DE2358510B2 - PROCESS FOR PRODUCING A UNIFORM, FINE GRAIN AND A HIGH ELONGATION IN COPPER-ALUMINUM ALLOYS - Google Patents

Description

The invention relates to a method according to the preamble of claim 1.

Copper-aluminum alloys made of 70 to 95% copper, 3 to 10% aluminum and 0.1 to 10% iron, which may contain additions of manganese, silicon, molybdenum, titanium, nickel, cobalt or chromium, are known per se ( DT-PS 6 80 213). The invention is based on the object of making available a process for producing a uniform, fine grain and high elongation in copper-aluminum alloys of the composition specified in the preamble of claim 1, which can be carried out in a simple manner.
The solution to this problem arises from the

in the characterizing part of claim 1.

It is known (GB-PS 10 85 988), copper-aluminum alloys with 9.0 to 11.8% aluminum, including zinc, iron, chromium and zirconium may contain, after a hot deformation, a cold deformation and a subsequent annealing undergo. The known method leads to alloys with high tensile strength, high ductility, quite fine grain and an elongation in the range of 9 to 12%. In GB-PS 10 85 988 it is stated that it is at the known process essentially depends on copper-aluminum alloys with 9.0 to 11.8% To use aluminum; such alloys contain a substantial proportion of beta phase. The after In contrast, the alloys to be processed according to the invention contain significantly less Aluminum.

The addition of grain-refining agents to single-phase mixed crystal alloys, as is also the case with those according to the invention Alloys to be processed is widely used to improve workability and / or to improve the properties of the alloys. Often this results in an equalization properties for a range of alloy compositions and processing conditions

j5 conditions, especially annealing temperatures. However are in many cases, for example when adding cobalt to copper-aluminum alloys, the grain refiners Means not stable in the whole temperature range up to the melting point of the alloy because it is dissolution, disintegration, conversion, changing solubility, and the like occurs. Furthermore is a Worsening of the normally achievable ductility of the alloy can be observed. If on the other hand, single-phase mixed crystal alloys without the addition of grain-refining agents at higher temperatures when heat treated, grain size and ductility increase while strength decreases.

Usually, one anneals at temperatures as high as they are in view of the desired strength

so are possible to high ductility or deformability in subsequent deformations, for example by stretch forming. However, excessive grain growth is what is called the so-called Can make orange peel noticeable and is particularly visible on very smooth surfaces, undesirable. Many fine-grained or with grain-refining agents provided copper alloys namely the undesirable property that any attempt to increase the grain size by adding grain refining

bo given stable level addition to enlarge, to a uncontrolled mixed grain size, which consists of very small and exceptionally large grains. This uneven grain growth is caused by effects such as secondary recrystallization that a direct consequence of the action of the second phase particles on the matrix during cold working and the subsequent glow. Material in which uneven or irregular grain growth

has taken place is not suitable for the production of parts that have smooth surfaces for a gloss treatment, need polishing and / or electroplating or electroplating. In addition, irregular ones are created mechanical properties.

In contrast, the method according to the invention leads to high, uniform ductility, too high Elongation and a controlled grain size. It is a small one as well as an even or regular one increased grain size achievable. In particular, uneven grain growth is avoided.

Preferred developments of the invention emerge from claims 2 to 10. It should be particularly emphasized a process management made possible in a further development of the invention with a decreasing sequence Cold deformation with inserted high-temperature annealing.

The invention is explained in more detail below with the aid of some more specific exemplary embodiments:

The method according to the invention can be used particularly favorably with an alloy that is 2.5 to Contains 3.1% aluminum,!, 5 to 2.1% silicon, 0.25 to 0.55% cobalt and the remainder copper (CDA alloy 638). There can be improved ductility in the further processed state, for example at least 40% elongation in the case of CDA alloy 638, without uneven grain growth.

In a first embodiment of the invention, an alloy is produced within the above composition ranges in the annealed condition, said alloy having been annealed at a temperature below 600 ^0C. The annealed alloy is then subjected to a final cold working of from about 8 to about 22%, preferably from about 10 to 20%. The cold worked alloy is then subjected to a final anneal at a temperature of from about 550 to about 715 ° C, preferably from about 650 to about 700 ° C.

It has been found that the elongation increases as the temperature of the final anneal increases. The inventive method results in a wrought alloy with a substantially uniform grain size of less than 0.025 mm, a tensile strength of at least 49.2 kp / mm ² , a 0.2% yield strength of at least 21.1 kp / mm ² and an elongation of at least 40%. It was possible with the CDA alloy 638 elongations of about 45% mm at a tensile strength of about 52 kgf / ² and a 0.2% yield strength of about 28.1 kgf / mm to produce ^{the second}

In accordance with preferred developments of the invention, the method is carried out with a series executed by cold deformation, inserted between each annealing at a relatively high temperature will.

According to a second embodiment of the invention, an alloy having a composition subject to cold deformation within the aforementioned ranges which is sufficient to cause recrystallization ensure at a temperature below about 600 ° C. Generally there is one for this Cold working of the alloy of at least 10% and preferably of at least 30% in question. Of the The highest amount of cold deformation is due to the required (final) dimensions of the alloy given. Then the cold worked alloy undergoes an intermediate anneal at a temperature of about 400 to about 600 ° C, preferably from about 450 to about 575 ° C. The intermediate annealed alloy

is then subjected to a final cold working of from about 8 to about 22%, preferably from about 10 to 20%. The final cold-worked alloy is then to about 715 ⁰ C, preferably, subjected to a final annealing at a temperature of about 550 of about 650 to about 700 ° C.

As in the method according to the previous exemplary embodiment, the elongation increases with the Final annealing temperature. Properties similar to those in the method according to the previous embodiment specified achieved. However, it was found that the temperature the intermediate annealing is of decisive influence insofar as temperatures above about 600 ° C lead to uneven grain growth in the alloy, if the alloy has previously increased by more when about 22% was cold worked.

According to a third exemplary embodiment of the invention, an alloy with a composition within the ranges given above is deformed by at least 10%, preferably by at least 30%, depending on the desired (final) dimensions. The cold-worked alloy is then at a temperature of about 400 to about 600 ⁰ C, preferably about 450 to about 575 ° C, intermediately.

The intermediate annealed alloy is then cold worked between about 25 and about 40% and then at a temperature of about 400 to about 600 ° C, preferably from about 450 to about 575 ° C, intermediate annealed. The alloy that has been annealed in this way is then subjected to a final cold working between approximately 8 and about 22%, preferably between about 10 and about 20%. The finally cold-formed Alloy is then at a temperature of about 550 to about 715 ° C, preferably from about 650 to about 700 ° C, finally annealed. This embodiment of the invention allows greater flexibility on inventive Way to achieve the required final dimensions; it also generally gives one more uniform recrystallization of the alloy and more uniform or more uniform properties.

As in the previous embodiment, the intermediate annealing temperatures are essential here Influence if the alloy has previously undergone cold deformation of more than 22%.

In all of the discussed exemplary embodiments of the invention, the process steps are final cold forming and the final annealing is critical to a further processed alloy or a wrought alloy with improved elongation without uneven grain growth. The by the invention The methods made possible create a uniform grain coarsening and essentially uniform Grain sizes below 0.025 mm. If the upper limit for the final annealing temperature according to the invention is exceeded, the alloy shows uneven or irregular grain growth. The same applies to the process step of the final cold deformation, since a deformation above 22% results in the onset of uneven grain growth.

Even though the invention has been explained in more detail with reference to specific exemplary embodiments, it is nevertheless possible to use further process steps in addition to the process steps according to the invention perform as long as the limits of the intermediate annealing temperature of the final cold forming and the final annealing hung are complied with.

The holding times at the corresponding temperature and the heating and cooling speeds at the annealing process steps according to the invention are not of decisive influence and can be used in In accordance with conventional practice, the types of alloys used can be arbitrarily set.

The following discussion is intended to expound the mechanisms that make up the crucial nature of the process measures according to the invention are based. The explained mechanisms should not be used in any Way to limit the invention.

The low stacking fault energy alloys containing dispersed particles of a second phase, e.g. B. the CDA alloy 638, cold deformation by 50% leads to a pronounced {110} [112] deformation texture or preferred orientation. When the CDA alloy 638 is ^{recrystallized at 500 to 600 °} C., it contains newly formed, undeformed, recrystallized grains of very small size. The strong grain boundary anchoring effect of finely divided CoSi particles of a second phase ensures the retention of a fine grain. At higher annealing temperatures above 600 ⁰ C, the anchoring force is reduced because the CoSi particles agglomerate and / or go back into solution. Under these conditions, new recrystallized grains with a (110) [112] annealing texture or preferred orientation grow preferentially into the ■ [110} [112] texture of the areas that are still deformed. Preferred grain growth continues even after recrystallization, since the larger grains of the preferred orientation may have higher growth rates than their smaller neighbors of different orientations. This preferred grain growth leads to the undesirable, irregular grain growth and results in a duplex microstructure.

It was found that the texture of the type (110) [112] the stable final texture in cold-rolled alloys with low stacking fault energy, e.g. B. the CDA alloy 638 is. Uneven grain growth

leads to an annealing texture of the type (110) [112]. It is believed that the development of the uneven Grain growth and the | 110) [112] glow texture with the Presence of a critical extent of | 110 | [112] Deformation texture before final recrystallization annealing related.

The terms texture or preferred orientation used in the present text refer to the planes of the grains that are parallel to the surface of the metal strip.

It has been found in connection with the invention that when the step of Final cold deformation within the aforementioned degree of deformation ranges lies, the extent of (110) [112] Deformation texture remains below the critical level, so that during the final annealing within the specified temperature ranges no uneven grain growth occurs. Therefore, with the Method according to the invention uniform grain coarsening without duplex structure or uneven Grain growth achieved.

The processes according to the invention are described in more detail below with the aid of further detailed examples explained. In the examples, the samples became one on all of the final anneals and intermediate anneals Maintained at the appropriate temperature for an hour. The term annealing temperature refers to In the context of the present text, the metal temperature rather than the furnace temperature.

example 1

Samples of CDA alloy 638 with a composition of 1.98% silicon, 2.5% aluminum, 0.42% cobalt, the remainder copper, are removed using standard equipment with a thickness of 2.29 mm manufactured. The samples are then treated according to the procedural steps given in the table below. The mechanical properties and grain sizes of the samples are listed in the table:

Treatment sequence tensile strenght 0.2% stretch (Fracture-)- Grain size border Guideline kp / nim ² kp / mm ² % mm A WV 50%, Gl 575 ⁰ C / 59.1 40.8 35 0.003 WV 50%, Gl 575 ° C B WV 45%, Gl 575 ° C / 54.1 28.8 40 0.010 WV 30%, Gl 575 ° C / WV 15%, Gl 575 ° C C WV 45%, Gl 575 ° C / 51.3 26.7 45 0.012 WV 30%, Gl 575 ° C / WV 15%, Gl 700 ° C

WV = rolling deformation; Gl = annealing.

This example shows that there is a range of elongation, strength properties and uniformity Grain coarsening, which leads to a suitable small grain size, with the method according to the invention can be reached.

The treatment sequence A corresponds to the conventional treatment for this alloy and does not fall under the scope of the method according to the invention. It is listed for comparison purposes.

The treatment sequences B and C make it clear that

when the step of final cold working is within the reduction range according to the invention is, even grain coarsening as well as considerable improvements in the elongation after a final annealing can be achieved in a range of annealing temperatures.

Example 2

Samples of CDA alloy 638 with a composition of 1.98% silicon, 2.5% aluminum,

0.42% cobalt, the remainder copper is now removed using standard equipment in a thickness of 2.03 ") manufactured. The samples are subjected to different final cold deformations and at different Annealed final annealing temperatures. The ratios listed below result:

Glow Grain size, mm deformation temperature 50% deformation 0.005 ⁰ C 15% 0.005 and 0.0302) 600 0.007 0.0603) 650 0.007 0.0803) 700 0.007 750 0.1203)

10

') Samples in the annealed condition, annealed at less than 600 ° C.

-1 duplex microstructure.

^J ) Grain size after the formation of the high-temperature grain growth texture.

This example illustrates the decisive influence of the final cold deformation and the upper limit for the final annealing temperature. Furthermore, the results of this example show that with a final cold working of 15% final annealing temperatures up to 700 ³ C can be used without uneven grain growth beginning. With a final cold deformation of 50%, however, uneven grain growth begins at 65O ⁰ C.

Example 3

Samples of CDA alloy 638 with a composition 1.98% silicon, 2.5% aluminum, 0.42% cobalt, the remainder copper are made using commercially available Devices manufactured in a thickness of 2.29 mm. The samples are made according to the treated in the following stages, the temperature of the intermediate annealing being varied. The results are in listed in the following table:

Treatment sequence:

Potash rolling by 45%, annealing at 575 ° C; Cold rolling by 30%, intermediate annealing; Cold rolling by 15%, annealing at 700 ° C.

45

Between Tensile strength 0.2% - (Fracture-)- grain glow speed Stretching strain size border ^D C kp / mm ² kp / mm ² % mm

51.3
50.6

26.7
25.3

45 47.5

0.010 4)

55

") Mainly 0.005 to 0.010 mm grains; there will be however, 0.030 mm grains were observed, indicating abnormally increased grain growth.

This example clearly illustrates the decisive influence of the intermediate annealing temperature. That Example shows that if the intermediate annealing temperature after cold working by at least about

b0 22% ^{exceeds about 600 0} C, the beginning of excessive grain growth can be expected.

Example 4

Samples of the CDA alloy 638 with a composition of 1.9% silicon, 2.5% aluminum, 0.42% cobalt, the remainder copper are produced using commercially available equipment with a thickness of 203 mm ⁵ '. Samples of the alloy are then cold rolled to four different final deformations, namely 15, 20, 25 and 30% and then at three Glühtemperaluren, namely 650, 700 and 725 ⁰ C annealed for an hour. The samples are evaluated metallographically in order to find out which deformation degree-temperature combinations produce uniform grain coarsening. The ratios listed in the following table resulted:

20th

Cold deformation Grain structure at a 700 725 Final annealing temperature, "C ⁸ ) ⁷ ) % 650 ⁸ ) ⁷ ) 15th ⁸ ) ⁷ ) ⁷ ) 20th ⁸ ) ⁷ ) ⁷ ) 25th ⁶ ) 30th ⁸ )

⁵ ) Samples in the annealed state, bloomed at less than 600 ° C.

⁶ ) Almost completely uniform structure, one or two scattered, large grains.

⁷ ) Duplex grain structure.

⁸ ) Uniform grain structure.

These results make it clear that final deformations within the ranges according to the invention result in a lead uniform grain structure, while deformations outside the range according to the invention, for example by 25% to uneven grain growth and a resulting duplex grain structure to lead. The results further make it clear that at final annealing temperatures outside of that in the Invention given range, d. H. above 715 ° C, a uniform grain structure at any one the listed degrees of cold deformation cannot be guaranteed.

The above examples clearly illustrate the decisive influence of the intermediate annealing temperature, the final cold working and the final annealing temperature as determined by the method according to the invention can be specified.

The invention has been accomplished through a single end cold working and a single end anneal described. It is understood, however, that a number of cold deformations and annealing within the areas of final cold working and final annealing can be used without it being used in the Alloy leads to uneven grain growth. So it also belongs to a number of several Deformations and anneals within the areas of the end deformation and the end annealing for Scope of the invention.

Claims (10)

Patent claims: 1. Process for producing an even, fine grain and high elongation Copper-aluminum lepings that contain 2 to 5% aluminum, less than 1% zinc, and one or several of the grain-refining additives 0.001 to 5% iron, 0.001 to 1% chromium, 0.001 to 1% zirconium, Contain 0.001 to 5% cobalt and the remainder copper, characterized in that the alloy final cold deformation with a degree of deformation of 8 to 22% and final annealing at a temperature between 550 and 715 ° C. 2. The method according to claim 1, characterized in that the degree of deformation between 10 and 20%. 3. The method according to claim 1 or 2, characterized in that the annealing temperature at 650 to 700 ° C. 4. The method according to any one of claims 1 to 3, characterized in that the alloy is deformed before the final cold deformation by at least 10%, but so much that it ^{recrystallizes at a temperature of less than about 600 0} C, is cold deformed and is then subjected to a first intermediate annealing at a temperature of 400 to 600 ° C, also before the final cold forming. 5. The method according to claim 4, characterized in that the first cold deformation with a Deformation degree of at least 30% is carried out and that the first intermediate annealing at a temperature between 450 and 575 ° C is carried out. 6. The method according to claim 4 or 5, characterized in that the alloy between the first intermediate annealing and the final cold deformation by 25 to 40% cold deformed and then with one Temperature between 400 and 600 ° C is annealed a second time. 7. The method according to claim 6, characterized in that the further intermediate annealing at a Temperature of 450 to 575 ° C is carried out. 8. The method according to any one of claims 4 to 7, characterized in that the cold deformation ^) before the final cold deformation by 10 to 20% is made and that the annealing temperature (s) before the final annealing between 650 and 700 ° C is (are). 9. Application of the method according to one of claims 1 to 8 to copper-aluminum alloys according to claim 1, which additionally contain 0.001 to 3% silicon. 10. Application of the method according to any one of claims 1 to 8 to copper-aluminum alloys according to claim 1 or 9, in which, however, the aluminum content 2.5 to 3.1%, the silicon content 1.5 to 2.1% and the cobalt content is 0.25 to 0.55%.