Advanced Feed System for Semi Solid Casting

Abstract

A feed system for introducing semi-solid metal alloy to a die casting machine includes a first chamber for receiving a metal alloy billet and for preparing the semi-solid metal alloy billet. The first chamber includes heaters and a cutting system. The metal alloy billet is heated by the heaters and cut by the cutting system into predetermined lengths to form semi-solid metal alloy portions. The feed system also includes a second chamber connected to the first chamber by a passage to receive the semi-solid metal alloy portions. The second chamber includes a door that opens and closes the passage and a plunger system that introduces the semi-solid metal portions to a die cast machine. An atmosphere control system is in fluid communication with the first chamber and the second chamber. The atmosphere control system removes oxygen from the feed system. A method using the feed system is also provided.

Description

The present invention relates to methods for metal casting, and particularly feed systems and methods for semi-solid metal (SSM) casting parts.

BACKGROUND OF THE INVENTION

Semi-solid metal (SSM) casting, also known as semi-solid forming, is a hybrid manufacturing method that incorporates elements of both casting and forging. Semi-solid metal casting (SSM) is a near net shape variant of die casting. Die casting is a popular metal forming technique for forming metal or metal alloy parts. Die casting finds broad application in diverse technologies such as automotive parts, plane parts, toys, utensils, and the like. In the typical die casting process, a molten metal or metal alloy is forced under high pressure into a mold cavity.

Unlike typical die casting, SSM process is to introduce raw materials with nondendritic microstructure in the semi-solid state. SSM is done at a temperature that puts the metal between its liquidus and solidus temperature. Ideally, the metal should be 30 to 65% solid. The metal must have a low viscosity to be usable, and to reach this low viscosity the material needs a globular primary surrounded by the liquid phase. The temperature range possible depends on the material and for aluminum alloys is 5-10° C., but for narrow melting range copper alloys can be only several tenths of a degree.

Semi-solid metal (SSM) casting is typically used for high-end castings with non-ferrous metals, such as aluminum, copper, and magnesium. For aluminum alloys typical parts include engine suspension mounts, air manifold sensor harness, engine blocks and oil pump filter housing.

In SSM process, the metal is usually prepared for introduction into a die cast machine by cutting a metal or metal alloy billet into predefined lengths and widths. The feedstock is then heated up into the semi-solid state and introduced into the casting machine. Since the metal is typically heated in ambient before being placed in the casting machine, the metal (surface) is subject to oxygen contamination often with a layer of oxide forming on the metal portions. Such contamination can degrade the quality of the parts being formed resulting in performance problems.

Accordingly, the present invention provides improved methods of making high quality semi-solid metal castings with the proposed advanced feed system and methods of making

SUMMARY OF THE INVENTION

The present invention solves one or more problems of the prior art by providing, in at least one embodiment, a feed system for semi-solid metal casting. The feed system includes a first chamber for receiving a metal alloy billet. The first chamber includes heaters and a cutting system. The metal alloy billet is heated by the heaters and cut by the cutting system into predetermined lengths to form semi-solid metal alloy portions. The feed system also includes a second chamber connected to the first chamber by a passage to receive the semi-solid metal alloy portions. The second chamber includes a door that opens and closes the passage and a plunger system that introduces the semi-solid metal portions to a die cast machine. An atmosphere control system is in fluid communication with the first chamber and the second chamber. The atmosphere control system removes oxygen from the feed system.

In another embodiment, a feed system for semi-solid metal casting is provided. The feed system includes a first chamber for receiving a metal alloy billet. The first chamber also includes heaters and a cutting system. The metal alloy billet is heated by the heaters and cut by the cutting system into predetermined lengths to form semi-solid metal portions. A second chamber is connected to the first chamber by a passage. The second chamber includes a door that opens and closes the passage and a plunger system that introduces the semi-solid metal portions to a die cast machine. A gas purging system is in fluid communication with and provides a positive pressure of an inert gas to the first chamber and second chamber.

In another embodiment, a method of feeding metal alloy billet to a die cast machine using the feed systems set forth above is provided. The method includes a step of introducing the alloy billet into a first chamber which has heaters and a cutting system. The alloy billet is heated in a first chamber under a substantially oxygen free environment to a temperature at which the alloy billet is a semi-solid. The alloy billet is then cut in the first chamber into semi-solid metal alloy portions having a predetermined length. The semi-solid metal alloy portions are introduced into a second chamber through a passage between the first and the second chamber. The second chamber includes a door that opens and closes the passage and a plunger system. The semi-solid metal alloy portions are introduced into the die cast machine by the plunger system.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:

FIG. 1 provides a schematic illustration of a feed system for feeding semi-solid metal or metal alloy to a die casting machine; and

FIGS. 2A, 2B, and 2C provide a schematic flowchart of a method of feeding semi-solid metal alloy to a die casting machine using the system of FIG. 1.

DESCRIPTION OF THE INVENTION

Reference will now be made in detail to presently preferred compositions, embodiments and methods of the present invention, which constitute the best modes of practicing the invention presently known to the inventors. The Figures are not necessarily to scale. However, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for any aspect of the invention and/or as a representative basis for teaching one skilled in the art to variously employ the present invention.

Except in the examples, or where otherwise expressly indicated, all numerical quantities in this description indicating amounts of material or conditions of reaction and/or use are to be understood as modified by the word “about” in describing the broadest scope of the invention. Practice within the numerical limits stated is generally preferred. Also, unless expressly stated to the contrary: percent, “parts of,” and ratio values are by weight; the description of a group or class of materials as suitable or preferred for a given purpose in connection with the invention implies that mixtures of any two or more of the members of the group or class are equally suitable or preferred; description of constituents in chemical terms refers to the constituents at the time of addition to any combination specified in the description, and does not necessarily preclude chemical interactions among the constituents of a mixture once mixed; the first definition of an acronym or other abbreviation applies to all subsequent uses herein of the same abbreviation and applies mutatis mutandis to normal grammatical variations of the initially defined abbreviation; and, unless expressly stated to the contrary, measurement of a property is determined by the same technique as previously or later referenced for the same property.

It is also to be understood that this invention is not limited to the specific embodiments and methods described below, as specific components and/or conditions may, of course, vary. Furthermore, the terminology used herein is used only for the purpose of describing particular embodiments of the present invention and is not intended to be limiting in any way.

It must also be noted that, as used in the specification and the appended claims, the singular form “a,” “an,” and “the” comprise plural referents unless the context clearly indicates otherwise. For example, reference to a component in the singular is intended to comprise a plurality of components.

Throughout this application, where publications are referenced, the disclosures of these publications in their entireties are hereby incorporated by reference into this application to more fully describe the state of the art to which this invention pertains.

The term “billet” as used herein refers to a raw metal stock such as a bar stock. Therefore, a metal alloy billet is a metal alloy bar stock.

With reference to FIG. 1, a schematic illustration of a feed system for feeding semi-solid metal or metal alloy to a die casting machine is provided. Feed system 10 introduces metal alloy billet into die casting machine 12. Feed system 10 includes first chamber 14 that receives metal alloy billet 16 into receiving section 18. In a refinement, metal alloy 16 is manually introduced into first chamber 14. In another refinement, metal alloy billet 16 is provided to first chamber 14 by motorized drive system 20. First chamber 14 also includes heaters 22 and cutting system 24. Metal alloy billet 16 is heated by heaters 22 to a sufficient temperature so that the billet becomes semi-solid. Metal alloy billet 16 is cut by cutting system 24 into predetermined lengths to form semi-solid metal alloy portions. The lengths that are cut are chosen to provide sufficient material for a part that is to be formed in die cast system 12. The semi-solid metal alloy portions are received into the transfer section of chamber 14. Feed system 10 also includes second chamber 28 connected to first chamber 14 by passage 30. Second chamber 28 includes door 32 that opens and closes passage 30. Second chamber 28 also includes plunger system 36 which introduces the semi-solid metal portions to die cast machine 12.

Still referring to FIG. 1, atmosphere control system 40 is in fluid communication with first chamber 14 and second chamber 28. Atmosphere control system 40 removes oxygen from the feed system. In a refinement, atmosphere control system 40 is an inert gas purging system that introduces an inert gas into the first chamber via inlet port 42. Typically, the inert gas is then introduced into the second chamber via passage 30. Examples of suitable inert gases include nitrogen, helium, argon and the like. In another refinement, atmosphere control system 40 is a vacuum system that excludes oxygen by maintaining feed system 10 at reduced pressure. Optional controller 41 may be used to control both the heaters and atmosphere control system 40.

Still referring to FIG. 1, plunger system 36 includes plunger 44 that pushes the semi-solid metal portions into die cast machine 12. Plunger 36 is positionable in a first position P1 such that the second chamber receives the semi-molten metal portion and in a second position P2 in which door 32 is closed. In the specific variation illustrated in FIG. 1, plunger system 36 further includes sheath 46 that operates as door 32 by moving with plunger 44. In this variation, section 48 of sheath 46 blocks passage 30 when plunger 42 is at position P2 while when at position P1, passage 30 is open. In a refinement, plunger system 36 further includes a biasing member such as spring 50 that contacts the sheath and acts to provide a biasing force that acts to moves sheath 46 towards die cast machine 12. In a refinement, plunger system 30 further includes hydraulic system 52 for moving the plunger between positions P1 and P2.

With reference to FIGS. 1 and 2A-C, a method of feeding metal alloy to a die cast machine is provided. FIGS. 2A-C provide a schematic flowchart of the method. Feed system 10 receives an alloy billet 16 into first chamber 14 as set forth in step a). In particular, alloy billet 16 is received into receiving section 18. As set forth above, first chamber 12 includes heaters 22 and cutting system 24. In step b), alloy billet 16 is heated in the first chamber 16 under a substantially oxygen free environment to a temperature at which the alloy billet 16 is a semi-solid which is identified by item number 16′ in FIG. 2A. Oxygen is excluded by the atmosphere control system by either inert gas purging or by maintaining the first chamber 14 under a vacuum. In step c), alloy billet 16 is cut in the first chamber 14 into semi-solid metal alloy portions 56 having a predetermined length. In step d), the semi-solid metal alloy portions 56 are introduced into (e.g., transported to) the second chamber 28 through passage 30 between the first and the second chambers. It should be appreciated that plunger 44 is positioned at position P1 so that passage 30 is open and one of the semi-solid metal alloy portions 56 can enter the second chamber 28. In step e), plunger 44 is moved to position P2 causing section 48 of sheath 46 to block passage 30. In step f), plunger 44 is moved further along direction d₁ so that one of the semi-solid metal alloy portions 56 is introduced into die casting machine 12. In step g), plunger 30 returns to position P1 so that another semi-solid metal alloy portion may be transported to the second chamber 28.

As set forth above, the variations and embodiments of the feed system and related method are used to introduce alloys into a die casting system. In a refinement, the metal alloy billets include an alloy with a freezing range (between liquidus and solidus). The presence of a freezing range will typically mean that the purely liquid and solid phases do not concurrently exist within this range. In a further refinement the freezing range is from about 5 to about 100 degrees C., depending alloy compositions. In another refinement, the metal alloy billet comprises an aluminum alloy. Such aluminum alloys typically include aluminum and a component selected from the group consisting of copper, magnesium, manganese, silicon, zinc, and combinations. In such aluminum alloys, the amount of aluminum is from about 80 weight percent to about 99.95 weight percent and the amount of other alloying elements is from about 0.05 to about 20 weight percent. In many aluminum alloys, the amount of aluminum is less than about 99 weight percent. Many cast aluminum alloys are hypoeutectic alloys having aluminum dendritic phase forming first during solidification. For example, one type of useful aluminum alloy includes aluminum and silicon. In such alloys, the amount of silicon is usually from about 4 to 14 weight % with the balance being aluminum (86 to 96 weight percent) or aluminum plus other alloying elements (0.05 to 20 weight percent) as above. In another refinement, the alloy billet comprises a component selected from the group consisting of magnesium alloys, tin alloys, zinc alloys, and copper alloys.

While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.

Claims

1. A feed system for semi-solid metal casting, the system comprising:

a first chamber for receiving a metal alloy billet, the first chamber including heaters and a cutting system, the metal alloy billet being heated by the heaters and cut by the cutting system into predetermined lengths to form semi-solid metal alloy portions;

a second chamber connected to the first chamber by a passage to receive the semi-solid metal alloy portions, the second chamber including a door that opens and closes the passage and a plunger system that introduces the semi-solid metal portions to a die cast machine; and

an atmosphere control system for removing oxygen from the feed system, the atmosphere control system being in fluid communication with the first chamber and the second chamber, the atmosphere control system including an inert gas purging system that introduces an inert gas into the first chamber via inlet port and then into the second chamber via the passage.

2. The feed system of claim 1 wherein the plunger system includes a plunger that pushes the semi-solid metal into the die cast machine.

3. The feed system of claim 2 wherein the plunger is positionable in a first position such that the second chamber receives the semi-solid metal and a second position in which the door is closed.

4. The feed system of claim 3 wherein the plunger system further includes a sheath that operates as the door, the sheath moving with the plunger.

5. The feed system of claim 4 wherein the plunger system further includes a biasing member that acts to move the sheath towards the die cast machine.

6. The feed system of claim 3 wherein the plunger system further includes a hydraulic system for moving the plunger.

7. (canceled)

8. The feed system of claim 1 wherein inert gas is introduced into the second chamber.

9. The feed system of claim 1 wherein the metal alloy billet comprises an alloy with a freezing range.

10. The feed system of claim 1 wherein the metal alloy billet comprises an aluminum alloy.

11. The feed system of claim 10 wherein the aluminum alloy comprises aluminum and a component selected from the group consisting of copper, magnesium, manganese, silicon, zinc, and combinations.

12. The feed system of claim 10 wherein the aluminum alloy comprises aluminum and silicon.

13. The feed system of claim 10 wherein the metal alloy billet comprises a component selected from the group consisting of magnesium alloys, tin alloys, zinc alloys, and copper alloys.

14. A feed system for semi-solid metal casting, the system comprising:

a first chamber for receiving an alloy billet, the first chamber including heaters and a cutting system, wherein the alloy billet is heated by the heaters and cut by the cutting system into predetermined lengths to form semi-solid metal portions,

a gas purging system providing a positive pressure of an inert gas to the first chamber; and

a second chamber connected to the first chamber by a passage, the second chamber including a door that opens and closes the passage and a plunger system that introduces the semi-solid metal portions to a die cast machine.

15. A method of feeding alloy billet to a die cast machine, the method comprising:

introducing the alloy billet into a first chamber including heaters and a cutting system;

heating the alloy billet in a first chamber under a substantially oxygen free environment to a temperature at which the alloy billet is a semi-solid;

cutting the alloy billet in the first chamber into semi-solid metal alloy portions having a predetermined length;

introducing the semi-solid metal alloy portions into a second chamber through a passage between the first and second chamber, the second chamber including a door that opens and closes the passage and a plunger system; and

introducing the semi-solid metal alloy portions into the die cast machine by the plunger system.

16. The method of claim 15 wherein inert gas is introduced into the second chamber.

17. The method of claim 15 wherein the alloy billet comprises an alloy with a freezing range.

18. The method of claim 17 wherein the alloy billet comprises an aluminum alloy.

19. The method of claim 18 wherein the aluminum alloy comprises aluminum and a component selected from the group consisting of copper, magnesium, manganese, silicon, zinc, and combinations.

20. The method of claim 18 wherein the aluminum alloy comprises aluminum and silicon.