Process for Refining Iron and Steel and other Metals.
Year: 1898

page_text: Reprinted as amended in accordance with the decision of the Comptroller-General,
dated the 19th day of November, 1900.
Date of Application, 15th Feb., 1898-Accepted, 28th May, 1898
[Communicated from abroad by BENJAMIN TALBOT, of Pencoyd, in the County of
Montgomery, State of Pennsylvania, United States of America, Metallurgical
Engineer.]
Process for Refining Iron and Steel and other Metals.
I, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.M.E., of the Agency for Foreign Patent
Solicitors, 322, High Holborn, in the County of Middlesex, 6, Lord Street, Liverpool,
and 6, Bank Street, Manchester, both in the County of Lancaster, and Lower Temple
Street, Birmingham, in the County of Warwick, 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 :-
My invention is more particularly a process for desiliconizing and otherwise
purifying liquid-east-iron for use in the manufacture of steel, puddle iron, malleable
iron-eastings, and-analogous products, as-alse for facilitating and cheapening the
manufacture of open hearth steel, as hereinafter set forth.
Previous to my invention, the customary method of making steel in the ordinary
Siemens regenerative or open hearth furnace has been to melt the pig iron or pig
iron and scrap in the furnace and to continue the operation therein until the impurities
in the charge had been removed and said charge converted into steel of the desired
quality, the furnace being then tapped and the hearth being completely emptied
of its contents prior to being charged again with fresh material for another heat.
My invention consists in retaining in the furnace a portion of the mass of molten
and purified steel metal, to which a charge of impure or partially purified molten metal
is added. When the slag is not heavily charged with impurities, I prefer to leave
some of this slag in the furnace with the body of purified metal steel retained therein,
but whether a portion of the slag is so retained or not, I preferably provide the bath
of purified metal steel remaining in the furnace with a covering of slag before intro-
ducing the additional supply of metal into the furnace.
When operating with a furnace having a basic or neutral lining, I prefer to proceed
as follows:
In any ordinary form of tipping furnace, that is to say, one which has its delivery
spout at or above the level of the liquid bath and which is capable of being tilted
so as to pour off either metal or slag, through one or more spouts, I make a heat of
steel metal, but of smaller weight than the full capacity of the furnace, say from sixty
to eighty per cent. of such capacity, but instead of pouring out the heat of steel meta!
when it has been properly purified, I pour into it a quantity of liquid pig iron, say
from forty to twenty per cent. of the furnace capacity, which may be pig iron obtained
directly from the blast furnace, cupola or other furnace, or it may be pig iron
desiliconized or partially purified in any available manner.

page_text: This metal, coming into contact with the liquid basic slag and highly heated bath
of purified steel metal in the furnace, rapidly purified and its temperature is so
raised by the furnace gases as to admit of its being successfully cast.
The smaller the percentage of impure metal added to the charge of purified metal
in the furnace the quicker will be the purification of this added metal be effected.
This per centage of added metal may be varied according to the speed at which it is
desired to obtain heats of purified steel metal from the furnace. If steel metal is
required as rapidly as possible, then the furnace should be of large capacity and
the percentage of added metal may be smaller than if it is given a longer time for
purification.
From time to time during the purification of this added metal further basic
additions are made when necessary, and as soon as the entire bath of metal is suffi-
ciently purified the furnace is tilted and the desired percentage of the entire charge
is poured into the ladle, the usual deoxidizing addition of ferro-manganese, spiegel,
or like material, being introduced into the steel metal in the ladle, or in any other
convenient and economical way. Or if it is desired to subject this purified steel metal
to further treatment in another furnace, as to reduce its carbon from a high degree to
low, or for admixture with other metal or alloys, or to eliminate phosphorus or or
other impurities further, the manganese may not be added until the further purifica-
tion has been effected.
A greater or less quantity of slag, according to the amount of impurities contained
therein, is flowed off, either before or after the metal is poured. Fresh basic additions,
such as oxide of iron and lime or limestone, either liquid or solid, are added to the
molten bath of purified metal retained in the furnace, and a fresh supply of impure
or partially purified metal is then poured into the furnace and the operation described
is repeated.
The pouring of the fresh supply of impure or partially purified metal through a
covering of basic slag, I consider to be a-preferable an important step in the process
of purification and, hence, in carrying out my invention, I always-prefer-to provide the
bath of purified metal steel remaining in the furnace with a covering of such basic
slag before adding the impure or partially purified metal thereto, although I do not
limit my invention to this as the oxide of iron and lime or limestone, or other slag
forming additions, may be introduced, when necessary, into the furnace after the
charge of impure or partially purified metal has been poured into the bath of purified
steel metal remaining in the furnace.
The economy of my improved process arises from the fact that as the impure or
partially purified metal is of less specific gravity than the purer charge contained in
the furnace, the former will rise to the top of the latter and the impurities will be
acted upon by the slag and furnaces gases more quickly and with better effect than if
they were distributed throughout the entire depth of the charge, and for this reason
the purifying action is expedited.
Solid scrap or pig iron may be charged with the liquid metal, but unless such solid
additions are cheaper than the liquid portions of the charge it is not advisable to use
them to such an extent as to appreciably lower the temperature and fluidity of the
bath, as this would delay the operation.
When operating with an acid-lined furnace, I proceed in the same manner as before
described excepting that the slag does not contain sufficient free base to attack the
lining beyond the susceptibility of ready repair during the running of the furnace.
When repairs are necessary on the slag line, a greater portion of metal can be
poured out of the furnace, so as to expose the worn parts above the bath, when these
can be repaired and the bath filled with metal again.
By the term "purification," as used in my specification and claims, as applied to
open hearth steel, is not necessarily meant the complete elimination of the impurities
from the iron, but only such elimination as will result in a product of the desired
grade, that is to say, one which will be theoretically known as steel by reason of the
percentage of its carbon contents, whether after treatment of the product is or is not
resorted to, for special reasons.

page_text: When-it-is desired-to-only-produce-a-desiliconised-metal in the furnace, but-one
that-is-cast-iron-the-eurbon contents may be retained-in-the-metal-so-as-to-produce
-product-of the-desired-grade. The mode-of operating the -furnace--would-be
practically the-samens-that-in-the-manufacture-of steel, previously described;-ns
the lining-of-the-furnace-may-be-basie, neutral or neid. It will not be necessary to
work the furnace at so high a temperature- as when steel is being made, since the
purified-enst-iron--would-contain-more-carbon and may have impurities in-grenter
and-consequently-is-more-Auid-ut-the-same-temperature:
This-east-iron-as-thus-refined-may be transferred to-another-furnace-and-may be
poured into a bath of purer metal and worked into steel by the continuous method
before described. Or it may be taken in liquid condition, preferably,-or-in-solid
condition,-and-put-into-another-furnace, by itself or mixed with serup. If sufficient
silicon-and-carbon be retained in the refined-iron,-it-may be-poured into-a-Bessemer
converter and there blown into-steel.
degree,
It is obvious-that-one-large-desiliconising furnace would furnish-sufficient-purified
metal-for-n-number-of-other-furnaces of smaller-capacity-working-this-metal-into
steel
When it is desired to make puddle iron from-the-desiliconised east-iron;-metul
can-be taken;-preferably-in-liquid-condition, and poured into-varions--puddling
furnaces, and-there-worked-down-rapidly-into-malleable iron. If the puddlers-tap
einder--is--sufficiently pure, from puddling the refined-iron, it may be returned;
preferably-in-liquid condition, to the desiliconising-furnnee:
Although I prefer to use a tilting furnace for carrying on my improved process, in
open hearth steel manufacture and in refining irons, the process may be carried on in
a fixed hearth, by having a number of tap-holes at various levels in the bath, but I do
not recommend this.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, as communicated to
me by my foreign correspondent, I declare that what I claim is :-
1. The process of refining metal, as herein described, which consists in inter-
mittingly charging unrefined metal into a-henting furnace containing refined molten
metal, and intermittingly drawing off portions of said-metal, as-it-is thus-refined:
2. The process of purifying-metal, ns. herein-described, which consists in pro-
viding a furnace with a partial-charge-of- purified-molten-metal,-intermittently
charging impure-or-partially-purified-metal-into-the-purified molten metal in said
furnace, and--intermittently--withdrawing--portions--of--said--metal-as -it-is--thus
purified.
3.-The-process-of-refining-metal, in-making open hearth-steel, which consists in
providing a furnace with a partial charge of purified molten metal, pouring-a-charge
or-charges of impure or partially purified-metal into the-partial-charge-of--purified
molten-metal-in said furnace, and, after the purification of the mixed charge is
effected, drawing off a portion of the same, leaving the remainder of the molten
charge-in-the-furnace for admixture with a fresh-charge or charges of impure or
partially-purified-metal,-substantially-as-specified.
4. 1. The process of refining metal, in making open hearth steel, which consists in
providing a furnace with a partial charge of purified molten steel metal, having a
covering of slag, pouring a charge of impure or partially purified molten metal
through said slag and into the partial charge of purified molten steel metal in said
furnace, and, after the purification of the mixed charge is effected, drawing off a
portion of the same, and leaving the remainder of the molten charge steel in the furnace
for admixture with a fresh molten charge of impure or partially purified metal,
substantially as specified.
5. 2. The process of refining metal, as herein described, which consists in inter-
mittingly charging unrefined metal into a heating furnace containing refined steel
metal having a covering of slag, and intermittingly withdrawing portions of molten

page_text: steel metal as it is refined by filtration through said covering of slag and admixture
with said refined molten steel metal.
6. The--process of refining metal,--as-herein--described, which comprises, first,
purifying liquid-pig-metal-by pouring it into a bath of desiliconised-metal, then,
pouring the metal thus purified into-a-second-buth-of-metal-of greater-purity;
thereby-producing steel-by-continuous refining.
W. P. THOMPSON & Co.,
322, High Holborn, London, W.C., Patent Agents for the Applicant.