Manufacturing process for obtaining high strength extruded products made from 6xxx aluminium alloys

A manufacturing process for obtaining extruded products made from a 6xxx aluminium alloy, wherein said manufacturing process comprises:

• a) homogenizing a billet cast from said aluminium alloy and then cooling the billet down to room temperature;
• b) heating the homogenized cast billet;
• c) extruding said billet through a die to form at least a solid or hollow extruded product;
• d) quenching the extruded product down to room temperature;
• f) ageing the extruded product without applying on the extruded product any separate post-extrusion solution heat treatment;
• wherein said 6xxx aluminium alloy comprises Si:
• 0.3-1.7 wt. %;
• Mg:
• 0.1-1.4 wt. %;
• Mn:
• 0.55-1.4%, and at least one dispersoid element comprising Cr (0.05-0.4 wt. %) or Zr (0.05-0.25 wt %), the rest being aluminium and inevitable impurities;
• and
• wherein:
• i) the heating b) is a solution heat treatment where:
• b1) the cast billet is heated to a temperature between Ts-15° C. and Ts, wherein Ts is the solidus temperature of said aluminium alloy and is at least 575° C.;
• b2) the billet is cooled until billet mean temperature reaches a value between 400° C. and 480° C. while ensuring billet surface never goes below 400° C.;
• ii) the billet thus cooled is immediately extruded in c after the end of b2,
• wherein the extruded product has an ultimate tensile strength higher than 380 MPa.