Preheating manner null of dies for aluminum extrusion

摘要

PROBLEM TO BE SOLVED: To maintain the surface of a die steel for long term to sound of time by preheating a die in nitrogen atmosphere after a oxidation preventive is coated on a bearing face before extrusion. ;SOLUTION: When preheating a die prior to hot extrusion, a BN or Al paste as an oxidation preventive is coated on a bearing face. Successively, it is heated in a range of 400-500°C. Heating is executed in the atmosphere replaced from open air of nitrogen. By controlling a preheating atmosphere and preheating temp. in this way, oxidation of a nitride layer formed on a die surface is suppressed. Thus, deterioration, peeling, etc., due to oxidation are not caused to the nitride layer of bearing face and necessary wear resistance is maintained. Accordingly, the die life is prolonged and the shape quality of a shape obtained is improved.;COPYRIGHT: (C)1997,JPO