Method of manufacturing a 2xxx-series aluminium alloy plate product having improved fatigue failure resistance
A method of manufacturing an AA2xxx-series aluminium alloy plate product having improved fatigue failure resistance and a reduced number of flaws, the method comprising the following steps (a) casting an ingot of an aluminium alloy of the 2xxx-series, the aluminium alloy comprising (in wt. %): Cu 1.9 to 7.0, Mg 0.3 to 1.8, Mn up to 1.2, balance aluminium and impurities, each 0.05 max, total 0.15; (b) homogenizing and/or preheating the cast ingot; (c) hot rolling the ingot into a plate product by rolling the ingot with multiple rolling passes characterized in that, when at an intermediate thickness of the plate between 100 and 200 mm, at least one high reduction hot rolling pass is carried out with a thickness reduction of at least 15%; wherein the plate product has a final thickness of less than 60 mm. The invention is also related to an aluminium alloy product produced by this method.
1. A method of manufacturing an AA2xxx-series aluminium alloy plate product, the method comprising the following steps:
(a) casting an ingot of an aluminium alloy of the AA2xxx-series;
(b) homogenizing and/or preheating the cast ingot;
(c) hot rolling the ingot into a plate product by rolling the ingot with multiple rolling passes, wherein when the plate product has reached an intermediate thickness of between 100 and 200 mm, at least one high reduction hot rolling pass is carried out with a thickness reduction of at least 15%, wherein each hot rolling pass before and after the high reduction hot rolling pass has a thickness reduction between 1% and 12%;
and wherein the plate product has a final thickness of less than 60 mm.
2. The method according to claim 1 , wherein the method further comprises the steps of:
(d) optionally pre-stretching or applying a skin pass by cold rolling of the plate product after the hot rolling;
(e) solution heat treating the plate product;
(f) cooling, of the solution heat treated plate product;
(g) optionally stretching the solution heat treated plate product; and
(h) natural ageing or artificially aging the solution heat treated and cooled plate product.
3. The method according to claim 1 , wherein the high reduction hot rolling pass is carried out with a reduction of at least 20%.
4. The method according to claim 1 , wherein a deformation rate during the high reduction pass is <0.77 s −1 .
5. The method according to claim 1 , wherein the intermediate thickness of the plate before the high reduction pass is carried out between 120 and 180 mm.
6. The method according to claim 1 , wherein the 2xxx aluminium alloy has a composition comprising, in wt. %:
Cu
1.9 to 7.0,
Mg
0.3 to 1.8,
Mn
up to 1.2,
balance aluminium and impurities.
7. The method according to claim 1 , wherein the 2xxx aluminium alloy has a composition comprising, in wt. %:
Cu
1.9 to 7.0,
Mg
0.3 to 1.8,
Mn
up to 1.2,
Fe
up to 0.40,
Si
up to 0.40,
Ti
up to 0.15,
Zr
up to 0.25,
Zn
up to 1.0,
Li
up to 2.0,
Ni
up to 2.5,
Ag
up to 0.80,
V
up to 0.25,
Cr
up to 0.35,
balance aluminium and impurities.
8. The method according to claim 1 , wherein the 2xxx aluminium alloy has a Cu-content of 3.0% to 6.8%.
9. The method according to claim 1 , wherein the 2xxx aluminium alloy has a Mg-content of 0.35% to 1.6%.
10. The method according to claim 1 , wherein the 2xxx aluminium alloy has a Mn-content of 0.2% to 1.2%.
11. The method according to claim 1 , wherein the Ti-content is within a range of 0.01% to 0.10 wt. %.
12. The method according to claim 1 , wherein the aluminium alloy has a composition in accordance with AA2024.
13. The method according to claim 1 , wherein the final thickness of the plate is less than 50 mm.
14. The method according to claim 1 , wherein the final thickness of the plate product is more than 10 mm.
15. The method according to claim 1 , wherein in the method step (c) the hot rolling mill exit temperature is more than 385° C.
16. The method according to claim 1 , wherein the plate product is naturally aged to a T3 temper.