Steel, and in Furnaces suitable to be Employed therein.
Year: 1885

page_text: Steel, and in Furnaces suitable to be Employed therein.
I CALVERT BERNARD HOLLAND General Manager of Ebbw Vale Iron and Steel
Works Monmouthshire 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 has for its object improvements in annealing thin sheets and
plates of iron and steel and in furnaces suitable to be employed therein, it relates
more especially to annealing or softening sheets and thin plates of steel and iron
of ordinary or special descriptions such as are made in sheet rolling mills for being
galvanized, tinned or coated with metals, or for "working up" or other purposes,
and also steel and iron blackplates (and Canada plates) such as are produced from
blackplate rolling mills for use as thin sheet iron, black taggers etc, or for the
purpose of being finished into various descriptions of tinplates, terne plates, tin
taggers, etc or for being coated with metals other than tin and lead.
"
Generally much of the iron and steel sheets made in a sheet mill is annealed or
softened in what is commonly designated an open" annealing furnace which
ordinarily has a fire grate at one end and a door for charging and drawing at the
other. The sheets to be softened are, as soon as convenient after they pass finished
from the rolls, placed on the bed of such a furnace and exposed thereon to flame
and heat derived from the grate and reverberated to the sheets on the bed by the
roof above.
A satisfactory result from this method can only be secured by the use of suitable
fuel and the exercise of much care and skilled judgment on the part of the
workman..
It is however, well known that in ordinary every day work the softening
effected in open annealing furnaces is variable in quality and sometimes entirely
unsatisfactory.
Furthermore "scaling" or oxidation is apt to occur to the sheets by this method
of annealing; and such a result when the sheets. have to be coated by other metals
involves more expense in pickling and cleaning them for the purpose. Besides
this "scaling" has other drawbacks known to manufacturers and consumers,
Din 32

page_text: In some sheet mills a portion of the produce is softened by a more costly method
known as "close" annealing. Under this method (which is also commonly
practiced by sheet galvanizers and other consumers) the sheets are ordinarily
placed in piles and then enveloped by pots or cases of various descriptions made
generally either of wrought or cast iron. The covered piles are then introduced to
an annealing chamber throughout which spread and travel the flames and gases
from a fire grate situated at one end of the furnace. In this method the function
of the pot or case used is to shield the sheets while being annealed from actual
contact with either the flame or heated gases enveloping the pile. The result from
"close" annealing is generally much better than from " open" annealing-the
sheets being softer, tougher, Hatter and much freer from scale and also smoke spots.
By this method of annealing the cases are subject to considerable local variations
of heat and consequent strains which lead to their distortion and cracking. Occa-
sionally cast iron pots crack the first time they are used for this purpose, but owing
to their considerable cost they are not put out of use when so cracked so long as it
remains possible to stop up the cracks and fractures with clay or some other
suitable material. Usually this "stopping" has to be repaired and in part renewed
each succeeding time the case is used. As however such stopping is liable to fall
away from the cracks while within the furnace the sheets are seldom so satisfactorily
anuealed in a cracked pot as in a perfect one-they being liable both to local
scaling and either a darkish or what is technically known as a "foxy" coloration
in the neighbourhood of such cracks. Blackplates are almost invariably softened
by the "close" aunealing method; and since the ordinary sizes of blackplate
range from 14 ins x 10 ins to 28 ins x 20 ins, and seldom more, it is customary
to place several encased piles of these plates together in one capacious heating
chamber for simultaneous softening. The pots or cases used for covering black
plates are usually smaller and much more portable than those used for sheets. The
cases used for black-plate frequently suffer cracking and fracture during use and
permit damage being done to the plates they enclose owing to the access to them
obtained in such instances by the surrounding oxidising gases.
By means of the improved furnace to which the present invention refers the
operation of softening or annealing is almost completely safeguarded from the
defects and imperfections incidental to ordinary "open and "close" annealing,
and a marked economy in cost of the process is effected by it in the matter of cases,
fuel and labour-besides which a much more uniform and satisfactory result in
softening is secured.
The improved furnace, which I will now proceed to describe more fully, has an
interior chamber for the reception of the sheets or blackplate (as the case may be)
to be treated and into this the flame and products of combustion for providing the
heat for annealing are not allowed to enter-they being restricted to circulating
under around and over the said internal chamber the contents of which are heated
by conduction and radiation from the walls of the chamber.
On the accompanying drawing Figure 1 shews a cross sectional elevation,
Figure 2 a longitudinal sectional elevation, and Figure 3 a sectional plan of my
improved furnace. Half of the sectional plan is drawn through the line A. B. on
the sectional elevation, and the other half of the plan is taken on the line C. D on
Figure 1-In the following explanation of the Figures 1. 2. and 3. the same letters
refer to like portions of the furnace. a. a. is the inner chamber in which the sheets
and other forms of metal to be annealed are placed. The front or charging end of
this chamber is closed either by means of a brick lined door travelling up and
down vertically by the aid of balance weights or by means of one or a pair of
brick lined doors swinging on hinges supported by one or both sides of the chamber
mouth. When the entrance is closed after the chamber has been charged some
clay or other luting is applied in the ordinary manner around the margin of the
door so as to effectually seal up the chamber. b. is the grate here shown to be one
of ordinary description of which c. c. c. are grate bars and d. d. bearing bars-e. is
a stoking hole and ƒ. an ash pit,

page_text: The heat and products of combustion from the grate b pass forward through the
longitudinal flues g. g. g. beneath the floor of the chamber a. a.
The flues g. 9. J.
deliver into the cross flue h. which is also under the floor of the chamber a. a. at
the front or charging end. By means of these basement flues the bottom of the
chamber a. a. is efficiently heated. From the flue h. the heat and products of
combustion enter the passages j. j. respectively-one being on either side of the
chamber a. a. and through these return to the back or fire end of the chamber-
The passages j. j. both deliver into the passage at the back end of the chamber-
k being a continuation of the said passages and common to both The passages or
flues jj. and . are as near as may be co-extensive with the superficial area of the
sides and back of the chamber a. a. and by means of these much heat is transmitted
to the chamber through its side and back walls.
From the passage k. at the chamber back the products of combustion with the
heat remaining in them rise up to the arched-over passage l. which is formed
immediately over the arched roof of the chamber a. a. and is approximately co-
extensive with it, and then travel forward through the said passage l. towards the
front end of the chamber whence they make their escape as spent gases through
the passages m. m. and chimney n. While the gases are travelling through the
passage l. they heat the roof of the chamber a. u. A damper is fixed at a suitable
position in the chimney n. or in any other arrangement of escape flue, for regu-
lating the draft through the grate b.
It is advantageous to afford some lateral support to the side walls of the
chamber a. a by means of a few bricks projecting from the outer side walls o. o. of
the furnace across the passages j. j. Some such supporting bricks marked p. p. p. p.
are shown on the cross and plan sections.
The following is a convenient means of charging to the chamber a. a. the sheets
or other forms of metal requiring to be annealed or softened :-Two longitudinal
cast iron bearers q. q. whole or in segmental lengths are laid along the floor of the
chamber and immediately above the two partition walls r. r. between the
flues g. g. g. The upper side of the bearers q. q. is chanueled to a V or circular
cross section to form a track upon which some spheres of iron may travel to aud
fro. An iron bed-plate of a form suitable for piling the sheets & of metal upon
and also for passing into and out from the chainber a. a. is provided having on its
underside two longitudinal bearers channeled on their lower face in a manner
corresponding to the channeling on the floor bearers q. q. before mentioned.
The longitudinal bearers projecting from the underside of the bedplate above
referred to are also spaced the same distance apart at their mid-widths as the floor
bearers q. q. by which means they will travel fairly and easily over the latter upon
spherical balls of iron when required. The bedplate before mentioned having been
placed upon iron balls at a convenient position before the mouth of the furnace, is
then loaded with the metal to be annealed in one or more piles or otherwise packed
to a suitable height.
The charge is now ready to be introduced to the chamber except that the pile or
piles are preferably covered by means of one or more light protecting cases made of
thin sheet iron.
When the charge within the furnace chamber is ready to be withdrawn the door
is opened and the bed-plate with its load inside is pulled out, and being got out of
the way the fresh charge of cold metal on its bedplate is introduced to the furnace
and the door closed and luted.-It is desirable to perform the operation of drawing
and charging in the shortest period of time possible.
For introducing a charge to the furnace it has been found convenient to use a
drum or ordinary crab winch placed somewhere outside at the back or fire end of
the furnace and from the drum to convey a chain through the hole 8 in the back
wall of the furnace structure and onwards through the chamber until the loaded
bed plate requiring to be charged is reached and to which it is fastened..
Upon revolving the drum the loaded bed plate can then be drawn into the
furnace by means of the chain-a sufficient number of iron balls at suitable

page_text: distances apart having previously been distributed over the channeled track.-
As soon as the bed plate has been got in the chain is detached from it and
withdrawn and the hole s is stopped up by means of a loose brick and clay
luting.
Withdrawing the charge may be conducted in a similar manner by means of a
chain and crab winch.
By means of a chambered furnace such as is herein before described and provided
that the walling forming the interior chambers is in a fairly perfect condition, a
charge of sheets or other forms of iron or steel or other metals can be satisfactorily
annealed without any case or covering of any kind being applied to the pile on the
bed plate, but upon withdrawal of the annealed pile while still at a red or annealing
heat it is necessary as quickly as possible to cover it with a case of some descrip-
tion a thin sheet iron one will do so as to protect the edges and margins of the
hot plates from the oxidizing influence of the atmosphere. In practice however it
has been found to be preferable to cover the pile or piles with a protection
consisting of thin sheet iron suitably applied before the charge is introduced to the
furnace. Such a covering does not materially retard the progress of the heating of
the charge whilst at the same time it affords ample protection against any slightly.
oxidizing atmosphere that might from time to time exist within the chamber a a
owing to any imperfection in its walls permitting a slight leakage of gases to its
interior. In addition to this the case when put on before the charge is introduced
to the chamber is ready in its proper place for protecting the annealed metal from
atmospheric oxidation upon withdrawal from the furnace and for this purpose it is
much more convenient to put on the case when the bed plate and its load are in a
cold state. It is to be remarked that with skill and carefullness in bricklaying and
with suitable bricks a chamber virtually gastight when heated can be made. It
has been found bricks having a longitudinal projection or feather at mid width on
one bed and a corresponding groove in the opposite bed to be very suitable for the
portions of the chamber to which they can conveniently be applied. In instances.
where from defective material or workmanship a slight leakage of gases to the
inside of the chamber a a becomes possible the presence of a case enclosing the
charge efficiently defends the latter against any scaling tendency of those gases.
Under ordinary circumstances such invading gases can only effect a limited
amount of oxidation because owing to the absence of draught within the
chamber aa there can be but very little movement among such gases and
renewal of them therein.
•
In common "close" annealing furnaces the maximum length of sheet which can
be treated is limited because the great weight of the cases required for greater
lengths renders it extremely difficult to handle the piles of sheets when covered
with them. I have found in practice that sheets twelve feet long are readily
handled and uniformly and efficiently annealed in an improved furnace of the forma
and dimensions shown on the drawings attached hereto and by the means herein
described, and that the sheets of that length can be as conveniently annealed as
those of half the length or less.
I have found that in an improved furnace of the form and dimensions just
referred to a charge of several tons of sheets can be readily and efficiently annealed
in 24 hours.
It has been found also that by this improved system the annealing or softening
operation is effected with great economy of fuel in comparison with either "open
or "close" annealing as customarily conducted and besides that it is not necessary
to use any special quality of fuel such as is advisable in the ordinary methods,
especially in the case of "open" annealing. Furthermore by means of my improved
furnace the charge of metal is less liable to be injured during the annealing
operation by any irregularity in the stoking or from what is technically known as
"holes in the grate" than is the case with either the ordinary "open" or "close"
annealing methods-in each of which both irregular stoking and neglected fire beds
are fruitful sources of injury to the charge in the furnace,

page_text: In carrying out this improved method of annealing I do not confine myself to
the precise details herein before described. For instance the improved furnace
might be heated by the combustion of generator gases or by other methods.
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. The process of annealing thin sheets of iron and steel by heating them when
piled one upon another in a furnace chamber from which products of combustion
are excluded but which is surrounded by flues in which such heated products
circulate substantially as described.
2. The process of annealing thin sheets of iron and steel by heating them when
piled one upon another and protected by a cover of thin sheet metal such beating
being performed in a furnace chamber from which products of combustion are
excluded substantially as described.
3. The improved furnace for annealing thin sheets of iron or steel such furnace
having a chamber from which products of combustion are excluded but which is
heated by flues where such heated products circulate, and which has also a bed
running into and out from the said chamber and receiving upon it the plates or
sheets to be annealed substantially as described.
4. The improved furnace for annealing thin sheets of iron or steel substantially
as described and represented by the annexed drawings.