Manufacturing method for molds and hollow shaft members

Abstract

The objective is to provide a method for manufacturing a mold and a hollow shaft member that allows for high workpiece processing speed. [Solution] The molding die 5 is for hot forging or warm forging and comprises a first die 5A having a molding hole 51 into which a workpiece 1a is inserted, and a pin 52 disposed inside the molding hole 51, and a second die 5B that is accessible to the first die 5A. The molding hole 51 has a constricted portion 510 on its inner circumferential surface that narrows in diameter from the rear to the front, with the front side in the direction of insertion of the workpiece 1a into the molding hole 51 being the front side and the opposite side of the front side being the rear side. The rear end 5212, which is the tip of the pin 52, is positioned so as to be included in the range from the front end position 5101 to the rear end position 5100 of the constricted portion 510.

Claims

1. A first mold having a molding hole into which a workpiece is inserted, and a pin disposed inside the molding hole, A second type that can approach the first type, A mold for hot forging or warm forging, comprising: With respect to the molding hole, the side in the direction of insertion of the workpiece is considered the front side, and the side opposite the front side is considered the rear side. The molding hole has a constricted portion on its inner circumferential surface that decreases in diameter from the rear to the front. The molding die is characterized in that the rear end, which is the tip of the pin, is positioned so as to be included in the range from the front end position to the rear end position of the constricted portion.

2. The workpiece after molding is a hollow shaft member comprising a shaft portion, a flange portion projecting radially outward from the shaft portion, and a hollow portion opening at least at the front end of the shaft portion, which is the front and rear ends. The molding die according to claim 1, wherein the second type has a cylindrical punch that is inserted into the molding hole from the rear.

3. The state of the workpiece before hole processing, which is inserted into the molding hole, is considered the standby state. The molding die according to claim 1, wherein in the standby state, the workpiece is positioned in a position that does not contact the rear end of the pin but contacts the constricted portion.

4. The molding die according to claim 3, wherein in the standby state, the workpiece is positioned by the rear end of the constricted portion.

5. The angle of inclination of the outer surface of the pin with respect to the front-to-back direction is defined as the draft angle. The molding die according to claim 1, wherein the pin has a gently sloping portion on its outer circumferential surface and a steeply sloping portion located behind the gently sloping portion and having a greater draft angle than the gently sloping portion.

6. The molding die according to claim 1, further comprising a cooling unit that supplies cooling air to the molding hole.

7. The first mold comprises a mold body having the molding hole and the pin, and a knockout member that presses the workpiece from the front, The knockout member has a head and a leg portion that protrudes forward from the head, The aforementioned pin has a base portion positioned on the front side of the head and fixed to the mold body, and a pin body protruding rearward from the base portion. The head has a head-side insertion portion through which the pin body is inserted so as to be movable in the front-rear direction, The mold according to claim 1, wherein the base portion has a base-side insertion portion through which the leg portion is inserted so as to be movable in the front-rear direction relative to the base portion.

8. A method for manufacturing a hollow shaft member, comprising repeating a hole forming step of drilling holes in a workpiece using the mold described in claim 1, using a plurality of pins with different lengths in the front-to-back direction on the same workpiece, thereby gradually creating a hollow hole in the workpiece, extending the hollow hole in the front-to-back direction, and manufacturing a hollow shaft member from the workpiece.

9. The method for manufacturing a hollow shaft member according to claim 8, wherein the amount of elongation in the front-rear direction of the hollow portion in at least one of the multiple hole-forming steps is 60 mm or less.

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