Method of and Apparatus for Producing Locally Annealed Steel and other Metal Plates.
Year: 1894

page_text: Date of Application, 18th Dec., 1894-Accepted, 2nd Feb., 1895
[Communicated from abroad by THOMSON ELECTRIC WELDING COMPANY, of
Lynn, Massachusetts, in the United States of America, Manufacturers.]
Method of and Apparatus for Producing Locally Annealed Steel and
other Metal Plates.
I, WALLACE FAIRWEATHER, C.E. of 62 Saint Vincent Street, in the City of
Glasgow, Chartered Patent Agent, do hereby declare the nature of this invention
and in what manner the same is to be performed, (as communicated to me) to be
particularly described and ascertained in and by the following statement :-
My invention relates to a novel method of obtaining hardened plates or other
pieces of metal such as steel locally softened to admit of cutting, tapping or
drilling, and is especially useful in the production of Harveyized armour plates
which require to be provided with bolt holes, countersinks, embrasures or other
holes or openings when in place upon the ship, though it is also applicable to other
plates or pieces of metal and whether hardened all through or merely at and near
the surface.
My invention consists essentially in hardening the whole piece of steel or other
metal, then locally heating the spot or portion in the body thereof to be softened,
to the proper temperature, by an electric current passed through the metal itself,
and then allowing the said portion to cool while keeping it supplied with a
gradually diminishing amount of heat from such current, the rate of diminution
being adjusted, as hereinafter described, to the tendency of the surrounding mass
of metal to carry the heat away, so as to cause it to cool gradually and at a
sufficiently slow or proper rate to become soft at such heated portion.
By producing the local heating through generation of heat in the desired portion
of metal itself by the passage of an electric current through such portion, the
heating may be much more closely confined or localized and the rate of cooling
better controlled.
My invention consists further in certain appliances designed to aid in the purpose
of locally beating by the electric current and of confining the heating to the
desired spot.
It is well known that an ordinary piece of steel, such as tool steel, manganese
steel, etc. which, through its peculiar chemical composition has been tempered or
hardened by plunging it in water after heating or by otherwise cooling it off
rapidly, may be softened again by bringing it to the right temperature and leaving
it in the open air to cool off gradually. It may of course be made softer yet by
decreasing the rate of cooling by surrounding the metal with some refractory or
beat insulating substance such as ashes, magnesia, etc., but for all practical purposes
an ordinary piece of steel may be annealed or softened by allowing it to cool in
the air.
If, however, the attempt be made to soften or draw the temper at an individual
spot in a large plate or piece of hardened metal by heating it to the right
temperature and then removing the heating influence suddenly, the surrounding
metal will carry the heat away so fast as to chill the heated portion and harden
the same as if the heated spot alone had been plunged into water or other cooling
medium. Moreover, no covering with any heat insulating material would prevent
this inasmuch as a large percentage of the hot metal is in direct contact with cold

page_text: metal from which it cannot be isolated by any known means. For this reason in the
production off Harveyized plates for armour plates, for instance, it has not been
found practical to first subject the whole plate to the hardening process and then
locally heat the part which is to be cut, tapped or drilled. Nor has it been found
practical to first cut, tap or drill the metal plate and subsequently harden it, for in
the hardening operation the plate is liable to become deformed or to crack around
the openings or holes. It has, therefore, been found necessary either to tap, cut or
drill the hardened metal at great difficulty and expense or else to locally apply some
material to parts of the plate which will prevent it from becoming hardened during
the hardening process.
My invention obviates the difficulties and objections heretofore met with in
dealing with hardened armour plate having a skin or coating of hardened metal as
well as in dealing with other large masses or pieces of hardened metal which require to
be cut or formed at some part, and consists essentially in first producing a complete
plate or piece of the hardened material including the portion to be cut or formed,
then by the passage of an electric current through the metal, heating the portion
to be formed or cut to the proper temperature for drawing the temper and then
allowing it to cool at such portion while supplying it with a gradually diminishing
amount of heat from such current to prevent the fall of temperature in the heated
portion due to the presence of the large masses of metal in direct contact with it
from being a ton rapid one.
By my invention the hard steel plate may be softened in isolated spots so that it
may be readily drilled and tapped at such isolated spots alone, or continuous lines
or extended surfaces may be softened for the purpose of allowing the material to be
cut along the softened line.
In carrying out my process by the use of electric currents a transformer having
a secondary adapted to supply current of large volume, such as is employed in
electric metal working operations, may be used and the terminals thereof brought
into contact with the previously hardened plate or mass of metal on either side of
the spot to be anuealed or softened. The current is made to enter the plate at onc
contact and leave it at the other bringing the intermediate portion to a dull red
heat. If the process were stopped at this point and the current withdrawn, the
metal would chill and be as hard in this spot as anywhere else but, if instead of
withdrawing the current suddenly it may be gradually diminished in amount in any
well known manner as, for instance, by proper regulating devices, the temperature
of the heated portion may be made to fall as gradually as it would if that portion
were separate from the whole piece and left to cool on its own account. The depth
to which this local softening process can be carried depends largely upon the
arrangement of the contacts or manner of introducing the electric current by
which the beat is generated in the body of the metal by the passage of the current
through it. If the plate or piece of metal be hard through its whole thickness and
not merely on its skin surface, the current may be made to enter at one side and
leave at the other passing entirely through the mass of metal. On the other hand
if only the skin is to be treated the contacts may be placed side by side upon the
same surface.
The diminution in the rate of flow of the current after the metal has been
brought to the proper heat may be produced by any desired form of current
regulator as for instance, by means of a reactive coil in series with the heating
apparatus or by a resistance in series with the field of the generator furnishing the
alternating currents for the heating transformer. Preferably, an automatically
operating regulator actuated by gravity or other power is employed. The action
of such regulator is adjusted to the desired rate by clockwork or any other time
adjusting means which shall produce the required rate of decrease of such heating
current in the metal.
The amount of heat furnished by the current might be gradually diminished or
removed by moving the electrodes along the surface of the metal at the parts
where it is to be locally heated and this may be a desirable way of producing a

page_text: softened line of material in the hardened mass the rate of movement being, of
course, adjusted to the particular circumstances of each case and being made slower
where the mass of surrounding cold metal is larger or heavier.
I have found, however, that good results may be obtained by adjusting the
action of a current regulating resistance applied to any proper portion of the
electric apparatus which furnishes the heating current in such manner as by its
action to cause a diminution in the flow of said current.
In order to prevent the current from spreading too much and heating the metal
beyond the desired zone of softening care should be taken not to use too heavy or
powerful an electric current. This is particularly the case where the attempt is
made to pass the current through the metal from one side of the plate to the
opposite side.
I have obtained good results in the case of Harveyized plates by means of two
copper contacts resting side by side upon the plate about one inch apart and each
copper contact being about one inch square, then passing the current through the
metal until the temperature between the contacts shows a just visible red, and then
reducing the heating current very gradually through a period of about ten minutes
in which period the metal is allowed to cool gradually past the critical stage or
temperature at which the material proceeds to set or become hard if the change of
temperature is at such point rapid or sudden.
In the accompanying drawings I have shown some of the electrical apparatus
that may be employed in practising my invention.
Fig. 1, is a general side elevation of an apparatus in which a transformer is used
for heating one side of a piece of metal at an isolated spot.
Fig. 2, is an edge elevation of the transformer.
Fig. 3, shows in end elevation the transformer electrodes or contacts.
Fig. 4, illustrates the manner of applying the electric contacts when the current
is to be passed through from one side to the opposite side of the plate.
Fig. 5, shows on a larger scale a vertical transverse section through the
carriage K, taken in the plane of the axis of rod I.
Fig. 6, is a vertical section taken longitudinally of the carriage in the planes
indicated by the line 7, 7, of Fig. 5; and
Fig. 7, is a vertical section through the electrodes B, B, taken in the plane of
the axes of pipes C, C, and c.
Referring to Fig. 1, A, indicates the transformer which may be of any usual
type suitable for generating heavy currents. S, is the secondary and B, B, the
contacts reduced towards their lower ends to produce small contact surfaces b, b,
and made, preferably, adjustable on the terminals of the secondary for the purpose
of varying the extent of heated metal between them. These contacts or electrodes
are preferably hollow and a stream of cooling liquid is circulated through them
by means of pipe C, C. At c, is a pipe connecting the two hollow electrodes.
One way of mounting and constructing the electrodes B, B, is illustrated in
Figs. 1, 2 and 7. Each electrode is seated in a slide formed between projections on
the lower end of the secondary S, and as a bolt a, passing through it and through slots
in said projections as shown. On the ends of these bolts are washers and nuts for
clamping the electrodes at the desired distance apart. The pipe c, is preferably
of insulating material and may be firmly attached at one end in the way of one
electrode while it slides through a gland in the wall of the other electrode, or it
may be of metal and be insulated from the electrodes by suitable bushings of
insulation. The water pipes C, may be rigidly secured in the electrodes and
move bodily therewith or they may pass through glands in the walls of the
electrodes as desired. I have shown them as rigidly attached to the electrodes
and, on account of their considerable length, depend upon their resilience in the
adjustment of the electrodes. By thus keeping the contacts artificially cool the
heating in the mass of metal is better localized at the portions thereof between
the electrodes themselves. In practice it will be found that when only slight
contact pressure is used there is a tendency of the metal at the surface in contact

page_text: with said electrodes to heat more than at the portion between them but by
artificially cooling the electrodes the heating may be better confined as stated.
The flexible conductors which supply the primary of the transformer are
indicated at D, D. In their circuit is shown a reactive coil E, of any suitable
construction whose core F, is suspended from an adjustable dash-pot G, of any
suitable character employed for the purpose of checking the descent of the core by
gravity into the reactive coils. By this device a retarded rate of action of the
regulator is obtained to produce the diminished rate of flow of the current. To
suit different cases, an adjustment may be provided to regulate the rate of descent
or movement of the movable portion of the regulator consisting, in this case, of
the movable core F. When a dash-pot is employed the adjustment may be
obtained by providing the dash-pot with a by-pass having a cock G', which will
regulate the rapidity of the flow of air or liquid in the dash-pot from one side of
its piston to the other. By adjusting this cock the flow of current may be caused
to diminish at the desired rate varying as will be understood under different
circumstances.
H, indicates a Harveyized plate under treatment for local softening and the
portion involved in the heating current is indicated by the shaded portion between
the electrodes. To aid in moving the transformer over the surface of the metal
plate H, it may be hung from a rod I, by a ball and socket joint or other flexible
suspension. The rod 1, is in turn mounted on a carriage K, which has wheels L,
running on the rails M, of a swinging crane or bracket N. Wheels P and R,
operate on suitable mechanism mounted on the carriage and connected with the
rod I, and the wheels L, to lower the transformer or to move it along the rails.
Various forms of mechanism may be devised for manipulating the transformer and
its carriage. For the purpose of illustration I have shown the carriage provided
with a recess for the reception of a steel nut T, through which and suitable ways
in the carriage passes the screw U, which is rotated by wheel R, in moving the
carriage and the suspended transformer over the plate. As a means for raising
and lowering the transformer, I have shown a worm nut as V, located in the frame
of the carriage and turned about the suspending rod I, by means of the worm W,
which is rotated by the hand wheel P. By these means and by the swinging
crane the transformer may be adjusted over any desired spot on the plate or mass
of metal H.
As will be seen in Figs. 3 and 4, the electrodes or contacts where they engage
with the mass of metal are made rather small, this being for the purpose of
localizing the heating current so far as possible and the undue heating at such
points is prevented by the artificial cooling.
Having thus particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, as communicated to me,
I declare that what I claim is :-
1. The herein described method of obtaining a hardened piece of metal with a
portion only in the body thereof softened, consisting in hardening the whole piece,
generating heat in the portion to be softened by an electric current passing
through the metal itself at the portion whose temper is to be drawn, and then
gradually diminishing the amount of heat supplied by the current to said heated
portion at such a rate that, at any period of time, the amount of heat supplied
is nearly but not quite equal to the amount of heat being absorbed by the
surrounding metal, as and for the purpose set forth.
2. In a transformer, the combination with the secondary, of hollow contacts
or electrodes connected thereto, feeding and discharge pipes connected respectively
to said electrodes, and a pipe of insulating material connecting said electrodes
for the purpose set forth.
3. In an apparatus for producing local annealing, the combination with the
heating device, of a swinging bracket provided with a track, a carriage running
on said track for carrying said heating device, a screw located in said bracket, a

page_text: nut in the carriage fitted to said screw, a hand wheel for turning the screw to
propel the carriage, and means for raising and lowering said device for the purpose
set forth.
4. In an apparatus for producing local aunealing, the combination with the
henting device, of an overhead track, a carriage on said track, a screw-threaded
rod connected to the heating device, a worm-nnt located on said carriage to receive
said rod, a worm for operating said nut to thereby raise and lower the heating
device, and means for moving the carriage along its track for the purpose set
forth.
5. The combination with an electric heating apparatus, of an automatically
operating current regulator, producing a diminished rate of flow of the heating
current, and means for giving the same an adjusted or retarded rate of action
according to the rate of diminution desired in the supply of heat.
Dated this 17th dow of December 1201
WALLACE FAIRWEATHER,
62, Saint Vincent Street, Glasgow, Chartered Patent Agent.