Copper Mold Research Articles

Vermicular and Chunky Graphite Nucleation during Chill Casting: Study on the Dynamics of Ductile Iron Recycling

AbstractThis investigation provides alternative insight into the dynamic behavior of spheroidal graphite structures throughout the remelting process during ductile cast iron recycling. Specifically, this study systematically analyzed the impact of the remelting process on graphite nucleation. Two approaches are included in this research: thermal analysis and the copper–mold chill casting method. Based on these results, different graphite structures nucleate in cast iron in response to the remelting and recasting processes, which correlate with the melting temperature, the cooling method, and the fading effect. Furthermore, it is indicated that the dissolution rate of spheroidal graphite is relatively slower than lamellar graphite, substantiated by the detection of residual graphite nodules in the case of low melting temperature applied during the remelting process. In addition, the formation of vermicular and potentially chunky graphite structures can also be observed to a certain extent during this set of investigations, thus providing further insight into their relation to the ductile cast iron production process. Graphical Abstract

Corrosion and wear mechanisms of rare earth (Gd, Sc, Y)-doped Zr-based amorphous alloys

Rare-earth elements have been utilized in the design and development of new amorphous alloys to improve the corrosion and wear resistance of Zr-based amorphous alloys. In this study, a rare-earth doped Zr-based amorphous alloy (Zr-BMG(RE)) was prepared by the copper mold casting method, which was investigated by corrosion and wear experiments. The results show that Zr-BMG(RE) has a completely amorphous structure, and the doping of rare earths Gd and Y raises the crystallization transition temperature of the amorphous. The addition of rare earth elements Gd and Sc increases the microhardness of Zr-based amorphous alloys, while rare earth element Y causes a slight decrease in microhardness. Gd and Sc will make Zr-based amorphous materials corrosion current density increases, the material pitting and localized corrosion, acid corrosion resistance is reduced. Y doping improves the self-corrosion potential of Zr-based amorphous alloys, reduces the corrosion current density, the surface passivation film is the densest, and the degree of charge transfer on the metal surface is the most difficult, Zr-BMG(Y) has a better corrosion resistance compared with other alloy materials. Zr-BMG(Gd) has the smallest friction rate (1.72×10-7mm3N-1mm-1), and the wear rates of the rare earth doped Zr-based amorphous alloys are all smaller than that of Zr-BMG, and the main loss mechanism of Zr-based amorphous alloys is the interaction of adhesive wear, abrasive wear, oxidative wear and fatigue wear. The mechanism of corrosion and wear resistance of rare earth to Zr-based amorphous alloys is discussed, which provides a new idea for the design of amorphous alloys.

Study of Li2O reduction in mould slag for continuous casting of low-carbon steel slab

The addition of Li2O increases production costs for continuous casting, despite its enhancement of the melting and flow properties of mould slag. Initially, laboratory research focused on assessing the individual impacts of Li2O, F, Na2O and Al2O3 on the viscosity and melting temperature of the slag, using a basicity of 0.95. Subsequently, four stages of industrial testing were conducted to optimise the slag, evaluating parameters such as temperature and friction force curves of the mould copper plate thermocouple, steel slag consumption per ton and strand surface quality. The optimised slag achieved a basicity of 0.98, a viscosity of 0.29 Pa·s and a melting temperature of 1115 °C, meeting all performance requirements for low-carbon steel mould slag. Compared to the original flux, the mass percentage of Li2O decreased significantly from 1.54 to 0 wt-%, while Na2O increased from 2.36 to 7.35 wt-%, and Al2O3 decreased from 7.28 to 3.49 wt-%. The operation of the optimised flux remained stable, with smooth fluctuations observed in the mould copper plate thermocouple temperature and friction force curves. These research findings hold significant reference and practical value for further development and application.

Study on the Interaction Dynamics of Magnesium and Molten Cast Iron: A Chill Casting Perspective

AbstractThis study presents a reassessment of the role of magnesium in the production process of cast iron. Through detailed experimentation involving an interrupted reaction process employing a chill casting approach in a copper mold, several reaction products that emerged during the high-temperature interaction between magnesium and cast iron were thoroughly examined. Two cast irons with different chemical compositions, notably different sulfur contents, were used to describe the contribution of magnesium during desulfurization and nodularization. The designed approach successfully revealed that rapid deoxidation and desulfurization reactions of cast iron involving liquid magnesium take place before following its ignition characteristics. Furthermore, the behavior of dissolved carbon concerning the remaining magnesium and magnesium-containing reaction products in molten iron is also empirically identified. Specifically, large graphite flakes and an indication of solidification behavior shifting are circumstantially detected in the magnesium-rich regions, which, to a certain extent, can provide additional insight into the role of magnesium during graphite nucleation.

Design and development of large-diameter Mg-Zn-Ca bulk metallic glass for biomedical applications: A mechanical and corrosion perspective

Being amorphous, bulk metallic glasses (BMGs) exhibit superior properties compared to their crystalline alloy counterparts. Amorphous materials are preferred for their excellent mechanical and degradation behavior. Among the various elemental combinations, MgZnCa has shown the most promising results, as evidenced by the literature. However, the maximum achievable size of the metallic glasses remains a bottleneck. The current work aims to address this challenge and achieve it splendidly with a systematic methodology by developing larger diameter MgZnCa BMGs through vacuum induction casting using a specially designed copper mold. The optimal composition was formalized for glass formation of the Mg65Zn31Ca4 system using the CALPHAD technique. As a result, a 6.5 mm diameter glassy alloy was successfully obtained. The XRD and TEM analysis experiments demonstrated a perfect amorphous structure of the developed sample. The anti-corrosion properties of the as-cast glass increased, followed by enhancement in the yield strength and hardness in contrast to the properties of the human bone. Furthermore, the surface wettability analysis showed an adequate surface obtained to promote fibroblast adhesion. In conclusion, the current work represents a notable progress in the fabrication of larger-diameter MgZnCa BMG for biomedical applications, considering that the biggest diameter ever reported in the MgZnCa system was more than a decade ago.

Multi-grooved channel design in continuous casting mold for enhancing heat transfer efficiency considering pressure drop and flow rate loss

An efficient, speedy, multi-grooved (ESMG) mold was designed and manufactured for optimization to address issues such as low heat transfer rate, slow casting speed, and quality defects in traditional continuous casting molds. The flow resistance mechanism of multi-grooved channels with varying parameters was investigated by considering the ESMG geometric model, the convective heat transfer characteristic variation trends were revealed with different channel designs. Considering constraints of the dimensional chain and supply pressure, variation trends and mechanisms of the pressure drop, flow rate loss, and convective heat transfer coefficient of the ESMG mold were explored using multiple channel variables. Based on the numerical model of the ESMG channel, temperature variation trends in the copper mold were verified by comparison with relevant literature data, supporting the convective-heat-transfer model and variation trends of the ESMG mold. A high-efficiency heat-transfer ESMG assembly that casts U71Mn high-carbon large rectangular billets was fabricated, achieving a closed-loop dimensional chain and replacing traditional molds. Experimental validation on the continuous casting machine (CCM) proved directly that redesigning the ESMG mold cooling channel improved heat transfer efficiency and reduced CO2 emissions. After 504 h on the CCM, the ESMG mold casting speed increased from 1.1 to 1.6 m/min, the heat transfer efficiency was 17.6% higher than that of traditional molds and CO2 emissions were estimated to decrease by 31.2%. The billets produced by the ESMG mold had no quality defects in shape or surface with the original casting conditions, which provided enhanced support for accelerating continuous casting lines.

Stress state of billet – mandrel system during production of hollow steel billet in a unit of continuous casting and deformation. Part 2

The paper presents the results of theoretical research of stress-strain state of a billet – mandrel system when producing steel hollow billets in a unit of combined continuous casting and deformation, in which the working surface of the calibrated anvils are made with a variable radius. The necessity of making the working surface of the calibrated anvils with a variable radius is substantiated and initial data for the calculations is given. The calculation results are considered along the lines of the volumetric model passing through the characteristic points of deformation centers. The authors determined the forces when the anvils compress the wall of a hollow billet and the force of pulling the hollow billet from the mold. The laws of metal axial displacements and stresses in the deformation centers during compressing the wall of a hollow billet was established at the combined process of continuous casting and deformation in the unit. Nature of the stressed state of the metal wall of a hollow billet is considered from the perspective of improving its quality. The technique studied allows to determine the stress-strain state of a mandrel when producing a hollow steel billet using such a unit. The authors provided the recommendations for reliable gripping and compression with calibrated anvils of a hollow steel billet coming from a water-cooled copper mold of the unit of combined continuous casting and deformation.

Optimizing Manufacturing of Zr–Cu–AI–NI Metallic Glasses via Laser Metal Deposition

Recently, it was discovered that the cutting-edge technique known as laser powder bed fusion (LPBF) is the best way to produce Zr-based bulk glasses made of metal (BMGs). While LPBF gives greater versatility, current state-of-the-art production techniques like copper mold casting and arc-melting have limits when it comes to implementing complicated designs. Furthermore, LPBF enables a delicate balance to be struck between producing intricate characteristics and sustaining suitable temperatures all through the whole operation. Because of its exceptional features and practical availability, this research focuses on optimizing the process variables for a specific Zr-based alloy, AMZ4, which is produced by additive manufacturing in order to optimize both its mechanical and thermal characteristics. Belonging to the class of zirconium-based alloys known as bulk metallic glasses (BMG), Zr57Cu15Ni10AI5 (or Vit-106) has an excellent glass-forming ability and shows great promise. By casting, a BMG alloy may be transformed into workpieces that are about one centimeter in size in all three dimensions. Nevertheless, crystallization is induced when the cast size is further increased since it reduces the cooling rate. By building a workpiece from many melt sections with the cooling rate maintained above the critical one, selective laser melt (SLM) is an established technique for overcoming size restrictions for BMGs. Partially crystallized BMG is now an issue with SLM-obtained components. The effect of SLM process variables on partial crystallization is investigated in this paper. You may regulate the size and intensity of the inclusion by altering the speed of the laser scanning. Microhardness and wear resistance may be improved by incorporating submicron crystalline inclusions into the amorphous matrix by SLM.

Differences in microstructure and properties of Ti-based amorphous composites between recrystallization and partial remelting and semi-solid isothermal treatment

The as-cast specimens of Ti48Zr18V12Cu5Be17 amorphous composites were prepared by copper mold suction casting. Next, the as-cast specimens were treated using semi-solid isothermal treatment (SSIT) and recrystallization and partial remelting (RAP). The effects of SSIT and RAP on the microstructure and plasticity were analyzed. The results showed that the microstructure changed from fine crystals in the as-cast specimens to coarse bar crystals and near-spherical crystals in the SSIT and RAP specimens, respectively. The crystals of RAP specimens were finer and rounder than those of SSIT specimens due to recrystallization. In addition, the RAP specimens had high plasticity (20.93%), which is 428.5% and 45.2% higher than the as-cast and SSIT specimens, respectively. By observing the shear bands of the fractured specimens, it was found that the expansion of shear bands could not be impeded by the fine β-Ti crystals in the as-cast specimens, leading to an infinite extension that induces brittle fracture in the specimens. The essential cause of the poor plasticity of the as-cast specimens was revealed. In addition, the coarse β-Ti crystals effectively blocked the shear band expansion in the SSIT specimens, and a large number of shear bands were generated in these crystals. In contrast, the crystals of the RAP specimens had a greater number and density of shear bands compared to those of the SSIT specimens, and these shear bands intersected with each other in different directions. This revealed the mechanism by which the SSIT and RAP methods enhance the plasticity of amorphous composites.

Chill-cast solidification of a peritectic Zn-10 Ag (+ 1.0 Mg) bioabsorbable alloy

In recent years, the Zn-Ag alloy demonstrated to be a potential candidate for biomedical applications as a bioabsorbable implant. Frequently, the microstructure of this alloy is composed of ε-AgZn3 dendrites enveloped by a peritectic η-Zn matrix, strongly influenced by the casting conditions. To study its growth, solidification experiments of the Zn-10.0Ag-1.0Mg wt% alloy were carried out on different copper mold geometries, including rectangular, wedge-shaped, and cylindrical. A range of microstructures between the limits of constitutional velocity (2.6 × 10−4 mm/s) and absolute stability velocity (3.3 × 102 mm/s) were achieved. Besides the ε-AgZn3 and η-Zn phases with different morphologies, Peritectic Coupled Growth (PCG) was found. The addition of Mg together with convection during solidification promotes PCG at a growth rate of ∼ 0.1 mm/s.

The impact of small Zr addition to Al–Ni cast alloy for elevated temperature applications

Most aluminium casting alloys are based on the eutectic system Al–Si, which has weak thermal properties. Alloys from the eutectic Al–Ni system on the other hand have higher thermal stability and good casting properties and are therefore promising for casting applications. Using casting simulations, a copper mold was designed to achieve cooling rates above 100 K/s with the aim of producing a Zr-rich supersaturated solid solution. Microstructural analysis revealed that the addition of Zr leads to notable changes in the microstructure characterised by the formation of primary Al3Zr and αAl dendrites. Subsequent heat treatment revealed that Zr-enriched alloys undergo significant age hardening, which showed an improvement in microhardness due to effective Al3Zr precipitation.

Study on precipitation in (CoCrFeMnNi)90Al6Ti4 high entropy alloy

(CoCrFeMnNi)90Al6Ti4 high entropy alloy (HEA) was prepared by adding Al and Ti elements into CoCrFeMnNi HEA. The alloy underwent processes including copper mold suction casting, 1473 K homogenization, 30 % cold rolling + 1273 K annealing + 1073 K aging, and water quenching and heating treatment. Microstructure and phase composition of both as-cast and heat-treated (CoCrFeMnNi)90Al6Ti4 HEA were studied using metallographic microscope, scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffractometer (XRD), and transmission electron microscope (TEM). The effect of heat treatment processes on the precipitation of second phases in (CoCrFeMnNi)90Al6Ti4 HEA was investigated, and mechanical properties of as-cast and heat-treated (CoCrFeMnNi)90Al6Ti4 HEA were studied via hardness tests. The results show that in as-cast (CoCrFeMnNi)90Al6Ti4 HEA, the second phase precipitated is primarily L21 structured AlTiNi2 phase. After homogenization, cold rolling, annealing, and aging processes, both the quantity and size of the second phase increase, with a small amount of nanoscale L12 phase appearing after aging treatment. With the progression of heat treatment, the hardness of (CoCrFeMnNi)90Al6Ti4 HEA increases, and mechanical properties are improved.

Improving TiB2 dispersion in Al-Si composites by interfacial projection: High-throughput first-principles calculations and experimental verification

The dispersion of reinforced particles is crucial in improving the mechanical properties of ceramic particles reinforced Al matrix composites. In this work, a novel interfacial projection strategy was proposed to improve the dispersion of TiB2 particles in Al-Si composites through high-throughput first-principles calculations with the experimental verification. Firstly, the Al(111)/TiB2(0001) interface model was constructed. Then, the pre-substitution of Si at 2 at. % concentration was employed to simulate the solutionized Al matrix. Secondly, alloying behaviors of 55 elements (10 substitution sites per element) in the Si-Al(111)/TiB2(0001) interface were studied by high-throughput first-principles calculations in terms of the relative interface formation energy and the relative work of adhesion. With these values, a theoretical alloying map for evaluating the dispersion ability of these alloying elements was plotted. Accordingly, the copper mold experiments were conducted to validate the theoretical alloying map. Based on the electron analysis, the enhanced interface bonds by alloying primarily attributed to electron accumulations around Si atom, indicating that the pre-substitution Si atom was vital for a reliable simulation result. Generally, this interfacial projection strategy provides a precise and potent approach in designing high-performance Al matrix composites, and should be applicable to other reinforced particles.

Longitudinal Ultrasonic Vibration-Assisted Planing Method for Processing Micro-Pyramid Arrays.

Micro-pyramid copper molds are critical components in the preparation of high-precision optical elements, such as light-trapping films and reflective films. Their surfaces are composed of micro-pyramid arrays (MPAs). The surface roughness and edge burrs of MPAs seriously affect the optical properties of optical elements. To reduce the surface roughness, as well as the sizes of the edge burrs, the longitudinal ultrasonic vibration-assisted planing (LUVP) method for processing MPAs was developed during this study. In addition, an experiment was conducted to compare the precision planing and LUVP methods of MPA generation. The results show that the tool nose amplitude of the LUVP experimental platform constructed during this study was 3.3 μm, and that the operating frequency was 19.85 kHz. An MPA processed by LUVP had a smaller surface roughness than that of an MPA produced by precision planing; it also had fewer and smaller edge burrs, and there was slightly less diamond tool wear. The MPA cut using the LUVP method had no corrugation on its surface. This research lays a foundation for developing higher-precision micro-pyramid plastic films.

Composition design and crystallization behavior of Zr–Cu–Ni–Al bulk metallic glasses

The Zr–Cu–Ni–Al system was explored in this study, and seven new compositions of Zr-based bulk metallic glasses (BMGs) were designed by combining different proportions of binary eutectic phases Zr38Cu62, Zr76Ni24 and Zr51Al49, and rod-like shape samples were prepared with different diameters using the copper mold casting method. Modifying the proportion coefficient of these eutectic units, the width of the supercooled liquid region was increased from 79 to 95 K, and the thermal stability of the prepared metallic glass was improved. Differential scanning calorimetry was used to investigate the non-isothermal and isothermal crystallization behavior of the prepared samples. Noticeably, there was a small low-temperature exothermic peak before the glass transition temperature Tg in the non-isothermal crystallization process, which was related to the structural relaxation. The crystallization transition activation energy fitted by the Kissinger equation had the same variation trend as that obtained by the Arrhenius equation. Among the four metallic glasses studied, the glassy phase of Zr55·5Cu23·25Ni9Al12.25 was more stable, showing higher glass transition activation energy and longer incubation time. In addition, the isothermal crystallization processes of four metallic glasses were studied according to the Johnson-Mehl-Avrami (JMA) model. The calculated average Avrami exponents were >2.5, indicating that the nucleation rate increased during the isothermal crystallization process.

Selective recovery of Cu from copper mold production waste by organic ligands

In the present study, organic acids - oxalic acid, citric acid, tartaric acid and siderophore Desferrioxamine B were evaluated for their efficiencies to selectively recover Cu from its mold production waste. XRD analysis showed that copper mold production waste mainly consisted of Fe and Cu. The complete dissolution of this waste in aqua regia and subsequent analysis via ICP-MS revealed metal contents of 355.3 mg/g Fe and 293.9 mg/g Cu. Among all the organic acids, citric acid had the highest leaching efficiency (58.5 %) for Fe while leaching <1 % of Cu. Whereas, the leaching of Cu and Fe was poor in oxalic acid medium and Cu leaching was also negligible in tartaric acid medium. Only Fe showed 11.2 % leaching efficiency at 2 mol/L tartaric acid. The step-by-step leaching of production waste with citric acid lead to 100 % leaching of Fe while leaving 93.1 % of Cu with a yield of >99 % in the solid residue in the 4th step. Further, the siderophore Desferrioxamine B could effectively leach Fe (91.2 %) while 21.4 % leaching of Cu in 30 days. The presence of Fe impedes the leaching of Cu from the waste as demonstrated by leaching and DFT calculations due to higher stability of Fe-citrate and Fe-desferrioxamine B complex compared to Cu-organic complexes. This recycling technique described herein is simple, reliable and environmentally friendly for recovery of Cu from copper mold production waste.

Unveiling the Microstructural Segregation and Micro-hardness Behaviour in Ti-6Al-4 V Alloy Prepared through Copper Mould Casting

Unveiling the Microstructural Segregation and Micro-hardness Behaviour in Ti-6Al-4 V Alloy Prepared through Copper Mould Casting

Mold material and dimension effects on the microstructural gradient in a glass-ceramic

Microstructural gradients can significantly affect the properties of glass-ceramics (GCs). Such spatial variations in glass-ceramic (GC) microstructure may result from a non-uniform cooling rate when the glass-forming liquid is cast into a mold. This study investigates the material and mold size influence on the cooling process, leading to a non-uniform distribution of crystalline nuclei in the parent glass. We used a high-nucleation rate, non-stoichiometric, lithium metasilicate GC as a model. Initially, the glass-forming liquid was cooled in cylindrical molds with diameters of 7 and 14 mm, made from copper and 304 stainless steel – materials with distinct thermal diffusivities. Simulated thermography, validated by thermocouple data, showed contrasting cooling profiles across the samples. Our key findings are: i) cooling rate: faster cooling in the smaller mold resulted in a lower crystal number density and a reduced crystallized volume fraction (αv) as expected; ii) mold material: surprisingly, copper molds led to quicker glass shrinkage, which facilitated the earlier formation of air gaps with reduced heat transfer and slower cooling than steel, favoring incipient crystallization during the cooling path; iii) microstructure: samples cooled in both molds exhibited higher αv in the central and upper (mold contact-free) regions due to slower cooling compared to the mold base and edges. Therefore, this study reveals how mold material and size affect microstructural gradients in GCs, paving the way for tailoring crystallization and microstructure through strategic mold design.

Numerical simulation and experimental study on effect of cooling rate on microstructure and strength of nanostructured materials

In this study, by numerical simulation (finite element method, FEM) and experimental, the cooling rate was investigated by changing the product thickness (20, 3, 2, 1, 0.5 and 0.3) mm of Al based two-phase nanostructured materials casted through a copper mold. The effect of cooling rate on the microstructure and strength of the alloy was studied. The Experimental results showed that the precipitated intermetallic phases have a decreasing size corresponding to the increasing cooling rates by simulation from ~102 K/s to ~104 K/s. The results show that an appropriate cooling rate can improve the microstructure and properties of the alloy. The Abaqus/Standard capability for uncoupled heat transfer analysis was intended to model solid body heat conduction with general, temperature-dependent conductivity; internal energy (including latent heat effects); and quite general convection and radiation boundary conditions. This study describes the basic energy balance, constitutive models, boundary conditions, finite element discretization, and time integration procedures used. The time step used an automatic algorithm through the smallest tolerance. The maximum temperature change was allowed over a period and the increment was adjusted for this parameter, as was the rate of convergence in the non-linear cases. First-order heat transfer elements used the rule of numerical integration with integrated stations located at the corners of the element for thermal capacitance terms. (Jacobian terminology). This approach is particularly effective when there is a strong latent thermal effect. Thus, first - order elements were used in the case of latent heat. The HEATCAP element is available for single - point pooled thermal capacitance modeling. Centralized film loading options between the mold and the casting were specified by the user.

Electropulsing of low-density duplex steel for strengthening and ductilization by microstructural refinement

The present investigation finds the effect of electropulsing treatment on the mechanisms of refining and reprecipitation of ordered L20 structure (B2) and its impact on tensile properties of low-density duplex steel of Fe-18Mn-10.5Al-1 C-6Ni composition. The selected composition without manganese is melted at 1600°C by induction heating in a vacuum but Mn is added into the melt at 1560°C, in the argon atmosphere to reduce the loss. The melt is cast into a plate form in a copper mold. The cast steel is homogenized, hot rolled, and annealed (PD1-A sample) to get elongated bands, spheroids, and platelets of B2 phase with an austenitic matrix which results in a yield strength of 1015 MPa, and tensile strength of 1285 MPa with a plastic elongation of 16.3%. Electropulsing partially dissolves the B2 phase at a temperature much lower than the equilibrium solvus by reducing barrier energy because of electron wind. As a result, the sizes of bands and spheroids are reduced, and platelets are disintegrated. Electron wind force deforms coarse precipitates, and fragments as well as spheroidized it. Electropulsing of annealed steel (PD1-AE) mobilizes dislocations, and recovers it in B2, but induces localized recrystallization of austenite. At a later time of the signal, the temperature rapidly falls and the matrix becomes supersaturated but electropulsing accelerates low-temperature precipitation of the B2 phase. Therefore, electropulsing can be adopted as a fast manufacturing process to dissolve, deform, fragment, spheroidize and reprecipitate high temperature phase at much lower temperature by dominant athermal effect of electron wind energy over thermal effect. Electropulsing also induces recovery and recrystallization at a relatively low temperature and reduces defect density. Reduction in the overall size of B2 and its distribution towards better uniformity provided an increased yield strength of 1077 MPa, tensile strength of 1355 MPa, and a plastic elongation of 21.6%. The selected duplex low-density steel follows two-stage work hardening of Ludwigson model with an additional stage of dynamic recovery. Fractography analysis confirms that both samples show mixed modes of ductile and brittle fracture, with an increase in size and area percentage of dimples.