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In this study, S1 and S2 with different Mn-Si contents and Mn/Si mass ratios are prepared for the film deposition and interfacial heat transfer experiments using the droplet solidification technique. The effect of Mn-Si contents and Mn/Si mass ratios on the film deposition and interfacial heat transfer behaviour are investigated. The results revealed that the increase of Mn content (from 0.403 wt.% to 0.621 wt.%) and Si content (from 0.145 wt.% to 0.171 wt.%) resulted in a higher film deposition rate (from 1.23μm to 1.43μm per droplet test), as evidenced by the enhancement of thickness (from 11.07 μm to 12.86 μm), particle size (from 1250 nm to 1340 nm), and surface roughness (from 2.580 μm to 3.217 μm) of the deposited film after 9 experiments. Moreover, an increase in the Mn/Si mass ratio of the sample from 2.78–3.63 leads to a corresponding enhancement (from 65.67 wt.% to 71.02 wt.%) in the MnO content within the film. As a result, the melting point (from 1319°C to 1348°C) and thermal resistance of the obtained film exhibit a gradual increase, thereby limiting the extent of improvement in interfacial contact conditions and ultimately diminishing the enhancement of interfacial heat transfer behaviour by the deposited film. Additionally, the transition point in interfacial heat transfer behaviour occurs earlier for a higher Mn and Si content and higher Mn/Si mass ratio due to a higher film deposition rate and melting point. [ABSTRACT FROM AUTHOR]

The elaboration of suitable NdFeB‐based permanent magnets is essential for high‐performance electrical machines in a number of applications. In this respect, the understanding of the relationship between heat transfer phenomena and the final solidified microstructure is the key to the control of the grain size and the improvement of the magnetic properties. The problem is even more acute with the emergence of new manufacturing processes, such as the laser powder bed fusion, where the cooling rates are much higher than those encountered in the standard strip casting process and where the microstructure can be considered as fixed from the fabrication step. The objective of the present work is to identify correlations between interstructural spacings in the solidified alloys and cooling conditions. This study is based on a methodology coupling experimental and numerical simulation approaches featuring three solidification processes: strip casting, arc melting, and laser fusion. The obtained results cover more than four orders of magnitude in terms of cooling rates R and allow to propose a reliable empirical relationship between the interstructural spacing λ and R of the form λ [μm] = 83 R [K s−1]−0.36. This relation can thus be used to estimate cooling rates from metallographic observations. [ABSTRACT FROM AUTHOR]

The interfacial wettability and heat transfer behavior are crucial in the strip casting of high phosphorus-containing steel. A high-temperature simulation of strip casting was conducted using the droplet solidification technique with the aims to reveal the effects of phosphorus content on interfacial wettability, deposited film, and interfacial heat transfer behavior. Results showed that when the phosphorus content increased from 0.014wt% to 0.406wt%, the mushy zone enlarged, the complete solidification temperature delayed from 1518.3 to 1459.4°C, the final contact angle decreased from 118.4° to 102.8°, indicating improved interfacial contact, and the maximum heat flux increased from 6.9 to 9.2 MW/m2. Increasing the phosphorus content from 0.081wt% to 0.406wt% also accelerated the film deposition rate from 1.57 to 1.73 µm per test, resulting in a thickened naturally deposited film with increased thermal resistance that advanced the transition point of heat transfer from the fifth experiment to the third experiment. [ABSTRACT FROM AUTHOR]

Conventional book casting of Sm2TM17-type alloys (where TM = Co, Fe, Cu, Zr) leads to a coarse, highly segregated microstructure, predominantly due to the slow, variable cooling rate from the mould surface towards the centre of the ingot. These cast alloys require a long homogenisation treatment to remove this segregation and develop a super-saturated, metastable SmTM7-type hexagonal phase. This SmTM7 phase is a vital precursor phase required during magnet production to develop the complex cellular structure responsible for high magnetic properties. In this work, strip casting was employed to facilitate rapid solidification to develop thin flakes (<0.5 mm thick) with a columnar grain structure. Rapid cooling has the potential to produce a homogenous microstructure consisting predominantly of the metastable SmTM7 phase. This could remove or significantly reduce the need for the energy-intensive homogenisation treatment usually required in conventional magnet manufacture. This paper investigates the effect of wheel speed (and hence cooling rate) on flake thickness, microstructure, and phase balance of the cast alloys. It was shown that for wheel speeds between 1.1 and 3.0 m/s, the microstructure showed large variation; however, in all cases, evidence of the columnar SmTM7 phase was presented. The adhesion between the melt and the wheel was deemed to be critical for the nucleation and subsequent columnar growth of SmTM7 grains, where the wheel speed controlled both the flow of the alloy onto the wheel and the thickness of the resultant flake. It was determined that in order to achieve a homogenous columnar SmTM7 structure, the maximum flake thickness should be limited to 270 μm to avoid the formation of equiaxed Sm2TM17 grains through insufficient cooling. [ABSTRACT FROM AUTHOR]

The non-oriented Fe-6.5wt.%Si alloy cast strip with a width of 100 mm and a thickness of 1.7 mm was prepared by the top side-pouring twin-roll-casting (TSTRC) process. The surface quality of the air-cooled and water-cooled cast strip was good. Compared with the Fe-6.5wt.%Si alloy ingot, the Fe-6.5wt.%Si alloy cast strip has a fine solidification structure and exhibits certain plasticity at room temperature. Microhardness, XRD, and TEM investigated the ordered structure and degree of Fe-6.5wt.%Si alloys prepared by three different cooling methods. The results show that the Fe-6.5wt.%Si alloy ingot prepared by the standard method has many B2-ordered phases and D03-ordered phases, and the order degree is high. The Fe-6.5wt.%Si alloy cast strip prepared by the TSTRC process has a low degree of order and only contains a small B2-ordered phase. The faster cooling rate effectively inhibits the formation of the D03-ordered phase and B2-ordered phase. The growth of the ordered phase also reduces the reverse domain boundary energy, reduces the motion resistance of superdislocations, and increases its mobility, thereby improving the room temperature plasticity of Fe-6.5wt.%Si alloy cast strips. [ABSTRACT FROM AUTHOR]

Twin‐roll strip casting is a near‐net‐shape casting technology that can produce thin steel strips directly from molten steel. Stably controlling the molten steel level is regarded as an important issue to ensure strip quality and casting process stability. As the control of the molten steel level is a time‐varying, nonlinear, and multidisturbance complex system, it is difficult to establish an accurate process model for designing a model‐based controller. Top side‐pouring twin‐roll casting is a new kind of twin‐roll strip casting technology. This study introduces the control system of the top side‐pouring twin‐roll casting process. A fuzzy logic controller (FLC) with its fuzzy rules optimized by particle swarm optimization (PSO) is developed to regulate the molten steel level. Simulation results show that the performance of the FLC can be improved while its fuzzy rules are optimized by PSO. The objective function of PSO has a great influence on the optimization of the fuzzy rules. The top side‐pouring twin‐roll casting experiments are carried out using the FLC with its fuzzy rules optimized by PSO; the results show that strip quality and casting process stability are guaranteed. [ABSTRACT FROM AUTHOR]

Conventional book casting of Sm2TM17-type alloys (where TM = Co, Fe, Cu, Zr) leads to a coarse, highly segregated microstructure, predominantly due to the slow, variable cooling rate from the mould surface towards the centre of the ingot. These cast alloys require a long homogenisation treatment to remove this segregation and develop a super-saturated, metastable SmTM7-type hexagonal phase. This SmTM7 phase is a vital precursor phase required during magnet production to develop the complex cellular structure responsible for high magnetic properties. In this work, strip casting was employed to facilitate rapid solidification to develop thin flakes (7 phase. This could remove or significantly reduce the need for the energy-intensive homogenisation treatment usually required in conventional magnet manufacture. This paper investigates the effect of wheel speed (and hence cooling rate) on flake thickness, microstructure, and phase balance of the cast alloys. It was shown that for wheel speeds between 1.1 and 3.0 m/s, the microstructure showed large variation; however, in all cases, evidence of the columnar SmTM7 phase was presented. The adhesion between the melt and the wheel was deemed to be critical for the nucleation and subsequent columnar growth of SmTM7 grains, where the wheel speed controlled both the flow of the alloy onto the wheel and the thickness of the resultant flake. It was determined that in order to achieve a homogenous columnar SmTM7 structure, the maximum flake thickness should be limited to 270 μm to avoid the formation of equiaxed Sm2TM17 grains through insufficient cooling.

The evolution of shear band (SB) and texture in strip-cast electrical steel was studied in order to investigate the crystallographic character of SB and its influence on recrystallization texture. Shear deformation in the form of SB played an effective role in tailoring the local lattice rotation to accommodate heavy deformation in the case of inhomogeneous deformation under conditions of initial coarse grain in strip-cast electrical steel. During rolling process, η-oriented SBs appeared at different stages of deformation as a result of geometric softening. Cube-oriented SB was mainly retained from initial exact Cube grain at early stage of shear deformation and Goss-oriented SB was newly developed during the formation of γ-fiber matrix after heavy deformation. {210} SB formed as a transition form among different SBs. Crystal rotation inside SB, SB dimension and SB boundary misorientation progressed in proportion to cold rolling reduction. It is demonstrated that crystallographic direction of SBs tended to be parallel to under the driving force of reduction in stored energy to maintain relatively quasi-stable state. Low orientation gradient as well as relatively low density of dislocations was developed within SB region, while high orientation gradient formed between SB region and surrounding matrix. Interestingly, the η-oriented cell blocks inside SBs provided preferential nucleation sites for Goss and Cube texture at early stage of recrystallization, which significantly contributed to beneficial recrystallization texture in a manner of texture inheritance and superior magnetic properties (B50 was as high as 1.81 T, and P1.5/50 was as low as 4.0 W/kg).

As a near-net-shape technology, the twin-roll strip casting (TRC) process can be considered to apply to the fabrication of TiAl alloy sheets. However, the control of the grain distribution is very important in strip casting because the mechanical properties of strips are directly determined by the solidification microstructure. A threedimensional (3D) cellular automation finite-element (CAFE) model based on ProCAST software was established to simulate the solidification microstructure of Ti-43Al alloy. Then, the influence of casting temperature and the maximum nucleation density (nmax) on the solidification microstructure was investigated in detail. The simulation results provide a good explanation and prediction for the solidification microstructure in the molten pool before leaving the kissing point. Experimental and simulated microstructure show the common texture <001> orientation in the columnar grains zone. Finally, the microstructure evolution of the Ti-43Al alloy was analyzed and the solidification phase transformation path during the TSC process was determined, i.e., L → L+β → β → β+α → α+γ+β/B2 phase under a faster cooling rate and L → L+β → β → β+α → γ+lamellar (α2+γ)+β/B2 phase under a slower cooling rate. [ABSTRACT FROM AUTHOR]

First, strip cast samples of high strength microalloyed steel with sub-rapid solidification characteristics were prepared by simulated strip casting technique. Next, the isothermal growth of austenite grain during the reheating treatment of strip casts was observed in situ through confocal laser scanning microscope (CLSM). The results indicated that the time exponent of grains growth suddenly rise when the isothermal temperature higher than 1000°C. And the activation energy for austenite grain growth were calculated to be 538.0 kJ/mol in the high temperature region (above 1000°C) and 693.2 kJ/mol in the low temperature region (below 1000°C), respectively. Then, the kinetics model of austenite isothermal growth was established, which can predict the austenite grain size during isothermal hold very well. Besides, high density of second phase particles with small size was found during the isothermal hold at the low temperature region, leading to the refinement of austenite grain. After isothermal hold at different temperature for 1800 s, the bainite transformation in microalloyed steel strip was also observed in situ during the continuous cooling process. And growth rates of bainite plates with different nucleation positions and different prior austenite grain size (PAGS) were calculated. It was indicated that the growth rate of the bainite plate is not only related to the nucleation position but also to the PAGS. [ABSTRACT FROM AUTHOR]

The comparisons of wear resistance and heat transfer behaviours of chromium and brass were conducted. The effects of different values of chromium coating average roughness (1.240, 4.576, 7.388, 9.323 μm) and thickness (15, 35, 55 μm) on the interfacial heat transfer behaviours were investigated with a novel droplet solidification technique. The results revealed that, compared with the brass, the chromium material has a significant improvement in the Vickers hardness and wear performance and a reduction of 25 percent interfacial heat transfer rate. Moreover, with the increase of the coating average roughness from 1.240 to 7.388 μm, the maximum heat flux between molten steel and cooling substrate decreases from 8.27 to 5.56 MW/m2 due to the enlargement of the air gap. As the coating average roughness further increases to 9.323 μm, the maximum heat flux increases to 6.50 MW/m2 because of the increasing contact area between molten steel and the cooling substrate. In addition, the maximum heat flux was reduced from 8.47 to 5.87 MW/m2, considering the enhancement of interfacial thermal resistance when the coating thickness increases from 15 to 55 μm. The results obtained have important implications for heat transfer control of the strip casting process by adjusting the coating average roughness and thickness. [ABSTRACT FROM AUTHOR]

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.

A novel Nb–V–Mo microalloyed steel with 1 GPa yield strength and high ductility was developed by strip casting. The effects of hot rolling on the microstructure and mechanical properties of the Nb–V–Mo microalloyed steel were investigated using scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy, atom probe tomography and tensile tests. Both the as-cast and hot-rolled specimens exhibit a microstructure characterized by lath-like bainite and (Nb, V, Mo)C clusters, while the bainite lath was refined after hot rolling. Tensile test results show obvious improvements in the yield strength, tensile strength, and elongation of the hot-rolled specimen (1008 MPa, 1075 MPa, 20.1 %, respectively), compared to that of the as-cast ones (879 MPa, 978 MPa, 19.0 %, respectively). Additionally, the hot-rolled specimen displays a similar dislocation multiplication and storage capacity to the as-cast specimen, resulting in a comparable work-hardening capability during plastic deformation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In strip casting grain-oriented silicon steels, the inheritance of coarse λ grains (〈100〉//ND, normal direction) can deteriorate their magnetic properties. To solve the problem, twinning behaviors in strip casting grain-oriented silicon steels during hot rolling were investigated in this work. It is found that after rolling at 650℃, a number of 112〈111〉deformation twins are formed in the coarse solidification microstructure of the steels, in contrast to the well-accepted view that it is difficult to trigger twinning at relatively high temperature in the grain-oriented silicon steels with high stacking-fault energy. The results indicate that the complex stress state during hot rolling may weaken the orientation dependence of deformation twinning. Due to higher stored energy, the intersections of twin/twin boundaries and twin/grain boundaries can act as the preferential nucleation sites for the recrystallized grains during normalizing annealing, leading to a significant increase of recrystallization rate. Because of the restriction from local strain partitioning and the limited size between the twins, the shape of new-formed recrystallized grains is mainly plate-shaped. Consequently, the fine grains with scattered orientations are formed in the normalized microstructure and the coarse λ grains in the solidification microstructure are eliminated. [ABSTRACT FROM AUTHOR]

Three TWIP steels based on the composition Fe-23Mn-3Si-3.3Al with different carbon concentrations were examined. The alloys were produced by rapid solidification in an experimental apparatus designed to simulate direct strip casting conditions. Examination of the driving force for solidification for this alloy showed the preference for BCC and FCC solidification were very close for this composition, within 10% of one another. This factor combined with the high undercooling resulted in the change in the primary solidified phase. Chemical analysis of the as-cast strip showed inter-dendritic segregation of Si and Al, but negligible segregation of Mn. A simple heat treatment was sufficient to chemically homogenise all alloys and produce microstructures comprising a fully austenitic structure, consistent with thermodynamic predictions. [ABSTRACT FROM AUTHOR]

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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.

Twin-roll strip casting (TRSC) technology has unique advantages in the production of non-oriented electrical steel. However, the hot deformation behavior of high-grade electrical steel produced by TRSC has hardly been reported. This work systematically studied the hot deformation behavior of free-Al 2.43 wt.% Si electrical steel strip produced by twin-roll strip casting. During the simulated hot rolling test, deformation reduction was set as 30%, and the ranges of deformation temperature and strain rate were 750~950 °C and 0.01~5 s -1 , respectively. The obtained true stress-strain curves show that the peak true stress decreased with an increase in the deformation temperature and with a decrease in the strain rate. Then, the effect of hot deformation parameters on microstructure and texture was analyzed using optical microstructure observation, X-ray diffraction, and electron backscattered diffraction examination. In addition, based on the obtained true stress-strain curves of the strip cast during hot deformation, the constitutive equation for the studied silicon steel strip was established, from which it can be found that the deformation activation energy of the studied steel strip is 83.367 kJ/mol. Finally, the kinetics model of dynamic recrystallization for predicting the recrystallization volume percent was established and was verified by a hot rolling experiment conducted on a rolling mill.

Given the sub-rapid solidification characteristics of twin-roll strip casting (TRSC), the solidification structure and growth process of precipitates during aging treatment were studied. The results showed that TRSC could refine the solidification structure and inhibit the microsegregation of Cu-3.2Ni-0.75Si alloy. During aging treatment, the precipitates mainly consisted of rod β-Ni3Si and disk δ-Ni2Si. The precipitate size was increased by increasing the aging time, which altered the mechanism of precipitation strengthening. Also, the experimental results indicated that precipitate strengthening arises either from the cutover mechanism or from the Orowan mechanism. Furthermore, the Avrami equation, which describes the kinetics of phase transformation and electrical conductivity during aging were established for the Cu-Ni-Si alloy, and the calculated results are consistent with the data. The Cu-3.2Ni-0.75Si alloy after aging treatment at 450 °C for 4 h exhibited optimum performance, and the tensile strength and electrical conductivity were as high as 711 MPa and 43.2% IACS, respectively. [ABSTRACT FROM AUTHOR]

The twin-roll strip casting technology was introduced into the process of manufacturing invar alloy. Using optical microscope， XRD， EBSD， micro hardness(HV) and tensile testing instruments， the evolution of microstructure， texture and mechanical properties of the strip-casted invar alloy were investigated. The results show that the solidification microstructure of the strip-casted invar alloy is dominated by the coarse columnar grains of austenite and the associated texture is mainly the strong λ-fiber texture(<100>//ND). Thereafter， a large amount of deformation substructures are formed during a cold-rolling process， which increase the hardness(HV) from 165 to 230~240， and the cold-rolled texture is mainly composed by the typical copper texture (112<111>) and S texture (123<634>). A recrystallization microstructure containing numerous annealing twins together with a weak texture is observed in the 0.7mm-thick sheet after annealing at 700℃ for 10min. The yielding strength， tensile strength and final elongation are 293MPa， 433MPa and 33.4%， respectively， which are similar to those of the 0.7mm-thick annealed sheet produced by the conventional process. [ABSTRACT FROM AUTHOR]

The antimicrobial and corrosion properties of Cu‐bearing steels fabricated via simulated strip casting are examined. Two distinct microstructures are observed: those alloys with Cu concentrations below 5 wt% retain the Cu in solid solution, and those alloys with high Cu concentrations form a two‐phase structure containing an austenite matrix and large Cu‐rich precipitates. The alloys display antimicrobial properties against Escherichia coli, causing up to 65% of bacteria death upon direct contact for 24 h. Surface analysis by X‐ray photoelectron spectroscopy indicates that after exposure to bacteria, the surface passive film remains enriched in Cu and its oxides, and immersion studies confirm gradual release of Cu ions from the passive film in a wet environment. Corrosion testing of the Cu alloys demonstrates that when the copper is retained in solid solution, the corrosion behavior is not markedly different from the copper‐free reference alloy. However, in those higher‐concentration alloys that contain Cu‐rich precipitates, the anticorrosion performance of the steel is greatly deteriorated, with the corrosion mechanism changing from pitting corrosion to selective corrosion. [ABSTRACT FROM AUTHOR]

• 3 %Si-Fe cast strip with equiaxed grains is prepared by the top side-pouring twin-roll casting method. • Goss grains can nucleate in {1 1 1} 〈1 1 2〉 deformed grains during annealing the cold-rolled sample. • Dispersed MnS can be formed after annealing the cold-rolled sample. • Short-process preparation of grain-oriented electrical steel can be achieved. The conventional production line of grain-oriented electrical steel (GOES) is long and the columnar grains in the cast slabs have adverse effects on GOES. In this paper, the short preparation process for GOES using top side-pouring twin-roll strip casting (TSTRC) was investigated. The results show that TSTRC can prepare cast strips with equiaxed grains. Conventional slab reheating, hot rolling, and normalization can be eliminated. The origin of Goss grains and the preparation of inhibitors were studied. [ABSTRACT FROM AUTHOR]

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.

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.

Based on conventional hot rolling processes and strip casting processes, Cu precipitation strengthening is used to improve the strength of non-oriented silicon steel in order to meet the requirements of high-speed driving motors of electric vehicles. Microstructure evolution was studied, and the effects of Cu precipitates on magnetic and mechanical properties are discussed. Compared with conventional processes, non-oriented silicon steel prepared by strip casting exhibited advantages with regard to microstructure optimization with coarse grain and {100} texture. Two-stage rolling processes were more beneficial for uniform microstructure, coarse grains and improved texture. The high magnetic induction B50 of 1.762 T and low core losses with P1.5/50, P1.0/400 and P1.0/1000 of 1.93, 11.63 and 44.87 W/kg, respectively, were obtained in 0.20 mm sheets in strip casting. Cu precipitates significantly improved yield strength over ~120 MPa without deteriorating magnetic properties both in conventional process and strip casting. In the peak stage aged at 550 °C for 120 min, Cu precipitates retained bcc structure and were coherent with the matrix, and the yield strength of the 0.20 mm sheet was as high as 501 MPa in strip casting. The main mechanism of precipitation strengthening was attributed to coherency strengthening and modulus strengthening. The results indicated that balanced magnetic and mechanical properties can be achieved in thin-gauge non-oriented silicon steel with Cu addition in strip casting.

Iron–silicon alloys with up to 6.5 wt.% Si offer an improvement of soft magnetic properties in electrical steels compared to conventional electrical steel grades. However, steels with high Si contents are very brittle and cannot be produced by cold rolling. In addition to solid solution hardening, it is assumed that the B2- and DO3-superlattice structures are responsible for the poor cold workability. In this work, two cast strips with 6.0 wt.% Si were successfully produced by the twin roll strip casting process and cooled differently by secondary cooling. The aim of the different cooling strategies was to suppress the formation of the embrittling superlattice structures and thus enable further processing by cold rolling. A comprehensive material characterization allows for the understanding of the influence of casting parameters and cooling strategies on segregation, microstructure and superlattice structure. The results show that both cooling strategies are not sufficient to prevent the formation of B2- and DO3-structures. Although the dark field images show a condition which is far from equilibrium, the achieved condition is not sufficient to ensure cold processing of the material.

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.

Abstract 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. [ABSTRACT FROM AUTHOR]

The removal of accumulated impurity elements during scrap refining has been regarded as the bottleneck to limiting scrap usage, among which copper is the crucial tramp element in scrap steel recycling, resulting in the final product's hot shortness and surface cracking. This study proposes sub-rapid solidification-based strip casting technology to eliminate the copper impurity introduced problems. The results reveal that strip casting could improve copper behavior in the as-cast sample. More importantly, the sub-rapid solidified sample has excellent high-temperature tensile properties and resistance to hot shortness. It suggested that strip casting technology could produce copper-bearing steel, which can tackle the hot shortness problem and provide a unique idea for steelmaking with scrap as raw materials. [Display omitted] [ABSTRACT FROM AUTHOR]

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 °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 °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 °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 °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 °C.

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 °C. The corresponding growth rates were in the range of 60–1400 μm/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 γ- 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.

Abstract In this study, 4 types materials, i.e., WC-12Co, WC-10Co4Cr, NiCr-Cr 3 C 2 and Ni60 were coated on the bare copper to simulate the wear resistant materials on the surface of strip casting rolls. Then, these coatings were characterized by the field emission scanning electron microscopy (FE-SEM), energy-dispersive spectrometer (EDS), X-ray diffraction (XRD), and laser scanning confocal microscope (LSCM). Next, the heat transfer performance of those coatings was evaluated through the droplet solidification tests. The results indicated that the maximum interfacial heat flux and the total heat-removed is varying with different coatings, in which the highest values of 6.25 MW/m2 and 7.21 MJ/m2 in the case of bare copper system could be reduced to 2.62 MW/m2 and 4.22 MJ/m2 with the application of WC-10Co4Cr coating. The heat transfer performance of different coatings is determined by the comprehensive effects of the characteristics of coatings, such as microstructure, porosity, phase composition, adhesion property, and thickness, etc. Furthermore, the results demonstrate that the Ni60 coating with a low porosity (0.78%), good adhesion property and thin thickness (14.1 μm), etc., shows a better heat transfer capability, through which the maximum heat flux is 5.24 MW/m2 and total heat removed is 5.78 MJ/m2, and shows great potential to be used in the strip casting process. Graphical abstract Image 1 Highlights • Characteristics of the coatings of strip casting rolls were investigated. • Heat transfer performance was evaluated by droplet solidification test. • Coating property exhibits significant effects on heat transfer performance. • The Ni-contained coatings show a better heat transfer performance than WC-contained coatings. [ABSTRACT FROM AUTHOR]

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' characteristics, and lower capital and operating costs. In the present paper, numerical simulations based on the Volume of Fluid method were utilized to test the performance of an optimized inclined feeding system that does not rely on the use of magnetohydrodynamics to slow the entry velocity of the liquid metal, so as to allow for a thicker film of liquid metal to be formed (10-15 mm), nor on the use of any moving side-dams so as to constrain the slab being formed. Rather, special attention was paid to the meniscus behaviour, including meniscus formation, meniscus renewal, meniscus turbulence, and the formation of tiny air pockets on the bottom surface of the forming strip. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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Copyright of Matériaux et Techniques is the property of EDP Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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 B 50 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. [ABSTRACT FROM AUTHOR]

The magnetic properties and phase composition of the Sm(Co0.45Fe0.15Cu0.40)5 alloy prepared by the strip-casting technique (the casting of alloy on a water-cooled copper wheel at a velocity of cooling surface of ~1 m/s) are studied. Curves of magnetization of thermally demagnetized starting plates (after strip casting) and plates subjected to low-temperature treatment at 350°С for 120 h and the hysteresis loops were measured in magnetizing fields of up to 140 kOe. It is shown that the magnetization of samples (σ140 and σr) substantially decreases after the annealing; in this case, the coercive force (jHc) increases abruptly. It is assumed that the observed regularities of magnetic hardening can be related to the existence of nanosized Cu-enriched areas, within which the antiferromagnetic order in the Sm(Co, Fe, Cu)5 lattice is realized. These areas in the ferromagnetic phase with the lower copper content can be domain-wall pinning centers. [ABSTRACT FROM AUTHOR]

Copyright of Journal of the Chinese Society of Rare Earths is the property of Editorial Department of Journal of the Chinese Society of Rare Earths and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

0.05–0.15 mm-thick ultra-thin grain-oriented silicon steel sheets were successfully produced by a novel processing route including strip casting, hot rolling, normalizing, two-stage cold rolling with intermediate annealing, primary recrystallization annealing and secondary recrystallization annealing. The evolutions of microstructure, texture and inhibitor along the processing were briefly investigated. The results showed that the initial Goss orientation originated due to the heterogenous nucleation of δ-ferrite grains during solidification. Because of the lack of shear deformation, only a few Goss grains were observed in the hot rolled sheet. After the first cold rolling and intermediate annealing, Goss texture was enhanced and distributed in the whole thickness. A small number of Goss grains having a high fraction of high energy boundaries exhibited in the primary recrystallization annealed sheet. A large number of fine and dispersed MnS and AlN and a few co-precipitates MnS and AlN with the size range of 10–70 nm were also observed. Interestingly, a well-developed secondary recrystallization microstructure characterized by 10–60 mm grains and a sharp Goss texture were finally produced in the 0.05–0.15 mm-thick ultra-thin sheets. A magnetic induction B 8 of 1.72–1.84 T was obtained. Another new finding was that a few {2 3 0}〈0 0 1〉 and {2 1 0}〈1 2 7〉 grains also can grow up abnormally because of the high fraction of high energy boundaries and the size and number advantage, respectively. These non-Goss grains finally deteriorated the magnetic properties of the ultra-thin sheets. In addition, low surface energies of {hk0} planes may also contribute to the abnormal growth of Goss, {2 3 0}〈0 0 1〉 and {2 1 0}〈1 2 7〉 grains. [ABSTRACT FROM AUTHOR]

In this study, the origin of Goss texture during intermediate annealing and Goss texture development during secondary annealing of strip cast grain‐oriented silicon steel are studied by electron backscattered diffraction (EBSD). The study indicates that Goss grains originate inside the shear bands of deformed {111}<112> and {111}<110> grains. Compared to {111}<110> grains, {111}<112> grains provide more number of nucleation sites for Goss grains. During subsequent recrystallization process, Goss grains exhibit a smaller growth rate than the average value of all the recrystallized grains. The development mechanism of Goss texture is concluded as oriented nucleation. Prior to secondary annealing, high fraction of high‐energy boundaries (20°–45° misorientation angle) are observed in the vicinity of Goss grains, while significantly low fraction of Σ5 + Σ7 + Σ9 boundaries are observed. During secondary annealing, the domination of high energy boundaries around Goss grains is maintained, but the fraction of Σ5 + Σ7 + Σ9 boundaries decrease to be similar to the matrix grains. After the onset of the abnormal grain growth, the growing Goss grains continue to consist of high fraction of high‐energy boundaries. These results are consistent with the high energy (HE) boundary model, which is used to explain the abnormal grain growth in the current strip casting route. [ABSTRACT FROM AUTHOR]

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.

Over the last 50 years, numerous slab continuous casters have been widely installed all over the world to take advantage of the enhanced productivity, yield, energy efficiency, and cost efficiency. To meet a variety of product quality demands from the steel market, the slab continuous casting process has been diversified into several types. In the 1960s, 200–300 mm thickness slab casters opened the continuous casting era by substituting the ingot process widely applied at that time, and now the major part of slab production is for the hot strip rolling. The thick slab of 400–600 mm thickness casting process with a casting speed range of 0.2–0.6 m/min was introduced to guarantee the internal quality of heavy gauge plates for the energy industry and shipbuilding applications. For the ultra-thick, over 600 mm, the semi-continuous casting technology with a casting speed of 0.05–0.2 m/min has been developed as an alternative way to replace the ingot process, with higher yield and productivity compared to the case of the ingot process.As a supplementary concept, the near-net-shape casting with 50–100 mm slab thickness was developed to minimize energy consumption, and consequently thin slab casting and rolling process (TSCR) was commercially adopted, with the development of high speed casting technology. Recently, the thin slab casting and rolling (TSCR) process was progressed further as an endless rolling process with a casting speed up to 8 m/min for ultra-thin high-strength strip production. As another extreme case, the strip casting process was developed to directly produce thin strips of less than 5 mm from molten steel at the highest casting speed of 30–100 m/min, which has been focused on producing the specific steel grade using its ultra-fast solidification features. This article discusses why the range of casting speed has been spread out as caster types. The continuous casting processes are briefly introduced, and the related key technologies and products are reviewed in the casting speed point of view, based on POSCO’s experience. [ABSTRACT FROM AUTHOR]