Metal Casting System, Engineered Molds, Process and Articles Made Thereby

• US 20080308249A1
• Filed: 01/03/2007
• Published: 12/18/2008
• Est. Priority Date: 01/03/2006
• Status: Active Grant

• Current Assignee: Adolf Hetke
• Original Assignee: Adolf Hetke
• Inventors: Hetke, Adolf
• Granted Patent: US 7,896,059 B2
• Time in Patent Office: Days
• US Class Current: 164/284
• CPC Class Codes: B22D 18/04 Low pressure casting, i.e. making use of pressures up to a few bars to fill the mould
• CPC Class Codes: B22D 18/06 Vacuum casting, i.e. making use of vacuum to fill the mould
• CPC Class Codes: B22D 21/007 with low melting point, e.g. Al 659 degrees C, Mg 650 degrees C

Abstract

Disclosed is a metal casting system, an engineered mold for use therewith, a process for utilizing the system and mold, and articles having a clean, oxide-free sand casting of molten metals that have been produced under an inert environment. This is especially advantageous for making automotive and airplane parts from the manufacture of lightweight metals, and more especially for the production of magnesium parts in order to reduce weight while maintaining properties found in other lightweight metals. Currently, sand cast articles are being used for automotive, aerospace and semiconductor parts and other industrial applications. The advantages of the present invention include a greatly reduced cycle time as conventional gating systems no longer apply; an ability to pour highly reactive metals by the use of a protective environment; even greater reduced cycle times because speed of metal delivery is greatly increased; carbon outgassing by binder resin is minimized since no oxygen is allowed into the process; sand and resin usage and disposal is minimized due to the new engineered mold; and cooling of the poured sand casting is much faster through these unique features.

Claims

1. A metal casting system (1) for continuous delivery of molten metal in a controlled environment, comprising:

a melting furnace (2) having a molten metal surface and an inert furnace atmosphere throughout the entire casting system, wherein said inert furnace atmosphere is inert to the metal being cast;

a pressurized metal delivery vessel (12) connected to the melting furnace (2) with a discharge opening dam (6) for maintaining a production level (4) of molten metal to continuously deliver clean, oxide-free metal from below the molten metal surface;

a treatment vessel (5) connected between the melting furnace and the metal delivery vessel to provide a continuous supply of molten metal from the melting furnace to the metal delivery vessel;

a transfer valve (9) that allows metal flow from the melting furnace to the metal delivery vessel; and

an engineered sand mold for receiving molten metal from the pressurized metal delivery vessel, wherein said engineered sand mold is at least partially encapsulated to contain a significantly reduced amount of sand in the sand mold and facilitating maintenance of a controlled atmosphere with inert gases.

2. The system of claim 1, wherein the melting furnace is a heated melting and treatment furnace connecting the pressure furnace by a launder.

3. The system of claim 1, wherein the inert metal casting system is a pressurized system that utilizes an inert atmosphere that is inert to the metal being cast, and wherein the atmosphere is selected from the group consisting of SF₆, N₂, Argon, helium, hydrogen and combinations thereof of those gases.

4. The system of claim 1, wherein the transfer valve includes a stopper rod and a filter to facilitate continuous pouring.

5. The system of claim 3, wherein the metal casting system exerts a cooling effect accomplished by the use of a heat transfer gas.

6. The system of claim 3, wherein the metal casting system exerts a cooling effect accomplished by the use of a helium-containing heat transport gas.

7. The system of claim 1, wherein said system is adapted for creating and maintaining a useful environment within the mold to allow for countergravity pouring with an inert atmosphere and high heat transfer characteristics that increase production.

8. The stopper rod of claim 6, wherein said stopper rod is made of steel.

9. The stopper rod of claim 8, wherein the stopper rod seals against a steel wool seal and a filter, without refractory materials.

10. The furnace system of claim 1, wherein a useful environment is created and maintained for counter gravity pouring of magnesium in its molten state, without the use of any ceramic parts, and having a controlled environment without any oxygen in the system to prevent oxidation during a pour.

11. An engineered sand mold for receiving molten metal from a pressurized metal delivery vessel, comprising:

an engineered mold at least partially encapsulated to contain a reduced amount of mold material in the mold to facilitate control of its atmosphere by being adapted for the application of a vacuum and the application of a desired gaseous controlled environment into the mold.

12. The engineered mold of claim 11, wherein the mold is self-contained to provide a controlled atmosphere of gas within the mold.

13. The engineered mold of claim 11, wherein the gaseous environment within the mold is protected from the ambient atmosphere, and contains only gases that have been introduced into the mold.

14. The engineered mold of claim 11, further comprising a gas impermeable exterior barrier layer incorporated into the exterior surface of the engineered mold.

15. The engineered mold of claim 14, wherein the exterior barrier layer provides environmental isolation from the ambient atmosphere.

16. The engineered mold of claim 14, wherein the exterior barrier layer is shrinkwrap plastic.

17. The engineered mold of claim 11, wherein the at least partial vacuum will help delivery of countergravity-poured molten light metal therein.

18. The engineered mold of claim 11, wherein the vacuum within the mold allows for the introduction of heat transfer gases that will enhance the cooling rate of the cast part within the mold.

19. The engineered mold of claim 11, wherein the gaseous environment atmosphere within the mold is oxygen-free.

20. The engineered mold of claim 11, further comprising at least an ingress portal for a source of cooling gas to cool the part for high volume production.

21. The engineered mold of claim 11, further comprising a thermally insulated gasket between the mold and the entry point of the molten metal, so as to avoid instantly melting the encapsulating material.

22. The engineered mold of claim 11, wherein the mold material is nearly entirely encapsulated with a material selected from the group consisting of plastic films, sealing paints, waxes, sealers, plastic shrinkwrap material, and combinations thereof, only leaving two portals open for ingress and egress of controlled atmosphere gases.

23. The engineered mold of claim 11, wherein the controlled environment ingress portal contained therein is sealed off with a metallic foil to seal off the portal made of a similar material that is going to be cast, so that when the hot molten lightweight metal pour encounters the engineered mold, the molten metal pour will melt through the metallic foil seal, thereby reducing contamination, and maintaining for environmental isolation.

24. The engineered mold of claim 23, wherein the environment is a self contained, oxygen-free, inert environment allowing for continuous flushing of a cooling gas at the end of the metal pour.

25. The engineered mold of claim 23, wherein the controlled atmosphere alleviates out-gasing.

26. A method of metal casting of molten metals in a controlled environment, comprising:

heating metal to a molten state to maintain a metal depth level to feed and compensate for the drawoff during the molding process;

maintaining an inert atmospheric environment over the metal;

drawing the molten metal into a low-pressure engineered mold that is at least partially encapsulated;

maintaining an inert atmosphere during heating, drawing, and molding;

pressurizing the molten metal in a molten bath tank to urge the molten metal countergravity up into the engineered mold which has been purged to maintain an inert atmosphere,

whereby non-turbulent filling of the mold is possible in a non-oxidative environment, allowing for rapid filling of the mold as no oxide issues are present.

27. The method of claim 26, further comprising continuously filling molds through countergravity filling and vacuum applied within the mold and low-pressure pushing onto the molten metal.

28. The method of claim 26, further comprising an additional step of applying a vacuum to the engineered mold prior to filling and purging with a heat transfer gas to prevent contamination and to allow for faster cycling times of the mold.

29. The method of claim 28, further comprising a step of incorporating a chill into the mold, whereby the heat transfer gas can cool both the mold and the chill, thereby enhancing the cooling efficiency and the cycle time of the mold.

30. A light metal casting, comprising:

a near net shape high integrity article made of a non-oxidized light metal, wherein said light metal is selected from the group consisting of magnesium, aluminum, titanium, sodium and combinations thereof and further wherein the casting material itself is high strength and light weight, having a low dendrite arm spacing with a very low porosity and small grain size.

31. The lightweight metal casting of claim 30, wherein said casting is a high integrity metallurgical structural thin wall near net shape casting.

32. The light metal casting of claim 30, wherein the grain size and dendrite arm spacing of the microstructure is less than 30 microns or micrometers.

33. The light metal casting of claim 30, wherein the resulting structural complex components are thin walled with a transitional cross section due to in-situ surface treatments and interior geometric structures.

34. The light metal casting of claim 30, wherein the casting is an automotive engine component selected from the group consisting of engine blocks, cylinder heads, intake manifolds, engine cradles, chassis subframes, upper and lower control arms, and large and small structural components for the automotive, aircraft, aerospace, and commercial industrial applications.