A method for manufacturing a forged component includes: performing hot forging on a material; heating the hot forged material to a first set temperature; and performing warm coining to correctly shape the heated material. The material may be heated to a second set temperature before hot forging. The material heated to the second set temperature may be hot forged. The second set temperature may be higher than the first set temperature. The hot forged material may be subjected to controlled cooling to a third set temperature at a predetermined cooling rate. The controlled cooled material may be heated to the first set temperature. The third set temperature may be lower than or equal to the first set temperature.

A method of manufacturing a crankshaft having weight-reducing forged holes can achieve lightening and precise forming by additionally including a punching process of using an individual hydraulic press. The method includes steps of: heating a steel bar, performing busting such that the heated steel bar is disposed in a cavity of a mold to be produced as a first intermediate shape of a crankshaft, performing brokering such that the first intermediate shape is produced as a second intermediate shape, performing finishing such that the second intermediate shape is produced as a third intermediate shape, performing trimming such that the third intermediate shape is produced as a complete shape of the crankshaft by cutting portions other than the shape of the crankshaft, and performing punching such that holes are formed in the complete shape of the crankshaft.

A method of manufacturing a crankshaft having weight-reducing forged holes can achieve lightening and precise forming by additionally including a punching process of using an individual hydraulic press. The method includes steps of: heating a steel bar, performing busting such that the heated steel bar is disposed in a cavity of a mold to be produced as a first intermediate shape of a crankshaft, performing brokering such that the first intermediate shape is produced as a second intermediate shape, performing finishing such that the second intermediate shape is produced as a third intermediate shape, performing trimming such that the third intermediate shape is produced as a complete shape of the crankshaft by cutting portions other than the shape of the crankshaft, and performing punching such that holes are formed in the complete shape of the crankshaft.

Provided is a production method, including a first preforming process for obtaining a first preform from a billet, a second preforming process for obtaining a final preform from the first preform, and a finish forging process for forming the final preform into a finishing dimension of a forged crankshaft. In the first preforming process, a plurality of flat parts are formed by pressing pin-corresponding parts and journal-corresponding parts in a direction perpendicular to an axial direction of the billet. The second preforming process includes: a process of pressing regions to be a plurality of journals with a width direction of the flat part as a pressing direction by using a pair of first dies; and a process of, after starting pressing by the first dies, decentering regions to be a plurality of pins with the width direction of the flat part as a decentering direction by using second dies.

Provided is a production method, including a first preforming process for obtaining a first preform from a billet, a second preforming process for obtaining a final preform from the first preform, and a finish forging process for forming the final preform into a finishing dimension of a forged crankshaft. In the first preforming process, a plurality of flat parts are formed by pressing pin-corresponding parts and journal-corresponding parts in a direction perpendicular to an axial direction of the billet. The second preforming process includes: a process of pressing regions to be a plurality of journals with a width direction of the flat part as a pressing direction by using a pair of first dies; and a process of, after starting pressing by the first dies, decentering regions to be a plurality of pins with the width direction of the flat part as a decentering direction by using second dies.

A forging process is conducted in a temperature range of 350-600° C. on at least a portion that is required to have a fatigue strength in an intermediate forged product having a ferrite and pearlite texture obtained by conducting a hot forging on a steel in which N is not greater than an amount at which N is unavoidably dissolved as a solid, thereby improving strength of the portion that is required to have a fatigue strength. With this, there is provided a forged product having a good strength and a low price.

A forging process is conducted in a temperature range of 350-600° C. on at least a portion that is required to have a fatigue strength in an intermediate forged product having a ferrite and pearlite texture obtained by conducting a hot forging on a steel in which N is not greater than an amount at which N is unavoidably dissolved as a solid, thereby improving strength of the portion that is required to have a fatigue strength. With this, there is provided a forged product having a good strength and a low price.

A forged crankshaft (1) includes a carbon steel containing S, wherein in a portion corresponding to a machined outer circumferential surface of a shaft part such as journals (J), crank pins (P), a front part (Fr), and a flange (Fl), a ratio x/y of an area rate x of sulfide in a position (X) corresponding to a parting surface of a die for finish forging to an area rate y of sulfide in a position (Y) corresponding to a bottom of a die impression of the die for finish forging is equal to or lower than 1.5. The forged crankshaft (1) can avoid an occurrence of machined surface cracks on the journals (J) and the crank pins (P) after the outer circumferential surface is machined.

A forged crankshaft (1) includes a carbon steel containing S, wherein in a portion corresponding to a machined outer circumferential surface of a shaft part such as journals (J), crank pins (P), a front part (Fr), and a flange (Fl), a ratio x/y of an area rate x of sulfide in a position (X) corresponding to a parting surface of a die for finish forging to an area rate y of sulfide in a position (Y) corresponding to a bottom of a die impression of the die for finish forging is equal to or lower than 1.5. The forged crankshaft (1) can avoid an occurrence of machined surface cracks on the journals (J) and the crank pins (P) after the outer circumferential surface is machined.

The invention relates to a device for the impact treatment of transition radii (8) of a crankshaft (4), in particular transition radii (8) between connecting rod bearing journals (5) and crank webs (7) and/or transition radii (8) between main bearing journals (6) and the crank webs (7) of the crankshaft (4). The device comprises an impact device (1) in order to introduce an impact force (FS) into at least one transition radius (8), wherein the impact device (1) has multiple impact heads (21) which are paired with the same transition radius (8).