DE1608104B1 - PROCESS FOR INCREASING THE SOFTENING TEMPERATURE OF A COPPER ALLOY - Google Patents

Description

The invention relates to a method for increasing the softening temperature of a copper-boron-sulfur alloy with good electrical conductivity. In the method according to the invention, if necessary provided to subject the alloy to an annealing treatment after cold working to thereby To obtain intermediate hardening.

It is well known that copper is the best conductor of electricity and heat alongside silver. The conductivity however, it is generally caused by the presence of traces of other elements in the copper greatly reduced.

Copper has found applications in the most varied of fields, with the metal - around it to make them usable for each special purpose - various other metals must be added. The good conductivity properties were inevitably lost.

There are already numerous. Attempts made have been to produce suitable copper alloys with good conductivity for special purposes. For example, a copper-boron alloy is known which consists of 0.02 to 0.1% boron, the remainder copper as well as inevitable impurities. This alloy is specially designed for use as a welding rod for connecting copper pieces.

When heated copper reserves up to a temperature of 175 ° C at its full hardness, but softened completely at 250 ⁰ C. Various attempts have therefore been made to increase the softening temperature of copper by adding it to the alloy. For example, copper alloys containing silver or cadmium are known, the softening temperatures of which have been increased to almost 300 or 400 ^° C. Cadmium copper shows z. B. after extensive rolling a tensile strength of 47.60 kg / mm ² and only softens after 10 minutes of heating to 400 ° C. However, the electrical conductivity of these alloys falls far below the conductivity value of 100% IACS for pure conductive copper.

The invention was based on the object of subjecting a copper alloy to such a treatment, that the high electrical conductivity of copper is largely retained and at the same time an increase in the softening temperature is achieved, so that the alloy to high temperatures can be heated without softening.

It has been found that a copper alloy is suitable for achieving the object of the invention is, which consists of 0.004 to 0.3% boron, 0.002 to 0.1% sulfur and optionally impurities in quantities succeed, the remainder is copper.

The treatment of these copper alloy according to the invention in such a manner ,, that the boron and sulfur is solution within the limits specified above containing alloy at temperatures of 900-1040 ⁰ C, then rapidly cooled to room temperature and is cold worked.

This gives an alloy whose softening temperature is above 450 ° C and which has an electrical conductivity of about 100% IACS.

The solution treatment is preferably carried out in a non-oxidizing atmosphere. aside from that it has proven to be advantageous if the alloy is quenched immediately after the solution heat treatment will. In a preferred embodiment of the method according to the invention, the quenching carried out for a time of less than 20 seconds.

The treatment according to the invention gives the alloy with good conductivity a high softening temperature awarded.

If necessary, the alloy to be treated according to the invention can thereby be brought to intermediate hardening that they are after annealing and cold working to a temperature below their softening temperature lying temperature is heated.

The term "softening stamp" used here means the lowest annealing temperature, which causes a noticeable decrease in hardness and tensile strength. It is also to be understood as the temperature, in which, as a function of the time, a constant temperature value is maintained, a gradual Change in these properties occurs. From a metallurgical point of view, this is due to changes in properties, which result from the sum of the following effects: recovery, recrystallization, grain growth and hardening effects caused by precipitation. ■

The following are preferred embodiments of the present invention are explained in more detail using examples.

For example

A sample of 1.65 cm of an alloy to be treated according to the invention made of 0.009% boron, 0.0026% Sulfur and two impurities of less than 0.002% iron and 0.002% silicon, the balance copper were solution heat treated for 1 hour in an argon-hydrogen atmosphere at 900 ° C and immediately then quenched with water to room temperature. After that, the sample was 0.165 cm (90% cold reduction) cold rolled. The samples were placed in a salt bath for measurement of tensile strength at 400, 450 and 500 ° C 3.6 and 12 minutes and heated to their tensile strength, yield point and Checked ductility. The results are compiled in the table below. As observed noticeable softening occurred only at 500 ° C. It could also be observed that the Reheating the cold rolled copper to a temperature below the softening temperature Ductility increases considerably without the yield strength being noticeably reduced. (The ductility was measured in a tensile strength test as the percentage elongation [elongation].)

sample train
strength
kg / mm ² Stretch
border
0.5 »/ ο
strain
kg / mm ² strain
(<5 5)
in "/ ο According to the invention, Γ
traded Cu alloy \
After 3 minutes
at 400 ° C
After 3 minutes
at 400 ° C
After 6 minutes
at 400 ° C
After 6 minutes
at 400 ° C 62.0
59.8
54.0
54.6
53.8
54.5 61.5
56.0
51.3
51.8
50.6
51.7 7.5
7th
6.5
8th
6.5
7th

sample

After 12 minutes

at 400 ⁰ C ....
After 12 minutes

at 400 ⁰ C ....
After 3 minutes

at 450 ° C ....
After 6 minutes

at 450 ° C ....
After 12 minutes

at 450 ° C ....
After 3 minutes

at 500 ° C ....
After 6 minutes

at 500 ° C

After 12 minutes

at 500 ° C

train
strength
kg / mm ² Stretch
border
0.5 /,
strain
kg / mm ² 54.7 51.9 54.1 51.1 48.5 44.4 47.8 43.1 47.0 42.0 45.3 31.5 38.1 22.5 36.2 20.3

Elongation (<S 5)
in %

10

11th

11.5

11.5

26th

31

Example 2

In a second example, a copper-boron-sulfur alloy with the following composition was used: 0.009% boron, 0.0021% sulfur, 0.001% iron, 0.002% silicon, the remainder being copper. The alloy was made into 1.152 cm wire and wound on a spool. The wire was heated in a strand annealing furnace in an atmosphere of cracked ammonia for 7 minutes in such a way that the wire was passed through a ^{zone about 4.5 m long and heated to 925 °} C. at a speed of about 0.6 m per minute passed. The wire was quenched in water and cold rolled to 0.15 cm. When the wire V processed in this way was exposed to a temperature of 450 ^° _{C. for 2} hours, no appreciable softening of the alloy could be observed.

As already mentioned, the aim is to increase the softening temperature of copper in alloys achieved with boron contents of 0.004 to 0.3% and sulfur contents of 0.002 to 0.1%. the end economic considerations are out however copper alloys with a boron content of about 0.007 to 0.015% and sulfur contents of about 0.003 to about 0.006% are particularly favorable.

Both with the aforementioned metals and with other samples used to determine the aforementioned Values had been established, the conductivity values were very close to 100% IACS, so that high conductivity alloys were obtained in many cases.

Comparative experiments showed that copper, which had been cold worked to 75 to 95%, having a softening temperature of about 25O ⁰ C. A silver-containing copper alloy, which was processed in the same manner, had a softening temperature of 300 ° C, while a similarly processed cadmium-copper alloy exhibits a softening temperature of 400 ⁰ C. In contrast, a softening occurs at an appreciable according to the invention treated alloy only at temperatures over 500 ⁰ C.

The following figures are intended to indicate the applicability of the alloys treated according to the invention to be shown. There are already several commercial items weighing over about 13 600 kg cast, rolled, annealed and how

ίο has been finish-rolled as described above. The borrowing varied between 0.007 and 0.015%, while the sulfur content between 0.0030 and 0.0059% lay. Metals were obtained that had the desired softening temperature and conductivity Properties. The conductivity values were between 100.7 and 101.4% IACS.

Finally, the following comparisons should be made: A rolled cadmium copper with a tensile strength of 47.60 kg / mm ² becomes soft after heating at 400 ^{° C. for 10 minutes.} The copper-boron-sulfur alloy to be treated according to the invention and produced on an industrial scale shows, after rolling, a tensile strength of 45.50 kg / mm ² . Their tensile strength drops to 39.90 kg / mm ² after 15 minutes

₅ a long heating at 400 ⁰ C and 32.90 kg / mm ² after 15 minutes heating to 450 ⁰ C. After lstündigem heating to 400 ⁰ C results in a tensile strength of 37.80 kg / mm ² and a tensile strength of 27 , 30 kg / mm ² after lstündigem heating to 450 ⁰ C. This gradual decrease within a predetermined period allows a glow on intermediate curing. This fact is of decisive advantage for the production of the alloy because the metal can be reduced to its final thickness during cold rolling and subsequently annealed to the desired intermediate hardness. It is therefore only necessary to keep a simple stock that can be subjected to a wide variety of curing conditions.

Claims (4)

Patent claims: 1. A method for increasing the softening temperature with good electrical conductivity of a copper alloy made of 0.004 to 0.3% boron, 0.002 to 0.1% sulfur, the remainder copper and unavoidable impurities, characterized in that the alloy at temperatures of 900 to 1040 ⁰ C solution annealed, then rapidly cooled to room temperature and cold-formed. 2. The method according to claim 1, characterized in that the solution heat treatment in a not oxidizing atmosphere is carried out. 3. The method according to claim 1 or 2, characterized in that the alloys in less be quenched for more than 20 seconds. 4. The method according to any one of claims 1 to 3, characterized in that the alloy according to cold deformation by heating to a temperature below its softening temperature lying temperature is annealed to an intermediate hardness.