Molten metal transfer pipe
A transfer pipe for molten metal includes a pipe wall comprised of graphite or ceramic. The graphite ceramic pipe wall can be surrounded by a pipe wall comprising a low thermally conductive material. Both the graphite or ceramic pipe wall and the low thermally conductive pipe wall can be encased in a rigid wall, for example steel. The transfer pipe can communicate with a molten metal pump to provide a system for moving molten metal.
The present invention is directed to a pipe element for transfer of molten metal. The invention is further directed to a system for transfer of molten metal.
BACKGROUNDIn the processing of molten metals it is often necessary to transfer the molten metal from one location to another. A molten metal pump is used to transfer molten metal from a furnace, for example, to a ladle, for example. Typically, a transfer pipe is the means through which the molten metal travels.
Several factors, which are listed hereafter in no particular order, are considered and balanced when designing a molten metal transfer pipe line. First, the transfer pipe must be able to withstand the thermal shock of the introduction of molten metal when a pumping element is turned on. Second, the change in temperature through the transfer pipe must be considered. Many situations require that the molten metal drop only a limited number of degrees in temperature between a first location where the metal is stored to a second location to where the metal is delivered. Third, the transfer pipe should be designed so that it can be manufactured at a reasonable cost. Fourth, the transfer pipe should provide an adequate life. Fifth, the molten metal that is pumped through the transfer pipe, for example aluminum, should not stick to the inner wall of the pipe. And sixth, managing the outer skin temperature of the pipe is desirable for safety reasons.
Known attempts to design a transfer pipe with these factors in mind resulted in pipes having a pipe wall made from a low thermal conductivity fiber such as an alumino-silicate fiber available under the trade name FIBERFRAX®. This fiber material is available in a sheet form that can be rolled around a mandrel to form a fiber pipe. The fiber sheets are wetted with a solution. The wet fiber sheet is rolled around the mandrel and then the wetted preform tube is cured in an oven to form the fiber pipe. Alternatively, the fiber can be extruded or vacuum formed and cured to form a fiber pipe.
The fiber pipe is then inserted into a steel pipe. The steel pipe provides mechanical strength to the fiber pipe. The rolled sheet or laminate fiber pipes advantageously provide a tortuous path through which the molten metal must travel if a crack is formed in the pipe wall. This is desirable so the molten aluminum that is passing through the transfer pipe does not contact the steel pipe wall.
Typically, transfer pipes made from the above-mentioned fiber have excellent thermal management properties. Known transfer pipes exhibit about a one degree F. per linear foot heat loss over the length of the pipe. What the known transfer pipes provide in thermal management, however, is traded off in durability.
Attempts to increase the durability of the rolled fiber pipes have included wrapping a first layer of a more durable and more expensive material around the mandrel and then finishing the wrapping with a plurality of layers of the typical fiber sheeting. This method improves durability, however this method of manufacture is difficult and costly. Also, transfer pipes have been produced by casting refractory materials into shape and inserting the cast refractory material into a steel tube. Pipes produced using this method have improved strength; however, thermal losses were great. Coatings have been employed to extend transfer pipe life. Durability of the heat transfer pipe has not been sufficiently improved by these methods to obviate the problem.
SUMMARYA transfer pipe for molten metal includes a pipe wall comprised of graphite or ceramic. The graphite ceramic pipe wall can be surrounded by a pipe wall comprising a low thermally conductive material. Both the graphite or ceramic pipe wall and the low thermally conductive pipe wall can be encased in a rigid wall, for example steel. The transfer pipe can communicate with a molten metal pump to provide a system for moving molten metal.
BRIEF DESCRIPTION OF THE DRAWINGS
With reference to
The second pipe wall 14 can be made from graphite or ceramic. A preferred graphite material from which the second pipe wall 14 can be made is treated graphite available under the trade names ST Graphite, SST Graphite and ZX Graphite available from Metaullics Systems Co. LP. Other similar graphite material, including untreated graphite, can be used that is available from other manufacturers, such as SGL Carbon and Union Carbide. Ceramic material can be materials such as Metaullics Advanced Ceramic (MAC®) available from Metaullics Systems Co., L.P.
With reference to
To manufacture the molten metal transfer pipe 10, the second, i.e. graphite or ceramic, pipe wall 14 can be manufactured in a number of methods. The second pipe wall 14 can be extruded and machined in a known manner. Additionally, the second pipe wall 14 can be made from a graphite cloth that is wrapped around a mandrel, similar to the manufacturing steps involved in making the known sheet fiber pipe. The graphite wrap forms a laminate pipe wall. The graphite pipe wall 14 is manufactured to a desired inner diameter and outer diameter.
For the embodiment depicted in
For the embodiment depicted in
An alternative method of manufacture can include extruding or casting the third pipe wall 22, in a known manner, curing, in a known manner, and inserting the second pipe wall 14 into the third pipe wall. Alternatively, the fiber sheet can be wrapped around a mandrel and cured before inserting the second pipe wall into the third pipe wall. A cement such as QF-150 or QF-180 can be used to secure the second pipe wall to the third pipe wall.
The molten metal transfer pipe 10 can be manufactured according to yet another method, which will be described with reference to
The embodiment of
Fittings can be provided to allow for bends in the molten metal pipe line. With reference to
A transfer pipe line can be provided using the above described pipe 10 and elbow 30. Other fittings can be provided as well. More thermal loss may be experienced than with known transfer pipes, however, the losses can be limited by using the low thermally conductive pipe wall. Furthermore, for short transfer pipe line runs the loss per foot will be low enough that the low thermally conductive pipe wall may not be needed. What may be sacrificed in thermal management is made up for in durability. The graphite or ceramic inner pipe wall is significantly more durable than known transfer pipe materials.
The transfer pipe 10 can communicate with a riser pipe 40 of a molten metal pump 42 as shown in
The transfer pipe and other components have been described with reference to the preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims
1. A molten metal transfer pipe comprising:
- an inner pipe wall comprising graphite or ceramic; and
- a metal outer pipe wall that receives the inner pipe wall.
2. The pipe of claim 1, wherein the inner pipe wall is cemented to the outer pipe wall.
3. The pipe of claim 1, wherein the inner pipe wall comprises a graphite laminate.
4. The pipe of claim 1, further comprising an intermediate pipe wall interposed between the inner pipe wall and the outer pipe wall.
5. The pipe of claim 4, wherein the intermediate pipe wall comprises a low thermally conductive material.
6. The pipe of claim 4, wherein the intermediate pipe wall comprises an alumino-silicate material.
7. The pipe of claim 4, wherein the intermediate pipe comprises fiber sheet.
8. The pipe of claim 4, wherein the intermediate pipe comprises extruded fiber.
9. A method for manufacturing a molten metal transfer pipe comprising:
- forming a graphite or ceramic inner pipe wall; and
- inserting the inner pipe wall into a rigid non-ceramic pipe wall.
10. The method of claim 9, further comprising affixing the inner pipe wall to the rigid pipe wall.
11. The method of claim 9, further comprising wrapping a low thermally conductive material around the inner pipe wall.
12. The method of claim 11, further comprising curing the low thermally conductive material.
13. The method of claim 11, wherein the step of inserting the inner pipe wall further comprises inserting the graphite pipe wall and the low thermally conductive material into the rigid pipe wall.
14. The method of claim 9, further comprising interposing a low thermally conductive material between the inner pipe wall and the rigid pipe wall.
15. The method of claim 14, wherein the step of interposing a low thermally conductive material comprises injecting low thermally conductive material into a gap between the inner pipe wall and the rigid pipe wall.
16. A molten metal transfer pipe comprising:
- an inner graphite or ceramic pipe wall;
- an intermediate pipe wall comprising a low thermally conductive material; and
- a rigid outer pipe wall.
17. The pipe of claim 16, wherein the rigid outer pipe wall comprises steel.
18. The pipe of claim 16, wherein the low thermally conductive material comprises an alumino-silicate material.
19. A method for manufacturing a molten metal transfer pipe fitting comprising:
- forming a first graphite or ceramic portion;
- removing material from the first graphite or ceramic portion to form a first graphite or ceramic wall;
- forming a second graphite portion having a complementary shape to the first graphite portion;
- removing material from the second graphite portion to form a second graphite wall; and
- attaching the first graphite wall to the second graphite wall.
20. A molten metal system comprising:
- a means for moving molten metal;
- a transfer pipe in communication with the means for moving molten metal, the transfer pipe including an inner pipe wall comprising graphite or ceramic and a metal outer pipe wall that receives the inner pipe wall.
Type: Application
Filed: Jun 24, 2004
Publication Date: Dec 29, 2005
Inventors: Richard Henderson (Solon, OH), Richard Chandler (Solon, OH), George Mordue (Ravenna, OH), Paul Campbell (North Ridgeville, OH), Lennard Lutes (Akron, OH), Harvey Martin (Birmingham, AL)
Application Number: 10/875,784