Upsetting method and upsetting apparatus

An upsetting method using an upsetting apparatus provided with a fixed die for securing a bar-shaped raw material, a guide having an insertion hole for receiving and holding a diameter expansion scheduled portion of the raw material in a buckling preventing state, and a punch, wherein a diameter expansion preventing protruded portion protruded in an axial direction of the guide is integrally formed at a part of a tip end portion of the guide,

• the method comprises:
• inserting and holding the diameter expansion scheduled portion of the raw material secured to the fixed die in the insertion hole of the guide;
• and
• subsequently expanding the diameter expansion scheduled portion of the raw material exposed between the tip end portion of the guide and the fixed die in a state in which diameter expansion of a contacting portion of the diameter expansion scheduled portion in contact with the diameter expansion preventing protruded portion is restrained by moving the guide in a direction opposite to a moving direction of the punch while moving the punch and pressurizing the diameter expansion scheduled portion of the raw material with the punch in an axial direction thereof,
• wherein the fixed die is provided with a molding dented portion and a slide groove portion to be slidably inserted by the diameter expansion preventing protruded portion of the guide in an axial direction of the fixed die, the slide groove portion being formed on a peripheral surface of the molding dented portion extended in the axial direction of the fixed die,
• wherein a side surface of the protruded portion of the guide with which a part of a peripheral surface of the diameter expansion scheduled portion of the raw material comes into contact is formed into a surface corresponding to a peripheral surface of a diameter expanded portion of the raw material,
• wherein the diameter expansion scheduled portion of the raw material secured to the fixed die is placed in the molding dented portion, the diameter expansion scheduled portion of the raw material is inserted and held in the insertion hole of the guide, and the protruded portion of the guide is inserted in the slide groove portion, and
• wherein the diameter expansion scheduled portion of the raw material is subsequently expanded in the molding dented portion.

An upsetting method using an upsetting apparatus provided with a fixed die for securing a bar-shaped raw material, a guide having an insertion hole for receiving and holding a diameter expansion scheduled portion of the raw material in a buckling preventing state, and a punch, wherein a diameter expansion preventing protruded portion protruded in an axial direction of the guide is integrally formed at a part of a tip end portion of the guide,

• the method comprises:
• inserting and holding the diameter expansion scheduled portion of the raw material secured to the fixed die in the insertion hole of the guide;
• and
• subsequently expanding the diameter expansion scheduled portion of the raw material exposed between the tip end portion of the guide and the fixed die in a state in which diameter expansion of a contacting portion of the diameter expansion scheduled portion in contact with the diameter expansion preventing protruded portion is restrained by moving the guide in a direction opposite to a moving direction of the punch while moving the punch and pressurizing the diameter expansion scheduled portion of the raw material with the punch in an axial direction thereof, wherein the diameter expansion scheduled portion of the raw material is expanded in diameter in a state in which a portion of the diameter expansion scheduled portion of the raw material corresponding to the tip end portion of the guide is partially heated, wherein the diameter expansion scheduled portion of the raw material is expanded in diameter in a state in which a portion of the diameter expansion scheduled portion of the raw material corresponding to a portion of the guide nearer the basal end side of the guide than the tip end portion of the guide by cooling means.