Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to the production of metal
castings and is described herein as applied to the production
of ductile iron castings, where the invention is especially
advantageous. Ductile iron is also referred to as nodular or
spheroidal graphite cast iron and ductile iron castings are
highly advantageous as compared to ~ray iron castings because
of their ductility and because they have increased tensile
strength and resistance to impact as compared to ordinary gray
iron castings. Also, ductile iron has much better castability
characteristics than steel and for an increasing number of uses
ductile iron castings can be used where steel castirlgs or forg-
in~s were formerly required.
Ductile iron is produced by innoculating molten iron
of the proper composition with a nodularizing agent that causes
the graphite flakes that are ordinarily present in gray cast
iron to assume a nodular or spheroidal form. It is this change
in the characteristic of the graphite present in the cast iron
that appears to give the ductile iron its advantageous charac-
teristics. Numerous nodularizers are known; they are ordinarily
alloys, compounds or mixtures embodying magnesium, calcium, sod-
ium, lithium, strontium, barium, cesium, and other similar
metals. Magnesium is the preferred nodularizing agent because
of its effectiveness and availability and because its cost is
less than other rarer metals that can be used. Magnesium and
the other nodularizing agents, in addition to their cost, pre-
sent problems because they have boiling points below the pouring
temperature of cast iron and because they are easily oxidized.
Because of these characteristics, attempts to add nodularizing
agents in the conventional manners employed in adding alloying
agents to molten iron, present serious difficulties in tha-t
the addition of the agents to a ladle, for example, is likely to
result in a violent reaction with a pyrotechnic display that
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~ 6 3~1~
results in a hazard to foundry personnel and serious atmospheric
contaminationO Also, some of the nodularizing agent is o~idiz-
ed or otherwise lost, making it necessary to supply nodularizing
agents in amounts in e~cess of the amounts required to effect
nodularization. Also "fading" or a reduction in the amount of
nodularizing agent in solution in the iron may take place dur-
ing the time that elapses between the innoculation of the iron
with the agent and the time the iron containing the nodulariz-
ing agent reaches the mold, causing unreliability and inconsis-
tency in the results.
Attempts have been made to eliminate these problemswith varying degrees of success. For example, the nodularizing
agent has been alloyed with another metal in order to slow down
the reaction that takes place when the nodularizing agent en-
counters molten iron. This system results in increased cost
for a given weight of nodularizing agent and further, the alloy-
ing metal employed may have an undesired effect on the casting.
According to another method, a special intermediate chamber in-
to which the nodularizing agent is disposed and through which
~0 the molten metal flows is interposed between the ladle and the
mold. The chamber in which the nodularizing agent is disposed
can be closed and the pyrotechnic display eliminated. However,
fading can occur during the travel of the iron from the chamber
in which the nodularizing aaent is disposed to the mold and
scrap losses are freauently increased because of iron remaining
in the intermediate chamber and passages. secause of the in-
creased scrap losses, correspondingly increased amounts of nodu-
larizing agents must be employed, adding to the cost of the
casting. A system of this type is illustrated in United States
Patent ~o. 3,819,365, issued June 25, 1974.
Another system, which is disclosed in Canadian Patent
No. 925,265 involves the use of an intermediate chamber in the
~6~7~3~
mold itself in which the nodularizing agent is disposed. This
system has met with some success but it is open to objection for
various reasons, including the ~act that since the nodularizing
agent is placed within the mold, it is not possible to inspect
the mold immediately prior to pouring to determine that the
nodularizing agent is, in fact, in place. Also, the necessity
of providing an intermediate chamber and additional gating with-
in the mold limits the size or number of the mold cavity or cavi-
ties that may be included in a mold of given external dimensions.
This reduces the productive capacity of the apparatus and makes
it necessary to employ a greater number of molds for a given
production of castings. While this method eliminates the prob-
lem of fading and also avoids pyrotechnics, another difficulty
has arisen because results are sometimes inconsistent insofar
as the characteristics of the cast metal are concerned. The
intermediate chamber in the mold also requires the pouring of
metal in an amount greater than would be required in a conven-
tional mold within an intermediate chamber and this additional
metal makes it necessary to supply a correspondingly increased
amount of nodularizing agent. Both of these factors increase
the cost of the castings.
A ~eneral object of the present invention is to pro-
vide a method and apparatus for supplying an addition agent such
as a nodularizing agent in the casting of molten metal such as
iron in which the problems noted above are largely eliminated.
Another object is to provide an improved method and apparatus
for making ductile iron castings. A further object is the pro~
vision of a method and apparatus for making iron castings that
is particularly adapted to automatic molding and automatic pour-
ing techniques whereby a high rate of production, reasonablecosts and excellent uniformity of quality of castings can be
obtained. Another object is the provision of a method and
1~63~9
apparatus for makin~ metal castings in which it is not necessar~
to employ a pouring cup and in which defects in castinys due to
aspiration of air into the mold passages during pouring and de-
fects due to slag inclusions in the metal are minimized. An-
other object is the provision of a method and apparatus for pro-
ducing iron castings that is particularly adapted for use with
vertically parted molds.
Briefly, according to the present invention, a chamber
is provided in the upper portion of the mold in which the cast-
ing is to be formed. An innoculating agent is deposited in thechamber and the molten metal flows into the chamber as it is
poured ~rom an appropriate supply into the mold. The chamber
in which the nodularizing agent is disposed is open at the top
and is connected to appropriate runners, sprues and the like
leading to the mold cavity or cavities in which the castings
are produced. ~t the time of pouring the molten metal, the nod-
ularizing agent is disposed in the chamber and the open top of
the chamber is closed by a separately formed refractory seal
that engages the top surface of the mold surrounding the cavity.
The metal flows through a launder from a furnace containing the
molten metal and which embodies a closed conduit that extends
through the seal. The metal is deposited by the conduit in a
pouring basin formed in the mold and also closed by the seal.
From the pourin~ basin the metal flows to the chamber in which
the nodularizing agent is disposed. From this chamber the
molten metal flows through gating passages such as runners,
sprues and the like to the mold cavity or cavities in which the
castings are formed. The seal prevents the discharge of noxious
fumes into the atmosphere during the pouriny operation and also
eliminates hazards that miyht otherwise occur from the pyro-
technics that can take place when molten iron encounters a nodu-
larizing agent containing magnesium. The seal and associated
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~0763~9
passages in the launder also provide a head of molten metal
over the pouring basin which minimizes slag inclusions and a-
spiration of air into the castings without requiring additional
passa~es or chambers in the mold itsel~ After the pouring
operation has been completed, the seal and the conduit that
extends through it are disen~aged from the mold and the mold
is moved away from the pouring apparatus where the metal is
permitted to cool and solidify and where, thereafter, the
castings are removed from the mold and preferably checked and
tested in accordance with usual practices. Preferably, a
~lurality of molds are moved successively to a pouring station,
~he~e each mold is stopped, enga~ed by the seal, poured, the
seal disengaged from it, and the mold then advanced and an-
other mold moved to the pouring station.
The invention consists in the provision o~ apparatus
for making iron castings comprising a mold having bottom, side
and top surfaces, a casting cavity, a chamber in the upper por-
tion of said mold and a gating passage connecting the chamber
with the casting cavity, the chamber having a floor and side
20 ~alls and being open at its top, the area of the open top of
the chamber being at least substantially equal to the area o~
~he floor thereof, and said gating passage being connected to
said ch~mbex at a level above the floor thereof, the level of
the connection of said gating passage to said chamber also be-
ing above the uppermost portion of the casting cavit~, said
chamber being adapted to have a nodularizing agent deposited
therein through the open top thereof, the open top of the
chamber being disposed at the level of the adjacent top sur-
face of the mold, a sealing member composed of refractory ma-
terial and adapted to make sealing engagement with the topsurface of the mold surrounding the open top of said chamber,
l -5 ~
~763~L~
means for placing said sealing member in sealing engagement
with the top surface of the mold and means for disengaging
it therefrom, a conduit extending through said sealing member
and adapted to deliver molten metal to said chamber, a launder
having a passage for molten metal leading to said conduit and
means for supplyi~g molten metal to said passage in said laun-
der and thereby supplying molten metal to said conduit and
said chamber.
The invention also consists in ~he provision of a
method of making metal castings comprising providing a mold
~aving bottom and side and top surfaces, a casting cavity, a
chamber and a gating passage providing communication between
said chamber and said mold, sai.d chamber having a floor and
side walls and being disposed in the upper portion of said
mold and being open at its top, the floor of said chamber he-
ing disposed at a level above the uppermost portion of the
casting cavity, engaging the top surface of the mold with a
seal that makes sealing contact with the top surface of the
mold surrounding said chamber, and supplying said mold with
sufficient molten metal to fill the casting cavity by causing
said molten metal to flow into said mold throug~ a downwardly
extending closed conduit and an opening extending through said
seal and in communication with said chamber, the metal flowing
downwardly from said chamber to the casting cavity.
Figure 1 is a plan view of a preferred form of ap-
paratus made according to the invention and adapted to perform
the method of the invention;
Figure ~ is an end elevational view of the apparatus
shown in Figure l;
Figure 3 is a vertical section o~ the apparatus,
taken as indicated by line 3-3 of Figure l;
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.~
~763~9
Figure 4 is a fragmentary section to an enlarged
scale, showing the launder and the upper part of the mold
shown in Figure 3;
Figure 5 is a section at right angles to Figure 4
and taken along line 5-5 of Figure 4;
Figure 6 is a sectional detail showing the launder
of the apparatus of Figure 1 in conjunction with fragmentary
portions of the furnace and the mold, the launder being shown
in its raised position;
Figure 7 is a fragmentary sectional view of the
parts shown in Figure 6 but illustrating the launder in pouring
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i~763~
position:
Figure 8 is a phantom view illustrating the cavities
and passages of a mold for use in the apparatus in carrying out
the process;
Figure 9 is a top plan view of the mold shown in
Figure 8;
Figure 10 is a section through the mold of Figure 9,
taken along line 10-10 of Figure 9.
As illustrated somewhat diagrammatically in Figures 1
and 2 of the drawings, a preferred form of apparatus for carry-
ing out the invention comprises a pouring rail 10 at the entry
cnd of which there is disposed an automatic molding machine 11
which may be any conventional type of molding machine, such as
the "Disamatic" machine produced by Dansk Industri Syndikat A/S.
This machine produces molds M successively and deposits them on
the pouring rail. With this type of machine, each following
mold is in engagement with a preceding mold and, in turn, is
engaged by another following mold. A hydraulic ram associated
with the molding machine pushes the whole series of molds along
~0 the pouring rail simultaneously, each mold being advanced a pre-
determined distance and then remaining stationary while another
mold is deposited on the pouring rail, after which the entire
series is again advanced. As will appear below, it is during
the intervals when the molds are stationary that the nodulariz- !
ing agent is introduced into the molds and the molds are poured.
As the molds travel along the pouring rail 10 they pass
beneath an alloy dispensing mechanism 12 which may be of a ~nown
type and is arranged to deposit a predetermined amount of nodu-
larizing agent in each mold. Each mold stops in register with
the alloy dispensing mechanism and while it is stopped, a pre-
determined amount of alloy is deposited into the nodularizing
chamber of the mold. Thereafter, the mold is advanced beyond
a~k
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;3~3
the alloy dispensing mechanism 12 and another mold is advanced
into a position in registration with the alloy aispensing mech-
anism where it, in turn, will receive a desired amount of nodu-
larizing material.
m e molds continue to be advanced step-by-step down
the pourin~ rail, passing a furnace indicated in general at 14,
which is also of known construction, and which is arranged to
deposit a predetermined amount of molten iron in a predetermined
time into each mold as it stops on the pouring rail opposite
the furnace. The molten metal is discharged from the furnace
into a launder, indicated in general at 16, and from the launder
the metal flows by gravity into the mold and to the casting
cavities thereo~ as described in detail below. Each mold stops
lon~ enough opposite the furnace to permit the discharge of
the required amount of iron into it and after this has taken
place, the molds are all advanced another step and a following
mold is disposed in pouring position opposite the furnace.
After the furnace, the molds continue on ln their
step-by-step movement down the pouring rail where the castings
are solidified, then into a coolin~ conveyor of known construc-
tion. Ultimately, the castings are removed from the molds,
trimmed and preferably inspected and tested. Conventional ex-
haust hoods as indicated at 17 and 18 may be placed over the
conveyor as desired.
Molten iron may be supplied to the furnace 14 by con~
ventional melting furnaces, not shown, disposed on the other
side of the furnace 14 from the pouring rail.
While the invention may be utilized with molds of vari-
ous types, the invention is described herein as used in conjunc-
tion with the production of castings in vertically partedflaskless molds, a typical mold of this type being ~hown in
Figures 8, 9 and 10.
~ ~63.~
As shown in these figures, each mold M may comprise
two parts 20 and 21, the parting plane of the two parts being
indicated at 22. The mold is shown as embodying a plurality of
(in this case twelve) casting cavities 24 that are connected by
ingates 25, to downsprues 26 which extend downwardly from the
runners 30. The runners 30 extend generally horizontally from
a centrally disposed nodularizing chamber 31 in which a nodular-
izing agent indicated at 32 (Figure 10) is disposed. It will
be noted that the exits 33 from the chamber 31 to the runners
30 are elevated above the floor 35 of the chamber 31. This en-
sures that the molten iron will react properly with the nodular-
izing agent in the chamber 31 before ~lowing into the runners
30 and thence to the downsprues 26, lateral ingates 25 and
casting cavities 24.
As shown particularly in Figures 4, 9 and 10, the nod-
ularizing chamber 31 is disposed in the upper portion of the
mold and is open at the top. The upper edges of the side walls
36 of chamber 31 lie in the same plane as the top surface 37 of
the mold.
In order to ensure that the molten iron will flow
smoothly and uniformly into the nodularizing chamber 31, the
upper portion of the mold is also provided with a shallow poux-
ing basin 39. The top edges of the walls 40 of the pouring
basin lie in the same plane as the top edges of the side walls
of chamber 31, which is the plane of the top surface 37 of the
mold.
With this construction of the mold it is possible to
seal the open tops of the nodularizing chamber 31 and the pour-
ing basin 39 by a refractory seal 41 (Figures 4-8) during the
pouring operation. The fact that the chambers and pouring
basins in the molds are open make it possible to check visually
the nodularizing chambers before pouring to determine that the
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~L~763~
nodularizing agent is present therein~ Also, the refractory
seal 41 seals in the products of the reaction between the nodu-
larizing agent and the molten iron, thus protecting the environ-
ment and personnel from hazards that might otherwise be en-
cou~tered. Furthermore, the location of the open topped pouring
basin and nodularizing chamber adjacent the top of the mold
results in a saving of space that would otherwise be occupied
in the mold if these chambers were incorporated in the interior
of the mold. Thus, the size and number of the casting cavity
or cavities that can be incorporated in a mold of a given size
is not substantially reduced as compared to conventional molds
by the use of the present invention; the reduction in size
and/or number of castin~s possible with a given size of mold
that occurs with systems in which the nodularizing chamber is
disposed internally of the mold is obviated.
As explained below with particular reerence to Fig-
ures 3-7, the present invention lends itself advantageously to
automatic pouring of the molten metal into the molds. ~ccord-
ing to a preferred form of the present invention, the furnace
~0 14 is of a known type that is adapted to deliver accurately
controlled quantities of molten iron at accurately controlled
temperatures within a predetermined period of time. Furnaces
of this type are known in the art and are commercially avail-
able. Suitable type furnaces and controls are illustrated and
described, for example, in United States Patents Nos~ 3,395,833
and 3,499,580, to which reference is hereby made~ Furnaces of
this general type are manufactured by Inductotherm Corporation
of Rancocos, ~ew ~ersey, U.S.A., and are marketed under the
tradename "Autopour". The furnace comprises a suitable pressure
vessel 42 that is usually round in cross section and which is
mounted on a movable carriage 43 so that its position can be
adjusted transversely of the pouring rail 10 in order to locate
~7~3.~
the furnace accurately with respect to the pouring basins of
the molds as they are successively moved along the rails. The
furnace is provided with heating elements and appropriate con-
trols to keep the molten iron within it at a temperature that
is accurately controlled. The furnace is under a con-trolled
super-atmospheric pressure of compressed air, the air pressure
being controlled by means of a detecting device positioned at a
fixed level beneath the molten iron within the furnace. The
detecting device measures the static pressure in the molten
metal at the level of the detecting device at all times. This
pressure is maintained at desired values by automatic controls
even though the level of molten iron in the furnace may vary
within a normal operating range. Since the mode of operation
and controls of various types of pressure pouring devices are
well known, the controls are not described in detail herein.
As shown in Figures 3, 6 and 7, the furnace has a
pouring spout 44 that is connected to a conduit 45 that extends
downwardly into the furnace vessel 42 ~o an open end disposed
substantially below the normal level of molten metal within the
vessel 42. Molten metal is supplied to the interior of the
vessel 42 through an inlet 46, a typical level of molten metal
in the vessel 42 being indicated by the dotted line in Figure 3.
The upper end of the conduit 45 terminates in the pouring spout
44, which is shown in the form of a trough. Slightly below
the juncture of the conduit 45 and the pouring spout 44, there
is a branch conduit 47 that is open at the top and functions to
limit the ferrostatic head of the molten metal that can be
developed in the conduit 45. This arrangement assists in main-
taining the rate of flow of molten metal in the conduit 45 sub-
stantially constant.
In operation, the controls maintain the pressure ofcompressed air on the surface of the molten metal within the
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~37~3~
pressure vessel 42 at a value such that the level of the molten
metal in the conduit 45 and branch conduit 47 is maintained at
a "ready to pour" level, indicated by the line 48 in Figures 3
and 6. During pouring, the pressure on the surface of the mol-
ten metal within the pressure vessel 42 is increased to raise
the level of molten metal in passage 47 to a pouring level such
as indicated at 50 in Figure 7, thus dischargin~ molten metal
from the pouring spout into the launder, which is then in its
lowered position. The flow of the molten metal is stopped
quickly by reducing the pressure within the vessel 42, causing
the level o~ metal in passage 47 to drop to the ready to pour
l~vel shown at 48 in Figure 6.
The end or lip 49 of the pouring spout is disposed
over the inner end 51 of the trough 52 of the launder 16, the
l~under being shown in its raised position in Figure 6 and in
pouring position in Figure 7.
The launder is supported from the furnace 14 by brack-
ets 53 disposed on either side thereof by pivotal connections
54. The opposite ends of the brackets are secured to a trans-
verse frame member 55 o~ the launder and the launder may bemoved between its raised position shown in Figure 6 and its
pouring position shown in Figure 7, by any convenient mechanism
such as a hydraulic piston and cylinder mechanism 56 acting
through toggle links 57 and 58.
The link 57 is pivotally supported by a bracket 59
carried by the furnace 14 and is pivoted to link 58 at 60.
Link 58 is pivotally connected to one of the brackets 53. The
cylinder of assembly 56 is also pivotally supported by the fur-
nace as at 61. The piston rod of assembly 56 is pivotally con-
nected to the pivotal connection 60. In the e~tended positionof the piston rod shown in Figure 6, the launder is in the raised
position shown thereinO In the retracted position of the piston
~ 7~
rod shown in Figure 7, the launder is lowered so that the re-
fractory seal 41 thereof firmly engages the top surface 37 of
the mold and makes a seal surrounding the open nodularizing
chamber 31 and pouring basin 39.
As shown particularly in Figures 6 and 7, the trough
of the launder is supported by cross member 55 and an intermedi-
ate support 62 that extends between the pivoted support arms 53.
If desired, mechanism can be provided to permit limited side-
ways adjustment of the launder along the pouring rail. The
trough comprises a refractory member 65 supported by a built-up
steel frame made of L-shaped side members 66 having bottom
1anges 67 and the cross member 55 which has flanges 68 and 69.
In order to support the refractory seal member 41, a
shallow metal securing member 71 is ad~ustably supported from
flanges 68, 72 and 73, respectively, welded to member 55 and
walls 66 of the launder and apertured to receive screws 68a~
74 and 75, the heads of which are welded to the securing member.
The screws are adjustably secured in the flanges as by nuts
76 and 77 50 that the securing member can be accurately
located.
m e refractory seal 41 is fastened in the securing
member by screws 78 that are threaded in nuts 79 welded to the
flanges. By this means the refractory sealing member can be
replaced readily if -that should become necessary.
In order to provide for the flow of molten me-tal into
the mold, the end of the trough in the launder remote from the
pressure vessel terminates in a downwardly extending closed con-
duit 80. Openings 81 and 82 aligned with the conduit are pro-
vided in the securing member 71 and in the sealing member 41.
With this arrangement, as will be seen from Figures 3-7, when
the launder is in its lowered position, molten metal discharged
from the pouring spout 44 of the furnace can flow down the
-12-
trough 52 to closed conduit 80, then through the registerin~
openin~s 81 and 82 directly into the pouring basin 39 of each
mold as it is positioned on the pouring rail in alignment with
the furnace.
In operation, the stroke of the hydraulic ram that
advances completed molds from the molding machine along the
pourin~ rail 10 is adjusted so that the molds are advanced a
distance equal to the width of a mold after each mold is deposit-
ed on the pouring rail. The position and amount of discharge
of the alloy dispensing apparatus 12 are adjusted so that the
apparatus will dischar~e the correct amount of alloy into the
nodularizing chamber 31 of each mold when the mold comes to rest
in registration with the dispensing apparatus 12. Similarly,
the position of the pressure vessel 42 and the attached launder
16, are adjusted with respect to the pouring rail so that as
each mold stops adjacent the furnace, the discharge of conduit
80 and the opening 81 in the sealing member 41 will be disposed
immediately above the pouring basin 39.
When these adjustments have been properly made and the
moldin~ machine started in operation, the molds will be advanced
successively to a position in which they are aligned with the
alloy dispensing apparatus 12 and then subsequently to a posi-
tion where they are aligned with the launder. m e alloy dis-
pensing apparatus is adjusted and timed so tha-t it will auto-
matically dischar~e the correct amount of alloy into the nodu-
larizin~ chamber 31 of each mold when it comes to rest. An
operator stationed on the platform P can readily observe whether
or not the alloy dispensing mechanism is operating correctly~
After the alloy has been deposited, the molds are suc-
cessively advanced step-by-step to the pouriny station adjacent
the launder 16. During the periods of time when the molds are
being moved, the hydraulic cyliner 56 is actuated to lift the
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~l~7~
launder to the raised position shown in Fi~ure 6 and the con-
trolling mechanism of the furnace maintains the level of molten
metal in the furnace at the ready to pour level indicated at 48.
When a mold is hrought into position and stopped immediat.ely
b~neath the launder, the cylinder 56 is controlled to permit the
launder to move to the pourin~ position shown in Figure 7 with
the refractory sealin~ member 41 in engagement with the top sur-
face of the mold, thereby sealing the surface of the mold
surrounding the open topped pouring basin 3g and the open topped
nodularizing chamber 31. Then the controls of the pressure
pouring apparatus of furnace 14 are actuated to increase the
pressure on the metal within the chamber 42 to a predetermined
amount which causes molten metal to rise to the pouring level
50 in branch conduit 47 and to flow out of the pourin~ spout 44
onto the inner end 51 of the trough 52 and down the trou~h 52
to the closed conduit 80 and throu~h the registering openin~s
81 and 82 into the pouring basin 39. From the shallow pouring
basin, the molten metal flows into the nodularizing chamber
where it is subjected to the action of the nodularizing alloy
disposed in the chamber.
When the level o~ molten metal in the nodularizing
chamber reaches the level of the openings 33 leading to the
runners 30, the molten metal enters the runners and flows
through the runners, down the downsprues 26 and the lateral
ingates 25, into the several casting cavities 24.
The rate of flow of molten metal from the pressure
vessel 42 is accurately controlled by accurate maintenance of
the temperature of the metal, the pressure within the vessel
and a timing means adjusted to stop the discharge o~ the molten
metal by quickly reducing the pressure within the pressure ves-
sel 42 so that the level of the metal in the conduits 45 and 47
is reduced to the ready to pour level 48. By this apparatus,
-14-
~B'7~
the amount of metal that is discharged into each mold and the
time required for the dischar~e (i.e., th~ rate of discharge)
can be controlled accurately so that waste of molten metal and
corresponding waste of nodularizing agent can be minimized.
A~ter the pouring is completed, the launder ls automatically
raised by the cylinder mechanism 56 and another mold is moved
into pouring position.
It is to be noted that in the pouring position the
refractory seal 41 reduces the amount of oxidation that takes
place when the iron reacts with t~e magnesium and also prevents
emission of contaminating reaction products into the atmosphere
and protects personnel and equipment from dangerous pyrotechnics
~hat frequently occur when magnesium e~posed to air encounters
molten iron. Also, the closed conduit 80 and openings 81 and
82 provide a closed passage that is several inches long from
the launder trough 52 to the pouring basin 39. This elevation
provides an additional ferrostatic head of metal in the mold
and this additional pressure makes it possible to utilize
runners, sprues and the like that are smaller in cross-section
2G than would otherwise be required, while securing a suf~iciently
rapid flow of molten metal at desired castingtempera~ures into
the casting cavities.
Furthermore, the rate of flow of metal from the fur-
nace and the dimensions of the passages in the mold are prefer-
ably correlated so that the molten metal is supplied to the
chamber 31 faster than it can flow out through the exit openings
33 into the runners 30. This results in the condition shown
diagrammatically in Figure 7, in which the chamber 31, the open-
ings 81 and 82 and the conduit 80 are all filled with molken
metal for the period of time during the pouring operation and a
head of metal as at 85 i9 formed at the lower end o~ the launder
above the passage or conduit 80. With this mode of operation,
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~6~
the tendency of the molten metal to carry slag and other unde-
sirable inclusions into the mold is reduced, since such inclu-
sion can rise to the surface of the head o~ metal 85 and ulti-
mately are retained in the chamber 31 and runners 30 when the
launder drains instead of being carried into the casting cavi-
ties 24 of the mold. Also, aspiration of air into the mold
passages and cavities and resultant oxidation is reduced as com-
pared to pouring practices where the metal falls to the mold in
an open stream.
Thus the invention not only provides for rapid auto-
matic production of iron castings, but because of the ferro-
static pressure obtained in the flow of metal through the con-
duits leading from the trough of the launder to the pouring
basin, the dimensions of the gating passages can be reduced as
compared to normal practice and the amount of scrap produced
for a given casting also can be reduced, thus reducing further
the amount of molten iron required, as well as the amount of
alloy required for each casting.
As an example, nodular iron insulating caps have been
produced in quantity with the apparatus. Each mold has twelve
casting cavities arranged generally as shown in Figure 8 of the
drawings with similar gating passages. The individual caps
hav~ a weight of one and one-half pounds and the total pouring
weight for each pour is thirty-five pounds. This gives a yield
in the castings themselves of 51.4% of the total metal poured.
For each pour, four and one-half ounces of nodulari~ing alloy is
deposited in the nodularizing cavity of each mold. The percent-
age of mangesium found in the casting and the scrap or gating
system amounts to 80% of the amount supplied and the total
pouring time per mold is six seconds.
It is to be noted that while the total pouring time is
six seconds, this is the amount of time that elapses from the
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~37~3~
beginning of the pouring operation to the completion of the
flow of metal out of ~he chamber 31 and to the runners, gates
and casting cavities. The furnace controls, however, are pre-
ferably ad]usted so that the required amount of metal, thirty-
five pounds in the example, is discharged by the furnace into
the launder within four seconds from the beginning of the pour-
ing operation, resulting in the filling of the chamber 31, open-
ings 81 and 82 and passage 30 and the formation of the head of
metal 85 with the advantages described above.
The maximum number of molds of this type that can be
poured per hour is 240. The molding and pouring operations are
carried out with a minimum number of personnel so that costs
are maintained at a reasonable value and the uniformity of the
pouring operation ensures that high quality castings are pro-
duced in which the nodularization of the iron is subtantially
complete.
To summarize, the method and apparatus of the present
invention result in greatly improved environmental conditions
and reduction in hazard to personnel because of the nodulariz~
~0 ing chamber being sealed. Furthermore, the size of the nodular-
izing chamber can be designed to make the most efficient use of
the nodularizing matexial for the size of the castings being
produced. The improved gating characteristics in the mold by
reason of the ferrostatic head of the launder seal reduces the
weight of the gating metal and thus also reduces the amount of
alloy required. The amount of alloy required is further reduc-
ed by the fact that the nodularizing chamber is completely
closed, thus waste of magnesium through oxidation is minimized~
The precise metering of the amount of molten iron supplied to
the mold makes it possible to eliminate waste and, for e~ample,
to permit draining of the iron completely from the horizontal
runners through which it is distributed to the down sprues.
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3~
Waste and scrap forma-tion are also reduced byelimination of
spillage of metal outside of the mold cavity and by the fact
t~at no convention pouring cup is required.
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