US20090050285A1

US20090050285A1 - Impact pad

Info

Publication number: US20090050285A1
Application number: US11/841,145
Authority: US
Inventors: Ronald Barrett
Original assignee: North American Refractories Co
Current assignee: North American Refractories Co
Priority date: 2007-08-20
Filing date: 2007-08-20
Publication date: 2009-02-26

Abstract

An impact pad for receiving a stream of liquid metal. The impact pad has a bottom wall with an upper surface against which the liquid metal is intended to impact. A side wall having an inner surface extends in an upward direction from the periphery of the bottom wall. The bottom wall and side wall define a metal receiving chamber having an open upper end. A plurality of spaced-apart cavities is formed in the inner surface of the side wall, the upper surface of the bottom wall or both.

Description

FIELD OF THE INVENTION

The present invention relates to a tundish impact pad, and more particularly to a tundish impact pad that reduces splashing and rebound due to a misaligned, incoming metal stream.

BACKGROUND OF THE INVENTION

Liquid metal, in particular liquid steel, is often poured from one vessel to another. For example, liquid metal may be poured from a furnace into a ladle, and then from a ladle into a tundish and from a tundish into a mold. When liquid is poured into the tundish from a ladle, it is normally poured into the tundish through an outlet in the bottom of the ladle. The stream of metal from the ladle is metered by a valve and the outlet stream may be enclosed in a ceramic tube, called a ladle shroud, which extends downward from the ladle bottom.
A typical tundish is a trough or box-shaped vessel having a generally horizontal or flat bottom with vertically arranged walls. The stream of metal poured from the ladle, i.e., incoming ladle stream or flow, enters the tundish and impacts the tundish bottom and spreads in all directions. It is known to use tundish impact pads to try to control an incoming ladle stream to reduce erosion of the tundish lining and to effect certain desirable flow patterns in the tundish. In this respect, prior patents purport to control the flow of the molten metal to prevent entrainment of slag and inclusion particles, to prevent disturbance of smooth metal flow, and further, to prevent thermal inhomogeneity, i.e., short circuit flow and different liquid metal residence times.
Most conventional impact pads have tried to minimize turbulence and effect better flow patterns through the use of baffle systems, or ledges or channels integrated in the design of the impact pad.
The present invention provides an impact pad having an inner surface designed to disperse the energy of an incoming metal stream to reduce the likelihood of lateral splashing and rebounding.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided an impact pad for receiving a stream of liquid metal. The impact pad has a bottom wall with an upper surface against which the liquid metal is intended to impact. A side wall having an inner surface extends in an upward direction along the periphery of the bottom wall. The bottom wall and side wall define a metal receiving chamber having an open upper end. A plurality of spaced-apart cavities is formed in the inner surface of the side wall.
In accordance with another aspect of the present invention, there is provided an impact pad as described above, further comprising spaced-apart cavities formed in the inner surface of the bottom wall.
In accordance with another aspect of the present invention, there is provided a method of forming an impact pad, comprising the steps of:
providing a cup-shaped outer mold defining an inner cavity;
providing a forming mandrel having a plurality of spaced-apart projections formed on the outer surface thereof;
positioning the forming mandrel within cavity, the mandrel being dimensioned to form a gap between the mandrel and inner surfaces of the mold;
filling the gap with a refractory castable to form a refractory shape; and
separating the forming mandrel from the mold after the refractory has hardened to release a cast refractory shape, the cast refractory shape having a cup-shape with a plurality of spaced-apart cavities along the inner surface thereof.
An advantage of the present invention is an impact pad for receiving a stream of molten metal.
Another advantage of the present invention is an impact pad as described above that dampens and contains a stream of molten metal.
Another advantage of the present invention is an impact pad as described above which reduces the likelihood of lateral splashing of incoming metal stream.
These and other advantages will become apparent from the following description of a preferred embodiment taken together with the accompanying drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may take physical form in certain parts and arrangement of parts, a preferred embodiment of which will be described in detail in the specification and illustrated in the accompanying drawings which form a part hereof, and wherein:

FIG. 1 is a cross-sectional view of a tundish, showing an impact pad according to the present invention on the bottom thereof;

FIG. 2 is a perspective view of the impact pad shown in FIG. 1, illustrating a preferred embodiment of the present invention;

FIG. 3 is a partially-sectioned, top plan view of the impact pad shown in FIG. 2;

FIG. 4 is a partially-sectioned, side elevational view of the impact pad shown in FIG. 2;

FIG. 5 is an enlarged, sectional view of a portion of the side wall of the impact pad shown in FIG. 2, showing cavities formed along the inner surface thereof;

FIG. 6 is a sectional view showing a variation of a cavity configuration shown in FIG. 5;

FIG. 7 is a sectional view showing another variation of a cavity configuration shown in FIG. 5;

FIG. 8A is a perspective view of a cavity formed in the inner surface of a side wall of an impact pad, illustrating another embodiment of the present invention;

FIG. 8B is a sectional view of the cavity shown in FIG. 8A;

FIG. 9 is a perspective view of a cavity formed in the inner surface of a side wall of an impact pad, illustrating yet another embodiment of the present invention;

FIG. 10 is a sectional view of a cavity formed in the inner surface of a side wall of an impact pad illustrating still another embodiment of the present invention;

FIG. 11 is a perspective view of a mold, mandrel and pattern layers used for forming an impact pad as shown in FIG. 2;

FIG. 12 is a partially-sectioned, side elevational view of an impact pad illustrating an alternate embodiment of the present invention;

FIG. 13 is a partially-sectioned, side elevational view of an impact pad illustrating yet another embodiment of the present invention; and

FIG. 14 is a partially-sectioned, side elevational view of an impact pad illustrating still another embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

Referring now to the drawings wherein the showings are for the purpose of illustrating preferred embodiments of the invention only, and not for the purpose of limiting same, FIG. 1 shows a conventional tundish 10 for use in a steel making process. Tundish 10 has an outer metallic shell 12 and an inner refractory lining 14. A ladle shroud 16 is positioned above tundish 10 to direct a stream 18 of molten metal from a ladle (not shown) into tundish 10 to form a molten metal bath 22. Tundish 10 includes a pair of well blocks 24 to allow molten metal from bath 22 to enter molds (not shown), as is conventionally known.
An impact pad 30, illustrating a preferred embodiment of the present invention, is positioned within tundish 10 below shroud 16 to receive stream 18. As best seen in FIGS. 2-4, impact pad 30 is generally cylindrical in shape and has a bottom wall 32 having a lower surface 34 (best seen in FIG. 4) and an upper, impact surface 36 adapted to receive stream 18 of molten metal. In the embodiment shown, bottom wall 32 has a flat, generally planar, upper, impact surface 36. A side wall 42 projects upwardly from the periphery of bottom wall 32. Side wall 42 has a cylindrical outer surface 44 and a generally cylindrical, inner surface 46 that is symmetrical about an axis “A” that extends generally perpendicular to upper, impact surface 36. Bottom wall 32 and side wall 42 together define an interior cavity or chamber 48 having an upper opening 49.
A plurality of spaced-apart cavities 52 is formed along inner surface 46 of side wall 42. A plurality of spaced-apart cavities 54 is formed along upper impact surface 36 of bottom wall 32. In the embodiment shown, cavities 52 and 54 have like dimensions and configurations. Only cavity 52 shall be described in detail, it being understood that, for the embodiment shown, such description applies equally to cavity 54. In the embodiment shown, cavity 52 is generally cylindrical in shape. More specifically, cavity 52, best seen in FIG. 5, has a generally cylindrical side portion 52 a and a flat bottom portion 52 b. Side portion 52 a is connected to bottom portion 52 b by a radiused or contoured corner 52 c. In one embodiment of the present invention, cavity 52 is dimensioned wherein cylindrical portion 52 a has a diameter “D” of about 1 inch. Cavity 52 has a depth “d” equal to about ½ inch. It is contemplated that the depth of cavity 52 (and cavity 54) may vary, as illustrated in FIG. 6, that shows a deeper cavity 52′. It is also contemplated that cavity 52 may have a depth less than that shown in FIG. 5. Cavity 52 (and cavity 54) may have a diameter “D,” ranging from about ¼ inch to about 3 inches, and a depth “d,” ranging from about ¼ inch to about 2 inches. A spacing “S” between adjacent cavities 52 (and cavities 54) ranges from about 1/32 inch to about 2 inches.
Based on the foregoing, cavities 52 are dimensioned and are of such numbers to produce a “cavity density” of between 6 cavities 52 and 1,764 cavities 52 per square foot of surface area of surface 46 of side wall 42. Similarly, cavities 54 are dimensioned and are of such numbers to produce a “cavity density” of between 6 cavities 54 and 1,764 cavities 54 per square foot of surface area of upper impact surface 36 of bottom wall 32.
Each cavity 52 preferably defines a surface opening in surface 46 of side wall 42 ranging between 0.049 in²(D=¼ inch) and 7.069 in²(D=3 inches). Similarly, each cavity 54 in upper impact surface 36 of bottom wall 32 preferably defines a surface opening in surface 46 of side wall 42 ranging between 0.049 in²(D=/4 inch) and 7.096 in²(D=3 inches).
FIGS. 1-4 show impact pad 30 having cavities 52, 54 of like size and configuration. It is contemplated that cavities 52 may be of different sizes and/or different configurations. In this respect, an impact pad 30 may have cavities 52 that have a number of different sizes, i.e., diameters “D” and depth “d.” Similarly, cavities 54 may be comprised of a number of different sizes, i.e., diameters “D” and depth “d.”
Still further, while cavities 52 and 52′ have generally cylindrical shapes, it is contemplated that the cavities in side wall 42 and bottom wall 32 may be comprised of other geometric shapes. By way of example and not limitation, FIG. 7 shows a semi-spherical cavity 52″. FIGS. 8A and 8B show a cylindrical cavity 62 without contoured corners. FIG. 9 shows a quadratic cavity 72, and FIG. 10 shows a conical cavity 82. As will be appreciated, other shapes, such as elliptical shapes or parabolic shapes may find advantageous application in forming cavities 52, 54 in bottom wall 32 and side wall 42.
Referring now to FIG. 11, a method of forming impact pad 30 is illustrated. FIG. 11 shows a mold 110 with a bottom wall 112 having a flat, upper surface 114. A cylindrical side wall 116 extends upwardly from bottom wall 112. Side wall 116 has a cylindrical inner surface 118. Mold 110 defines a cylindrical cavity 122 that is symmetrical about an axis A. A mandrel 130 is shown above mold 110. Mandrel 130 is cylindrical in shape and has a cylindrical outer surface 132 and a flat, bottom end surface (not shown). Mandrel 130 is symmetrical about axis A and is adapted to be movable along axis A to a position wherein the bottom end of mandrel 130 is spaced from surface 114 of mold 110. Mandrel 130 is dimensioned such that an annular gap is defined between outer surface 132 of mandrel 130 and inner surface 118 of mold 110 when mandrel 130 is positioned within cavity 122 of mold 110. Pattern layers 142, 144 are provided to cover respectively, cylindrical outer surface 132 and bottom end surface of mandrel 130. In the embodiment shown, pattern layer 142 is a rectangular sheet dimensioned to wrap around cylindrical outer surface 132 of mandrel 130, as illustrated in FIG. 11. A plurality of spaced-apart projections or protrusions 146 is formed along one surface of pattern layer 142. In the embodiment shown, projections 146 are generally cylindrical in shape with rounded contoured ends. Pattern layer 144 is circular in shape and includes a plurality of spaced-apart projections 148 on one surface thereof. In the embodiment shown, projections 148 are generally similar in shape to projections 146. Pattern layers 142, 144 are respectfully secured to cylindrical outer surface 132 and bottom end surface of mandrel 130 with projections 146, 148 extending outwardly from mandrel 130. In the embodiment shown, double-sided adhesive strips 152 are used to attach pattern layers 142, 144 to mandrel 130.
Pattern layers 142, 144 may be formed of a resilient, flexible polymer material, such as by way of example and not limitation, rubber. In one embodiment of the present invention, Bubble Wrap® air cellular cushion sheets, manufactured by Sealed Air Corporation of Saddlebrook, N.J., are used to form pattern layers 142, 144. In the embodiment heretofore described, Bubble Wrap® cushion sheets having a bubble diameter of about 1¼ inches and a bubble height of about ½ inch are used.
With pattern layers 142, 144 attached to mandrel 130, mandrel 130 is positioned within mold 110 with layer 144 on the bottom end surface of mandrel 130 spaced from surface 114 of bottom wall 112 of mold 110, and with a uniform, annular gap defined between pattern layer 142 on mandrel 130 and inner surface 118 of side wall 116 of mold 110.
As will be appreciated, the space between mandrel 130 and mold 110 defines a mold cavity having the shape of impact pad 30. A refractory castable is prepared and poured into the cavity between mandrel 130 and mold 110. Impact pad 30 may be formed of many different types of refractory materials, but in a preferred embodiment, it is formed of a high-alumina refractory manufactured and sold by North American Refractories Co., Pittsburgh, Pa. under the trade designation HP-CAST ULTRA. The refractory castable is allowed to set and harden within the mold. Once the refractory castable is hardened, mandrel 130 is separated from mold 110 and the molded impact pad 30 is removed from mold 110.
Referring now to the operation of impact pad 30, as indicated above, impact pad 30 is disposed within tundish 10 so as to be disposed below stream 18 of molten metal to receive the same. Impact pad 30 is dimensioned such that the opening of impact pad 30 is larger than the diameter of stream 18. As stream 18 impacts upper surface 36 of bottom wall 32, molten metal is directed into cavities 54. Upon engaging cavities 54, the molten metal is turned and directed outwardly in all directions. In this respect, vertical stream 18 hitting cavities 54 is analogous to water from a faucet hitting a bowl. The outward flow of the molten metal from one cavity 54 is dampened by similar outward flow of the molten metal from adjacent cavities 54. In addition, the outward flow from one side of a cavity is dampened by outward flow from the opposite side of a cavity. The net result is a dampening effect as each cavity 54 distributes and diverts a portion of incoming stream 18. Cavities 52 and side wall 42 produce a similar effect in causing flow thereagainst to be distributed outwardly from an axis of a cavity 52. In other words, the metal is re-directed and turned by the cavities, as illustrated by the arrow in FIG. 5. The multiple cavities 52, 54 within impact pad 30 constantly re-direct flow impinging thereon thereby producing a dampening and cushioning effect on stream 18. Even as metal begins to fill impact pad 30, cavities 54 above the level of the molten metal continue to capture metal directed thereagainst and retard the flow of re-directed metal. In this respect, rather than having a smooth, cylindrical inner surface along which molten metal is directed and can easily flow, the plurality of cavities 52 or inner surface 46 of side wall 42 creates turbulence and distortion of the stream thereby cushioning and reducing the flow of the metal stream along inner surface 46 of impact pad 30.
The foregoing description is a specific embodiment of the present invention. It should be appreciated that this embodiment is described for purposes of illustration only, and that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. For example, it is contemplated that cavities of different sizes and geometric shapes could be formed in an impact pad. Moreover, the shape of an impact pad is not limited to a cylindrical shape as shown in the drawings. It is contemplated that an impact pad 30, as described above, may include drain holes 162, as illustrated in FIG. 12. In addition, it is contemplated that the upper surface of the bottom wall of the impact pad may have, for example, a concave or convex shape with cavities formed therein, as shown in FIGS. 13 and 14. It is also contemplated that the side walls may be angled relative to the incoming stream of metal. Likewise, a rectangular impact pad with a plurality of cavities along the inner surfaces thereof is also contemplated. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.

Claims

1. In an impact pad for receiving a stream of liquid metal, said impact pad having a bottom wall with an upper surface against which said liquid metal is intended to impact, a side wall having an inner surface extending in an upward direction from the periphery of said bottom wall, said bottom wall and side wall defining a metal receiving chamber having an open upper end, the improvement comprising:

a plurality of spaced-apart cavities formed in one of the following, the inner surface of said side wall, the upper surface of said bottom wall or the inner surface of said side wall and the upper surface of said bottom wall.

2. An impact pad as defined in claim 1, wherein said cavities are generally cylindrical in shape.

3. An impact pad as defined in claim 1, wherein said cavities are generally spherical in shape.

4. An impact pad as defined in claim 1, wherein said cavities are generally conical in shape.

5. An impact pad as defined in claim 1, wherein said cavities in said side wall and said bottom wall have like configurations.

6. An impact pad as defined in claim 1, wherein said impact pad has an outer surface that is generally cylindrical in shape.

7. An impact pad as defined in claim 1, wherein said upper surface of said bottom wall is flat.

8. An impact pad as defined in claim 1, wherein said metal receiving chamber is cylindrical in shape.

9. An impact pad as defined in claim 1, wherein said cavities have a density ranging between about 6 cavities per square foot and about 1,764 cavities per square foot.

10. An impact pad as defined in claim 1, wherein said bottom wall is generally concave.

11. An impact pad as defined in claim 1, wherein said bottom wall is generally convex.

12. An impact pad as defined in claim 1, wherein said side wall includes a drain opening therethrough.

13. A method of forming an impact pad, comprising the steps of:

providing an outer mold defining an inner cavity;

providing a forming mandrel having a plurality of spaced-apart projections formed on the outer surface thereof;

positioning said forming mandrel within said inner cavity, said mandrel dimensioned to form a gap between said mandrel and an inner surface of said mold;

filling said gap with a refractory castable to form a refractory shape; and

separating said forming mandrel from said mold after said refractory has hardened to release a cast refractory shape, said cast refractory shape having a cup-shape with a plurality of spaced-apart cavities along the inner surface thereof.

14. A method of forming an impact pad as defined in claim 13, wherein said forming mandrel is cylindrical in shape and has a removable outer layer having said projections thereon.

15. A method of forming an impact pad as defined in claim 14, wherein said projections on said outer layer are semi-spherical in shape.

16. A method of forming an impact pad as defined in claim 15, wherein said outer layer is comprised of Bubble Wrap®.

17. A method of forming an impact pad as defined in claim 16, wherein said outer mold is generally cup-shaped.