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
  • B22D41/30—Manufacturing or repairing thereof
• • 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 a process for repairing worn valve plates for use in slide gate valves for controlling a flow of molten metal, and specifically for a valve plate that is resistant to cracks caused from thermomechanical stresses.
• 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.
• 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 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.
• the throttle plate is slidably manipulated between the stationary plates by means of a hydraulic linkage.
• 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 through a surface that becomes its support surface and cooperating with the other plate through a surface that becomes its sliding or working surface.
• 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. However, despite the heat and erosion resistance of such refractory materials, the severe thermomechanical stresses that they are subjected to ultimately causes some degree of cracking to occur.
• each valve plate is subjected to temperatures of approximately 1600°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 imrnediately surrounding its orifice expands at a substantially greater rate than the balance of the plate.
• the clamping forces are not uniformly focused where the maximum amount of cracking occurs, i.e., in the vicinity of the orifice where the greatest amount of thermomechanical stresses are present.
• the applicants have observed that, generally, the angular orientation of the truncated corners in such plates does not optimally prevent the spreading of cracks, as previously thought.
• Such non-optimality results from the fact that crack formation is not uniformly distributed 360° around the orifice, but instead is biased along the longitudinal center line of all valve plates whether stationary or movable.
• Such an asymmetrical distribution of cracks around the plate orifices is believed to occur as a result of the longitudinal sliding action of the throttle plate across the faces of the stationary plates.
• the USP 5,626,164 discloses a crack resistant valve plate; the shape of said plate being designed to prevent the formation and spreading of cracks therein.
• This plate has an axis, and an orifice for conducting molten metal that is positioned along said axis, and truncated corners for focusing a clamping force toward said axis in the vicinity of said orifice, wherein each of said truncated corners is orthogonal to a line extending between a tangent point to said orifice, across said axis, and through an intersection of lines drawn parallel to converging plate edges that are spaced from said edges a distance equal to one- half of a width of said orifice.
• the International Patent application WOO 1/41956 discloses 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 or that at least equals the performance of the plate disclosed in USP 5,626,164.
• This document relates thus to a refractory plate for a slide gate valve which may be circumscribed by an elongated rectangle R having two sides parallel to the direction of its elongation.
• the rectangle R has a longitudinal axis which is defined as its longest symmetry axis and that will coincide with the preferential sliding trajectory of the plate. It is however to be clearly understood that this concept of preferential sliding trajectory is an intrinsic characteristic of the plate according to this document and that this plate may be slid in a gate valve according to a direction which is not the optimal or preferential one.
• the plate has an orifice - the pouring hole - for conducting molten metal. Most often said orifice is circular, more generally, it is circumscribed by a circle C of diameter ⁇ .
• the rectangle R is divided into four quadrants by two perpendicular lines intersecting at the center of the circle C, one of these lines extending in the middle between the parallel sides of the rectangle R.
• Each quadrant has intersecting diagonals: diagonals Dl, D3, D5, D7 joining the center of the circle C to the corners of the rectangle R and diagonals D2, D4, D6 and D8 joining adjacent intersections of the perpendicular lines intersecting at the center of the circle C with the sides of the rectangle R.
• the pouring hole may be centrally located in the plate, but most often, it is offset along the longitudinal axis so that throttling may be effected on a longer area.
• the pouring hole may also be slightly offset along an axis perpendicular to the longitudinal axis.
• the plate has angularly oriented edges - figuring the truncated corners of the rectangle R - for focusing clamping forces toward the vicinity of the orifice and toward the throttling area to prevent the formation and spreading of cracks therein.
• edges are defined as follows:
• a further advantage of this plate is that since very few cracks have been observed, the plate can be easily and quickly repaired after having been used. This is why the present invention concerns a process for repairing the used plates disclosed in the WO01/41956.
• the plate may be symmetrical with respect to its longitudinal axis, but in the preferred embodiment, the plate is not symmetrical with respect to the longitudinal axis. [0020] Thanks to this asymmetry, the plate may only be mounted in one position in the upper indentation and in one position in the lower indentation so that the support surface of the plate becomes its sliding or working surface when the plate passes from one position to the other in case recycling of the plates is desirable.
• the plate may have only four edges defined as above, but in order to avoid sharp angles, it may have more edges.
• the supplemental edges may (or not) be parallel and/ or perpendicular to the longitudinal axis.
• the plate it must be understood that it is not mandatory that the plate be polygonal. On the contrary, in case a clamping band is used around the plate, such clamping band can apply localized mechanical stresses - which could turn into cracks - onto the vertex defined by adjacent edges. Therefore, it is advantageous that the corner be rounded. [0023] In the preferred embodiment, only a portions of the edges satisfy the above definition. More preferably, the balance of the edges are comprised of curves joining the said edges portions and most preferably of transition radius of the said edges.
• a "plate” means also a plate of an assembly (fixed or removable) such as a monobloc nozzle plate, a monobloc inner nozzle plate, a monobloc tube plate, etc.
• the present invention concerns thus a process for repairing a worn refractory plate for a slide gate valve, which may be circumscribed by an elongated rectangle R having two sides parallel to the direction of its elongation and having a pouring hole positioned eccentrically in the middle between the parallel sides of the rectangle R and circumscribed by a circle C, the rectangle R being divided into four quadrants by two perpendicular lines intersecting at the center of the circle C, one of these lines extending in the middle between the parallel sides of the rectangle R, each quadrant having intersecting diagonals: Dl, D2 and D3, D4 and D5, D6 and D7, D8, respectively, wherein the corners of the rectangle R are cut away and replaced by inclined edges and the direction of at least a portion of those edges which are farest from the pouring hole deviate at maximum 5° from the direction of the diagonal which does not intersect the respective corner; and - the direction of the edges which are the closest to the pouring hole deviate at maximum 5° from one of the following directions
• the repairing process comprises a step of patching the cracks with mortar, preferably with a mortar capable of resisting the molten steel such as a phosphatic mortar, for example REFRACOL 620 PL 45.
• the excess of mortar is removed and the plate is allowed to dry. Drying can be carried out at ambient temperature for at least 4 hours, preferably at least 8 hours or in an oven for example at 120°C for 1 hour.
• the plate can then be cured. This curing step might be performed at 350-450°C during one hour. In a variant, curing can also occur during use of the repaired plate when it is subjected to high servicing temperatures.
• the plate is preheated for example at about 80-120°C, so that the mortar penetrates deep into the cracks and sets quickly.
• the mortar comprises a hardener so that, even at ambient temperature, it sets up quickly.
• the pouring orifice In case the pouring orifice is damaged, it can also be repaired.
• a tubular article such as a pipe, a rod or a mandrel
• Mortar (generally the same as the one used for the cracks) is patched around the tubular object, dried and eventually cured.
• a hole preferably coaxial with the original pouring orifice and having a diameter preferably at least 50% greater than the original diameter of the pouring orifice
• the insert is preferably made of a material at least as resistant as the original material of the plate. It may be convenient to provide the external walls of the insert with protrusions or holes so that the mortar and the insert are interpenetrated. It is also possible to use stepped insert shaped as two (or more) superimposed coaxial tubes having the same inner diameter but different external diameters.
• FIGS. 1 and 2 are top plan views of plates of WO-Al-01/41956.
• a valve plate 1 for use in a slide gate valve of the type used to regulate a flow of molten steel or other metal from a tundish to a mold or from a ladle to a tundish.
• the plate 1 has an orifice 3 for pouring the molten metal stream. Said pouring hole 3 is circumscribed by a circle C of center 4.
• Fig. 1 illustrates a plate with a non circular pouring hole and
• Fig. 2 shows a plate with a pouring hole 3 corresponding to the circle C.
• Rectangle R is visible on Figs. 1 and 2. Rectangle R circumscribes plate 1 and has its longest sides parallel to the sliding trajectory of the plate in the slide gate valve. For construction purpose, it is necessary to draw two perpendicular lines 5 and 6 which cross at the center 4 of the circle C and which are parallel to the short and long sides of the rectangle R. These lines define thus four quadrants of the rectangle R.
• Each quadrant has intersecting diagonals: Dl, D3, D5 and D7 joining the center 4 of the circle C to the four corners (7, 8, 9, 10) of the rectangle R and D2, D4, D6 and D8 joining adjacent intersections (11, 12, 13, 14) of the lines 5 and 6 with the sides of the rectangle R.
• the edges of the plate specially designed to focus the clamping forces in the throttling area i.e. the edges 15 and 16 which are the farest from the pouring hole 3, thus closest to the throttling area, have at least a portion (against which the clamping force will be applied) that is parallel to the diagonal D2 or D4 of the quadrant containing said edge.
• edges 15 and 16 are parallel to the diagonal D2 and at least a portion of the edge 16 is parallel to the diagonal D4.
• the entire edges 15 and 16 are parallel to the diagonals D2 and D4 while on Fig. 2, only a portion of the edges 15 and 16 is parallel to the diagonals D2 and D4.
• the edges of the plate which are specifically designed to focus the clamping forces around the pouring hole 3, i.e. the edges 17 and 18 which are the closest from the pouring hole 3 may be shaped perpendicular to the diagonals D5 or D7 of the quadrant containing said edge or, in other words, parallel to a direction 19 or 20 defined as a perpendicular to the diagonals D5 or D7.
• edges 17 and 18 of Fig. 2 which are respectively perpendicular to diagonals D5 and D7.
• edges 17 and 18 may be shaped parallel to the diagonals D6 or D8 of the quadrant containing them as is illustrated on edges 17 and 18 of Fig. 1 which are parallel to diagonals D6 and D8.
• edges 17 and 18 may be oriented in a direction comprised between the two above defined directions.
• edges 15, 16, 17 and 18 may contact each other, defining thus a tetragonal plate 1, defined by the joint diagonals D2, D4, D6 and D8. Obviously, to avoid mechanical stresses, it is preferred to avoid such tip-shaped corners. Therefore, preferably, the edges 15, 16, 17 and 18 do not contact directly. They may be separated by straight lines, preferably parallel to the sides of the rectangle as illustrated on Fig. 1. [0045] Even more preferably, they are separated by transition curves. [0046] On Fig. 2, edges 15 and 16 and edges 17 and 18 are joined by transition radii 21 and 22. [0047] The essential parameter is the orientation of the edges 15, 16, 17 and 18, which will determine the way they focus the clamping forces to avoid the cracks.
• edges 15, 16, 17 and 18 are not too long to avoid the mechanical stresses due to the tip-shaped corners, nor too short for efficiently focusing the clamping forces where it is necessary.
• edges 15 and 16 should preferably cut the short side of the rectangle R in a region comprised respectively between 1/8 and 3/8 and between 5/8 and 7/8 of the length of the short side of the rectangle R.
• This requirement is less important on the other side of the plate (i.e. the side where the edges are closest to the pouring hole), so that edges 17 and 18 (or their projection) should preferably cut the short side of the rectangle R in a region comprised between 1/ 10 and 9/ 10 of the length of the short side of the rectangle R.
• the document WOO 1/41956 describes a method to determine whether or not a plate is designed according to its teachings.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Casting Support Devices, Ladles, And Melt Control Thereby (AREA)
• Laminated Bodies (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Sliding Valves (AREA)
• Check Valves (AREA)
• Furnace Housings, Linings, Walls, And Ceilings (AREA)
• Sliding-Contact Bearings (AREA)
• Polishing Bodies And Polishing Tools (AREA)

Priority Applications (2)

Applications Claiming Priority (4)

Publications (2)

Family

ID=8184929

Family Applications (1)

Country Status (20)

Cited By (1)

Families Citing this family (8)

Family Cites Families (10)

• 2002
  • 2002-03-01 TW TW091103809A patent/TW526315B/zh not_active IP Right Cessation
  • 2002-03-04 JP JP2002569330A patent/JP2004521746A/ja not_active Withdrawn
  • 2002-03-04 WO PCT/BE2002/000025 patent/WO2002070173A1/en active IP Right Grant
  • 2002-03-04 HU HU0303409A patent/HUP0303409A3/hu unknown
  • 2002-03-04 PL PL02363265A patent/PL363265A1/xx unknown
  • 2002-03-04 CA CA002438967A patent/CA2438967A1/en not_active Abandoned
  • 2002-03-04 AU AU2002238307A patent/AU2002238307B2/en not_active Ceased
  • 2002-03-04 ES ES02704500T patent/ES2239218T3/es not_active Expired - Lifetime
  • 2002-03-04 DE DE60204294T patent/DE60204294T2/de not_active Expired - Fee Related
  • 2002-03-04 BR BR0207478-8A patent/BR0207478A/pt not_active Application Discontinuation
  • 2002-03-04 KR KR10-2003-7011683A patent/KR20030080076A/ko not_active Application Discontinuation
  • 2002-03-04 EP EP02704500A patent/EP1372892B1/de not_active Expired - Lifetime
  • 2002-03-04 AT AT02704500T patent/ATE296176T1/de not_active IP Right Cessation
  • 2002-03-04 PT PT02704500T patent/PT1372892E/pt unknown
  • 2002-03-04 CN CNA02806089XA patent/CN1525893A/zh active Pending
  • 2002-03-04 MX MXPA03008113A patent/MXPA03008113A/es active IP Right Grant
  • 2002-03-04 DK DK02704500T patent/DK1372892T3/da active
  • 2002-03-04 RU RU2003125180/02A patent/RU2277455C2/ru not_active IP Right Cessation
  • 2002-04-03 UA UA2003087484A patent/UA75633C2/uk unknown
• 2003
  • 2003-08-06 ZA ZA200306068A patent/ZA200306068B/en unknown

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events