CA1166818A - Method and installation for low pressure casting of metal parts in a thin-walled sand impression - Google Patents
Method and installation for low pressure casting of metal parts in a thin-walled sand impressionInfo
- Publication number
- CA1166818A CA1166818A CA000351042A CA351042A CA1166818A CA 1166818 A CA1166818 A CA 1166818A CA 000351042 A CA000351042 A CA 000351042A CA 351042 A CA351042 A CA 351042A CA 1166818 A CA1166818 A CA 1166818A
- Authority
- CA
- Canada
- Prior art keywords
- casting
- mould
- sand form
- mass
- box
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D18/00—Pressure casting; Vacuum casting
- B22D18/04—Low pressure casting, i.e. making use of pressures up to a few bars to fill the mould
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Casting Devices For Molds (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
In a method of low-pressure casting, a sand form is packed within a mass of compacted magnetisable particles, which are rigidified prior to casting by means of a magnetic field. The compacting is carried out by vibrating the mould.
In a method of low-pressure casting, a sand form is packed within a mass of compacted magnetisable particles, which are rigidified prior to casting by means of a magnetic field. The compacting is carried out by vibrating the mould.
Description
6 ~ :1 8 The present lnvention relates tq the low Rressure casting o~ metal parts, for example from pig iron, in a mould compX;~sing a thin-walled form made of a hardened mixture of sand and res~n.
Low pressuxe casting~ in which ~ound~y ~oulds are supplied from the bottom at a pressure greater than atmospheric pressure, but substantially less than 2 bars, is known. The advantage of the latter is that it facilitates the filling of forms of complicated shape, which would be poorly filled by simple gravity casting, and that it lends itseld to automation in the control of successive casting operations, whilst elimin-ating troublesome and dangerous operations of handling tilting casting ladles or casting ladles comprising a stopper-rod.
lS Furthermore, by using suitable means for supplying the mould and controlliny the pressure (see for example French Patent No. 7,442,713 in the name of the Applicant published under No.
Low pressuxe casting~ in which ~ound~y ~oulds are supplied from the bottom at a pressure greater than atmospheric pressure, but substantially less than 2 bars, is known. The advantage of the latter is that it facilitates the filling of forms of complicated shape, which would be poorly filled by simple gravity casting, and that it lends itseld to automation in the control of successive casting operations, whilst elimin-ating troublesome and dangerous operations of handling tilting casting ladles or casting ladles comprising a stopper-rod.
lS Furthermore, by using suitable means for supplying the mould and controlliny the pressure (see for example French Patent No. 7,442,713 in the name of the Applicant published under No.
2,295,808), low pressure cas-ting can eliminate shrinkage-heads and certain casting appendages.
It is known that low pressure casting is frequently carried out in sand forms, in particular in order to ob~ain certain metal structures. This is the case, for example, when it is desired to produce from spheroidal graphite cast iron rough-cast parts which have no carbides in the rough-cast state, without the need for any subsequent thermal trea-tment.
~:f - 2 8 :1. t~3 This result is due essentiall~ to the re~xactory nature of the sand~ ~hich forms a therm~1 barrier that eliminates a hardenin~ phenomenon of the cast me~al.
In addition, one thus benefits from the permeability to gases of the sand.
Thus, moulds with walls consistlng of sand prevent cast-ing faults and reduce rejects.
Xowever, the use in this method of conventional sand moulds, which are solid, causes difficulties: on account of the fact that the filling pressure is maintained for a prolonged per-iod of time, the moulds must have a relatively high mechanical strength. It is therefore necessary to use sand comprising a greater proportion of binding agent and/or moulds which are thic-ker than in the case of simple gravity casting. But this in-creases the cost price of the parts, since the moulds, which can be used only once, are more expensive to produce, and cooling of the parts becomes too slow, which considerably reduces the pro-duction rate, if only on account of the delay necessary for the solidification of the inlet point of the metal into the moulding cavity.
This is why an attempt has been made to limit the quan-tity of sand used. In a known solution (see the Applicant's French Patent No. 77 08 364 published under No. 2,384,568), the sand form is enclosed in a metal shell. The shell must thus be ` changed for each shape of cast part. In addition, the shell fre-quently requires . .
i.-I 166~
machining, albeit rough machining.
The object of the present invention is to provide another solution which is more flexible and more economical, for casting of this type, thus, ensuring an effective support for the sand form, and enabling the latter to withstand the force of the metal under pressure.
According to the present invention there is provided in a method of low-pressure casting metal parts in a thin-walled sand form, the improvement comprising packing the sand form within a mass of magnetisable particles, compacting the mass prior to casting, and rigidifying the mass of particles by means of a magnetic field.
The invention also relates to a mould for use in the low-pressure casting of metal parts, comprising a closed box having in an upper part -thereof a closable opening enabling it to be filled with magnetisable particles, a casting orifice in the bottom of the box, and a sand form adapted to rest on the bottom of the box and be packed within the magnetisable particles, said sand fo.rm having a casting orifice in communication with the casting orifice in the closed box.
. The invention also relates to a low-pressure casting installation of metal parts, comprising a reservoir for molten metal, a substantially vertical supply pipe in the reservoir, means for supporting a mould as defined above and pressing the casting orifice thereof against the upper end of the supply pipe, means for supplying propellent gas to thP reservoir to force .
_ ~ _ .~ .
molten metal up the supply pipe, and an electro-magnet which is placed around the mould during a casting operation to rigidify the magnetisable particles.
The inv~ntion will now be described in mora detail, by way of example only, with reference to the accompanying drawings in which:-Figure 1 is a partial diagrammatic view ofvertical section of an installation according to the Figure 2 is a partial plan view of this installation.
The low pressure casting installation illustrated comprises a casting ladle 1, a frame 2 and a number of identical moulds 3, of which only one has been shown. The dimensions of the mould 3 have been exaggerated with respect to those of the ladle 1 for the sake of clarity.
The ladle 1 comprises a container 4 of large dimensions containing liquid metal 5 and comprising an oblique filling spout 6 closed by a lid 7. A vertical supply pipe 8 of refractory material passes through the upper wall of this container. It descends virtually to the bottom of the lattPr and projec~s thereabove over a short length, where it is surrounded by a reinfoxcing ~0 11B~8~
nozzle 9 of general frustoconical shape. The upper end of the pipe 8 is conta.ined in.the same horizontal plane ~ as the fla~
upper side of the nozzle 9.
A pipe 10 co.mmunicating with the inside of the container 4 may be connected, under the control of a v~l~e 11, either to a source of compressed gas, for example compressed air, or to the outlet.
The frame 2 comprises four telescopic uprights 12 pro~
vided with helical springs 13. The uprights 12 support a hori-zontal table 14 pushed permanently upwards by the springs 13.
Fixed below the table 1~ are vibrating devices 15, whereas an electro-magnet 16 of U shape comprising two parallel sides or arms 17 connected by a coil 17a is positioned on this table.
The table 14 comprises a frustoconical orifice 18 mating with the outer surface of the nozzle 9. In the lower position of the table, the orifice 18 bears on this surface and the upper side of the table is contained in the plane P described above.
The frame also comprises a retractable vertical jack 19 located at a slightly higher level,strai~ht above the ladle 1.
The mould 3 is constituted by a box 20, sand form 21, and a mass of particles 22. The box and mass 22 are common to all the moulds, in contrast to the sand form 21.
~, ' .
~ 1 66~ 3 The box 20 is a para:Llelepipedal metal box whereof the length is s]ightly less than the distance separating ~he two sides 17 of the electro-magnet 16. I'he base of this box h~s a frustoconical opening 23, which .is convergent in the downwards direction, whereas its upper wall constitutes a removable lid or pressing plate 24. The opening 23 opens to the ou-tside in a xebate 25 of slight depth.
The sand form 21 is in the form of a thin-walled shell consisting of a hardened mixture of sand and theremosetting re-sin, such as an isocyanate resin or a phenol-formaldehyde resin.
This shell, divided into two halves along a horizontal interface Q, defines with an inner core 2~, a moulding cavity 27 in the shape of a part to be cast, which is for example a gate-valve body.
The lower half-shell comprises a tubular extension 28, which defines a main conduit or inlet 29 of the same diameter as the pipe 8. Externally, this projection is frustoconical and fits the opening 23 in the box. When it is fitted in this open-ing, its end face is flush with the bottom of the rebate 25.
The conduit 29 comrnunicates with the moulding cavity solely through a small horizontal conduit or secondary inlet 30.
2~ Externally, the shell 21 has annular stiffening or streng-thening projections, one of which, bearing the reference numeral 31, is at a distance from the extension ~ 8 -- .
28. ~.~en the shell is pl~ced i~ the box 20, which leaves a considerable clearc~ce on all sides, the pro3ection ~1 rests on the botto~l of this bo~, possibly throu~h the intermedi.ary of a wedge 32 as illustrated. ~he shell is thus perfectly positioned, in ~ stable man~er, without the sand being subjected to excessive stress~ ~he space remaining free in the box 20 is filled with the mass 22 constituted by compressed ma~netisable iron shot~ the grain si.ze of which is 17/10 mm for exaL~pleO
. ~
~e operation of this installation is as follows.
At the beginnin~, the casting ladle 1 containing liquid metal 5, for example pig iron, is kept under a moderate air press~re, for examp].e of ~he order of 1 bar, through the conduit 10. Under the effect of thi~
pressure, the pig iron is`located in the suppl-~ pi.pe 8 at a level ~ substantially lower than the lev~l of t;he outlet operling o.f this pipe. rrhe tablc ~14 is in the upper position unde~ the action of the springs 13~ -the jack 19 being retracted as i.s the lid 24. ~he LatJGer -may moreover be integral with the piston rod of the jack 19.
An adhesive sealing washer ~3, for example of the type described in the c~orementioned ~rench Pate~t No. ..
. 74 42 713, is placed in the reba.te 25 of the bo~ 20, which is then placed on the table 1~ between the arms o the electro-magnet 16 c~d positiorled so that its orifice 23 is centered Oll the orifice 18 of this tableO
~
.. _.. . ~.. ,___ ..
- I 1 6~8:~
A slight clearance, for example of 0.5 n~, not visible in the drawin~, then e~ists between each arm 17 and the adjacent side of the bax 20. ~ shell 21 is placed len~thwise on the base of the box 7 in order tobe ~ppoxted by its pxojection 31 and po-sitioned and supported by its extension 28.
Despite the weight of the ~ould and of -the electromag-net, the springs 13 are not completely compressed and thus lift the table 14 slightly, so that the washer 33 is still not com-pressed.
Magnetisable iron shot is then poured or blown into thebox 20 in order to fill its lower part, between the shell 21 and the bottom of the box, as well as its upper part, in order that the shell is covered completely. The outer shape of the shell 21, constituted almost e~clusively by rounded surfaces, promotes the introduction of shot below the shell Then, the vibrators 15 are set in action, in order to cause the table 14 to vibrate on its springs 13 and to pack the mass of shot 22 in a suitable manner~
During this packing o~eration, the level of shot in ~ the box 20 drops. The latter is then topped-up with shot and packing and refilling are recommenced until the level of shot is flush with the upper part of the box 2n. When it has been pac-ked in a suitable manner, the mass of shot 22 has the minimum of gaps therebetween, in particular in the vicinity of the shell and the maximum density.
_ ~ I
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After vibration and packing, -the electro-m~gnet 16 is excited, and subjects the ma~s of shot 22 to ~ powerful m~gnetic field, which rigidifies it. The vibrations are sto~ped immedia-tely after the shot-fillin~ opexation and be~ore the excitation of the electro-ma~net.
The mass 22, packed in this way and hardened, provides an excellent rigid support for the shell 21. The arrangement is virtually equivalent, from the mechanical point of view, to the metal shell lined internally with sand and described in the afore-said French Patent No. 77 08 364.
The pressure plate 24 is then put in position and lower-ed by the jack 19 in order to press the mould 3 with force against the vibrating table 14. This compresses the springs 13 and pres-ses the opening 18 in the table agains-t the nozzle 9. The seal-ing washer 33 is compressed between the latter and the bottom of its housing.
For reasons of safety, at least one clamp 34 can be placed around the mould 3 and the table 13 in order to complete the inter-locking of these two parts of the installation, which is now ready for casting.
In order to carry out the latter, the valve 11 is opened and air, for example at a pressure in the order of 1.2 bars, is introduced into the container 4 above the liquid pig iron 5.
The pig iron rises, through the pipe 8, 6 8 :~. '`3 the main inlet 2~ and the secondary i~let 30 into khe said ~orm, which it fills completel~. The force which the metal introduced under pressure exerts on the walls of the shell 21 is counter-balanced by the resistance offered by the mass of shot 22, which is packed and rigidified, and bythe pressure plate 24, which pre-vents rising of the mould 3 above the table 14.
During casting, the magnetic mass 22 remains relatively cold, in particular in the vicinity of the shell 21, where its temperature scarcely exceeds 200C owing to thè refractory nature of the shell, which does not transmit the heat from the cast iron.
In the upper part of the mould, the mass of shot is quite cold.
This mass thus remains magnetic and rigid, since it is far from the Curie point of 750C at which iron loses its magnetic pro-perties.
It will be noted that, during casting, no gas is liber-ated outside the mould 3, although the gases produced are able to leave the casting form through the porous shell 21 and the permeable mass of shot 22. It is considered that, since the mould 3 is completely filled with shot in its upper part and the mass 22 remains cold, the gases spread out in this mass with a tendency towards condensation, which prevents them from rising to the upper end of the mould.
~ . . .
t 1 6~
- 12 ~
~ so~ f~
~3 Af-ter :Eilling the ~ YY~5~ with liquid plg i.rorJ
and after the pres~u.re is maintai~ed for a c~rtai.n relatively short period of time., correspondin~r to the solidification of the secondary inlet 30 after a~
adequate supply of pig iron to th.e impression, as described iIl the said ~rench Patent No- 74 ~2 713, the pressure ls released in the laclls 1 by supplying through the conduit 10 a pressure which is less than the casting pressure b~t,sufficient to restore the pig iro~ solely to a leval N1 illustrated in broken lineg close to the upper part of th~ noæzle 9.
~he supply of electric current to the electro magnet 16 is -theIl cutr The pressure plata 2~ is raised and retracted with the jack 19 and the mass of shot 22 is removed at least p~rtly from the mould 3 which has just been filled with cast iron. ~his operation takes place under a hood which is not shown, since it is at thi~ ti.me that the gases formed {~uri~g caæting and which have been .r~tained up till then in the upper part of the mass of shot 22, outside the shell 21, are liberated, probabl~
by evaporationO When this shell has been exposed suff1.ciently from the mass of shot9 it is removed with the caæting, stripping of which is then carried out.
~or the subseque~t casting operation~ it is su~'ficient to introduce a new shell 21 provided with itæ core 26, L
into the remalning shot, in the same box 20 once more placed cn the table 145` then to complete the operation o~
~illingr wi-th shot, usin~ -t~e shot which has just been removed from the preceding mould 3 and to carry ~ut packing and the other successive opera-tions which have been described. In practice, it is unnece~sary to remove all the shot after each castingg since the latter retains its confi~uration to a certain extent, when the shell 21 is extracted therefrom~
As a n~nerlcal example, l~ o~der to cast a ~alve body from cast iron having a weight of` 60 kg with a tubular diameter of 200 mm, the box 20 measuring 850 x 95Q x 500 mm, the mass 22 i5 ~ubjected to a ma~netic f~ad of 4000 gauss, this field depending on the section of sho' to be made rigid and thus ~n the distance between the arms 17 of the electro-magnet. ~he grain size of the shot is chosen to be sufficientl~r fi~e to leave the minimum nurnber of gaps, 3ince gaps lsad to ~m increase in the ma~netic field necessary~ without however loading the mou]d excessively. '~he cast part o~t~lned has a skin, i.e. an outer surface condition, of very fine -20 appe~ra~ce a~d has very accurate dimensions.
Since a low pressure casting process is u~ed 9 liquid metal which is alway~ ho-t is introduced into the-6s~
and this liquid metal is naver apparent externally, which guarantees the comfort and safet~r of the operators who may be in the vicinity of the installation.
Furthermore, the risin~ and falling of the iquid r~etal in the pipe 8 takes place simply by operati~g the valve 11 - - `
-- ,4 --and con.~ection to a sol~ee of suitable p~es~11re or to a discharge, which can b~ easily autom~ted. Thus, the supply of liquld metal to the mould has no -troublesome nor d.angerous ~eat~res, Owing to t-h~ vibrating means 15, the density o~ the mass 22 is s~fficient to guarr~tee that there are no loeal gaps in contaet with the shell eausi.ng locally defec-tive external support for the latter and consequently a risk o~ deformation and rupture under the foroe of liquid metal~ despite the fac-t that . ~-, .
the mass 22 ls made rigld by the magnetic field.
r~he mass of shot 22 :is inter-ehangeable and eompletely reusable whatever the shape of casting impression r~.d the eomplementar~r equipment eonstituted by the vibrato.rs 15 and eleetro-magnet 16 comprise solely parts whieh are easily avai.lable. ~he method of the invention i.s -thus very eeonomieal.
~he casting method described is well ~uited -to producin~ parts of' com~licated shapes. ~he o~l~
limitations as regards volume and weiOht of the castings which are able to be east are dependent on the power of the maglietie f-.ield which can be produced bv means of the el~ctro-magQet 16~ Thus? with a ma~neti.c field of 4000 ~auss, one can produee p~rts weig~ing up to 500 kg.
As a variation, the mould 3 eould be filled with shot and vihrated a.way from the casting station~ o~
ano~her vibra-ting ~.a~le~ In thls case~ the table 149 serving ~olely to reeeive the mould at the casting station , 1 1 6B ~ 3 ~nd to support the electxo-ma~net 169 would no longer b0 provi.d.ed wit~ vibrati.ng mea~s 15.
In a1l cases, one attempts to ~ive the shell exte~nal shape which .~aci.litates good distribution o~
the shot, even if the mould.~ng cavit~ doe~ not have correspondingr shapesO ?.he la-tter ma~ be rounded surfaces~ as in the example illustrated~ or an~ other sultable deI~lecting shape according to the technique of filling the box.
It is known that low pressure casting is frequently carried out in sand forms, in particular in order to ob~ain certain metal structures. This is the case, for example, when it is desired to produce from spheroidal graphite cast iron rough-cast parts which have no carbides in the rough-cast state, without the need for any subsequent thermal trea-tment.
~:f - 2 8 :1. t~3 This result is due essentiall~ to the re~xactory nature of the sand~ ~hich forms a therm~1 barrier that eliminates a hardenin~ phenomenon of the cast me~al.
In addition, one thus benefits from the permeability to gases of the sand.
Thus, moulds with walls consistlng of sand prevent cast-ing faults and reduce rejects.
Xowever, the use in this method of conventional sand moulds, which are solid, causes difficulties: on account of the fact that the filling pressure is maintained for a prolonged per-iod of time, the moulds must have a relatively high mechanical strength. It is therefore necessary to use sand comprising a greater proportion of binding agent and/or moulds which are thic-ker than in the case of simple gravity casting. But this in-creases the cost price of the parts, since the moulds, which can be used only once, are more expensive to produce, and cooling of the parts becomes too slow, which considerably reduces the pro-duction rate, if only on account of the delay necessary for the solidification of the inlet point of the metal into the moulding cavity.
This is why an attempt has been made to limit the quan-tity of sand used. In a known solution (see the Applicant's French Patent No. 77 08 364 published under No. 2,384,568), the sand form is enclosed in a metal shell. The shell must thus be ` changed for each shape of cast part. In addition, the shell fre-quently requires . .
i.-I 166~
machining, albeit rough machining.
The object of the present invention is to provide another solution which is more flexible and more economical, for casting of this type, thus, ensuring an effective support for the sand form, and enabling the latter to withstand the force of the metal under pressure.
According to the present invention there is provided in a method of low-pressure casting metal parts in a thin-walled sand form, the improvement comprising packing the sand form within a mass of magnetisable particles, compacting the mass prior to casting, and rigidifying the mass of particles by means of a magnetic field.
The invention also relates to a mould for use in the low-pressure casting of metal parts, comprising a closed box having in an upper part -thereof a closable opening enabling it to be filled with magnetisable particles, a casting orifice in the bottom of the box, and a sand form adapted to rest on the bottom of the box and be packed within the magnetisable particles, said sand fo.rm having a casting orifice in communication with the casting orifice in the closed box.
. The invention also relates to a low-pressure casting installation of metal parts, comprising a reservoir for molten metal, a substantially vertical supply pipe in the reservoir, means for supporting a mould as defined above and pressing the casting orifice thereof against the upper end of the supply pipe, means for supplying propellent gas to thP reservoir to force .
_ ~ _ .~ .
molten metal up the supply pipe, and an electro-magnet which is placed around the mould during a casting operation to rigidify the magnetisable particles.
The inv~ntion will now be described in mora detail, by way of example only, with reference to the accompanying drawings in which:-Figure 1 is a partial diagrammatic view ofvertical section of an installation according to the Figure 2 is a partial plan view of this installation.
The low pressure casting installation illustrated comprises a casting ladle 1, a frame 2 and a number of identical moulds 3, of which only one has been shown. The dimensions of the mould 3 have been exaggerated with respect to those of the ladle 1 for the sake of clarity.
The ladle 1 comprises a container 4 of large dimensions containing liquid metal 5 and comprising an oblique filling spout 6 closed by a lid 7. A vertical supply pipe 8 of refractory material passes through the upper wall of this container. It descends virtually to the bottom of the lattPr and projec~s thereabove over a short length, where it is surrounded by a reinfoxcing ~0 11B~8~
nozzle 9 of general frustoconical shape. The upper end of the pipe 8 is conta.ined in.the same horizontal plane ~ as the fla~
upper side of the nozzle 9.
A pipe 10 co.mmunicating with the inside of the container 4 may be connected, under the control of a v~l~e 11, either to a source of compressed gas, for example compressed air, or to the outlet.
The frame 2 comprises four telescopic uprights 12 pro~
vided with helical springs 13. The uprights 12 support a hori-zontal table 14 pushed permanently upwards by the springs 13.
Fixed below the table 1~ are vibrating devices 15, whereas an electro-magnet 16 of U shape comprising two parallel sides or arms 17 connected by a coil 17a is positioned on this table.
The table 14 comprises a frustoconical orifice 18 mating with the outer surface of the nozzle 9. In the lower position of the table, the orifice 18 bears on this surface and the upper side of the table is contained in the plane P described above.
The frame also comprises a retractable vertical jack 19 located at a slightly higher level,strai~ht above the ladle 1.
The mould 3 is constituted by a box 20, sand form 21, and a mass of particles 22. The box and mass 22 are common to all the moulds, in contrast to the sand form 21.
~, ' .
~ 1 66~ 3 The box 20 is a para:Llelepipedal metal box whereof the length is s]ightly less than the distance separating ~he two sides 17 of the electro-magnet 16. I'he base of this box h~s a frustoconical opening 23, which .is convergent in the downwards direction, whereas its upper wall constitutes a removable lid or pressing plate 24. The opening 23 opens to the ou-tside in a xebate 25 of slight depth.
The sand form 21 is in the form of a thin-walled shell consisting of a hardened mixture of sand and theremosetting re-sin, such as an isocyanate resin or a phenol-formaldehyde resin.
This shell, divided into two halves along a horizontal interface Q, defines with an inner core 2~, a moulding cavity 27 in the shape of a part to be cast, which is for example a gate-valve body.
The lower half-shell comprises a tubular extension 28, which defines a main conduit or inlet 29 of the same diameter as the pipe 8. Externally, this projection is frustoconical and fits the opening 23 in the box. When it is fitted in this open-ing, its end face is flush with the bottom of the rebate 25.
The conduit 29 comrnunicates with the moulding cavity solely through a small horizontal conduit or secondary inlet 30.
2~ Externally, the shell 21 has annular stiffening or streng-thening projections, one of which, bearing the reference numeral 31, is at a distance from the extension ~ 8 -- .
28. ~.~en the shell is pl~ced i~ the box 20, which leaves a considerable clearc~ce on all sides, the pro3ection ~1 rests on the botto~l of this bo~, possibly throu~h the intermedi.ary of a wedge 32 as illustrated. ~he shell is thus perfectly positioned, in ~ stable man~er, without the sand being subjected to excessive stress~ ~he space remaining free in the box 20 is filled with the mass 22 constituted by compressed ma~netisable iron shot~ the grain si.ze of which is 17/10 mm for exaL~pleO
. ~
~e operation of this installation is as follows.
At the beginnin~, the casting ladle 1 containing liquid metal 5, for example pig iron, is kept under a moderate air press~re, for examp].e of ~he order of 1 bar, through the conduit 10. Under the effect of thi~
pressure, the pig iron is`located in the suppl-~ pi.pe 8 at a level ~ substantially lower than the lev~l of t;he outlet operling o.f this pipe. rrhe tablc ~14 is in the upper position unde~ the action of the springs 13~ -the jack 19 being retracted as i.s the lid 24. ~he LatJGer -may moreover be integral with the piston rod of the jack 19.
An adhesive sealing washer ~3, for example of the type described in the c~orementioned ~rench Pate~t No. ..
. 74 42 713, is placed in the reba.te 25 of the bo~ 20, which is then placed on the table 1~ between the arms o the electro-magnet 16 c~d positiorled so that its orifice 23 is centered Oll the orifice 18 of this tableO
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- I 1 6~8:~
A slight clearance, for example of 0.5 n~, not visible in the drawin~, then e~ists between each arm 17 and the adjacent side of the bax 20. ~ shell 21 is placed len~thwise on the base of the box 7 in order tobe ~ppoxted by its pxojection 31 and po-sitioned and supported by its extension 28.
Despite the weight of the ~ould and of -the electromag-net, the springs 13 are not completely compressed and thus lift the table 14 slightly, so that the washer 33 is still not com-pressed.
Magnetisable iron shot is then poured or blown into thebox 20 in order to fill its lower part, between the shell 21 and the bottom of the box, as well as its upper part, in order that the shell is covered completely. The outer shape of the shell 21, constituted almost e~clusively by rounded surfaces, promotes the introduction of shot below the shell Then, the vibrators 15 are set in action, in order to cause the table 14 to vibrate on its springs 13 and to pack the mass of shot 22 in a suitable manner~
During this packing o~eration, the level of shot in ~ the box 20 drops. The latter is then topped-up with shot and packing and refilling are recommenced until the level of shot is flush with the upper part of the box 2n. When it has been pac-ked in a suitable manner, the mass of shot 22 has the minimum of gaps therebetween, in particular in the vicinity of the shell and the maximum density.
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After vibration and packing, -the electro-m~gnet 16 is excited, and subjects the ma~s of shot 22 to ~ powerful m~gnetic field, which rigidifies it. The vibrations are sto~ped immedia-tely after the shot-fillin~ opexation and be~ore the excitation of the electro-ma~net.
The mass 22, packed in this way and hardened, provides an excellent rigid support for the shell 21. The arrangement is virtually equivalent, from the mechanical point of view, to the metal shell lined internally with sand and described in the afore-said French Patent No. 77 08 364.
The pressure plate 24 is then put in position and lower-ed by the jack 19 in order to press the mould 3 with force against the vibrating table 14. This compresses the springs 13 and pres-ses the opening 18 in the table agains-t the nozzle 9. The seal-ing washer 33 is compressed between the latter and the bottom of its housing.
For reasons of safety, at least one clamp 34 can be placed around the mould 3 and the table 13 in order to complete the inter-locking of these two parts of the installation, which is now ready for casting.
In order to carry out the latter, the valve 11 is opened and air, for example at a pressure in the order of 1.2 bars, is introduced into the container 4 above the liquid pig iron 5.
The pig iron rises, through the pipe 8, 6 8 :~. '`3 the main inlet 2~ and the secondary i~let 30 into khe said ~orm, which it fills completel~. The force which the metal introduced under pressure exerts on the walls of the shell 21 is counter-balanced by the resistance offered by the mass of shot 22, which is packed and rigidified, and bythe pressure plate 24, which pre-vents rising of the mould 3 above the table 14.
During casting, the magnetic mass 22 remains relatively cold, in particular in the vicinity of the shell 21, where its temperature scarcely exceeds 200C owing to thè refractory nature of the shell, which does not transmit the heat from the cast iron.
In the upper part of the mould, the mass of shot is quite cold.
This mass thus remains magnetic and rigid, since it is far from the Curie point of 750C at which iron loses its magnetic pro-perties.
It will be noted that, during casting, no gas is liber-ated outside the mould 3, although the gases produced are able to leave the casting form through the porous shell 21 and the permeable mass of shot 22. It is considered that, since the mould 3 is completely filled with shot in its upper part and the mass 22 remains cold, the gases spread out in this mass with a tendency towards condensation, which prevents them from rising to the upper end of the mould.
~ . . .
t 1 6~
- 12 ~
~ so~ f~
~3 Af-ter :Eilling the ~ YY~5~ with liquid plg i.rorJ
and after the pres~u.re is maintai~ed for a c~rtai.n relatively short period of time., correspondin~r to the solidification of the secondary inlet 30 after a~
adequate supply of pig iron to th.e impression, as described iIl the said ~rench Patent No- 74 ~2 713, the pressure ls released in the laclls 1 by supplying through the conduit 10 a pressure which is less than the casting pressure b~t,sufficient to restore the pig iro~ solely to a leval N1 illustrated in broken lineg close to the upper part of th~ noæzle 9.
~he supply of electric current to the electro magnet 16 is -theIl cutr The pressure plata 2~ is raised and retracted with the jack 19 and the mass of shot 22 is removed at least p~rtly from the mould 3 which has just been filled with cast iron. ~his operation takes place under a hood which is not shown, since it is at thi~ ti.me that the gases formed {~uri~g caæting and which have been .r~tained up till then in the upper part of the mass of shot 22, outside the shell 21, are liberated, probabl~
by evaporationO When this shell has been exposed suff1.ciently from the mass of shot9 it is removed with the caæting, stripping of which is then carried out.
~or the subseque~t casting operation~ it is su~'ficient to introduce a new shell 21 provided with itæ core 26, L
into the remalning shot, in the same box 20 once more placed cn the table 145` then to complete the operation o~
~illingr wi-th shot, usin~ -t~e shot which has just been removed from the preceding mould 3 and to carry ~ut packing and the other successive opera-tions which have been described. In practice, it is unnece~sary to remove all the shot after each castingg since the latter retains its confi~uration to a certain extent, when the shell 21 is extracted therefrom~
As a n~nerlcal example, l~ o~der to cast a ~alve body from cast iron having a weight of` 60 kg with a tubular diameter of 200 mm, the box 20 measuring 850 x 95Q x 500 mm, the mass 22 i5 ~ubjected to a ma~netic f~ad of 4000 gauss, this field depending on the section of sho' to be made rigid and thus ~n the distance between the arms 17 of the electro-magnet. ~he grain size of the shot is chosen to be sufficientl~r fi~e to leave the minimum nurnber of gaps, 3ince gaps lsad to ~m increase in the ma~netic field necessary~ without however loading the mou]d excessively. '~he cast part o~t~lned has a skin, i.e. an outer surface condition, of very fine -20 appe~ra~ce a~d has very accurate dimensions.
Since a low pressure casting process is u~ed 9 liquid metal which is alway~ ho-t is introduced into the-6s~
and this liquid metal is naver apparent externally, which guarantees the comfort and safet~r of the operators who may be in the vicinity of the installation.
Furthermore, the risin~ and falling of the iquid r~etal in the pipe 8 takes place simply by operati~g the valve 11 - - `
-- ,4 --and con.~ection to a sol~ee of suitable p~es~11re or to a discharge, which can b~ easily autom~ted. Thus, the supply of liquld metal to the mould has no -troublesome nor d.angerous ~eat~res, Owing to t-h~ vibrating means 15, the density o~ the mass 22 is s~fficient to guarr~tee that there are no loeal gaps in contaet with the shell eausi.ng locally defec-tive external support for the latter and consequently a risk o~ deformation and rupture under the foroe of liquid metal~ despite the fac-t that . ~-, .
the mass 22 ls made rigld by the magnetic field.
r~he mass of shot 22 :is inter-ehangeable and eompletely reusable whatever the shape of casting impression r~.d the eomplementar~r equipment eonstituted by the vibrato.rs 15 and eleetro-magnet 16 comprise solely parts whieh are easily avai.lable. ~he method of the invention i.s -thus very eeonomieal.
~he casting method described is well ~uited -to producin~ parts of' com~licated shapes. ~he o~l~
limitations as regards volume and weiOht of the castings which are able to be east are dependent on the power of the maglietie f-.ield which can be produced bv means of the el~ctro-magQet 16~ Thus? with a ma~neti.c field of 4000 ~auss, one can produee p~rts weig~ing up to 500 kg.
As a variation, the mould 3 eould be filled with shot and vihrated a.way from the casting station~ o~
ano~her vibra-ting ~.a~le~ In thls case~ the table 149 serving ~olely to reeeive the mould at the casting station , 1 1 6B ~ 3 ~nd to support the electxo-ma~net 169 would no longer b0 provi.d.ed wit~ vibrati.ng mea~s 15.
In a1l cases, one attempts to ~ive the shell exte~nal shape which .~aci.litates good distribution o~
the shot, even if the mould.~ng cavit~ doe~ not have correspondingr shapesO ?.he la-tter ma~ be rounded surfaces~ as in the example illustrated~ or an~ other sultable deI~lecting shape according to the technique of filling the box.
Claims (12)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a method of low-pressure casting metal parts in a thin-walled sand form, the improvement comprising packing the sand form within a mass of magnetisable particles, compacting the mass prior to casting, and rigidifying the mass of particles by means of a magnetic field.
2. A method according to Claim 1, wherein the magnet-isable particles comprise iron shot.
3. A method according to Claim 2, wherein the mass is compacted by causing it to vibrate.
4. A mould for use in the low-pressure casting of metal parts, comprising a closed box having in an upper part thereof a closable opening enabling it to be filled with magnetisable particles, a casting orifice in the bottom of the box, and a sand form adapted to rest on the bottom of the box and be packed within the magnetisable particles, said sand form having a casting orifice in communication with the casting orifice in the closed box.
5. A mould according to Claim 4, wherein the casting orifice of the sand form is formed by a tubular extension of the sand form fitting in the casting orifice of the closed box.
6. A mould according to Claim 5 wherein the lower part of the sand form has at least one supporting projection, spaced apart from said tubular extension,adapted to rest on the bottom of the closed box.
7. A mould according to Claim 4, wherein the free surfaces of the sand form are rounded.
8. An installation for the low pressure casting of metal parts, comprising a reservoir for molten metal, a substantially vertical supply pipe in the reservoir, means for supporting a mould as claimed in Claim 4 and pressing the casting orifice thereof against the upper end of the supply pipe, means for supplying propellent gas to the reservoir to force molten metal up the supply pipe, and an electro-magnet which is placed around the mould during a casting operation to rigidify the magnetisable particles.
9. Installation according to Claim 8, wherein the electro-magnet is supported by the means for supporting the mould.
10. Installation according to Claim 8, wherein the means for supporting the mould comprises a table supported by springs, and a jack is provided for urging the table downwards.
11. Installation according to Claim 10, wherein the jack acts on the lid of said closable opening.
12. Installation according to Claim 10 or 11, further comprising means for vibrating the table to compact the magnetisable particles.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR7911067A FR2455491A1 (en) | 1979-05-02 | 1979-05-02 | LOW PRESSURE MOLDING METHOD AND INSTALLATION FOR THIN WALL SAND FOOTPRINT |
| FR7911067 | 1979-05-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1166818A true CA1166818A (en) | 1984-05-08 |
Family
ID=9224935
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000351042A Expired CA1166818A (en) | 1979-05-02 | 1980-05-01 | Method and installation for low pressure casting of metal parts in a thin-walled sand impression |
Country Status (11)
| Country | Link |
|---|---|
| BE (1) | BE883075A (en) |
| BR (1) | BR8002692A (en) |
| CA (1) | CA1166818A (en) |
| CH (1) | CH637314A5 (en) |
| DE (1) | DE3016325C2 (en) |
| DK (1) | DK165823C (en) |
| ES (1) | ES491058A0 (en) |
| FR (1) | FR2455491A1 (en) |
| GB (1) | GB2050220B (en) |
| IN (1) | IN154288B (en) |
| IT (1) | IT1128781B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4830085A (en) * | 1986-12-29 | 1989-05-16 | Brunswick Corporation | Vacuum lift foam filled casting system |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2559407B1 (en) * | 1984-02-15 | 1986-09-05 | Pont A Mousson | FOUNDRY MOLDING PROCESS AND MOLD FOR PRECISION CASTING UNDER LOW PRESSURE, WITH GASIFIABLE MODEL AND SAND MOLD WITHOUT BINDER |
| DE3824609C1 (en) * | 1988-07-20 | 1990-01-18 | Bayerische Motoren Werke Ag, 8000 Muenchen, De | |
| US4957153A (en) * | 1989-05-02 | 1990-09-18 | General Motors Corporation | Countergravity casting apparatus and method |
| GB8914012D0 (en) * | 1989-06-19 | 1989-08-09 | Davy Mckee Sheffield | Taper rolling-direct length measurement |
| GB9522741D0 (en) * | 1995-11-07 | 1996-01-10 | Firth Vickers Centrispinning L | Making a metal shape by casting |
| GB2322585B (en) * | 1995-11-07 | 1999-09-29 | Firth Vickers Centrispinning L | Making a metal shape by casting |
| CN107486551B (en) * | 2017-08-29 | 2019-06-14 | 中国兵器工业第五九研究所 | A kind of casting technique and solidified structure regulation method of aluminium alloy thin-walled cabin casting |
| CN113414375B (en) * | 2021-06-30 | 2023-07-21 | 广西鑫锋新能源科技有限公司 | Electromagnetic low-pressure casting device and method for lead-acid battery grid |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB746091A (en) * | 1954-01-15 | 1956-03-07 | Shell Cast Alloys Ltd | Backing shell moulds in mould boxes |
| DE1301439B (en) * | 1966-11-11 | 1969-08-21 | Hofmann | Method and device for producing a casting mold by means of a magnetizable material |
| DE1806277A1 (en) * | 1968-10-31 | 1970-05-06 | Bbc Brown Boveri & Cie | Magnetisable material is used to support metal - casting masks |
| FR2295808A1 (en) * | 1974-12-24 | 1976-07-23 | Pont A Mousson | LOW PRESSURE CASTING PROCESS AND PLANT IN SAND MOLD |
| FR2384568A1 (en) * | 1977-03-21 | 1978-10-20 | Pont A Mousson | LOW PRESSURE CASTING MOLD |
-
1979
- 1979-05-02 FR FR7911067A patent/FR2455491A1/en active Granted
-
1980
- 1980-04-28 DE DE3016325A patent/DE3016325C2/en not_active Expired
- 1980-04-29 DK DK184280A patent/DK165823C/en not_active IP Right Cessation
- 1980-04-30 ES ES491058A patent/ES491058A0/en active Granted
- 1980-04-30 IT IT67689/80A patent/IT1128781B/en active
- 1980-04-30 GB GB8014335A patent/GB2050220B/en not_active Expired
- 1980-04-30 BE BE0/200439A patent/BE883075A/en not_active IP Right Cessation
- 1980-04-30 BR BR8002692A patent/BR8002692A/en not_active IP Right Cessation
- 1980-05-01 CH CH338280A patent/CH637314A5/en not_active IP Right Cessation
- 1980-05-01 CA CA000351042A patent/CA1166818A/en not_active Expired
- 1980-05-13 IN IN347/DEL/80A patent/IN154288B/en unknown
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4830085A (en) * | 1986-12-29 | 1989-05-16 | Brunswick Corporation | Vacuum lift foam filled casting system |
Also Published As
| Publication number | Publication date |
|---|---|
| DK165823C (en) | 1993-06-21 |
| DE3016325C2 (en) | 1984-01-26 |
| GB2050220B (en) | 1983-05-18 |
| IT1128781B (en) | 1986-06-04 |
| FR2455491A1 (en) | 1980-11-28 |
| IN154288B (en) | 1984-10-13 |
| BR8002692A (en) | 1980-12-16 |
| DE3016325A1 (en) | 1980-11-13 |
| ES8102866A1 (en) | 1981-02-16 |
| CH637314A5 (en) | 1983-07-29 |
| DK184280A (en) | 1980-11-03 |
| ES491058A0 (en) | 1981-02-16 |
| DK165823B (en) | 1993-01-25 |
| FR2455491B1 (en) | 1983-11-10 |
| AU5804080A (en) | 1980-11-06 |
| GB2050220A (en) | 1981-01-07 |
| IT8067689A0 (en) | 1980-04-30 |
| BE883075A (en) | 1980-10-30 |
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