| 摘要 |
PURPOSE:To widen manufacturable limit of shape in forging a crude section of valve having an umbrella part and a shaft part, by giving taper to the end of the shaft before free extrusion of the shaft, and making it a guide for insertion into a die in the process of free extrusion. CONSTITUTION:In the process of cold-warm forging of a crude section 4 of an engine valve having an umbrella part and a shaft part, a billet 1 is forcibly extruded to form an intermediate formed product 2, and a tapered part 6 is formed at the end of the shaft to make an intermediate formed product 2a. The intermediate formed product 2a is inserted into a die and formed to an intermediate formed product 3 by free extrusion. At this time, the tapered part 6 is used as a guide for insertion into the die. Thus, insertion into the die in free extrusion of the crude sectiin of the valve becomes easy, and manufacturable limit of shape is widened. |
