Aluminum strip for lithographic printing plate supports
An aluminum strip for lithographic printing plate supports, from which printing plate supports can be produced with an improved roughenability and at the same time improved mechanical properties, particularly after a burn-in process, is formed of an aluminum alloy which has the following proportions of alloy constituents in wt. %: 0.05%≦Mg≦0.3%, 0.008%≦Mn≦0.3%, 0.4%≦Fe≦1%, 0.05%≦Si≦0.5%, Cu≦0.04%, Ti≦0.04%, inevitable impurities individually max. 0.01%, in total max. 0.05% and remainder Al.
1. Aluminum strip for lithographic printing plate supports, consisting of an aluminum alloy,
wherein the aluminum alloy has the following proportions of alloy constituents in wt. %:
0.05
%
≤
Mg
≤
0.3
%
,
0.05375
%
≤
Mn
≤
0.3
%
,
0.43
%
≤
Fe
≤
1
%
,
0.05
%
≤
Si
≤
0.5
%
,
Cu
≤
0.04
%
,
0
%
<
Ti
≤
0.04
%
,
inevitable impurities individually max. 0.01%, in total max. 0.05% and remainder Al, and
wherein at room temperature the aluminium strip has a yield point Rp0.2 at least 180 Mpa and a tensile strength Rm of at least 190 Mpa in the rolling direction and/or room temperature a yield point Rp0.2 of at least 190 Mpa and a tensile strength Rm of at least 200 Mpa transversely to the rolling direction.
2. Aluminum strip according to claim 1 , wherein the aluminum alloy has a Ti content in wt. % of at most 0.01%.
3. Aluminum strip according to claim 1 , wherein the aluminum strip after a heat treatment at 240° C. for 10 min. has a yield point Rp0.2 of at least 140 MPa and a tensile strength of at least 150 MPa transversely to or in the rolling direction.
4. Aluminum strip according to claim 1 , wherein the bending cycle endurance of the aluminum strip in the rolling direction is more than 3000 bending cycles, in the rolling direction over a radius of 30 mm.
5. Aluminum strip according to claim 1 , wherein the bending cycle endurance of the aluminum strip after a heat treatment at 240° C. for 10 min. in the rolling direction is more than 3300 bending cycles, in the rolling direction.
6. Aluminum strip according to claim 1 , wherein the aluminum strip has a surface comprising fine globulitic grains with more than 250 grains per mm2.
7. The aluminium strip according to claim 1 , wherein the ration of the proportions of the alloy constituents Fe/Mn is from 3 to 8.
8. The aluminium strip according to claim 1 , wherein aluminium alloy has an Mn content in wt. % of 0.05375%≦Mn≦0.1%.
9. The aluminium strip according to claim 1 , wherein the ratio of the proportions of the ally constituents Fe/Si is at least 2.
10. The aluminium strip according to claim 1 , wherein the sum of Mg and Mn contents is more than 0.3 wt. % and less than 0.6 wt. %.
11. A lithographic printing plate support comprising an aluminum strip consisting of an aluminum alloy wherein,
the aluminum alloy has the following proportions of alloy constituents in wt. %:
0.05
%
≤
Mg
≤
0.3
%
,
0.05375
%
≤
Mn
≤
0.3
%
,
0.43
%
≤
Fe
≤
1
%
,
0.05
%
≤
Si
≤
0.5
%
,
Cu
≤
0.04
%
,
0
%
<
Ti
≤
0.04
%
,
inevitable impurities individually max. 0.01%, in total max. 0.05% and remainder Al;
hot-rolling the ingot to form a hot strip; and
cold-rolling the hot strip to a final thickness with or without intermediate anneals, and
wherein at room temperature the aluminium strip has a yield point Rp0.2 at least 180 Mpa and a tensile strength Rm of at least 190 Mpa in the rolling direction and/or room temperature a yield point Rp0.2 of at least 190 Mpa and a tensile strength Rm of at least 200 Mpa transversely to the rolling direction.
12. Method for producing an aluminum strip for lithographic printing plate supports,
comprising casting an ingot of an aluminum alloy having the following alloy constituents in wt. %:
0.05
%
≤
Mg
≤
0.3
%
,
0.05375
%
≤
Mn
≤
0.3
%
,
0.43
%
≤
Fe
≤
1
%
,
0.05
%
≤
Si
≤
0.5
%
,
Cu
≤
0.04
%
,
0
%
<
Ti
≤
0.04
%
,
inevitable impurities individually max. 0.01%, in total max. 0.05% and remainder Al;
hot-rolling the ingot to form a hot strip; and
cold-rolling the hot strip to a final thickness with or without intermediate anneals, and
wherein at room temperature the aluminium strip has a yield point Rp0.2 at least 180 Mpa and a tensile strength Rm of at least 190 Mpa in the rolling direction and/or room temperature a yield point Rp0.2 of at least 190 Mpa and a tensile strength Rm of at least 200 Mpa transversely to the rolling direction.
13. Method according to claim 12 , wherein at least one intermediate anneal is carried out during the cold rolling and the rolling factor to final thickness is between 65% and 85% after the intermediate anneal.
14. Method according to claim 12 , wherein the final thickness of the aluminum strip is from 0.15 mm to 0.5 mm.
15. Method according to claim 12 further comprising casting the ingot continuously or in batches.
16. Method according to claim 12 further comprising preheating or homogenising the ingot before hot-rolling.