DE2233028B2 - USE OF AN ALZNMG ALLOY FOR WELDABLE PANEL PLATES - Google Patents

Description

The invention relates to the use of an AlIZnMg alloy that is less sensitive to quenching Material for armor plates.

Alloys that are intended for use as armor plates must have certain properties, which make them suitable for that purpose. An armor plate alloy must have both high tensile strength as well as toughness. You must have a high elongation at break so that it is able to absorb a large part of the kinetic energy of the projectile. At the same time, the slope from which Backside of the plate splinters detaching as a result of the impact of a projectile should be as small as possible. the Development of high tensile strength of all high-strength aluminum alloys depends on a solution heat treatment and subsequent quenching, which is usually followed by artificial aging.

If the alloy is to be heat-treated in the form of a thick plate, as is the case with armor plates If so, it is desirable that it not be sensitive to quenching so that the tensile strength across the thickness the plate is relatively uniform. It is known that the Strength of some high-strength aluminum alloys depends considerably on quenching speed depends and that it is therefore difficult. the same strength / u over the entire cross-section because the cooling rate is slower in the center of the plate than on the surface. An exception results from the use of very low quenching speeds.

An aluminum alloy used as an armor plate should have good resistance to stress corrosion cracking and have a low tendency to chip.

It is already known to armor plates made of aluminum alloys according to US standard AA 7039, such as specified below to be used:

Cu%

si%

0.4 max. 0.10 max. 0.3 max.
(others maximum 0.05 per component)

Mn% Mg%

0.10-0.40 2.3-3.3

Cr ° / o Zn% Ti% Al

0.15-0.25 3.5-4.5 0.1 max remainder

The tensile strength and elongation at break specified for this material are as follows:

tensile strenght

0.2 grc

Elongation at break

12.5 to 50 mm thick

379.2 N / mm- '

310.3 N / mm '
10%

4 »The tensile strength of the above alloy is seen as unsuitable a! And successful attempts have been made to provide improved alloy to provide greater strength. However, the stress corrosion cracking resistance of the alloy is low.

A typical example of the improved alloy has the following composition:

Fe ° / o Si ° / o Mn% Mg%

0.25 0.15 (max.) 0.3 2.5

Zn%
4.3

Other %

0.05 each
0.15 total

Al
rest

This improved alloy has a tendency to be sensitive to chipping. It is believed that this is due to the Presence of chromium is due.

I) T-AS 14 83 324 describes the use of aluminum alloys with copper, manganese and chromium as material for armor plates. In each of the examples in this published publication, a chromium content of 0.13 to O ₁ Ib ¹ Vo is given; It can be assumed that a (chromium content in such amounts / u leads to an undesirable risk of damage, (in accordance with example J of this publication, a sheet is now produced; with such a thin sheet, the cut-off sensitivity does not necessarily have to be clear, but it is Armor plates are usually at least 25 mm thick; the resulting sensitivity to quenching is a major disadvantage.

An Al / .nMg alloy used according to the invention is hardenable, has comparable strength properties switch and superior stress corrosion cracking resistance and in particular results in terribly insensitive ones Armor plates.

The invention relates to the use of an AIZnMg alloy consisting of 5.0 to b, 0% zinc, 1.7 to 2.1% magnesium, 0.05 to 0.2% zirconium, 0.1 to 0.15% copper , 0.3 to 0.4% manganese, up to 0.1% titanium, up to 0, Wi) dissolve, up to 0.3% silicon and the remainder aluminum with a total of less than 0.1

0.05% more impurities than. more deterrent Material for armor plates that must be weldable without cracking.

It is found that Ti, Fe and Si are impurities and do not represent alloying additions up to the amounts specified in the composition

.ri2finö> l nob'iov / miioloi

Copper can in amounts exceeding 0.15% cannot be tolerated, as the material with a higher copper content is not without the risk of cracking can be welded.

The alloy used in the invention is prepared for Punzerplatten mm for armored combat vehicles in a thickness of less than 25, solution heat treated, quenched and artificially aged, for example, during 12 hours at 135 C ^J. While prolonged artificial aging reduces tensile strength, it increases elongation at break and reduces the tendency of the alloy to chip off under projectile impact, and so may be desirable in certain circumstances.

It has now been found that the aluminum alloy plate according to the invention can be welded without extensive cracking of the weld seams.

example

An alloy with the following composition was assumed:

5.5% Zn, 2.0% Mg, 0.15% Zr. 0.12% Cu, 0.4% Mn, 0.2% Fe, <0.01% Cr, remainder Al with inclusion of melt-related Impurities.

Plates with a thickness of 30 mm and 45 mm were made from this alloy. The plates were at Solution annealed to 450 ° C for 30 minutes, quenched in cold water, for 5 days at room temperature aged and then heated up to 150 ° C at a rate of 20 "C / h held at this temperature for 8 hours and then cooled. The following mechanical Properties were obtained:

thickness ι »): 'II! Λ hardness Stressful
Corrosion
Life
duration mm N / mm- ¹ N / mm ³ % (Tagt ·) 15th
30th 442
456 488
496 ι lo
11.5 76
76 > 15

In order to reduce the tensile strength and to increase the toughness, the plates were for 7 hours at 160'C artificially aged. The following mechanical properties were obtained:

thickness (Ji) 2 or % skirt
well-
hardness Stressful
Corrosive
Life
duration mm N / mm ³ N / mm- ' 11.5
12.5 (Days) 45
30th 399
402 454
458 70
71 > 15

-5 The slight difference between the properties, obtained on plates of various thicknesses illustrates that this alloy is only one has a low risk of deterrence.

Samples from the alloy were staged

: -o machined to provide open surfaces at varying depths within the thickness / u (it has previously been found that the exfoliation behavior can vary considerably with the thickness of the metal specimens). The samples were exposed to a 5% sodium chloride solution in a salt spray chamber for 168 hours, which had been acidified with acetic acid to a pH of 2.8. After removal, the samples were cleaned with nitric acid, rinsed and tested. It turned out that the

Samples made from the alloy used according to the invention, the aging was negligible.

Claims (1)

Claim: Use of an AlZrMg alloy, consisting of from 5.0 to 6.0% zinc, Ί.7 to 2.1% magnesium, 0.05 up to 0.2% zirconium, 0.1 to 0.15% copper, 0.3 to 0.4% manganese, up to 0.1% titanium, up to 0.5% iron, up to 0.3% silicon and the remainder aluminum with a total of less than 0.5%, but individually less than 0.05% further impurities as deterrent ι ο sensitive material for armor plates, which without Cracking must be weldable.