SEE US ON
Aluminum Extrusion Dies
In current industrial practice, aluminum extrusion plants commonly use nitriding to surface-harden dies. Apart from the initial treatment, nitriding is used to recondition the working surfaces of dies after a number of extrusion runs, when the nitrided case has suffered damage through wear and prolonged heating. Depending on the profile thickness and complexity, this re-nitriding operation may be repeated many times.
1: A most serious factor causing deterioration of the nitrided surface is prolonged preheating in air. If the time of preheating is limited to approximately 4 hours, or at least not more than 5 hours, this initial deterioration is not significant.
2: A better method of limiting the destructive effect of air oxygen would be to preheat dies in a protective gas atmosphere, for example in nitrogen. Protective atmospheres prolong the allowable pre-heating time and protect the nitrided surface against oxidation. (See Die Preheat Ovens)