US 3779304 A
In an oxygen flush presure injection die casting system, the molten metal is introduced into the die cavity in a turbulent condition to achieve efficient mixing with the oxygen gas in such cavity and thus promote reaction of the metal with the gas and minimize the presence of blow holes in the cast product.
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Description (OCR text may contain errors)
United States Patent 1191 Miki Dec. 18, 1973 1 INJECTION GATE SYSTEM  lnventor: Isao Miki, Fuji, Japan  Assignee: Nippon Light Metal Company Limited, Tokyo, Japan  Filed: July 13, 1971  Appl. No.: 162,249
3,349,833 10/1967 11611161 1. 164/113 3,382,9[0 5/1968 Radtke .1 164/55 FOREIGN PATENTS OR APPLICATIONS 224,008 II/l968 U.S1S.R 164/55 Canada 164/315 Primary Examiner-.1. Spencer Overholser Assistant ExaminerJohn E. Roethel Attorney-William J. Daniel  ABSTRACT In an oxygen flush presure injection die casting system, the molten metal is introduced into the die cavity in a turbulent condition-to achieve efficient mixing with the oxygen gas in such cavity and thus promote reaction of the metal with the gas and minimize the presence of blow holes in the cast product.
5 Claims, 2 Drawing Figures INJECTION GATE SYSTEM This invention relates to an improved injection gate for oxygen flush pressure die casting system.
One of the major problems encountered in the conventional pressure die casting is the presence of air in the die cavity and the injection sleeve which is entrapped in the injected molten metal and appears in the casting product in the form of blow-holes.
To overcome this difficulty in conventional pressure die casting, the oxygen flushing pressure die casting method has been proposed. In this method, injection casting of molten metal is carried out as before except that the air present in the die cavity and the injection sleeve is displaced with oxygen gas, this gas when entrapped in the injected molten metal reacts with the molten metal to become fine metal oxide particles during solidification of the metal, thereby avoiding the presence of blow-holes in the casting.
However, satisfactory castings are not always obtained by carrying out this oxygen flush pressure die casting method because the injected metal solidifies so rapidly that reaction between the molten metal and oxygen gas is not carried out completely and a considerable amount of blow-holes remain in the casting due to oxygen gas which has not reacted with the molten metal.
As a result of numerous experiments carried out by the inventor, it was found that the reaction between the molten metal and oxygen gas can be promoted considerably by designing the gate system in the oxygen flush die casting method to introduce the molten metal into the die in a turbulent condition.
It is therefore an object of this invention is to provide an improved injection gate for oxygen flush pressure die casting for obtaining castings which are substantially free from blow-holes caused by the presence of occlusions of unreacted oxygen gas.
Another object of this invention is to provide an improved injection gate for oxygen flush pressure die casting which promotes chemical reaction between the injected molten metal and oxygen gas in the die cavity.
These and other objects and advantages of this invention will appear more clearly from the following description with reference to accompanying drawings, in which:
FIG. 1 is a sectional view of an oxygen flush pressure die casting machine provided with the injection gate design of this invention, and
FIG. 2 is an enlarged sectional view of the injection gate design of this invention.
In FIG. 1, the numeral 1 designates a stationary supported die plate, to which is attached a fixed die 2. A movable die 3 which contacts the fixed die 2 to form a die assembly by operating clamping piston 4, and therebetween is provided a die cavity 5 having an injection gate design 6 which consists of runner 7 and gate 8. 9 is an injection sleeve which passes through the die plate 1 which receives molten metal M for injection into the die cavity 5 by the operation of a plunger 10 having a reciprocating motion. 11 is a molten metal inlet provided on the upper part of sleeve 9 and 12 is an oxygen gas feed nozzle inserted into the molten metal inlet 11.
As shown in the enlarged sectional view in FIG. 2, a
sharp-edged constriction 13 is formed in the gate design of this invention at the interconnection of the runner 7 and the gate 8, and the runner 7 and gate 8 each have diverging walls which extends oppositely from constriction 13 towards their respective opening ends.
Accordingly, when carrying out the injection casting of the molten metal by the oxygen flush die casting method using the gate design of this invention, air present in the sleeve 9 and the die cavity 5 is first displaced by oxygen gas introduced into sleeve 9 by way of oxygen feed nozzle 12, the velocity of the molten metal M which is fed into sleeve 9 by way of inlet 11 and pressed into the runner 7 by operating reciprocating plunger 10 is accelerated by converging walls of the runner 7 and on passing the constriction 13 is injected in violent turbulent condition in the gate 8 because the gate is formed with diverging walls having a suitable expanding angle (a). In this way, the molten metal is injected in a dispersed state into the die cavity 5 from the wide end of the gate 8 to carry out reaction of the molten metal and the oxygen gas thoroughly and quickly.
The preferred expanding gate angle (a) which is formed at the constricted part by the wall is 5 l8", more preferably 7 14, in order to obtain effective turbulence and dispersion of the injected metal in the gate of this invention and also, it is preferable to form the gate wall in a concave shape.
The molten metal is injected into the die cavity in a dispersed state by using such a gate and as a result, metal oxide which is the reaction product of molten metal and oxygen gas is uniformly dispersed and remains in the casting as fine particles. Thus, casting which is almost free from blow-holes can be obtained by'this invention.
What I claim is:
]l. A die casting apparatus comprising a set of cooperating dies defining therebetween a die cavity, a gate opening into said die cavity and a runner connected to said gate, an injection sleeve connected to said runner,
a plunger reciprocating in said sleeve for injecting molten metal from said sleeve into said die cavity through said gate and runner, and means for feeding oxygen gas into said sleeve and cavity to displace air therefrom prior to injection of molten metal, and means in said gate for imparting a turbulent condition to the metal injected therethrough to achieve efficient mixing and thus efficient chemical reaction between the metal and oxygen gas to minimize the presence of blow holes containing unreacted oxygen gas, said latter means comprising a constriction adjacent the inlet opening of the gate and from which the downstream walls of the gate expand outwardly in a concave configuration.
2. The die casting apparatus of claim 1 wherein said constriction is sharp-edged.
3. The die casting apparatus of claim I wherein the overall angle of expansion of the downstream gate wall is 5l 8.
4. The die casting apparatus of claim 3 wherein the overall angle of expansion is 7-l4.
5. The die casting apparatus of claim 1 wherein said gate and runner are each formed in bell shape and interconnect at their lesser diameter ends to define a constriction therebetween.
UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,779,304 Dated December 18, 1973 Inventor(s) ISaO MIKI It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
In the Heading of the Patent, insert Foreign Application Priority Data July 15 1970 Japan 70109/45 Signed and sealed this 9th day of April 197L (SEAL) Attest:
EDl-JAHD M.FLETCEIER,JH. C. MARSHALL DANN Attesting Officer Commissioner of Patents I FORM uscoMM-Dc scan-ps9 I i 11.5. GOVERNMENT PRINT NG OFFICE i I", 0-3..334