METHOD FOR PREHEATING DIE FOR EXTRUDING ALUMINUM AND EXTRUDING DIE

摘要

PROBLEM TO BE SOLVED: To efficiently manufacture an aluminum extruded shape having good surface properties by maintaining a nitrided layer in the sound state over a long period. ;SOLUTION: At the time of preheating an extruding die before hot extrusion, the extruding die is heated to 410-550°C in a non-oxidizing atmosphere where the concentration of residual oxygen is ≤500ppm. As the non-oxidizing atmosphere, a vacuum atmosphere, nitrogen atmosphere, or argon atmosphere is used. In this extruding die, a surface layer in which the X-ray intensity ratio of Fe₃O₄ to Fe₃N is ≤20% is formed on the surface of the die just before extrusion. Then, the oxidization and disappearance of a while layer is prevented, the service life of the die is prolonged and the extruded shape having good surface properties is manufactured over a long period.;COPYRIGHT: (C)1997,JPO