Ever since the improvements that have been introduced into the
manufacture of steel, and especially into the erection of works for its
production, have made it possible to obtain this metal in very large
masses, it has necessarily been preferred to iron for all pieces of
large dimensions, inasmuch as it possesses in the highest degree that
homogeneousness and resistance which are so difficult to obtain in the
latter metal. It has consequently been found necessary to construct
engines sufficiently powerful to effect the forging of enormous
ingots, as well as special furnaces for heating them and apparatus for
manipulating and transporting them.
The greatest efforts in this direction have been made with a view to
supplying the wants of heavy artillery and of naval constructions;
and to these efforts is metallurgy indebted for the creation of
establishments on a scale that no one would have dared a few years ago
to think of. The forging mill which we are about to describe is one of
those creations which is destined to remain for a long time yet very
rare; and one which is fully able to respond, not only to all present
exigencies, but also, as far as can be foreseen, to all those that may
arise for a long period to come. The mill is constructed as a portion of
the vast works that the Compagnie des Forges et Aciéries de la Marine
own at Saint Chamond, and which embrace likewise a powerful steel works
that furnishes, especially, large ingots exceeding 100 tons in weight.
The mill consists, altogether, of three hammers, located in the same
room, and being of unequal powers in order to respond to different
requirements. The largest of these hammers is of 80 tons weight, and
the other two weigh respectively 35 and 28 tons. Each of them has
a corresponding furnace for heating by gas, as well as cranes for
maneuvering the ingots and the different engines. The general plan view
in Fig. 4 shows the arrangement of the hammers, cranes, and furnaces in
the millhouse.
[Illustration: FIG. A.--ELEVATION OF A HAMMER. FIG. B.--PROFILE VIEW]
The gas generators which supply the gas-furnaces are located out of
doors, as are the steam-generators. The ingots are brought from the
steel factory, and the forged pieces are taken away, by special trucks
running on a system of rails. We shall now give the most important
details in regard to the different parts of the works.
_The Mill-House_--This consists of a central room, 262 feet long, 98
feet wide, and 68 feet in height, with two lean-to annexes of 16 feet
each, making the total width 100 feet. The structure is wholly of metal,
and is so arranged as to permit of advantage being taken of every foot
of space under cover. For this purpose the system of construction
without tie-beams, known as the "De Dion type," has been adopted. Fig.
1 gives a general view of one of the trusses, and Fig. 5 shows some
further details. The binding-rafters consist of four angle-irons
connected by cross-bars of flat iron. The covering of corrugated
galvanized iron rests directly upon the binding-rafters, the upper parts
of which are covered with wood for the attachment of the corrugated
metal. The spacing of these rafters is calculated according to the
length of the sheets of corrugated iron, thus dispensing with the use of
ordinary rafters, and making a roof which is at once very light and very
durable, and consequently very economical. Rain falling on the roof
flows into leaden gutters, from whence it is carried by leaders into a
subterranean drain. The vertical walls of the structure are likewise of
corrugated iron, and the general aspect of the building is very original
and very satisfactory.
_The 80 Ton Hammer_--The three hammers, notwithstanding their difference
in power, present similar arrangements, and scarcely vary except in
dimensions. We shall confine ourselves here to a description of the 80
ton apparatus. This consists, in addition to the hammer, properly so
called, of three cranes of 120 tons each, serving to maneuver the pieces
to be forged, and of a fourth of 75 tons for maneuvering the working
implements. These four cranes are arranged symmetrically around the
hammer, and are supported at their upper extremity by metallic stays.
Besides the foregoing there are three gas furnaces for heating the
ingots. Figs. 1, 2, and 3 show the general arrangement of the apparatus.
_Foundations of the Hammer and Composition of the Anvil-Bed_--To obtain
a foundation for the hammer an excavation was made to a depth of 26 feet
until a bed of solid rock was reached, and upon this there was then
spread a thick layer of beton, and upon this again there was placed a
bed of dressed stones in the part that was to receive the anvil-stock
and hammer.
On this base of dressed stones there was placed a bed formed of logs
of heartwood of oak squaring 16 inches by 3 feet in height, standing
upright, joined together very perfectly, and kept in close juxtaposition
by a double band of iron straps joined by bolts. The object of this
wooden bed was to deaden, in a great measure, the effect of the shock
transmitted by the anvil-stock.