Abstract: The objective of the present invention is to provide a forging method that improves workability in machining, by turning the metallographical structure of products subject to impact load to a fine ferrite-perlite structure, without adopting the method of quenching and tempering, to obtain, as strength, a yield point (YP value) exceeding that obtained by the method of quenching and tempering, and making the tensile strength (TS) smaller compared with the method of quenching and tempering. A material to be forged has at least one kind of group 5 metal added thereto and is heated to a temperature suitable for hot forging. After forging to prescribed shape, cooling, and holding for a prescribed set time in a furnace at a tempering temperature, the material is further cooled to normal temperature by natural cooling.

Abstract: For the purpose of providing a speed-changing gear manufacturing apparatus capable of forming back-tapered spline teeth having a chamfer at the tip with high accuracy, by forming both side faces of spline teeth in back-tapered shape and forming the tip in chamfered shape at a time, the present invention is a speed-changing gear manufacturing apparatus comprising dies formed at regular intervals on a circumference, to enable to move a plural number of spline teeth forming units for forming back-tapered spline teeth on lines extending radially from the center axis of the gear material, and a pressing member for moving the spline teeth forming units toward the center axis of the gear material, by pressing the outer circumferential face of the spline teeth forming units of the dies, wherein said spline teeth forming units are constructed in a way to form an open space in which to form both side faces of spline teeth in back-tapered shape and form the tip in chamfered shape at a time, in contact with the adjacent

Abstract: The objective of the present invention is to provide a forging method realized in a way to improve workability in machining, by turning the metallographical structure of products subject to impact load to a fine ferrite-perlite structure, without adopting the method of quenching and tempering, to obtain, as strength, a yield point (YP value) exceeding that obtained by the method of quenching and tempering, and making the tensile strength (TS) smaller compared with the method of quenching and tempering.

Abstract: For the purpose of providing a speed-changing gear manufacturing apparatus capable of forming back-tapered spline teeth having a chamfer at the tip with high accuracy, by forming both side faces of spline teeth in back-tapered shape and forming the tip in chamfered shape at a time, the present invention is a speed-changing gear manufacturing apparatus comprising dies formed at regular intervals on a circumference, to enable to move a plural number of spline teeth forming units for forming back-tapered spline teeth on lines extending radially from the center axis of the gear material, and a pressing member for moving the spline teeth forming units toward the center axis of the gear material, by pressing the outer circumferential face of the spline teeth forming units of the dies, wherein said spline teeth forming units are constructed in a way to form an open space in which to form both side faces of spline teeth in back-tapered shape and form the tip in chamfered shape at a time, in contact with the adjacent