| 摘要 |
PURPOSE:To prevent generation of defects such as wrinkle and insufficient shank by constituting a lower die in such a way that said die can be energized upward and can be thereby moved vertically in the stage of forging a blank material for forging consisting of a shank and a head by means of upper and lower dies. CONSTITUTION:The shank 3 of the blank material 2 for forging is inserted into the hole 18 of the lower die 3 and is perpendicularly imposed on the lower die 7. The lower die 7 is lifted upward by a spring 20, by which a clearance is provided between the bottom end of the shank 3 and the top end of an ejector pin 8. The head 4 of the material 2 is supported in the circular conical recess 17 of the lower die 7 in tight contact therewith. The upper die 9 is lowered to press the material 2, thereby executing the extrusion forging until the top end of the pin 8 controls the shank 3. The die 7 descends by compressing the spring 20 during this time and the extrusion forging of the shank 3 is completed when the die 7 descends down to the mid-way. The upsetting forging of the head 4 is started as the upper die 9 descends further. The upsetting forging of the head 4 is completed when the die 7 attains the lowermost limit position and when the die 9 descends down to the lowermost position.
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