JPS63312939A - Electrode material for ignition plug - Google Patents

Abstract

PURPOSE:To obtain an electrode material having excellent durability which is essentially used for an ignition plug in internal combustion engines by incorporating specific amounts of Ni, Cr, Fe, C, Mn and Si and one or more kinds among Ti, Mg and Al into said material. CONSTITUTION:The above-mentioned electrode material contains, by weight, >=72% Ni, 14-17% Cr, 6-10% Fe, 0.15% C, <=1% Mn and 0.2-0.5% Si and one or more kinds among Ti, Mg and Al. In said electrode material, the diffusion of oxygen atoms. onto the surface of grain boundaries is prevented. As the result, the consumption of an electrode is effectively prevented to suppress the extension of the electric discharging gap, by which a longer service life free from maintenance can be attained.

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]

Ni-based alloys, specifically Nl, Cr, are used exclusively as electrode materials for spark plugs for automobile engines and the like.

An alloy to which one or more of St, 'rt, Aj, etc. is added in a weight ratio of 1 to 10% has been used.

In addition, recently, Inconel-based materials (
Cr-Fa-Ni) alloy JIS NCF600 is also widely used. The composition of the alloy is shown in the table below.

[Problem that the invention seeks to solve]

The above-mentioned conventional electrode materials have excellent high-temperature oxidation resistance, economic efficiency, and thermal conductivity, but they are difficult to discharge at high voltage in the combustion chamber of an engine, where high temperature and highly corrosive particles and gases are present. Since the spark energy during repetition is extremely large instantaneously, the surface of the electrode may become locally hot and partially melt or evaporate, or the spark surface may be damaged due to collision of cations and electrons between the negative and positive electrodes. The electrode was abnormally easy to wear out, such as sputtering (the part indicated by the chain line in FIG. 2). In particular, the Inconel alloy contains 90% by weight of Ni.
The wear was more severe than that of other Ni-based alloys.

Early electrode wear is a fatal problem for spark plugs, and now there is a strong demand for maintenance-free spark plugs.
The solution is the most important thing! II! ! It is no exaggeration to say that it is.

The purpose of this invention is to solve such problems.

[Means for solving problems]

The electrode material of this invention contains 72% or more of Ni and C by weight ratio.
r 14-17%, Fe 6-10%, C 0.15%
Below, Mn is 1% or less, Si is 0.2 to 0.5%, and other components include Ti, Mg, /lj! It is characterized by a composition containing one or more of the following.

In other words, the inventor investigated the defective part to find the cause of early wear of conventional electrode materials, and found that oxygen was abnormally segregated (diffused from within) at the grain boundaries on the surface. It was discovered that some compounds with Fe and Cr were formed to accelerate the consumption of the material.

However, even with the latest melting method (vacuum degassing method), oxygen in the material can only be removed to a maximum of about 50 PPI'1, and it is difficult to eliminate it completely.

Therefore, we came up with the idea of adding an additive that has a very strong affinity for oxygen, and using that additive to fix a stable compound or oxygen within the alloy, thereby preventing oxygen atoms from diffusing to the grain boundary surface. By doing so, he succeeded in achieving his goal.

5iSTiSA1 and Mg are both components that have a strong affinity for oxygen, and by adding them, stable confinement of oxygen atoms is realized.

In addition, the content of these components is based on the result of trial production of materials.
t is 0.2 to 0.5%, more preferably 0.3 to 0.5
%.Furthermore, for Ti, Aj, and Mg, when only two types of Ti and Al are added, the total of both is 0. O1~0.
0.05%, and when adding a combination of Ti or AI and Mg, Tl or Al is added to 0.05%. O1~0°05%, Mg 0.0
01 to 0.01%, and when adding a combination of Ti and Al1Mg, the total amount of Ti and Al is 0.01 to 0.0%.
It was found that it is sufficient to set the Mg content to 5% and 0.001 to 0.01%.

Si is also necessary to improve oxidation resistance, but 0
．． If it is less than 2%, sufficient bonding with oxygen cannot be expected;
．． If it exceeds 5%, especially 0.7%, the problem of excessive hardening will occur and processing will become impossible.

TtSAm! If it is less than 0.01%, the bond with oxygen will be insufficient. In particular, if it is less than 0.005%, almost no effect is seen, and if it exceeds 0.05%, it may form intermetallic compounds or become inclusions, impairing workability. This problem becomes extremely noticeable when the amount reaches 0.08%.

Similarly, Mg has no effect when added below 0.001%.
On the other hand, if it exceeds 0.01%, especially 0.05%, inclusions tend to form.

In addition, C is effective in improving workability. The effect occurs when the content is below 0.15%, but 0.02%
It has also been confirmed through prototype experiments that the maximum value can be obtained if the following conditions are met.

〔Example〕

First, Fe, Cr, and Ni were melted and mixed in a vacuum melting furnace, and Si, Mg, Ti, and Al were added during the process to make an ingot.

Next, the ingot is hot forged and then made into a rolled material with a diameter of 1ON, which is then made into a 4φ round wire and a 2.5X
The material was processed into a rectangular material of size 1.8, which was further softened and then canted to a predetermined size to obtain an electrode having the composition shown in Table 1. The electrodes were then welded together to make spark plugs. The discharge gap G (see Figure 1) between the electrodes at this time was set to 1.0 fl, and in order to see the effects of the present invention, the plug, the conventional plug, and the comparative plug with the composition listed in Table 1 were compared. An engine ignition test was conducted. The electrode performance was evaluated based on the amount of gap G expansion after 100 hours of engine operation.

〔effect〕

As can be seen from the comparative tests of the above examples, the electrode material of the present invention prevents oxygen atoms from diffusing to the grain boundary surface, and as a result, electrode wear is effectively prevented and the discharge gap is reduced. Spreading is suppressed, extending the life of the spark plug,
The effect of being maintenance-free can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the discharge gap between the electrodes of a spark plug, and FIG. 2 is a diagram showing the parts where the electrodes are consumed.

Claims (2)

[Claims] (1) 72% or more Ni and 14-17% Cr by weight
, Fe 6-10%, C 0.15% or less, Mn 1%
Below, Si is 0.2 to 0.5% and other components are T.
An electrode material for a spark plug comprising one or more of i, Mg, and Al. (2) The content of the above C is 0.02% or less, and the content of other components is 0.01 to 0 in total when combining Ti and Al.
．． 05%, Ti or Al0.01 when combining Ti or Al and Mg
0.05%, Mg 0.001 to 0.01%, the electrode material for a spark plug according to claim 1.