A cold repeated forming process of compacts for producing metal form was developed to strongly bond powder particles. In this process, the compact undergoes severe deformation for the strong bonding of particles by repeated backward extrusion and cup compression, and thus the compact largely foams owing to the accumulation of foaming gas inside the compact during heating. The cold repeated forming process without heating is much simpler than that for the conventional hot extrusion. The relative density of the foam was decreased by adding silicon powder to the compact, and an aluminum foam having a relative density of 0.27 was obtained using 2 repeats of backward extrusion and cup compression, 1.5 mass% titanium hydride powder and 4 mass% titanium silicon powder. In addition, one-piece foam was successively produced from the bonding of two compacts during the foaming in a die. It was found that the cold repeated forming of compacts is effective for the production of metal foam.

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In recent years, forming processes of ultrafine and precise products have been playing a key role in the enhancement of the performance and functions of machines and equipment. In particular, ultrathin wire is expected to be used as a material with versatile functions. Wire drawing using hole dies has conventionally been used in the manufacture of thin and ultrathin wires. In thin conventional drawing, dozens of dies with specified hole diameter corresponding to each target diameter of wires are needed. Moreover, in the recent trend of miniaturizing dimensions, the die itself would be difficult to manufacture. In this research, a new wire-drawing method without a die is proposed. The proposed method has a similar machine composition to two roll straighter, i.e. wire is deformed between two skewed rolls. A series of finite element analysis was carried out to examine the suitable roll profile and the effect of crash and tension on the reduction in wire diameter. On the basis of the analysis, a prototype machine was designed and used to verify the efficiency of the new method. Results showed that an 11% reduction in diameter was achieved under optimum condition.

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Diamond-like-carbon-containing silicon coating (DLC-Si), which has a high adhesion strength, was evaluated by the ball penetration test under typical lubricated conditions for cold forging. Although DLC-Si did not prevent friction increase under no lubricated condition, DLC-Si showed lower frictional property than conventional TiN and VC when inactive oils containing only oiliness agent and a small quantity of oil were applied. The combination of DLC-Si and oils containing active additives exhibited excellent tribological properties such as antigalling and low friction. Moreover, the only-sodium stearate coating showed the same performance as the normal sodium/zinc stearate and phosphate (normal soap and phosphate) coating when the normal soap and phosphate, zinc stearate and phosphate, and only-sodium stearate coatings were tested with the DLC-Si coated ball. We found that DLC-Si with a high adhesion strength for a die material has great potential to reduce the amount of lubricant oil used and emission generated by conventional phosphate treatment.

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