The New York herald., 1879-02-28
STEEL SHIPS.
Their Superiority Set Forth by an Ac-
knOwledged Authority.
IMPORTANT COMPARATIVE TESTS
Iron Shown To Be in Most Respects
an Inferior Material

The HEnALD's articles ON "safety at Sea" have re-
vved the discussion of the merits of steel as ship
building material and its advocates announce them
selves in great numbers In this connection paper
written by Mr. H. Martell chief surveyor OF Lloyds
Register, furnishes most reliable and instructive
data. At its nineteenth session it was read before
the Institution of Naval Architects April IL. 1878,
Lord Hampton being in the chair. Mr. Martel con-
tends the superiority of steel over iron for ship
building. the ground both of security and OF
economy. He claims that the great utility which
mild steel has of late years been proved to possess,
has drawn to it the attention of shipowners as
body and almost all of them look for
ward to its general employment ins prefer
ence to iron. 1t is also held that its cost. with
especial reference to the reduction OF weight. Will
warrant its adoption a stronger and more buoyant
material. That this view is becoming more preva-
lent, he said, is shown by the number OF steel YES
sells in of construction During the preceding
twelve months there had been laid before the COM
mittee of Lloyds Register the particulars OF sailing
vessels aggregating 5000 tons and OF steamers
aggregating $4,000 tons, which were to be built or
steel large number of small vessels and some
even Of more than 1000 tons, had been built ior
special purposes of trade and had been successfully
used one of them Of 200 tons having already been
In service for fourteen years. In previous shipbulld
Ing in which steel had been employed 1t had been
found that among tne plates WLiCu "erc
turned out there would be great many
extremely brittle ones. and it had therefore
been looked upon for long time with
very general distrust. 1t has been shown, however.
by experiment that mild steel, possessing uniform
ductiity, elasticity and tensile strength can be
manufactured at comparatively low cost. and
would be much superior TO ordinary iron. lit Is at
che same time" says Mr.. Martell, capable of being
welded with much and as satisfactorily as
iron This has been shown to the entire satisfaction
of many of surveyors y and it is also
confirmed in a specimen which has been forwarded
to me by Mr.. Kirk. Of Glasgow"
WAS TESTED.
This specimen was shingled from the cuttings of
steel plates in ordinary use, in the same way and at
The same heat would be used with common scrap
iron. It bent (cold) till the ends closed and
finally broke. piece of the same material was
tested found to stand tensile strain of twenty
six tons to the square inch. Mr. Kirk observes =
"In all this it behaves just ordinary IRON. 1t
YIELDS freely ron does not lose its strength by
the process. and in fact is cleaner more perfect
IN the YIELDS"
RIvETINa MATERIAL.
In reference to the means OF connecting the parts
of steel ship Mr.. Marteu acknowledges that it has
been found in experience that risk has been incurred
by using steel rvets unless special care is taken to
insure their being of very mild quality and uni
their efficiency be insured their greater strength
which is one-6ourth in resisting shearing. will
constitute far better joints than any made of ron
though the latter be larger. If they
specially prepared with competent, skilled labor and
not with the assistance of mere boys, there is no
reason, says Mr.. Marte, with no more evidence OF
danger than we at present possess, why their use
should be restricted. There is still for valu-
able experiment in rivetng. The best diameter and
plates are yet to be determined and it yet
tainy ascertaired whether iron or steel offers the
greater advantages.
INTERESTING ExPERIMENTs.
Statements of the results of tests effected by him
are made by Mr.. Martell. Iron plates connected by
iron butt straps of the thickness, double chain
riveted with iron and having the holes punched.
showed mean tensile strength OF 17.9 tons per
square inch and in every case the break took place
through the rivet holes. Steel plates not annealed
after punching connected by steel butt strap of the
same thickness. double chain riveted with iron,
wthstood tensile strain of 1877 tons per square
inch Of rivet area. the tension the plate between
the holes being only 1873 tons per square inch when
the rivets sheared In another experiment. similar
TO the last except that the rvets arranged zig
Eag, they sheared at strain of 1872 tons per
square inch. Steel plates not annealed after punch
ing connected by steel butt straps of the same thick
ness. double chain riyeted with steel. showed mean
tensile strength of 225 per square inch
cases the rvets shearing and in others the plates
breaking. 1t appears. therefore. that the full
strength obtained from double riveting with iron
does not exceed of 10 tons per square inch,
while that sho wn by steel rivets in steel plates un-
snnealec was 2as tons at the rivet holes Mr. Mar
tells conclusion is that in order to insure the whole
butts would have to be either treble riveted with
iron double riycted with steel"
PUNCHING AND DRILLING.
The process OF punching through metal plates is
productive of certain change in the structure of those
parts bordering on the holes and consequent dete-
rloration of their strength. Engineers have paid
particular attention to the problem of obvating this
injury, and in referring TO 1t Mr. Marten announces
the following results of experiments which have
been made, showing the comparative advantages Of
l. That very thin steel plates suffer less from
punching than iron plates
2. That tho difference in loss of strength in punch
ing in steel and in punching in iron does not appear
sufficiently great to require special precautions in
the of steel up to of an inch in
5. in plates above eightsixteenths of an inch
in thickness the loss of strength in iron plates by
punching ranged from 20 to 23 per cent while in
steel plates of the same thickness 1t ranged from -
to 81 per cent.
4. That by annealing, after punching. the whole
sf the lost strength restored, and I'm some in
stances greater relative strength obtained than
g. That in punching the steel was injured for only
. small distance around the holes. end that by rim
ing with drill larger than the punch previously
used from one-sixteenth to oneeighth OF an inch
around them the injured part was removed aud
loss of strength was then observed.
g. That in drilled plates appreciabe loss of
tensile strength could be discovered.
Here again" continued Mr.. Martell, 1--WE must
fall back upon the comparison with ron When
hear the complaint that steel loses so much by
punching, 1t often escapes attention that iron also
loses considerably from the same cause. IT, then,
We start with iron at a normal strength OF twenty
tons and twenty eight tons per square inch
and suppose the reduction scantlings in steel is
~ per cent from those Of iron, IT easily be
shown that If the steel loses 30 per cent by punch
Llg and tho iron ~ per cent the balance OF
strength still remains slightly with the steel.
The loss due to punching is nevertheless
most inpor ant matter. Punching with
open die has been strongly recommended as
means of reducing the loss. on the other
hand improvements In this method have been sug-
gcsted. step in the direction of rendes-
Ing annealing or trimming after punching unneces-
has been taken by the Introduction of the spiral
punch. II has been found that after its the
strength OF the material about two and half tons
Der square inch greater than the ordinary method
Of perforation while greater ductty existed about
the holes. The spiral punch requires only about
twothrds the power required by an ordinary
punch. aud Il expends its the injury of
tine piece which excised than upon the neighborng
material.
steel ship Practically the holes in the outside