JPH07268522A - Electrode material for spark plug excellent in high temperature strength - Google Patents

Abstract

PURPOSE:To produce a material having high temp. strength higher than that of NCF600 and having thermal conductivity, oxidation resistance and cold workability practically free from problems as a spark plug. CONSTITUTION:This electrode material for a spark plug excellent in high temp. strength is the one contg., by weight, <=0.10% C, <=1.0% Si, <=2.0% Mn, 12 to 30% Cr, 4 to 12% of one or two kinds of Mo and W so as to satisfy Mo+1/2W, <=20% Fe, and the balance essential Ni if excluding impurities. If required, it may furthermore be incorporated with one or two kinds among <=1% Al, <=1% Ti and one or >= two kinds of Nb and Ta in the range of <2.5% so as to satisfy Nb+1/2Ta.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material for a spark plug used in an internal combustion engine such as an automobile, which has high strength especially at high temperature.

[0002]

2. Description of the Related Art For electrodes of spark plugs for automobile engines and the like, there is required a material which has little oxidation and spark consumption, is resistant to corrosion by combustion gas, has high temperature strength, and has good workability. Conventionally, alloys in which a small amount of Si, Mn, Cr, Al, Ti, etc. are added to Ni are mainly used because they have a high melting point and good thermal conductivity, but some of them have higher corrosion resistance and high temperature strength. An excellent Ni-16% Cr-8% Fe alloy (JIS NCF600, trade name Inconel600 equivalent) is also used. Further, various studies have been made to further improve NCF600, for example, improvement of corrosion resistance (Japanese Patent Laid-Open Nos. 63-118039 and 63-118040,
JP-A-1-180934 and Japanese Patent Publication No. 5-40808) and those with improved cold workability (Japanese Patent Publication No. 5-14781 and Japanese Patent Publication No. 5-40807) have been proposed.

[0003]

In recent years, along with the improvement in engine performance, even the above-mentioned NCF600 may not have sufficient high-temperature strength. Therefore, in addition to the improvement of corrosion resistance and cold workability, the high-temperature strength is further improved. Materials have come to be required. The materials proposed in the above-mentioned respective publications are mainly aimed at improving corrosion resistance, cold workability or oxidation resistance, and none of them mention high temperature strength targeted by the present invention. As a result of the inventor's investigation of the materials proposed in the above-mentioned publications, when the high temperature strength is insufficient or the high temperature strength is high, cold workability may be insufficient. There was a problem that I was not always satisfied with the material. An object of the present invention is to provide a material that has a higher high-temperature strength than NCF600 and has thermal conductivity, oxidation resistance, and cold workability to the extent that there is no practical problem as an ignition plug.

[0004]

Usually, when the high temperature strength is improved, the room temperature strength is also inevitably increased, so that the bending process during the manufacture of the plug becomes difficult, which is not preferable as the material for the plug electrode. Therefore, as a material for a spark plug, it is necessary to satisfy the contradictory requirements of improving the high temperature strength and suppressing the increase of the room temperature strength as much as possible, and no conventional alloy has satisfied such requirements. In addition to the above requirements for strength, the present invention further provides oxidation resistance,
This is done by carefully controlling the type, amount, and combination of alloying elements in consideration of thermal conductivity and the like. As a result of various studies for solving the above problems, the inventor has found that Mo and W are particularly effective, and that it is important to adjust the amounts of Cr and Fe added.

That is, according to the present invention, in% by weight, C 0.10% or less, Si 1.0% or less, Mn 2.0% or less, Cr 12 to 30%, and one or two kinds of Mo and W at Mo + 1 / 2W 4%. ~ 12%, Fe 20% or less, the balance is essentially Ni except for impurities, is an electrode material for a spark plug excellent in high temperature strength, and, if necessary, Al, Ti, Nb , Ta can be added alone or in combination.

That is, a material based on the above material and further added with Al has a weight percentage of C 0.10% or less, Si 1.
0% or less, Mn 2.0% or less, Cr 12 to 30%, 1 or 2 kinds of Mo and W at Mo + 1 / 2W 4 to 12%, Fe 20% or less, Al 1% or less, and the balance excludes impurities It is an electrode material for spark plugs excellent in high temperature strength, which is essentially composed of Ni, and a material to which Ti is added is, by weight%, C0.10% or less,
Si1.0% or less, Mn2.0% or less, Cr12-30%, Mo and W 1 or 2 with Mo + 1 / 2W 4-12%, Fe20% or less, Ti1%
It is an electrode material for spark plugs excellent in high temperature strength, characterized in that the remainder includes essentially Ni except for impurities, and the material to which Al and Ti are further added, in weight%,
C0.10% or less, Si1.0% or less, Mn2.0% or less, Cr12-30
%, 1 type or 2 types of Mo and W with Mo + 1 / 2W 4-12%, Fe
An electrode material for a spark plug excellent in high temperature strength, which is characterized by containing 20% or less, Al 1% or less, Ti 1% or less, and the balance being essentially Ni except impurities.

The desirable composition range of the material of the present invention is
% By weight, C0.05% or less, Si0.5% or less, Mn0.8% or less,
Cr15-25%, Mo2-10%, W2-10% (however Mo + 1 / 2W
5-10%), Al0.02-0.5%, Ti0.02-0.5%, Fe2-15
%, And the balance is essentially Ni except for impurities, which is an electrode material for a spark plug excellent in high temperature strength. The above materials are Nb + 1/2 with one or two of Nb and Ta.
It can contain less than 2.5% Ta.

[0008]

[Function] The function of each element will be described below. C is
It is necessary to add a small amount because it forms a carbide in combination with Cr, Ti, Nb, Mo, W, etc. and is effective in preventing the coarsening of crystal grains. However, excessive addition reduces the cold workability due to the formation of a large amount of carbide, so the content is limited to 0.10% or less. The desirable C range is 0.003 to 0.05%. Si and Mn are added as deoxidizing elements. However, since excessive addition of both causes reduction in high temperature strength, Si is limited to 1% or less and Mn is limited to 2% or less. Desirably, Si is 0.5% or less and Mn is 0.8% or less. Cr
Is an important element for imparting oxidation resistance and corrosion resistance, and at least 12% is required. However, excessive addition causes a decrease in cold workability and an increase in electric resistance, so the content is made 30% or less. The desirable Cr range is 15 to 25%.

Mo and W contribute to the increase in high temperature strength by solid-solution strengthening the austenite matrix, and are important elements in the material of the present invention, and it is essential to add one or two. The strengthening effect of Mo and W can be roughly summarized as Mo + 1 / 2W, and the value must be at least 4% to obtain high temperature strength of NCF600 or higher. However, as described above, the cold workability decreases as the amount of these strengthening elements increases. Therefore, the value of Mo + 1 / 2W should be 12% or less. In addition, as a result of various studies to increase the high temperature strength while suppressing the room temperature strength, it is better to add Mo and W in combination because it is more effective to contain both elements in a composite form. . Desirable ranges are Mo2-10%, W2-10% (however
Mo + 1 / 2W is 5-10%).

In the alloy system of the material of the present invention, Fe acts to reduce both high temperature strength and room temperature strength, but it is not always necessary to add it. However, when Fe and Mo are added appropriately, Fe has the effect of considerably lowering the ordinary temperature strength without significantly lowering the high temperature strength, so it is preferable to add an appropriate amount. However, if added excessively, the high temperature strength and the oxidation resistance are deteriorated, so the content is limited to 20% or less. desirable
The range of Fe is 2 to 15%. Al is added as a deoxidizer and contributes to the improvement of oxidation resistance, so it is added as necessary. However, if Al is excessively added, cold workability is deteriorated, so the upper limit of Al is preferably 1% or less. The desirable Al range is 0.02-0.5%. Ti forms carbides and nitrides and is effective in preventing crystal grain coarsening, so Ti is added as necessary. However, if Ti is excessively added, cold workability is deteriorated, so the upper limit of Ti is preferably 1% or less. The desirable Ti range is 0.02 to 0.5%.

Nb and Ta are solid solution strengthening and precipitation strengthening elements, and since addition of a small amount has a great effect of improving strength, one or two kinds can be added as required. However, excessive addition deteriorates the cold workability, so Nb and
It is recommended that one or two of Ta be Nb + 1 / 2Ta and less than 2.5%. By the way, Nb and Ta are effective when high temperature strength is important, but at the same time, room temperature strength is considerably improved. Therefore, it is not preferable for manufacturing a plug, and rather, it is better to prepare by proper addition of Mo and W. Overall preferred. Further, to the alloy system of the material of the present invention, elements within the following ranges can be added for the purpose of obtaining the effects described below. B ≦ 0.015%, Zr ≦ 0.1%, Hf ≦ 0.2% Mg ≦ 0.02%, Ca ≦ 0.2% Y ≦ 0.1%, REM ≦ 0.1%

The effects of each element are as follows.
That is, B and Zr enhance strength and ductility at high temperature as grain boundary strengthening elements, Mg and Ca enhance deoxidation and desulfurization elements, cleanliness of alloys and ductility at high temperature, and Y and REM improve oxidation resistance. . However, if the amount of each element exceeds the above amount, the initial melting temperature is lowered and the hot workability is deteriorated.

[0013]

EXAMPLES Examples of alloys having the compositions shown in Table 1 were prepared by vacuum induction melting.
A 10 kg ingot was melted, and a 30 mm square rod was manufactured by hot working. After holding it at 1000 ℃ for 1 hour and subjecting it to solid solution treatment by air cooling, tensile test at room temperature and 800 ℃, electrical resistance at 800 ℃ and oxidation loss after holding at 900 ℃ × 100 were measured. 2 shows. The electrical resistance was measured to estimate the thermal conductivity, and a high electrical resistance indicates a low thermal conductivity.

[0014]

[Table 1]

[0015]

[Table 2]

The materials of the present invention have a tensile strength at room temperature of 840 MPa or less, even though the tensile strength at 800 ° C. is as high as 240 MPa or more, indicating that they have excellent cold workability. On the other hand, the conventional material NCF600 has a tensile strength at 800 ° C. of 186 MPa, which indicates that the material of the present invention has excellent high temperature strength. Further, the electric resistance of the material of the present invention is slightly higher than that of the conventional material, NCF600, but at a practical level. Furthermore, the oxidation resistance is equal to or higher than that of NCF600. On the other hand, Comparative Material 31 lacks in Mo and W contents, and therefore lacks in high temperature strength. The comparative material 32 has high strength at high temperature due to the addition of Nb, but also has high strength at room temperature, is difficult to mold, and has deteriorated oxidation resistance. Comparative material 33 is Mo,
Since the amount of W and the amount of Cr of the comparative material 34 are too large, the strength and electric resistance at room temperature are high. Since the comparative material 35 has a large amount of Fe, its high temperature strength is insufficient and its oxidation resistance is poor. Since the comparative material 36 contains too much Al and Ti, it has high strength and electrical resistance at room temperature.

[0017]

The alloy of the material of the present invention is NC which is a conventional alloy.
Higher temperature strength than F600 and as a spark plug, it has thermal conductivity, oxidation resistance and corrosion resistance to the extent that it does not pose a problem in practical use, and it has good cold workability by appropriately lowering room temperature strength. . By using the alloy of the material of the present invention, it is possible to easily manufacture the spark plug and to improve the performance of the engine.

Claims (7)

[Claims] 1. By weight%, C 0.10% or less, Si 1.0% or less, Mn 2.0% or less, Cr 12 to 30%, one or two of Mo and W or 2.
An electrode material for a spark plug excellent in high temperature strength, characterized in that it contains 4 to 12% of Mo + 1 / 2W and 20% or less of Fe, and the balance is essentially Ni except impurities. 2. By weight%, C 0.10% or less, Si 1.0% or less, Mn 2.0% or less, Cr 12 to 30%, one or two of Mo and W or 2.
An electrode material for a spark plug excellent in high-temperature strength, characterized in that it contains 4 to 12% of Mo + 1 / 2W, Fe of 20% or less and Al of 1% or less, and the balance is essentially Ni except impurities. 3. By weight%, C 0.10% or less, Si 1.0% or less, Mn 2.0% or less, Cr 12 to 30%, one or two of Mo and W or 2.
An electrode material for a spark plug excellent in high temperature strength, which is characterized by containing 4 to 12% of Mo + 1 / 2W, Fe of 20% or less, and Ti of 1% or less, and the balance being essentially Ni except impurities. 4. By weight%, C 0.10% or less, Si 1.0% or less, Mn 2.0% or less, Cr 12 to 30%, one or two of Mo and W or 2.
Seed with Mo + 1 / 2W 4-12%, Fe 20% or less, Al 1% or less, Ti
An electrode material for a spark plug excellent in high-temperature strength, characterized by containing 1% or less, and the balance being essentially Ni except impurities. 5. By weight%, C0.05% or less, Si0.5% or less, Mn0.8% or less, Cr15-25%, Mo2-10%, W2-10%
(However, Mo + 1 / 2W: 5-10%), Al0.02-0.5%, Ti0.0
An electrode material for a spark plug excellent in high-temperature strength, characterized by containing 2 to 0.5% and Fe 2 to 15%, and the balance being essentially Ni except impurities. 6. One or two of Nb and Ta is Nb in weight%.
The electrode material for a spark plug excellent in high temperature strength according to any one of claims 1 to 5, containing less than 2.5% in +1/2 Ta. 7. A tensile strength at 800 ° C. of 240 MPa or more,
An electrode material for an ignition plug having excellent high temperature strength according to any one of claims 1 to 6, which has a tensile strength at room temperature of 840 MPa or less.