EP0679727A2 - Method for producing a copper-nickel-silicon alloy and use of the same - Google Patents

Abstract

The mfr. of a copper-nickel-silicon alloy with compsn. 1.5-5.5% Ni, 0.2-1.0% Si, 0-0.5% Fe, 0-0.1% Mg and balance Cu comprises: (a) casting the alloy; (b) soln. annealing to 700-900 degrees C for 14 hrs.; (c) cold rolling with a redn. of at least 80%; (d) heating up to 950 degrees C; and (e) cooling at up to 100 degrees C/min. to at least 350 degrees C.

Description

The invention relates to a method for producing a copper-nickel-silicon alloy with a composition Cu (balance), Ni 1.5 - 5.5%, Si 0.2 - 1.0%, Fe 0 - 0, 5%, Mg 0-0.1% (all figures in percent by weight). Alloys of this type have been known for a long time and are used with or without further additives, in particular as a conductor material in electrical engineering, in particular as a conductor material for electronic components.

DE-AS 1 278 110, for example, describes a copper-nickel-silicon alloy consisting of 2% Ni and 0.5% Si, the rest being copper, in which, however, the deformability is assessed as very poor while having good strength . This publication also describes copper-nickel-silicon alloys (CuNiSi), in which the addition of small amounts of chromium is essential. These alloys have good cold formability, whereas the question of conductivity plays no role in the application described there.

From DE 34 17 273 A1, a copper-nickel-silicon alloy with the addition of phosphorus as an electrical conductor material is also known. This alloy focuses on good electrical conductivity with sufficient strength.

The invention, on the other hand, turns to another technical field. It should be used where there is good electrical conductivity, good cold formability during the process and very high Yield strength arrives, with the peculiarity that the yield strength of the alloy increases when cooling from high temperatures. A preferred field of application of the invention is therefore in metal housings capable of pressure glazing, in particular those in which a hermetic seal of the pressure glazing in the housing is important.

The object of the invention is therefore to provide a method with which a copper alloy can be produced which increases its yield strength during cooling and which, in addition to a very high yield strength, has good conductivity (electrical and thermal) and cold formability.

• a) Guß der Legierung
• b) Lösungsglühen bei 700 - 900 °C während 14 bis 1 Stunde
• c) Kaltwalzen mit einer Reduzierung von wenigstens 80 %
• d) Aufheizen auf 950 °C
• e) Abkühlen mit höchstens 100 °C/Min auf mindestens 350 °C.

According to the invention, such an alloy (CuNiSi) of the composition mentioned at the outset is produced using the following process steps.

• a) Cast the alloy
• b) Solution annealing at 700 - 900 ° C for 14 to 1 hour
• c) Cold rolling with a reduction of at least 80%
• d) heating to 950 ° C
• e) cooling at a maximum of 100 ° C / min to at least 350 ° C.

What is essential for achieving a high yield strength, which, as will be explained below, differs surprisingly from that of conventional CuNiSi alloys, is heating and cooling the alloy in accordance with features d) and e). The value of 950 ° C should be approximately maintained, ie with a tolerance limit of 20 to 30 ° C. It is also important for the remarkably high yield strength that additives to other elements are only present to a very limited extent, but are preferably avoided entirely. The procedural step b) Solution annealing is advantageous, but not essential in the sense of the invention.

The cooling rate in process step e) should be at most 100 ° C./min, preferably lower but not higher.

The alloys produced by the process according to the invention reach yield strengths of 400 to 450 N / mm². The conductivity reaches values up to a maximum of about 36% IACS.

A further improvement in the abovementioned properties of the alloy is achieved by additional aging of the alloy after it has cooled. This aging takes place in a development of the invention at 300 to 600 ° C for a period of 8 to 1 hour. The yield strength values rise up to 550 N / mm², the conductivity reaches values up to 50% IACS. Proportional to the electrical conductivity, the thermal conductivity increases from around 150 W / m ° k to values of 200 W / m ° k.

According to a further development of the invention, the deep-drawing ability of the alloy is improved in that an intermediate soft annealing step is switched on at 400 ° C. to 750 ° C. for 8 hours to 1 minute after the cold rolling.

Further developments of the invention provide for hot forming and forging after the alloy has been cast.

According to a further embodiment of the invention, the yield strength, high conductivity and good cold-formability of the alloy with a composition of Cu (rest), Ni 1.8-4.7%, Si 0.4-0.9%, Fe 0-0.1 %, but the composition Cu (balance), Ni 2.3-4.5%, Si 0.4-0.9% is particularly preferred.

The invention will be explained in more detail below with reference to the drawings.

Abb. 1

den Zusammenhang zwischen Streckgrenze und Nickelgehalt,

Abb. 2

den Zusammenhang zwischen Leitfähigkeit und Nickelgehalt,

Abb. 3

den Zusammenhang zwischen Kaltverformbarkeit, Streckgrenze und Nickelgehalt bei konstant Si 0,7 %,

Abb. 4

den Nutzungsbereich der Legierung in Abhängigkeit von Nickel- und Siliziumgehalt,

Abb. 5

den Zusammenhang zwischen Streckgrenze und Leitfähigkeit und Auslagerungstemperatur,

Abb. 6

den Einfluß von Zusätzen auf die Streckgrenze.

Show it:

Fig. 1

the relationship between the yield point and the nickel content,

Fig. 2

the relationship between conductivity and nickel content,

Fig. 3

the relationship between cold formability, yield strength and nickel content at constant Si 0.7%,

Fig. 4

the area of use of the alloy depending on the nickel and silicon content,

Fig. 5

the relationship between the yield strength and conductivity and aging temperature,

Fig. 6

the influence of additives on the yield strength.

When examining the alloys, it was surprisingly found that intermediate annealing at a temperature of approximately 950 ° C. and certain cooling to approximately 350 ° C. resulted in an unusual increase in the yield strength. A high yield strength, which arises with increasing tendency in the cooling of the alloy from high temperatures, is essential for those applications where the alloy is used to manufacture housings in which the wire feedthroughs take place from the outside into the interior of the housing in the form of pressure glazing (hybrid housing ). The pressure glazing and its problems are in detail described in more detail, for example, in patent application P 42 19 953.0. Due to the high yield strength of the proposed alloy, there is still sufficient residual stress when the metal is cooled after the pressure glazing in order to achieve a hermetic seal in the area of the pressure glazing. This high yield strength is accompanied by very good electrical and thermal conductivity. In connection with a previous thermoforming cut, it is also possible to forge the alloy instead of deep drawing.

Tables 1 and 2 show the alloys examined with their composition and the resulting properties. Table 1 Alloys Leg.No. Cu Ni Si Mg Fe 1873 98.26 1.01 0.64 1874 97.61 1.70 0.65 1875 96.92 2.42 0.65 1876 96.20 3.15 0.65 1877 95.48 3.85 0.66 1878 94.70 4.57 0.70 1879 93.98 5.30 0.66 1880 98.98 0.56 0.37 1881 98.15 1.36 0.38 1882 97.51 2.09 0.36 1883 96.82 2.50 0.67 1884 97.57 1.86 0.52 1885 98.76 0.96 0.27 1886 95.60 3.50 0.95 1887 94.28 4.60 1.16 1898 96.61 2.99 0.39 1899 95.10 4.50 0.41 1900 96.84 2.27 0.86 1901 94.96 4.08 0.89 1902 94.12 4.96 0.90 1903 93.24 5.83 0.86 1904 97.17 2.38 0.47 1905 96.26 3.28 0.47 1906 95.37 4.07 0.49 1908 96.72 2.75 0.56 1892 96.73 2.5 0.7 0.052 1909 96.71 2.52 0.70 0.029 1910 96.82 2.46 0.67 0.056 1896 96.64 2.48 0.7 0.11 1911 96.30 2.55 0.68 0.46 1912 96.01 3.30 0.66

The following tendencies regarding conductivity, yield strength and cold formability can be seen from the above test results.
If the silicon content is kept constant, conductivity (electrical and thermal) and yield strength increase with increasing nickel content (with the exception of the alloy with 0.4% Si).
If the nickel content is kept constant, these values increase with increasing silicon content.
The cold formability becomes better with decreasing silicon content and / or with decreasing nickel content.

It was also found that a further increase in the yield strength and conductivity can be achieved by aging after the targeted cooling.

The tables also show that the preferred usable range of the composition of the alloy for nickel is about 1.8 to 4.7% and that of silicon is 0.4 to 0.9%, the rest copper. An addition of iron of up to 0.1% leads to a slight increase in the yield strength, which decreases again with higher iron contents. The same applies to magnesium, in which up to 0.07% of the yield point can be increased, but with higher magnesium contents this drops sharply. Additions of other elements such as P, Cr, Mn, Zr, Al and Ti are conceivable, but they significantly reduce the yield strength and are therefore not advantageous for this reason alone.

One explanation for the increase in the yield strength with increasing nickel content can be seen in the fact that more and more nickel silicides separate out at the grain boundaries. This creates a grain boundary hardening, which brings about the effect of increasing the yield strength. If the nickel content is too high, the precipitations increase the grain boundaries together, the resulting brittleness of the alloy prevents good cold formability. See also Fig. 1 and 3. If the nickel content or the silicon content is too low, the yield strength drops too much, the alloy is no longer usable for the intended application. From Fig. 1 it can be seen that with a constant silicon content, the yield strength increases very steeply within a small range of changes in the nickel content. In the area of this steep rise, namely at its upper end, the particularly preferred composition of the alloy is to be sought for the intended purpose. Fig. 2 shows that, with the exception of alloys with a silicon content of 0.4% (or below), the conductivity in the preferred ranges of the nickel content also takes very good values.

Fig. 3 shows the cold formability and the change in the yield strength with a constant silicon content of 0.7% depending on the changing nickel content. It can be seen that the cold deformability is approximately inversely proportional to the change in the yield strength.

In Fig. 4, the two outer curves enclose the area "A" that can be used by the alloys described, which is between 0.2 and 1.0% in a region of silicon and between 1.5 and about 5.5% for nickel. lies. The particularly preferred range "B", in which high yield strength combined with high conductivity and good cold formability is between 0.4 and 0.9% Si and 2.3 and 4.5% Ni. It can also be seen from the figure that the Ni / Si ratio can vary within wide limits between 1.6 and 11.2%, preferably between 2.5 and 11.2%.

Fig. 5 shows the dependence of the yield strength and the, shown on the alloy No. 1876, with a composition Cu (rest), Ni 3.15%, Si 0.65% Conductivity from aging temperature, the last step in the manufacturing process. It can be seen from the figure that beginning with aging at a temperature of 350 ° C, the yield strength increases from about 510 to about 570 N / mm² at a temperature of 500 ° C and then drops steeply. In terms of conductivity, the increase in the same temperature range is much steeper to 50% IACS with a drop at higher temperatures.

Finally, Fig. 6 shows the influence of additions of magnesium and iron to the proposed alloy. It can be seen that the additives are only very weak and only effective up to small additions.

• a) Guß der Legierung
• b) Lösungsglühen bei 700 - 900 °C während 14 bis 1 Stunde
• c) Kaltwalzen mit einer Reduzierung von wenigstens 80 %
• d) Aufheizen auf 950 °C
• e) Abkühlen mit höchstens 100 °C/Min auf mindestens 350 °C.

The proposed method for producing the alloy is basically built up from the following steps.

• a) Cast the alloy
• b) Solution annealing at 700 - 900 ° C for 14 to 1 hour
• c) Cold rolling with a reduction of at least 80%
• d) heating to 950 ° C
• e) cooling at a maximum of 100 ° C / min to at least 350 ° C.

By adding a process step f), namely aging the alloy at 300 to 600 ° C. for 8 to 1 hour, the improvements mentioned in conductivity and increase in yield strength occur.

By inserting a step g) between steps c) and d), namely soft annealing at 400 to 750 ° C. for 8 hours to 1 minute, a subsequent deep drawing according to step h) is promoted. When inserting a step i) thermoforming according to a) or b), the alloy is also forged [process step hh) instead of h)] possible.

• Gießen der Legierung in einer Kupferkokille
• Lösungsglühen bei 800 °C während 4 Stunden
• Fräsen an 115 x 39 x 11 mm
• Kaltwalzen von 11 mm an 0,5 mm
• Glühen bei 575 °C während 4 Stunden
• Tiefziehen
• Aufheizen auf 950 °C
• Abkühlen auf etwa 300 °C in 25 Minuten
• Abkühlen in Luft
• Auslagern bei 400 °C in 8 Stunden.

A sample production of the proposed alloy with a composition Cu (rest), Ni 2.9%, Si 0.67% was carried out as follows.

• Pour the alloy in a copper mold
• Solution annealing at 800 ° C for 4 hours
• Milling on 115 x 39 x 11 mm
• Cold rolling from 11 mm to 0.5 mm
• Annealing at 575 ° C for 4 hours
• Deep drawing
• Heating up to 950 ° C
• Cool to about 300 ° C in 25 minutes
• Cooling in air
• Storage at 400 ° C in 8 hours.

The solution annealing process step has proven to be advantageous, but not mandatory, for sample production. This process step is common in the production of copper-nickel-silicon alloys, but in the sense of the invention it may also be unnecessary.

In step e), after the fairly rapid cooling to 350 ° C., a slow cooling to room temperature is advantageous. This can be done by cooling in air or in a cooling section.

Claims (10)

Process for producing a copper-nickel-silicon alloy with a composition Cu (balance), Ni 1.5 - 5.5%, Si 0.2 - 1.0%, Fe 0 - 0.5%, Mg 0 - 0.1%,
characterized by the following process steps a) Cast the alloy b) Solution annealing at 700 - 900 ° C for 14 - 1 hour c) Cold rolling with a reduction of at least 80% d) heating to 950 ° C e) cooling at a maximum of 100 ° C / min to at least 350 ° C. Method according to claim 1 with an alloy of the composition mentioned therein,
characterized by the following process steps a) Cast the alloy b) Solution annealing at 700 - 900 ° C for 14 to 1 hour c) Cold rolling with a reduction of at least 80% d) heating to 950 ° C e) cooling at a maximum of 100 ° C / min to at least 350 ° C f) aging of the alloy at 300-600 ° C for 8 to 1 hour. Method according to one of claims 1 and 2 with an alloy of the composition mentioned therein,
characterized by the following process steps a) Cast the alloy b) Solution annealing at 700 - 900 ° C for 14 to 1 hour c) Cold rolling with a reduction of at least 90% g) Soft annealing at 400 - 750 ° C for 8 hours to 1 minute h) deep drawing d) heating to 950 ° C e) Cooling at about 30 - 40 ° C / min to at least 350 ° C f) aging at 300 - 600 ° C for 8 to 1 hour. Method according to one of claims 1 to 3 with an alloy of the composition mentioned therein,
characterized,
that a procedural step i) thermoforming after a) or b) is switched on. Process according to claims 3 and 4,
characterized,
that instead of process steps g) and h) a process step hh) forging is provided. Method according to one of claims 1 to 5,
characterized by the application of the process steps to an alloy of the composition Cu (rest), Ni 1.8 - 4.7%, Si 0.4 - 0.9%, Fe 0 - 0.1%. Method according to one of claims 1 to 5,
characterized by the application of the process steps to an alloy of the composition Cu (balance), Ni 2.3 - 4.5%, Si 0.4 - 0.9%. Method according to one of claims 1 to 5,
characterized by the application of the process steps to an alloy of the composition Cu (balance), Ni 2.9%, Si 0.7%. Use of an alloy produced by the method according to one of claims 1 to 8 for the production of pressure-glazed housings. Use of an alloy produced by the method according to one of Claims 1 to 8 for the production of hermetically sealed housings for electronic components capable of being pressurized.

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