Welding of copper alloy and steel, such as stainless steel, involves a combination of high thermal conductivity and high mechanical strength, so it is expected to be used for heat exchangers or pipe arrangement. However, welding of copper alloy and steel is difficult, because copper and steel have different thermal properties, such as thermal conductivities and melting point. In addition, copper and iron, which hare the main constituents of steel, do not form an alloy. Here, laser butt welding of brass plate and stainless steel plate 1.5 mm in thickness was examined using a disk YAG laser. The bondable welding conditions were selected, and the structures of welded copper and stainless steel were evaluated by tension test, watertight test, EPMA, and X-ray diffraction. The results indicated good bond strength and water tightness when laser irradiation position was put in the brass side from 0.1 mm to 0.2 mm.

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Soft magnetic powder cores are used for electromagnetic conversion coils, which are essential for automotive, home appliance, and electronics industries. These cores, manufactured by compacting pure iron powder covered with an insulation film, are distinguished by their high electromagnetic conversion efficiency. However, the electromagnetic conversion efficiency decreases markedly when they are subjected to the conventional finishing process. This is directly attributable to the conductive layers formed on the finished surface that significantly reduce the electrical resistance of the core surface. To solve this problem, we have developed an electrolytic re-insulation grinding method that finishes the core while an electric current is applied to the interface between the core and the grinding wheel. This method regenerates the insulation properties of soft magnetic powder cores through electrolytic removal of the conductive layers formed during the finishing process to improve electrical resistance. This process enables the manufacture of soft magnetic powder cores without compromising their electromagnetic conversion efficiency.

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This report describes an abrasive-free polishing method utilizing nano-bubble water and vacuum high-energy ultraviolet light irradiation as a technique for obtaining ultra-smooth rolled oxygen-free copper. Nano-bubble water was generated by injecting hydrogen and oxygen gas into pure water or electrolyzed water. This nano-bubble water was utilized as the polishing fluid for abrasive-free polishing. Final polishing experiments for removal of nanometer-sized projections under different polishing fluid conditions of pH and oxidation-reduction potential were carried out. The results indicated that the removal rate of projections was increased by vacuum ultraviolet light irradiation, and high pH and high oxidation-reduction potential polishing fluid was suitable for final polishing. In addition, dissolved hydrogen and dissolved oxygen in the polishing fluid were decomposed by vacuum ultraviolet light irradiation, which led to etch-pit generation as surface defects. Therefore, nitrogen nano-bubble water was generated by injecting nitrogen gas into electrolyzed reduced water to decrease the amounts of dissolved hydrogen and dissolved oxygen. High performance final polishing was achieved by utilizing this nitrogen nano-bubble water as the polishing fluid.

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Microstructures and micropatterns with unique functions are applied to electric sensor devices and medical devices. To fabricate μm order micropatterns, this report describes the drawing characteristics of a drawing system with an air-pulse-type dispenser and the profile accuracy of micropatterns using a high-viscosity UV resin of about 10000 cP. For fabrication of dot patterns, the gap between the nozzle and the workpiece was shown to markedly affect the drawing accuracy. In addition, pins were fabricated with top flatness of less than 1 μm using this drawing system and grinding machining. For fabrication of line patterns, the relationships between drawing accuracy and drawing conditions, drawing speed, gap, and air-pulse pressure were clarified. Under optimized drawing conditions, the edge unevenness and the height accuracy of the line pattern became 2 μm and ±2 μm, respectively.

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