An Improved Method of Treating Metallic Articles to Render them Non-corrodible.
Year: 1888

page_text: COMPLETE SPECIFICATION.
An Improved Method of Treating Metallic Articles to Render them
Non-corrodible.
I, GEORGE WELTDEN GESNER of 45 Cliff Street, New York in the County and
State of New York United States of America, Consulting chemist and 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 relates to the treatment of metals in order to render them non-
corrodible.
The object of the invention is to heat metals whereby a surface will be imparted
thereto composed of an alloy or compound homogeneous with the body of the metal
of a practically non-corrodible nature, and at the same time the ductility, toughness,
and tensile strength will not be diminished, without any material increase in the
dimensions of the articles and without the formation of scale or film.
My invention consists in the method of treating metallic articles in a suitable retort
from which atmospheric air is excluded by the application to said articles of super-
heated steam, next in applying to said articles commingled superheated steam and
hydrocarbon vapors to form an alloy or compound with the metal treated, and finally,
in the application of a fixing agent whereby the alloyed or compound surface previously
formed is fixed, the said articles by this treatment having their surfaces changed so as
to be practically non-corrodible.
Further, consists in the treatment of metallic articles in a retort from which
atmospheric air is excluded by superheated steam of approximately the same or of a
higher temperature than that maintained within the retort, by the vapors of commingled
superheated steam and hydrocarbon, and, finally, by a fixing agent, whereby the alloyed
or compound surface formed by the action of the first three agents is fixed by the action
of the last.
In the accompanying drawings, Figure 1 represents a muffle with the superheater
inclosed within the same, with articles to be treated supported within the vertical
portion of the muffle. Fig. 2 is a section of a retort, showing a suitable reservoir for

page_text: the liquid naphtha or other agents used in the treatment of the articles. Fig. 3
represents a modified form of muffle for treating large articles. Figs. 4 and 5 are
detail views of a form of superheater.
Heretofore it has been proposed to treat metals for the purpose of surfacing them by
the use of superheated steam and hydrocarbon vapour by the application first of the
superheated steam and then of the hydrocarbon vapor, or of the two together, these
two constituting the steps of the process, which might be repeated any desired number
of times, such repetition, however, being always a repetition of the two steps, in
which the application of the hydrocarbon vapour was always the last step.
Heretofore superheated steam, when introduced into a closed retort or muffle for the
treatment of metals, has not been at the temperatures required for the treatment of
different classes of articles, and as uniformity in temperature between the superheated
steam used and the articles under treatment while in preparation for the formation of
a homogeneous alloy thereon is important therefor, 1 have endeavored to obtain the
desired result by arranging superheaters in the bench containing the muffles and also
superheaters within the muffles themselves and heated by the same fire that heats the
muffles, whereby the superheated steam passing from the superheater in the inuffle
upon the heated metallic articles under treatment therein shall have its temperature
automatically maintained at or nearly the same degree of Fahrenheit as the articles
then under treatment, varying in temperature whenever the temperature of the muffle
is varied to meet the varying conditions of such treatment.
A
In Fig. 1. I have shown at A an ordinary form of muffle from which the atmospheric
air is excluded, which, it will be understood, may be one of many within a bench.
The opening in the horizontal part of the muffle is provided with the ordinary mouth-
piece and lid, as shown. A suitable furnace is shown below the muffle, and this may
be fed with coal or liquid fuel, gases, or vapors in any well known manner.
superheater, C, is shown as located upon the floor of the muffle, and may be of the
form shown or of any suitable construction. The steam-pipe, a, leading to it may
come from any suitable source, such as a boiler or supplemental superheater. The
particular form of superheater represented within the muffle is shown in detail in
Figs. 4 and 5. It consists of a chamber in arched form, the steam from the boiler or
supplemental superheater entering at the front wall, and, after being superheated to
the same temperature as the retort, passes out at the rear into the retort. I also use
hydrocarbon oil or the vapors of hydrocarbon, or both, in my process, as described
hereinafter, and the pipe for the liquid or vapor is represented at 6. The arched form of
superheater permits a branch, c, of the pipe to extend through the same and the liquid
hydrocarbon (if liquid be used) to be partially vaporized in its passage, this pipe uniting
with the pipe for the superheated steam in the rear of the superheater. The articles to
be treated are arranged within the muffle either horizontally or vertically, and are
supported in such a manner as to expose the greatest amount of surface for the action
of the different agents used.
In Fig. 1 I have shown as one means of support grate bars having knife-edges
providing ample support and at the same time allowing the agents used to reach all
parts of the surface of the articles under treatment. It will be understood that many
modified forms of these devices may be used, varying according to conditions. The
hydrocarbon used may be, as I have before stated, either in liquid form or in the form
of vapor from a suitable vaporizer, and I have shown in Fig. 2 one form of reservoir
for liquid hydrocarbon. In this figure the muffle is shown at A, with the hydrocarbon
reservoir at B, contained within a steam-space, and having a funnel-shaped mouth with
a suitable valve to allow its being filled with the liquid. The lower end of the reservoir
is contracted into the form of a nipple, and extends into the pipe which conveys the
superheated steam to the muffle. A suitable valve is also located at the lower end of
the reservoir, to control the feed of the contents. A spraying device of any suitable
form is located upon the end of the pipe within the muffle for the better distribution of
the superheated steam and the mingled steam and hydrocarbon vapor. The vapor is fed
out by gravity and by injection.
It will be understood that while I have shown in one figure the superheater as

page_text: being within the muffle I do not limit myself to one superheater only, as others may
he located at any convenient place within the bench, it being necessary only that the
steam should be superheated by the same fire which heats the muffle, and thereafter
be delivered upon the articles under treatment in the muffle at a uniform temperature
equal to that which is at that time required for the articles under treatment.
In the treatment of metals by my improved method I place the articles to be treated
within the muffle and support them, as before described, so that all parts will be
exposed to the action of the agents employed, it being understood that the niuffle is
previously heated, the temperature varying according to the requirements of the article
to be treated. After the articles are heated to the temperature of the muffle, I
subject the article to the action of superheated steam, which is at the same or a higher
temperature than the muffle in which the articles are treated, and the effect of this
treatment is to open the pores and to prepare the article for the subsequent treatment.
After the action of the superheated steam has continued for a proper length of time,
(the time varying with the character of the article to be treated,) I subject the article
to the action of superheated steam, and the vapor of hydrocarbon either mingled outside
the muffle or within, and the effect of this is to complete the combination and to fill up
the pores of the article previously prepared with the carbon thus introduced. (I have
found by experiment that in the treatment of some articles hydrocarbon in a liquid form
discharged into the muffle is desirable, and for other articles I have found the vapor to
give the best results.) After the articles have been subjected a proper length of time,
(which, as in the first case, varies with the character of the articles to be treated,)
shut off the superheated steam and hydrocarbon and then subject the articles to the
action of a fixing agent, such as superheated steam, which completes the treatment
necessary to preserve the homogeneous non-corrodible compound.
The
In the treatment of large articles-as for instance, a piece of ordnance-the
temperature of the muffle must not be less than 1,000° Fahrenheit during the treatment
to form the surface. The superheated steam must be admitted to the muffle at the
stated or a higher temperature, and the article is subjected to the action of the steam,
varying from thirty to ninety minutes, according to the density of the metal.
mingled steam and vapour is then admitted and the article subjected to the action
thereof from ten to twenty minutes, and finally to the action of the fixing agent from
five to twenty minutes. As above stated, the temperatures and time of treatment by
the various agents employed vary according to the size of the article and the density
of the metal. The exact operation of the superheated steam as a fixing agent from a
chemical point of view I am at present unable to fully explain but I have found by
actual experiment that it removes from the surface all extraneous matter, leaving it
perfectly clean, absorbing any excess of hydrocarbon, and that it serves to give a superior
hardened and finished surface not obtainable when the iron is subjected to a final
treatment under exposure to any hydrocarbon vapor or similar gas; but my invention
is distinguished in this respect from any similar processes heretofore known to me in
which the fixing agent, whether it be superheated steam or hydrogen or equivalent gas
under high heat and without the presence of oxygen or atmospheric air, is used as a
surfacing agent.
:
While I prefer to use superheated steam as the fixing agent, other agents-such as
hydrogen gas or carbonic-oxide or carbonic-acid gas mixed with steam-may be used.
It is important, in the method above described, that the superheated steam should be
of at least the same temperature as that of the muffle, and never below it.
As a continuation of the treatment just described, I withdraw the articles from the
muffle and immerse them while hot, but at a lower temperature than when treated, in a
fluid tempering bath. This latter step in the process increases the non-corrodible nature
of the articles; but it will be understood that many articles will not require this
latter step.
In Fig. 3 I have represented a muffle for the treatment of large articles, such as
ordnance.
The process heretofore described is carried on in like manner except as to variation
of the time required, and after the surface of the article has become homogeneous and

page_text: non-corrodible by the treatment the muffle is made to serve the purpose of an annealing
chamber by providing a fan to draw off the heated contents of the chamber and by
reducing the heat of the furnace, and I then apply to the article a freezing-mixture
supplied from a suitable reservoir, which is an equivalent and acts in substantially the
same manner as the tempering-bath referred to for articles of smaller size. By this
method of treatment the heaviest articles can be treated in one chamber without the
necessity of their removal until they are finished.
1 have shown in Fig. 1 a pipe leading from the muffle to a hydraulic seal for
regulating the pressure within the muffle, and I connect the cap of this seal with a
pipe extending to the point of combustion of the furnace over the grate. A discharge
siphon-trap is connected with the hydraulic seal. When the pressure within the muffle
is ordinary, the gases escape through the pipe, passing upward, being cleansed in the
water of the seal, and through the connecting-pipe to point of combustion, where they
are burned; but in case the pressure is excessive and the connecting-pipe to the point
of combustion not sufficient to carry them off, they are simply blown out through the
siphon. This automatic regulator saves the muffle from any injurious effects caused
by sudden increase of pressure.
Having now particularly described and ascertained the nature of my said Inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. The described method of treating metallic articles for changing their surfaces to
an alloy or compound homogeneous with the body metal of a practically non-corrodible
nature, consisting in applying to said articles within a suitable retort from which
atmospheric air is excluded, first, superheated steam; second, commingled superheated
steam and hydrocarbon to form the alloy or compound, and, finally a fixing agent
whereby the alloyed surface previously formed is fixed, substantially as described.
2. The described method of treating metallic articles to change the surface to an
alloy or compound homogeneous with the body metal, consisting in the treatment of
said articles in a retort from which atmospheric air is excluded by superheated steam
of the same or a higher temperature as the retort: second by commingled superheated
steam and hydrocarbon, and, finally, by a fixing agent, whereby the alloyed or com-
pound surface formed by the action of the first three agents is fixed by the action of
the last, substantially as described.