DE1533245C - Aluminum alloy - Google Patents

Description

The invention relates to aluminum alloys, in particular to be used 35 than 0.7%, since larger amounts as a result

special aluminum casting alloys of high strength- the high silver price the costs only unnecessarily

ability, and process for their manufacture. would increase without the physical properties

There has long been a need for cast barrels to be considerably changed or the tendency to

pieces made of aluminum alloys with high strength stress corrosion would be further reduced,

speed, and not only as a replacement for the expensive 40 A further development of the alloy according to the invention

Aluminum parts of high strength, which is due to an additional content of 0.5 to

Forging, extrusion, cold rolling and machining 4.0%, preferably 1.0 to 3.0% zinc.

This zinc addition causes a further improvement

production of complex shaped parts. There are of tensile strength, 0.2 limit and elongation,

aluminum casting alloys, but the 45 Another development of the invention

Castings have a lower strength than machined alloy has an additional content of 0.15

Machined heavy plates and billets, machining up to 0.7%, preferably 0.2 to 0.3% titanium. This

worked forgings and guaranteed by non-cutting titanium additive in an advantageous manner

formation received orders. fine-grain structure of the alloy, what a unique

The invention creates an improved aluminum 50 wall free solution heat treatment is important. In some

alloy, in which essentially no stress cases, the titanium content is at the lower limit

Corrosion problems occur and are kept out of the castings, and more is added when the

can be produced, which a tensile strength is melted over alloy, 'because thereby the grain

49 kp / mm ² , a 0.2 limit over 42 kp / mm ² and a structure is improved.

Have elongation of 4 to 10% or more. In particular, 55 According to another embodiment of the present invention in sondere engineered castings alloy can contain these 0.001 to 0.01% boron. Chills with a tensile strength of up to 45.7 kgf / This boron content is indeed, for the preparation of ² mm a 0.2 limit up to 38.7 kgf / mm ² and an alloy not essential. In general, stretching up to 8% is recommended to be guaranteed. In sand casting, however, this additive is remelted if the alloy is remelted for assembly without chill layers, an improvement in the tensile strength of its grain structure.
speed of 42 kp / mm ² , a 0.2 limit of 35 kp / mm ² for some applications of the invention and an elongation of 3% can be achieved. This cast aluminum alloy according to the present invention can be advantageous. Up to now, parameters could only be in forgings if they contain up to 0.3% manganese, molybdenum from aluminum, but not in castings made from aluminum and / or cerium and up to 0.5% chromium ,
minium can be achieved. 65 In the table given below, broad and narrow ranges of the aluminum according to the invention are made up of 4.2 to 6.0% copper, 0.05 to 3.0% silver, cast alloy and the alloy content of a spe-0 , 15 to 0.4% magnesium, the remainder aluminum specified with a specific example:

table

elements

Wide range 0.5 to 6.0 rest Narrow area rest Sample value ^ Weight percent) up to 3.0 to 4.0 (Weight percent) 1.0 to 3.0 (Weight percent] 4.2 up to 0.4 4.7 to 5.3 4.9 0.05 up to 0.7 0.40 to 1.0 0.60 0.15 0.15 0.20 to 0.30 0.24 0.15 0.15 0.20 to 0.30 0.25 up to 0.01 0.03 0 0.3 0.03 0 0.001 0.3 0.001 to 0.01 0.002 0.3 0.3 0 0.5 0.3 0 0.05 0.3 0 0.15 0.3 0 0.05 0 0.15 0 ■ rest 2.0

copper

silver

magnesium

Titanium (if desired) .......

Silicon (max.)

Iron (max.)

boron

Manganese (max.)

Molybdenum (max.)

Cerium (max.)

Chrome (max.)

other (maximum per element)
others (maximum total).

aluminum

Zinc (if desired)

A melt of the alloy was produced as follows: About 54 kg of returned material to be remelted (sprues and risers from previous casting operations) together with about 22.7 kg of high-purity aluminum (99.8 to 99.99%) and about 1.8 kg of a Aluminum-titanium master alloy (5% titanium, remainder aluminum) melted in a gas-heated furnace in a silicon carbide crucible. The temperature was controlled with the aid of a chrome-alumel thermocouple and a potentiometer. After a temperature of about 704 ^° C. was reached, 1.25 kg of electrolytic copper and 0.15 kg of silver were added. If zinc content is desired, the zinc is added along with the copper and silver. After the metals had dissolved, a further 20.4 kg of returned material from previous melts was added to the crucible, so that a composition within the ranges given in the table above was obtained. When the temperature had risen again to 704 ° C., nitrogen was bubbled through the melt with the aid of a graphite tube in order to remove harmful gases, for example hydrogen generated by the decomposition of moisture. The temperature was raised to 76o ⁰ C allowed to rise. About 0.23 kg of an aluminum-titanium-boron alloy (5 ° / ₀ titanium, 1 ° / ₀ boron, the remainder essentially completely aluminum) was added, then about 0.082 kg of pure magnesium. It was checked whether the metal still contained dissolved hydrogen. If so, more nitrogen was bubbled through until the test for hydrogen was negative.

Thereafter, about 0.045 kg of a grain refining agent (mixture of two parts of titanium-potassium fluoride with one part of potassium borofluoride) was added to the melt. Waited for at least 10 minutes. When the casting temperature of about 718 to 774 ^° C. was reached (depending on the shape and size of the casting), the melt was poured into a mold, also into a test piece mold, and a sample was taken for chemical analysis. A casting temperature of 746 ⁰ C is suitable for the most diverse parts. Too low a casting temperature leads to poorer mechanical properties.

A modified embodiment of this meltdown process has also been used with success.

In this case, 28 g Hexachloräthanpillen were about introduced per 68 kg of metal in the melt after it had reached 704 ⁰ C. In this way, any traces of sodium present were removed. Chlorine gas can be used for the same purpose. Then the magnesium and the aluminum-titanium-boron alloy are added. After the melt had been deslagged, the grain refining agent was added and nitrogen was bubbled through the melt until a test showed that the metal was free of gas. At the same time the temperature was increased to about 746 to 774 ^° C. The preferred casting temperatures are the same for both meltdown processes.

A casting mold made of anhydrous sand is preferably used. One can also be bound natural or use synthetic sand, but gas uptake often occurs as a result of the reaction between the metal and the moisture of the sand.

The cast alloy was then subjected to in an electric furnace with quench dip tank to solution by the casting was maintained from 3 to 8 hours at 527-538 ⁰ C. The casting was then quenched in water at a temperature not exceeding 54 ° C. When quenching, the casting sometimes throws itself and is then straightened in a press or with a plastic or wooden mallet. When the casting had been straightened as required over the next 3 hours, it was tempered for 8 to 20 hours at 138 to 171 ° C.
The purpose of quenching is to maintain the solution annealed condition. The quenching should take place as quickly and suddenly as possible without the formation of stress cracks. In a water quenching the alloy of 543 ⁰ C even cracks occurred in small portions. When the alloy test rods were quenched at 538 ° C, the test rods did not crack, but some slight surface cracks were found in some areas of more complex castings. When the alloy was quenched at 535 ° C., cracks occurred in complex castings with strong chill layers, but no cracks in the same castings with no chill layers. In a water quenching the alloy of 53o C ⁰ occurred in castings in a length of up

no cracks up to 150 cm. Therefore, the invention Alloy preferably quenched from a temperature of 350 ° C even if the solution heat treatment takes place at 535 or 538 ° C. In this case, the temperature before quenching becomes preferable reduced to about 530 ° C. 25 to 38 cm long parts made of the alloy with a wall thickness of 6 to 19 mm was quenched from 535 ° C without cracking. The temperature of the water is preferable not higher than 49 ° C. Quenching in water at room temperature improves apparently the resistance to stress corrosion.

The solution treatment is used for dissolving the copper-rich compound which is deposited during the solidification of the alloy to the aluminum-rich matrix around without '■ that one of the components melts. Taking into account the size, shape and thickness of the casting, the temperature and duration of the solution heat treatment are chosen so that the eutectic is practically completely dissolved in the basic mass. This is verified by microscopic examination.

In general, a solution heat treatment of about 5 hours is sufficient for 64 mm thick parts. Satisfactory results were obtained with a solution heat treatment at a temperature in the range from 530 to 538 ° C. The best results were obtained when the temperature reached 535 ° C for 2 to 3 hours after solution treatment for 5 hours. In one embodiment, the solution heat treatment, the temperature was maintained at 530 ° C for 1 hour, then 3 hours at 535 ⁰ C and finally 1 hour so that the treatment lasted again to 530 ° C a total of 5 hours.

For castings with a size of not more than 38 x 38 cm and a thickness of not more than 19 mm a perfect solution annealing can be done by the parts are heated at 535 ° C for 5 hours. Smaller castings on the order of about 203 -25-13 mm can be treated at 538 ° C for about 4 hours.

The parts are swapped out to precipitate the copper compound, which hardens the alloy. The temperature and duration of the aging treatment depend on which properties are most desired. With a longer duration and higher temperature of the aging treatment, the 0.2 limit is increased, with a shorter duration and lower temperature, on the other hand, the elongation is increased. A higher notched impact strength is obtained when aging is carried out at a lower temperature for a longer period of time, e.g. B. for at least 5 days at room temperature, but then the 0.2 limit is lower. By aging the alloy at 160 ° C. for a period of about 20 hours, a very stable material was obtained that did not change over time and was also very resistant to stress corrosion. At a higher temperature of 171 ° C, perfect curing could be achieved in a shorter time, but the elongation was a few percent lower. An alloy with usable, well-coordinated physical characteristics is achieved when aging at 146 ^° C.

A typical solution heat treatment of a casting, for example a strut for an aircraft chassis, was carried out as follows: 1 hour at 53O ° C., 3 hours at 535 ° C. and 1 hour at 530 ° C. with a total solution heat treatment time of 5 hours. Then quench in room temperature water for a period of 5 seconds. The casting was then kept for 24 hours at room temperature and then for 20 hours aged at ⁰ C 16Q.

From castings which had been produced according to the above information, with the known measures promoting a progressive, directional solidification ίο, test specimens were removed by machining and subjected to mechanical tests. The following results were obtained: tensile strength 42.9 to 49.3 kp / mm ² , 0.2 limit 34.8 to 45.3 kp / mm ² , elongation 6 to 17%. The chemical analysis of the test items had the following result:

Element weight percent

Copper 4.74 to 5.55

Magnesium 0.20 to 0.31

Titanium 0.22 to 0.28

Silver 0.54 to 0.61

Silicon-iron 0

Aluminum rest

A high copper content is used in the alloy according to the invention, so that the compound CuAl _{2 is present} in a larger amount. This connection must be broken up by the solution heat treatment. The solubility of the compound increases with temperature. This is probably due to the fact that the solution heat treatment within the scope of the invention is carried out at 530 to 538 ° C.

The analysis of another test rod resulted in the following composition:

Element weight percent

Copper 4.73

Silver 0.61

Magnesium 0.21

Iron 0

Silicon 0

Manganese 0.01

Titanium 0.27

Chrome 0

Nickel 0.02

Aluminum rest

Tests have shown that the best properties with a copper content of about 4.7 to 5.3% can be obtained. For example, we had test rods that differed in each set only by the copper content differentiated, the following tensile properties after the same heat treatment:

⁵⁵ set
No. 60 2 Cu
(Weight tensile strenght 0.2 limit Deh
tion percent) (kp / mm ² ) (kp / mm ² ) (%) 1 3 4.20 30.2 18.3 13th 4.75 40.8 24.6 14th 65 4 4.75 43.6 29.5 7.5 5.75 ■ 39.4 23.2 2.0 5 5.25 42.9 30.9 5.5 5.75 40.8 26.7 4.0 3.2 37.5 33.2 8.0 5.0 47.5 42.6 5.5 5.0 42.0 35.4 4.4 6.0 38.8 37.5 1 ?
X, -

Magnesium is sometimes considered undesirable in high strength aluminum-copper cast alloys. In the context of the invention, however, it has been found that when used in the correct amounts it increases the 0.2 limit of the alloy according to the invention. For example, test bars that differed only in their magnesium content had the following tensile properties after the same heat treatment: '

Mg
(Weight tensile strenght 0.2 limit strain : Percent) (kp / mm ² ) - (kp / mm ² ) (Vo) 0.19 45.4 39.4 5.5 0.29 49.6 46.7 3.0 0.38 49.5 47.4 2.0 0.48 21.0 - 0.5

In the test piece containing 0.48% magnesium, some burns occurred. The magnesium content is preferably about 0.20 to 0.30%. As can be seen from the example above, a magnesium content in this range increases the tensile strength and 0.2 limit by about 10%.

The addition of elemental silver to the alloy increases its mechanical strength and its loading

resistance to stress corrosion. The mechanical strength of the alloy will already be improved by adding only 0.2% silver. With a silver content of 0.4 to 1.5%, the alloy is essentially free from stress corrosion. The mechanical strength apparently reaches at a silver content of about 0.5% is an optimum, but is only slightly at a silver content of up to 3.0% degraded. The effect of silver on the characteristic values can be seen from the following tests with test rods emerged:

sentence
No. 15th T-I 20th Ag
(Weight tensile strenght 0.2 limit Deh
tion percent) (kp / mm ² ) (kp / mm ² ) (Vo) 2 O 41.8 31.3 6.0 0.60 48.5 40.2 8.5 0 42.2 35.2 4.4 0.20 47.1 42.9 2.5 0.30 47.1 41.5 5.0 0.70 47.8 42.6 4.6

Another set also contained varying amounts of magnesium, but here too had a higher one Silver content has no adverse effect on tensile strength.

sentence Ag Mg tensile strenght 0.2 limit strain No. (Weight percent) (Weight percent) (kp / mm ² ) (kp / mm ² ) (%) 3 0.60 0.19 45.4 39.4 5.5 1.1 0.20 44.7 39.7 4.5 1.6 0.15 43.5 33.8 10.0 2.1 0.15 43.5 32.8 8.0 2.6 0.19 44.9 33.8 8.0

A zinc content of around 1.0 to 3.0% does not seem to lead to a higher strength a considerable improvement in strength and reduces elongation. This comes from the speed. This can be seen from the following test results test of the following test objects: nissen:

Zn Tensile strength 0.2 limit strain (Vo) (kp / mm ² ) (kp / mm ⁸ ) (Vo) 0 45.9 39.7 5.0 1.0 47.8 40.6 9.0 2.0 50.8 44.9 5.0 3.0 51.1 45.1 5.0 4.0 48.5 45.8 2.0

Ti
(Weight
45 percent) •Tensile strenght
(kp / mm ² ) 0.2 limit
(kp / mm ² ) strain 0.24
0.39
0.54
⁵⁰ 0.69 42
41.8
42.5
42.3 35.4
35.2
35.9
37.5 4.4
4.2
4.2
3.0

Titanium is a good grain refiner. With a titanium content of 0.20 to 0.30%, the alloy has a fine grain which during the required distribution of copper throughout the alloy of solution annealing, so that castings can be obtained which are much stronger than castings, which have been produced with the known aluminum casting alloys. A higher titanium die other elements contained in the alloy are impurities. Two of them, silicon and Iron are common impurities in the aluminum matrix and are used in the alloy according to the invention harmful. In general, the iron and silicon content should be less than 0.15%, preferably less than 0.03%. With two sets of specimens, the following results were obtained:

sentence c; 0.16 tensile strenght 0.2 limit strain No. 0 (kp / mm ¹¹ ) (kp / mm ² ) (Vo) 1 0.15 0.16 46.4 36.6 2.5 0 0.65 48.5 40.2 8.5 2 0.15 42.0 35.4 4.4 0.15 31.6 24.9 2.0

209 552/153

The above results were obtained with test rods which were used in Sand molds had been cast and had a diameter of 12.7 mm and a 57.2 mm long portion of smaller diameter. The results of the individual sentences cannot be compared with one another, because the sentences differ from one another in other points as well.

Of the other elements which are ent ^ some are very harmful, some somewhat harmful and others have none or even none a slightly beneficial effect on the alloy.

A cadmium content of 0.30% resulted in the Solution annealing leads to severe burns and cracks, reducing the strength and elongation properties completely lost.

A sodium, calcium, and lithium content of 0.02% resulted in a reduction in tensile strength of 10 to 20 ° / ₀ and elongation by 30 to 40%, and the occurrence of errors in the group consisting of the alloy test bars.

A cobalt content of 0.30 ° / ₀ resulted in a reduction of the tensile strength by 20% and elongation by 30% and to a Kornvergföberung.

A tin content of 0.005 ° / ₀ did not affect the properties of the alloy, however, resulted in the presence of 0.005% bismuth during solution heat treatment to strong combustion phenomena and cracks.

An antimony content of 0.005% led to a ίο decrease in tensile strength by 10% and to a similar reduction in elongation.

A chromium content of 0.25% and a molybdenum content of 0.25% resulted in a slight increase the tensile strength. At 0.50% molybdenum, the tensile strength was slightly reduced, while a chromium content of 0.50% did not cause any significant changes. Manganese, nickel and cerium had amounts of each 0.30% had no noticeable effect on the properties of the alloy. A zirconium content of 0.25% resulted in a slight reduction in tensile strength.

Claims (6)

I 533 245 1 2 the usual production-related impurities. Patent claims- This aluminum casting alloy not only has better characteristics than all other known aluminum casting alloys, according to one embodiment 1. Aluminum casting alloy, consisting of 4.2 5 castings obtained from the invention retained over it up to 6.0%, preferably 4.7 to 5.3%>, copper, 0.05 also good characteristics even at elevated temperatures to 3.0%, preferably 0.4 to 1.0%, silver, 0.15 values. Compared to the French patent up to 0.4%, preferably 0.2 to 0.3%, Magne- writing 463 853 known aluminum casting sium, the remainder being aluminum with the usual herbal alloys, which in addition to aluminum also contain copper and positional impurities. 10 contains silver, the aluminum according to the invention has 2. Alloy according to claim 1 with a zinc cast alloy due to the addition of magnesium additional. Content from 0.5 to 4.0%, preferably increased strength. The after an execution 1.0 to 3.0, zinc. Example of the invention obtained castings 3. An alloy according to claims 1 or 2 with at 26O ⁰ C a tensile strength of more than 23 kgf / mm ^2, an additional content of 0.15 to 0.7% of, 15 a 0.2-value of more than 22 kp / mm ² and one preferably 0.2 to 0.3%, titanium. Elongation of 14%. Even at 316 ° G, the cast 4. Alloy according to one of claims 1 to 3 pieces a tensile strength of more than 13 kp / mm ² , with an additional content of 0.001 to 0.01%, a 0.2 limit of over 13 kp / mm ² and a Deh -Boron. around 16%. The majority of the previously 5. Alloy according to one of claims 1 to 4, 20 known aluminum casting alloys lose their the up to 0.3% manganese, molybdenum and / or cerium strength at such high temperatures almost fully and contains up to 0.5% chromium. constant. 6. Alloy according to one of claims 1 to 5 While the silver used in the invention with a maximum of 0.15, preferably a maximum of 0.03%, alloy to about 0.05 to 3.0%, preferably to Silicon, at most 0.15, preferably at most 35, about 0.40 to 1.0% is contained, apparently the Ver-0.03%, Iron and a maximum of 0.15% in total, division of copper in the alloy improved, sometimes individually but a maximum of 0.05%, other impurities are increased by their strength and furthermore worked. the high copper content of 4.2 to 6.0, preferably 4.7 to 5.3%, attributable slope of the AIu- 30 minium cast alloy for stress corrosion counteracts, the addition of magnesium increases by 0.15 to 0.4%, preferably 0.2 to 3.0%, the strength. It has been shown that there is little point in having one Silver content of more than 1.0% or even more