Forging method forged product and forging apparatus

A forging method using a swaging apparatus equipped with a fixing die for fixing a bar-shaped raw material, a guide having an insertion passage for inserting and holding the raw material in a buckling preventing state, and a punch for pressing the raw material inserted in and held by the insertion passage of the guide in an axial direction of the raw material,

• wherein a scheduled enlarged diameter portion of the raw material fixed to the fixing die with the scheduled enlarged diameter portion protruded is inserted into the insertion passage of the guide, and
• thereafter, while pressing the raw material with the punch by moving the punch, in a state in which a part of a peripheral surface of an exposed portion of the raw material exposed between the guide and the fixing die is restrained or an entire peripheral surface of the exposed portion of the raw material is not restrained, the scheduled enlarged diameter portion of the raw material is subjected to swaging processing by moving the guide in a direction opposite to a moving direction of the punch,
• where
• “P” is an average moving speed of the punch from an initiation of a movement thereof;
• “G” is an average moving speed of the guide from an initiation of the movement thereof;
• “X0” is a buckling limit length at the cross-sectional area of the raw material before the swaging processing;
• “X1” is a buckling limit length at the cross-sectional area of the enlarged diameter portion of the raw material after the swaging processing;
• “X” is an initial clearance between the guide and the fixing die (O≦X≦X0);
• “t0” is a time lag from the initiation of the movement of the punch to the initiation of the movement of the guide (0≦t0);
• “L” is a length of the enlarged diameter portion of the raw material after the swaging processing;
• “l0” is a length of the raw material in the state prior to the swaging processing required for the enlarged diameter portion;
• and
• “T” is a swaging processing time from the initiation of the movement of the punch, if t0<T,
• “G” satisfies the following relational expression:
• (LX)/[(l0−L)/P−t0]≦G≦P(X1X)/(l0−X1−Pt0).

A forging apparatus, comprising a swaging apparatus,

• wherein the swaging apparatus includes:
• a fixing die for fixing a bar-shaped raw material;
• a guide having an insertion passage for inserting and holding the raw material in a buckling preventing state;
• a punch for pressing the raw material inserted in and held by the insertion passage of the guide in an axial direction of the raw material;
• and
• a guide driving device for moving the guide in a direction opposite to a moving direction of the punch so that a length of the exposed portion of the raw material exposed between the guide and the fixing die becomes a buckling limit length or less at a cross-sectional area of the exposed portion of the raw material.