AU649536B2 - Process for the production of copper alloys - Google Patents

Description

P/00/01 1 ReguLation 3.2 953

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

TO BE COMPLETED BY APPLICANT :.Name of Applicant: DIEHL GMBH CO.

*::Actal Inventor(s): Dr. Wolfgang Hornig, Dipl.-Ing.

Address for Service: CALLINAN LAWRIE, 278 High Street, Kew, 3101, Victoria, Australia Invention Title: "PROCESS FOR THE PRODUCTON OF COPPER ALLOYS" The following statement is a full description of this invention, Including the best method of performing it known to me:- -1A- DIEHL GMBH CO, D-8500 Nuremberg Process for the production of copper alloys The invention relates 'to a process for the production of copper alloys of very high strength and very good transformability, with a content of from 2 to nickel and from 2 to 12% tin, the balance being copper, and the usual impurities.

The invention relates generally to the field of precipitation-hardening alloys, in particular so-called spinodal alloys. The field of spinodal alloys is still little researched and it is known hitherto that there are not many spinodal alloy systems, but there is still little clarity about the properties on the basis of which it is possible to predict whether a spinodal alloy is or is not produced. Spinodal alloys are distinguished in comparison to the normal precipitation-hardenitng alloys by a substantially increased level of strength, in consideration of a structure which :'t5 is better, namely finer, by orders of magnitude. That structure occurs because there are no precipitation particles in the metal matrix, but only diffusion zones in the range of nanometres. With the copper-nickel-tin alloy system, increases in strength to two to three times the normal alloy are possible. While for example with a commercially available alloy CuNi9Sn2, produced by means of the normal *2 .20 process, strengths of about 600 N/nmn can be expected, with the spinodal alloys which are produced in accordance with the invention strengths of up to 1500 N/mm 2 are possible.

The object of the present invention was thereiore that, starting from a -2conventional alloy composition, of providing a process which, in comparison with processes used hitherto, gives substantially greater strength and better transformability in the resulting alloy.

To attain that object, the invention proposes the following steps: a) casting of the alloy in blocks, b) solution treatment at from 650 0 C to 800 0 C for from 4ehours, c) cooling down, e o d) ageing at from 260 0 C to 380 0 C for from\14 days 4 itaJIeat and e) cooling down in air.

The alloy produced in accordance with the above-described process is distinguished not only by unusual strength but also by excellent transformation properties, that is to say very good deep-drawability. In consideration of those properties, the novel alloy is highly usable not only in the electronics industry, therein in particular in modules, or in the construction art, uses in the automobile Sart also present themselves where good resistance to corrosion is required as well as a high level of strength, but there is also the possibility of use in the aircraft art in the case of high-strength castings or in the transmission art. By virtue of the e.

good material properties, use can also be envisaged where friction and wear are 20 important aspects.

Although the range of contents of nickel and tin is really great, the higher contents for nickel and tin have nonetheless shown themselves to be particularly advantageous. In accordance w'th the invention therefore, contents <SAln -3of from 6 to 9% of nickel and from 6 to 10% of tin and preferably 0.05 to 0.6% manganese, with the balance being copper, are particularly preferred.

More specifically it was found that it is already possible to achieve very good strength values when processing the commercially available alloy CuNi9Sn2 in accordance with the process according to the invention. If however the tin content is raised to values of from 8 to 10% tin, with the nickel content remaining the same, the strength level rises quite unusually. At the same time, due to the increase in the tin content, the excellent opportunity decisively to reduce the ageing time presents itself.

In consideration of the foregoing, as an essential basic concept of the invention, it is to be emphasised that no cold working may be effected after solution treatment of the alloy, but ageing must be effected after suitable cooling.

The ageing time is reduced, the higher the temperature within the specified temperature range, and, as already stated, it decreases, the higher the zinc content. On the other hand, strength and conductivity increase with increasing S: ageing time.

A ratio of the constituents nickel to tin of between 0.3:1 and 1:1 has proven to be particularly advantageous in accordance with the invention.

o The cooling operation between the solution treatment step and the 20 ageing step is not critical, in terms of the cooling rate. The cooling step can be oC effected both by quenching and also at a medium cooling rate, for example by blowing with air.

Casting of the alloy may be effected not only in blocks but also in a -4strip, in which case a cold rolling operation must be effected prior to the solution treatment step.

The above-mentioned low manganese content is not imperative in accordance with the invention but it is advantageous in order to produce a porefree casting. In that respect the amount of manganese added must remain so low that the manganese does not become an alloy constituent. In consideration of the high degree of affinity of the manganese for oxygen, the air present in the molten materials is bound so that the casting is pore-free.

Further processing operations on the finished alloy, which generally means effecting cold working, increase the strength of the alloy still more, but in that case ductility has a tendency to decrease, and likewise conductivity, in regard to which mean values of up to about 35% IACS can be achieved on the basis of the process according to the invention.

An example for production of the alloy according to the invention will be described in detail below.

The alloy is firstly cast in blocks. A solution treatment is then effected at a temperature of 750 0 C for a period of 4 hours. After quenching of the blocks in cold water, they are aged at ai temperature of 320 0 C for a period of 19.5 hours 4 4 and then cooled in a stream of air.

If particularly high strength values of more than 1300 N/mm are to be g achieved, it is desirable for the starting product used to be a cast strip which was then cold-rolled. Solution treatment is then effected at a temperature of 750 0 C for a period of 1 hour. After quenching in cold water, ageing is also effected again at 320 0 C for a period of 19.5 hours. In both the Examples the composition of the alloy was 9% Ni, 11% Sn, 0.14% Mn, the balance Cu and impurities.

In regard to reducing the aging time by the use of higher tin contents, the following results were obtained in tests. In order to achieve a mean strength value of 600 N/mm 2 after a preceding solution treatment at 750 0 C for 30 minutes on the starting product, cold-rolled strip, at an ageing temperature of 320 0 C, the periods of time required were as follows: CuNi9Sn2 6 days 4 hours CuNi9Sn7 30 minutes It can be seen therefrom that the increase in tin contents gives a substantial reduction in the ageing time and therewith a substantial reduction in production costs. If higher strength values and/or conductivity levels are required, the ageing time must be correspondingly increased. Attention is directed to the :-Is above-described Example.

The result of the above-described process according to the invention S therefore is an alloy of unusual strength, high transformability and mean conductivity, which can be produced at advantageous cost.

0o

Claims (9)

1. A process for the production of copper alloys of very high strength and very good transformability, with a content of from 2 to 10% Ni and from 2 to 12% Sn, the balance Cu and usual impurities, said process including the steps of: a) casting of the alloy in blocks, b) solution treatment at from 650 0 C to 800 0 C for from 1 to 24 hours, c) cooling down, d) ageing at from 260 0 C to 380 0 C for from 15 minutes to 14 days, and e) cooling down in air.

2. The process according to claim 1, applied to alloys with a content of from 6 9% Ni and from 6 10% Sn as well as from 0.05 0.6% Mn, the balance being Cu and usual impurities.

3. The process according to claim 1 or claim 2, wherein the ratio of the constituents nickel to tin is between 0.3:1 and 1:1. e

4. The process according to any one of claims 1 to 3, wherein step b) is effected at a temperature of 750 0 C for a period of 4 hours.

5. The process according to any one of claims 1 to 4, wherein a the cooling operation of step c) is effected by quenching. 0

6. The process according to any one of the preceding claims, wherein step a) is by strip casting with subsequent cold rolling. 17o4GVI370G.CPe0 -7-

7. The process according to claim 6, in relation to an alloy with a content of 9% Ni, 11% Sn, 0.14% Mn, balance Cu and usual impurities, wherein said solution treatment in step b) is at 750 0 C for a period of between 1 and 4 hours, and said ageing in step d) is at 320 0 C for a period of 19.5 hours.

8. The process according to claim 6 or claim 7, wherein in step b) said solution treatment is effected at 7500C for a period of 1 hour.

9. A process for the production of copper alloys, substantially as hereinbefore described with reference to the Example. DATED this 17th day of February 1994. DIEHL GMBH CO. By their Patent Attorneys: CALLINAN LAWRIE O o ITZ94GV1537.SPe7 1 C -8- ABSTRACT The invention relates to a process for the production of copper alloys of very high strength and very good transformability with a content of from 2 to Ni, from 2 to 12% Sn, the balance Cu and usual impurities. Strengths of up to 1500 N/mm are achieved by a solution treatment after the casting operation at from 650 0 C to 800 0 C for a period of time of from 24 hours to 3 hours and after previous quenching and in the absence of cold working ageing for a period of time of from 14 days to 15 minutes at a temperature in the range of from 260 0 C to 380 0 C. a. a a a a a