JP2011140704A - Copper alloy, copper alloy member and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novel copper alloy excellent in a damping property, a copper alloy member made of the copper alloy and a method for producing the same. <P>SOLUTION: When whole is 100 mass% (hereinafter referred to as %), the copper alloy contains 13 to 27% of antimony (Sb), zinc (Zn) and the balance comprising copper (Cu), inevitable impurities and/or a modifying element wherein sum of Sb and Zn is 50 to 60%. The copper alloy can obtain a high loss factor in a high frequency region and with low strain amplitude and is excellent in the damping property. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a copper alloy exhibiting excellent vibration damping properties and the like.

  An apparatus or device having a movable part that is mechanically movable often generates vibrations in each part, with the movable part serving as an excitation source. Such vibration is generally not preferable because it causes various noises and leads to a decrease in fatigue life. In order to suppress such vibration, a damping material is often used.

  As such a vibration damping material, for example, a member that does not require very severe mechanical properties such as strength and rigidity, heat resistance, etc., a resin material that easily absorbs vibration, or a material partially using the resin ( For example, a damping steel plate in which a resin material is sandwiched between steel plates is used.

  However, mechanical properties such as strength are required, and such a damping material cannot be easily used for a member used in a high temperature atmosphere, and a damping material made of a metal material is required. As such a damping material, in addition to a damping alloy based on Mn (Patent Document 1), a damping material made of a Cu-Zn-Sn-based or Cu-Al-Mn-based copper alloy (Patent Document 2, Patent Document 3) has been proposed. However, it is not always clear in which region these damping materials are excellent in damping performance.

Japanese Patent Laid-Open No. 7-242977 JP 2003-73759 A JP 2004-10997 A

  The present invention has been made in view of such circumstances, a copper alloy having a novel damping composition that is completely different from a conventional alloy, a copper alloy member comprising the copper alloy, and a method for producing the copper alloy. The purpose is to provide. In particular, an object of the present invention is to provide a copper alloy or the like that exhibits excellent vibration damping properties in a high frequency region and a low strain amplitude region, in which vibration damping properties are insufficient with conventional alloys.

  The present inventor has intensively studied to solve this problem, and as a result of repeated trial and error, a copper alloy containing Zn in a Cu—Sb alloy exhibits high damping properties in a high frequency region and a low strain amplitude region. I found out. The present invention described below has been completed by developing this result.

"Copper alloy"
When the copper alloy of the present invention is 100% by mass as a whole (hereinafter simply referred to as “%”), 13% to 27% of antimony (Sb), zinc (Zn), and the balance being copper (Cu ) And inevitable impurities and / or modifying elements, and the sum of Sb and Zn is 50% or more and 60% or less, and is excellent in vibration damping.

  The copper alloy of the present invention is basically a ternary copper alloy of Cu—Sb—Zn containing Cu as a main element and Sb and Zn as its alloy elements.

  First, the Cu—Sb binary copper alloy is excellent not only in vibration damping properties but also in mechanical properties (hardness, strength, etc.) due to the alloy element Sb. Furthermore, by adding Zn to the Cu—Sb binary copper alloy, further excellent vibration damping properties are exhibited. The mechanism and reason why the copper alloy of the present invention (including a copper alloy member described later) containing a predetermined amount of Sb and Zn exhibits excellent vibration damping properties are not necessarily clear, but at present, it is considered as follows.

  The vibration damping property of the copper alloy of the present invention is reduced when vibration energy is partially absorbed inside the vibration damping material, and the absorbed vibration energy is mainly converted into thermal energy and released to the outside. It is considered that the transmission of vibration is inhibited. In general, as a mechanism for absorbing and reducing such vibration energy (damping mechanism), a ferromagnetic type that absorbs vibration by moving a domain wall (boundary of a magnetic domain), a dislocation that absorbs vibration by movement of a dislocation in a metal crystal It is said that there are two types: a twin type that absorbs vibration by the movement of twins formed by a martensitic transformation, and a composite type that absorbs vibration by viscous flow near the interface between the matrix and soft dispersed particles.

  The damping mechanism of the Cu—Sb—Zn ternary copper alloy seems to be mainly the twin type described above. In particular, the copper alloy of the present invention has an acicular metal structure due to its component composition. It is considered that friction is generated at a portion intertwined in a needle shape to absorb vibration energy and converted into heat energy. Of course, this vibration suppression mechanism is also considered to exhibit excellent vibration suppression properties by the fusion of the above-mentioned plurality of vibration suppression mechanisms. For example, in the case of a copper alloy member obtained by subjecting the copper alloy of the present invention to plastic working, vibration may be absorbed by the movement of dislocation. The details of such a vibration control mechanism are currently under investigation.

By the way, when the copper alloy (copper alloy member) of the present invention was analyzed, it was found that the vibration damping property in the low strain amplitude region in the high frequency region was particularly good. Specifically, in the low distortion amplitude region (1 × 10 ⁻⁶ to 1 × 10 ⁻⁵ ) and the high frequency region (1000 to 20000 Hz), the loss coefficient (η) indicating the attenuation is 0.004 or more. It was found that it was 0.005 or more, 0.006 or more, 0.007 or more, 0.008 or more, 0.009 or more, 0.010 or more, or 0.020 or more.

This loss factor was obtained by the central excitation method (see FIG. 1). That is, the difference between the measurement frequency (f ₁ , f ₂ ) measured at the end of the test piece with respect to the excitation frequency (f ₀ ) when the center of the test piece (copper alloy member) is vibrated at various frequencies ( Δf = f ₂ −f ₁ ) (η = Δf / f ₀ ). A specific measurement method will be described later.

  Incidentally, as an index indicating the vibration damping ability, there are a logarithmic damping factor δ, a specific damping ability W, and the like in addition to the loss coefficient η mainly used in the present specification. These are related to each other and are related by a relational expression of δ = πη or W = 2πη. Therefore, even when the vibration damping ability indexes are different, they can be compared with each other by conversion using these relational expressions.

The above-described copper alloy of the present invention includes a material (copper alloy material) before processing or before heat treatment, but mainly a member (copper alloy member) subjected to plastic working or heat treatment. Similarly, in the case of this copper alloy member, the loss coefficient indicating the damping property in the low distortion amplitude region of 1 × 10 ⁻⁶ to 1 × 10 ⁻⁵ and the frequency region of 1000 to 20000 Hz is 0.004 or more. A damping member of 0.01 or more is preferable.

<< Method for Manufacturing Copper Alloy Member >>
In the case of the copper alloy of the present invention, the vibration damping property can be further enhanced by performing a specific heat treatment. Therefore, the present invention can be grasped not only as a copper alloy (member) but also as a heat treatment method (manufacturing method) thereof.

  That is, according to the present invention, when the total is 100% by mass (hereinafter simply referred to as “%”), 13% to 27% of antimony (Sb), zinc (Zn), and the balance being copper (Cu). And a heating step of heating a copper alloy material having a total of Sb and Zn of 50% or more and 60% or less to a heating temperature not lower than the phase transformation point, and after the heating step. And a quenching step of quenching the copper alloy material, and the copper alloy member described above is obtained.

<Others>
The “modifying element” referred to in this specification is an element other than Cu, Sb and Zn, which is effective for improving the characteristics of the copper alloy. There are no limitations on the types of properties to be improved, but there are vibration damping, hardness, strength, toughness, ductility, high temperature stability, and the like. The combination of each element which can become a modification element is arbitrary, and these elements are usually a trace amount.

  “Inevitable impurities” are impurities contained in the raw material, impurities mixed in at each step, and the like, and are elements that are difficult to remove due to cost or technical reasons. In the case of the copper alloy according to the present invention, for example, Al, Si, S, Fe and the like. Of course, the smaller the inevitable impurities, the better. The composition is not particularly limited.

  Unless otherwise specified, “x to y” in the present specification includes the lower limit x and the upper limit y. Further, the lower limit and the upper limit described in the present specification can be arbitrarily combined to constitute a range such as “ab”. Furthermore, numerical values arbitrarily selected from the numerical value range can be used as the upper and lower limit values.

  The form of “copper alloy” or “copper alloy member” in this specification is not limited. In particular, the copper alloy may be a material such as a bulk shape, a plate shape, a rod shape, or a tubular shape, or may be a final shape or a structural member close to the final shape.

  In addition, the copper alloy material used as these materials may be a melted material or a sintered material, but if it is a melted material, a dense and stable quality material can be obtained at low cost. On the other hand, in the case of a sintered material, a copper alloy material in a state close to the final product shape can be obtained by a (near) net shape. In any case, it is preferable to be manufactured in an oxidation-preventing atmosphere. For example, in the case of a melted material, it is preferable that the copper alloy material is melted in a vacuum. Incidentally, the degree of vacuum in this case is preferably about 10 to 100 Pa.

  The copper alloy and copper alloy member of the present invention exhibit a high loss factor in a high frequency range and a low strain amplitude, and are excellent in vibration damping properties. The copper alloy member of the present invention can be easily obtained by the method for producing a copper alloy member of the present invention.

It is explanatory drawing which shows the calculation method of the loss factor which indexes damping property. It is a microscope picture which shows the metal structure of the copper alloy of this invention, and shows the test material of Cu-15% Sb-40% Zn. It is a microscope picture which shows the metal structure of the copper alloy of this invention, and shows the test material of Cu-25% Sb-30% Zn. It is a microscope picture which shows the metal structure of the copper alloy of a comparative example, and shows the test material of Cu-15% Sb-30% Zn. It is a microscope picture which shows the metal structure of the copper alloy of a comparative example, and shows the test material of Cu-25% Sb-20% Zn. It is a graph which shows the loss coefficient of the copper alloy from which a component composition differs. It is a graph which shows the correlation with a frequency and a loss factor about the copper alloy of this invention.

  The present invention will be described in more detail with reference to embodiments of the invention.

  In addition, the content demonstrated by this specification including the following embodiment is suitably applied not only to the copper alloy which concerns on this invention but to a copper alloy member and its manufacturing method. For this reason, the configuration selected from the following can be added to any of the inventions, in a superposed manner or arbitrarily over the category, to the above-described configuration of the present invention. For example, if it is the structure regarding the composition of a copper alloy, it is related also to the manufacturing method as well as a copper alloy member. Even if it looks like a configuration related to a manufacturing method, if it is understood as a product-by-process, it can also be a configuration related to a copper alloy. Note that which embodiment is the best depends on the target, required performance, and the like.

<Alloy composition>
The copper alloy, the copper alloy member, and the copper alloy material (hereinafter simply referred to as “copper alloy”) of the present invention are composed of Cu, Sb, and Zn as main components. Specifically, the copper alloy of the present invention is composed of 13 to 27% of Sb and 50 to 60% of Zn in total, with the balance being Cu and inevitable impurities and / or modifying elements. These essential elements are described below.

  Sb is an element effective for improving the vibration damping property. When Sb is too small, the ratio of the Cu—Sb-based β phase having high damping properties in the β phase (face-centered cubic crystal) that causes twinning decreases. On the other hand, if Sb is too small, a needle-like structure that produces vibration damping cannot be obtained, and sufficient vibration damping cannot be obtained. If the amount of Sb is excessive, the copper alloy becomes brittle. For example, cracking may occur or the toughness may be reduced during cold working (cold rolling or the like). Therefore, Sb is set to 13 to 27% as described above. The preferred Sb content is 14.5 to 26.5%, more preferably 15 to 25%.

  Zn is an element effective for greatly improving the damping properties of the copper alloy on the premise of the presence of Sb. The Zn content affects the vibration damping properties while correlating with the Sb content. A copper alloy having a higher Sb content tends to have a higher Zn concentration in the α phase, which affects the formation of a needle-like structure. Therefore, Zn is 50-60% in total with Sb. If the total of Sb and Zn is too small, a needle-like structure that produces vibration damping cannot be obtained, and a sufficient vibration damping improvement effect cannot be obtained. If the sum of Sb and Zn is excessive, the copper alloy becomes brittle. The total content of Sb and Zn is 53 to 57% in total, and more preferably 54.5 to 55.5%.

  The copper alloy of the present invention containing Sb and Zn in the above range may have a needle-like metal structure. The acicular structure is a grain boundary precipitate composed of one or more of an Sb—Zn compound, a Cu—Sb compound, and a Cu—Zn compound. This needle-like structure is considered to greatly improve the vibration damping property of the Cu—Sb—Zn alloy. The acicular structure can be easily confirmed by observing the melted copper alloy of the present invention under a microscope.

"Production method"
<Copper alloy material>
The copper alloy material may be a melted material or a sintered material as long as it has the above-described composition. However, the damping properties and mechanical properties of the copper alloy can be reduced by the inclusion of oxides and the like, so the copper alloy material is preferably cast or sintered in an antioxidant atmosphere or a vacuum atmosphere.

  The copper alloy material may be obtained by subjecting a cast or sintered copper alloy to plastic working such as hot working (hot rolling, hot forging, etc.) or cold working. It is preferable that a copper alloy material having a final product (copper alloy member) shape or a shape close to it by this plastic working is subjected to a heat treatment described later, since the processing strain introduced by the plastic working is eliminated.

<Heat treatment>
The heat treatment (process) according to the present invention includes a heating process for heating the copper alloy material to a heating temperature equal to or higher than the phase transformation point, and a rapid cooling process for rapidly cooling the copper alloy material after the heating process. By performing such a heat treatment (so-called solution treatment), the vibration damping property of the copper alloy member can be greatly improved as compared with the case where the heat treatment is not performed or only the so-called annealing or normalization is performed. This is because a β phase stable at high temperature can be maintained at room temperature by rapidly cooling from high temperature to near room temperature. When the cooling rate is low, the β phase exhibiting high vibration damping properties is transformed into the δ phase, and hardly exhibits vibration damping properties. And by performing such a heat treatment, the acicular structure is also maintained.

  The phase transformation point referred to here is a temperature at which the α phase or the δ phase transforms into the β phase in the Cu—Sb—Zn ternary copper alloy, and not the martensite transformation temperature.

  Although the preferable heating temperature of a heating process changes with component compositions of a copper alloy, if it is in the range of this invention, it is suitable in it being 450-600 degreeC further 470-500 degreeC. This heating time is preferably a time at which the copper alloy can be sufficiently homogenized and productivity can be improved, for example, 0.5 to 3 hours, and further preferably 1 to 2 hours.

  A preferable cooling rate in the rapid cooling step is a rate at which a high-temperature copper alloy material can retain the β phase even at room temperature. The specific cooling rate varies depending on the composition of the copper alloy, but is preferably 300 to 1000 ° C./second, more preferably 800 to 900 ° C./second.

  In addition to these heat treatments, the copper alloy of the present invention may be further subjected to low-temperature annealing, aging treatment, or the like within a range where the vibration damping properties are improved or not extremely reduced.

<< Copper alloy parts >>
The copper alloy member of the present invention may be of any shape or application, but as an example, there is the above-described vibration damping member.

  As a specific example related to the vibration damping member, there is a vibration buffering body interposed in a vibration portion of the internal combustion engine. More specifically, a washer interposed in a bolt for fixing the engine oil pan to the cylinder block, a washer interposed between the fuel injector and the cylinder head, an insulator for shielding engine exhaust heat, and a bolt for fixing the same. In addition to the washer interposed between the oil pan, the oil pan, the intake pipe, the head cover, and the like.

  Since the copper alloy member of the present invention is made of metal, it is excellent in various mechanical properties such as strength, rigidity, toughness and elongation in addition to the above-described vibration damping properties. For example, the hardness is 200 HV or higher, further 400 HV or higher, and is sufficiently hard. Thus, since it is excellent in various mechanical characteristics, the copper alloy of the present invention can be sufficiently used as a structural member.

The present invention will be described more specifically with reference to examples.
<Manufacture of test pieces>
(1) Melting of copper alloy material Ingots of pure Cu, pure Sb and pure Zn were prepared as raw materials, and blended in various alloy compositions shown in Table 1. These blended raw materials were put in a graphite crucible and melted in a high frequency vacuum melting furnace. In this dissolution, after evacuating to (I) 0.1 to 0.5 torr (13.322 to 66.661 Pa), (II) introducing argon gas to 100 torr (13332.2 Pa), (III) and further degassing, 500 torr ( 66661 Pa) in an atmosphere in which Ar gas was introduced. The melting temperature at this time was 1050 ° C., and 5 kg of molten metal was prepared by one melting.

The molten copper alloy thus obtained was poured into an alumina mold under an Ar gas atmosphere and solidified by natural cooling. Thus, a test piece material (copper alloy material) having a cylindrical shape (φ70 mm × 130 mm) was obtained.
(2) Heat treatment The test piece material after hot rolling was placed in a heating furnace in the air atmosphere and heated at 500 to 600 ° C. for 1 hour (heating step), and then rapidly cooled by water cooling (rapid cooling step). The cooling rate at this time was about 900 to 1000 ° C./second. Various measurements and observations were performed using the test pieces (copper alloy members) thus obtained.
<Evaluation>
<Measurement of loss factor>
The loss factor was measured by the central excitation method using the various test pieces described above. The center excitation method is a method in which the center of a test piece is supported by a triangular jig, a predetermined vibration is applied to the triangular jig, and the frequency of vibration transmitted at the end of the test piece is measured. In the vibration applied in this example, the frequency was 0 to 20000 Hz, and the distortion amplitude was 1 × 10 ⁻⁶ to 1 × 10 ⁻⁵ .

  The frequency response function in the said frequency range was calculated | required by changing a frequency. The loss factor was calculated from the frequency response function by the half-width method. An outline of this calculation method is shown in FIG.

<Microscope observation>
The metal structure of each test piece shown in Table 1 was observed with a metallographic microscope. The respective micrographs are shown in FIGS. In each micrograph, the bright portion was the α phase, and the dark portion was the β phase. In FIG. 2 and FIG. 3, a needle-like structure was observed in the β phase that appeared dark.

  FIG. 6 shows the loss factor of each test piece. Specimens # 01 and # 02 exhibited excellent vibration damping properties with a loss factor of η> 0.01 regardless of whether the frequency was 1500 Hz or 4000 Hz. On the other hand, the loss factors of the test pieces # C1 and # C2 were very low in any case. The major difference between the test pieces # 01 and # 02 and the test pieces # C1 and # C2 was in the metal structure. In the test pieces # 01 and # 02 (FIGS. 2 and 3), needle-like tissues that were not found in the test pieces # C1 and # C2 (FIGS. 4 and 5) were observed.

  Further, as apparent from FIG. 7, the test pieces # 01 and # 02 showed high loss coefficients in a wide frequency range. All the test pieces showed a high loss factor even in a high frequency region. Specifically, # 01 showed η> 0.01 in a wide frequency range, and η = 0.0001 at 4000 Hz. # 02 showed η> 0.01 at 4000 Hz or less, and η = 0.110 at 4000 Hz, and η = 0.00697 at 12000 Hz.

  FIG. 7 shows the loss coefficient η in the range of 1000 to 8000 Hz for the test pieces # 01 and # 02. It is predicted from FIG. 7 that the test pieces # 01 and # 02 exhibit η> 0.004 even at 15000 Hz or 20000 Hz.

Claims (7)

When the total is 100% by mass (hereinafter simply referred to as “%”),
13 to 27% antimony (Sb),
Zinc (Zn);
A copper alloy characterized in that the balance is made of copper (Cu) and inevitable impurities and / or modifying elements, and the total of Sb and Zn is 50% or more and 60% or less and has excellent vibration damping properties.   The copper alloy according to claim 1, wherein the total of Sb and Zn is 53% or more and 57% or less.   The copper alloy according to claim 1 or 2, which has a needle-like metal structure. A copper alloy member comprising the copper alloy according to claim 1,
Copper having a loss factor of 0.004 or more indicating a damping property in a low distortion amplitude region of 1 × 10 ⁻⁶ to 1 × 10 ⁻⁵ and a frequency region of 1000 to 20000 Hz Alloy member. A heating step of heating the copper alloy material according to any one of claims 1 to 3 to a heating temperature equal to or higher than a phase transformation point;
A rapid cooling step of rapidly cooling the copper alloy material after the heating step;
A copper alloy member manufacturing method according to claim 5 or 6, wherein the copper alloy member according to claim 5 or 6 is obtained.   The method for producing a copper alloy according to claim 5, wherein a heating temperature in the heating step is 450 to 600 ° C.   The method for producing a copper alloy member according to claim 5, wherein the copper alloy material is a melted material melted in a vacuum.