed to decreased inhibiting force drop rate between abnormal grain growth of precise Goss and deviated Goss grains with increased rolling reduction. Another interesting aspect is enhancement of magnetic induction B8 and significant reduction in high frequency (400–1000 Hz) core losses with increase in second rolling reduction. Optimal magnetic properties are obtained in the steel subjected to 82.7% rolling reduction. The present study suggests that strip casting is an effective approach to fabricate grain-oriented high silicon steel, especially thin-gauged steels with superior magnetic properties.

Here, the authors elucidate the microstructure and texture evolution in ultra-low carbon grain oriented silicon steels with (Cu,Mn)S and Nb(C,N) as inhibitors. Both Cu- and Nb-bearing steels exhibit microstructural and texture gradients across the thickness. The surface layer is characterized by recrystallized equiaxed grains, while the subsurface layer is dominated by strong Goss texture, and the center layer is composed of elongated deformed bands with strong α-fiber including {100} ∼{223} texture. In contrast to the Cu-bearing hot rolled sheet, the deformed center zone of Nb-hot rolled sheet is broadened and indicate a new {111} component, while the neighboring Goss zone, which act as the nuclei for secondary recrystallization is reduced. Also, the fraction of Goss texture in Nb-primary recrystallized sheets is lower than Cu-primary sheets in a series of specimens subjected to identical annealing temperature prior to secondary recrystallization because of inheriting texture of hot rolled sheets. On the other hand, compared to the (Cu,Mn)S particles, the Nb(C,N) particles significantly hinder the primary recrystallized grain growth. The onset of secondary recrystallization for Cu-bearing steel is 950 °C, while the growth of Nb-primary grains continue to be strongly inhibited at 975 °C. After high-temperature annealing, a high magnetic induction (B8 is ≈1. 8 T) is obtained in Cu-bearing steel. In contrast, in Nb-bearing steel, there is no secondary recrystallization or the non-Goss grain ({113} ) is abnormal growth, and the magnetic induction B8 is ≈1.48–1.5 T. The lower magnetic induction of Nb-bearing silicon steel is related to the lower fraction of primary Goss texture and the stronger pinning effect of Nb(C,N) inhibitors.