Improvements relating to the Purification of Metals in their Moulds,. and in the Production of Dense and Flawless Castings, and to Apparatus therefor.
Year: 1893

page_text: Date of Application, 16th Feb., 1893
Complete Specification Left, 16th Dec., 1893-Accepted, 20th Jan., 1894
PROVISIONAL SPECIFICATION.
Improvements relating to the Purification of Metals in their Moulds,.
and in the Production of Dense and Flawless Castings, and to
Apparatus therefor.
I, EDUARD TAUSSIG, of Bahrenfeld, Holstein, in the Empire of Germany,
Manufacturer, do hereby declare the nature of this invention to be as follows:?
My invention relates to the purification of metals in their moulds and in the
production of dense and flawless castings, and to apparatus therefor.
It is well known that moro or less rapid or slow cooling of metals after the
melting has a considerable effect upon the physical condition and more especially
upon the density and strength of the casting. The reason for this lies not only in
a different grouping of the particles of the material, but also, as I have ascertained,
in the generation of gases which takes place at the commencement of the cooling,
these gases 'aiding in the formation of flaws and in the formation of cavities in the
casting.
With the object of remedying these defects the metal is subjected in the mould
(after the completion of the casting) to renewed melting, the gases generated being
sucked off at the same time, inasmuch as the casting takes place in a vacuum and
the cast metal is exposed to the action of the electric current, the strength of which
is such that in consequence of the heat of resistance it will keep the metal at the
melting point. For this purpose it is expedient to arrange at the lower part of the
mould an electrode extending to the metal to be taken up so that this electrode may
be readily joined to one pole (preferably positive) of a source of electricity. The
electrode connected with the other pole (negative) is arranged to dip at the upper
end into the mould in such a manner that the metal flowing into the latter will.
close the electric circuit only when the said mould is wholly filled or nearly so...
The casting operation and the action of the electric current upon the casting take
place, as above mentioned, in an hermetically closed space in which a vacuum or
nearly a vacuum has been established by means of a fan or the like, so that not.
only the generation of gases in the metallic bath is greatly promoted but such
gases are also removed from the mould and from the space wherein the casting is
effected.
In case metallic moulds (chill moulds) are employed these may at the same time.
serve as an electrode.
In the apparatus which I use for carrying my improved method into practice the
mould, supported upon a truck on rails, is moved so far into a receptacle, adapted
to be hermetically closed by a door, that its ingate or tedge will be placed below
the orifice of a pipe coming from the melting furnace. As soon as this condition is
fulfilled the electrode at the lower end of the mould may be connected by means of
a coupling with an electric conductor extending through a stuffing box to form an
air-tight joint, while the second electrode at the top which is connected with the
electric conductor also extending through a stuffing box is let down from above
into the mould.
In order to close the circuit between the two electrodes I may, after the filling of
the mould to be observed through a peep hole, either dip the upper electrode into
the liquid metal, or adjust it at once so that the circuit is automatically closed
through the metal as it rises in the mould. The formation of a vacuum in the
receptacle and the suction of the gases generated take place through the pipe
connected in any suitable manner with a fan or the like.
In the above described arrangement it has been supposed that the melting takes

page_text: place in the ordinary manner. In another arrangement electric conductors lead
from the source of electricity by means of branches to the electrodes of an electric
melting furnace. The electric current is therefore first utilized for melting the
metal and then for acting upon the casting in the mould, into which the molten
metal flows through a channel. In this case the arrangement may be such that the
mould can take up the whole contents of the melting furnace so that at the moment
when the latter is emptied and consequently the electric connection between the
electrodes is interrupted the entire quantity of current will traverse the casting in
the mould. When the melting of the metal also takes place in a vacuum it is
expedient to join the suction pipe of the aforesaid receptacle to that of the melting
furnace.
Dated this 16th day of February 1893.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements relating to the Purification of Metals in their Moulds,
and in the Production of Dense and Flawless Castings, and to
Apparatus therefor.
I, EDUARD TAUSSIG, of Bahrenfeld, Holstein, in the Empire of Germany,
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 the purification of metals in their moulds and in the
production of dense and flawless castings, and to apparatus therefor.
It is a well known fact that more or less rapid or slow cooling of metals after the
melting has a considerable effect upon the physical conditions and more especially
upon the density and strength of the casting. The reason for this lies not only in
a different grouping of the particles of the material, but also, as I have ascertained,
in the generation of gases which takes place at the commencement of the cooling or
congelation, these gases aiding in the formation of defects, such as flaws and blow
holes in the castings.
With the object of remedying these defects the metal is subjected in the mould
(after the completion of the casting) to renewed melting, the gases generated being
sucked off at the same time, inasmuch as the casting takes place in a rarefied
atmosphere and the cast metal is exposed to the action of the electric current, the
strength of which is such that in consequence of the heat of resistance it will keep the
metal at the melting point. For this purpose it is expedient to arrange at the lower
part of the mould an electrode extending to the metal to be taken up so that this
electrode may be readily joined to one pole (preferably the positive) of a source of
electricity. The electrode connected with the other or negative pole is arranged
to dip at the upper end into the mould in such a manner that the metal flowing into
the latter will close the electric circuit only when the said mould is wholly filled or
nearly so. The casting operation and the action of the electric current upon the
casting take place, as above mentioned, in an hermetically closed space in which a
vacuum or nearly a vacuum has been established by means of a fan, vacuum pump.
or the like, so that not only is the generation of gases in the metallic bath greatly
promoted but such gases are also removed from the mould and from the space
wherein the casting is effected.
.
In case metallic moulds (chill moulds) are employed these may at the same time
serve as an electrode.
In order to make my present invention more clearly understood, I have
represented it by way of example in the accompanying drawing in which
Figure 1 is a sectional side elevation of an apparatus which I use when the
melting of the metal is intended to take place in an ordinary melting furnace, and

page_text: Figure 2 is a sectional side elevation of an apparatus shown in connection with
an electric melting furnace in which also the melting takes place in a rarefied
atmosphere.
Similar letters of reference indicate corresponding parts throughout the several
views.
In the arrangement illustrated by Figure 1, the mould a, supported upon a.
truck on rails c, is moved so far into the air-tight chamber e, adapted to be
hermetically closed by a door d, that its ingate or tedge a¹ will be placed below the
orifice of a pipe f coming from the melting furnace. As soon as this condition is
fulfilled the electrode at the lower end of the mould may be counected by means
of a coupling g with an electric conductor extending through a stuffing box k to
form an air-tight joint, while the second electrode ¹ at the top, which is connected
with the electric conductor also extending through a stuffing box 1, is let down
from above into the mould a.
In order to close the circuit between the two electrodes I may, after the filling of
the mould which can be observed through a sight-hole m, either dip the upper
electrode into the liquid metal, or adjust it at once so that the circuit is
automatically closed through the metal as it rises in the mould. The formation of
a vacuum in the chamber e and the suction of the gases generated take place
through a pipe n connected in any suitable manner with a vacuum pump, fan, or
the like.
In the above described arrangement it is supposed that the melting takes place
in the ordinary manner. In the arrangement, shown in Figure 2, the electric
conductors, lead from the source of electricity by means of branches i³, it to
the electrodes o o' of an electric melting furnace p. The electric current is
therefore first utilized for melting the metal and then for acting upon the casting
in the mould a into which the molten metal flows through a channel f. In this
case the arrangement may be such that the mould can take up the whole contents.
of the melting furnace, so that at the moment when the latter is emptied and
consequently the electric connection between the electrodes o, o' is interrupted the
entire quantity of current will pass through the casting in the mould a. When the
melting of the metal also takes place in a rarefied atmosphere it is expedient to
join the suction pipe n of the aforesaid chamber e to the pipe q of the melting
furnace p.
I am aware that prior to my invention it has been attempted to keep the metal.
after casting hot in its mould by forming one or more electric arcs between the top
of it and carbon terminal, or by passing an electric current through a bad conductor,.
such as clay. I therefore do not broadly claim the purification of the metals in
their moulds by means of electricity.
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. The process of purifying metals in their moulds which consists in subjecting
the metal after casting in its mould to renewed melting by passing through it a
current of electricity in a rarefied atmosphere, substantially as and for the purpose
set forth.
2. The combination of an hermetically closed chamber, a mould enclosed by said
chamber and designed to receive the molten metal from the melting furnace, means
for conducting a current of electricity through the metal in the mould, and an
exhauster for rarefying the air in said chamber, substantially as and for the purpose
set forth.
Dated this 10th day of December 1895.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.