WO2005059185A1

WO2005059185A1 - Temperature sensing stopper rod

Info

Publication number: WO2005059185A1
Application number: PCT/US2004/042405
Authority: WO
Inventors: Quentin K. Robinson; Yong Mook Lee; Michael Stephenson
Original assignee: Vesuvius Crucible Company
Priority date: 2003-12-16
Filing date: 2004-12-16
Publication date: 2005-06-30

Abstract

A stopper rod (20) according to the present invention comprises a body (22) having a distal end (28) designed to mate with a tundish nozzle, and having an inner wall (34) defining a axial channel (32) within the body (22). The stopper rod (20) further comprises in insert (36) disposed within the axial channel (32) and a temperature-sensing device (30) disposed within the insert (36).

Description

Temperature Sensing Stopper Rod. Specification.

Cross-reference to related applications.

[0001] This application claims the benefit under 35 U.S.C. §120 of the filing date of U.S. Provisional Application No. 60/529,837 filed December 16, 2003. Field of the invention.

[0002] The present invention generally relates to a stopper rod for use in a tundish for molten metal-producing applications. More specifically, the present invention relates to an improved stopper rod capable of sensing the temperature of the molten metal. Description of the related art.

[0003] In the processing and handling of molten metals, a metallurgical casting vessel, for example, a tundish, is used to transfer molten metal from a ladle to a casting operation. Typically, there is a tundish nozzle located at the bottom of the vessel through which the molten metal flows on its way to the casting operation. The flow of the molten metal through the tundish nozzle is most often regulated by the use of a stopper rod or plug that mates with the tundish nozzle. When the stopper rod is lowered into contact with the tundish nozzle, the flow of the molten metal is slowed or stopped. As the stopper rod is raised, the flow of the molten metal proceeds at an increasing rate through the tundish nozzle.

[0004] A common problem with the use of such stopper rods to regulate flow is that slag tends to build up around the rounded end or nose of the stopper rod. Such slag build-up can come between the stopper rod and the tundish nozzle, thus preventing full closure of the tundish nozzle. This leads to a situation where flow of the molten metal cannot be stopped until the tundish is emptied.

[0005] In order to prevent slag formation on the stopper rod, it is common to provide a flow of an inert gas, for example, argon, through the rounded end of the stopper rod. For example, U.S. Patent No. 4,691 ,901 to Dobner discloses a stopper rod having an axial gas passage though its center, and a gas permeable member in the rounded end. An inert gas flows through the axial gas passage, through the gas permeable member and out of the rounded end of the stopper rod. Likewise, U.S. Patent No. 5,361 ,825 to Lax et al. (the '"825 Patent") discloses a stopper rod having a central axial channel that is utilized to supply an inert gas to an opening in the rounded end for the purpose of preventing slag formation on the stopper rod.

[0006] it is advantageous for the operators of a molten metal-producing process to monitor the temperature of the molten metal in the tundish. Quite often, this is accomplished through the use of thermocouples located throughout the tundish. However, it is often very expensive and labor intensive to handle thermocouples located at the bottom of the tundish. It is also desirable to have an indication of the temperature of the molten metal as it leaves the tundish. To that end, the '825 Patent also discloses the placement of a thermocouple inside the stopper rod. In order to accommodate the thermocouple, a rib is formed on one side of the stopper rod. The axial channel that holds the thermocouple is located inside the rib. The purpose of the rib is to allow fast temperature response by the thermocouple as compared to the response experienced when the thermocouple is placed in the center of the rod. This increased response is attributed to the placement of the thermocouple closer to the molten metal than the center of the rod. The rib also shields the thermocouple from the flow of the inert gas. If the inert gas is permitted to flow in direct contact with the thermocouple, it can have the effect of cooling the thermocouple.

If this occurs, the thermocouple will indicate a temperature that is lower than the actual temperature. Therefore, in order to ensure that the thermocouple is providing an accurate reading, it is desirable to shield the thermocouple from the flow of the inert gas. However, the addition of the rib requires additional refractory material, which increases the cost of the stopper rod.

[0007] It is therefore desirable to produce a stopper rod for the regulation of the flow of molten metal out of a tundish, that has the capability of measuring the temperature of the molten metal.

The stopper rod desirably uses a minimum amount of refractory material, yet still provides a fast response by the thermocouple or other temperature sensing device.

Summary of the invention.

[0008] In order to achieve the listed objectives, a stopper rod for preventing the flow of molten metal through a tundish nozzle is provided. A stopper rod according to the present invention comprises a body having a proximal end and a distal end. It further comprises a nose on the distal end of the body and an axial channel within the body. Finally, a temperature sensing device is disposed within the axial channel; and a means for supplying gas from approximately the proximal end of the body to approximately the distal end of the body is provided.

[0009] In an alternate embodiment, a stopper rod for preventing the flow of molten metal through a tundish nozzle is provided. A stopper rod according to the present invention comprises a body having a proximal end and a distal end. It further comprises a nose on the distal end of the body and an axial channel within the body. Finally, a temperature sensing device is disposed within the axial channel and insert within the axial channel is provided.

Brief description of the several drawings.

[0010] FIG. 1 is a schematic illustration of a process for making molten metal in accordance with the present invention.

[0011] FIG. 2 is a cross-sectional view of a stopper rod in accordance with a first embodiment of the present invention.

[0012] FIG. 3 is a cross-sectional view of a stopper rod in accordance with an alternate embodiment of the present invention.

[0013] FIG. 4 is a cross-sectional view of a stopper rod in accordance with an alternate embodiment of the present invention.

[0014] FIG. 5 is a cross-sectional, cut-away view of a stopper rod in accordance with an alternate embodiment of the present invention.

Detailed description of the preferred embodiments. [0015] FIG. 1 schematically illustrates a portion of a metal production process, for example, a steel-making process. A tundish 2 is a metallurgical vessel that contains a volume of molten metal 4. The molten metal 4 is supplied to the tundish 2 by a plurality of ladles (not shown), and the tundish 2 contains the molten metal 4 until it is allowed to flow out of the tundish into a casting operation. At the bottom of the tundish 2 is a tundish nozzle 6 that is secured to an orifice in the bottom of the tundish 2. The tundish nozzle 6 facilitates the transfer of the molten metal 4 from the tundish 2 to the casting operation.

[0016] The flow of the molten metal 4 out of the tundish 2 and through the tundish nozzle 6 is regulated by a stopper rod 8. The stopper rod 8 is attached to a mechanism 10 that raises and lowers the stopper rod 8 into and out of the tundish nozzle 6. Typical mechanisms 10 and means for attaching them to a stopper rod 8 are well known to those of ordinary skill in the art. Any such mechanisms 10 and compatible means for attaching them may be used in connection with a stopper rod in accordance with the present invention.

[0017] FIG. 2 illustrates a stopper rod 20 in accordance with the present invention. The stopper rod 20 comprises a body 22. The stopper body 22 may be any shape, but preferably, the stopper body 22 is substantially cylindrical in shape. The stopper body 22 has a proximal end 24 and a distal end 26. The stopper body 22 preferably comprises a refractory material able to withstand the thermal shock and erosion that the stopper rod 20 will experience inside the tundish as it is exposed to the molten metal. Suitable refractory materials include alumina graphite, magnesia graphite, zirconia, silica graphite and spinel graphite, or any suitable combination of those materials. Preferably, the stopper body 22 comprises alumina graphite. [0018] The dimensions of the stopper body 22 will be determined by the specific application in which it is used. For example, a typical steel making application will require a stopper rod 20 having a length of approximately 300 mm to 2500 mm, and a total diameter of approximately 20 mm to 300 mm. However, it will be understood by those of ordinary skill in the art that the dimensions of the stopper rod 20 may vary to meet the specific requirements of the desired application and may depend upon the diameter of the tundish nozzle.

[0019] As also shown in FIG. 2, the distal end 26 of the stopper rod 20 is substantially rounded in shape. The rounded end 28 is sized and shaped to mate with the orifice at the bottom of the tundish such that, when the stopper rod 20 is lowered, the rounded end 28 of the stopper rod 20 forms a seal with the orifice sufficient to substantially prevent the flow of molten metal out of the tundish. The rounded end 28 of the stopper rod 20 will generally comprise the same material as the rest of the stopper body 22, but can also comprise other materials generally known in the art, depending on the operating conditions.

[0020] As discussed above, the proximal end 24 of the stopper rod 20 includes means 27 for attaching the stopper rod 20 to a mechanism suitable for raising and lowering the stopper rod 20. The means for attachment 27 may include, for example, a ceramic or metal nut, such as those disclosed in U.S. Patent Nos. 4,946,083 to Fishier, et al. and 5,851,414 to Ando, et al., the entire contents of which are hereby incorporated by reference. The means for attachment 27 also include a bore therethrough. The bore may provide space for a thermocouple and thermocouple wiring to pass through

[0021] The stopper rod 20 further comprises an axial channel 32 formed within the body 22 of the stopper rod 20. Preferably, the axial channel 32 is disposed along the center axis of the stopper rod 20. Alternatively, the axial channel 32 may also be disposed slightly off-center. The axial channel 32 is defined by an interior wall 34 of the body 22 of the stopper rod 20.

[0022] The stopper rod 20 further comprises an insert 36 disposed within the axial channel 32 of the stopper rod 20. The insert 36 is sized and shaped so as to fit within the axial channel 32.

The insert 36 may contain at least one bore therethough to accommodate the thermocouple 30.

The bore to accommodate the thermocouple 30 need not pass entirely through the insert 36.

Instead, the end 38 of the thermocouple 30 will sit within the bore, and will be held in place by the insert 36.

[0023] As discussed above, it is desirous for the thermocouple 30 to provide a response time that is as small as possible. In order to facilitate this, the insert 36 comprises a material having a relatively high thermal conductivity. The insert 36 may comprise graphite, silicon carbide, silicon nitride, magnesia graphite or alumina graphite, as well as other materials having similar thermal properties. Preferably, the insert 36 comprises graphite. In this way, the rate of heat transfer from the molten metal outside of the stopper rod 20, through the stopper rod 20, including the insert 36, to the thermocouple 30 is high when compared to the heat flow to a thermocouple disposed in the same location of a stopper rod made entirely of a low thermal conductivity material.

[0024] The insert 36 may be held in place within the axial channel 32 through the use of an adhesive material disposed between the interior wall 34 of the stopper rod 20 and the insert 36.

Acceptable adhesive materials include refractory mortars such as alumina, magnesia, zirconia, calcium oxide or silica. Alternatively, the insert 36 may be sized and shaped to fit snugly within the axial channel 32. Further, if materials such as graphite, alumina graphite or magnesia graphite are used in the insert 36, the insert 36 will expand when the stopper rod 20 is heated, thereby impinging itself upon the interior wall 34 of the stopper rod 20. In this way, the frictional forces between the insert 36 and the interior wall 34 of the stopper rod 20 will hold the insert 36 in place.

[0025] In one embodiment, the body 22 and the insert 36, may be made of the same high thermal conductivity material. In this embodiment, the high thermal conductivity material is preferably alumina graphite or magnesia graphite.

[0026] The insert 36 may be located anywhere along the length of the axial chamber 32 within the body 22 of the stopper rod 20. However, it is preferably located between the longitudinal mid-point of the stopper rod 20, and the end 39 of the axial chamber 32 within the body 22 of the stopper rod 20.

[0027] Attention is now drawn to an alternate embodiment illustrated in FIG. 3. it is noted that the reference numerals utilized in FIG. 2 will continue to indicate the same relative components in the figures for alternate embodiments, but increased by increments of 100. In the embodiment illustrated in FIG. 3, a means for supplying gas 140 from approximately the proximal end 124 of the body 122 to approximately the distal end 126 of the body 122 is provided. The inert gas is used to prevent slag build up around the rounded end 128 of the stopper rod 120, as described above. The means for supplying gas 140 may include any means known to those in that art that will deliver gas from an outside source to approximately the distal end 126 of the stopper rod 120. For example, suitable means include a supply pipe that runs approximately the length of the stopper rod and through the insert 136 (not shown), or a supply pipe that provides pressurized gas to the axial channel 132 in combination with a supply pipe 142 that passes through the insert 136 to supply the gas to the axial chamber at a point 144 below the insert 136, thereby supplying gas to the distal end 126, while at the same time, shielding the sensing tip 146 of the thermocouple 130 from the flow of the inert gas. [0028] In this embodiment, the rounded end 128 must also includes a means for allowing the inert gas to flow out of the stopper rod 120. The means for allowing the inert gas to pass out of the stopper rod 120 may include a porous material used as the material for the rounded end 128. The porous material may comprise any material or configuration known in the art. For example, the porous section may also comprise a section of porous material such as alumina, magnesia or zirconia. In such an embodiment, the inert gas simply flows through the natural passages formed in the material. Preferably, alumina is used as the porous material. [0029] Alternatively, as illustrated in FIG. 3, the means for allowing the inert gas to pass out of the stopper rod 120 may comprise at least one aperture or calibrated hole 148 in the rounded end 128 through which the inert gas may flow. Multiple apertures or holes 148 may be utilized to allow the inert gas to pass out of the stopper rod 120.

[0030] In an alternate embodiment illustrated in FIG. 4, a void is formed within the body 222 to accommodate an inert gas supply pipe 250 that serves as the means for supplying gas. In this embodiment, the supply pipe 250 provides the inert gas to the axial channel 232 at a location 244 beneath the insert 236. In this embodiment, the amount of processing needed to form the insert 236 is minimized, as a second bore within the insert 236 is not necessary. As discussed above with respect to the embodiment illustrated in FIG. 3, when the inert gas is supplied to the axial channel 232 at a location 244 beneath the insert 236, the inert gas may then flow through means 248 for allowing the inert gas to pass out of the stopper rod 220 located in the rounded end 228 of the stopper rod 220.

[0031] In an alternate embodiment illustrated in FIG. 5, the interior wall 334 of the stopper rod 320 protrudes out into the axial channel 332. The protrusion forms a shelf or a ledge 360 that is used to support the insert 336 and prevent it from moving further down the axial channel 332. In this embodiment, the ledge 360 may be used in addition to an adhesive material, as described above, to keep the insert 336 in place. Alternatively, the ledge 360 may be used in lieu of the adhesive material. [0032] In another alternate embodiment (not illustrated), an insert within the axial chamber is not used. Instead, the thermocouple simply sits within the axial chamber. In this case, the means for supplying gas from approximately the proximal end of the body to approximately the distal end of the body is still provided. In this embodiment, it is still desirable to shield the thermocouple from the flow of inert gas. Therefore, the use of a supply pipe is the preferable means for supplying gas from approximately the proximal end of the body to approximately the distal end of the body. Alternatively, the supply pipe may bypass most of the axial chamber, as done in the embodiment illustrated in FIG. 4.

[0033] As discussed above, the proximal end of the stopper rod includes means for attaching the stopper rod to the mechanism. The means for attachment may include, for example, a ceramic or metal nut, such as those disclosed in U.S. Patent Nos. 4,946,083 to Fishier, et al. and 5,851 ,414 to Ando, et al., the entire contents of which are hereby incorporated by reference. The means for attachment also include several bores therethrough. The bores may provide space for thermocouple wiring to pass through, or space for an inert gas supply pipe to pass through. The inert gas supply pipe is used to transfer the inert gas to the rounded end of the stopper rod. Alternatively, the supply pipe may enter the stopper rod though one of the side walls of the cylindrical body at a position that is close to the proximal end of the stopper rod. [0034] Obviously, numerous modifications and variations of the present invention are possible. It is, therefore, to be understood that within the scope of the following claims, the invention may be practiced otherwise than as specifically described

Claims

Claims.We claim:

1. A stopper rod comprising: a) a body having a proximal end and a distal end; b) a nose on the distal end of the body; c) an axial channel within the body; d) a temperature sensing device disposed within the axial channel; and e) a means for supplying gas from approximately the proximal end of the body to approximately the distal end of the body.

2. The stopper rod of claim 1 , further comprising an insert within the axial channel.

3. The stopper rod of claim 2, characterized in that the temperature sensing device is located at least partially within the insert.

4. The stopper rod of claims 1 to 3, characterized in that the axial channel is substantially centered about the central axis of the stopper rod.

5. The stopper rod of claims 1 to 4, characterized in that the means for supplying gas comprises a supply pipe.

6. The stopper rod of claims 2 to 5, characterized in that the insert comprises at least one bore therethrough.

7. The stopper rod of claim 6, characterized in that the supply pipe is at least partially located within the bore.

8. The stopper rod of claim 2, characterized in that the means for supplying gas is not located at all within the insert.

9. The stopper rod of claim 8, characterized in that the means for supplying gas comprises a supply pipe that is located within the body of the stopper rod and supplies gas to the axial channel at a point between the insert and the distal end of the stopper rod.

10. The stopper rod of claims 1 to 9, further comprising means for attaching the stopper rod to a mechanism for lifting and lowering the stopper rod.

11. The stopper rod of claims 1 to 10, characterized in that wherein the body of the stopper rod comprises a material selected from the group consisting of alumina graphite, magnesia graphite, zirconia, silica graphite, spinel graphite and combinations thereof.

12. The stopper rod of claim 11 , characterized in that the body of the stopper rod comprises alumina graphite.

13. The stopper rod of claims 2, 3 and 6 to 12, characterized in that the insert comprises a material selected from the group consisting of graphite, silicon carbide, silicon nitride, magnesia graphite and alumina graphite.

14. The stopper rod of claim 13, characterized in that the insert comprises graphite.

15. The stopper rod of claims 1 to 14, characterized in that the substantially rounded end includes a means for allowing the inert gas to flow out of the stopper rod.

16. The stopper rod of claim 15, characterized in that the means for allowing the inert gas to flow out of the stopper rod comprises a porous material.

17. The stopper rod of claim 16, characterized in that the porous material is selected from the group consisting of alumina, magnesia and zirconia.

18. The stopper rod of claim 17, characterized in that the porous material comprises alumina.

19. The stopper rod of claim 15, characterized in that the means for allowing the inert gas to flow out of the stopper rod comprises at least one aperture formed in the rounded end.

20. A stopper rod comprising: a) a body having a proximal end and a distal end; b) a nose on the distal end of the body; c) an axial channel within the body; d) a temperature sensing device disposed within the axial channel; and e) an insert within the axial channel.

21. The stopper rod of claim 20, further comprising a means for supplying gas from approximately the proximal end of the body to approximately the distal end of the body.

22. The stopper rod of claims 20 to 21 , characterized in that the temperature sensing device is located at least partially within the insert.

23. The stopper rod of claims 20 to 22, characterized in that the axial channel is substantially centered about the central axis of the stopper rod.

24. The stopper rod of claims 21 to 23, characterized in that the means for supplying gas comprises a supply pipe.

25. The stopper rod of claims 20 to 24, characterized in that the insert comprises at least one bore therethrough.

26. The stopper rod of claim 25, characterized in that the supply pipe is at least partially located within the bore.

27. The stopper rod of claim 21 , characterized in that the means for supplying gas is not located at all within the insert.

28. The stopper rod of claim 27, characterized in that the means for supplying gas comprises a supply pipe that is located within the body of the stopper rod and supplies gas to the axial channel at a point between the insert and the distal end of the stopper rod.

29. The stopper rod of claims 20 to 28, further comprising means for attaching the stopper rod to a mechanism for lifting and lowering the stopper rod.

30. The stopper rod of claims 20 to 29, characterized in that wherein the body of the stopper rod comprises a material selected from the group consisting of alumina graphite, magnesia graphite, zirconia, silica graphite, spinel graphite and combinations thereof.

31. The stopper rod of claim 30, characterized in that the body of the stopper rod comprises alumina graphite.

32. The stopper rod of claims 20 to 31 , characterized in that the insert comprises a material selected from the group consisting of graphite, silicon carbide, silicon nitride, magnesia graphite and alumina graphite.

33. The stopper rod of claim 32, characterized in that the insert comprises graphite.

34. The stopper rod of claims 20 to 33, characterized in that the substantially rounded end includes a means for allowing the inert gas to flow out of the stopper rod.

35. The stopper rod of claim 34, characterized in that the means for allowing the inert gas to flow out of the stopper rod comprises a porous material.

36. The stopper rod of claim 35, characterized in that the porous material is selected from the group consisting of alumina, magnesia and zirconia.

37. The stopper rod of claim 36, characterized in that the porous material comprises alumina.

38. The stopper rod of claim 34, characterized in that the means for allowing the inert gas to flow out of the stopper rod comprises at least one aperture formed in the rounded end.

39. The stopper rod of claim 20, further comprising a ledge formed from the body which supports the insert.