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Патент USA US2410837

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Nov. 12, 1946. -
A. T. PETERS
‘
'
2,410,837
'
CAST. I'NGOT
Filed- April 17, 1944
4 Sheets-Sheet‘ 1
-
'
.- INVENTOR;
Adolph 7.'Pe_fcr.5
BY
Mgw
v
I
ATTOEMEKS
.
~
Nov. 12, 1946.
A. T. PETERS
‘CAST INGOT
2,410,837
_
Filed April 17, 1944
4 Sheets-Sheet 2
‘A
'1'
17
INVEN TOR.
Ado/pf? 7i Pefens
M ,4 M4
ATTORNEYS
Nov. v12, 1946.
A. T. ‘PETERS
CAST INGOT
Filed April 17,1944
2,410,837
4 Sheets-Sheei; 5
\
\
52
O
IN VEN TOR. '
Adolph 7'. Ps/ers
ATTORNEYS
I
NOV. 12, 19.46.
V
A, T_ PETERS
7
2,410,837
CAST INGOT
Filed April 17, 1944
$41.4.
4 Sheets-Sheet 4
W544
Patented Nov. 12, 1946
2,410,831?
UNITED STATESTPATENT orrics _
Adolph T. Peters, Midland, Mich., assignor to The
Dow Chemical Company, Midland, Mich., a cor
' poration of Michigan
Application April 17, 1944, Serial No. 531,313‘
7 Claims.
1
.
The invention relates to cast metal. It more
particularly concerns improved cast ingot and a
method of and means for ‘casting the same of
alloyed magnesium, the liquidus of which passes
through a wide range of temperature as it solidi
?es.
(Cl. 22—200.1)
~
~ 2
temperature of the freezing range so de?ned is
the melting point of the lowest melting eutectic if
such exists.- Molten magnesium alloy having a
temperature above the maximum of the freezing
range contains “superheat” and is referred to
herein as “superheated."
Wide freezing range magnesium alloys, particu
My invention is predicated upon the discovery
larly those used for structural purposes, generally
that by cooling the upper end of the preformed
solidify in two principal phases, a solid solution
which constitutes the major portion of the solid 10' ingot of alloyed magnesium, the alloy having a
wide freezing range, positioned adjacent to the
metal and an intermetallic compound formed be
larger end of a shallow mold, the inside tapering
tween magnesium and the principal alloying con
inwardly from the bottom; adding to the mold
stituent, comprising the balance. Attempts to
molten superheated alloyed magnesium having a
cast such alloys in ingot form have heretofore
wide freezing range while preventing loss of heat
yielded a product lacking in uniformity, of com
therefrom through the mold wall so as to main—
position as regards the average concentration of
tain a pool of liquid metal therein turning to
alloying constituents from point to point
slush at the bottom thereof in contact with the
throughout the ingot and having an undesirable
cooled
ingot as heat from the slush is removed
metallographic structure particularly as‘ regards
the particle size and distribution of the second 20 substantially wholly by conduction through the
ingot, slush being thereby molded to the form of
phase throughout the solid solution phase and
the ingot and then frozen thereto to increase its
the nature of the distribution of’the dissolved
length, the unfrozen portion of the slush acting
constituent in the same solid solution phase.
to seal the mold against escape of liquid metal
The maldistribution of the alloying metal and
between the frozen slush and the mold wall; low
particle size of the second phase is responsible. 25 ering
the so lengthened ingot at a rate equivalent
in considerable measure, for the undesirable vari
to the rate at which such increase in length occurs
ations in physical properties developed in wrought
and in alignment with the mold so as to withdraw
products formed from conventional ingots of al
from the mold slush as it is molded, sound ingot
loyed magnesium.
w
A particular object is to provide an alloyed 30 is obtained having a unique metallographic struc-'
ture and substantial uniformity of composition
magnesium ingot yielding superior wrought metal
throughout
its length and breadth adapted for.
on being mechanically deformed thereinto as by
mechanical deformation into wrought products
forging, rolling, and extrusion.
possessing superior ‘strength properties.
Another object is to provide a method of cast
The invention then consists in the ingot, meth
ing ingot of the aforesaid character in a continu
od, and apparatus hereinafter fully described and
ous length,
'
Another object is to provide an apparatus suit
able for casting wide freezing range metal in a
particularly pointed out in the claims, the an
nexed drawings and the following description set
‘ting
forth certain means and mode of carrying
continuous length.
‘
.
out the invention.
Other objects and advantages will appear as 40
In the said annexed drawings:
the description proceeds.
Fig.1 is a side elevation partly in section of
The term “freezing range,” as used herein and
an embodiment of the ingot casting apparatus
in the appended claims, means the difference be
showing ingot being cast from slush metal in a
tween the temperature of the molten alloy when
solid metal ?rst appears on cooling the same and
the' temperature of the alloy when it has just en
tirely solidi?ed from the molten state under equi
librium conditions. The term “liquidus” refers
metal holder or mold.
‘
Fig. 2 is a similar view showing a portion of -
the apparatus of Fig. 1 arranged for starting its
operation with a dummy block.
Fig. 3 is a, similar view of a portion of Fig.1
to the curve relating the temperature and com
position of the liquid portion of the alloy as it is 50 showing the formation of slush in the metal
holder ontop of the dummy block as pouring of
cooled through the freezing range in_contact with
ingot is commenced.
'
the solid portion of the alloy thereby deposited
Fig. 4 is a similar view of. a portion of Fig. 1' .
from the liquid; and the term “solidus” refers to
showing a short section of ingot formed on the '
the curve relating the temperature and composi
dummy block.~
tion of the solid metal so deposited. The lower 55 Fig. 5 isa similar but enlarged fragmentary
2,410,887
3
'
'
view of a portion of Fig. l'showlng in detail the
‘transformation of liquid metal into slush, mold
ing it to the form of ingot, and freezing‘the same
into solid ingot in continuous sequence./
Fig. 6 is a photomicrograph, at 100 ,diameters,
showing the metallographic structure of Dow
metal‘ J-l cylindrical 13-inch diameter ingot,
cave head 44 engages the bottom end I I of the '
liquid metal and slush holder II to form a bottom
closure therefor, .as shown particularly in Fig. 2.
The dummy block is preferably made by casting
a length or ingot in the usual manner‘ or other
wise of a magnesium alloy having a similar com
position to that to be cast, although other metals
may be used.
'
.
taken at a point 1 inch from the cylindrical sur
Cooling
water
is
directed
against
the
dummy
face in a plane perpendicular to the axis, the
ingot being cast in accordance with the inven 10 block by opening the valve in the cooling water
supply line 2| thereby providing a curtain of
tion.
".
water 45 from the Jets 2! drenching the vertical
Fig. 7 is a similar photomicrograph to Fig. 6,
surface
of the block. In so drenching the sur
taken 3 inches from the cylindrical surface of
face of the ingot, it is desirable that the water
the ingot.
‘ .
he directed downwardly at an angle to the ver
Fig. 8 is a similar photomicrograph to Fig. 6,
taken on the axis of the ingot.
.
Fig. 9 is a similar photomicrograph to Fig. 6
but more deeply etched, revealing coring of the
solid solution phase, magni?cation 200 diameters.
. tical, as with the apparatus provided, so that
thewater is uniformly distributed and directed
away from contact with the bottom ii of the‘
metal holder l0.
.
While the dummy bloclcis thus cooled molten
In the several figures like numerals refer to 20 magnesium
alloy to be cast into ingot and con
like parts.
.
training a sufiicient amount of superheat is in
Referring to the drawings, numeral i0 is a
troduced into the metal holder in from the top,
vertically disposed metal holder or mold, open
as by ladling in the manner indicated in Fig. l, ‘
at the top and bottom, for molten metal‘ and
to a depth approaching the brim ll of the metal
slush formed thereof. The inside wall of the 25 holder Ill. The average temperature of the wall
mold slopes inwardly from the bottom Ii which
of the metal holder or mold is maintained above
is the larger end of the mold and opens down
the temperature of the liquidus of the alloy in
wardly. The metal holder is provided with
the mold by the superheat of the liquid metal
introduced
thereinto, loss 0! heat from the mold
ing of thermal insulation l2. If desired, a thin 30' being precluded
by insulation l2. or by the use
metal ring 28 is attached close to the bottom of
of an external heater around the mold (not
the mold to hold the insulation in place. The rim
shown), so as to prevent the formation of solid
i3 is attached to the top of the mold i0 and rests
alloy particles by abstraction of latent heat
upon a support ll carried on legs l5 and i8.
through the mold wall. Since ‘the metal holder
Means for imparting vibration to the mold. such
i0 is insulated, as with the insulation 12, or
as an air operated vibrator I1, is shown mounted
otherwise made proof against substantial heat
on the beam l8 carried by supports it and 20,
loss, heat from the liquid metal (i. e. superheat
the lower ends of which are attached to diametri
of the liquid and latent heat) immediately begins
cally opposite points 21 and 22, respectively, on
to be conducted away substantially wholly
the rim i3.
40
through the head 44 into the cooled dummy
Means are provided for bringing molten metal
block
43. The effect of such heat transfer is to
to the metal holder such as the tilting ladle 23
bring about crystallization of solid metal within
carried by ball 24 which is shown in Fig. 1 resting
the liquid- to form therewith a bed of slush l1
upon the hook 25, although other means may be
means to preclude loss of heat, such as a cover
used, such as a syphon or liquid metal pump,
delivering molten metal to the holder or mold
- of solid metal particles mixed with liquid metal
' which it frictionally mes, so that the con
76 dicated at ‘I. The unfrolen slush also acts to
supported by the wall of the mold and the top
of the dummy block as shown in Fig. 3.
through a pipe.
The slush bed thus formed is of gradually de
A cooling water launder 21, such as one hav
creasing density (i. e. ratio of volume of solid
ing a right triangular cross-section, is arranged
adjacent to the bottom of the metal holder. Ex 50 metal particles to that of liquid) toward the
supernatant liquid metal 48. The slush adjacent‘
tending around the inner circumferential face 28
to the top of the dummy block becomes increas
of the launder are parallel rows of uniformly
ingly dense as the liquid therewith cools until it
spaced small holes 28, drilled perpendicularly to
all freezes. I have found that as this slush be
the face 28 and thereby forming iets directed
comes increasingly dense, it passes through va
at an‘ angle, such as 45°, to the vertical. The
stage in which it is moldable and use is made of
launder is provided with a cooling water con
this property in my process by shaping or mold
nection 20 to a valved water supply ll.
ing the slush to the cross-sectional form of the
Guide wheels 82 and 3; are arranged so that
ingot desired before final freezing occurs. This
their treads 3! and 35. respectively, are in ver
shaping is accomplished adjacent to the big in
tical alignment with the inner circumference of
wardly tapered end I l where the slush approaches
the larger end ll of the metal holder; Driving
its maximumdensity and takes the cross-sec
wheel 38 has a tread 31 in vertical alignment
tional form of the opening of the mold before final
with a diametrically opposite point on the inner
freezing of the entrained liquid alloy occurs.
circumference of the metal holder from that of
The slush thus shaped is lowered from the mold
the treads of guide wheels 32 and 33. The driv- >
by lowering the dummy block thereby bringing
me wheel 36 is rotated by worm gear it operated
a further quantity of slush into molding position.
by worm pinion 39 driven through reduction gear
while the molded slush is being thus lowered, the
40 by motor 4i provided with speed regulation
liquid therein freezes forming of the slush a solid
controls l2.
'
In starting the process, a-dummy block I; of 70 body of metal having the cross-section of the
ingot desired. A portion of ingot ll thus pro
suitable length and having the cross-sectional
ducedis shown in Fig. 4.‘ resting on the top H of
form of the ingot to be cast, is positioned against
the dummy block ~43, the line of demarkation
the treads ll and 35 of the guitk wheels 32 ‘and 33
between the frozen and unfrozen slush being in
and. the tread 31 of the driving wheel 3', with
_
2,410,337
6
seal the bottom of the metal holder against leak
age of the supernatant liquid metal 48, the depth
may be from about 1 to 2 inches and the height
of the upper edge of the solidi?ed ingot 50 may
of which is kept shallow so as to minimize the
' liquid pressure head. on the slush.
be as high as 1 inch insideithe bottom of the
metal holder or as low as 14 inch below the same,
Complete
solidi?cation of the metal into ingot ‘is thus
brought about below or just inside the bottom of
this height being controlled by suitably regulating
the rate of lowering the formed ingot as afore
said. In Fig. 5, the molded slush emerging below
wall thereof being maintained by the liquid metal
the mold as the slush slumps therein is indicated
introduced above the lowest temperature reached
at 5| adjacent to the frozen-top edge 52 of ‘the
on the liquidus curve when the liquid metal is all 10 ingot, as when the process is- operated so. that _ ‘
just frozen, usually the eutectic melting point.
?nal freezing of the ingot occurs wholly outside
In carrying out the method in continuous man
or below the mold.
-.
ner, after forming a body of slush "as described,
meet 50 formed in this manner may be in
the dummy block 43 is lowered continuously at
creased in length as much as desired. In Fig. 1,
a rate such that ‘only the relatively dense molded
the
ingot is shown increased in length to below
slush emerges from the metal holder, the balance.
the ‘guide wheel 33 with the dummy block still
, the mold or holder ID, the temperature of the
of the slush slumping downwardly, forming a seal
while liquid metal is added, preferably at a sub
stantially constant rate, so as to maintain its
level and the inventory of slush therein, at a sub
attached. This may be cut off, as with a travel
ing saw (not shown), and the ingot cut in a
similar manner into convenient lengths, if desired,
as ingot is produced.
stantially constant shallow depth. ' Too rapid
lowering of the slush through the big end II is
revealed bya loss of the sealing action, while, if '
,
,
which extends over a substantial range of tem
the lowering is too slow, the lower portion of the
perature and composition as the alloy solidi?es.
slush tends to freeze to a completely solid mass
within the metal holder, hindering lowering.
Regulation of the rate of lowering of the dummy
block, and the ingot metal which'follows it, as
the operation proceeds, as shown in Fig. 3, is
accomplished by adjusting the speed of the motor 30
4| with controls 42. The speed of the driving
wheel 36 is thereby adjusted to the proper value.
The proper speed varies primarily with the alloy
composition, initial temperature (extent of super
heating) of the liquid metal, diameter of the cast 35
ingot, and temperature and volume of cooling
water and‘ is readily ascertained by trial. As an
illustration, in casting 12-inch diameter ingot of
-.
The method maybe practiced with any 01’ the
magnesium-base alloys, the liquidus curve- of
This is the case with the alloys of magnesium‘
usually used for the manufacture of extrusions,
forgings, rolled and drawn products, which have a
freezing range of more- than 125 Fahrenheit de
grees. Such alloys usually contain aluminum, as
the principal solid solution and intermetallic com
pound forming alloying ingredient, in amount
between about 3 per cent and 10 per cent, al
though, in some cases, the aluminum content may
be as high as 12 per cent or more. Zinc also forms
solid solutions and sometimes intermetallic com
pounds with magnesium and may be present in '
the alloys in amount between about 0.5 and 3 per
cent or more, either as the sole alloying agent or
“Dowmetal O” (nominally composed of 8.5 per cent
in combination with other alloying constituents,
aluminum, 0.2 per cent manganese, and 0.5 per 40 particularly
aluminum. In the magnesium-base
cent zinc, the balance being magnesium), using
alloys
containing
both aluminum and zinc as al
a. pouring temperature of 1260° F. (i. e. tempera
ture at which the metal is introduced into the
metal holder) in a frusto-conical metal holder
loying constituents in the aforesaid amounts, the
solid solution contains most of the aluminum and
substantially, if not all, the zinc, the balance of
tapering inwardly from the bottom at the rate of
the
aluminum and zinc, if any, forming. inter
1A, inch per foot, and having a depth of 8 inches,
metallic compound. Manganese in small amount,
formed of 1%, inch boilerplate surrounded by 1
e. g. 0.1 to 0.3 per cent, is generally added to the
inch thick asbestos thermal insulation, and using
magnesium alloys to enhance corrosion resistance '
about 20 gallons per minute of cooling water at
and it does not substantially a?ect the freezing
45° F., a suitable rate of lowering is between 50 range. Examples of such alloys containing alu
about 2.0 and about 2.7 inches per minute, about
minum, zinc, and manganese are given in the ac-~
2.5 inches being preferred.
‘
companying table, together with the freezing tem- I
As the operation proceeds, cohesion betweenv
perature, that is, the temperature at which solid
the solid metal particles and the ingot is largely
particlesbegin to deposit and form slush as the
relied upon to move the slush downwardly 55 molten alloy is slowly cooled,,as under equilibrium
through the metal holder in, which molds the
conditions. Temperatures whlch‘are 125 to 250
slush as it passes therethrough, however, some of
Fahrenheit degrees or more below the freezing
the metal particles in the slush may tend to stick
temperature are usually required to completely ‘
to the mold surface, necessitating the provision of
solidify these alloys.
means to dislodge them as by the use of a vibrator 60
Table I
(air hammer), such as that shown as I‘! in Fig. 1,
which vibrates or preferably imparts a continuous
series of sharp blows to the metal holder. I have
found that by making the total depth of the slush
and supernatant liquid metal between about 5 65
inches and 9 inches and preferably about 7
inches, using a metal holder tapering inwardly
from the bottom at a rate between about 1/8 inch
and 1% inch per foot, continuous downward move
ment of the slush is readily obtained using vibra~
tions at the rate of 20 per second and an ampli~
tude of not over about 0.07 inch or a series of
sharp blows at one second intervals moving the
mold rapidly a distance not over about 0.07 inch.
Nominal composition, percent Freezing
Dowmeial alloy
lamp"
4]
rs and rs-i __________
0.3
Zn
Mg
F~
1.0
Balance
_ _ _ _ _.
0.6
0.2
1.0
.._do.___.
1,145
0 and O-l ______________ __
8. 5
0. 2
0. 5 __.do...__
1,130
Jand J-l _ _ . . _ .
3.0
Mn
1, ice
By thus manipulating the slush so as to mold
it as it is formed, substantially wholly abstracting
its heat through the ingot into which it solidi?es,
and regulating the rate of lowering of the slush
so that the solidi?cation occurs adjacent the bot
In such operation, the depth of the slush bed 75 tom of the mold, preferably substantially wholly
below the-mold, a unique metallographic struc
2,410, 887
8
.
a rectangular bar 1/2 by 6 inches in cross-section
and the tensile and compression properties of the
ture results in the ingot. This structure is char
acterized by (1) substantially uniform but small
extrusion measured. For the extrusion, a 16
inch length of the cast ingot was heated to 600°
Fahrenheit, placed in the heated container of an
extrusion press having a die opening of 1/2 inch
by 6 inches, and then extruded at the rate of five
feet per minute,. thereby forming a bar 18 feet
sized masses of cored solid solution phase of one
or more alloying constituents in magnesium and
(2) a second phase which is generally an inter
metallic compound of magnesium and the prin
cipal alloying ingredient (e. g. MgnAlu in mag
nesium-base alloys containing aluminum as the
principal alloying metal) in exceedingly small
'long. Tensile strength properties of specimens
particles having a maximum width of 0.0006 inch 10 cut from the extruded bar at 31/2 feet, 81/2 feet,
and 15 feet from the end first issuing from the
distributed through the solid solution phase. In
die, measured in the direction parallel to the di
Figs. 6, 7, and 8, the intermetallic compound is
rection of extrusion are tabulated in Table II.
shown as small light particles having widths of
up to about 0.0004 inch surrounded by a dark line
Table II
of demarkation, the remaining, light background 15,
being the cored solid solution phase. In Fig. 9,
the background of cored solid solution phase is
accentuated by the deeper etch. This reveals the
aluminum concentration gradient in the cored
solid solution phase, the aluminum concentration 20
being greatest adjacent the particles of the inter
metallic compound.
{is regards uniformity of composition, typical
analysis of representative samples from scalped
12-inch diameter Dowmetal J-l ingot cast, in 25
accordance with the invention, and sampled at
the center line, and at 3 inches, and 6 inches
therefrom in a plane perpendicular to the axis,
Longitudinal strength in thousands of pounds
per square inch
Temple“,
lest distdainoe
mm
s
3. 6
8. 5
15. 0
'
Yield 1
Ultimate
elongation ,
Per cent
Com ressicn
26. 8
27.2
27. 2
44. 2
45. 2
45. 8
l3. 0
14.2
14.2
23. 9
25.1
25. l
yll’eld
I At 0.2 per cent deviation from the modulus line.
i In 2 inches.
\
For comparison, the properties of similar test
pieces cut from the same, size bar extruded sim
ilarly but from conventionally cast ingot are
6.6 per cent, and 6.6 per cent, respectively. Simi 30 tabulated in Table III.
lar samples taken from adjacent sections of the _
Table III
ingot showed similar values for the aluminum
concentration. The variations in the aluminum
Longitudinal strength in thousands oi pounds
show an aluminum concentration of 6.5 per cent,
concentration in ingot similarity cast in other
per square inch
magnesium-base alloys do not exceed the fore 35
going and all such variations are less than about
2 per cent of the total amount of alloying in
'l‘estpiece
feet distance
gredient from place to place-throughout the in
got, the size of the sample being large enough,
e. g. 5 to 10 grams, to be representative. In com
Tensile
from die
Com rfgsion
Yieidl
Ultimate
Per cent
elongation ,
ye
40~
3.6
22.5
41.4
13.7
20.0
parison with this, similar sampling of conven
8. 5 .
23. 2
42. 7
l5. 6
19. l
tional 12-inch diameter ingot of the same alloy
15. 6
25. 6
44. 5
l6. 0
18.3
cast in 30“inch lengths gave aluminum concentra
tions varying both from the center toward the
I and lé-see Table II.
outside and from top to bottom, the variations 45 While the invention has been illustrated with
from top to bottom, respectively, being from 6.0
the use of a mold having a circular cross-section
per cent to 6.8 per cent along the axis, 6.4 per cent
(frusto-conical) other shapes may be used such
_to 6.8 per cent 3 inches from the axis, and 6.6
as those of rectangular cross-section or those
per cent to 6.7 per cent 6 inches from the axis.
formed of combinations of plane and curved
As regards the uniformity of distribution of man 50 walls, as an oblong section with rounded sides. In
ganese, that of the ingot of thc invention showed
all such molds the inside is made to slope in
no signi?cant variation from center to outside and
wardly from the bottom with a substantial taper,
lengthwise of the ingot, while the concentration
such as 1/8 inch to % inch per foot, as aforesaid,
in conventional ingot varied from a minimum of
the taper exceeding the slope required merely
55 for relieving frictional resistance as employed in
0.16 per cent to a maximum of 0.33 per cent.
By virtue of the unique metaliographic struc
conventional molds.
ture, especially the uniform distribution and
Among the advantages or the method are that
smallness of the particle size of the second phase,
oxidation of the ingot surface, which occurs be
even spacing and sharp concentration gradient
tween the ingot and mold wall in conventional
of the coring oi’ the solid solution phase, and 60 continuous casting, is obviated as the mold is so
uniformity of composition, the ingot has its prin
?lled with metal below the liquid‘ line that air
' cipal utility as stock material for making
cannot attack the metal surface adjacent to the
wrought products such as extrusions.
,
mold. Also, the interior of the mold wall below
In such uses, an important advantage is tha
the liquid level is not subject to severe abrasion
the extruded product not only exhibits high values 65 since substantially only either liquid or slush
for strength properties but also greater uniform
is present in the mold. ' In addition, the ingot
ity of properties from point to point throughout
does'not su?'er from the defects which result
the extrusion compared to extrusions made from
from contact with the wall of the mold common
conventionally cast ingot. For example, Dow
in conventional continuous casting. For this
metal J-l cast into 8-inch diameter cylindrical 70 reason, also, sticking of the ingot to the mold is
ingot. in accordance with the method described,
obviated.
in which the second phase was in the form of
particles having a maximum width of 0.0004
Iclaim:
.
inch distributed between evenly spaced adjacent
1. The method of casting ingot of alloyed mag
nesium having a wide freezing range which com
masses of cored solid solution, was extruded into
prises continuously supplying tbeymolten alloy
2,410,887
a
to a vertically disposed'mold, the inside of said
10
‘
_
5. In a method of casting ingot of alloyed
magnesium in a continuous length, the steps
which consist in cooling a, section of the precast
ingot near oneend thereof; positioning the cooled
mold sloping inwardly from the bottom, while
continuously lowering ingot from below the mold;
drenching the sides of the ingot with a coolant
so as to carry away heat from the metal sup
end adjacent to the bottom of a, vertically dis
plied to the mold thereby to form a bed of slush
therein of liquid metal mixed with solid metal
posed mold insulated against substantial heat
loss and havinginsides sloping inwardly from
particles, the lower portion of the bed adJacent
the bottom; introducing molten magnesium alloy
to the upper end of the ingot freezing thereto
and increasing its length; and regulating the rate
of lowering of the ingot so that the unfrozen
portion of the slush in contact with the ingot is
maintained adjacent to the bottom of the mold
into the mold so as to maintain a, pool of liquid
metal at a substantially constant level therein,
thereby cooling the alloy by transferring'heat to
the cooled end of the ingot and forming a body
of slush of solid metal particles mixed with liquid
forming a seal with the mold preventing leakage’
metal beneath the pool, the slush adjacent to the
of liquid metal therefrom.
16 ingot conforming to ‘the shape of the mold and
2. The method of casting ingot of alloyed mag-_
freezing onto the end of the ingot to‘ form an
nesium having a wide freezing range which com
extension thereof, and the unfrozen slush form
prises continuously supplying the molten alloy to
ing a seal preventing the liquid metal from escap
a vertically disposed thermally insulated mold at
ing from the mold between it and the extension
a rate such that a substantially constant level 20 of the end of the ingot; and lowering the ingot
of liquid metal is established therein, the inside
at a rate sufficient to compensate for the exten
wall of said mold sloping inwardly from the bot
sion thus produced so as to maintain its position
tom, while lowering ingot from below and in line
just below the mold without breaking the seal '
with the mold; drenching with a coolant the
formed by the slush.
sides of the ingot as it is lowered so as to carry
6. In a method of casting ingot of alloyed mag
away heat from the metal supplied to the mold
nesium in a continuous length, the steps which
thereby to form a bed of slush therein of liquid
' consist in cooling 9. section of the precast ingot
metal mixed with solid metal particles, the por
near one end thereof; positioning the cooled end
tion adjacent to the upper end of the ingot freez
adjacent to the bottom of a vertically disposed
ing thereto and increasing its length, the un 30 mold insulated against substantial heat loss and
frozen portion forming a seal between the mold
having insides sloping inwardly from the bottom;
and the frozen slush preventing escape of liquid
introducting molten magnesium alloy into the
metal from the mold; and regulating‘the rate of
mold so as to maintain a pool of liquid'metal at
lowering of the ingot so that the freezing of the
a substantially constant level therein, thereby
slush onto the end of the ingot occurs substan
cooling the alloy by ‘transferring heat to the
tially whollybelow the mold while maintaining - cooled and of the ingot and forming a body of
the aforesaid seal.
slush of solid metal particlesmixed with liquid
3. The method of casting ingot of alloyed mag
metal beneath the pool, the slush adjacent to the
nesium having a freezing range of more than 125
ingot conforming to the shape of the mold and
Fahrenheit degrees which comprises continuously 40 freezing onto the end. of the ingot to form an
supplying the molten alloy to a vertically disposed
extension thereof, and the unfrozen slush form
mold, the inside wall of said mold sloping in
ing a seal preventing the liquid metal from escap
wardly from the bottom at a rate of about $4; to
ing from the mold between it and the extension
1% inch per foot while continuously lowering in
of the end of the ingot; lowering the ingot at a
got from below the mold; drenching the sides
rate sumcient to compensate for the extension
of the ingot with a coolant so as to carry away
thus produced so as to maintain its position just
heat from the metalsupplied to the mold thereby
below the mold without breaking the seal formed
to form a body ofslush therein of liquid metal
by the slush; and vibrating the mold so as to
mixed with solid metal particles, the lower por
ldislodge'alloy particles tending to stick thereto.
tion adjacent to the upper end of the ingot
'7. The method of continuously casting ingot ,
feezing thereto and'increasing its length; and 50 of alloyed magnesium having a wide freezing
regulating the rate of lowering of the ingot so ' range which comprises maintaining the precast
that the freezing of the slush onto the end of the
end of the ingot directly below and adjacent to
ingot occurs substantially wholly below the mold,
the bottom ‘of a short vertically disposed mold,
the unfrozen portion of the slush forming a seal
the inside wall of said mold sloping inwardly from
between the mold and the frozen slush thereby
the bottom; continuously supplying the molten
to prevent escape of liquid metal from the mold.
alloy to .the mold so as to form a pool therein
4. The method of casting ingot of alloyed mag
over the end of the ingot; applying a coolant to
nesium having a freezing range of more than 125
the sides of the ingot so as to carry away heat
Fahrenheit degrees which comprises continuously
supplying the molten alloy to a, vertically dis
posed thermally insulated mold, the inside wall
of said mold sloping inwardly from the bottom
from the liquid metal in the mold thereby to form
a body of slush of liquid metal mixed with solid
metal particles beneath the pool, the lower por
tion of the slush adjacent to the precast end of
the ingot freezing thereto and increasing its
at the rate of from % to ‘Apinch per foot, while
continuously lowering ingot from below the
>mold; vibrating the mold; drenching the sides of
length; continuously lowering the ingot while
supplying the molten metal to the mold and vi
the ingot with a coolant so as to carry away heat
brating the mold; and regulating the lowering
from the metal supplied to the mold thereby to
rate of the ingot so that the freezing of slush
form a bed of slush therein of liquid metal mixed
thereonto occurs substantially wholly below the
with, metal particles, the portion of the bed ad 70 mold, the unfrozen portion of the slush forming
jacent to the upper end'of the ingot freezing
a seal between the mold and the frozen slush
solid thereto and increasing its length; and reg;
ulating the rate of lowering of the ingot so that
the freezing of the slush into ingot occurs sub
stantially wholly below the mold.
thereby to prevent escape of liquid metal from’
the mold.
‘
.
ADOLPH T. PETERS.
76
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