Copper Billets Research Articles

Analysis of the Development of Downstream Copper Industry in Indonesia to Obtain Maximum Added Value Using Dynamic Systems

This research aims to design a dynamic system model for the downstream copper processing industry. The secondary data obtained is data provided by the BKPM Strategic Investment Downstreaming Expert Team. Vensim software is used to simulate downstream development in the form of CLD and SFD from 2024 to 2045. The results of the value-added simulation resulted in an increase in the added value of copper cathode by 2.15 times, the added value of cathode slab by 1.62 times, the added value of copper billet by 1.65 times, the added value of copper bar &rods by 1.08 times, the added value of copper tube by 1.02 times, the added value of copper strip by 1.39 times, and the added value of copper wire by 1.58 times. After a sensitivity analysis of the selling price at CAGR and an increase in energy costs by 20%, there was a change in the average value-added margin, so that the increase in added value changed which resulted in an added value of copper cathode of 1.9 times, added value of cathode slab of 1.47 times, added value of copper billet of 1.49 times, added value of copper bar &rods of 1.26 times, added value of copper tube of 0.93 times, added value of copper strip of 0.98 times, and added value of copper wire of 1.44 times.

Dynamic modelling and efficiency prediction for forging operations under a screw press

Accurate predictions concerning a forging process can be obtained by numerical simulation, but only with a thorough knowledge of the main process variables. The material flow behavior and the interface effects are already well studied in the literature, but not the machine behavior, although it is required to estimate blow efficiency and deduce the energy actually transmitted to the workpiece. In this paper, an experimental methodology was applied to determine a spring-mass-damping model and its associated parameters for a screw press. The model and its parameters were identified with press strikes performed without billet. For validation, simulations were performed to predict blows on copper billets. The model’s predictions were in good agreement with the experimental measurements for ten consecutive blows on a copper billet. The decrease of process efficiency and the evolution from inelastic blows to elastic blows were correctly depicted by the model.

Surface modifications to reduce wear in hot extrusion of copper

During hot extrusion of copper, the material tends to stick to the extrusion die due to strong adhesive forces between hot working steel and copper at high temperatures. In this context, surface modifications like nanocomposite coatings deposited by plasma enhanced chemical vapor deposition or boriding of nickel-based alloy 718 (DIN 2.4668) create hard and wear resistant thin solid films that offer high temperature stability. Ti–Si–B–C–N nanocomposite coatings consist of nanocrystalline grains embedded in a thin amorphous matrix. Due to this particular nanostructure, hardness values of up to 39.3 GPa were reached. Boriding of alloy 718 leads to formation of phases consisting of alloying elements like nickel, iron, and chromium and the diffusing element boron. The borides form a boriding zone that offers high hardness. Extrusion of Ø122 mm × 300 mm copper billets preheated to 850 °C was carried out and adhesive wear on tool's surfaces was analyzed. The comparison between hot working steel DIN 1.2367 without surface modification and with Ti–Si–B–C–N coating or borided alloy 718 showed remarkable differences between conventional tools made of hot working steels/alloy 718 and tools with surface modification. A strong decrease particle adhesion was observed.

Investigation of the Efficiency of Roll Profiles and Technological Schemes of Deformation of Asymmetric Rolling in Relief Rolls of C11000 Copper Alloy by FEM Simulation

In this paper, finite element simulation of asymmetric rolling in relief rolls of C11000 copper alloy in order to analyze the effectiveness of possible roll profiles and technological schemes of deformation was performed. The scientific innovation of this work lies in determining the patterns of development of stress-strain state parameters for various configurations of rolls, as well as determining the effectiveness of metal processing using various technological schemes. It was found that the use of trapezoidal relief makes it possible to increase the level of metal processing by almost 5 times compared with the use of radial relief. Comparison of technological schemes of deformation showed that deformation with 180° workpiece turning between passes significantly reduces the influence of the asymmetry factor. Deformation without changing the workpiece position between the passes has the opposite effect, and such a scheme significantly increases the influence of the asymmetry factor. Deformation with a transverse workpiece shift for the relief period between passes has the effect of a “golden mean.” The conducted laboratory experiment for lead billet showed that the shape change of lead billet during computer simulation has a high level of convergence with real conditions. At each stage of deformation, the difference in the geometric parameters of the workpiece between the model and the experiment did not exceed 3-5%. When deforming a copper billet, the maximum difference level was 8%, which is the result of the low rigidity of the rolling cage with smooth rolls.

In situ temperature measurement of a deforming interface with thermoelectricity

Accurate temperature measurement is critical to understanding the thermomechanical conditions and microstructural evolution that materials experience during severe plastic deformation (SPD). Others have previously measured the interface between a non-deforming tool and metal workpiece using thermocouples, infrared measurement, and the thermoelectric principle. Measuring temperature within the deforming material itself, especially at a high-shear deforming interface, has proven to be extremely difficult, thus limiting the application of these measurements to fundamental SPD research. In this study, the thermoelectric principle is used to directly measure temperature at the interface between copper and nickel billets undergoing SPD. This is done by utilizing the deforming materials themselves as two halves of a thermocouple junction. The spatial resolution of this measurement is shown via microscopy to be less than 1 micron. Temperature changes are sensed almost instantly, with time delays on the order of the data logger frequency (0.01 seconds). Process variations that are both very brief (<0.05 seconds) and minute (<3°C) are able to be detected by this method.

Experimental Investigation to Study the Feasibility of Fabricating Ultra-Conductive Copper Using a Hybrid Method.

Ultra-conductive copper (UCC) has an enormous potential to disrupt the existing electrical and electronic systems. Recent studies on carbon nanotubes (CNTs), a new class of materials, showed the ballistic conductance of electricity. Researchers around the world are able to demonstrate ultra-conductivity in micro- and millimeter-length sections using various processing techniques by embedding CNTs in the copper matrix. Although multiple methods promise the possibility of producing copper-based nanocomposites with gains in electrical conductivity, thus far, scaling up these results has been quite a challenge. We investigated a hybrid method of both hot-pressing followed by rolling in order to produce UCC wire. Cu/CNT billets of 1/10%, 1/15%, and 1/20% were hot-pressed and the conductivity results were compared to a hot-pressed pure copper billet. Our results indicated that this method is not a viable approach, as the gains in electrical conductivity are neutralized, followed by attenuation of the wire cross-section.

FEM simulation of C45 steel and Cu-ETP billet shaping at hot upsetting between convex conical dies

On the basis of finite element analysis (FEA), geometric differences in the shaping during hot upsetting of cylindrical billets with a height-to-diameter ratio of 1.0 and 2.0 made of C45 (1.0503) steel and copper (Cu-ETP) between pointed convex conical dies with a cone slant angle of 12.5°, 15.0° and 17.5° are considered. The stroke velocity of the upper die is 0.5 m/s; process temperature (t) and accepted surface friction coefficient (|μ): for steel - t = 1100 °C, μ = 0.32, for copper - t = 850 °C, μ = 0.34. An equation is obtained for the relation between values of reduction in height ratio and engineering strain on height of workpiece during upsetting between conical dies, taking into account the initial billet dimensions and unevenness of forming due to the geometry of tool. The presence of qualitative and quantitative differences in shaping along the height of upset steel and copper billets was revealed, i.e. influence on unevenness of forming the rheological properties of materials under process conditions. It is advisable to use the results obtained to design and improve of technological processes of open die and closed die forging with preforming of billets.

Stages of technological improvement of the process of continuous casting of iron-carbon and copper billets

In the article there are presented the stages of improvement of the process of continuous casting. It is revealed, that at the each stage of technological improvement of the process of continuous casting, the damage parameters of billets were reduced. Improvement of the process of continuous casting leads to the improvement of the mechanical properties of the billets and the performance of continuous casting machines. The first stage is shown as the process of transition of the number of experimental developments into quality, during which the casting of billets passed from an unstable process to a stable one. The second stage is characterized by the creation of new improved continuous casting processes. So, besides the existing machines of the vertical type, radial, curvilinear and horizontal casting machines were invented. By the end of the twentieth century, this technological process reached the limit of the possibilities for increasing the quality of performs, and the productivity of continuous casting machines. It is shown that the third stage is intended for continuous casting of copper alloys and is based on the influence of the frequency of the movement of the billets and the reverse movement of the perform during overcoming the static friction force. It was determined that for the frequency of movement of billets made of copper alloys, which are in the range of 2.5...7.5 min-1, the direction of its movement during overcoming the static friction affects the mechanical properties of the billet. The fourth stage - causes an increase in the mechanical properties of the billet due to the use of inertia forces in the alternating movement of the billet. It was revealed that at the fourth stage the mechanical properties of the billets increased most effectively, and the linear performance increased from 0.4...0.8 to 2.5...4.0 m/min, and in some cases to 5.0...7.0 m/min.

Study on Solidification Structure Evolution of Direct-Chill Casting High Purity Copper Billet Using Cellular Automaton-Finite Element Method

A heat transfer model and a cellular Automation-Finite Element (CAFE) coupling model were established to analyze the solid/liquid (S/L) interface and solidification structure evolution of high purity copper Direct-chill (DC) casting billet under different casting conditions. The simulation and actual experimental results of liquid sump shape and solidification structure were first compared to verify the accuracy of the model. It is proved that the model is effective for simulating the solidification structure of the actual DC casting high purity copper billet. After that, the model was used to predict the solidification structure under different casting temperatures, casting speeds, and heat transfer coefficients. It is shown that, with the increase of casting temperature, the grain size decreases first and then increases. There is a compromise between grain size and its uniformity, and the grain size is more uniform at higher casting temperature. With the increase of casting speed, the depth of liquid sump and the height of the S/L interface increase, but the total grain number of the billet cross-section decreases gradually. As the heat transfer coefficient increases, the depth of the casting liquid sump becomes shallow, but the height of the solid-liquid interface increases and the grain size increases gradually. For the preparation of high purity copper billets with large cross-sectional dimensions by DC casting, a fine solidified structure could be obtained by appropriately reducing the casting speed and cooling intensity.

Failure investigation of welded 430 stainless steel plates for conveyor belts

Failure investigation considering the material aspects, was conducted on butt welded conveyor belt used in copper billet casting processes, that suffered from cracking. The belt is made of AISI 430 ferritic stainless steel. The results of the investigation indicate that the butt welded joint is in sound condition, without any evidence on the lack of weld penetration, and no void or porosity is found. Thus, the welding procedures are not suspected to be the cause of the failure. The cracking of the welded joint initiated at the grain boundaries in the heat-affected zone (HAZ) and propagated along the weld line and across the welded joint. The failure mode is concluded to be the intergranular stress corrosion cracking (IGSCC), and accelerated by the presence of high temperature and humid environment.

Microstructural and Textural Evolutions of OFHC Cu during the CECC Process and Annealing Treatment

The bulk Cu billets with ultrafine-grained microstructure were successfully processed from full-annealed coarse grained oxygen-free high conductivity (OFHC) Cu by the cyclic extrusion and closed compression (CECC), subsequently annealed at different temperatures. The evolution of the microstructure and mechanical properties was systematically studied. The results show that the effective strain per CECC process is ε=2.77, with further annealing treatment, a high-efficiency grain refinement is realized. After two cycles of CECC process and annealing at 350 °C for 1 h, the grain size refined to ～3 μm, the tensile strength increased to 280 MPa with a high ductility of 54%. Furthermore, a homogeneous structure and mechanical properties in the bulk copper billets for post-forging could be obtained.

Investigation of internal defects formation reasons in copper billet obtained at rotary continuous casting machine (CCM)

A physical model has been created that simulates the cross section of a continuous casted trapezoidal copper billet. The results of physical modeling of continuously cast copper billets solidification process are presented. The features of the trapezoidal continuously casted copper billet crystal structure formation during the casting of metal on a rotary caster are shown. During physical modeling, it was found that the solidification mechanism of the model substance in the study of the formation of the crystalline structure of the copper trapezoidal billet has significant differences from the "classical" crystallization mechanism, in which the crystals grow parallel to each other. The main feature of the copper billet crystal structure formation is that in most cases dendrites growth direction is chaotic relative to the surface of the heat flow, and the growth rates of individual crystals differ by 25–35 %. In this case, the development of nearby crystals ceases due to a collision with the secondary branches of more intensively developing dendrites. It was also established during the modeling process that during crystallization of the melt according to the described above mechanism, a collision of the most intensively developing crystals growing on neighboring faces is possible, in which the closing main axes of the dendrites separate part of the liquid phase from the total volume. This isolated volume of the liquid phase cannot be feed by the melt from the axial part of the billet. The shrinkage of such areas during solidification is the reason for the formation of pores inside the billet. The disordered arrangement of internal pores in the cross section of a trapezoidal copper billet is explained by the randomness of the dendritic crystals growth directions and of the difference in their growth rates.

The Influence of A Cross-Channel Extrusion Process on The Microstructure and Properties of Copper.

A new cross-channel extrusion (CCE) method with the application of a back pressure (BP) is proposed and experimentally tested. The introduction of pressure blocks the free flow of material by using an additional set of pistons, which prevents the loss of consistency. The paper presents results of experimental trials of CCE process. Between one and eight passes of CCE with and without a BP were applied to pure copper billets to refine their initial coarse-grained microstructure at room temperature. It was found that processing by CCE results in the formation of a lamellar structure along the extruded axis and the fine-grained structure in the remaining volume. The material exhibited dynamic recrystallization, which results in the formation of 0.5- to 2-μm grains after one pass and 2- to 8-μm grains after four CCE passes. The fine-grained material had YS of 390-415 MPa. An increase in the microhardness from 70 to 130 HV02 after one pass and then a decrease after four passes were observed. This might indicate that secondary recrystallization and selective grain growth occur, because an exothermic peak (158.5 °C, 53 ± 2.1 J/mol) was observed during DSC (differential scanning calorimetry) testing. The resistivity of the once deformed copper significantly decreases, while its further processing causes the resistivity to increase.

Obtaining hexagon-shaped billets of copper with gradient structure by twist extrusion

Processing by twist extrusion was used to produce copper billets with a hexagonal cross-section. A special feature of the billets is their gradient microstructure owing to a specific strain pattern: an undeformed core and a deformed outer sheath. The initial sample with a 40 mm diameter was processed at room temperature by four twist extrusion passes through a twist die having a hexagonal cross-section and a small twist-line slope angle β = 40° with a back-pressure of 100 MPa. The results showed that the processed sample had an undeformed core 20 mm in diameter and a deformed outer sheath with a gradient microstructure in which the average grain size decreased gradually from 50 μm to 0.5 μm towards the periphery along a radius direction. The microstructure gradient represented the various stages of the grain refinement process corresponding to increasing shear strain. The texture revealed two different shear deformation modes whose shear planes were perpendicular and parallel to the extrusion axis. The measured Vickers hardness showed good agreement with the microstructure. In the deformation zone, the classical Hall-Petch relation between the hardness and the grain size of the various characteristic areas formed by twist extrusion was found.

Experimental investigation of wear resistance of copper coated electrode-tool during electrical discharge machining

In this study, electrode-tools with excellent electrical and thermal properties were manufactured for use in die-sinker Electrical Discharge Machining. The most common materials, nowadays, for the manufacture of electrode tools are copper and graphite. The traditional method of obtaining complex profile electrodes tools is multi-axis metal cutting blade processing. The low utilization rate of the tool material during the shaping of complex-profile electrodes significantly affects the cost of a suitable product. The paper proposed a method of fabricating electrodes obtained by casting methods with the subsequent application of electro-erosion resistant coatings. The study of the investigating the durability of the coated electrode during the processing of 34CrNiMo6 steel has been carried out. It has been established that to obtain a uniform copper coating with a thickness of 300 μm, it is necessary to use a current density in the course of galvanic deposition of 1.3 A / mm2 at an exposure of 5 hours. An experimental study of the durability of the coating during the die-sinker Electrical Discharge Machining of 34CrNiMo6 steel showed that with an increase in the current intensity above 8A, the copper coating burns out. Based on the research, it was found that the processing of 34CrNiMo6 steel with electrode having copper coating on aluminum alloy AK12 as a base metal showcased superior processing capacity. The economic efficiency of using coated electrodes was enhanced by 35% as compared to the technology for obtaining a tool from a solid copper billet.

Forming Limit in the Nosing Process of Micro Copper Cups

This study used finite element simulations and experiments to investigate the forming limit in the nosing process of micro copper cups, and to establish the limit nosing curves in terms of nosing ratio, die angle, and friction factor. Two-stage processes, including backward extrusion and nosing processes, were considered in simulations and experiments at micro scale. The copper billets with 1 mm diameter and length were backwards extruded to produce the 1 mm diameter cups with 0.1 mm wall thickness. The cups were later used in the nosing processes under different forming conditions. By analysing the results of the nosed cups from the simulations, it is possible to identify the safe and failure forming conditions and establish the limit nosing curves for the nosing process. The simulation results show that the limit nosing ratio increases as the die angle or friction factor decreases. Two predicted results for poor and well lubricated conditions have been examined and are in good agreement with those from experiments. The study not only explores the characteristics of the noise process of copper cups at micro scale but also establishes the limit nosing curves which could be the guidelines for the design of micro metal components.

Microstructure and Mechanical Properties of Copper Billets Fabricated by the Repetitive Extrusion and Free Forging Process

In the present study, with the aim of obtaining a weakened texture, grain refinement and improved mechanical properties, copper billets were successfully fabricated using the severe plastic deformation method of repetitive extrusion and free forging (REFF) without using any additional tools or devices. The evolution of the microstructure, texture and mechanical behavior of the ultrafine grain copper billets over an increasing number of REEF cycles was also systematically studied. Our results show that the effective strain per REFF process was ε = 2.35. After two cycles of REFF process, the sum effective strain became ε = 4.7, leading to high efficiency of grain refinement. The grain size was refined from 50 to 0.8 μm; the yield strength was increased to 462 MPa, and we obtained a weakened texture in the pure copper billets. By increasing the number of cycles, the grain refinement ability was decreased, and the texture was thus strengthened further. Therefore, two cycles of REFF were a reasonable process for producing ultrafine-grained copper billets.

Prediction of Potential Fracturing During Radial-Shear Rolling of Continuously Cast Copper Billets by Means of Computer Simulation

Based on the results of experimental radial-shear rolling of continuously cast anodic copper billets (rods) using a 10-30 mini-mill at 750 and 850°C, a part-through fracturing from within the billets has been discovered. The volume of cavities formed as a result of such fracturing appears to be more significant at 750°C. A simulation of rolling under experimental conditions was performed using DEFORM software, and the efficiency of applying a finite-element analysis computing environment for predicting fracturing was evaluated. An adequate correlation was established between the obtained estimates of the metal ductility under different deformation temperatures, as well as the probability of formation and dimensions of discontinuities and experimental data. The comparison between the shrinkage cavity depths of the billets based on the results of computer simulation has shown that the ductility of the rod material is higher at 800°C. Based on the analysis of variation in values of the rigidity coefficient under stress condition along the radius of the billet near the end of it, as well as analysis of the path described by the points located along the billet radius in the “cumulative deformation – rigidity coefficient under stress condition” coordinates while in the deformation zone, obtained as a result of computer simulation, it has been established that fracturing at 750°C should be more significant than at 800°C. Recommendations are provided regarding further use of the results of computer simulation to estimate the size of the regions, within which fracturing is expected to occur under the given rolling conditions.

Examining the microstructure of production defects in brass and copper billets for industrial applications

Examining the microstructure of production defects in brass and copper billets for industrial applications

Friction Stir Radial Backward Extrusion (FSRBE) as a new grain refining technique

A new method entitled Friction Stir Radial Backward Extrusion (FSRBE) is presented for processing fine-grained tubes. In FSRBE technique, an initial pure copper billet is placed inside a cylindrical chamber. The billet is pushed toward a rotating tool which results in radial and backward flow of the material while is frictionally stirred. The microstructure evolution during FSRBE was investigated through experimental observations and cellular automaton (CA) modeling. The observations reveal that the microstructure with initial grain size of 75μm was refined to a fine-grained structure with an average grain size of 12μm. The results of tensile tests demonstrate slight improvement in the value of yield and ultimate strength, elongation and microhardness. The microstructural evolution during FSRBE processing in the micro-level was studied using a coupled cellular automaton algorithm and finite element model. First, the macroscopic plastic flow behavior of material during FSRBE was calculated using FEM simulation method. Next, by tracing the plastic strain, the strain rate and temperature, in the deformation domain of cellular automaton, the DRX kinetics of pure copper is obtained in a devised post-processing step. The microstructure observations showed that the proposed model predictions were in reasonably good agreement with the experimentally obtained results.