Patent ID: 8312750
Filing Date: 2012-11-20
Classification: B21H

Abstract:
1. Method for the production of a rotationally symmetrical hollow metal part, comprising the steps of: providing a bar-shaped ductile solid material; heating the solid material to a temperature sufficient to enable forging of the solid material; transversally spline-rolling the solid material until weakenings are created in core zone of the solid material and the solid material is torn open; introducing two mandrels into the center of the bar-shaped solid material during the rolling process, one of the mandrels being inserted from each of opposite ends of the bar-shaped ductile solid material to a point before contacting of the mandrels would occur, in a manner hardening a peripheral mantle layer of the solid material and embrittling an inner core of the solid material while each of the the mandrels produces a bore-hole in an axially extending portion of the bar-shaped ductile solid material; and retracting a first one of the mandrels while a second one of the mandrels continues advancing to a point overlapping a portion of a zone worked by the retracted first mandrel so as to produce a tubular part with a bore hole extending completely therethrough.