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A process for the production of steel strips with an optimized cross section by means of twin-roll strip casting has recently been developed at the Institute of Metal Forming and offers considerable technical and commercial potentials. This production concept is based on the use of profiled casting rolls which continuously transfer the profile geometry to the solidified strip. In order to reduce the internal porosity and improve the surface finish the cast strip was hot rolled using profiled rolls. Offline and inline rolling experiments were performed to prove the effectiveness of this combined forming process. This paper describes the design of a proper rolling tool and the effect of this forming step on the final profile geometry, surface quality, internal porosity and mechanical properties of the strip. The experiments showed that a rolling step with 15 % thickness reduction already allows the global internal porosity to be reduced by 48 % and the strip surface roughness to reach a minimum value of R = 2.3 µm. The tensile strength is improved after the hot rolling operation and the obtained values are within the 500-700 MPa range specified by the norm EN 10088-3 for the stainless steel AISI 304. The prescribed ultimate elongation of 45 % is also reached. [ABSTRACT FROM AUTHOR]

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 {110} fiber has been founded in thin as-cast sheets. The in-grain shear bands with the Cube orientation can be observed in deformed {110}<1 10> 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. [ABSTRACT FROM AUTHOR]

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

Abstract: The specimens were taken from the 304 austenite stainless steel. Based on the measured results of the phase transformation temperature and phase structure curves of the 304 stainless steel, the finite element model was established. According to the simulated temperature field of 304 stainless steel during twin-roll strip casting process and the mechanical properties of 304 stainless steel determined, the stress field of the 304 stainless steel during twin-roll strip casting process was simulated. Meanwhile, the effect of different technologic parameters, such as casting speed, casting temperature, roller radius and strip thickness at the exit, on the stress field of the 304 stainless steel during twin-roll strip casting process was simulated too in this work. The results show that the largest tensile stress appears on the contact interface between strip and roller located 5–10° away from exit. The tensile stress appears on the surface and the compressive one in the center of the strip. The larger roller radius and strip thickness at the exit are, the larger the tensile stress on the surface of 304 stainless steel during twin-roll strip casting process is. However, the larger the casting speed and the casting temperature are, the smaller the tensile stress on the surface of 304 stainless steel is. [Copyright &y& Elsevier]

The fluid transport characteristics and level fluctuations in the pool of twin-roll strip casting are studied using a water model and mathematical simulations. The level profile depends on the transport characteristics of the flow in the pool. A full scale water modeling experiment has been conducted to address the relationship between the fluid flow and level fluctuation in the narrow strip pool. The residence time of fluid at the ports of nozzle and nip points of caster are measured to evaluate the fluid flow uniformity in the caster. The level fluctuations are measured with wave gauge and sensors. Mathematical modeling is also established to help anticipate flow patterns in the pool and residence time at the exits of nozzle and caster. The results show that a strong jet flow impinging on the both sides of delivery system is generated and free surface oscillations increase at the most lateral ports of delivery system. The fluids are uniformly distributed along the direction of roll width at the narrow pool zone. The flow patterns are complex near side dams' zone. Calculated results are in good agreement with residence time and average wave height measurements. [ABSTRACT FROM AUTHOR]

The article discusses the study which examined the effects of heat transfer and permeability constant in twin-roll strip casting. In the study, a 3D coupling temperature-flow mathematical model was developed to examine the flow and heat transfer in the mushy zone and the entire pool during the casting process. The study also used a Darcy's Law-type of porous media treatment to account for the effect of mushy zone on flow and solidification.

Abstract: In this paper, twin-roll cast strips of 17%Cr ferritic stainless steel were produced with a pilot caster. The effects of melt superheat on solidification structure and texture of cast strips were investigated, and the relationship between the percentage of equiaxed grains in the solidification structure and melt superheat was established. It was observed that the equiaxed grained strip exhibited a weak and random texture, and the columnar grained strip possessed a strong through-thickness <001> fiber texture tilted by about 15° from the normal direction (ND) of the strip. [Copyright &y& Elsevier]

Fe-3.2%Si steel strips were produced using vertical type twin casting process, and the changes of microstructure and texture trough thickness direction were analyzed. The equiaxed grains of approximately 44.6µm were observed in the center layer, the great mass of columnar dendrite was formed near the surface, and the dendrite truck mainly developed in the transverse direction with respect to the casting direction of about 45° or less. From the subsurface to the center, the volume fraction of the Goss texture (110)[001] gradually decreases. The Goss {110} <001> components at the surface are two times those at the center layer, the {001} <100> components are three times those at the center layer, and the overall texture components are similar to that of the hot-rolled oriented silicon steel strip. The minor α texture could be found from the φ2=45° sections of ODF, and there is no remarkable composition segregation of Si element in the thickness direction of thin strip. [ABSTRACT FROM AUTHOR]

Cu-based amorphous alloy plates with good mechanical properties have tremendous potential applications as structural materials. However, there is a lack of effective methods for preparing such plates. In this work, 0.53-mm-thick Cu 47 Zr 45 Al 8 (at.%) and 0.25-mm-thick Cu 64 Zr 36 (at.%) amorphous-alloy plates were prepared continuously by twin-roll strip casting, and their mechanical properties were investigated through both experiments and in-situ observations. The Cu-based amorphous-alloy plates prepared by strip casting were found to have good surface quality and shape; these plates did not exhibit tensile plasticity, but showed excellent bending and compression plasticity at room temperature. Such plasticity is achieved through the formation and evolution of multiple shear bands. Overall, the present study proves the feasibility of continuous preparation of amorphous Cu-based alloy plates with good plasticity by twin-roll strip casting and serves as a guide for this process in the future. [ABSTRACT FROM AUTHOR]

The article discusses the physical simulation of nozzle electromagnetic brake in twin-roll strip casting. This study presents the Nozzle Electromagnetic Brake consisting of an imposing stationary magnetic field with direct current inside the nozzle which controls the flow thereby suppressing the free surface fluctuation.

Abstract: In twin-roll strip casting process, metal flow and temperature distribution in the molten pool directly affect the process stability and the quality of products. In this paper, a 3D coupling temperature-flow finite element method (FEM) simulation has been carried out and an inverse method was used to determine the boundary conditions between the roll and molten pool. For twin-roll casting of stainless steel, the influences of key processing parameters such as the pouring temperature and the height of liquid level on the temperature and flow fields are discussed. Calculated strip surface temperatures for different pouring temperatures are compared with the measured values, which shows they are in agreement. [Copyright &y& Elsevier]

Abstract: In this study, effects of various crystalline particles formed in strip-cast Zr-base amorphous matrix composites on deformation behavior were investigated. The compressive and fracture toughness test results indicated that the ductility of the strip-cast alloys containing hard/brittle crystalline particles as well as containing ductile β-phase particles was higher than that of the monolithic amorphous alloy. From finite element calculations and in situ microfracture observations, this ductility improvement could be explained by the role of the particles to initiate shear bands and to block the shear band propagation. However, this improvement could be obtained only when the size and volume fraction of crystalline particles and characteristics of amorphous matrix were optimized by controlling the strip casting conditions. [Copyright &y& Elsevier]

Abstract: Continuous strip casting and direct rolling method are receiving attention as the integrated producing process to obtain wrought magnesium alloys. In this research, AZ61 strip was cast from molten metal by twin-roll strip caster and rolled by “Structure-Control rolling process”. The effects of casting conditions and rolling parameters on surface aspects and microstructure of the rolled sheet were investigated. The results obtained were as follows: (1) By casting 1.5mm strip, a better surface and finer microstructure were obtained compared to 3mm strip. (2) By using structure-control rolling with R.T. pass, a microstructure of mean grain size of 5μm was obtained. (3) By lowering the starting rolling temperature, mean grain size and duplex grain size degree decreased and hardness increased. In addition, the deformation resistance decreased and the fracture strain increased. [Copyright &y& Elsevier]

Abstract: In this paper, a developed micro-segregation model was used to simulate the micro-segregation of solutes in twin-roll casting of carbon and stainless steels. The relationship between the solidus fraction in solidification and temperature was given, which was used to determine the LIT, ZST and ZDT temperatures in the period of non-equilibrium solidification. Based on the experiment of twin-roll thin strip casting in lab, the cooling rate was determined. The effects of the cooling rate and temperature on the micro-segregation were discussed. When the cooling rate increases the micro-segregation between the dendrites becomes large, and it is small within the dendrite. According to the computational results, the solidification completion temperature in the twin-roll strip casting was then determined, which can provide a basis for dealing with casting process and quality controlling. [Copyright &y& Elsevier]

Coiled strip can be directly produced through the twin-roll strip casting process from the melt by incorporating casting and hot rolling together into a single step. In this unique process, the strip formation from the molten metal critically relies upon the casting rolls. Thus, the design of the rolls is extremely essential. The coupled heat transfer and deformation analysis of the casting roll is carried out in a two-dimensional numerical model, using a finite element program (MARC) to examine the thermal stress and displacement. The effects of several factors such as the nickel overlay thickness on the roll surface, the casting speed, and the roll diameter on thermal characteristics are investigated. [Copyright &y& Elsevier]

A magnesium alloy containing essential, non-toxic, biodegradable elements such as Ca and Zn has been fabricated using a novel twin-roll casting process (TRC). Microstructure, mechanical properties, in vivo corrosion and biocompatibility have been assessed and compared to the properties of the rare earth (RE) element containing WE43 alloy. TRC Mg-0.5 wt% Zn- 0.5 wt% Ca exhibited fine grains with an average grain size ranging from 70 to 150 μm. Mechanical properties of a TRC Mg-0.5Zn-0.5Ca alloy showed an ultimate tensile strength of 220 MPa and ductility of 9.3%. The TRC Mg-0.5Zn-0.5Ca alloy showed a degradation rate of 0.51 ± 0.07 mm/y similar to that of the WE43 alloy (0.47 ± 0.09 mm/y) in the rat model after 1 week of implantation. By week 4 the biodegradation rates of both alloys studied were lowered and stabilized with fewer gas pockets around the implant. The histological analysis shows that both WE43 and TRC Mg-0.5Zn-0.5Ca alloy triggered comparable tissue healing responses at respective times of implantation. The presence of more organized scarring tissue around the TRC Mg-0.5Zn-0.5Ca alloys suggests that the biodegradation of the RE-free alloy may be more conducive to the tissue proliferation and remodelling process., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2021 The Authors.)

A novel high magnetic induction Fe-6.5%Si alloy with B 800 that reached up to 1.77 Telsa was prepared by twin-roll strip casting. Electron backscattered diffraction (EBSD) investigations demonstrated that Σ3 grain boundaries formed in the body-centered cubic (BCC) metal solidified microstructure without phase transition where the ratio of grain boundaries was greater than 20%. Transmission electron microscopy (TEM) revealed that the partial Σ3 grain boundaries are BCC structured twinning. A certain amount of Σ3 boundaries were inherited from the process of warm rolling, cold rolling and annealing, which acted to stabilize the matrix grain boundaries, resulting in the formation of a perfect Goss microstructure with excellent magnetic properties. Image, graphical abstract [ABSTRACT FROM AUTHOR]

High borated steels have been applied in the nuclear power industry as excellent neutron-shielding materials, but their ductility was relatively low due to the large and brittle borides, restricting their wider utilization. In this work, the high-performance borated steels containing 2.40 wt% B were fabricated through a designing combination of titanium-alloying along with twin-roll strip casting technology. It was found that titanium addition facilitated the increasing boron content of eutectic point for steels. The TiB 2 particles solidifying firstly from molten steel depleted massive boron atoms in advance, leading to an as-cast microstructure consisting of more γ-Fe and less M 2 B-type borides comparing with titanium-free steels. Besides, TiB 2 particles were 200–240 nm, and they could act as heterogeneous nucleation cores for M 2 B borides. Thus dispersive and fine M 2 B borides smaller than 5 μm were produced in as-cast microstructure. After subsequent hot-rolling and solution-treating, ultra-fine borides were obtained with more than 80% of which in a size range of 0.1–2 μm. In this case, the steels exhibited an excellent total elongation of 16.2% that was twice as high as that of titanium-free steels. Additionally, the relations between microstructure and mechanical properties of hot-rolled and solution-treated steels were clarified. The ductility of steels was determined by the volume fraction of γ-Fe matrix that could accommodate large deformation, but the strength of steels was dominated by the volume fraction of borides that provided the strengthening effects including grain refinement, load transfer term and hindering the dislocation slip. This work provided a new promising method to enhance the ductility of such high borated steels. [ABSTRACT FROM AUTHOR]

Cube texture and microstructural evolution of as-cast non-oriented silicon steel (1.3% Si) during cold rolling and annealing were studied. The results showed that the as-cast microstructure with grain size in the range of 100–500 μm had a weak texture. The strong orientation was mainly located at {100} and {110} planes. A significant content of shear-deformed grains oriented with {110}<110> were obtained by cold-rolling, and many regions oriented with Cube texture were distributed in the shear bands. During cold-rolling, the orientation of the shear-deformed microstructure tilted towards the {111}<112> orientation, while the matrix orientation retained {110}<110>. On further cold-rolling, the residual part of {110}<110> experienced shear deformation, forming more shear bands, strengthening the Cube orientation. During annealing, Cube orientation grains nucleated in the shear bands leading to strong Cube texture, and corresponding B50 was 1.83T/1.79T. [ABSTRACT FROM AUTHOR]

The oxide metallurgy was employed in the fabrication of twin-roll strip casting low carbon steels. The quantitative dependences of the microstructure and mechanical properties on cooling parameters were revealed and emphatically investigated. After twin-roll strip casting, a two-step cooling route closed to the actual process was designed and the cooling rates exhibited great influences on the proportion of polygonal ferrite (PF) and acicular ferrite (AF). With increasing cooling rates in both steps, the AF volume fraction raised from 0.04 to 0.75 because the rapid cooling restrained the formation of PF. The AF laths were induced by fine Al–Si–Ti–Mn composite oxides (0.2–2 μm), leading to a heterogeneous microstructure consisting of PF and AF clusters with high proportion of large-angle (≥15°) grain boundaries. It was found that the AF laths kept K–S relationship with austenite and AF laths with collinear growth direction belong to the same codirectional variants group in one AF cluster. With the increase of AF volume fraction, the yield strength (YS) and the ultimate tensile strength (UTS) were improved, while the strip retained excellent elongation. The improved YS was mainly ascribed to the grain boundary strengthening and dislocation strengthening. [ABSTRACT FROM AUTHOR]

The Nb-bearing grain-oriented silicon steel sheets were produced by conventional route and novel twin-roll casting route, respectively. The microstructure, texture and precipitate evolution were comparatively investigated by using electron backscattered diffraction (EBSD) and transmission electron microscope (TEM). The findings revealed that the precipitation behavior and the texture evolution were totally different between the two processing routes. In the conventional route, a great number of nanoscale niobium nitride particles (NbN), which acted as mainly grain growth inhibitors were precipitated during hot rolling, while in the twin-roll casting route, due to the rapid solidification, the precipitation of NbN were suppressed and a new type Nb-bearing precipitate enriched with sulfur element was observed in the as-cast strip. Besides, the primary recrystallized texture of conventional specimens was characterized by strong γ-fiber with a peak at {111} <110>, together with very few Goss components. While in the case of twin-roll casting specimens, the strongest primary recrystallized texture was {111} <112> texture and the area fraction of Goss component was much higher than that of conventional specimens. After final high temperature annealing, complete secondary recrystallization was obtained in twin-roll casting specimens and the magnetic induction of B8 was 0.1 T higher than that of conventional specimens. [ABSTRACT FROM AUTHOR]

In this study, a specific warm rolling was implemented to process Fe-2.8%Si steel by novel twin-roll strip casting. The impact of warm deformation on mechanical behavior, microstructural evolution and magnetic properties is presented. The study indicated that dynamic strain aging (DSA) occurred in the temperature range of 150–300 °C. The elevated rolling temperature strengthened DSA effect and promoted the formation of shear bands. The nucleation process of Cube ({100} 〈001〉) grains during annealing was weakened on introducing warm rolling, while that of Goss grains ({110} < 001>) was enhanced. Moreover, the recrystallization texture pattern of (Cube + Goss) gradually transformed into a pattern of only pronounced Goss texture. The corresponding values of magnetic induction B 50 at rolling direction and transverse direction were obviously improved. This confirms the feasibility of processing ultra-high-permeability non-oriented silicon steel based on twin-roll strip casting combined with DSA-control rolling. However, the rolling process increased the nucleation site for recrystallization and decreased the size of precipitates in annealed sheet, leading to a reduction in grain size and an increase in core loss. • Ultra-high magnetic induction B 50 was obtained by novel strip casting combined with DSA-control rolling. • Effect of warm deformation on evolution of microstructure and texture in strip-cast non-oriented silicon steel was studied. • Recrystallization texture pattern of Cube + Goss transformed into only strong Goss texture after warm rolling at 300 °C. [ABSTRACT FROM AUTHOR]

Twin‐roll strip casting (TRSC) technology is successfully applied to obtain 6.5 wt% Si electrical steel (6.5 wt% Si steel) in a laboratory platform, although there are problems in the strip surface quality control restricting further industrial applications of the TRSC. Hot temperature mechanical behavior in the mushy zone associated with the cracking susceptibility of 6.5 wt% Si steel is studied using the Gleeble‐3800 simulation system in the temperature range of 1350–1435 °C and a strain rate of 3 s−1. The characteristic temperatures including zero strength temperature (ZST) and zero ductility temperature (ZDT) are qualitatively determined, and the hot brittle temperature range in the mushy zone is further confirmed. Results indicate the tensile strength and ductility both increase with decreasing tensile temperature once the solidus fraction reaches a critical value. The ZST and ZDT in the mushy zone are determined to be ≈1427 and ≈1390 °C, respectively, and the hot brittle temperature range is 1390–1427 °C. The critical strain for internal crack generation in the hot brittle temperature range is estimated to be ≈0.24% on the basis of an empirical model developed by Y. M. Won. To reduce the cracking susceptibility of studied 6.5 wt% Si steel under TRSC, a rolling process is prohibited in the temperature range of 1390–1427 °C. [ABSTRACT FROM AUTHOR]

Abstract: The twin-roll strip casting is regarded as the most prospective technology of near-net-shape casting. The control of the grain structure is of primary importance in twin-roll strip casting because the solidification microstructure has great influence on the quality and mechanical properties of strips. In this paper, a three-dimensional cellular automation (CA) finite-element (FE) model within CALCSOFT3D package is used to simulate the microstructure of steel strip twin-roll casting. The Gaussian distribution of nucleation sites is adopted both at the mold surface and in the melt. The KGT model is used to describe the growth kinetics of dendrite tip. Then the influence of the casting conditions such as pouring temperature and heat transfer coefficient between the rolls and the solidified strip on the strip solidification microstructure is detailed investigated. The predictions show that the temperature profile and solidification microstructure are most sensitive to the pouring temperature. And with the increase of the pouring temperature, grain density obviously increases. However, the influence of three bottom cooling conditions on microstructure formation has little difference in this study. [Copyright &y& Elsevier]