Improvements in the Treatment of Waste Tinned Steel or Iron.
Year: 1891

page_text: Date of Application, 12th May, 1891-Accepted, 20th June, 1891
COMPLETE SPECIFICATION.
Improvements in the Treatment of Waste Tinned Steel or Iron.
I, BENJAMIN JOSEPH BARNARD MILLS of 23 Southampton Buildings in the
County of Middlesex Patent Agent do hereby declare the nature of this invention
a communication to me from William Lorenzo Brockway of the City County
and State of New York, United States of America Manufacturer, and in what
manner the same is to be performed to be particularly described and ascertained in
and by the following statement:—
The invention consists in treating old tinned steel or iron and especially the
material of old tin cans and like articles in a certain manner whereby the sheet iron
or steel, which is ordinarily of very good quality, the tin thereon and the lead in
the solder when such solder is used, are separated and saved, and are so treated
that each material becomes commercially valuable. Since the improvement does
not reside in any particular apparatus, but may be practiced by any apparatus
adapted to accomplish the steps hereafter recited no apparatus is illustrated."
It has been heretofore proposed to separate the iron or steel, tin and lead, and to
utilize one or more of the materials. According to one method, the old material
was placed in a suitable receptacle and heated by an electric current to a
temperature sufficiently high to melt and remove the tin and lead. This method
has been found objectionable by reason of its expensiveness and because the paper,
dirt, grease &c. on the old material seriously interferes with the proper passage of
the current. In other methods certain chemical substances have been employed to
dissolve or combine with one or more of the metals. This class of processes is also
expensive, because the chemical substances used are expensive, and because it
requires one or more additional steps to reduce the compound formed to metallic
tin, lead or iron as the case may be. According to a third process the cans &c.
were placed in a suitable oven and the temperature raised to a high heat-about
1000° Fahrenheit-which was found sufficient to melt and remove the tin and lead.
The iron was allowed to cool gradually and was thereby partially annealed after
which the bodies of the cans were straightened, and were then in condition to be
used. By this process the tin and lead were not saved, the heat in the open oven
being such as to oxidize and practically destroy them.
It has been found that by heating the waste material in a furnace, the heating
chamber of which is hermetically scaled or from which air is wholly or to a large
extent excluded the temperature of the furnace can be raised as high as above
indicated (10000) Fahrenheit or somewhat higher without injuring the steel or iron,
and without oxidizing the tin to a harmful extent. This heating of the cans or
other old tinned metal in a furnace from which the air is practically excluded forms
one feature of the invention. After heating, the cans are removed from the furnace
and straightened out, and the bottoms and the bodies of the cans put in piles by
themselves and are afterwards carefully annealed, and when cold are rolled down
to the required thinness. Several plates are cold rolled at once.
'
I will now describe the best manner of carrying out the improvements. Into a
heating chamber of a furnace of any suitable construction I place a charge of tin
cans or other old tinned iron or steel. If the cans are of the size ordinarily used
The
for fruits, vegetables &c. the charge may consist of several hundred cans."
furnace is then closed and the iron of the cans or other material brought to a cherry
red or approximately to that temperature. Tin melts at about 450° Fahrenheit
but will not entirely leave the iron or steel until subjected to a temperature of about
1000° Fahrenheit. At this high temperature there is danger of oxidizing the iron

page_text: and volatilizing the tin, but the use of a closed furnace, as described in this
Specification very largely removes this danger.
When
This step of the process may take from three to seven minutes, the time depending
on the size and weight of the cans and other modifying causes. The draught of
the furnace should be so regulated by dampers that the air entering the combustion
chamber will be thoroughly consumed or oxidized, so that the heated products of
combustion may pass to the heating chamber practically free from air, and may
thus be unable to oxidize the metals therein. The tin and lead will drop to the
bottom of the furnace, and may be directed into proper receptacles, after which the
tin and lead may be separated and put in proper form for the market.
the material consists of cans the bodies of the cans are partially straightened out and
put into a press, or are run through rolls, and thoroughly flattened out and are then
bound up into bundles preferably weighing about seventy five pounds, since such
bundles are of convenient size for handling. Said bundles are put into tightly
closed annealing pots, the plates preferably being placed on edge and supported
above the bottom of the annealing pot or chamber so that the heat can circulate
entirely around the plates, and the pots are placed in the furnace and the plates
thoroughly annealed. It is well though not essential, to prolong this step to ten or
more hours.
When the plates are thus freed from tin, and are annealed, they are placed in a
pickle to remove the small amount of scale that is formed on them after which they
are dried. Several of the plates are then piled together and passed between heavy
rolls until they are reduced to the desired thinness. The body of an ordinary fruit
can when straightened out is about 5" x 13" inches, and in thickness is from
about No. 28 to No. 30 Stubs gauge and when rolled to form a plate of about
9 × 13 inches it will be from No. 34 to No. 38 gauge in thickness. By rolling the
plates cold, and several together, as above described, they can be made as thin as
foil. It is found that this cannot be done practically with hot rolling, since the
plates crack during the treatment. When very thin plates are desired it is some-
times necessary or best to anneal the iron one or more times during the rolling.
After the rolling is completed I sometimes anneal the plates, preferably by placing
several plates together, then placing on them a weight in the form of a thick iron
plate, adding more of the thin plates and another weight until a pile of sufficient
size is obtained. The weights serve to hold the thin plates in shape. When the
plates are removed from the annealing pot they will have an uniform dead black
color.
The iron plates produced as above described are trimmed to remove the ragged
edges, and are then ready for market. The trimming may be done before the
annealing if desired. The plates produced form a fine grade of Taggers iron or
steel (or when tinned of Taggers tin) are superior in quality and finish to the plates
made from original ore. The cold rolling process gives the surface a hard smooth
finish admirably adapted to receive a polish, a copper, a nickel or other plating,
enamelling, a coating of tin &c.
It is proposed to employ the bottoms of ordinary tinned iron or steel cans when
freed from tin and annealed, but without rolling down, for making blacking boxes
and other articles of marketable value, since the bottoms are about the right size,
can be stamped up very readily; after being stamped they may be tinned or
otherwise coated.
and
The bodies of the cans, when treated as I have above set forth may be used for
making buttons, ferro-type plates, lye cans, copper plated, brass plated, tinned
nickled, or other foil or plates, or for any other purpose to which a tough, high
grade, iron plate or tin foil is adapted. When used for ferro-type plates and
certain other articles, it is found desirable, after treating the plates as above
described, to pass them separately between heavy rollers for still further com-
pressing, polishing and finishing the surface. After the tin is removed the iron
may be used without going through the subsequent steps for binding trunks &c.

page_text: Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is.
The improvements in the treatment of waste tinned iron or steel, whereby the
tin, iron and other metal are saved, which consists in heating the tinned metal to a
temperature sufficient to melt and remove the tin, in a heating chamber from which
air is excluded to prevent oxidation, collecting the tin; and cold rolling the iron
or steel plates from which the tin has been removed, with or without annealing
said plates.
R
1001
Dated bis 12 qty of
LOOL
B. J. B. MILLS.
By Harris & Mills,
23, Southampton Buildings, London, Agents.