Note: Descriptions are shown in the official language in which they were submitted.
The present invention relates to the metallur~ical i-~dus-
tr~, and more particularly it relates to metnods of stir~ir~g
liquid metals being molten directly in the metal baths ol ~e~ -
ing furnaces, which stirring ~ore often than not speeds ~p tre
melting process, promotes the homo~reneity of the chemical com-
position ol the molten metal body and enhances a uniform t~mpe-
rature field of this molten met~l body~
At present, there are already known methods of stirring
liquid metals directl~ in the bath of a melting furnace, viz.
the ~echanical method, the electromagnetic method, the gas-
-dynamic method and others. ~he present invsntion relates to
the most simple and promising one of these methods, na~ely,
the method of gas-d~namic stirring of liquid metals, particu-
larly such corrosive ones as aluminum alloys and the like.
This known per se general method, although ~ielding
definite advantages in the productivity o~ the melting process,
is not free from serious drawbacks. ~he permanent time interval
between the co~pressed-gas pulses acting upon a metal portion
in the tube, which may be the optimum one for one of ~he stages,
is not, however, the optimum one for the two other stages.
Moreover, the energ~ of the compressed gas is~ ar no~
completely employed for the acceleration of the ~etal in the
tube to the re~uired speed. This is explained by the fact that
the considerable part of the energ~ of a compressed-gas pulse ~-
is spent on arresting the metal in the tube within the period
of withdrawinæ it from the hath~ A portion of this energy is
spent directl~ on arresting the metal, while the o~her portion
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is spent on cut'cing off the suction from the ~,Jork ng space
of the pu~p; and it is onl~ the rest of the ener~rg cf the
pulse which is used ~o accelera~e the metal to a certain speed~
Obviously, more often than not it is practically impossible
to attain the r~uired sp~ed of the outflow of the metal fro~
the tube, this speed being, however, essential for the effecti-
veness of the stlrring of the metal. On the other hand, it is
not altogether advisable to follow the path of increasing the
initial energ~ of a compressed-gas pulse, since the counter-
-action of the metal risin~ in the tube and of the compressed-
-gas flow arre~ting the progress o~ the metal results, as a
rule, in a certain degree of gas saturation of the ~etal.
Thus, if the pulse energy is stepped up, it is guite
natural ~o expect that the ga~ content in the metal would
grow, which is undesir~bleO
~ he pre~ent invention is ai~ed at intensif~ing the pro-
cess of stirring molten metal, e.g. of ~olten aluminum and its
alloys in combustion rev2rberator~ ~u~lnaces of a great capacity,
particularl~ those of a rectangular cross-section, wherein
the depth of the ~ody of the molte~ metal is a fraction of the
length of the ~urnace.
There are known a. method and an apparatus for stirring
molten metal, disclosed in th~ US Patent ~o. 4,008,884;
US Cl. 266-233; Int.Cl.2 C 2Z ~ 9/02, file~ June 17, 1976,
by ~igel Patrick Fitzpatrick~ Jame~ Ne~ille Byrnl et al.~ assig-
~ors to Alcan Research and Develop~ent ~imlted, Montreal,
Canada .
This molten metal stirring method includes alter~atingl~
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thdrawing ~oltcn metal from ~he molten mletal GGd~ ir'co Si
confined spac~, e.g. a tubular vessel1 to a cer-t~in level
above ~he molten metal body in the bath, and e-~pellin~ tr.e
wit~ldrawn moltel metal into the molten ~etal bod~ as a s~b~e -
ged high-velocity je', for stirring the ~etal body, the sub-
merged jet being directed horizontall~ within the lower par~
of the metal body, to a distan~e substantiall~ in excess o
the depth of this body.
In accordance with this known method, the alternating
withdrawing and expelling s-tage~ are effectuated by ~upplyinG
suction and pres~urized gaseous fluid into the confined space
above the molten met~l body (i.e. into the top part of the
tubular vessel), the withdrawing of the liguid metal being
effected through an orifice of this ves~el at a lower part of
the molten metal body, and the expelling of the submer~ed jet
taking place horizontally in the lower area of the metal body.
~ he method is further b~sed on each suction stage inclu-
ding feeding out a suction isignal upon measuring the suction
value in the top portion o~ the vessel and monitoring the
duration of the suction ~tep in accordance with the suction
value being maintained at a preset level, communicating the
suction to raise the molten metal in th~ vessel, determining
the level of the rising metal and terminating the suction supply
upon the metal having risen to the predetermined level~
In accordance with the disclo~ure in the abo~ementioned
US Patent ~o. 4,008,884, the apparatus for stixri~ molten
mstal include~ a tubul~r vessel having at the lower extremit~
thereof a noz~le su~merged into the molten metal bod~, the
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upper extremity of the tubular vessel having a device (of the
aspiration type) for alternatingly withdrawing metal (by suc-
tion) into said vessel to a specified level above the molten
metal body and expelling the withdrawn metal into the molten
metal body via the nozzle under the action of the gaseous
fluid. This gaseous fluid, i.e. air is supplied from a receiver
into the aspiration device via charging and discharging solenoid
valves.
The se~uence of the charging and discharging operations
is controlled by a vacuum switch and an electric timer. To
preset the maximum premissible level of the raising of the
molten metal, the internal space of the tubular vessel receives
therein an electric level sensor connected with a switch-off
relay n
However, the known method described above and apparatus
for gas-dynamic stirring of liquid molten metals suffer from
disadvantages which to a certain degree curb down their wider
application.
The stationary arrangement of the tube of the pump
in the bath of the furnace provides for active stirring within
a limited area, which means that furnaces of great capacities
re~uire a plurality of such pumping arrangements.
When metal is molten in furnaces of eitner circular
or square shape, even those of relatively small capacities, at
least two pumps are to be installed to attain adequately
swift melting and dissolving of the alloying additives. On
the other hand, the arrangement of a plurality of the pumps
on a melting furnace is often associated with difficulties~
'
vo say ,~thin~ of -the i~creased CGnsu~n?tion 5L' CO.r~ip-'r-S'- ed
air, T~rle withdra~ral or ex~elling of the ~e'tal av a ce~iri~,
ri~cd height ebove the hearth of the furnace is i;-l vhe ,;e7
of employing to the fulles-' poss~ble degree the broed ca~,2-
bilities of the method being discussed, ~rom the point of
view of the provision of the optimum condi-tions for ~eat
and. mass e~{chun~e. ~his drawback becomes particularly prono~ln-
ced in the ca~e of the melting of solid charge, when t~e
temp2ratllre of the molten metal is still relatively lo~l, and
the washing over of the solid lumps of the charge with the
relatively low-temperature ~etal jet would not yield the op-
timum outcome, as far as the melting rate and the utilization
of the heat in the furnace are con-~erned.
In furnaces with ~ol-ten metal bodies of a considerable
depth the hitherto known method likewise would not ~ield the
best resul-ts. In this case it is relatively difficult to se-
lect the optimum arrangement of the pumps verticall~ of the
molten metal body~ with the latter's le~el being variable
within a relativel~ broad range.
~ urthermore, the energy of the compressed-g0s pulse
is not utilized to the full capacity, with the compressed
gas.commencing its action upon either rising, or, in the
best case, stationary portion of the liquid ~etal in the ~ube
of the pump. This would not ena~le to attain the maximum
speeds of the jet of the metal issuing from the tube of the
pump for a given gas pressure. With the gas pressure being
stepped up, the energy cost factor rises accordingly, with
the condition~ being created for an increased gas content
in the -~leca
I~he operatiori at a preset vacuum or suc~iO;~ alue ccn-
trolled b~ the suction switch for each incividu~' ~)ump ~rould
not enable to s.eed up noticeabl~ the withdra"al OI a metal
portion in-to the tube of the pump, i.e. to cut ~he time of
the wil.hdra~J~l s-tep. Moreover, the creation of the suc~ion
b-~ the aspiration device molmted on the pump and put into
action only f`ollo~ing the termination of the supplying of ~he
compressed-gas pulse via the respective solenoid-^ontrolled
valve obviously increases the time of withdrawing metal into
the tube. In this case, too t there no efficient ~Jay of speea-
ing up the withdrawal of the metal into -the tube of the pump.
~he two last-discussed factors affect the efficiency o~ the
operation of the pump, particularly, at the stage of melting
soli~ charge, when the increased frequency of the alternation
of the withdrawal-expelling c~cles is required.
It is the main object of the present invention to c~eate
a method and apparatus for gas-dg~amic stirring of molten
liquid metals, which should enhance the efficienc~ of stirring
liquid metals in high-capacit~ furnaces and ~hould eliminate
the drawbacks of the hitherto known methods and apparat.us
used for the same purpose~
It is a not less important of -the present invention to create
a method of gas-d~namic stirring of liguid molten metals,
which should of`fer more economical and full utilization of
the ener~ of the compressed gas.
It is an object of the ~resent in~ention to provide
a method of ~as-d~namic s-tirring of liquid molte~ ~etals~
- 7 ~
hich should enhance thG ~etal gu21i~y ~ re~ucin~ -the gas
conten-t therein~
It is a further object of the present invention to
cre~te an apparatus l`or gas-dynamic stirring, capable o~
performing the a~ovemen-tioned method, which should provide
for its accessible mouthing on high-capacit~J melting furna-
ces without any reconstruction of the latter, and 7,rhich
should provide conditions for effective stirring of the metal.
It is a still another object of the present invention
to create an apparatus for gas-dynamic stirrin~ of liquid
molterl metals, which should provide for reduci~g the gas
saturation of the metal while the latter is being expelled.
These and other objects are at~ained in the herein ais-
closed ~ethod of gas-dynamic stirring of, liquid molten metals,
including alternatingl~ withdrawing portions of the metal from the
molten body into the tube of the pump by the use of suction
and expelling these portions of the metal back into the molten
body by acting thereupon b~ compressed-gas pulses, in which
method, in accordance with the present invention, directl~
prior to the suppl~ing of said compressed-gas pulse into the
~ube of the pump, the action of the suction i~ terminated, to
provide for free descent of the raised metal portion b~ gra-
~ity.
~ his technical solution enables to step up the effecti-
veness of stirring molten metals in high-capacit~ for accelera-
ting metal portions bein~ expelled into the metal body to
higher speed~ with the compressed-gas pulse acting upon
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the ~ithdr~rQ r~ tal po~"tion ~rhicn has alread-J be~u-r. its ~-^env
under the gravity forces. I~ this case t.qe enti e ener~J o~
the compressed-gas pulse is spen-t on accelera~ing the me~l
portion already ;~aving some initial speed, T~hich eventuail~
resul~s in the higher speed of the exit of the ~etal jet from
thc ~ump tube, and, hence, in a longer path of t~.is jet ithin
the molten metal bod~, which is essential for high-capacitJ
plants. ~he action of the compressed~gas pump upon the retreatin~ -
metal hampers the conditions o~ saturating the metal witn the
gas , as compared with their motion against each other~
It is expedient that prior to suppl~ing said compressed-
-~as pulse to expel the withdrawn metal portion from the tube,
the space in the tube of the pump above the metal portion -
should be communicated to the ambient atmosphere.
~ he above feature provides for a more economical use
of the compressed-gas energ~, owing to the arresting and
preacceleration of the withdrawn metal portion being effect-
ed by the energy of the a~bient atmosphere, with the metal
being preaccelerated in this case b~ gravity alone. The energy
of the compressed-gas pulse is then entirel~ spent on the
acceleration o~ the alread~ moving metal portion in the tube,
which enables to step up the speed of the exit of the metal
jet from the tube, to prolong the path of the jet within the
molten metal bod~ and to intensif~ the stirring process.
It is further expedient that the said compressed-gas
pulse be timed with the commencing of the free gravity descent
of the -~etal portion.
~ his feature enables to utilize the energ~ of the comp-
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.r-~ssed ~as -o thC .lig~he t ~egree, c~;rin~ to the cc~-~rresce~ g-_
r-trea~. ~assing h~ minimuT~ necessa~ pa-t~ bO e;ecV~ er v`^l-
liquid me~al in he t~be, which nas alreaay beg~ its dr-sce tS
so that i-~ e~ti~e energ~ is spent on accele~ating the .~.~era
It is still further e~pcdient to perform vhe herein
clisclosed method of gas-dynamic stirring of molten liq~id
metals in an appa~atus co~prising a -tube with a re~lovable
cover, a system ~`or s~pplying a pulse of compressed gas from
a pressure accumulator via a dist.ributor into the outlet nozzle,
a suction system for withdrawing metal portions, including a
suction cut~off device, and a sensor of the metsl level in the
molten metal bath,in which apparatus, in accordance with the
present invention, the outlet no~zle is di.rected upwardly to-~rard
the cover of the tube of the pu~p and is received within a
movable annular sleeve ~rith a shoulder, the cover having ~oun-
ted therein rod-type valves cooperating with said shoulder of
the movable sleeve to communicate the internal space of the
tube with the ambient atmosphere, upon the valves being raised
by the movable sleeve, the latter being ope.rativel~ connected
with a float submerged in the body of the raising metal portion.
The apparatus of this kind enables to mount the pump on -~
a hi~h-capacity melting furnace without the necessity of re-
constructing the latter, and to provide the prerequisi~es for
efficient stirring, owing to the device for communicating
the internal space of the pump ~rith the ambient atmosphere
being accom~odated within said space and emplo~ing for open-
in~ ~ne communication the ener~y of the metai portion ascend-
ing in the tube. ~he operative connection of this device with
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-~-he rr.e ~al via ~re float ensures tnat the i~l'cer~lal ,pa!e of t~-
pump is co~mur~icated ~sith the am~Dien-t atr"lospnere ~aca succe~
ve c~cle of withdra~ing a metal portion into t~e tube, a.~d,
consequently, provides the necessar~ prerequisites for a~vain-
in~ a high speed of the exit of the metal jet fro-~ ~he tube,
hen the oncoming compressed-gas pulse acts thereupon.
It is ex~edient, that said cover of the pump be provided
OIl the in~ernal side thereo~ with a tapering dissector of ~he
gas stream~ arran~ed axially o~ the outlet nozzle and merging
wi-th an annular toroidal cavity having said rod-type valves arran-
ged in the indentation thereof~
~ his feature enables to create conditions for reducing
the gas saturation of the metal being expelled b~ the action
of the compressed-gas pulse thereupon, owing to the compressed-
-~as stream being dissecte~ and uniformly distributed over
the entire cross section of the tube of the pump.
It is further expedient that the float be connected
with the ~ovable annular sleeve with aid of links of adjust-
able len~th, interconnected through detachment assemblies.
~ his feature enables to conduct the operation of the
pump at dif'ferent rates of the ascent of withdrawn metal por-
tions in the tube, b~ ad7ustin~ the spacing between the float
and the sleeve and by selectlng their optimum relative posi-
tions in accordance with the ascent rate. Moreover, ~rovision
is made for replacin~ the float and the sleeve, whenever ne-
cessary.
It is further e~pedient that the cover of the tub~
of the pump should have mounted therein an electric contact
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~e~ice -n the LOL'~ Oi ~ probe wired i~to ~Lhe ciro~i J cc.r.'c'~o7-
, the suppl~fi~g of compressed-gas pulse~, the ~ g-t`rl G~
~his probe wi~hin tne internal space of ~he tu~De beilng sel~c-
tea so thev tre ti,me o~ the passage of -the wit'ndra1,.Tn mev~l pG ~ -
tion along the probe up to the moment of the raisi~g of the
rod-type valves should be in excess of the time of the respor.se
of said system for supplying a compressed-gas pulse.
~ his feature enables to speed up the rate of the ascent
of the metal in the tube of the pump, owing to the possibility
of operating a~ suction values whereat the metal could have
been theoretically raised above the cover of the pump~ In trlis
case it is feasible, and that without any additional monitoring
and control means, to time the commencing of a compressed-~as
pulse with the commencing of the gravity descent of the metal
portion.
It is still further expedient that the said probe of the
electric contact device be mounted in the cover ~f the tube
of the pump in a collet chuck providing for the advustment
of the axial protrusion o~ this probe,
~ his feature enables to adjust the extent of the ascent
of the metal along the probe, and, hence to time accurately
the co~mencing of a compressed-gas pulse with the commencing
of the gravity descent of the metal portion.
Xt is further expedient that said outlet nozzle should
have at the inlet thereof the said suction cut-off device,
connected in parallel with the system L or withdrawing metal
portions by suction and with the syste~ for supplying compres-
sed-gas pulses, the suction cut~off device including a movable
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r~
nozzle r~ounted a~ a v~lve mcmber in anGthcr outer cor.icsl
nozzle a~d ~Gvable relative ~o the latter b~ a s~ing of
~rhich the efior~ is adjusted to close off the flow ~assage
arld to set orle nozzle into the other one, as a co~pressed-
-~as pulse is supplied.
~ his feature enables to eliminate the influence of the
suction syste~ on the conditions created for timing the co~en-
cing of the co~pressed-gas pulse with the commencing of the
gravit~ descent of the metal portion, owing to the vacuum or
suction system becoming disconnected from the internal space
of the tube of the pump at the supplying of the compressed-gas
pulse and not inter~ering with the commencing of this gravity
descent of the metal in the tube~ ~he feature also facilitates
the corresponding adjustment of the precise ti~ing of the two
operations.
~ urther~re, the last described feature enables to speed
up the action of the apparatus, and, hence, the productivit~
of the pump, owing to neither specific equipment nor corres-
ponding time being reguired for connecting the suction s~stem
to the internal space of the tube of the pump upon the termi-
nation of the action of a co~pressed~gas pulse. The frequency
of the cycles~ on the other hand, is in this case readily
adjustable by incorporating and adjustment throttle governing
the rate of the building up o~ suction in the tube, and, conse-
quently, the rate of the withdrawa~ of a metal portion from
the metal molten body.
The present invention will be further described in con-
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'lCC '-ion w -th i-t~ preferreà embcdiment ir. t~le follG~ .g da-,ai~a~
desc~ tion thereo~ ith reference bein~ made ~o tha accGmpa.
ii.g dra~Tings, w~arein:
lIG. 1 illus-trates schematically the state of a ~rit'~dra~,.r
metal portion in the tube of the pump;
~ 'IG~ 2 is a chart OI variation of the speed of ~he ~otio-,~
of the metal portion bein~ returned into the molten metal bod~,
versus time;
~ IG~ 3 is a longitudinal sectional view of the stirring
apparatus, with tha control system shown schematically;
~ IG. 4 is a sectional view of the end portion of the
tuhe associated with the valve in the apparatus illustrated
in ~IG. 3, at the time of the suppl~ of a compressed-gas pulse;
~ IG, 5 is a sectional view of the end portion of the
tube associated wi-th the valve in the apparatus illustrated
in FIG. 3, when the interior of the tube com~unicates with
the ambient atmosphere;
~ IG. 6 is a diagram of the control s~stem of the suppl~
of compressed~gas pulses i~ the apparatus illustrated in
G. 3;
~ IG. 7 illustrates the mounting of the electric contact
device - the probe ~ on the cover in the apparatus illustrated
in ~IG. ~,
~ -LG. 8 illustrates the suction cut-off device of the
app~ratus shown in ~IG. 3.
~ he conductin~ of the gas-d~namic stirring procass in
accordance with the disclosed method i.s schematicall~ illustra-
ted in the appended drawings, ~igs. 1 and 2, wherein there
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is shown the c~Jcie diagra~n of 'che opera tion O t,~4e pvmp, 7-
lated to the p-rogress of the metal in the tube oP the ~u~p, CO7-
responding to each successive step of the opera~ing cycle o~
the pump~ where
V iS the rate of thè progress of metal in the tube,lJi~.
the "~" and tt_ll signs desig~ating, respectively, ascent and
dcscent;
~ is ti~e;
P1 and P2 are the pressure values, correspondir.g,respec-
tively, to the main pulse /1/ and auxiliar~ pulse /2/. - -
'l'he ~ash line irl tle al~win~ illustrates for comparison the
acceleration of metal in the tube in accordance with the met~od
of the prior art~
~ rom the ~etal body in the bath 1, e~g~ of a melting
furnace, there is ~Jithdrawn into the tu~e of a gas-d~namic
pump ~ a metal portion 3 (of a preset volume) at a certain
ra~e ~V, b~ suction in the working space 4 of the tube.
~ hen the metal portion in the tube is acted upon b~ an
auxiliary pulse of a compressed gas at a pressure P2, e.g. air
under atmospheric pressure, with the suction supply being
simultaneously cut off from the working interior of the tube
of the pump. Owing to this, the rate of ascent of the metal
drops -to zero, so that the metal halts in the tube at a certain
preset level, ~Jhereafter it starts descending in the tube~ i.e.
acguires an initial rate of the motion in the opposite direc-
tion. At this moment a co~trol signal~ i.e~ one sent b~ a
cor.tact-type level sensor~ initiates the supplying of the
main compressed gas pulse, which accelerates the met~l in the
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tube to a ~i~re~ s~d. 'nhG rletal jet issu~ at ~ni~ e~ i-i~c
the ~,~olten metal body, enga~in~ the adjacent me~al la~elc a~~
thus agita-ting the metal throughout -the l~olume of ~he -~olten
bod~J O
~ onducting the herein disclosed method with the timed
feed o~ the two pulses is possible with either manual control
from a control panel, or fro~ a control co~puter, with aid of
a specific device for cutting off the suction supply and
commencing simultaneously the suppl~ of the auxiliary pul~e
at a pressure precluding the saturation of the metal in the
tube with ~as. It is expedient to conduct the herein disclosed
method with the auxiliary pulse being followed b~ the ~ain
pulse with a delay egualling the time of passage of the control
action through the system.
Given hereinbelow is an exa~ple of employing the herein
disclosed method at the melting of alu~inum alloy, with the
molten metal body being stirred at every melting stage in a
meltin~ furnace of the 30-ton capacity.
~ he gas-d~namic pump was operated with the freguency or
rate of the supply of compressed-gas pulses within a range
from 4 to 20 pulses per minute. While the metal portion in
the tube was accelerated and expelled into the molten metal
body, it was successivel~ ac-ted upon by two pulses. ~he first
pulse - t-~ie auxiliary o~e - was with aix under the pressure
of 1 atmosphere abs., i.e~ under the atmospheric pressure, by
simultaneously cutting o~f the suctio~ suppl~ to the worXing
space and communicatin~ the latter with the ambient atmosphere.
~his resulted in the rate of ascent of the ~etal in the tube
16 -
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d-ro-~pin~ i o~ 1~ m/s (et O,L~ a-tm suctiorl) -tG ~f,rO aLd cha~g Ig
to a descent in 0.~ .~. 0.8 second, following -t~e inltia'io. 5-
tl~e auxiliary p~essure pulse supply. So, in 0.5 seco~d afte~
t~le initiation of the auxiliar-~ pulse supply the control
signal was sent, and in about 0~1 second after that t`ne actuav-
in~ T2ember - the distributor - responded, and the main pressure
pulse at a 5.0 atm~ pressure accelerated the metal from the
initial ra-te o~ 0~5 m/s (following the termination of the action
of the auxiliary pulse) to about ~.5 m/s b~ the time of the
termination of the action of the main cor~pressed-gas pulse.
~ hus, in the abovedescribed manner there was effectuated
the acceleration of metal portions for gas~d~namic stirring
at ever~ melting stage, irrespectivel~ of the ratf of the
supplying of the pressure pulses, which enabled to cut down
the melting time b~ 10%, as compared with the method of the
prior art.
~ he abo~edescribed stirring mode was maintained until the
mol~e~l ~etal was poured out into the mixer.
r~he above example of conducting the method, quite under-
standabl~, doe~ not by far restrict the parameters of the
process or preclude other ways of conducting the method as de-
fined in the Claims to follow.
~ he herei~ disclosed method, a~ experience shows, enables
to step up the ef~ici0nc~ of the stirring and to cut down
the melting ti~e b~ as much as 15%.
Indicated with arrows in Fig~ 3, 4 and 5 of the append-
ed dra~Jings are the xespective directions of the progress of
the metal and of the gas streams. In a preferred embodiment,
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-the ~u~ --or ga~ JnamiC sti.ring oi liquid ~e~<-ll 5 in vhr-
bath Or a furrace 6 includes an interrAall~ lin~d ~u~e 7 wi~h
a removable cov~r 8 and a nozzle 9 having i~s outl~t direo~ed
toward the cover ~ he nozzle 9 is connected via a line 10
with a d~vic~ 'i1 for cutting oif the vacuum or suction
suppl~ fro~ the tube. ~he device 11 is also opera~ivel~
colmected ~ith a distributor controlling the suppl~ing of
pulses of compressed gas (nitrogen, argon, etc.) from a pres-
sure accumulator 13. ~he pressure accumulator 1~ is of a
given appropriate volume, with provisions for adjusting -this
volume in accordance with the pressure of the gas, maintained with
a pressure regulator 14. ~he intexnal working space of the tube
7 is in permanent communication via the nozzle ~, the line 10
and an injector 11 with a suction line 15 including a controllable
throttle 16 which enables to ~overn the rate of ascent of metal
in the tube. ~here is a contact sensor (not shown) of the me~al
level in the tube, wired to send a control signal to the sole-
noid of the distributing valve 12.
The cover 8 is provided with a tapering dissecting element
17 adapted to dissect the stream of the gas, the dissecting els-
ment 17 being arranged axially of the nozzle 9 and ~erging
with a torodial annular cavit~ 18 intended to st~bilize the
gas strea~ in the tube o~ the pumpv ~he nozzle 9 is encompassed
b~ an annular sleeve 19 with a shoulder, movable along this
nozzle 9~ ~he sleeve 19 abuts against a ring 20 adJustable
longitudinall~ of the nozzle, i~ which wa~ the required clear-
ance between the sleeve 19 and the cover 8 can be set~ ~he
- 18
sleeve 1~ is operativel~ connected by adjustaDle-length 1L~ S
21 to a floa~ 22. This connection enables to adjust the spa-
cing between the sleeve 19 and the float 22, and thus to
time the ~ornent when the sleeve 19 closes away the suctiGn
line and co~unicates the workin~ space wi-th the a~bient
atmosphere. '~he float 22 is preferably made of a light~eight
refractory material, e.g. asbestos-thermosilicate and the li~e,
or else it can be a hollow member with the case made of a ~etal
insoluble in the alloy being stirred. The float 22 is preferably
streamlined to minimize its opposition to the ~as stream. It
ma~ have an arcuate ~op, or a truncated bottom; alternativel~,
it may be droplet~shaped, conical, etc. ~reel~J suspended fro~
the cover 8 are rod-type valves 23 with dishes 24 adapted
to close the passages 25 commu~icating the worXin~ space of
the tube 7 with the a~bient atmosphere. In a modification
of the apparatus, this communication is not with the ambient
air, but with a space ~illed with a gas under gauge pressure
below that in the pressure accumulator, to provide a "soft"
pulse.
~he herein disclosed pump operate~$ as follows.
With the metal 5 filling the bath of the furnace 6 to
a certai~ level whereat the outlet of the tube 7 is not expo-
sed~ the suction li~e 15 is co~nected to the i~texnal working
space o~ the tube 7, and the pressure accumulator 13 is connec-
ted to a compressed~gas source via the distrib~ti~g device 12
and the pressure re~ulator 14. Simultaneousl~ voltage is sup-
plied to the coil of the solenoid of the distributing device
12; the rod o~ the contact ~enæor bein~ lowered to a preselect-
-- 19 --
ed level, depen~ing on the setting of the throt~le 16 arl~ 'vhexelative posivions of the float 22 and t~e sleeve ~I9.
~ he suction raises the li~uid metal into the tube 7 to a
certain height, the float 22 with the sleeve 19 bein~ raised
accordingly. Eventially the sleev2 19 raises the rod-type valves
2~ b~ its shoulder, the dishes or valve members 24 opening
the passages 25 communicating the interior of the tube with
the ambient atmosphere, while the sleeve 19 starts closing
the connection between the working space of the tube and the
suction souxce. ~he metal ascends at a slowing rate and at a
certain moment stops on account of the lifting force resulting
fro~ the pressure drop and the weigh-t of the metal counter-
balancing each other. ~t this ~oment the contactwtype level
sensor responds, and the solenoid of the distributor 12 operates,
whereb~ the pressure accumulator 1~ becomes connected with the
working interior of the tube 7 via the injector 11, the line
'lO and the no~zle 9, the injector cutting of`f the suction suppl~,
and the compressed gas from -the pressure accumulator 13 swiftly
flowing into the working space. ~he pressure pulse acts upon
the metal body in the tube and expels it at a high velocit~
into the molten metal bod~ in the bath. The duration of the
pulse can be extended b~ any suita'ole known per se means used
for the purpose. ~he metal portion expelled in a high-velocity
jet from the tube advances through the bath and enga~es the
adjacent layexs of the molten metal body, in which way the
whole volu~e of the molten metal bod~ in the bath is agitated.
; ~pon the ~etal in the tube clearing the rod of the con-
tact sensor, the solenoid of the distributlng dsvice 12 is
'
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6~
dc~ne~ized, and the cor~pressed ~as is suppiie~ rito t~e ~
sure accumulator 13 from the co~pressed gas source. Tr,en a~o~.-e--
portion of liquid me~al is withdrawn by suctio~ into the tube,
and ~h~ abovedescribed operating c~cle of the apparatus i5 re-
peated.
The apparatus in accordance with the present invention
is operable equally efficiently ~ith the tube of the pu~p
bein~ either stationar~ or movable.
~ he herein disclosed pump enables to stap up the effici-
ency of the meltin~ process and to cut down the melting time~
e.~O of aluminum alloys by as much as 15%.
~ he cover 26 of the apparatus has mounted thereon, in
the presently described embodiment, the main contact-type level
sensor o~ which the probe 27 is connected to one of the contacts
of the solenoid of the distributin~ device 28, while 12 V voltage
is supplied to the other contact~ ~he metal bod~ in the bath
is earthed, therefore, upon the metal contacting the probe 27, the
solenoid of the distributing device operates, with the line
"12V voltage source - eaxth" being completed. ~he probes 27 of thc
contact-t~pe sensors are mounted in nut-tightened collet chucks
29, which enables to easil~ adjust the spacing of the probes
froTn the cover 26, and thus to adjust the operative volume
of the wor~ing space of the ~ube ~00 ~ throttling, it is
~possible to adjust the time of attaining the reguired
subatmospheric pressure in the working space of the tube, and
t'nus to adjust the rate of the ascent of the me~al to the preset
height.
~he hérein described em~odiment o~ the apparatus operates,
^ 21 -
;
as follows.
~ ith thc molten metal in the bath of the fur;^ace a~telrl-
ing a given per~.issible level whereat the outlet of the ~u~e
~0 is no~ ~xposed, the vacuum or suction line 31 is connected
to the workin~ space of the tube 30, and the pressure accumula-
tor ~2 is connected -to a compressed gas source via the dis~ri- -
buting device 28 and the pressure regulator 33. Simultaneously,
voltage is supplied to -the coils of the solenoids of the discri-
buting device 28, the probes ~7 of the level sensors having been
lowered to a preselected level in accordance with the setting
of the throttling member governlng the rate of ascent of the
metal in the tube 30 at the ~iven subatmospheric pressure -
suction - in the suction s~stem.
~ he liquid metal is lifted b~ suction in th~ tube 30 to
the preset height whereat it contacts the probe 27 of the
contact sensor, whereb~ the electric line "earth - 12V source"
is completed, and the solenoid of the distributing device
28 operates~ ~he pressure accumulator 32 is connected to the
working space of the tube 30 via the line 3'l and the nozzle
34, and ~he compressed gas stored in the pressure accu~ulator
swiftl~ flows into the ~orking space. The compressed-gas
pulse acts upon the bod~ of metal in the tube and expels it in
a high-velocit~ ~et into -the metal bod~ in the bath~ The por-
tion of the liquid metal expelled from the tube moves through
the metal bod~ in the bath, engaglng the adJacent layers of
metal and thus agitat~.ng the entire metal body in the bath.
Upon the metal in the tube clearing the probe 27, the
completed electric lins "earth - voltage source`' becomes bro-
22 -
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ken, the solenoid o~ the distributing de~ice 2~ is deerie,g-zed;
and compress~d gas starts flowin~ into the p~essure accu~-.u}~-
tor 32 from the pressure line 35. ~.hen liquid metal is orce
again withdrawn b~ suction in-to tAe tube, and the abovedesc~.i-
bed cycle of the operation of the apparatus is repeated,
The abovespecified structure of -the apparatus for stirring
liquid metal of~ers a greater efficienc~ and capacity, o~ring
to the filler utilization of the working volume of the tube,
with relatively high suction values in the system.
Described hereinbelow in more detail is the prefe~red
embodiment of the suction cut~off device of the gas-dynamic
pump.
~ he suction cut-off device of the gas-d~namic pump for
stirring molten metal includes the chamber of the stationary
nozzle 36. Received within the nozzle 36 is a movable nozzle
37 connected via the line~ 31 (~IG. 6) with the distributing
device 28 of the s~stem supplying pulses of compressed gas
(nitrogen, argon, etc r ) ~ ~rom the pressure accumulator 32
filled from the pressure supply lin~ through the pressure
regulator 33. Interposed.between the shoulder 38 of the
nozzle and the annular groove 39 merging with the tapering
surface 40 of the chamber is a xesilient member, e.g. a
compression sprin~ 44 maintaining the nozzle 37 in a suspen-
ded or floating state. ~he clearance between the end face of the
no~zle 37 and the tapering surface 40 is adJus-table with aid of a
lid 41 threadedly connected with the nozzle 36. ~he outle-t
portion of the nozzle 37 has made therein passages 42 communi-
- 23 -
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, . .
- . ,, '' -.
ca~ing the co~pressed-gas pulse suppl~ line ~ri~h the space L~
iIlter~ediate tne external and internal surfaces ol the nozzl~
37 and of thc cha~ber of the nozzle ~6, respectively. ~he de-
vice operates, as follows~
In -the initial position, shown in ~i~. 8, the suc-tion
line ~ communicates with the chamber of the nozzle 36, ~.rhile
compressed gas is supplied vla -the distributing device 23
(~`IG. 6) into the pressure accumulator 32, With the distribut-
ing device 28 switchin~ over, the co~pressed gas stored in
the accumulator 32 flows via the line 31 to the nozzle 37
(~IG. 8). With thc gas ~lowin~ through the nozzle ~ nere
is created a pressure drop across the nozzle, i.e, before
and after the nozzle~ At the same time, compressed gas flows
via the passages 42 into the chambsr ~3 and acts upon the area
defined by the surface of the shoulder of the nozzle. The
nozzle 37 is driven by the pressure of compresse~ gas upon
the shoulder 38 until the end ~ace of the nozzle 37 abuts
against the tapering surface 40 of the passage~ cutting off
the suctionsupply line from the internal space of the tube.
The spring 44 is compressed by this same effort and remains
compressed until the compressed-gas pulse is terminated. With
the pulse terminated, the sprin~ 44 returns the nozzle 37
upwardl~ into the initial position.
Then ~he abovedescribed operating c~cle is repeated in
the sa~e sequence.
~ he last described general structure can be associated
both with a stationar~ pump tube and a mobile one, its incor-
poration enabling to step up the productivity of the pump used
with suction plants b~ 8 .,. '10% on the average.
~24-
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