Pittsburg dispatch. [volume] (Pittsburg [Pa.]) 1880-1923, 1890-07-31
TESTS OF STRENGTH.
Methods Used to Determine the DUAL.
ity of Steel Made for
UNCLE SANS NAVAL MONITORS.
The High Standard Set Up by the Govern
ment officials.
NEWS OF The BUSY WORLD OF INDUSTRY

to its order in a local mill has drawn NOR,
or less attention to the question of Govern
mental inspection, and to the manner in
which the tests into the suitability, dura
bllity, etc., of steel for naval purposes il
made. Pittsburg has gained such pre-emi
nence for the quality Of its iron and steel
commodities that it is not without some
demur that citizens find disposition on the
part OF the Government to cast shade oil
doubt over the quality of its output of steel
plates.
Recent writers treating of the tests ap.
| piled to steel plates for naval purposes hold
that there will be no durability or safety in
steel vessels of war until there is an estab-
| lished constitutional makeup of the differ
ent varieties of iron and steel that is under
| stood by metslurgists and engineers. and
until there is a recognized practical science
of the art of steel making.
A STANDARD NEEDED.
These hold that the tests now in vogue
are insufficient, and that Government should
establish standard, based upon the chemi-
cal electrical properties of metals on the
plea that something more than mere me-
chanical test of iron and steel for armor
plates is required.
The tests employed at Homestead are of
three kinds, namely: Surface, chemical and
physical. The surface test, as its name i'm
plies, is purely superficial. but withal very
necessary. Imperfections may exist in the
plates which the chemical and ph ysi-
cal tests would fail to discover,
such as snakes, pittings, laminations
and cobblings. Snakes are scarcely
apparent assures due to the absence of
homogeneousness in the material. Pitting
is the result OF a soft spot in the plate and
into which piece of scale has been rolled.
Vigorous tapping with hammer over the
surface of the plate sufices to bring to view
the soft spot in the plate. Cobbling is due
to an imperfection in the rolls whereby the
plate is unevenly rolled, being thicker or
thinner in some parts than others. Every
plate that passes the rolls is inspected for
these imperfections, but the Homestead mills
make such a quality of steel, and by such
improved machinery, that few plates, if
any, are found wanting on these accounts.
THE CHEMICAL TEST.
Tests as to the chemical properties of the
material are made both by the firm and by
the Government officers. The firm tests
for carbon, phosphorus, manganese
and sulphur, and hands a re-
port on each heat to the inspectors
They, in turn, make two special tests for
sulphur and phosphorus. For example,
ship plates are ordered of quality of about
% of carbon, 40 of sulphur, 60 of manga
nese, and 40 of phosphorus. One point
above or below these figures is allowed on
carbon, and from .055 to .070 on phosphorus.
In the test phosphorus must show above
.060, and sulphur above .040, else the plate
is rejected. The chemical analysis of each
heat is duly recorded both by the firm and
Government inspectors. Each heat has its
number, and at any moment, however long
afterward, or wheresoever the plate may
have been delivered, the chemical constitu-
ents of the plate may be ascertained by
reference to the records.
The physical test shows the actual strain
or pressure which the plate will bear. Tests
the heat of ship plates.
THE GOVERNMENT REQUIREMENTS
for these plates are that they shall show
tensile strength of at least $4,000 pounds,
and 25 per cent reduction in inches with
out breaking. In the test for tensile
strength one piece Of the four may fall to
So, 900 pounds, or one piece may stand only
% per cent of reduction without breaking If
the other three fill both requirements. But
if two plates out of the four fail, one in ten
sile strength and the other in its percentage
of reduction, the entire heat is rejected.
This is the first physical test to which the
plates are subjected
Ship plates are subjected to still more
severe test. Pieces from two of the four
plates are turned over fiat upon themselves,
and under such pressure as to become almost
one piece, The steel is cold when so bent
This is called the cold bent test. Neither
flaw nor crack must appear at the bend else
the heat will be declared rejected. Strips
from the other two of the four plates from
the heat are subjected to the quenching test.
A HARD STRAIN.
This is declared to be the hardest of ALL |
The strips are placed in furnace and |
heated to cherry red; next dipped in tub |
of water of temperature of 800 and then |
bent over fiat to about one-half its thick |
ness. As before, it must not exhibit |
any imperfection at the bend. As a
practical illustration of the test, a
strip OF plate about II inches long, slightly |
over inches wide and about three-eighths
thick, was, for the benefit of THE DIS
representative subjected to the
trial. The strip was placed between the
jaws of a hydraulic press, which, on appli-
cation of the power, commenced to draw the
piece out 1t broke at pressure of 63, 400
pounds, or at pressure equivalent to 66, 400
pounds to the square inch. The area of the
piece was .954S, or nearly square inch, and
was reduced at the breaking point to SIG
per cent of its size. 1t was elongated % in
8 inches, or 2711 per cent; in other words
ha cira hod 9 81 q |
inches before breaking. It will be seen
that these figures exceeded the requirements
10 pass the inspectors. The piece was SUBJ
bent, and so closely that light
could not pass between. The bend was
smooth as glass and without the faintest in
1ication of strain or break.
BOILER PLATE TESTS.
The specification for high boiler plates
,alls for tensile strength of from 5S, 900 to
s., 900 pounds. Transverse pieces must show
p per cent of elongation. and the Iongi-
.udinal stretch must be at least 25 per cent. |
The elastic minimum limit for these plates
IS $4,000. These plates are subjected to the
.old bent test as already described. For
ow boiler plates tensile strength of from
50, 900 to $4,000 pounds is required.
with 26 per cent longitudinal
md transverse elongation. These plates
Ire tested by the quenching process, as
already described, as being the most severe
% which they can be submitted. Protected
lrmor plates are required to stand, singly,
! pressure OF $4,000 pounds. Tested by
heats these plates must stand 80, 900 pounds
and an elengation of Is per cent
n 2 inches. The plates are inches thick
md turned down in lathe to 2 inches by
lalf an inch, and then tested as in other
1 Al |
%, 900 where plates are tested singly, the
lnnnntinn mnst he annmanted hu 4 "a |