Aluminum alloys and methods for producing the same
Heat treatable aluminum alloy strips and methods for making the same are disclosed. The heat treatable aluminum alloy strips are continuously cast and quenched, with optional rolling occurring before and/or after quenching. After quenching, the heat treatable aluminum alloy strip is neither annealed nor solution heat treated.
1. A method comprising:
(a) continuously casting, via a horizontal casting apparatus, a 7xxx heat treatable aluminum alloy strip;
(i) wherein the continuous casting comprises casting at a speed of 25-400 feet per minute and using roll separating forces of from 25 to 300 pounds per inch of width cast;
(ii) wherein the 7xxx heat treatable aluminum strip exits the casting apparatus at a temperature below its solidus temperature;
(iii) wherein the 7xxx heat treatable aluminum strip has a gauge of from 0.04 inch to 0.249 inch;
(b) after the continuously casting step, hot rolling and quenching the 7xxx heat treatable aluminum alloy strip;
(i) wherein the quenching occurs (a) during the hot rolling (b) after the hot rolling or (c) both during and after the hot rolling;
(c) after the hot rolling and quenching step, artificially aging the 7xxx heat treatable aluminum alloy strip;
wherein the method excludes both annealing of the 7xxx heat treatable aluminum alloy strip and solution heat treating of the 7xxx heat treatable aluminum alloy strip.
2. The method of claim 1 , comprising:
after the quenching step (b) and prior to the artificially aging step, cold rolling the 7xxx heat treatable aluminum alloy strip.
3. The method of claim 2 , wherein the continuously casting step (a) comprises:
(A) delivering a molten aluminum alloy to a pair of spaced apart rotating casting rolls defining a nip therebetween;
(B) advancing the molten aluminum alloy between surfaces of the casting rolls, wherein a freeze front of metal is formed at the nip; and
(C) withdrawing the 7xxx heat treatable aluminum alloy strip from the nip.
4. The method of claim 2 , wherein the continuously casting step (a) comprises:
(A) delivering a molten aluminum alloy to a pair of spaced apart rotating casting rolls defining a nip therebetween;
(B) advancing the molten aluminum alloy between surfaces of the casting rolls, wherein the advance comprises:
(I) first forming two solid outer regions adjacent surfaces of the casting rolls;
(II) second forming a semi-solid inner region containing dendrites of the molten aluminum alloy;
(III) wherein the inner region is located between the two outer concentration regions;
(IV) wherein the first forming and second forming steps are completed concomitant to one another;
(V) breaking the dendrites in the inner region at or before the nip; and
(C) solidifying the semi-solid inner region to produce the 7xxx heat treatable aluminum alloy strip comprised of the inner region and the outer regions.
5. The method of claim 4 , wherein breaking the dendrites in the inner region is completed at or before the nip, and wherein solidification of the inner region is completed at the nip.
6. The method of claim 4 , wherein the casting rolls are rotating at a casting speed ranging between 25 to 400 feet per minute.
7. The method of claim 4 , wherein a roll separating force applied by the casting rolls to the molten aluminum alloy passing though the nip is between 25 to 300 pounds per inch of width of the strip.
8. The method of claim 4 , wherein the casting rolls each have a textured surface, and wherein the method comprises brushing the textured surfaces of the casting rolls.
9. The method of claim 2 , wherein the method consists of steps (a), (b), and the artificial aging step (c).