US1097572A - Method of treating armor-plate. - Google Patents

Description

neonate.

SAMUEL S. WALES, 01F MUNHALL PENNSYLVANIA, ASST&NOR T0 CARNEGIE STEEL COMPANY, 015 PITTSBURGH, PENNSYLVANIA, A CQRJPORATION OF NEW JERSEY.

No Drawing.

Specification of Letters Patent.

Patented May f0, 1914.

Application filed November 15, 1906. Serial No. 343,545.

To all whom it may concern:

' Be it known that T, SAMUEL S. WALES, of Munhall, in the county of Allegheny, State of Pennsylvania, have invented a new and useful Method of Treating Armor-Plate, of which the following is a specification.

@f recent years it hasbeen the practice in the manufacture of armor plate to make the plate of steel having substantially the following theoretical composition :-carbon .28 per cent., manganese .35 per cent., nickel 3.7 5 per cent., chromium 1.70 per cent., the sulfur and silicon being low,-below .04: per cent. The steel of this composition is then treated by the Harvey or Krupp processes by which its surface is highly supercarburized for the purpose of rendering it more resistant to the impact of projectiles. While the rocess of supercarburizing improves the sur "ace it is detrimental in its eflect upon the body of the late.

l have discovered a new composition and a new process of treatment, by which I am enabled to make armor plate of homogeneous chemical composition without the necessity of supercarburizing the surface, and my plate will give much better results in resist- 1n the impact of projectiles than have hereto ore been obtained. For example, a sixinch plate which I have made according to my invention, has resisted the impact of a shell having a velocity 15 to 20 per cent. greater than that which could be resisted by the best Krupp plates of similar thickness. My invention is therefore of great importance, because it enables me to produce an armor plate having great tenacity and strength, of homogeneous composition, and capable of resisting shocks much better than any armor plate which heretofore has been produced.

The elements which I alloy with the iron in order to produce my new steel, are as follows, and in stating. them ll desire to premise that in addition to those elements, those skilled in the art may add other elements if desired, or may vary the proportions within certain limits, the proportions which ll give being those which I have heretofore found best suited to the purpose: carbon .15 to .25 per cent., manganese .15 to .35 per cent.,

- nickel 5. to 12. per cent., chromium .15 to .25

per cent., tungsten .50 to .70 per cent. To these elements ll may add vanadium or molybdenum from .20 to .50 per cent., or T may substitute vanadium or molybdenum in place of tungsten in whole or in part.

Thesteel which if employ is open hearth steel, and l prefer to add the nickel as a part of the charge of the furnace in a cold condition and to add the manganese, chromium and tungsten in the ladle, or to add them in the furnace just before tapping, although the time and manner of addition may be varied. The proper proportion of carbon is had by recarburizing in accord ance with usual methods. The silicon content of the steel should be as low as possible, say less than .15 per cent. The sulfur and phosphorus are respectively preferably less than .04 per cent.

The new heat treatment to which I subject the steel and which I desire to claim broadly, as Well as in its application to steel having the particular range of composition stated above, is as follows:-Having cast the ingot and forgedit at the ordinary forging temperature, if it is to be reforged it is subjected to a heat treatment in which it is raised to a temperature of about 700 degrees C, and cooled slowly, preferably in air. llt may then be reforged at the usual reforging temperature, and is then heated to a temperature of about 875 degrees (3., which is higher than that to which the plates are reheated in the Krupp process. It is then quenched with water, the duration of the water treatment being prefer- Y ably about one minute per inch of thickness,

the time varying according to the chemical compositlon of the steel, being preferably somewhat less when the carbon content is higher. If the steel is not reforged, the heating to 875 degrees C. and the quenching will immediately follow the forging; the plate not being allowed to become cold in the meantime. The steel is then raised to a temperature above 710 degrees C. and

erably to about 500 degrees C. by one or more successive treatments, and is allowed plish this water-hardening by a new method, in which I heat the entire bpdy of the plate uniformly to a temperature of about 725 to 775 degrees (1, and then quench it with water applied simultaneously on both surfaces so as to hardenthe plate uniformly throughout its body. I then soften the plate on one surface by heating it on one side only, while the other surface is protected from the heat by loam or otherwise, the temperature being carried preferab'ly to say 500.to 550 degrees C., the effect of which is to soften one surface of the plate, leaving'the other side with substanti-ally its original hardness. On removing it from the furnace I spray the harder surface of theplate in order to prevent the equalization of the heat in the'body of the plate and its softening throughout.

Those skilled in the art will be able to modify the steps of the heat treatment above described within certain limits, since What I claim is 1. The herein described method of treating armor plates which consists in heating a forged plate to a temperature of about 875 degrees 0., then cooling it quickly, again. heating the plate to a temperature of about 775 degrees C., allowing it to cool slowly, and then annealing the plate by heatingv to a temperature of about 500 degrees C.

2. The herein described method of treat- 111g armorplate'which consists in heating the forged plate to a temperature ofabout 700 degrees C., then re-forging the plate, then heating it to a temperature of about 875 degrees C. and quenching, then heating the plate to a temperature of about 775 degrees -C and allowing it to cool, then machining the plate, and then re-heating it to a somewhat less temperature than that of the last re-heating," and forming the plate, thenannealing the plate and machin- -then hardening the plate ing it, and then water hardening the machined plate. a

3. The herein described method of treating armor plate which consists in'heat-ing the forged plate to atemperature of about 875 degrees C. and quenching, then heating the plate to a temperature. of about 775 degrees C. and allowing it to cool, then heating the plate to a temperature less than 750 degrees C. and forming the plate, and then again heating the plate to about 500 degrees C. and annealing it, then machining the annealed plate, and then water hardening the machined plate.

4. The herein described method of treating plates which consists in heating a forged plate and cooling it quickly, again heating the plate to a somewhat less temperature and annealing, again heating and then hardening the plate substantially equally throughout, and then applying heat to one surface of the hardened plate while preventing material heating of the opposite hardened surface thereof to soften the heated surface while maintaining the opposite surface of substantially its original hardness. r A 5. The herein described method of treating plates which consists in heating a forged plate and cooling it quickly, again heating the plate to a somewhat less temperature'a-n'd annealing, again heating and substantially equally throughout, then applying heat to one surface of the hardened plate while preventing material heating of the opposite hardened surface thereof to soften the heated surface while maintaining the opposite surface of substantially its original hardness and spraying the hardened surface to prevent equalization of the temperature throughout the plate while air cooling the opposite heated surface.

I11 testimony whereof, I have hereunto set my hand.

' SAMUEL s. WALES.

Witnesses CHAS. E. Narornan; IV. H. Comsn'rr.