JPH10251786A - Electrode material for spark plug - 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 and corrosion resistance. SOLUTION: An Ni-base alloy, which has a composition consisting of, by weight ratio, <=0.1% C, 0.5-3% Si, 0.5-2% Mn, 2.5-6% Cr, <=0.05% Al, <=1% Ti, and the balance essentially Ni and satisfying the conditions of inequalities 4.0<=Si+Mn+Cr<=8.0 and (Si+Mn)/Cr<=1, is used. In order to improve oxidation resistance to a greater extent, 0.001-0.1%, in total, of one or two kinds among Y and rare earth element can be incorporated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrode material used for a spark 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.
It has been proposed to add elements such as Al and Ti in order to compensate for the decrease in oxidation resistance (for example, Japanese Patent Publication No. 43-43).
19749, JP-B-52-39141). There is also a proposal to add a rare earth (see, for example,
-18033).

[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]

The inventors of the present invention have studied electrode materials for a spark plug. As one of the major factors for improving the oxidation resistance of an alloy for a spark plug, as one of the major factors, an acid resistance within a range in which the thermal conductivity can be maintained high. It has been found that it is necessary to determine the amount of the added element for improving the chemical property. And
Further studies have shown that in order to increase the thermal conductivity while maintaining the basic characteristics of the ignition plug, the Al content is 0.05%.
wt% or less, and within a range that does not lower the thermal conductivity while ensuring the effect of securing oxidation resistance.
i is added in an amount of 1 wt%, the total amount of Cr, Si, and Mn is restricted to a specific range of 4.0 to 8.0 wt%, and the amount of Cr is specified so that the amount of Cr does not become too small in the ratio of (Si + Mn) to Cr. The present invention has been found to be effective.

[0005] That is, the present invention provides a method for producing a steel sheet containing 0.1% or less of C, 0.5 to 3% of Si, 0.5 to 2% of Mn,
-6%, Al 0.05% or less, Ti 1% or less,
The electrode material for a spark plug uses a Ni-based alloy that satisfies the conditions of the following relational expressions and the balance is substantially Ni. Further, in the present invention, in order to further improve the oxidation resistance, one and two or more kinds of Y and rare earth elements are added in a total amount of 0.001 to 0.001.
0.1% can be contained. 4.0 ≦ Si + Mn + Cr ≦ 8.0 (Si + Mn) / Cr ≦ 1

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the present invention limits the amount of Al in order to increase the thermal conductivity, and adjusts the amounts of Cr, Si, and Mn in order to achieve both oxidation resistance and high thermal conductivity. It has become. According to the study of the present inventor, by increasing the thermal conductivity, the material temperature can be lowered when used as a spark 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. , 0.05% 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, 0.001
-0.05%.

In the present invention, Ti is an essential element for improving the oxidation resistance without significantly lowering the thermal conductivity in an alloy in which Al is limited, and it is necessary to contain 1 wt% or less. In the present invention, Ti is Si,
It is also an element that improves the adhesion of an oxide film, such as Cr, and is expected to have the effect of further improving oxidation resistance. In the present invention, Ti is preferably 0.1 to
1.0 wt% is added.

[0008] In the present invention, Si is an element effective for suppressing the increase in oxidation and improving the oxidation resistance. In order to exhibit the effect, it is contained in 0.5% or more. But 3%
If added in excess of, the workability and thermal conductivity decrease, so
The range of i is set to 0.5 to 3%. Desirable range is 1 to
2.5%. In the present invention, Mn is an element which suppresses the increase in oxidation by adding an appropriate amount in the same manner as Si and improves the oxidation resistance.
It is necessary to contain 5% or more. However, if it exceeds 2%, on the contrary, the oxidation resistance and the thermal conductivity decrease, so the range of Mn is set to 0.5 to 2%. Desirable range is 0.7-
1.3%.

[0009] Cr is an element necessary for enhancing corrosion resistance and oxidation resistance. If its content is less than 2.5%, its effect is poor, and if it exceeds 6%, its thermal conductivity is reduced and its workability is further reduced. Therefore, the range is set to 2.5 to 6%. A desirable range is 3.0 to 4.5%. 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. Limited to the following. The desirable range of C is 0.05% or less.

In the present invention, Si, Mn and Cr have the same effect in that they increase the oxidation resistance but lower the thermal conductivity, so that the total amount must be specified.
In terms of securing oxidation resistance, Si + Mn + C
The amount of r needs to be 4.0%, and it is necessary to limit it to 8.0% or less in terms of securing the thermal conductivity. More preferably, it is 5.0 to 7.0%.

In order to improve the oxidation resistance, it is effective not only to suppress the increase in the oxidation amount but also to prevent the oxide film from peeling off. Of the above-mentioned Si, Mn and Cr, S
When the content of i and Mn is high and the content of Cr is low, the oxide film tends to peel off. Therefore, after controlling the total amount as described above, (Si + Mn) / Cr
Is important. In the present invention, the above-mentioned quantitative ratio is set to 1 or less in order to suppress the increase in the amount of oxidation and prevent the separation of the oxide film.

The oxidation resistance can be further improved by adding Y and / or one or more rare earth elements such as La and Ce to the alloy composition of the present invention as required. In order to bring out the effect, it is necessary to use 0.
It is desirable to add 001% or more. However, 0.1
%, The weldability is reduced.
Limited to 1%.

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

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. 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.

[0015]

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.

[0016]

[Table 1]

[0017]

[Table 2]

In Table 1, sample No. Nos. 1 to 3 vary the amount of Al added within the scope of the present invention. As shown in Table 2, 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. A
It can be seen that in the sample 21 of the comparative example in which the content was increased while the value of l was as small as 0.22%, the thermal conductivity was reduced. Samples 6 to 15 of the present invention were modified in composition within the scope of the present invention, but all had good thermal conductivity,
It turns out that it shows oxidation resistance.

On the other hand, Comparative Example 2 containing no Ti shown in Table 1
In No. 2, the oxidation resistance was poor. Comparative Example 2 in which the total amount of Si, Mn, and Cr exceeds 8%
In No. 4, although the oxidation resistance was excellent, the thermal conductivity was significantly reduced. Also, (Si + Mn) / Cr
In Comparative Examples 23 and 25 in which the ratio by weight exceeds 1, the result was inferior oxide film adhesion.

[0020]

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 (2)

[Claims] C. 0.1% or less by weight, Si 0.5
3%, Mn 0.5-2%, Cr 2.5-6%, Al0.
An electrode material for a spark plug, comprising a Ni-based alloy containing not more than 0.05% and not more than 1% of Ti, and satisfying the conditions of the following relational expressions, with the balance being substantially Ni. 4.0 ≦ Si + Mn + Cr ≦ 8.0 (Si + Mn) / Cr ≦ 1 2. The spark plug electrode material according to claim 1, wherein one or more of Y or a rare earth element is contained in a weight ratio of 0.001 to 0.1% in total.