Patent EA-002898-B1 (EA)
Title: Process of treating an aluminium alloy containing magnesium and silicon
Inventor: TUNDAL ULF
IPC: C22C21/06
Filed: 1999-02-12
Abstract: 1. Process of treating an aluminium alloy consisting of 0.5 - 2.5 % by weight of an alloying mixture of magnesium and silicon, the molar ration of Mg/Si lying between 0.70 and 1.25, an additional amount of Si equal to 1/3 of the amount of Fe, Mn and Cr in the alloy, as expressed by % by weight, - other alloying elements and unavoidable impurities, and - the rest being made up of aluminium, which alloy after cooling has been submitted to homogenising, preheating before extrusion and ageing, which ageing takes place after extrusion as a dual step ageing operation to a final hold temperature between 160 degree C and 220 degree C,characterized in that the ageing includes a first stage in which the extrusion is heated with a heating rate above 100 degree C/hour to a temperature between 100-170 degree C, a second stage in which the extrusion is heated with a heating rate between and 50 degree C/hour to the final hold temperature, and in that the total ageing cycle is performed in a time between 3 and 24 hours. 2. A process according to Claim 1, characterized in that the alloy contains between 0.60 and 1.10 % by weight of the alloying mixture of magnesium and silicon and that it has a tensile strength in the class F19 - F22. 3. A process according to Claim 1, characterized in that the alloy contains between 0.80 and 1.40 % by weight of the alloying mixture of magnesium and silicon and that it has a tensile strength in the class F25 - F27. 4. A process according to Claim 1, characterized in that the alloy contains between 1.10 and 1.80 % by weight of the alloying mixture of magnesium and silicon and that it has a tensile strength in the class F29 - F31. 5. A process according to Claim 2, characterized in that the alloy contains between 0.60 and 0.80 % by weight of the alloying mixture of magnesium and silicon and that it has a tensile strength in the class F19 (185 - 220 MPa). 6. A process according to Claim 2, characterized in that the alloy contains between 0.70 and 0.90 % by weight of the alloying mixture of magnesium and silicon and that it has a tensile strength in the class F22 (215 - 250 MPa). 7. A process according to Claim 3, characterized in that the alloy contains between 0.85 and 1.15 % by weight of the alloying mixture of magnesium and silicon and that it has a tensile strength in the class F25 (245 - 270 MPa). 8. A process according to Claim 3, characterized in that the alloy contains between 0.95 and 1.25 % by weight of the alloying mixture of magnesium and silicon and that it has a tensile strength in the class F27 (265 - 290 MPa). 9. A process according to Claim 4, characterized in that the alloy contains between 1.10 and 1.40 % by weight of the alloying mixture of magnesium and silicon and that it has a tensile strength in the class F29 (285-310 MPa). 10. A process according to Claim 4, characterized in that the alloy contains between 1.20 and 1.55 % by weight of the alloying mixture of magnesium and silicon and that it has a tensile strength in the class F31 (305 - 330 MPa). 11. A process according to any one of the preceeding Claims, characterized in that the final ageing temperature is at least 165 degree C. 12. A process according to any one of the preceeding Claims, characterized in that the final ageing temperature is at most 205 degree C. 13. A process according to any one of the preceeding Claims, characterized in that in the second heating stage the heating rate is at least 7 degree C/hour. 14. A process according to any one of the preceeding Claims, characterized in that at the end of the first heating step the temperature is between 130 and 160 degree C. 15. A process according to any one of the preceeding Claims, characterized in that the total ageing time is at least 5 hours. 16. A process according to any one of the preceeding Claims, characterized in that during the preheating before extrusion the alloy has been heated to a temperature between 510 and 550 degree C, after which the alloy has been cooled to normal extrusion temperatures.