DE2543899C3 - Aluminum alloy electrical conductors - Google Patents

Description

The invention relates to electrical conductors based on an aluminum alloy with improved mechanical properties and electrical properties containing 0.1 to 0.7% magnesium, 0.1 to 0.6% silicon as well as iron and Contains nickel and / or cobalt.

The conductors according to the invention are primarily for house installations, for telephone cables and for manufacture mainly made of enamelled wires intended for windings.

The first overhead lines consisted of aluminum alloys or aluminum with <0.5% impurities or accompanying substances (A 5 / L) in the 4/4 "hard" condition. These conductors had a core made of steel in aluminum. Homogeneous conductors with greater strength (A-G S / L) then contained about 0.7% magnesium, about 0.6% Silicon and up to 0.35% iron.

This alloy can obtain corresponding mechanical properties, namely breaking load σβ35 kg / mm ² and elongation 7%, through heat treatment, namely solution annealing, quenching, drawing and artificial aging. The specific resistance ρ 3.25 μΩ cm is, however, much higher than that of A 5 / L

The use of aluminum alloys as conductor material was then applied to insulated cables Power transmission extended, for which the alloy A 5 / L was generally used.

For other electrical applications than power lines or insulated cables such as for house installation or telephone cable is needed a twist that one Has electrical conductivity similar to that of alloy A 5 / L, but with the same elongation (approx 10%) higher breaking strength possesses other properties such as flow behavior, foldability and drawability at high speed are also required

It is known (FR-PS 20 53 838 and FR-Note 72 12 569), the alloy for these applications AGS / L to be used, but in such a metallurgical state that the electrical conductivity increases and their breaking strength is reduced compared to AGS / L for overhead lines.

It is known that alloys containing Mg and Si improved mechanical properties can be obtained by hardening. Such a heat treatment includes the following stages:

1. Solution heat treatment for intermetallic compounds of the cast structure. In the case of A-GS / L it acts is the intermetallic compound Mg2Si and the temperature for the solution heat treatment is 500 up to 600 ° C;

2. Quenching, whereby the elements of the intermetallic compound are in supersaturated solution remain;

3. Hardening by artificial aging at around 165 ° C, whereby magnesium and silicon precipitate as a needle phase / J'Mg2Si.

The mechanical and electrical properties of the alloy A — GS / L develop around this as follows:

4 ^r > quenched, artificially aged:

Breaking strength 22 kg / mm ²

Elongation at break 20%

spec. Resistance 3.6 μΩ cm

drawn, artificially aged:
Breaking strength 35 kg / mm ² breaking elongation 7%
spec. Resistance 3.25 μΩ ■ cm

The comparison shows that the specific electrical resistance of the quenched metal, the Magnesium and silicon in solid solution is considerably higher than that of the artificially aged Metal in which the intermetallic compound Mg2Si has partially precipitated out of the solid solution.

The following heat treatment is known from FR-PS 20 53 838:

Solution annealing and quenching of the wire rod, drawing of the wire rod to its final thickness, Recrystallization (2 to 4 hours at 250 ° C).

bo Through this heat treatment, a wire is obtained that fully meets the requirements of "cahier des charges provisoire UTE" for wires made of aluminum alloys for house installation. This regulation requires that the elongation is> 5%, whether 15.9 kg / mm ² and ρ <2.95 μπιΩ · cm.

This good combination of mechanical and electrical properties is based on partial recrystallization of MgiSi to a considerable extent in the

final heat treatment, whereby the specific resistance is reduced.

The FR note 72 12 569 it can be seen that, surprisingly, similar properties can be achieved with the alloy A — GS / L, which is not quenched and is produced by continuous casting, e.g. B. on a Properzi machine is obtained. It is sufficient in this case to move on such a wire directly to keep desired final thickness, and finally a few hours at 250 ⁰ C to ρ, for example, an elongation of 6%, o _B 16-18 kg / mm ² and 2.85 -230 μβ cm.

While these ways of working are interesting, they have one drawback:

The conditions of the final heat treatment for the combination of mechanical and electrical properties are not "convenient". This concept of a lack of "comfort" expresses the fact that even slight fluctuations in the conditions of the final treatment (time and, above all, temperature) result in considerable fluctuations in the values for ob and D. In other words, the slope of the curves aefCo and D = g (T) at constant time (T = temperature) is large in the area of the breaking loads and elongations, which are important for the new areas of application. It is known that in practice it is difficult - especially with rings - to maintain absolutely precise treatment temperatures and times.

In addition, there are irregularities in the heating, quenching or cooling speed of the individual windings in the ring also on the drawn wire due to irregularities in the mechanical and electrical properties.

From FR-PS 21 40 481 a huge variety of aluminum alloys is known, in which in addition to Nickel and iron one or more alloying elements from a total of 33 in an amount of a maximum 2% can be present, any relation of the individual alloy elements to one another is this patent specification not to be found.

The object of the invention is an alloy of the type AGS / L with iron, nickel and / or cobalt, which one has improved "comfort" and a combination of mechanical and electrical properties shows which corresponds better to the intended use.

The invention is based on a conductor, in particular a wire, based on an aluminum alloy which, in addition to the usual accompanying elements, contains 0.10 to 0.70% magnesium, 0.10 to 0.60% silicon and iron and nickel and / or Contains cobalt; it is characterized in that the weight ratio Si: Mg is given by the relationship (Si) -0.59 (Mg) <0.25% and the iron is almost exclusively as an intermetallic compound Al - F - Ni or Al - Fe - Co is present, contains 0.1 to 0.6% iron and 0.05 to 0.6% nickel and / or cobalt and the weight ratio ^Nl + ^{Co is} 0.5 to 1.5 and

MgzSi is partially eliminated.

It has been shown, surprisingly, that you get better mechanical properties with appropriate Conductivities, in particular increased elongation without a decrease in conductivity, can be achieved at quite certain coordination of the individual alloy elements and the precipitation of Mg2Si. In other words, in the conductors according to the invention, not only is the coordination of some alloying elements with one another, i.e. the chemical analysis, but also the microstructure, i.e. in what form precipitations of which metals are present, is essential. Only if these conditions are observed will the unexpected results with the inventive Get ladders.

The final heat treatment takes place at 200 to 400 ° C

The alloys according to the invention are processed into any optionally insulated conductors, for example on wires, narrow rails and cables.

The influence of iron and nickel on the conductivity of aluminum was mainly discussed by G. G. Gauthier in "The conductivity of super-purity aluminum: the influence of small metallic additions," Journal of Institute of Metals No. 2, Vol. LIX-1936, pages 129 and 150, who comes to the following conclusions that the elements are divided into three groups can, with little effect (gold, gallium, nickel, silicon, iron and zinc), with more effect (Copper, silver and magnesium) and with considerable effect (titanium, vanadium, manganese and chromium).

This low influence of iron and nickel on the conductivity of the alloy is the result of the low Solubility in the aluminum matrix and its presence in the alloy in the form of irreversible dispersed precipitates, d. H. that no heat treatment will practically bring them back into solution can.

These dispersed or dispersoid precipitates contribute to the improvement of the mechanical Properties as well as the combination of breaking strength + elongation, which are mainly in the recrystallized and partially recrystallized state are important.

According to the invention, the effect of the reversible Mg2Si dispersoid is combined with the effect of the irreversible Dispersoids from the elements aluminum, iron, nickel and cobalt combined Surprisingly shown that the alloy comprising both types of dispersoids, the desired "Convenience" of the final heat treatment as well as improved properties at the same time Retention of the properties of the hardened alloys A — GS / L Presence of irreversible dispersoids with regard to the homogeneity of the final properties large-scale production important. To get better combinations of mechanical properties with To achieve electrical properties, some conditions must be met according to the invention:

1. The amount of free silicon, that is to say that is present in excess over the stoichiometric compound Mg ₂ Si, should not amount to more than 0.25%, in other words the relationship applies

(Si) -0.58 (Mg) <0.25%

60 should be 0.5 to 1.5,

2. The weight ratio ^ y ^
preferably about 1.

Under these conditions, the only compounds that occur are Mg ₂ Si and aluminum-iron-nickel or aluminum-iron-cobalt, but not <x-Al — Fe Si, which is very favorable for the satisfactory mechanical and electrical properties.

If these conditions are met, one obtains

especially for wires with a thickness of 0.05 to 6 mm, conductivities according to IACS of 57% (3.02 μΩ cm), which can also exceed 59.5% (2.90 μΩ cm), and breaking strengths of 13 to 19 kg / mm ² and elongations - measured on a 200 mm test specimen - of more than 5%.

One can do without the properties of the alloy change, add a certain number of elements, especially copper <0.2%, boron <0.1%, beryllium <0.1%, cadmium <0.1%, antimony <0.1%, rare earth metals <0.5% and zirconium <0.1%.

The manufacture of the conductors according to the invention comprises a treatment at a relatively high temperature for the partial precipitation of the intermetallic compound Mg ₂ Si after cold forming (partial recrystallization).

To produce wire, wire rod (7.5 to 12.5 mm in diameter) is produced in the usual way, for example round billets are cast semicontinuously or by pouring water and these are drawn into wire. Two » square billets can also be rolled on a rolling mill; however, casting the alloy on a cooled copper wheel is preferred. This gives an approximately trapezoidal cross-section. The wire is cut to the required size and then wound up on a series of drawing or rolling stands with either 2 ¹ S three rolls (PROPERZI) or with calibres (SPIDEM). When potting between the wheel and the roller with subsequent rolling, the wire is preferably quenched after the roll stand on z. B. in below 150 ⁰ C.

The wire rod obtained in this way is then drawn to its final thickness and subjected to the final heat treatment for partial recrystallization of Mg2Si. This happens at 200 to 300 ⁰ C; the wire rings then remain 1 to 12 in the oven.

It is also possible to work continuously, for example by automatically heating the wire using Joule heat or, for the production of coated wires, by running the wire through a coating oven. In these heat treatments, the throughput time is very short (for example in the order of 1 min) and the metal temperatures are higher, in particular up to 400 ^° C., and the furnace temperatures can even be considerably higher.

The amount of Mg2Si precipitated is less than at temperatures of 200 to 300 ° C, because the solubility of the components in aluminum increases with temperature, but interesting combinations of mechanical properties are achieved in this way: ρ <3.02 μΩcm with breaking strengths of 13 to 19 kg / mm ² combined with an elongation (200 mm) of> 5%.

Surprisingly, the mechanical properties are extremely little affected by the throughput time of the wires affected by the ovens. The wire enamel is particularly interesting because this is where the Pulling the wire through the painting furnace is used as a final heat treatment.

For ladder rails, one starts with strips (for example hot-rolled strip), which are then cold be reshaped, for example by rolling to the final dimension without quenching and without in between to temper or to warm out. This is followed by the final heat treatment above. b5

The electrical conductors according to the invention can be thin strips for windings, multi-core Cables, connecting rods, rails, sheaths and the like.

act, as they do in house installation, as telephone cables and wire windings, especially painted, find diverse uses.

The invention is illustrated by the following examples:

example 1

The following melts (remainder AI with companions) were produced (% by weight):

a b 1 2 3 4th Mg 0.38 - 0.40 0.42 0.41 0.30 Si 0.44 - 0.43 0.26 0.45 0.20 Fe 0.21 0.50 0.23 0.53 0.53 0.50 Ni - 0.53 0.21 0.53 0.53 0.53

To separate the main part of titanium and vanadium, boron is treated as usual and billets - 100 mm 0 - are cast semicontinuously using the water casting process, and these are pressed into wires - 9.5 mm 0. Then, it is drawn to 2mm0 without intermediate annealing or quenching or the like. Six samples were taken from this wire. A test piece was not treated and the other finally 3 hours at 220 ⁰ C, 240 ⁰ C, 260 ° C, 280 ° C or 300 ° C retained, after which the breaking strength _ft o elongation D (test length 200 mm) and the specific Resistance ρ were determined. For the same alloy, each type of final heat treatment resulted in different combinations of σ » D and ρ.

One can thus compare D with constant ob, Q with constant σ β etc. for the different alloys.

In all tables, ob is given in kg / mm ² , D in% and ρ in μΩ · cm.

Elongation against breaking load

20th 18th 16 14th 12 kg / mm ² a 4th 4.4 5.6 8.5 16.4% b 5 5.2 6.7 14th 26% 1 4.8 7.4 8th 14th -% 2 3.6 6.0 8.8 16.4 28.8% 3 6.8 7.8 9.8 18.4 -% 4th 6.6 7.6 10.4 17.2 31.6%

The first two lines show the alloy A-GS / L (a) and aluminum-iron-nickel (b) according to the prior art and the four further lines show the alloys according to the invention (1 to 4). The comparison shows that in the range ob = 14 to 18 kg / mm ² - which is important for the intended application, namely wires for household appliances - the elongation values of the alloys according to the invention are considerably higher than those of the prior art alloys.

Specific resistance (μι · ■ cm) against breaking load

20th 18th 16 14th 12 kg / mm ² a _ 2.801 2.791 2.785 b 2,840 2.824 2.809 2,800 2.791 1 2.814 2.804 2,798 2,795 - 2 - 2.856 2.846 2.837 2.837 3 - 2.861 2.854 2.845 - 4th - 2.851 2.839 2.827 2.825

It is found that the particularly interesting Combination of the above and D obtained with these new alloys in a slight increase the specific resistance, which however remains considerably below the maximum value, which according to "cahier des charges provisoire UTE" is fixed at 2.95 μπιΩ · cm.

If one compares alloy 3, which is less good in terms of conductivity, with alloy b according to the prior art, it is found that the elongation increases ^{at a breaking strength of 18 kg / mm 2}

7.8% - 5.2%
5.2%

= 50%

while increasing the resistivity only

2.861-2.824
2.824

= 1.3%

matters.

Example 2

As in the previous example, 5 alloys were cast into billets with a diameter of 100 mm. the Comparative alloy c contained 0.51% iron, 0.53% nickel, the remainder aluminum with usual companions. the other alloys were in accordance with the invention and had those in Example 1 for alloys 1, 2, 3 and 4 specified composition. The billets were pressed into wires with a diameter of 9.5 mm.

Without intermediate annealing or quenching and without renewed starting of the wire at 0.5 mm 280 was pulled and 6 test specimens, of which one was untreated and the other to a final heat treatment of 3 hours at 220 ⁰ C, 240 ⁰ C, 260 ° C, ° C and 300 ° C.

The elongation values at constant breaking strength are just like for wire with a diameter of 2 mm for the alloys according to the invention are considerably higher than in the case of the comparison alloy c according to the prior art Technology.

Specific resistance to breaking load

20th

18th

14th

12 kg / mm ²

The resistivity of the invention

Alloys increases slightly, but this stands

Increase out of proportion to the increase in

Strain. The increase in specific resistance

^r > is only 2.2% in the worst case.

Example 3

The comparison alloys a and b of Example 1 and an alloy d containing iron 0.48%, silicon

ίο 0.06%, cobalt 0.54%, remainder aluminum with usual Companions were cast into billets - 0 100 mm. The alloy 5 according to the invention contained 0.41% magnesium, 0.44% silicon, 0.22% iron, 0.22% cobalt, the remainder aluminum and companion. The clubs

i ") were added to a wire rod - 0 9.5 mm -. pressed and this drawn without preliminary or intermediate heat treatment up to 0. 2 mm, as in the previous examples were specimens of the final heat treatment for 3 hours at 22O ⁰ C, 240 ⁰ C , 260 ° C

2 »or 280 ° C and determined the properties.

Elongation against breaking load

ill

20th 18th 16 kg / mm ² a 4th 4.4 5.6% b 5 5.2 6.7% d - 2.0 6.7% 5 5.4 6.4 7.8%

r> Alloy 5 shows significantly improved elongation values compared to the alloys according to the prior art.

Specific resistance to breaking load

20th

16 kg / mm

Stretching against 20th Breaking load 16 14th 12 kg / mm ² a
b 43 L. jl) 2.8 18th 4.3 15.2 -17% d
5 ever C. -5.5 3.6 8.3 13.8 -20% di 1 -3.2 6.5 10.4 17.8 > 25% 2 -6.6 5.2 12.6 17.8 > 22% 3 -5.0 8.8 9.8 17.6 > 23% 4th 6.6

- 2.801 2.824 2.809 2.818 2.805 2.817 2,795

2,840

The specific resistance of the alloy according to the invention is of the same order of magnitude, isl but somewhat less than the prior art alloys.

Example 4

On a continuous casting and rolling plant, wire rods - Ø 12.5 mm - from the following Alloys made (remainder Al with companions):

55 feet
^b0 Si
Ni
Mg

0.25
0.42
0.01
0.42

0.22
0.37
0.23
0.39

0.54% 0.39% 0.53% 0.41%

C. 2.856 2.838 2.820 2.797 1 - -2.810 2.804 2.803 2 - 2.860 2,850 2.851 3 - 2,868 2.857 2.860 4th - 2,878 2.853 2.843

- The various melts were poured into the throat — 2.830 65 of a copper wheel, which was injected into the mold

Water was chilled. The cross-section of the trapezoidal blank was about 10 cm ² . This blank was

- on 8 caliber rollers first to an oval and then ζ

an approximately round cross-section - 0 12.5 mm - rolled. Without further heat treatment of the wire rod was then pulled mm 2 and 3 h held at 28O ⁰ C, were determined after which fracture strengths, elongation and resistivity.

13th
13th
13th

13% 16% 22.5%

2.825 2.845 2.900

The comparison shows that alloys 6 and 7 according to the invention, with the same breaking strength of 13 kg / mm ^{2, have} considerably higher elongation values than comparison alloy e (A-GS / L). This leads to a somewhat higher specific resistance, which, however, in the worst case does not exceed 2.7%.

Example 5

A wire made of alloy 4 of Examples 1 and 2, reshaped to 0 0.5 mm according to Example 2, was Immediately after drawing in a 5 m long oven, the temperature of which is between 200 and 400 ° C lay.

The following properties were found at different running speeds:

Running speed

O\\

26 m / min
22 m / min
18 m / min
14 m / min

16.3
16.5
16.2
16.3

15.5
16.0
15.5
15.5

2.889 2.916 2.920 2.929

ίο As you can see, the properties are excellent and are very little influenced by the running speed.

Example 6

The wire made of alloy 4, formed according to Example 2 to 0 0.5 mm; was in a resistance furnace continuously started; the running speed was constant. By regulating the furnace accordingly the extent of tempering and thus the properties change. For these different ones Oven conditions result in the following wire properties:

oven 17.4 D. 2.945 25th condition 16.8 2.960 1 16.5 6.5 2.965 2 16.8 9.0 3.005 30th 3 14.5 4th 14.0

The comparison shows that greater elongation does not lead to a deterioration in strength.

Claims (6)

Patent claims: 1. Electrical conductors based on an aluminum alloy containing 0.10 to 0.70% magnesium, 0.10 up to 0.60% silicon and iron and nickel and / or cobalt, characterized in that the Weight ratio Si: Mg is given by the relationship (Si) -0.58 (Mg) <0.25% and the iron is almost exclusively present as an intermetallic compound Al — Fe-Ni or Al-Fe-Co, 0.1 to 0.6% Fe and 0.05 to 0.6% Ni and / or Co are contained and the ratio <0.5 to 1.5 and Mg2Si is partially excreted 2. Electrical conductor according to claim 1, characterized in π characterized that the ratio is 0.8 to 1.2 3. Electrical conductor according to claim 1 or 2, characterized in that the aluminum alloy contains at least one of the following elements: copper <0.2%, boron <0.1%, beryllium <0.1%, cadmium <0.1%, antimony <0.1%, rare earth metals <0.5%, zirconium <0.1%. 4. A method for producing the ladder according to any one of claims 1 to 3, characterized that the cast aluminum alloy after hot forming and cold forming for partial precipitation and recrystallization 1 to 12 hours at 200 to 300 ° C 5. A method for producing the conductor wires according to any one of claims 1 to 3, characterized characterized in that the cast aluminum alloy after continuous casting, rolling and Pulling the wire rod for partial precipitation and recrystallization from 1 to 12 h for 200 to Holds 300 ° C. 6. Modification of the method "according to claim 5, characterized in that the final Heat treatment after continuous casting, rolling and drawing of the wire rod continuously up to 400 ° C.