Five Mile Beach weekly journal., 1917-04-27

In These Modern Projectile Resisting
Warship Jackets.
Only armored warships could live in
a naval battle with modern big gun
projectiles in use, and hence the max
ing of armor plate has become a
science. The manufacture of armor
plate has developed considerably in re-
cent years, and in 40 branch of the
steel industry is there greater oppor-
tunity for engineering and mechanical
skill, coupled with m~etallurgical knowl-
edge, than in the operations of forging
and rolling. followed by the exact heat
treatment essential to produce the al
most conflicting properties necessary
in modern mt
The plate must be hard, glass hard,
to resist penetration by heavy projec-
tiles moving at tremendous yelocities,
yet tough and ibrous enough to take
up the momentum without cracking or
distortion. Mechanically. then. the
plate must have an extremely hard
surface and a fibrous backing. These
requirements were attained in part by
the old compound armor. Molten steel
was poured ON to a wrought iron plate
and cooled. The slab was then re
heated, forged and rolled to the re-
quired dimensions. If the operations
were successfully carried out the line
of demarcation was scarcely visible.
Recently a modification of this proc
ess was introduced to cheaper and
render less tedious the production of
m A layer of hard steel vas
poured into a cooled mold, the under
side quickly setting. On the still fluid
or pasty surface a thick layer of soft
steel was poured. By careful manipu-
lation the union of the surfaces vas
almost complete, and it was impossi-
BILE to detect the break In composition
On viewing the fractured section. This
method of manufacture was undoubt-
eddy an improvement on the old CON-
pound method.
The increasing size, velocity and
hardness of modern armor piercing
projectiles have necessitated the intro
duction of the modern armor. The
process of manufacture essentially
consists in case hardening to a depth
of about two inches the surface of
a homogeneous tough nickel chrome
steel. Special air or self hardening
nickel and more complex steels are
used for lighter armor, gun shields
and cast armored structures.
The steel is made in Siemens fur
naces and carefully cast into ingots
up to eighty tons in weight. These In
COTS are then stabbed under powerful
hydraulic presses $4,000 tons) or roll
ed direct to the required dimensions,
depending on the power of the mills
and appliances. During the rolling
operation, which lasts about an hour,
the slab is reversed and inverted to at
tain uniformity of working, and scale
is removed by wood fagots and wa
ter jets. After rolling the plate is
usually quenched.
The next operation is that of case
hardening, and in this two plates are
put face to face, separated by a layer
of the carburizing reagent If it be
solid, or if gaseous hydrocarbons be
used the plates are slightly separated,
to allow free passage for the harden
ing gases, by bricks arranged in rows.
The plates are maintained at redness
in a car furnace for three weeks and
withdrawn after the hardening carbon
has penetrated to the required depth.
The plates are thus carburiZed and so
made capable of being hardened, but
they are not yet actually hard. At this
stage all holes are drilled and plugged,
and any bending or machining neces-
sary is carried out.
From this point onward the treat
ments differ. Some makers insist on
heating and quenching in oil or water
to remove any coarse structure that
may have been formed during the
long %annealing while c~arburizing. The
next essential operation is that of
hardening, and this is usually car
ried out in one of two ways. Either
the plate is uniformly heated to the
hardening temperature and quenched
by a series of water jets playing on the
upper surface with sufficient force to
prevent the formation of steam or by
a process known as "differential
q~uenchlng, by which the carDurlzed
surface is heated to a temperature
from which it will harden and the
under side kept well below, so attaining
a gradual fall in temperature from the
top to the bottom. The whole plate is
then immersed in water, the hotter sur
face alone being hardened, while the
bark is toughened. Further mechanical
operations can be carried out only by
grinding or cutting with oxyacetylene,
as the plate has now undergone the
treatment comforting maximum hard
ness.
In resume, it will be noted that there
are three distinct operations in modern
methods of manufacture-the mechani-
cal working of the plate to the required
dimensions. the carburization of the