Patent ID: 6349583
Filing Date: 2002-02-26
Classification: B21D,Y10T

Abstract:
A method of forming a hollow workpiece having open ends by inner pressure in a multi-part forming tool, the method comprising the steps of:heating a forming tool having a forming mold; placing the workpiece of aluminum or an aluminum alloy into the forming mold of the forming tool; inserting closing plugs into the open ends of the workpiece to seal off the open ends, wherein the closing plugs are components of closing cylinders, and closing the forming tool; introducing nitrogen as a heated pressure fluid into the hollow workpiece through at least one of the closing plugs which has been heated via the forming tool, the hollow workpiece having been heated and plasticized; pressing at a temperature of between 250Â° C. and 350Â° C. and at an inner pressure of between 180 bar and 250 bar the material of the hollow workpiece with the heated nitrogen into the forming mold of the forming tool; and adjusting the inner pressure by a control valve, provided in a supply line for the nitrogen, as a function of a heating temperature of the workpiece and the heating temperature of the forming tool.