US3746072A

US3746072A - Method of pouring molten metal

Info

Publication number: US3746072A
Application number: US00107917A
Authority: US
Inventors: B Richardson
Original assignee: Southwire Co LLC
Current assignee: Southwire Co LLC
Priority date: 1971-01-20
Filing date: 1971-01-20
Publication date: 1973-07-17
Anticipated expiration: 1990-07-17

Abstract

A molten metal pouring method and apparatus for use with a continuous metal casting machine wherein molten metal is poured from a pouring vessel through a pouring spout into an arcuate mold formed by the peripheral groove of a casting wheel and a continuous band surrounding a portion of the casting wheel. The pouring spout is formed with a passage having a reduced diameter at its outlet opening, and the molten metal is initially flowed at a high flow rate to purge substantially all of the air from the internal passage of the pouring spout, and pool the metal in the larger diameter portion of the pouring spout. The absence of air in the pouring spout is effective to reduce voids and blisters in the cast bar and the build up of solidified metal in the internal passage of the pouring spout.

Description

United States Patent [191 Richardson METHOD OF POURING MOLTEN METAL [75] Inventor: Billy Joe Richardson, Carrollton, Ga.

[73] Assignee: Southwire Company, Carrollton, Ga.

[22] Filed: Jan. 20, 1971 [21] Appl. No.: 107,917

Related US. Application Data [62] Division of Ser. No. 809,241, March 21, 1969,

FOREIGN PATENTS OR APPLICATlONS Great Britain 164/278 51 July 17,1973

Primary: ExdminerR. Spencer Annear Attorney-l-lerbert M. Hanegan [57] ABSTRACT A molten metal pouring method and apparatus for use with a continuous metal casting machine wherein molten metal is poured from a pouring vessel through a pouring spout into an arcuate mold formed by the peripheral groove of a casting wheel and a continuous band surrounding a portion of the casting wheel. The pouring spout is formed with a passage having a reduced diameter at its outlet opening, and the molten metal is initially flowed at a high flow rate to purge substantially all of the air from the internal passage of the pouring spout, and pool the metal in the larger diameter portion of the pouring spout. The absence of air in the pouring spout is effective to reduce voids and blisters in the cast bar and the build up of solidified metal in the internal passage of the pouring spout.

3 Claims, 3 Drawing Figures Patented July 17, 1973' I 7 3,746,072;

2 Sheets-Sheet 1 i BILLY JOE RICHARDSON VAN C. WILKS BY H. M. HANEGAN ATTORNEYS Patented July l 7, 1973 R 3,746,672

2 Sheets-Sheet 2 PRIOR ART INVENTOR BILLY JOE RICHARDSON VAN C. WILKS H. M. HANEG'AN ATTORNEYS METHOD OF POURING MOLTEN METAL CROSS-REFERENCE TO RELATED APPLICATIONS This is a division of copending application Ser. No. 809,241, filed Mar. 21, 1969, now abandoned.

BACKGROUND OF THE INVENTION A typical casting machine for continuously casting metal comprises a rotatable casting wheel defining a peripheral groove, a flexible band surrounding a portion of the casting wheel and defining with the peripheral groove an arcuate mold, a pouring vessel positioned adjacent the arcuate mold, and a pouring spout extending from the pouring vessel toward the arcuate mold. The molten metal flows from the pouring vessel through the pouring spout into the arcuate mold, and the casting wheel continuously rotates to carry the molten metal from the entrance to the exit of the arcuate mold. Coolant is applied to the external surfaces of the casting wheel and flexible band to extract the heat from the molten metal which results in solidifying the molten metal, and the solidified metal is extracted from the peripheral groove of the casting wheel as the metal reaches the end of the arcuate mold.

During the operation of the casting machine the rotational speed of the casting wheel and the flow of metal from the pouring vessel to the arcuate mold are controlled by the machine operator or by an automatic control system to maintain a level or pool of molten metal in the arcuate mold. When the casting machine is first placed in operation, the casting wheel is usually rotated at a slow speed and the metal is poured at a relatively high rate of flow from the pouring vessel until the pool of metal is established in the arcuate mold and the lead end of the cast bar has been extracted from the casting wheel and led to the rolling mill or other subsequent processing equipment. When the pool of molten metal has been properly established and the equipment is ready for higher capacity operation, the operator increases the rotational speed of the casting wheel and adjusts the flow of molten metal to continuously maintain the pool of molten metal in the arcuate mold. After the higher capacity casting has been established, the main control function of the operator is achieved by adjusting the flow of molten metal from the pouring vessel into the arcuate mold. This is usually accomplished with the metering pin which varies the opening between the pouring vessel and the pouring spout, and results in more or less molten metal flowing through the pouring spout.

When molten metal flows from the pouring vessel through the pouring spout into the arcuate mold formed by the casting wheel and the flexible band, the pouring spout is usually not fully occupied with molten metal; that is, an air gap is usually present in the pouring spout between the flowing metal and the inner surface of the passageway through the pouring spout. When the flow of metal is increased through the pouring spout some of this air is displaced by the additional volume of metal and forced through the outlet of the spout. When the outlet of the spout is submerged in the pool of molten metal in the arcuate mold, the air forms bubbles in the molten metal which are frequently carried with the molten metal as it is cooled and solidified into a cast bar. Also, when the flow of molten metal through the pouring spout is reduced, the decreasing volume of flowing metal in the pouring spout creates a reduced pressure in the accompanying air gap in the spout. This reduced pressure frequently causes air to bubble up through the outlet opening of thepouring spout if the outlet opening of the pouring spout ever breaks the surface of the pool of meta] formed in the arcuate mold. Thus, bubbles are again created in the flowing metal, which are likely to be carried with the flowing metal as-it travels about the casting wheel.

When the molten metal is subsequently cooled and solidified, the bubbles appear as internal voids or surface blisters in the cast bar. These voids and blisters weaken the bar so that when the bar is extracted from the casting wheel it is more likely to split or crack. When the cast bar passes to a rolling mill, the blisters and voids may not be worked out of the metal as the metal is worked in the rolling mill and may pass with the metal as it is formed into rod. Of course, these imperfections in the rod cause poor grain structure and form a weaker rod. As the rod is further processed into wire by drawing, the rod or wire is likely to break during the drawing process.

During the normal operation of a casting machine there is a gradual build up of solidified metal on the surfaces of the internal passage of the pouring spout. This build up of solidified metal results from the molten metal cooling inside the pouring spout before it reaches the arcuate mold. While the temperature of the molten metal leaving the pouring vessel is usually high enough above its solidification temperature to pass through the pouring spout without solidfying, the entire surface of the pouring spout is not contacted by the molten metal, but is partially contacted by air, so that the heat from the molten metal does not maintain the entire body of the pouring spout at a temperature above the temperature of solidification of the molten metal. Thus, when the flow of metal through the pouring spout decreases or shifts from one surface of the pouring spout passageway to another surface of the passageway due to flow turbulence, machine vibrations, etc., the residue of metal left on the first surface is left to cool as the air is displaced around the passageway, and the residue of metal solidifies and clings to the passageway of the pouring spout. When the flowing metal again shifts back to its original position, the solidified residue has formed a new surface in the passageway of the pouring spout, and the residue of metal left on the second path of metal flow on the surface of the passageway also begins to cool and eventually solidifies. As the flow of molten metal continues to increase and decrease and to shift within the passageway of the pouring spout, the solidified residues eventually build up and reduce the internal cross-sectional area of the passageway, which reduces the flow capacity of the pouring spout. Eventually, the flow capacity of the pouring spout is reduced to a level that is not sufficient for proper operation of the casting machine; that is, when the operator withdraws the metering pin so as to achieve maximum flow of molten metal from the pouring vessel to the arcuate mold, the capacity of the pouring spout is not sufficient to maintain the pool of molten metal in thecasting wheel. The operator then must reduce the rotational speed of the casting wheel to maintain the pool of molten metal, and this results in lower capacity casting.

SUMMARY OF THE INVENTION Briefly described, the present invention comprises a method and apparatus for pouring molten metal in a continuous casting system which eliminates air flow from the pouring spout into the pool of metal in the casting machine, eliminates the bubbles in the molten metal and the resulting voids and blisters in the cast bar, and prevents the build up of solidified metal within the passageway of the pouring spout from reducing the flow capacity of the pouring spout. The pouring spout is formed with a reduced diameter passageway at its exit opening, and the operator initially flows the molten metal at a high rate of flow to purge substantially all of the air from the passageway of the pouring spout and pool the molten metal in the larger diameter portion of the pouring spout passageway. When the flow of molten metal through the pouring spout is reduced, the smaller diameter exit opening of the pouring spout will remain submerged below the pool of metal to form a liquid seal such that no air will flow in either direction through the smaller diameter portion of the passageway. In this manner, molten metal is maintained in contact with the entire surface of the smaller diameter portion of the passageway of the pouring spout at all times, which prevents the displacement of any air through the pouring spout passageway and prevents the build up of solidified metal in this portion of the passageway.

Thus, it is an object of this invention to provide a molten metal pouring method and apparatus that eliminates voids and blisters from forming in the cast bar.

Another object of this invention is to provide a molten metal pouring method and apparatus for a continuous metal casting machine which prevents the build up of solidified metal within the pouring spout of the casting machine.

Another object of this invention is to provide a pouring spout for a continuous metal casting machine that maintains substantially constant flow rate capacity throughout the entire casting operation of the casting machine.

Other objects, features and advantages of the present invention will become apparent upon reading the following specification, when taken in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a partial side cross-sectional view of a pouring vessel, a pouring spout and a casting wheel, with parts broken away for clarity.

FIG. 2 is a partial side cross-sectional view of a pouringspout, showing a modified pouring spout.

FIG. 3 is a partial side cross-sectional view, similar to FIG. 1, but showing a prior art continuous casting system.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now in more detail to the drawing, in which like numerals indicate like parts throughout the several views, FIG. I shows a portion of a casting machine which includes casting wheel 11, flexible band 12, pouring vessel 13, and pouring spout assembly 14. Casting wheel 11 defines a peripheral groove 16, and flexible band 12 moves with casting wheel 11 in the direction as indicated by arrow 17, and forms arcuate mold 18. Band 12 is guided away from peripheral groove 16 at another point about the casting wheel 11 (not shown) to open arcuate mold 18. Pouring vessel 13 is displaced to the side of casting wheel 11 and pouring spout assembly extends from pouring vessel 13 over the intersection of the band and the casting wheel to guide molten metal from the pouring vessel to the mold.

Pouring vessel 13 has concave or sloped bottom walls 19 which define an outlet opening. Pouring spout assembly is T-shaped and includes T-shaped connecting pipe 20 which has its base leg inserted into the outlet opening of the pouring vessel and extends over the mold, pouring spout 21 which projects into the mold, and vent tube 21a which extends away from the pouring spout. Pouring spout 21 defines passageway 22 throughout its length, and passageway 22 includes inlet opening 23 which opens into connecting pipe 20 and outlet opening 24 which opens into arcuate mold l8. Passageway 22 is tapered at 25 which divides passageway 22 into upper or inlet end 26 and lower or outlet end 27. Outlet end 27 is of smaller cross-sectional area or diameter than inlet end 26. Inlet end 26 of'passageway 22 is of constant cross-sectional area and extends along a major portion of pouring spout 21 while outlet end 27 is also of constant cross-sectional area. The external surface of pouring spout 21 is of constant diameter from inlet opening 23 toward the tapered portion 25 of passageway 22, and then is tapered to a smaller diameter at outlet opening 24. Thus, the thickness of the annular wall surrounding passageway 22 is generally constant throughout the entire length of pouring spout 21.

FIG. 2 shows a modified pouring spout 29, which has a passageway 30 with a gradual tapered portion 31. The remaining dimensions and shapes of pouring spout 29 are essentially the same as those of pouring spout 21.

OPERATION When operating the prior art pouring equipment as shown in FIG. 3, the metering pin (not shown) is withdrawn from the donut which leads to pouring spout assembly 37 to create a flow 39 of molten metal from the pouring vessel to the arcuate mold of the casting machine. The internal passageway of the pouring spout 38 is of constant cross-sectional area throughout its entire length, and when the metering pin is withdrawn so as to completely open communication between the pouring vessel and the pouring spout assembly to create a maximum metal flow through pouring spout 38, the acceleration of the metal flow 39 due to the effects of gravity will cause the diameter of the metal flow at the outlet opening 40 of pouring spout 37 to be smaller than the diameter of the metal flow at the inlet opening 41. The flowing metal clings to the internal surface of the passageway, and an air gap 42 extends up the passageway from outlet opening 40 to a position where the entire passageway of the pouring spout is occupied by the stream of metal.

Due to adjustments in the position of the metering pin, the turbulence of the flowing metal 39, the vibra tion of pouring spout 38, and other factors, the flowing metal frequently changes position within the passageway of the pouring spout 38, and clings to a different surface of the passageway from time to time. When the flowing metal 39 shifts to a different position within the passageway, the surface from which it shifts is left with a residue of metal. This residue clings to the surface of the passageway and cools, and eventually solidifies if the flowing metal does not shift back to the residue to maintain its temperature above its temperature of solidification. After the molten metal shifts a number of times and the different residues of molten metal have been allowed to solidify, the effective opening of the passageway will begin to choke up or close, which reduces the flow capacity of pouring spout 38. Eventually the build up of solidified metal in the passageway will be sufficient to reduce the flow capacity of the pouring spout to a level below that sufficient for the operator to maintain the pool of metal in the arcuate mold of the casting machine, and the smaller capacity flow of molten metal through the pouring spout will have to be compensated for by a reduction in speed of the casting wheel. Of course, this reduces the capacity of the casting machine, and the pouring spout must eventually be replaced.

Moreover, when the metering pin in the pouring vessel is adjusted to increase the flow of metal through pouring spout 38, the increased volume of flowing metal causes a displacement of air from the pouring spout. If the outlet opening is properly submerged inthe pool 19 of metal, the air forms bubbles 43 in the molten metal which are frequently carried with the molten metal in the areuate mold, and when the metal solidifies the bubbles appear as internal cavities or surface blisters in the cast bar. When metering pin is adjusted to decrease the flow of metal through pouring spout 38, the reduced volume of flowing metal in the pouring spout causes a reduction of pressure in air gap 42 which tends to increase the size of air gap 42 and bubble air into the pouring spout when the outlet 40 of the spout breaks the surface of pool 19. This flow of air also tends to form bubbles in the flowing metal and results in internal cavities and surface blisters appearing in the cast bar. Also, a reduction in metal flow through the pouring spout leaves a metal residue on the surface of the passageway which eventually solidifies.

As is shown in FIG. 1, the opening of passageway 22 of pouring spout 21 is reduced at its outlet opening 24. When the operator of casting machine establishes a flow of molten metal through the pouring spout, the metering pin is opened wide to establish a maximum flow, to purge substantially all of the air from passageway 22. After the air has been purged, the metering pin is adjusted to establish the proper flow relationship with the casting wheel. The dimension of outlet portion 27 of passageway 22 will not allow air to pass up into passageway 22 through outlet opening 24. The dimension of inlet portion 23 of passageway 22 is established so that the pouring friction between the surface of passageway 22 and the flowing metal is negligible and this portion of the passageway becomes a reservoir or pool and supplies molten metal to outlet portion 27. Tapered portion 25 of passageway 22 is shaped so as to allow a smooth transition of metal flow between inlet portion 26 and outlet portion 27. Thus, the pooling of the metal in the inlet portion of the spout causes any air in the spout to be displaced upwardly and out vent tube 21a. The pool of metal can also extend up vent tube 21a under maximum flow conditions.

After the flow of molten metal through pouring spout 21 has been initially established and virtually all of the air has been purged from passageway 22, the flowing metal will be under positive pressure throughout the entire length of passageway 22 when metering pin 32 has been completely withdrawn from its donut to create a maximum opening between passageway 22 and pouring vessel 13. This creates a maximum flow from pouring vessel 13 to arcuate mold 18 of casting machine 10, and the flow rate of the flowing metal will be determined to some extent by the head of metal between the surface of the metal in pouring vessel 13 and pouring spout outlet opening 24; that is, if the level of molten metal in pouring vessel 13 is high, the flow rate through pouring spout'2l will be high and the level of the pool of metal established in pouring spout 21 will be high. When it is desired to reduce the flow rate through pouring spout 21, the metering pin is moved toward its donut to reduce the effective opening between pouring vessel 13 and pouring spout 21. This increases the friction or turbulence of metal flow and the rate of metal flow from pouring vessel 13, and the level of the pool of metal within the pouring spout is reduced, which reduces the effective head and rate of metal flow through the pouring spout. Of course, the mass of metal extending from outlet opening 24 toward inlet opening 23 of passageway 22 is effective to maintain the flow of metal within pouring spout 21 as long as metal is supplied from pouring vessel 13 to passageway 22 of pouring-spout 21. As the metering pin is moved further into its donut the flow of metal from pouring vessel 13 is further reduced and the level of the pool of metal in the pouring spout decreases which reduces the head and rate of flow through the pouring spout. When the metering pin is adjusted to increase the flow of metal'from the pouring vessel, the pool of metal in the pouring spout builds up and displaces the air above the pool out through the vent tube.

If a metal residue builds up on the inner surface of passageway 22 due to the shifting of the flowing metal and the varying height of the pool of metal, the build up of the metal residue will be isolated to the larger diameter inlet portion 26 of passageway 22 and will generally not be effective to reduce the flow capacity of pouring spout 21 for a prolonged period of time, or until the reduction in the flow capacity of the larger diameter portion of passageway 22 is below the flow capacity of outlet portion 27 of passageway 22.

The shape of pouring spout 21 and its flow characteristics virtually eliminate the possibility of an increasing metal flow rate through the spout displacing air from the spout into the pool of molten metal in the arcuate mold and the hazard of forming bubbles in the molten metal in the arcuate mold is substantially eliminated by the elimination of air surging into or out of pouring spout 21. Thus, the hazard of blisters or cavities being formed in the cast product is substantially eliminated.

While this invention has been described in detail with particular reference to preferred embodiments thereof, it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinbefore and as defined in the appended claims. 2

I claim:

1. A method of pouring molten metal from a pouring vessel into a wheel-band type metal casting machine through an inclined spout having a restricted outlet portion, comprising:

initially purging substantially all air from the outlet portion of the spout by flowing the molten metal at a high flow rate which is sufficient to substantially fill the interior of the spout with molten metal thereby forcing all air contained therein out through the outlet opening thereof,

flowing the molten metal through the inclined spout at a rate which will establish and maintain at least the outlet portion of the inclined spout submerged in a pool of molten metal in the casting machine thereby I establishing a liquid seal in at least the outlet portion of the inclined spout,

the liquid seal preventing the flow of any air through the inclined spout into the pool of molten metal during the pouring operation.

1 g 2. The method of claim 1 wherein the step of establiquid seal.

Claims

1. A method of pouring molten metal from a pouring vessel into a wheel-band type metal casting machine through an inclined spout having a restricted outlet portion, comprising: initially purging substantially all air from the outlet portion of the spout by flowing the molten metal at a high flow rate which is sufficient to substantially fill the interior of the spout with molten metal thereby forcing all air contained therein out through the outlet opening thereof, flowing the molten metal through the inclined spout at a rate which will establish and maintain at least the outlet portion of the inclined spout submerged in a pool of molten metal in the casting machine thereby establishing a liquid seal in at least the outlet portion of the inclined spout, the liquid seal preventing the flow of any air through the inclined spout into the pool of molten metal during the pouring operation.

2. The method of claim 1 wherein the step of establishing a liquid seal in the inclined spout comprises maintaining the restricted outlet portion of the inclined spout completely filled with molten metal during the pouring operation.

3. The method of claim 1 including continuing the high flow rate until at least a portion of the inclined spout is submerged in the molten metal, and then reducing the flow rate to a level sufficient to maintain the liquid seal.