ES2848423T3 - Advanced Material Overflow Transfer Pump - Google Patents

Abstract

A molten metal pump (30) comprising an elongated tube having a base end (80) and an upper end, a shaft (36, 116, 212, 411) disposed within said tube, and an impeller (102, 175 , 412) rotatable by said shaft (36, 116, 212, 411), said impeller (102, 175, 412) disposed near said base end (80), said base end (80) including a inlet (120, 220) and said upper end including an outlet (229), characterized in that said elongated tube is composed of a reinforced fiber material, RFM, and in that said pump (30) further includes a bearing ring (44 , 56, 86, 221, 307) composed of reinforced fiber material, RFM and arranged in the inlet (120, 220).

Description

DESCRIPTION

Advanced Material Overflow Transfer Pump

BACKGROUND

The present exemplary embodiment relates to pumps for pumping molten metal and will be described with particular reference thereto. The present pump embodiment may find particular use in handling molten aluminum, zinc, lead and / or magnesium and alloys thereof. However, it should be appreciated that the present exemplary embodiment is also suitable for other similar applications. Molten metal pumping pumps are used in furnaces in the production of metal articles. An example of such a molten metal pump is known from US / 2013/101424 A1. Today, many metal die casting facilities employ a main hearth that contains most of the molten metal. Solid metal bars can be cast periodically into the main hearth. A transfer pump can be located in a separate well adjacent to the main hearth. The transfer pump draws molten metal from the well in which it resides and transfers it to a ladle or chute and from there to the smelters that form the metal items. The present invention relates to pumps used to transfer molten metal from a furnace to a die casting machine, ingot mold, DC cold casting machine or the like. The pump in question can similarly be used as a transportable apparatus for use on demand and / or for emergency pumping situations.

SHORT DESCRIPTION

In accordance with one embodiment of this disclosure, there is provided a molten metal pump according to claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description and drawings set forth certain illustrative implementations of the disclosure in detail, which are indicative of various exemplary ways in which the various principles of the disclosure may be carried out. The illustrated examples, however, are not exhaustive of the many possible embodiments of the disclosure. Other objects, advantages and features of the disclosure will be set forth in the following detailed description of the disclosure when considered in conjunction with the drawings, in which:

FIG. 1 is a perspective view showing a molten metal transfer system including the pump arranged on a furnace platform;

FIG. 2 is a perspective view in partial cross section of the system of FIG. 1;

FIG. 3 is a side cross-sectional view of the system shown in FIGS. 1 and 2;

FIG. 4 is a perspective view of the pump chamber;

FIG. 5 is a top view of the pump chamber;

FIG. 6 is a view along the line A-A of FIG. 5;

FIG. 7 is a representative impeller design;

FIGS. 8 (a) and 8 (b) depict a lower end of a suitable pumping chamber from a cross-sectional perspective view and a cross-sectional plan view, respectively;

FIG. 9 is a schematic cross-sectional plan view of a reciprocating pump configuration; FIG. 10 is a schematic cross-sectional plan view of another reciprocating pump configuration; FIG. 11 is a cross-sectional perspective view of the pump of FIG. 10;

FIGS. 12 (a) and 12 (b) represent a suitable impeller for use in the pump in question;

FIGS. 13 (a), (b), (c), (d) are respectively a perspective view of a reciprocating pump configuration, a detailed view of the volute chamber, a perspective view of the RFM pump body ( fiber reinforced material) and an end view of the pump body;

FIG. 14 is a side elevation view (partially in cross section) of another alternate pumping chamber configuration;

FIG. 15 is a bottom view of the pump chamber of FIG. 9; and

FIG. 16 is a perspective view of a crucible configured to include the transfer pump of the present disclosure.

DETAILED DESCRIPTION

The exemplary embodiment has been described with reference to preferred embodiments. Modifications and alterations will be evident when reading and understanding the detailed description. The exemplary embodiment is intended to be construed to include all such modifications and alterations insofar as they fall within the scope of the appended claims.

This pump is designed to smoothly transfer molten metal from crucibles or smelting / holding furnaces. It has particular utility in foundry and casting room applications, such as transferring metal from a furnace to a crucible, casting a crucible, and / or transferring to melt / crucible and furnace-to-furnace machines. The pump can empty small crucibles because the pump can be manufactured to be relatively compact (for example, depth of immersion of metal in the container: 1100 or 800 mm; diameter of the container: 275 (top) to 235 mm (bottom)) .

Furthermore, using the rolling technique of RFM fabrication, it is feasible to construct an elongated pump chamber having a substantially constant diameter, for example, an inner diameter of 185mm or less and / or an outer diameter of 235mm or less. . Given RFM's high strength and thermal shock resistance, it is equally possible to construct a relatively thin-walled pump chamber (eg <50mm). As such, a pump capable of being inserted into tight spaces, for example a space less than 25 cm in diameter is feasible.

Advantageously, the pump has a main body constructed of a composite ceramic material that is resistant and tolerant of mechanical abuse, making the system container very durable, rigid, and easy to use. These materials are referred to herein as fiber reinforced materials (RFM).

The benefits of building the pump chamber with RFM include improved safety: eliminates manual emptying procedures, tilting or the use of tap ports; improved metal quality; increased productivity; and minimal preheating is necessary.

RFM provides at least the following additional benefits:

A. The system is easy to remove and reinsert into molten metal due to its light weight (the system could be permanently mounted, but is not required).

B. A thinner wall can be designed (contributing to lighter weight and low thermal mass). C. Good resistance to thermal shock.

D. No Preheating Needed - After heating the system (above 100 ° C) to ensure that there is no residual moisture in the refractory, the RFM can be immersed directly into the molten metal without preheating.

E. Can be used to transfer from foundry crucibles to other vessels.

Advantageously, the present pump construction allows 40% or more of the elongated tube to extend above the metal line.

With reference to FIGS. 1-3, the molten metal pump 30 of the present invention is shown in association with a furnace 28. The pump 30 is suspended by means of a metal frame 32 that rests on the walls of the furnace platform 34 (a transportable version in FIGS. 13 (c) - (d) where no support structure is required). A motor 35 rotates a shaft 36 (composed of graphite or ceramic, for example) and the attached impeller 38. A body 40 of fiber reinforced material (RFM) forms an elongated and generally cylindrical tube or pump chamber 41. Although the tube and pump chamber are generally depicted herein as cylindrical, it is noted that other shapes are also contemplated. For example, cylindrical is intended to encompass conformations such as elliptical, parabolic, and hyperbolic cylinders. Furthermore, it is envisaged that the pump can operate with chamber cross-sectional geometries such as rectangular or square. Furthermore, it is envisioned that the cross-sectional geometry may vary along the length of the pumping chamber.

Body 40 includes an inlet 43 that receives impeller 38. Bearing rings 44 may be provided to facilitate uniform wear and rotation of impeller 38 therein. In operation, molten metal is introduced into the impeller through the inlet (arrows) and is forced upward into tube 41 in the form of a forced vortex ("equilibrium"). At the top of the tube 41 a volute-shaped chamber 42 is provided to direct the molten metal vortex created by the rotation of the impeller outward into the channel 44. The channel 44 can be joined / coupled with additional channel or pipe elements to direct molten metal to its desired location, such as a casting apparatus, ladle, or other mechanism known to those skilled in the art.

Although shown as a volute cavity, an alternative mechanism could be used to deflect the rotating molten metal vortex into the channel. In fact, a tangential outlet extending even from a cylindrical cavity of equal size and concentric to the tube 41 can achieve a tangential flow of molten metal. However, a diverter, such as a wing that extends into the flow pattern or other element that directs molten metal into the channel, may be beneficial.

Also, in certain environments, it may be desirable to form the base of the tube generally bell-shaped, rather than flat. This design can produce a deeper vortex and allow the device to have an improved function as a scrap dipping unit.

Pump 30 includes a metal frame 108 that surrounds the top (outlet chamber) of RFM tube 41, and includes a motor bracket 102 that is attached to pump 30. A piece of compressible fiber may be provided (not shown ) between the steel frame and the refractory vessel to accommodate variations in thermal expansion rates. In addition, the outlet chamber is provided with an overflow notch 123 to safely return molten metal to the furnace in the event of a downstream obstruction blocking channel 44. Overflow notch 123 has a shallower depth than channel 44 .

Turning now to FIGS. 4-6, the body 40 is shown in greater detail. FIG. 4 shows a perspective view of the RFM body. FIG. 5 shows a top view of the volute design and FIG. 6 shows a cross-sectional view of the generally cylindrical elongated pumping chamber. These views show general design parameters where pump chamber 41 is at least 1.1 times larger in diameter, preferably at least about 1.5 times, and most preferably, at least about 2.0 times larger than diameter. of the impeller. However, for higher density metals, such as zinc, it may be desirable for the impeller diameter relative to the pumping chamber diameter to be in the lower range of 1.1 to 1.3. Furthermore, it can be seen that the pump chamber 41 has a length significantly greater than the height of the impeller. Preferably, the length (height) of the pump chamber is at least 0.9m (three feet), or at least 1.5m (five feet), or at least 2.1m (seven feet). The pump head from inlet to outlet is expected to be less than 6m (20ft) or less than 4.2m (14ft). Without wishing to be bound by theory, these dimensions are believed to facilitate the formation of a desirable forced vortex ("equilibrium") of molten metal as shown by line 47 in FIG. 6.

FIG. 7 depicts an impeller 38 that includes an upper section 68 having vanes 65 (or passages) supplying the induced flow of molten metal and a bushing 50 for engaging the shaft 36. An inlet guide section 70 defines a hollow central portion 54. Bearing rings 56 may be provided to provide smooth rotation of the impeller within body 40. The impeller can be constructed of graphite or other suitable refractory material, such as ceramic. It is envisioned that any traditional cast metal impeller design having a bottom inlet and side outlet (s) would be functional in the present overflow vortex transfer system.

FIGS. 8 (a) and 8 (b) provide a detailed view of an exemplary base end of pump chamber 41. In these illustrations, the base end 80 includes side wall 82, bottom wall 84, and a sealing ring. RFM 86 bearing (not shown in the preceding figures). An impeller receiving inlet 88 is formed in the bottom wall 84 and bearing ring 86 through which molten metal is received.

The RFM material used to construct selected pump components, including body 40, can include a ceramic matrix material with a fiber fill material. The ceramic matrix material can be a mixture of, for example, wollastonite and colloidal silica. An exemplary fiberfill material is fiberglass. These materials are mixed to form a suspension.

The body can be constructed in a series of layers, placing pre-cut measurements of woven fabric on a mandrel, adding the suspension and impregnating it into the fabric to ensure that the fabric is fully soaked through. This is repeated to form successive layers of fabric and matrix material, until the desired thickness is achieved. An exemplary cloth material is glass.

Once the product has reached the desired thickness, it is machined green (unbaked) to conform to the outer surface of the tubular body. The tubular body is then removed from the mandrel and placed in an oven to dry. A release coating can be applied, for example boron nitride. The present pump can be considered a portable overflow pump having particular suitability for the foundry market. The pump can be designed to smoothly lift and transfer molten metal from small crucibles or smelting or holding furnaces. It can be used in foundry and casting room applications such as pumping metal from one furnace to a crucible, pouring a crucible, transferring metal to smelting machines, and moving metal from one furnace to another.

The pump's compact size makes it easy to transport from container to container, and its RFM construction allows for rapid metal insertion due to minimal preheat requirements. Its design lifts and transfers molten metal efficiently, producing less slag than traditional transfer procedures. It is safer to use than traditional transfer procedures that require operators to empty, tilt, or use tap ports manually.

The design benefits of the RFM overflow pump include reduced slag formation during the transfer process and a constant metal flow rate. Although it has a small diameter build surface, its design allows it to deftly empty a small crucible weighing approximately 500 kilograms (1,100 pounds) in less than approximately one minute.

The pump is lightweight and has excellent mechanical strength, does not wet cast aluminum, and has better heat retention and better service life compared to cast iron, fiber-laminated cardboard, and other pre-cast ceramic materials. RFM can reduce downstream oxides and inclusions, help prevent slag build-up, help lower furnace holding temperatures, and produce higher quality castings. It can also be formed into complex designs and is highly resistant to thermal shock.

The inorganic material used to make the matrix (RFM) can be of any type as long as it is compatible with the tissue that is embedded in it; it can be molded or thermoformed; and it is rigid, strong, and heat resistant enough to handle molten metal and remain rigid at molten metal temperature.

The inorganic material can be a glue made from colloidal silica like the one sold by Unifrax under the trade name QF-150 and 180. It can also be a suspension of sodium or potassium silicate or a zirconium-based coating like the one sold. tradename EZ400 by Pyrotek, Inc.

In one example, the RFM may comprise from 8 to 25% by weight of an aqueous solution of phosphoric acid having a phosphoric acid concentration ranging from 40 to 85% with up to 50% of the main acid function of the acid, acid phosphoric neutralized by reaction with vermiculite. It also comprises 75 to 92% by weight of a mixture containing wollastonite or a mixture of wollastonite of different grades, and an aqueous suspension containing 20 to 40% by weight of colloidal silica, such as that marketed under the trademark LUDOX h S-40 from Sigma-Aldrich. The weight ratio of the aqueous suspension to the wollastonite within the mixture can vary from 0.5 to 1.2.

To prepare the tube, a suspension of the selected RFM can be prepared and an open tissue impregnated with the suspension, either by direct application or by immersion. The resulting product can be left in a preselected shape mold until the matrix has set. The rigid tube can be removed from the mold in less than two hours, without the need for any drying and / or heating step, although a 10 hour drying step at room temperature followed by several hours of cooking at elevated temperature (such as 375 ° C).

Although the pump and driver designs depicted in FIGS. 2-8 (b) (a first embodiment) are highly effective in achieving the transfer of molten metal from a furnace, their utility may be more effective with furnace environments where the molten metal is at a high temperature, for For example, above 760 ° C (1400 ° F). In environments where the temperature of the molten metal is lower, for example 10 ° C (50 ° F) above the melting point of the metal being transferred, an alternative design may be desirable. Furthermore, in a relatively low temperature molten metal environment, it is feasible that the relatively high mass base and impeller components of the first embodiment can cause a decrease in the temperature of the molten metal within the pump body resulting in This results in hardening of the metal and potential damage to the pump assembly.

For example, the test was performed using the first embodiment of the pump equipped with external and internal thermocouples in the base region. The bomb was immersed in molten metal at a temperature of 732 ° C (1350 ° F). The following table summarizes recorded dive temperatures, where temperatures in ° C can be calculated from temperatures in ° F using the following formulas: ° C = (-32 ° F) / 1.8.

As will be appreciated by one of ordinary skill in the art, the initial insertion of the pump into the molten metal can cause a significant decrease in the temperature of the molten metal within the pump chamber. This decrease in temperature is reinforced by the presence of the impeller. If the associated furnace keeps the molten metal being transferred at a temperature relatively close to the temperatures of the metal solid, the pump may freeze.

In accordance with an example that is not part of the present invention, the bottom wall of RFM 84 has been removed (see FIGS. 8 (a) and (b)). The RFM 86 bearing ring has also been removed and the impeller mass has been reduced.

With particular reference to FIG. 9, a base region of a pump chamber 100 receives an impeller 102. Instead of forming an interface between the impeller and a lower wall of the elongated tube, a dynamic seal 104 is formed between an upper surface 106 of the main body 108 of the impeller and a lower edge 110 of a tube body 112.

The impeller 102 may include a bushing 114 that receives a shaft 116. The vanes 118 extend from the bushing on the upper surface 106. An inlet 120 is provided on a lower surface 122 with passageways (not shown) extending through the main body 108 for conveying metal from outside the pump to pump chamber 100.

As used herein, the term "dynamic seal" is intended to reflect a seal formed between the rotating impeller and the tube body. The dynamic seal is intended to span a range of fluid tightness from substantially absolute in which a lubricating film of molten metal forms between the impeller and the tube body, but through which substantially no flow of fluid occurs. molten metal during operation to a situation where a measurable amount of molten metal can pass between the impeller and the tube body. However, it is desirable that the maximum amount of molten metal entering the pump chamber through the dynamic seal is less than the amount entering through the impeller inlet. In addition, it may be more desirable for the tube body to act as a bearing surface during rotation of the impeller.

Returning to FIGS. 10 and 11, an alternate configuration is depicted in which a dynamic edge seal 150 is formed between the radial edge 152 of the impeller 102 and an inner wall 156 of the tube body 112. In any example not part of the present invention It is conceivable that the impeller includes a radial bearing ring 158, but such a bearing ring is optional, particularly if the impeller is constructed of a ceramic material. Also contemplated, but not illustrated, is a slight lower protrusion (eg, "j" end portion) of the tube body configured to form a dynamic seal with one impeller corner facing downward.

Turning now to FIGS. 12 (a) and 12 (b), an impeller 175 (composed of graphite or ceramic, for example) is shown without a bearing ring (composed of silicon carbide, for example). The impeller 175 includes a disc-shaped body 177 having a top surface 179 on which a plurality of blades 181 are disposed. The blades 181 extend from a hub 183 in which a shaft can be received (not shown). The bushing 183 can be configured to include recesses 185 to receive pins that provide an interface through which the shaft imparts torque to the impeller. The impeller 175 further includes an inlet 187 on a lower surface 188 in fluid communication with a plurality of passages 189 by means of which molten metal passes through the disk-shaped body 177 for discharge on the adjoining upper surface 179 where they act. therein the vanes 181 to impart the desired radial flow that creates the vortex through which the molten metal rises upward into the tube for eventual discharge from the raised outlet.

As a visual comparison between the impeller of FIG. 7 and the impeller of FIGS. 12 (a) and (b) it will be shown that a significant amount of mass has been removed from the impeller by providing an open top blade architecture and an inwardly lowered inlet. In certain cases, it may be desirable for the RFM tube adjacent to the impeller to have an internal diameter of between about 15 and 30 centimeters and for the impeller to have a volume of between about 500 to 1500 cubic centimeters. As an example, it may be desirable to characterize this ratio as a ratio of impeller volume to tube cross-sectional area of less than about 3: 1. In addition, it may be desirable for the walls of the RFM tube adjacent to the impeller to be in a range of about 1.27 to 3.81 centimeters wide. In addition, it may be desirable to provide an impeller that has vanes spaced from the pump tube walls to a greater extent than the portion of the impeller that forms the dynamic seal to increase the amount of molten metal residing therein. For example, the blades may extend less than 75% of a distance between the hub and the radial edge of the disc-shaped body.

Referring now to FIGS. 13 (a), (b), (c), (d), the advantages of using an RFM tube are obvious. More particularly, in the illustrated design, pump 200 is constructed to selectively move between locations that require lift and transfer of molten metal. More particularly, the tube 201 can be constructed with a relatively thin wall, for example between about 18 and 50 mm due to the high strength and structural integrity of the RFM material. Furthermore, the tube can be constructed to have a cylindrical shape of at least a substantially uniform diameter over its entire length. This is advantageous for inserting the pump in tight spaces. In the embodiment shown, a motor mount 203 is superimposed on the volute chamber 205 and posts 207 secure the motor mount to a metallic liner 209 attached to an upper edge of the volute chamber. The motor 211 is attached to the motor bracket 203. A shaft 212 extends between the motor and an impeller (not shown) disposed in the base region 214.

Three lifting eyes 213 are provided on motor bracket 203 to facilitate movement of pump 200 between desired locations. In addition, the pump 200 can be lifted by means of the eyes 213 using a forklift or hoist and can be transported to a crucible or furnace pit to remove molten metal. The pump 200 can be temporarily positioned by the lift mechanism in the apparatus which is emptied and withdrawn when the desired amount of molten metal has been removed.

Referring to FIG. 13 (c) and (d), the pump body shows the inlet 220 in the base region 214. The inlet 220 includes an RFM bearing ring 221. The pump body further includes three legs 223 that allow pump 200 rests on the furnace / crucible floor while inlet 220 is positioned above the floor to avoid ingesting an excessive amount of solids. Volute end 225 of the pump is also illustrated and includes volute chamber 227 and outlet 229. Overflow spillway 231 is also illustrated.

In operation, the feed motor 211 rotates the shaft 212 and the impeller provided in which the rotation of the impeller draws molten metal through the inlet 220. The impeller ejects the molten metal radially within the tube 201 (the internal diameter being greater than the outer diameter of the impeller at the impeller outlet). The radially ejected molten metal forms a rotating vortex of molten metal that rises up the walls of the tube, reaching the volute chamber 227 where it is directed horizontally outward through the outlet 229.

Turning now to the embodiment of FIGS. 14 and 15, an alternative pump chamber construction is shown. More particularly, the pump chamber 300 has been constructed of RFM and includes three legs 301 that can be used to raise the chamber 300 above the floor of the container that includes molten metal, which has been found to reduce the tendency to clog. . Furthermore, in this embodiment chamber 300 is provided with a plurality of holes 303 oriented to receive bolts 305 intended to retain a bearing ring of RFM 307, positioned to mate with a corresponding bearing ring of an impeller (not shown) .

Turning next to FIG. 16, the pump concepts of the invention contained in this disclosure apply to a configured crucible. In addition, the provided crucible 400 includes a tubular column 401 adjoining a side wall 403. The tubular column 401 will include an inlet 402 in fluid communication with the main molten metal-containing region 404 of the crucible. The crucible and / or tubular column can be constructed of RFM. The tubular column 401 is provided with a volute top 405 that facilitates the discharge of molten metal from the crucible by means of a nozzle 407. A selectively removable motor 409, motor bracket 410, shaft 411 and impeller 412, collectively a set 413 , can be fed into tubular column 401, where rotating the impeller by the motor creates the molten metal vortex within tubular column 401, lifting molten metal to the top of volute 405 for final discharge by means of nozzle 407.

The side wall of the crucible 403 can be equipped with posts 415 configured to receive and releasably engage with the motor mount 410. In this manner, the assembly 413 can be selectively associated with a crucible for removal of molten metal and then separated. as desired. Advantageously, the assembly can be used to service multiple crucibles.

This design has many advantages as it creates a balancing vortex at low impeller RPM, creating a smooth surface with little or no air intake. Consequently, the vortex is non-violent and generates little or no slag. Furthermore, the present pump creates a forced vortex that has a constant angular velocity so that the rotating molten metal column rotates as a solid body with very little turbulence.

Other advantages include the elimination of the riser component in traditional cast metal pumps which can be brittle and prone to clogging and damage. Additionally, the design provides a very small build surface relative to the traditional transfer pump base and has the ability to locate the impeller very close to the bottom of the deck, allowing for very low metal reduction. As a result of the small construction area. The device is suitable for current refractory furnace designs and will not require significant modifications to it.

The pump has excellent flow adjustability, its open design structure provides easy access for simple and easy cleaning. Advantageously, generally only spare parts will be required for the shaft and impeller. In fact, it is generally self-cleaning in that slag formation in the riser is eliminated because the metal level is high. In general, a lower torque motor, such as an air motor, will suffice due to the low torque experienced.

Optional additions to the design include the location of a filter at the base of the pumping chamber inlet. It is further anticipated that the pump would be suitable for use in molten zinc environments where very long pull is required (eg 4.2 m (14 ft)). Such a design may preferably include the addition of a bearing mechanism at a location on the rotary shaft between the motor and the impeller.

Claims (6)

A molten metal pump (30) comprising an elongated tube having a base end (80) and an upper end, a shaft (36, 116, 212, 411) disposed within said tube, and an impeller (102 , 175, 412) rotatable by said shaft (36, 116, 212, 411), said impeller (102, 175, 412) disposed near said base end (80), said base end (80 ) an inlet (120, 220) and said upper end including an outlet (229), characterized in that said elongated tube is composed of a reinforced fiber material, RFM, and in that said pump (30) further includes a bearing ring (44, 56, 86, 221, 307) composed of reinforced fiber material, r Fm and arranged at the entrance (120, 220). The molten metal pump of claim 1, wherein said elongated tube includes a side wall thickness of between about 18 and 50mm. The molten metal pump of claim 2, wherein said elongated tube includes a length of at least two meters. The molten metal pump of claim 1, wherein said shaft (36, 116, 212, 411) and impeller (102, 175, 412) form an assembly, said assembly being selectively removable as a unit of said tube. The molten metal pump of claim 1 including at least three legs (223, 301) projecting from the end of the base (80). The molten metal pump of claim 1, further comprising at least three holes configured to mount a bearing ring (44, 56, 86, 221, 307).