DE2715799A1 - COPPER ALLOY - Google Patents

Description

Dipl.-lnq. H. MITSCHE ^ UCH Dipl.-In ₉ . K. GUNSCHMANN

Dr. re r. η at. W. KÖRBER Dipl.-Ing. J. SCHMIDT-EVERS PATENT LAWYERS

D-8000 MÖNCHEN 2 2 Steinsdorfstrasse 10

& (089) '29 66 84

April 7, 1977

KENNECOTT COPPER CORPORATION 161 East 42nd Street
New York, NY, V.St.A.

Patent application

Copper alloy

7098A3 / 0S24

DESCRIPTION

The invention relates to copper alloys.

When copper-based alloys are exposed to air at room temperature for long periods of time, uneven oxide films of ugly appearance develop on them; this phenomenon is usually called "tarnishing" designated. In order to prevent such tarnishing, various clear or transparent coatings have already been proposed which are either costly or damaged in use, so that under the cover local tarnishing or corrosion occurs. It is true that most copper-based alloys have the means to manufacture them Required formability of everyday objects, but the tarnishing described leads to a limitation the usability of such alloys in cases where the products made from them also have a decorative Should have an effect.

For many years, attempts have been made to find a copper-based alloy that does not tarnish or fog, that is to say that does not require the application of a protective coating. For example, the International Copper Research Association (INCRA) has developed an alloy that is relatively resistant to tarnishing and has become known under the legally protected name INCRA C-57. This alloy is made of copper containing 5 wt _e? -9i contains tin and 7 wt .- 6 aluminum. However, this alloy can only be processed with difficulty using the methods customary in brass works. More specifically, this alloy cannot be rolled very well when hot, and its cold-rollability is also rather limited. Furthermore, the formability of the finished alloy is relatively poor, which means that the

7Ü98A3 / 082A

availability of the alloy for the production of shaped products is significantly limited. So it is until now Achieving resistance to tarnishing a copper-based alloy required to choose compositions that allow workability and formability is limited for natural reasons. Mainly for the reasons mentioned, such alloys have therefore in the Practice found no greater widespread use.

The invention has now created an alloy that can be used in a wide variety of objects can be processed, which can be used indoors without any protective coating in the same way as those made of stainless steel. In view of this property of the alloy according to the invention, it is up to the designer possible to opt for the warm coloring of a copper alloy, with the added benefit of that it is not necessary to apply a protective coating to maintain this appearance "

The alloy according to the invention is a copper-based alloy containing 7.0-8.5 wt. 96 aluminum and 1.5-2.5% by weight of nickel, with the remainder of 89-91.5% by weight consisting essentially of copper. The invention Alloys not only need to have the above composition, they also need to have the capability have to spontaneously form a thin, almost transparent film at room temperature, which has an electrical polarization resistance of at least 95 kiloohms when this is in a neutral salt solution when a DC voltage is applied is measured «This high film resistance is achieved by treating the alloy under conditions which lead to a structure that consists of a matrix of a solid Copper-aluminum-nickel solution of uniform composition consists of an intermetallic solution in a very fine dispersion Contains nickel-aluminum compound,

709843/0824

The alloy of the invention is for indoor use suitable, and it has been found that it is not only very resistant to tarnishing, but also excellent Has strength and malleability properties. In the open air, the alloy according to the invention shows a very high corrosion resistance, but it loses its luster over time and takes on an even, dark bronze color.

By the invention, a copper-based alloy has thus been created which is oxidation and at room temperature is corrosion-resistant, which takes on a uniform color, which not only has an aesthetic effect, but is also relatively durable, in which the pleasing appearance of the surface is retained without the need to Apply protective coatings that can be easily processed into a wide variety of everyday objects, and the good formability is characterized by high strength.

Embodiments of the invention are based on the following explained in more detail by graphic representations and microphotographs. It shows:

1 shows part of the ternary copper-aluminum-nickel phase diagram, in particular the area applicable to the alloy according to the invention, with one zone poor formability and a range of low film resistance is shown which for not alloys falling within the scope of the invention apply, and where the numerical values assigned to the points in the phase diagram are each the film resistance denote in kilo ohms;

Figure 2 is a graph of tensile strength properties above the annealing temperature for an alloy according to the invention;

7ü9 843/082 *

3 shows the fine structure of alloy C according to Table I. in the cast state;

FIG. K shows the fine structure of alloy B according to Table I in the cast state; FIG.

5 shows the fine structure of alloy B according to Table I in the quenched and tempered state; and

6 shows the fine structure of alloy B according to Table I.

in the hot-rolled, cold-rolled and annealed condition.

First, the alloy according to the invention will be described in its most general form; then a preferred embodiment will be discussed in more detail.

As shown in Fig. 1 by the areas within the parallelograms ABCD and EFGH, the alloy is composed of three components, namely copper, aluminum and nickel, the aluminum content in the range from 7.0 to 8.5 wt. 96 and preferably between 7.7 and 8.3 wt. 96 and the nickel content in the range of 1, ^F - 2.5 wt. 96 and preferably between 1.8 and ?, 2 wt. 96, during the The remainder consists essentially of copper. In addition to the substances mentioned above, the alloys according to the invention can contain impurities such as are normally found in commercially available copper-based alloys. These common contaminants can include lead, tin, phosphorus, iron, manganese, zinc and silicon for a total of 0.5% by weight.

The areas mentioned above with reference to FIG. 1 for the The aluminum, nickel and copper contents are of crucial importance for the following reasons. Aluminum contents of less than 7.0% by weight lead to a lower one

7 ir. 843/08 2 4

Resistance to tarnishing, the behavior of the alloys not being significantly better than that the well-known aluminum bronzes, e.g. those of type CA 61400ο have aluminum contents of over 8.5 wt .- # to a drastic reduction in the formability and ductility of the alloy due to the occurrence of the under Brittle intermetallic phases with a complex structure, known as beta and gamma. Furthermore, nickel contents lead of less than 1.5% by weight to a reduction in the Resistance to tarnishing as well as lower strength of the alloy, while nickel contents of over 2.5 wt .- # to the formation of too large amounts of intermetallic Lead nickel-aluminum compounds, which not only cause a reduction in formability, but the combine with some of the aluminum so that aluminum is removed from the solid solution, thereby increasing its resistance reduced against tarnishing. In Fig, 1 certain properties of alloys are shown, whose composition is outside the range according to the invention. Inside by the parallelogram ABCD-designated areas for the mentioned constituents can be the desired properties with regard to the resistance against tarnishing, formability and strength by further optimizing the fact that the aluminum content within the preferred range of 7.7-8.3% by weight and keeps the nickel content in the preferred range of 1.8-2.2% by weight, as corresponds to the parallelogram EFGH. the Not only must the alloy be in the range indicated by the parallelogram ABCD, but it must also have the capability have to form a stable oxide film with a film resistance of at least 95 kiloohms. Such a high film resistance can be obtained in an alloy according to the invention when it is used in the manner described below Treated The processes in question lead to the formation of a fine structure, which turns out to be an alpha-phase alloy matrix can be identified, the small amounts of a finely divided

7 ü : ■> 8 A 3/0 8 2 U

ten nickel-aluminum compound contains. Keeping the beta and gamma phases out of the alloy is in part for the to blame high resistance to tarnishing. Neither from the specialist literature nor from the state of the art It is known in the art that it is necessary to choose a particular composition as well as the structure to affect if a workable copper-aluminum-nickel -Alloy high resistance against tarnishing is to be achieved.

As mentioned, a special property is that of the invention Alloy can be attributed to the formation of a film consisting of reaction products, which has a high resistance against electrons and ions. It is crucial to achieve maximum resistance Meaning that metal ions are present in the correct amount in the film. The presence of one too large or one too small an amount of ions of a certain metal in the film leads to a lower film resistance and therefore too a faster oxidation, if the right amounts of the If metal ions are to be respected in the film, it is important that both the structure and the composition the underlying metallic alloy, the atoms of which are included in this protective oxide coating Requirements.

The electrical resistance of the protective oxide film can be measured using an electrochemical method called linear polarization. It has been found that, with the alloy according to the invention, a very high film resistance together with sufficient processability can only be achieved within the range of the composition according to the invention. The film resistance was determined by the fact that the alloy was subjected to an accelerated corrosion, whereupon the film resistor by means of linear polarization was measured _o Alloys

7 ti 343/0824

in which the content of aluminum and / or nickel was below the range according to the invention, the result is a lower film resistance, so that these alloys are not significantly better than the known commercially available aluminum bronzes. Alloys with a higher content of aluminum and / or nickel containing deleterious amounts of undesired phases, for example, the _o brittle gamma and Be ta-phase ,, If, for these unwanted phases in larger quantities exist, they lead to a drastic reduction in the processability and Malleability. It is therefore important to ensure that the alloys of the invention are kept free of the beta and gamma phases. Thus, according to the invention, a high resistance to tarnishing is achieved in an alloy by choosing a specific composition and by producing a specific structure through an appropriate treatment.

In the following the invention is illustrated in more detail by examples, however, to which the invention is not limited.

Example I Resistance to start-up

Alloys of the composition according to the following Table I were produced in that the metals mentioned under a charcoal blanket were melted together in a clay-graphite crucible. After thorough mixing were The batches were poured into steel molds. The resulting structure varied between essentially one single-phase structure according to FIG. 3 in the case of alloy C in the cast state and a two-phase structure according to FIG. 4 with an alpha phase and 1096 a beta phase in the as-cast state for alloy B. Because of the relatively fast Cooling during pouring, during which the

7GU343 / 0824

Components takes place, non-equilibrium structures occur in the cast alloy where there are phases that are not to be expected according to the equilibrium diagram, and there are local ones Composition differences from point to point in the alloy, known as coring are designated. These phenomena are sufficient to reduce the film resistance considerably below the values which can be achieved if the metal with regard to the distribution of the Alloy constituents is homogeneous. Furthermore, coarse grain boundary precipitations of a Niekel aluminum compound can lead to a low film resistance. this is illustrated by the information in Table I for the quenched and tempered condition of alloy B, in general a lower film resistance is found when the structure contains coarse precipitates, as shown in FIG Table 1 applies. If the nickel-aluminum compound is finely distributed throughout the structure, as is the case with alloy B is the case when it has been treated according to the invention as indicated in Table I for the hot rolled, cold rolled and annealed condition of alloy B, the structure of which can be seen from FIG. 6, there is an improvement in the resistance to tarnishing and mechanical properties. Confirm the information given in Table I on the film resistance the above findings.

70 ^ 843/0824

Table I. Film resistance, kilohms

cast hot and cold rolled alloy composition cast and tempered * and annealed 3 **

A 7.98% Al, 2.09% Ni, remainder Cu 57 93 105

3.28% Al, 2.46% Ni, remainder Cu 57 66 100

(Fig. 4) (Fig. 5) (Fig. 6)

C (hQ3) 7.68% Al, 1.91% Ni, remainder Cu 91 64 114

(Fig. 3)

D (LQh) 7.67% Al, 2.39% Ni, remainder Cu 62 85 117

^ Cast material, homogenized at 900 C for 1 hour, Quenched in water and then calcined at 525 ° C for 11 days.

♦♦ cast material at 900 - 600 ⁰ C hot-rolled, cooled in air, brought about by cold rolling to 50% of the cross section, 1 annealed at 700 ⁰ C, with two repetitions of the cold rolling and annealing.

-with.

It should be noted that even if the alloy contains the correct ingredients in the ranges given, the purpose of the invention is only achieved if the alloy contains neither the gamma nor the beta phase, and when most of the aluminum is in solid solution, any excess aluminum and Nickel is distributed in the form of a fine nickel-aluminum dispersion within the entire matrix of the solid solution.

A composition of the alloy, the 7.7 - 8.3 Gewr96 aluminum and contains 1.8-2.2 wt. 96 nickel, with the remainder consisting of copper, apparently gives optimal results, however, high tarnishing resistance is within the entire larger range of 7.0-8.5 wt Aluminum and 1.5-2.5 wt. 96 nickel, with the remainder consisting essentially of copper, to be observed when the alloy a treatment according to the invention experiences »here the resistance of the alloy to tarnishing is considerably improved, so that it can be used indoors without Protective coatings can be used. Although the oxidation is very slow, the alloy eventually forms instead of the uneven and unsightly looking discoloration that occurs with most of the alloys currently in use copper-based creates a uniform film · This very desirable behavior of the alloy will not due to impurities present in the usual quantities like iron, zinc, manganese, tin, lead, silicon or phosphorus. The alloy can be made using the in Brassworks produce facilities available relatively easily. The malleability of the finished sheet metal and strip material meets the requirements of most users «,

When evaluating the copper-side corner of the copper-aluminum-nickel system, alloys with 6-10 wt Aluminum and 1-7% by weight nickel are possible. The best of these

7ü YES 3/08

Alloys in terms of film resistance and processability and formability were those in the preferred range of 7.7-8.3 wt% aluminum and 1.8-2.2 wt% Nickel. Alloys with this composition can be hot and cold rolled very well, they can be drawn or stretched and bending are well deformed, and they form an excellent film of under the influence of the environmental conditions high resistance »

Example II Tarnish Resistance

Alloys with the composition given in Table II below were produced from electrolytic toughening copper, nickel pellets and aluminum pellets. The procedure was as follows: copper rods were melted under a charcoal blanket and heated to about 1150 ° C; Part of the desired amount of aluminum or the entire amount of aluminum was added to the melt and stirred in at the same temperature; then nickel was added in the form of nickel pellets or a master alloy with 50% copper and 50% nickel, whereupon the melt was kept at a temperature of about 1095 1260 ^° C. until complete dissolution was achieved. Finally, the aluminum that was still required was added and stirred in. The melt became stable at a temperature of about 1150 ° C
in which she froze.

stabilized at about 1150 ° C and poured into a steel mold,

The ingots so produced were again at about 820 - heated 900 ⁰ C and up to hot-rolled to a cross-sectional reduction of at least 75%, wherein the finish rolling carried out at about 540 ° C. The material was then cold rolled from about 6.35 mm to about 3 mm thickness placed, for 45 minutes at about 710 ° C annealed brought by cold rolling to thickness about 1.5 now, 45 min again annealed at about 710 ⁰ C, and finally Cold-rolled to a thickness of about 0.75 mm "The tensile strength inherent" =

7lk: over 43/0824

Shafts were determined after cold rolling to 50% of the original thickness and after annealing at temperatures of about 275 and 680 ^° C. respectively. Samples of the various alloys were abraded with a silicon carbide abrasive and then subjected to an accelerated atmospheric corrosion test; alternated this moist from with dry periods, a weak sodium bisulfite solution was used which had been specifically set for the purpose to produce oxide films of the same type as they are on copper alloys after several years of outdoor use in an urban industrial environment.

The relative ohmic resistances of the oxide films on the alloy samples were measured using the electrochemical method known as linear polarization. Here is the ohmic resistance from a graphic representation of the DC current determined over DC voltage in a sample that is exposed to an electrolyte in which the Film is stable. The DC voltage is regulated with the help of a so-called potentiostat.

It has been shown repeatedly that the rate of corrosion and thus the speed of starting is inversely proportional to the resistance of the oxide film, and that the measurements of the film resistance give a picture of the crucial importance of the composition and the leather give the alloy according to the invention.

The data in Table II below show that in alloy compositions that are outside of the fiction , "(Within a wide range, film resistance values give that are significantly lower than with the alloys within the specified range,

The alloy / · 1 ·; inch of Table 11 is in the specified Area and 'eif.1 a relative film resistance of 13d KiIo

v · ■ ■ ', ι / η R? /,

-J- 27Ί5799 A

ohm; in the case of alloy F with an aluminum content below the stated range, a film resistance of only results 45 kilo ohms; in the case of alloy C with an aluminum content in the range mentioned, but in which the nickel content is above is within the range mentioned, the result is a film resistance of only 64 kiloohms; in the case of alloy H with an aluminum content, which is still in the range mentioned, but at its lower end, with the nickel content above that mentioned Range, the film resistance is only 52 kiloohms; in the case of alloy I, in the case of both the aluminum content and the nickel content is above the stated range, but only slightly above, the film resistance is only 91 kiloohms, and at the same time there is a considerable loss of formability and processability, the due to the presence of excessive amounts of beta and gamma intermetallic compounds with limited ductility is. In order to be considered tarnish-resistant according to the invention, the alloy must, as mentioned, have a film resistance of at least 95 kilo ohms, and preferably at least 100 kilo ohms.

Table II

Film resistance, alloy composition. Weight - # Kiloohm

E 90.22 Cu + 7.66 Al + 2.12 Ni 136

F 91.31 Cu + 5.85 Al + 2.84 Ni 45

G 86.78 Cu + 8.19 Al + 5.03 Ni 64

H 88.46 Cu + 7.32 Al + 4.22 Ni 52

I 85.87 Cu + 9.02 Al + 5.11 Ni 91

Example III Mechanical Properties and Formability

The alloys according to the invention, e.g. alloy E, are due to high strength, good ductility and good formability

7UU843 / 0824

labeled Fig. 2 illustrates the excellent mechanical Properties of alloy E according to Table II, which result after cold rolling. a reduction in cross section to 50% and when annealing at different temperatures can be achieved. The alloys listed in Table III below were produced in the same manner as in Example II, and they were examined for their mechanical properties and moldability. If the content is of aluminum and / or nickel above the specified values, as is the case with alloys G and I, the Ductility and formability decrease significantly. Is the The amount of aluminum and / or nickel, as in the case of alloys F and J, is below the values mentioned, although the ductility decreases to, but the strength suffers a significant loss. For comparison, Table III shows the properties of the commercially available ones Brass type 70/30 called.

7 u., 8 A 3/0 8 2

OO

O OO

Composition, Cu Weight-96
Al Ni Table III annealed 39 89.93 7.98 2.09 32 86.78 8.19 5.03 Tensile strength properties, Tensile strength
* speed, p elongation
kp / cm% 30th alloy 85.87 9.02 5.11 60.5 62 A. 91.31 5.85 2.84 * Stretching
border 64.6 50 G 90.30 5.89 3.81 37.2 66.8 64 I. 70Cu 30Zn 43.6 46.4 F. 47.8 50.6 J 12.6 34.4 260 32.7 9.8

Formability drawing Max. Einbeulhöhe

relationship

2.12
2.03
1.93
2.12
2.06
2.15

after Olsen

10.46

8.94

8.91 12.47 10.10 11.10 *

♦ Determination of the yield point for 0.2% elongation.

NO

cn

CD CD

Example IV Effect of Impurities

An alloy was made according to Example III containing 7.97% aluminum and 2.0396 nickel, the remainder being copper and the following impurities: 0.0396 lead, 0.03% tin, 0.03% phosphorus , 0.03% silicon, 0.05% iron, 0.05% manganese and 0.10% zinc »This alloy had the following mechanical properties: After cold rolling at 50% reduction in cross-section, the yield strength was about 80.1 kg / mm, the tensile strength about 99.1 kg / mm and the elongation 2.8%; after annealing at 700 ^° C., the yield point was about 32.3 kp / mm, the tensile strength about 59.7 kp / mm and the elongation 38.5% «. The maximum draw ratio was 2.12 and the Olsen bulge height was about 10.5 mm. The relative oxide film resistance had decreased slightly to 95 kilohms due to the presence of the impurities. Thus, the presence of a relatively large total amount of impurities did not lead to any deterioration in mechanical properties or formability as compared with the known alloys, and there was only a moderate decrease in tarnishing strength.

The patent attorney:

709843/0824

Claims (6)

Claims 1, copper alloy, characterized in that it essentially contains the following components in the mentioned quantities contains: Aluminum 7.0 - 8.5 wt _o -% Nickel 1.5 - 2.5% by weight Copper 89.0 -91.5 wt. -96, that the alloy has a film resistance of at least 95 kiloohms and that its fine structure is less than Contains 2 Vol-96 of the intermetallic beta and gamma phases. 2. Alloy according to claim 1, characterized in that it is the usual in commercial copper-based alloys contains typical impurities. 3β alloy according to claim 1 or 2, characterized in that that they contain contaminants from the lead, tin, phosphorus, iron, manganese, zinc and silicon and mixtures thereof Contains group in a total amount of 0.5 wt. 96 or less. 4. Alloy according to one of claims 1 to 3 »characterized through a film resistance of at least 100 kiloohms 5. Copper alloy, characterized in that it consists essentially of the following components in the specified quantities consists of: Aluminum 7.0 - 8.5 wt. 96 Nickel 1.5-2.5 wt. 96 Copper from 89.0 to 91.5 percent by _e -96, ORIGINAL INSPECTED and that it has a film resistance of at least 95 kilo ohms. 6. Alloy according to one of claims 1 to 5, characterized in that that it is a wrought alloy.