Key Points of Heat Treatment for Aluminum Profile Extrusion Dies

1. The quality of heat treatment of aluminum extrusion dies directly affects the service life of the extrusion die. The dies undergo quenching and multiple tempering processes to achieve the required hardness. Quenching is to increase the hardness of the die, and multiple temperings are to improve the toughness of the die and stabilize the internal structure. The hardness requirements for die heat treatment are as follows: large aluminum extrusion dies (F > 500mm), HRC 45-48; medium dies (F 300~500mm), HRC 47-50; small extrusion dies (F < 300mm), HRC 48-51. For a set of dies, three points are tested on the same plane, and the hardness at each point must be within the specified range to be considered qualified.

2. Special attention should be paid to several points during the heat treatment of extrusion molds:

a. The heating rate in the high-temperature section should be fast, and the holding time should not be too long to prevent the extrusion die from overheating or overburning. Overheating leads to coarse grains, and overburning causes low-melting-point elements and inclusions to dissolve;

b. Aluminum extrusion dies should be tempered promptly after quenching to prevent cracking;

c. If the hardness of the extrusion die is found to be insufficient or uneven after heat treatment, it should be annealed and re-heat-treated according to the process (if the hardness value is <HRC35, annealing can be skipped and heat treatment can be done directly);

d. For large aluminum extrusion dies or finished dies with complex cavities, an additional stress-relief tempering process should be carried out (to eliminate the stresses from EDM and machining, that is, to remove thermal stress and structural stress);

e. The quenching oil temperature for the die should be ≥100°C to ensure the quenching effect.