Impact extrusion molded article, and impact extrusion molding method, and an impact extrusion molding apparatus

1. An impact extrusion molding method characterized by extruding a protrusion to be formed on the bottom of a semifinished product, which is being molded halfway alone molding process, in an equal direction to the progress direction of a punch when a cylindrical product is impact extrusion molded using a punch and a dice, and which protrusion is being molded while suppressing the metal-flow from the bottom of a slug set in the dice toward the side of the molded product article,

wherein a convex portion, for forming an annular groove in the inner surface of the bottom of the molded product article, is provided on the top end of said punch, and

wherein, when a protrusion extruded into the hole in the bottom of the said dice is cut around a portion of the annular groove formed in the inner surface of the bottom of the molded product article, a cut region is discharged from within the dice.

2. The impact extrusion molding method according to claim 1 , wherein a hole going through the bottom of the dice is opened, when a pressing force of said punch reaches a predetermined value or more, and/or said punch is lowered to a predetermined position by pressurizing, by the punch, a slug set in said dice while closing the hole.

3. An impact extrusion molding apparatus comprising

a punch;

a dice, having a hole going through the bottom of the dice;

an opening and closing means, for opening and closing the hole by raising and lowering said hole; and

a rod on the upper end of which the opening and closing means is provided,

wherein said opening and closing means is controlled for back pressure in the direction opposite to said punch that is applied to the opening and closing means, to close said hole, at least when a slug set in said dice starts to be pressurized by the punch, and so that said back pressure is relieved from the opening and closing means, when a pressing force of said punch reaches a predetermined value or more, and/or said punch is lowered to a predetermined position, and wherein the rod is adapted to slide a distance that gives minimum volume suppressing metal-flow from a bottom of slug set in a dice toward a side of a molded product article, and

wherein a convex portion, for forming an annular groove in the inner surface of the bottom of the molded product article, is provided on the top end of said punch, and

said impact extrusion molding apparatus comprising a mechanism to discharge a cut region from within the dice, when a protrusion extruded into the hole in the bottom of the said dice is cut around a portion of the annular groove provided in the inner surface of the bottom of the molded product article.

4. The impact extrusion molding apparatus according to claim 3 , wherein said opening and closing means is attached to the top end of the rod raised and lowered in the hole in the bottom of said dice, and said back pressure is applied and relieved on and from the opening and closing means through said rod.