Title:
Method of making precursor hollow castings for tube manufacture
Kind Code:
A1


Abstract:
A tubular formation technique utilizing centrifugal casting incorporating a moveable launder system to deliver molten alloy along an extended length within a centrifugal caster to form a hollow tubular precursor of extended length. The technique is adaptable to all alloy systems but may be particularly suited for so called “hard alloys” that are susceptible to substantial work hardening or are difficult to extrude.



Inventors:
Sachdev, Anil K. (Rochester Hills, MI, US)
Balasubramanian K. (Hyderabad, IN)
Application Number:
11/853900
Publication Date:
04/24/2008
Filing Date:
09/12/2007
Assignee:
GM GLOBAL TECHNOLOGY OPERATIONS, INC. (DETROIT, MI, US)
Primary Class:
Other Classes:
164/114, 164/286
International Classes:
B22D13/02
View Patent Images:



Primary Examiner:
LIN, KUANG Y
Attorney, Agent or Firm:
GENERAL MOTORS LLC (DETROIT, MI, US)
Claims:
What is claimed is:

1. A casting system comprising: a centrifugal caster having an interior and a material acceptance opening; and an elongate moveable launder adapted for insertion through the material acceptance opening and into the interior of the caster for delivery of molten metal to positions along the interior of the caster spaced away from the material acceptance opening.

2. The casting system of claim 1, wherein the elongate moveable launder is moveable in reciprocating relation relative to the caster.

3. The casting system of claim 2, wherein the elongate moveable launder is mounted on rails.

4. The casting system of claim 1, wherein the molten metal is selected from at least one of the group consisting of: aluminum, aluminum alloys, magnesium, magnesium alloys, titanium and titanium alloys, copper and copper alloys, and refractory metals and their alloys.

5. Billets formed by the casting system of claim 1.

6. The casting system of claim 1, further comprising a flow forming apparatus adapted to process billets from the caster.

7. A method of centrifugally casting a tubular billet, the method comprising the steps of: providing a centrifugal caster having an interior and a material acceptance opening; providing an elongate moveable launder adapted for reciprocating insertion and withdrawal through the material acceptance opening and into the interior of the caster for delivery of molten metal to positions along the interior of the caster spaced away from the material acceptance opening; inserting a distal portion of the launder into the interior of the caster; delivering a quantity of molten metal along the launder from a position outside the caster to the interior of the caster for deposit at locations spaced away from the material acceptance opening; and expelling hollow substantially tubular billets from the caster.

8. The method as recited in claim 7, wherein the molten metal is deposited as the launder is moved in reciprocating relation to the caster such that the molten metal is deposited in layers along the length of the caster, and where the individual layers can be a different metal or alloy.

9. The method as recited in claim 7, wherein the elongate moveable launder is mounted on rails.

10. The method as recited in claim 7, wherein the molten metal is selected from at least one of the group consisting of: aluminum, aluminum alloys, magnesium, magnesium alloys, titanium and titanium alloys, copper and copper alloys, and refractory metals and their alloys.

11. A method of centrifugally casting and flow forming a tubular billet, the method comprising the steps of: providing a centrifugal caster having an interior and a material acceptance opening; providing an elongate moveable launder adapted for reciprocating insertion and withdrawal through the material acceptance opening and into the interior of the caster for delivery of molten metal to positions along the interior of the caster spaced away from the material acceptance opening; inserting a distal portion of the launder into the interior of the caster; delivering a quantity of molten metal along the launder from a position outside the caster to the interior of the caster for deposit at locations spaced away from the material acceptance opening; expelling hollow substantially tubular billets from the caster; and delivering the tubular billets to a wall thinning flow forming apparatus adapted to process the billets from the caster.

12. The method as recited in claim 11, wherein the molten metal is deposited as the launder is moved in reciprocating relation to the caster such that the molten metal is deposited in layers along the length of the caster, and where the individual layers can be a different metal or alloy.

13. The method as recited in claim 11, wherein the elongate moveable launder is mounted on rails.

14. The method as recited in claim 11, wherein the molten metal is selected from at least one of the group consisting of: aluminum, aluminum alloys, magnesium, magnesium alloys, titanium and titanium alloys, copper and copper alloys, and refractory metals and their alloys.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of and priority from U.S. Provisional Application 60/862,056 filed Oct. 19, 2006 the contents of which are hereby incorporated by reference in their entirety.

TECHNICAL FIELD

The present invention relates generally to the field of hollow tube manufacture and more particularly to the field of centrifugal casting of elongate hollow tube precursors adaptable for flow forming or other treatments.

BACKGROUND OF THE INVENTION

It is well known to form tubes from materials such as aluminum and magnesium using extrusion techniques or seam welding rolled sheet stock. Tubes of such materials may also be formed by drawing a hollow blank over a mandrel or flow forming an extrusion formed precursor over a mandrel. While such techniques for forming tubes may be suitable for many materials, they may be difficult to apply to alloys such as high ductility aluminum alloys that exhibit substantial work hardening or to magnesium alloys that do not exhibit good hot deformation behavior unless extremely low extrusion speeds are utilized. Alloys that are characterized by substantial amounts of work hardening may be desirable to accommodate deformation strain during fabrication of complex shapes, or in the case of magnesium alloys for light weight.

SUMMARY OF THE INVENTION

The present invention provides advantages and alternatives over prior practices by providing tubular formation techniques that are particularly suited for so called “hard alloys” that are susceptible to substantial work hardening or are difficult to extrude.

According to one aspect, a process is provided utilizing centrifugal casting incorporating a moveable launder system to deliver molten alloy along an extended length within a centrifugal caster to form a hollow tubular precursor of extended length.

According to another aspect, a process is provided utilizing centrifugal casting incorporating a moveable launder system to deliver layers of alloy and/or composite material along an extended length within a centrifugal caster to form a hollow tubular precursor of extended length.

According to still another aspect, a process is provided wherein a centrifugal caster incorporating a moveable launder system delivering molten alloy along an extended length within the caster is mated with a flow forming procedure to yield a tube of desired thickness formed from a work hardenable alloy or from alloys that are difficult to hot work by standard methods like extrusion.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings which are incorporated in and which constitute a part of this specification illustrate exemplary practices in accordance with the present invention and, together with the general description above and the detailed description set forth below, serve to explain the principals of the invention wherein:

FIG. 1 is a view illustrating a casting system incorporating a retractable elongate launder in inserted relation within a centrifugal caster;

FIG. 2 is a view similar to FIG. 1 with the launder retracted towards the mouth of the caster;

FIG. 3A is a side view of cast billets of tubular construction formed by the system illustrated in FIGS. 1 and 2;

FIG. 3B is an end view of cast billets of tubular construction formed by the system illustrated in FIGS. 1 and 2; and

FIG. 4 is a schematic view of a tube flow forming operation that may be paired with a casting system as illustrated in FIGS. 1 and 2.

While embodiments of the invention have been illustrated and generally described above and will hereinafter be described in connection with certain potentially preferred procedures and practices, it is to be understood and appreciated that in no event is the invention to be limited to such embodiments and procedures as may be illustrated and described herein. On the contrary, it is intended that coverage shall extend to all alternatives and modifications as may embrace the broad principals of the invention within the true spirit and scope thereof.

DETAILED DESCRIPTION

Reference will now be made to the various drawings wherein like elements are designated by like reference numerals throughout the various views. As illustrated, in accordance with the present invention a centrifugal caster 10 is mated with a moveable launder 20. The launder 20 preferably includes a proximal reservoir portion 22 for acceptance of a molten alloy and a distal insertion portion 24 of reduced hemispherical cross section for insertion an extended length into the caster 10.

As shown, the launder 20 may be mounted on a carriage assembly 30 for reciprocating movement in axial relation to the caster 10. While the carriage assembly 30 is illustrated as a cart mounted on rails, it is likewise contemplated that virtually any supporting structure adapted to translate reciprocal movement to the launder may be used.

In operation the insertion portion 24 of the launder 20 may be projected through a mouth opening of the caster 10 a predetermined length along the interior of the caster. While the insertion portion 24 is within the caster 10, a molten alloy may be delivered to the reservoir portion 22 thereby causing the alloy to flow along the insertion portion for deposit at the interior of the caster 10. As will be appreciated, the moveable nature of the launder 20 permits the location of alloy deposit to be moved inwardly away from the mouth of the caster. Moreover, the alloy can be deposited progressively along the length of the caster 10 by inserting or withdrawing the insertion portion 24 while the alloy is being delivered. Moreover, by use of controlled reciprocation, layers of similar or dissimilar material may be deposited at the interior of the caster 10 so as to form layers within the final cast billets. While the process may be used with substantially any metal system, it is contemplated that the system may be particularly useful for aluminum, aluminum alloys, magnesium, magnesium alloys, titanium and titanium alloys, copper and copper alloys, and refractory metals and their alloys.

By use of the reciprocating launder system it has been found that it may be possible to increase the thickness of billets formed within the caster 10 and/or to cast alloys that may not be suitable for centrifugal casting or for casting into standard extrusion billets. By way of example only, it has been found that tubes of high ductility aluminum alloys may be formed with substantial wall thickness on the order of about 10 mm or greater. Benefits are also believed to be applicable to alloys of materials such as magnesium and titanium that are characterized by limited extrudability.

It is also contemplated that billets cast using the reciprocating launder system may be more amenable to subsequent tubular flow forming resulting in a lengthened and thinned structure. By way of example only and not limitation, a representative flow forming process is illustrated in FIG. 4. As shown, in this process a centrifugal casting 50 engages a chuck 52 with a support tool 54 held at the interior of the casting 50. As the casting 50 is rotated, and the support tool 54 may or may not be rotated, the casting 50 engages a spinning forming tool 56 which causes the walls of the casting to be thinned and elongated.

It is to be understood that while the present invention has been illustrated and described in relation to potentially preferred embodiments, constructions, and procedures, that such embodiments, constructions, and procedures are illustrative only and that the invention is in no event to be limited thereto. Rather, it is contemplated that modifications and variations embodying the principals of the invention will no doubt occur to those of skill in the art. It is therefore contemplated and intended that the present invention shall extend to all such modifications and variations as may incorporate the broad aspects of the invention within the true spirit and scope thereof.