Search

This work studies the solidification processes and microstructures of Zr55Cu30Al10Ni5 (at. pct) and Cu64Zr36 (at. pct) amorphous alloy sheets fabricated by twin-roll strip casting. A largely excessive volume was frozen in the alloy during the twin-roll strip-casting process, resulting in many soft regions and the inhomogeneity of the microstructure in the amorphous alloy sheet. The results provide insights into the solidification process of amorphous alloys and guidelines for adjusting their microstructure.

In this paper, two near-net-shape continuous casting technologies (strip casting and compact strip production) were used to produce a typical Si–Mn bearing Advanced High Strength Steel (AHSS) slab/strip, aiming to provide a clear understanding on the cooling rate on the solidification structure and corresponding properties. The results showed that strip casting (SC) technology under sub-rapid cooling conditions owns a higher heat transfer efficiency, and the solidified grains have been obviously uniformed and refined. Meanwhile, a substituted quenching process has been completed under high cooling strength of SC, leading the structural transformation from the initial ferrite/pearlite to the composite structure of martensite and bainite, which provides a very good structural basis for the excellent comprehensive mechanical performance of Si–Mn AHSS.

The study described here is aimed at illuminating deformation mechanism involved in Twin-roll Thin Strip Casting Process (TRSC) with respect to high-permeability 6.5 wt.% Si electrical strip (6.5 wt.% Si strip) in terms of crystal plasticity (CP) theory, and a Visco-plastic Self-consistent model (VPSC) was utilized to explore the deformation mechanism by applying crystallographic orientation (OR) analysis. Results underscore that the activation of overall potential single slip system with regard to studied 6.5 wt.% Si strip including { 110 } 111 > , { 112 } 111 > as well as { 123 } 111 > can contribute to the OR conversion from Cube texture to Rotated-Cube texture, α-fiber texture as well as γ-fiber texture, while with different evolution rate during deformation. The potential multi-slip system of { 112 } 111 > + { 123 } 111 > with average number of activated slip system per grain ~9.1–9.4, and multi-slip system of { 110 } 111 > + { 112 } 111 > + { 123 } 111 > with average number of activated slip system per grain ~10.4–10.8 are identified to be the predominant slip systems during deformation by comparing to the actual OR features obtained from TRSC-processed 6.5 wt.% Si strip. The CP-based method proposed in present study is deemed as a reference to investigate deformation behavior involved in the other semi-solid forming process.

High strength and ductility are vital material properties required in alloys used for structural applications at cryogenic temperatures. However, the simultaneous provision of these characteristics is challenging because the two properties are mutually contrasting from the perspective of dislocation motion. Herein, we prepare binary Al-xMg alloys supersaturated with Mg using a combined technique of twin-roll strip casting and subsequent thermo-mechanical treatment; this produces Al alloys with both high strength and ductility at cryogenic temperatures. Experiments show that gradually adding Mg to Al significantly improves cryogenic tensile properties of the alloys. At the cryogenic temperature of the liquid N2 (−196 °C), the Al-5Mg and Al-7Mg alloys exhibit the ultimate tensile strength (UTS) of 370 and 450 MPa with the corresponding ductility of 93% and 87%, respectively. Comparing Al-xMg alloys with differing Mg contents elucidates avenues of simultaneously improving these properties for utilization at cryogenic temperature. This study provides a simple and robust approach for producing low-cost Al-xMg alloys with excellent cryogenic properties for structural applications.

The solidification process in strip casting using a vertical-type high-speed twin-roll caster was clarified by inserting a 0.1 mm diameter K-type thermocouple into a strip during casting. The roll speeds of the copper rolls were 10 m/min and 30 m/min, and the roll loads were 5 kN and 20 kN. Al-Si alloys with a Si content of 2%, 6%, and 12% were used to investigate the influence of latent heat and viscosity in the semisolid state. The strip temperature increased after exiting the rolls. This indicated that the inside of the strip had not completely solidified at the roll bite, and secondary cooling was necessary to rapidly solidify the inside of the strip. The distance from the roll bite to the solidification starting position ranged from 30 mm to 63 mm. The cooling rate and degree of supercooling increased as the Si content decreased. The cooling rate ranged from 400 °C/s to 4000 °C/s. The cooling rate and degree of supercooling decreased as the viscosity of the semisolid increased.

High strength Al 7075 alloy was manufactured via twin-roll strip casting (TRC) process, and its microstructure, tensile and fatigue properties were investigated. Commercial Al 7075 alloy fabricated via direct-chill (DC) casting process was also used for comparison. T6 and T651 heat treatments were implemented for both the materials to precipitate MgZn2(η) phases. The TRC alloy showed globular grain shape with η phases evenly distributed at the grain boundary and matrix interior, while the DC alloy showed elongated grains due to hot forging process and η phases clumped together at grain boundaries. The TRC alloy’s yield strength was 518.5 MPa, tensile strength was 578.2 MPa, and elongation was 6.9%. Comparing both the alloys’ mechanical properties, the TRC alloy’s strength was at least about 40 MPa higher and elongation was about 4% lower than the DC alloy. The TRC alloy showed about 20 MPa higher fatigue (fatigue limit) than the DC alloy. The DC alloy was observed to have coarse cracks on fatigue fractured surface. By contrast, the TRC alloy showed uniform fractured surface without coarse cracks, and the evenly-distributed η phases improved fatigue resistance efficiently. The present study sought to examine the correlation among TRC process-led microstructure, tensile and high-cycle fatigue properties while discussing the strengthening mechanism.

Al 3003 alloy was manufactured by strip casting process, and the effect of post heat-treatment on tensile and fatigue properties was investigated. The strip cast Al 300 alloy exhibited a unique globular shaped rapid-cooled solidification structure, and the microstructural characteristic remained after heat-treatment. Asstrip cast (F) and heat-treated (O) alloys were commonly composed of Al matrix and strengthening phases such as Al6(Mn,Fe), α-Al(Mn,Fe)Si. In the phase analysis and Factsage simulation result, Al6(Mn,Fe) fraction increased while α-Al(Mn,Fe)Si fraction decreased after heat-treatment. Strengthening phases were more uniformly and finely distributed in the case of O alloy, than F alloy. In the Vickers hardness results, F alloy (measured 59.7 Hv) showed higher hardness than O alloy (measured 53.4 Hv). The yield strengths (YS) and ultimate tensile strengths (UTS) measured 124.8 MPa and 166.4 MPa (F alloy), and 111.2 MPa and 167.2 MPa (O alloy), respectively. F alloy exhibited superior YS compared to O alloy, while UTSs were similar in both alloys. For elongation, the F alloy (19.6%) had a lower value than the O alloy (23.0%). High cycle fatigue tests were performed at room temperature under a stress ratio (R) of 0.1 and frequency (F) of 10 Hz. The F alloy exhibited higher fatigue than the O alloy under all cyclic stress conditions. However, the deviation in the fatigue property of the F alloy was relatively broader than the O alloy. Tensile and fatigue fracture surfaces were examined, and the tensile and fatigue deformation mechanisms of the strip cast Al 3003 alloy were also discussed.

Metals 11(10), 1508 (2021). doi:10.3390/met11101508 special issue: "Special Issue "Casting and Rolling of Alloys" / Special Issue Editor: Dr. tech. n. (NMetAU) Olexandr Grydin, Guest Editor", Published by MDPI, Basel

Sub-rapid solidification and its related interfacial heat-transfer behaviors of molten steel during the process of strip casting are very important, as the total solidification time is less than 0.2 s, and the heat transfer would directly determine the surface defects and the final quality of cast strips during initial solidification of molten steel. In this article, four main topics, including the main research techniques for the study of strip casting technology, the effect of deposited films on heat transfer, the effect of coating on heat transfer, and the steel’s sub-rapid solidification microstructure are reviewed with the purpose to explore the intrinsic mechanism of the complex sub-rapid solidification process and its related interfacial heat-transfer behaviors. The results summarized here can provide guidelines for the optimization of the strip casting process.

In the present work, the microstructure, mechanical properties and corrosion resistance of 2507 super duplex stainless steel (SDSS) fabricated by conventional hot-rolling and strip casting were investigated, respectively. Large deformation in the course of conventional hot-rolling destroyed the coherency of ferrite/austenite interphase and leaded to a deviation from the ideal K-S orientation relationship, which accelerated the precipitation of sigma phase at the phase interface in 2507 SDSS. These brittle particles provided numerous potential void nucleation sites and promoted the propagation of cracks along the ferrite/austenite interface, resulting in severe cracking during conventional hot-rolling. High-quality thin strip without edge cracking was manufactured by strip casting and the edge cutting-off of hot-rolled products was avoided, leading to a significant reduction in cost compared to the conventional process. Meanwhile, the mechanical properties and corrosion resistance of 2507 SDSS fabricated by this new technology reached the same standard of conventional productions. High Temperature-Short Time (HTST) heat treatment was applied in the preparation of the final product, which significantly improved the strength of 2507 SDSS.

Grain-oriented silicon steels were produced by the shortest processing route involving twin-roll strip casting, two-stage cold rolling with intermediate annealing, and simulated continuous annealing. The secondary recrystallization behavior of grain-oriented silicon steels under different inhibition conditions was in-situ observed by combining the confocal laser scanning microscopy (CLSM) and electron backscattered diffraction (EBSD) techniques. The results revealed that the optimal temperature of secondary recrystallization showed a proportional relationship with the Zenner pinning force. In the case of weak pinning force, the abnormal grain growth occurred quickly at ~1050 &deg, C. The corresponding growth rates were in the range of 60&ndash, 1400 &mu, m/min and decreased gradually as the secondary recrystallization proceeded. In the case of strong pinning force, the incubation time and onset temperature of the secondary recrystallization was significantly increased, but the total time of the secondary recrystallization was obviously shortened from 685 s to 479 s, and the final magnetic induction of B8 was increased from 1.7 T to 1.85 T. After the secondary annealing, some island grains and coarse primary grains were retained. The formation of island grain was related to the low migration of grain boundaries. The findings of coarse &gamma, grains indicated that the primary grain size also played a crucial role during secondary recrystallization, apart from the primary recrystallized texture, which attracted more attention previously.

In this study, two types of as-cast microstructure produced by strip casting were cold rolled and annealed to investigate the effect of initial microstructure on the textural evolution and magnetic properties of non-oriented silicon steel. The results indicated that the cold-rolled sheets of coarse-grained strip with pronounced {100} components exhibited stronger λ fiber (〈100〉//ND) and weaker γ fiber (〈111〉//ND) texture as composed to the fine-grained strip with strong Goss ({110}〈001〉) texture. After annealing, the former was dominated by η fiber (〈001〉//RD) texture with a peak at {110}〈001〉 orientation, while the latter consisted of strong {111}〈112〉 and relatively weak {110}〈001〉 texture. In addition, a number of precipitates of size ∼30–150 nm restricted the grain growth during annealing, resulting in recrystallization of grain size of ∼46 μm in the coarse-grained specimen and ∼41 μm in the fine-grained specimen. Ultimately, higher magnetic induction (∼1.72 T) and lower core loss (∼4.04 W/kg) were obtained in the final annealed sheets of coarse-grained strip with strong {100} texture.

Horizontal Single Belt Casting is by far the simplest of all near net shape casting machines and is ideally suited to replace current slab caster operations, given its matching productivity, ‘green...

Large-scale fabrication of Cu36Zr48Al8Ag8 amorphous alloy sheets having with lengths above 250 mm was performed using atmosphere-controlled twin roll strip casting. By constructing a contin...

We investigated the additional (secondary) cooling effect of casted strips on the magnetic properties of Nd–Fe–B sintered magnets. The Nd–Fe–B sintered magnets were fabricated with the casted strips prepared without and with additional cooling. Additional cooling was achieved by blowing Ar gas at various pressures (0.1, 0.3, and 0.6 MPa) on the free-side surface of the strips during the strip-casting process. The higher magnetic properties of Hc, Br, and (BH)max of the final Nd–Fe–B sintered magnets were obtained for 0.1 MPa rather than for 0.0 MPa. The best microstructure of the columnar grains in the casted strips was produced with the aid of a lower pressure of gas on the free-side surface. It was found that the microstructure of the strips affects the distribution of grains grown in the sintered magnets. This report demonstrates that the improved magnetic performance of Nd–Fe–B sintered magnets was achieved via additional gas cooling.

In this study, the effect of the hot-cold rolling process on the evolution of the microstructure, texture and magnetic properties of strip-cast non-oriented electrical steel was investigated by introducing hot rolling with different reductions. The results indicate that hot rolling with an appropriate reduction, such as the 20% used in this study, increases the shear bands and {100} deformed microstructure in the cold roll sheet. As a result, in our study, enhanced η and Cube recrystallization texture and the improved magnetic induction were obtained. However, hot rolling with excessive reduction (36–52%) decreased the shear bands and increased the α-oriented deformation microstructure with low stored energy. It enhanced the α recrystallization texture and weakened the η texture, resulting in a decrease in the magnetic induction. In addition, hot rolling promoted the precipitation of supersaturated solid solution elements in the as-cast strip, thereby affecting the subsequent microstructure evolution and the optimization of its magnetic properties.

Refereed/Peer-reviewed A dual phase steel has been produced directly from the liquid under conditions that simulate direct strip casting and thin slab casting. The kinetics of polygonal ferrite formation during the inter-critical anneal were quantified using the JMAK approach, and this revealed significantly retarded transformation kinetics in the strip cast samples compared to the commercial steel that was processed through the conventional hot rolling approach. The transformation rate in the strip cast samples were as much as three orders of magnitude slower compared to the commercial steel. It was found that the kinetics of the ferrite formation were retarded principally by the large prior austenite grain size in the strip cast samples, and this hypothesis was tested experimentally by both coarsening of the prior austenite grain size, and by refinement of the prior austenite grain size. However, even after grain size normalization, small differences in transformation kinetics between the direct strip cast and commercial steel specimens were observed. These differences were explained by investigation of MnS precipitation in the steels. It was found that the transformation rate is high when the solutes are in solid solution, and that the rate of transformation slows significantly when precipitation of nano-precipitates occurs.

Two low-C steels microalloyed with niobium (Nb) were fabricated by simulated strip casting, one with molybdenum (Mo) and the other without Mo. Both steels were heat treated to simulate coiling at 900 &deg, C to investigate the effect of Mo on the precipitation behaviour in austenite in low-C strip-cast Nb steels. The mechanical properties results show that during the isothermal holding at 900 &deg, C the hardness of both steels increases and reaches a peak after 3000 s and then decreased after 10,000 s. Additionally, the hardness of the Mo-containing steel is higher than that of the Mo-free steel in all heat-treated conditions. Thermo-Calc predictions suggest that MC-type carbides exist in equilibrium at 900 &deg, C, which are confirmed by transmission electron microscopy (TEM). TEM examination shows that precipitates are formed after 1000 s of isothermal holding in both steels and the size of the particles is refined by the addition of Mo. Energy dispersive spectroscopy (EDS) and electron energy loss spectroscopy (EELS) reveal that the carbides are enriched in Nb and N. The presence of Mo is also observed in the particles in the Nb-Mo steel during isothermal holding at 900 &deg, C. The concentration of Mo in the precipitates decreases with increasing particle size and isothermal holding time. The precipitates in the Nb-Mo steel provide significant strengthening increments of up to 140 MPa, higher than that in the Nb steel, ~96 MPa. A thermodynamic rationale is given, which explains that the enrichment of Mo in the precipitates reduces the interfacial energy between precipitates and matrix. This is likely to lower the energy barrier for their nucleation and also reduce the coarsening rate, thus leading to finer precipitates during isothermal holding at 900 &deg, C.

The effect of a simulated coiling treatment on a strip cast Nb-containing steel has been investigated. A lath ferritic supersaturated microstructure was observed in the as-cast condition with no coiling. The microstructure remained lath like during coiling at high temperature (850 °C) and the formation of chemically complex Nb-rich precipitates containing C, N, Si and S was observed. Coiling at an intermediate temperature (700 °C) caused the formation of polygonal ferrite with a dendritic morphology due to chemical micro-segregation. The polygonal ferrite contained Nb(C,N) precipitates. The microstructure remained lath like at the lowest coiling temperature (600 °C). In the latter case the precipitation of Nb-rich clusters was observed, and atom probe tomography revealed them to be ∼85% Fe. Small angle neutron scattering and transmission electron microscopy were used to quantify precipitation kinetics during coiling and the mechanical properties were evaluated with a shear punch apparatus. A yield strength model was developed to describe the observed mechanical behaviour, and this showed that the two largest contributors to strength were the bainitic microstructure and the Nb-rich precipitates. Strategies to further strengthen these materials are suggested. Refereed/Peer-reviewed

As-cast strip of 6.5 wt pct Si steel was fabricated by twin-roll strip casting. After hot rolling at 1323 K (1050 °C), thin sheets with the thickness of 0.35 mm were produced by warm rolling at 373 K (100 °C) with rolling reductions of 15, 25, 35, 45, 55, and 65 pct. Influence of warm rolling reduction on ductility was investigated by room temperature bending test. The measurement of macro-hardness showed that “work softening” could begin when the warm rolling reduction exceeded 35 pct. The room temperature ductility of the thin sheets gradually increased with the increase of warm rolling reductions, and the plastic deformation during bending began to form when the warm rolling reduction was greater than 45 pct, the 65 pct rolled thin sheet exhibited the maximum plastic deformation of about 0.6 pct during bending at room temperature, with a few small dimples having been observed on the fracture surfaces. B2-ordered domains were formed in the 15, 25, 35, 45, and 55 pct rolled specimens, and their average size decreased with the increase of warm rolling reductions. By contrast, no B2-ordered domain could be found in the 65 pct rolled specimen. It had been observed that large-ordered domains could be split into several small parts by the slip of partial super-dislocations during warm rolling, which led to significant decrease of the order degree to cause the phenomenon of deformation-induced disordering. On the basis of these results, cold rolling schedule was developed to successfully fabricate 0.25-mm-thick sheets with good surface qualities and magnetic properties from warm rolled sheets.

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.

The Fe- and Mn-rich intermetallics are of great effect on the mechanical properties of the AA5083 type alloy (Al–5Mg–0.8Mn). The effect of Fe, Si and cooling rate on the formation of the intermetallics were investigated by analyzing the microstructures of the alloys with different Fe and Si contents. The results indicated that increasing the Fe content resulted in the increase of the Al6(Fe,Mn) phase in both amount and size. In the alloys with high Fe content, the platelet-like Al6(Fe,Mn) compounds lined up and formed a band. Increasing the content of Si resulted in the increase of the Mg2Si phase which formed a network structure. Increasing the cooling rate significantly refined the intermetallics. However, increasing the cooling rate did not change the characteristic of the intermetallic compounds in the alloys with low or medium Si contents. For the alloys with high contents of Fe and Si under the condition of near-rapid cooling, the Fe- and Mn-rich intermetallic compound changed to the quaternary Al15(Fe,Mn)3Si phase and displayed a fine fish bone or Chinese script structure. The refinement of the intermetallics would allow higher tolerance of Fe and Si contents in the AA5083 alloy produced, for instance, via the continuous strip casting process.

Low silicon non-oriented electrical steel is produced using a novel strip casting processing route. The focus is on investigating the effects of coiling temperature after hot rolling on microstructure, texture evolution, and magnetic properties. A fine microstructure with weak λ-fiber texture is formed after coiling at 650 °C. By contrast, a much coarser microstructure with a much stronger λ-fiber texture is produced after coiling at 750 °C. After cold rolling and annealing, a fine and inhomogeneous recrystallization microstructure dominated by mild λ-fiber, α-fiber, and γ-fiber recrystallization texture is formed in the case of coiling at 650 °C. By contrast, a coarse and inhomogeneous recrystallization microstructure characterized by strong Goss, α-fiber, and weak λ-fiber together with extremely weak γ-fiber recrystallization texture is formed in the case of coiling at 750 °C. Much lower iron loss and higher magnetic induction are obtained in the latter case as a result of the more desirable recrystallization microstructure and texture. It underscores that the relatively higher temperature of coiling has a similar effect as the conventional hot-band normalizing. Hence, the hot-band normalizing might be omitted in the fabrication of high-performance non-oriented electrical steels using this novel and compact strip casting production route.

A 0.27 mm-thick grain-oriented silicon steel sheet with extra-low carbon was successfully produced by a novel processing route including strip casting, normalizing, two-stage cold rolling with an intermediate annealing, primary annealing, and secondary recrystallization annealing. The evolutions of microstructure and texture along the whole processing route were investigated with a special emphasis on the effects of two-stage cold rolling schedule. It was found that Goss orientation originated in the first cold rolling due to shear banding and relatively strong Goss texture evolved through the whole thickness after intermediate annealing. This is significantly different from the results in conventional process in which the origin of Goss texture is in the hot rolling stage and Goss texture only develops below the sheet surface. Besides, it was found that cold rolling schedule had significant influences on microstructure homogeneity, evolution of λ-fiber texture in primary annealed state and, thus, on secondary recrystallization. In case of appropriate cold rolling schedule, a homogeneous microstructure with Goss texture, relatively strong γ-fiber texture and medium α-fiber texture was observed in the primary annealed strip. Although Goss texture in primary annealed state was much weaker than that in two-stage route in conventional process, a perfect secondary recrystallization microstructure was produced and the magnetic induction B8 was as high as 1.85 T. By contrast, when the cold rolling schedule was inappropriate, the primary annealed strips exhibited inhomogeneous microstructure, together with weak γ-fiber texture, medium α-fiber and λ-fiber texture. Finally, the sheets showed incomplete secondary recrystallization microstructure in which a large number of fine grains still existed.

Preliminary mathematical analyses of different interdendritic cracks associated with variation of heat transfer and generation of interdendritic strain in horizontal twin-roll strip casting have been investigated. A 1-D transient finite difference model of heat flow, dendritic solidification and interdendritic thermo-metallurgical strain has been developed. The model contains two cracking criteria to predict qualitatively and quantitatively the tendency of interdendritic crack formation during dendritic solidification of pure aluminium and 6022 aluminium alloy. The model predictions are compared to available analytical methods and previous measurements. This is to verify and calibrate the model where good and reasonable agreements are obtained, respectively. The variations of heat transfer modes during different contact cooling zones and their effects on the generation of interdendritic thermo-metallurgical strain at the surface and central strip locations have been analysed. The model predictions point o...

There is currently a significant interest in extending the application of novel strip casting technology to a wide range of high strength steels because it allows strip to be cast directly from the liquid metal with minimal rolling. In view of the current interest in developing strip casting technology, we explore here the structure-property relation in extra-low carbon steel, with particular emphasis on an important parameter, the rolling temperature after reheating. The as-cast strip exhibited continuous yielding behavior, significantly lower yield ratio and higher elongation than hot rolled sheets. Coarse and recovered microstructure with Luders-like deformation bands was formed when the reheating temperature was in the range of 800–900 °C and followed by one-pass hot rolling, while coarse-fine mixed microstructure and fine and homogeneous microstructure was formed at 950 and 1000 °C, respectively. These differences in microstructure led to a transition from continuous yielding to discontinuous yielding with increase in reheating temperature from 800 to 1000 °C and followed by hot rolling. The present study underscores that a good combination of yield strength and elongation that is comparable to conventional hot rolled sheets can be successfully obtained through optimization of hot rolling temperature after reheating in the strip casting process.

In this article, evolution of microstructure and texture in non-oriented electrical steels along novel strip casting route and conventional route are comparatively investigated in detail. It demonstrates the similar and important role of the microstructure and texture prior to cold rolling to finally obtain desirable recrystallization microstructure and texture in both routes. In both routes, a high intensity of cube-fiber texture and a low intensity of γ-fiber texture can be acquired in hot strips by optimizing the hot rolling and thermal treatment parameters. Accordingly, after cold rolling and annealing, a lower intensity of γ-fiber texture together with a higher intensity of cube-fiber texture, which are favorable for high-permeability materials, can be obtained in both routes. The desired large grain size in the finally annealed materials to obtain low magnetic losses may be gained by choosing appropriate annealing conditions after the first stage of recrystallization. The features of microstructure and texture are similar at comparable stages. The main differences in the regarded different processing routes are in the practical efforts. The detailed results and deeply corresponding discussion on how the microstructure and texture develop during cold rolling and annealing in differently processed samples will be given in the future work.

Optimization of the microstructure of plates from alloys of the R – Fe – B (R: Nd, Dy) system obtained by pouring the melt onto a rotating copper drum by the method of strip casting is studied. The strip-cast Nd – Fe – B and Nd – Dy – Fe – B alloys with optimized microstructure are used to produce high-energy and high-coercivity sintered magnets.

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.

A grain-oriented silicon steel as-cast strip was produced by twin-roll strip casting. Then the as-cast strip was symmetrically and asymmetrically hot rolled, respectively. The microstructure and texture evolution was investigated by a combination of optical microscopy, X-ray diffraction, and electron backscattered diffraction methods. The microstructure of the as-cast strip consisted of ferrite matrix and martensite, and the texture was characterized by pronounced {001} 〈0vw〉 fiber texture in the outer layers and nearly random texture in the inner layers. After symmetric hot rolling, the microstructure was composed of deformed ferrite grains, proeutectoid ferrite grains and pearlite. The texture was characterized by pronounced {001} 〈0vw〉 fiber texture in the outer layers and mild γ-fiber texture in the inner layers. By contrast, when asymmetric hot rolling was applied, considerably dispersive proeutectoid ferrite and pearlite and relatively strong Goss texture were observed, together with strong {001} 〈0vw〉 fiber texture in the outer layers.

Strip cast samples with different copper content have been developed by simulated direct strip casting. The as-cast microstructures were characterized by optical microscopy and electron microscopy. The microstructures mainly consisted of polygonal ferrite and Widmanstatten ferrite in as cast condition. X-ray diffraction showed that the copper was in solid solution in the as-cast condition. It was found that the equivalent tensile yield and maximum strengths, both increased with an increase in copper content. The strip cast samples were cold rolled to 70% reduction and then annealed isothermally at 600, 650 and 700 °C for various times to study the recrystallization and precipitation kinetics. After annealing, the hardness and strength were found to be decreased due to recovery and recrystallization. It was found that an increase in copper content retarded the recrystallization kinetics. During annealing, precipitation of copper was observed. The copper precipitates were bimodal with respect to particle size and distribution. The size and spacing of the particles were measured and the Zener pinning effect of the particles was calculated. High pinning forces of more than 2 MPa were predicted, and this correlated well with the observed decrease in recrystallization kinetics.

Instead of conventional steel making and continuous casting followed by hot and cold rolling, strip casting technology modified with the addition of a continuous annealing stage (namely, modified strip casting) is a promising short-route for producing ferrite-martensite dual-phase (DP) and multi-phase transformation-induced plasticity (TRIP) steels. However, at present, the multi-phase steels are not manufactured by the modified strip casting, due to insufficient knowledge about phase transformations occurring during in-line heat treatment. This study analysed the phase transformations, particularly the formation of ferrite, bainite and martensite and the retention of austenite, in one 0.17C-1.52Si-1.61Mn-0.195Cr (wt. %) steel subjected to the modified strip casting simulated in the laboratory. Through the adjustment of temperature and holding time, the characteristic microstructures for DP and TRIP steels have been obtained. The DP steel showed comparable tensile properties with industrial DP 590 and the TRIP steel had a lower strength but a higher ductility than those industrially produced TRIP steels. The strength could be further enhanced by the application of deformation and/or the addition of alloying elements. This study indicates that the modified strip casting technology is a promising new route to produce steels with multi-phase microstructures in the future.

We investigated the feasibility of producing high strength Al alloy sheets with high solute contents using a twin roll strip caster equipped with an asymmetric nozzle. The combination of twin roll casting and the asymmetric nozzle used in this study reduced centreline segregation and hot tear, thereby increasing the casting speed. These features of the strip casting allowed the dissolution of more solute elements, suggesting the potential development of high strength Al alloys with a range of Mg contents up to 10 wt-%. The workability and mechanical properties of the cast strips were also evaluated to assess the feasibility of producing high strength Al alloy sheets superior to the present limit of conventional techniques.

A commercial prototype facility for rapid cooling of melts of Fe – Nd – B alloys is designed and produced. The use of the facility for casting alloy Fe – 32% Nd – 1.3% B – 2% Dy – 0.5% Ti raises the magnetic characteristics of sintered magnets. Variation of optimum process modes for making sintered magnets from alloys produced in the facility is described.

The properties of sintered permanent magnets produced by the traditional process (TP) and by a low-oxygen process (LOP) with the use of (Nd, Dy) – Fe – B rapidly hardened plate alloys are compared. Optimization of the LOP gives highly coercive magnets with world-level properties, i.e., B r ≥ 12.7 kGs, H c ≥ 25.0 kOe, and (BH )max ≥ 38 MGs ∙ Oe.

An Fe–6.2 wt%Si strip with equiaxed grains and mild {0 0 1}〈0 v w 〉 fiber texture was produced by twin-roll strip casting process. Then the as-cast strip was treated with or without the hot rolling prior to the warm rolling and annealing. When the hot rolling was not introduced, a fine and heterogeneous warm-rolled microstructure was produced and led to a fine recrystallization microstructure and very weak {0 0 1}〈0 v w 〉 fiber texture in the annealed sheets. When the hot rolling was introduced, a coarse and homogeneous warm-rolled microstructure was produced and led to a very coarse recrystallization microstructure and much stronger {0 0 1}〈0 v w 〉 fiber texture in the annealed sheets. The annealed sheets with hot rolling showed a higher magnetic induction and a higher core loss than those without hot rolling.

Rapid thick strip casting (RTSC) by Anton Hulek, Inventmetall®, is an innovative concept for the production of hot strips with a final as-cast thickness of about 25 mm before rolling. The innovation of the mechanism consists in a vertical mould performing a caterpillar motion. This moving mould has an unconventional parallelogram-shaped cross-section. The conventional rectangular shape is formed in the shaping machine, which is placed straight below the mould. Further elements of the technology are state-of-the-art. For the investigation of this new casting system theoretical calculations were complemented with practical experiments. The investigation focused mainly on two key aspects: the characteristics of the mould and the shaping process. For the practical analysis a static mould with three pairs of elements in laboratory scale was developed and commissioned by the Dept. of Ferrous Metallurgy @ RWTH Aachen University. The shaping experiments were carried out in model scale with two different materials and in variable boundary conditions. The results of these experiments delivered important mechanical as well as thermal informations about the casting system.

The development of continuous casting technology of electrical steel was analyzed. The technologies and products characteristics of conventional continuous casting, thin slab continuous casting and rolling, middle thin slab continuous casting and rolling and twin-roll thin strip were compared. Conventional continuous casting technology was widely adopted in producing electrical steel; thin slab continuous casting and rolling and middle thin slab continuous casting and rolling technology industrialized electrical steel; and study of twin-roll thin strip casting technology was focused on fundamental experiments.