JPS63153236A - Electrode material for spark plug - Google Patents

Abstract

PURPOSE:To develop an electrode material excellent in durability for use in spark plug for internal combustion engine, by adding small amounts of one or more elements among Y, Ca, Zr, Sc, and La to an Ni-Fe-Cr alloy having a specific composition. CONSTITUTION:One or more elements among Y, Ca, Zr, Sc, and La are added by 0.01-0.3%, by weight, to the Ni-Cr-Fe alloy having a composition consisting of >72% Ni, 14-17% Cr, 6-10% Fe, <0.5% Si, and <1.0% Mn, which is melted. Then, an ingot of the above molten metal is subjected to hot rolling and cold working, so that an electrode used for spark plug for internal combustion engine can be manufactured. In this way, the electrode material in which consumption due to the peering of oxide film is inhibited and which has superior durability can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates primarily to a highly durable electrode material used in a spark plug for an internal combustion engine.

[Conventional technology]

As the electrode material for spark plugs used in internal combustion engines such as automobile engines, Ni-based alloys, specifically Ni and M
, SC, , S, , T, , /1, etc., are generally used in alloys to which one or more types are added in an amount of about 1 to 10% by weight. Furthermore, recently, among Ni-based alloys, Inconel-based (C-F-Ni) alloys, such as JIS NCF600, are being used from the viewpoint of high-temperature corrosion durability. The table below shows typical components of NCF600.

[Problem that the invention seeks to solve]

Conventional electrode materials as described above have excellent high-temperature oxidation resistance, economic efficiency, and thermal conductivity, but they suffer from repeated oxidizing and reducing atmospheres generated during the combustion process of gasoline engines.
Furthermore, C, , Ni, and F, which have excellent high-temperature acid layer resistance, are produced by compressing and combusting a gasoline/air mixture gas, and by exhausting and inhaling the same gas to repeatedly cycle through high-temperature and cooling conditions.
The surface oxide of a is peeled off, which causes the underlying metal to wear out and the plug to break off.This problem has come into the spotlight recently as there has been a strong demand for maintenance-free and long-life spark plugs. This has become an important issue that needs to be resolved.

[Means for Solving the Problems] In order to eliminate the above problems, the present invention includes a trace amount of an additive element (rare earth metal) in the composition of NCF00.

Specifically, Ni is 72% or more and Cr is 14 to 14% by weight.
17%, Fa 6-1O%, S, 0.5% or less, M,
N containing 1% or less.

-,C,-Fa alloy contains YSC,,Z, ,s,,L
0.01-0.3% of one or more elements selected from a
NCF600 is added in a range of We have created an electrode material that is extremely durable.

[Effect]

Rare earth metals such as Y, Z, , C, , S, , La,
Even if it is contained in a small amount, it will preferentially (actively) form a dense and minute oxide at high temperatures, so its addition will allow the electrode material to form a good film even under oxidizing high-temperature conditions. However, even if left for a long time, oxidation does not increase beyond a certain level. Further, even in a reducing atmosphere, the oxide film is not completely reduced and returns to a metal layer, and the film has the characteristic that there is very little increase or decrease in the film. Therefore, the base metal of the electrode is protected by being covered with the always present oxide film, which prevents the base metal from being worn out and increases the durability of the electrode.

Here, the reason why the content of the rare earth metal is limited to 0.01 to 0.3% is as follows. That is, if the content is less than 0.01% by weight, the modification effect is weak and a dense oxide film cannot be obtained.On the other hand, if the content is more than 0.3% by weight, the modification effect reaches a ceiling, and conversely, preferential oxidation Therefore, the oxide film becomes excessively thick and easily peels off, and the discharge performance is deteriorated. In particular, if the amount added exceeds 0.4% by weight, it tends to be work hardened, making it unsuitable as an electrode material.

A more preferable addition amount of this rare earth metal is in the range of 0.02 to 0.1%.

Note that the C component in the composition should be kept as low as possible for the purpose of actively oxidizing the rare earth metal and improving the workability of the material (cold workability when making it into an electrode for a plug). It is essential. It has been found that the C content is particularly preferably 0.01% by weight or less, but there is no problem with the peeling resistance of the oxide film even if it is 0.15% or less, and it is fully possible to use it as an electrode material. .

[Example] Metal powders having the components and weight ratios shown in the following table were blended, melted in a high frequency melting furnace, hot rolled, and then molded to obtain an electric material.

Next, in order to find out the effects of this invention, the material was cold-worked into a plug electrode of a predetermined size, and this was subjected to a characteristic evaluation test.

Characteristic evaluation tests were conducted by heating to 1000°C in air, holding that temperature for 24 hours, then rapidly cooling, and then heating to 700°C.
One cycle is the process of reducing for 4 hours in an H2 atmosphere heated to , followed by cooling, and the cycle is repeated the number of times shown in the table, after which the oxidation weight increase and the peeling state of the surface oxide layer are visually inspected. .

Further, the spark abrasion resistance was judged from the surface condition after 1000 cycles by blowing sparks on the obtained electrode.

For comparison, the same test was also conducted on a conventional product and a product whose component ratio was slightly different from that of the present invention product (comparative products in the table).

From the table above, it can be seen that in the case of conventional Inconel-based alloys, the oxide film gradually becomes thicker due to repeated oxidation and reduction, but by adding rare earth elements, this increase in thickness can be effectively suppressed. .

It can also be seen that the spark wear resistance is also better than before.

Furthermore, it can be seen that depending on the adjustment of the component ratio (depending on the amount of rare earth element added), a difference appears in the peeling resistance of the oxide film.

〔effect〕

As described above, this invention has excellent high-pressure oxidation resistance, economic efficiency, and thermal conductivity, but under usage conditions where oxidation, reduction, high temperature, and rapid cooling are repeated, the surface oxide film peels off and the underlying metal The conventional NFC600 is said to suffer from wear and tear.
Its properties have been modified by adding a small amount of rare earth elements to its composition, which suppresses oxidation increase and also improves fireworks wear resistance, making it suitable for use in spark plugs for internal combustion engines such as gasoline engines. Even when the spark plug is used, it exhibits perfect durability and contributes to maintenance-free spark plugs and longer lifespans.

Claims (1)

[Claims] By weight ratio, Ni is 72% or more, Cr is 14-17%, Fa
Y, Ce, Zr, Sc,
One or more elements selected from La 0.01 to 0.3
An electrode material for spark plugs containing additives in the range of %.