Strip Casting Research Articles

Corrosion behavior of Zr55Cu30Al10Ni5 amorphous alloy produced by two-roll strip casting in aqueous environments

Corrosion behavior of Zr55Cu30Al10Ni5 amorphous alloy produced by two-roll strip casting in aqueous environments

A simple route for preparation of TRIP-assisted Si–Mn steel with excellent performance using direct strip casting

A simple route for preparation of TRIP-assisted Si–Mn steel with excellent performance using direct strip casting

Reduction of Elongation Anisotropy of Roll-Cast Strips by Cold Rolling and Annealing

Roll-cast strips are usually cold-rolled and annealed before forming. The elongation of these strips is known to be different between the casting and lateral directions after thinning by cold rolling. Whether cold rolling is the main factor determining the anisotropy of the elongation is not clear. Likewise, it is not clear whether the elongation anisotropy can be reduced by conventional cold rolling. Roll-cast strips have centerline segregation, forming a so-called band area. The relationship between the anisotropy of the elongation and these defects is not clear. A strip cast using an unequal-diameter twin-roll caster also has a band area but a strip cast using a single-roll caster equipped with a scraper has no centerline segregation or band area. Strips made this way were cold-rolled in the casting and lateral directions, and tensile testing was conducted on the cold-rolled and annealed strips. In this study, the ability of conventional cold rolling and one-time annealing to reduce the elongation anisotropy of a cast strip was clarified. Moreover, the influence of the band area and Fe impurities on the elongation anisotropy was determined.

Construction of Tb-rich shells via novel interdiffusion approach to tackle coercivity-remanence trade-off

The strategic introduction and efficient utilization of heavy rare earth elements within Nd-Fe-B-based permanent magnets are instrumental in achieving an optimal balance between remanence (Br) and high coercivity (Hcj). Herein, we propose a novel interdiffusion approach based on hydrogen decrepitation (HD) for the cost-effective and high-performance sintered Nd-Fe-B magnets. With the aim of generating continuous Tb-rich shells on the grain surface, which favors high Br and high Hcj, strip cast (SC) flakes homogeneously mixed with 0.9 wt% Tb were processed by the HD. It is shown that the formation of (Nd, Tb)-Fe-B by the interdiffusion of Nd-Fe-B and Tb during de-hydrogenation, as well as the interdiffusion of Nd-Fe-B and (Nd, Tb)-Fe-B during sintering and tempering, is the key to the construction of Tb-rich shells. As a result, a magnet (Mag-Tb&HD) with maximum magnetic energy product ((BH)max) of 52.21 MGOe was achieved, which is superior to magnet prepared form SC flakes containing 0.9 wt% Tb (Mag-Tb&SC, (BH)max=49.36 MGOe) and the magnet prepared by adding 0.9 wt% Tb to the jet milling (Mag-Tb&JM, (BH)max=50.41 MGOe).

Effect of hot rolling process on the microstructure and mechanical properties of a high-strength strip casting microalloyed steel

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.

Heat transfer, crack, and wear resistance of a newly designed heat-treated Ni/Cr multilayer composite coating for strip casting rolls

A new heat-treated Ni/Cr multilayer composite coating for strip casting rolls was designed in this contribution. The results revealed that the addition of the middle layer of the Ni layer was conducive to enhancing the heat transfer capacity. Insignificant improvement was found in the crack resistance of the Ni/Cr coating when compared to the Cr coating. However, the heat-treated Ni/Cr coating exhibited remarkable cracking resistance due to intensified binding force with the matrix. Also, the wear resistance of Ni/Cr and heat-treated Ni/Cr was superior to that of Cr coating.

Sub-rapid solidification microstructure characteristics and control mechanisms of twin-roll cast aluminum alloys: A review

Rapid growth in industrial sectors such as automotive and shipbuilding has highlighted the significance of strip casting technology to produce lightweight alloys, particularly aluminum alloys widely used in both industrial production and daily life. Twin-roll casting (TRC), as an economically and environmentally friendly method for slab/strip production and processing, has attracted significant interest from researchers. However, the development of TRC aluminum alloys faces many challenges due to limited understanding of microstructural characteristics and control mechanisms. To further enhance comprehension of TRC aluminum alloys, this article reviews the influencing parameters, control methods, and existing issues related to TRC sub-rapid solidification (SRS) microstructure. It firstly summarizes TRC equipment types and their solidification characteristics, followed by a detailed analysis on key parameters affecting the evolution of TRC microstructure including rolling speed, roll separation force (RSF), and heat transfer coefficient (HTC). Finally, solutions to TRC defects are summarized and evaluated alongside their underlying mechanisms. This article provides a comprehensive review of the characteristics and control mechanisms of TRC microstructure while offering valuable insights for the future production of high-quality TRC aluminum strips.

Research on temperature field and thermal deformation characteristics of casting rollers in twin-roll casting process

The twin-roll casting (TRC) process is considered a revolutionary technology in the metallurgical field and has garnered significant attention and research in recent years. The casting rollers used in the TRC process are crucial for achieving the desired shape of the casting strip. This study investigates the temperature distribution and thermal deformation of casting rollers in the TRC process using numerical simulation. A novel model for predicting the thermal resistance distribution at the circumferential interface between the casting roller and the molten pool has been introduced. The study examined the effects of various factors including casting roller diameter, water channel position, number, and diameter on temperature, thermal deformation, and heat flux. The findings reveal that increasing the casting roller diameter from 460 mm to 500 mm or augmenting the distance from the water channel to the casting roller surface from 35 mm to 55 mm resulted in a 37 % and 30 % increase in the maximum surface temperature of the casting roller, respectively. Additionally, an increase in the number of water channels from 30 to 50 and a growth in their diameter from 20 mm to 28 mm resulted in the average heat flux of the casting roller remaining stable, with fluctuations less than 1 MW/m2. Leveraging the insights gained from the thermal deformation behavior of the casting roller and the ideal shape of the casting strip, a comprehensive control approach for the casting roller profile was developed. The outcomes of this research provide a valuable theoretical framework for enhancing the design of casting roller structures in the TRC process.

Inline Hot Rolling of Al-5%Mg Strip Cast Using an Unequal Diameter Twin-Roll Caster.

One advantage of twin-roll casting for aluminum alloys is that hot rolling can be omitted, thus shortening the process. The effect of inline hot rolling on the anisotropy of the mechanical properties, especially the elongation, of the roll-cast strip has not been investigated. In a high-speed twin-roll caster, inline hot rolling forms the metal shape before the temperature of the cast strip decreases below the temperature needed for hot rolling. In this study, inline hot rolling of Al-5%Mg strips cast using an unequal diameter twin-roll caster was performed to validate the technique and evaluate its ability to reduce surface cracking and improve the elongation anisotropy. A rolling speed of 30 m/min was used, and the effects of temperature and thickness reduction during inline hot rolling on the surface and mechanical properties were investigated. Inline hot rolling was found to effectively reduce the formation of surface cracks and the anisotropy of the mechanical properties.

Assessing the stability of protective structures in preparatory mining workings under conditions of static load

The object of this study is the deformation processes in protective structures under the action of static load in the coal massif in order to preserve the integrity of the side rocks and the operational condition of mine workings. Under laboratory conditions, the deformation characteristics of rigid and flexible protective structures, as well as supports made of crushed rock, were studied on experimental samples. The samples were subjected to uniaxial compression. It was established that there is a functional relationship between the coefficient of transverse deformation ν and the relative change in the volume δV of protection structures, which makes it possible to estimate their bearing capacity. For rigid protection structures (coal pillars, cast strip, cement blocks, blocks of reinforced concrete bollards, bundles of wooden racks), the deformed state of the structures determines their behavior. This happens at values of ν=0.3–0.5 and δV£0.09. Their stability is fixed within the safe deformation resource. An increase in the deformation energy density of such structures beyond the safe deformation resource leads to their destruction due to a change in shape. For flexible protection structures (bundles of wooden racks, rolling bundles made of wooden sleepers), which have a transverse deformation coefficient ν=0.02, at a relative change in volume δV£0.3, the compaction of structures is observed. Increasing their stiffness allows limiting the convergence of side rocks. For a support made of crushed rock, at ν=0.25–0.32 and a relative volume change of 0.12£δV£0.32, its compaction and increase in resistance occur. Under such conditions, the convergence of side rocks is limited. In order to preserve the integrity of the lateral and operational condition of preparatory workings in the excavation areas of coal mines, it is advisable to use flexible protective structures made of wood or supports made of crushed rock

Hot Deformation Behavior of Free-Al 2.43 wt.% Si Electrical Steel Strip Produced by Twin-Roll Strip Casting and Its Effect on Microstructure and Texture.

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.

Cluster mediated high strength and large ductility in a strip casting micro-alloyed steel

Exhibiting exceptional mechanical properties and formability, high strength low alloy steels characterized by a single ferrite microstructure with finely dispersed nano-precipitates (ferritic HSLA steel) have garnered notable attention in the automotive industry. Nevertheless, to maximally utilize the precipitation hardening effect, these steels necessitate substantial additions of carbide-forming elements, unavoidably narrowing the process window and escalating the cost. Strip casting, featuring a streamlined process chain and high energy efficiency, has emerged as a promising technique for developing ferritic HSLA steels. In this work, leveraging the process characteristics of strip casting, we report that a novel single ferrite microstructure with multi-atomic layered clusters distributed in both interphase-precipitation and random fashions was engineered in a low Nb micro-alloyed ferritic HSLAs via raising the coiling temperature to 650 ℃. The multi-atomic layered clusters play a pivotal role in tailoring dislocation behaviors, facilitating local double cross-slips, contributing to dislocation multiplication and homogeneous distribution. These mechanisms collectively sustain mild work hardening to higher strains, leading to combined strength and ductility increments. In comparison to their cluster-free bainitic counterparts coiled at 480 ℃, the results demonstrate significant mechanical improvements with an increase in ultimate strength (630 MPa to 670 MPa) and a 90 % rise in plasticity (10.3 % to 19.1 %), signifying an alternative pathway for advancing the utilization of strip casting technology in designing and processing novel low-cost, high-performance HSLAs.

Effect of Sc addition on downstream processing of twin-roll cast Al−Cu−Li−Mg−Zr-based alloys

A processing scheme for preparing strips of Al−Cu−Li−Mg−Zr-based alloys microalloyed with Sc was proposed. This scheme includes a twin-roll casting of strips with a near-net-shaped 3 mm-thick gauge and a homogenization/solution treatment processing step. Two twin-roll cast Al−Cu−Li−Mg−Zr-based alloys were studied, one with an addition of 0.17 wt.% Sc, and the other without addition of Sc. Both alloys were annealed at 300 °C for 30 min, 450 °C for 30 min, and 530 °C for 30 min and quenched into room temperature water. The first two annealing steps provide a fine dispersion of Al3Zr/Al3(Sc,Zr) particles. The final annealing step serves as homogenization/solution treatment. A fine crystallization structure of the twin-roll cast materials enables the dissolution of primary particles containing the main alloying elements during a relatively short annealing time. Shorter soaking duration limits the depletion of surface layers from Li and significant coarsening of Al3Zr/Al3(Sc,Zr) dispersoids. The Sc-containing material has significantly finer grains already in the as-cast state. The Al3(Sc,Zr) dispersoids formed during the homogenization/solution treatment step prevent grain coarsening at high temperatures. Strengthening θ′(Al2Cu), T1(Al2CuLi), and rare S’(Al2CuMg) phases are formed during subsequent artificial aging at 180 °C. The increase in yield strength was 200 MPa in the peak-aged conditions. This value is comparable to the ones reported in similar direct-chill cast materials, thus validating the proposed processing scheme.

The comprehensive study on texture evolution and recrystallization behavior of twin-roll strip casting Fe-50 %Co alloy

The iron-cobalt soft magnetic alloy exhibits excellent properties such as high saturation magnetic induction, high magnetic permeability, and high Curie temperature, making it widely used in areas like aviation generators and electric motors. However, traditional iron-cobalt alloy strip materials often suffer from a high magnetic anisotropy constant, which hinders their performance in practical applications. In this study, twin-roll strip casting was employed to produce Fe-50Co soft magnetic alloy cold-rolled strip materials. The research findings reveal that the initial microstructure of the Fe-50Co alloy strip prepared through twin-roll strip casting is primarily composed of coarse columnar grains and equiaxed grains, with a strong {001} orientation for the columnar grains. Notably, a significant number of Σ3 grain boundaries are present within the cast strip. These grain boundaries effectively reduce dislocation accumulation during the cold rolling process and subsequently minimize the nucleation sites for γ-texture during subsequent annealing. Furthermore, a strong {001}<uv0> texture is formed in the finished strip material after cold rolling and annealing, resulting in superior magnetic properties. The alloy exhibited excellent magnetic properties after annealing at 900 ℃ for 5 h followed by furnace cooling to 750 ℃ with the cooling rate of 50 ℃/h and then to 300 ℃ with the cooling rate of 180 ℃/h, the B5000 was ∼ 2.417 T, P1.5/400 was ∼22.651 W/kg and P2/1000 was 183.51 W/kg. These findings provide valuable insights for the development of Fe-50Co alloys with excellent magnetic properties.

Correlation between hydrogen absorption capacity and microstructure of Fe-rich Sm-Co-Fe-Cu-Zr permanent magnetic alloys

The correlation between hydrogen absorption capacity (HAC) and the microstructure of Sm26.2CobalFexCu4.0Zr2.3 (x = 23 wt%, 25 wt%, 27 wt%, 30 wt%) ingots and cast strips was systematically investigated. As the temperature rises from 373 to 423 K, the activation time, hydrogen absorption time and HAC of the Sm26.2CobalFe23Cu4.0Zr2.3 ingot decrease by 14.4%, 14.1%, and 19.3%, respectively. Dispersed 1:5 phase provides more channels for hydrogen diffusion, which is the main reason that HAC increases with the x increasing. The HAC of the same compound strips increases as the particles size of the pre-crushed decreases. However, no further embrittlement behavior appears in pre-crushed strips, which reaches an equal HAC as ingots. Micro-computerized tomography reveals that ingots contain small spherical-like holes and large flake micro-cracks, whereas strips mainly contain elliptical pores. The effects of grain size and inner defects size on structure stability were invested by Abaqus. Simulation results reveal that the superior embrittlement behavior of the ingots is predominantly influenced by the presence of large flake-like micro-cracks.

Effect of phosphorus content on interfacial heat transfer and film deposition behavior during the high-temperature simulation of strip casting

Effect of phosphorus content on interfacial heat transfer and film deposition behavior during the high-temperature simulation of strip casting

The Effect of Rare Earth Y on the Inhibitor Precipitation Behavior of Strip‐Cast Grain‐Oriented Silicon Steel

0.3 mm‐thick grain‐oriented silicon steel sheets with varying Y contents are produced via twin‐roll strip‐casting and two‐stage cold rolling process. This study primarily investigates the evolution of microstructure, texture, and precipitation along the processing. Specifically, the effect of rare earth Y on second‐phase particle precipitation in ultralow carbon grain‐oriented silicon steel is examined. Results indicate that higher Y content will consume beneficial inhibitor elements such as S and N, leading to the formation of coarse rare earth inclusions (≈10 μm) in the cast strip. This significantly diminishes inhibition ability and magnetic induction (B8 = 1.58 T≈1.71 T). On the contrary, the addition of trace Y can accelerate the precipitation of inhibitors. During the intermediate annealing stage, steel with trace Y exhibits a significant enhancement in precipitate distribution density (from 2.8 μm−2 to 13.6 μm−2), and the final magnetic induction B8 increases from 1.86 T to 1.91 T compared to steel without Y. In addition, the results of first‐principle calculations based on density functional theory reveal that the doped Y atom prefers to segregate at the Al–N interface, and the interface energy reduces from 1.871 J m−2 to 1.024 J m−2, thereby promoting the precipitation of AlN.

Strip Casting of Sm2TM17-Type Alloys for Production of the Metastable SmTM7 Phase

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 (&lt;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.

Tuning heterogeneous microstructure and improving mechanical properties of twin-roll strip cast low carbon steels by on-line heat treatments

Coarse austenite grains are unavoidable in the low carbon steels processed by twin-roll strip casting. Unfortunately, the polygonal ferrite (PF) grains cannot be refined by conventional on-line cooling process, resulting in low strength. In this work, an on-line heat treatment including reaustenitizing and subsequent controlled cooling was performed in laboratory to form heterogeneous microstructures composed of PF and acicular ferrite (AF). It has been founded that increased prior austenite grain size and the cooling rate led to more AF laths, which inhibited the growth of PF grains. When the prior austenite grain size is less than 60 μm, the formation of AF is suppressed. The tensile tests indicate that the heterostructured steels exhibited higher yield strength than the samples without AF. The improvement of yield strength can be attributed to the grain boundary strengthening, dislocation strengthening and back stress strengthening. The higher AF volume fraction leads to higher dislocation density in PF grains, and more AF/PF interfaces may increase the amount of accumulated geometrically necessary dislocations. Therefore, the contributions of dislocation and back stress strengthening increase with the increase of AF volume fractions. High dislocation density and the generation of back stress contribute a high strain hardening rate to delay the necking and sustain good plasticity. Moreover, the heterostructured steels exhibit the two-stage work hardening behavior during tensile test, which indicates that plastic deformation starts in PF grains while the AF laths remain in elastic state, and then plastic deformation occurs in both strain hardened PF grains and AF laths.

Macroscopic phenomenon of exchange coupling and microscopic effect on magnetization reversal in sintered Nd–Fe–B magnets

Permanent magnets of Nd13.5Fe79.18M1.52B5.8 and Nd13.5Fe79.76M0.94B5.8 were prepared, respectively, via strip casting, jet milling and sintering followed by annealing. By adding the non-ferromagnetic elements M (Al, Cu, Ga and Zr) into the magnets, it could not only modify the microstructure, but also regulate the exchange coupling effect in the sintered magnets. From the macroscopic point of view, the recoil loops exhibit spring behavior in Nd13.5Fe79.76M0.94B5.8, indicating that the energy barrier can be overcome by the intergranular exchange coupling. From the microcosmic point of view, the exchange coupling can increase the domain wall size by suppressing the nucleation of reversed domains, and so the activation volume increases with thermal activation. In Nd13.5Fe79.76M0.94B5.8 the exchange coupling effect is stronger, and both the coercivity of 15.0 kOe and the remanence of 14.3 kGs are a little higher than those of Nd13.5Fe79.18M1.52B5.8 magnets in which the content of non-ferromagnetic elements is a little higher and the exchange coupling effect is weaker. Thus, the exchange coupling does not decrease the coercivity due to the exchange coupling suppressing the nucleation of reversed domains, though the microstructure is inhomogeneous in the sintered magnets of Nd13.5Fe79.76M0.94B5.8. Reducing the defect size and decreasing the defect concentration should be a practical way to improve the coercivity in Nd–Fe–B permanent magnets.