US1711519A - Steel alloy - Google Patents

Description

Ratented May 7, 1929.

UNITED STATES A JOKE L. COX, PHILADELPHIA, PENNSYLVANIA.

STEEL ALLOY.

No Drawing.

My invention relates to a steel alloy and more especially to a steel alloy adapted for use under conditions of relatively high tem-' perature. The alloy in accordance with my invention is especially adaptable for use in the construction of valves and for the construction of which a steel alloy containing chrgmium and tungsten has heretofore been use Valve steels containing chromium and .tungsten are open to a'serious objection in that at high temperatures tungsten steel scales very badly, so that after a short run at a temperature of, say, as high as 1600 F. scale will fall from the surface of a valve in sheets, interferin with the proper seating of the valve an surface.

In. an efiort to prevent the scaling of tunsten steel articles, such as valves, the articles have been sub'ected to the so-called calorizing process w 'ch consists in im-- pregnating the surface of the article with aluminum, which on heating oxidizes and 2 protects the material beneath. Calorizing 1s, however, not a satisfactory remedy, since the surface only of the article is protected and where the article is a valve only a limited amount of grinding may be performed so before the effect of the calorizing is lost.

Now, it is. the object ofmy invention to provide a steel alloy including chromium and tungsten, which will not scale, under conditions of high tem erature and which willl lend itself especial y to use as a valve stee e In accordance with my invention I form a steel alloy containing chromium and tungsten, in such proportions as are usually 40 met with in steel makin practice, and in addition aluminum, the a uminum being incorporated in'the composition of the orig inal metal and being uniform in amount throughout the steel. The aluminum may 5 be present in amount ranging from 1% to 6% depending upon the amount of chromium and tungsten resent.

The steel alloy emliodying my invention The remainder principally iron.

destroying the seating vention, it being Application filed remar iz, 1027. Serial No. 187,873.:

may contain the following ingredients within the' ranges specified y I v A Per cent. Carbon, from 0.5- 1.50- Chrominum, from 4.0-20.0 Tungsten, from 6.0-18.0

Aluminum, from 1.0- 6.0

Another typical composition embodying my lnvention is the following:'-

Per cent. Carbon, about 0.9 Chromium, about 14.5 Tungsten, about 6.25 Aluminum, about 1.85

In eneral, the percentage of aluminum shoul increase as the percentage of tungsten increases, but not necessarily in the same proportion; that is, an alloy relatively high in tungsten should contain more aluminum than an-alloy relatively-low in tungsten.

It will be understood that other allo 5. may be included in the composition of t e steel alloy without departing from my in-,

noted, for example, that; silicon may be added within the ranges; usually encountered in steel making .prac-' tice, which varies from .05 to 1.75 per cent.

In the composition according to my invention molybdenum may be substituted for tungsten in whole or in part. However, when molybdenum is substituted for tungsten, whether in whole or in part, it should go be substituted for tungsten in the proportion of from of the tungsten, and where, in the claims, proportions of tungsten are specified, molybdenum, in the lesser pro ortion stated, is to be considered an equiva cut of tungsten.

In the steel alloy according to my invention, the aluminum, being more oxidizable than the iron, chromium or tungsten, is first attacked by oxygen and forms a protective coating, which is firmly adherent and beals proceeds but slowly.

The aluminum, since it is incorporated in the composition of the original metal, is uniformly distributed in amount through out the steel and the protective coating formed is continuously renewed. as the surface wears. When the steel is used for the production of a valve, the protective cdatying is continuously renewed as the valvev Wears and the valve may be ground without fear of subsequent scaling slnce the aluminum distributed through the mass of the valve will oxidize and renew the protective coatin removed by wear or grinding.

In the steel alloy 1n accordance with my invention'the advantages of hardness, etc.',.

inherent in tungsten steels are retained and the scaling is entirely suppressed. Under conditions of high temperature the steel, with certain composition within the ranges mentioned by me, will suffer only such discoloration as would occur in the tempering of a polished hardened steel article, while with other compositions the steel may become coated with a dark oxide, which is uzfually' firmly adherent and.will not flake o Havin now fully described my invention, what I c aim and desire to protect by-Letters Patent is o 1. A forgeable steel alloy containing carbon .35-1.5%, chromium 1-20%, tungsten 618% and aluminum 16%, the remainderand dominating proportion of the eomposi tion being principally iron, the proportionof tungsten being .not less than one-fourth .the proportion of chromium and the proportion of aluminum-beingmot less than one-sixth the proportion of tungsten.-

2. As a new article of manufacture, a forged valve composed of a steel alloy comprising carbon .35'1.5%', chromium 1-20%, tungsten 618%, and aluminum '16%,' the proportion of tungsten being not less than one-fourth the proportion of chromium and the proportion of aluminum being not less than one-sixth the proportion of tungsten, the remainder and domlnatmg proportion oflthe composition being principally 'iron, said valve being characterized, at highztemperatures, by being substantially neath which the oxidation of the other met- "to 6 per cent and silicon'not over"l.75 per cent, the remainder and dominating proportionof the composition being principally iron, the proportion of aluminum being not less than one-sixth the proportion of tungsten.

forged valve composed of a steel alloy comprising carbon .35 to 1.5 per cent, chromium 4:130 less than 20 per. cent, tungsten 6 to 18 per cent, aluminum 1 to 6 per cent and sili con not over 1.75 per cent, the remainder and dominating proportion of the composition beingprincipally iron, said valve being characterized, at high temperatures, by being substantially non-scaling and compara tively hard.

,5. A steel alloy containing carbon .35 to 1.5 per cent, chromium 4 to less than 10 per cent, tungsten 6 to 18 per cent, aluminum 1 to 6 per cent and silicon riotover 1.75

'4. As a new article of manufacture, a

per cent, the remainder and dominating proportion of the composition beig priclpally iron, the proportion of aluminum being not less than one-sixth the proportion of tungsten. 4

6. As a new article of manufacture, a forged valve composed of a steel alloyc'ompr sing carbon .35'to 1.5 per cent, chromium .4 -to less than 10 per cent,3tungsten 6 to 18 percent, aluminum one to 6 per cent, and silicon not over 1.75 per cent, the remainder and dominatin sition being'principally iron, said val ing characterized, at high temperatures, by

1 being substantiallynon-scaling'and compar' atively hard. a

In testimony of which invention, I have hereunto set my hand, at Philadelphia,

Pennsylvania, on this twelfth day of February, 1927.' I

" JOHN L. COX.

proportion of the compo- 1 vee- 95