Abstract: The present invention relates to a method of forming a cam shaft by assembling a preliminary shaft having a predetermined outer diameter and a cam lobe including a cam-lobe shaft hole having a diameter larger than the outer diameter of the preliminary shaft.

Abstract: The present invention is a fusion-bonded product having a high-strength part, comprising: a first preform (2a) constituted by integrally, frictionally pressure-welding a first low-carbon steel part (L1) made of low-carbon steel containing less than 0.45% of C and a high-carbon steel part (H) made of high-carbon steel containing not less than 0.45% of C; and a second preform (2b) having a second low-carbon steel part (L2) made of second low-carbon steel containing less than 0.45% of C; wherein the high-carbon steel part (H) of the first preform (2a) is provided with a high-strength part (9) that has been previously formed into a desired shape and quenched, the second low-carbon steel part (L2) of the second preform (2b) has been previously formed into a predetermined shape, and the first low-carbon steel part (L1) of the first preform (2a) and the second low-carbon steel part (L2) of the second preform (2b) are bonded to each other by fusion welding.

Abstract: In a differential gear, a differential case includes: a first differential case on a side ranging from a pinion-shaft installation part on which a pinion shaft is installed, to a ring gear; and a second differential case on a side opposite to the side ranging from a pinion-shaft installation part on which the pinion shaft is installed, to the ring gear. The first differential case is integrally molded from only a low-carbon steel containing less than 0.45% of C, by forging or by forging and cutting. The second differential case is integrally molded from only a low-carbon steel containing less than 0.45% of C, by forging or by forging and cutting. The first differential case and the second differential case are bonded to each other by welding.

Abstract: A forming method of a tooth trace of a gear according to the present invention includes: a first step of preparing a preformed gear made of metal including a cylindrical main body and a tooth part having a flat tooth flank having a uniform thickness in a tooth trace direction inside of the main body; and a second step of conducting a surface treatment locally to an outside surface of the main body in order to deform the outside surface of the main body in such a manner that the same becomes concave, so that a crowning bulging in the tooth trace direction is formed on the tooth flank of the tooth part.

Abstract: The present invention relates to a method of forming a cam shaft by assembling a preliminary shaft (10) having a predetermined outer diameter and a cam lobe (20) including a cam-lobe shaft hole (21) having a diameter larger than the outer diameter of the preliminary shaft (10).

Abstract: In a differential gear, a differential case includes: a first differential case on a side ranging from a pinion-shaft installation part on which a pinion shaft is installed, to a ring gear; and a second differential case on a side opposite to the side ranging from a pinion-shaft installation part on which the pinion shaft is installed, to the ring gear. The first differential case is integrally molded from only a low-carbon steel containing less than 0.45% of C, by forging or by forging and cutting. The second differential case is integrally molded from only a low-carbon steel containing less than 0.45% of C, by forging or by forging and cutting. The first differential case and the second differential case are bonded to each other by welding.

Abstract: The present invention is a fusion-bonded product having a high-strength part, comprising: a first preform (2a) constituted by integrally, frictionally pressure-welding a first low-carbon steel part (L1) made of low-carbon steel containing less than 0.45% of C and a high-carbon steel part (H) made of high-carbon steel containing not less than 0.45% of C; and a second preform (2b) having a second low-carbon steel part (L2) made of second low-carbon steel containing less than 0.45% of C; wherein the high-carbon steel part (H) of the first preform (2a) is provided with a high-strength part (9) that has been previously formed into a desired shape and quenched, the second low-carbon steel part (L2) of the second preform (2b) has been previously formed into a predetermined shape, and the first low-carbon steel part (L1) of the first preform (2a) and the second low-carbon steel part (L2) of the second preform (2b) are bonded to each other by fusion welding.

Abstract: A forming method of a tooth trace of a gear according to the present invention includes: a first step of preparing a preformed gear made of metal including a cylindrical main body and a tooth part having a flat tooth flank having a uniform thickness in a tooth trace direction inside of the main body; and a second step of conducting a surface treatment locally to an outside surface of the main body in order to deform the outside surface of the main body in such a manner that the same becomes concave, so that a crowning bulging in the tooth trace direction is formed on the tooth flank of the tooth part.