Seamless Compound Ingots or Bars and Wire.
Year: 1890

page_text: Date of Application, 4th Mar., 1890-Accepted, 19th Apr., 1890
COMPLETE SPECIFICATION.
Seamless Compound Ingots or Bars and Wire..
1, LEVI LYMAN BURDON, of Providence in the State of Rhode Island, United States
of America, Manufacturer, 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 seamless compound ingots or wire, adapted more particularly
to be worked into articles of jewellery, such as watch-chains, bracelets, finger-rings, &c.
and it consists essentially of a base metal core (made say of suitably alloyed copper)
having a seamless shell of fine metal, as gold or silver (also suitably alloyed)
welded or united to the outer surface of the core by the "sweating" process, so
called, thereby producing a ductile ingot which can be reduced to seamless
plated wire.
My present invention so far as I am aware differs from others of this class, some of
which I have already patented in this country, in that the latter have the gold shell
united to the baser metal or core, by means of an interposed layer or film of solder.
All plated wire heretofore produced by the sweating process, and being round or
polygonal in cross-section, has a longitudinal seam extending throughout its length;
this seam for many uses for which the wire is employed necessitates that it be soldered,
thereby obviously materially increasing the cost of the wire.
The object I have in view is to overcome in wire the longitudinal seam above
referred to and to that end my improved wire is drawn or reduced from a substantially
cylindrical-shaped ingot having a base-metal core to which is united a seamless
unsoldered exterior shell of fine metal, the parts being united while in a. semi-
solid state thereby producing ingots possessing a high degree of plasticity and
ductility.
In the sweating process, that is when no solder is applied, it is necessary that the
gold alloy and base-metal shall possess inherent qualities such that when the metals
are subjected to a suitable temperature they will become united. These qualities may
be attained by an increased proportion of the easy-fusing metals which form a part of
the two metals to be united. My practice has been to use for this purpose
silver and zinc which are respectively incorporated with the gold alloy and base-
metal, because of the apparent affinity of the silver and zinc for one another. I
would state here that it may not be possible with the aid of published data to name a
very approximate temperature at which the fusion and union of the two metals occurs
because "the inelting point of alloys does not follow the ratios of those of their
constituent metals:"
In the accompanying drawings, Fig. 1 represents a side elevation (in partial
section) of my improved ingot, in which the outer shell of fine metal is united to the
core by "sweating." Fig. 2 is a cross-sectional view taken on line A A of Fig. 1.
Fig. 3 is a view similar to Fig. 1, the ingot being slightly larger at one end than the
other, or tapering. Fig. 4 is a side elevation, also in partial section, of my improved
ingot having a hollow core. Fig. 5 is a transverse sectional view of the same,
taken on line B B; Fig. 6 represents a piece of seamless wire reduced from the
ingot shown in Figs. 1 and 3. Fig. 7 is a similar piece of wire reduced from the
ingot shown in Fig. 4, and Fig. 8 is a transverse sectional view of my improved
seamless ingot having a polygonal form.
A manner of producing my improved ingot a and the wire to drawn therefrom is as
follows:-
b indicates the cylindrical base-metal core portion made substantially as shown
in Figs. 1 and 2, or even annular, as represented in Figs. 4 and 5, that is having a
central hole d extending throughout the length of the ingot. The core may be made

page_text: of an alloy composed of copper, zinc, and tin in the usual proportions for the base of
plating metal.
c designates the fine metal, as suitably alloyed gold; the same is tubular in form
and seamless throughout. The shell can be produced as follows: The metal c is first
reduced to a flat plate form having any designated thickness; a disk is then cut from
the gold plate and by means of a series of suitably operating dies and plungers the
disk is gradually transformed into a tube of the proper diameter and having a closed
end. During the making of the tube it is frequently annealed as usual to facilitate
its reduction thereby producing a seamless shell or gold tube c. Assuming now that
the interior diameter of the tube is the same as the outer diameter of the core b the
closed end portion of the tube is then cut-off, leaving it preferably somewhat shorter
than the core. The two surfaces which are to be united are next thoroughly cleaned
and covered with borax. The shell is forced to its position on the core, the ends of
the latter, preferably projecting beyond the shell. The whole, but more especially the
said end portions, is then subjected to a comparatively high temperature at the same
time directing a series of flame-jets against the gold shell c, the whole being slowly
revolved axially meanwhile. The heat by conduction gradually raises the tempera-
ture, of the, core lying within the shell until a point is reached equal to the fusing
point of the zinc, or other low-fusing metal forming a part of the core; the heat
upon the exterior of the shell at the same time transforming the low-fusing metal, as
silver, with which the gold shell is alloyed, into a semi-solid state and by means of
the flux (borax) readily unites or commingles with the zinc of the core. At the
same time as the base-metal core b expands more relatively than the gold or fine
metal shell c it follows that the contiguous surfaces are brought into closest contact
thereby. In order to prevent the shell from dropping from the core, as possibly it
might do before the core is sufficiently heated, I sometimes form a stop by inserting
a pin p transversely into the lower portion of the core, as shown in the drawings.
By means of uniting the shell and core as above described it is obvious that the
union is effected entirely without the employment of solder. The workman, must
however, possess considerable skill and experience to successfully "sweat" the
surfaces together, so that when the ingot is reduced to wire it shall be free from
blisters," i.e. portions of the gold surface which are disconnected from the core by
reason of the non-fusing of the alloys.
66
a
"
The fusing of the zinc, &c., can be somewhat facilitated by the employment of
core having a central hole d therein, as in Figs. 4 and 5. In this form the
heat is applied both to the interior and exterior of the ingot.
"
After the shell is sweated to the core the ingot can be reduced to wire by first
repeatedly passing it through a suitable swaging-press until it is reduced in size to
enter a draw-plate" which latter finally reduces it to the desired size, the stock
meanwhile being frequently annealed as usual in the process of wire-drawing. From
experiments which I have made in producing wire w from my sweated ingot a I have
found that the fine metal is firmly welded to the core, the two parts retaining the same
relative proportions they possessed in the ingot.
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. As an improved article of manufacture plated or compound wire having a
seamless exterior surface of fine metal sweated to the core by a fusion of the
metal or metals forming a part of the alloys of the inner and outer portions of
the wire.
2. The compound ingot a herein before described, consisting of the centre or base-
metal core portion 6 and the seamless shell portion c of fine metal united to said core
by sweating, i.e. a union without solder of the more easily fused metal or metals
forming a part of the alloys of the said core and shell, substantially as set forth and for
the purpose specified.

page_text: 3. The compound hollow-wire wherein before described consisting of the central
hollow base-metal core band an unsoldered or seamless exterior surface c of fine
metal sweated to the said centre or core portion.
Dated this 4th day of March 1800.
LEVI LYMAN BURDON,
Hughes, Eli & Hughes,
Inventor.
76, Chancery Lane, London, W.C., Agents for the Applicant.