Sliding contact material and method for manufacturing same

Abstract

The present invention is a sliding contact material having a composition of Cu of 6.0% by mass or more and 9.0% by mass or less, Ni of 0.1% by mass or more and 2.0% by mass or less, an additive element M of 0.1% by mass or more and 0.8% by mass or less, and the balance being Ag. The additive element M is at least one element selected from the group consisting of Sm, La and Zr. The present sliding contact material has a material structure in which dispersion particles containing an intermetallic compound containing at least both Ni and an additive element M are dispersed in an Ag alloy matrix. It is required that the ratio of a Ni content (% by mass) and a content of an additive element M (% by mass) (K.sub.Ni/K.sub.M) in the dispersion particles falls within a predetermined range. The present invention is an Ag alloy-based sliding contact material more excellent also in abrasion resistance than conventional ones, and a material adaptable to higher rotation numbers of micromotors.

Claims

1. A sliding contact material, comprising: Cu of 6.0% by mass or more and 9.0% by mass or less; Ni of 0.1% by mass or more and 2.0% by mass or less; an additive element M of 0.1% by mass or more and 0.8% by mass or less; and the balance being Ag and inevitable impurities, wherein: the additive element M is at least one element selected from the group consisting of Sm, La and Zr; the sliding contact material has, as a material structure thereof, a material structure in which dispersion particles containing an intermetallic compound containing at least both of Ni and an additive element M are dispersed in an Ag alloy matrix; and a ratio of a Ni content (% by mass) and a content of an additive element M (% by mass) (KNi/KM) in the dispersion particles falls within a range below, when an additive element M is Sm or La: 1.50 or more and 2.50 or less; when an additive element M is Zr: 1.80 or more and 2.80 or less.

2. The sliding contact material according to claim 1, comprising Sm as an additive element M, and having a ratio of Ni concentration (S.sub.Ni: % by mass) and concentration of an additive element M (S.sub.M: % by mass) (S.sub.Ni/S.sub.M) of 0.80 or more and 5.0 or less.

3. The sliding contact material according to claim 1, comprising La as an additive element M, and having a ratio of Ni concentration (S.sub.Ni: % by mass) and concentration of an additive element M (S.sub.M: % by mass) (S.sub.Ni/S.sub.M) of 1.50 or more and 5.0 or less.

4. The sliding contact material according to claim 1, comprising Zr as an additive element M, and having a ratio of Ni concentration (S.sub.Ni: % by mass) and concentration of an additive element M (S.sub.M: % by mass) (S.sub.Ni/S.sub.M) of 1.40 or more and 6.7 or less.

5. The sliding contact material according to claim 1, comprising Zn of 0.1% by mass or more and 2.0% by mass or less.

6. The sliding contact material according to claim 1, comprising Mg of 0.05% by mass or more and 0.3% by mass or less.

7. A method for manufacturing a sliding contact material, the material being defined in claim 1, comprising a step of generating molten metal of an Ag alloy and subsequently cooling and solidifying the molten metal, wherein: the molten metal of an Ag alloy comprises Cu of 6.0% by mass or more and 9.0% by mass or less, Ni of 0.1% by mass or more and 2.0% by mass or less, an additive element M of 0.1% by mass or more and 0.8% by mass or less, the balance being Ag and inevitable impurities; temperature of the molten metal of the Ag alloy before the cooling is 1300 C. or higher; and a cooling rate in cooling is set to be 100 C./min or larger, thereby producing the sliding contact material of claim 1.

8. A cladding material formed by combining either Cu or a Cu alloy with the sliding contact material being defined in claim 1.

9. The sliding contact material according to claim 2, comprising La as an additive element M, and having a ratio of Ni concentration (S.sub.Ni: % by mass) and concentration of an additive element M (S.sub.M: % by mass) (S.sub.Ni/S.sub.M) of 1.50 or more and 5.0 or less.

10. The sliding contact material according to claim 2, comprising Zr as an additive element M, and having a ratio of Ni concentration (S.sub.Ni: % by mass) and concentration of an additive element M (S.sub.M: % by mass) (S.sub.Ni/S.sub.M) of 1.40 or more and 6.7 or less.

11. The sliding contact material according to claim 3, comprising Zr as an additive element M, and having a ratio of Ni concentration (S.sub.Ni: % by mass) and concentration of an additive element M (S.sub.M: % by mass) (S.sub.Ni/S.sub.M) of 1.40 or more and 6.7 or less.

12. The sliding contact material according to claim 2, comprising Zn of 0.1% by mass or more and 2.0% by mass or less.

13. The sliding contact material according to claim 3, comprising Zn of 0.1% by mass or more and 2.0% by mass or less.

14. The sliding contact material according to claim 4, comprising Zn of 0.1% by mass or more and 2.0% by mass or less.

15. The sliding contact material according to claim 2, comprising Mg of 0.05% by mass or more and 0.3% by mass or less.

16. The sliding contact material according to claim 3, comprising Mg of 0.05% by mass or more and 0.3% by mass or less.

17. A method for manufacturing a sliding contact material, the material being defined in claim 2, comprising a step of generating molten metal of Ag alloy and subsequently cooling and solidifying the molten metal, wherein: the molten metal of an Ag alloy comprises Cu of 6.0% by mass or more and 9.0% by mass or less, Ni of 0.1% by mass or more and 2.0% by mass or less, an additive element M of 0.1% by mass or more and 0.8% by mass or less, the balance being Ag and inevitable impurities; temperature of the molten metal of the Ag alloy before the cooling is 1300 C. or higher; and a cooling rate in cooling is set to be 100 C./min or larger, thereby producing the sliding contact material of claim 2.

18. A method for manufacturing a sliding contact material, the material being defined in claim 3, comprising a step of generating molten metal of an Ag alloy and subsequently cooling and solidifying the molten metal, wherein: the molten metal of an Ag alloy comprises Cu of 6.0% by mass or more and 9.0% by mass or less, Ni of 0.1% by mass or more and 2.0% by mass or less, an additive element M of 0.1% by mass or more and 0.8% by mass or less, the balance being Ag and inevitable impurities; temperature of the molten metal of the Ag ahoy before the cooling is 1300 C. or higher; and a cooling rate in cooling is set to be 100 C./min or larger, thereby producing the sliding contact material of claim 3.

19. A cladding material formed by combining either Cu or a Cu alloy with the sliding contact material being defined in claim 2.

20. A cladding material formed by combining either Cu or a Cu alloy with the sliding contact material being defined in claim 3.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 shows a state diagram of a SmNi system for describing an intermetallic compound generated in the present invention.

(2) FIG. 2 shows a state diagram of a LaNi system and a state diagram of a NiZr system for describing an intermetallic compound generated in the present invention.

(3) FIG. 3 shows a view for depicting a test method of a sliding test performed in the present embodiment.

(4) FIG. 4 shows metal structure photographs in Examples 11 and 13, and EDS analysis result in Example 11.

(5) FIG. 5 shows metal structure photographs in Comparative Examples 1 and 2, and EDS analysis result in Comparative Example 2.

DESCRIPTION OF EMBODIMENTS

(6) Hereinafter, an embodiment of the present invention will be described. In the present embodiment, there was manufactured a sliding contact material in which Ni and an additive element, such as Sm, were added to an AgCu alloy etc., and abrasion resistance was evaluated. A test material was manufactured by mixing highly pure raw materials so as to give a predetermined composition, subjecting the mixture to high frequency melting to give molten metal, heating the molten metal with the measurement of temperature so as to become 1300 C. or higher, and thereafter quenching the same to give an alloy ingot. The cooling rate at this time is 100 C./min. Then, the alloy ingot was subjected to rolling processing and annealing at 600 C., and thereafter was subjected again to rolling processing and to cutting processing to give a test piece (length: 45 mm, width: 4 mm, thickness: 1 mm).

(7) In the present embodiment, as Examples 1 to 29, sliding contact materials of various compositions were manufactured through the above-described manufacturing process. Further, as Comparative Examples, there were manufactured alloys to which only one of Ni and Sm had been added (Comparative Examples 1, 2), and an alloy having an excessive Ni concentration (Comparative Example 3). In addition, there was also manufactured a sample to which Eu, which is a rare earth element other than Sm and La, had been added as an additive metal (Comparative Example 4).

(8) Further, in the present embodiment, influence due to manufacturing conditions of an alloy is also examined. Here, the molten metal temperature was set to lower (1100 C.) than the temperature (1300 C.) in respective Examples, from which the molten metal was chilled and alloys were manufactured (Comparative Examples 5, 7 and 8). Moreover, while the molten metal was kept at 1300 C. or higher, the molten metal was gradually cooled at less than 100 C./min through furnace cooling to manufacture an alloy (Comparative Example 6). Meanwhile, the alloys in Comparative Examples 5 and 6 have the same composition as in Example 13. Moreover, the alloy in Comparative Example 7 has the same composition as in Example 2, and the alloy in Comparative Example 8 has the same composition as in Example 7.

(9) Respective manufactured samples were first subjected to structure observation by SEM and presence or absence of precipitation of dispersion particles was checked. Then, 20 dispersion particles were selected randomly, qualitative analysis of the dispersion particles was performed by EDX to measure a Ni content and an M content in the dispersion particles, and the ratio thereof (K.sub.Ni/K.sub.M) was calculated. Regarding Examples 1 to 29, it was confirmed that K.sub.Ni/K.sub.M fell within the proper range in all the measured dispersion particles, and then an average value thereof was calculated. Regarding Comparative Examples, presence or absence of a dispersion particle containing both Ni and an additive element M was first examined for observed dispersion particles, and, when a dispersion particle containing Ni and an additive element M was not observed, the instance was decided that No dispersion particle existed. Moreover, when dispersion particles containing Ni and an additive element M were observed, after it was confirmed that all of K.sub.Ni/K.sub.M fell outside the proper range, an average value thereof was calculated. As the result, in Comparative Examples 3, 5 to 8, although dispersion particles containing Ni and an additive element M were observed, dispersion particles having values of K.sub.Ni/K.sub.M within the proper range could not be found.

(10) Further, for respective test pieces, a sliding test for evaluating abrasion resistance was performed. FIG. 3 roughly describes a method of the sliding test. In the test, each of test pieces according to respective Examples was used as a fixed contact, on which a wire material of AgPd50 processed as a movable contact assuming a brush was abutted and slid. On this occasion, the movable contact was applied with a load of 40 g while being constantly energized with 6 V and 50 mA, and, with one cycle defined such that when the movable contact moved total 20 mm after reciprocating back and forth 5 mm from a starting point (10 mm), was slid 50000 cycles (total sliding length was 1 km). After that, abrasion depth of a slid part was measured. Results are shown in Table 1. There are also shown in the evaluation results of measurement values of sliding contact materials composed of an AgCu alloy, AgCuZn alloy being a conventional technique.

(11) TABLE-US-00001 TABLE 1 Composition (% by mass) Dispersion Abrasion Additive element M particle volume Ag Cu Zn Mg Ni Sm La Zr Eu S.sub.Ni/S.sub.M K.sub.Ni/K.sub.M m.sup.2 Example 1 Balance 6.00 0.50 0.50 1.00 2.18 784 Example 2 0.30 0.10 3.00 2.32 795 Example 3 0.30 0.20 1.50 2.25 760 Example 4 1.00 0.40 2.50 2.09 755 Example 5 1.00 0.80 1.25 2.10 648 Example 6 2.00 0.80 2.50 2.21 720 Example 7 0.50 0.30 0.20 1.50 1.99 722 Example 8 8.00 0.30 0.40 0.75 2.28 662 Example 9 1.00 0.40 2.50 2.14 505 Example 10 0.80 1.25 2.17 430 Example 11 1.00 0.93 0.50 1.80 2.13 275 Example 12 0.20 0.20 1.00 2.09 792 Example 13 0.50 0.50 1.00 2.07 746 Example 14 0.80 0.80 1.00 1.87 757 Example 15 0.50 0.40 1.25 2.20 353 Example 16 0.10 5.00 1.63 508 Example 17 0.30 1.67 2.24 400 Example 18 0.10 5.00 2.15 547 Example 19 0.30 1.67 2.60 642 Example 20 0.05 0.50 0.50 1.00 1.50 665 Example 21 0.50 0.70 0.71 2.13 823 Example 22 1.80 0.30 6.00 2.35 883 Example 23 0.15 0.40 0.38 1.55 895 Example 24 0.80 0.60 1.33 1.86 899 Example 25 0.10 0.30 0.20 1.50 1.96 786 Example 26 8.80 1.00 0.80 1.25 2.15 683 Example 27 2.00 0.80 2.50 2.63 452 Example 28 2.00 0.30 0.20 1.50 1.95 623 Example 29 0.30 0.50 0.20 2.50 2.12 792 Comparative Balance 6.00 1.00 0.50 None 1930 example 1 Comparative 8.00 1.00 0.30 None 1112 example 2 Comparative 2.80 0.50 5.60 4.18 993 example 3 Comparative 0.50 0.30 1.67 None 1540 example 4 Comparative 0.50 0.50 1.00 0.83 983 example 5 Comparative 1.20 1010 example 6 Comparative 6.00 0.30 0.10 3.00 0.96 1206 example 7 Comparative 0.50 0.30 0.20 1.50 1.12 1125 example 8 Conventional Balance 8.00 None 4233 example 1 Conventional 1.00 None 3326 example 2

(12) From Table 1, it is confirmed that alloys to which Ni and additive element M (Sm, La, Zr) were concurrently added (Examples 1 to 29) have abrasion resistance dramatically improved as compared with conventional examples 1 and 2. Regarding Ni and the additive element M, addition of both is indispensable, and addition of only either one does not exert the effect. This can be grasped from comparison relative to Comparative Examples 1 and 2. In Comparative Examples 1 and 2, no intermetallic compound was generated, and Ni and Sm that could not be solid-dissolved to an Ag alloy being a matrix were dispersed separately.

(13) FIG. 4 shows metal structure photographs in Examples 11 and 13. In either sample, there are seen spherical dispersion particles caused by formation of an intermetallic compound of Ni and Sm. The alloy in Example 11 was an alloy showing the least abrasion volume and was excellent in abrasion resistance. In FIG. 4, an EDS analysis result of the dispersion particle in Example 11 is also shown as an example, from which it is known that the particle contains Ni and Sm in a proper quantity. On the other hand, FIG. 5 shows metal structure photographs in Comparative Examples 1 and 2. In Comparative Example 1, Ni alone is added, and a Ni phase of a long needle shape is seen. In Comparative Example 2, Sm alone was added, and no dispersion particle differing from Examples 11 and 13 was seen. In Comparative Example 2, an observed precipitation phase was subjected to EDS analysis, and naturally, the precipitation phase did not contain Ni.

(14) When Comparative Examples 3 to 8 are referred to in point of the constitution of the dispersion particle, it can be understood that the control of the ratio of a Ni content and a content of an additive element M (K.sub.Ni/K.sub.M) is necessary. That is, in each of Examples, there were not observed dispersion particles having a K.sub.Ni/K.sub.M value falling outside the regulated range corresponding to each additive element. In contrast, in each of Comparative Examples, there were not observed an alloy in which a dispersion particle (intermetallic compound) did not exist and a dispersion particle having a K.sub.Ni/K.sub.M value falling within a suitable range, although dispersion particles had been precipitated. For example, when Ni is exessive as is the case for Comparative Example 3, a dispersion particle with much Ni is generated. The Comparative Example 3 shows a slightly improved abrasion resistance but cannot be said to be good, as compared with Comparative Examples 1 and 2 and conventional examples 1 and 2.

(15) Further, when results of respective Examples are examined in detail, it is possible to say that the selection of Sm, La, and Zr as an additive element is effective. This can be understood from the fact that, although Eu being a rare earth element was added in Comparative Example 4, an intermetallic compound was not generated and no improvement of abrasion resistance was observed. Moreover, from results in Examples 21 to 24, it is possible to say that the control of the ratio of Ni concentration and the concentration of an additive element M (S.sub.Ni/S.sub.M) in the overall composition of an alloy is preferable in order to cause the alloy to exert more suitable abrasion resistance. Because, in these Examples, an abrasion volume exceeds 800 m.sup.2 and the abrasion resistance is considered to be slightly inferior to those in other Examples.

(16) Meanwhile, the present invention is based on alloys in which Ni and Sm and the like are added in an AgCu alloy (Examples 1 to 6, Examples 8 to 10, Examples 26 and 27). Further, by adding Zn to the alloy system constituting the base, it is furthermore reinforced (Examples 7, 11 to 25, 28). Moreover, Mg may be added (Example 29).

(17) In addition, from the results in Comparative Examples 5 to 8, it is known that setting of manufacturing conditions is important in order to obtain a suitable alloy. That is, Comparative Examples 5 and 6 are the same as Example 13 in terms of the composition, but the alloy was manufactured under such a manufacturing condition as low molten metal temperature or a slow cooling rate. While Comparative Examples 7 and 8 were also common to Examples 2 and 7 respectively in terms of the compositions, and the alloys were cast at molten metal temperature set to be low. In these Comparative Examples, no effective intermetallic compound is generated, the composition of dispersion particles falls outside the range, and abrasion resistance is also inferior. Accordingly, it is confirmed that the evaluation of the material according to the present invention based only on the composition (overall composition) is not preferable, but that a material structure associated with manufacturing conditions should be considered.

INDUSTRIAL APPLICABILITY

(18) As described above, the sliding contact material according to the present invention has high abrasion resistance relative to that of conventional Ag-based sliding contact materials. The present invention is particularly useful as a sliding contact material of a commutator of micromotors for which smaller size and higher rotation number progress. Further, motors such as micromotors produced by use of the sliding contact material according to the present invention are motors with high performance and high durability.