CA1048227A - Die-casting using reactive gas and force-rod concepts - Google Patents
Die-casting using reactive gas and force-rod conceptsInfo
- Publication number
- CA1048227A CA1048227A CA75224853A CA224853A CA1048227A CA 1048227 A CA1048227 A CA 1048227A CA 75224853 A CA75224853 A CA 75224853A CA 224853 A CA224853 A CA 224853A CA 1048227 A CA1048227 A CA 1048227A
- Authority
- CA
- Canada
- Prior art keywords
- die
- casting
- molten metal
- reactive gas
- cavity
- 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
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D17/00—Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
- B22D17/14—Machines with evacuated die cavity
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Molds, Cores, And Manufacturing Methods Thereof (AREA)
- Mold Materials And Core Materials (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A process and apparatus for die casting metal parts, for example, zinc, aluminum, magnesium and alloys thereof, wherein air is purged from the die cavity by flushing with a reactive gas such as oxygen; thereafter the molten metal is injected into the die cavity, and thereafter a force member is forced into the die cavity while the injected molten metal is still in a sufficiently molten state so that the force member may be forced into the in-completely solidified metal.
A process and apparatus for die casting metal parts, for example, zinc, aluminum, magnesium and alloys thereof, wherein air is purged from the die cavity by flushing with a reactive gas such as oxygen; thereafter the molten metal is injected into the die cavity, and thereafter a force member is forced into the die cavity while the injected molten metal is still in a sufficiently molten state so that the force member may be forced into the in-completely solidified metal.
Description
'7 This invention relates to an improved die-casting method and provides a method by which, in forming metal casting parts by -the use of die casting, sound die casting parts may be efficiently obtained which have a minimum of internal faults that might be caused by blow-holes or shrinkage holes.
The die-casting method is an effective casting method by which one can efficiently mass-produce metal casting parts which have precise dimensions and attractive surface skin, but, die-casting has been considered unsuitable for forming mechanical parts, structural members and the like which require a high degree of precision, strength, air tightness and the like, because faults such as a large number of blow-holes and shrinkage holes are present internally in the casting parts thus formed.
Recently there has been proposed a die-casting method referred to as the pore free die casting method or reactive gas die-casting method disclosed and claimed in United States patent 3,382,910 of Radtke et al., wherein a gas such as oxygen having a high degree of reactivity with the molten metal which is to be cast is pre fed into the die casting machine, said gas replacing the air within the , .
The die-casting method is an effective casting method by which one can efficiently mass-produce metal casting parts which have precise dimensions and attractive surface skin, but, die-casting has been considered unsuitable for forming mechanical parts, structural members and the like which require a high degree of precision, strength, air tightness and the like, because faults such as a large number of blow-holes and shrinkage holes are present internally in the casting parts thus formed.
Recently there has been proposed a die-casting method referred to as the pore free die casting method or reactive gas die-casting method disclosed and claimed in United States patent 3,382,910 of Radtke et al., wherein a gas such as oxygen having a high degree of reactivity with the molten metal which is to be cast is pre fed into the die casting machine, said gas replacing the air within the , .
- 2 -die castincJ machine. In -~his way, most o the gas which is dra~n into the die castiny machine ~Ji-th -the molten metal, is reacted with the injected metal and -thereby chanyed into a fine solid p~rticle Eorm dispersed throughout the soIid S casting thus formed. By using such a methad, the faults due to the presence of blow-holes in the solid castiny pro-duced in a die casting method and apparatus has been overcome to some extent. There still remains a problem, however, that shrinkage holes in the cast part may occur and thus there re mains the problem of the precision of dimensions and reliabi~
lity of the parts required fox mechanical parts or stxuc~ural material made by the die casting method and apparatus.
In the United States patent 3,1~6,002 of Bauer, there is disclosed a die casting method which is said to produce a lS sound non-porous body o~ metal ~y loweriny the temperature of the interior of the casting below the melting point ana there-after displacing metal within a heavy section of the castin~
by forcing a displacing member into such heavy section under forging pressure. No mention is made, however, in the Bauer patent of any method for solving the pro~lem of blow-holes in castings.
The present invention provides a method and apparatus for casting sound die casting parts which are free of internal faults such as blow-holes, shrinkage holes and the like, whereby in the performance o die casting metal parts by the use of the reactive gas process xeferred to above, molten metal is injected into a die cavity, after which a orce rod which is mounted in the die is projected into the die cavity while a part of the molten metal in the die cavity is still in the molten or incom-pletely solidified state, thereby forcing -the force rod into the molten metal whlch is being solidi-Eied.
--3~
.
2~508 I
l~V9L~7 Generally, in thc process of die casting, solidi-fication of the ~olten metal which is injec-ted in-to the die cavity section is rapidly initiated from the surface portion which is in contact with the die cavity of low temperature, and is then extended into the inside of the casting. The portion thus firs-t solidified tends to draw metal due -to shrink- ll age at the time of solidification, from other portions of the ~¦
casting which are more slowly solidi:Eied, so that after solidi- I
fication is complete, a considerable quantity of the molten metal I
in the vicinity of the central or thicker part of the casting ¦
is drawn toward the first solidified portion of the casting, thereby tending to produce shrinkage holes.
In accordance with the present invention, in the die casting of metal parts by the use of the reactive gas die cast-ing method, a force rod which is mounted in the die, is projectedinto the die cavity at the time when molten metal which has been injected into the die cavity is not fully solidified and is still internally held in a sufficiently molten state so that the forcing of the force rod into the still molten portion is possible. Tha force rod is ~orced into the still molten portion of the casting by extending it through the solidified portion of the surface of the injected molten metal, or forcing the soli- ;
dified portion of the surface of the injected molten metal into the mo7ten portion by the action of the force rod which is being projected, so that a portion, considerable in volume, of molten metal~-solidifies, and -the shrinkage which would normally occur is com pensated by the injection of the force rod or the volume which is occupied by the solidified metal thus displaced. In this way _ g _ ': ' by utilizing the method of the present invention, shrinkage holes in die casted parts are almost completely avoided. Thus, the die casting me-thod according to the present invention affords the advantage of achieving sound die casting parts which are almost free of internal faults by utilizing the force rod just described, together with the reactive gas process also previously mentioned which tends to recluce or eliminate the presence of blow-holes in the die cast parts. The metals which may be used include zinc, al~inum or magnesium, or alloys thereof.
The excellent effects of the present invention which are obtained by forcing the aforementioned force rod into the injected molten metal while utilizing the reactive ~as in the die casting method referred to above will not be obtained when utilizing the force rod but without the-reactive gas. The reason for this is that the blow-holes which are contained within the casting parts are further pressurized by forcing of the force rod into the casting, thereby resulting in deforming of the casting by the expansion of the highly compressed ~low-holes when the casting part is taken out of the die, whereupon the 2~ inflation or e~pansion of the gas in the blow-holes, especially such holes near the surface of the casting, will cause dis-figuring. ~herefore the castiny parts must not be taken from the die until the parts are sufficiently solidified so as to maintain their shape and surface integrity.
figuring and the formation of pock marks in the surface of the casting. Therefore the casting parts must not be taken from the die until the parts are sufficiently solidified so as to maintain their shape and surface integrity.
- It is important that the force rod of the present invention be forced into the casting at the time when the casting part has not yet been internally solidified, with the result that high pressure similar to that required in the process of forging - is not necessary. ~~
More particularly there is provided a die casting method comprising purging air from within the die cavity by flushing said cavity ~ith a reactive gas, subsequently injecting molten metal into the reactive gas filled cavity, and, thereaftèr, after partial solidification of the injected molten metal, forcing a force member into the die cavity while the molten metal is still internally held in a sufFiciently molten state so that the force member may be forced into the molten metal.
~ . ' - 5a - :
The presen-t invention will hereinafter be described in detail with re~erence to the accompanyin~ drawings, which illustrate a preferred mode of embodiment thereof.
Figure 1 is a longitudinal sectional view illus-trating principal portions of an apparatus ~or carrying out the method of the present invention;
Figure 2 is a perspective view of a casting part tthe cover of a high pressure vessel~ in a particular emb~diment of the present invention;
Figure 3 is a cross sectional view of the casting part shown in Figure 2 taken on a vertical plane passing through the center of the casting, but formed by a process of die casting in accordance with the prior art; and Figure 4 is a sectional view similar to Figure 3 throuyh a casting formed in accordance with the present invention.
Figure 1 schematically illustrates an apparatus for carrying out the method in accordanc~ with the present invention.
In Figure 1, the apparatus comprises a die plate 1, a stationary die 2 mounted on the die plate 1, a movable die 3 arranged for advancement or retreat by means of a suitable advancement and retreat driving means not shown, to come into close contact with the stationary die 2, and a cavity 4 which is formed in the con-tact surface between the stationary die 2 and the movable die 3 to form a castlng part of desired shape. An injection port 5 for the molten metal is similarly formed in the contact surface.
An injection sleeve 6 for the molten metal is provided and extends through the die plate 1 so that the extended end t^ereof may just ', ~ .
.
reach th~ injection por-t S which is formed in the contact surface of the dies. A supply port 7 for the molken metal is formed in the upper surace oE the injection slee~e 6 which is outside of the die. Th~ injection sleeve G is provided with a plung~r 8 for injectirlg under pressure the molten metal M which is supplied through the supply port 7 into khe die cavity 4 through the injection port 5O Furthermore, a gas feeding nozzle 9 is provided on the supply port 7, to replace air which is within the die casting machine, by reactive gas.
Disposed in the stationary die 2 is a force rod 10, the remote end or extremity of which is in the die cavity 4. The force rod 10 is directly connected to a hydraulic cylinder mean~ 11 which is similarly dispo.sed in the stationary die 2 so that . the hydraulic cylinder means 11 may be operated by means not shown to project the force rod 10 a suitable distance into the die cavity 4.
In carrying out the method of the present invention with the apparatus described above, in accordance with the operating procedure of the conventional reactive gas die cast-ing method, a reactive gas such as oxygen is first fed into theinjection sleeve 6 through the reactive gas feeding nozzle 9 to replace the air which is present within the injection sleeve 6 and the die cavity 4 with oxygen gas, and the molten metal is fed into the injection sleeve 6 thxough the molten metal supply port 7, after which the plunger 8 is operated to pressure inject the molten metal within the injection sleeve 6 into the die cavity 4 through the injection port 5. Then, the oxygen gas which is drawn or sucked into the die cavity 4 with the molten metal at ~7~
the time o:f injecting mol-~en metal lnto the die cavity 4, is brought into inunecliatè reaction with the molten metal within the die cavity 4 t.o form metal oxide which is then dispersed and contained in the molten me-tal which becomes solidi~ied.
Immediately afte.r the injection casting has been completed, the hydraulic cylinder means 11 which is disposed on the stationary die 2 is operated while the molten metal within the die cavity 4 is still held in a sufficiently molten state so that the force rod 10 connected to the hydraulic means 11 may be projected into the cavity 4, ~hereby forcing the force rod into the injected molten metal which is being solidified. In this manner, the molten metal which formerly occupied the space now being occupied by the projected force rod 10, is removed by the solidified portion of the sur~ace of the injected molten metal which is forced by the force rod 10 or the projection of the force rod lO, and simultaneously therewith the molten metal which is presant in the aforemention-ed portion is displaced and occupies space which other~ise would form shrinkage holes, so that shrinkage holes are thereby substantially completely prevented from forming in the vicinit~
of the portion of the casting part where the force rod 10 is forced into the casting, as well as in the space adjoining it.
In accordance with the present invention, the dimension, shape and length of the force rod which is injected into the casting are suitably determined depending upon the shape-of the casting parts. Furthermore, the position in which the force rod is ~orced into the molten metal within the cavity may also be determined depending upon the shape of the casting parts. It is, however, generally true that the force rod is projected into the 2~i1 casting in the thicker portions of the casting wherein shrinkage holes generally tend to be produced.
The timing of the forcing of the force rod into the casting is also important and exerts an influence upon the effect produced on the casting. If the force rod is forced into the molten metal too soon so that the molten metal at the injection port is not sufficiently solidified, the molten metal will backflow through the injection port, thus eliminating the desired effects of the pxesent invention.
Also, conversely, if the timing of the injection is too late, an excesslve pressure is required to force the force rod into the casting and furthermore, the solidification of the metal may have advanced to the point where the shrinkage holes will not be filled up, thus preventing the realizatlon of the desired results of the present invention.
Experiments have shown -that the time required to solidify the molten metal at the injection port to such an extent that it will not backflow from the force exerted by - the force rod, is generally about 1 to 3 seconds after com-pletion of the injection. The time required to complete the solidification of the molten metal within the cavity where the forced rod is injected is represented by the approximate value, S = ~0.04 to 0.06) x D2 ~where S is the solidification time in seconds, D is the thicXness of the casting part in milli~
meters). It is therefore to be understood that the forcing of the force rod may be accomplished between these limits.
As concerns the pressure necessary to force the force rod, the pressure will generally be such as is necessary to penetrate ' ~2soa the sur~ace layer a~ter solidification, tha-t is approximately 500 to 30~ Kg/cm2 o~ pressure at the ex-trernity of the force rod is sufficient t:o o~tain the cleslred effect.
The followin~ examples are presented to illustrate the invention without, however, ~imiting the scope of prot~c-tion thereof.
Figurcs 2 to 4 illustrate the effects obtained by carrying out the present inv~ntion wherein a cold chamber type die casting machine having a die clamping force of 3~0 tons is used. The apparatus il'lustrated in Figure 1 is used for die casting a cover of an aluminum pressure vessel. Figure 2, as sta-ted above, is a perspec~ive view of the cover of such a ' pressure vessel and Figure 3 illustrates the internal portion of the cover of the pressure vessel formed by the die casting, in accordance with the prior art reactive gas die casting - method. ~igure 4 illustrates the internal portion of the identi-cal cover formed by the die casting method in accordance with the present invention.
As shown in Figure 2, the cover of the pressure vessel comprises a semi-circular cover boay 12, a mounting flange 13 which is adapted to secure the cover to the vessel body, said flanye being formed at the lower periphery of the cover 12, and a knob mounting projection 14 at the top of the cover 12.
The thickest portion of the casting part it will be noted, is in the projection 14, the thickness being approximately 15 mm. ' The knob mounting projection 14 is further formed with a recess 15 which has a diameter of about 12 mm. and is 10 mm. deep.
In die casting the pressure vessel top as described , 4~
above by the us~ of the p.rior a:rt reactive gas die casting method, fine pin holes due to the presence of blow-holes are not produced, but countless shrin]cage holes may be ~ound to be produced in the vicinity of the projection 14 which, as noted above, has the greatest thickness. On the other hand, when the method o the present invention is used, that is, after the lapse of four seconds ater molten metal has been injected in accordance wi-th the prior art reactive gas die casting method, the ~orce rod 10 of a d.iameter of 1~ mm. is projected about lQ mm. into the casting under a forced pres-" :
sure o ~250 kg/cm6 into the iniected molten metal within the .
cavity. The projectio~ of the force roa 10 is made into the knob mounting projection 14 portion of the casting which has the greatest thickness of all of the portions. of the cast part. It is in this part that shrinkage holes ordinarily tend ':
.~ to be produced. As a consequence of following the method of the present invention, no shrinkage holes are found to be pro-duced in the casting part. This is shown in Figure 4~ It will also ke noted that as a consequence of the projection of the rod 10, the recess 15 is simultaneously formed.
- Results ohtained by measuring the specific gravity :
of twenty pieces of die cast parts so formed, both in accord-ance with the prior art reactive gas die casting method, and the method of the present invention, whioh uses both the react1ve gas die casting method and the force rod, are given in the follow ing table which represent average values:
~ Prior Art Method 698 `~ . Present Invention 2.743 As is apparent :~rom the results appear~ng in -the above table, the die cast parts made according to the present invention have relati-vely greater specific gravity than those made by the method of the prior art. This means that the metho~ of the present invention p~oduces much fewer or less shrinkage holes in the die cast parts as compared .with the method of the prior art. : :
As described above, the present invention has the advantage o~ forming sound die cast parts which are substan-tially ~ree of internal faults hy almost completely removiny blow-holes. Furthermoxe, the present inve~tion also provides various other desirable effects, one of which is that the internal pressure oE the molten metal within the cavity ~ay be increased by forcing the force rod into the molten metal 15 which is injected into the cavity to prevent the occurrence.
oE metal-deficient portions in the casting and prevent the occurrence oE surface deficiencies or blemisnes, such as ~.
shrinkage recesses on the outer surface due to the inadequate ~ :
. filling of molten metal into the die which often occurs in ~ ~
large size die cast parts, especially those which are compli- - .
cated in sha~e. `:~ :
. -12-' ;`~
~.
lity of the parts required fox mechanical parts or stxuc~ural material made by the die casting method and apparatus.
In the United States patent 3,1~6,002 of Bauer, there is disclosed a die casting method which is said to produce a lS sound non-porous body o~ metal ~y loweriny the temperature of the interior of the casting below the melting point ana there-after displacing metal within a heavy section of the castin~
by forcing a displacing member into such heavy section under forging pressure. No mention is made, however, in the Bauer patent of any method for solving the pro~lem of blow-holes in castings.
The present invention provides a method and apparatus for casting sound die casting parts which are free of internal faults such as blow-holes, shrinkage holes and the like, whereby in the performance o die casting metal parts by the use of the reactive gas process xeferred to above, molten metal is injected into a die cavity, after which a orce rod which is mounted in the die is projected into the die cavity while a part of the molten metal in the die cavity is still in the molten or incom-pletely solidified state, thereby forcing -the force rod into the molten metal whlch is being solidi-Eied.
--3~
.
2~508 I
l~V9L~7 Generally, in thc process of die casting, solidi-fication of the ~olten metal which is injec-ted in-to the die cavity section is rapidly initiated from the surface portion which is in contact with the die cavity of low temperature, and is then extended into the inside of the casting. The portion thus firs-t solidified tends to draw metal due -to shrink- ll age at the time of solidification, from other portions of the ~¦
casting which are more slowly solidi:Eied, so that after solidi- I
fication is complete, a considerable quantity of the molten metal I
in the vicinity of the central or thicker part of the casting ¦
is drawn toward the first solidified portion of the casting, thereby tending to produce shrinkage holes.
In accordance with the present invention, in the die casting of metal parts by the use of the reactive gas die cast-ing method, a force rod which is mounted in the die, is projectedinto the die cavity at the time when molten metal which has been injected into the die cavity is not fully solidified and is still internally held in a sufficiently molten state so that the forcing of the force rod into the still molten portion is possible. Tha force rod is ~orced into the still molten portion of the casting by extending it through the solidified portion of the surface of the injected molten metal, or forcing the soli- ;
dified portion of the surface of the injected molten metal into the mo7ten portion by the action of the force rod which is being projected, so that a portion, considerable in volume, of molten metal~-solidifies, and -the shrinkage which would normally occur is com pensated by the injection of the force rod or the volume which is occupied by the solidified metal thus displaced. In this way _ g _ ': ' by utilizing the method of the present invention, shrinkage holes in die casted parts are almost completely avoided. Thus, the die casting me-thod according to the present invention affords the advantage of achieving sound die casting parts which are almost free of internal faults by utilizing the force rod just described, together with the reactive gas process also previously mentioned which tends to recluce or eliminate the presence of blow-holes in the die cast parts. The metals which may be used include zinc, al~inum or magnesium, or alloys thereof.
The excellent effects of the present invention which are obtained by forcing the aforementioned force rod into the injected molten metal while utilizing the reactive ~as in the die casting method referred to above will not be obtained when utilizing the force rod but without the-reactive gas. The reason for this is that the blow-holes which are contained within the casting parts are further pressurized by forcing of the force rod into the casting, thereby resulting in deforming of the casting by the expansion of the highly compressed ~low-holes when the casting part is taken out of the die, whereupon the 2~ inflation or e~pansion of the gas in the blow-holes, especially such holes near the surface of the casting, will cause dis-figuring. ~herefore the castiny parts must not be taken from the die until the parts are sufficiently solidified so as to maintain their shape and surface integrity.
figuring and the formation of pock marks in the surface of the casting. Therefore the casting parts must not be taken from the die until the parts are sufficiently solidified so as to maintain their shape and surface integrity.
- It is important that the force rod of the present invention be forced into the casting at the time when the casting part has not yet been internally solidified, with the result that high pressure similar to that required in the process of forging - is not necessary. ~~
More particularly there is provided a die casting method comprising purging air from within the die cavity by flushing said cavity ~ith a reactive gas, subsequently injecting molten metal into the reactive gas filled cavity, and, thereaftèr, after partial solidification of the injected molten metal, forcing a force member into the die cavity while the molten metal is still internally held in a sufFiciently molten state so that the force member may be forced into the molten metal.
~ . ' - 5a - :
The presen-t invention will hereinafter be described in detail with re~erence to the accompanyin~ drawings, which illustrate a preferred mode of embodiment thereof.
Figure 1 is a longitudinal sectional view illus-trating principal portions of an apparatus ~or carrying out the method of the present invention;
Figure 2 is a perspective view of a casting part tthe cover of a high pressure vessel~ in a particular emb~diment of the present invention;
Figure 3 is a cross sectional view of the casting part shown in Figure 2 taken on a vertical plane passing through the center of the casting, but formed by a process of die casting in accordance with the prior art; and Figure 4 is a sectional view similar to Figure 3 throuyh a casting formed in accordance with the present invention.
Figure 1 schematically illustrates an apparatus for carrying out the method in accordanc~ with the present invention.
In Figure 1, the apparatus comprises a die plate 1, a stationary die 2 mounted on the die plate 1, a movable die 3 arranged for advancement or retreat by means of a suitable advancement and retreat driving means not shown, to come into close contact with the stationary die 2, and a cavity 4 which is formed in the con-tact surface between the stationary die 2 and the movable die 3 to form a castlng part of desired shape. An injection port 5 for the molten metal is similarly formed in the contact surface.
An injection sleeve 6 for the molten metal is provided and extends through the die plate 1 so that the extended end t^ereof may just ', ~ .
.
reach th~ injection por-t S which is formed in the contact surface of the dies. A supply port 7 for the molken metal is formed in the upper surace oE the injection slee~e 6 which is outside of the die. Th~ injection sleeve G is provided with a plung~r 8 for injectirlg under pressure the molten metal M which is supplied through the supply port 7 into khe die cavity 4 through the injection port 5O Furthermore, a gas feeding nozzle 9 is provided on the supply port 7, to replace air which is within the die casting machine, by reactive gas.
Disposed in the stationary die 2 is a force rod 10, the remote end or extremity of which is in the die cavity 4. The force rod 10 is directly connected to a hydraulic cylinder mean~ 11 which is similarly dispo.sed in the stationary die 2 so that . the hydraulic cylinder means 11 may be operated by means not shown to project the force rod 10 a suitable distance into the die cavity 4.
In carrying out the method of the present invention with the apparatus described above, in accordance with the operating procedure of the conventional reactive gas die cast-ing method, a reactive gas such as oxygen is first fed into theinjection sleeve 6 through the reactive gas feeding nozzle 9 to replace the air which is present within the injection sleeve 6 and the die cavity 4 with oxygen gas, and the molten metal is fed into the injection sleeve 6 thxough the molten metal supply port 7, after which the plunger 8 is operated to pressure inject the molten metal within the injection sleeve 6 into the die cavity 4 through the injection port 5. Then, the oxygen gas which is drawn or sucked into the die cavity 4 with the molten metal at ~7~
the time o:f injecting mol-~en metal lnto the die cavity 4, is brought into inunecliatè reaction with the molten metal within the die cavity 4 t.o form metal oxide which is then dispersed and contained in the molten me-tal which becomes solidi~ied.
Immediately afte.r the injection casting has been completed, the hydraulic cylinder means 11 which is disposed on the stationary die 2 is operated while the molten metal within the die cavity 4 is still held in a sufficiently molten state so that the force rod 10 connected to the hydraulic means 11 may be projected into the cavity 4, ~hereby forcing the force rod into the injected molten metal which is being solidified. In this manner, the molten metal which formerly occupied the space now being occupied by the projected force rod 10, is removed by the solidified portion of the sur~ace of the injected molten metal which is forced by the force rod 10 or the projection of the force rod lO, and simultaneously therewith the molten metal which is presant in the aforemention-ed portion is displaced and occupies space which other~ise would form shrinkage holes, so that shrinkage holes are thereby substantially completely prevented from forming in the vicinit~
of the portion of the casting part where the force rod 10 is forced into the casting, as well as in the space adjoining it.
In accordance with the present invention, the dimension, shape and length of the force rod which is injected into the casting are suitably determined depending upon the shape-of the casting parts. Furthermore, the position in which the force rod is ~orced into the molten metal within the cavity may also be determined depending upon the shape of the casting parts. It is, however, generally true that the force rod is projected into the 2~i1 casting in the thicker portions of the casting wherein shrinkage holes generally tend to be produced.
The timing of the forcing of the force rod into the casting is also important and exerts an influence upon the effect produced on the casting. If the force rod is forced into the molten metal too soon so that the molten metal at the injection port is not sufficiently solidified, the molten metal will backflow through the injection port, thus eliminating the desired effects of the pxesent invention.
Also, conversely, if the timing of the injection is too late, an excesslve pressure is required to force the force rod into the casting and furthermore, the solidification of the metal may have advanced to the point where the shrinkage holes will not be filled up, thus preventing the realizatlon of the desired results of the present invention.
Experiments have shown -that the time required to solidify the molten metal at the injection port to such an extent that it will not backflow from the force exerted by - the force rod, is generally about 1 to 3 seconds after com-pletion of the injection. The time required to complete the solidification of the molten metal within the cavity where the forced rod is injected is represented by the approximate value, S = ~0.04 to 0.06) x D2 ~where S is the solidification time in seconds, D is the thicXness of the casting part in milli~
meters). It is therefore to be understood that the forcing of the force rod may be accomplished between these limits.
As concerns the pressure necessary to force the force rod, the pressure will generally be such as is necessary to penetrate ' ~2soa the sur~ace layer a~ter solidification, tha-t is approximately 500 to 30~ Kg/cm2 o~ pressure at the ex-trernity of the force rod is sufficient t:o o~tain the cleslred effect.
The followin~ examples are presented to illustrate the invention without, however, ~imiting the scope of prot~c-tion thereof.
Figurcs 2 to 4 illustrate the effects obtained by carrying out the present inv~ntion wherein a cold chamber type die casting machine having a die clamping force of 3~0 tons is used. The apparatus il'lustrated in Figure 1 is used for die casting a cover of an aluminum pressure vessel. Figure 2, as sta-ted above, is a perspec~ive view of the cover of such a ' pressure vessel and Figure 3 illustrates the internal portion of the cover of the pressure vessel formed by the die casting, in accordance with the prior art reactive gas die casting - method. ~igure 4 illustrates the internal portion of the identi-cal cover formed by the die casting method in accordance with the present invention.
As shown in Figure 2, the cover of the pressure vessel comprises a semi-circular cover boay 12, a mounting flange 13 which is adapted to secure the cover to the vessel body, said flanye being formed at the lower periphery of the cover 12, and a knob mounting projection 14 at the top of the cover 12.
The thickest portion of the casting part it will be noted, is in the projection 14, the thickness being approximately 15 mm. ' The knob mounting projection 14 is further formed with a recess 15 which has a diameter of about 12 mm. and is 10 mm. deep.
In die casting the pressure vessel top as described , 4~
above by the us~ of the p.rior a:rt reactive gas die casting method, fine pin holes due to the presence of blow-holes are not produced, but countless shrin]cage holes may be ~ound to be produced in the vicinity of the projection 14 which, as noted above, has the greatest thickness. On the other hand, when the method o the present invention is used, that is, after the lapse of four seconds ater molten metal has been injected in accordance wi-th the prior art reactive gas die casting method, the ~orce rod 10 of a d.iameter of 1~ mm. is projected about lQ mm. into the casting under a forced pres-" :
sure o ~250 kg/cm6 into the iniected molten metal within the .
cavity. The projectio~ of the force roa 10 is made into the knob mounting projection 14 portion of the casting which has the greatest thickness of all of the portions. of the cast part. It is in this part that shrinkage holes ordinarily tend ':
.~ to be produced. As a consequence of following the method of the present invention, no shrinkage holes are found to be pro-duced in the casting part. This is shown in Figure 4~ It will also ke noted that as a consequence of the projection of the rod 10, the recess 15 is simultaneously formed.
- Results ohtained by measuring the specific gravity :
of twenty pieces of die cast parts so formed, both in accord-ance with the prior art reactive gas die casting method, and the method of the present invention, whioh uses both the react1ve gas die casting method and the force rod, are given in the follow ing table which represent average values:
~ Prior Art Method 698 `~ . Present Invention 2.743 As is apparent :~rom the results appear~ng in -the above table, the die cast parts made according to the present invention have relati-vely greater specific gravity than those made by the method of the prior art. This means that the metho~ of the present invention p~oduces much fewer or less shrinkage holes in the die cast parts as compared .with the method of the prior art. : :
As described above, the present invention has the advantage o~ forming sound die cast parts which are substan-tially ~ree of internal faults hy almost completely removiny blow-holes. Furthermoxe, the present inve~tion also provides various other desirable effects, one of which is that the internal pressure oE the molten metal within the cavity ~ay be increased by forcing the force rod into the molten metal 15 which is injected into the cavity to prevent the occurrence.
oE metal-deficient portions in the casting and prevent the occurrence oE surface deficiencies or blemisnes, such as ~.
shrinkage recesses on the outer surface due to the inadequate ~ :
. filling of molten metal into the die which often occurs in ~ ~
large size die cast parts, especially those which are compli- - .
cated in sha~e. `:~ :
. -12-' ;`~
~.
Claims (5)
1. A die casting method comprising purging air from within the die cavity by flushing said cavity with a reactive gas, subsequently injecting molten metal into the reactive gas filled cavity, and, thereafter, after partial solidification of the injected molten metal, forcing a force member into the die cavity while the molten metal is still internally held in a sufficiently molten state so that the force member may be forced into the molten metal.
2. The method as described in claim 1 wherein the force rod is forced into the cavity within the time interval in the range from 1 to 3 seconds after completion of the in-jection to a time represented by the formula S = (0.04 to 0.06) x D2 wherein S is the solidification time in seconds and D is the thickness of the casting part in millimeters.
3. The process of claim 1 wherein the reactive gas is oxygen.
4. The process of claim 3 wherein the molten metal is selected from the group consisting of zinc, aluminum, magnesium, zinc alloys, aluminum alloys, and magnesium alloys.
5. The process of claim 1, wherein the casting contains portions of relatively greater thickness, and portions of relatively less thickness, and the force member is forced into said portions of relatively greater thickness.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4344174A JPS50136231A (en) | 1974-04-19 | 1974-04-19 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1048227A true CA1048227A (en) | 1979-02-13 |
Family
ID=12663774
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA75224853A Expired CA1048227A (en) | 1974-04-19 | 1975-04-17 | Die-casting using reactive gas and force-rod concepts |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS50136231A (en) |
| CA (1) | CA1048227A (en) |
| DE (1) | DE2517140C2 (en) |
| FR (1) | FR2267846B1 (en) |
| GB (1) | GB1473279A (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS51104429A (en) * | 1975-03-12 | 1976-09-16 | Sadakichi Sugimura | Daikyasutochuzono ketsukanboshiho |
| DE2953474C2 (en) * | 1979-02-14 | 1984-06-07 | Nippondenso Co., Ltd., Kariya, Aichi | Die-casting process with redensification |
| GB2055645B (en) * | 1979-02-14 | 1983-01-26 | Nippon Denso Co | Die casting machines |
| ZA811792B (en) * | 1980-03-21 | 1982-10-27 | Dana Corp | Method of bonding piston ring insert |
| JPH1157973A (en) * | 1997-08-19 | 1999-03-02 | Kayaba Ind Co Ltd | Die casting device |
| DE102011052062A1 (en) * | 2011-07-22 | 2013-01-24 | MAGNOTEC Gmbh | Mold for casting a casting material, mold assembly with at least two molds, method for casting a casting material with such mold or mold assembly and a cast metal anode by this method |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3106002A (en) * | 1960-08-08 | 1963-10-08 | Nat Lead Co | Die-casting method |
| GB1002546A (en) * | 1963-06-24 | |||
| NL135443C (en) * | 1966-06-30 |
-
1974
- 1974-04-19 JP JP4344174A patent/JPS50136231A/ja active Pending
-
1975
- 1975-04-17 CA CA75224853A patent/CA1048227A/en not_active Expired
- 1975-04-17 FR FR7511932A patent/FR2267846B1/fr not_active Expired
- 1975-04-18 DE DE19752517140 patent/DE2517140C2/en not_active Expired
- 1975-04-18 GB GB1608775A patent/GB1473279A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS50136231A (en) | 1975-10-29 |
| DE2517140A1 (en) | 1975-11-20 |
| FR2267846A1 (en) | 1975-11-14 |
| GB1473279A (en) | 1977-05-11 |
| FR2267846B1 (en) | 1979-03-09 |
| DE2517140C2 (en) | 1983-03-31 |
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