| 摘要 |
PURPOSE:To shorten process time and improve mechanical characteristics by heating up a material to temperature possible to make hot forging and making hot upsetting, and then making complete annealing after performing upsetting of the head and forward extrusion of the shaft at the same time. CONSTITUTION:A material 1 cut to the specific size is heated up to about 1,200 deg.C, and hot upsetting is made to the mass 2. This mass is made to the mushroom shape 3 by performing hot upsetting of the head 31 and forward extrusion of the shaft 32 at the same time, and complete annealing is made. By cooling the formed product slowly, toughness is given, and a scale or the like is removed from the surface by shot blast. At the next process, lubrication film forming treatment is made, and the head 31 is formed to a cup shape by cold backward extrusion. Then, low temperature annealing is made to remove internal stress generated by cold working, and surface treatment is made again. Further, ironing is made to the outer circumference of cup shape head 31 to increase accuracy. At the last, hardening is made. |
