2013 年 54 巻 627 号 p. 363-367
The effects of the thermal conductivity of die materials on hot-forging characteristics were investigated on a servo press. Stellite (Co-28 mass% Cr, thermal conductivity: approximately 15 W·m-1·K-1) and tungsten carbide (WC-20 mass% Co, thermal conductivity: approximately 70 W·m-1·K-1) were used as die materials with low and high thermal conductivities, respectively. In upsetting of a chrome steel at 1273 K, the stellite die reduced forging load by approximately 20% at a forging speed of 5 mm·s-1 because the die with a low thermal conductivity was effective in keeping the specimen at a high temperature during upsetting. Furthermore, the stellite die was effective to fill the specimen into a die cavity part (inlet diameter: φ3 mm, depth: 32 mm) in hot upsetting.