Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D41/00—Casting melt-holding vessels, e.g. ladles, tundishes, cups or the like
  • B22D41/14—Closures
  • B22D41/22—Closures sliding-gate type, i.e. having a fixed plate and a movable plate in sliding contact with each other for selective registry of their openings
  • B22D41/28—Plates therefor

Definitions

• 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 assembly that is resistant to cracks caused from thermal stresses.
• Slide gate valves are commonly used to control a flow of molten metal in steel making and other metallurgical processes.
• Such valves 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.
• 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 usually longer than the stationary throttle plates 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.
• the throttle plate is slidably manipulated between the stationary plates by means of a hydraulic linkage.
• Both the throttle plate and the stationary plates of such slide gate valves are formed from heat and erosion resistance refractory materials, such as aluminum oxide, alumina-carbon, zirconium oxide.
• heat and erosion resistance refractory materials such as aluminum oxide, alumina-carbon, zirconium oxide.
• each valve plate is subjected to temperatures of approximately 2900° 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 mechanical stress as the area of each plate immediately surrounding its orifice expands at a substantially greater rate than the balance of the plate.
• clamping systems have been developed that comprise a frame having screw-operated wedges which engage corners of the plate that have been truncated in an angle that is complementary to the angle of the wedges. While such frame and wedge type clamping mechanisms constitute a clear advance over the mere use of steel banding around the perimeter of the plates, the inventors have further noted at least two shortcomings with this design that prevent it from achieving its full, crack-retarding potential. In all of the variations of this design that the applicants are aware of, the angle of each of the truncated corners with respect to either the lengthwise or widthwise edge of the plate is the same, regardless of the position of the orifice along the longitudinal center line of the plate.
• a final shortcoming associated with such valve plates in general is their lack of any optimization of the length of the truncated corners, or the lengths and widths of the plate with respect to the diameter of its orifice. While the corner lengths should be of a certain minimal size in order to avoid the production of unwanted localized mechanical stresses in these regions of the plate, they should not be made overly large, either.
• the invention is a crack resistant valve plate assembly for use in a slide gate valve that overcomes or at least ameliorates all of the disadvantages associated with the prior art.
• the assembly comprises a refractory valve plate having a orifice for conducting molten metal that is positioned along a center line of the plate, and truncated corners for focusing a clamping force toward the center line in the vicinity of the orifice to prevent the formation and spreading of cracks therein, wherein the angular orientation of each of the truncated corners varies with the position of the orifice along the center line.
• the assembly further comprises a clamping frame for applying the required clamping force to each of the truncated corners.
• each of the truncated corners is orthogonal to a line falling within an angle whose vertex is defined by a point tangent to the orifice diameter.
• One side of the angle is defined by a line extending from the tangent point across the center line, and through a point where converging edges of the plate would intersect but for the presence of the truncated corner.
• the other side of the angle is defined by a line extending from the tangent point across the center line, and through an intersection of lines drawn parallel to the converging plate edges that are spaced from these edges a distance equal to the orifice diameter.
• each of the truncated corners is orthogonal to a line extending between the tangent point to an orifice having the maximum diameter that the plate can operate with, across the center line, and through an intersection of lines drawn parallel to the converging plate edges that is spaced from the edges a distance equal to one-half of a maximum orifice diameter.
• each of the corners is truncated along a line that is orthogonal to the aforementioned line and which extends through an intersection of one of the parallel lines and the lengthwise edge of the plate.
• the plate assembly may be movable along an axis within the slide gate valve that is coincident with its longitudinal center line, or it may be stationary with respect to the slide gate valve.
• the plate includes an orifice along one of its center lines, and truncated corners cut in accordance with the same geometric formula as previously described with respect to the first valve plate.
• a clamping frame is provided for applying the required clamping force onto the truncated corners.
• the plate of the movable assembly is preferably rectangular in shape, having a length of between amount 5.5 and 5.75 orifice diameters, and a width of between about 2.9 and 3.1 orifice diameters.
• the length and width of the movable plate are 5.66 and 3.0 orifice diameters, respectively.
• the plate of the stationary assembly is likewise preferably rectangular in shape, having a length of between about 4.5 and 4.75 orifice diameters, and a width of between about 2.9 and 3.1 orifice diameters.
• the length and width of the stationary valve plate is 4.66 and 3.0 orifice diameters, respectively.
• valve plate assembly of the invention provides a crack-resistant valve plate having shut-off and front and back throttling capabilities with a minimum amount wasted ceramic material.
• Figure 1 is a schematized, cross-sectional side view of a slide gate valve installed in a tundish that utilizes valve plate assembly of the invention
• FIG. 2 is a top plan view of the throttle plate assembly of the invention
• Figure 3 is a top plan view of the lower stationary plate assembly of the invention
• Figures 4 through 10 are bottom plan views of the plate used in the lower stationary plate assembly of the invention, illustrating a preferable method of proportioning this plate, and how the angles of the truncated corners are determined;
• Figures 11, 12, and 13 are top plan view of the plate used in the throttle plate assembly, illustrating a preferable method of proportioning this plate, and how the angles of its truncated corners are determined;
• Figure 14 is a top plan view of the upper stationary plate superimposed over the throttle plate in a shut-off position
• Figure 15 is the same top plan view of the plates illustrated in Figure 14 wherein the throttle plate has been longitudinally slid into a back throttling position with respect to the stationary top plate.
• valve 1 includes both movable and stationary valve plate assemblies 1 for use in a slide gate valve 2 of the type used to regulate a flow of molten steel or other metal from a tundish 3.
• the slide gate valve 1 is secured onto a mounting plate 5 which in turn is connected to the tundish shell 7 by a mounting structure not illustrated.
• Valve 1 includes a nozzle 9 formed from a ceramic material having a funnel-shaped bore 10 for directing a cylindrically-shaped flow of molten metal out of the tundish 3.
• the nozzle 9 is mechanically mounted in the bottom wall of the tundish 3 by way of a packing of heat resistant, particulate ramming material 11.
• the principal purpose of the valve plate assembly 1 of the invention is to modulate the flow of molten metal exiting the bore 10 of the nozzle 9.
• the invention includes upper and lower stationary plate assemblies 13 and 17, with a slidably movable throttle plate assembly 23 sandwiched therebetween.
• the upper stationary plate assembly 13 includes a stationary plate 14 of ceramic material having a circular orifice 15 for conducting a flow of molten metal from the bore 10.
• the lower stationary plate assembly 17 likewise has a stationary plate 18 of refractory material with an orifice 19 that is the same size as, and is concentrically aligned with the orifice 15 of the upper stationary plate 14.
• both the upper and lower stationary plates 14, 18 have the same length and width.
• the tube fixture 20 is mounted on the lower surface of the lower stationary plate 18 which may be used, for example, for directing a flow of molten steel into a continuous casting mold.
• the tube fixture 20 includes a tube mounting plate 21 that is integrally connected to a tube shroud 22.
• a mounting assembly (not shown) secures the plate 21 of the tube fixture 20 into the position illustrated in Figure 1.
• the tube fixture 20 isolates the modulated flow of liquid metal exiting the valve plate system 1 from ambient air in order to prevent ambient oxygen from reacting with the molten metal.
• the throttle plate assembly 23 is slidably mounted between the upper and lower stationary plate assemblies 13 and 17.
• the throttle plate assembly 23 likewise includes a plate 24 formed of a ceramic material having an orifice 25 which may be circular, and the same diameter as the orifice 15 of the upper stationary plates 14.
• the orifice 18 of the lower stationary plate 18 is larger than that of the orifices 25 and 15 to avoid trapping steel in the throttle plate 24 during a shut-off operation.
• the throttle plate 23 is longer than the upper and lower stationary plates 13 and 17.
• the throttle plate 24 is slidably and reciprocally moved by means of a hydraulic linkage (not shown) along an axis A that corresponds with the longitudinal center lines of the plates 13, 17, and 24.
• truncated corners 30a-d are provided on the generally rectangularly shaped throttle plate 24 in order to focus clamping forces near the orifice 25 along the lengthwise center line 92 (which is collinear with the axis A shown in Figure 1).
• a hoop of steel banding 31 is provided in tension around the perimeter of the throttle plate 24 in order to enhance the integrity of the plate.
• Both the plate 24 and banding 31 are surrounded by a clamping frame 33 that applies substantial compressive clamping forces to the aforementioned truncated corners 30a- d.
• the clamping frame 30 has a stationary clamping member 35 with opposing clamping feet 37a,b that are aligned at the same angle with respect to the truncated corners 30a,b on the left side of the plate 34 to avoid the generation of localized stresses.
• Clamping frame 33 further includes a pair of spaced apart, parallel frame legs 39 to which a movable clamping assembly 41 is attached.
• the assembly 41 includes a movable clamping member 43 likewise having opposing clamping feet 45a,b that are disposed at the same angle as the truncated corners 30c,d present on the right side of the plate 24.
• This operation in turn causes the clamping feet 37a,b of the stationary clamping member 35 to apply clamping pressure onto the truncated corners 30a,b on the left side of the plate 24.
• the lower plate assembly 17 includes a lower stationary plate 18 having an orifice 19 which may be circular and identical in diameter to the orifice 25 of the throttle plate 24.
• the stationary plate 18 has truncated corners 54a- d for focusing a clamping force along the longitudinal center line 70 of the plate near the vicinity of the orifice 19.
• the lower stationary plate assembly 17 further includes a clamping frame 58 for applying clamping forces onto the truncated corners 54a-d.
• the clamping frame 58 includes a rectangularly shaped frame assembly 59 (illustrated in phantom) that contains, on its left end, a stationary clamping member 60 having clamping feet 62a,b which work in the same fashion as the feet 37a,b described with respect to clamping member 35.
• the frame assembly 59 further contains, on its right side, a movable clamping member 64.
• Clamping member 64 includes clamping feet 66a,b which may be compressively engaged against the truncated corners 54c,d of the plate 18 by the turning of a clamping screw 68 that operates in the same fashion as the previously described screw 49.
• angles ofthe truncated corners 54a-d and the clamping feet 62a,b and 68a,b are the same so that broad area contact is made between these components, thereby avoiding localized stresses which could cause unwanted cracks in the plate 18 in the corner locations.
• Figure 4 illustrates how the lengthwise and widthwise dimensions of the preferred embodiments of each of the stationary plates 14 and 18 are determined as a function of the maximum diameter D of the orifice 19 that the plates can (as a practical matter) operate with.
• the length of the upper half of the plate 18 from the center point of the orifice 19 must be able to accommodate a shut-off stroke Ss of at least 1.5 orifice diameters. While it is theoretically possible for a shut-off stroke to be only a little larger than a single orifice diameter, such a sizing scheme would not take into consideration the substantial elongation that occurs of the orifice 19 along the lengthwise center line 70 of the plate 18 due to erosion.
• the shut-off stroke must be at least 1.5 orifice diameters.
• Such a stroke would position the orifice 25 of the throttie plate 24 in the position illustrated in phantom on top of the plate 18.
• it is necessary to have an additional length D of stationary plate beyond the center point of the orifice 25, making the total length of the plate 18 from the center of the orifice 19 to be 1.5D + ID 2.5 D.
• the length of the bottom half of the plate 18 is .66D (which allows the throttle plate orifice 25 ' to arrive in the maximum back throttling position illustrated in Figure 4) plus an additional length of plate equal to 1.5 orifice diameters so that the stationary plate 18 provides sufficient support for the throttle plate 24 within the structure of the slide gate valve 2.
• the first step of this angle determimng method is the provision of construction lines along the inner perimeter of the plate 18 that are parallel but spaced apart from the outer edges of this plate a distance of one-half of an orifice, or .5D. These construction lines are illustrated in Figure 5 as lines 72a-d. These lines intersect at corners 74a-d as shown.
• Figure 6 illustrates the next step of the angle determining method.
• lines 78a-d are drawn between the corners 74a-d of the construction lines, and tangent points 76a- d with an orifice 19 of maximum diameter, wherein each of the lines 78a-d crosses the lengthwise center line 70.
• the next step of the method determines not only the angle, but the length of the truncated corners.
• lines 80a-d are drawn which are both perpendicular to tangent lines 78a-d and which intersect with the horizontal construction lines 72b,d. These lines 80a-d are used as guides for a corner cutting operation of the rectangular refractory plate 18 to arrive at truncated corners 54a-d.
• Figure 6 also illustrates a more generalized method whereby the angle of the truncated corners 54a-d may be determined.
• construction segments 82a,b are drawn at right angles to the length and width of the plate to form a square as shown.
• the angle of the truncated corners 54a-d is any line falling within the angle B defined at its vertex by tangent point 76c, and on one of its sides by a line extending through the intersection 84 of the aforementioned segments 82a,b and on its other side by the intersection 86 of the converging lengthwise and widthwise edges of the plate 18 prior to truncation.
• Any of the lines within the angle B may be used to create a truncation angle by the construction of a line at right angle to any one of these family of lines. Each such right-angled line should extend through the intersection of the horizontal construction lines 72b,d so that the length of the truncated corners may be determined as well as the angle.
• Figure 8 illustrates a plate 18 whose corners 54a-d have been truncated in accordance with the more specific embodiment ofthe method, wherein lines at right angles to the tangent lines 78a-d are used to determine the specific truncation angles. After the corners have been so truncated, they are preferably radiused at their ends as 90 as is illustrated in Figure 9. Such rounding of the corners helps to prevent the generation of localized stresses in the corner regions of the plate 18.
• Figure 10 illustrates the final product of the proportioning and corner truncation method of the invention.
• the 3.0D width of the plate 18 allows it to accommodate the tube fixture 20, which has a mounting plate 21 which is 2.5 orifice diameters in both length and width.
• FIGS 11 through 13 illustrate a method that may be used to determine both the length and width proportions of the throttle plate 24 relative to maximum orifice diameters D, as well as the angle that the corners 30a-d should be truncated.
• the shut-off stroke requires, as it did in the case of the stationary plate 18, at least one and one-half maximum orifice diameters or 1.5D.
• the angle of the truncated corners 30a-d of the throttle plate 24 are determined by precisely the same methodology as described with respect to the stationary plate 18 (and in particular, Figure 6). Accordingly, there is no need to repeat the details of this step of the method. It should be noted that, in addition to the specific method described with respect to Figure 6 wherein the angle of the truncated corners is determined by lines constructed at right angles to the previously described tangent lines 78a-d, the generalized method step described with respect to the upper right hand corner of the plate 18 in Figure 6 may also be applied to the corners of the throttie plate 24.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Casting Support Devices, Ladles, And Melt Control Thereby (AREA)
• Sliding Valves (AREA)

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Applications Claiming Priority (5)

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ID=27507846

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Citations (5)

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• 1995
  • 1995-08-02 ES ES95928161T patent/ES2163524T3/es not_active Expired - Lifetime
  • 1995-08-02 AT AT95928161T patent/ATE208241T1/de not_active IP Right Cessation
  • 1995-08-02 CZ CZ1998281A patent/CZ293025B6/cs not_active IP Right Cessation
  • 1995-08-02 CN CN95197962A patent/CN1104983C/zh not_active Expired - Lifetime
  • 1995-08-02 BR BR9510629-4A patent/BR9510629A/pt not_active IP Right Cessation
  • 1995-08-02 WO PCT/US1995/009495 patent/WO1997004904A1/en active IP Right Grant
  • 1995-08-02 CA CA002227535A patent/CA2227535C/en not_active Expired - Lifetime
  • 1995-08-02 SK SK128-98A patent/SK282940B6/sk unknown
  • 1995-08-02 EP EP95928161A patent/EP0842002B1/en not_active Expired - Lifetime
  • 1995-08-02 JP JP9507539A patent/JPH11512026A/ja active Pending
  • 1995-08-02 DE DE69523785T patent/DE69523785T2/de not_active Expired - Fee Related
• 1996
  • 1996-10-03 ZA ZA968327A patent/ZA968327B/xx unknown

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