JPH08232030A - Electrode material for spark plug - Google Patents

Abstract

PURPOSE: To produce an electrode material for spark plug, which satisfies all the required characteristics with respect to spark consumption characteristic, lead attack resistance, and high temp. oxidation resistance and in which the necessity of the proper use of alloy compositions according to service conditions is obviated. CONSTITUTION: This electrode material has a composition in which 1.3-2.0% Si, 1.0-1.8% Cr, 0.2-1.2% Al, 0.25-0.8% Mn, and 0.003-0.05% C, by weight ratio, are incorporated into Ni. Further, it is preferable that conditions of Al+Mn<=1.5% and Si+Cr+Al+Mn+C<=5% and simultaneously a condition of Cr/(Si+Al)>0.5 are satisfied. By this method, all of the three characteristics mentioned above can meet requirements and also it is made possible to meet the demands by using the material of the same composition even if service conditions are changed.

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 spark plugs, and more particularly to an electrode material having excellent durability and heat resistance used for a spark electrode of a plug for an internal combustion engine.

[0002]

2. Description of the Prior Art Generally, Ni is used as an electrode material (spot electrode 1 and center electrode 2 in FIG. 1) of a spark plug for automobile engines and the like.
Base alloy (Ni-Si-Cr-Mn system), specifically Ni
In addition, Si is 1.0 to 2.0% and Cr is 1.0 to 2.0.
%, And an alloy containing 1.5 to 2.5% of Mn is used.

In recent years, engine output and rotation speed have been increasing, and therefore, high temperature oxidation resistance is excellent, wear between electrodes due to spark discharge (spark wear) is small, and resistance to using leaded gasoline is low. Since a material having excellent lead attack property has been demanded, JP-A Nos. 63-89638 and 63-896 have been demanded to meet the demand.
An electrode (Ni-Si-Cr-Mn-Al system) obtained by adding Al to a Ni-based alloy as shown in Japanese Patent No. 39, etc. has been put into practical use.

In addition to this, the Inconel alloy (JISNCF6), which has a particularly low spark consumption, but is particularly excellent in high temperature oxidation resistance.
(00: Ni-16% Cr-8% Fe) Platinum is welded to the center of the electrode to spark between the platinum, and an expensive platinum plug that is maintenance-free (longer life) is realized. ing.

[0005]

[Problems to be Solved by the Invention] Platinum plugs are expensive and are not suitable as general-purpose products. Therefore, the above-mentioned Ni-based alloy (Ni-Si-Cr-Mn system, Ni-
(Si-Cr-Mn-Al system) is generally used, but it does not satisfy all of the characteristics of spark consumption, lead attack resistance, and high temperature oxidation resistance, and any one of these characteristics is used. Therefore, it is necessary to select various alloy compositions depending on the environment, application, engine, and country in which the product is used. Is the reality.

Therefore, the present invention has excellent resistance to high-temperature oxidation, low spark consumption and excellent lead (sulfur) attack resistance regardless of the environment.
It is intended to provide a plug electrode material that does not require proper use depending on the use environment.

[0007]

According to the present invention, in order to improve high-temperature oxidation resistance, spark exhaustion resistance, and lead attack resistance, the electrode material composition is 1.3 to 2.0% by weight of Si and Cr. Content of 1.0 to 1.8%, Al of 0.2 to 1.2%, Mn of 0.25 to 0.8%, and C of 0.003 to 0.05% or less, and the balance of impurities. Except for this, the composition is substantially Ni.

Further, more preferably, in addition to the above setting of the compounding ratio, the additive elements except Ni are Al + Mn ≦ 1.5.
%, Si + Cr + Al + Mn + C ≦ 5.0% or less, and the ratio of Cr, Si, and Al is Cr / (Si + A
l) Make the composition satisfying both conditions of 0.5.

[0009]

[Function] To improve high temperature oxidation resistance and lead attack resistance, N
It can be seen from the aforementioned publications that the addition of Cr, Si, Mn, and especially Al to the i-based alloy is effective, but when the amount of Al is 0.2% or less, the high temperature oxidation resistance is still insufficient, On the other hand, if it is 1.2% or more, the spark consumption tends to deteriorate. The inventors conducted a test evaluation on several hundred compositions to elucidate the cause, and regarding the improvement of high temperature oxidization,
Each component of Al, Cr, Si, and Mn acts in a complex manner to produce an effect, but if the total addition amount becomes 6%, the specific resistance value of the material increases, and internal heat generation causes a dense oxide film in the surface layer portion. It was found that the particles were exfoliated by the discharge energy of the sparks and the spark depletion property deteriorated. Further, regarding the lead attack resistance, it was also found that the required characteristics cannot be obtained unless the Mn component is changed with respect to the increase / decrease of Al.

Then, based on the result, the amount of the additional element was determined as follows.

Al is a very important and indispensable component with respect to oxidation resistance, lead attack resistance, and spark consumption. This A
l is 1.2 to 1.6% for improving high temperature oxidation resistance.
It is necessary to add some, but add too much Al + Cr +
If the total amount of Si + Mn + C is 5%, especially 6% or more, the spark discharge property is deteriorated and the lead attack resistance is also adversely affected. Therefore, in order to maintain the high temperature oxidative property, it is important to suppress the amount of Al and increase the amount of Cr added. On the other hand, if Al is excessively reduced, the high temperature oxidation resistance is impaired, so that the amount of Al is 0.2 as a range in which the problem does not occur.
It was set to 1.2%.

Si is a basic component for high-temperature oxidation resistance and lead attack resistance, but addition of a large amount deteriorates the workability of the material. In addition, the effect alone is small, and when combined with Al, the spark depletion property and the high temperature oxidation property are improved. Therefore, the proper range of the amount depends on the added amount of Al, and
1: The effective amount of Si is 1.3 to 0.2% to 1.2%
It was 2.0%.

[0013] Mn is a component necessary to supplement the high temperature oxidizability in consideration of the amount of Al added and to maintain hot workability, and is also effective in preventing embrittlement due to sulfur in gasoline. Also, in order not to impair the spark consumption, Al + Cr
It is desirable to keep the total weight of + Si + Mn + C within 5%. From this aspect, the amount is set to 0.25 to 0.8%.
When Mn is 0.25% or less, particularly 0.2% or less, the effect of addition is not strong, while 0.8%, especially 1.5%.
If the amount exceeds 5, the total added weight of each component exceeds 5%, which causes a problem in spark exhaustion. Further, Mn is a component that improves the lead attack resistance in cooperation with Al, and Al + Mn ≦ 1.5% was preferable from the viewpoint of the lead attack resistance.

Cr is an indispensable component in general heat-resistant materials, and functions to enhance high-temperature oxidation resistance, lead attack resistance, spark consumption, and the like. This Cr was set to 1.0 to 1.8% in relation to the added amounts of Al and Si. This Cr is 1.0%
If it is less than the above, basic properties such as oxidation resistance cannot be obtained, and
If it is 1.8% or more, the cold workability when the material is processed into a wire material is significantly deteriorated. Further, in order to maintain the lead attack resistance and the high temperature oxidation characteristics, the ratio of Cr / (Al + Si) is 0.5 while satisfying the condition of Al + Mn ≦ 1.5%.
It turned out that the above is very effective.

The C content is set to 0.05% or less in order to enhance the cold workability and facilitate the bending work. However, if the C content is too small, it causes the generation of blowholes in the material. 0.003 to 0.05%. This C is an important component for sufficiently exerting the effects of the above-mentioned added components.

In addition to the above-mentioned additive components, the amount of gas contained in the material is an important factor that determines whether or not the additive element acts effectively. It is desirable that the amount of oxygen is 40 PPM or less, the amount of nitrogen is 30 PPM or less, and the amount of hydrogen is 3 PPM or less with respect to the addition amount of each of the above addition components.

FIG. 2 shows Al and S in order to check the spark consumption.
The relationship between the total weight of i, Cr, Mn, and C and the spark consumption rate is shown. When the total addition amount exceeds 5% and becomes 5.5% or more, the spark consumption property deteriorates rapidly. I understand.

[0018]

EXAMPLES Tables 1, 2, and 3 show the electrode materials of the present invention (Examples 1 to 5), and comparative materials (Comparative Examples 1 to 15) in which the amounts of additive elements were out of the range of the present invention. The respective compositions of conventional electrode materials (conventional examples 1 to 5) are shown.

For these materials, raw materials mixed with predetermined components are melted in a vacuum melting furnace and cast into ingots, which are then forged and hot rolled into 10 mm wire rods, and the wire rods are cold drawn. Then, a lateral electrode material having a thickness of 1.3 mm and a width of 2.7 mm and a center electrode material having a diameter of 4.2 mm and a length of 7.0 mm were prepared. Then, this was subjected to final molding processing to make an ignition plug as shown in FIG.

Next, for each trial material,
An evaluation test of lead attack resistance and spark consumption was performed.

The contents of the evaluation test are shown below. Also,
The evaluation results are also shown in Tables 1 to 3.

* Spark consumption: The distance between the electrodes of the plug is 1 m.
m was set, and during that period, sparks were generated at 200 times / sec for 1 hour in the atmosphere, and the residual rate of the base material after that was examined (the numbers in the table represent the original base material as 100).

* Lead attack resistance: PbO: Pb = 1: 1
The residual ratio of the base material after holding for 2 hours at 900 ° C. in the mixing bath was examined.

* High temperature oxidation resistance: 1000 ° C x 4 minutes +30
The residual rate of the base material was examined after the heat cycle of 0 ° C. × 2 minutes was repeated 2000 times.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

The spark consumption, lead attack resistance, and high temperature oxidation resistance are evaluated by 70% or more, particularly 75%.
% Or more, there is no fear of damaging the plug characteristics. The electrode material of the present invention shows the same or higher performance than the conventional product in any of the above three required characteristics, and the same material can be used for any required characteristics, so it is necessary to use various alloy compositions properly. There is no.

[0029]

As described above, since the spark plug electrode material of the present invention satisfies all the required characteristics of spark consumption, lead attack resistance, and high temperature oxidation resistance, it can be used according to usage conditions. There is no need to use different compositions, and product types can be integrated, resulting in benefits such as improved productivity and mass productivity.
Further cost reduction due to mass production (unlike platinum plugs, it is originally cheap), simplification of distribution, etc. will be brought about.

[Brief description of drawings]

FIG. 1 is a front view of a spark plug.

FIG. 2 is a chart showing the test results of the relationship between the total amount of added elements and spark depletion.

[Explanation of symbols]

 1 Insulator 2 Center electrode 3 Terminal 4 Mounting screw 5 Side electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junichi Kagawa 14-18 Takatsujicho, Mizuho-ku, Aichi Prefecture Nagoya City Nihon Special Ceramics Co., Ltd.

Claims (2)

[Claims] 1. The weight ratio of Si is 1.3 to 2.0%, and Cr is
Of 1.0 to 1.8%, Al of 0.2 to 1.2%, Mn of 0.25 to 0.8%, and C of 0.003 to 0.05%. An electrode material for an ignition plug, which is substantially made of Ni. 2. Al + Mn ≦ 1.5%, Si + Cr + A
1 + Mn + C ≦ 5.0% condition and Cr / (Si + A
The electrode material for a spark plug according to claim 1, which also satisfies the condition 1)> 0.5.