Twin Roll Research Articles

Globular Crystals in the Center of Roll Cast Aluminum Alloy Strips

This study investigated the crystallization position and formation mechanism of globular crystals at the center area in the thickness direction of aluminum alloy strips cast by a high-speed twin roll caster. Twin roll casters for single strips and clad strips were used, as well as twin roll casters equipped with a cooling slope. The globular crystals were formed from dividing arms of dendrites of the solidified layer facing the center area at the roll gap. The arms of isolated dendrite also divided. No globular crystals were formed at the interfaces of clad strips with different solidification temperatures because of the temperature gradient at the interface which inhibited division of the dendrite arms. It was demonstrated that globular crystals at the center area of the thickness direction were formed by dendrite-arm-dividing at the roll gap by the strip casting clad strip. Experiments by semisolid-strip casting with the cooling slope showed that globular crystals in the molten metal existed in the solidification layers.

Microstructure and mechanical properties of Al-7.9Zn-2.7Mg-2.0Cu (wt%) alloy strip fabricated by twin roll casting and hot rolling

High Zn content Al-7.9Zn-2.7Mg-2.0Cu (wt. %) aluminum alloy strip with 5.5 mm thickness was successfully fabricated by twin roll casting (TRC). Fine grain size, second phase and second dendrite arm spacing (SDAS) were obtained in the cast strip due to the high cooling rate during TRC process. Short-time annealing treatment of 480 ºC-1 h could effectively reduce the second phases, and the elongation of the strip was improved. The TRC alloy sheet with 2.0 mm thickness was fabricated by the annealing treatment (480 ºC-1 h) and hot rolling. The yield strength, tensile strength and elongation along the rolling direction of the TRC sheet after solution treatment, pre-aging and natural aging were 398 MPa, 590 MPa and 15.74%, respectively. After bake-hardening, the yield strength, tensile strength and elongation along the rolling direction were 550 MPa, 605 MPa and 10.07%, respectively.

Advanced comminution modelling: Part 1 – Crushers

Particle scale modelling of comminution processes can provide significant insight into the flow of particles, their breakage, the effect of slurry, wear and energy utilisation within these machines. The ability to use such models to assist in faster and lower cost design of new comminution devices and in the improvement of existing ones will be critical to the ability of industry to respond to the substantive challenges facing mineral processing in the next decade. These challenges are reviewed and drivers for change are discussed. Understanding individual unit process performance needs to be in the context of the flowsheets in which they are used so this is also reviewed. Advances in particle based comminution modelling are presented with this work divided into two parts. This first part focuses on recent advances in particle based modelling of crushing. Three crusher types are used to demonstrate these capabilities:1. Twin roll crusher2. Cone crusher3. Vertical Shaft Impactor (VSI)These show the nature and level of fidelity that is now possible to include in particle scale crusher models including breakage of non-spherical particles and prediction of the product size distribution and throughput.

Two-phase viscoplastic model for the simulation of twin roll casting

Abstract A two-phase Eulerian-Eulerian volume-averaged model was used to predict the outcome of the twin-roll casting process for inoculated Al-4 wt.% Cu alloys. The model is able to address the deformation of the mush during hot rolling by treating the solid/liquid mixture as a viscoplastic skeleton saturated with liquid. A parameter measuring the mean absolute deviation around the nominal composition was applied to the normalized macrosegregation distribution and the results were then used to determine an optimal process window where minimal compositional variation is achieved in the final strip. In the case of casting an 8 mm thick Al-4%Cu strip with rolls of 800 mm diameter, casting speeds between 40 and 42 mm/s and heat transfer rates given by HTCs between 5000 and 5250 W/m2/K minimize the macrosegregation deviations in the strip and thus predict an optimal strip quality.

Modelling and Experimental Characterization of Processing Parameters in Vertical Twin Roll Casting of Aluminium Alloy A356

Modelling and Experimental Characterization of Processing Parameters in Vertical Twin Roll Casting of Aluminium Alloy A356

Casting of High Aluminum Content AM Series Magnesium Alloys by Using a Horizontal Twin Roll Caster

In this paper, twin roll casting of magnesium alloys with high aluminum content such as, Mg-11 mass%Al-0.2 mass%Mn, Mg-12 mass%Al-0.2 mass%Mn, Mg-13 mass%Al-0.2 mass% have been performed for the purpose of use as an original material for hot forging. Also the mechanical properties of the cast materials were examined. A 10 miri-meters thick strip was cast by the use of a horizontal twin roll caster. The microscopic observation was conducted to investigate into the precipitation of the metal compounds such as Mg17Al12, and the Vickers hardness of the cast strips test were performed. From the result of the roll casting experiments, a 10 mm thick strip was continuously cast at a roll speed of 3.1 m/min. The average grain size of the casting strips was about 46 micron meters. When the aluminum content was 13%, the hardness of the twin roll cast (TRC) strips became 1.7 times higher than that of extruded AZ 31. Also, a uniaxial compression test at elevated temperature was conducted to obtain a true strain-true stress curve for examining possibility of direct hot forging (DHF) of TRC magnesium alloys with high aluminum content.

Influence Research of Al and Zn Addition for Twin Roll Casting Magnesium During Multi-Pass Hot Rolling

This study was aimed at revealing the influence of Al and Zn additions on microstructure, texture evolution and mechanical properties of twin roll casting Mg during multi-pass hot rolling. Firstly, both pure Mg and AZ31 sheets were rolled 9 passes with ∼80% thickness reduction. More effective grain refinement in AZ31 compared to pure Mg after hot rolling, which caused by the pinning effect from fine Mg17Al12 particles present in AZ31 alloy. Meanwhile a strong basal texture gradually formed with increasing thickness reduction in pure Mg. With Al and Zn adding, the texture intensity of AZ31 was much lower than pure Mg in each rolling-pass. The 5th AZ31 sample features a maximum intensity of ∼12.9, which is reduced by 50.6% as compared to the value of ∼26.1 for pure Mg. Compared to pure Mg, the Al and Zn solutes and weakened texture in AZ31 favor the strong work hardening, which promotes a simultaneous high ultimate tensile strength of ∼270 MPa and ductility of ∼22% in the 5th AZ31 sample. The results will be helpful for the TRCed Mg alloys with huge potential for industrial application.

Investigation of Burr on Strips Cast by Vertical-Type High-Speed Twin Roll Caster

The factors affecting the shape and size of burrs that form at the edges of strips cast by a vertical type twin roll caster were investigated in this study. The size of the burr was found to be affected by the Si content of the strip. When the Si content was larger than 7 mass%, the burrs became larger. The position of the lower edge of the side dam plate also affected the shape of the burr. The burrs that formed were generally perpendicular to the strip surface but changed to being parallel to the strip surface as the position of the lower edge of the side dam plate was displaced upward from the center of the rolls.

Formation of Naturally Deposited Film and Its Effect on Interfacial Heat Transfer during Strip Casting of Martensitic Steel

A strip-casting simulator has been successfully developed to simulate the initial contacting conditions between the twin roller and melt during the strip-casting process, in which the peak/average heat flux, secondary dendrite arm space and cooling rate of the martensitic strip cast are similar to those observed in the actual strip caster. During the casting experiments, a layer of dark deposited film can be found on the substrate, whose composition is 69.66Mn-15.36O-11.03Fe-3.95Si (wt.%). The deposited film starts to melt during the 5th immersion experiment and the melting area of the film increases with the repeat of the immersion test. The presence of solid deposited film first impairs the interfacial heat transfer; however, with the accumulation of the deposited film, melting of the film occurs that enhances the interfacial heat fluxes due to the improved melt/substrate interfacial contact, as the cavities or air pockets between the melt and the substrate are gradually filled with the increasing of the melting area of the deposited film. Compared with substrate roughness, the effect of the deposited film on heat transfer is more significant.

Fabrication and Characterization of GFRP Composites by Using Twin Roll Technique

Fabrication and Characterization of GFRP Composites by Using Twin Roll Technique

MAS-NMR studies of carbonate retention in a very wide range of Na2O-SiO2 glasses

Glasses that contain carbon are of geological interest, and the form of that carbon can be probed by Magic-Angle Spinning Nuclear Magnetic Resonance (MAS-NMR) spectroscopy. Previous studies of the Na2O-SiO2 glass system could only reach 56 mol% Na2O. Here we reproduce and extend those studies to cover a very wide compositional range, from 20 to 70 mol% Na2O, by using a combination of conventional melt-quench and twin roller quenching technologies on natural and 99% 13C-enriched sodium silicate glasses. 13C MAS-NMR reveals that measurable levels of carbon retention occur above at least 40 mol% Na2O, and takes the form of CO32− ions incorporated in the glass structure. These CO32− anions are surrounded by Na+ cations, forming nanoscale domains in a sodium silicate glass network. 23Na MAS-NMR showed a linear decrease in mean Na—O bond length with increasing Na2O content, up to 60 mol% Na2O, above which the mean Na—O bond length increased. Elemental analysis detected significant (>5%) carbon dioxide by mass in the 65 and 70 mol% Na2O glasses. For the 70 mol% Na2O glass, 13C and 23Na MAS-NMR detected ordered nanoscale domains composed of only Na2O and CO2. These results have shown the quantity and nature of carbon retention in the archetypal sodium silicate glass system, which will better inform structural models and carbonate solubility limits.

Interfacial Reaction in Twin-Roll Cast AA1100/409L Clad Sheet During Different Sequence of Cold Rolling and Annealing

Besides cold rolling reduction and annealing temperature and time, sequence of cold rolling and annealing also affects interfacial reaction in twin roll cast (TRC) clad sheet. This is because of short contacting time between Al melt and steel and small rolling reduction in as-cast TRC sheet, which results in small and uneven distribution of metallurgical bonding in the sheet. In as-cast sheet, no intermetallic compound (IMC) appears at the bonding interface after 510 °C × 1.5 h annealing and the sheet has a high peeling strength of 21.5 N/mm. However, incubation period of IMC is shortened in the 40% cold rolled sheet. A 2.2 μm thick IMC layer appears in the 40% sheet after 510 °C × 1.5 h annealing and the peeling strength decreases to 15.5 N/mm. 25% reduction cannot reduce the incubation period. This is because the bonding interface becomes tight enough and its energy storage increases after 40% cold rolling and as a result, the inter-diffusion of Al and Fe atoms is enhanced during annealing.

Continuous Strip Casting of Aluminum Alloy AC7A Using Commercial Scale Twin Roll Caster

This paper describes a commercial scale twin roll strip casting process for producing aluminum alloy strip of AC7A. Twin roll casting process is able to produce a strip from molten metal directly. Thus this process has a possibility to reduce total cost of strip making. However, strip casting process has some disadvantage. Casting speed depends on the material properties. It is difficult to decide the casting conditions. Many paper on the strip casting are reported. However, there are few reports on the commercial scale machine. In this study, the effect of roll speed on the strip casting was investigated. Continuous strip could not be produced at the roll speed 5 m/min. Continuous strip could be produced at the roll speed 10 m/min. However, the cracks were observed. Continuous strip was produced at the roll speed 20 m/min. However, cracks were observed too.

The effect of inline rolling on Al-Mg alloy strip cast by the unequal diameter twin roll caster

The effect of inline rolling on Al-Mg alloy strip cast by the unequal diameter twin roll caster

Reduction of Edge-Bur of Strip Cast Using a High Speed Twin Roll for Light Metal

Reduction of Edge-Bur of Strip Cast Using a High Speed Twin Roll for Light Metal

Strip casting of aluminum alloy for casting using a vertical type high speed twin roll caster and investigation of strip

Strip casting of aluminum alloy for casting using a vertical type high speed twin roll caster and investigation of strip

Thin Plate Production of Copper Alloy C19210 by Twin Roll Casting Using Commercial Scale

Thin Plate Production of Copper Alloy C19210 by Twin Roll Casting Using Commercial Scale

Continuous Strip Casting of High Mg-containing Aluminum Alloy using Commercial Scale Twin Roll Casting Machine

Continuous Strip Casting of High Mg-containing Aluminum Alloy using Commercial Scale Twin Roll Casting Machine

Microcharacterization and mechanical performance of an Al-50Si alloy prepared using the sub-rapid solidification technique

In this reported work, the hypereutectic Al-50Si alloys with a wide mushy zone of 465 °C were successfully fabricated using twin roll casting technique. The experimental results showed that the overall hardness of the roll-cast alloy increased, as a result of the decrease in the size of Si crystal and the increase in the relative solubility of Si in the α-Al. However, the EBSD results showed that the primary Si crystals in the twin-roll cast alloy grew according to twin plane re-entrant edge (TPRE) mechanism.

Comparison of the Mechanical Properties and Forming Behavior of Two Texture-Weakened Mg-Sheet Alloys Produced by Twin Roll Casting

The influence of rolling and annealing on the resulting mechanical properties and forming behavior of Mg-Zn-RE and Mg-Zn-Ca alloys produced via twin roll casting is investigated. After hot rolling followed by an annealing treatment, both alloys develop a fine-grained microstructure with average grain sizes less than 10 µm. A distinctive development of a texture with a pronounced split of the basal poles in the transverse direction, so called TD-split, is observed in both alloys during the annealing. Due to the fine microstructure and weak texture, which enhances the activation of basal slip, both alloys show large ductility with fracture strain higher than 30%. However, due to the TD-split texture, a high asymmetry of the yield stress is observed, where the yield stress in rolling direction is significantly higher than the yield stress along 45° and the transverse direction. Both alloys show high stretch formability at room temperature with Erichsen indices around 7. Despite a low planar anisotropy and high stretch formability, the Mg-Zn-RE alloy shows undesirable earing behavior, while the Mg-Zn-Ca alloy fractures during warm deep drawing. Moreover, the deep drawing operation using the as-rolled sheet of Mg-Zn-RE alloy can be successfully done. It is observed that the earing behavior can be effectively reduced by deviating from the TD-split texture. In this regard, cold rolling was explored to reduce the anisotropy of the ductile and formable alloy.