An Improved Process for Treating Iron, Steel, and other Metals, to Prevent Oxidation thereof while in a Heated State.
Year: 1889

page_text: Date of Application, 20th Aug., 1889-Accepted, 21st Sept., 1889
COMPLETE SPECIFICATION.
[Communicated from abroad by GEORGE WYCKOFF CUMMINS, Student, and JAMES
HENRY COLEMAN, Engineer, both of No. 337, West 57th Street, in the City and
State of New York, United States of America.]
An Improved Process for Treating Iron, Steel, and other Metals, to
Prevent Oxidation thereof while in a Heated State.
I, HENRY HARRIS LAKE, of the firm of Haseltine, Lake & Co. Patent Agents,
Southampton Buildings, in the County of Middlesex 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 :-
This invention relates to an improved process of preventing the oxidation of iron,
steel or other metals while in a heated condition, notably while undergoing such
heating as is usual in annealing operations, which invention is hereinafter fully set
forth.
An apparatus or plant suitable for carrying out this invention is illustrated in the
accompanying drawing in which :-
Figure 1 shows, in sectional side elevation, a view of the entire plant.
Figure 2 shows, in front elevation, a generator or furnace, forming part of
Figure 1.
Figure 3 is a rear elevation of said generator or furnace.
In said Figures the same parts are indicated by similar numbers and letters of
reference.
1 indicates a gas generator; 2 a cooler; 3 a desiccator, and 4 an annealing pot or
chamber. The cooler and annealing pot may be cylindrical in exterior shape, if
preferred; and the desiccator preferably square or rectangular. The several parts
above named may be described as follows:-
The furnace or generator 1, consists of cast-iron retorts A, two or more in number,
protected by fire-brick B, set within ordinary brickwork A¹, such as is used for the
setting of coal-gas-retorts. The retorts A are heated by a furnace or furnaces C
provided with grates c and appropriate flues, as in furnaces for the generation of
coal gas.
The retorts A are each closed by doors d at each end, and provided, at one end
with an inlet pipe D, and at the other end with an outlet pipe E each of which out-
lets delivers into one common outlet pipe H. The pipe F connects the two pipes E,
and from the pipe F the pipe G leads to the escape flue or chimney I; valves K, L
and M, govern the flow of the gas as desired the special office of which valves will
be hereinafter more particularly described.
The cooler 2 may be made with a worm was shown in the drawing, for the gas
to pass through like any common "still" or condenser, any moisture condensed within
said worm from the gas being drawn off through the cock N, the cooling water
entering at a and leaving at b, or vice versa.
A gas holder of any common and well known form, such as is used for storing
common illuminating gas, may be, if desired, located between the cooler 2 and the
desiccator 3. The size of this holder will be determined by the quantity of gas
desired to be stored; the smaller its size, however, the less costly the construction
and materials of the holder will be.
The desiccator 3 consists of a closed box or chamber, containing trays or shelves t
on which is placed fused calcium chloride. Said trays are so arranged that the gas
entering at o must pass over a considerable surface of said chloride before emerging
at P. Instead of calcium chloride, pumice stone moistened with concentrated
sulphuric acid may be substituted. This substituted desiccating material has the
advantage that the pumice stone does not need removal or renewal; for, so long as

page_text: supplied with the acid, it is a rapid and thorough desiccator. The acid is readily
renewed without opening the desiccator, by permitting it to trickle or fall in drops
on the pumice stone, through suitable pipes or orifices in the walls of the desiccator,
over the pumice stone.
Of course it is understood that iron or steel when heated to redness, readily absorbs
oxygen at its surface from atmospheric air, or any other source from which it can
obtain oxygen; the surface of the metal thereby becoming rough and covered with
scales of oxide. The endeavour, therefore, under such circumstances in the treatment
of metals, is to exclude as far as possible from the presence of the hot metal all
sources or media whence it can absorb oxygen. Even in annealing heretofore, while
the annealing vessels were closed air-tight, the residual atmosphere present always
exercised deleterious influence upon the metal being annealed.
This invention excludes the atmosphere and substitutes therefor an artificial atmos-
phere, which entirely surrounds the metal from before it is heated until it has been
cooled, or through the annealing process of both heating and again cooling. The
artificial atmosphere or gas, used by me for this purpose may be said to be a mixture
of nitrogen, carbonic oxide and carbonic acid (N., CO, CO₂) entirely freed from the
vapor of water.
Without confining myself to these proportions, it may be stated
that the gas may consist of about 68 per cent. of nitrogen; about 27 to 33 per cent. of
carbonic oxide; and from a trace to about four per cent. of carbonic acid. The gas as
prepared in the process below described is non-inflammable and non-explosive and is
entirely inert as to any action upon iron or steel or other oxidizable metals, at any
temperature, but a perfect preventive of oxidation while the metal is excluded from
the air by its presence.
The method of manufacturing the gas necessary for conducting the operation of
treating the metal therewith and the process of so treating the metal will now be
described.
When the retort A has been heated to incandescence by the furnace C, the former
is filled with charcoal, or coke, which, as soon as it becomes sufficiently heated,
evolves a gas somewhat of the nature of ordinary coal gas, but as such gas had nearly
all been previously removed from the charcoal or coke, in the production of the same,
the evolution of such gas is of short duration.
This preliminary gas product is inflammable, and not at all suited to the purposes
of the invention. On the contrary it is injurious to the metal to be treated. Said
gas is therefore permitted to escape through the pipes G and For F¹ provided with
the valves K, K₁ and L, L.
When the evolution of said gas ceases, a current or blast of air is introduced at J,
through the pipe or pipes D, and valve or valves M from any suitable blower (not
shown) and forced through the mass of incandescent charcoal or coke. This blast is
permitted for a short time to escape into the atmosphere, through the pipe G and flue
or chimney I. When all watery and hydrocarbon vapors have been thus expelled
from the charcoal or coke, the gas then evolved by the blast of air may be regarded
as consisting essentially of nitrogen, carbonic oxide and carbonic acid, the first and
last gases being considerably in excess of the carbonic oxide. This mixture of gases,
though possibly retaining a trace of watery vapor, is ready and fit to be passed from
the generator 1 to the cooler 2, and thence through the desiccator 3.
In its passage
through this latter vessel, the last trace of watery vapor is removed from the gas, and
it is then in suitable condition to be passed into the annealing chamber or pot, or it
may be first stored in a gas holder, such as above described, until needed for use in
the annealing process.
In the practical conduct of the operation only one of the retorts A need be used at
the same time for the production of the blast gas. Immediately upon ceasing to use
the gas from one retort and commencing to use it from the other, the charge of char-
coal, or coke is renewed in the first retort and allowed to become heated until the
charge in the second retort is about half exhausted by the air blast. By this time.
the charge in the first retort has reached the condition of freedom, more or less com-
plete, from watery and hydrocarbon vapors previously described, and the blast of air

page_text: is again passed through the first retort, when the second retort is recharged and the
same round of operations continuously carried on at will.
By such mode of operation a constant production and supply of suitable blast-gas is
secured.
The annealing chambers, boxes or pots, are kept filled with the gas under a steady
pressure while the same are both being heated and while being permitted to cool, the
gas entering through pipe S and valve R and leaving through pipe T and valve V.
Upon the removal therefrom of the articles subjected to such gas in the annealing
process no change whatever will be observed to have been produced in bright iron,
steel or other oxidizable metal due to its exposure to such gas.
The air is forced through the retorts by displacement rather than exhausted there-
from, because any leakage that may occur must be outwards and not inwards; for, if
the leakage were inwards, the admixture of external air that would in such manner
take place would change essentially and deteriorate the properties of the gas.
Even were the blast-gas absolutely free from watery vapor when leaving the
retorts, the interposition of the cooler is necessary; for, if the blast gas were permitted
while hot to enter the cold annealing vessels, and while the metal therein was sur-
rounded with cold air, the admixture of the hot gas with such cold air would create a
As it is necessary to
medium surrounding the metal that would oxidize the metal.
start the operation only when the annealing vessel is cold and to keep up the blast of
gas until the annealing is complete, by which time the annealing vessel has cooled
down considerably, though not necessarily enough for a fresh start, the further cooling
of such a vessel may be hastened somewhat, if desired, by passing the cold gas through
it before starting a new annealing operation.
Oxidizable metals treated by this process are especially well suited to be plated
with non-oxidizable metals (or galvanized) by reason of the bright, smooth and clean
surface they possess, entirely free from the roughness and foreign element of
oxidation.
I do not confine myself to the apparatus or plant herein described for generating
and applying the gases named, as it is evident that the apparatus may
be greatly
varied without changing the process or the product.
Having now particularly described and ascertained the nature of the said invention
and in what manner the same is to be performed as communicated to me by my
Foreign Correspondenis I declare that what I claim is :-
First. The hereinbefore described process of treating metals to prevent their oxida-
tion while in a heated state, consisting in subjecting such metals in an air-tight vessel
to an atmosphere composed of the gases derived from passing atmospheric air over
incandescent carbonaceous material in a retort, after the earlier gaseous products of
distillation have been removed from said carbonaceous material, substantially as and
for the purposes set forth.
Second. The herein before described process of treating metals to prevent their
oxidation, while in a heated state, consisting in subjecting such metals to an atmo-
sphere composed of nitrogen and carbonic oxide, with or without carbonic acid, the
carbonic oxide being in sufficient excess to overcome any tendency of the carbonic
acid, if present, to oxidize the metal, substantially as set forth.
Dated this 2011 ICA 1920
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.