JP2011096543A - Spark plug - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spark plug equipped with a central electrode and the like superior both in corrosion resistance and workability. <P>SOLUTION: The spark plug 1 is equipped with an insulator 2 having an axial hole 4 extending in an axial line CL1, and the central electrode 5 inserted into the extremity of the axial hole 4. At least a part of the central electrode 5 contains Ni as a main component, Cr in the range from 15 through 33 mass%, Mn in the range from 0.05 through 2 mass%, and Fe in the range of 0.3 mass% or below. At the same time, the same part of the central electrode has at least one out of Zr in the range from 0.15 through 3 mass%, Ta in the range from 0.5 through 8 mass%, Mo in the range from 4 through 8 mass%, and V in the range from 0.5 through 10 mass%. Further, the part is formed by an alloy comprising Zr, Ta, Mo and V in a total content of 12 mass% or below. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a spark plug used for an internal combustion engine or the like.

  The spark plug is attached to, for example, an internal combustion engine (engine) or the like, and is used to ignite an air-fuel mixture in the combustion chamber. In general, a spark plug is an insulator having a shaft hole, a center electrode inserted through the tip end of the shaft hole, a metal shell provided on the outer periphery of the insulator, and a tip of the metal shell. And a ground electrode that forms a spark discharge gap with the electrode.

  By the way, the center electrode and the ground electrode that are placed under high-temperature conditions during use are required to have excellent corrosion resistance. In recent years, there has been a demand for downsizing of the spark plug, and the center electrode and the ground electrode can be further reduced in diameter. Therefore, it is desirable that the alloy constituting the center electrode and the like is excellent in both corrosion resistance and workability.

  Here, as an alloy which comprises a center electrode and a ground electrode, nickel (Ni) is a main component, 10 mass%-20 mass% chromium (Cr), and 5 mass%-10 mass% iron (Fe ) Is known (see, for example, Patent Document 1). Moreover, as an alloy which comprises a center electrode etc., what contains 10 mass%-45 mass% Ni etc., and the remainder consists of Cr is proposed (for example, refer patent document 2 etc.).

Japanese Patent Laid-Open No. 9-291327 Japanese Patent Laid-Open No. 3-111534

  However, in the technique described in Patent Document 1, since Fe that is relatively easy to oxidize is contained in a large amount of 5% by mass or more, corrosion resistance may be insufficient.

  Further, in the technique described in Patent Document 2, since a large amount of Cr is contained, the melting point of the alloy is lowered, and the corrosion resistance may be deteriorated. In addition, by increasing the Cr content, the alloy phase becomes a two-phase mixed state of the Ni phase and the Cr phase, and as a result, there is a risk that the hardness of the alloy is increased, and consequently the workability is reduced. .

  This invention is made | formed in view of the said situation, The objective is to provide the spark plug provided with the center electrode etc. which were excellent in both corrosion resistance and workability.

  Hereinafter, each configuration suitable for solving the above-described object will be described in terms of items. In addition, the effect specific to the corresponding structure is added as needed.

Configuration 1. The spark plug of this configuration includes a cylindrical insulator having an axial hole extending in the axial direction,
A spark plug comprising a center electrode inserted on the tip side of the shaft hole,
At least a part of the center electrode is mainly composed of nickel (Ni), chromium (Cr) in an amount of 15 mass% to 33 mass%, manganese (Mn) in an amount of 0.05 mass% to 2 mass%, iron ( Fe) 0.3% by mass or less,
0.15 wt% or more and 3 wt% or less of zirconium (Zr), 0.5 wt% or more and 8 wt% or less of tantalum (Ta), 4 wt% or more and 8 wt% or less of molybdenum (Mo), Containing at least one of 5 mass% or more and 10 mass% or less of vanadium (V),
It is characterized by being formed of an alloy having a total content of Zr, Ta, Mo, and V of 12% by mass or less.

According to the said structure 1, the alloy which comprises a center electrode contains Cr comparatively a large amount with 15 mass% or more. Therefore, it is possible to form a Cr ₂ O ₃ film having a sufficient thickness over a relatively wide range of the surface of the center electrode (particularly the surface exposed in the combustion chamber). As a result, the penetration of corrosive gas (oxygen or the like) into the center electrode can be effectively suppressed.

In addition, the alloy contains at least one of Zr of 0.15 mass% or more, Ta of 0.5 mass% or more, Mo of 4 mass% or more, and V of 0.5 mass% or more. Has been. Since these elements (hereinafter also referred to as “additive elements”) have a relatively large atomic radius, the lattice structure of the alloy can be distorted, and the diffusion of Cr inside the alloy can be promoted. Therefore, the Cr ₂ O ₃ film forming ability can be increased, and even if the Cr ₂ O ₃ film is peeled off due to the thermal stress caused by the cooling cycle in the combustion chamber or the vibration accompanying the operation of the internal combustion engine, etc. _{The 2} O ₃ coating can be reformed more reliably and more quickly.

Further, the alloy contains a relatively large amount of Mn of 0.05% by mass or more. Therefore, it is possible to increase the flexibility of the Cr ₂ O ₃ film, it is possible to effectively suppress separation of the thus Cr ₂ O ₃ coating. Further, when Zr is contained, the adhesion of the Cr ₂ O ₃ film can be further improved by the wedge effect of Zr, and the peeling of the Cr ₂ O ₃ film can be more effectively suppressed. .

As described above, according to the present configuration 1, the Cr ₂ O ₃ coating excellent in the effect of suppressing the invasion of corrosive gas is formed with a sufficient thickness over a wide range of the center electrode surface, and the Cr ₂ O ₃ coating Is difficult to peel off, and even if it peels off, the Cr ₂ O ₃ coating is rapidly re-formed. That is, according to Configuration 1, the corrosion resistance of the center electrode can be drastically improved by the synergistic action of additive elements such as Cr, Mn, and Zr and Ta.

  Further, in the alloy, the contents of Cr, Mn, each additive element, and the upper limit of the total content of the additive elements are defined as shown in the above configuration 1. For this reason, it can prevent that an alloy phase will be in a two-phase mixed state with a Ni phase and another metal phase, and can suppress the raise of alloy hardness and the weakening of an alloy. Thereby, the outstanding workability is realizable.

  Even if the content of Cr, Mn, or the like is within the above-described range, if an excessive amount of Fe is contained, the effect of improving the corrosion resistance may be insufficient. Therefore, the smaller the Fe content, the better. The Fe content is preferably 0.3% by mass or less, and more preferably 0.2% by mass or less.

  In addition, when Cr exceeding 30 mass% is contained, the hardness of the alloy slightly increases, and it may be necessary to anneal the alloy when processing the center electrode. Therefore, from the viewpoint of further improving the workability, the Cr content is more preferably 30% by mass or less. Further, when Zr is contained, the increase in the hardness of the alloy can be suppressed by setting the content of Zr to 2% by mass or less, thereby further improving the workability.

Configuration 2. The spark plug of this configuration includes a cylindrical insulator having an axial hole extending in the axial direction,
A center electrode inserted on the tip side of the shaft hole;
A cylindrical metal shell provided on the outer periphery of the insulator;
A spark plug that includes a ground electrode that extends from a tip of the metal shell and forms a gap with the center electrode,
At least a part of the ground electrode contains Ni as a main component, Cr is 15 mass% to 33 mass%, Mn is 0.05 mass% to 2 mass%, and Fe is 0.3 mass% or less. ,
0.15 to 3% by weight of Zr, 0.5 to 8% by weight of Ta, 4 to 8% by weight of Mo, and 0.5 to 10% by weight of Mo Containing at least one of V,
It is characterized by being formed of an alloy having a total content of Zr, Ta, Mo, and V of 12% by mass or less.

  According to the configuration 2, in the spark plug including the ground electrode, at least a part of the ground electrode is formed of the above-described alloy. Therefore, both the corrosion resistance and workability of the ground electrode can be dramatically improved.

  The technical ideas of the above configurations 1 and 2 may be combined. That is, both the center electrode and the ground electrode may be formed of the above-described alloy. In this case, the corrosion resistance of both electrodes can be drastically improved, and the life of the spark plug can be greatly extended.

  Configuration 3. The spark plug of this configuration is the above configuration 1 or 2, wherein the alloy contains 0.5% by mass or more and 3% by mass or less of aluminum (Al), and the total of Zr, Ta, Mo, V, and Al. Content is made into 12 mass% or less, It is characterized by the above-mentioned.

  According to the said structure 3, 0.5 mass% or more of Al is contained in the said alloy. Here, Al is an element that is easily oxidized as compared with additive elements such as Zr and Ta. Therefore, Al is oxidized ahead of Zr, Ta, etc., and as a result, oxidation of Zr, Ta, etc. can be suppressed. For this reason, the effect of promoting the diffusion of Cr that is exhibited by containing Zr, Ta, or the like is sustained over a longer period, and as a result, the corrosion resistance can be further improved.

  If the Al content exceeds 3% by mass or the total content of additive elements such as Zr and Ta and Al exceeds 12% by mass, the alloy hardness increases, There is a risk of causing a decline in sex. Therefore, in order to ensure excellent workability, the content of Al is preferably 3% by mass or less, and the total content of additive elements and Al is preferably 12% by mass or less.

  Configuration 4. The spark plug of this configuration is the above-described configuration 1 or 2, wherein the alloy contains 0.5% by mass or more and 3% by mass or less of silicon (Si), and a total of Zr, Ta, Mo, V, and Si. Content is made into 12 mass% or less, It is characterized by the above-mentioned.

According to the configuration 4, since 0.5% by mass or more of Si is contained, the SiO ₂ film can be generated immediately below the Cr ₂ O ₃ film. As a result, even if the Cr ₂ O ₃ coating is peeled off, the corrosion inside the alloy can be suppressed by the SiO ₂ coating, and the corrosion resistance can be further improved.

  If the Si content exceeds 3% by mass or the total content of additive elements such as Zr and Ta and Si exceeds 12% by mass, the alloy hardness increases, There is a possibility that the workability is lowered. For this reason, the Si content is preferably 3% by mass or less, and the total content of the additive element and Si is preferably 12% by mass or less.

  The technical ideas of the above configurations 3 and 4 may be combined. That is, both Al and Si may be included in the alloy.

  Configuration 5. In the spark plug of this configuration, in any one of the above configurations 1 to 4, the alloy includes 20 mass% to 33 mass% of Cr, 0.1 mass% to 0.5 mass% of Mn, and 0 to Zr. It is characterized by containing 2% by mass or more and 3% by mass or less.

According to the above configuration 5, since the content of Cr is 20 mass% or more, it is possible to Cr ₂ O ₃ coating is also more rapidly reform the Cr ₂ O ₃ film as the peeling. Furthermore, since Zr is further contained in an amount of 0.2% by mass or more, the diffusion of Cr can be further promoted. In addition, the wedge effect due to the inclusion of Zr and the further excellent flexibility improvement effect of the Cr ₂ O ₃ coating due to the inclusion of Mn in a larger amount of 0.1% by mass or more are combined. Thus, it is possible to more reliably prevent the Cr ₂ O ₃ film from peeling off. That is, according to the configuration 5, the invasion of the corrosive gas into the electrode can be extremely effectively suppressed, and the corrosion resistance can be remarkably improved.

It is a partially broken front view which shows the structure of a spark plug.

  Hereinafter, an embodiment will be described with reference to the drawings. FIG. 1 is a partially cutaway front view showing a spark plug 1. In FIG. 1, the direction of the axis CL <b> 1 of the spark plug 1 is the vertical direction in the drawing, the lower side is the front end side of the spark plug 1 and the upper side is the rear end side.

  The spark plug 1 includes an insulator 2 as a cylindrical insulator, a cylindrical metal shell 3 that holds the insulator 2, and the like.

  As is well known, the insulator 2 is formed by firing alumina or the like, and in its outer portion, a rear end side body portion 10 formed on the rear end side, and a front end than the rear end side body portion 10. A large-diameter portion 11 that protrudes radially outward on the side, a middle body portion 12 that is smaller in diameter than the large-diameter portion 11, and a tip portion that is more distal than the middle body portion 12. On the side, a leg length part 13 formed with a smaller diameter than this is provided. In addition, of the insulator 2, the large diameter portion 11, the middle trunk portion 12, and most of the leg long portions 13 are accommodated inside the metal shell 3. A tapered step portion 14 is formed at the connecting portion between the middle body portion 12 and the long leg portion 13, and the insulator 2 is locked to the metal shell 3 at the step portion 14.

  Further, the insulator 2 is formed with a shaft hole 4 penetrating along the axis CL1, and a center electrode 5 is inserted and fixed to the tip end side of the shaft hole 4. The center electrode 5 is made of a Ni—Cr alloy containing Ni as a main component and containing Cr (details will be described later). The center electrode 5 has a rod shape (cylindrical shape) as a whole, and a tip portion of the center electrode 5 projects from the tip of the insulator 2.

  A terminal electrode 6 is inserted and fixed on the rear end side of the shaft hole 4 in a state of protruding from the rear end of the insulator 2.

  Further, a cylindrical resistor 7 is disposed between the center electrode 5 and the terminal electrode 6 of the shaft hole 4. Both ends of the resistor 7 are electrically connected to the center electrode 5 and the terminal electrode 6 through conductive glass seal layers 8 and 9, respectively.

  In addition, the metal shell 3 is formed in a cylindrical shape from a metal such as low carbon steel, and a screw for attaching the spark plug 1 to a combustion device such as an internal combustion engine or a fuel cell reformer on the outer peripheral surface thereof. A portion (male screw portion) 15 is formed. In addition, a seat portion 16 is formed on the outer peripheral surface on the rear end side of the screw portion 15, and a ring-shaped gasket 18 is fitted on the screw neck 17 on the rear end of the screw portion 15. Furthermore, a tool engagement portion 19 having a hexagonal cross section for engaging a tool such as a wrench when the metal shell 3 is attached to the combustion device is provided on the rear end side of the metal shell 3. A caulking portion 20 for holding the insulator 2 is provided.

  A tapered step portion 21 for locking the insulator 2 is provided on the inner peripheral surface of the metal shell 3. The insulator 2 is inserted from the rear end side to the front end side of the metal shell 3, and the rear end of the metal shell 3 is engaged with the step portion 14 of the metal shell 3. It is fixed by caulking the opening on the side radially inward, that is, by forming the caulking portion 20. An annular plate packing 22 is interposed between the step portions 14 and 21 of both the insulator 2 and the metal shell 3. Thereby, the airtightness in the combustion chamber is maintained, and the fuel gas entering the gap between the leg long portion 13 of the insulator 2 exposed to the combustion chamber and the inner peripheral surface of the metal shell 3 is prevented from leaking outside.

  Further, in order to make the sealing by caulking more complete, annular ring members 23 and 24 are interposed between the metal shell 3 and the insulator 2 on the rear end side of the metal shell 3, and the ring member 23 , 24 is filled with powder of talc (talc) 25. That is, the metal shell 3 holds the insulator 2 via the plate packing 22, the ring members 23 and 24, and the talc 25.

  In addition, a substantially intermediate portion is bent back at the distal end portion 26 of the metal shell 3, and a ground electrode 27 whose distal side surface faces the distal end portion of the center electrode 5 is joined. The ground electrode 27 is made of the same alloy as the Ni—Cr alloy constituting the center electrode 5.

  In addition, a spark discharge gap 33 is formed as a gap between the tip of the center electrode 5 and the tip of the ground electrode 27. In the spark discharge gap 33, spark discharge is performed in a direction substantially along the axis CL1.

  Next, the alloy constituting the center electrode 5 and the ground electrode 27 will be described in detail.

  The alloy is composed mainly of Ni and containing 15% by mass to 33% by mass of Cr. In addition, the alloy contains 0.05% by mass or more and 2% by mass or less of Mn and 0.3% by mass or less of Fe. In addition, it is good also as not containing Fe.

  Further, the alloy includes 0.15% by weight to 3% by weight Zr, 0.5% by weight to 8% by weight Ta, 4% by weight to 8% by weight Mo, and 0.5% by weight. % And 10 mass% or less of V is contained, and the total content of Zr, Ta, Mo, and V is 12 mass% or less.

  The alloy may contain 0.5% by mass or more and 3% by mass or less of Al. In this case, the total content of Zr, Ta, Mo, V, and Al is 12% by mass or less.

  Moreover, it is good also as containing 0.5 mass% or more and 3 mass% or less of Si in the said alloy. In this case, the total content of Zr, Ta, Mo, V, and Si is set to 12% by mass or less.

  In addition, the contents of Cr, Mn, and Zr in the alloy may be changed as follows. That is, in the alloy, the Cr content is 20% by mass to 33% by mass, the Mn content is 0.1% by mass to 0.5% by mass, and the Zr content is 0.2% by mass. % Or more and 3% by mass or less. Moreover, it is good also considering the upper limit of Cr content as 30 mass%. Furthermore, it is good also considering the upper limit of content of Zr as 2 mass%.

As described above in detail, according to the present embodiment, the alloy constituting the center electrode 5 and the ground electrode 27 contains a relatively large amount of Cr of 15 mass% or more. Accordingly, it is possible to form a Cr ₂ O ₃ film having a sufficient thickness over a relatively wide range of the surfaces of the electrodes 5 and 27. As a result, the penetration of corrosive gas (oxygen or the like) into the electrodes 5 and 27 can be effectively suppressed.

In addition, the alloy contains at least one of Zr of 0.15 mass% or more, Ta of 0.5 mass% or more, Mo of 4 mass% or more, and V of 0.5 mass% or more. Has been. Since these elements have a relatively large atomic radius, the lattice structure of the alloy can be distorted, and the diffusion of Cr inside the alloy can be promoted. Therefore, it is possible to increase the Cr ₂ O ₃ coating-forming ability, as Cr ₂ O ₃ coating had peeled, reliably the Cr ₂ O ₃ film, and, to be more quickly re-formed it can.

Further, the alloy contains a relatively large amount of Mn of 0.05% by mass or more. Therefore, it is possible to increase the flexibility of the Cr ₂ O ₃ film, it is possible to effectively suppress separation of the thus Cr ₂ O ₃ coating. In the case of containing Zr, the adhesion effect of the Cr ₂ O ₃ film can be further improved due to the wedge effect of Zr, and the peeling of the Cr ₂ O ₃ film can be more effectively suppressed. .

As described above, according to the present embodiment, the Cr ₂ O ₃ coating excellent in the effect of suppressing the invasion of corrosive gas is formed with a sufficient thickness over a wide range of the surfaces of the electrodes 5 and 27, and the Cr ₂ O ₃ Even if the coating is difficult to peel off, even if it is peeled off, the Cr ₂ O ₃ coating is rapidly re-formed. That is, according to the present embodiment, the corrosion resistance of the center electrode 5 and the ground electrode 27 can be drastically improved by the synergistic action of Cr, Mn, Zr, Ta, and the like.

  Further, in the alloy, the contents of Cr, Mn, each additive element, and the upper limit of the total content of the additive elements are defined as described above. For this reason, it can prevent that an alloy phase will be in a two-phase mixed state with a Ni phase and another metal phase, and can suppress the raise of alloy hardness and the weakening of an alloy. Thereby, the outstanding workability is realizable.

  Furthermore, the content of Fe that is relatively easy to oxidize is 0.3% by mass or less. Therefore, the above-described effect of improving the corrosion resistance can be exhibited more reliably.

  Next, a corrosion resistance evaluation test and a workability evaluation test were performed in order to confirm the effects obtained by the above embodiment.

  The outline of the corrosion resistance evaluation test is as follows. That is, an alloy having Ni as a main component and various contents of Cr, Mn, Fe, and Zr, Ta, etc. is manufactured, and each alloy is used to make an alloy having a length of 10 mm and a thickness of 1. A plurality of electrode samples having a rod shape (needle shape) of 3 mm and a width of 2.7 mm were produced. Each sample is heated for 1 minute so that the surface temperature becomes 1100 ° C., and then cooled for 30 seconds so that the surface temperature becomes 200 ° C. For 3000 cycles, 10000 cycles, or 30000 cycles. After the cooling test of each cycle was completed, the sample was cut along the longitudinal direction of the sample so as to include the central axis, and the cross section was observed by SEM to identify the corroded portion (internal corroded portion) inside. And while measuring the length of the internal corrosion part along the longitudinal direction of a sample, the ratio (corrosion rate) of the length of the internal corrosion part with respect to the full length (10 mm) of a sample was computed. Here, a sample having a corrosion rate of less than 10% is evaluated as “◯” as being excellent in corrosion resistance, while a sample having a corrosion rate of 10% or more is inferior in corrosion resistance. An evaluation of “x” was made.

  The outline of the workability evaluation test is as follows. That is, a rod-shaped sample having a predetermined shape assuming a center electrode and a ground electrode was manufactured from the above-described alloy having Ni as a main component and various contents such as Cr and Mn. And when the manufactured sample was observed and "crack" was not confirmed in the sample, it was decided to give "(circle)" evaluation that it was excellent in workability. On the other hand, when “cracking” was confirmed in the sample, the evaluation of “x” was made because the workability was inferior. In each test, the element concentration (content) of each alloy was measured by WDS using EPMA (X-ray microanalyzer).

  Table 1 shows the test results when a corrosion resistance evaluation test of 10,000 cycles was performed on samples using Ni-0.5Zr-Cr-Mn alloys with various contents of Cr and Mn, and processing The result of a sex evaluation test is shown. Table 2 shows the test results when performing a corrosion resistance evaluation test of 30000 cycles and the results of the workability evaluation test for samples using the same alloy.

表１に示すように、Ｃｒ含有量を１５質量％未満としたサンプルは、耐腐食性が不十分となってしまうことが明らかとなった。これは、Ｃｒ含有量が比較的少なかったため、サンプル表面にＣｒ₂Ｏ₃被膜が十分に形成されなかったことによると考えられる。一方で、Ｃｒ含有量の増大に伴い、耐腐食性の向上が図られることが認められたが、Ｃｒ含有量が３３質量％を超えると、加工性が不十分なものとなってしまうことが分かった。これは、Ｃｒ含有量が過度に多かったため、サンプルの合金相がＮｉ相及びＣｒ相の二相混合状態となってしまい、合金の硬度が著しく上昇してしまったことに起因すると考えられる。また、Ｃｒ含有量を３０質量％以下とすることで、合金の硬度上昇が抑制され、加工性に極めて優れることが確認された。

As shown in Table 1, it was revealed that the sample having a Cr content of less than 15% by mass has insufficient corrosion resistance. This is considered to be because the Cr ₂ O ₃ film was not sufficiently formed on the sample surface because the Cr content was relatively small. On the other hand, it was confirmed that the corrosion resistance was improved with an increase in Cr content. However, when the Cr content exceeds 33% by mass, workability may be insufficient. I understood. This is thought to be because the Cr content was excessively high, so that the alloy phase of the sample was in a two-phase mixed state of Ni phase and Cr phase, and the hardness of the alloy was significantly increased. Moreover, it was confirmed that the hardness increase of an alloy is suppressed and the workability is extremely excellent by setting the Cr content to 30% by mass or less.

  Furthermore, it became clear that when the Mn content exceeds 2% by mass, the corrosion resistance decreases. This is presumably because the Mn content was relatively large, so the formation of Mn sulfide inside the sample was promoted, and as a result internal corrosion progressed.

In contrast, a sample in which the Cr content is 15% by mass to 33% by mass and the Mn content is 0.05% by mass to 2% by mass is both corrosion resistant and workable. It became clear that it has excellent performance. This was because the Cr content was sufficiently high, so a Cr ₂ O ₃ film having a sufficient thickness was formed over a wide area of the sample surface, and the invasion of corrosive gas into the sample could be suppressed. and, in that it contained 0.05% by mass or more of Mn, it is possible to increase the flexibility of the Cr ₂ O ₃ coating, that could effectively suppress separation of the thus Cr ₂ O ₃ coating It is thought to be caused.

  In addition, as shown in Table 2, even when the corrosion resistance evaluation test was performed under extremely severe conditions with the number of cycles being 30000 cycles, the Cr content was 20 mass% or more and 33 mass% or less. At the same time, the sample having a Mn content of 0.1% by mass or more and 0.5% by mass or less has a corrosion rate of 4% or less, and was confirmed to have very excellent corrosion resistance.

  Next, Table 3 shows test results obtained when 3000 cycles of corrosion resistance evaluation tests were conducted on samples using Ni-15Cr-Zr-Mn alloys obtained by variously changing the contents of Zr and Mn, and processing. The result of a sex evaluation test is shown. Table 4 shows the test results when a corrosion resistance evaluation test of 10,000 cycles was performed on samples using Ni-25Cr-Zr-Mn alloys with various contents of Zr and Mn, and processing The result of a sex evaluation test is shown. Further, Table 5 shows the test results and workability when a 10,000 cycle corrosion resistance evaluation test was performed on a sample using the same alloy (Ni-15Cr-Zr-Mn alloy) as the alloy shown in Table 3. The result of an evaluation test is shown. In addition, Table 6 shows the test results when a sample using the same alloy (Ni-25Cr-Zr-Mn alloy) as shown in Table 4 was subjected to a corrosion resistance evaluation test of 30000 cycles, and processing The result of a sex evaluation test is shown.

表３及び表４に示すように、０．０５質量％以上２質量％以下のＭｎを含有し、かつ、Ｚｒを０．１５質量％以上含有してなる合金を用いたサンプルは、耐腐食性に優れることが明らかとなった。これは、Ｚｒの原子半径が比較的大きいことから合金における格子構造を歪ませることとなり、Ｃｒの拡散が促進され、ひいてはＣｒ₂Ｏ₃被膜の形成及び剥離後の再形成がより促進されたこと、及び、Ｚｒを含有したことで被膜が内部側に食い込む形状となる効果（くさび効果）が発揮され、Ｍｎを含有したことによる剥離抑制効果と合わせて、被膜の剥離が一層抑制されたことに起因すると考えられる。

As shown in Tables 3 and 4, the sample using the alloy containing 0.05% by mass or more and 2% by mass or less of Mn and containing 0.15% by mass or more of Zr is corrosion resistant. It became clear that it was excellent. This is because the atomic radius of Zr is relatively large, which distorts the lattice structure in the alloy, which promotes the diffusion of Cr, and further promotes the formation of the Cr ₂ O ₃ film and the re-formation after peeling. In addition, the effect (wedge effect) of forming the film into the inner side due to the inclusion of Zr was exhibited, and in addition to the effect of suppressing the peeling due to the inclusion of Mn, the peeling of the film was further suppressed. It is thought to be caused.

  In particular, as shown in Tables 5 and 6, samples with Mn content of 0.1 mass% or more and 0.5 mass% or more and Zr content of 0.2 mass% or more are more severe. Even when the corrosion resistance evaluation test was performed under the conditions, it was confirmed that the internal corrosion was sufficiently suppressed and the corrosion resistance was excellent.

  However, it was found that if the Zr content exceeds 3% by mass, the workability deteriorates. This is presumably because the relatively large amount of Zr contained the alloy phase in a two-layer mixed state of the Ni phase and the Zr phase, leading to an increase in the hardness of the alloy. Therefore, it can be said that the Zr content is preferably 3% by mass or less. In addition, it was confirmed that the hardness increase of an alloy was suppressed and workability was extremely excellent because the Zr content was 2% by mass or less.

  Next, with respect to a sample using a Ni-15Cr-0.5Zr-Fe-Mn alloy in which the contents of Fe and Mn are variously changed, test results and workability when performing a 3000 cycle corrosion resistance evaluation test Table 7 shows the results of the evaluation test.

表７に示すように、Ｆｅの含有量が０．３質量％を超えると、耐腐食性が低下してしまうことが分かった。これは、Ｆｅが非常に酸化しやすい物質であることから、０．３質量％を超えて多量に含有されたことで、内部腐食が急速に進んでしまったためであると考えられる。

As shown in Table 7, it was found that when the Fe content exceeds 0.3% by mass, the corrosion resistance decreases. This is considered to be because internal corrosion rapidly progressed because Fe is a substance that is very easily oxidized and contained in a large amount exceeding 0.3 mass%.

  Next, Table 8 shows test results obtained when 3000 cycles of corrosion resistance evaluation tests were performed on samples using Ni-15Cr-Ta-Mn alloys having various contents of Ta and Mn, and processing. The result of a sex evaluation test is shown. Table 9 shows a test using a Ni-15Cr-0.5Zr-Ta-Mn alloy in which the contents of Ta and Mn are variously changed and a corrosion resistance evaluation test of 10,000 cycles. A result and the result of a workability evaluation test are shown. Further, Table 10 shows the test results when a 10,000 cycle corrosion resistance evaluation test was performed on a sample using a Ni-25Cr-0.2Mn-0.2Zr alloy having various Ta contents. The results of the workability evaluation test are shown.

表８〜１０に示すように、０．０５質量％以上２質量％以下のＭｎを含有し、かつ、Ｔａを０．５質量％以上含有してなる合金を用いたサンプルは、耐腐食性に優れることが明らかとなった。これは、Ｔａを含有することで、Ｚｒを含有した場合と同様に、Ｃｒの拡散性を高めることができ、Ｃｒ₂Ｏ₃被膜の形成がより促進されたことによると考えられる。尚、Ｔａの含有量を増大させることで、腐食率をより低減させることができたが、Ｔａの含有量が８質量％を超えると、合金相が二相混合状態となり、加工性が低下してしまうことが分かった。従って、耐腐食性及び加工性の双方において優れた性能を実現すべく、Ｔａの含有量を０．５質量％以上８質量％以下とすることが好ましいといえる。

As shown in Tables 8 to 10, a sample using an alloy containing 0.05% by mass or more and 2% by mass or less of Mn and containing Ta by 0.5% by mass or more is resistant to corrosion. It became clear that it was excellent. This is considered to be due to the fact that by containing Ta, the diffusibility of Cr can be increased as in the case of containing Zr, and the formation of the Cr ₂ O ₃ film is further promoted. Although the corrosion rate could be further reduced by increasing the Ta content, if the Ta content exceeds 8% by mass, the alloy phase becomes a two-phase mixed state and the workability decreases. I found out. Accordingly, it can be said that the Ta content is preferably 0.5 mass% or more and 8 mass% or less in order to achieve excellent performance in both corrosion resistance and workability.

  Next, in Table 11, with respect to a sample using a Ni-15Cr-Mo-Mn alloy in which the contents of Mo and Mn are variously changed, test results when performing a 3000 cycle corrosion resistance evaluation test, The result of a workability evaluation test is shown. Table 12 shows a test using a Ni-15Cr-0.5Zr-Mo-Mn alloy in which the contents of Mo and Mn are variously changed, and a 10,000 cycle corrosion resistance evaluation test. A result and the result of a workability evaluation test are shown. Furthermore, Table 13 shows the test results when a 10,000 cycles corrosion resistance evaluation test was performed on a sample using a Ni-25Cr-0.2Mn-0.2Zr alloy with various changes in the Mo content. The results of the workability evaluation test are shown.

表１１〜１３に示すように、０．０５質量％以上２質量％以下のＭｎを含有し、Ｍｏを４質量％以上８質量％以下含有してなるサンプルは、耐腐食性及び加工性ともに優れることが確認された。これは、４質量％と比較的多量のＭｏを含有したことで、Ｃｒの拡散を促進することができた一方で、Ｍｏの含有量を８質量％以下としたことで、合金相が二相混合状態となってしまうことを防止できたことに起因すると考えられる。

As shown in Tables 11 to 13, the sample containing 0.05% by mass or more and 2% by mass or less of Mn and containing 4% by mass or more and 8% by mass or less of Mo is excellent in both corrosion resistance and workability. It was confirmed. This was because the diffusion of Cr was promoted by containing a relatively large amount of Mo of 4% by mass, while the alloy phase was two-phased by making the Mo content 8% by mass or less. This is considered to be due to the fact that the mixed state can be prevented.

  Next, in Table 14, with respect to a sample using a Ni-15Cr-V-Mn alloy in which the contents of V and Mn are variously changed, the test results when performing a 3000 cycle corrosion resistance evaluation test, The result of a workability evaluation test is shown. Table 15 shows a test using a Ni-15Cr-0.5Zr-V-Mn alloy in which the contents of V and Mn are variously changed and a 10,000 cycle corrosion resistance evaluation test. A result and the result of a workability evaluation test are shown. Furthermore, Table 16 shows the test results when a 10,000 cycles corrosion resistance evaluation test was performed on a sample using a Ni-25Cr-0.2Mn-0.2Zr alloy with various changes in the V content. The results of the workability evaluation test are shown.

表１４〜１６に示すように、０．０５質量％以上２質量％以下のＭｎを含有し、Ｖを０．５質量％以上１０質量％以下含有してなるサンプルは、耐腐食性及び加工性ともに優れることが確認された。これは、０．５質量％以上のＶが含有されたことで、Ｃｒの拡散が促進されるとともに、Ｖの含有量が１０質量％以下とされたことで、合金相が二相混合状態となってしまうことを防止できたためであると考えられる。

As shown in Tables 14 to 16, samples containing 0.05% by mass or more and 2% by mass or less of Mn and V containing 0.5% by mass or more and 10% by mass or less are resistant to corrosion and workability. Both were confirmed to be excellent. This is because when 0.5% by mass or more of V is contained, the diffusion of Cr is promoted and the content of V is 10% by mass or less, so that the alloy phase is in a two-phase mixed state. This is thought to be because it was possible to prevent this from happening.

  Next, Table 15 shows a Ni-15Cr-0.05Mn-0.2Zr alloy, Ni-15Cr-0.05Mn-0.5Ta alloy, Ni-15Cr-0.05Mn- Test when performing corrosion resistance evaluation test of 10,000 cycles on a sample using 4Mo alloy, Ni-15Cr-0.05Mn-0.5V alloy, or Ni-25Cr-0.2Mn-0.2Zr alloy A result and the result of a workability evaluation test are shown.

表１７に示すように、同様の試験を行った、表５の「Ｎｉ−１５Ｃｒ−０．０５Ｍｎ−０．２Ｚｒ合金」や表８の「Ｎｉ−１５Ｃｒ−０．０５Ｍｎ−０．５Ｔａ合金」等と比較して、Ａｌを０．５質量％以上含有するサンプルは、より優れた耐腐食性を実現できることが明らかとなった。これは、Ａｌがいわゆる酸素ゲッター元素として機能し、ＺｒやＴａ等よりも率先して酸化したことで、ＺｒやＴａ等の酸化が防止され、ひいてはＺｒやＴａ等を含有したことによる上述の作用効果がより長期間に亘って、かつ、より効果的に発揮されたためであると考えられる。

As shown in Table 17, "Ni-15Cr-0.05Mn-0.2Zr alloy" in Table 5 and "Ni-15Cr-0.05Mn-0.5Ta alloy" in Table 8 etc., which were subjected to the same test, etc. It was revealed that the sample containing 0.5% by mass or more of Al can realize more excellent corrosion resistance. This is because Al functions as a so-called oxygen getter element and is oxidized ahead of Zr, Ta, etc., so that oxidation of Zr, Ta, etc. is prevented, and as a result, the above-mentioned action due to containing Zr, Ta, etc. This is considered to be because the effect was exhibited more effectively over a longer period of time.

  However, if the Al content exceeds 5% by mass, the alloy phase becomes a two-phase mixed state, and the workability is lowered. Therefore, when Al is contained, it can be said that the content is desirably 0.5% by mass or more and 5% by mass or less in order to improve both corrosion resistance and workability.

  Next, in Table 18, Ni-15Cr-0.05Mn-0.2Zr alloy, Ni-15Cr-0.05Mn-0.5Ta alloy, Ni-15Cr-0.05Mn- with various Si contents changed Test when performing corrosion resistance evaluation test of 10,000 cycles on a sample using 4Mo alloy, Ni-15Cr-0.05Mn-0.5V alloy, or Ni-25Cr-0.2Mn-0.2Zr alloy A result and the result of a workability evaluation test are shown.

表１８に示すように、同様の試験を行った、表５の「Ｎｉ−１５Ｃｒ−０．０５Ｍｎ−０．２Ｚｒ合金」等と比較して、Ｓｉを０．５質量％以上含有するサンプルは、耐腐食性により優れることが明らかとなった。これは、Ｓｉを添加したことで、ＳｉＯ₂被膜がＣｒ₂Ｏ₃被膜の直下に形成され、その結果、Ｃｒ₂Ｏ₃被膜が剥離したとしてもＳｉＯ₂被膜により合金内部への腐食ガスの侵入が抑制されたためであると考えられる。

As shown in Table 18, a sample containing 0.5% by mass or more of Si as compared with the “Ni-15Cr-0.05Mn-0.2Zr alloy” and the like in Table 5 which were subjected to the same test, It became clear that it was superior in corrosion resistance. This is because by adding Si, a SiO ₂ film is formed immediately below the Cr ₂ O ₃ film, and as a result, even if the Cr ₂ O ₃ film is peeled off, corrosion gas intrudes into the alloy by the SiO ₂ film. This is considered to be because of the suppression.

  However, when the content of Si exceeds 5% by mass, the alloy phase becomes a two-phase mixed state, and the workability is lowered. Therefore, it can be said that the Si content is preferably 0.5% by mass or more and 5% by mass or less in order to improve both corrosion resistance and workability.

  Next, the alloy containing Ni as a main component, containing 33% by mass of Cr, 0.2% by mass of Mn, and variously changing the contents of Zr, Ta, Mo, and V is described above. A workability evaluation test was conducted. Tables 19 to 29 show test results of workability evaluation tests for the respective alloys.

表１９〜２９に示すように、Ｚｒを３質量％超、Ｔａを８質量％超、Ｍｏを８質量％超、又は、Ｖを１０質量％超含有する合金は、上述の通り、加工性が不十分であったが、Ｚｒを３質量％以下、Ｔａを８質量％以下、Ｍｏを８質量％以下、又は、Ｖを１０質量％以下としても、Ｚｒ、Ｔａ、Ｍｏ、及び、Ｖの総含有量が１２質量％を超えると、加工性に劣ることが明らかとなった。これは、合金相が多相化してしまい、合金硬度が上昇してしまったことによると考えられる。

As shown in Tables 19 to 29, an alloy containing more than 3% by mass of Zr, more than 8% by mass of Ta, more than 8% by mass of Mo, or more than 10% by mass of V has a workability as described above. Although it was insufficient, even if Zr was 3% by mass or less, Ta was 8% by mass or less, Mo was 8% by mass or less, or V was 10% by mass or less, the total of Zr, Ta, Mo and V When the content exceeded 12% by mass, it became clear that the processability was inferior. This is considered to be due to the alloy phase becoming multiphase and the alloy hardness being increased.

  Next, Ni is the main component, Cr is 33% by mass, Mn is 0.2% by mass, and Al or Si is contained, and Zr, Ta, Mo, V, and Al (or Si) The above-described workability evaluation test was performed on alloys formed by variously changing the content of. Table 30 shows the test result of the workability evaluation test in the alloy containing Al, and Table 31 shows the test result of the workability evaluation test in the alloy containing Si.

表３０及び表３１に示すように、Ｚｒ、Ｔａ、Ｍｏ、Ｖ、及び、Ａｌ又はＳｉの総含有量が１２質量％を超えるサンプルは、加工性が不十分となってしまうことが分かった。これは、合金相が多相化してしまい、硬度が上昇してしまったことが原因であると考えられる。

As shown in Table 30 and Table 31, it was found that samples having a total content of Zr, Ta, Mo, V, and Al or Si exceeding 12% by mass had insufficient workability. This is considered to be because the alloy phase is multiphased and the hardness is increased.

  As mentioned above, from the viewpoint of comprehensively considering the results of each test and improving both corrosion resistance and workability, Ni is the main component, Cr is 15% by mass to 33% by mass, and Mn is 0.1%. 0.5 mass% or more and 2 mass% or less of Zr, 0.15 mass% or more and 3 mass% or less of Zr, 0.5 mass% or more of 8 mass% or less of Ta, 4 mass% or more of 8 mass% or less of Mo, and A center electrode or a ground electrode by an alloy containing at least one of V of 0.5 mass% to 10 mass% and having a total content of Zr, Ta, Mo and V of 12 mass% or less It can be said that it is preferable to form.

  Further, from the viewpoint of further improving the corrosion resistance while maintaining excellent workability, Al or Si is contained in an amount of 0.5 mass% or more and 3 mass% or less, and Al or Si, Zr, Ta, It can be said that the total content of Mo and V is preferably 12% by mass or less.

  Further, in order to further improve the corrosion resistance, the Cr content is 20% by mass or more and 33% by mass or less, the Mn content is 0.1% by mass or more and 0.5% by mass or less, and the Zr content is 0.8%. It can be said that it is more desirable to set it to 2 mass% or more and 3 mass% or less.

  In addition, the iron content is set to 0.3% by mass or less (preferably 0.2% by mass or less) in order to more reliably exert the effect of improving the corrosion resistance by containing each element described above. It is preferable to do so.

  In addition, from the viewpoint of further improving the workability, it can be said that the Cr content is preferably 30% by mass or less, or the Zr content is preferably 2% by mass or less.

  In addition, it is not limited to the description content of the said embodiment, For example, you may implement as follows. Of course, other application examples and modification examples not illustrated below are also possible.

  (A) In the above embodiment, the spark plug 1 is configured to include the ground electrode 27, but the ground electrode 27 may be omitted. That is, the technical idea of the present invention may be applied to a spark plug in which spark discharge is performed between the center electrode and the metal shell.

  (B) In the above embodiment, the center electrode 5 and the ground electrode 27 are made of the above-described alloy, but at least a part of at least one of the center electrode 5 and the ground electrode 27 (for example, the tip of the center electrode 5) Only) may be made of the above-described alloy.

  (C) In the above embodiment, the center electrode 5 and the ground electrode 27 are made of a single alloy, but the center electrode 5 and the ground electrode 27 are made of copper or a copper alloy having excellent heat conductivity. An inner layer may be provided, and the center electrode 5 and the ground electrode 27 may be configured in a multilayer structure including an outer layer and an inner layer. In this case, at least a part of the outer layer of the center electrode 5 and the ground electrode 27 is made of the above-described alloy.

  (D) Although not specifically described in the above embodiment, a noble metal tip made of a noble metal alloy (for example, Pt alloy or Ir alloy) is provided on at least one of the tip of the center electrode 5 and the tip of the ground electrode 27. It is good.

  (E) In the above embodiment, the case where the ground electrode 27 is joined to the distal end portion 26 of the metal shell 3 is embodied. The present invention can also be applied to the case where the ground electrode is formed so as to cut out a part of (see Japanese Patent Laid-Open No. 2006-236906, etc.).

  (F) In the above embodiment, the tool engaging portion 19 has a hexagonal cross section, but the shape of the tool engaging portion 19 is not limited to such a shape. For example, it may be a Bi-HEX (deformed 12-angle) shape [ISO 22777: 2005 (E)].

  DESCRIPTION OF SYMBOLS 1 ... Spark plug, 2 ... Insulator (insulator), 3 ... Main metal fitting, 4 ... Shaft hole, 5 ... Center electrode, 27 ... Ground electrode, 33 ... Spark discharge gap (gap), CL1 ... Axis line.

Claims (5)

A cylindrical insulator having an axial hole extending in the axial direction;
A spark plug comprising a center electrode inserted on the tip side of the shaft hole,
At least a part of the central electrode contains nickel as a main component, chromium is contained in an amount of 15 mass% to 33 mass%, manganese is contained in an amount of 0.05 mass% to 2 mass%, and iron is contained in an amount of 0.3 mass% or less. ,
0.15 mass% to 3 mass% zirconium, 0.5 mass% to 8 mass% tantalum, 4 mass% to 8 mass% molybdenum, and 0.5 mass% to 10 mass% Contains at least one of vanadium,
A spark plug characterized by being formed of an alloy having a total content of zirconium, tantalum, molybdenum, and vanadium of 12% by mass or less. A cylindrical insulator having an axial hole extending in the axial direction;
A center electrode inserted on the tip side of the shaft hole;
A cylindrical metal shell provided on the outer periphery of the insulator;
A spark plug that includes a ground electrode that extends from a tip of the metal shell and forms a gap with the center electrode,
At least a part of the ground electrode contains nickel as a main component, chromium is contained in an amount of 15 mass% to 33 mass%, manganese is contained in an amount of 0.05 mass% to 2 mass%, and iron is contained in an amount of 0.3 mass% or less. ,
0.15 mass% to 3 mass% zirconium, 0.5 mass% to 8 mass% tantalum, 4 mass% to 8 mass% molybdenum, and 0.5 mass% to 10 mass% Contains at least one of vanadium,
A spark plug characterized by being formed of an alloy having a total content of zirconium, tantalum, molybdenum, and vanadium of 12% by mass or less.   The alloy contains 0.5 mass% or more and 3 mass% or less of aluminum, and the total content of zirconium, tantalum, molybdenum, vanadium, and aluminum is 12 mass% or less. The spark plug according to 1 or 2.   The alloy contains silicon in an amount of 0.5 mass% to 3 mass%, and the total content of zirconium, tantalum, molybdenum, vanadium, and silicon is 12 mass% or less. The spark plug according to 1 or 2.   The alloy contains 20% to 33% by mass of chromium, 0.1% to 0.5% by mass of manganese, and 0.2% to 3% by mass of zirconium. Item 5. The spark plug according to any one of Items 1 to 4.

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