EP1910582B1 - Method for producing a copper alloy having a high damping capacity and its use - Google Patents

Description

The invention relates to a method for producing a copper alloy with adjusted to the application of the components alloy properties and specifically with targeted improved, or optimally adjusted mechanical damping, which is particularly suitable for mechanically, for example, by vibration, impact or shock, loaded components. Furthermore, the invention relates to the use of the alloy obtained by the method for reducing vibrations and noise attenuation of mechanically loaded components.

Metallic materials or alloys with high damping capacity are known in principle and are also referred to as HIDAMETs (Hlgh DAmping METals).

For example, high mechanical damping capacity is desirable for reducing vibration and noise reduction. Such alloys are therefore particularly suitable for the manufacture of ship propellers and pump housings, as well as for use in vibrating machines and for preventing vibration disturbances in various precision apparatuses and electronic instruments. At the same time high wear resistance, the alloys are also suitable for use in various tools that are exposed to vibrations and / or shocks during operation, such as punches or dies in sheet metal forming or in lathes and milling machines.

There are a variety of HIDAMETs known that can be used for noise damping and vibration absorption. However, the fields of application of a large part of these materials, in particular of magnesium and magnesium alloys, are severely limited by their insufficient mechanical and corrosion properties.

HIDAMETs with martensitic phase transformations are of particular importance in the art for achieving high attenuation properties. Alloys with martensitic phase transformations have a different atomic arrangement in the solid state at high temperatures than at low temperatures. The high temperature phase is referred to as "austenite" and the low temperature phase as "martensite". The transformation of austenite into martensite takes place on cooling of the material from the austenitic state and begins at the martensite start temperature MS. The martensitic transformation is completed when the martensite finish temperature MF is reached. The transformation of martensite into austenite takes place when the material is heated from the martensitic state, starts at the austenite start temperature AS and is completed when the austenite finish temperature AF is reached. In general, the attenuation in the martensite range (T <MF) is higher because of the much higher defect density than in the austenite range (T> AF).

The best known alloys of the type mentioned are Ni-Ti alloy ("Nitinol"), Cu-Zn-Al alloys ("Proteus") and Mn-Cu alloys ("Sonoston"). However, these three types of alloys have disadvantages that significantly limit their applications. Ni-Ti alloys must be produced consuming under vacuum and are also very expensive due to the alloying elements involved. In comparison with nitinol, Cu-Zn-Al alloys are much cheaper. The limited corrosion resistance and the tendency to brittle fracture behavior are significant disadvantages of these alloys. In addition, they are extremely severe in both the austenitic and the martensitic state to aging. The widely used Mn-Cu alloys have been specially developed for the manufacture of ship propellers. Due to the relatively wide solidification interval of about 130 ° C, these alloys are prone to hot cracking. In addition, aging effects also occur here, so that a significant decrease in the damping effect occurs already at room temperature after storage for about 1000 hours.

The patent US Pat. No. 3,868,279 discloses high-damping Cu-Mn-Al alloys and a way to improve their damping properties by heat treatment. These ternary alloys contain 32-42% by weight of Mn, 2-4% by weight of Al and the remainder of Cu, the Mn content preferably being 40% and the Al content preferably being 2-3%. These alloys are cold rolled and heat treated at temperatures between 649 ° C and 760 ° C, quenched in water, then aged at 204 ° C to 482 ° C for 1.5 to 24 hours and cooled in air. It is described a significant improvement in damping properties with less brittleness compared to the prior art Heusler alloys.

< Zheng-Qi, Cheng Xiao-Nong: "High-performance capacity of shape memory alloys" CHINESE JOURNAL OF NONFERROUS METALS, Vol. 14, No. 2, February 2004 (2004-02), pages 194-198, XP001248141 > shows the damping properties of Cu-Al-Mn shape memory alloys, depending on their composition. Here, high damping capacities were found for martensite and mother phase (parent phase) in both cases.

A technically interesting material alternative to the HIDAMETs described above are Cu-Al-Mn shape memory alloys. These materials also exhibit a thermoelastic martensite transformation. The patent US 4,146,392 describes Cu-Al-Mn shape memory alloys containing in addition to the main constituent copper as alloying constituents 4.6 to 13 wt .-% manganese and 8.6 to 12.8 wt .-% aluminum and have a good resistance to aging. These are alloys whose austenite-martensite transformation takes place at temperatures below 0 ° C. and whose shape memory effect is exploited, for example to produce pipe connection elements.

From the DE 2055755 For example, a method of manufacturing copper base alloy articles capable of changing shape as the temperature changes is known. The alloys proposed for this purpose contain, in addition to copper and aluminum, for example, an element from the group of zinc, silicon, manganese and iron.

Despite the very favorable combination of mechanical properties and achievable martensitic transformation temperatures, the use of Cu-Al-Mn shape memory alloys for noise and vibration damping materials has not yet been considered, as the mechanical damping properties could not previously be targeted and possibly even varied greatly from batch to batch.

The invention therefore an object of the invention to provide heavy-duty and corrosion-resistant HIDAMETs with a precisely adjustable even in the decisive for the intended application temperature range high damping capacity and a method for their production.

The object of the invention is achieved by the method according to claim 1 and the use according to claim 13.

Steps c) and d) may be repeated as many times as necessary until the desired adaptation of the transformation temperatures or intervals is achieved.

• 2 bis 12 Gew.-% Mangan,
• 5 bis 14 Gew.-% Aluminium und
• einzeln oder in Summe
• 0 bis 18 Gew.-% eines oder mehrerer der Elemente Nickel, Eisen, Cobalt, Zink,
• Silizium, Vanadin, Niob, Molybdän, Chrom, Wolfram, Beryllium, Lithium, Yttrium,
• Cer, Scandium, Calzium, Titan, Phosphor, Zirkonium, Bor, Stickstoff, Kohlenstoff,
  jedoch je Element nicht mehr als 6 % und
  ad 100 Gew.-% Kupfer.

The composition for the alloy is selected from the components:

• From 2 to 12% by weight of manganese,
• 5 to 14 wt .-% aluminum and
• individually or in total
• 0 to 18% by weight of one or more of the elements nickel, iron, cobalt, zinc,
• Silicon, vanadium, niobium, molybdenum, chromium, tungsten, beryllium, lithium, yttrium,
• Cerium, scandium, calcium, titanium, phosphorus, zirconium, boron, nitrogen, carbon,
  however, each item does not exceed 6% and
  ad 100% by weight of copper.

The alloys obtained by the process according to the invention are otherwise produced by conventional melting and casting processes. Apart from cast alloy, the alloy can also be used as wrought alloy. The alloy can be cold or hot formed. The alloys described herein are particularly advantageous for all applications where a high mechanical damping capacity is required, i. especially for mechanically loaded components, devices or housings that are subject to vibrations, impacts or shocks.

The alloys differ from Sonoston in significantly higher aluminum and significantly lower manganese contents. The high aluminum content improves the strength of the material according to the invention and at the same time increases its resistance to abrasion, erosion and cavitation. The reduced manganese concentration has a positive effect on the cast-technological properties of the alloy due to the reduction in the solidification interval. Thus, dense, oxide and warm crack-free casts can be produced with unit weights of several tons without quality problems.

In order to obtain the optimum properties for a desired application, the proportions of the alloy components are usually varied, for. B. as described in more detail below. It has been found that the mechanical damping capacity, which frequently fluctuates greatly with variation of the composition , can be optimized and set to higher values with the aid of a targeted fine tuning of the contents of the individual alloy components than if only the martensitic region were preferred for better reproducible damping properties. as is usual in the prior art.

For the targeted improvement of the mechanical damping, the martensit austenitic transformation temperatures or the associated intervals M _s to M _F and / or A _s to A _F adapted to a predetermined operating or operating temperature, which will occur in the intended use of the alloy in a "component". As a result, a high internal friction is set at the same time. The term "component" is intended to cover all conceivable practical applications and include both individual parts, such as more complex composite components, housings, machines and the like. Both the operating temperature and the working temperature can be medium temperatures, ie average values from a working or application area. Optionally, both transition temperature intervals, the martensitic and the austenitic, may be used to set to one or more different operating temperature ranges. The adjustment is made by varying the weight proportions of the above alloying ingredients during the melting of the alloy.

With the help of the elements nickel, iron, cobalt, zinc, silicon, vanadium, niobium, molybdenum, chromium, tungsten, beryllium, lithium, yttrium, cerium, scandium, calcium, titanium, phosphorus, zirconium, boron, nitrogen, carbon it is possible to specially adapt the properties of the alloy obtained by the process to the particular application. For example, addition of nickel or silicon increases corrosion resistance and strength properties. The elements iron, vanadium, niobium, molybdenum, chromium, tungsten, yttrium, cerium, scandium, calcium, titanium, zirconium, boron are important for achieving grain refining. Nitrogen and carbon together with transition elements improve the mechanical properties of the alloy obtained according to the invention. The aging resistance of the alloy in both austenitic and martensitic states is increased by the addition of cobalt. Beryllium and phosphorus protect the melt from oxidation. By various combinations of the alloying elements, an influence of varying influence on the transformation temperatures of the alloy according to the invention can furthermore be taken in order to optimally fulfill the requirement profile for a specific application.

The alloy therefore preferably contains between 1 and 4% by weight of nickel. A preferred embodiment of the alloy contains between 11.6 and 12% by weight, preferably about 11.8% by weight of aluminum. Furthermore, manganese contents between 8 and 10 wt .-% are preferred in the alloy. The alloy may further preferably contain between 0.01 and 1% by weight of cobalt.

The structure of the cast alloy is characterized by relatively large cast grains and is preferably grain-fined to achieve optimum mechanical properties. become. Boron additions between 0.001 and 0.05% by weight and / or chromium additions between 0.01 and 0.8% by weight and / or iron additions of 2 to 4% by weight are particularly effective for this purpose. In addition, the grain refining can be carried out by adding rare earths up to 0.3% by weight.

The alloy may further contain between 2 and 6% zinc.

The alloys may preferably have MS temperatures> 0 ° C, without the invention being limited thereto.

The invention provides a significant improvement in the damping properties, since only by the invention, the optimal adjustment of these properties while taking into account other desired properties is possible. The method according to the invention makes it possible to adapt the transformation temperatures in the material to the respective conditions of use such that the specific damping capacity of the alloys according to the invention reaches up to 80% and more at the intended application temperature.

A particularly composed copper alloy contains as alloying components
more than 4% by weight of manganese,
more than 10% by weight of aluminum,
0.01 to 0.8 wt .-% chromium and
individually or in total
0 to 18% by weight of one or more of the elements nickel, iron, cobalt,
Zinc, silicon, vanadium, niobium, molybdenum, chromium, tungsten, beryllium, lithium, yttrium, cerium, scandium, calcium, titanium, phosphorus, zirconium, boron, nitrogen,
Carbon, but each element does not exceed 6% and
contains 100 wt .-% copper.

A selected copper alloy, which is suitable in particular for mechanically loaded components with specifically improved mechanical damping, contains as alloy constituents
> 4 to 12% by weight of manganese,
> 10 to 14% by weight of aluminum,
0.01 to 0.8 wt .-% chromium and
individually or in total
0 to 18% by weight of one or more of the elements nickel, iron, cobalt,
Zinc, silicon, vanadium, niobium, molybdenum, chromium, tungsten, beryllium, lithium, yttrium, cerium, scandium, calcium, titanium, phosphorus, zirconium, boron, nitrogen, carbon, but each element not more than 6% and
ad 100% by weight of copper.

The copper alloy may preferably contain between 1 and 4 wt% nickel.

The copper alloy may preferably contain between 11.6 and 12% by weight, more preferably about 11.8% by weight of aluminum.

The copper alloy may preferably contain between 8 and 10% by weight of manganese.

The copper alloy may preferably contain between 2 and 4% by weight of iron and / or between 0.001 and 0.05% by weight of boron.

The copper alloy may preferably contain between 0.01 and 1 wt% cobalt.

The copper alloy may preferably contain between 0.01 and 0.3 wt% of rare earths.

The copper alloy may furthermore preferably contain between 2 and 6% by weight of zinc.

This abovementioned copper alloy can be obtained according to the invention by adapting the martensit-austenitic transformation temperatures or the associated intervals MS to MF and / or AS to AF to a predetermined operating or operating temperature of the component, as described above.

For existing HIDAMETs with martensitic phase transformations, it has been described in the prior art that the maximum attenuation upon cooling from the austenite state occurs near the MS temperature and when heated from the martensite state in the region of the AS temperature. These attenuation maxima are not used in the art because the transformation temperatures of the material with the existing methods are poorly reproducible. Apparently small changes in the chemical composition due to oxidation or burning of the alloying elements cause shifts in the transformation temperatures, which can be more than 100 ° C. Therefore, it is not yet possible to reproducibly set the MS or AS temperature in the range ± 10 ° C by very accurate gating and careful melt flow. In the production of conventional HIDAMETs, it is therefore deliberately avoided to achieve the maximum attenuation in favor of the smaller but better reproducible attenuation values in the purely martensitic state.
This disadvantage is overcome by the invention.

Experiments by the inventors show that addition of copper raises the transformation temperatures. Additions of other alloying elements reduce the transformation temperatures. A particularly strong influence on the martensitic transformation temperatures can be achieved by adding aluminum and manganese. In a preferred embodiment, therefore, the correction of the transformation temperatures during melting by additions of copper or aluminum is achieved. Due to the high melting point of manganese and the high

Affinity to oxygen is preferable to adding aluminum to lower the transition temperatures to an addition of manganese.

The maximum values for the specific damping capacity occur in the alloy according to the invention during cooling from the austenite state in the range between M _s and M _F and when heating from the Martensitzustand between A _s and A _F.

Therefore, the temperature in the middle of the martensitic or austenitic phase transition interval should be as close as possible to the operating temperature of components made from the alloy of the invention. It is therefore possible with the invention to produce alloys for specific predetermined service or operating temperatures or temperature ranges, which are then particularly suitable for certain applications and components.

The exact adjustment of the transformation temperatures is made with a sample taken during the melting process which allows an express control of the transformation temperatures for the liquid alloy. As a sample for the express control, it is preferable to use a cast wire drawn from the melt by means of a quartz tube in which a negative pressure is generated. The determination of the transformation temperatures can be carried out on this sample, depending on the expected application either in the casting state or after the heat treatment by known experimental methods for the detection of Phasentibergängen.

Preferably, the transformation temperature on the sample may be by calorimetry, dilatometry, electrical conductivity measurement, light microscopy, or acoustic emission measurement.

Based on the results of the examination of the Express sample, an immediate correction of the chemical composition of the melt, as described above, preferably with copper or aluminum. With the method according to the invention it is thus possible, the transformation temperatures in the material so adjust the alloy to the maximum possible damping capacity at the intended application temperature. This ensures an efficient adaptation of the material to the respective conditions of use.

The martensitic transformation can also be initiated in a defined temperature range via externally applied voltages. In this case, the transformation temperatures in the material increase linearly with the load. This increase in the transformation temperatures must already be considered in the production of components made from the alloy according to the invention, if mechanical stresses are to be expected there.

In addition to the influencing factors already mentioned, the damping maximum is also considerably influenced by the microstructure of the alloy, with larger grains leading to better damping properties. By appropriate alloying measures, the grain size of the alloy can be adjusted so that for each specific application, an optimal compromise between the damping capacity and the mechanical properties is achieved.

It has also been found that an improvement of the damping properties can be achieved by a heat treatment. As particularly effective has an annealing at temperatures of 650 ° C to 950 ° C with subsequent cooling or quenching (quenching) in liquid or gaseous media such. As air, liquid nitrogen, water, salt bath or oil proved. The temperature of the quenching medium should preferably be above the M _s temperature in order to avoid uncontrollable shifts in the transformation temperatures in the material. The aging sensitivity of the transition temperatures can be reduced according to the invention by an additional aging of the quenched alloy at a temperature of 150 ° C to 250 ° C. Expediently, such outsourcing takes 5 to 120 minutes.

On large and solid castings of the alloy according to the invention, which can not be subjected to heat treatment and quenching, a martensitic structure can be produced in the surface layer according to a further feature of the invention by laser remelting. In this case, the surface layer takes over the damping role, without the entire component must be subjected to a costly heat treatment. In the production of such castings, the transformation temperatures of the alloy during melting by the express control are adjusted so that, taking into account the cooling conditions in the laser remelting, the transition temperatures in the surface layer correspond to the application temperature of the component.

The alloys obtained by the process according to the invention can be used particularly advantageously for reducing vibrations for noise damping on mechanically loaded components, in particular in ship propellers, machine housings, in particular pump housings, generator housings, vibrating machines, precision apparatus, electronic instruments, tools which, during operation, oscillate and / or or are exposed to blows or generate them, in particular stamps, dies, machine hammers, turning and milling tools.

The invention is explained in more detail below with reference to an embodiment.

example

To produce noise-damping compressor housings or various hydraulic components, it is possible to use an alloy which unfolds its maximum damping properties at a temperature of approximately 120 ° C.

• Grundzusammensetzung:
  • 84 Gew.% Kupfer
  • 12 Gew.-% Aluminium
  • 4 Gew.% Mangan

For this purpose, the following alloy was produced in an induction furnace in air:

• Basic composition:
  • 84% by weight of copper
  • 12% by weight of aluminum
  • 4% by weight of manganese

Express-sampling:

For the express control of the transformation temperatures, the following procedure was developed: The sample is a cast wire having a length of 10 to 150 mm (preferably 15 to 100 mm) and a cross-sectional area of 0.2 to 7 mm ² , preferably 0.7 to 3.2 mm ² . This is pulled out of the melt with the help of a quartz tube, in which a negative pressure is generated. This sample can be used directly and very quickly with known detection methods. In a preferred method also used here, the acoustic emission is tracked over a temperature profile.

The first sample for express control of the melt transition temperatures with the base composition provided A _F = 100 ° C; A _s = 52 ° C; M _s = 68 ° C and M _F = 15 ° C.

wiedergegeben wird.By adding copper, the transformation temperatures of this melt were corrected to higher values. In the following express sample, A _F = 145 ° C, A _s = 74 ° C; M _s = 102 ° C and M _F = 43 ° C determined. These transformation temperatures are well suited for achieving maximum attenuation values at 120 ° C. The melt was poured into a preheated to 300 ° C mold. Samples for the damping measurement were worked out from the castings obtained. To characterize the damping behavior, the specific damping capacity was used. The internal friction was measured at a bending vibration frequency of 0.1 Hz under a constant heating and cooling rate (1 K / s). For these purposes, the 2980 DTMA V1.7B was used by TA Instruments. The internal friction is parameterized in terms of the phase angle between stress and strain. To characterize the damping behavior was a specific damping capacity, by the formula $$\mathrm{Spec}\mathrm{,}\mathrm{D}\ddot{\mathrm{a}}\mathrm{mpfungskapazität}\mathrm{=}\mathrm{2}\mathrm{\pi \; tan\phi }$$

is reproduced.

The damping behavior of the alloy produced in this way is in FIG. 1 play.

Fig. 1 : Formation of specific damping capacity of the alloy of the example taken for a heating and cooling cycle

FIG. 1 shows a measurement diagram that have been taken to the example described above. The specific damping capacity is plotted in% above the temperature in ° C. The temperatures were passed through in a heating and cooling cycle from below zero to 200 ° C and back. As can be seen, in the example alloy in the austenitic interval much higher attenuation can be achieved than in the martensitic, so that the frequently occurring in the art restriction to martensitic structures must lead to significant disadvantages for the alloy properties.

The example alloy achieves its maximum damping properties at a temperature of 120 ° C and thus successfully fulfills the stated task. The achievable damping is over 70%.

Claims (13)

1. Process for specifically improving the mechanical damping of a mechanically stressed component by matching the martensite-austenite transformation temperatures of an alloy used in the component to a predetermined use or working temperature for the component in such a way that the planned use temperature for the component is between the transformation limits M_s and M_f and/or A_s and A_f, where the matching of the transformation temperatures is effected by varying the alloy composition during melting of the alloy during its production, where the alloy comprises, as constituents of the alloy,
   from 2 to 12% by weight of manganese,
   from 5 to 14% by weight of aluminum and, individually or together,
   from 0 to 18% by weight of one or more of the elements nickel, iron, cobalt, zinc, silicon, vanadium, niobium, molybdenum, chromium, tungsten, beryllium, lithium, yttrium, cerium, scandium, calcium, titanium, phosphorus, zirconium, boron, nitrogen, carbon, but each element in an amount of not more than 6%, and copper to 100% by weight, and, in the process,

   a) a composition having a martensite-austenite transformation is selected for the alloy and the constituents are melted in a customary way at a suitable temperature,

   b) during this melting, at least one of the martensitic and austenitic transformation temperatures M_s, M_F, A_s and A_F is determined on a sample taken from the melt,

   c) these transformation temperatures are increased or reduced on the basis of a predetermined use or working temperature of the component by targeted addition of at least one constituent of the alloy and thus matched to the use or working temperature,

   d) the new transformation temperatures and, if appropriate, ranges are checked by means of a further sample and

   e) the alloy is cast into the desired mold.
2. Process according to Claim 1, characterized in that the steps c) and d) are repeated as often as necessary.
3. Process according to Claim 1 or 2, characterized in that correction of the transformation temperatures is carried out during melting by addition of copper or aluminum.
4. Process according to any of Claims 1 to 3, characterized in that the transformation temperatures are set so that the temperatures in the middle of the martensitic or austenitic range of the phase transformation are very close to the predetermined use or working temperature.
5. Process according to any of Claims 1 to 4, characterized in that the alloy in the form of a shaped part obtained initially by casting or forging and if appropriate forming is subjected to heat treatment at temperatures of from 650°C to 950°C and subsequent cooling or quenching in liquid or gaseous media, in particular air, liquid nitrogen, water, a salt bath or oil.
6. Process according to Claim 5, characterized in that the temperature of the quenching medium is above the M_s temperature of the alloy.
7. Process according to any of Claims 1 to 6, characterized in that the alloy in the form of a shaped part obtained initially by casting or forging and if appropriate forming is heat treated/aged at a temperature of from 100 to 300°C for from about 5 to 120 minutes.
8. Process according to any of Claims 1 to 7, characterized in that the alloy is subjected to one or more thermal cycles between the austenitic state and the martensitic state and back.
9. Process according to any of Claims 1 to 8, characterized in that heat treatment of the outer layer of a shaped part obtained from the alloy by casting or forging and if appropriate forming is effected by means of laser remelting of the outer zone.
10. Process according to any of Claims 1 to 9, characterized in that the sample for quick monitoring of the transformation temperatures is taken by means of a fused silica tube in which a subatmospheric pressure is produced.
11. Process according to any of Claims 1 to 10, characterized in that the transformation temperatures are determined on the sample by calorimetry, dilatometry, measurement of the electrical conductivity, optical microscopy or measurement of the acoustic emission.
12. Process according to any of Claims 1 to 11, characterized in that the damping behavior is additionally influenced by targeted alteration of the grain size.
13. Use of the copper alloy obtained by a process according to any of Claims 1 to 12 for the reduction of vibrations and for noise damping on mechanically stressed components, for ships' propellers, machine housings, in particular pump housings, generator housings, vibrating machines, precision apparatuses, electronic instruments, tools which are subjected to vibrations and/or impacts during operation or produce these, in particular for punches, dies, machine hammers, lathe tools and milling tools.

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