EP0095111A2

EP0095111A2 - Roll caster with isothermal shell cooling

Info

Publication number: EP0095111A2
Application number: EP83104755A
Authority: EP
Inventors: Robert Allen Ramser
Original assignee: Aluminum Company of America
Current assignee: Howmet Aerospace Inc
Priority date: 1982-05-17
Filing date: 1983-05-13
Publication date: 1983-11-30
Also published as: JPS58209452A; NO831747L; AU1422683A; CA1208877A; EP0095111A3

Abstract

A roll caster for continuous casting of metals in strip form wherein each of the casting rolls has a roll and a shell over each roll. Each roll has at least one axial feed bore for supplying coolant into the roll and at least one axial drain bore for draining the coolant from the roll. A plurality of parallel annular groove surround the roll for flowing coolant between the roll and the shell. A plurality of radial feed passageways and radial drain passageways connect each axial feed bore and each axial drain bore, respectively, to annular grooves with each of said radial feed passageways and each of said radial drain passageways servicing at least one annular groove and with the radial feed passageway connected to an annular groove on the generally opposite side of the roll from the radial drain passageway for the same groove; and with each radial feed passageway extending radially outwardly from an axial feed bore in a direction generally opposite from each immediately adjacent radial feed passageway and with each radial drain passageway extending radially outwardly from an axial drain bore in a direction generally opposite from each immediately adjacent radial drain passageway to provide substantially isothermal cooling of the casting roll's shell.

Description

The present invention relates to an apparatus for the continuous casting of metals in strip form and, more particularly, to a new and improved roll caster providing substantially isothermal cooling of the casting roll's shell.
The use of internally chilled rollers in the continuous casting of molten metal in strip form is well known. U.S. Patent 2,850,776 to Hunter discloses a roller for continuous casting machines having a plurality of helical coolant channels. Each coolant channel's helical, single convolution construction allows the coolant flowing in each channel only one revolution. The patent states that this arrangement permits the equal exposure of the coolant in all the channels to the shell of the roller and the uniform extraction of heat from the roller's shell. However, the Hunter patent states that a slight temperature gradient is present from one end of the roller to the other during the casting process as well as states that this temperature gradient has no noticeable effect on roller operation.
West German Auslegeschrift No. 1,508,927, published December 6, 1973, discloses an internally cooled roller having a core and a sleeve. Helical coolant channels run between the core and the sleeve having inlets alternately on one or the other front face of the roller. The infeed and the run-off channels enter and discharge on the same facial side of the core of the roller.
U.S. Patents 3,712,366 and 3,845,810 to Gerding both describe a rotatable drum which is liquid cooled internally having a spider carrying rollers in radial slots which roll on the drum's inner surface by centrifugal force. The spider rotates at an appropriate speed such that the cooling liquid is thrown against the drum's inner surface by centrifugal force. These patents also state that the action of the rollers on the drum's inner surface breaks up incipient film boiling.
U.S. Patent 4,074,750 to Beghin discloses an internally cooled roll having two coaxial trunnions and a cylindrical body. The internally cooled roll could have a plurality of cylindrical longitudinal conduits evenly spaced about the axis of the cylindrical body in an annular arrangement with a tubular conduit located in each longitudinal conduit, or could have a singular annular longitudinal conduit having either tubular conduits evenly spaced within the singular annular longitudinal conduit or a single tube coaxially located within the singular annular longitudinal conduit, or could have a cylindrical longitudinal conduit with a tubular conduit coaxially located within the cylindrical longitudinal conduit. Cooling fluid is circulated through the conduits and the means for supplying the cooling fluid to one of the conduits and removing the cooling fluid from the other conduit include a fluid collector element in a passage in one of the trunnions.
U.S. Patent 3,757,847 to Sofinsky et al. describes a roll mould with a cooling system. Each roller has a shaft within a sleeve, a central bore, circular passageways and radial passageways. A header is provided in the central bore to divide the radial passageways into separate sections; one part for supplying cooling fluid and the other part for draining cooling fluid. The patent states that uniform heat removal from the hot metal over the length and height of the crystallization zone is achieved since coolant of the same temperature and in a constant amount is supplied to the cooling system.
U.S. Patent 2,790,216 to Hunter discloses a cooling system in rollers for the continuous casting of metal. Each roller has a core and a shell over the core. The core's surface has longitudinal channels whose ends are in communication with annular grooves and radiating passages intersect the annular grooves. The roller has a central bore, which is counterbored. Through the counterbore there is extended a conduit forming an inner passageway communicating with the central bore. Coolant flows through the counterbore and then proceeds in an outwardly direction through one set of radiating passages to the longitudinal channels. The coolant flow continues through the longitudinal channels returning through another set of radiating passages to the central bore, the conduit extending through the counterbore and a return pipe.
British Patent Specification 897,412 discloses a cooling system for casting rolls. Each casting roll has a core and over the core is a sleeve. Within the core are two longitudinal inlet channels and two longitudinal outlet channels. The longitudinal inlet and longitudinal outlet channels communicate with the core's periphery by means of small channels. These small channels open into annular grooves at the core's periphery. Coolant enters through the longitudinal inlet channels and flows upwardly to the annular grooves through the connecting smaller channels. The coolant then flows through the annular grooves and exits the annular grooves through those smaller channels which connect to the longitudinal outlet channels.
British Patent Specification 1,319,185 describes an internally cooled roller. Each casting roller is hollow and is mounted on two hollow shafts. The first hollow shaft serves as an inlet for the coolant and the second hollow shaft serves to discharge the coolant. The first hollow shaft communicates with a plurality of pipes radially disposed in the roller. Each radially disposed pipe communicates with a horizontal pipe appropriately spaced within the roller. The horizontal pipes have nozzles to spray the coolant at the roller's inner surface. The coolant is discharged from the casting roller by the second hollow shaft. The second hollow shaft extends centrally within the casting roller and has perforations through which the coolant can be discharged.
The objective of the present invention is to provide a new and improved roll caster for use in an apparatus for the continuous casting of metal in strip form whereby substantially isothermal cooling is provided to the casting roll's shell.
Two important objectives for a cooling system for casting rolls are: first, to reduce the thermal axial camber on the casting rolls resulting from the molten metal contacting the casting rolls; and second, to provide substantially uniform heat removal from the molten metal as it contacts the casting rolls to promote the production of high quality metal in strip form. Thermal axial camber may cause variations in the casting gap, that is the gap between a pair of parallel casting rolls in a roll caster, which may result in unacceptable gauge variations in the cooled and solidified metal. In the present invention, substantially isothermal cooling is provided to the casting roll's shell so the casting roll's shell surface temperature will be substantially constant and little or no thermal axial camber will be present in either the roll necks or the shell of the casting roll. Thus, thermal axial camber on the casting roll is greatly reduced, the casting gap remains substantially constant, and substantially uniform heat removal from the molten metal contacting the casting roll's shell is provided. Prior art cooling rolls have not as efficiently or effectively met these objectives since either temperature variations are present around the casting roll's shell caused by the coolant temperature's rise as the coolant circulates through the cooling system or thermal axial camber develops in the casting roll's necks or shell caused by one-half on the casting roll running at a warmer temperature than the other one-half of the casting roll as the coolant circulates through the cooling system. In some cases, both temperature variations around the casting roll's shell and thermal axial camber are present during operation of the cooling system. An important advantage of the isothermal shell cooling method of the present invention is that the rate of coolant flow and the degree of temperature rise of the coolant as it circulates through the cooling system are not considered to be critical.
According to the invention there is provided a casting roll for use in a roll caster for continuous casting of metals in strip form, said casting roll comprising a roll and a shell therearound characterized by at least one axial feed bore for supplying cooling fluid into the roll and at least one axial drain bore for draining cooling fluid from the roll, a plurality of parallel annular grooves around the roll for flow of cooling fluid between the roll and the shell, a plurality of radial feed passageways connecting each axial feed bore to the annular grooves and a plurality of radial drain passageways connecting each axial drain bore to the annular grooves with each of said radial feed and radial drain passageways servicing at least one groove and with the radial feed passageway connected to the groove on the generally opposite side of the roll from the radial drain passageway for the same groove and with each radial feed passageway extending radially outwardly from an axial feed bore in a direction generally opposite from each immediately adjacent radial feed passageway and with each radial drain passageway extending radially outwardly from an axial drain bore in a direction generally opposite from each immediately adjacent radial drain passageway to provide substantially isothermal cooling of said shell.
The invention also provides a roll caster for continuous casting of metals in strip form which comprises a pair of such casting rolls spaced slightly apart to receive and carry another metal therebetween as it is cooled to solidify the same. Radial is defined as radiating from the axial feed bore or axial drain bore, respectively, to the annular grooves.
In a preferred embodiment of the present invention, each radial feed passageway and each radial drain passageway services two adjacent annular grooves and each casting roll has two axial feed bores and two axial drain bores which alternate in servicing the radial feed passageways and the radial drain passageways along the length of the roll.
To assist in understanding the present invention, the attached drawings described below are illustrative of the preferred embodiment.

Figure 1 is an elevational view of a single casting roll of a roll caster constructed in accordance with the principles of the invention having a portion of the sleeve removed.
Figure 2 is a cross-section taken along line 2-2 of Fig. 1.
Figure 3 is a cross-section taken along line 3-3 of Fig. 1.
Figure 4 is a fragmentary top view of a portion of the left portion of Fig. 1 where the sleeve has been broken away to expose the roll of the roll caster of Fig. 1. Figure 4 is shown proportionately larger than Figs. 1, 2 and 3 for ease of viewing.
Figures 5 and 6 are schematics showing the flow of cooling fluid to, through and from adjacent pairs of adjacent annular grooves.

Fig. 1 shows a single casting roll 10 of a roll caster of the present invention in an elevational view. Preferably, at least one pair of casting rolls would be used in the practice of the present invention. The casting roll is comprised of a roll 12 having a sleeve 14 over the roll 12. The roll 12 has roll neck portion 16 disposed at each end thereof. A portion of the sleeve 14 has been removed in Fig. 1 to show a portion of roll 12. A plurality of parallel annular grooves 18 are provided in the outer surface of roll 12. Preferably, the parallel annular grooves 18 are evenly spaced along the length of roll 12; and, preferably, each of the grooves 18 has substantially the same dimensions.
Figs. 2 and 3 are cross-sections taken along lines 2-2 and 3-3, respectively, of Fig. 1. The cross-sections show roll 12 with axial feed bores 20a and 20b and axial drain bores 22a and 22b preferably generally disposed about and evenly spaced around the central area of roll 12. The preferred embodiment of a casting roll of the present invention shown in the drawings has two axial feed bores 20a and 20b and two axial drain bores 22a and 22b. However, a casting roll may have one or more axial feed bores and one or more axial drain bores in other embodiments of the present invention, if appropriate. Also, it is preferred that the number of axial feed bores equal the number of axial drain bores in a casting roll of the present invention; and it is preferred that each of both the axial feed bores and the axial drain bores has substantially similar dimensions for length and for diameter.
Radial feed passageways 24a and 24b and radial drain passageways 26a and 26b are shown in Figs. 2 and 3. It is preferred that each of both the radial feed passageways and the radial drain passageways has substantially similar dimensions for length and for diameter. In the preferred embodiment of the invention, each radial feed passageway connects two adjacent annular grooves to an axial feed bore; and each radial drain passageway connects two adjacent annular grooves to an axial drain bore. Radial feed passageway 24a and radial drain passageway 26a shown in Fig. 2 service adjacent annular grooves 18a and 18b shown in Fig. 1; and radial feed passageway 24b. and radial drain passageway 26b shown in Fig. 3 service adjacent annular grooves 18c and 18d of Fig. 1. While in the preferred embodiment of the invention each radial feed passageway and each radial drain passageway service two adjacent annular grooves, each of said radial feed and radial drain passageways could service only one annular groove or could service three or more adjacent annular grooves in other embodiments of the invention, if appropriate.
As illustrated in Figs. 2 and 3, the axial feed bores 20a and 20b alternate in servicing the radial feed passageways; and the axial drain bores 22a and 22b alternate in servicing the radial drain passageways. In this preferred embodiment of the present invention, the alternating pattern for the axial feed bores and the axial drain bores to service the radial feed passageways and the radial drain passageways, respectively, would continue along the length of roll 12. In another embodiment of the invention, now shown in the drawings, if, for example, only a single axial feed bore and only a single axial drain bore are utilized to service the radial feed passageways and the radial drain passageways, respectively, an alternating pattern for servicing the radial feed passageways and the radial drain passageways clearly would not be present. However, in other embodiments of the invention, if more than two axial feed bores are utilized to service the radial feed passageways, preferably the axial feed bores would alternate in servicing the radial feed passageways along the length of the roll, or if more than two axial drain bores are utilized to service the radial drain passageways, preferably the axial drain bores would alternate in servicing the radial drain passageways along the length of the roll.
In Fig. 2, the bottom surface of annular groove 18b is indicated by dotted line 28; and annular groove 18b is not visible in this cross-section except in the general areas of the intersections of radial feed passageway 24a and radial drain passageway 26a with annular groove 18b. Likewise, in Fig. 3 the bottom surface of annular groove 18d is indicated by dotted line 30; and annular groove 18d is not visible in this cross-section except in the general areas of the intersections of radial feed passageway 24b and radial drain passageway 26d with annular groove 18d. The arrows in Figs. 2 and 3 indicate the direction of flow of the cooling fluid.
Fig. 4 is a refractory top view of a portion of roll 12 of Fig. 1 showing radial feed passageway 24a servicing adjacent annular grooves 18a and 18b and radial drain passageway 26b servicing adjacent annular grooves 18c and 18d. The arrows in Fig. 4 indicate the direction of flow of the cooling fluid.
Considering Figs. 2, 3 and 4, it can be seen that the radial feed passageway connects to two adjacent annular grooves on the generally opposite side of roll 12 from the radial drain passageway for the same two adjacent annular grooves. In other embodiments of the invention, regardless of whether a radial feed passageway and a radial drain passageway service a singular annular groove or two or more adjacent annular grooves, the radial feed passageway connects to the annular groove or adjacent annular grooves on the generally opposite side of the roll from the radial drain passageway for the same annular groove or adjacent annular grooves.
Also, as can be seen from Figs. 2 and 3, radial feed passageway 24a is generally disposed on the opposite side of roll 12 from adjacent radial feed passageway 24b; and radial drain passageway 26a is generally disposed on the opposite side of roll 12 from adjacent radial drain passageway 26b. Along the entire length of the roll, each radial feed passageway extends radially outwardly from an axial feed bore in a direction generally opposite from each immediately adjacent radial feed passageway and each radial drain passageway extends radially outwardly from an axial drain bore in a direction generally opposite from each immediately adjacent radial drain passageway in the preferred embodiment or in any other embodiment of the present invention to provide the desired isothermal cooling.
Figs. 5 and 6 schematically show preferred flow patterns for cooling fluid through adjacent annular grooves 18a and 18b and through adjacent annular grooves 18c and 18d. Fig. 5 shows the flow of cooling fluid from axial feed bore 20a through radial feed passageway 24a, adjacent annular grooves 18a and 18b and radial drain passageway 26a into axial drain bore 22a. Fig. 6 shows the flow of cooling fluid from axial feed bore 20b through radial feed passageway 24b, adjacent annular grooves 18c and 18d, and radial drain passageway 26b into axial drain bore 22b. The arrows indicate the direction of flow of the cooling fluid.
From Figs. 5 and 6 it can be seen that the flow of cooling fluid through annular grooves 18a and 18b is opposite to the flow of cooling fluid through annular grooves 18c and 18d. The flow of cooling fluid through annular grooves 18a, b, c and d shows the alternating, opposing flow pattern for the cooling fluid present in a casting roll of the present invention. In the preferred embodiment of the present invention, the flow pattern commences in these two adjacent pairs of adjacent annular grooves and continues throughout the entire length of the roll. Therefore, in the preferred embodiment of a casting roll of the present invention, the flow of cooling fluid through each pair of adjacent annular grooves serviced by the same radial feed passageway and by the same radial drain passageway would be opposite to the flow of the cooling fluid through an adjacent pair of adjacent annular grooves serviced by an adjacent radial feed passageway and by an adjacent radial drain passageway. This alternating, opposing flow pattern is achieved by alternating the placement of the radial feed passageways from generally one side of the roll to the other along the length of the roll such that each radial feed passageway extends radially outwardly from an axial feed bore in a direction generally opposite from each immediately adjacent radial feed passageway and by alternating the placement of the radial drain passageways generally from one side of the roll to the other along the length of the roll such that each radial drain passageway extends radially outwardly from an axial drain bore in a direction generally opposite from each immediately adjacent radial drain passageway, as well as by having the radial feed passageway servicing two adjacent annular grooves connect on the generally opposite side of the roll from the radial drain passageway servicing the same annular grooves.
With regard to other embodiments of the invention, since a single radial feed passageway and a single radial drain passageway could possibly service a single annular groove or two or more adjacent annular grooves, it would by apparent to those skilled in the art that in a casting roll constructed in accordance with the principles of this invention, an alternating, opposing flow pattern for the cooling fluid would be present in the annular grooves along the entire length of the roll in other embodiments of the invention. Since, in other embodiments of the present invention, the flow of cooling fluid through the annular groove or grooves, as the case may be, serviced by the same radial feed passageway and by the same radial drain passageway would be opposite to the flow of cooling fluid through the adjacent annular groove or grooves, as the case may be, serviced by an adjacent radial feed passageway and by an adjacent radial drain passageway.
This alternating, opposing flow pattern promotes the isothermal cooling of the casting roll's shell by providing a means for substantially uniform heat removal from the shell of the casting roll. The alternating placement of the radial feed passageways and the radial drain passageways along the length of the roll, as previously described, allows relatively cool coolant entering the annular grooves or groove, as the case may be, to then circulate next to and opposite to relatively warmer coolant circulating through the adjacent annular grooves or groove, as the case may be, to substantially uniformly balance along the casting roll's shell the heat being transferred from the molten metal. By balancing the heat transfer in this manner, the temperature of the casting roll's shell will be substantially uniform both around the shell's circumference and across the roll's width.
The balancing of the heat transferred through the casting roll is also enhanced by the placement in the casting roll in accordance with the invention of the radial feed passageways carrying the relatively cool entering coolant and the radial drain passageways carrying the warmer exiting coolant. By having a radial feed passageway carrying the cool entering coolant servicing the annular groove or grooves, as the case may be, on the generally opposite side of the roll from a radial drain passageway carrying the warmer exiting coolant from the same annular groove or grooves and by having the radial feed passageways alternate with the radial drain passageways along both sides of the roll along the length of the roll, it can be seen that the cooler entering coolant flowing in the radial feed passageways substantially balances throughout the casting roll the heat flow from the warmer exiting coolant flowing in the radial drain passageways to promote substantially uniform heat distribution throughout the casting roll.
In the preferred embodiment of the invention, the balancing of the heat transferred through the casting roll is further enhanced by the use of two axial feed bores and two axial drain bores which alternate in servicing the radial feed passageways and the radial drain passageways, respectively, along the length of the roll. By arranging the two axial feed bores and the two axial drain bores in the casting roll as shown in Figs. 2 and 3 such that the axial feed bores and the axial drain bores are generally disposed about and evenly spaced around the central area of the casting roll with the axial feed bores being generally disposed diagonally opposite from each other and the axial drain bores being generally disposed diagonally opposite from each other, the cooler entering coolant flowing in the axial feed bores helps to substantially balance the heat flow from the warmer exiting coolant flowing in the axial drain bores thereby assisting with the substantially uniform distribution of heat through the casting roll.
Thus, the present invention's capability to substantially uniformly balance and distribute the heat being transferred from the molten metal throughout the casting roll provides substantially isothermal cooling of the casting roll's shell.

Claims

1. A casting roll for use in a roll caster for continuous casting of metals in strip form, said casting roll comprising a roll and a shell therearound characterized by at least one axial feed bore for supplying cooling fluid into the roll and at least one axial drain bore for draining cooling fluid from the roll, a plurality of parallel annular grooves around the roll for flow of cooling fluid between the roll and the shell, a plurality of radial feed passageways connecting each axial feed bore to the annular grooves and a plurality of radial drain passageways connecting each axial drain bore to the annular grooves with each of said radial feed and radial drain passageways servicing at least one groove and with the radial feed passageway connected to the groove on the generally opposite side of the roll from the radial drain passageway for the same groove and with each radial feed passageway extending radially outwardly from an axial feed bore in a direction generally opposite from each immediately adjacent radial feed passageway and with each radial drain passageway extending radially outwardly from an axial drain bore in a direction generally opposite from each immediately adjacent radial drain passageway to provide substantially isothermal cooling of said shell.

2. A casting roll according to claim 1, characterized by the fact that the roll has two axial feed bores which alternate in servicing the radial feed passageways and two axial drain bores which alternate in servicing the radial drain passageways along the length of the roll.

3. A casting roll according to claim 2, characterized by the fact that the two axial feed bores and the two axial drain bores are generally disposed about and evenly spaced around the central area of the roll with the axial feed bores being generally disposed diagonally opposite from each other and with the axial drain bores being generally disposed diagonally opposite from each other.

4. A casting roll according to any one of the preceding claims, characterized by the fact that each radial feed passageway and each radial drain passageway services two adjacent annular grooves.

5. A roll caster for continuous casting of metals in strip form comprising a pair of parallel casting rolls according to any one of the preceding claims spaced apart slightly to receive and carry molten metal therebetween as it is cooled to solidify the same.