DE2511831C2 - Use of an aluminum alloy - Google Patents

Description

The invention relates to the use of an aluminum alloy for the production of lithographic Printing plates, such as an offset printing plate.

The offset printing process is a widely used printing process in which a printing plate is treated in such a way that parts of the printing plate accept water and other parts of the printing plate accept one Are oil-based paint. The printing process consists of first putting water on the plate and then the color. After the water and paint have been applied, the aluminum plate will come into contact

JS with a rubber roller, some of the paint from the aluminum plate being transferred to the rubber roller. The rubber roller is then brought into contact with a sheet of paper. The picture on the Paper is created, corresponds directly to the original on the aluminum plate. The aluminum plate is usually prepared by a photographic process. In a variant of this process, a Layer of a photosensitive polymer applied to the surface of the printing plate or film, which over a light and shadow pattern corresponding to the image to be printed is exposed. Then removed a developer the photosensitive polymer layer that was not exposed. Due to the effects of surface tension, the paint adheres to areas where the photosensitive layer remains, while the water adheres Areas adheres where the original surface of the aluminum sheet or foil is exposed. From one Such a printing plate can produce a large number of copies, sometimes more than one Million. Well, the resulting printed image depends on the surface properties of the aluminum plate or foil It is very important that the original surface of the sheet of film be smooth, even and free from defects. γ, Aluminum surrounds are widely used in the manufacture of offset printing plates. Difficulties jf occurred in cases where the printing plates were used in extraordinarily long production runs. This $

Such difficulties include cracking or tearing and excessive wear of the panels. This difficult- |?

Celts based on low fatigue strength and excessive wear are related to the inability to j $ j

the alloy together to harden further in operation. Usually the standardized American | ' ^:

Alumlnlumleglerungen of the type 3000 and 1100 used, which in the hard condition a fatigue strength sfi

of about 68.5 N / mm ² at 500,000,000 load changes. i

It is a process for the production of high strength aluminum linings with a content of less than. · $

10% Mg, less than 1% Cu, 0.05 to 1% Fe, 0.5 to 3% Sl and other alloy components known ''

(US-PS 34 90 955), followed by a cold deformation annealing at temperatures between 120 J.

and 350 ° C and then cold working is carried out again. ;

However, the above-mentioned difficulties can be increased by using aluminum.

W) Strength cannot be eliminated because the usual commercial processes do not result in a semi-finished product of the required width. Flatness and surface quality can be produced using an alloy that has a tensile strength above 241 N / mm ² .

The invention is based on the object of specifying an aluminum alloy for lithographic printing plates with which the above-mentioned difficulties can be overcome. To solve this problem is

<i5 according to the invention an aluminum alloy with 0.2 to 0.9% magnesium, 0.35 to 0.7% copper, 0.1 to 0.7% Elsen, up to 0.3% silicon, the remainder aluminum, is used. The one used according to the invention is expedient Alloy produced as specified in claim 7 or 8. An aluminum alloy suitable for the purpose of the invention has a moderate in the re-annealed state

Tensile strength of about 171.5 N / mm ² . The tensile strength is comparable to that of the commonly used aluminum alloys, while the fatigue strength or fatigue strength of 88 to 103 N / mm ² and thus 30 to 50% higher than the fatigue strength of other conventional aluminum alloys used for printing plates. This increase in fatigue strength represents the decisive advantage of the new alloy with regard to its use as a material for lithographic printing plates.

The aluminum alloy to be used according to the invention can be produced in the usual way and for surface-treated for graphic purposes, e.g. B. be granular.

When the aluminum alloy is used in the back-annealed state, the foregoing strengths can be obtained, and the aluminum alloy maintains sufficient solidification so that the Wear and tear is reduced during operation.

The invention is explained in more detail below with reference to exemplary embodiments.

A further range and a restricted preferred range for the composition of the aluminum alloy according to the invention are given in Table I.

Table I.

Component in% Component in% -0.6 (wide area) (preferred area) -0.6 magnesium 0.2 - 0.4 -0.65 copper 0.35- 0.5 -0.2 iron 0.1 - 0.4 - 0.05 silicon until - 0 -0.05 manganese 0 - 0 - 0.015 zinc 0 - 0 -0.05 titanium 0 - 0.0075 - 0.015 chrome 0 - 0 boron 0 - 0.005 -0.9 -0.7 -0.7 -0.3 -0.05 -0.05 -0.03 -0.05 -0.02

The essential components of the aluminum alloy are magnesium, copper, Elsen and silicon. The other constituents indicated in Table I can be added up to the maximum in Table I specified concentrate tones can be used without harmful effects. Titanium can be considered more useful Addition for grain refinement should be added. Of course, all of those can be considered not essential specified elements may be present as traces in the order of magnitude of 0.001%.

The alloy components of the aluminum alloy are chosen so that the resulting alloy in its final state has a minimum of alloy constituents that are not in solid solution.

Table II gives the approximate solid solubility of the alloy components at a temperature of about 275 ° C. This temperature was chosen because it is used for the final annealing in the context of the Use according to the invention is representative. Table U also shows the approximate percentages of Alloy components specified that are not in solution under unfavorable conditions, which is the case, if the alloy components are present in their maximum amounts. The Sum of Not In Solution contained alloy components is less than 0.9% according to the table.

The composition of the alloy is preferably chosen so that the maximum amount of alloying elements which are not in solution is less than 0.9% and preferably less than 0.7%. Diesel amount will of course even smaller if the preferred amounts of alloy components according to the right column In Table I are present in the alloy.

Tables

element

Solubility in aluminum at about 275 ° C

max percentage

maximum percentage except Solution at about 275 ° C

Mg 8.0 Cu 2.0 Fe 0.02 Si 0.15 Mn 0.05 Zn 45.0 Ti 0.01 Cr 0.01 B. 0.005

0.75 - 0.7 - 0.7 0.68 0.3 0.15 0.05 - 0.05 - 0.03 0.02 0.05 0.04 0.015 0.01

Examples

A series of aluminum coatings with a constant iron content (0.45%) and different Magnesium, copper and silicon contents were cast for test purposes. The composition of the ingots or blocks are given along with other details such as the initial homogenization given in Table III. The ingots were warmed from 38 mm thick to a final 5 mm thick at a Rolled down temperature of 440 ° C. The bars were for 5 minutes after each reduction in thickness 2.5 mm warmed up again. The bars were then rolled down from 5 mm to 2.5 mm with a reduction in thickness of about 10% per pass. The cold rolled billets were then kept at 330 ° C for 3 hours annealed. Some ingots were heated and cooled again at a controlled rate of 14 ° C / hr before and after annealing to simulate larger size commercial practice. The bars that controlled crwfirmt and cooled are separately identified in Table HI.

The soft-annealed bars were then reduced in thickness by 10% per roll pass to 1.52 or 1.1 mm rolled down. The cold rolled billets were then annealed at 330 ° C for 3 hours. With this glow all bars were cooled and heated at a controlled rate of 14 ° C / h. The annealed bars were then turned around one Thickness decrease of 10% per roll pass rolled to a thickness of 0.76 mm. This represents a decrease in thickness of 50% for the 1.52 mm thick bars and a thickness decrease of 30% for the 1.1 mm thick bars. Finally, the alloys were re-annealed as indicated in Table III.

The alloys treated as indicated above were examined for mechanical properties, yield strength, tensile strength and elongation. The results are given in Table III. The alloys were also tested for their fatigue strength. The fatigue strengths given in Table III represent the stress in N / mm ² which the respective alloy withstood at 10 ⁷ load changes.

CU 0.45 Fe serial no. Homogenization N / mm ² and failure after controlled % Cold deformation Back glow Yield point . - • st % Strain O -r- - .... U, K) and O Warming up and during finish rolling (N / mm ² ) Table III 0.48 other Cooling down at to 0.75 mm tensile strenght Fatigue 0.48 0.25 Si Intermediate annealing (N / mm ² ) strength OO 0.46 0.25 Si (N / mm ² ) OJ Analyzed alloys 0.46 0.11 Si 11A H 510 ° C / 12-16h NO 50 220 ° C / lh 172.5 6.0 after 10 load (Content in%) 0.56 0.11 Si 11B H510 ° C / 12-16h NO 30th 135 ° C / lh 176.5 3.0 switch 0.38 0.11 Si 12A H510 ° C / 12-16h NO 50 135 ° C / lh 180.5 202.0 4.0 99.0 MG 0.54 0.09 Si 12B H510 ° C / 12-16h NO 30th NO 168.5 198.0 2.0 89.2 0.54 0.10 Si 18th H 565-590 ° C / 12hC NO 50 145 ° C / I ¹ Ah 194.0 196.0 4.7 90.2 0.86 0.54 0.10 Si 20th H 565-590 ° C / 12hC NO 50 205 ° C / I ¹ Ah 167.0 170.5 5.5 89.2 0.86 0.06 0.10 Si 22nd NO NO 50 145 ° C / 1 ¹ Ah 181.5 219.5 4.2 97.0 0.35 0.15 0.2 Si 26A H 565-590 ° C / 12hC YES 50 NO 181.5 196.0 2.0 96.0 0.35 1.2 Mn 26B H 565-590 ° C / 12hC YES 50 145 ° C / 3h 173.5 210.5 5.5 103.0 0.76 16% plated 0.2 Si 5050-H36 *) H 565-590 ° C / 12hC YES 50 145 ° C / 3h 160.0 183.2 4.0 95.0 0.63 alloy 205.5 108.0 0.69 3003-H16 H 590-620 ° C / 8hC NO 50 NO 172.5 179.5 3.5 75.4 ') 0.45 unplated alloy 5050-H36 NOT KNOWN YES 147.0 5.9 0.45 (0.29 mm) 192.3 80.3 1.2 H- 28 ° C / h heating 1100-H16 NOT KNOWN NO 143.0 170.5 4.2 77.5 - C - 2 ( (0.29 mm) *) IO% plated with 1145 alloy 148.0 62.7 i ° C / h cooling ' ¹ J at 75.8 4 ■ 10 ⁶ load changes at 82.7 N / mm ² Ui 3 κ »ro
Vl O

Table IV shows the compositions of the Al alloys cited under the US designation.

Table IV

Si

Fe

Cu

Mn

Cr

Zn

1100 max. 1.0 Si + Fe 0.05-0.20 max. 0.05

1145 max.0.55 Si + Fe max.0.05 max.0.05

3003 max. 0.6 max. 0.7 0.05-0.20 1.0-1.5

5050 max. 0.4 max. 0.7 max. 0.20 max. 0.10

max.0.10

max. 0.10 1.1-1.8 max. 0.1 max. 0.25

The alloys to be used according to the invention have average fatigue strengths of the order of 98.1 N / mm ² , while common alloys for the production of graphic plates, which are also given in Table IH, fatigue strengths of the order of 68.7 N / mm ² to have. The improvement in fatigue strength is achieved without any noticeable change in the other mechanical properties. The yield strength and the tensile strength of the alloys to be used according to the invention are slightly higher than in the case of the usual alloys, while the elongation of the alloys to be used according to the invention is somewhat lower than in the case of the usual alloys examined. The proof stress can be controlled by controlling the back glow. The data in Table III illustrate the importance of the last back anneal for achieving improved fatigue strength. For example, the alloy under serial number 26 has a fatigue strength of 95.3 N / mm ² in the non-annealed condition and a fatigue strength of 108 N / mm ² after annealing, which corresponds to an improvement of 13.4%. The back anneal also improved the elongation, which is a measure of the remaining solidification, between 2.0 and 5.5%. The yield strength was not noticeably influenced by the stabilization, while the tensile strength was only slightly increased (19.6 to 34.3 N / mm ² ). It can thus be seen that back annealing plays an important role in producing alloys with high fatigue strength. The conditions for the back-annealing were chosen so that a yield strength of about 172 N / mm ^{2 was} achieved. An alloy having such a yield strength can be made using standard commercial processes.

The sample pieces of the alloys listed under the serial numbers 12 A, 12 B, 26 A and 26 B. have also been tested for their usefulness for graphic plates by using lithographic printing plates made from these alloys. The study of the results obtained with such plates Printed images showed that the alloys were excellently suited for the production of printing plates. The printed images were extremely sharp and none could be seen by the surface condition of the Defects caused by the alloy can be detected.

The aluminum alloy to be used according to the invention, which according to the claims 7 and 8 Said Process is Treated 1st, Has Superior Fatigue Resistance, and Is Excellent for Manufacture of long run lithographic printing plates, d. H. a large number of prints, suitable. With printing plates For extremely large print serrations, the common practice is to have a plating of electroplated copper on the To bring the surface of the pressure plate to create a wear-resistant surface. According to the invention Alloy to be used can easily be clad with copper, and the obtained copper clad Surface is free from defects. The thickness of the copper plate is generally between 0.0125 and O,! 25 mm. The plating can be applied in the usual way.

Claims (8)

Patent claims: 1. Use of an aluminum alloy made from 0.2 to 0.996 magnesium, 0.35 to 0.7% copper, 0.1 to 0.7 » Elsen, up to 0.3% silicon and aluminum as the remainder for the production of lithographic printing plates. 2. Use of an aluminum alloy according to claim 1, which additionally contains up to 0.05% manganese, up to 0.05% Contains zinc, up to 0.03% titanium, up to 0.05% chromium and up to 0.02% boron, for the purpose of claim 1. 3. Use of an aluminum alloy according to claim 2, which is between 0.0075 and 0.0150% titanium and containing between 0.005 and 0.015% boron for the purpose of claim 1. 4. Use of an aluminum alloy according to any one of claims 1 to 3 containing 0.4 to 0.6% magnesium contains, for the purpose of claim 1. 5. Use of an aluminum alloy according to any one of claims 1 to 4 containing 0.5 to 0.6% copper contains, for the purpose of claim 1. 6. Use of an aluminum alloy according to one of claims 1 to 5, the 0.4 to 0.65% Elsen contains, for the purpose of claim 1. ■ 5 7. Use of an aluminum alloy according to one of claims 1 to 6, which is back-annealed after the final cold rolling, so that at most 0.7% of the alloy components are not in solid solution for the purpose of claim 1. 8. Use of an aluminum alloy according to claim 7, which by the method steps casting. Homogenization of the cast blanks at temperatures between 480 and 620 ° C below the target temperature door of the alloy over a period of between 2 and 24 hours, hot rolling at a temperature between 400 and 480 ⁰ C, cold rolling and soft annealing to final dimensions with intermediate annealing at 315 to 400 ° C for a period of 1 minute to 6 hours, final cold rolling with a reduction in thickness of at least 20% and back-annealing at temperatures between 120 and 260 ° C for a period of 1 minute to 4 hours, for the purpose of claim 1.