Electrode material for thermal-fuse movable electrode

Abstract

The present invention is an electrode material constituting a movable electrode of a thermal fuse, having a five-layer clad structure including a core material layer, an intermediate layer formed on the both sides of the core material layer, and a surface layer formed on the intermediate layer, wherein the core material layer includes Cu, the intermediate layer includes an AgCu-based alloy, the surface layer includes an AgCuO-based oxide-dispersed strengthened alloy, and the ratio of the thickness of the intermediate layer to the thickness of the surface layer (intermediate layer/surface layer) is 0.2 or more and 1.0 or less. This electrode material can be manufactured by partially internally oxidizing a three-layer clad material in which plate materials made of an AgCu-based alloy are clad-jointed to both sides of the plate material made of Cu.

Claims

1. An electrode material constituting a movable electrode of a thermal fuse, comprising: a five-layer clad structure comprising a core material layer comprising Cu, an intermediate layer comprising an AgCu-based alloy formed on the both sides of the core material layer, and a surface layer comprising an AgCuO-based oxide-dispersed strengthened alloy formed on each intermediate layer, wherein the AgCu-based alloy as an intermediate layer does not have a dispersion layer, the ratio of the thickness of the intermediate layer to the thickness of the surface layer is 0.2 or more and 1.0 or less, and the thickness of the surface layer comprising an AgCuO-based oxide-dispersed strengthened alloy is 15 m or more.

2. The electrode material according to claim 1, wherein the AgCuO-based oxide-dispersed strengthened alloy constituting each surface layer is obtained by internally oxidizing either an AgCu alloy of 3 to 12% by mass of Cu and the balance Ag or an AgCuNi alloy of 3 to 12% by mass of Cu, 0.03 to 0.7% by mass of Ni and the balance Ag.

3. The electrode material according to claim 2, wherein the AgCu-based alloy constituting each intermediate layer comprises either an AgCu alloy of 3 to 12% by mass of Cu and the balance Ag or an AgCuNi alloy of 3 to 12% by mass of Cu, 0.03 to 0.7% by mass of Ni and the balance Ag.

4. The electrode material according to claim 3, wherein Cu constituting the core material layer is either an oxygen-free copper or a tough pitch copper.

5. The electrode material according to claim 4, wherein the surface layer is formed by partially internally oxidizing a monolayer plate material comprising an AgCu-based alloy.

6. The electrode material according to claim 3, wherein the surface layer is formed by partially internally oxidizing a monolayer plate material comprising an AgCu-based alloy.

7. The electrode material according to claim 2, wherein Cu constituting the core material layer is either an oxygen-free copper or a tough pitch copper.

8. The electrode material according to claim 7, wherein the surface layer is formed by partially internally oxidizing a monolayer plate material comprising an AgCu-based alloy.

9. The electrode material according to claim 2, wherein the surface layer is formed by partially internally oxidizing a monolayer plate material comprising an AgCu-based alloy.

10. The electrode material according to claim 1, wherein the AgCu-based alloy constituting each intermediate layer comprises either an AgCu alloy of 3 to 12% by mass of Cu and the balance Ag or an AgCuNi alloy of 3 to 12% by mass of Cu, 0.03 to 0.7% by mass of Ni and the balance Ag.

11. The electrode material according to claim 10, wherein Cu constituting the core material layer is either an oxygen-free copper or a tough pitch copper.

12. The electrode material according to claim 11, wherein the surface layer is formed by partially internally oxidizing a monolayer plate material comprising an AgCu-based alloy.

13. The electrode material according to claim 10, wherein the surface layer is formed by partially internally oxidizing a monolayer plate material comprising an AgCu-based alloy.

14. The electrode material according to claim 1, wherein Cu constituting the core material layer is either an oxygen-free copper or a tough pitch copper.

15. The electrode material according to claim 14, wherein the surface layer is formed by partially internally oxidizing a monolayer plate material comprising an AgCu-based alloy.

16. The electrode material according to claim 1, wherein the surface layer is formed by partially internally oxidizing a monolayer plate material comprising an AgCu-based alloy.

17. A method for manufacturing the electrode material as defined in claim 1 comprising the steps of: jointing an intermediate layer plate material comprising an AgCu-based alloy to both sides of a core material layer comprising Cu to form a clad material; and heat-treating the clad material to internally oxidize a part of the intermediate layer plate material comprising an AgCu-based alloy to form a surface layer comprising an AgCuO-based oxide-dispersed strengthened alloy.

18. The method for manufacturing the electrode material according to claim 17, wherein heat-treating the clad material is performed at a heat-treating temperature of 500 to 700 C., an oxygen partial pressure of 0.01 MPa to 0.3 MPa, and a heat-treating time of 3 to 15 hours.

19. The method of claim 17, wherein the AgCuO-based oxide-dispersed strengthened alloy constituting each surface layer is obtained by internally oxidizing either an AgCu alloy of 3 to 12% by mass of Cu and the balance Ag or an AgCuNi alloy of 3 to 12% by mass of Cu, 0.03 to 0.7% by mass of Ni and the balance Ag.

20. The electrode material according to claim 17, wherein the AgCu-based alloy constituting each intermediate layer comprises either an AgCu alloy of 3 to 12% by mass of Cu and the balance Ag or an AgCuNi alloy of 3 to 12% by mass of Cu, 0.03 to 0.7% by mass of Ni and the balance Ag.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 illustrates a structure of a general thermal fuse.

DESCRIPTION OF EMBODIMENTS

(2) Hereinbelow, preferred examples of the present invention will be described. In the present embodiments, an electrode material having a five-layer clad structure applying Cu as a core material layer and forming an AgCu alloy (Cu content: 10% by mass) on both sides of this core material layer as intermediate layers, and an AgCuO alloy (Cu content: 10% by mass (12% by mass in terms of CuO)) as surface layers were manufactured, and the characteristics were evaluated.

EXAMPLE 1

(3) First, each metal was weighed so as to have an alloy composition of 90.0% by mass of Ag, 10.0% by mass of Cu, and an AgCu alloy was melted and cast. Thereafter, an AgCu alloy ingot was rolled to a thickness of 4.15 mm and cut to manufacture an AgCu alloy plate with a width of 115 mm and a length of 195 mm. Moreover, an oxygen-free copper ingot was rolled to manufacture a Cu plate with a width of 120 mm, a length of 200 mm and a thickness of 9 mm, and the above AgCu alloy plate was stacked on both sides of this Cu plate. After cold crimping at a pressure of 150 t, the laminate was maintained at 800 C. for 60 minutes in a mixed gas of nitrogen and hydrogen, and then hot crimped at a pressure of 100 ton. The crimped three-layer (AgCu alloy/Cu/AgCu alloy) clad material was subjected to rolling processing to manufacture a clad material tape.

(4) Next, the clad material tape described above was rolled to 450 m, to be a three-layer clad material tape made of an AgCu alloy layer with a thickness of 110 m and a core material layer with a thickness of 230 m. The ratio of the thickness of the AgCu alloy layer to the core material layer was almost the same as the ratio of the thickness of the AgCu alloy plate to the Cu plate before crimped. This three-layer clad material tape was internally oxidized to form an AgCuO alloy layer as a surface layer. The internal oxidation treatment was carried out in an internal oxidation furnace in the conditions of a heat treatment temperature of 600 C., an oxygen partial pressure of 0.02 MPa, and a heat treatment time of 8 hours. According to the internal oxidation treatment, an AgCuO alloy layer with a thickness of 70 m and an AgCu alloy layer with a thickness of 40 m were formed. Moreover, the internally oxidized alloy plate was further rolled to manufacture a clad material tape with a five-layer structure. The manufactured clad material tape has a total thickness of 89 m of AgCuO (15 m)/AgCu (7 m)/Cu (45 m)/AgCu (7 m)/AgCuO (15 m). The resulting clad material tape was cut to make an electrode material for evaluation with a dimension of 7 mm in width and 50 mm in length. The thickness of each layer was measured from cross-sectional observation with a metallurgical microscope.

EXAMPLE 2

(5) In Example 1, in the internal oxidation of the three-layer clad material (AgCu alloy/Cu/AgCu alloy), the heat treatment time was set at 10 hours, thereby forming an AgCuO alloy layer with a thickness of 91 m and an AgCu alloy layer with a thickness of 19 m. Thereafter, the resulting alloy plate was rolled in the same manner as in Example 1 to manufacture a clad material tape with a five-layer structure. The manufactured clad material tape has a total thickness of 89 m of AgCuO (18.3 m)/AgCu (3.7 m)/Cu (45 m)/AgCu (3.7 m)/AgCuO (18.3 m). The resulting clad material tape was cut to make an electrode material for evaluation.

EXAMPLE 3

(6) In Example 1, in the internal oxidation of the three-layer clad material (AgCu alloy/Cu/AgCu alloy), the heat treatment time was set at 3 hours, thereby forming an AgCuO alloy layer with a thickness of 55 m and an AgCu alloy layer with a thickness of 55 m. Thereafter, the resulting alloy plate was rolled in the same manner as in Example 1 to manufacture a clad material tape with a five-layer structure. The manufactured clad material tape has a total thickness of 89 m of AgCuO (11 m)/AgCu (11 m)/Cu (45 m)/AgCu (11 m)/AgCuO (11 m). The resulting clad material tape was cut to make an electrode material for evaluation.

COMPARATIVE EXAMPLE

(7) In Example 1, in the internal oxidation of the three-layer clad material (AgCu alloy/Cu/AgCu alloy), the heat treatment time was set at 12 hours, thereby forming an AgCuO alloy layer with a thickness of 100 m and an AgCu alloy layer with a thickness of 10 m. Thereafter, the resulting alloy plate was rolled in the same manner as in Example 1 to manufacture a clad material tape with a five-layer structure. The manufactured clad material tape has a total thickness of 89 m of AgCuO (20 m)/AgCu (2 m)/Cu (45 m)/AgCu (2 m)/AgCuO (20 m). The resulting clad material tape was cut to make an electrode material for evaluation.

CONVENTIONAL EXAMPLE AND REFERENCE EXAMPLE

(8) The AgCu alloy plate manufactured in Example 1 was rolled to 450 m, and the internal oxidation was carried out at a heat treatment temperature of 740 C., an oxygen partial pressure of 0.5 MPa, and a heat treatment time of 48 hours to form an AgCuO alloy (monolayer) as whole. This AgCuO alloy was further rolled to form a tape material of 89 m (conventional example). In addition, an oxygen-free copper in Example 1 was rolled to form a tape material of 89 m (reference example).

(9) For each electrode material of Examples 1 to 3, comparative example, conventional example and reference example manufactured as described above, the spring deflection limit was measured according to a spring deflection limit test to evaluate spring property. The results are shown in Table 1.

(10) TABLE-US-00001 TABLE 1 Thickness of Each Layer AgCuO AgCu Cu Intermediate Spring (Surface (Intermediate (Core Material Layer/Surface Deflection Layer) Layer) Layer) Layer Limit Example 1 15 m 7 m 45 m 0.47 227N/mm.sup.2 Example 2 18.3 m 3.7 m 45 m 0.2 215N/mm.sup.2 Example 3 11 m 11 m 45 m 1.0 244N/mm.sup.2 Comparative 20 m 2 m 45 m 0.1 205N/mm.sup.2 Example Conventional 89 m (0) 206N/mm.sup.2 Example (Monolayer) Reference 89 m 188N/mm.sup.2 Example (Monolayer)

(11) Based on the results of Examples 1 to 3, as the thickness of the AgCu alloy layer that is the intermediate layer increases (the ratio increases), the spring deflection limit tends to increase. In this regard, comparative example has a thin intermediate layer (intermediate layer/surface layer: 0.1) and has the same strength as the AgCuO alloy pure material that is a conventional example. In the present invention, the introduction of a copper layer that is the core material layer aims for cost reduction through the reduction of the use amount of Ag. However, in terms of strength, the AgCu alloy layer is set to 0.2 times or more based on the surface layer, whereby enough strength can be obtained.

(12) In addition, for each electrode material of Example 1, conventional example and reference example, the conductivity (% IACS) was measured to evaluate conductivity. As the measurement of conductivity, each electrode material with a thickness of 89 m was cut into 7 mm in width and 150 mm in length, then a current terminal was clamped at both ends thereof and a voltage terminal was clamped between 100 mm inside thereof to measure electrical resistance, and IACS was calculated. The measurement results are shown in Table 2.

(13) TABLE-US-00002 TABLE 2 Thickness of Each Layer AgCuO AgCu Cu (Surface (Intermediate (Core Material Conductivity Layer) Layer) Layer) (IACS/%) Example 1 15 m 7 m 45 m 96 Conventional 89 m 75 Example (Monolayer) Reference 89 m 101 Example (Monolayer)

(14) It can be seen from the results in Table 2 that Cu having conductivity higher than the AgCuO-based alloy is used as a core material layer as in Example 1, whereby showing conductivity higher than a conventional AgCuO-based alloy monolayer material. The conductivity of Example 1 is a characteristic close to the electrode material of a copper layer monolayer.

INDUSTRIAL APPLICABILITY

(15) The present invention is an electrode material that adopts a clad structure in which an AgCu alloy layer of an intermediate layer is set while using a copper layer as a core material, thereby being excellent in conductivity, and being capable of satisfying both cost and strength, and is suitable for a movable electrode of a thermal fuse. In addition, the thickness of the intermediate layer is set to the proper range, whereby the electrode material is also excellent in welding resistance of the AgCuO alloy of a surface layer. According to the present invention, the operational failure of the thermal fuse can be suppressed, and reliability of various electric devices can be ensured.