To secure the shape precision of a finally manufactured engine valve while keeping an axial straightness of a first intermediate body formed from a bar-shaped work.
The method for manufacturing the engine valve comprises; a first process (a blank cut-off) for forming a fixed size of the bar-shaped work 6 by cutting off the bar-shaped work 6; a second process (upsetting) for forming the primary intermediate body 7 having dumpling-state expanding diameter part 7a by upsetting the one end part of the bar-shaped work 6 while heating it; a third process (forging) for forming the secondary intermediate body 8 having the original shape near the engine valve by forging the primary intermediate body 7; and a forth process (annealing, strain-removing, before-processing, surface treatment and pre-processing). Especially, in the forge-compacting processing in the secondary process, the bar-shaped work 6 is pressed in the axial direction toward the metallic mold with a pressing element while holding with a holding body through a prescribed gap.
COPYRIGHT: (C)2007,JPO&INPIT
Next Patent: APPARATUS AND METHOD OF LOW PRESSURE CASTING