We investigated the effect of graphite on sliding characteristics of Ag–Graphite composite plating. Friction coefficient and contact resistivity were measured during the sliding test. We also observed test samples after the sliding test. It was found that excellent sliding characteristics of Ag–Graphite composite plating are achieved by graphites in the sliding area which inhibit the adhesion of Ag plating. Graphites existing on the plating surface have a lowering effect on insertion force, but the effect gradually decreases with removal of graphites by sliding. Graphites inside the plating also have some lowering effect on insertion force, and its effect sustains during the sliding test for more than 20000 times. Considering the contact reliability of Ag–Graphite composite plating, although graphites exist on the surface, contact resistance was low since silver is exposed in some parts. From above, Ag–Graphite composite plating is expected to be applied to terminals that require high reliability.

This study is aimed at clarifying the factors that affect the properties of Ag–Nano C composite films on Cu alloys as automotive connectors. The content of Nano C in Ag matrix was mainly dependent on current density and stirring strength during electroplating. The hardness of Ag–Nano C composite films increased 13–58% compared to pure Ag film depending on stirring intensity. Especially, it was found in wear tests that the inclusion of Nano C in Ag films inhibited effectively the adhesive phenomenon at the early stage, and delivered lower friction coefficient at stable region, thus producing less worn volume than that of pure Ag film. Moreover, the observation of tribofilms on plate specimens after wear tests indicates that the Ag–Nano C composite films exhibited an abrasive wear mode with smooth wear tracks, whereas the pure Ag films delivered normally an adhesive wear mode with a coarse wear track. The enhancement on wear resistance of Ag–Nano C composite films can be mainly attributed to the excellent lubrication of Nano C as graphene in Ag matrix film during friction, which included in wear powder between the connectors, thus maintaining both the lubrication and the electric contact resistance.

Reflow tin plating with high heat resistance was developed for in–vehicle connectors. The plating consists of three layers, with tin as the top layer, Cu–Sn intermetallic compounds（IMCs）Cu₆Sn₅ and Cu₃Sn as the middle, and nickel as the bottom layer and lies on surface of the copper alloy substrate. Contribution of each layer to heat resistance was investigated. Cross–sectional microstructure of the plating and surface of the nickel layer were examined by scanning electron microscopy. It was found that degradation of heat resistance in high temperature environment is caused by defects in the nickel layer located immediately below areas where thin IMCs layer was present. By increasing the coverage ratio of Cu₃Sn before heat treatment, the amount of thin areas of IMCs was decreased, and defects in the nickel layer was suppressed.

In addition to increasing the coverage ratio of Cu₃Sn, by thickening the tin and nickel layer a heat resistance of 175°C for 1000h was achieved.

The influence of material surface form on a fretting corrosion phenomenon of reflowed tin plating was investigated. This paper reports and discusses experimentally observed results on contact resistance behavior and wear behavior during fretting corrosion testing using samples with different surface roughness. The main results are summarized as follows. （a） The results of the fretting corrosion test showed the peak value of contact resistance decreased with the rough–surface samples. In addition, the amount of the deposited tin abrasion powder in the contact area was reduced in the rough–surface samples. （b） The rough–surface samples had both convex and concave areas. It is thought that the convex areas promote the discharge of tin abrasion powder to the outside of the contact area or to concave areas. （c） When the surface was flat, the deposited tin abrasion powder was found to be finely crushed. It is thought that oxidation of the abrasion powder was promoted by this condition of being finely crushed.

In this study, the flow pattern of condensate liquid film and condensation heat transfer characteristics of low GWP refrigerants outside a horizontal smooth tube and a three–dimensional microscopic–grooved tube were experimentally verified. As test refrigerants, R1233zd(E) and R1224yd(Z), which are considered as substitutes for R245fa, were used. The experiments were performed at refrigerant saturation temperatures of 40 and 30°C, and the cooling water flow rate and inlet temperature were varied stepwise. The following conclusions are obtained. (1) The condensate flooding angle of a microscopic–grooved tube can be generally predicted by Honda’s equation. (2) The three–dimensional microscopic–grooved tube has a larger amount of condensate liquid, and transition from the droplet mode to the coexistence droplet–column mode, column mode, at the same wall subcooling degree ΔT than the smooth tube. (3) The experimental values of R245fa, R1233zd(E) and R1224yd(Z) outside the smooth tube can be ± 10% predicted by Nusselt’s equation. (4) The heat transfer enhancement ratio of the microscopic–grooved tube was highest 4.9–6.2 times for R245fa, next 3.9–4.9 times for R1233zd(E), and 3.5–4.0 times for R1224yd(Z).

The temperature dependence on mechanical properties in a metal material relates to its crystal structure. In a bcc metal, the strength increases with lowering temperature though the ductility decreases drastically at a low temperature. While mechanical properties in an fcc metal hardly depend on temperature, and thus the fcc metal exhibits high elongation even at low temperatures. In this study, the microstructure and low temperature tensile properties in Cu–50mass％Fe alloy consisting of fcc （Cu） and bcc （Fe） dual phase structure were investigated. Cu and Fe layers were aligned along the rolling direction. The microstructure after annealing at 1023 K for 1.8 ks maintained a deformation structure, while it after annealing at 1123 K for 1.8 ks was the recrystallized ultra–fine grain. In both annealing temperature, Cu and Fe precipitated in Fe and Cu layers, respectively. The elongation in the specimen annealing at 1123 K for 1.8 ks was higher than that of the specimen annealing at 1023 K for 1.8 ks. The recovery of strain and ultra–fine grains should improve the elongation in the specimen annealing at 1123 K. The tensile strength at 77 K was higher than that at 293 K in both specimens annealing at 1023 K and 1123 K. Nevertheless, the elongation at 77 K was nearly equivalent to that at 293 K. Therefore, the fcc and bcc dual phase structure has a superior temperature dependence on mechanical properties： high strength in bcc structure and high elongation in fcc structure at low temperature. A dimple fracture surface appeared at 77 K, meaning that the ductile fracture occurs in both phases. Hence, the Fe phase has enough ductility even at 77 K. The superior low temperature tensile properties may be due to strengthening by the Fe phase and suppressing brittle fracture of the Fe phase by the ductile Cu phase.

The aim of present study is to investigate the deformation behavior of single crystal Oxygen Free Copper （OFC） micropillars under compressive loading. First, the inverse pole figure map of polycrystalline OFC sample is measured by Electron Back Scatter Diffraction （EBSD） device. Based on the result, four kinds of single crystal micropillars having different crystal orientations are fabricated by using Focused Ion Beam （FIB）. Second, the compression tests are performed for micropillars by using in–house micro compression machine. As a result, macroscopic stress–strain curves are measured for single crystal Cu micropillars. In addition, the microscopic deformation behavior such as the initiation and growth of slip in single crystal Cu micropillar is investigated from the SEM image after uniaxial compressive loading. Finally, the relationship between macroscopic deformation behavior and microscopic deformation behavior is discussed based on the present experimental results.

Tensile deformation behavior of high–strength nanostructured Cu–Si solid–solution alloys processed by high–pressure torsion （HPT） with 5 rotations was investigated at room and low temperatures. With increasing Si concentration, tensile strength of the nanostructured Cu–Si solid–solution alloys was significantly increased. The maximal tensile strengths were 980 MPa at room temperature, and 1350 MPa at 77 K in a Cu–2.04wt.％Si alloy. This significant strengthening was achieved by grain refinement and increased dislocation density through severe plastic deformation （SPD） with the effect of Si addition on the decreasing stacking fault energy of the Cu–Si alloy. With increasing Si concentration, strain–rate sensitivity of the nanostructured Cu–Si solid–solution alloys was decreased due to the increased dislocation density, resulting in accelerating plastic instability of tensile specimens, caused by the diminishing strain–rate hardening capacity after necking.

Ultra–precision cutting has its own problems that are not taken into the consideration in ordinary cutting. One of such problems is grain boundary step （GBS） formation. The GBS is a step forming along a grain boundary on ultra–precision finished surface of polycrystalline metals. The height of GBS can be higher than that of cutting marks, resulting in reducing the quality of the finished surface. Although grain boundary sliding is considered as the origin of GBS formation, the growth mechanism of GBSs is still not clear. In the studies of grain boundary sliding in creep phenomenon, the apparent activation energy was calculated from the temperature dependence of creep strain rate, and the mechanism of grain boundary sliding was proposed based on the calculated activation energy. The apparent activation energy will be effective measure to study the growth mechanism of GBSs. In this study, in order to calculate the apparent activation energy of GBS growth process, the change in the height of GBS at －30°C, 25°C, 60°C and 90°C was measured. The height of GBS saturated in shorter time at higher temperature. The height increasing with time was higher at higher temperature. The value of the apparent activation energy was about 20 kJ/mol, which was significantly smaller than the apparent activation energy of the grain boundary diffusion （104 kJ/mol）. Such difference in the apparent activation energy indicates that the growth of grain boundary steps on ultra–precision finished surface originates from mechanisms different from the grain boundary diffusion.

In the past, leaded brass has been used in various applications because its micro cutting is easy due to good machinability. However, leaded brass cannot be used under the EU RoHs Directive；thus unleaded brass is supposed to be used. The machinability of unleaded brass is poor compared with that of leaded brass. In order to improve machinability, cutting fluid is used. The cutting fluids contain oily additives, preservatives, rust inhibitors, and extreme–pressure agents in the base oil. The extreme–pressure agent achieves lubrication under high pressure. There are a few extreme–pressure agents；among them, chlorinated paraffins have the highest lubrication capability. However, the abolition of short–chain chlorinated paraffins has been decided in the COP8 （Eighth session of the Conference of the Parties）. Medium–chain chlorinated paraffins （MCCPs） generate short–chain chlorinated paraffins as byproducts thus their use also has some issues. Hence, the development of extreme–pressure agents that can achieve comparable machinability to that of chlorinated paraffins has been awaited. However, the efficiency of new extreme–pressure agents is difficult to investigate because the effect of chlorinated paraffins has not been clarified in the drilling of fine holes with a micro drill.

In this study, wet drilling of fine holes was carried out with a micro drill using cutting fluids. The cutting fluids contained two kinds of MCCP and a long–chain chlorinated paraffin （LCCP） as the extreme–pressure agent. We investigated the effect of these chlorinated paraffins on cutting behavior. The tool life of micro drills became longer with an increase the amount of added LCCP. When the added LCCP was 50 weight％, more than 500 fine holes could be drilled. It was also clarified that the cutting resistance was higher for MCCP than for LCCP；however, the tool life of the micro drill was longer for MCCP than for LCCP.

Review of End–of Life Vehicles Directive and Restriction of Hazardous Substances Directive was postponed to July 2021, and discussion is ongoing in each of the relevant industries as to whether further postponement is necessary. Assuming that C6932, a lead–free, Cu–Zn–Si copper alloy, will be used for small components in the automobile, electronic, and electric fields, we have examined machinability of the alloy when drilling small holes of 1.0 mm in diameter and 10 mm in depth. And, we have confirmed that 10000 holes can be continuously drilled with a carbide drill available in the market by adjusting drilling speed to 94 m/min, feed rate to 0.1 mm/rev, and drilling depth per stroke to 2.0 mm.

Thin rods are manufactured by a repeated process of annealing and drawing. We have studied the influence of annealing on drilling small holes of 1.0 mm in diameter and 10 mm in depth in C6932 materials to find out whether drilling such small holes in an annealed material was possible, the results of which are reported in this paper. It was able to drill 10000 small holes continuously both in a simply extruded material and an extruded and annealed material. Gamma phase is eliminated in the course of annealing, which causes stress concentration sources to reduce. If stress concentration sources are reduced, cutting chips become less brittle, and eventually, they become slightly larger. However, they do not turn into a kind of mass which may cause the thrust resistance to rise, i.e., the influence of annealing is not to the extent that dischargeability of cutting chips is seriously affected, and an addition of annealing process does not cause deterioration in machinability when drilling small holes.

We believe that application of C6932 can be well expanded to small components which include drilling small holes in their production process.

Lead–added free cutting brass has been widely used as a valve material for water supply, air conditioning equipment and small parts for watches, etc. because of its excellent machinability, it is called free–cutting brass. The concentration of lead in brass is regulated in several countries and regions because its lead may cause health problems in the human body. In consideration of this problem, raw material suppliers have developed several types of lead–free brass in recent years. However, since the machinability of lead–free brass is lower than that of free–cutting brass, cutting force is large and problems such as handling of long chips are pointed out. Therefore, improvement of machinability of lead–free brass is required. In previous study, it was found that the PCD tool has the remarkable effect in cutting force reduction, it is possible to process with the same cutting force as conventional leaded free–cutting brass with sintered carbide cutting tool. On the other hand, serious problem of long continuous chip generation by using PCD tool still remained. In this study, FEM analysis was applied to predict the suitable shape of chip–breaker on tool rake surface. Commercially available FEM software was adopted and the stress and strain relationship at high–temperature and high–strain rate was measured for cutting simulation. The Greeble test was used to measure stress–strain relationship at RT, 200°C and 350°C and deformation speed of 100mm/s and 0.1mm/s. We found that calculated temperature, principal cutting force, chip thickness and tool–chip contact were close to measured values. A step with 0.7mm width and 0.2mm depth formed on tool rake by laser processing as a chip breaker show the best chip–breaking effect in cutting experiment and this is also shown in cutting simulation.

It is known that an acidic solution containing bismuth （Ⅲ） ion turns yellow by thiourea. In this study a colorimetric method with thiourea was investigated as a rapid and simple detection method of bismuth in bronze castings. Bismuth in bronze castings was dissolved in a hydrogen peroxide and nitric acid solution at room temperature for a short time. It was confirmed that the solution dissolved bismuth turned yellow by adding thiourea.

Copper slag obtained as a by–product of copper smelting is generating in large quantities in various countries accompanied with copper production. Therefore, the development of new uses for copper smelter slag is required. Nevertheless there are few studies on application development focusing on the chemical composition of copper slag. For this reason, we are studying the possibility of using the copper smelter slag as a chemical reaction catalyst aiming to application development focusing on the chemical composition of copper slag. The Fenton reaction is a catalytic reaction catalyzed by iron （II） ions used in the oxidation process of organic compounds. In this reaction, a target organic substance is oxidatively decomposed by reactive oxygen species such as a hydroxyl radical generated catalytically from hydrogen peroxide. In this study, granulated copper slag was used as a catalyst for the Fenton reaction, and its reactivity was investigated. First, slag was added to aqueous hydrogen peroxide containing methylene blue, and the change in methylene blue concentration was observed, to confirm the activity for Fenton reaction of copper slag. As a result, methylene blue was decomposed and a remarkable decrease in the concentration was observed. This suggested that the reactive species was generated catalytically by the copper slag or the components eluted therefrom. Next, the time evolution of decomposition was examined. As a result, methylene blue concentration showed an exponential decay behavior in the presence of hydrogen peroxide and slag. The observed reaction rate was slower than the Fenton reaction catalyzed by iron （II） ion, and was close to the heterogeneous Fenton–like reaction catalyzed by iron compounds. On the other hand, analysis of the reaction residue revealed no elution of iron ions. These results revealed that the copper smelter slag can be used as a catalyst for decomposing organic dyes in the presence of hydrogen peroxide, and that the catalytic activity is based on the iron oxide component in the slag.

Refining of low-grade copper alloy by electrolysis in sulfamic acid media was investigated. Binary Cu-1 mass％X (X＝Ni, Pb, Sb, Bi, As, Se, Ag, Au) alloys and a low-grade copper alloy assaying 70 mass％ Cu containing Ni, Pb, Sb, Bi, As, Sn, Se, Ag, and Au were synthesized and served as anode material. Galvanostatic electrolysis at 300 A · m⁻² was carried out using pure copper anode and Cu-1 mass％X alloy anodes in 1.63 mol · L⁻¹ H₂SO₄-0.63 mol · L⁻¹ Cu(II) aq. at 40 °C and 1.03 mol · L⁻¹ HSO₃NH₂-0.63 mol · L⁻¹ Cu(II) aq. at 25 °C, where the solubility of the copper salts in their corresponding media was almost same. Pure copper was passivated in the sulfuric acid media likely due to the formation CuSO₄ · 5H₂O in 23 hours. Impurities such as Ni, Se, Ag, and Au promoted passivation. On the other hand, all anodes tested in the sulfamic acid media were not passivated in 24 hours. The refining of the low-grade copper alloy was examined in 0.51 m o l · L⁻¹ HSO₃NH₂-0.63 mol · L⁻¹ Cu(II) aq. at 25 °C by galvanostatic electrolysis at 200 A · m⁻². As a result, dense copper cathode of 99.99 mass％ purity was obtained. The current efficiency was approximately 98.5 ％. During electrolysis, the terminal voltage periodically increased to 2.0 V and then returned to its initial value. However, the anode was not completely passivated. The energy loss due to such an increase and decrease of the terminal voltage was evaluated to be approximately 13 ％. The mechanism of the fluctuation of the terminal voltage was considered.

In general, a flux is used to braze a copper alloy. Defects （mainly voids） are formed when spreading a molten brazing filler metal in the joint gaps owing to such factors as the brazing conditions, vaporized flux and its residue. Previous studies have confirmed that the gap shape and the gap size affect void formation. Furthermore, it was confirmed that the behavior of the flux （gas and residue, which are generated from the flux） affected the void formation. Therefore, in this study, we conducted the brazing experiment in which the amount of flux was varied in order to suppress the generation of gas and residue and reduce the void ratio.

Using C3604 as a base metal, two specimen shapes and three gap sizes were prepared. The specimen was heated in an electric furnace, X–rays were irradiated onto the side surface of the test piece during the temperature increase, and a video was taken. From the X–ray transmission images, it was found that the void ratio decreased as the flux decreased at the gap 500 µm and the gap 800 µm. Further, it was confirmed from the video that the gas generated from the flux decreased with the decrease in the flux, and that the void formation was suppressed. It was also found that the void ratio increased as the flux decreased at the gap 100 µm. From these results, between the gap 100 µm to 500 µm, it was considered that the void formation factor changes from the flux to the size of the gap.

Brass has excellent ductility and workability. Lead–free brass containing Bi and Si has been put into practical use to comply with environmental regulations such as water quality standards. For actual use, brass soldering with lead–free solder is required. Therefore, a method is needed to estimate the solderability of the solder on brass. In the previous report, the experiment was performed using parallel two–plate specimens. The voids in the soldering area are classified into four types： “（Ⅰ） voids that can be used as soldering areas”, “（II） spherical voids”, “（Ⅲ） non–spherical voids”, and “（Ⅳ） heat shrinkage voids”. It was found that the number of spherical voids decreased when the amount of solvent in the flux was reduced. It is known that voids form when the temperature rises. The purpose of this study was to investigate the effect of heating rate on soldering using in situ observations.

In–situ observations and soldering experiments were performed. The experiment was conducted using a parallel two–plate specimen. A hot plate was used as a heat source. In–situ observation experiments revealed that the state of the specimen changed when the heating rate changed. In the soldering experiment, X–ray transmission images were acquired and evaluated. However, detailed evaluation was not possible with the conventional evaluation method. Therefore, a new evaluation method called “solder spread linear velocity” was defined. When we evaluated using this evaluation method, we were able to evaluate this experiment. The heating rate has a large effect on solder wetting. It was found that the higher the heating rate, the higher the spread linear velocity of the solder and the larger the spread of the solder.

The effect of oxygen content on the surface defect generation in pure copper castings was investigated. The castings under lower oxygen content show the skin–formation type solidification, in which flow marks are sometimes generated. These are significantly affected by both the progress of solidification during mold filling and the stepwise elevation of the melt surface. On the other hand, the casting under higher oxygen content show the mushy type eutectic solidification, in which burning of silica sand （penetration into the sand molds） often occurs. These are not only because the melt under higher oxygen content shows better wettability with the silica sand but also because the melt contacts with the sand mold for a prolonged time due to the wider freezing range. These results suggest that the generation tendencies of the surface defects can be evaluated on the basis of the parameters reflecting the solidification behavior of the castings.

In the continuous casting process of copper and copper alloys, the heat extraction in the mold accounts for a large proportion of the heat extraction of the entire ingot. In order to perform appropriate heat extraction and obtain a stable quality ingot, it is important to understand the heat transfer coefficient between the ingot and the mold and to maintain the heat transfer rate appropriately. However, in the past report examples, as the heat transfer coefficient between the ingot and the mold, the average value of the entire mold or the value between the solid phase and mold are considered but few examples focus on the heat transfer coefficient between liquid phase and the mold. Also, in the field of mold casting, there are few examples in which the liquid–phase heat transfer coefficient is measured clearly distinguished from the solid–state heat transfer coefficient. In this report, the heat transfer coefficient between the liquid phase and the mold was clearly separated from the heat transfer coefficient of the solid phase, and the actual measurement was performed. As a result, it was found that the value was several times to an order of magnitude larger than the value conventionally reported in copper continuous casting. Using the obtained thermal conductivity values, a thermal fluid simulation of copper continuous casting was performed. As a result, there was no significant difference in the mold temperature or the final solidification depth of the ingot as compared with the case where the conventional values ​​were used. But there was a clear difference in the solidification start position.