Year: 1888

page_text: 1, GUSTAV LINDENTHAL, residing at Lewis Block, in the city of Pittsburgh,
County of Allegheny and State of Pennsylvania, one of the United States of
America, Civil Engineer, do hereby declare the nature of this Invention and in what
manner the same is to be performed to be particularly described and ascertained in
and by the following statement:—
The object of my Invention is to retain the fluidity of the bath of molten iron,
for the purpose of a more thorough dephosphorization in the presence of basic
material.
My Invention consists in the process hereinafter described, of refining iron by the
addition of aluminium to the molten metal in the presence of a basic material whereby
the metal is dephosphorized, desulphurized and purified.
•
In the conversion of pig iron into the malleable iron the impurities are removed,
either in a reverberatory furnace or in a Bessemer-converter by the air-blast.
As is well known the silicon and carbon are burned out first, while the sulphur and
phosphorus, having a greater affinity to the iron, leave the same towards the end
of the refining process only in the presence of basic material, with which they may
unite and go into the slag. The iron. thereby, becoming purer, becomes less fluid;
because the melting point of pure iron is higher (about 4000 F.) than that of impure
iron, or iron alloys.
When the molten iron becomes pasty, an intimate contact of the same with the
basic material is prevented, and the dephosphorization and desulphurization practically
ceases.
If, on the other hand, the fluidity of purer iron is increased by the application of
external heat, as in a reverberatory or puddling. furnace, then the greater affinity of
phosphorus to iron at a higher.heat, forms another obstacle to its purification.
From this, it will be seen, that the essential and simultaneous-conditions
for a more complete elimination of phosphorus are as follows:
necessary.
1. The more or less complete absence of silicon and carbon in the iron bath,

page_text: 2. The greater fluidity of the bath for a more intimate contact of the molten iron
with the basic material.
3. A temperature lower than needed for melting good wrought iron, for bringing
the basic material into contact with the molten iron, when its affinity to phosphorus
is weakened.
The addition of aluminum, either alone or as an alloy or other suitable combination,
to molten iron has the well known effect of increasing the fluidity of the same
without detriment to its quality, or in other words, aluminium reduces the melting
point of iron 300 to 500 degrees, according to the amount added. I avail myself of
this property of aluminium to effect a more efficient dephosphorization of iron in the
following manner:
The molten pig iron is first desiliconised or decarbonized in one of the usual
manners: i.e. in a reverberatory or puddling furnace, by burning out under a
reverberatory flame with or without the addition of iron ore for a more efficient
oxidation of the impurities, then towards the end of the refining process after the
silicious slag has been drawn off, or removed from the bath, the addition of the
crushed fresh iron ore, calcined dolomite 'and aluminium is made; the latter preferably,
in the more convenient and cheaper form of an aluminium alloy previously melted in
a separate furnace or cupola.
Another and a more efficient method is, to first desiliconise and decarburize the molten
pig iron in a Bessemer-converter, having an acid lining and then to transfer the same
for the intended further purification to a reverberatory, puddling or rotary furnace.
The aluminium can be added to the metal in the converter, before pouring into the
ladle, or into the ladle itself, so that it shall thoroughly mix with the iron before
transfer to a separate furnace, where the dephosphorization is effected, on a basic
lining and by additions of basic material, preferably calcined dolomites.
It is immaterial whether the refining process, the elimination of silicon, carbon and
phosphorus and other impurities take place in the same furnace and in one continuous
operation as in the open hearth and puddling furnace or whether the first part of the
refining process, i.e. the desiliconisation and decarburation takes place in a separate
furnace, as in the open hearth; or in the Bessemer-converter and the dephosphorization
and desulphurization takes place in another furnace, as in a puddling, rotary or
revolving furnace, or in another converter, all of them having a basic lining. In any
of these steps or combination of steps the addition of aluminium should preferably
take place after the silicon and carbon have been for the greater part removed from
the bath and after the silicious slag has been drawn off.
The best result in practice, I obtained by refining the iron first in a Bessemer-
converter and then transferring the charge mixed with the proper amount of
aluminium to a rotary furnace, having an iron ore or basic lining. The molten iron
which in this manner, had been purified of the silicon and carbon in the converter
and then transferred to the rotary furnace, ordinarily assumes a pasty condition or
comes to nature in about 3 to 5 minutes; but with the aluminium added to it, it
requires nearly twice as long for coming to nature, and during this longer time, a
more complete dephosphorization takes place. The amount of aluminium ordinarily
added, either pure or in the cheaper form of an alloy or like combination, is about
one tenth per cent. A phosphor iron will of itself have more fluidity than a purer
iron. But as the dephosphorization progresses, it would soon lose the same, so that
the amount of aluminium does not primarily depend on the greater or smaller amount
of phosphorus in the pig iron..
":
An amount of aluminium, greater than two (2) per cent causes the iron to be red
short,,while a smaller amount is without detrimental effect on the same, but rather
improves the quality of the iron. .
I am aware that the addition of aluminium to molten wrought iron or steel is not
new, but has been patented and is practised in the manufacture of steel and wrought
iron castings. I do not therefore claim the addition of aluminium to iron, or the
fusing of the same together for improving the quality of the metal, or of any products
manufactured from such metal...
$4°

page_text: Having now particularly described and ascertained the nature of my said
Invention and in what manner the same is to be performed, I declare that what
I claim is :
1st. The process, hereindescribed, of purifying cast or pig iron, which consists in'
first desiliconizing and decarbonizing the metal, then adding aluminium to the molten
metal, and bringing the same in contact with basic material to react on the phosphatic
and other impurities, in the iron, as set forth.
2nd. The process hereindescribed, of purifying iron, which consists in desiliconizing
and decarbonizing the cast iron, then adding aluminium to the molten metal and
bringing the same into contact with iron ore, to react on the phosphatic and other
impurities in the iron as set forth.
3rd. The process hereindescribed, of refining iron which consists in, first desili-
conizing and decarbonizing the molten cast iron, then adding aluminium and bringing
the molten metal into contact with iron or iron ore or other suitable basic material,
to react on the phosphatic and other impurities, then subjecting the charge to a
puddling action until the metal is reduced to wrought condition, to form a ball or
loop, as set forth.