RU2277455C2 - Method of repairing crack-resistant plate of sliding gate valve - Google Patents

Abstract

FIELD: metallurgy; pouring of molten metal.

SUBSTANCE: proposed method of repairing of refractory plate includes coating of cracks with solution. Plate has outline which can be inscribed into elongated rectangle. Plate is furnished with pouring hole located eccentrically between parallel sides of rectangle. At least one section of plates edges is arranged at angle to provide optimum concentration of clamping force in rate control area and around pouring hole.

EFFECT: prevention of forming and developing of cracks in said areas of plate.

6 cl, 2 dwg

Description

The present invention relates generally to a method for repairing worn valve plates for use in gate valves, for example to control the flow of molten metal, and more particularly to a valve plate that is resistant to cracking caused by thermomechanical stresses.

Gate valves are usually used to control the flow of molten metal in steel production, as well as in other metallurgical processes. Such gates typically comprise a support frame, an upper stationary valve plate having an opening aligned with a casting trough or a glass of a steel pouring ladle through which a stream of molten metal is passed, and a throttle valve (plate), which also has a hole for passing metal, this valve being made with the possibility of sliding movement under the stationary valve plate. In gate valves, which are used in conjunction with molds for continuous casting, a lower stationary valve plate is provided, which is mounted under a movable throttle valve, which also has a hole for passing metal, mainly aligned with the hole of the upper stationary plate. The flow rate of molten metal depends on the degree of overlap of the opening of the sliding throttle valve with the hole of the upper stationary plate. The movable throttle valve is usually longer than the stationary plate in order to allow the flow rate (throttle) of the molten metal to be controlled from both the front and rear edges of its own hole, as well as to completely shut off the flow when its hole is completely removed from the overlap with the stationary holes plates. Typically, the throttle valve is slidably moved between the stationary plates using a hydraulic mechanism.

The throttle valve (plate) and the stationary plate are installed respectively in the lower groove and in the upper groove, each of these plates abutting in the groove with the help of the surface, which becomes its supporting surface, and interacts with the other plate with the help of the surface, which becomes its sliding surface or work surface.

Both the butterfly valve and the stationary plates of such gate valves are made of heat-resistant and erosion-resistant refractory materials, such as alumina, alumina-carbon, zirconia. However, despite the thermal and erosion resistance of such refractory materials, the high thermomechanical stresses that affect them ultimately lead to some cracking. For example, in steelmaking, each valve plate is exposed to temperatures of about 1600 ° C in the area directly surrounding its flow-through opening, while the outer edges of the opening have an ambient temperature. The resulting high temperature gradient creates high thermomechanical stresses, since the area of each plate directly covering its hole expands at a significantly higher speed than the rest of the plate. These stresses lead to the formation of cracks that extend radially outward from the hole of the plate. If nothing is done to restrain the propagation of these cracks, they can reach the outer edges of the plate and cause its destruction.

Various technical solutions have already been proposed to prevent the propagation of such cracks and the resulting destruction of the valve plates. First of all, improved clamping devices have been proposed. The objective of such devices is to apply substantial pressure along the perimeter of the plate so that the crack emerging from the hole cannot propagate to the edges of the plate. One such device has a frame with wedges clamped by screws that come into contact with the corners of the plate, which, in turn, are beveled at an angle additional to the angle of the bevels of the wedges. Such a system is disclosed in DE-C23522134. Despite the fact that such a frame and wedge-type clamping devices form a certain progress (in the art), it cannot be used to fully realize the braking potential of crack propagation. Typically, the clamping forces are not concentrated uniformly in the area where the maximum number of cracks is formed, that is, in the immediate vicinity of the hole, where there are maximum thermomechanical stresses. Moreover, the applicants have found that the angular orientation of the beveled corners of such plates does not provide optimal prevention of crack propagation, as previously thought. Such non-optimal results are explained by the fact that the formation of cracks does not occur uniformly in the 360 ° range around the hole, but instead is displaced along the longitudinal axial line of any valve plates, both stationary and moving. It can be assumed that such an asymmetric distribution of cracks around the plate openings occurs as a result of the longitudinal sliding of the throttle valve over the surfaces of stationary plates.

US Pat. No. 5,626,164 discloses a crack-resistant valve plate, the shape of such a plate being chosen so as to prevent crack formation and propagation therein. This plate has an axis, a hole for transmitting molten metal, which is located on the specified axis, and beveled corners for concentrating the clamping force in the direction of the specified axis in the immediate vicinity of the specified hole, each such beveled angle being orthogonal to the line between the touch points of the specified holes, transverse to the specified axis, and through the intersection of lines parallel to the converging edges of the plate, which are offset from these edges by a distance equal to half the width of the decree The leg openings.

Publication WO-A 1-98 / 05451 discloses an embodiment of the solution described above in which the angles between the sides of the plate are selected so as to increase the life of the plate.

While the technical solution in accordance with US patent No. 5626164 represents significant progress compared with previously known technical solutions, applicants have set themselves the task of further optimizing the shape of the plate.

It is obvious that there is a need to create a valve plate, the shape of which allows one to optimally concentrate the clamping forces in the area of the plate most susceptible to cracking, in order to maximally inhibit the elongation of any such cracks. Ideally, the angles should be long enough to avoid the formation of undesired localized mechanical stresses in the corners.

International patent application WO 01/41958 discloses a crack-resistant assembly of a valve plate for use in a slide gate, which eliminates or at least mitigates the drawbacks of previously known technical solutions, wherein the performance of said assembly is at least equal to the quality of the plate disclosed in US Pat. 5626164.

In accordance with this publication, a refractory plate for a slide gate is proposed, which can be inscribed in an elongated rectangle R, the two sides of which are parallel to the direction of its extension. The rectangle R has a longitudinal axis, which is defined as the longest axis of its symmetry and which coincides with the preferred trajectory (direction) of sliding of the plate. However, it should be borne in mind that this concept of a preferred sliding path is an internal (integral) characteristic of the plate in accordance with this publication, and the plate may slide in the slide gate in a direction that is not optimal or preferred. The plate has a hole (hole for casting), designed to pass molten metal. Most often, this hole is round, and in a more general form it can be inscribed in a circle C with a diameter F.

For design reasons, the rectangle R is divided into four quadrants by two perpendicular lines intersecting in the center of the circle C, and one of these lines goes in the middle between the parallel sides of the rectangle R. Each quadrant has intersecting diagonals: diagonals D1, D3, D5, D7 that connect the center of the circle C with the corners of the rectangle R, and the diagonals D2, D4, D6 and D8, which connect the adjacent intersections of the perpendicular lines intersecting in the center of the circle C with the sides of the rectangle R.

The fill hole can be located in the center of the plate, but most often it is offset along the longitudinal axis, so that flow control can be carried out in a longer area. The fill hole may also be slightly offset along an axis perpendicular to the longitudinal axis.

The plate has edges oriented at an angle (beveled corners of the rectangle R), designed to concentrate the clamping force in the direction of the vicinity of the hole and in the direction of the flow control region to prevent the formation and propagation of cracks in them.

According to WO 01/41956, at least one of the edge portions is defined as follows:

- the edges farthest from the fill hole (and therefore closest to the flow control area) deviate by a maximum of 5 ° from the directions of the diagonals that do not intersect the corresponding angle, and

- the edges closest to the filling hole (and therefore the most distant from the flow control area) deviate by a maximum of 5 ° from one of the following directions

(i) the direction perpendicular to the diagonal crossing the corresponding angle;

(ii) the directions of the other diagonal of the corresponding quadrant;

(iii) - a direction intermediate between directions (i) and (ii).

Applicants have determined that this form (configuration) of the plate optimally concentrates the clamping force in two different areas of the plate. On the one hand, the flow control region is kept in compression, which prevents cracks in this area, and, on the other hand, the perimeter of the fill hole is also kept in compression, which prevents the propagation of cracks extending along the radii from the fill hole.

Applicants are convinced that the newly designed plate has very preferred characteristics. First of all, less cracking is observed. Secondly, even if they appear, then the cracks do not extend to the edges of the plate, so that the ingression (penetration) of air is significantly reduced. Thirdly, when the plate is used in combination with an appropriate clamping device, then cracks (if any) appear only in an acceptable (acceptable) area, that is, they do not occur either in the flow control area or directly in the area between the filling hole and the nearest edges.

An additional advantage of this plate is that since very few cracks are observed, the plate can be easily and quickly repaired after use. That is why in accordance with the present invention, a method for repairing worn plates made in accordance with WO 01/41956 is provided.

The plate may be symmetrical about its longitudinal axis, however, according to a preferred embodiment, the plate is not symmetrical about the longitudinal axis.

Due to this asymmetry, the plate can be installed in only one position in the upper groove and in one position in the lower groove, so that the supporting surface of the plate becomes its sliding surface or working surface when the plate is moved from one position to another, in the case when reuse of plates is desirable.

A plate may have only four edges as defined above, however, to avoid the presence of sharp corners, it may have a larger number of edges. In this case, the additional edges may (or may not) be parallel and / or perpendicular to the longitudinal axis.

It should be borne in mind that the plate does not have to be polygonal. In contrast, when using a clamping tape that runs around the plate, such a clamping tape can introduce localized mechanical stresses - which can lead to cracking - at the tip formed by adjacent edges. Therefore, the angle should preferably be rounded.

According to a preferred embodiment, only predetermined edge portions satisfy the above definition. According to a most preferred embodiment, the remaining edge portions are curves that connect the indicated edge portions, most preferably they are the transition radius of these edges.

It should also be borne in mind that in accordance with the present invention, “plate” is understood to mean a plate of a node (stationary or movable), such as a plate of a monoblock casting nozzle, a plate of a monoblock internal casting nozzle, a plate of a monoblock tube, etc.

In accordance with the present invention, there is provided a method of repairing a worn gate valve refractory plate that can be inscribed in an elongated rectangle R, two sides of which are parallel to the direction of its extension, having a filling hole that is asymmetrically located in the middle between the parallel sides of the rectangle R and can be is inscribed in a circle C, and the rectangle R is divided into four quadrants with the help of two perpendicular lines intersecting at the center of the circle C, one of these lines being in the middle between the parallel sides of the rectangle R, and each quadrant has intersecting diagonals: D1, D2 and D3, D4 and D5, D6 and D7, D8, respectively, and the corners of the rectangle R are cut and replaced by inclined edges wherein the direction of at least one portion of said edges that are farthest from the fill hole deviates at most 5 ° from the direction of the diagonal that does not intersect the corresponding angle;

and

- the direction of the edges that are closest to the fill hole deviates by a maximum of 5 ° from one of the following directions:

(i) - directions perpendicular to the diagonals crossing the corresponding angle;

(ii) the directions of the other diagonal of the corresponding quadrant;

(iii) - a direction intermediate between directions (i) and (ii).

Any suitable repair method may be used. It should be borne in mind that it is precisely due to their exceptional resistance to cracking that these plates can be easily, quickly and effectively repaired.

Typically, the repair method includes the operation of filling the cracks with a mortar, and preferably with a mortar that is resistant to molten steel, such as a phosphate mortar, for example, REFRACOL 620 PL 45.

If necessary, it may be necessary to grind the surface of the plate before filling the cracks, for example, to remove traces of steel from the surface of the plate. For this, any known technology can be used, such as grinding, sandblasting, blasting with water, etc.

After filling the cracks, the excess solution is removed and the plate is dried. Drying can be carried out at ambient temperature for at least 4 hours, and preferably for at least 8 hours, or in a drying oven at 120 ° C., for example, for 1 hour.

Then the plate can be subjected to thermal stabilization. This operation of thermal stabilization can be carried out at a temperature of 350-450 ° C for 1 hour. In one embodiment, thermal stabilization can also occur during the use of a repaired plate when it is exposed to high operating temperatures.

In accordance with a preferred embodiment, the plate is preheated, for example, to a temperature of about 80-120 ° C, while the solution penetrates deep into the cracks and quickly sets.

In accordance with another embodiment, the solution contains a hardener, due to which it quickly sets, even at ambient temperature.

If the fill hole is damaged, it can also be repaired. For this purpose, a circular cross-sectional part (such as a pipe, bar or mandrel) having a diameter mainly equal to the initial diameter of the pouring hole is usually introduced into the pouring hole. Smear with a solution (mainly the same as for puttying cracks) the places around the part of circular cross section, and then drying, and, if necessary, thermal stabilization.

In accordance with one of the options, you can drill a hole (mainly along the axis of the original hole for pouring and with a diameter of at least at least 50% larger than the original diameter of the hole for pouring), and then insert the insert into the newly drilled hole and cover it with a solution. Such an insert is advantageously made of a material having at least the same resistance as the raw material of the plate. It is desirable to provide the outer walls of the insert with protrusions or holes for the penetration of the solution. You can also use a stepped insert formed of two (or more) overhead coaxial pipes having the same inner diameter but different outer diameters.

1 and 2 show a top view of the plates in accordance with patent EP 99870258.3, where similar components have the same reference designations. Figure 1 shows a valve plate 1 for use in a slide gate used to control the flow of molten steel or other metal flowing from a casting trough into a mold or from a ladle into a casting trough.

Plate 1 has an opening 3 for passing a stream of molten metal. This fill hole 3 may be inscribed in circle C with center 4. FIG. 1 shows a plate with a non-circular fill hole, and FIG. 2 shows a plate with a fill hole 3 corresponding to circle C.

Figures 1 and 2 show a rectangle R. This rectangle R, into which the plate 1 is inscribed, has long sides parallel to the sliding paths of the plate in the slide gate. For structural purposes, it is necessary to draw two perpendicular lines 5 and 6, which intersect in the center of 4 circles C and which are parallel to the short and long sides of the rectangle R, respectively. These lines define the four quadrants of the rectangle R. Each quadrant has intersecting diagonals D1, D3, D5 and D7 connecting the center of 4 circles C with the four corners (7, 8, 9, 10) of the rectangle R, as well as the diagonals D2, D4, D6 and D8 connecting the adjacent intersections (11, 12, 13, 14) of lines 5 and 6 with the sides of the rectangle R.

The edges of the plate, which have a special shape for concentrating the clamping forces in the area of flow control, namely the edges 15 and 16 farthest from the filling hole 3 (and, therefore, closest to the flow control zone), have at least one section (to which a clamping force will be applied) parallel to the diagonals D2 or D4 of the quadrant, which contains the corresponding edge.

Figures 1 and 2 show at least one edge portion 15 parallel to the diagonal D2, and at least one edge portion 16 parallel to the diagonal D4. In figure 1, the edges 15 and 16 are completely parallel to the diagonals D2 and D4, while in figure 2 only the portion of the edges 15 and 16 is parallel to the diagonals D2 and D4.

The edges of the plate, which have a special shape for concentrating the clamping forces around the filling hole 3, that is, the edges 17 and 18, which are located closest to the filling hole 3, can go perpendicular to the diagonals D5 or D7 of the quadrant that contains the corresponding edge, or in other words, parallel to the direction 19 or 20, which is defined as perpendicular to the diagonals D5 or D7. This option is shown in figure 2, where both edges 17 and 18 are perpendicular to the corresponding diagonals D5 and D7.

Alternatively, said edges 17 and 18 may run parallel to the diagonals D6 or D8 of the quadrant in which they are located, as shown in FIG. 1 for edges 17 and 18 that are parallel to the corresponding diagonals D6 and D8.

In another embodiment, the edges 17 and 18 may be oriented in a direction located between the two directions defined above.

The edges 15, 16, 17 and 18 can be in contact with each other, while defining a quadrangular plate 1 bounded by the connecting diagonals D2, D4, D6 and D8. However, it is obvious that in order to avoid mechanical stresses, the presence of acute angles arising from this should be predominantly avoided. Therefore, the edges 15, 16, 17 and 18 mainly do not contact directly with each other. They can be separated by straight lines, mainly parallel to the sides of the rectangle, as shown in figure 1. According to a most preferred embodiment, the edges can be separated (connected) by transition curves. Figure 2 shows that the edges 15 and 16 and the edges 17 and 18 are connected using the corresponding transition radii 21 and 22.

An essential parameter is the orientation of the edges 15, 16, 17 and 18, which determines the concentration of the clamping forces to avoid cracks. The position of the edges relative to the filling hole 3, that is, the position of the edges 15, 16, 17 and 18 along the respective diagonals D1, D3, D5 and D7, is less important for fulfilling this criterion. However, the edges 15, 16, 17 and 18 should preferably not be too long to avoid mechanical stresses caused by sharp corners, or too short to effectively concentrate the clamping forces when necessary.

In this regard, the edges that are closest to the flow control region, that is, the edges 15 and 16 (or their projections), should preferably intersect the short sides of the rectangle R in the region between 1/8 and 3/8 and between 5/8 and 7/8 the length of the short side of the rectangle R.

This requirement is less important for the other side of the plate (that is, for the side where the edges are closest to the fill hole), so that the edges 17 and 18 (or their projections) should preferably intersect the short sides of the rectangle R in the region between 1/10, respectively and 9/10 the length of the short side of the rectangle R.

WO 01/41956 describes a method for determining the correct design of a plate in accordance with the instructions given.

Claims (6)

1. A method of repairing a worn refractory plate (1) for a slide gate, which includes the operation of lubricating cracks with a solution, characterized in that the plate (1) has a configuration that can be inscribed in an elongated rectangle R, the two sides of which are parallel to the direction of its extension and which is divided into four quadrants using two perpendicular lines (5,6) intersecting in the center (4) of circle C, one (6) of these lines (5, 6) runs in the middle between the parallel sides of the rectangle R, and each quadrant hasintersecting diagonals D1, D2 and D3, D4 and D5, D6 and D7, D8, while the plate has a filling hole (3), which is located eccentrically in the middle between the parallel sides of the rectangle R and is inscribed in a circle C with center (4), and inclined edges (15-18), which are cut corners (7-10) of the rectangle R, and the direction of at least one portion of these edges (15, 16), the most distant from the filling hole (3), is deviated by a maximum of 5 ° from the direction of the diagonal, which does not intersect the corresponding angle, and the direction of Mok (17, 18), which are closest to the filling hole (3), is deviated by a maximum of 5 ° from one of the following directions: (i) the direction perpendicular to the diagonal crossing the corresponding angle; (ii) the directions of the other diagonal of the corresponding quadrant; (iii) - a direction intermediate between directions (i) and (ii). 2. The method according to claim 1, characterized in that the solution is a phosphate solution. 3. The method according to claim 1 or 2, characterized in that they carry out the drilling of the hole, mainly coaxial with the initial hole for filling and having a diameter of at least 50% more than the diameter of the original hole for filling, insertion of the insert into the drilled hole and putty with a solution places between the insert and the walls of the drilled hole. 4. The method according to one of claims 1 to 3, characterized in that the coated plate is dried. 5. The method according to one of claims 1 to 3, characterized in that the thermostabilized plate is thermally stabilized. 6. A reusable refractory plate (1) of a slide gate, the cracks of which are coated with a solution, characterized in that it has a configuration that can be inscribed in an elongated rectangle R, the two sides of which are parallel to the direction of its extension and which is divided into four quadrants by two perpendicular lines (5, 6) intersecting in the center (4) of circle C, one (6) of these lines (5, 6) runs in the middle between the parallel sides of the rectangle R, and each quadrant has intersecting diagonals D1, D2 and D3, D4 and D5, D6 and D7, D8, while the plate has a hole for pouring (3), which is located eccentrically in the middle between the parallel sides of the rectangle R and is inscribed in a circle C with the center (4), and inclined edges (15-18), which are cut corners (7 -10) of the rectangle R, and the direction of at least one portion of these edges (15, 16), farthest from the fill hole (3), is deviated by a maximum of 5 ° from the direction of the diagonal, which does not intersect the corresponding angle, but the direction of the edges ( 17, 18) that are closest to the hole w pouring (3) rejected maximum 5 ° from one of the following directions: (i) the direction perpendicular to the diagonal crossing the corresponding angle; (ii) the directions of the other diagonal of the corresponding quadrant; (iii) - a direction intermediate between directions (i) and (ii).

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