Electrode

Abstract

To provide a technology to improve the wear resistance of an electrode.SOLUTION: An electrode is made of an alloy containing aluminum and two or more metal elements other than aluminum, and the number of moles of each metal element contained in the alloy is 0.85 to 1.6 times the number of moles of aluminum contained in the alloy.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an electrode. [Background technology]

[0002] Discharge electrodes have been known for some time (for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-069826 [Patent Document 2] Japanese Patent Application Publication No. 9-291327 Summary of the Invention [Problem to be solved by the invention]

[0004] However, even with prior art such as that disclosed in Patent Document 1, there is still room for improvement in the technology for improving the wear resistance of electrodes.

[0005] An object of the present invention is to provide a technique for improving the wear resistance of an electrode. [Means for solving the problem]

[0006] The present invention has been made to solve at least part of the above-mentioned problems, and can be realized in the following aspects.

[0007] (1) According to one aspect of the present invention, there is provided an electrode made of an alloy containing aluminum and two or more metal elements other than aluminum, wherein the number of moles of each of the metal elements contained in the alloy is 0.85 to 1.6 times the number of moles of aluminum contained in the alloy.

[0008] According to this configuration, the electrode is made of an alloy containing aluminum and two or more metal elements other than aluminum. The number of moles of each of the two or more metal elements contained in the alloy is 0.85 to 1.6 times the number of moles of aluminum contained in the alloy. As a result, the alloy contains a certain amount or more of aluminum, which has excellent corrosion resistance, and also contains two or more metal elements that complement the low melting point of aluminum, thereby reducing the amount of wear of the electrode 1 during use. Therefore, wear resistance can be improved.

[0009] (2) In the electrode of the above embodiment, each of the metal elements may be any one of scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, and copper. According to this configuration, the alloy contains a transition metal element of the fourth period, which has excellent corrosion resistance and a relatively high melting point. This further improves wear resistance.

[0010] (3) In the electrode of the above embodiment, the alloy may contain nickel, iron, and chromium. With this configuration, the alloy contains nickel, iron, and chromium, which have even better corrosion resistance and relatively high melting points. This can further improve wear resistance.

[0011] (4) In the electrode of the above embodiment, each of the metal elements may be any one of scandium, titanium, vanadium, chromium, iron, cobalt, nickel, and copper. According to this configuration, each of the two or more metal elements contained in the alloy includes a transition metal element of the fourth period elements, excluding manganese, which has relatively low corrosion resistance. This can suppress a decrease in wear resistance.

[0012] (5) In the electrode of the above embodiment, the alloy may have a single-phase crystalline phase. According to this configuration, the alloy has a single-phase crystalline phase. As a result, when the electrode is used for discharge, the discharge surface wears evenly, thereby suppressing localized wear. Therefore, partial detachment of the electrode is suppressed, thereby improving wear resistance.

[0013] (6) In the electrode of the above embodiment, the alloy may have multiple crystalline phases with different compositions, and the multiple crystalline phases may have the same crystalline structure. According to this configuration, the alloy has multiple crystalline phases with different compositions but the same crystalline structure. As a result, when the electrode is used for discharge, the discharge surface wears evenly, thereby suppressing localized wear. Therefore, partial electrode detachment is suppressed, thereby further improving wear resistance.

[0014] The present invention can be realized in various forms, for example, in the form of an apparatus including an electrode, a method for manufacturing an electrode and an apparatus including an electrode, a method for controlling an apparatus including an electrode, an apparatus for manufacturing an electrode, a computer program for causing an apparatus for manufacturing an electrode to manufacture an electrode, or the like. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is an external view of a spark plug equipped with an electrode according to a first embodiment. [Figure 2] FIG. 10 is a diagram illustrating the results of a first evaluation test on electrodes. [Figure 3] FIG. 10 is a diagram illustrating a test method for a first evaluation test. [Figure 4] FIG. 10 is a diagram illustrating a first result of a second evaluation test on an electrode. [Figure 5] FIG. 10 is a diagram illustrating a second result of a second evaluation test on electrodes. DETAILED DESCRIPTION OF THE INVENTION

[0016] First Embodiment 1 is an external view of a spark plug equipped with an electrode according to a first embodiment. The spark plug 10 of this embodiment is attached to, for example, an internal combustion engine (not shown) and generates a discharge to combust fuel supplied into a cylinder. The spark plug 10 of this embodiment includes an insulator 11, an electrode 1, a metallic shell 12, and a ground electrode 13.

[0017] The insulator 11 is a substantially cylindrical member formed to extend along the central axis C10 of the spark plug 10. The insulator 11 is made of a material having excellent insulating properties, heat resistance, and thermal conductivity, such as alumina (Al2O3). A terminal 14 is provided at one end 11a of the insulator 11. An electrode 1 electrically connected to the terminal 14 is provided at the other end 11b of the insulator 11.

[0018] The electrode 1 is an alloy containing multiple metal elements. The electrode 1 is held by the insulator 11 by being partially inserted into a hole (not shown) formed in the other end 11b of the insulator 11. The tip 1a of the electrode 1 is formed so that the outer diameter becomes smaller as it gets further away from the insulator 11.

[0019] The electrode 1 is made of an alloy containing aluminum (Al) and two or more metal elements other than aluminum, and the number of moles of each metal element contained in the alloy is 0.85 to 1.6 times the number of moles of aluminum contained in the alloy. Here, "two or more metal elements other than aluminum" refers to metal elements (constituent elements) other than aluminum contained in the alloy that account for 5 mol% or more of the alloy in terms of mole percentage. Each of the two or more metal elements other than aluminum contained in the alloy of the electrode 1 is a transition group element of the fourth period elements, and is one of scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu). The alloy of the electrode 1 of this embodiment contains four metal elements other than aluminum: nickel, iron, chromium, and cobalt, but does not contain manganese. The metal elements contained in the alloy of electrode 1 are identified using an electron probe microanalyzer (EPMA) or a scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS). The alloy of electrode 1 may contain a few percent of yttrium by weight. In addition to the four metal elements, the alloy of electrode 1 may also contain impurities.

[0020] The alloy of electrode 1 of this embodiment has a single crystalline phase. The crystalline phases constituting the alloy of electrode 1 of this embodiment have a face-centered cubic (FCC) structure of the same composition. The crystalline structure of the crystalline phase of the alloy of electrode 1 is identified by a combination of visual observation of the cross section in an SEM image and X-ray diffraction (XRD) using an X-ray diffractometer. Note that in this embodiment, "the alloy has a single crystalline phase" also includes cases where, in addition to a single crystalline phase, trace components such as the above-mentioned yttrium and impurities are contained.

[0021] The metallic shell 12 is a generally cylindrical metal member formed to extend along the central axis C10 of the spark plug 10. The metallic shell 12 is formed of a conductive metal such as low-carbon steel or a metallic material primarily composed of iron. The metallic shell 12 is provided so as to partially cover the insulator 11. The metallic shell 12 has a seat portion 12a that protrudes radially outward from the metallic shell 12, and a body portion 12c having a thread groove 12b formed on its outer periphery. When the spark plug 10 is mounted in an internal combustion engine, the thread groove 12b of the body portion 12c is fitted into a threaded hole formed in the internal combustion engine, whereby an annular gasket (not shown) is sandwiched between the seat portion 12a and the body portion 12c, ensuring airtightness of the threaded hole of the internal combustion engine.

[0022] The ground electrode 13 is a metal member joined to the body portion 12c of the metallic shell 12 on the side opposite to the seat portion 12a. The ground electrode 13 is formed of a metal material such as a Ni-based alloy containing nickel as a main component. Examples of alloying elements added to the Ni-based alloy of the ground electrode 13 include manganese, chromium, and aluminum. The ground electrode 13 has a shape that is bent into a substantially L-shape, and a tip portion 13a is positioned to face the electrode 1.

[0023] Next, a method for manufacturing the electrode 1 will be described. In manufacturing the electrode 1, first, elemental metals of aluminum, nickel, iron, chromium, and cobalt are placed in a copper container so that the number of moles is the same. The five types of elemental metals placed in the copper container are arc-melted in an argon atmosphere to produce an ingot of a metal represented by the composition formula AlNiFeCrCo. The produced metal ingot is processed into the shape of the electrode 1 to produce the electrode 1 of the spark plug 10. Note that the method for manufacturing the alloy of the electrode 1 is not limited to this. It may also be high-frequency melting, the Bridgman method, metal additive manufacturing, powder sintering, mechanical alloying, or the like.

[0024] Next, we will explain the evaluation test of the electrode. In this evaluation test, multiple electrode samples were produced that differed in at least one of the number and type of metal elements contained in alloys that can be used for the electrode, and two types of evaluations were performed on the wear resistance of the electrode.

[0025] Figure 2 is a diagram illustrating the results of the first evaluation test for electrodes. In the first evaluation test, the volume (consumed volume) that was reduced when used as a discharge electrode was measured for each of the 12 types of samples shown in Figure 2, which differ in the number and type of metal elements, and the wear resistance when used as an electrode was compared.

[0026] Each of the 12 types of samples shown in FIG. 2 was manufactured by a method similar to the manufacturing method of the electrode 1 of the first embodiment. Specifically, for each of the 12 types of samples, the elemental metals of the multiple metal elements shown in FIG. 2 were first placed in a copper container so as to have the molar percentages shown in FIG. 2. The multiple elemental metals placed in the copper container were arc-melted in an argon atmosphere to produce metal ingots that would become each of the 12 types of samples. The manufactured metal ingots were then machined into a shape to be used in the discharge test described below. All of the 12 types of samples shown in FIG. 2 contain 20 mol % or more of aluminum.

[0027] Figure 2 shows "Rm," which is the ratio of other metal elements when the mole percentage of aluminum is set to 1, for each of the 12 types of samples used in the first evaluation test. "Rm" shown in Figure 2 is the value obtained by dividing the mole percentage of each metal element shown in the "Mole percentage of metal elements contained in the sample" in Figure 2 by the mole percentage of aluminum. In other words, "Rm" indicates the ratio of each metal element contained in the alloy to the number of moles of aluminum contained in the sample (alloy).

[0028] FIG. 3 is a diagram illustrating the test method of the first evaluation test. In the first evaluation test, a discharge test was conducted to measure the volume consumed by each sample using the evaluation device Ex1 shown in FIG. 3. The evaluation device Ex1 includes a chamber Ch and a power supply unit Ps. The chamber Ch can accommodate a sample Sp and a counter electrode Ce therein. The sample Sp and the counter electrode Ce in the chamber Ch are arranged so that a gap Gp is ​​1.05 mm. The sample Sp and the counter electrode Ce in the chamber Ch are each connected to a power supply unit Ps, and discharge occurs using electricity supplied by the power supply unit Ps. In the discharge test, first, the weight W0 of the sample before it was attached to the chamber Ch was measured. Next, the chamber Ch containing the sample Sp was placed under predetermined conditions (nitrogen atmosphere, room temperature), and discharge was conducted at a frequency of 100 Hz for 3 hours. After discharging for 3 hours, the weight W1 of the sample was measured, and the consumed volume of the sample "ΔVol (mm 3 ) was calculated.

[0029] In Figure 2, the results of the wear resistance assessment based on the calculated "wear volume" are shown as "Assessment." The "Assessment" was classified into the following symbols S, A, B, C, and D according to the size of the calculated "wear volume." The "wear volume" of the sample was 0.08 mm 3 Smaller is desirable (i.e., for "judgment," S, A, B, and C are acceptable). S:ΔVol<0.02mm 3 A: 0.02 mm 3 ≦ΔVol<0.04mm 3 B: 0.04 mm 3 ≦ΔVol<0.06mm 3 C: 0.06 mm 3 ≦ΔVol<0.08mm 3 D: 0.08 mm 3 ≦ΔVol

[0030] As shown in FIG. 2 , among Samples 1 to 12, Samples 5 to 12 were graded S, A, B, or C based on the "consumed volume," demonstrating superior wear resistance compared to Samples 1 to 4, which were graded D. Each of Samples 5 to 12 is an alloy containing aluminum and two or more metal elements other than aluminum, with the number of moles of each metal element being 0.85 to 1.6 times the number of moles of aluminum contained in the alloy. This suggests that the alloys contain a certain amount of aluminum, which has excellent corrosion resistance, as well as two or more metal elements that can compensate for the low melting point of aluminum, thereby improving the wear resistance of the alloys. On the other hand, Sample 1, unlike the alloy of Electrode 1 of this embodiment, contains only two metal elements, including aluminum. Each of Samples 2 to 4 contains aluminum and two or more metal elements other than aluminum, but the "value of manganese relative to the number of moles of aluminum as 1" is less than 0.85 or more than 1.6.

[0031] Of Samples 5 to 12, Samples 9 to 12 were given a grade of S, A, or B, confirming that they had even better wear resistance than Samples 5 to 8, which were given a grade of C. In each of Samples 9 to 12, the alloy contains two or more metal elements other than aluminum, each of which is one of the following metal elements: scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, and copper, which are fourth-period transition metals that have excellent corrosion resistance and relatively high melting points. This is thought to have further improved the wear resistance of the alloy.

[0032] Of Samples 9 to 12, Samples 10 to 12 were given a grade of S or A, confirming that they have even better wear resistance than Sample 9, which received a grade of B. Each of Samples 10 to 12 contains nickel, iron, and chromium in addition to aluminum. Nickel, iron, and chromium are particularly excellent in corrosion resistance among the fourth period transition metals. This is thought to have further improved the wear resistance of the alloys.

[0033] Of Samples 10 to 12, Samples 11 and 12 received an S rating, confirming that they have even better wear resistance than Sample 10, which received an A rating. Sample 10 contains manganese, which has relatively low corrosion resistance, as two or more metal elements other than aluminum. On the other hand, Samples 11 and 12 do not contain manganese as two or more metal elements other than aluminum. For this reason, it is believed that Samples 11 and 12 have less deterioration in wear resistance than Sample 10.

[0034] Figure 4 illustrates the first results of the second evaluation test on the electrodes. Figure 5 illustrates the second results of the second evaluation test on the electrodes. In the second evaluation test, Samples 11 and 12, out of the 12 samples tested in the first evaluation test, were evaluated for their crystalline structure and wear resistance with and without heat treatment. In the second evaluation test, samples with heat treatment were prepared by arc-melting multiple metal elements and then cooling the melt at 500°C for 2 hours. On the other hand, samples without heat treatment were prepared by lowering the temperature without maintaining it at a specific temperature. The crystalline structure of the samples was confirmed by visually observing the cross-sections in SEM images and XRD using an X-ray diffractometer, as with the alloy of Electrode 1. The "ΔVol" representing the wear volume shown in Figures 4 and 5 was calculated using the same method as in the first evaluation test. The "Judgment" results shown in Figures 4 and 5 were determined using the same method as in the first evaluation test.

[0035] Figure 4 shows the results of evaluating the effects of heat treatment on Sample 11. As shown in Figure 4, multiple types of crystal structures (FCC structure, BCC structure, B2 structure) were confirmed in Sample 11 with heat treatment. On the other hand, only one type of crystal structure (FCC structure) was confirmed in Sample 11 without heat treatment, which suggests that Sample 11 without heat treatment has a single crystal phase. The volume of consumption due to discharge, "ΔVol," was larger in Sample 11 with heat treatment than in Sample 11 without heat treatment, which revealed that heat treatment, which maintains the alloy at a certain temperature or higher, during alloy production reduces its consumption resistance.

[0036] Figure 5 shows the results of evaluating the effect of heat treatment on Sample 12. As shown in Figure 5, multiple types of crystal structures (BCC structure, B2 structure, and LAVES phase) were confirmed in Sample 12 with heat treatment. On the other hand, only one type of crystal structure (BCC#1 structure and BCC#2 structure) was confirmed in Sample 12 without heat treatment, despite its different composition. This suggests that Sample 12 without heat treatment has multiple crystal phases. The volume of dissipation due to discharge, "ΔVol," was larger in Sample 12 with heat treatment than in Sample 12 without heat treatment. This indicates that, similar to Sample 11, heat treatment, which maintains the alloy at a temperature above a certain level during alloy production, reduces dissipation resistance.

[0037] According to the electrode 1 of this embodiment described above, the electrode 1 is made of an alloy containing aluminum and two or more metal elements other than aluminum. The number of moles of each of the two or more metal elements contained in this alloy is 0.85 to 1.6 times the number of moles of aluminum contained in the alloy. As a result, the alloy contains a certain amount or more of aluminum, which has excellent corrosion resistance, and also contains two or more metal elements that compensate for the low melting point of aluminum, thereby reducing the amount of wear of the electrode 1 during use. Therefore, the wear resistance of the electrode 1 can be improved.

[0038] Furthermore, according to the electrode 1 of this embodiment, the alloy contains any one of scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, and copper, which are transition metal elements of the fourth period elements that have excellent corrosion resistance and relatively high melting points, thereby further improving the wear resistance of the electrode 1.

[0039] Furthermore, according to the electrode 1 of this embodiment, the alloy contains nickel, iron, and chromium, which have even better corrosion resistance and relatively high melting points, thereby further improving the wear resistance of the electrode 1.

[0040] Furthermore, according to the electrode 1 of this embodiment, each of the two or more metal elements contained in the alloy includes a transition metal element of the fourth period, excluding manganese, which has relatively low corrosion resistance, thereby preventing a decrease in the wear resistance of the electrode 1.

[0041] Furthermore, according to the electrode 1 of this embodiment, the alloy has a single crystal phase. This allows the discharge surface of the electrode 1 to wear uniformly, thereby suppressing localized wear. This prevents partial detachment of the electrode 1, further improving the wear resistance of the electrode 1.

[0042] <Modification of this embodiment> The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit of the invention. For example, the following modifications are also possible.

[0043] [Variation 1] In the above-described embodiment, the alloy of the electrode 1 contains four metal elements, nickel, iron, chromium, and titanium, in addition to aluminum, but does not contain manganese. The types of metal elements contained in the electrode alloy are not limited to these. Each of the two or more metal elements other than aluminum is preferably a transition group element of the fourth period elements, and is preferably one of scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, and copper. This can further improve the wear resistance of the electrode 1. Furthermore, it is preferable that nickel, iron, and chromium are contained as metal elements other than aluminum. This can further improve the wear resistance of the electrode 1. Furthermore, it is preferable that manganese is not contained as a metal element other than aluminum. Manganese has relatively low corrosion resistance, so by not including manganese, the deterioration of the wear resistance of the electrode can be suppressed.

[0044] [Variation 2] In the above-described embodiment, the electrode 1 is made of an alloy containing aluminum and two or more metal elements other than aluminum, and the number of moles of each of the two or more metal elements contained in the alloy is between 0.85 and 1.6 times the number of moles of aluminum contained in the alloy. The alloy may contain at least two metal elements in moles that are between 0.85 and 1.6 times the number of moles of aluminum contained in the alloy. For example, in the case of an alloy containing aluminum and four metal elements other than aluminum, wear resistance can be improved if the number of moles of at least two of the four metal elements other than aluminum is between 0.85 and 1.6 times the number of moles of aluminum contained in the alloy. Therefore, even if the number of moles of one of the four metal elements other than aluminum is less than 0.85 or more than 1.6 times the number of moles of aluminum contained in the alloy, wear resistance can be improved if the number of moles of at least two or more metal elements is between 0.85 and 1.6 times the number of moles of aluminum contained in the alloy.

[0045] [Variation 3] In the above-described embodiment, the alloy of electrode 1 has a single crystalline phase. However, as explained in FIG. 5 , the alloy of electrode 1 may have multiple crystalline phases, and these multiple crystalline phases may have different compositions but the same crystalline structure. Furthermore, the multiple crystalline phases of the electrode alloy may have different crystalline structures. However, if the electrode alloy has multiple crystalline phases with different compositions and the multiple crystalline phases have the same crystalline structure, the discharge surface wears evenly, suppressing localized wear and reducing the variation in discharge voltage.

[0046] [Variation 4] In the above embodiment, the electrode 1 is provided in a spark plug. However, the application field of the electrode is not limited to this. For example, the electrode may be applied to a plasma generating device, a discharge device, or the like.

[0047] This aspect has been described above based on embodiments and modifications. However, the above-described embodiments are intended to facilitate understanding of this aspect and are not intended to limit this aspect. This aspect may be modified or improved without departing from the spirit and scope of the claims, and equivalents thereof are included in this aspect. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate.

[0048] <Application example 1> An electrode, It is made of an alloy containing aluminum and two or more metal elements other than aluminum, The number of moles of each of the metal elements contained in the alloy is 0.85 to 1.6 times the number of moles of aluminum contained in the alloy. electrode. <Application example 2> The electrode according to Application Example 1, Each of the metal elements is one of scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, and copper. electrode. <Application example 1> The electrode according to Application Example 1 or Application Example 2, The alloy contains nickel, iron, and chromium. electrode. <Application Example 4> The electrode according to any one of Application Examples 1 to 3, Each of the metal elements is one of scandium, titanium, vanadium, chromium, iron, cobalt, nickel, and copper. electrode. <Application example 5> The electrode according to any one of Application Examples 1 to 4, The alloy is characterized in that the crystalline phase is a single phase. electrode. <Application Example 6> The electrode according to any one of Application Examples 1 to 5, The alloy has a plurality of crystalline phases with different compositions, The plurality of crystalline phases have the same crystalline structure. electrode. [Explanation of symbols]

[0049] 1...Electrode

Claims

1. An electrode, It is made of an alloy containing aluminum and two or more metal elements other than aluminum, The number of moles of each of the metal elements contained in the alloy is 0.85 to 1.6 times the number of moles of aluminum contained in the alloy. electrode.

2. 10. The electrode of claim 1, Each of the metal elements is one of scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, and copper. electrode.

3. 3. The electrode according to claim 1 or claim 2, The alloy contains nickel, iron, and chromium. electrode.

4. 10. The electrode of claim 1, Each of the metal elements is one of scandium, titanium, vanadium, chromium, iron, cobalt, nickel, and copper. electrode.

5. 3. The electrode according to claim 1 or claim 2, The alloy is characterized in that the crystalline phase is a single phase. electrode.

6. 3. The electrode according to claim 1 or claim 2, The alloy has a plurality of crystalline phases with different compositions, The plurality of crystalline phases have the same crystalline structure. electrode.

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