WO2008116055A1

WO2008116055A1 - Crack resistant plate

Info

Publication number: WO2008116055A1
Application number: PCT/US2008/057638
Authority: WO
Inventors: Patrick King
Original assignee: Vesuvius Crucible Company
Priority date: 2007-03-22
Filing date: 2008-03-20
Publication date: 2008-09-25

Abstract

A crack resistant valve plate for use in a slide gate valve is configured so that stresses induced by clamping and/or driving the plate are concentrated toward the bore to counteract the expansion at the bore. The plate has a working end and a shutoff end; the bore is placed closer to the working end. The working end and shutoff end both contain an arc having its center within the bore.

Description

Docket No. 1537

TITLE

[0001] Crack Resistant Plate

BACKGROUND OF THE INVENTION

(1) Field of the Invention

[0002] This invention generally relates to valve plates for use in slide gate valves for controlling a flow of molten metal, and is specifically concerned with a valve plate that is resistant to cracks caused from thermomechanical stresses.

(2) Description of Related Art including information disclosed under 37 CFR 1.97 and 1.98.

[0003] Slide gate valves are commonly used to control a flow of molten metal in steel making and other metallurgical processes. Such valves generally comprise a support frame, an upper stationary valve plate having an orifice in registry with a tundish or ladle nozzle for conducting a flow of molten metal, and a throttle plate likewise having a metal conducting orifice that is slidably movable under the stationary valve plate. In slide gate valves used in conjunction with continuous casting molds, a lower stationary valve plate is provided beneath the movable throttle plate which likewise has a flow conducting orifice that is substantially aligned with the orifice of the upper stationary plate. The rate of flow of molten metal is dependent upon the degree of overlap of the orifice of the slidably movable throttle plate with the orifice of the upper stationary plate. The movable throttle plate is sometimes longer than the stationary throttle plate in order to give it the capacity of throttling the flow of molten metal from both the front and back edges of its own orifice, as well as the ability to shut off the flow altogether by bringing its orifice completely outside of any overlap with the orifices of the stationary plate. Typically, the throttle plate is slidably manipulated between the stationary plates by means of a hydraulic linkage. [0004] The throttle plate and the stationary plate are mounted in respectively a lower indentation and an upper indentation, each of these plates resting in an indentation Docket No. 1537

through a surface that becomes its support surface and cooperating with the other plate through a surface that becomes its sliding or working surface. [0005] Both the throttle plate and the stationary plates of such slide gate valves are formed from heat and erosion resistant refractory materials, such as aluminum oxide, alumina-carbon, zirconium oxide. However, despite the heat and erosion resistance of such refractory materials, the severe thermomechanical stresses that they are subjected to ultimately cause some degree of cracking to occur. For example, in steel making, each valve plate is subjected to temperatures of approximately 1600 degrees C. in the area immediately surrounding its flow-conducting orifice, while its exterior edges are experiencing only ambient temperature. The resulting large thermal gradient creates large amounts of thermomechanical stress as the area of each plate immediately surrounding its orifice expands at a substantially greater rate than the balance of the plate. These stresses cause cracks to form which radiate (outwardly) from the outside toward the orifice of the plate. If nothing is done to contain the spread of these cracks, they can extend all the way to the orifice of the plate, causing it to break.

[0006] To prevent the spreading of such cracks and the consequent breakage of the valve plates, various solutions have been developed in the prior art. These include the use of clamping mechanisms to supply pressure to the plate to counter the spread of cracking, and the development of plates with various shapes.

SUMMARY OF THE INVENTION

[0007] Generally speaking, the invention is a crack resistant valve plate for use in a slide gate valve.

[0008] The invention relates to a plate in which stresses induced by clamping and/or driving the plate are concentrated toward the bore to counteract the expansion at the bore.

[0009] The invention relates thus to a refractory plate for a slide gate valve which may be circumscribed by an elongated rectangle R having two elongated sides parallel to the direction of its elongation, and two shortened sides or ends perpendicular to the direction of its elongation. The rectangle R has a longitudinal axis, which is defined as its longest symmetry axis. The longitudinal axis may coincide with the sliding trajectory of the plate. It is however to be clearly understood that this plate may be Docket No. 1537

slid in a gate valve according to a direction which does not coincide with the longitudinal axis of the refractory plate.

[0010] The plate contains a bore extending from one plane of the elongated rectangle R to the opposite plane. The bore is offset towards one end of rectangle R. The end of rectangle R (a first shortened side) towards which the bore is offset is designated the working end. The plate has a working end adjacent to the working end of rectangle R. The end of rectangle R (a second shortened side) away from which the bore is offset is designated the throttling end or shutoff end. The plate has a throttling end or shutoff end adjacent to the throttling end or shutoff end of circumscribing rectangle R. The plate has sides adjacent to the respective sides of the circumscribing rectangle R.

[0011] The size and shape of the plate are based on the maximum design bore diameter for the plate (D) and the stroke designed into the system in which the plate is to be used. The stroke would typically be in the range of 1.5 D to 2.5 D, inclusive. The stroke of the slide gate valve represents the displacement of the refractory plate from the fully open position of the valve to a position, at the end of the sliding trajectory, at which the valve is fully closed, designated the shutoff position. The distance from the longitudinal axis to each side of the plate may be within the range of 1.4 D to 1.6 D, inclusive, for example, 1.5 D. The distance from the center of the bore to the working end may be within the range of 1.9 D to 2.1 D, inclusive, for example, 2.0 D. The portion of the plate between the bore and the working end allows for erosion on the edge of the bore closest to the working end of the plate. The distance from the center of the bore to the throttling end or shutoff end may be the length of the stroke plus a length of 1.4 D to 1.6 D, inclusive, such as 1.5 D. [0012] In one embodiment of the invention, flow alteration configurations to address plugging utilize a bore displaced toward the shutoff direction of the sliding gate valve, as shown in U.S. Patent No. 6,783,038, which is incorporated by reference. This displacement may be within the range of 0.15 D to 0.45 D, inclusive, for example, 0.25 D or 0.35 D.

[0013] Clamping forces are compressive forces on the plate exerted by a constraining device in contact with the ends of the plate. These forces act perpendicularly to the contact points on the ends of the plate. Driving forces are forces exerted by driving the plate along its sliding trajectory. In the configuration in which the sliding trajectory coincides with the longitudinal axis of the plate, and the bore is disposed Docket No. 1537

symmetrically about the longitudinal axis of the plate, the driving forces are directed perpendicularly to the contact points of the driving members. In the configuration in which the ends of the plate are defined as arcs centered on the center of the bore, all of the clamping forces are directed to the center of the bore. In a configuration in which the working end is shaped so that the radii of the arc is displaced from the center of the bore by a distance of 0.35 D or less in the shutoff direction, and the shutoff end is defined as an arc centered on the center of the bore, the focal points of radii of both ends are within the bore. The intersections of the sides of the plate with the ends of the plates may be provided with transition curves, these transition curves may be configured such that they are defined by transition radii. This facilitates manufacture of the plate and any plate containment. The refractory plate may be encased in a steel can, or a steel band may be applied to the plate. [0014] Articles of the invention may be refractory articles, and may be manufactured from compositions containing Alumina, Magnesia, Zirconia to which graphite, tar, resin, and other materials known in the art may be added singly or in combination to impart desirable properties. Pressures at or above 10,000 psi may be used to press articles of the invention. Subsequently, articles of the invention may be heat-treated; this heat-treating may include firing.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0015] Figs. 1 - 4 are top plan views of an article of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0016] With reference now to FIG. 1 , wherein like numbers designate like components throughout the figures, the invention relates to a plate 10 for use in controlling the flow of molten metal, circumscribed by rectangle R, having opposite sides 12 and 14, and a longitudinal axis 16. A working end 20 has a working end arc radius 22. The working end arc radius 22 is centered on longitudinal axis 16. Working end 20 is tangent to one end of rectangle R. A working end focus latitudinal axis 24 is a line perpendicular to the longitudinal axis 16 at the point of intersection of the working end arc radius 22 with the longitudinal axis 16. A throttle end 30 has a throttle end arc radius 32. The throttle end arc radius 32 is centered on longitudinal Docket No. 1537

axis 16. Throttle end 30 is tangent to the other end of the rectangle R. A throttle end focus latitudinal axis 34 is a line perpendicular to the longitudinal axis 16 at the point of intersection of the arc radius 32 with the longitudinal axis 16. A bore 40, circumscribed by a circle having a diameter D, is disposed on the face of article 10 so that longitudinal axis 16 passes through bore 40; in the embodiment shown, longitudinal axis bisects bore 40. A bore latitudinal axis 42 is a line perpendicular to longitudinal axis 16 that passes through the center of bore 40. In the embodiment shown in Fig. 1 , bore latitudinal axis 42 is collinear with throttle end focus latitudinal axis 34. When the plate is in the shutoff position, a shutoff portion 50 represents the portion of plate 10 that occupies the volume that was occupied by the bore 40 when plate 10 was in the fully open position. In the embodiment depicted in Fig. 1, the distance along longitudinal axis 16 from the center of bore 40 to working end 20 is 2.0 D, the distance along longitudinal axis 16 from the center of shutoff portion 50 and throttle end 30 is 1.5 D, the distance between longitudinal axis 16 and side 12 is 1.5 D, the distance between longitudinal axis 16 and side 14 is 1.5 D, and the distance between bore latitudinal axis 42 and working end focus latitudinal axis 24 is 0.45 D. [0017] FIG. 2 depicts plate 10 having opposite sides 12 and 14, and longitudinal axis 16. Working end 20 has working end arc radii 22. Working end arc radii 22 are perpendicular to the tangent of the arc described by working end 20. A working end focus latitudinal axis 24 is a line perpendicular to the longitudinal axis 16 at the point of intersection of working end arc radii 22 with the longitudinal axis 16. A throttle end 30 has throttle end arc radii 32. Throttle end arc radii 32 are perpendicular to the tangent of the arc described by throttle end 30. Throttle end focus latitudinal axis 34 is a line perpendicular to the longitudinal axis 16 at the point of intersection of the throttle end arc radii 32 with the longitudinal axis 16. Bore 40 circumscribed by a circle having a diameter D is disposed on the face of article 10 so that longitudinal axis 16 passes through bore 40; in the embodiment shown, longitudinal axis bisects bore 40. A bore latitudinal axis 42 is a line perpendicular to longitudinal axis 16 that passes through the center of bore 40. In the embodiment shown in Fig. 2, bore latitudinal axis 42 is collinear with throttle end focus latitudinal axis 34. When the plate is in the shutoff position, a shutoff portion 50 represents the portion of plate 10 that occupies the volume that was occupied by the bore 40 when plate 10 was in the fully open position. Docket No. 1537

[0018] FIG. 3 depicts an embodiment of plate 10 in which, with respect to the embodiment depicted in Fig. 1, the location of bore 40 has been shifted by 0.25 D in the direction of throttle end 30. An unshifted bore position 60 and an unshifted bore latitudinal axis 62 are depicted in the figure.

[0019] FIG. 4 depicts plate 10 having opposite sides 12 and 14, longitudinal axis 16, working end 20 and throttle end 30. Bore 40 circumscribed by a circle having a diameter D is disposed on the face of article 10 so that longitudinal axis 16 passes through bore 40; in the embodiment shown, longitudinal axis bisects bore 40. A bore latitudinal axis 42 is a line perpendicular to longitudinal axis 16 that passes through the center of bore 40. When the plate is in the shutoff position, a shutoff portion 50 represents the portion of plate 10 that occupies the volume that was occupied by the bore 40 when plate 10 was in the fully open position. In the embodiment depicted, the corners formed by the intersections of sides 12 and 14 with working end 20 and throttle end 30 have been joined by transition curves defined by transition radii. [0020] Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. The present invention is not to be limited by the specific disclosure herein.

Claims

Docket No. 1537CLAIMS I claim:

1. A refractory plate for a slide gate valve, comprising a shape circumscribed by a rectangle having two elongated sides, a first shortened side, a second shortened side and a longitudinal axis passing through a pouring hole circumscribed by a circle having a diameter D; the plate having a working end located adjacent to the first shortened side; the plate having a shutoff end located adjacent to the second shortened side; the plate having sides located to the elongated sides; the bore placed closer to the working end; the working end forming an arc having its center within the bore; the shutoff end forming an arc having its center within the bore.

2. The plate of claim 1, wherein the shutoff end forms an arc having its center at the center of the bore.

3. The plate of claim 1, wherein the working end forms an arc having its center at the center of the bore.

4. The plate of claim 1, wherein the working end forms an arc having its center displaced from the center of the bore by a value equal to either, or within the range between, 0.15 D and 0.45 D.

5. The plate of claim 1, wherein the working end forms an arc having its center displaced from the center of the bore by 0.35 D.

6. The plate of claim 1, wherein the intersections of the sides and the working end, and the intersections of the sides and the shutoff end, are joined by transition curves.

7. The plate of claim 6, wherein a transition radius defines the transition curves.

8. The plate of claim 1, wherein the plate is asymmetrical with respect to the longitudinal axis. Docket No. 1537

9. The plate of claim 1, wherein the distance from the center of the bore to the working end is equal to either, or lies between, 1.9 D and 2.1 D.

10. The plate of claim 1, wherein the distance from the center of the bore to the working end is equal to 2.0 D.

11. The plate of claim 1, wherein the distance from the longitudinal axis to each side of the plate is equal to either, or lies between, 1.4 D and 1.6 D.

12. The plate of claim 1, wherein the distance from the longitudinal axis to each side of the plate is equal to 1.5 D.

13. A sliding gate valve adapted to receive a refractory plate as described in clam 1.