US2046168A - Machine element - Google Patents

Description

Patented June 30,1936

PATENT OFFICE MACHINE ELEMENT Augustus B. Kinzel, Douglaston,

Crafts, Niagara Falls, N. Y.,

and Walter assignors, by

mesne assignments, to Union Carbide and Carbon Corporation, a corporation of New York No Drawing.

Original application October 4, 1933, Serial No. 692,228.

Divided and this application July 3, 1935, Serial No. 29,762

6 Claims.

The invention relates to machine elements subject to impact shock at low temperatures, and more especially to axles, toothed gears, and pressure vessels subject to shock at -20 C. to 80 5 C. This application is a division of application Serial No. 692,228, filed October 4, 1933.

It has long been recognized that ordinary carbon steels lose their shock resistance and toughness at low temperatures. This has been a mat-- l ter of considerable concern wherever moving machine elements are subjected to sub-zero conditions; Gears and axles of stationary engines, locomotives, and automobiles used in exceptionally cold climates, and the moving parts of rei frigerating machinery, are subject to failure unless designed with an abnormally large factor of safety. Aircraft which are to fly at high altitudes must be designed in all their parts to withstand the eifects of very low temperatures: at an altitude of 30,000 feet, for example, the temperature is about 40 C.

The addition of relatively large amounts of certain alloying metals, notably nickel, is known to impart resistance to this effect of low temperatures; but no steels containing relatively small amounts of alloyed additions, and having a relatively great resistance to shock at low temperatures, have heretofore been known.

In the course of an investigation of the properties of numerous types of steels at low temperatures, we have discovered that low-carbon steels containing moderate amounts of zirconium exhibit a remarkably high resistance to impact at temperatures between about -20 C. and 80 C. The present invention is an application of this discovery.

Gears, axles, and other machine elements subject to shock, for instance, compressor pistons and connecting rods, locomotive cross-heads and connecting rods, shafting, and the like, should have at the working temperature an impact re- (Cl. Fi l-434) sistance equivalent to at least 10 foot pounds as measured by the Izod impact machine having an initial energy level of 120 foot pounds on a standard notched sample one square centimeter in cross-sectlon. It is an object of the invention to provide machine elements having an impact resistance fulfilling this requirement at temperatures between 20 and 80 C.

According to the invention, machine elements subject to shock at temperatures between about 20 C. and 80 C. comprise a steel containing substantially 0.05% to 2% zirconium, a low content of carbon not more than about 0.25%, and the remainder chiefly iron together with incidental impurities. Moderate amounts of metal not detrimental to the shock resistance of the articles may be present. In general, not more than 2% manganese, 1% silicon, 1.5% copper, 5% nickel, and a total of 3% other non-ferrous metals should be present. The carbon content of the steel is preferably no greater than about 0.15%,

and the'zirconium content preferably lies between about 0.25% and about 0.50%.

Experiments which we have made demonstrate the great resistance of the articles of the invention to shock. The following table gives representative results of these experiments. The ex periments were made with an Izod impact machine having an initial energy level of 120 foot pounds, using notched specimens one square centimeter in cross-sectional area, the notch angle being and the notch being 0.079 inch deep. The specimens were cooled to the desired temperature by immersing them in a liquid medium for one-half to one hour, and then quickly transferred to the impact machine and tested. The elapsed time between the removal of each specimen from the cooling medium and the completion of the test on that specimen was in all cases between three and four seconds.

. Impact strength Analysis Ft. lb. per sq. cm. 45 Steel No.

' C Zr Mn Si Ni Cu Fe +28 C. 50 C. 80 C.

.Annco" 64 9 3 0. 2O (S. A. E. 1020) 7 2 0. 07 0.20 0. 017 0. 35 78 ll 0. l6 0. 06 0. 37 0. 58 87 71 34 0.16 0. 97 l. 51 0. 60 82 35 28 0.19 0. 29 0.37 0. 84 (in 23 8 0, 2i 0. 0. 33 0. 07 55 20 14 0. 22 0. 26 O. 35 0. 69 7B 20 15 0. 30 0. 15 0. 33 0. 80 34 10 5 Vanadium may be substituted for zirconium, either wholly or in part, and is to be considered as the equivalent of zirconium for the purposes of the present invention.

Pressure vessels subject to two or three dimensional stress and to bending moments are afiected by notch brittleness in much the same way as machine elements subject to shock, and are equivalent to such elements within the spirit of the invention.

We claim: I I 1. A machine element designed to withstand shock at temperatures between about 20 C. and -80 C. and having at said temperatures an Izod impact strength of at least about 10 foot pounds; said element being composed of an alloy steel containing not over 0.25% carbon, and 0.05% to 2% zirconium, remainder chiefly iron.

2. A machine element designed to withstand shock at temperatures between about 20 C. and 80C. and having at said temperatures an Izod impact strength of at least about 10 foot pounds; said element being composed of an alloy steel containing substantially 0.05% to 2% zirconium, not over 0.15% carbon, remainder chiefly gear being composed of an alloy steel containing I substantially 0.25% to 0.50% zirconium, not over 0.15% carbon, not over 2% manganese, not over 1% silicon, not over 1.5% copper, not over 5% nickel, and not over a total of 3% other non- 0.15% carbon, not over 2% manganese, not over 1.

1% silicon, not over 1.5% copper, not over 5% nickel, and not over a total of 3% other nonferrous metals, the balance being iron.

5. A pressure vessel subject to two or three dimensional shock and to bending moments at temperatures below about 20 C. and having at said temperatures an Izod impact strength of at least about foot pounds; said vessel being composed of an alloy steel containing not over 0.25% carbon, 0.05% to 2% zirconium, and remainder chiefly iron.

6. A pressure vessel subject to two or three dimensional shock and to bending moments at temperatures below about C. and having at said temperatures an Izod impact strength of at least about 10 foot pounds; said vessel being composed of an alloy steel containing not over 0.15% carbon, 0.05% to 2% zirconium, and remainder chiefly iron.

AUGUSTUS B. mNZEL. WALTER CRAFTS.