Strip Casting Research Articles

Numerical simulation of the nozzle configuration in strip casting process

This work examines the design of nozzles in continuous strip casting process. Three-dimensional (3D) simulations of steady turbulent (k-ε) flow are done at the upper part of the mould using a finite-volume (CFX) model. This is performed for different inlet systems, including the inlet nozzle jets with a free stream, the submerged nozzle jets, the slot inlet system, and the slot-submerged inlet system. The resulting heat flux to the solidifying shell has also been studied. Numerous operating parameters are examined, including the shape, size, position, and thickness of the ports and the bottom geometry. It is found that different inlet nozzle configurations change the molten flow and heat patterns, mainly in the upper region of the mould. By applying the slot nozzle inlet system, turbulence and values of the averaged velocity field in that area decrease significantly.

Fabrication and analysis of mischmetal MM-Fe-B magnetic alloy

Mischmetal (MM30Nd70)30.4Fe68.2Al0.4Cu0.2B0.8 bulk magnets have been prepared with strip casting method followed by hydrogen decrepitating, jet milling, sintering and annealing. Process conditions to achieve optimum magnetic properties have been established through experimentations. XRD studies revealed main tetragonal RE2Fe14B phase and less RE-rich and CeFe2 phases. Microscopic examinations elucidated that magnet microstructure composed of main magnetically MM2Fe14B hard phase, RE-rich intergranular phase and magnetically soft CeFe2 phase. Henkel plot demonstrated the existence of exchange coupling between magnetic phase grains. Thermal studies showed Curie temperature of 278 °C for the Mischmetal (MM30Nd70)30.4Fe68.2Al0.4Cu0.2B0.8 magnet. Magnetic evaluations provoked coercivity Hcj of 619kA/m, remanenec Br of 1.15 T and maximum energy product density of 241 kJ/m3 for the (MM30Nd70)30.4Fe68.2Al0.4Cu0.2B0.8 magnetic alloy.

Role of Hot Rolling in Microstructure and Texture Development of Strip Cast Non-Oriented Electrical Steel

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.

Direct Strip Casting of Magnesium

AbstractA new interest in magnesium alloys has arisen since lightweight constructions have become more and more attractive. Products that are currently available are mostly cast, forged, and extruded. A cost-effective production of sheet metals will render new perspectives in the design of lightweight constructions [1, 2].The development of new casting technologies like thin slab casting or strip casting with an in-line rolling process is expected to result in a shorter processing time featuring a high potential of saving energy, time, and cost [3, 4, 5, 6, 7, 8, 9]. Particular attention is paid to the casting process parameters such as casting speed and solidification speed. This article deals with some aspects of a magnesium-adapted singlebelt caster. Results of casting experiments and material examination are shown as well as some advices given concerning safety and handling of liquid magnesium [10].

Crystallization behavior and properties characterization for high-energy state FeSiBCuC metallic glass produced by strip casting

High-energy state Fe-based amorphous ribbons produced by twin-roll strip casting with significant thickness always suffer catastrophic coercivity (Hc) and annealing brittleness. The microstructure and property of the Fe78.9B11.8Si7.6C1Cu0.7 amorphous ribbon were investigated. After annealing with a high heating rate of 6 × 103 K/min, the saturated magnetic induction (Bs) of the twin-roll ribbon significantly improves, yet the Hc remains at an inferior level. However, compared with traditional annealing, a much lower Hc is obtained for twin-roll ribbons through multiple-rapid annealing (MRA). The improvement of soft magnetic property stems from various aspects. Due to completely released internal stress and smaller activation energy in MRA treated twin-roll ribbon, many fine α-Fe(Si) grains (20.7 nm) are precipitated on the amorphous matrix, significantly eliminating the magnetocrystalline anisotropy and neutralising the magnetostriction coefficient, reducing the Hc. On the other hand, fine α-Fe(Si) grains with volume fraction up to 80% are favorable to improve the Bs further. Besides, some shear bands appear in the fracture surfaces of MRA treated twin-roll ribbon, indicating that annealing brittleness can be restored to a certain extent. Finally, the twin-roll Fe78.9B11.8Si7.6C1Cu0.7 nanocrystalline alloy shows a high Bs of 1.72 T, low Hc of 6.2 A/m, and high hardness of 10.9 GPa by MRA treatment.

Comparison of the casting process of 3.0% Si steel between the top side-pouring twin-roll casting and twin-roll strip casting

Comparison of the casting process of 3.0% Si steel between the top side-pouring twin-roll casting and twin-roll strip casting

The Effect of Direct Strip Casting on the Kinetics of Phase Transformation of a Dual Phase Steel

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.

Effects of Zr Distribution on High‐Temperature Oxidation Resistance of a FeCrAlZr Alloy

Two FeCrAlZr alloys are fabricated by twin‐roll strip casting (TRSC) and ingot casting (IC), and different Zr distributions are formed. After cyclic oxidation tests at 1200 °C for 200 h in air, it is found that the scale spallation resistance in the FeCrAlZr alloy is improved by homogenizing the Zr distribution by TRSC. To understand the improvement in oxidation resistance, the composition and microstructure of the thermally grown scales are investigated. During oxidation, Zr diffuses toward the scale and forms ZrO2 particles in the scale and at the surface of the oxide scale. Meanwhile, the outward diffusion of Zr inhibits the formation of interfacial voids and S segregation regardless of Zr distribution. However, the TRSC sample with a more uniform Zr distribution can form the high‐density oxide penetrations, keying the scale to the matrix and improving scale adhesion. The Zr fluxes toward the scales are calculated to explain the difference in the distribution of oxide penetrations in the TRSC and IC samples during oxidation.

Recycling Al-Si Alloy by Semisolid Material Dragged during Continuous-Casting Strip Processing

Recycled Al–Si (9.2%) alloy contaminated with Fe (0.3%), Pb (3.1%) and Sn (11.4 %) was cast and poured at 650 oC, approximately 50 oC above the liquidus line. A cooling slope was used to obtain a semisolid material that feeds a ceramic nozzle designed to function as a good contact area for solidification and improve the quality of strip casting. The internally cooled material rolls in soluble oil (1 oil / 9 water) at a rate of 0.2 l/s and works as a heat exchanger which drags the metallic slurry puddle generated at the roll surface at a speed of 0.12 m/s. This forms a metallic strip with a thickness of 2 mm and a width varying from approximately 45 mm to 60 mm. The cooling system of the rolls, combined with four springs placed at the housing screw, prevented adhering of the metallic strip during production at a pressure of approximately 450 N. Cracks were observed on the strip surfaces; however, these defects did not interrupt the continuous flow of the solidified strip during manufacturing. The strip’s poor surface quality could be related to the Pb and Sn contamination as well as cold cracks due to the low pouring temperature. Al-Si eutectics positioned at a grain boundary of α-Al globular structures, as well as the presence of a Sn phase, resulted in a metallic strip with a yield stress, maximum stress and elongation of 94.5 MPa, 100.2 MPa and 1.6%, respectively.

The microstructure of high manganese TWIP steels produced via simulated direct strip casting

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.

New technical solutions in the field of protection and fastening of mine workings

The article discusses the features of fastening preparatory workings in difficult geological conditions, which are studied in three directions: improving concrete, arch and anchor fasteners with the consideration of the initial physical and mechanical properties of the rock mass; introduction of steel-polymer anchor; improvement of cast strips designs in combination with arch and anchor fasteners for reuse. Protection methods of mine workings and means of fastening often do not correspond to the peculiarities of the manifestation of rock pressure at the end sections of lavas and in zones of tectonic disturbances, as a result of which can become the main cause of the unsatisfactory state of the mine workings. Mathematical modeling of the rock massif stress-strain state has been carried out by the finite element method. Rigid and pliable cast strips, various technologies for erecting a cast strip, as well as a combination of cast strips with anchor and arch fasteners are modeled. The locations and sizes of rocks destruction zones, stresses in the rock mass for different options of fastening have been determined. The drawbacks of the existing technologies for the construction of cast strips are revealed and the factors for increasing their technical efficiency are established.

An experimental and numerical study on the modelling of fluid flow, heat transfer and solidification in a copper continuous strip casting process

An experimental and “numerical study (first part of this study study) was carried out to investigate the solidification process in a copper continuous strip casting process. The model has been tuned by experimental results (i.e. cooling water flow measurements, temperature measurements and metallographic analysis). Further, the results have been used to study the possibility of improved productivity. In this report (second of the study) the flow pattern of the molten copper during a strip casting process as a manufacturing method has been studied using a full-scale water model. The dynamic similarity between model and real system has been studied. Six different types of inlet system to the mould have been studied: inlet nozzle jets with free stream, submerged nozzle jets, slot-submerged inlet system, semi slot-submerged inlet system, submerged-slot inlet nozzle jets and finally submerged-slot inlet nozzle jets with jet killer. Moreover, the effects of nozzle angle, nozzle diameter, casting speed, tundish adjustment and misalignment of the inlet nozzle jets on the flow pattern have been investigated. The vortex formation and bubble entrainment, depending upon the nozzle configuration, immersion depth and the fluid level in the mould have also been studied. It was found that the slot-submerged inlet nozzle jets with jet killer arrangement showed an obvious improvement of the fluid flow characteristics, yielding better tracer distribution in the flow pattern, lower values of back mixing flow, lower turbulence and lower vortex and recirculation flow.

Research methods and influencing factors of interfacial heat transfer during sub-rapid solidification process of strip casting

Research methods and influencing factors of interfacial heat transfer during sub-rapid solidification process of strip casting

A Training-Free Data-Driven Method for Input-Output Modeling of Complex Processes

In a variety of human-in-the-loop systems, variations among human operators can result in inconsistencies in process operation and product quality. While a variety of methods exist to mitigate this issue, they often require some model of the relationship between the human input and system output; unfortunately, obtaining such a model continues to be very difficult for highly complex processes such as industrial manufacturing processes. In this paper, we propose an innovative training-free data-driven (TFDD) modeling method that directly predicts the next state from the state transition information of all samples in a database. Because the prediction is directly derived from the database, the model does not require any training, nor does the model architecture change from one application to another. Through a case study on human operator supervisory control of twin-roll steel strip casting, we demonstrate the performance and advantages of the proposed TFDD method as compared to a baseline nonlinear autoregressive network with exogenous inputs (NARX) model trained using the same dataset.

Twin-roll strip casting of advanced metallic materials

Twin-roll strip casting of advanced metallic materials

Composition design and properties characterization for FeSiBCuC metallic glasses with large plasticity

Fe-based metallic glasses have low magnetic induction and inferior plasticity because of inevitable doping of non-magnetic constituents. The study proposes an innovative composition design strategy considering the nature of elements, binary eutectic, atomic configuration, and mixing entropy in the alloy system. A novel composition of Fe78.9B11.8Si7.6C1Cu0.7 was adopted, adding a total of only 8.3 wt% non-magnetic elements. The critical size of Fe78.9B11.8Si7.6C1Cu0.7 bulk metallic glass was ~1 mm, and an ultra-thick ribbon of ~150 µm was obtained by twin-roll strip casting. Excellent soft magnetic properties with high saturation magnetization (Bs) of 1.68 T and low coercivity (Hc) of 7.1 A/m outperformed current conventional counterpart. Meanwhile, the high breaking strength of 2654 MPa and distinctive plastic strain of 2%, normally less than 0.5% in most Fe-based metallic glasses, was demonstrated in Fe78.9B11.8Si7.6C1Cu0.7 bulk metallic glass. This novel alloy composition and design strategy is expected to facilitate the development of next-generation magnetic materials.

Effect of rolling reduction on microstructure, texture and magnetic properties of twin-roll casting non-oriented 6.5 wt% Si electrical steel

In this study, an as-cast strip of non-oriented 6.5 wt% Si electrical steel with an equiaxed structure was fabricated by twin-roll strip casting and then treated by hot and warm rolling with different reductions, and annealing. The results showed that the as-cast microstructure was gradually pancaked and then underwent dynamic and static recrystallization as the hot rolling reduction exceeded 52%. The subsequent warm rolling brought about shear bands in part of the deformed grains. The texture evolution in the multiple rolling routes basically conformed to the classical gain-orientation rotating paths. The {001}∼{118} 〈110〉, {223} 〈110〉 and {111} 〈110〉 texture components were intensified after warm rolling. A decreased hot rolling reduction accompanied by an increased warm rolling reduction raised the number of shear bands in the warm rolled sheets and decreased the annealing grain size. An improper combination of hot and warm rolling reductions tended to make the γ nuclei gain the superiority in number through grain-boundary or shear-band nucleation, leading to the prevalence of the γ annealing texture. By comparison, an alternative rolling regime adopting moderate hot (∼50%) and warm rolling (∼70%) reductions promoted the oriented nucleation of λ, {114} 〈48¯1〉 and many other non-γ nuclei in shear bands of the {223} 〈110〉 deformed grains which had already acquired a high volume fraction in the warm rolled sheet. Consequently, mixed λ, α* and γ annealing textures were formed, giving rise to enhanced magnetic properties. The combined oriented nucleation and oriented growth mechanism was responsible for the overall evolutions of the annealing textures.

Microstructure and Wear Properties of Al 7075 Alloy Manufactured by Twin-Roll Strip Casting Process

Al 7075 alloy was manufactured using the twin-roll strip casting (TRC) process, and the mechanical and wear properties of the fabricated TRC process were investigated. To compare the properties of the alloy manufactured by TRC, another Al 7075 alloy was fabricated by conventional direct chill (DC) casting as a comparative material. Based on initial microstructure observations, the Al 7075 alloy manufactured by the DC process showed relatively elongated grains compared to the Al 7075 alloy by TRC process. In both alloys, η(MgZn2) phases were present at the grain and grain boundaries. In the Al 7075 alloy manufactured by the DC process, the η(MgZn2) phases were coarse with a size of ~86 nm and were mainly concentrated in the local area. However, the Al 7075 alloy manufactured by TRC had relatively fine η(MgZn2) phases size of ~40 nm, and they were evenly distributed throughout the matrix. When the mechanical properties of the two alloys were compared, the TRC process showed higher hardness and strength properties than the DC process. In room temperature wear test results, the TRC process exhibited lower weight loss and wear rates compared to the DC process at all wear loads. In other words, the TRC process resulted in relatively superior wear resistance properties compared to the conventional DC process. The wear behavior of both alloys changed from abrasive wear to adhesive wear as the wear load increased. However, the TRC process maintained abrasive wear up to higher loads. Based on the above results, a correlation between the microstructure and wear mechanism of the Al 7075 alloy manufactured by TRC is also suggested.

Microstructure Characteristics and Strengthening Behavior of Cu-Bearing Non-Oriented Silicon Steel: Conventional Process versus Strip Casting

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.

Thin-gauge non-oriented silicon steel with balanced magnetic and mechanical properties processed by strip casting

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