US919859A - Manufacture of armor-plates and other articles. - Google Patents

Description

UNITED sTAras RATENT OFFICE.

WILLIAM ARCHBOLD HARTLEY AND BEDFORD HENRY DEBY, OF SHEFFIELD, ENGLAND MANUFACTURE OF AIiMOR-PLATES AND OTIIER ARTICLES.

Specification of Letters Patent.

Patented April 27, 1909.

- Application filed July 10, 1908. Seria1'No.442,91 9.

Armor-Plates and other Articles, of which the following is a specification.

This invention has for its object the manu factureof armor plates and other articles of a composite character, in which the face possesses extreme hardness and the remainmg portions are ductile and tenacious.

n the ordinary process of armor plate manufacture, the above conditions are at tained by a differential heating and cooling,

so arranged that the face is raised to the hardening temperature while the remaining parts are kept much coole Afterward the face portion is sprayed with cold water. This procedure has the disadvantage of producing unequal strains in the finished plate.

According to the present invention, un-

equal strains are obviated in the following manner:-It is known that in order to in-" duce the maximum degreeof hardness in steel, it is. necessary'to heatgt'he' steel to a temperature in excessofthe transformation or critical oint of the steel; It is also known that certain classes of steel known as perlitic steels have two critical points namel thatwhi'ch occurs on heating and that whic 1 occurs at recalescence on cooling the latter being at a lower temperature than the former. In this specification for the sake of clearness the former will be termed the critical temperature and the latterv the temperature of recalescence. The present invention takes advantage of these facts by em loying a perlitic steel preferably one in whic there is a considerable difference between the critical'temperature and the temperature of recalescence and then first heating that portion of the plate which is required to be hard, to a temperature" higher than the critical temperature ofthe steel, the remaining parts being ke t much below this critical temperature. ff now the hotter part of the plate be allowed to cool, the temperatureof the remaining portions being at the sametime per-,

entirely immersed in; or sprayed with, a suitable chilling, liquid; after which the portion of the plate which had previously been heated to a temperature in excess of the critical temperature, will be hard, and the remaining portions will be ductile and tenacious. Also on account of the equalized chilling temperature and uniform manner of chilling, all

dan erous strains will have been avoided.

\T iis process may be advantageouslyl employed with compound plates in whic the initial ingot is cast in two or more successive layers, the chemical composition of the two layers being different and such that the critical temperature of the face is considerably above that of the back. For instance the back of the plate may be cast of steel with a suitable proportion of nickel and chromium; immediately after the solidification of this alloy, the face portionpreferably containing certain porportions of molybdenum, chromium,-tungsten or other special hardening elements, is cast on to one side of it, thus insuring a sound interfusion free from imprisoned oxids etc. Thefollowingpercentages are suitable Face of plate :Carbon .5 to 1.0%; chromium, tungsten or molybdenum, or any two or all three, 1.0 to 3.0%; nickel 2.0 to 6.0%, Back of plate :'Garbon .10 to 30%; nickel 2% to 6%; chromium .75 to 3.0%; vanadium .25 to 1.0% separably or together. The compound ingot thus obtained is rolled, forged or pressed. The resulting plate is next heated to a hardening temperature and oil quenched. It is now reheated in such a manner that the de sired thickness of the face portion will reach a temperature higher than the critical temperature of either'of the alloys composin the plate, the remainder of the plate being e t considerably below that temperature; t e temperature of the face ortion is now al-' lowed to fall while that o theback is raised and the whole is-thus equalized at a temperature lower than the critical temperatures of the two alloys but above the temperatures of. recalescence of the face; the plate is now uniformly chilled,'either by immersion in, or

spraying with,,water or other suitable chilling medium. B this means the zone d viding the hardene from the unhardened portions of the face, is removed away from the line ofinterfusion 'of the face" with the back;

alsoby finally chillingthe whole" of the plate,

are avoided. 9

11'0 .at a uniform temperature, unequal strains away from the line of interfusion of the face In carr ing out this invention use is made I of a suitable vertical expanding ingot mold. The back ortion of the ingot is cast first, and imme iately after the solidification of 1 this alloy, the face portion is cast on to one side of it, thus insuring a sound interfusion, free from imprisoned oxids etc. The com- E pound ingot thus obtained is rolled, forged or pressed. The resulting plate is next I heated to a hardening temperature, 1'. e. i above 800 C. and oil quenched. It is now p reheated in such a manner that the desired thickness of the face portion will reach a temperature hi her than the critical teml peratures of eit er of the alloys composing 3 the plate, c. e. from 750 C. to 900 C. The remainder of the plate being kept considerably below those temperatures say at about 550 C. This may conveniently be done by placing the plate face upward in a furnace I in which the flames can play direct upon the i face while the back and edges are protected by refractory material. The temperature of the face ortion is now allowed to fall while that of t e back is raised say by lifting the plate out of the protecting material, the temperature of the whole being thus equal- I ized at a point lower than 750 C; the plate i is now uniformly chilled, either by immersion in, or' spraying with, water or other} suitable chilling medium. By this means the zone dividing the hardened from the unhardened portions of the face, is removed with the back; also by finally chilling the whole of the plate at a uniform temperature, une ual strains are avoided.

hat we claim is 1. In the manufacture of articles such as i i l i l i i l the remainder of the plate is kept considerably below that temperature, then allowing the temperature of the face to fall and raising the temperature of the remainder in such a manner that the temperature of the whole of the plate is equalized at a point lower than the critical temperature but above the temperature of recalescence and then uniformly chilling the whole of the plate substantially as described.

2. In the manufacture of articles such as armor plates which consists of two parts of differing composition, the face being of perlitic steel heating the plate in such a manner that a desired thickness of the face portion reaches a temperature higher than the critical temperature of either alloy of which the plate is composed while the remainder of the plate is kept considerably below the critical temperature of either alloy, then allowing the temperature of the face to fall and raising the temperature of the remainder in such a manner that the tern erature of the whole of the plate is equalize at a point lower than the critical temperature of either alloy but above the temperature of recalescence of the face and then uniformly chilling the whole of the plate, substantially as described.

WILLIAM ARCllliOhl) HARTLEY. BEDFORD HENRY DEBY. Witnesses:

LUTHER J. PARR, CHAs. N. DANIEL.