US2266318A - Alloy for use in spark plug electrodes and the like - Google Patents

Description

Patented Dec. 16," 1941 UNITED STATES 2,266,318 PATIENT OFFICE ALLOY FOR- USE IN SPARK PLUG ELECTRODES AND THE LIKE Walter F. Heller, Flint, ma. assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware No Drawing. Application August 23, 1940, Serial N0. 353,842

'9 Claims. (Cl. 123-169) This invention has to do with an improved alloy'resistant to heat and corrosion especially produce rapid deterioration of most alloys ordi- 1o narily regarded as resistant to heat and corrosion.

An electrode alloy. that has been found to be particularly useful for this service is disclosed in Randolph Patent No. 2,001,888 granted May 21,

1935. This alloy consists essentially of nickel and chromium together with a small proportion of .barium. In addition to durability and relatively good heat conductivity, this alloy possesses the advantage of lowering the sparking voltage owing tothe quantity of low work function material-in this instance barium-contained in it. In its inclusion of low work function material the Randolph alloy constitutes an embodiment of "the invention described and claimed in Patent No. 1,872,065 issued to Rabezzana and Duffendack on August 16, 1932.

I have succeeded in substantially improving the alloy of the Randolph patent as well as similar alloys in which barium is omitted by the addition of a small proportion of columbium, pref e'rably on the order of from .1 to- 10%. The columbium greatly increases resistance to corrosion and wear and together with the other additions hereinafter described improves the life and performance of the electrodes. The following is the alloy composition at present preferred for production:

Per cent Chromium 3.5 0 Barium .02 Columbium 1.5 Iron 1.0 Manganese 1.0 Silicon 1.0 Magnesium A trace Nickel Balance Alloys of 'marked superiority have also been employed having compositions falling withinthe following range:

- Per cent Chromium .5 to 15 Barium 0to .3 columbium .1 to 10 5 Manganese Q 0 to 6 Iron 0 to 10 Silicon 0 to 5 Magnesium A trace Nickel Balance 6 The high temper- 5 i I tion of this material is increased.

The improved alloy is subject to considerable modification in practice. If lowered sparking voltage is not desired, barium'may be omitted. The use of other alkaline earth metals such as calcium and strontium to replace barium in whole or in part is indicated as these likewise possess low work function and tend to reduce the sparking voltage.

It will usually be found tobe desirable to use smaller amounts of columbium because of the high cost of this material although improvement in corrosion resistance increasesas the proporvenient and most economical way to add columbium is in the form of a ferro-columbium alloy,

hence the iron content of my improved alloy..

Manganese is employed as a deoxidizer to prevent intercrystalline corrosion and increase the workability of the material. Other known deoxidizers may be employed for the same purpose.

Silicon is introduced for the purpose of further increasing resistance to wear and corrosion. It may be omitted if desired.

The trace of magnesium is the residue of a small amount, usually about .1%, added to facilitate drawing.

Cobalt is indicated as a substitute in whole or in part for nickel but nickel base alloys have proven much more corrosion-resistant.

The alloy is preferably prepared in substantially the same way as the alloy of the Randolph patent, that is, all of the materials except barium are melted together and then barium, preferably wrapped in nickel foil to exclude air, is introduced beneath the surface of the melt, followed by casting in ingots and drawing to shape.

Electrodes made of the new composition have I proven on many exhaustive tests in severe service to have exceptionally long life'and to give' unusually satsifactory performance. Inasmuch as electrode life is an important factor limiting spark plug performance especially in the case of high quality plugs such as are used in modern airplane engines, the marked improvement obtainable with the alloy here disclosed is of great practical value.

While both the center and side electrodes may be made of'the new alloy I have found it best to use the new alloy only for the side electrode and the lower part of the center electrode, em-

ploying for the' balance of the center electrode material, such as copper, possessing better, heat conductivity. If preferred the upper part of the electrode may be encased in a sheathof the new alloy forming a continuation of the lower part of the electrode so as to protect it from the cor- .rosive action of combustion chamber gases. It

is important in spark plugdesign that the center electrode be well sealed in the insulator so as to I prevent loss of compression. Such sealing also.

The most conprevents the combustion gases from attacking the upper portion of the electrode.

I claim: Y

1. A spark plug having an electrode made of an alloy having as its major constituent a metal of the group consisting of nickel and cobalt, together with chromium and columbium to improve the resistance to corrosion.

2. A spark plug having an electrode made of an alloy having as its major constituent a metal of the group consisting of nickel and cobalt, toather with chromium and columbium to improve the resistance to corrosion, and a small proportion of a material of low work function to reduce the sparking voltage.

. 3. An electrode for spark plugs and the like made of an alloy of nickel, chromium and columbium together with a small proportion of barium to reduce the sparking voltage.

4. An electrode for spark plugs and the like made of an alloy consisting substantially of from .5 to 15% chromium, 0 to 3% barium, .1 to 10% columbium, 0 to 6% of a suitable deoikidizer such as manganese, 0 to 10% iron, 0 to 5% silicon, and the balance nickel.

5. An electrode for spark plugs and the like made of an alloy consisting substantially of from .5 to 15% chromium from .01 to .3% barium, from .1 to 10% columbium, and the balance nickel. I

6. An electrode for spark plugs and the like made of an alloy consisting of approximately 3.5% chromium, .02 barium, 1.5% columbium,

1.0% iron, 1% manganese, 1% silicon and the balance nickel.

7. A heat and corrosion-resistant alloy consisting substantially of from .5 to 15% chromium, 0 to .3% barium, .1 to 10% columbium, 0 to 6% of a suitable deoxidizer such as manganese, 0 to 10% iron, 0 to 5% silicon, and the balance nickel.

8. A heat and corrosion-resistant alloy consisting substantially of from .5 to 15% chromium, from .01 to .3% barium, from .1 to 10% columbium, and the balance nickel.

9. A heat and corrosion-resistant alloy consisting of approximately 3.5% chromium, .02% barium, 1.5% columbium, 1.0% iron, 1% manganese, 1% silicon and the balance nickel.

WALTER F. HELLER.