Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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SPECIFICATION
APPARATUS FOR PRODUCING SEMISOLID SHAPING METALS
Technical Field
This invention relates to an apparatus for producing
semisolid shaping metals. More particularly, the invention
relates to an apparatus with which semisolid metals
suitable for semisolid shaping that have fine primary
crystals dispersed in the liquid phase and that have a
uniform temperature distribution can be produced in a very
convenient and easy way.
Background Art
A thixo-casting process is drawing researcher's
attention these days since it involves a fewer molding
defects and segregations, produces uniform metallographic
structures and features longer mold lives but shorter
molding cycles than the existing casting techniques. The
billets used in this molding method (A) are characterized
by spheroidized structures obtained by either performing
mechanical or electromagnetic agitation in temperature
ranges that produce semisolid metals or by taking advantage
of recrystallization of worked metals.
On the other hand, raw materials cast by the existing
methods may also be molded in a semisolid state. There are
three examples of this approach; the first two concern
magnesium alloys that will easily produce an equiaxed
microstructure and Zr is added to induce the formation of
finer crystals [method (B)] or a carbonaceous refiner is
added for the same purpose [method (C)); the third approach
concerns aluminum alloys and a master alloy comprising an
A1-5~ Ti-1$ B system is added as a refiner in amounts
ranging from 2 - 10 times the conventional amount [method
(D)). The raw materials prepared by these methods are
heated to temperature ranges that produce semisolid metals
and the resulting primary crystals are spheroidized before
molding.
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It is also known that alloys within a solubility limit
are heated fairly rapidly up to a temperature near the
solidus line and, thereafter, in order to ensure a uniform
temperature distribution through the raw material while
avoiding local melting, the alloy is slowly heated to an
appropriate temperature beyond the solidus line so that the
material becomes sufficiently soft to be molded [method
(E)]. A method is also known, in which molten aluminum at
about 700 is cast to flow down an inclined cooling plate
to form partially molten aluminum, which is collected in a
vessel [method (F)].
These methods in which billets are molded after they
are heated to temperatures that produce semisolid metals
are in sharp contrast with a rheo-casting process (G), in
which molten metals containing spherical primary crystals
are produced continuously and molded as such without being
solidified to billets. It is also known to form a rheo-
casting slurry by a method in which a metal which is at
least partially solid, partially liquid and which is
obtained by bringing a molten metal into contact with a
chiller and inclined chiller is held in a temperature range
that produces a semisolid metal [method (H)].
Further, a casting apparatus (I) is known which
produces a partially solidified billet by cooling a metal
in a billet case either from the outside of a vessel or
with~ultrasonic vibrations being applied directly to the
interior of the vessel and the billet is taken out of the
case and shaped either as such or after reheating with r-f
induction heater.
However, the above-described conventional methods have
their own problems. Method (A) is cumbersome and the
production cost is high irrespective of whether the
agitation or recrystallization technique is utilized. When
applied to magnesium alloys, method (B) is economically
disadvantageous since Zr is an expensive element and
speaking of method (C), in order to ensure that
carbonaceous refiners will exhibit their function to the
fullest extent, the addition of Be as an oxidation control
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element has to be reduced to a level as low as about 7 ppm
but then the alloy is prone to burn by oxidation during the
heat treatment dust prior to molding and this is
inconvenient in operations.
In the case of aluminum alloys, about 500 um is the
crystal grain size that can be achieved by the mere
addition of refiners and it is not easy to obtain crystal
grains finer than 200 um. To solve this problem, increased
amounts of refiners are added in method (D) but this is
industrially difficult to implement because the added
refiners are prone to settle on the bottom of the furnace;
furthermore, the method is costly. Method (E) is a thixo-
casting process which is characterized by heating the raw
material slowly after the temperature has exceeded the
solidus line such that the raw material is uniformly heated
and spheroidized. In fact, however, an ordinary dendritic
microstructure will not transform to a thixotropic
structure (in which the primary dendrites have been
spheroidized) upon heating. According to method (F),
partially molten aluminum having spherical particles in the
microstructure can be obtained conveniently but no
conditions are available that provide for direct shaping.
What is more, thixo-casting methods (A) - (F) have a common
problem in that they are more costly than the existing
casting methods because in order to perform molding in the
semisolid state, the liquid phase must first be solidified
to prepare a billet, which is heated again to a temperature
range that produces a semisolid metal. In addition, the
billets as the starting material are difficult to recycle
and the fraction liquid cannot be increased to a very high
level because of handling considerations.
In contrast, method (G) which continuously generates
and supplies a molten metal containing spherical primary
crystals is more advantageous than the thixocasting
approach from the viewpoint of cost and energy but, on the
other hand, the machine to be installed for producing a
metal material consisting of a spherical structure and a
liquid phase requires cumbersome procedures to assure
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effective operative association with the casting machine to
yield the final product. Specifically, if the casting
machine fails, difficulty arises in the processing of the
semisolid metal.
Method (H) which holds the chilled metal for a
specified time in a temperature range that produces a
semisolid metal has the following problem. Unlike the thixo-
casting approach which is characterized by solidification
into billets, reheating a.nd subsequent shaping, the method
(H) involves direct shaping of the semisolid metal obtained
by holding in the specified temperature range for a
specified time and in order to realize industrial
continuous operations, it is necessary that an alloy having
a good enough temperature distribution to establish a
specified fraction liquid suitable for shaping should be
formed within a short time. However, the desired rheo-
casting semisolid metal which has spherical primary
crystals, a fraction liquid and a temperature distribution
that are suitable for shaping cannot be obtained by merely
holding the cooled metal in the specified temperature range
for a specified period. Too rapid cooling will deteriorate
the temperature distribution. In addition, if the cooling
means is contacted by the melt, a solidified metal will
remain either on the cooling means or within the holding
vessel, making it impossible to perform continuous
operation.
In method (I), a case for cooling the metal in a
vessel is employed but the top and the bottom portions of
the metal in the vessel will cool faster than the center
and it is difficult to produce a partially solidified
billet having a uniform temperature distribution and
immediate shaping will yield a product of nonuniform
structure. What is more, considering the need to satisfy
the requirement that the partially solidified billets as
taken out of the billet case have such a temperature that
the initial state of the billet is maintained, it is
difficult for the fraction liquid of the partially
solidified billet to exceed 50~ and the maximum that can be
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attained practically is no more than about 40~, which makes
it necessary to give special considerations in determining
injection and other conditions for shaping by diecasting.
If the fraction liquid of the billet has dropped below 40~,
it-could be reheated with a r-f induction heater but it is
still difficult to attain a fraction liquid in excess of
50~ and special considerations must be made in injection
and other shaping conditions. In addition, eliminating any
significant temperature uneveness that has occurred within
the partially solidified billet is a time-consuming
practice and it is required, although for only a short
time, that the r-f induction heater produces a high power
comparable to that required in thixo-casting. In addition
it is necessary to install multiple units of the r-f
induction heater in order to achieve continuous operation
in short cycles.
Another problem with the industrial practice of
shaping semisolid metals in a continuous manner is that if
a trouble occurs in the casting machine, the semisolid
metal may occasionally be held in a specified temperature
range for a period longer than the prescribed time. Unless
a certain problem occurs in the metallographic structure,
it is desired that the semisolid metal be maintained at a
specified temperature; in practice, however, particularly
in the thixo-casting process where the semisolid metal is
held with its temperature elevated from room temperature,
the metallographic structure becomes coarse and the billets
are considerably deformed (progressively increase in
diameter toward the bottom}. In addition, unless their
temperatures are individually controlled, such billets are
usually discarded and cannot be used as thixo-billets.
The present invention has been accomplished under
these circumstances of the prior art and its principal
object is to provide an apparatus that does not require to
use billets or any cumbersome procedures but which ensures
that semisolid metals (including those which have higher
values of fraction liquid than what are obtained by the
conventional thixo-casting process) which are suitable for
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subsequent shaping on ac~~ou:rit:. o.f. bc~t:~ a t:~niform structure
containing spheroiclized primax,~y c:x°yst~l~ and uniform
temperature distribution ca.n be produced in a convenient,
easy cast--ef fect ive:~ way. Tn a~.d i t i,r.,ra , i ~: the need. az i.ses to
control. the sem.isol id medal. b~~ holding ~.t ~.~t: a specified
temperature during prolonged machine trouble or in the case
where a semisolid rraetal. ilav:i~zc~ <:r spe;~rfi.F~d fraction liquid is
rapidl~~ produced to perm:i.t high shot-=~yr_.e operations and
where it is adjusted to tal:~ within a specified temperature
range prior to molc~.ing, i:he appazxat:u~ ;i;; capable of producing
a semisolid metal suitab!a t~~i: semi.s~~.i..:i.d shaping by holding
the metal' s temperature unitoz~mly at ..~ cc:nstant level with
such great rapidit,y~ that t:hc:.> powex r~=_,:;~~ixement of the ar-f
induction heater is no more than 50°s caf what. :i.s comm.only
spent in shaping by the thif~co--c:astir~g prc:c~as.
Disclosure of Invention
Th.e stated «bject at: t~m~ ix~verut:icar~ rar:c be attained by an
apparatus for prod~~.cing t~ sk=_rn:isoii<1 5~uapi.ng metal. that has
fine primary crystals di:~persed in the liquid phase and which
also has a uniform tempt>t~ati :ra ,~list:ri.~:a~.ztpor:~, said apparatus
comprising a melt ~~ouri.rm scac:t;ir;m c~orxr~,:wi~;:ir.,q a melting
furnace which melts and holds a metal and a pouring device
which lifts out thc:r molt:e:n ctAet.a.l.. i°rosn said melt ing
furnace,
adjusts it to a specified temperature arid pours it in a
holding vessel, a nucleating section which generates crystal
nuclei in the melt as i.t:: is >v.z,p~:~l. ~..ed f: ~::orra said pouring
device
into said holding vessel, a crystal ~:~enerating section which
performs temperature adjustment such t: hat. the metal obtained
from said nucleat~:i~r.g sr~ct ~.orc fa:l-l.s wi.t:;.k~irG a desired molding
temperature range ,~s it a s cvooled t.o <~. mol.d.ing temperature at
which it is partially solid, part.ial_Lr liquid, a holding
vessel condit.io:nin~:~ section wtaic:h inv.rr~rts t:he holding vessel
by turning it upside down so that a partially molten metal is
discharged and whicrh txier~ c.:Learm the inner surfaces of the
holding vessel, and a vesse:)_ t:rar~spc:~7:~t:i.rlg sec~t;ion fuz~nished
with an automating device incluaic~g a robot with which the
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partially molten metal from said nucleating section is
transpc>rted into t.l~:E.e inj F~cti.carx s1 eevn r.> f: a molding machine .
Accordingly, cane aspect. of the p7~esE:nt i.nven.t.icrn :resides
in the melt pouring sect:LOn oi' the apparatus eomprising:(1) a
high-temperature melt ho.l.di~m~ fo.xrnac,~e <~nci ~~ low-t:emper<~ture
melt holding furnace furnis.~ed with a pouring ladle, or {2) a
pouring ladle furn:i shed witA:a ;,~ r.~ef:i.r~er t:eeci una..t a.nd.. a
temperature control cooling jig inse.r~:irrg device and. a high-
temper<~.ture melt holding fu:r~rsar.:r:~, or iB) a low-temperature
melt holding furnace furnisized with a pouri.xxg 1-adle and a
refiner-rich melt holding faxr2ace als~~ furnished with a
pouringW.adl.e, (4) a pc>uu-i.n<:x Lac:llc-~, tar-xr:i.~.hr>.c.~ with a
r~e:Einer
melting radio-frequency i.nd:zct:ior_ hea::er and a 1ow-
tempera.ture melt holding ve:~:>Fal.,. ox; ( -P) a 7.c>w-temperature
melt holding vessel furnished with. a g?oux ing ladle, anti
wherein the nucleat:ing sf:ct:i.c:-.rz i.,~. t:. ha ln.oldi.ng vessel.
In another aspect:, the 17~~e:.;er~t :L~u~~rer:.tion x:~es;ides in the
nucleating means comprisvng ei.t:h er a lrol.dineg vessel tilting
or inverting unit. ~y w.hic~h ,:lie angl.e c~f inc°:L:Lnati.on ~:>f the
holding vessel can be varied freely and. automatically as
required during an~~ aftem pr>urirzg of r:Lmrne~.'l.t~ i.n acccardance
with its volume, or a holdi.rzg vessel a~.ool ir.~g accelerating
unit capable of coc~liry :~ai.cl 3,oldix:r~~ ~rryssel. externally during
and after pouring :~f the= me:l.t::, .~r- lac:t~ c>f ;aid holding vessel
tilting or invertirug unit. arid said ho:i.di.ng vessel cooling
accelerating unity .
In a further aspect, the present invention resides in
the melt pouring mans wl~icl2 is a :l.~aw -terrkperature me.:lt
pouring furnace f_u:rwished w:a th ,a paur:,ng ladle anal the
nucleating means cc:mprises ~~. vibrati~y jig and the holding
vessel, said vibra;:ing y ig :'w.cr~part:i.n<~ -,~ibrat:i.onw; to the melt
as it is poured into said holding vessel which is capable of
vertical movement:.
In another aspect, the present .invention resides in the
melt pouring means being a melt hold:i.c~c~ fuxwnace furnished
with a pouring ladle and the nucleat irxg means compri. ses an
inclining cooling j ig arid tlue ~icoldiazy vessel, said cc.>oling
j ig being such that: th.~- angn.e coC inr::a ~-r~.at ion can be varied
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freely and automat~.cally dur-:i_rzg and ,~tt.er: pouring of the melt
in accordance with its volume.
Ire a furthe.t: ~spec:t, tam present. ::i.nv°ent:ion resides in
the crystal generat: ing mean.:; ~.:,ompr~.s:ing a vertically movable
frame on which the holding ~ressel is placed and which is
either furnished with a ;~ou:r:ore fc>r ho<zti.r:;g the bottom portion
of said holding vessel om f~:~rmed of an insulating material
for hea.t--retainiru~ said k7ottv.c~m ,~7orz::i.a::~; , ~; vertically movable
lid that is either furnished witkr a he~ati.ng source for
heating the top portion of ~ai.d r.c~l.d:~_~c~ z,~essel or formf=_d of
an insulating matei:ial f<:~r heat--reta.irzi.ng said tap portion
and which is furnished with ~~ t.~~rx~p~'az:::~*:u,a:vm ~.aetmc~r for
measuring the temperature of t:h,e me 1. s= in the holding vessel,
and a cooling unit pro vided e~;t:er ir~xr ~.r~ sa:i.r~ holding vessel
for injecting air ~f a specified tempc~rat:ur-e against the
outer surface of said hoidimg vessel..
In. another aspect, the pr'e~;erzt l. mrent.i.on resides in the
crystal generating means comprising :gin induction apparatus
furniskled with a h~aata.t~g co ~._:1 wkxi.ufr L:s pxo~~~:ided around the
holding vessel for controlling the ternpexat.ure of the metal
in the holding vessel, a fra:xrne~ t: hat: i~.; c:~apa.ba.e of heat--
retaining or heating the bottom portion of the holding vessel
and which is ver-t:i~~ally mc:w~zk~:l.e for ~:~e>.t:aa~ ping or l ift: mg out
said holding vesse.a. and for ack.jr.zstin~~ itposition within the
heating coil of thL induction apparat:=us, a vertically movable
lid that is capabl=~~ of km:aat. -ret.3.ina,z~.C:~ c~z:~ heat:ing the top
portion of said holding vessel and wtni.c:h is furnished with a
temperature sensor for rnE~as!zr~.n.~,.~ t:he .E:mpwratuxe of the metal
in the holding vessel, and _z pooling unit. provided exterior
to wick heating co l l f-t~x:~ ~Lr~ ec~t a.nc~ ;~..i_r. of a specified
temperature against. the outer surface of said holding vessel.
In a further =~spe~t, ttrE~e pzese:clt i.nv~~:rat~:ior:~. r'esic:ie:~ in
the crystal generating mE~an4~ compri.s~-ng a:ra induction
apparatus furnishe,~~i with a '~ieati.ng ~°~r:~:! :E. wfnz.c:~h is
provided
around the holding vessel. f~-~r c;ont.ro-.a.. ing the temperature of
the metal in the hr~ldiag ve:~sel, a frame ~~hat is capable of
heat-retaining ~~x° :Neat i.racx tree. b~:~t.tom ,~;:~cui.-t:i.on of
the holding
vessel and which is not only vertically movable but also
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rotatable for retaining, lifting out or replacing said
holding vessel and for a<l.ju.~t:irzg i_t:s r~osl.t LOn wit~hir.~ the
heating coil of the induction apparatus, a vertically movable
lid that is capable of h~.~at.--ret.aa.rnrxg o:r~ hE:ating the top
portion of said holding vessel arid which is furnished with a
temperature sensor for meastarv.rac~ tire ::ennper-atuz:e of tht=_ metal
in the holding vessel, and ,-~ c:oul irrg uxritw provided exterior
to said heating c:o:il. fc>r :in.jF~c:;t~:i.ng a:ir t:~3. ~~ specified
temperature against the outer surface of said holding vessel.
The crystal generating means comprises-~ a plurality of units
which rotate or pivot about a si.ngl..e ,.xx:i.;.
In. another aspect, t: he present ij:r~,remti.on resides in the
crystal generating means cornfar:i.::,i.xy ~:~ :~r:~s.rne~ that is capable
of heat-retaining or heating the bot.t,~>m portion of the
holdinc3 vessel, a verti.c~~:Llya movable . i.c~ that is eapab:Le of
heat-retaining or heating the top por~=ior. of said holding
vessel and which is fuirm,:i.sh~.~:~. w~.tl~n a °z:em~;rexv~tune sensor
for
measuring the temperature o~ the met~~L ir: the holding vessel,
a cooling zone com~risinc:~ a. cc.-~o?..i.ng -~.zru:i.t: which irrject~s air
or
water of a specified temperature, as :Vequired, against the
outer surface of s<~id t~c:al.diric; ve.sse.l, ,~nc~ a temperat;a.rE~
adjusting zone having an induction apparatus furnished with a
heating coil which is pa:-c.>vic:~t:~u. ~~rc~un~:::~ said Luolciirxg vessel.
for
controlling the temperature of the metal in said holding
vessel.
In a further aspect, tl~e present .invention resides in
the crystal generating means fu.xvthe:r ;.a~cl.uding an. aut.ornatic
transport unit witr~. wh:ick~ tjne holding vessel containing the
metal cooled to a :.~pec~i f~ l.ed tr:em~>el: a.to..A:p:~F~ i.n t:he coolixxg
zone
is moved at a specified speed to the temperatm°e adjusting
zone which is adapted to be such. that e:i.thex~ the heating coil
of the induction ar~par:atus ~~>r tree h~~~lc:li.ng vessel moves so
that the temperatwre of the metal in tL~e ho:Lding ves se7_ is
controlled withixa the tz~>.atizy cc>i. ~ .
In another aspect , the present. :i.ra.vention resides in the
crystal. generating means fu:r:t;.Laex~ i.rm::i.v.~dir~g a t:ranspox°t
unit
comprising an automating device including a robot with which
the holding vessel ~con.t,~i.nir:~g t:~re met:.~,:1. r_ooled to a :;pacified
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temperature i.n the caal:iang ~<<>.ne i s rru~°,reca to the temperature
adjusting zone whic-:h is adapted to bP such that eitr.er the
heating ccil of the indu~=tioru. appaxwtus c.~r t:he holding vessel
moves so that the t.emper<~tuGVe n.o:: t.rne .~c~et.~l in the hal.d:ing
vessel is controlled within the heating coil.
In a further aspect,, tam present invention resides in
the holding vessel cond:it:ioz~irrg mea.n:~ c.c~n~pmisirzg a.t least two
of the following three unit;, i.e., a holding vessel cooling
unit that is capable of uotax y' and v;r~:r t:ica:L movements and
which i.s also capable <>f .in;j<~c:~t.i.ng al:: 1.~~~ast one of. a gas, a
liquid aid a solid material, an air blcawing unit that is
capable of rotary a.nd ~,re~:-ti<~c~l moverrsarnt s and optional air
injection, and a cleaning uauit. i=;~r ~~l~:xar~z:ncr them i.n.ne:r
surfaces of the holding vessel which has a brush that is
capablE: of rotary a.nd vea:~t.ic::a~, cxmverr~~rnts arr<i aa.r injection,
as well as a spray unit:. t:~haj: S.s c~apa~a:A..e c:f rotary and
vertical movements and appl:icaticn of a nonmetallic coating,
and a holding vessel rotc~tir~g and t;r~ar:rs~::'c:~:~:~t::izng unit with
which the holding vessel, w:i_th i..ts o~?E~r~ir~g facing down,, can
be moved to and fixed on the top port:i.on of each of said
cooling unit, said aix- b~_ow:i.r~g ~.{nit: ,~r:rd said <,leani.ng unit,
and which is vent i~~~ally rnovab7.e .
In another aspect, the present invention resides in the
holding vessel ccrrr,iitic>n:.i.ng means corn~:ox°isir..cy a cleaning
unit
and a spray unit, said c:i.eani..ng unit e:vcamprising a. jig f_or
cleaning the inner surfaces of the hu~dir~g vessel which has a
brush that is capable of x~ot:ax°y and ~,rc::r-t:ica.:L mave.ments and
air injection and ~~ vert:;_ca~.:l.y movabL~;~ yi:~ for fixing the
holding vessel, and said sp:rvay unit c.carc~prising a vertically
movable jig for applyi..nc~ a :rlonmct~al:l:i.c.: ::gating onto t~hE. inner
surfaces of the holding ves:~el :end a vertically movable jig
for fixing the holding vcss~.~l.
In a furthez: ~rspewt:, tx:rte p:cvesent invention reside: in
the temperature of the holding vesse. being adjusted when it
is empty.
In a further ~;~spe~:ut:, tr:re p:reseszt:. a.nvent;:ion resides in an
apparatus for producing a semisolid shaping metal that
contains fine primary ~~:x-yst~~ls c~i~>~>t~:-:,<.~ci :in t:he li.qui.d phase
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and which also has uniform t.ernperatur~ distribution, said
apparatus comprisir:~g: melt. ,pc~~x i.rzg mE.a~zs c°°omprisirrg
a melting
furnace which melts and :~olcis a metal and ~z pouring device
which lifts the molten mf:>ta~ c:>i.:cc:: of- ~~;:rid melting furnace,
adjusts it to a specified temperature and. pours it into a
holding vessel ; nuc~leat.irag znea.na whi ~.~n ~y;nNrates c~ryst<~1
nuclei in the molten metal; and crystal generating means
which cools the c~r~rstal rnu.c L~=:.i -c:~c::nex:wt:~c>ci mc>~.t~em nre.tal
:in the
vessel at an average rate of c~.0~ to 3.c.~"C~'sec to a desired
moldin<y temperature:::, whereb°~ r_~,c-~zvvc::art ~;ag the= cr~Tst;a.l
nuclei-
generated molten metal.. into a part i.a1 i.y so:l. id, partially
liquid metal cantaa.ni.nc~ :I::in~.>_ L.~r:i.ma.ry ~:-~i:y.~t:als dispersed in
liquid phase and halving lznifiorm temp watG~re distribution.
Brief Description ~:_af the Drawings
Fig. 1 is a p:Lan view Showing thE_ general layout of the
apparatus of the ic::menticjn ~:cr~ ~.~rc_~ciu:, a.ncy a semisolid shaping
metal.
Fig. 2 is a side view c>f a. clea.:cz.ng ur:ci.l~ i.n the holding
vessel conditioning section of the i:zvention apparatus.
Fig. 3 i.s a v~rti~:~wz:!. sfer:~tican sh~.owinc~ e,::rz:lax~ged the
essential components of the cleaning ;.snit.
Fig. 4 is a v...>rti.ca:l sf:aot'.ic:~n of t one hc~:l.di.rrg vesse:l
heating section of the invention appa-atus.
Figs. 5a-5e .i.~.lust.rat:e ~.:~~.e step c>.fgeryerating nuclei in
the nucleating section of the invention apparatus by low-
temperature melt, pouring t~ec::hn.i.clues .
Fig. 6 illustrates t-.he step cf gr~nerating nuclei an the
nucleating section of Lrm:~ ir-merztiorr apparatus by a vibration
technique.
Fig. 7 illustrates the step of generating nuclei in the
nucleating section of t'.hc~ .iauvent.ion apparatus by co:nt~aca with
a cooling plate.
Fig. 8 is a v~~rtica7. s~~~ct.iton. of t:r.lecrystal generating
section of the invention apparatus.
Fi.g. 9 is a t:L.ows~nee~t i :i_7..ustrat ~.r.g the process aor
producing a semisolid shaping metal using the apparatus of
the invention.
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Fig. 10 is a ~~ycle chart fc~r the continuous semisolid
shaping operation using the i.r~verFtian ap~rai-atus.
Fig. 11 is a ciiag:e'arnma~ic repz'es~nta.tion of a micrograph
showing the metallcygraph:'~_c~ ~t:z:~.uc::t~x.x'~.~ ~at ~., ~;l~aped part
:From
the shaping metal. ~iroc~i.zc<~d ~.~;,~ i:.lm :i.n~;rsarata.ar~.
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-12-
Fig. 12 is a plan view showing the general layout of
an apparatus for producing a semisolid shaping metal which
comprises a crystal generating means and a holding vessel
conditioning means which have rotating capabilities
according to the invention.
Fig. 13a is a plan view showing details of the crystal
generating means shown in Fig. 12. Fig. 13b is vertical
section A-A of Fig. 13a.
Fig. 14 is a side view of the rotating and
transporting unit and the cleaning unit in the holding
vessel conditioning means of the invention.
Fig. 15 is a side view of a holding vessel tilting or
inverting device according to the invention.
Fig. 16 is a plan view showing the general layout of
an apparatus for producing a semisolid shaping metal which
has a crystal generating means comprising a cooling zone
and a temperature adjusting zone according to the
invention.
Fig. 17a is a plan view showing details of the crystal
generating means shown in Fig. 16.
Fig. 17b is vertical section B-B of Fig. 17a.
Fig. 18 is a plan view showing the general layout of
an apparatus for producing a semisolid shaping metal which
has a stationary crystal generating means comprising a
cooling zone and a temperature adjusting zone according to
the invention.
Fig. 19a is a plan view showing details of the crystal
generating means shown in Fig. 18.
Fig. 19b is vertical section C-C of Fig. 19a.
Best Mode for Carrying Out the Invention
In the present invention, a metal melted in a melting
furnace is treated by either one of the following methods
to generate crystal nuclei within the melt: it is directly
poured into a holding vessel as a low-temperature melt
that contains a specified refiner and which is held
superheated to less than 50~ above the liquidus temperature
of the metal; it is poured into the holding vessel as a low-
CA 02242407 2003-06-02
temperature melt. that i:~ meld auperLrEaatYed to less than 50°C'
above the liquidus temperature of the metal with vibrations
being a~>plied tc~ thc=~ melt i.n t.~~xe ~zo:l.di.rrg ',re;;sel as it is
poured
into the latter; or the melt is poured int:..o the holding vessel
as it is brought into c on:ar_t: w:il:..rc a c~:~~~~_::i.ng plate treat can be
inclined at varying angles. '~~~E: melt:. havir~g crystal rxuclei
generated therein ire t~h.c. ;:~ry:~tal c~ez:~.cx-.ati.r~g section is ~sooled
to a temperature where a specif ied frat~t i.c:~n 1 iquid is
established, with tlvae trap or be>t::l::om c:nf ti:tc:~ holding vessel being
heat-retained or heated and with opta.onal, r--f induction
heating, so that a semisolid :;rp.apa.ng xm,eta:,f. having a Laniform
temperature distribution rind fine non-renc~ra..ta.c (sphe,rical)
primary crystals is prcc~u~~ed xac:>t; :l~zt::e:r than the start o:f
shaping; the holding vessel i.s then transported by means of a
robot into the inj ecaticx:~ sleeve ::~f a rru:;~ ldi rzc~ machine such as a
die-casting machine for subsequent sha~irsc~ .
Examples of tire i.nvEnt ~.c:rrx will rm~w be described in detail
with reference to ac~companyi:t~.c~ dr_awing~~ f~.gs. 1--19, in which:
Fig. 1 is a plan view showing t..ixe gex~ee_a1 layout of an
apparatus for producing a sernisc>lici sh~~zl~i.r~g metal; Fig. 2 is a
side view of a cleax=ing unit in tr:e: ho.Ldi.rxg vessel conditioning
section of the app,ar_atus; Fi~:l. 3 i:~ a ~.,~F,~~x°t;ic:al :sec;tion
showing
f~nlarged the essential compoxxertts of n::~ne c:le:aning unit; Fig. 4
is a vertical sectican of t:he L~ol.ciixxg v~.~ ssel. heating' section of
the apparatus; Figs. 5a - 5e illustrate the step of generating
nuclei in the nucleating ,~eck.=i.c~r~ of: t:~~:: appa.:ratus by :Low-
temperature melt pouring tecfnniques; Fi.g. 6 iJ.lustrates the
;step of generating tnucl~e::. :i.n t~k-~e nucl.r~~xt~,i.x°a.g sect:ion
by
vibration technique; Fig. 7 illustrates the step of generating
nuclei in the nuc:l.eating ;~ect::~.crn k.~y c~ot-ttacit with a ceol:Lng
plate; Fig. 8 is a vertical section of the nucleating
section; Fig. 9 is =~ fl:~wshekvtv i_i..lLi:;tr.-zting the process for
producing a semisolid shaping metal; ~ Lg. l0 is a cycle
c=hart for the contir~uou:; ;enti.ar.>l~.ci s:kx,-ig:>i.rt.c~ operation; Fig.
11
is a diagrammatic representat:.ion of a rnicrojraph showing
CA 02242407 1998-06-19
-14-
the metallographic structure of a shaped part obtained from
the shaping metal produced by the invention; Fig. l2 is a
plan view showing the general layout of an apparatus for
producing a semisolid shaping metal which comprises a
crystal generating means and a holding vessel conditioning
means which have rotating capabilities; Fig. 13a is a plan
view showing details of the crystal generating means shown
in Fig. 12; Fig. 13b is vertical section A-A of Fig. 13a;
Fig. 14 is a side view of the rotating and transporting
unit and the cleaning unit in the holding vessel
conditioning means; Fig. 15 is a side view of a holding
vessel tilting or inverting device; Fig. 16 is a plan view
showing the general layout of an apparatus for producing a
semisolid shaping metal which has a crystal generating
means comprising a cooling zone and a temperature adjusting
zone; Fig. 17a is a plan view showing details of the
crystal generating means shown in Fig. 16; Fig. 17b is
vertical section B-B of Fig. 17a; Fig. 1$ is a plan view
showing the general layout of an apparatus for producing a
semisolid shaping metal which has a stationary crystal
generating means comprising a cooling zone and a
temperature adjusting zone; Fig. 19a is a plan view showing
details of the crystal generating means shown in Fig. 18;
and Fig. 19b is vertical section C-C of Fig. 19a.
As Fig. 1 shows, the apparatus of the invention for
producing semisolid shaping metals which is generally
indicated by 100 comprises the holding vessel conditioning
section 10, the holding vessel heating section 20, the
crystal generating section 30, a melt pouring section 40, a
nucleating section 50 and a vessel transporting section 60.
A molding machine 200 is an example of the machines for
shaping a semisolid metal MB produced by the invention
apparatus 100.
As also shown in Fig. 1, the holding vessel
conditioning section 10 comprises a cleaning unit 12 and a
spray unit 14. As shown specifically in Fig. 2, the
cleaning unit 12 is comprised of a vertically movable
cylinder 12a, a motor 12b mounted at the distal end of the
CA 02242407 1998-06-19
-15-
piston rod on the cylinder 12a and a brush 12c which is
pushed into the holding vessel 1 by means of the motor 12b
and rotates to inject air. After the end of melt pouring, a
robot 62 in the vessel transporting section 60 which will
be described later transports the holding vessel 1 into an
infection sleeve 202a; the vessel is replaced upside down
on a receiving stage 13 and a holding vessel retainer 13a
provided just above the receiveing stage 13 is lowered
gently by means of a vertically moving cylinder 13b, so
that the bottom of the vessel 1 is lightly pressed downward
until it is secured to the receiving stage.
Thereafter, the brush 12c going up into the vessel 1
is driven to rotate so that all of its inner surfaces
including the bottom and lateral side are cleaned to
dislodge the residual metal deposit on those surfaces. As
shown, a closing cover 12d is provided downward around the
receiving stage 13 and the dropping metal deposit is
collected by a receiving tray 12e.
After the cleaning operation, the brush 12c is
retracted downward and the receiving stage 13 and vessel
retainer 13a, with the holding vessel 1 retained
therebetween, and the vertically moving cylinder 13b make a
lateral shift in unison from the cleaning position to the
spray position (the position of the spray unit 14 indicated
in Fig. 1) by means of a shift cylinder indicated by 15 in
Fig. 1. As shown specifically in Fig. 3, the spray unit 14
comprises a vertically movable cylinder 14a, a pipe 14b
fitted at the distal end of the piston rod on the cylinder
I4a and a spray nozzle 14c at the distal end of the pipe
14b. A water-soluble coating containing a nonmetallic
substance and air are infected through the nozzle 14c for a
specified time so that all inner surfaces of the holding
vessel 1 including the bottom and lateral side are sprayed
with the coating; the applied coating is dried with air to
make the inner surfaces of the holding vessel 1 cleaner.
The cleaning unit 12 and the spray unit 14 may be
operated in every shot or they may be activated at regular
intervals consisting of several shots. Any nonmagnetic
CA 02242407 1998-06-19
-16-
substance that deposited on the inner surfaces of the
holding vessel and which has been removed in the cleaning
operations is recovered from the receiveing tray 12e at
regular intervals of time. The spraying operation is for
avoiding direct contact between the inner surfaces of the
holding vessel 1 and the molten metal being poured into it
and must be performed if it is made of a metal. The coating
to be applied is selected from the group consisting of
graphite-based mold releases, non-graphite-based mold
releases (containing talc, mica, etc.) and BN.
As shown specifically in Fig. 4, the holding vessel
heating section 20 comprises a cylinder frame 2l, a
vertically movable cylinder 22 extending up and down
through the frame 21 for use in heating the holding vessel
1, support frame 23 that can be moved up and down by means
of the cylinder 22, a ceramic frame 24 fixed on the support
frame 23 for use in heating the holding vessel 1 and a
heating furnace 25 for heating the holding vessel 1 placed
on the frame 24.
After cleaning and spraying with the cleaning unit 12
and the spray unit 14, respectively, in the holding vessel
conditioning section 10, the holding vessel 1 is picked up
by the robot 62 and replaced on the frame 24, which then is
moved up by means of the cylinder 22. When the support
frame 23 and the frame 24 have ascended to the positions
indicated in Fig. 4, the holding vessel 1 will enter the
heating furnace 25, which is then closed off. The heating
furnace 25 may have an internal heater or, alternatively, a
hot blast may be blown from the outside.
After a specified time, the holding vessel 1 on the
frame 24 which has been heated to a specified temperature
(say, 2000 is taken out of the furnace by the descent of
the cylinder 22. The heated holding vessel 1 is picked up
by the robot 62 and transferred to the melt pouring section
40, where it is charged with a melt and thereafter
transferred to the nucleating section 50. The "holding
vessel" as used in the invention is a metallic or
nonmetallic vessel (including a ceramic vessel), or a
CA 02242407 1998-06-19
-17-
metallic vessel having a surface coated with nonmetalic
materials, or a metallic vessel composited with nonmetallic
materials. The wall thickness of the holding vessel 1
should be such that no solidified layer will form on the
inner surfaces of the vessel immediately after pouring the
melt or that even if a solidified Layer forms, it will
easily remelt upon heating with an induction heater 31 to
be described later.
Each of the melt pouring section 40 and the nucleating
section 50 is constructed differently depending upon the
method of generating crystal nuclei. Figs. 5a - 5d are side
views of the melt pouring section 40 and the nucleating
section 50 for the case where nucleation is effected by
pouring a low-temperature melt in the presence of a
refiner.
Fig. 5a shows the case where the melt pouring section
40 consists of a high-temperature melt holding furnace 41
and a low-temperature melt holding furnace 42 which is
furnished with a pouring ladle 42a. The high-temperature
melt holding furnace 41 holds a high-temperature molten
metal M1 which has a high-melting refiner (A1-Ti-H alloy) N
dissolved therein and which is held at 650°C or above,
preferably at 680 or above. The molten metal M1 is poured
from the high-temperature melt holding furnace 41 into the
low-temperature melt holding furnace 42, where it is held
at a lower temperature such that it is superheated to no
more than 50L above the liquidus temperature of the metal.
The resulting low-temperature melt M2 is poured into the
holding vessel 1 (i.e., the nucleating section 50) by means
of the ladle 42a, whereupon crystal nuclei form in the
melt. If Ti is the sole refiner in the melt, it is held
superheated to no more than 30°C above the liquidus
temperature of the metal. In the case of a magnesium alloy
containing both Sr and Si or containing Ca alone, the
degree of superheating should be no more than 25°C. If this
upper limit is exceeded, fine spherical primary crystals
will not form.
Fig. 5b shows the case where the melt pouring section
CA 02242407 1998-06-19
-18-
40 consists of a pouring ladle 42a furnished with a refiner
feed unit 43 and a temperature control cooling jig
inserting device 51 and a high-temperature melt holding
furnace 41. A high-temperature molten metal M3 which has a
refiner N (containing Ti) dissolved therein and which has
been held at 650 or above, preferably at 680 or above, in
the high-temperature melt holding furnace 41 is lifted out
with the ladle 42a and supplied with an additional refiner
(A1-Ti-B alloy) N from the refiner feed unit 43.
Thereafter, a cooling dig 51a on the device 51 is submerged
into the melt in the ladle 42a so that it is cooled to such
a temperature that it is superheated to no more than 50~
above the liquidus temperature of the metal. This yields a
low-temperature molten metal. In order to prevent the
formation of a solidified layer, the melt must be vibrated
as the cooling jig 51a is submerged. However, if the
temperature of the molten metal in the holding vessel 1 is
such that it is superheated to at least 10~ above the
liquidus temperature of the metal, one cannot expect nuclei
to be generated by vibrations. Therefore, the low-
temperature melt M2 in the ladle 42a is poured into the
holding vessel 1 (i.e., the nucleating section 50),
whereupon crystal nuclei are generated.
Fig. 5c shows the case where the melt pouring section
40 consists of a low-melt holding furnace 42 furnished with
a pouring ladle 42a and another low-temperature melt
holding furnace 42 which is also furnished with a pouring
ladle 42a and which is capable of holding a melt rich in a
refiner Al-Ti-B alloy. A Ti-containing low-temperature melt
M5 which is lifted out of the low-temperature melt holding
furnace 42 by means of the ladle 42a is mixed and diluted
with a low-temperature melt of high Ti and B contents M4
that is lifted out of the other low-temperature melt
holding furnace 42 by means of the ladle 42a. The low-
temperature melt M2 in the ladle 42a is poured into the
holding vessel 1 (i.e., the nucleating section 50),
whereupon crystal nuclei are generated.
Fig. 5d shows the case where the melt pouring section
CA 02242407 1998-06-19
-19-
40 consists of a pouring ladle 42a furnished with a refiner
melting r-f induction heater 44 and a low-temperature melt
holding furnace 42. A Ti-containing low-temperature molten
metal M5 is lifted out of the low-temperature melt holding
furnace 42 by means of the ladle 42a, into which a refiner
(A1-Ti-B alloy) N is charged after being melted by means of
a r-f induction coil 44a. The low-temperature melt M2 in
the ladle 42a is poured into the holding vessel 1 (i.e.,
the nucleating section 50), whereupon crystal nuclei are
generated.
Fig. 5e shows the case where the melt pouring section
40 consists of a pouring ladle 42a and a low-temperature
melt holding furnace 42. A low-temperature molten metal M6
near the melting point in the holding ladle 42a is poured
into the holding vessel 1 (i.e., the nucleating section
50), whereupon crystal nuclei are generated. If Ti is the
sole refiner in the melt, it is held superheated to no more
than 30~ above the liquidus temperature of the metal.
Fig. 6 is a side view of the melt pouring section 40
and the nucleating section 50 for the case of generating
nuclei by applying vibrations. The melt pouring section 40
consists of the low-temperature melt holding furnace 42
furnished with the pouring ladle 42a, a submergible
vibrating jig 52 that can be moved up and down by means of
a vertically moving cylinder 52a, and a jig 53 for
vibrating the holding vessel 1. To generate crystal nuclei
in the Ti-containing low-temperature molten metal M5 being
poured into the holding vessel 1 from the ladle 42a,
vibrations are applied by the following two methods:
submerging the vibrating jig 52 into the surface of the
melt M5 and placing the vibrating jig 53 into contact with
the outer surface of the holding vessel 1. It should be
mentioned that crystal nuclei can be generated even if no
refiners are contained in the melt being poured into the
holding vessel 1. In order to ensure that there will be no
uneven temperature distribution about it, the submerged
vibrating jig 52 should be disengaged from the surface of
the melt as soon as the pouring step has ended. The term "
CA 02242407 1998-06-19
-~U-
vibration" as used herein is in no way limited in terms of
the type of the vibrator used and the vibrating conditions
(frequency and amplitude) and any commercial pneumatic and
electric vibrators may be employed. As for the applicable
vibrating conditions, the frequency typically ranges from
lOHz to 50kHz, preferably from 50Hz to 1 kHz, and the
amplitude ranges from lmm to O.lum, preferably from 500um
to l0um, per side.
Fig. 7 is a side view of the melt pouring section 40
and the nucleating section 50 for the case of generating
nuclei by contact with a cooling plate. The melt pouring
section 40 consists-of a melt holding furnace assembly 40A
(comprising a high-temperature melt holding furnace 41 and
a low-temperature melt holding furnace 42) furnished with a
pouring ladle 42a. The temperature of the melt in the melt
holding furnace assembly 40A is not limited to any
particular value; however, if its temperature is unduly
high, it will become superheated to at least 10°C above the
liquidus temperature of the metal after it has passed over
an inclining cooling jig 70 and no crystal nuclei will be
formed. Therefore, the melt in the holding furnace assembly
40A is preferably superheated to no more than 50°C above the
liquidus temperature of the metal. The nucleating section
50 consists of the inclining cooling jig 70 and the holding
vessel 1. The cooling jig 70 has a water tank 71 that is
freely and automatically adjustable during and after
pouring of the melt in accordance with the angle of
inclination of the jig 70 and the pour volume of the melt.
As the volume of the molten metal that is poured from the
ladle 42a into the holding vessel 1 while making contact
with the inclined cooling jig 70 approaches the upper
limit, the angle of inclination of the jig 70 is reduced by
means of a vertically movable cylinder 72. After the end of
the pouring of the melt, the cooling jig 70 is inclined in
opposite direction so that the metal deposit on the surface
of the jig 70 drops into a metal deposit recovery tank 73.
In the cases described above, the melt pouring section
40 uses the pouring ladle 42 but this may be replaced by a
CA 02242407 1998-06-19
-21-
pouring pump.
Fig: 8 shows the details of the crystal generating
section 30. As shown, it comprises an induction heater 31
furnished with a heating coil 31a which is provided around
the holding vessel 1 for controlling the temperature of the
metal in it, a vertically movable cylinder 32, a support
frame 33 that can be moved up and down by means of the
cylinder 32 for retaining or lifting out the holding vessel
1 and for adjusting its position within the heating coil
31a, ceramic frame 34 placed on the support frame 33, a
ceramic lid 35 capable of heat-retaining or heating the top
of the holding vessel 1 and which is furnished with a
thermocouple 36 for measuring the temperature of the metal
in the holding vessel 1, a cooling unit 37 which is
provided exterior to the heating coil 31a for injecting air
of a specified temperature against the outer surface of the
holding vessel 1, and a protective cover 38 surrounding the
induction heater 31, frame 34, lid 35 and cooling unit 37.
The induction heater 31 is effective for providing a
uniform temperature distribution and ensuring a constant
temperature after the temperature of the metal in the
holding vessel has been lowered rapidly or when a trouble
occurs to the molding machine 200. If it is necessary to
cool the metal faster than when it is cooled with air, the
cooling unit which injects air may be replaced by a device
which sprays the holding vessel 1 with water before it
ascends to the position where the induction heater 31 is
provided.
After being charged with the molten metal MA into
which crystal nuclei have been introduced in the nucleating
section 50, the holding vessel 1 is picked up by the robot
62 and replaced on the ceramic frame 34, which then is
moved up by means of the cylinder 32 until it stops at a
specified position in the induction heater 31. Thereafter,
the ceramic lid 35 is placed on top of the holding vessel 1
and fixed in position. Subsequently, air is blown from the
cooling unit 37 against the outer surface of the holding
vessel 1 for a specified period of time at a specified
CA 02242407 1998-06-19
-22-
timing, both being determined by a specific need, such that
the molten metal MA within the holding vessel 1 is cooled
at an average rate of 0 . 01 °C /s - 3 . 0 °C /s f rom the
temperature right after the pouring of the melt until just
before the start of the molding step, thereby generating
fine primary crystals within the alloy solution; at the
same time, temperature adjustment is effected by means of
the induction heater 31 such that the temperatures of
various parts of the semisolid metal MB in the holding
vessel 1 will fall within the desired molding temperature
range for establishment of a specified fraction liquid not
later than the start of the molding step. To enable
temperature control of the semisolid metal MB, the ceramic
frame 34 is so designed that it can be finely adjusted
automatically to a desired height within the heating coil
31a. If it is not critical that the semisolid metal MB be
maintained at a constant temperature before molding, there
may be a case where the induction heater 31 need not be
operated.
When the semisolid metal MB in the holding vessel 1 on
the ceramic frame 34 has been held for a specified time at
a specified fraction liquid, the cylinder 32 is lowered so
that the holding vessel 1 is taken out of the induction
heater 31, picked up by the transport robot 62 and
immediately inserted into the injection sleeve 200a which
is of a vertical type (or a horizontal type 200b) in the
molding machine 200.
The term "a specified fraction liquid" means a
relative proportion of the liquid phase which is suitable
for pressure forming. In high-pressure casting operations
such as die casting and squeeze casting, the fraction
liquid is less than 75$, preferably in the range of 40~ -
65~. If the fraction liquid is less than 40~, not only is
it difficult to recover the alloy from the holding vessel 1
but also the formability of the raw material is poor. If
the fraction liquid exceeds 75~, the raw material is so
soft that it is not only difficult to handle but also less
likely to produce a homogeneous microstructure because the
CA 02242407 1998-06-19
-23-
molten metal will entrap the surrounding air when it is
inserted into the sleeve for injection into a mold on a die-
casting machine or segregation develops in the
metallographic structure of the casting. For these reasons,
the fraction liquid for high-pressure casting operations
should not be more than 75~, preferably not more than 65~.
However, in the case of alloys that have low shaping and
flowing properties or to yield products that are difficult
to shape, it is sometimes desirable to perform the shaping
operation with a fraction liquid higher than 75$. In this
case, a semisolid metal having a fraction liquid higher
than 75$ may be poured from the holding vessel into the
sleeve.
In extruding and forging operations, the fraction
liquid ranges from 1.0$ to 70~, preferably from 10~ to 65~.
Beyond 70$, an uneven structure can potentially occur.
Therefore, the fraction liquid should not be higher than
70$, preferably 65~ or less. Below 1.0$, the resistance to
deformation is unduly high; therefore, the fraction liquid
should be at least 1.0$. If extruding or forging operations
are to be performed with an alloy having a fraction liquid
of less than 40$, the alloy is first adjusted to a fraction
liquid of 40~ and more before it is taken out of the
holding vessel and thereafter the fraction liquid is
lowered to less than 40$.
The robot 62 in the vessel transporting section 60 is
a known multi-joint robot capable of three-dimensional
movements. The robot may be automated by means of a
programmable personal computer or sequencer of a
programmable controller.
According to the invention, semisolid metal forming
will proceed by the following specific procedure. In step
(1) of the process shown in Fig. 9, a complete liquid form
of metal M is contained in the ladle 42a. In step {2), the
metal M is poured into the holding vessel 1 (which may be a
ceramic-coated metallic vessel) as it is contacted by the
inclined cooling jig 70 [see step (I-a)], or with the melt
being held superheated to less than 50~, preferably less
CA 02242407 1998-06-19
-24-
than 30~, above the liquidus temperature of the metal [see
step {I-b)1, or with the vibrating jig 52 (specifically,
vibrating rod 52A) being submerged in the melt to impart
vibrations as it is progressively poured into the holding
vessel 1 (see step (I-c)]. As a result, there is obtained
an alloy that contains crystal nuclei (or fine crystals)
either just above or below the liquidus temperature of the
metal.
In subsequent step (3), the alloy is cooled at an
average rate of 0.01 ~/s - 3.0 ~/s and held as such within
the holding vessel 1 until just prior to the start of
shaping under pressure so that fine primary crystals are
generated in said alloy solution; at the same time,
temperature adjustment is effected with the induction
heater 31 such that the temperatures of various parts of
the alloy in the vessel 1 will fall within the desired
molding temperature range (~5~ of the desired molding
temperature) for establishment of a specified fraction
liquid not later than the start of the molding step. In
this case, a specified amount of electric current is
applied before the representative temperature of the metal
slowly cooling in the holding vessel 1 from the temperature
right after the start of melt pouring has dropped to at
least 10~ below the desired molding temperature and, hence,
the induction heater 31 needs to produce a comparatively
small output power. For cooling the alloy, air is blown
against the holding vessel 1 from its outside. If
necessary, both the top and bottom portions of the holding
vessel 1 may be heat-retained with a heat insulator or
heated so that the alloy is held partially molten to
generate fine spherical (non-dendritic) primary crystals
from the introduced crystal nuclei [see step (3-a) and (3-
b)~.
Metal MB thus obtained at a specified fraction liquid
is inserted from the inverted holding vessel 1 [see step (3-
c)1 into the injection sleeve 200a of the molding machine
(e. g. die casting machine) 200 and thereafter pressure
formed within the mold cavity 208 on the molding machine to
CA 02242407 1998-06-19
-25-
produce a shaped part. In order to ensure that the
semisolid metal MB being discharged from the inverted
vessel will not be contaminated by oxides, it is necessary
that the surface portion of the metal which was situated in
the top of the vessel 1 should face a plunger tip 210.
Fig. 10 is a cycle chart for the continuous semisolid
shaping operation. To facilitate explanation, the chart
assumes the use of a small number of induction heaters
which are each operated for 60 seconds. The general layout
of the production apparatus 100 is shown in Fig. 1. The
specific operating conditions were as follow.
(1) Induction heater . Three units
(8 kHz, 10 kW)
(2) Holding vessel . One unit
heating furnace
(accommodating five vessels)
(3) Molding cycle . Sixty seconds
(4) Melt pouring and :Refiner (containing 0.15 Ti
nucleating conditions and 0.002~B); melt poured into
holding vessel at 635; See
Fig. 5a.
(5) Time of holding metal . 150 seconds
partially molten under
air cooling and r-f
induction heating
(6) Alloy :AC4CH (m. p. 6150
The time course in each step of the semisolid shaping
process is shown in Fig. 10 for each of the 8 holding
vessels used. Obviously,casting is performed at 60-sec
intervals. Fig. 10 also shows the position of the holding
vessel before and after the casting, as well as the
operations performed at those times. The semisolid shaping
metal produced by the process was shaped under pressure and
a diagrammatic representation of a micrograph showing the
metallographic structure of the shaped part is given in
Fig. 11, from which one can see that the shaped part
according to the invention has a fine structure which is by
no means inferior to that of the best semisolid shaped
CA 02242407 1998-06-19
-26-
product ever known.
The obvious differences the invention process has from
the conventional thixocasting and rheocasting methods are
clear from Fig. 9. In the invention method, the dendritic
primary crystals that have been generated within a
temperature range of from the semisolid state are not
ground into spherical grains by mechanical or
electromagnetic agitation as in the prior art but the large
number of primary crystals that have been generated and
grown from the introduced crystal nuclei with the
decreasing temperature in the range for the semisolid state
are spheroidized continuously by the heat of the alloy
itself (which may optionally be supplied with external heat
and held at a desired temperature). In addition, the
semisolid metal forming method of the invention is
characterized by the production of a uniform microstructure
and temperature distribution by r-f induction heating with
lower output and it is a very convenient and economical
process since it does not involve the step of partially
melting billets by reheating in the thixo-casting process.
Fig. l2 is a plan view showing the general layout of
an apparatus for producing a semisolid shaping metal which
is indicated by 101 and which comprises a crystal
generating section 30 and a holding vessel conditioning
section 10 which have rotating capabilities. The apparatus
101 comprises the holding vessel conditioning section 10,
the crystal generating section 30, a melt pouring section
40, a nucleating section 50 and a vessel transporting
section 60. A shaping apparatus indicated by 200 in Fig. 12
is an example of the machine for shaping a semisolid metal
MB produced with the apparatus 101 of the invention.
The holding vessel conditioning section 10 comprises a
holding vessel cooling unit 11, an air blowing unit 16, a
cleaning unit 12, a spray unit 14 and a holding vessel
rotating and transporting unit 17. The holding vessel
rotating and transporting unit 17 and the cleaning unit 12
in the holding vessel conditioning section 10 are shown
specifically in Fig. 14. The holding vessel rotating and
CA 02242407 1998-06-19
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transporting unit 17 is composed of rotary actuators 17a
and 17b and a vertically moving cylinder 17c. After
inserting the semisolid metal MB into the injection sleeve
200a, water and air are successively injected into the
holding vessel 1 by means of a device which, as shown in
Fig. 3, has a cylinder and a motor-driven vertically moving
and rotating nozzle; the thus cooled and air-blown holding
vessel 1 is transported by means of the unit 17 and lowered
to rest on the receiveing stage 13 and fixed in position.
Thereafter, as shown in Fig. 2, the brush 12c is rotated to
clean the inner surfaces of the holding vessel 1. After the
brush 12c is lowered, the unit 17 as it keeps retaining the
holding vessel 1 is raised and moved to the position of the
spray unit 14. Thereafter, as shown in Fig. 3, a water-
soluble coating containing a nonmetallic substance is
injected from the spray unit 14 so that the inner surfaces
of the holding vessel 1 are sprayed with the coating, and
the applied coating is dried with air.
After the spray unit is lowered, the holding vessel 1
is moved to the position of a holding vessel tilting or
inverting device 18, where it is turned upside down and
replaced within a holding vessel holder indicated by 18a in
Fig. 15. The holding vessel tilting or inverting device 18
comprises an LM guide 18b, a linking rod 18c and a flexible
joint 18d. The holding vessel holder 18a is allowed to tilt
by means of the device l8 in accordance with the pouring of
the melt from the pouring ladle 42a. The molten metal M6
which contains Ti as the sole refiner and which should be
held superheated to no more than 30~ above the liquidus
temperature of the metal is poured in using a holding
vessel cooling accelerating unit 19 as required. The molten
metal M6 poured into the holding vessel 1 is transported to
the crystal generating section 30 by means of a robot 62.
Thereafter, the molten metal M6 is cooled down to a shaping
temperature. The holding vessel cooling accelerating unit
19 may be such that it injects air or water directly
against the outer surface of the holding vessel or,
alternatively, a chilling member may be brought into
CA 02242407 1998-06-19
-28-
contact with the holding vessel.
Fig. 13a is a plan view showing details of the crystal
generating section of the apparatus shown in Fig. 12 for
producing a semisolid shaping metal, and Fig. 13b is
vertical section A-A of Fig. 13a. As shown in Figs. 13a and
13b, the crystal generating section 30 comprises an
induction apparatus 31 furnished with a heating coil 31a
which is provided around the holding vessel 1 for
controlling the temperature of the metal in the holding
vessel 1, a ceramic frame 34 that is capable of heat-
retaining or heating the holding vessel 1 and which is
placed on a vertically movable support table 33 for
retaining or lifting out said holding vessel 1 or replacing
it by means of a secondary rotating shaft 39a (i.e.,
replacement of a holding vessel of molten metal MA
containing crystal nuclei with a holding vessel of
semisolid metal MB which has been cooled to the shaping
temperature) and for adjusting the position of the holding
vessel 1 within the heating coil 31a of the induction
apparatus 31, a vertically movable lid 35 that is capable
of heat-retaining or heating the top portion of the holding
vessel 1 and which is furnished with a thermocouple 36 for
measuring the temperature of the metal in the holding
vessel 1, a cooling unit 37 provided exterior to the
heating coil 31a for injecting air of a specified
temperature against the outer surface of the holding vessel
1, a protective cover 38 surrounding the above-mentioned
components, and a primary rotating shaft 39 on which four
units of the crystal generating section can rotate or
pivot.
When the holding vessel la of molten metal MA
containing crystal nuclei is placed on the ceramic frame 34
on the support table 33, the holding vessel 1b of semisolid
metal MB which has been adjusted to the shaping temperature
within the induction apparatus 31 is lowered by means of a
vertically moving cylinder and then rotated by the
secondary rotating shaft 39a to be situated outside the
crystal generating section 30. At the same time, the
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holding vessel la of molten metal MA is raised by a
vertically moving cylinder 32 to a specified position in
the heating coil 31a of the induction apparatus 31, where
the metal MA is cooled to a specified temperature by means
of the cooling unit 37 and its temperature is subsequently
adjusted by the induction apparatus 31. Other units of the
holding vessel 1 are subjected to the same sequence of
actions as described above. The holding vessel 1b of
semisolid metal MB which has thusly become situated outside
the crystal generating section 30 is subsequently
transported by the robot 62. Holding vessels le/lf and
lg/lh which are situated far from the robot are pivoted
(rotated through 90 degrees) by means of the primary
rotating shaft 39 to move to the positions of holding
vessels lc/ld and la/lb, respectively.
The function of the induction apparatus 31, as well as
the conditions for cooling molten metal MA in the apparatus
31 and the method of controlling its temperature are
essentially the same as outlined in Fig. 8.
Fig. 16 is a plan view showing the general layout of
an apparatus for producing a semisolid shaping metal which
is indicated by 102 and which has a moving crystal
generating section 30 comprising a cooling zone 47 and a
temperature adjusting zone 48 having an induction apparatus
31.
The apparatus 102 comprises a holding vessel
conditioning section 10, the crystal generating section 30,
a melt pouring section 40, a nucleating section 50 and a
vessel transporting section 60. A shaping apparatus
indicated by 200 in Fig. 16 is an example of the machine
for shaping a semisolid metal MB produced with the
apparatus 102 of the invention.
Fig. 17a is a plan view showing details of the crystal
generating section of the apparatus shown in Fig. 16 and
Fig. 17b is vertical section B-B of Fig. 17a. The apparatus
102 is identical with what is shown in Figs. 12 and 13,
except for the crystal generating section. Therefore, only
the crystal generating section 30 will be described below
CA 02242407 1998-06-19
-30-
in detail.
As shown in Figs. 17a and 17b, the crystal generating
section 30 comprises a frame 34 capable of heat-retaining
or heating the bottom portion of a holding vessel 1, a
vertically movable lid 35 that is capable of heat-retaining
or heating the top portion of the holding vessel 1 and
which is furnished with a thermocouple 36 for measuring the
temperature of the metal in the holding vessel 1, a cooling
zone 47 comprising a cooling unit 37 which injects air or
water of a specified temperature, as required, against the
outer surface of the holding vessel I, an automatic
transport unit 49 for rotating the holding vessel l at a
constant speed, and a temperature adjusting zone 48 having
an induction apparatus 31 furnished with a heating coil 31a
which is provided around the holding vessel 1 for
controlling the temperature of the metal in it.
Only after a holding vessel 1i is rotated by means of
the automatic transport unit 49 to come to the position of
a holding vessel lm, the induction apparatus 31 comes into
action to adjust the temperature of the metal in the
holding vessel 1. The apparatus 31 is either raised or
lowered by a vertically moving cylinder 32 and stops in a
specified position where it surrounds the holding vessel 1.
Fig. 18 is a plan view showing the general layout of
an apparatus which is indicated by 103 and which has a
stationary crystal generating section 30 comprising a
cooling zone 47 and a temperature adjusting zone 48 having
an induction apparatus 31. Fig. 19a is a plan view showing
details of the crystal generating section of the apparatus
shown in Fig. 18 for producing a semisolid shaping metal
and Fig. 19b is vertical section C-C of Fig. 19a. The
crystal generating section 30 comprises a frame 34 capable
of heat-retaining or heating the bottom portion of the
holding vessel 1, a vertically movable lid 35 that is
capable of heat-retaining or heating the top portion of the
holding vessel 1 and which is furnished with a thermocouple
36 for measuring the temperature of the metal in the
holding vessel 1, a cooling zone 47 comprising a cooling
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-31-
unit 37 which injects air or water of a specified
temperature, as required, against the outer surface of the
holding vessel 1, and a temperature adjusting zone 48
having an induction apparatus 31 furnished with a heating
coil 31a which is provided around the holding vessel 1 for
controlling the temperature of the metal in it. Unlike in
the case shown in Figs. 16 and 17, the holding vessel 1 in
the crystal generating section shown in Fig. 19 is of a
stationary type and, therefore, the holding vessel 1 is
transported by a robot 62 to the temperature-adjusting zone
48 after it has been cooled to a specified temperature by
means of the cooling unit 37. Then, as in the case shown in
Fig. 13, the holding vessel 1 is replaced on the ceramic
frame 34 and the temperature of the metal in it is adjusted
by means of the induction apparatus 31.
The criticality of the conditions for cooling the
holding vessel in the step of spheroidizing primary
crystals in the process shown in Fig. 9 may be explained as
follows.
If the upper or lower portion of the holding vessel 1
is not heated or heat-retained while the alloy MB poured
into the vessel is cooled to establish a fraction liquid
suitable for molding, dendritic primary crystals are
generated in the skin of the alloy MB in the top and/or
bottom portion of the vessel or a solidified layer will
grow to cause nonuniformity in the temperature distribution
of the metal in the holding vessel 1; as a result, even if
r-f induction heating is performed, the alloy having the
specified fraction liquid cannot be discharged from the
inverted vessel 1 or the remaining solidified layer within
the holding vessel 1 either introduces difficulty into the
practice of continued shaping operation or prevents the
temperature distribution of the alloy from being improved
in the desired way. In order to avoid these problems, if
the poured metal is held in the vessel for a comparatively
short time until the molding temperature is reached, the
top and/or bottom portion of the holding vessel is heated
or heat-retained at a higher temperature than the middle
CA 02242407 1998-06-19
-32-
portion in the cooling process; if necessary, both the top
and bottom portions of the holding vessel 1 may be heated
not only in the cooling process after the melt pouring but
also before the pouring step.
If the holding vessel 1 is made of a material having a
thermal conductivity of less than 1.0 kcal/mh~C, the cooling
time is prolonged to a practically undesirable level;
hence, the holding vessel 1 should have a thermal
conductivity of at least 1.0 kcal/mh°C. If the holding
vessel 1 is made of a metal, its surface is preferably
coated with a nonmetallic material (e. g. BN or graphite).
The coating method may be either mechanical or chemical or
physical.
If the alloy MA poured into the holding vessel 1 is
cooled at an average rate faster than 3.0 °C/s, it is not
easy to permit the temperatures of various parts of the
alloy to f all within the desired molding temperature range
for establishment of the specified fraction liquid even if
induction heating is employed and, in addition, it is
difficult to generate spherical primary crystals. If, on
the other hand, the average cooling rate is less than 0.01
/s, the cooling time is prolonged to cause inconvenience in
commercial production. Therefore, the average rate of
cooling in the holding vessel 1 should range preferably
from 0.01 °C/s to 3.0 °C/s, more preferably from 0.05
°C/s to
1 °C / s .
Industrial Applicability
As will be understood from the foregoing description,
the apparatus of the invention for producing semisolid
shaping metals offers the advantage that shaped parts
having fine and spherical microstructures can be mass-
produced automatically and continuously in a convenient,
easy and inexpensive manner without relying upon agitation
by the conventional mechanical and electromagnetic methods.
CA 02242407 1998-06-19
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Scope of Demand for Patent
1 _ An apparatus for producing a semisolid shaping metal
that has fine primary crystals dispersed in the liquid
phase and which also has a uniform temperature
distribution, said apparatus comprising:
a melt pouring means comprising a melting furnace
which melts and holds a metal and a pouring device which
lifts out the molten metal from said melting furnace,
adjusts it to a specified temperature and pours it into a
holding vessel;
a nucleating means which generates crystal nuclei in
the melt as it is supplied from said pouring device into
said holding vessel;
a crystal generating means which performs temperature
adjustment such that the metal obtained from said
nucleating section falls within a desired molding
temperature range as it is cooled to a molding temperature
at which it is partially solid, partially liquid;
a holding vessel conditioning means which inverts the
holding vessel by turning it upside down so that a
partially molten metal is discharged and which then cleans
the inner surfaces of the holding vessel; and
a vessel transporting means furnished with an
automating device including a robot with which the
partially molten metal from said nucleating means is
transported into the injection sleeve of a molding machine.
2 _ The apparatus according to claim 1, wherein the melt
pouring means comprises:
(1) a high-temperature melt holding furnace and a Iow-
temperature melt holding furnace furnished with a pouring
ladle; or
(2) a pouring Ladle furnished with a refiner feed unit and
a temperature control cooling jig inserting device and a
high-temperature melt holding furnace; or
(3) a Low-temperature melt holding furnace furnished with
a pouring ladle and a refiner-rich melt holding furnace
CA 02242407 1998-06-19
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also furnished with a pouring ladle; or
(4) a pouring ladle furnished with a refiner melting radio-
frequency induction heater and a low-temperature melt
holding vessel; or
(5) a low-temperature melt holding vessel furnished with a
pouring ladle; and wherein the nucleating means is the
holding vessel.
3 _
The apparatus according to claim 2, wherein the
nucleating means comprises either a holding vessel tilting
or inverting unit by which the angle of inclination of the
holding vessel can be varied freely and automatically as
required during and after pouring of the melt in accordance
with its volume, or a holding vessel cooling accelerating
unit capable of cooling said holding vessel externally
during and after pouring of the melt, or both of said
holding vessel tilting or inverting unit and said holding
vessel cooling accelerating unit.
4 _ The apparatus according to claim 1, wherein the melt
pouring means is a low-temperature melt holding furnace
furnished with a pouring ladle and wherein the nucleating
means comprises a vibrating jig and the holding vessel,
said vibrating jig being capable of vertical movement and
imparting vibrations to the melt as it is poured into said
holding vessel.
_ The apparatus according to claim 1, wherein the melt
pouring means is a melt holding furnace furnished with a
pouring ladle and wherein the nucleating means comprises an
inclining cooling jig and the holding vessel, said cooling
jig being such that the angle of inclination can be varied
freely and automatically during and after pouring of the
melt in accordance with its volume.
6 _ The apparatus according to claim 1, wherein the
crystal generating means comprises:
CA 02242407 1998-06-19
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a vertically movable frame on which the holding vessel
is placed and which is either furnished with a heating
source for heating the bottom portion of said holding
vessel or formed of an insulating material for heat-
retaining said bottom portion;
a vertically movable lid that is either furnished with
a heating source for heating the top portion of said
holding vessel or formed of an insulating material for heat-
retaining said top portion and which is furnished with a
temperature sensor for measuring the temperature of the
metal in the holding vessel; and
a cooling unit provided exterior to said holding
vessel for injecting air of a specified temperature against
the outer surface of said holding vessel.
7 _ The apparatus according to claim 6, wherein the
crystal generating means comprises:
a frame that is capable of heat-retaining or heating
the bottom portion of the holding vessel and which is
vertically movable for retaining or lifting out said
holding vessel and for adjusting its position within the
heating coil of the induction apparatus;
a vertically movable lid that is capable of heat-
retaining or heating the top portion of said holding vessel
and which is furnished with a temperature sensor for
measuring the temperature of the metal in the holding
vessel;
an induction apparatus furnished with a heating coil
which is provided around the holding vessel for controlling
the temperature of the melt in the holding vessel; and
a cooling unit provided exterior to said heating coil
for injecting air of a specified temperature against the
outer surface of said holding vessel.
8 _ The apparatus according to claim 6, wherein the
crystal generating means comprises:
an induction apparatus furnished with a heating coil
which is provided around the holding vessel for controlling
CA 02242407 1998-06-19
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the temperature of the metal in the holding vessel;
a frame.,that is capable of heat-retaining or heating
the bottom portion of the holding vessel and which is not
only vertically movable but also rotatable for retaining,
lifting out or replacing said holding vessel and for
adjusting its position within the heating coil of the
induction apparatus;
a vertically movable lid that is capable of heat-
retaining or heating the top portion of said holding vessel
and which is furnished with a temperature sensor for
measuring the temperature of the metal in the holding
vessel; and
a cooling unit provided exterior to said heating coil
for injecting air of a specified temperature against the
outer-surface of said holding vessel, and wherein the
crystal generating means comprises a plurality of units
which rotate or pivot about a single axis.
9 _ The apparatus according to claim 6, wherein the
crystal generating means comprises:
a frame that is capable of heat-retaining or heating
the bottom gortion of the holding vessel;
a vertically movable lid that is capable of heat-
retaining or heating the top portion of said holding vessel
and which is furnished with a temperature sensor for
measuring the temperature of the metal in the holding
vessel;
a cooling zone comprising a cooling unit which injects
air or water of a specified temperature, as required,
against the outer surface of said holding vessel; and
a temperature adjusting zone having an induction
apparatus furnished with a heating coil which is provided
around said holding vessel for controlling the temperature
of the metal in said holding vessel.
1 O _ The apparatus according to claim 9, wherein the
crystal generating means further includes an automatic
transport unit with which the holding vessel containing the
CA 02242407 1998-06-19
_3~_
metal cooled to a specified temperature in the cooling zone
is moved at a specified speed to the temperature adjusting
zone which is adapted to be such that either the heating
coil of the induction apparatus or the holding vessel moves
so that the temperature of the metal in the holding vessel
is controlled within the heating coil.
1 1 _ The apparatus according to claim 9, wherein the
crystal generating means further includes a transport unit
comprising an automating device including a robot with
which the holding vessel containing the metal cooled to a
specified temperature in the cooling zone is moved to the
temperature adjusting zone which is adapted to be such that
either the heating coil of the induction apparatus or the
holding vessel moves so that the temperature of the metal
in the holding vessel is controlled within the heating
coil.
1 2 _ The apparatus according to claim 1, wherein the
holding vessel conditioning means comprises:
at least two of the following three units, 1.e., a
holding vessel cooling unit that is capable of rotary and
vertical movements and which is also capable of injecting
at least one of a gas, a liquid and a solid material, an
air blowing unit that is capable of rotary and vertical
movements and optional air injection, and a cleaning unit
for cleaning the inner surfaces of the holding vessel which
has a brush that is capable of rotary and vertical
movements and air injection;
a spray unit that is capable of rotary and vertical
movements and application of a nonmetallic coating; and
a holding vessel rotating and transporting unit with
which the holding vessel, with its opening facing down, can
be moved to and fixed on the top portion of each of said
cooling unit, said air blowing unit and said cleaning unit,
and which is vertically movable.
1 3 _ The apparatus according to claim 1, wherein the
CA 02242407 1998-06-19
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holding vessel conditioning means comprises a cleaning unit
and a spray unit, said cleaning unit comprising a jig for
cleaning the inner surfaces of the holding vessel which has
a brush that is capable of rotary and vertical movements
and air injection and a vertically movable jig for fixing
the holding vessel, and said spray unit comprising a
vertically movable jig for applying a nonmetallic coating
onto the inner surfaces of the holding vessel and a
vertically movable jig for fixing the holding vessel.
1 4 _ The apparatus according to claim 1, which further
includes a holding vessel heating means for adjusting the
temperature of the holding vessel when it is empty.
