DE1284095B - Process for producing aluminum alloy sheets with high creep rupture strength - Google Patents

Description

Aluminum alloy sheets, which should be used for the outer skins moderate diffusion of copper and magnesium into those of supersonic aircraft, avoid a cladding layer, which prevents their high static tensile strength from being reduced by the cladding layer after thousands of hours of operation with the high corrosion protection .
Temperatures to which such outer skins have 5 It has now surprisingly been found that are exposed. Furthermore, such sheets must have a high creep and creep strength through a suitable choice of the decrease in thickness. The individual cold rolling passes and the duration and the sheets can be used unplated or at the temperature of the solution annealing sheet made of aluminum one or both surfaces a cladding layer of alloys still to be described pure aluminum, an Al-Zn alloy with 0.8 to io setting with about coaxially aligned grain 1.2 ° / ₀ zinc or a warmaushärtbaren, corrosion can be produced which is small enough to be resistant AlMgSi alloy with an equal ', and the occurrence of the adverse effects of the wear amount of zinc. To prevent the thickness of such an "orange peel" after deformation, the cladding layer is usually between 3 and with the sheet metal also 7% of the total thickness of the clad sheets after artificial aging. 15 has a significantly better creep resistance

Such AlMgSi alloys contain z. B. 0.4 has.

to 1.4% magnesium, 0.2 to 1.3% silicon, 0.8 to According to the invention, in a method for

1.2 ° / ₀ of zinc and up to 1.0 ° / ₀ and up 0.3% manganese producing aluminum alloy sheets of high

Chromium, the remainder aluminum with the usual impurity creep strength provided that a hot rolling

worked. 20 aluminum alloy plate composed of

For the plating, preference is given to a setting according to

of the British Standards Specification 1470 as "HS.30" - _,. _{0 70 /}

designated AlMgSi alloy, which has the 1 ί ^: '2tiW

has the following composition: Up to 0.1% Kup- * '*? £ V

fer, 0.4 to 1.3 ° / ₀ magnesium, 0.5 to 0.6% silicon, _a5 '"£ *? J ^ f ₀ /'

0.4 to 1% manganese, up to 0.3% chromium, up to 0.2% titanium ^O 'l? JJ J »J JP

and / or other grain-refining elements, up to 0.1% "'* Γ. itt ₀ ' 9

Impurities rest aluminum of this AlMgSi- Aii ( ⁰

Impurities, the remainder being aluminum. This AlMgSi

0.8 to 1.2% zinc are added to the alloy,

to make the final alloy for cladding 30

obtain. This alloy is produced in the following as »HS.30, that the hot rolled plate of a multitude of

+ 1% Zn «. number of cold rolling passes in which

It is well known that the creep resistance decreases each thickness not less than about of aluminum alloys by the grain size of the 12% and no greater than about 50% that between Material is influenced and that with increasing 35 the individual cold rolling passes a recrystallization grain size the creep resistance increases. Other annealing is carried out; that the rolled sheet on the other hand, too coarse a grain is undesirable for sheet metal, then initially at a temperature between which are deformed by bending, stretching or pulling at 525 and 545 ° C for 15 to 50 minutes should become a solution because the product is subjected to a de-annealing and then quenched and warm like treatment the unwanted surface 40 is swapped out *; ■

known as "orange peel". If necessary, the aluminum alloy contains

Aluminum and one or more of the metals antimony to be further processed by forging,

However, alloys can have a coarse creep beryllium, cerium, chromium, cobalt, manganese, molybdenum,

Resistance-increasing grain size because niobium, silver, vanadium, zirconium and zinc are in

forged workpieces normally after their 45 an amount up to 0.3% each and with a total

Manufacturing cannot be further deformed. amount of not more than 1 ⁰ J ₀ . The salary can be

It is known to cut aluminum alloy sheets out of silver by up to 0.5% to 0.8% at a corresponding rate Manufacture recrystallized hot rolled plates by increasing the total amount of additives, if this of a large number of cold rolling passes with one of the copper content at least by that percentage decrease in thickness in the order of 50 rate below 2.5%, by that of the silver-50 to 60% or more, the content exceeding 0.5%. In addition, the AI can in between For each stitch, a recrystalline aluminum alloy or several of the elements annealing is carried out. After one on-,. Barium, calcium and strontium in one total following solution annealing, the sheet does not contain more than 0.2%. Furthermore, she can relatively fine grain, which contains one or more of the elements tin, arsenic, bismuth, processing facilitated by deformation. Cadmium, Boron, Lithium, Sodium and Potassium up to

The final grain size of the sheet will mainly contain a total of 0.1%,
mainly on the decrease in thickness during the last cold rolling pass and on the duration and temperature of the recovery heat treatment, which is determined over a period of subsequent solution heat treatment. If the sheet is rolled down for 15 minutes to 3 hours at a temperature of 1.5 to 11% between 150 and 300 ⁰ C - that is, at a temperature of its previous thickness during the last cold rolling pass, the result is below that at which the grain growth at the subsequent solution heat treatment takes place a coarse - extends, improves the creep resistance grain, then stood by solution heat treatment and

It is customary to continue the annealing time of the solution annealing 65 artificial aging of treated sheet metal. One

to a minimum, namely to less uniform improvement in creep resistance

than 15 minutes to stop grain growth was found on a sheet placed between the

avoid and, in the case of clad sheets, a final cold rolling pass and solution heat treatment and

the subsequent artificial aging had been aged for a few months at room temperature.

The improvement in creep resistance is even more noticeable when the billets are pre-hot-rolled cannot be homogenized.

In the case of a homogenization annealing that is desired for other reasons, the bars are at or slightly below the temperature at which the solution heat treatment after cold rolling is carried out, depending on their thickness and weight, annealed for about 10 to 48 hours. Thereafter the bars are either cooled to the temperature required for hot rolling and immediately then hot-rolled or cooled to room temperature and before hot-rolling reheated to the required temperature.

The aluminum alloys used according to the invention are preferably used in a conventional semi-continuous or continuous casting process produced.

Sheet metal produced with the method according to the invention has a grain diameter between 0.04 and 0.017 mm. The sheet metal can be deformed without the appearance of an "orange peel" and its creep resistance is significantly higher than that of commonly produced sheet metal. When the grain size of a solution-annealed sheet exceeds 0.064 mm, a subsequent deformation occurs by bending, pulling or stretching the "orange peel" is very likely. Operations with severe deformations can even lead to visible intergrain cracks on the sheet metal surface.

Examples of clad aluminum alloy sheets and processes for their manufacture according to FIG Invention are described in detail below and their properties with those of sheet metal compared those produced in the usual processes and special processes deviating from the invention are.

example 1

Seven clad sheets, designated A through G below, include within the following Limits varied alloy components:

2.35 to 2.65% Cu,
1.35 to 1.65% Mg, 0.18 to 0.22% Si, 0.95 to 1.15% Fe, 1.00 to 1.30% Ni, 0.05 to 0.10% Ti, 5

Aluminum and traces of one or more of the additional elements mentioned above form the Remainder. To produce the same, non-homogenized bars of the above composition were used in

ίο Usually clad on both sides by hot rolling. The cladding had a nominal thickness of 5% of the total thickness of the respective sheet.

The plating for sheets A, B, C and D consisted of commercially available pure aluminum with 0.8 up to 1.2% zinc. For the plates E, F and G, a thermosetting, corrosion-resistant plating was used Alloy used, which is made of commercially available pure aluminum with approximately 0.7% magnesium, 1.0% silicon, 0.55% manganese and about 1.0% zinc as well

ao consisted of the usual impurities.

The sheets were then processed further by cold rolling. The thickness reductions in the cold rolling passes before and after the last recrystallization annealing are listed in Table 1. For the purpose of recrystallization, the sheets were annealed for 6 to 8 hours at 360 to 385 ° C. between the cold rolling passes. A sheet was then solution heat treated in a salt bath for 10 minutes at 53o C ^0. The sheets B to G were solution annealed for 40 minutes at the same temperature. After quenching, the metal sheets were subjected to the smallest possible degree of cold deformation during normal straightening, because greater cold deformation at this stage has an unfavorable effect on the subsequent creep resistance. All sheets were finally artificially aged 20 to 24 hours at 190 ⁰ C in an air circulation oven.

Samples of the artificially hardened sheets were examined for the grain size of the core alloy. The results are shown in Table 1. Samples taken transversely to the direction of the final rolling were tested for their creep resistance in a customary time interval test. The permanent creep of these samples after 500 hours-long exposure of about 18.9 kp / mm ² at 150 ⁰ C is also shown in Table 1 below.

Table 1

Plating

Al99 + 1 ° / "Zn | HS. 30 + 1% Zn

Designation of the sheet

B I C I D I E I F I G

Thickness decrease in% in the cold rolling pass
before the last recrystallization annealing.

Thickness decrease in% in the cold rolling pass
after the last recrystallization annealing

Sheet thickness in mm

Grain size in mm after artificial aging ..

Permanent creep strain in% after 500
Hours load of 18.9 kp / mm ²
150 ⁰ C

55

47
1.64

0.025

0.027

0.195

37 41 37 37 37 15th 24 27 55 15th 1.64 1.64 1.40 0.90 1.65 0.035
until
0.038 0.030
until
0.032 0.025
until
0.027 0.0200
until
0.0224 0.035
until
0.038 0.093 0.106 0.120 0.131 0.076

37

27 1.40

0.030 to 0.032

0.107

A comparison of the sheets with one another, those with the non-thermosetting cladding Al 99 +1% zinc clad shows that sheets B, C and D made according to the invention are suitably small , Have grain size and at the same time have a considerably greater creep resistance than sheet A, which was produced in a conventional process.

In the same way, the sheets F and G made according to the invention and with the thermosetting Plating from HS.30 + 1% zinc were provided, a smaller grain size, and her Creep resistance is much higher than that of the corresponding sheet E, which is in one out of the frame The special process falling out of the invention was produced.

Example2

As an example of the effect of "recovery annealing" without prior homogenization of the cast ingots, some sheets _{composed and manufactured like sheets C and F ao were} annealed for 2 hours at 275 ° C. after the last cold rolling pass according to Table 1 and then the solution heat treatment in a salt bath Subjected at 530 ° C for 30 minutes. After quenching, the sheets were stored for 20 hours then heat at 190 ° C and after 500 hours exposure to 18.9 kgf / mm ² at 150 ⁰ C, as in Example 1, examined for grain size and permanent creep. It was found that the grain size of the sheet made from sheet C was 0.030 to 0.032 mm and the permanent creep strain was only 0.083%. In the case of the sheet made from sheet F, the grain size after this treatment was 0.035 to 0.038 mm, and the permanent creep was only 0.068%.

Example 3

The effect of a previous homogenization of the cast ingots with and without "recovery annealing" following the cold rolling is shown in Example 3: An ingot of a composition according to Example 1 was homogenized for 20 hours at 520 ° C. before hot rolling and, like sheets A to D, on both The surfaces were provided with a plating which made up about 5% of the total thickness of the sheet, 99% ^{of which was} commercially available pure aluminum and 1% of zinc. The hot-rolled plate produced from the billet by hot rolling was cold-rolled in essentially the same manner as sheet C in Example 1. Part of the sheet was not subjected to any "recovery annealing" after cold rolling; this part was designated as sheet J. A second part was subjected to a "recovery anneal" for 2 hours at 285 ° C after cold rolling; this sheet was referred to as sheet K.

Samples were cut from the two sheets J and K, solution annealed and artificially aged at the same temperatures for the same times as the sheets from Example 2. The samples were then measured for grain size and permanent creep strain after 500 hours of loading at 18.9 kp / mm ^a tested at 150 ° C. The results of these experiments are shown in Table 2.

Tabel

J 42 Plating
A199 + 1% zinc 24 Designation Thickness decrease in% in the cold rolling pass before
final recrystallization annealing 1.6 Thickness decrease in% in the cold rolling pass after
final recrystallization annealing 0.030
to 0.032 Sheet thickness in mm 0.098 Grain size in mm after artificial aging Permanent creep strain in% after 500 hours
Load of 18.9 kp / mm ² at 150 ° C ; of the sheet
K 42 24 1.6 0.035
to 0.038 0.090

Claims (11)

Claims: 55 1. A method for producing aluminum alloy sheets of high creep strength, thereby characterized in that an aluminum alloy hot rolled plate of the composition 2.2 to 2.7% copper, 1.3 to 1.7% magnesium, 0.12 to 0.25% silicon, 0.9 to 1.2% iron, 0.9 to 1.4% nickel, 0.02 to 0.15% titanium, remainder aluminum, is produced that the hot rolled plate is subjected to a large number of cold rolling passes, in which the decrease in thickness is not significantly less than 12% and not significantly greater than 50%, that a recrystallization annealing is carried out between the individual cold rolling passes, that the rolled sheet is then initially at a temperature between 525 and 545 ⁰ C for a period of 15 to 50 minutes is subjected to a solution heat treatment and then quenched and rolled hot. 2. Application of the method according to claim 1 to hot rolled plates made of an aluminum alloy according to claim 1, which additionally contains one or more of the metals antimony, beryllium, cerium, Does not contain chromium, cobalt, manganese, molybdenum, niobium, silver, vanadium, zirconium, and zinc in an amount up to 0.3 per ° / ₀ and in a total amount of 1%. 3. Application of the method according to Claim 1 to hot rolled plates of an aluminum alloy according to claim 2, the silver content may be increased by up to 0.5% to 0.8 ° / ₀ in accordance with increased total amount of additives, when the copper content at least to those percentage is / ₀ decreased less than 2.5 °, exceeds by which the silver content is 0.5 ° / _0th 4. Application of the method according to Claim 1 to hot rolled plates of an aluminum alloy according to claims 1 to 3, which does not include even one or more of the elements barium, calcium and strontium in a total amount of more than 0.2 ° / _0th 5. Application of the method according to claim 1 to hot rolled plates made of an aluminum alloy according to claims 1 to 4, which contain one or more of the elements tin, arsenic, bismuth, cadmium, boron, lithium, sodium and potassium up to a total amount of 0.1% contains. a ₅ 6. The method according to claim 1, characterized in that the decrease in thickness of the hot rolled plate is between 14 and 45% for each cold rolling pass. 7. The method according to claim 1, characterized in that the solution heat treatment at a temperature takes place between 528 and 535 ° C. 8. The method according to claim 1, characterized in that the artificial aging takes place at a temperature of about 175 to 210 ⁰ C for about 4 to 30 hours. 9. The method according to claim 1, characterized in that the sheet between the cold rolling and the solution heat treatment, a recovery heat treatment for about 15 minutes to about 3 hours at a temperature between about 150 and about 300 ° C. 10. The method according to claim 1, characterized in that the ingot to be hot-rolled with a plating is provided. 11. The method according to claim 10, characterized in that a plating on the bars made of pure aluminum, an Al-Zn alloy with about 0.8 to 1.2% zinc or a thermosetting, corrosion-resistant AlMgSi alloy with 0.8 to 1.2% zinc, 0.4 to 1.4% magnesium, 0.2 to 1.3% silicon, 0 to 1.0% manganese, 0 to 0.3% chromium, the remainder aluminum in addition to the usual Impurities is applied. 809 639/1565