Towards the decarbonized society, manufacturing industry have innovated new processes using renewable energy. However, the current situation is that economical and stable renewable energy is not yet available. So, the first task is to strongly promote the establishment of more efficient manufacturing technology. In this background, we focus on the melting and casting process that is the most energy–consuming work to produce copper material. Then, most of the loss in this continuous casting process is caused by the instability of the solidification–shell of the ingot. Therefore, for improving the stability of this cooling, we create a unique experimental device to evaluate the heat transport molten copper–alloy to mold with molten Flux in Na₂O–B₂O₃ system.

The following was confirmed by inverse analysis these experimental results.

1） The evaluation device is effective to estimate heat transport molten copper to mold with molten Flux.

2） The conductive heat transfer accounts for 40% of the heat transfer molten copper alloy to copper mold with molten Flux layer of 0.8mm. As thickness of molten Flux is from 1.8 to 4.4mm, it is 80%.

3） A variation of heat transfer coefficient from solid Flux to copper mold at 66.7–80.0 mol%B₂O₃–Na₂O system becomes large. These coefficients have an inverse relationship with temperature range of Mushy zone at Flux.

It is well known that inclusions deteriorate the quality of copper products. To improve the quality, it is necessary to make clear the kinetic behavior of inclusions in molten copper and optimize operation conditions and processes. However, a model that can predict the number concentration and distribution of inclusions in molten metal has not been developed enough. Therefore, the kinetic behavior on coagulation of inclusions, entrapment of inclusions at liquid/liquid interface, such as between molten copper and flux, and removal by bubble flotation was investigated. In present study, a change in particle number density with time was measured by a water model experiment using a gas stirred vessel. And a predictive model of particle number density by coagulation, entrapment at liquid/liquid interface and bubble flotation was constructed and verified comparing with the experimental values. As a result, the calculated values agreed with experimental values approximately and the present model was appropriate. In the analysis using the model, it was found that the effect of entrapment on change in particle number density was dominated at the low particle number density and the effect of coagulation was dominated at the high particle number density. From the viewpoint of inclusion removal, it was considered that the entrapment was main mechanism in the present experimental condition and the effect of bubble flotation on inclusion removal became relatively large in the case that gas flow rate was increased.

We investigated Co effect in precipitation behavior in Cu–Ni–Si alloy by analyzing the cohesive and interfacial energies of the second phase doped with Co based on the density functional theory (DFT) calculations. Co atoms are expected to reduce the cohesive energy of Ni₂Si, but increase the interfacial energy between Cu and Ni₂Si, resulting in the increment of the activation energy of Ni₂Si precipitation. Higher activation energy of (Ni,Co)₂Si precipitation leads a higher aging temperature or a longer aging time for precipitation compared to Cu–Ni–Si alloy. The experimental results and DFT calculation have a good agreement. And the DFT calculations predict that aspect ratio of (Ni₁–_x,Co_x)₂Si precipitates decreases according to Co concentration. Besides, experiments show that the precipitates in Cu–Ni–Co–Si alloy changed to a more spherical shape not only in the matrix but also at the grain boundary.

The effects of the largest crack–size and size–difference among cracks on the critical current and n–value of the copper–stabilized coated superconducting tape, in which multiple cracks are formed in the superconducting layer, were investigated. As the tools, the model of current shunting at cracks, Monte Carlo simulation method, monitoring method of the crack size and the size–difference among cracks, and calculation method of the upper and lower bounds of the critical current and n–value at the largest crack–size were employed. The main results are summarized as follows. (1) The increase in the largest crack–size with the increase in the crack size distribution width works to reduce both the critical current and the n–value. On the other hand, the increase in the size–difference among the cracks works to raise the critical current value and to reduce the n–value. (2) When the crack size distribution width increases, the effect of reducing the critical current due to the increase of the largest crack–size and the effect of raising the critical current due to the increase of the size–difference among the cracks take place, and the critical current is determined by the sum of these effects. Since the effect of the former is larger than that of the latter, the critical current value decreases with increase in the crack size distribution width. (3) With increase in the crack size distribution width, the effect of reducing the n–value due to the increase in the largest crack–size and the effect of reducing the n–value due to the increase in the size–difference among the cracks take place, and the n–value is determined by the sum total of these effects. Since both of these two effects work to reduce the n–value, as the crack size distribution width increases, the n–value decreases relatively sharply with respect to the critical current.

It is widely known that copper and its alloys, e.g., Brass, form different rolling textures. This is due to the difference of the plastic deformation mechanisms for pure Cu and its alloys. In turn, detailed study for the texture formation can reveal their deformation mechanisms. In this study, the numerical texture formation simulation is carried out by using visco–plastic self–consistent model. The copper–type texture is reproduced by considering {111} <110> slip and plain strain compression. The consideration of latent hardening, assuming the effect of decomposition of dislocation, realizes more decent prediction for pure copper but not for the alloys. The alloy–type texture with high orientation density at brass orientation is closely reproduced by considering the deformation twinning. However, the predominantly twin reorientation scheme cannot precisely predict the texture. This is due to the assumption that a single orientation reorients to a single twinning orientation, which is not realistic in face–centered cubic metals.

Since the die casting mold repeats rapid heating and cooling during operation, the defects such as heat check generate. Therefore, the quality and the life of the mold are degraded. To improve these demerits, the improvement of the thermal conductivity of the mold material is effective. In this study, the fabrication of composites with high thermal conductivity by adding carbon fiber to the SKD61 tool steel used for hot mold was attempted. Since carbon fiber has a chemical reaction with steel, electroless copper plating was applied to carbon fiber in order to suppress the reaction. The composites were fabricated by the unidirectional arrangement of carbon fibers and spark plasma sintering. The results obtained are as follows. 1) Carbon fiber/SKD61 composites with a high relative density were obtained. It is considered that the copper plated on the carbon fiber acted as a sintering accelerator. Furthermore, the plated copper remained around the carbon fibers in the composite, and it seems copper prevented the direct reaction between carbon and steel. 2) The composites had higher thermal conductivity than monolithic SKD61 block. As increasing the carbon fiber content, the thermal conductivity increases. 5vol.% copper–plated carbon fiber/SKD61 composites have a thermal conductivity of 42 W/mK.

Most industrial products and components have been made of steel or another monolithic material. Recently, multi–material structure is often adopted to improve the performance. In the multi–material design, a few constituent materials should be selected and configured at appropriate locations. However, the optimization method has not been well established. With changing material properties intensively, further optimization is supposed to be possible. The authors propose the multi–property design method, where a material having prescribed properties is fabricated on demand. In this study, cold extrusion of multi–filament billets, where copper, iron, and aluminum filaments and copper sheath were used, was conducted. By changing materials and numbers of filaments to insert, three properties (density, yield strength, electrical resistivity) of extruded bars were controlled. As the measured three properties are close to the predictions by the mixture rule, the multi–property design is found to be feasible by the cold extrusion.

Cold extrusion is applied to produce a clad bar from an assembled billet where a core is inserted into a sheath. A hard–core billet was prepared with copper core and aluminum sheath, while a soft–core billet was prepared by swapping copper and aluminum arrangements. The billets with core diameter of 4mm, 6mm and 8mm were prepared under the outer diameter of 10.9mm. Two dies with different hole diameters were prepared to change the extrusion ratio. In this study, sliding between the core and the sheath was constrained by adding threads on the interface. Working conditions were limited by fracture of core or sheath. The soft–core billet had a wider working window in the extrusion ratio and the volume fraction of the core material to produce sound product when threaded. On the other hand, the working window of the hard–core was limited by sausaging and void formation at center in case of low extrusion ratio. Fracture of the sheath took place when the extrusion ratio was low and that the volume fraction of the core was high. It is concluded that the threads on the interface is effective to widen working limit of the soft–core materials.

The development of new applications for copper smelter slag is important for the maintaining and progression of the copper industry. Gypsum, a by–product of copper smelting as well as copper slag, is widely used as a raw material for plasterboard. The preparation method of the composite of a copper slag with gypsum was studied and the mechanical strength of the composite was evaluated. The composite of copper slag and gypsum was successfully prepared and its mechanical strength was higher than that of the original plasterboard. The ability of the composites to shield against radiation was evaluated by Monte Carlo simulations on X–ray radiation transport. As a result, it was found that the composite plasterboard has a possibility to shield against radiation.

We attempted to fabricate high–strength and high–electrical conductive copper–indium (Cu–In) solid solution alloy wires. It was confirmed that the In solution in Cu matrix promoted an effective solid–solitoin strengthening without deteriorating the conductivity. When Cu–5 at.% In alloy was drawn severely, the wire contained high–dense deformation twins, and eventually formed ultra–fine grains with a size of 60 to 80 nm in average, which is attributed to lowering the stacking fault energy by solute In. The severely drawn Cu–5 at.% In alloy wire possessed an excellent combination of tensile strength of 1340 MPa, and conductivity of 24%IACS, which was comparable to that of competitive Cu–Be alloy wire with the combination of tensile strength and conductivity (approximately 1400 MPa, 22%IACS). The high strengthening in Cu–5 at.% In alloy wire by drawing was primarily due to grain refinement strengthening, and secondary to dislocation strengthening.

Demand for lead–free, free–cutting brass is increasing in response to lead regulations in Europe. The authors of this paper have attempted to develop a lead–free brass with an α+β two–phase microstructure, which is different from existing C6932 alloy. As a result of basic investigations, it was found that the addition of Si to β–brass dramatically reduces the cutting resistance due to an effect that appears to be a reduction in the stacking defect fault energy, and that if phosphorus compounds are dispersed in such β–brass, the compounds make stress concentration sources improving chip fragmentation during cutting. Based on these findings, we have succeeded in developing a new free–cutting α+β brass (62.5Cu–1Si–0.07P–Zn). The developed alloy contains about 55% alpha phase and has excellent machinability and 1.3 times higher strength than C3604.

Pure copper, specifically oxygen–free copper (OFC), is widely used in superconductive and low temperature refrigeration technologies for its high electrical (and thermal) conductive properties at cryogenic temperatures. This property, commonly expressed in Residual Resistivity Ratio (RRR), is associated with purity, or impurity concentration. A high purity copper with low impurity concentration will exhibit high RRR. In addition to impurity concentration, the form in which the impurities exist within the matrix affects RRR, which is influenced by heat treatment. Specifically, for OFC, heat treatment at high temperatures will cause the impurities to dissolve into the matrix, resulting in decrease in RRR. Thus, to obtain high RRR, it is necessary to decrease impurity concentration, which often requires complex purification processes. In this research, we aimed to develop a pure copper material that offers high RRR over a wide heat treatment temperature range, using industrially feasible methods and with OFC as the base material. Impurities having negative effect on RRR were investigated, and an additive element was selected to target and minimize the negative effect of the impurities without itself causing a negative effect on RRR. As a result, we developed a pure copper material using an extremely small amount of calcium as an additive element, that not only exhibits RRR comparable to higher purity copper, but also maintains high RRR over a wide heat treatment temperature range due to the formation of CaS.

Lunar and deep–space exploration and astronomical observation missions equipped with cooling systems for high–sensitivity observations require thermal switches (also called heat switches) that can adjust the heat flow to control the temperature inside spacecraft appropriately. In this study, we proposed a mechanical heat switch utilizing a single–crystal Cu–Al–Mn shape memory alloy for its drive unit. The effect of aging treatment on the martensitic transformation temperature (heat switch drive temperature) of a Cu–17Al–11.6Mn (at.％) alloy was investigated, and it was found that the transformation temperature could be adjusted in the range of −80 to −50°C by varying the duration from 15 min to 2 h at an aging temperature of 150°C. A prototype heat switch was fabricated using a single crystal with an orientation exhibiting a large transformation strain. Cooling–heating tests for the drive unit demonstrated thermal drive with a large displacement of approximately 0.8 mm and a small temperature hysteresis, indicating that the single–crystal Cu–Al–Mn shape memory alloy is highly applicable to heat switches.

Copper alloy suspension wires are used in optical pickups and image stabilization mechanisms of mobile cameras. The durability of the suspension wire used in mobile cameras is greatly affected by the increase in the weight of the lens part due to the high image quality of the camera. Therefore, there is a need to improve the durability of the wire. In this study, the stress reduction effect of the twisted wires suspension are investigated using finite element method (FEM) analysis. In addition, a practical equation is obtained to facilitate the structural design. From this study, and the following conclusions were obtained. In contrast to the conventional single–wire structure, the twisted wire structure enables a significant reduction in the stress generated while maintaining the stiffness. A simple formula that approximates the results of many FEM analyses was proposed. This enables rapid product design.

Copper alloys for terminals need to have both strength and bendability. It is difficult to predict bending workability only from mechanical properties. Therefore, it was examined to experimentally measure the strain generated by bending and use it as an index of bendability. Materials with different mechanical properties were produced by changing the rolling reduction rate of cold rolling process. When processed under the same bending conditions, high cold rolling reduction material had more cracks and wrinkles than the low cold rolling reduction material. In addition, the surface strain measured experimentally increased with the increase of cracks and wrinkles. From the above, it was confirmed that the surface strain generated by bending affects wrinkles and cracks. The results of the analysis showed that the strains were almost the same, but the deformation on the compression side tended to have a large deviation from the actual experimentally measurement.

In this study, in order to simulate the shape fixing heat treatment after twisting of ultrafine wires, we developed a test method that enables heat to be applied to the wire with a strain equivalent to that applied during twisting. Cu–Ag alloy wire (Ag：10 mass％) with an diameter of d=0.02 mm was used as the material. The test jig was U–shaped, consisting of a straight part and a curved part, to facilitate the measurement of the spring–back angle. A tube furnace with an inner diameter of 25 mm was used for heating, and the heating temperature was set at four levels：200°C, 300°C, 400°C and 500°C. The heating time was varied from about 30 s to 180 s. When a rigid punch was used, it was found that the wire moved in the jig and could not be held stably. Therefore, we devised a punch that can be flexibly deformed using stainless steel foil. We found that the punch could hold the wire stably. Following conclusions were obtained as a result of tests using the devised jig. (1) It was shown that it is possible to evaluate the shape fixability of ultrafine wires by small die and stainless steel foil and heating the entire jig. (2) The test conditions in this study are short and high temperature compared to the stress relaxation test of terminal materials, because the twisted wire processing is assumed. It was found that Larson–Miller parameter was also useful to summarize the results in this test range.

We found that Bathocuproinedisulfonic acid used for colorimetric reagent for copper ion was simply immobilized to cellulose membrane with alginate. Moreover, the color of immobilized Bathocuproinedisulfonic acid was changed with copper ion concentration. In addition, we had reported simple color analyzer by the use of smart device with original application software in previous work. Based on these finding, the objective of study is development of simple analysis for copper ion using original test paper immobilized Bathocuproinedisulfonic acid with alginate and simple color analyzer with smart device. As a results, the detection limit (3σ) was 0.8 ppm. Moreover, this method can be employed for the determination of copper ion in tap water.