METAL WORKING.
EARLY IRON FURNACE--OPERATIONS OF LORD DUDLEY, ABRAHAM DARBY AND
HENRY CORT--NEILSON’S HOT BLAST--GREAT BLAST FURNACES OF MODERN
TIMES--THE PUDDLING FURNACE--BESSEMER STEEL AND THE CONVERTER--OPEN
HEARTH STEEL--SIEMENS’ REGENERATIVE FURNACE--SIEMENS-MARTIN PROCESS
--ARMOR PLATE--MAKING HORSE SHOES--SCREWS AND SPECIAL MACHINES--
ELECTRIC WELDING, ANNEALING AND TEMPERING--COATING WITH METAL--METAL
FOUNDING--BARBED WIRE MACHINES--MAKING NAILS, PINS, ETC.--MAKING
SHOT--ALLOYS--MAKING ALUMINUM, AND METALLURGY OF RARER METALS--THE
CYANIDE PROCESS--ELECTRIC CONCENTRATOR.
Take away iron and steel from the resources of modern life, and the
whole fabric of civilization disintegrates. The railroad, steam engine
and steamship, the dynamo and electric motor, the telegraph and
telephone, agricultural implements of all sorts, grinding mills,
spinning machines and looms, battleships and firearms, stoves and
furnaces, the printing press, and tools of all sorts--each and every one
would be robbed of its essential basic material, without which it cannot
exist. Steam and electricity may be the heart and soul of the world’s
life, but iron is its great body. King among metals, it gives its name
to the present cycle, as the “Iron Age,” and the Nineteenth Century has
crowned it with such refinements of shape, and endowed it with such
attributes of utility, and such grandeur of estate, that its powers in
organized machinery have, for effective service, risen to all the
functions and dignity of human capacity--except that of thought.
A crude gift of nature, in the mountain side, it remained, however, a
sodden mass until extracted, refined, and wrought into shape by the
genius of man. Yielding to the magical touch of invention, it has been
cast in moulds into cannon, mills, plowshares, and ten thousand
articles; it has been drawn into wire of any fineness and length to form
cables for great suspension bridges; it has been rolled into rails that
grill the continents; into sheets that cover our roofs; and into nails
that hold our houses together. It has been wrought into a softness that
lends its susceptible nature to the influence of magnetism, and has been
hardened into steel to form the sword and cutting tool. From the
delicate hair spring of a watch to the massive armor plate of a
battleship, it finds endless applications, and is nature’s most enduring
gift to man--abundant, cheap, and lasting.
Metallurgy is an ancient art, and the working of gold, silver and copper
dates back to the beginning of history. Being found in a condition of
comparative purity, and needing but little refinement, they were, for
that reason, the first metals fashioned to meet the wants of man. Iron,
somewhat more refractory, appeared later, but it also has an early
history, and is mentioned in the Old Testament of the Bible (Genesis
iv., 22), in which reference is made to Tubal Cain as an artificer in
brass and iron. The iron bedstead of Og, King of Bashan, is another
reference. That it was known to the Egyptians and the Greeks at least
1000 B. C., seems reasonably certain. The Assyrians were also acquainted
with iron, as is clearly established by the explorations of Mr. Layard,
whose contributions to the British Museum of iron articles from the
ruins of Ninevah include saws, picks, hammers, and knives of iron, which
are believed to be of a date not later than 880 B. C.
Iron ore is usually found in the form of an oxide (hematite), and its
reduction to the metallic form consists in displacing the oxygen, which
is effected by mixing carbon in some form with the ore, and subjecting
the mixture to a high heat by means of a blast. The carbon unites with
the oxygen and forms carbonic acid gas, which escapes, while the
metallic iron fuses and runs out at the bottom of the furnace, and when
collected in trough-shaped moulds, is known as pig iron.
[Illustration: FIG. 249.--PRIMITIVE IRON FURNACE OF HINDOSTAN.]
The first iron furnaces were known as _air bloomeries_, and had no
forced draft. The first step of importance in iron making was the forced
blast. An early form of blast furnace is shown in Fig. 249, which
represents an iron furnace of the Kols, a tribe of iron smelters in
Lower Bengal and Orissa. An inclined tray terminates at its lower end in
a furnace inclosure. Charcoal in the furnace being well ignited, ore and
charcoal resting on the tray are alternately raked into the furnace. The
blowers are two boxes, connected to the furnace by bamboo pipes, and
provided with skin covers, which are alternately depressed by the feet
and raised by cords from the spring poles. Each skin cover has a hole in
the middle, which is stopped by the heel of the workman as the weight of
the person is thrown upon it, and is left open by the withdrawal of the
foot as the cover is raised. The heels of the workman, alternately
raised, form alternately acting valves, and the skin cover, when
depressed, acts as a bellows. The fused metal sinks to a basin in the
bottom of the furnace, and the slag or impurities run off above the
level of the basin at the side of the furnace.
The great modern art of iron working dates from Lord Dudley’s British
patent, No. 18, of 1621, which related to “The mistery, arte, way and
meanes of melting iron owre, and of makeing the same into cast workes or
barrs with seacoales or pittcoales in furnaces with bellowes of as good
condicon as hath bene heretofore made of charcoale.”
The next step of importance after the blast furnace was the substitution
of coke for coal for the reduction of the ore, which was introduced by
Abraham Darby, about 1750.
Next came the conversion of cast iron into wrought iron. This was mainly
the work of Mr. Henry Cort, of Gosport, England, who, in 1783-84,
introduced the processes of puddling and rolling, which were two of the
most important inventions connected with the production of iron since
the employment of the blast furnace. Mr. Cort obtained British patents
No. 1,351, of 1783, and No. 1,420, of 1784, for his invention. His first
patent related to the hammering, welding, and rolling of the iron, while
in his second patent he introduced what is known as the reverberatory
furnace, having a concave bottom, into which the fluid metal is run from
the smelting furnace, and which is converted from brittle cast iron,
containing a certain per cent. of carbon, into wrought iron, which has
the carbon eliminated, and is malleable and tough. This process is
called _puddling_, and consists in exposing the molten metal to an
oxidizing current of flame and air. The metal boils as the carbon is
burned out, and as it becomes more plastic and stiff it is collected
into what are called blooms, and these are hammered to get rid of the
slag, and are reduced to marketable shape as wrought iron by the
process described in his previous patent. Mr. Cort expended a fortune in
developing the iron trade, and was one of the greatest pioneers in this
art.
The first notable development of the Nineteenth Century was the
introduction of the hot air blast in forges and furnaces where bellows
or blowing apparatus was required. This was the invention of J. Beaumont
Neilson, of Glasgow, and was covered by him in British patent No. 5,701
of 1828. This consisted in heating the air blast before admitting it to
the furnace, and it so increased the reduction of refractory ores in the
blast furnace as to permit three or four times the quantity of iron to
be produced with an expenditure of little more than one-third of the
fuel.
[Illustration: FIG. 250.--MODERN HOT BLAST FURNACE.]
An illustration of a modern blast furnace plant is given in Fig. 250. A
is the furnace, in which the iron ore and fuel are arranged in alternate
layers. The hot air blast comes in through pipes _t_ at the bottom,
called tuyeres. As gas escapes through the opening _b_ at the top, it is
first cleared of dust in the settler and washer B, and then passes
through the pipe C to the regenerators D D D, where it is made to heat
the incoming air. The gas mixed with some air burns in the
regenerators, and, after heating a mass of brick within the regenerators
red hot, escapes by the underground passageway to the chimney on the
right. When the bricks are sufficiently hot in one of the regenerators,
gas is turned off therefrom, and into another regenerator, and fresh air
from pipe H is passed through the bricks of the heated regenerator, and
being heated passes out pipe F at the top and thence to the pipe G and
tuyeres _t_, to promote the chemical reactions in the blast furnace.
In the earlier blast furnaces a vast amount of heat was allowed to
escape and was wasted. The utilization of this heat engaged the
attention of Aubertot in France, 1810-14; Teague in England (British
patent No. 6,211, of 1832); Budd (British patent No. 10,475, of 1845),
and others. To enable the escaping hot gases to be employed for heating
the hot blast regenerators a charging device is now used, as seen at a
in Fig. 250, in which the admission of ore and fuel is regulated by a
large conical valve, and the gases are compelled to pass out at _b_ and
be utilized.
Among the world’s largest blast furnaces may be mentioned the Austrian
Alpine Montan Gesellschaft, which concern owns thirty-two furnaces. This
is said to be the largest number owned by any one concern in the world,
but most of them are of small size and run on charcoal iron. The
furnaces of the United States are, however, of the largest yield, and
the leading ones of these are:
No. Annual capacity
Furnaces. in tons.
Carnegie Steel Co. 17 2,200,000
Federal Steel Co. 19 1,900,000
Tennessee Coal and Iron Co. 20 1,307,000
National Steel Co. 12 1,205,000
The present annual output of pig iron in the United States is about ten
million tons, of which these four companies make about one-half.
[Illustration: FIG. 251.--PUDDLING FURNACE.]
When the iron runs from the bottom of the blast furnace it is allowed to
flow into trough-like moulds in the sand of the floor, and forms pig
iron. Pig iron can be remelted and cast into various articles in moulds,
but it cannot be wrought with the hammer, nor rolled into rails or
plates, nor welded on the anvil, because it is still a compound of iron
and carbon with other impurities, and is crystalline in character. To
bring it into wrought iron, which is malleable and ductile, it is
puddled and refined, which involves chiefly the burning out of the
carbon and silicon. The pig iron is remelted (see Fig. 251) in the
tray-shaped hearth _b_ from the heat of the fire in the reverberatory
furnace _a_, the reverberatory furnace being one in which the materials
treated are exposed to the heat of the flame, but not to contact with
the fuel. The hot flame mixed with air beating down upon the melted iron
on hearth _b_ for two hours or so, burns out the silicon and carbon, the
process being facilitated by stirring and working the mass with tools.
During the operation the oxygen of the air combines with the carbon and
forms carbonic acid gas, which, in escaping from the metal, appears to
make it boil. When the iron parts with its carbon it loses its fluidity
and becomes plastic and coherent, and is formed into balls called
_blooms_. These blooms consist of particles of nearly pure iron
cohering, but retaining still a quantity of slag or vitreous material,
and other impurities, which slag, etc., is worked out while still, hot
by a squeezing, kneading, and hammering process to form wrought iron
that may be worked into any shape between rolls or under the hammer.
[Illustration: FIG. 252.--BESSEMER CONVERTER DURING THE “BLOW.”]
_Bessemer Steel._--Steel is a compound of iron and carbon, standing
between wrought iron and cast iron. Wrought iron has, when pure,
practically no carbon in it, while cast iron has a considerable
proportion in excess of steel. Steel making consists mainly in so
treating cast iron as to get rid of a part of the carbon and other
impurities. Of all methods of steel making, and in fact of all the steps
of progress in the art of metal working, none has been so important and
so far reaching in effect as the Bessemer process: It was invented by
Henry Bessemer, of England, in 1855. About fifty British patents were
taken by Mr. Bessemer relating to various improvements in the iron
industry, but those representing the pioneer steps of the so-called
Bessemer process are No. 2,321, of 1855; No. 2,768, of 1855, and No.
356, of 1856. The process is illustrated in Figs. 252, 253 and 254. The
converter in which the process is carried out is a great bottle-shaped
vessel 15 feet high and 9 feet wide, consisting of an iron shell with a
heavy lining of refractory material, capable of holding eight or more
tons of melted iron, and with an open neck at the top turned to one
side. It is mounted on trunnions, and is provided with gear wheels by
which it may be turned on its trunnions, so that it may be maintained
erect, as in Fig. 252, or be turned down to pour out the contents into
the casting ladle, as in Figs. 253 and 254. At the bottom of the
converter there is an air chamber supplied by a pipe leading from one of
the trunnions, which is hollow, and a number of upwardly discharging air
openings or nozzles send streams of air into the molten mass of red hot
cast iron. The red hot cast iron contains more or less carbon and
silicon, and the air uniting with the carbon and silicon burns it out,
and in doing so furnishes the heat for the continuance of the operation.
When the pressure of air is turned into the mass of molten iron a tongue
of flame increasing in brilliancy to an intense white, comes roaring out
of the mouth of the converter, and a violent ebullition takes place
within, and throws sparks and spatters of metal high in the air around,
producing the impression and scenic effect of a volcano in eruption. In
fifteen minutes the volume and brilliancy of the flame diminish, and
this indicates the critical moment of conversion into tough steel, which
must be adjusted to the greatest nicety. When the carbon is sufficiently
burned out the blast is stopped and the converter turned down to receive
a quantity of ferro-manganese or spiegeleisen (a compound of iron
containing manganese), which unites with and removes the sulphur and
oxide of iron, and then the lurid monster, with its breath of fire
abated, and its energy exhausted, bows its head and vomits forth its
charge of boiling steel, to be wrought or cast into ten thousand useful
articles.
[Illustration: FIG. 253.--POURING THE MOLTEN METAL.]
[Illustration: FIG. 254.--SIDE VIEW, SHOWING TURNING GEARS.]
Like most all valuable inventions, Mr. Bessemer’s claim to priority for
the invention was contested. An American inventor, William Kelly, in an
interference with Mr. Bessemer’s United States patent, successfully
established a claim to the broad idea of forcing air into the red hot
cast iron, and United States patent No. 17,628, June 23, 1857, was
granted to Mr. Kelly. The honor of inventing and introducing a
successful process and apparatus for making steel by this method,
however, fairly belongs to Mr. Bessemer, to whose work was to be added
the valuable contribution of Robert F. Mushet (British patent No. 2,219,
of 1856) of adding spiegeleisen, a triple compound of iron, carbon and
manganese, to the charge in the converter. This step served to regulate
the supply of carbon and eliminate the oxygen, and completed the process
of making steel. The Holly converter, covered by United States patents
No. 86,303, and No. 86,304, January 26, 1869, represented one of the
most important American developments of the Bessemer converter.
The importance of Bessemer steel in its influence upon modern
civilization is everywhere admitted. It has so cheapened steel that it
now competes with iron in price. Practically all railroad rails, iron
girders and beams for buildings, nails, etc., are made from it at a cost
of between one and two cents per pound.
In recognition of the great benefits conferred upon humanity by this
process, Queen Victoria conferred the degree of knighthood upon the
inventor, and his fortune resulting from his invention is estimated to
have grown for some time at the rate of $500,000 a year. In a historical
sketch of the development of his process, delivered by Sir Henry
Bessemer in December, 1896, before the American Society of Mechanical
Engineers at New York, Mr. Bessemer was reported as saying that the
annual production of Bessemer steel in Europe and America amounted to
10,000,000 tons. The production of Bessemer steel in the United States
for 1897 was for ingots and castings 5,475,315 tons, and for railroad
rails 1,644,520 tons. The extent to which steel has displaced iron is
shown by the fact that in the same year iron rails to the extent of
2,872 tons only were made, as compared with more than a million and a
half tons of Bessemer steel.
In the popular vote taken by the _Scientific American_, July 25, 1896,
as to what invention introduced in the past fifty years had conferred
the greatest benefit upon mankind, Bessemer steel was given the place of
honor.
A recent improvement in the handling of iron from the blast furnace is
shown in Fig. 255. Heretofore, the iron was run in open sand moulds on
the floor and allowed to cool in bars called “pigs,” which were united
in a series to a main body of the flow, called a “sow.” To break the
“pigs” from the “sow,” and handle the iron in transportation, was a very
laborious and expensive work. The illustration shows two series of
parallel trough moulds, each forming an endless belt, running on wheels.
The molten cast iron is poured direct into these moulds, and as they
travel along they pass beneath a body of water, which cools and
solidifies the iron into pigs, and then carries them up an incline and
dumps them directly into the cars.
[Illustration: FIG. 255.--CASTING AND LOADING PIG IRON.]
_Open Hearth Steel_ is not so cheap as Bessemer steel, but it is of a
finer and more uniform quality. Bessemer steel is made in a few minutes
by the most energetic, rapid and critical of processes, while the open
hearth steel requires several hours, and its development being thus
prolonged it may be watched and regulated to a greater nicety of result.
For railroad rails and architectural construction Bessemer steel still
finds a great field of usefulness, but for the finest quality of steel,
such as is employed in making steam boilers, tools, armor plate for war
vessels, etc., steel made by the open hearth process is preferred. It
consists in the decarburization of cast iron by fusion with wrought
iron, iron sponge, steel scrap, or iron oxide, in the hearth of a
reverberatory furnace heated with gases, the flame of which assists the
reaction, and the subsequent recarburization or deoxidation of the bath
by the addition, at the close of the process, of spiegeleisen or
ferro-manganese. The period of fusion lasts from four to eight hours.
The advantages over the Bessemer process are, a less expensive plant and
the greater duration of the operation, permitting, by means of
sampling, more complete control of the quality of the product and
greater uniformity of result.
The British patents of Siemens, No. 2,861, of 1856; No. 167, of 1861,
and No. 972, of 1863, for regenerative furnaces, and the British patents
of Emile and Pierre Martin, No. 2,031, of 1864; No. 2,137, of 1865, and
No. 859, of 1866, represent the so-called _Siemens-Martin_ process,
which is the best known and generally used open hearth process.
[Illustration: FIG. 256.--SIEMENS REGENERATIVE FURNACE.]
_The Siemens Regenerative Furnace_, in which this process is carried
out, is seen in Fig. 256. Four chambers, C, E, E′, C′, are filled with
fire brick loosely stacked with spaces between, in checker-work style.
Gas is forced in the bottom of chamber C, and air in bottom of chamber
E, and they pass up separate flues, G, on the left, and being ignited in
chamber D above, impinge in a flame on the metal in hearth H, the hot
gases passing out flues F on the right, and percolating through and
highly heating the checker-work bricks in chambers E′ and C′. As soon as
these are hot, gas and air are shut off by valves from chambers C and E,
and gas and air admitted to the bottoms of the now hot chambers C′ and
E′. The gas and air now passing up through these chambers C′, E′, become
highly heated, and when burned above the melted iron on hearth H produce
an intense heat. The waste gases now pass down flues G, and impart
their heat to the checker-work bricks in chambers C and E. When the
bricks in E′ C′ become cooled by the passage of gas and air, the valves
are again adjusted to reverse the currents of gas and air, sending them
now through chambers C and E again. In this way the heat escaping to
the smoke stack is stored up in the bricks and utilized to heat the
incoming fuel gases before burning them, thus greatly increasing the
effective energy of the furnace, saving fuel, and keeping the smoke
stack relatively cool.
_Armor Plate._--In these late days of struggle for supremacy between the
power of the projectile and the resistance of the battleship, the
production of armor plate has become an interesting and important
industry.
Three methods are employed. One is to roll the massive ingots directly
into plates between tremendous rolls, a single pair of which, such as
used in the Krupp works, are said to weigh in the rough as much as
100,000 pounds. Usually there are three great rollers arranged one above
the other, and automatic tables are provided for raising and lowering
the plates in their passage from one set of rolls to the other. The man
in charge uses a whistle in giving the signals which direct these
movements, and without the help of tongs and levers the glowing blocks
move easily back and forth between the rollers. The men standing on both
sides of the rollers have only to wipe off the plates with brooms and
occasionally turn the plates.
[Illustration: FIG. 257.--14,000-TON HYDRAULIC PRESS FORGING AN ARMOR
PLATE.]
The second method utilizes great steam hammers weighing 125 tons, and
striking Titanic blows upon the yielding metal. The most modern method,
however, is by the hydraulic press forge, now used in the shops of the
Bethlehem steel works in the production of Harveyized armor plate. In
Fig. 257 is seen the great 14,000-ton hydraulic press-forge squeezing
into shape a port armor plate for the battleship “Alabama.” After
leaving the forge, the plate is trimmed to shape by the savage bite of a
rotary saw and planer, seen in Figs. 258 and 259, whose insatiable
appetites tear off the steel like famished fiends. The plate is then
taken to be Harveyized by cementation, hardening, and tempering, as seen
in Figs. 260, 261, and 262. The 125-ton mass of metal representing the
plate in the rough, and weighing more than a locomotive, is thus handled
and brought to shape with an ease and dispatch that inspires the
observer with mixed emotions of admiration and awe.
_Making Horse Shoes._--Anthony’s patent, April 8, 1831; Tolles’, of
October 24, 1834, and H. Burden’s, of November 23, 1835, were pioneers
in horse-shoe machines. Mr. Burden took many subsequent patents, and to
him more than any other inventor belongs the credit of introducing
machine-made horse shoes, which greatly cheapened the cost of this
homely, but useful article. Nearly 400 United States patents have been
granted for horse-shoe machines.
[Illustration: FIG. 258.--ROTARY SAW, CUTTING HEAVY ARMOR PLATE.]
[Illustration: FIG. 259.--ROTARY PLANER, TRIMMING HEAVY ARMOR PLATE.]
[Illustration: FIG. 260.--THE CEMENTATION FURNACE.]
[Illustration: FIG. 261.--HARDENING THE PLATE BY JETS OF WATER.]
[Illustration: FIG. 262.--OIL TEMPERING.]
_Making Screws, Bolts, Nuts, Etc._--Screw-making according to modern
methods began between 1800-1810 with the operations of Maudsley. Sloan,
in 1851, and Harvey, in 1864, made many improvements in machines,
operating upon screw blanks. The gimlet-pointed screw, which allows the
screw to be turned into wood without having a hole bored for it, was an
important advance in the art. It was the invention of Thomas J. Sloan,
patented August 20, 1846, No. 4,704, and was twice re-issued and
extended. In later years the rolling of screws, instead of cutting the
threads by a chasing tool, has attained considerable importance, and
provides a simpler and cheaper method of manufacture. Knowles’ United
States patent of April 1, 1831, re-issued March 1, 1833, described such
a process, while Rogers, in patents No. 370,354, September 20, 1887; No.
408,529, August 6, 1889; No. 430,237, June 17, 1890, and No. 434,809,
August 19, 1890, added such improvement in the process as to make it
practical.
In the great art of metal working the names of Bramah, Whitworth,
Clements and Sellers appear conspicuously in the early part of the
century as inventors of planing, boring and turning machinery for
metals. Our present splendid machine shops, gun shops, locomotive works,
typewriter and bicycle factories, are examples of the wonderful
extensions of this art. In later years the field has been filled so full
of improvements and special machines for special work, that only a brief
citation of a few representative types is possible, and even then
selection becomes a very difficult task. Many special tools,
particularly those designed for _bicycle work_, have been devised, as
exhibited by patent to Hillman, August 11, 1891, No. 457,718. In
_turning car wheels_, an improvement consists in bringing the wheel to
be dressed into close proximity to the edge of a rapidly revolving
smooth metal disk, whereby the surface of the wheel is melted away
without there being any actual contact between the wheel surface and the
disk. This is shown in patent to Miltimore, August 24, 1886, No.
347,951. In _metal tube manufacture_ three processes are worthy of
mention: (1) Passing a heated solid rod endwise between the working
faces of two rapidly rotating tapered rolls, set with their axes at an
angle to each other, as shown in Mannesmann’s patent, April 26, 1887,
No. 361,954 and 361,955. (2) Forcing a tube into a rapidly rotating die,
whereby the friction softens the tube, and the pressure and rotation of
the die spin it into a tube of reduced diameter, shown in patent to
Bevington, January 13, 1891, No. 444,721. (3) Placing a hot ingot in a
die and forcing a mandrel through the ingot, thereby causing it to
assume the shape of the interior of the die, and greatly condensing the
metal, shown in patents to Robertson, November 26, 1889, No. 416,014,
and Ehrhardt, April 11, 1893, No. 495,245.
In _welding_, the employment of electricity constitutes the most
important departure. This was introduced by Elihu Thomson, and is
covered in his patents Nos. 347,140 to 347,142, August 10, 1886, and No.
501,546, July 18, 1893. In _annealing_ and _tempering_, electricity has
also been employed as a means of heating (see patent to Shaw, No.
211,938, February 4, 1879). It supplies an even heat and uniform
temperature, and is much used in producing clock and watch springs. The
making of iron castings malleable by a prolonged baking in a furnace in
a bed of metallic oxide was an important, but early, step. It was the
invention of Samuel Lucas, and is disclosed in his British patent No.
2,767, of 1804.
The _Harvey process_ of making armor plate is an important recent
development in _cementation_ and _case hardening_, and is covered by his
United States patents No. 376,194, January 10, 1888, and No. 460,262,
September 29, 1891. It consists, see Fig. 260, in embedding the face of
the plate in carbon, protecting the back and sides with sand, heating to
about the melting point of cast iron, and subsequently hardening the
face. The Krupp armor plate, now rated as the best, is made under the
patent to Schmitz and Ehrenzberger, No. 534,178, February 12, 1895.
In _coating with metals_, the so-called “galvanizing” of iron is an
important art. This was introduced by Craufurd (British patent No.
7,355, of April 29, 1837), and consisted in plunging the iron into a
bath of melted zinc covered with sal ammoniac. In more recent years the
tinning of iron has become an important industry, and machines have been
made for automatically coating the plates and dispensing with hand
labor, examples of which are found in patents No. 220,768, October 21,
1879, Morewood; No. 329,240, October 27, 1885, Taylor, _et al._, and No.
426,962, April 29, 1890, Rogers and Player.
In _metal founding_ the employment of chill moulds is an important step.
Where any portion of a casting is subjected to unusual wear, the mould
is formed, opposite that part of the casting, out of metal, instead of
sand, and this metal surface, by rapidly extracting the heat at that
point by virtue of its own conductivity, hardens the metal of the
casting at such point. The casting of car wheels by chill moulds, by
which the tread portion of the wheel was hardened and increased in
wearing qualities, is a good illustration. Important types are found in
patents to Wilmington, No. 85,046, December 15, 1868; Barr, No. 207,794,
September 10, 1878, and Whitney, re-issue patent, No. 10,804, February
1, 1887.
In _wire-working_ great advances have been made in machines for making
_barbed wire fences_. The French patent to Grassin & Baledans, in 1861,
is the first disclosure of a barbed wire fence. This art began
practically, however, with the United States patent to Glidden and
Vaughan for a barbed wire machine, No. 157,508, December 8, 1874,
re-issued March 20, 1877, No. 7,566, and has assumed great proportions.
A machine for making wire net is shown in patent to Scarles, No.
380,664, April 3, 1888, and wire picket fence machines are shown in
patents to Fultz, No. 298,368, May 13, 1884, and Kitselman, No. 356,322,
January 18, 1887. Machines for making wire nails were invented at an
early period, but the product found but little favor until about 1880,
when they began to be extensively used, and have almost entirely
supplanted cut nails for certain classes of work, since their round
cross section and lack of taper give great holding power and avoid
cutting the grain of the wood. In 1897 the wire nails produced in the
United States amounted to 8,997,245 kegs of 100 pounds each, which
nearly doubled the output of 1896. The output of cut nails for the same
year was 2,106,799 kegs.
The bending of wire to form chains without welding the links has long
been done for watch chains, etc., but in late years the method has
extended to many varieties of heavy chains. The patents to Breul, No.
359,054, March 8, 1887, and No. 467,331, January 19, 1892, are good
examples.
An interesting class of machines, but one impossible of illustration on
account of their complication, are machines for making pins. In earlier
times pins had their heads applied in a separate operation. Making pins
from wire and forming the heads out of the cut sections began in the
Nineteenth Century with Hunt’s British patent No. 4,129, of 1817. This
art received its greatest impetus, however, under Wright’s British
patent No. 4,955, of 1824. A paper of pins containing a pin for every
day in the year, and costing but a few cents, gives no idea to the
purchaser of the time, thought and capital expended in machines for
making them, and yet were it not for such machines, rapidly cutting
coils of wire into lengths, pointing and heading the pins, and sticking
them into papers, the world would be deprived of one of its most
ubiquitous and useful articles. Many tons of pins are made in the United
States weekly, and it is said that 20,000,000 pins a day are required to
meet the demand.
In the metal working art the making of firearms and projectiles has
grown to wonderful proportions. Cutlery and builders’ hardware is an
enormous branch; wire-drawing, sheet metal-making, forging, and the
making of tools, springs, tin cans, needles, hooks and eyes, nails and
tacks, and a thousand minor articles, have grown to such proportions
that only a bird’s-eye view of the art is possible.
In the _making_ of _shot_, the old method was to pour the melted metal
through a sieve, and allow it to drop from a tower 180 feet or more in
height. David Smith’s patent, No. 6,460, May 22, 1849, provided an
ascending current of air through which the metal dropped, and which, by
cooling the shot by retarding its fall and bringing a greater number of
air particles in contact with them, avoided the necessity of such high
towers. In 1868, Glasgow and Wood patented a process of dropping the
shot through a column of glycerine or oil. Still another method is to
allow the melted metal to fall on a revolving disk, which divides it
into drops by centrifugal action.
_Alloys._--Over 300 United States patents have been granted for various
alloys of metals. The so-called _babbit metal_ was patented in the
United States by Isaac Babbit, July 17, 1839, and in England, May 15,
1843, No. 9,724. This consists of an antifriction compound of tin, 10
parts, copper, 1 part, and antimony, 1 part, and is specially adapted
for the lubricated bearings of machinery. _Phosphor bronze_, introduced
in 1871, combines 80 to 92 parts copper, 7 of tin, and 1 of phosphorus
(see United States patents to Lavroff, No. 118,372, August 22, 1871, and
Levi and Kunzel, No. 115,220, May 23, 1871). The addition of phosphorus
promotes the fluidity of the metal and makes very clean, fine and strong
castings. In alloys of iron, _chromium steel_ is covered by patents to
Baur, No. 49,495, August 22, 1865; No. 99,624, February 8, 1870, and
No. 123,443, February 6, 1872; _manganese steel_, by Hadfield’s patent,
No. 303,150, August 5, 1884; _aluminum steel_, by Wittenström’s patent,
No. 333,373, December 29, 1885, and _phosphorus steel_, by Kunkel’s
patent, No. 182,371, September 19, 1876. The most recent and perhaps
most important, however, is _nickel steel_, used in making armor for
battleships. This is covered by Schneider’s patents, Nos. 415,655, and
415,657, November 19, 1889.
In 1878 England led the world in the iron industry with a production of
6,381,051 tons of pig iron, as compared with 2,301,215 tons by the
United States. In 1897 the United States leads the world in the
following ratios:
Tons Pig Iron. Tons Steel.
United States 9,652,680 7,156,957
Great Britain 8,789,455 4,585,961
Germany 6,879,541 4,796,226
France 2,472,143 1,312,000
The United States made in that year 29.30 per cent. of the world’s
production of pig iron, and 34.58 per cent. of its steel. The total
output of the whole world in that year was 32,937,490 tons pig iron, and
20,696,787 tons of steel.
_Metallurgy of Rarer Metals._--Although less in evidence than iron, this
has engaged the attention of the scientist from the earliest years of
the century. The full list of metals discovered since 1800 may be found
under “Chemistry.” The more important only are here given. Palladium and
rhodium were reduced by Wollaston in 1804. Potassium and sodium were
first separated in metallic form by Sir Humphrey Davy in 1807, through
the agency of the voltaic arc; barium, strontium, calcium and boron by
the same scientist in 1808; iodine by Courtois in 1811; selenium by
Berzelius in 1817; cadmium by Stromeyer in 1817; silicon by Berzelius in
1823, and bromium by Balard in 1826. Magnesium was first prepared by
Bussey in 1829. Aluminum was first separated in 1828 by Wohler, by
decomposing the chloride by means of potassium. Oersted, in 1827,
preceded him with important preliminary steps, and Deville, in 1854,
followed in the first commercial applications. In late years the
metallurgy of aluminum has made great advances. The Cowles process heats
to incandescence by the electric current a mixture of alumina, carbon
and copper, the reduced aluminum alloying with the copper. This process
is covered by United States patents to Cowles and Cowles, No. 319,795,
June 9. 1885, and Nos. 324,658 and 324,659, August 18, 1885. It has,
however, for the most parts been superseded by the process patented by
Hall, April 2, 1889, No. 400,766, in which alumina dissolved in fused
cryolite is electrically decomposed.
In the metallurgy of the precious metals probably the most important
step has been the _cyanide process_ of obtaining gold and silver. In
1806 it was known that gold was soluble in a solution of cyanide of
potassium. In 1844 L. Elsner published investigations along this line,
and demonstrated that the solution took place only in the presence of
oxygen. McArthur and Forrest perfected the process for commercial
application, and it is now extensively used in the Transvaal and
elsewhere. It is covered by their British patent, No. 14,174, of 1887,
and United States patents No. 403,202, May 14, 1889, and No. 418,137,
December 24, 1889, which describe the application of dilute solutions of
cyanide of potassium, not exceeding 8 parts cyanogen to 1,000 parts of
water: the use of zinc in a fine state of division to precipitate the
gold out of solution, and the preparatory treatment of the partially
oxidized ores with an alkali or salts of an alkali. By this
solution-process gold, in the finest state of subdivision, which could
not be extracted by other processes from the earthy matters, may be
recovered and saved in a simple, practical and cheap way.
[Illustration: FIG. 263.--EDISON MAGNETIC CONCENTRATING WORKS. THE GIANT
CRUSHING ROLLS.]
[Illustration: FIG. 264.--EDISON MAGNETIC CONCENTRATOR.]
In the working of ores of gold and silver the old method of comminution
of the rock and the separation of the gold and silver by amalgamation
with mercury has given birth to thousands of inventions in stamp mills,
amalgamators, ore washers, concentrators and separators. In the
treatment of iron ores, and especially those of low grade, the magnetic
concentrator is an interesting and striking departure. This method goes
back to the first half of the Nineteenth Century, an example being found
in the patent to Cook, No. 6,121, February 20, 1849. Edison’s patent,
No. 228,329, June 1, 1880, is however, the basis of the first practical
operations in which magnets, operating by attraction upon falling
particles of iron ore, are made to separate the particles rich in iron
from the sand. In Fig. 263 is shown the Edison magnetic concentrating
apparatus. The ore, in masses of all sizes up to boulders of five or six
tons weight, is dumped between the giant rolls, and these enormous
masses are crunched and comminuted more easily than a dog crunches a
bone. These gigantic rolls are six feet in diameter, six feet long, and
their surfaces are covered with crushing knobs. They weigh with the
moving machinery seventy tons, and when revolved at a circumferential
speed of 3,500 feet in a minute, their insatiable and irresistible bite
soon chews the rock into fragments that pass into similar crushing rolls
set closer together until reduced to the desired fineness. The sand is
then raised to the top of the concentrating devices, shown in Fig. 264,
and is allowed to fall in sheets from inclined boards in front of a
series of magnets, of which four sets are shown in the figure. These
magnets deflect the fall of the particles rich in iron (which are
attracted), while the non-magnetic particles of sand drop straight down.
A thin knife-edge partition board, arranged below the falling sheets of
sand, separates the deflected magnetic particles from the
straight-falling sand. These magnetic particles are then collected and
pressed into little bricks, which are now so rich in iron, by virtue of
concentration, as to make the final reduction of the iron in the blast
furnace easy and profitable. More recent developments in this art are
shown in patents to Wetherill, No. 555,792, March 3, 1896, and Payne,
No. 641,148, January 9, 1900.
In the production of copper the well-known Bessemer process for refining
iron is now largely used, as shown in patent to Manhes, No. 456,516,
July 21, 1891, in which blasts of air are forced through the melted
copper to remove sulphur and other impurities. Electrolytic processes of
refining copper are also largely used, as described in Farmer’s patent,
No. 322,170, July 14, 1885.
The production of metals, other than iron, in the United States for the
year 1897, was as follows:
Gold, 2,774,935 ounces; worth $57,363,000.
Silver, 53,860,000 ounces; worth $32,316,000.
Copper, 220,571 long tons.
Lead, 212,000 short tons.
Zinc, 99,980 short tons.
Aluminum, 4,000,000 lbs.; worth (37½ cents lb.) $1,500,000.
(This was three times the product of 1896.)
Mercury, 26,691 flasks; worth $993,445.
Nickel, 23,707 pounds; worth (33 cents pound) $7,823.