DE1558624C - Copper alloy with improved strength and elongation - Google Patents

Description

1 2

The invention relates to copper alloys with a. The object of the invention is therefore to improved strength and elongation. The creation of such improved copper alloys in accordance with the invention appropriate copper alloys, which zinc, aluminum which the favorable strength properties with the same- and nickel, have improved physical properties with the least possible impairment of their properties and are suitable for many applications. ... dung purposes, including for the manufacture of cast addition, it lies in the nature of the invention that pieces and forgings, for extrusion: the improved copper alloys with relative as well as for the production of hot rolled and cold can be produced low cost so that they can also rolled or drawn products. The inven- tive on an industrial scale in an economical manner Appropriate alloys are particularly good for the io apply. Suitable for use as a wrought alloy. It has now been shown that the above

Over the years, numerous attempts have been made to simplify and more conveniently according to the invention

has been taken to achieve the strength properties of the way.

ductile brass without impairing its performance. The copper alloys according to the invention are daformbarke.it to improve. These tests are characterized by the fact that they consist of 66 to 76% copper,. ·

finally to achieve such a goal to 15.0 to 32.5% zinc, 2.5 to 4.5% aluminum and

the use of a large number of alloys - 0.4 to 5% nickel in addition to manufacturing-related

additives concentrated. Some such alloy impurities exist.

However, additives are quite expensive and therefore contribute to the alloys according to the invention within contributes significantly to the manufacturing cost of the alloy. 20 of the above areas apply with regard to

From the book by B r u η h u b e r, »Alloy composition, the further rule is that the AIu-

rungshandbuch der Nichteisenmetalle ”, 1960, p. 155, minium and zinc content in order to achieve their

a copper-zinc alloy (27% zinc and 70% strength properties according to the following

Copper), which also contains 2% aluminum according to the equation

and contains 1% nickel. In the heat-treated to- 25 al- ft ^ no / 7 -u in 1 j-? S

However, this alloy does not have the desired ~ ~ '■ ·' ° ⁺ ' ^{± 1} ^ ⁵ -

Combination of high strength and high dimension.

formability on, as shown in a series of experiments. It has been shown that the copper alloys with

will show. the composition given above

Furthermore, British patent specification 30 reveals significantly improved physical properties in 578 873 copper-aluminum-zinc alloys with very little impairment of the deformability, the composition and heat treatment of which have. For example, the invention shows that they are selected in such a way that optimal corrosion-related improved alloys are achieved in their full resistance. An improvement in the annealed condition yield strength of at least strength properties · with good encryption 35 31.50 kg / mm ^2, while commonly used for Verforformbarkeit but not intended, and it mung purposes copper alloys used in full is continuously annealed and no instruction to achieve this State generally only apparent. Yield strengths in the range from 7.03 to 17.5 kg / mm ²

Furthermore, from British patent specification 831,454 and rarely above 21.00 kg / mm ² . The inven-

and Metals Handbook, 1948, p. 897, additions of 40 alloys according to the invention also show accordingly

Arsenic, phosphorus and / or antimony as inhibitors result in higher yield strengths in the cold-worked state

against the dezincification of copper-aluminum alloy a thickness reduction of at least 50%

in corrosive media. 63.30 kg / mm ² . The corresponding strength values

However, these alloy additions have no effect. of the usual alloys, however, fall under the

with regard to the strength and deformation properties, conditions in the range from 35.00 to

th. ν; ■:. :: -; ,. ' 52.50 kg / mm ² .

In addition, there are numerous, otherwise uncommon also - and this is of great importance -

Carefully examined heat treatment processes stand out the alloys according to the invention

been made to the strength properties without impairment by a high deformability. fm compared to

to improve the deformability. '50 an extremely well deformable 7O / 3O measuring

With the sing developed according to the prior art as a standard, the alloy according to the invention show

For high-strength brass types, there is generally a corresponding deformability: This

NEN to multiphase alloys with limited fact in view of the high strength

Ductility and cold deformability. Such alloys, the alloys according to the invention, are particularly

genes are therefore particularly suitable for manufacture 55 surprisingly. · ·; .. '· .. ■ -.

of castings and thermoformed products? These amazing properties of a cheap leather

Despite this extensive research, it has become. gation are particularly unexpected in terms of.

over the years a,; 7p / 30 brass as the best and most extensive research done on this

most economical! copper alloy for under strict area would be carried out with the aim of becoming such

Deformation processes taking place under conditions must approximate properties. _^::

grasslands. -, The alloys according to the invention belong to

It is a main object of the present invention to group the modified aluminum-brass types,

a copper that is further improved in its deformability and they basically have one of the two

alloy available. . standing structure types, namely (1) pure α-phase

Another object of the invention is the sheep 65 (face-centered cubic) or (2) "phase in combination

Function of a copper alloy with improved strength with a limited amount of the / 3 phase:

strength values both in the fully annealed and (body-centered cubic),

also in the cold processed state. It has long been known that an addition of aluminum

minium has a strength-increasing effect on copper-zinc alloys. A disadvantage of such. However, the addition of aluminum consists in the fact that in alloys with a saturated α-phase, which have the highest strengths, even small changes in the aluminum content generally give rise to large changes in ductility and strength. These major changes are the result of the structure of such a saturated alloy, which changes significantly depending on the aluminum content. For example, a change in Aluminiumgehält to / _0, an increase in the proportion of beta-phase up to 33% produce only l °.

According to the invention it has now surprisingly been found that by adding nickel in the range from 0.4 to 5%. remove the disadvantages of the ternary copper-aluminum-zinc alloys and that the properties and the structure become more uniform within a practical range for the aluminum content. In addition, the addition of nickel results in a very pronounced grain refinement, which is also very advantageous . ■: 'ν ■ ■'. ^: - ^:. _; ■. ''"■ ■ '

According to the teaching of the invention, it is of critical "importance that the concentrations of the alloy components in the above-mentioned ranges fall. The copper concentration must be in the range of 66 to 76%, and it is preferably 70 to 76%. The strength decreases noticeably below a copper concentration of 66%, and above 76% In saturated alloys, there can be an additional so-called y-phase with a complex cubic crystal structure occur, which limits the ductility of the alloy.

Similarly, the zinc content must be in the range of 15.0 to 32.5%, and it is preferably 21 to 28%. The aluminum concentration must be in the range from 2.5 to 4.5%, while the nickel content must be in the range from 0.4 to 5% . .- ■: · ■.; · ■■ ·. ■■. ■■■■

In order to achieve the maximum ductility and formability at a given copper and Aluminiumgehält, the nickel content should be between 0.4 and 1.0%, while the nickel content can be adjusted to values of up to 5% for greater strength and lower ductility. At even higher nickel contents, however, the ductility is reduced to such an extent that its usefulness as a wrought alloy is impaired. -

In general, alloys with a lower nickel content are high-strength and very ductile materials, while the alloys with higher nickel contents have even higher strengths but lower ductility. «

The alloys according to the invention have in the cold processed or; errt-white-annealed state as a structure either: (1): a matrix of fine-grained ί face-centered cubic "phase: (practically, - saturated;. saturated) or (2) a saturated" phase with a proportion of / 3- Phase on, with very finely divided intermetallic compounds and ^ or aus- in both structures _; precipitated particles are present as a dispersion.

In addition to the components specified above, the alloys according to the invention can also contain production-related impurities typical of commercial copper alloys. Usual impurities are z. B. lead, tin, phosphorus, iron, manganese and silicon. In order to avoid a reduction in the zinc content in a corrosive environment, the addition of arsenic, antimony or phosphorus in an amount of 0.02 to 0.10% can prove to be advantageous.

The alloys according to the invention can be used for a large number of purposes. As a result Their high strength and high ductility make them particularly suitable as wrought alloys. the Oxidation resistance and the castability of the alloys according to the invention are very excellent, and they are therefore also very suitable as high-strength and cheap casting alloys, while their excellent They can also be thermoformed for the production of forgings and for extrusion makes suitable. In general, more favorable combinations can be made with the alloys according to the invention of mechanical properties at a lower cost than any of the previously produced copper alloys was possible, regardless of the price.

The processing and treatment of the alloys according to the invention do not require any special measures. For example, one proceeds in the production of sheet metal as follows: Melting and casting takes place under very similar conditions as in the case of brass alloys. Direct chill casting is particularly suitable for this. The hot rolling is carried out in a simple manner by means of the rolling measures that are also customary for brass. If the cooling is too rapid, a non-equilibrium structure can form, which reduces the initial cold rollability. This can be counteracted by intermediate annealing in the range from 538 to 650 ° C, whereby the x- and the / J-phases are created practically in equilibrium proportions.

It has been found in the treatment of the alloys according to the invention that they respond extremely well to stress relief annealing carried out at a low temperature following cold working. In general, in copper alloys that have been severely cold-worked, stress-relieving annealing at temperatures below the recrystallization temperature increases the yield point only up to. about 15%. In addition, this increase in strength occurs in virtually bedeutsamem "extent only within a relatively narrow range of annealing temperature during quenching and tempering;. (27.8 to 55.6 ⁰ C) In the inventive alloys, however, increases were the yield point-of 30 to 40% is observed, if the material, cold-rolled to a thickness reduction of 50%, were subjected to a stress relief anneal at a lower temperature The magnitude of the improvements in the strength properties can be seen from the following examples which illustrate the invention.: Another special property of the alloys according to the invention consists in a remarkable improvement in the resistance to stress corrosion. The usual copper-zinc-brass types are extraordinary I am prone to stress corrosion cracking when exposed to a corrosive environment. This susceptibility increases proportionally with the zinc content, and therefore alloys become

with a content of more than 15 ° / ₀ Zinc rarely selected for use in corrosive media at voltage stress. It has now been shown that the nickel-modified aluminum-brass types according to the invention have a significantly improved resistance to cracking caused by stress corrosion compared to the known binary copper-zinc alloys. This special property is also confirmed by the following examples. Coupled with this resistance to stress corrosion is a high degree of resistance to general corrosion phenomena.

The importance of adjusting the aluminum and zinc content according to the equation

Al - -0.30 ° / ₀ Zn + 10.3 ± 1.25

results from a series of tests in which a known alloy W and other comparative alloys X and Y have been examined and compared to an alloy Z according to the invention. a) There were four different alloys with the compositions given in Table A under Use of cathode copper, plate zinc, metallic nickel and Ahiminiummetall in the form of Pellets made. For the production the following

lu geriden procedural steps complied with:

First pieces of cathode copper and nickel metal were melted under charcoal, then the required amount of aluminum was added and stirred in, and finally pieces of the zinc metal were added and stirred in. The melt was poured into a casting mold at a temperature of about HOO ⁰ C and allowed to solidify in the mold. .

Table A.

alloy aluminum
Weight percent zinc
Weight percent . . nickel
Weight percent copper
Weight percent W (state of the art) 2.0
4.5
1.5
3.5 27.0
29.5
21.5
23.5 -1 -
1 .
1
1 70
66
76
72 X (not according to the invention)
Y (not according to the invention)
Z (according to the invention)

The composition of the alloy X has an aluminum content which is greater than that according to the teaching of the invention in relation to the zinc content may be. Alloy Y has an aluminum content based on the zinc content, which is smaller than according to the teaching of the invention. the Alloy Z corresponds to a composition according to the invention, the aluminum content being exactly the zinc content has been adjusted. Alloy W corresponds to that in the »Alloy Handbook for Non-Ferrous Metals« (1960) on p. 155 mentioned alloy No. 1211.

b) The metal bars obtained were heated to about 900 ° C. and then from 44.45 to 5.1 bis 7.6 mm hot rolled down. The alloy X with too high an aluminum content showed during the The rolling process has slight surface cracks and also cracks on the edges.

Then all four alloys were made except for 5.1 mm cold rolled.

Eventually the alloys W, Y and Z further rolled down to 3.1 mm cold.

Alloy X with too high an aluminum content could not be cold-rolled and, after a thickness reduction of about 15 ° / _0, already showed severe cracking.

The four alloys were annealed 4 hours at about 577 ⁰ C in order to stabilize the structure.

In a further processing step, the alloys W, Y and Z. were cold-rolled down to 1.51 mm (Thickness reduction 50%), then annealed for 1 hour at about 577 ° C and then up to cold rolled down to a thickness of 0.77 mm. The properties of the three alloys in this cold rolled Condition were then determined (see Table B).

The three alloys W, Y and Z were also redone after rolling down to 0.77 mm Annealed at 577 ° C. for 1 hour, and their properties were determined after this final heat treatment (see Table B). ;

Attempts continued to be made to alloy X after the 4-hour stabilization annealing at 577 ° C continued to roll cold, but already occurred after one Thickness reduction of about 7% strong cracking.

Table B ■

alloy

', ...' ". Properties, After the last heat treatment 'Yield strength I tensile strength elongation ■

kg / mm ²

kg / mm ¹

in the cold-rolled condition

Yield strength kg / mm ^!

tensile strenght kg / mm *

strain

W.
X
Y
Z

31.6

26.4
34.2

48.3

45.2
52.3

31

36 34 63.2

61.2
65.7

73.5 -

71.0 '
80.6

2.5

3.5
2.0

From the above test data, 65 results, especially after the last heat treatment.

It is quite clear that the alloy Z according to the invention is a simultaneous improvement in the strength

in comparison to the alloy biscuit and elongation properties known from the literature. It is extraordinary

tion W has significantly improved properties. lent surprisingly that not only the yield point and

the tensile strength, but also the elongation has increased at the same time. This fact is in contrast to the observations made in the case of the usual alloys, where an increase in strength is always accompanied by a Reduction in deformability must be bought.

The same favorable properties are found in the Alloy Z according to the invention observed in the cold-rolled state, in particular the considerable Increase: the tensile strength is remarkable. The examples illustrate the invention.

'■ B e is ρ ie Ii

Alloys with the compositions given in Table I were prepared using .Kathode copper, plate zinc, metallic nickel and aluminum metal in the form of pellets. The following process steps were observed for the production: First: pieces of cathode copper and, of: nickel metal were melted under charcoal, then the desired amount of aluminum was added and stirred in, and finally pieces of zinc metal were added and stirred in. The melt was poured into a cast iron mold at a temperature of about 1100 ^° C. and allowed to solidify in the mold. ·

The metal bars obtained in this way were heated to 815 to 898 ° C and then from 44.45 to 7.62 mm rolled down hot, the rolling stopped at about 538 ° C. Then the metal was up on 3.11mm cold rolled, annealed for 1 hour at 538 ° C, further rolled down to .1.51mm cold, annealed again for 1 hour at 538 ° C and

ίο finally rolled down to 0.77 mm cold. The rolled material was in both the 50 ° / ₀ strength cold-rolled final state having a thickness of 0.77 mm as measured with respect to in the interannealed state of its properties.

is For comparison purposes, a standard 70/30 brass and a copper-aluminum-zinc alloy subjected to the same treatment with the modification that the 70/30 brass at this temperature , temperature of 427 instead of 538 ° C was interannealed-Die measured physical properties are summarized in the table below, namely the yield point at a permanent elongation of 0.1%, the tensile strength and the elongation, namely im cold-rolled as well as in the intermediate annealed condition.

75.9 Cu composition 4.0Al 0.7 Ni - Table I ^: - strain 1 hour at 538 ° train
strength C annealed 74.2 Cu Weight percent 3.5 al 0.5 Ni Cold rolled % Stretch
border kg / mm ² Legie
tion 71.3 Cu 19.4 Zn 4.0Al 3.0 Ni Stretch
border (50 ° / ₀ thickness
inferior)
Tensile strenght . 1.7 kg / mm ^! 55.55 72.0 Cu 21.8 Zn 2.5 al 0.5 Ni. kg / mm ² kg / mm ² 2.0 34.80 54.84 I. 76 Cu 21.7 Zn 4 al 67.15 87.20. . 2.0 34.45 62.58 II 25.0 Zn 60.40 87.90 3.0 43.59 58.36 III 70- Cu 20 Zn 64.00 90.00 2.0 37.26 45, -70 IV 64.00 85.80 18.98 50.62 ν. 30 notes 62.58 80.15 3.5 28.82 *) 37.26 15.32 *) VI 52.40 63.30 strain % 38 36.5 26th 34 57. 39 50

· ■ *) Annealed at 427 ^° C.

In game 2, the alloy V described in Example 1 was The results obtained confirm that the improved alloys according to the invention are a

1 hour at 45 equal relied 70/30 brass annealed after the final cold-rolling treatment with respect to the 190.6 ⁰ C. Afterwards it had practically correspond to the following deep-drawability and only one properties:

Tables

have little lower deep-drawing deformability during stretching than such a 70/30 brass.

Cold rolled
(50% thickness
^; . reduction) Cold rolled
... (50% thickness
^: decrease with
subsequent
one hour glow
at 190.6 ° C Stretch limit..
tensile strenght
strain 64.00 kg / mm ²
90.00 kg / mm ²
2.0% 80.50 kg / mm ²
92.81 kg / mm ²
l, 2 ° / "_; ^:

Table III

■ .. ·. '. Example 3 ~,

Several of the alloys produced according to Example 1 were tested for their ductility by means of evaluated two common measuring methods, namely with regard to the deep-drawability by determining the Limit drawing ratio and with regard to deep-drawing deformability using the Olsen Cup test run (Cup deep drawing test, compare e.g. "Metals Handbook" [1948], pp. 128 to 131). The one with it

alloy Border drawing
. ratio Olsen cupping
-! in mm II
. ^ v iv: ■■
■ ■ _'-:: ■■■■■ · .v': ■
■■ .. · ■■■ .- .. Vi- - .- \ '
(70/30 alloy
for comparison) ; 2.240
;.; ·. 2,225-; ■; -.-;
2.225 _; ;
2.260 9,694
9.401
9,922
10.662

■ "; ■ - ■ - .; ■■■■■ :." At game 4; '■

In many applications, resistance to stress corrosion cracking is important. With regard to this property, the improved alloys according to the invention are substantially superior to the usual types of brass. In an accelerated test in a solution containing (NH ₄ ) ₂ SO ₄ , CuSO ₄ and NH ₄ OH

109

contained, highly stressed strip-shaped samples showed a high resistance to cracking, which far surpassed that of a 70/30 brass or an 85/15 brass. In the following Table IV lists these values along with data on resistance to through Stress corrosion cracking generated in industrial atmospheres.

Table IV Time until
Failure in
industrial
Atmospheres alloy Time until
Failure at
accelerated
Test attempt or
Degree of relaxation
within 500 hours no failure
after 4 months
no failure
after "10 months
8 to
15 weeks
no failure
after
12 months I.
II
VI
(70 / 30-
Brass)
85/15 brass 14% relaxation,
500 hours
43% relaxation,
500 hours
full
Failure after
4 hours
full
Failure after
48 to 72 hours

Claims (4)

Patent claims: 1. Copper alloy with a yield point in the fully ^ ^ quenched ^{and tempered condition of at least Sl.S.kg/mm '2} ' and. irri cold processed condition with a thickness reduction of 50% of at least 63.3 kg / mm ² , the structure corresponding to the α-phase with finely dispersed particles, characterized in that it consists of 66 to 76% copper, 15.0 to 32, 5% zinc, 2.5 to 4.5% aluminum and 0.4 to 5.0% nickel in addition to production-related impurities, with the proviso that the aluminum and zinc content according to the equation. ΑΓ = -0.30% Zn + 10.3 ± 1.25 are sized. 2. Copper alloy according to claim 1, characterized in that it contains zinc in an amount of Contains 21 to 28%. . 3. Copper alloy according to claim 1> characterized in that it contains copper in an amount of 70 to 76%. . ■ '.. 4. Copper alloy according to claim 1, characterized characterized in that they additionally arsenic, phosphorus and / or antimony in an amount of 0.02 to 0.10% contains ..