Molten metal transfer and degassing system

Abstract

Disclosed, among other things, is a transfer chamber constructed inside of or next to a vessel used to retain and degas molten metal. The transfer chamber is in fluid communication with the vessel so molten metal from the vessel is pulled through the vessel by the pump as it is degassed. This helps maintain a generally constant flow of molten metal through the degassing vessel. Other aspects relate to a system and method for efficiently performing maintenance on components positioned in a vessel.

Claims

1. A system for transferring molten metal out of a vessel, the system comprising: (a) a vessel, the vessel having an inlet, a cavity and including a transfer chamber having an opening at the bottom of the transfer chamber, the opening in communication with the cavity; (b) the transfer chamber including an uptake section above the opening; (c) an outlet in communication with the uptake section and that is positioned above the opening and leads out of the vessel; and (d) a molten metal pump having a motor, a drive shaft having a first end connected to the motor, the drive shaft extending into the uptake section that is above a rotor, the drive shaft having a second end connected to the rotor, wherein the rotor is in or beneath the uptake section and configured to move molten metal upward into the uptake section, where it exits the outlet and exits the vessel.

2. The system of claim 1 wherein the molten metal pump does not include a pump housing.

3. The system of claim 1 wherein the pump does not include support posts.

4. The system of claim 1 wherein the rotor comprises one or more rotor blades, and each blade includes: (a) a first portion having (i) a leading edge with a thickness of or greater, (ii) a first upper surface angled to direct molten metal upwards, and (iii) a first bottom surface with an angle equal to or less than the angle of the first upper surface as measured from a vertical axis; and (b) a second portion integrally formed with the first portion, the second portion having (i) a second upper surface angled to direct molten metal upwards, the angle of the second upper surface being greater than the angle of the first upper surface as measured from the vertical axis, and (ii) a second bottom surface, the second bottom surface having an angle greater than the angle of the first bottom surface as measured from the vertical axis.

5. The system of claim 1 wherein the rotor comprises one or more blades and each blade is vertically oriented and straight.

6. The system of claim 1 wherein the vessel is comprised of refractory material.

7. The system of claim 1 wherein the vessel has an inner bottom surface and the inner bottom surface is angled downwards towards the opening.

8. The system of claim 1 wherein the rotor has a diameter and is positioned in the transfer chamber and the portion of the transfer chamber in which the rotor is positioned in is circular and has a diameter of 1/32 or greater than the diameter of the rotor.

9. The system of claim 1 wherein the opening has a diameter of 1/32- greater than the diameter of the rotor.

10. The system of claim 1 wherein the transfer chamber has a first section having a first cross-sectional area and a second section having a second cross-sectional area, the second section adjacent the opening and for receiving the rotor, and the second cross-sectional area being smaller than the first cross-sectional area.

11. The system of claim 10 that has a third section having a third cross-sectional area, the third section being between the first section and the second section, and the third cross-sectional area being smaller than the first cross-sectional area, but larger than the second cross-sectional area.

12. The system of claim 10 that further includes a superstructure for supporting the motor.

13. The system of claim 1 that includes one or more brackets for supporting the pump above the vessel.

14. The system of claim 13 wherein the vessel has a first side wall and a second side wall opposite the first side wall and the bracket comprises two metal beams that extend from the first side wall to the second side wall, and each bracket is connected to the first side wall, the second side wall and a superstructure of the pump.

15. The system of claim 1 that further includes a first tap-out opening in communication with the vessel cavity, the first tap-out opening being positioned lower than the rotor.

16. The system of claim 15 that includes a second tap-out opening on a side of the vessel opposite the side that includes the first tap-out opening.

17. The system of claim 16 that further includes a wall dividing the vessel into a first section that retains the transfer chamber and a second section that retains one or more degassers, the wall having an opening that keeps the first section and second section in fluid communication.

18. The system of claim 17 wherein there is a plurality of degassers.

19. The system of claim 18 that has three degassers.

20. The system of claim 18 wherein each at least two of the plurality of degassers are separated by a dividing wall wherein each dividing wall has one or more openings for allowing molten metal to pass through.

21. The system of claim 18 that includes at least one heating element between two of the plurality of degassers.

22. The system of claim 17 that includes a heating element between at least one degasser and the pump.

23. The system of claim 21 that includes a heating element between at least one degasser and the pump.

24. The system of claim 1 wherein the inlet and outlet are on the same side of the vessel.

25. The system of claim 1 wherein a launder extends from the outlet.

26. The system of claim 25 wherein the launder is between 6 and 6 in length.

27. The system of claim 25 wherein the launder is formed at a horizontal angle of one or more of the group selected from: 0, an angle tilting backwards towards the outlet of between 1 and 3, an angle tilting backwards towards the outlet of between 1 and 10.

28. The system of claim 1 wherein there is a wall that separates the cavity from the transfer chamber and a channel is formed in the bottom of the wall and allows molten metal to pass from the cavity to the opening.

29. The system of claim 1 wherein the vessel has an upper perimeter, and the transfer chamber has an upper perimeter, and a platform of the molten metal pump is supported by at least the upper perimeter of the transfer chamber in order to support the pump.

30. The system of claim 29 wherein the platform of the molten metal pump also rests on at least the upper perimeter of the vessel.

31. The system of claim 29 wherein the transfer chamber includes a first wall having a first outer surface and a second wall having a second outer surface, and one side of the platform includes a first centering bracket and the opposite side of the platform includes a second centering bracket; the first centering bracket being juxtaposed the first outer surface and the second centering bracket being juxtaposed the second outer surface to help center the shaft and rotor in the transfer conduit.

32. The system of claim 1 wherein the rotor has a plurality of blades.

33. The system of claim 32 wherein each blade is has a flat surface that pushes molten metal outward.

34. The system of claim 32 wherein each blade is dual-flow, with a first, angled portion that moves molten metal upward and a second portion that moves molten metal outward, the second portion positioned above the first, angled portion.

35. The system of claim 1 wherein the vessel includes a top and one or more access doors covering at least part of the top in order to keep heat in.

36. The system of claim 1 wherein the pump does not include a superstructure.

37. The system of claim 2 wherein the pump does not include a superstructure.

38. The system of claim 2 wherein the pump does not include support posts.

39. The system of claim 36 wherein the pump does not include support posts.

40. The system of claim 39 that further includes one or more rotary degassers.

41. The system of claim 40 wherein each of the one or more rotary degassers is between the inlet and the transfer chamber.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a top, perspective view of a system according to the invention, wherein a transfer chamber is included installed in a vessel designed to contain molten metal.

(2) FIG. 2 is a top view of the system according to FIG. 1.

(3) FIG. 3 is a side, partial cross-sectional view of the system of FIG. 1.

(4) FIG. 4 is a top view of the system of FIG. 1 with the pump removed.

(5) FIG. 5 is a side, partial cross-sectional view of the system of FIG. 4 taken along line B-B.

(6) FIG. 6 is a cross-sectional view of the system of FIG. 4 taken along line C-C.

(7) FIG. 7 is a top, perspective view of another system in accordance with the invention.

(8) FIG. 8 is a top view of the system of FIG. 7 attached to or formed as part of a reverbatory furnace.

(9) FIG. 9 is a partial, cross-sectional view of the system of FIG. 8.

(10) FIG. 10 is a top view of an alternate system according to the invention.

(11) FIG. 11 is a partial, cross-sectional view of the system of FIG. 10 taken along line A-A.

(12) FIG. 12 is a partial, cross-sectional view of the system of FIG. 10 taken along line B-B.

(13) FIG. 13 is a top view of a rotor according to the invention.

(14) FIGS. 14 and 15 are side views of the rotor of FIG. 13.

(15) FIGS. 16 and 17 are top, perspective views of the rotor of FIG. 13 at different, respective positions of the rotor.

(16) FIG. 18 is a top view of the rotor of FIG. 13.

(17) FIG. 19 is a cross-sectional view of the rotor of FIG. 18 taken along line A-A.

(18) FIG. 20 is a side, partial cross-sectional view of an alternate embodiment of the invention.

(19) FIG. 21 is a top, partial cross-sectional view of the embodiment of FIG. 20.

(20) FIG. 22 is a partial, cross-sectional side view showing the height relationship between components of the embodiment of FIGS. 20-21.

(21) FIG. 23 is a front, perspective view of an alternate embodiment according to the invention.

(22) FIG. 24 is a top view of the embodiment of FIG. 23.

(23) FIG. 25 is a cross-sectional, side view of the embodiment of FIG. 23.

(24) FIG. 26 is a cross-sectional, end view of one of the ends of the embodiment shown in FIG. 23.

(25) FIG. 27 is a top view of the vessel portion of FIG. 20 that receives an embodiment of a transfer pump according to the invention.

(26) FIG. 28 is a cross-sectional view of the vessel portion of FIG. 27 taken along lines D-D.

(27) FIG. 29 is a cross-sectional view of the vessel portion of FIG. 27 taken along lines E-E.

(28) FIG. 30 is a side, perspective view of the refractory portion of the vessel portion of FIG. 27.

(29) FIG. 31 is a front, perspective view of the refractory portion of the vessel portion of FIG. 27.

(30) FIG. 32 is a front, perspective view of an alternate embodiment according to aspects of the invention.

(31) FIG. 33 is a rear, perspective view of the embodiment of FIG. 27 with the components in their raised positions.

(32) FIG. 34 is a rear, perspective view of the embodiment of FIG. 27 with the components removed for maintenance purposes.

(33) FIG. 35 is a cross-sectional, side view of the embodiment of FIG. 27 with the components in their operating position.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(34) Turning now to the drawings, where the purpose is to describe a preferred embodiment of the invention and not to limit same, systems and devices according to the invention will be described.

(35) The invention includes a transfer chamber used with a vessel for the purpose of transferring molten metal out of the vessel in a controlled fashion using a pump, rather than relying upon gravity. It also is more preferred than using a transfer pump having a standard riser tube (such as the transfer pumps disclosed in the Background section) because, among other things, the use of such pumps create turbulence that creates dross and the riser tube can become plugged with solid metal.

(36) FIGS. 1-6 show one preferred embodiment of the invention. A system 1 comprises a vessel 2, a transfer chamber 50 and a pump 100. Vessel 2 can be any vessel that holds molten metal (depicted as molten metal bath B), and as shown in this embodiment is an intermediary holding vessel. Vessel 2 has a first wall 3 and a second, opposite wall 4. Vessel 2 has support legs 5, inner side walls 6 and 7, inner end walls 6A and 7A, and an inner bottom surface 8. Vessel 2 further includes a cavity 10 that may be open at the top, as shown, or covered. An inlet 12 allows molten metal to flow into the cavity 10 and molten metal flows out of the cavity 10 through outlet 14. At the top 16 of vessel 2, there are flat surfaces 18 that preferably have metal flanges 20 attached. A tap-out port 22 is positioned lower than inner bottom surface 8 and has a plug 22A that can be removed to permit molten metal to exit tap-out port 22. As shown, inner bottom surface 8 is angled downwards from inlet 12 to outlet 14, although it need not be angled in this manner.

(37) A transfer chamber according to the invention is most preferably comprised of a high temperature, castable cement, with a high silicon carbide content, such as ones manufactured by AP Green or Harbison Walker, each of which are part of ANH Refractory, based at 400 Fairway Drive, Moon Township, Pa. 15108, or Allied Materials. The cement is of a type know by those skilled in the art, and is cast in a conventional manner known to those skilled in the art.

(38) Transfer chamber 50 in this embodiment is formed with and includes end wall 7A of vessel 2, although it could be a separate structure built outside of vessel 2 and positioned into vessel 2. Wall 7A is made in suitable manner. It is made of refractory and can be made using wooden forms lined with Styrofoam and then pouring the uncured refractory (which is a type of concrete known to those skilled in the art) into the mold. The mold is then removed to leave the wall 7A. If Styrofoam remains attached to the wall, it will burn away when exposed to molten metal.

(39) Transfer chamber 50 includes walls 7A, 52, 53 and 55, which define an enclosed, cylindrical (in this embodiment) portion 54 that is sometimes referred to herein as an uptake section. Uptake section 54 has a first section 54A, a narrower third section 54B beneath section 54A, and an even narrower second section 54C beneath section 54B. An opening 70 is in communication with area 10A of cavity 10 of vessel 2.

(40) Pump 100 includes a motor 110 that is positioned on a platform or superstructure 112. A drive shaft 114 connects motor 110 to rotor 500. In this embodiment, drive shaft 114 includes a motor shaft (not shown) connected to a coupling 116 that is also connected to a rotor drive shaft 118. Rotor drive shaft 118 is connected to rotor 500, preferably by being threaded into a bore at the top of rotor 500 (which is described in more detail below).

(41) Pump 100 is supported in this embodiment by a brackets, or support legs 150. Preferably, each support leg 150 is attached by any suitable fastener to superstructure 112 and to sides 3 and 4 of vessel 2, preferably by using fasteners that attach to flange 20. It is preferred that if brackets or metal structures of any type are attached to a piece of refractory material used in any embodiment of the invention, that bosses be placed at the proper positions in the refractory when the refractory piece is cast. Fasteners, such as bolts, are then received in the bosses.

(42) Rotor 500 is positioned in uptake section 54 preferably so there is a clearance of or less between the outer perimeter of rotor 500 and the wall of uptake section 54. As shown, rotor 500 is positioned in the lowermost second section 54C of uptake section 54 and its bottom surface is approximately flush with opening 70. Rotor 500 could be located anywhere where it would push molten metal from area 10A upward into uptake section 54 with enough pressure for the molten metal to reach and pass through outlet 14, thereby exiting vessel 2. For example, rotor 500 could only partially located in uptake section 54 (with part of rotor 500 in area 10A, or rotor 500 could be positioned higher in uptake section 54, as long as it fit sufficiently to generate adequate pressure to move molten metal into outlet 14.

(43) Another embodiment of the invention is system 300 shown in FIGS. 7-12. In this embodiment a transfer chamber 320 is positioned adjacent a vessel, such as a reverbatory furnace 301, for retaining molten metal.

(44) System 300 includes a reverbatory furnace 302, a charging well 304 and a well 306 for housing a circulation pump. In this embodiment, the reverbatory furnace 302 has a top covering 308 that includes three surfaces: first surface 308A, second, angled surface 308B and a third surface 308C that is lower than surface 308A and connected to surface 308A by surface 308B. The purpose of the top surface 308 is to retain the heat of molten metal bath B.

(45) An opening 310 extends from reverbatory furnace 302 and is a main opening for adding large objects to the furnace or draining the furnace.

(46) Transfer well 320, in this embodiment, has three side walls 322, 324 and 326, and a top surface 328. Transfer well 320 in this embodiment shares a common wall 330 with furnace 302, although wall 330 is modified to create the interior of the transfer well 320. Turning now to the inside structure of the transfer well 320, it includes an intake section 332 that is in communication with a cavity 334 of reverbatory furnace 302. Cavity 334 includes molten metal bath B when system 300 is in use, and the molten metal can flow through intake section 332 into transfer well 320.

(47) Intake section 332 leads to an enclosed section 336 that leads to an outlet 338 through which molten metal can exit transfer well 320 and move to another structure or vessel. Enclosed section 336 is preferably square, and fully enclosed except for an opening 340 at the bottom, which communicates with intake section 332 and an opening 342 at the top of enclosed section 336, which is above and partially includes the opening that forms outlet 338.

(48) In order to help form the interior structure of well 320, wall 330 has an extended portion 330A that forms part of the interior surface of intake section 332. In this embodiment, opening 340 has a diameter, and a cross sectional area, smaller than the portion of enclosed section 336 above it. The cross-sectional area of enclosed section 336 may remain constant throughout, may gradually narrow to a smaller cross-sectional area at opening 340, or there may be one or more intermediate portions of enclosed section 336 of varying diameters and/or cross-sectional areas.

(49) A pump 400 has the same preferred structure as previously described pump 100. Pump 400 has a motor 402, a superstructure 404 that supports motor 402, and a drive shaft 406 that includes a motor drive shaft 408 and a rotor drive shaft 410. A rotor 500 is positioned in enclosed section 336, preferably approximately flush with opening 340. Where rotor 500 is positioned it is preferably or less; or or less, smaller in diameter than the inner diameter of the enclosed section 336 in which it is positioned in order to create enough pressure to move molten metal upwards.

(50) A preferred rotor 500 is shown in FIGS. 13-19. Rotor 500 is designed to push molten metal upward into enclosed section 336. The preferred rotor 500 has three identically formed blades 502, 504 and 506. Therefore, only one blade shall be described in detail. It will be recognized, however, that any suitable number of blades could be used or that another structure that pushes molten metal up the enclosed section could be utilized.

(51) Blade 504 has a multi-stage blade section 504A that includes a face 504F. Face 504F is multi-faceted and includes portions that work together to move molten metal upward into the uptake section.

(52) A system according to the invention may also utilize a standard molten metal pump, such as a circulation or gas-release (also called a gas-injection) pump 100 Pump 100 is preferably any type of circulation or gas-release pump. The structure of circulation and gas-release pumps is known to those skilled in the art and one preferred pump for use with the invention is called The Mini, manufactured by Molten Metal Equipment Innovations, Inc. of Middlefield, Ohio 44062, although any suitable pump may be used. The pump 100 preferably has a superstructure 112, a drive source 110 (which is most preferably an electric motor) mounted on the superstructure 112, support posts (not shown), a drive shaft 72, and a pump base not shown. The support posts connect the superstructure 112 to a base 30 in order to support the superstructure 112.

(53) Drive shaft 72 preferably includes a motor drive shaft (not shown) that extends downward from the motor and that is preferably comprised of steel, a rotor drive shaft 118, that is preferably comprised of graphite, or graphite coated with a ceramic, and a coupling (not shown) that connects the motor drive shaft to end 116 of rotor drive shaft 32.

(54) The pump base includes an inlet (not shown) at the top and/or bottom of the pump base, wherein the inlet is an opening that leads to a pump chamber (not shown), which is a cavity formed in the pump base. The pump chamber is connected to a tangential discharge, which is known in art, that leads to an outlet, which is an opening in the side wall (not shown) of the pump base. In the preferred embodiment, the side wall of the pump base including the outlet has an extension (not shown) formed therein and the outlet is at the end of the extension.

(55) In operation, the motor rotates the drive shaft, which rotates the rotor. As the rotor (also called an impeller) rotates, it moves molten metal out of the pump chamber, through the discharge and through the outlet.

(56) A circulation or transfer pump may be used to simply move molten metal in a vessel towards a transfer chamber according to the invention where the pump inside of the transfer chamber moves the molten metal up and into the outlet.

(57) Alternatively, a circulation or gas-transfer pump 1001 may be used to drive molten metal out of vessel 2. As shown in FIGS. 20-22, a system 1000 as an example, has a dividing wall 1004 that would separate vessel 2 into at least two chambers, a first chamber 1006 and a second chamber 1008, and any suitable structure for this purpose may be used as dividing wall 1004. As shown in this embodiment, dividing wall 1004 has an opening 1004A and an optional overflow spillway 1004B, which is a notch or cut out in the upper edge of dividing wall 1004. Overflow spillway 1004B is any structure suitable to allow molten metal (designated as M) to flow from second chamber 1008, past dividing wall 1004, and into first chamber 1006 and, if used, overflow spillway 1004B may be positioned at any suitable location on wall 1004. The purpose of optional overflow spillway 1004B is to prevent molten metal from overflowing the second chamber 1008, by allowing molten metal in second chamber 1008 to flow back into first chamber 1006 or vessel 2 or other vessel used with the invention.

(58) At least part of dividing wall 1004 has a height H1, which is the height at which, if exceeded by molten metal in second chamber 1008, molten metal flows past the portion of dividing wall 1004 at height H1 and back into first chamber 1006 of vessel 2. Overflow spillway 1004B has a height H1 and the rest of dividing wall 1004 has a height greater than H1. Alternatively, dividing wall 1004 may not have an overflow spillway, in which case all of dividing wall 1004 could have a height H1, or dividing wall 1004 may have an opening with a lower edge positioned at height H1, in which case molten metal could flow through the opening if the level of molten metal in second chamber 1008 exceeded H1. H1 should exceed the highest level of molten metal in first chamber 1006 during normal operation.

(59) Second chamber 1008 has a portion 1008A, which has a height H2, wherein H2 is less than H1 (as can be best seen in FIG. 2A) so during normal operation molten metal pumped into second chamber 1008 flows past wall 1008A and out of second chamber 1008 rather than flowing back over dividing wall 1004 and into first chamber 1006.

(60) Dividing wall 1004 may also have an opening 1004A that is located at a depth such that opening 1004A is submerged within the molten metal during normal usage, and opening 1004A is preferably near or at the bottom of dividing wall 1004. Opening 1004A preferably has an area of between 6 in..sup.2 and 24 in..sup.2, but could be any suitable size.

(61) Dividing wall 1004 may also include more than one opening between first chamber 1006 and second chamber 1008 and opening 1004A (or the more than one opening) could be positioned at any suitable location(s) in dividing wall 1004 and be of any size(s) or shape(s) to enable molten metal to pass from first chamber 1006 into second chamber 1008.

(62) Optional launder 2000 (or any launder according to the invention) is any structure or device for transferring molten metal from a vessel such as vessel 2 or 302 to one or more structures, such as one or more ladles, molds (such as ingot molds) or other structures in which the molten metal is ultimately cast into a usable form, such as an ingot. Launder 2000 may be either an open or enclosed channel, trough or conduit and may be of any suitable dimension or length, such as one to four feet long, or as much as 100 feet long or longer. Launder 2000 may be completely horizontal or may slope gently upward, back towards the vessel. Launder 2000 may have one or more taps (not shown), i.e., small openings stopped by removable plugs. Each tap, when unstopped, allows molten metal to flow through the tap into a ladle, ingot mold, or other structure. Launder 2000 may additionally or alternatively be serviced by robots or cast machines capable of removing molten metal M from launder 20.

(63) It is also preferred that the pump 1001 be positioned such that extension 31 of base 3000 is received in the first opening 1004A. This can be accomplished by simply positioning the pump 1001 in the proper position. Further the pump may be held in position by a bracket or clamp that holds the pump against the dividing wall 1004, and any suitable device may be used. For example, a piece of angle iron with holes formed in it may be aligned with a piece of angle iron with holes in it on the dividing wall 1004, and bolts could be placed through the holes to maintain the position of the pump 1001 relative the dividing wall 1004.

(64) In operation, when the motor is activated, molten metal is pumped out of the outlet through first opening 1004A, and into chamber 1008. Chamber 1008 fills with molten metal until it moves out of the vessel 2 through the outlet. At that point, the molten metal may enter a launder or another vessel.

(65) If the molten metal enters a launder, the launder preferably has a horizontal angle of 0 or is angled back towards chamber 1008 of the vessel 2. The purpose of using a launder with a 0 slope or that is angled back towards the vessel is because, as molten metal flows through the launder, the surface of the molten metal exposed to the air oxidizes and dross is formed on the surface, usually in the form of a semi-solid or solid skin on the surface of the molten metal. If the launder slopes downward it allows gravity to influence the flow of molten metal, and tends to pull the dross or skin with the flow. Thus, the dross, which includes contaminants, is included in downstream vessels and adds contaminants to finished products.

(66) It has been discovered that if the launder is at a 0 or horizontal angle tilting back towards the vessel, the dross remains as a skin on the surface of the molten metal and is not pulled into downstream vessels to contaminate the molten metal inside of them. The preferred horizontal angle of any launder connected to a vessel according to aspects of the invention is one that is at 0 or slopes (or tilts) back towards the vessel, and is between 0 and 10, or 0 and 5, or 0 and 3, or 1 and 3, or a backward slope of about for every 10 of launder length.

(67) Turning now to FIGS. 23-26, an alternate embodiment of aspects of the invention is shown. System 2000 is similar to the previously described systems in that the pump 2010 maintains a constant flow of molten metal out of vessel 2002 regardless of the level of molten metal in vessel 2002 and regardless of the flow rate of molten metal into vessel 2002 (unless the level becomes so low that the molten metal can no longer be pumped).

(68) As shown herein, vessel 2002 is constructed differently than vessel 2, but vessel 2 could also be used to degas metal in the manner described herein with the same pumping structures described previously.

(69) System 2000 is for degassing molten metal. In additional to pump 2010, system 2000 preferably includes one or more degassers 2020. The degassers 2020 are rotary degassers and can be of any suitable design and size for system 2000. Generally, each of the rotary degassers 2020 has a motor 2022, a shaft 2024 that connects the motor 2022 to a rotor, and a rotor 2026. As is known in the art, gas passes through shaft 2024 and is released through or under rotor 2026. As shown, system 2000 has three rotary degassers 2020 in line with the path of molten metal flow through vessel 2002.

(70) System 2000 also may include one or more immersion heaters to keep the molten metal at a desired temperature and such heaters are known in the art. In the embodiment shown, there is an immersion heater 2040 between two of the degassers 2020 and another immersion heater between a third rotary degasser and the pump 2010. Any appropriate number of immersion heaters, however, may be used, or none may be used.

(71) Turning now to vessel 2002, it is supported by legs 2004, has sides 2006, 2008, and ends 2050, 2052. Vessel 2002 its preferably comprised of suitable refractory material, the compositions and method of manufacture of same being known to those skilled in the art. Each end 2050 and 2052 has a tap-out plug 2054 having a launder-type exit 2056. Vessel 2002 as shown comprises two cemented vessel portions 2002A and 2002B. Vessel portion 2002A retains two rotary degassers 2020 and an immersion heater 2040, although it could hold only one degasser 2020 and no immersion heaters 2040, or no degassers 2020 or no immersion heater 2040. Further, if dimensioned differently, it could retain more degassers 2020 or immersion heaters 2040 than shown.

(72) Vessel portion 2002A includes an inlet 2100 through which molten metal enters vessel 2002. Often the molten metal entering inlet 2100 ebbs and flows at different rates so the level of molten metal in vessel 2 can vary. Vessel portion 2002A has metal frame portions to assist in mounting structures to it and in it, and such frame structures are known to those skilled in the art.

(73) Inside of vessel portion 2002A, as best seen in FIG. 24 are separate compartments for housing rotary degassers 2020. Compartment 2020A is separated from compartment 2020B by immersion heater 2040, with molten metal preferably passing under or around immersion heater 2040 to move from chamber 2020A to chamber 2020B. Alternatively, any other structure could be used to separate these rotary degassers 2020 or no structure could be used. The purpose of using immersion heater 2040 is to maintain the molten metal at a proper temperature because vessel 2002 has no heat source, and because dividing the vessel portion 2002A into two degassing chambers leads to better degassing because the molten metal is retained in a smaller space while being degassed.

(74) As shown, section 2002B is connected to section 2002A and includes a rotary degasser 2020, an immersion heater 2040 downstream of the rotary degasser 2020, and a pump transfer chamber (also called a transfer chamber or transfer conduit) downstream of the immersion heater 2040. One or both of rotary degasser 2020 and immersion heater 2040 may not be included in section 2002B, although for the best results they are included.

(75) Pump transfer chamber 2300 and pump 2010 are each preferably of the same respective structures described previously for transferring molten metal through an uptake section and out of the outlet 2200 in an relatively even, constant flow. Using such a structure, the flow of molten metal through vessel 2002, which begins at inlet 2100 and moves through compartments 2020A, 2020B and 2020C and then through the transfer chamber 2300 and out of outlet 2200, is relatively consistent regardless of the flow into inlet 2100 or the level of molten metal in vessel 2002 (unless it becomes so low that pump 2010 can no longer generate a proper flow). This because the flow is controlled by the pump 2010 instead of the amount of molten metal entering inlet 2100.

(76) Alternatively, instead of the pump transfer chambers and pumps described above, the molten metal flow through chamber 2002 and out of outlet 2200 may be controlled by a pump structure as disclosed in Ser. No. 13/797,616, filed Mar. 12, 2013, by Paul V. Cooper, the disclosure of which is incorporated herein by reference.

(77) FIGS. 27-29 show views of section 2002B of vessel 2000 with the components removed. FIGS. 30 and 31 show views of the refractory portion of section 2002 with the components and metal framing removed.

(78) In FIG. 23 of system 2000, a jib crane is shown, but this is merely a device for lifting and removing components from the vessel 2002 and is not part of the invention.

(79) FIGS. 32-35 show an alternate system 3000 of the invention that utilizes the same rotary degassers, immersion heaters, pump structures, and transfer chamber structures as previously described with respect to system 2000 except that in this embodiment there is a one-piece vessel 3002, two rotary degassers 3020 with an immersion heater 3040 between them, and a pump 3010 with an immersion heater between it and the nearest degasser 3020.

(80) In this embodiment, molten metal flows into vessel 3002 through inlet 3100, moves through chambers 3020A and 3020B and then enters the transfer chamber (or pump transfer chamber or transfer conduit) where it is pumped out of vessel 3002 through outlet 3200 by pump 3010 in a relatively even flow regardless of the rate of flow into inlet 3100 or the level of molten metal in vessel 3002 (unless the level becomes so low that pump 3100 cannot function properly).

(81) This embodiment also optionally includes fixed-position lifting structures 3700 that may be permanently fixed to the rotary degassers 3020 and pump 3010 to insert and remove them quickly from vessel 3002, and to rotate these components, without having to move the lifting structures, to a position where maintenance can be performed. This method is shown in FIGS. 32-34 and is a major advantage over existing methods of removal for maintenance, which usually require removing the components one at a time by a jib crane and then moving the components to a separate area for maintenance, or to remove each component using a forklift and again moving each to a separate area for maintenance.

(82) Using the lifting devices of the present invention, which are fixed in place and rotate, the components can be lifted straight up with little chance of damaging them and simply rotated to a maintenance position.

(83) After maintenance is completed, the components can be rotated back above vessel 3002 and lowered vertically down into vessel 3002 in the proper position, which again eliminates the chance of damage. So, this system and method saves time and reduces the likelihood of components being damaged.

(84) System 3000 also includes access doors 3600, which help to keep heat from escaping vessel 3002 and that can be opened to access the interior cavity of 3002.

(85) Having thus described some embodiments of the invention, other variations and embodiments that do not depart from the spirit of the invention will become apparent to those skilled in the art. The scope of the present invention is thus not limited to any particular embodiment, but is instead set forth in the appended claims and the legal equivalents thereof. Unless expressly stated in the written description or claims, the steps of any method recited in the claims may be performed in any order capable of yielding the desired result.