JPH10251787A - Electrode material for spark plug, excellent in thermal conductivity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode material for spark plug, capable of meeting the recent demand for heavy load and high performance of an internal combustion engine and excellent in manufacturability as well as in oxidation resistance. SOLUTION: This material has a composition which consists of, by weight ratio, <=0.1% C, 0.5-3% Si, 0.5-2% Mn, 1-6% Cr, 0.005-0.5%, in total, of either or both of Hf and Re, and the balance essentially Ni and in which the content of Al contained as an additive or an impurity is limited to <=0.05%. It is desirable to incorporate >3% Cr in order to improve corrosion resistance and high temp. strength, and further, Ti can be added to improve oxidation resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode material for an ignition plug of an internal combustion engine.

[0002]

2. Description of the Related Art As an electrode material for a spark plug used in an internal combustion engine of an automobile or the like, a Ni-based alloy is widely used because it requires oxidation resistance and high-temperature strength. For example, as disclosed in JP-A-62-50430, in order to improve corrosion resistance and high-temperature strength in particular, high Cr containing 14% or more of Cr is used.
Electrode materials for system plugs have been proposed. In addition, since the above-described high Cr material deteriorates workability, there is a proposal that the content of Cr is reduced to about 5% or less and an additive element for improving oxidation resistance and high-temperature strength is contained. Oxidation resistance of low Cr materials is lower than that of high Cr materials.
Proposals have been made to add one or more elements such as Si, Mn and Al, or to add Y or a rare earth element in order to compensate for the deterioration of oxidation resistance.
-89638, JP-A-2-163335 and the like. Japanese Patent Laid-Open No. 34736/1990 proposes an alloy in which Hf and Re are added to a low Cr or Cr-free material to increase the high-temperature strength.

[0003]

The above-mentioned material in which Cr is suppressed to a certain low level is a promising material from the viewpoint of workability. However, due to the recent high performance of internal combustion engines, high combustion efficiency, high load by conversion of combustion mechanism, etc., the environment for spark plug alloys has become more severe.
With the above-mentioned alloys, satisfactory characteristics cannot always be obtained. In view of the above circumstances, an object of the present invention is to provide an electrode material for a spark plug that has excellent oxidation resistance, corrosion resistance, and excellent manufacturability in response to a higher load and higher performance of an internal combustion engine. It is to be.

[0004]

SUMMARY OF THE INVENTION The present inventors have studied electrode materials for spark plugs. As one of the major factors for improving the oxidation resistance of an alloy for spark plugs, it is necessary to increase the thermal conductivity. I found something. In order to increase the thermal conductivity while maintaining the basic characteristics of the spark plug, an alloy having basic high-temperature strength, oxidation resistance and corrosion resistance by specifying Cr, Si, Mn, and C is required. On the other hand, while restricting Al to as low as 0.05% or less,
One or two of Hf and Re are used in a total of 0.005 to 0.5.
It was found that containing 5% was effective, and the present invention was reached.

That is, the present invention provides C0.1% by weight.
Hereinafter, Si 0.5 to 3%, Mn 0.5 to 2%, Cr 1
6%, a total of 0.005 of one or two of Hf and Re
It is an electrode material for a spark plug having a composition of about 0.5%, the balance substantially consisting of Ni, and having a composition in which Al added or contained as an impurity is regulated to 0.05% or less.

In the present invention, it is desirable to contain more than 3% of Cr in order to increase corrosion resistance and high-temperature strength, and it is possible to add Ti in order to increase oxidation resistance.

[0007]

DETAILED DESCRIPTION OF THE INVENTION As described above, the present invention restricts the amount of Al to increase the thermal conductivity, and
The addition of e has important characteristics. According to the study of the present inventors, by increasing the thermal conductivity, the material temperature can be lowered when used as an ignition plug, and as a result, oxidation resistance and corrosion resistance can be improved. In the present invention, Al is an element that deteriorates the thermal conductivity even in a small amount, and excessive addition of Al decreases weldability or cold workability or promotes grain boundary oxidation of the internal structure. , 0.0
Restrict to 5% or less. In addition, a small amount of Al is inevitably contained, and addition of a small amount is acceptable because addition of Al has an effect of improving oxidation resistance. Preferably,
The range is 0.001 to 0.05%.

In the present invention, the addition of one or two of Hf and Re is an essential addition element to the invention alloy capable of improving oxidation resistance and high-temperature strength while maintaining high thermal conductivity. . One or two types of Hf and Re are used in 0.1.
005% or more must be contained. But H
f and Re are expensive elements, and if their sum exceeds 0.5%, the material becomes expensive, which is not preferable. Desirably, one or two of Hf and Re are used in an amount of 0.05% to 0.1%.
It is better to add 2%.

Cr is the corrosion resistance of the spark plug electrode material,
It is a basic element for improving oxidation resistance and high-temperature strength, and requires 1% or more. On the other hand, when Cr is added in an increased amount, the thermal conductivity is lowered and the workability is deteriorated. In the present invention, the lack of corrosion resistance, oxidation resistance, and high-temperature strength due to the suppression of Cr to 6% or less is determined by the regulation of Al and H.
It is supplemented by the action of adding f or Re. In the present invention, the desirable range of Cr is 3.2 to 4.5%.
It is.

In the present invention, C is preferably low in order to improve the workability. If the weight ratio exceeds 0.1%, the hardness after annealing increases, and the cold workability decreases. 0.1%
Limited to the following. The desirable range of C is 0.05% or less. In the present invention, Si is an element effective for improving oxidation resistance, and it is necessary to contain 0.5% or more to exhibit its effect. However, if the addition exceeds 3%, the workability and the thermal conductivity decrease, so the range of Si is set to 0.5 to 3%. A desirable range is 1 to 2.5%. In the present invention, Mn is also an element that improves oxidation resistance by adding an appropriate amount, and if it is less than 0.5%, it has no effect, so it is necessary to contain 0.5% or more. However, when the content exceeds 2%, the oxidation resistance is reduced, so that Mn
Is set to 0.5 to 2%. Desirable range is 0.7-
1.3%. According to the above-mentioned component range, in the present invention, 19.5 W at room temperature (25 ° C.) is preferable.
/ (M · K) or more.

In the present invention, Ti can be added. Ti is effective as an element for improving the adhesion of the oxide film. On the other hand, the addition of Ti must be limited to lower the thermal conductivity. According to the study of the present inventor, T
Since i does not lower thermal conductivity as much as Al, 1% or less can be added to improve adhesion.

In the present invention, a property improving element can be added as long as the thermal conductivity is not deteriorated.
For example, B: 0.015% or less Zr: 0.1% or less Ca: 0.2% or less Mg: 0.02% or less Fe: 3% or less Rare earth elements such as La and Ce and Y: 0.1% or less It is possible to add

The effects of the additional elements described above are as follows. That is, B and Zr enhance the high-temperature strength and ductility as grain boundary strengthening elements, and Mg and Ca enhance the cleanliness of the alloy and enhance the high-temperature ductility as deoxidizing and desulfurizing elements.
Fe of 3% or less may be contained because it does not particularly affect the properties of the alloy. In order to improve oxidation resistance, L
A rare earth element such as a or Ce and Y and 0.1% or less may be contained. According to the present invention, it is preferable to adjust the alloy components such that the thermal conductivity at room temperature is 19.5 W / (m · K) or more.

[0014]

EXAMPLES Examples of the present invention will be described specifically. Alloys having the compositions shown in Table 1 were melted in a vacuum melting furnace, and then hot-rolled. Thereafter, annealing was performed under the conditions of 730 ° C. × 1 hr to obtain samples for the following tests. Table 2 shows the results of measuring the hardness, the thermal conductivity, the increase after the oxidation resistance test, and the amount of scale peeling of the obtained sample. The oxidation resistance test was performed by exposing the sample to the atmosphere at 1000 ° C. for 100 hours. The thermal conductivity shows a value at 25 ° C.

[0015]

[Table 1]

[0016]

[Table 2]

In Table 1, sample no. Nos. 1 to 5 are obtained by adding Hf and changing the amount of Al added. In the sample of the present invention in which the addition amount of Al is 0.05% or less, the thermal conductivity does not significantly deteriorate. On the other hand, in the sample 5 of the comparative example in which the content was increased while the content of Al was as small as 0.2%, the thermal conductivity was clearly reduced. Sample No. 6
Nos. 11 to 11 are obtained by adjusting Al to around 0.04% and changing the added amounts of Hf and Re. Compared to Sample 11 of the comparative example to which Hf or Re was not added, Hf or R
In Samples 6 to 10 of the present invention to which e was added, the amount of increase in oxidation was small and the amount of peeling of the scale was small, indicating that good oxidation resistance was obtained. Further, it was confirmed that the sample of the present invention hardly increased in hardness after annealing and had good workability.

Also, in samples 12 to 23 whose compositions were changed within the specified range of the present invention, good oxidation resistance and high thermal conductivity were achieved. In the case of Sample 12 having a higher Cr content of 5.25% and Sample 17 having a higher content of Si of 2.54%, the thermal conductivity tends to decrease. Samples 13 and 14, which had a Cr content of 3% or less, had slightly inferior oxidation characteristics as compared with other samples of the present invention in which the Cr content exceeded 3%. In addition, a comparative example in which Nb known as a heat resistance improving element was added without adding Hf or Re is shown in Sample 24, and the effect of improving the oxidation resistance by adding Nb at about 0.5% is shown. Is hardly confirmed, and it is confirmed that the thermal conductivity tends to decrease. That is, it is understood that Hf and Re are additive elements excellent in that they do not decrease the thermal conductivity and increase the oxidation resistance.

[0019]

According to the present invention, it is possible to provide an electrode material for a spark plug which is excellent in heat conductivity, has good oxidation resistance and good workability, and is capable of suppressing the cost and improving the performance of the engine. It is industrially very effective because it can cope with the change in the production.

Claims (3)

[Claims] C. 0.1% or less by weight, Si 0.5
3%, Mn 0.5 to 2%, Cr 1 to 6%, one or two of Hf and Re in total of 0.005 to 0.5%, and the balance substantially consisting of Ni; An electrode material for an ignition plug having excellent thermal conductivity, characterized by having a composition in which Al contained as an impurity is regulated to 0.05% or less. 2. The spark plug electrode material according to claim 1, which contains more than 3% of Cr. 3. The electrode material according to claim 1, which contains 1% or less of Ti.