JPS6244545A - Material for electrode for spark plug - Google Patents

Abstract

PURPOSE:To improve the hot durability of a speak plug by forming the central electrode with an Ni-Cr-Fe alloy having a lowered C content as a material for an electrode for a spark plug so as to prevent abnormal corrosion and hot embrittlement due to Cu. CONSTITUTION:An Ni-Cr-Fe alloy consisting of, by weight, 14-25% Cr, <1% Fe, <0.05% C and the valance Ni; an Ni-Cr-Fe alloy consisting of, by weight, 5-18% Cr, <1% Fe, <0.05% C, <0.3% one or more kinds of elements selected among alkaline earth metals and rare earth elements such as Ce, Ca, Th and Y and the balance Ni; or an Ni-Cr-Fe alloy consisting of, by weight, 5-18% Cr, <1% Fe, <0.05% C, 0.5-2% Al or Si and the balance Ni is used as a material for an electrode for a spark plug.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a Ni alloy electrode material for spark plugs, which is an FCA electrode material with excellent corrosion resistance that does not cause abnormal corrosion or hot embrittlement due to Cu in spark plug electrodes. The aim is to provide materials.

Conventional technology Conventional nickel alloys for spark plug electrodes are required to have low oxidation wear and spark wear, as well as low corrosion by combustion residues such as PbO, but in recent years the range of use for spark plugs has expanded. With the shift to so-called small id ranges, it has become common to use center electrodes whose core is fully encapsulated with a material with good thermal conductivity such as Ag*Cu, and whose outer periphery is made of a Ni alloy with good corrosion resistance.

In this case, in order to manufacture composite electrodes, the Ni alloy is required to have good cold workability, and in many cases 90% or more Ni
Although a Ni alloy containing k was used for rL'fc, 72% Ni-16Cr-8Fe (trade name Inconel 600) became necessary due to the requirement for high-temperature corrosion resistance.

However, this alloy produces noise due to poor cold workability compared to conventional materials, and furthermore, it is assumed that at high temperatures of 900°C or higher, the Fe in this alloy induces diffusion of the core member Cu and grain boundary segregation. This results in grain boundary embrittlement and deterioration in high temperature strength.

Problems to be Solved by the Invention In view of the above problems, the present invention solves the following problems:
This is an improvement in grain boundary embrittlement and cold workability of the alloy. The results of testing various Ni-Cr-Fe alloys for the occurrence of hot embrittlement and abnormal corrosion due to Cu are shown in Table 1. As shown in Table 1, hot embrittlement and abnormal corrosion were observed only in alloys containing Fe. Corrosion occurred.

However, in Table 1, the X mark indicates occurrence, hot embrittlement is the result of a bending test at 800°C, and abnormal corrosion is the result of immersion in molten Cu at 1100°C for 15 minutes.

Means for solving the problem Therefore, when the plug electrode temperature rises to 100°C or more due to abnormal combustion, the above-mentioned lNC60 as a heat-resistant electrode material
As mentioned above, the addition of Fe, which may cause abnormal corrosion, is suppressed as much as possible, and the development of a heat-resistant material using Ni-Cr alloy system Bene was carried out.

As shown in Figure 1, the oxidation resistance increase in the Ni-Cr binary alloy shows that the corrosion resistance is best at around 40% Cr, but the cold workability as a bladder electrode material deteriorates significantly. Desirably, Cr is 25% or less. Particularly advantageous in cold workability is 16% or less. This alloy has been developed as a nichrome heating wire, but its cold workability has been improved by suppressing C in particular.

V cold workability improves by lowering Crk, but the first
As shown in the figure, oxidation resistance deteriorates. So A.I.
S i 'f: Add in the range of 0.5 to 2%A
1 e S 1 in place of Ce*Ca*ThtY, etc.Example Oxidation weight gain of the Ni alloy electrode material of the present invention after holding at 1000" CX10 hours and surface hardness after 50% compressive deformation. The results shown in Table 2 above 0 indicate that a decrease in C improves cold workability, and addition of YeCetA1.Si and the like contributes to improvement in oxidation resistance.

Effects of the Invention By using the Ni alloy electrode material for spark plugs of the present invention for the center electrode, f) the hot durability of the spark plug is improved without causing abnormal corrosion or hot embrittlement due to CuVc.

[Brief explanation of drawings]

FIG. 1 is a graph showing the oxidizability of the Ni-Cr binary alloy.

Claims (3)

[Claims] (1) Cr14-25%, Fe1% or less, C0.05%
Spark plug electrode material consisting of the following and the remainder being Ni: (2) 5 to 18% Cr, 1% or less Fe, 0.05% or less C, and contains at least one or more of alkaline earth and rare earth elements such as Ce, Ca, Th, Y, etc.
．． Ni alloy electrode material for spark plugs characterized by adding 3% or less (3) Ni alloy electrode material for spark plugs characterized by containing 5 to 18% Cr, 1% or less Fe, 0.05% or less C, and adding Al or Si in the range 0.5 to 2%.