EP1061146B1 - Copper alloy containing tin, iron and titanium - Google Patents

Abstract

Copper-based alloy contains (in wt.%): 4-12 tin, 0.1-4 iron, 0.01-0.6 titanium and a balance of copper.

Description

The invention relates to a CuSnFeTi alloy and its use. CuSn alloy are widely used both as cast materials and as kneading materials used. This class of materials can be found in numerous applications in electrical engineering, machine and apparatus construction and precision engineering but also in the jewelry industry. The usual compositions are in Range from 0.1 to 11% Sn, 0.01 to 0.4% P, balance Cu. (Here and below the contents of individual alloy additives are given as a mass fraction in% by weight.) The advantages of these so-called phosphor bronzes are that they are very good worldwide are available and inexpensive as well as the designer in addition to very good physical Properties also excellent parameters for mechanical strength and offer ductility. They bring sufficient corrosion resistance for a wide variety of applications.

Especially for the production of components with small dimensions and complicated Geometry, the use of kneadable CuSn materials is particularly attractive. So are, for example, in DIN17662 for a wide range of applications 4 up to 8 percent bronzes defined, which in addition to Sn up to 8.5% also P as alloy component prescribe from 0.01 to 0.35%. As other admixtures Fe up to 0.1%, Ni up to 0.3%, Zn up to 0.3% and Pb up to 0.05%.

Especially for requirements with requirements for electrical conductivity and suitability For electromechanical components, numerous improvements have been made for them Material class presented. The latest examples are WO98 / 20176 and WO98 / 48068 mentioned. This work focuses essentially on the Improvement of the electrical conductivity and relaxation resistance of the traditional CuSn materials. Such special alloys are increasingly used in the applications of electrical engineering and electromechanics, since the improvements achieved are significant for these special applications.

For use in machine and apparatus construction, in precision engineering and in However, the improvements achieved appear to the jewelry industry to be of little consequence Interest to be. The classic P-bronzes are still almost exclusively here used. This may be due to the fact that this group of materials regarding the properties that can be adjusted by cold forming for a large one Number of use cases is very well sufficient. However, some are Defects obvious.

Joining operations are often also required for the production of functional parts. Welding and brazing processes are often used for this. By the Heat input into the components to be joined leads to losses in strength in the heat affected zone caused by recovery or recrystallization. This is special important when using fusion welding processes and brazing processes. To keep the loss of strength as low as possible, wherever possible to use brazing instead of welding. With the working temperatures soldering from 450 ° C can be carried out in a way that is a compromise from remaining high strength and good resilience of the joint require.

When using an additional material, namely the solder, the strength plays of the solder used for the mechanical stability of the bonded assembly also a role. Therefore there is a desire for unbreakable solders. Higher strength solders but usually require higher working temperatures. This increases naturally the heat input into the joined parts, resulting in an increased loss of strength results in the areas near the soldering gap. So the result is Necessity to use materials that are resistant to softening, if the strength of the bonded composite is to be optimized.

In the past, there has been no shortage of attempts for certain construction tasks Materials with high softening resistance for such applications propose. This is what developments in the area of Ni-free materials for the eyewear industry is a good example. Here were different compositions formulated on the basis of CuAl and CuTi systems. They offer better spring properties and softening resistance than that of today, for example, for temple pieces used phosphor bronze.

When using these Ni-free alloys, it has now been shown that particularly Brazing under protective gas causes considerable problems because these materials also react with a low-oxygen atmosphere, which causes the wetting of the Component surfaces are severely hindered with the solder. The processability by brazing is only under the aid of aggressive fluxes in the desired Scope possible. The use of such aggressive fluxes appears today under the aspects of occupational safety and environmental protection as nothing more contemporary. In addition, there must also be color changes to the joined components are removed by the flux and residues of the flux. Unavoidable is this cleaning when it comes to visible surfaces or from others For reasons of uniform appearance. Regardless of the use of fluxes, CuSn alloys tend to discolor when heated. This phenomenon is known as tarnishing. This also requires if necessary, cleaning the joined components. These post-treatments are costly and therefore undesirable.

JP-A-63038544 describes a highly conductive copper alloy good solderability, which includes the alloying elements Sn, Fe or Co, P and Mn and at least one further element from the group Zn, B, Al, Mg, Si and Ti or Cr contains and is used for electrical components and electronic apparatus. So the desire for materials comes to mind, on the one hand in terms of strength and softening characteristics are equivalent to the specialties shown above, but on the other hand offer the advantages of the very well brazable Sn bronzes. In addition, there is a reduction in the tendency to form tarnishes welcome.

The object achieved by the present invention is achieved by an alloy solved, in the case of copper 4 to 12% Sn, an Fe content of 0.1 to 4% and 0.01 - 0.6% Ti is alloyed. The alloy according to the invention is characterized by a particularly high strength and resistance to softening. Contrary to So far, the usual view is deoxidation with P, as above described, not necessary. When setting Fe contents in the invention Alloy becomes apparent the appearance of the dreaded Sn oxide prevented to the extent that additional deoxidizing measures are dispensed with can be. The Fe additives also ensure the alloys according to the invention surprisingly for an improvement in the resistance to discoloration in the warmth.

The resulting semi-finished product is manufactured using the classic archetype and Forming process easy to handle. At the same time is the invention Alloy extremely hard to solder with a wide variety of solders. Obviously none of those oxides are formed with the Fe and Ti contents according to the invention on the surface, which has poor wettability or poor solder flow would cause.

Preferred alloy compositions are the subject of claims 2 to 9th

Alloying of Ti is particularly advantageous. To do this, it is necessary to combine Ti in one Mass ratio Fe / Ti ≥ 2.5 to the added Fe of the alloy according to the invention to alloy. Because Ti is an alloying element that is very easy to use with oxygen the heat reacts to oxides and leads to surface layers, which the wetting with this deterioration is very surprising.

It turns out that a copper-tin alloy with 4 - 12% Sn when added of only 0.05% Ti in the solderability is drastically deteriorated. A soldering can only be carried out successfully with the help of flux. However, Ti will added to the alloy according to the invention in relation to Fe, the solderability is not impaired but at the same time the softening characteristic the alloy according to the invention sustainably improved. The Ti addition causes the time course of the softening is significantly delayed. A delayed one Softening means for the industrial implementation of brazing operations a higher reproducibility and a further optimization of the mechanical Strength of the bonded bond.

Due to the known properties of the elements this is known Situation to be expected that Ti through its related elements Zr and Hf can be replaced in whole or in part. These elements work together same behavior with the CuSnFe base alloy according to the invention.

To make the alloy cheaper, parts of copper can be separated by Mn and Zn or be replaced together. However, more than 10 wt% copper should not be replaced by these metals, since this makes the castability significantly more difficult and the good corrosion property of the alloy according to the invention becomes clear deteriorate. The P that is often added to CuSn alloys should be added Not be alloyed in the presence of Ti. Needles are formed in the melt Titanium phosphides, which make the semi-finished product very difficult and the material properties spoil.

Preferred areas of application of the alloy according to the invention are in the claims 10 to 14 listed.

Example:

Kokillenguß von Blöcken,

Homogenisierung bei 700°C/6 h,

Warmwalzen bei 760 °C der überfrästen Gußblöcke mit einer Querschnittsabnahme von 45 %,

Kaltwalzen der überfrästen Warmwalzstreifen mit einer Querschnittsänderung von 50 % bezogen auf den Querschnitt der überfrästen Warmwalzstreifen Glühbehandlung bei 500 °C/ 4 h,

Fertigwalzen an 1 mm mit einer Querschnittsänderung von 75 % bezogen auf den Querschnitt nach der ersten Kaltumformung.

The embodiment of the invention can be shown using the following example. The alloys were made into sheet metal strips 1 mm thick as follows:

Die casting of blocks,

Homogenization at 700 ° C / 6 h,

Hot rolling at 760 ° C of the milled ingots with a cross-sectional decrease of 45%,

Cold rolling the milled hot rolled strips with a change in cross section of 50% based on the cross section of the milled hot rolled strips annealing treatment at 500 ° C / 4 h,

Finishing rolls at 1 mm with a cross-sectional change of 75% based on the cross-section after the first cold forming.

The compositions of the tapes are summarized below: alloy Cu /% Sn /% Fe /% Ti /% P /% Al /% 1 91.37 8.57 0.03 2 91.11 8.55 0.30 3 91.08 8.22 0.66 4 91,20 8.05 0.64 0.074 5 90,60 8.47 0.64 0.244 6 90.44 8.53 0.64 0.358 7 89,10 8.74 1.73 0.387 8th 90.87 8.61 0.31 0.1724 9 91.09 8.58 .2862 10 90.89 8.49 0.31 .2739 11 90.02 8.61 1.04 .2821 12 91,90 8.06 0.024

The following table shows the results of tensile tests carried out on the finished rolled strips alloy R _p0.2 I MPa R _m / MPa R _p0.2 / R _m A ₁₀ /% 1 843 872 0.97 3.3 2 882 907 0.97 2.6 3 837 895 0.94 2.3 4 * 849 890 0.95 2.1 5 * 824 909 0.90 3.1 6 825 914 0.90 3.6 7 * 837 937 0.89 3.9 8th 923 953 0.97 3.3 9 873 906 0.96 3.8 10 874 912 0.96 3.5 11 888 919 0.97 2.3 12 828 895 0.93 2.4

The measured values for the elongation at break A ₁₀ and the yield _{point ratio} R _p0.2 / R _m , which were determined on the alloys according to the invention, are in good agreement with the corresponding values which are obtained after comparable processing steps for the alloy 12 deoxidized with P. Since one can deduce the effectiveness of deoxidation from the amount of elongation at break ¹ , it can be concluded from this agreement that Fe and Ti have a positive effect on the primary and forming of CuSn alloys in the same way as P.

To characterize the soldering behavior, 2 strips of the same alloy were each brazed after their surfaces were degreased and mechanically cleaned. A commercially available silver solder with a working temperature of 710 ° C was used. Soldering was carried out under protective gas without the use of a flux. The result of the soldering was evaluated both by mechanical torsion testing and by metallographic inspection. The strength of the joined materials in the immediate vicinity of the soldering gap - in other words in the heat affected zone (HAZ) - was characterized by the Vickers hardness HV. The table below shows the results obtained. alloy Hardness HV base material Lowest hardness in HA after brazing Structure in WEZ and basic material Quality brazing 1 263 84 okay moderate 2 273 95 okay Good 3 267 111 okay Good 4 267 115 okay Good 5 279 111 okay Good 6 276 129 coarse particles over 10 µm not usable 7 284 151 okay Good 8th 276 112 okay moderate 9 273 87 okay not usable 10 274 103 okay not usable 11 279 121 okay not usable 12 275 81 okay Good

The results prove the extremely beneficial effect of iron on residual hardness after soldering. It is clear that failure to comply with the invention FeTi ratio an improved resistance to softening, but none good brazeability is given (alloys 1 and 6, compared to conventional Alloy formulation 12).

To check the material softening during soldering, sections of the cold deformed strip sections were annealed at 700 ° C for up to 5 minutes in a salt bath and the residual hardness HV was measured after different times t. This gives the isothermal softening characteristic HV (t) of the material under consideration. The hardness curve over time is important for assessing the strength after soldering and the safety in the industrial production of joined components: The higher the residual hardness HV (300 s) after five minutes of annealing treatment, the higher the mechanical stability to be expected solder; The less the hardness changes over time, the more uniform the quality of the joined components and the more robust the manufacturing process is against unavoidable fluctuations in the process parameters. On the one hand, the amount of residual hardness of the alloy Y (Y = 1.2 ... 12) after five minutes of annealing treatment was evaluated in relation to the usual phosphor bronze alloy 12: HV (Y, 700 ° C, 300 s) / HV (12, 700 ° C, 300 s) - 1. On the other hand, alloys Y were compared with alloy 12 in terms of reducing the difference between the hardness after 60 s and 300 s: 1 - [HV (Y, 700 ° C, 60 s) - HV (Y, 700 ° C, 300s)] / [HV (12, 700 ° C, 60 s) - HV (12, 700 ° C, 300s)]. Good materials in comparison show particularly large, positive values for both evaluations. alloy Hardness HV start Hardness HV after 60 s Hardness HV after 180 s Hardness HV after 300 s Residual hardness HV (300 s) compared to Leg. 12 Verringg. d. Hardness drop v. 60 to 300 s against Leg. 12 1 263 83 84 79 8th% 75% 2 273 90 79 79 8th% 31% 3 267 118 108 108 48% 38% 4 267 112 107 107 47% 69% 5 279 123 118 117 60% 63% 6 276 132 129 122 67% 38% 7 284 157 145 141 93% 0% 8th 276 106 105 102 40% 75% 9 273 85 82 82 12% 81% 10 274 97 96 95 30% 88% 11 279 122 119 116 59% 63% 12 275 89 80 73 0% 0%

It can be seen that with the addition of iron a good gain in residual hardness is achieved can be, the reduction in hardness drop with extended holding times on temperature but is particularly favorably effected with additions of titanium.

zwölfminütiges Glühen der Bänder in Formiergas (95 % N₂, 5 % H₂) bei 700 °C,

Ofenabkühlung auf 200°C,

Abkühlung auf Raumtemperatur in ruhender Laborluft.

In addition to the tests described above, strip sections were heat-treated in a protective gas atmosphere as follows:

annealing the strips in forming gas (95% N ₂ , 5% H ₂ ) at 700 ° C for 12 minutes,

Furnace cooling to 200 ° C,

Cooling down to room temperature in still laboratory air.

With this experiment, the soldering process is qualitatively adjusted under protective gas, with the difference that ß fluctuations are excluded by the production process. The evaluation of the test includes the assessment of the strips with regard to their surface discoloration and their structure. The following table shows that the tarnishing behavior of the alloys in the composition according to the invention is comparable to that of the usual phosphor bronzes. With high Fe contents, the discoloration is even less than with the common CuSn alloys. In this case, a beautiful post-treatment of the surfaces in the vicinity of the solder seam is only necessary to a reduced extent or not at all. alloy Change in surface color after the heat treatment described compared to the unannealed initial state 1 significant discoloration 2 significant discoloration 3 slight discoloration 4 * weak discoloration 5 * slight discoloration 6 significant discoloration 7 * slight discoloration 8th significant discoloration (peeling scale layer) 9 very strong discoloration 10 very strong discoloration 11 very strong discoloration 12 significant discoloration

The microstructure of the alloys according to the invention is mentioned above Characterize heat treatment as follows: The structure is free of oxides, although as is commonly considered necessary as in the prior art no phosphorus was alloyed. Only excretions can be proven in which the alloy elements Fe or Ti according to the invention are enriched are. The average grain sizes in the alloys according to the invention are after the above heat treatment only approx. 25 µm. This is due to the grain refining effect attributed to the Fe. If desired, it is also possible to use the ones according to the invention Reshaping alloys after joining without being on the component surface Roughness arises, as can be seen from tin bronze alloys knows the state of the art.

The following overview results for the overall assessment of the alloys examined: alloy Structure in WEZ and basic material Quality brazing Residual hardness HV (300 s) compared to Leg. 12 Verringg. d. Hardness drop v. 60 to 300s against Leg. 12 Discoloration of the surface after heat treatment in a protective gas atmosphere Relative overall suitability compared to Leg. 12 1 ok (= 100%) moderate (= 50%) 8th % 75% clear (50%) 33% pts 2 ok (= 100%) good (= 100%) 8th % 31% clear (50%) 39% pts 3 ok (= 100%) good (= 100%) 48% 38% weak (100%) 136% pts 4 ok (= 100%) good (= 100%) 47% 69% weak (100%) 166% pts 5 * ok (= 100%) good (= 100%) 60% 63% weak (100%) 173% pts 6 coarse particles over 10 µm (= 0%) not usable (= 0%) 67% 38% clear (50%) not usable 7 * ok (= 100%) good (= 100%) 93% 0% weak (100%) 143% pts 8th ok (= 100%) moderate (= 50%) 40% 75% clear (100%) 115% pts 9 ok (= 100%) not usable (0%) 12%. 81% strong (0%) not usable 10 ok (= 100%) not usable (0%) 30% 88% strong (0%) not usable 11 ok (= 100%) not usable (0%) 59% 63% strong (0%) not usable 12 ok (= 100%) good (= 100%) 0% 0% clear (50%) 0% pts

It is clear that there is a high gain with the alloys according to the invention is achieved in overall suitability. The gain is measured in percentage points the comparison variant Leg. 12, which is a conventional phosphor bronze. It is obvious that with the alloys according to the invention the task is solved in an excellent way.

Claims (9)

1. A copper-tin-iron-titanium alloy consisting of

   from 4 to 12 % tin;

   from 0.1 to 4 % iron;

   from 0.01 to 0.6 % titanium,

   wherein the weight ratio of iron to titanium is at least 2.5;
   optionally up to 10 % zinc and/or manganese;
   optionally up to 3 % lead and/or intermetallic phases;
   the remainder copper and usual impurities.
2. A copper alloy according to claim 1, characterised in that it comprises from 6 to 10 % tin; from 0.5 to 2.5 % iron; from 0.05 to 0.4 % titanium.
3. A copper alloy according to claim 1, characterised in that it comprises from 7 to 9 % tin; from 1 to 2 % iron; from 0.05 to 0.3 % titanium.
4. A copper alloy according to claim 1, characterised in that it comprises from 10 to 12 % tin; from 2.5 to 4 % iron; from 0.1 to 0.5 % titanium.
5. The use of a copper-tin-iron-titanium alloy consisting of

   from 4 to 12 % tin;

   from 0.1 to 4 % iron and/or cobalt;

   from 0.01 to 0.6 % titanium and/or zirconium and/or hafnium and

   optionally up to 10 % zinc and/or manganese;
   optionally up to 3 % lead and/or intermetallic phases;
   the remainder copper and usual impurities for the manufacture of soldered or welded pieces of jewellery, clothing accessories, spectacles and spectacle parts.
6. The use of a copper alloy according to claim 5, characterised in that when iron and titanium are used the weight ratio of iron to titanium is at least 2.5.
7. The use of a copper alloy according to claim 5 or 6, characterised in that it comprises from 6 to 10 % tin; from 0.5 to 2.5 % iron; from 0.05 to 0.4 % titanium.
8. The use of a copper alloy according to claim 5 or 6, characterised in that it comprises from 7 to 9 % tin; from 1 to 2 % iron; from 0.05 to 0.3 % titanium.
9. The use of a copper alloy according to claim 5 or 6, characterised in that it comprises from 10 to 12 % tin; from 2.5 to 4 % iron; from 0.1 to 0.5 % titanium.