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US 6,634,412 B1Granted
Magnesium pressure casting
AssigneeCommonwealth Scientific and Industrial Research Organisation
InventorsMorris Taylor Murray, Matthew Alan Cope
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AssigneeCommonwealth Scientific and Industrial Research Organisation
InventorsMorris Taylor Murray, Matthew Alan Cope
Estimating the term…
The provision or use, for the pressure casting of magnesium alloy in a molten or thixotropic state with a pressure casting machine having a mould or die which defines a die cavity, of a metal flow system which includes a die or mould tool means which defines at least one runner from which molten magnesium alloy is able to be injected into the die cavity. The metal flow system is of a form providing for control of metal flow velocities within the flow system, whereby substantially all of the metal flowing throughout the die cavity is in a viscous or semi-solid state. Filling of the die cavity is able to proceed progressively by semi-solid fronts of metal moving away from a gate or other site of injection. The flow of magnesium alloy from the runner may be via at least one controlled expansion region of the metal flow system in which region the metal flow is able to spread laterally, with respect to its direction of injection, with a resultant reduction in its flow velocity relative to its velocity in the runner.
A process for producing a casting of a magnesium alloy, using a pressure casting machine having a mould or die which defines a die cavity, wherein the process includes the steps of supplying molten metal to a metal flow system which includes a die or mould tool means which defines at least one runner of the system into which molten magnesium allow is received and from which alloy is injected into the die cavity, and controlling metal flow velocities in the system whereby substantially all of the metal flowing throughout the die cavity is in a semi-solid state, and wherein said controlling includes causing the alloy from the runner to flow through a controlled expansion region whereby metal flow spreads laterally in said region, with respect to its direction of injection, with a resultant reduction in its flow velocity relative to its velocity in the runner;
A process or producing a casting of a magnesium alloy, using a pressure casting machine having a mould or die which defines a die cavity, wherein the process includes the steps of supplying molten metal to a metal flow system which includes a die or mould tool means which defines at least one runner of the system into which molten magnesium alloy is received and from which alloy is injected into the die cavity, and controlling metal flow velocities in the system whereby substantially all of the metal flowing throughout the die cavity is in a semi-solid state, and wherein said controlling includes causing the alloy from the runner to flow through a controlled expansion region whereby metal flow spreads laterally in said region, with respect to its direction of injection, with a resultant reduction in its flow velocity relative to its velocity in the runner;
A process for producing a casting of a magnesium alloy, using a pressure casting machine having a mould or die which defines a die cavity, wherein the process includes the steps of:
A process for producing a casting of a magnesium alloy, using a pressure casting machine having a mould or die which defines a die cavity, wherein the process includes the steps of:
In a process for pressure casting magnesium alloy in a die cavity by a flow in a flow direction defined by a runner of the magnesium alloy in a molten state, the improvement comprising:
Dependencies are inferred from the claim text.
No related US applications are recorded in the indexed filing history.
Drawings are temporarily unavailable. Open the PDF at USPTO
Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure: semi-solid pressure die…
Cold chamber machines, i.e. with unheated press chamber into which molten metal is ladled: with vertical press motion
Accessories: Details: accessories for supplying molten metal, e.g. in rations
Castings of light metals: with low melting point, e.g. Al 659 degrees C, Mg 650 degrees C
Term ended 28 Jun 2020 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
This invention relates to an improved metal flow system, for use in the production of pressure castings made from magnesium alloys in a molten or thixotropic state and suitable for use with existing machines in various forms including hot and cold chamber die casting machines.
An understanding has developed throughout the international pressure casting industry that, because of the lower heat capacity of magnesium alloys compared to zinc and aluminium alloys, it is necessary to use large runners and gates to prevent premature freezing of the molten magnesium alloy metal. Indeed, this is considered best practice by the industry, although interpretations vary considerably.
Within the industry, there are many different design methods which are thought to provide satisfactory castings from magnesium alloys. However, the magnesium alloy pressure castings produced by these methods generally exhibit a greater degree of surface defects, when compared to zinc or aluminium pressure castings, although castings may be of servicable quality.
In order that the invention may more readily be understood reference now is directed to the accompanying drawings, in which:
FIG. 1 is a sectional view showing part of a die casting system for the production of door handles of magnesium alloy, according to the present invention;
FIG. 2 is a view of the system taken from the right hand side of FIG. 1;
In the system 10 of FIGS. 1 and 2, there is shown a die 12 which defines a number of radially disposed cavities 14 (of which only one is shown) in each of which a respective door handle, somewhat of the form shown in FIG. 4, is able to be cast. Die 12 has a fixed part 16 and a movable part 17 and is shown in its closed condition, but its parts 16, 17 are able to separate on parting line P. A plug 20 incorporated in die part 17 has an ejection pin 18 slidably mounted therein; pin 18 and at least one further pin (not shown) being extendible for ejecting a casting at the end of each operating cycle.
Opposed to plug 20, die part 16 includes a bush 22, the bore 22a of which is lined with a sleeve 24. While bush 22, like plug 20, is made of a suitable steel such as used for parts 16, 17 of die 12, sleeve 24 preferably is made of a material of relatively low thermal conductivity, such as partially stabilised zirconia or other suitable ceramic.
The adjacent ends of plug 20 and bush 22 are of complementary frusto-conical form. Their ends are such that, with die 12 closed, plug 20 and bush 22 achieve a seal between contacting opposed end surfaces. However, the end surface of plug 20 defines a respective groove 21 for each die cavity 14, with the groove 21 co-operating with the end of bush 22 to define a runner 26 for that cavity 14. The runner 26 communicates with the cavity 14 via a gate 28.