US2051562A - Alloys - Google Patents

Description

Patented Aug. 18, 1936 UNITED STATES PATIENT OFFlCE ALLOYS James M. Lohr, Morristown, N. J., assignor to Driver-Harris Company, Harrison, N. J., a corporation of New Jersey Application June 14, 1935,

No Drawing.

Serial No. 26,621

2 Claims,

of other known alloys, when used under high temperature conditions.

While nickel-chromium and nickel-chromiumiron alloys having the ability to resist oxidation at high temperatures are known, their period of usefulness in service is often not as long as desired. I have found that the addition of small quantities of zirconium to such nickel-chromium alloys greatly increases their period of life when employed under conditions where they are subjected to high temperatures. The alloys forming the subject matter of the present application may also contain small quantities of either silicon or manganese or both of these elements.

In carrying out my invention I add small quantities of zirconium with or without silicon or manganese to nickel-chromium or nickelchromium-iron alloys. The nickel-chromium alloy most generally'used in the art consists of 80 parts of nickel and parts of chromium and I find it advantageous to add the other metals mentioned above to nickel-chromium alloys of substantially these proportions. The proportions of nickel and chromium in the alloy may bevaried. Thus the chromium content may be from 15 to percent and the balance nickel. 35 Likewise the most generally used proportions of nickel, chromium and iron in nickel-chromium-iron alloys is 60 percent nickel, 10 to 15 percent chromium and the balance iron and I find it advantageous to employ substantially 40 these proportions of those ingredients, and add the zirconium. These proportions may also be varied, the nickel, however, forming the major part of the alloy, and the nickel-chromium content beingsuch that the alloy will have the char- 45 acteristics of a non-ferrous alloy.

In preparing alloys containing zirconium, the quantities of it are subtracted from the nickel content, as for example, when zirconium is added to an alloy containing "15 to 25 percent chromium 50 and the balance nickel, the final alloy will contain 15 to 25 percent chromium and zirconium in the percentages herein stated and the balance nickel.

The proportions of zirconium may vary within 55 certain limits. I have found that best results are obtained when this metal is present in the nickelchromium or nickel-chromium+ir'0n alloy within the following limits: Percent Zirconium .01.50 5

If manganese or silicon are employed, they may be used within the following limits:

' Percent Manganese 0.02-2.0 10 Silicon 0.02-2.0

The preferred proportions of the alloying agents are as follows:

Nickel-chromium and nickel-chromium-iron alloys containing zirconium within the proporg0 tions given have been found by tests to have a greatly increased period of life when exposed to high temperatures. For the purpose of determining the life of such alloys at high temperatures I have tested them by the method of test 25 outlined in Tentative Accelerated Life Tests for Metallic Materials for Electrical Heating of the American Society for Testing Materials described in vol. 29 of the Proceedings of the Thirty- Second Annual Meeting of the American Society 30 for Testing Materials" beginning on page 613. The method is substantially as follows:

A sample of the wire to be tested, free from kinks, approximately ,twelve inchesJong and of about .025" diameter, is mounted vertically on the test board, the upper end being held in position by means of a suitable binding post. A 10 gram weight is attached to the lower/end of the specimen. A short piece of wire is attached to the 10 gram weight and projects downward into a cup of mercury where it may move freely up and down. A rheostat and an interrupter are connected in series with the specimen to the power supply. The test is run on constant temperature at a standard temperature chosen for the alloy under consideration for the first twenty-four hours. Thereafter it is run on constant voltage to the burnout. The life in hours up to a 10 percent increase in resistance is known as useful life while the life to the burnout is known as total life. Throughout the test the power is on two minutes and off two minutes. This is accomplished by means of an interrupter.

In testing the alloys of my invention according to the above described method a reference samchromium and no alloy addition having an approximate lite of 90 hours was used. This value is considered as 100 percent and the useful life of the samples tested is determined in sponding percentage values. r

The addition of zirconium to such alloys within \the limits set forth above increases the useful life to nearly- 200 percent where the wire is exposed to a hightemperature.

In the alloys referred to herein, small amounts correaosuoz of phosphorus andsulphur may be present as impurities. The nickel may also contain about 1 percent of cobalt.

I claim:

2. An electric resistance element consisting I essentially of 15 to 25 percent chromium, substantially JAMES M. LOHR.

.25 percent zirconium, balance nickel. 10