US2059746A - Homogeneous armor plate - Google Patents

Description

Nov. 3, 1936 F. RITTERSHAUSEN HOMOGENEOUS ARMOR PLATE Filed Oct. 27, 1932 off/5 9.. 0 6 6. 1w. 2. 0. 8 6. 1+. l a. 6.. rv. r9. 5 ,5 5 5 1t b. L. h. 1+

v Ritented Nov. '3, 1936 UNITED sTATEs PATENT OFFICE'l 2,059,746 HOMOGENEOUS ARMOR.y PLATE Fritz Rittershausen, Essen, Germany, assigner to Fried. Krupp Aktiengesellschaft, Essen-onthe-Ruhr, Germany applicati@ october 27, 1932, serial No. 639,881

. In Germany December 15, 1931 Claims.

5 and showing a uniform texture on its entire cross section, that is a plate which for example is not hardened on one side or cemented and hardcned.

The known homogenous armor plates of high- 1o est quality are made from steel alloys which con.-

tain about 0.25 to 0.35% carbon, 3 to 5% nickel, l

1 to 1.8% chromium and sometimes up to 0.5%

` molybdenum, the addition of molybdenum serving in these known armor plates to facilitate the heat treatment and to avoid the danger of tempering brittleness. The nickel is considered as the bearer of the toughness, and since great value is attached to very high toughness, the nickel content generally is fixed at 3.5% at least.

Exhaustive researches have now shown that the toughness of armor plates and thus' their resistance to striking projectiles, especially toy oblique fire, and their safety against being pierced by bursting shells, is not only not reduced but can even be considerably improved by reducing the nickel content to about 3% or less, provided the carbon content is -kept on about 0.12 to 0.42% and the chromium content on 2 to about 3.75%, and molybdenum is present in the alloy in an amount from -0.2 to 1%, while the total of chromium and nickel should lnot be higher than indicated by the curve A of the acg companying drawing. It is of particular advantage so to determine the composition of the armor plates that it comes .within the hatched area B of the drawing, wherein the compositions situated in the upper part thereof and containing higher totals of chromium and nickel are especially suited for thicker p1ateswhilst for plates of smaller thickness the compositions coming within the lower part of the area B are especially flt. The effect of the molybdenum may be obtained also by about 1.5 to 3 times as much tungsten. In certain cases the nickel may be entirely dispensed with. The cause of the superiority explained above of the proposed composition of armor plates is to be seen, in the opinion of the inventor, in thefeature that in heating the plates the Aci critical point, which must not be exceeded in the heat treatment following the hardening treatment, is substantially higher in the new armor plates than with the known plates richer in nickel, so that it is possible to reheat the new plates even at tempera- 56 tures up to about '100 C. This higher reheating (Cn. 14s-21.5)

treatment, however, which cannot be employed with the known plates, richer in nickel and poorer in chromium, imparts to the plates a substantially higher toughness and thus a substantially improved resistance to being damaged by pro- 5 jectiles. For heat treated armor plates, that is plates of the above composition and hardened and reheated in the above-described manner show a, notch toughness of about 35 mkg/cm (normal Charpy test) and a tensile strength of 10 about lig/mm2. y

The same high toughness, butwith e. slightly lower tensile strength, can be obtained, by virtue of the high critical point, even by a simple heating at temperatures up to about 750 C. 15

The armor plates forming the subject-matter of the present invention are distinguished for the advantage of having a substantially higher resistance to projectiles and of being manufactured at substantially lower costs,.owing to the m nickel content being smaller or dispensed with altogether.

Particularly advantageous examples of the armor plates according to the invention are the following:

1. Homogeneous armor plate of 'l0 mm. thickness, containing about 0.2% carbon, 2.4% chromium, 0.4% `molybdenum, no nickel.

2.' Hom'ogeneous armor plate of 100 mm. thickness, containing about 0.19% carbon, 2.3% 30 chromium, 0.4% molybdenum and 1.5% nickel.

3. Homogeneous armor plate of mm. thickness, containing about 0.32% carbon, 2.6% chromium, 0.6% nickel, and-0.38% molybdenum.

4. Homogeneous armor plate of mm. thlck- 35'- ness, containing aboutA 0.39% carbon, 2.5% chromium, 1.8% nickel and 0.45% molybdenum,

What I claim and desire to secure by Letters Patent is:-

1. The process of heat treating a homogeneous v40 armor plate made from a steel alloy containing about 0.12 to 0.42% carbon, about 2 to 3.75% chromium, an appreciable amount of nickel not Over about 3%, and metal selected from the group molybdenum, tungsten in the proportion 0.2 to 45 1% molybdenum, 0.3 to 3% tungsten, the remainder substantially all iron, the total-of chromium and nickel referred tothe carbon content being not higher than indicated by the curve A of the drawing, which process consists in harden- 50 ing the plates throughout by a uniform heat treatment and reheating them at a temperature of about '700 C.

2. The process oi heat treating a homogeneous armor plate made from a steel alloy containingy about 0.12 to 0.42% carbon, about 2 to 3.75% chromium, an appreciable amount oi' nickel not over about 3%, and metal selected from the group molybdenum, tungsten in the proportion 0.2 to 1% molybdenum, 0.3 to 3% tungsten, the remainder substantially all iron, the carbon and chromium plus nickelcontent of which comes within the area B of the drawing, which consists in hardening the plates throughout by a unii'orm heat treatment and reheating them at a temperature of about 700 C. g

3. Homogeneous armor plate made from a steel alloy containing about 0.12 to 0.42% carbon, about 2 to 3.75% chromium, an appreciable amount of nickel not over about 3%, and metal selected from the group molybdenum, tungsten in the proportion 0.2 to 1% molybdenum, 0.3 to 3% tungsten,

the remainder substantially all ironr the totalof chromium and nickel, referred to the carbon content, being not higher than indicated by the curve A of the drawing, said steel alloy being in a substantially homogeneous hard and tough condition throughout resulting from a hardening heat treatment followed by reheating to about 700 C.

4. Homogeneous armor plate made from a steel v-alloy containing about 0.12 to 0.42% carbon,

about 2 to 3.75% chromium, an appreciable amount of nickel not over about 3%, and about 0.2 to 1% molybdenum, the total of. chromium and nickel, referred to the carbon content, being not higher than indicated by the curve A of the drawing,fsaid steel alloy being in a substantially homogeneous hard and tough condition throughout resulting from a hardening heat treatment followed by reheating to about 700 C., said plate being characterized by a particularly high resistance to penetration by projectiles.

5. Homogeneous armor plate made from a steel alloy containing about 0.12 to 0.42% carbon, about 2 to 3.75% chromium, an appreciable amount of nickel not over about 3%, and metal selected from the group molybdenum, tungsten in the proportion 0.2 to 1% molybdenum, 0.3 to 3% tungsten, the remainder substantially all iron, the nickel content being at a gure between the limits stated determined according to a direct ratio between thickness of the armor plate Aand nickel content, the total ofy chromium and nickel, referred to the carbon content, being not higher than indicated by the curve A of the drawing, said steel alloy being in a. substantially homogeneous hard and tough condition throughout resulting from a hardening heat treatment followed by reheating to about 700 C. y

FRITZ RI'ITERSHAUSEN.

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