Improvements in the Manufacture of Tin, Terne, and like Plates.
Year: 1898

page_text: Date of Application, 6th May, 1898
Complete Specification Left, 28th Jan., 1899-Accepted, 25th Mar., 1899
[Communicated from abroad by WILLIAM ROGERS, of Leechburg, in the County
of Armstrong, State of Pennsylvania, one of the United States of America,
Engineer.]
Improvements in the Manufacture of Tin, Terne, and like Plates.
I, WILLIAM BURGELAND JOHNSON, of 4, Clayton Square, Liverpool, in the
County of Lancaster, Engineer, do hereby declare the nature of this invention
to be as follows:-
My improved process consists of two principal steps first, the annealing and
purifying of the sheets of iron from oxygen and carbon before tinning, and,
second, the coating of the sheets with tin or, other suitable metal.
In the ordinary process of making tin plate the sheets, having been hot rolled
to the desired size and thickness, are first pickled in heated sulphuric or hydro-
chloric acid to remove the surface oxide or scale, which is called black pickling,
and then washed several times in water to remove all trace of the acid; they are
then placed in a closed iron box and subjected to the heat of a furnace to anneal
or soften them, and gradually cooled, out of access to the atmosphere; they are
then cold rolled between polished rolls to remove the roughness of the surface
caused by the formation and removal of surface oxide, which gives them a close
texture and a polished appearance; they are then again annealed in like manner
as before, pickled and washed, after which they are ready for tinning. This second
pickling is usually necessary to remove the oxide from the edges of the sheet and
is injurious to the central part of the sheet from which the oxide has been removed
by the first pickling.
In my process the preparing of the plates for tinning differs essentially from
that just described, among others, in the following important particulars: First.
Great care is taken to protect the sheets after they are rolled and during the
annealing process from the action of oxygen of the atmosphere, and to surround
them with a substance which is neither carburizing nor oxidizing, for the exclu-
sion of atmospheric air, so that the formation of further scale on the surface of
the iron is prevented, and by the mutual reaction of the oxide on the surface of
the iron sheets and of the carbon contained in the body of the iron, it may be
both deoxidized and decarburized on exposure to the heat of the furnace. By
this means the removal of the scale resulting from the exposure of the heated
plates to the air during rolling is rendered not only unnecessary, but undesirable,
and the roughness of the sheets caused by the formation of scale and its removal
by acid treatment is largely prevented. The body of the metal in the sheets
being thus purified by the complete decarbonization resulting from my process
of annealing, and by the reduction of any surface oxide, the sheets acquire a
remarkable degree of softness and flexibility indicating an unusual degree of
freedom from either carbon or oxygen.
By my process, therefore, I dispense with the black pickling in acid, ordinarily
practiced after hot rolling, because the surface scale then formed is not only

page_text: removed by the annealing process, but serves a useful purpose in the annealing
chamber, and I also dispense with the cold rolling ordinarily practiced after the
first annealing, because such rolling has the effect of compacting the iron, and
if practiced in my process would tend to destroy its porous condition resulting
from decarbonization; and as a consequence, I further dispense with the second
annealing of the sheets which is practised in the usual method for the purpose of
removing the stiffness due to the cold rolling.
The result of the porous texture given to the iron sheets by my method of
annealing is that the tin or other coating metal, when in a liquid condition,
enters the pores of the iron, forming an union more resembling a chemical than
a mechanical combination of the iron and coating metal, and is pressed into a
very perfect union by the final rolling; besides which the great freedom of the
iron from the presence of either carbon or oxygen gives it an extraordinary degree.
of softness and flexibility.
In practicing my invention the sheets of iron, having been first hot rolled in
the usual way to the desired size and thickness, are placed, without previous
removal of scale by pickling or otherwise, in a pack of say 500 to 600 sheets,
more or less, in an annealing box, so constructed as to permit of the sheets being
easily placed therein and removed therefrom, and at the same time to permit the
use of means to exclude the admission of atmospheric air.
For annealing the plates or sheets I use an annealing box made preferably of
cast-iron, though strong wrought-iron plates may be used in its construction, or
clay, such as is used in the manufacture of glass-melting pots. This box is
closed at the top and at the sides, being made air-tight, and in use is set with
the open bottom downwards on a base plate on which the open end of the box
rests. The base-plate is surrounded with a flange, so that pulverized material,
sufficiently refractory to stand the heat of the furnace, such as pulverized iron
ore, sand, or dolomite, is placed so as to prevent the access of air into the box.
The sheets of iron or steel are placed in a pack on the base-plate and are covered
by an envelope, preferably of sheet iron, which may be made in the shape of a
box, either in one part with an open bottom, or in two parts fitting telescopically
one over the other. The outer box is then placed over the envelope and is large
enough to leave a space of about two inches on top and around the inner box
or envelope which covers the sheets, and in this space is introduced sand, pulver-
ized iron ore, or dolomite, which will resist the action of the heat. This pul-
verized material is inserted into the space around the sheets through small openings
in the top of the outer box and may be rammed compactly by means of an iron
rod.
Another construction of annealing box consists of a box of cast-iron or other
suitable material, closed at bottom and open at top, where it is enclosed by a
covering plate. The sheets of iron or steel are placed in a pack surrounded by a
case or envelope, preferably of sheet iron, which is covered over at the top to
prevent the entrance of sand, iron ore, or dolomite placed within the outer anneal-
ing box, and on top and around the sides of the inner box to a thickness of about
two inches and may be rammed in place. The purpose of this arrangement is
not merely to exclude the atmospheric air, nor is the pulverized material designed
to act chemically on the sheets of metal, but the purpose is to enclose them, as
it were, in an oven, so that, under the influence of the furnace heat to which
the annealing box is exposed, the oxygen of the surface scale or oxide on the
sheets, and the carbon contained in the body of the iron may mutually re-act,
forming carbon dioxide which escapes from the iron sheets. It may, in some
cases, be found desirable, where the amount of oxide on the surface of the iron
is considerable, to place some sawdust or other carbonaceous matter around the
bottom of the pile of sheets within the envelope, but this I have found to be
ordinarily unnecessary, and as a general practice I prefer to introduce nothing
into the annealing box around the sheets that will have any decided chemical
action thereon; but I have also found that iron ore (oxide) in a pulverized cou-

page_text: dition operates well and does not seem to hinder the deoxidation of the sheets.
The annealing box with its contents is then placed in a reverberating or other
suitable furnace, and is therein exposed to a suitable heat, say about 2500 degrees
Fahrenheit, for about ten hours, more or less, according to the size of the anneal-
ing box and the amount of sheets of iron to be. annealed.
Preferably these annealing boxes are removable from the furnace for the pur-
pose of charging them and of removing the contents. It is necessary that the
sheets when removed from the annealing box should be cold, or so nearly so as
not to be liable to the danger of oxidation of the surface of the metal when
exposed to the air.
The sheets of iron should be allowed to become sufficiently cold to prevent
oxidation on exposure to the external air, before their removal from the anneal-
ing-box.
The result of annealing the sheets in the manner described is that they are of
a dull silver-like or leaden appearance, and are, when removed from the anneal-
ing box, very flexible, indicating that reaction between the oxide scale on the
surface of the iron, and the carbon contained in the body of the iron, has resulted
in the removal of the oxygen and carbon which was present on or in the sheets of
iron before the annealing operation commenced.
If there should be any appearance of surface oxidation remaining on any of
the sheets when removed from the annealing box, such sheets should be sub-
jected, for a few minutes only, to immersion in a bath of a weak solution of
muriatic or sulphuric acid in water, and then thoroughly washed with alkaline
water, such as lime water, to remove any trace of acid which would be injurious
to the sheets.
Another advantage of the method of annealing the sheets which I have described
is that the effect on each sheet is very uniform so that the edges are deoxidized
as thoroughly as other parts of the sheets, a result difficult to attain by the
ordinary methods.
After the sheets have been annealed, and freed from scale as described, and
cool enough to prevent oxidation, they are immersed in water for about half an
hour to wash off any particles of oxide which may yet remain adhering to their
surface, and are then ready for the tinning process, as before stated, the iron
being in a slightly porous condition, so that the coating of tin takes a firmer
hold on the surface of the plates.
In my process of tinning the sheets are first dipped in a pot of grease which
may be of any desired construction, and therefore does not need any special
description. The grease I prefer to use is a tallow, which should be as free as
possible from acid, and which is kept in a melted condition by the frequent con-
tact with the iron sheets which are still warm enough for the purpose; or,
the grease used is of such consistency as to require it, a furnace may be placed
under the grease pot with side flues. These sheets, with their coating of grease,
are then placed one by one in a vertical position in a rack which may hold any
convenient number of plates, say from 50 to 100. This rack is suspended verti-
cally over a tin pot, from a small steam cylinder or other device, by which the
rack, with its burden of iron plates, may be repeatedly and rapidly raised and
lowered. The tin pot is heated by a furnace placed underneath it and hot air
flues at the sides.
The purpose of the rack is not chiefly the convenience of handling, but it also
enables the sheets to be repeatedly and quickly dipped into the molten tin, the
effect of which is that as the molten tin has a greater affinity for oxygen than
has the black plate (iron or steel) at a temperature of about 450 degrees F., this
fact, together with the friction created between the melted tin and the surface
of the sheets, aids in the removal therefrom of any particles of scale or oxide
which may have been formed on their surfaces during the water washing before
mentioned.
The tin in this pot or tank should be kept at as nearly a constantly uniform.

page_text: temperature of about 400 degrees Fahrenheit as possible, or at a heat sufficiently
above the melting point of the coating metal, whatever it may be, to keep it in
a perfectly liquid condition, and the immersion of the sheets in the tin bath
should be continued for about ten minutes.
The sheets thus tinned are then removed from the rack to another bath of
molten tin which is at a temperature somewhat (say about 25 degrees Fahrenheit)
lower than the tin in the first tin pot. This bath may be of less width than the
first tin pot, because the sheets need not be held apart at this dipping as they
are by the rack. This bath may be heated by a furnace with side flues. From
this bath the tinned sheets are removed one by one to a grease pot which is heated
by a furnace and side flues.
The grease pot contains grease, but if desired it may also contain molten tin,
if a third dipping in tin is deemed desirable. The tank may be filled with molten
tin up to a certain line and when this is the case the grease, of course, floats on
the surface of the molten metal. In order to prevent the grease being set on fire
by the heat of the molten tin, it is kept comparatively cool by means of a set of
horizontal pipes passed through the tank near to its upper edge, through which
cold water or air is caused to pass, and then the grease is kept at a temperature
of about 150 Fahrenheit. Into this pot, whether it be filled with grease alone,
or also with melted tin, the sheets are immersed one by one in a vertical or sub-
stantially vertical direction, and are immediately raised and delivered out of the
pot, the delivering rolls forcibly compressing the tinned sheet and giving it a
polished surface. This is effected by means of two pairs of rolls (preferably,
although one pair might suffice). The upper pair are made of polished steel, the
lower pair preferably of copper. These rolls are placed near the top of the grease
pot so as to be immersed in the grease, and if tin is used, in contact therewith,
so that both pairs of rolls shall be coated with tin.
The rolls of each pair are preferably geared together by cogwheels located on
their shafts outside of the grease pot with an interposed idler wheel so as to
secure the requisite motion. Rotary motion is given to these rolls in any suitable
manner, which may be conveniently effected by means of a pair of belts with
fast and loose pulleys, so that the motion of the rolls may be reversed as the sheets
are alternately dipped into and raised out of the grease pot. This third dipping
into tin may be dispensed with, if desired, in which case grease only is placed
in the pot.
The rolls of the upper pair, or, if desired, also of the lower pair are furnished
with screws or other well known device by which they can be forced into close
surface contact with each side of the tinned sheet as it passes between them.
The object of this pressure thus applied to the delivering and finishing rolls, is
not only to lower and raise the sheets into and out of the pot, and to give them
a smooth surface and finished appearance, but also and chiefly to cause the tin
to penetrate the pores of the sheet which have been left open by reason of the
deoxidation and decarbonization as before described and by the absence of roll-
ing before tinning.
Instead of having separate furnaces under the grease pot and tin pots they may
be so arranged as to be heated by a common furnace, the degree of heat applied
to each pot or tank being regulated by means of dampers connected, in the usual
way, with the flues, surrounding each of these vessels.
In the above description I have spoken of my invention as applied to the pur-
pose of making tin-plate, but its is also applicable to the manufacture of terne
plate, or sheet iron covered with a mixture in various proportions of tin and
lead, or of zinc or other metal which is capable of being coated on to the surface
of sheet metal.
My invention is also applicable to the manufacture of tin plate from rolled
sheets of steel, but in this case it will be necessary to introduce into the annealing
boxes some pulverized oxide in order to decarburize the steel plate, the propor-
tion of which will depend upon the percentage of carbon in the steel and of oxygen

page_text: in the oxide; and I desire it to be specially observed that sheets of steel decar-
burized and then tinned in the manner I have described produce a very superior
quality of tin plate.
By the terms "iron" and "wrought-iron" in the specification, as applied to
sheet iron to be treated as described in this specification, I refer to sheet iron,
substantially such as is produced by the ordinary processes of manufacturing
sheet iron, having the property of malleability, and containing carbon in a less
amount than either cast iron or steel.
Improvements in the Manufacture of Tin, Terne, and like Plates.
I, WILLIAM BURGELAND JOHNSON, of 4, Clayton Square, Liverpool, in the
County of Lancaster, 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, reference being had to the
accompanying drawings forming part of this specification, in which :-
Figures 1 and 2 are vertical sections of the apparatus which I employ for con-
taining the sheets of iron when subjected to the process of annealing, decarboni-
zing and deoxidizing them, preparatory to tinning or coating with metal. Figure 3
is a vertical section of a grease pot, in which the annealed sheets are prepared
for tinning or coating. Figure 4 is a vertical section of the tank for the melted
tin or other metal and of the apparatus for suspending and dipping the sheets
therein. Figure 5 is a vertical section of a smaller tin pot for second tinning or
coating. Figure G is a vertical section of apparatus for subjecting the tinned
or coated sheets to final treatment, rolling and compression.
In several figures, like letters of reference denote similar parts of my apparatus.
My improved process consists of two principal steps, first, the annealing and
purifying of the sheets from oxygen and carbon before tinning, and, second the
coating of the sheets with tin or other suitable metal.
In the ordinary process of making tin plate or like plates the sheets, having
been hot rolled to the desired size and thickness, are first pickled in heated sul-
phuric or hydrochloric acid to remove the surface oxide or scale, which is called
black pickling, and then washed several times in water to remove all trace of
the acid; they are then placed in a closed iron box and subjected to the heat of
a furnace to anneal or soften them, and gradually cooled, out of access to the
atmosphere; they are then cold rolled between polished rolls to remove the rough-
ness of the surface caused by the formation and removal of surface oxide, which
gives them a close texture and a polished appearance; they are then again
annealed in like manner as before, pickled and washed, after which they are ready
for tinning or coating. This second pickling is usually necessary to remove the
oxide from the edges of the sheet and is injurious to the central part of the sheet
from which the oxide has been removed by the first pickling.
In my process the preparing of the plates for tinning or coating differs essen-
tially from that just described, among others, in the following important par-
ticulars. First. Great care is taken to protect the sheets after they are rolled
and during the. annealing process from the action of oxygen of the atmosphere,
and to surround them with a substance which is neither carburizing nor oxidizing,
for the exclusion of atmospheric air, so that the formation of further scale on the
surface of the iron is prevented, and by the mutual reaction of the oxide on the

page_text: surface of the iron sheets and of the carbon contained in the body of the iron,
it may be both deoxidized and decarburized on exposure to the heat of the furnace.
By this means the removal of the scale resulting from the exposure of the heated
plates to the air during rolling is rendered not only unnecessary, but undesirable,
and the roughness of the sheets caused by the formation of scale and its removal
by acid treatment is largely prevented. The body of the metal in the sheets
being thus purified by the complete decarbonization resulting from my process
of annealing, and by the reduction of any surface oxide, the sheets acquire a
remarkable degree of softness and flexibility indicating an unusual, degree of
freedom from either carbon or oxygen.
By my process, therefore, I dispense with the black pickling in acid, ordinarily
practiced after hot rolling, because the surface scale then formed is not only
removed by the annealing process, but serves a useful purpose in the annealing
chamber, and I also dispense with the cold rolling ordinarily practiced after the
first annealing, because such rolling has the effect of compacting the iron, and if
practiced in my process would tend to destroy its porous condition resulting from
decarbonization; and as a consequence, I further dispense with the second anneal-
ing of the sheets which is practiced in the usual method for the purpose of remov-
ing the stiffness due to the cold rolling.
The result of the porous texture given to the iron sheets by my method of
annealing is that the tin or other coating metal, when in a liquid condition, enters
the pores of the iron, forming an union more resembling a chemical than a
mechanical combination of the iron and coating metal; and is pressed into a
very perfect union by the final rolling; besides which the great freedom of the
iron from the presence of either carbon or oxygen gives it an extraordinary degree
of softness and flexibility.
In practicing my invention the sheets of iron, having been first hot rolled in
the usual way to the desired size and thickness, are placed, without previous
removal of scale by pickling or otherwise, in a pack of say 500 to 600 sheets,
more or less, in an annealing box, so constructed as to permit of the sheets being
easily placed therein and removed therefrom, and at the same time to permit the
use of means to exclude the admission of atmospheric air.
In the drawings, Figures 1 and 2, I have shown two constructions of anneal-
ing box which I have devised for this purpose.
Figure 1 represents, partly in section, an annealing box a made preferably
of cast iron, though strong wrought iron plates may be used in its construction
.or clay, such as is used in the manufacture of glass-melting pots. This box a ia
closed at the top and the sides, being made air tight, and in use is set with the
open bottom downwards on a base-plate 6 on which the open end of the box rests.
The base-plate is surrounded with a flange c, so that pulverised material,
sufficiently refractory to stand the heat of the furnace, such as pulverised iron
ore, sand, or dolomite, is placed as shown at d so as to prevent the access of air
into the box. The sheets of iron or steel are placed in a pack on the base-plate b
and are covered by an envelope e, preferably of sheet iron, which may be made
in the shape of a box, either in one part with an open bottom, or in two parts
.fitting telescopically one over the other. The outer box a is then placed over
the envelope e and is large enough to leave a space of about two inches on top
and around the inner box or envelope e which covers the sheets, and in this space
is introduced sand, lime pulverized iron ore, dolomite, or other suitable material
which will resist the action of the heat. This pulverized material is inserted
into the space around the sheets through small openings f in the top of the outer
box and may be rammed compactly by means of an iron rod.
The other construction of annealing box is shown in Figure 2, which repre-
sents a box a¹ of cast iron or other suitable material, closed at bottom and open
at top, where it is enclosed by a covering-plate f¹. The sheets of iron or steel
are placed in a pack surrounded by a case or envelope el preferably of sheet iron,
which is covered over at the top to prevent the entrance of sand, iron ore, or

page_text: dolomite placed within the outer annealing box a', and on top and around the
sides of the inner box e¹ to a thickness of about two inches and which may be
rammed in place. The purpose of this arrangement is not merely to exclude the
atmospheric air, nor is the pulverized material designed to act chemically on the
sheets of metal, but the purpose is to enclose them, as it were, in an oven, so that,
under the influence of the furnace heat to which the annealing box is exposed,
the oxygen of the surface scale or oxide on the sheets, and the carbon contained
in the body of the iron may mutually re-act, forming carbon dioxide which
escapes from the iron sheets. It may, in some cases, be found desirable, where
the amount of oxide on the surface of the iron is considerable, to place some saw-
dust or other carbonaceous matter around the bottom of the pile of sheets within
the envelope e¹, but this 1 have found to be ordinarily unnecessary, and as a
general practice I prefer to introduce nothing into the annealing box around the
sheets that will have any decided chemical action thereon; but I have also found
that iron ore (oxide) in a pulverized condition operates well and does not seem
to hinder the deoxidation of the sheets. The annealing box with its contents is
then placed in a reverberating or other suitable furnace, and is therein exposed
to a suitable heat, say about 2500 degrees Fahrenheit, for about ten hours, more
or less, according to the size of the annealing box and the amount of sheets of
iron to be annealed.
Preferably these annealing boxes are removable from the furnace for the pur-
pose of charging them and of removing the contents. It is necessary that the
sheets when removed from the annealing box should be cold, or so nearly so as
not to be liable to the danger of oxidation of the surface of the metal when
exposed to the air.
The sheets of iron should be allowed to become sufficiently cold to prevent
oxidation on exposure to the external air, before their removal from the annealing
box.
The result of annealing the sheets in the manner described is that they are
of a dull silver-like or leaden appearance, and are, when removed from the
annealing box, very flexible, indicating that reaction between the oxide scale on
the surface of the iron, and the carbon contained in the body of the iron, has
resulted in the removal of the oxygen and carbon which was present on or in
the sheets of iron before the annealing operation commenced.
If there should be any appearance of surface oxidation remaining on any of
the sheets when removed from the annealing box, such sheets should be subjected
for a few minutes only, to immersion in a bath of a weak solution of muriatic or
sulphuric acid in water, and then thoroughly washed with alkaline water, such
as lime water, to remove any trace of acid which would be injurious to the sheets.
Another advantage of the method of annealing the sheets which I have
described is that the effect on each sheet is very uniform so that the edges are
deoxidized as thoroughly as other parts of the sheets, a result difficult to attain
by the ordinary methods.
After the sheets have been annealed, and freed from scale as described, and
cool enough to prevent oxidation, they are immersed in water for about half an
hour to wash off any particles of oxide which may yet remain adhering to their
surface, and are then ready for the tinning or coating process, as before stated, -
an effect of the treatment being to leave the iron in a slightly porous condition
so that the coating of tin or other metal takes a firmer hold on the surface of
the plates.
In the process of tinning or coating I employ the apparatus shown in Figures 3,
4, 5 and 6. The sheets are first dipped in a pot of grease w, such as shown in
Figure 3, which may be of any desired construction, and therefore does not need
any special description. The grease I prefer to use is a tallow, which should be'
as free as possible from acid, and which is kept in a melted condition by the
frequent contact with the iron sheets which are still warm enough for the pur-
pose; or, if the grease used is of such consistency as to require it, a furnace c

page_text: may be placed under the grease pot w with the side flues n, n as shown in Figure 3.
These sheets, with their coating of grease, are then placed one by one in a vertical
position in a rack (see Fig. 4) which may hold any convenient number of plates
say from 50 to 100. This rack is suspended vertically over the tin pot k, from
a small steam cylinder or other device, by which the rack, with its burden of
iron plates, may be repeatedly and rapidly raised and lowered. The tin pot k is
heated by a furnace m placed underneath it and hot air flues n, n at the sides,
as shown in Figure 4.
The purpose of the rack j is not chiefly the convenience of handling, but it
also enables the sheets to be repeatedly and quickly dipped into the molten tin,
the effect of which is that as the molten tin has a greater affinity for oxygen
than has the black plate (iron or steel) at a temperature of about 450 degrees F.,
this fact, together with the friction created between the melted tin and the sur-
face of the sheets, aids in the removal therefrom of any particles of scale or oxide
which may have been formed on their surfaces during the water washing before
mentioned.
The tin in this pot or tank k should be kept at as nearly a constantly uniformi
temperature of about 400 degrees Fahrenheit as possible, or at a heat sufficiently
above the melting point of the coating metal, whatever it may be, to keep it in a
perfectly liquid condition, and the immersion of the sheets in the tin bath should
be continued for about ten minutes.
The sheets thus tinned are then removed from the rack j to another bath o of
molten tin which is at a temperature somewhat (say about 25 degrees Fahren-
heit) lower than the tin in the tin pot k. This bath may be of less width than the
tin pot k, as shown in the drawing Fig. 5, because the sheets need not be held
apart at this dipping as they are by the rack j. This bath o may be heated, as
shown in the drawings, by a furnace y with side flues n, n. From this batho the
tinned sheets are removed one by one, to the grease pot 7 (see Fig. (i) which is
heated by a furnace q and side flues n, n.
The grease pot p contains grease, but if desired it may also contain molten
tin, if a third dipping is deemed desirable. In the drawing, Fig. 6, the tank
is shown filled with molten tin up to the line -, and when this is the case the
grease, of course, floats on the surface of the molten metal. In order to prevent
the grease being set on fire by the heat of the molten tin, it is kept comparatively
cool by means of a set of horizontal pipes s, s, passed through the tank near its
upper edge, through which cold water or air is caused to pass, and then the
grease is kept at a temperature of about 150° Fahrenheit. Into this pot (Fig. 6),
whether it be filled with grease alone, or also with melted tin, the sheets are
immersed one by one in a vertical or substantially vertical direction, and are
immediately raised and delivered out of the pot, the delivering rolls forcibly
compressing the tinned sheet and giving it a polished surface. This is effected
by means of two pairs of rolls (preferably, although one pair might suffice). The
upper pair t, t, are made of polished steel, the lower pair preferably of copper.
These rolls are placed near the top of the grease pot p so as to be immersed in
the grease, and if tin is used, in contact therewith, so that both pairs of rolls
shall be coated with tin.
The rolls t,t; u, u of each pair are preferably geared together by cogwheels
located on their shafts outside of the grease pot with an interposed idlerwheel v
EC as to secure the requisite motion. Rotary motion is given to these rolls in
any suitable manner, which may be conveniently effected by means of a pair
of belts with fast and loose pulleys, so that the motion of the rolls may be reversed.
as the sheets are alternately dipped into and raised out of the grease pot. This
third dipping into tin may be dispensed with, if desired, in which case grease
only is placed in the pot p.
The rolls of the upper pair t, t, or, if desired, also of the lower pair u, u, are
furnished with screws or other well known device by which they can be forced
into close surface contact with each side of the tinned sheet as it passes between

page_text: them. The object of this pressure thus applied to the delivering and finishing
rolls, is, not only to lower and raise the sheets into and out of the pot, and to give
them a smooth surface and finished appearance, but also and chiefly to cause the
tin to penetrate the pores of the sheet which have been left open by reason of the
deoxidation and decarbonization as before described and by the absence of rolling
before tinning.
Instead of having separate furnaces m, q, x, and y, under the grease pot and tin
pots they may be so arranged as to be heated by a common furnace, the degree
of heat applied to each pot or tank being regulated by means of dampers con-
nected, in the usual way, with the flues n, n, surrounding each of these vessels.
In the above description I have spoken of my invention as applied to the pur-
pose of making tin-plate, but it is also applicable to the manufacture of terne
plate, or sheet iron covered with a mixture in various proportions of tin and
lead, or of zinc or other metal which is capable of being coated onto the surface
of sheet metal.
My invention is also applicable to the manufacture of tin plate from rolled
sheets of steel, but in this case it will be necessary to introduce into the anneal-
ing boxes some pulverized oxide in order to decarburize the steel plate, the pro-
portion of which will depend upon the percentage of carbon in the steel and of
oxygen in the oxide; and I desire it to be specially observed that sheets of steel
decarburized and then tinned in the manner I have described produce a very
superior quality of tin plate.
By the terms "iron" and
wrought iron" in the specification and claims,
as applied to sheet iron to be treated as described in this specification, I refer to
sheet iron, substantially such as is produced by the ordinary processes of manu-
facturing sheet iron, having the property of malleability, and containing carbon
in a less amount than either cast iron or steel.
I desire it to be understood that I do not claim broadly as preparatory to the
tinning of sheet metal, subjecting the sheets to heat in a closed box and then
cooling before exposure to the atmosphere.
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:.
1. As a step in the process of coating sheets of iron or steel with tin or other
coating metal or alloy, preparing the sheets 'by subjecting them, after rolling
and without previous pickling for removing the scale, to heat in a suitable fur-
nace while enclosed in a pack in a suitable vessel or box and protected from the
access of atmospheric air by surrounding them with pulverized sand, lime, iron
ore, or other suitable material, whereby is effected a mutual reaction between
the external oxide scale and the internal carbon of the sheets; substantially as
and for the purpose described.
2. In the process of preparing sheet iron for coating with tin or other metal
or alloy, deoxidizing and decarburizing the sheets without removal of the iron
scale, by enclosing them in a pack within a suitable receptacle, and preventing
the access of atmospheric air by surrounding them with sand or pulverized
material, such as dolomite or iron ore, placed within the receptacle, the sheets
being protected from actual contact with such pulverized material by an envelope
or enclosure composed preferably of sheet iron, and subjecting the sheets thus
surrounded to heat in a suitable furnace, and thereby effecting a mutual reaction
between the external oxide (scale) and the internal carbon of the sheets: sub-
stantially as described.
3. The process of reducing the oxide and largely eliminating the carbon from
sheets of rolled wrought iron, at one operation, by subjecting them, without pre-
vious removal of the oxide coating, to furnace heat, when enclosed in a substan-
ially air tight receptacle, and protected from access of external air, effecting
.

page_text: thereby a mutual reaction between the oxide of the external scale and the internal.
carbon of the sheets; substantially as described.
4. As a finishing step in the process of manufacturing tin plate, or other metal-
coated sheets, subjecting the sheets to the compressive and polishing action of
burnished steel rolls coated wholly or partially with grease, said sheets having
been first treated, without removal of the surface oxides, by simultaneous deoxi-
dizing and decarburizing operation of heating in a substantially air-tight recep-
tacle, and then coated by dipping in molten metal; substantially as described.
5. The process of making tin plate or other metal-coated sheet iron, by sub-
jecting the metal sheets to a process of simultaneous deoxidation and decarburi-
zation, by exposure to heat in a suitable vessel protected from access of external
atmosphere for the purpose of effecting a mutual reaction between the external
oxide (scale) and the internal carbon of the sheets, then coating the wrought iron
sheets by dipping in tin or other coating metal in a molten condition, and finally
subjecting the sheets to the compressive action of polished steel rolls, to compact
the pores of the metal sheet, and effect a firmer adherence of the coating metal;
substantially as described.
6. The process of coating sheet iron with tin or other metal or alloy, consisting
in the following steps, viz: deoxidizing, decarburizing, and softening the sheets
in the manner hereinbefore described without previous removal of the surface
oxide by subjecting them to heat in a furnace when enclosed in a substantially
air-tight receptacle, protected from access of external atmosphere, then coating
such sheets with melted grease, then dipping the sheets repeatedly in a tank of
melted metal at a lower temperature and finally subjecting sheets so prepared
and coated to rolling pressure while immersed in melted grease, substantially as
described.