US2018267A - Machine element - Google Patents

Description

UNITED. STATE Patented Oct. 22, 1935 2,018,267 MACHINE ELEMENT Augustus B. Kinzel,

Flushing, and Walter Crafts,

No Drawing.

4 Claims.

The invention relates to machine elements subject to impact. shock at low temperatures, and more especially to axles and toothed gears subject to shock at 20 C. to C.

It has long been recognized that ordinary carbon steels lose their shock resistance and toughness at low temperatures. This has been a matter of considerable concern wherever moving machine elements are subjected to subzero conditions. I Gears and axles of stationary engines, locomotives, and automobiles used in exception: ally cold climates, and the moving parts of refrigerating 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 effects 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 smallamounts of alloyed additions, and having a relatively great resistance to shock at low tempera-- tures, 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 chromium and copper 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 resistance equivalent to at least 10 foot pounds as Application October 4, 1933, Serial No. 692,228

measured by the Izod impact machine having an initial energy level of foot pounds on a standard notched sample one square centimeter in cross-section. It is an object of the invention to provide machine elements having an impact resistance fulfilling this requirement at temperatures between 20 C. 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 0.25% to 3.25% chromium together with 1.25% to 0.25% copper, a low content of carbon not more than about 0.5%, and the remainder chiefly iron together with incidental impurities. Moderate amounts of metal not detrimental to the shock resistance of the articles may be pres-.

ent. In general, not more than 2% manganese, -1% silicon, 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 a high copper content should be associated with a low chromium content, and vice-versa, within the stated range.

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 experiments were made with an Izod impact ma- Steel analysis I pact ra l ng a. lb. per

N0. o. Mn Cr S1 Cu F 0 0 o. c.

l nrmco M 9 3 Iron 2 0.2 Bosh--- 0s 7 2 s. A. E. 1020 a 0.10 0.24 0.83 0.24 0.53 Bean... as 02 n Pressure vessels subject to two or three dimensional stress and to bending moments are affected 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

1. A machine element designed to withstand shock at temperatures between about -20 C. and 80 C. and having at said temperaturesan Izod impact strength of at least about 10 foot pounds," said element being composed of an alloy steel containing substantially 0.25% to 3.25% chromium, 1.25% to 0.25% copper, not over 0.5% carbon, remainder chiefly iron. 2. A toothed gear subject to impact 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 gear being composed of an alloy steel containing substantially 0.25% to 3.25% chromium, 1.25% to 0.25% copper, not over 0.15% carbon, not over 2% manganese, not over 1% silicon, not over 5% nickel, and not over a total of 3% other non-ferrous metals, the balance being iron.

3. An axle subject to impact shock at tefizperatures between about -20 C. and -80 C. and having at said temperatures on Izod impact strength of at least about 10 toot pounds; said axle being composed of an alloy steel containing substantially 0.25% to 3.25% chromium, 1.25% to 0.25% copper, not over 0.15% carbon, not over 2% manganese, not over 1% silicon, not over 5% niolzel, and not over a total 0 3% other non-ferrous metals, the balance being iron.

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 10 foot pounds; said vessel being composed of an alloy steel containing not over 0.5% carbon, 0.25% to 3.25% chromium, and 1.25% to 0.25% copper, and remainder chiefly iron.

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