While during extrusion it is essential to create oxygen free atmosphere at least for initial 300mm of Extrusion as well as to prevent the die bearing from overheating. GALCO’s all state of art extrusion dies are compatible for Nitrogen surrounding resulting much better quality of extrusions supplied.
In the extrusion process, two properties of nitrogen are used,
- Nitrogen is inert to aluminium and
- Liquid nitrogen at -320oF, has excellent cooling properties. First, the hot section of the profile is surrounded by protective nitrogen gas. Also, the die and the extruded product are cooled by the nitrogen.
During extrusion the temperature of the die is further raised by friction and plastic deformation of the aluminium. By cooling the tool assembly, particularly the die with liquid nitrogen, extrusion rates can be increased without raising the section temperature above the permissible level. The increase in extrusion speed will largely depend on the alloy and profile being extruded.
Improved surface quality
In relation to aluminium, nitrogen is an inert gas at extrusion temperatures. The nitrogen is applied either in liquid or gaseous form-to-form an inert atmosphere surrounding the section as it emerges from the die. This decreases the formation of aluminium oxide, as the oxidation is most severe at this point where the profile is at it's hottest. In addition to this, the profile is cooled by the nitrogen, which further decreases the degree of oxidation.
Prolonged die life
Nitrogen cooling reduces wear on the die, which means that more profiles can be extruded before the die has to be repaired or replaced.