JP7610117B2 - Tundish - Google Patents

Description

The present invention relates to a tundish.

In continuous casting, in order to steadily pour molten steel into the mold, a vessel called a tundish is used to temporarily receive the molten steel transported by the ladle to the mold before it is poured into the mold. The tundish not only receives and stabilizes the molten steel from the ladle, but also removes inclusions from the molten steel, improving the cleanliness of the molten steel.

In a tundish, refractory material is applied to the inner surface of the steel shell, which is the outer shell of the vessel. The refractory material of a tundish is generally designed to have a three-layer structure or more in order to prevent the outflow of molten steel. For example, the following refractory materials are applied from the molten steel side inside the vessel toward the steel shell side. The coating material is a component that comes into direct contact with molten steel and is renewed each time. The wear material comes into contact with molten steel if the coating material melts or peels off. The permanent material comes into contact with molten steel in an emergency if the wear material melts or peels off.

Here, when the tundish is being maintained, the metal, slag, and coating material remaining inside are removed to prevent contamination of the molten steel during the next casting. This work is carried out by tilting the tundish. During this process, the refractory material inside the tundish may fall off due to its own weight, so it is necessary to support the wear material or permanent material so that they do not fall off the tundish.

As a method for preventing refractory from falling off the workpiece, for example, Patent Document 1 discloses a lance pipe in which multiple metal studs are provided on the outer periphery of a metal pipe with two or more legs, and the refractory covering the outer periphery of the metal pipe is supported by the studs. By each stud having two or more legs, the cooling effect of the studs obtained from the metal pipe through the legs is improved. This suppresses the thermal expansion of the studs and suppresses damage to the refractory, preventing the refractory from falling off.

For example, Patent Document 2 discloses an anchor hardware that supports a refractory material on an outer shell such as a steel shell. The anchor hardware described in Patent Document 2 has a base end that is attached to the mounting surface and a protruding portion that protrudes from the base end, with at least a portion of the protruding portion being formed of a coil spring. The coil spring expands and contracts in the axial direction and also deforms so as to curve in the axial direction. When the refractory material held by the protruding portion expands and contracts, the coil spring expands and contracts and deforms in response to the expansion and contraction. This suppresses the occurrence of thermal stress between the protruding portion of the anchor hardware and the refractory material, and suppresses the occurrence of cracks in the refractory material.

JP 2019-196525 A JP 2014-163659 A

However, even if a support for a refractory material is provided on the inner surface of a tundish that holds molten steel, it is difficult to achieve a configuration that provides a high cooling effect like the lance pipe studs described in Patent Document 1.

In addition, if the anchor hardware described in Patent Document 2 is installed on the inner surface of the tundish, the expansion and contraction and deformation of the coil spring of the anchor hardware will suppress the generation of thermal stress between the refractory material, making it less likely for cracks to occur in the refractory material. However, if too many anchor hardware pieces are installed, even if the thermal stress between the refractory material and the anchor hardware is suppressed, the possibility of cracks occurring in the refractory material will increase because thermal stress occurs at each of the installation points of the anchor hardware. In particular, if a crack occurs in the refractory material in the steel bath part where the tundish comes into contact with molten steel, there is a risk that the molten steel will flow out. Therefore, it is important to install the anchor hardware so as to suppress the generation of cracks in the refractory material in the steel bath part of the tundish.

The present invention has been made in consideration of the above problems, and the object of the present invention is to provide a tundish that can suppress the occurrence of cracks in the refractory material in the steel bath portion of the tundish.

In order to solve the above problems, according to one aspect of the present invention, a tundish is provided that has a steel shell that forms the outer shell of a vessel that holds molten steel, a wear material that covers the inner surface of the steel shell, and a number of metal supports that are fixed to the inner surface of the steel shell and support the wear material, and the number of supports are arranged so that the arrangement density decreases from the top to the bottom in the height direction of the vessel.

In the height direction of the vessel, when the bottom side from the set height position of the molten steel surface held in the vessel is the steel bath portion, and the upper side from the set height position of the molten steel surface is the non-steel bath portion, the multiple supports may be provided only in the non-steel bath portion.

A permanent material is provided between the shell and the wear material, except for the support installation portion where the support is provided on the shell, and each of the supports may be fixed to the inner surface of the shell via a fixing member fixed to the shell at the support installation portion corresponding to the support. The fixing member has a first portion that supports the support, an upper permanent material located above the support installation portion, and a lower permanent material located below the support installation portion, and a second portion that extends from the first portion to the inner surface of the container along the upper end surface of the lower permanent material.

It is preferable that a gap is provided between the first portion and the upper permanent material at room temperature.

The fixing member may have a third portion that extends from the second portion along the lower permanent material toward the bottom side of the container.

The permanent material is a firebrick, and the third portion may be provided to serve as a pair of horizontally adjacent firebricks and support both of the pair of firebricks.

The support may be made of a rod-shaped member, extend along the inner surface of the shell, have a base that is fixed to the shell, and a support that extends from the base toward the inner surface of the vessel.

As described above, the present invention can suppress the occurrence of cracks in the refractory material in the steel bath portion of the tundish.

FIG. 2 is a schematic end view of a tundish according to one embodiment of the present invention as viewed from the side. 2 is a schematic cross-sectional view of the tundish taken along the line AA in FIG. 1 . FIG. 2 is a schematic end view of the tundish taken along line B-B in FIG. 1 . FIG. 2 is a schematic diagram showing a steel bath portion and a non-steel bath portion of a tundish. 7 is a schematic plan view showing an example of a support fixed to an iron shell using a fixing member, as viewed from a position along the line D-D in FIG. 6. FIG. 6 is a partial cross-sectional view showing a state at room temperature as viewed from the position of the CC cutting line in FIG. 5. FIG. 2 is a partial enlarged view of a side wall of a tundish showing an example of an arrangement of supports and fixing members.

The preferred embodiment of the present invention will be described in detail below with reference to the attached drawings. Note that in this specification and the drawings, components having substantially the same functional configuration are designated by the same reference numerals to avoid redundant description.

[1. Configuration of the tundish]
First, a schematic configuration of a tundish according to one embodiment of the present invention will be described with reference to Figures 1 to 3. Figure 1 is a schematic end view of the tundish 1 according to this embodiment when viewed from the side. Figure 2 is a schematic cross-sectional view of the tundish 1 taken along the line A-A in Figure 1. Figure 3 is a schematic end view of the tundish 1 taken along the line B-B in Figure 1. In the following description, the width direction of the tundish 1 is taken as the X direction, the length direction as the Y direction, and the height direction as the Z direction. In Figures 1 and 3, only the outer contour of the wear material 30 applied to the tundish 1 is shown by a two-dot chain line.

The tundish 1 according to this embodiment is a vessel that temporarily receives the molten steel transported to the mold by the ladle before pouring it into the mold. As shown in Figs. 1 to 3, the space V for holding the molten steel in the tundish 1 is formed by four side walls 1a to 1d and a bottom surface 1e. The inner surfaces of the four side walls 1a to 1d are flat, and each of the side walls 1a to 1d has a generally trapezoidal shape in which the upper bottom of the upper part of the vessel is longer than the lower bottom of the bottom of the vessel. Alternatively, each of the side walls 1a to 1d may be rectangular. The bottom surface 1e is provided with nozzles 3a to 3c for pouring the held molten steel into the mold. The top of the vessel is open. By forming the side walls 1a to 1d of the tundish 1 into a flat shape and forming the tundish 1 into a shape with a large opening at the top, the tundish 1 can be tilted to facilitate the removal of the metal, slag, and coating material remaining inside.

In the tundish 1, refractory material is applied to the inner surface of the steel shell 10, which is the outer shell of the vessel. In the tundish 1 shown in Figures 1 to 3, the refractory materials are a coating material (not shown), a wear material 30, and a permanent material 20 applied from the molten steel side inside the vessel toward the steel shell 10 side.

The coating material is applied to simplify the removal of the metal and slag remaining inside the tundish 1 after casting, and to protect the wear material 30. The coating material is dismantled and reapplied after each cast. This keeps the areas in contact with the molten steel clean and prevents contamination of the molten steel. For example, a magnesia (MgO) material is used as the coating material, and it is applied by troweling or spraying.

The wear material 30 is a refractory material that comes into contact with molten steel when the coating material is melted or peeled off. For example, an alumina-silica (Al ₂ O ₃ —SiO ₂ ) refractory material is used as the wear material 30. Since the wear material 30 requires frequent repairs, an unshaped refractory material that is easy to apply is often used.

The permanent material 20 is a refractory material applied to the inner surface of the steel shell 10, and may be, for example, a firebrick or an unshaped refractory material. When firebricks are used as the permanent material 20, the firebricks are stacked as shown in Figures 1 and 3 to cover the inner surface of the vessel of the tundish 1. The permanent material 20 comes into contact with molten steel in an emergency when the wear material 30 melts or peels off.

The tundish 1 according to this embodiment has a plurality of metal supports 40 fixed to the inner surface of the iron shell 10 on the inner surface of the side walls 1a to 1d, and supporting the wear material 30. The supports 40 are also called studs. The supports 40 are covered by the wear material 30, and prevent the wear material 30 and the permanent material 20 from falling off. The arrangement of the supports 40 and the method of fixing them to the iron shell 10 will be described later.

2. Support
[2-1. Arrangement of Support]
The supports 40 provided on the inner surfaces of the side walls 1a to 1d of the tundish 1 are members that support the wear material 30. Since the supports 40 are made of metal, they expand when exposed to heat from the molten steel during use of the tundish 1. If the amount of expansion of the supports 40 is large, the wear material 30 is pushed apart and cracked. The cracks that occur in the wear material 30 can become a path for the outflow of molten steel. In particular, if cracks occur in the wear material 30 in the steel bath portion where the tundish 1 comes into contact with the molten steel, the possibility of the molten steel outflow increases. On the other hand, if the number of supports 40 is reduced in order to prevent cracks from occurring in the wear material 30, the support force of the wear material 30 and the permanent material 20 will be insufficient, and the wear material 30 or the permanent material 20 may fall off when the tundish 1 is tilted.

In the tundish 1 according to this embodiment, the supports 40 are provided on the inner surfaces of the side walls 1a to 1d so that the arrangement density decreases from the top to the bottom in the height direction of the vessel. As a result, the number of supports 40 installed is smaller on the bottom side of the vessel where the molten steel is held than on the top side of the vessel, so that the possibility of cracks occurring in the wear material 30 can be reduced and the outflow of molten steel can be prevented. The arrangement density d [pieces/mm] of the supports 40 may be expressed, for example, by the number n [pieces] of supports 40 installed relative to the height h [mm] from the bottom surface 1e of the tundish 1 (d = n/h).

In order to more reliably prevent the outflow of molten steel from the tundish 1, the support 40 should be provided only in the non-steel bath portion of the tundish 1. Here, FIG. 4 shows the steel bath portion S2 and the non-steel bath portion S1 of the tundish 1. As shown in FIG. 4, in the height direction (Z direction) of the vessel, the bottom side of the set height position Lv of the molten steel surface held in the vessel is the steel bath portion S2, and the upper side of the set height position Lv of the molten steel surface is the non-steel bath portion S1.

The set height position Lv of the molten steel surface is a value that is set according to the shape of the tundish 1, the residence time of the molten steel in the tundish (the time from when it flows in from the ladle to when it flows out of the tundish 1) taking into account the process of removing inclusions from the molten steel, and the like, and it changes. For this reason, the steel bath section S2 and the non-steel bath section S1 also change. If the height of the side walls 1a-1d of the tundish 1 is H, the height of the non-steel bath section S1 is H1, and the height of the steel bath section S2 is H2, for example, the set height position Lv of the molten steel surface can be set so that the height H2 of the steel bath section S2 is about 60-80% of the height H of the side walls 1a-1d.

The height H1 of the non-steel bath portion S1 may be at least 50 mm. This allows the surface of the molten steel held in the tundish 1 to be near the upper end of the tundish 1, preventing the molten steel from flowing out of the tundish 1.

By providing the support 40 only in the non-steel bath portion S1 of the tundish 1 and not in the steel bath portion S2, it is possible to avoid the wear material 30 becoming a path for molten steel outflow even if a crack occurs in the wear material 30, and it is possible to more reliably prevent the outflow of molten steel from the tundish 1. Furthermore, since the support 40 is more significantly affected by the heat of the molten steel in the steel bath portion S2, providing the support 40 in the steel bath portion S2 increases the amount of thermal expansion, making it more likely that cracks will occur in the wear material 30. From the viewpoint of suppressing the occurrence of cracks in the wear material 30, it is desirable to provide the support 40 only in the non-steel bath portion of the tundish 1.

Moreover, the support 40 itself cannot suppress the outflow of molten steel from the tundish 1. By providing the support 40 in the wear material 30, the effective thickness (effective thickness t _w1 in FIG. 5 described later) at which the wear material 30 can prevent the outflow of molten steel is reduced. From the viewpoint of extending the life of the wear material 30 in the steel bath portion S2 and preventing the outflow of molten steel from the tundish 1, it is effective to provide the support 40 only in the non-steel bath portion S1 of the tundish 1 and not in the steel bath portion S2.

[2-2. Installation of support using fixing member]
In the tundish 1 according to the present embodiment, the supports 40 are provided on the inner surfaces of the side walls 1a to 1d so that the arrangement density decreases from the top side to the bottom side in the height direction of the vessel, thereby reducing the installation density of the supports 40 in the steel bath section S2 and suppressing the occurrence of cracks in the wear material 30. Here, since the installation density of the supports 40 is higher in the non-steel bath section S1 than in the steel bath section S2, the possibility of cracks occurring in the wear material 30 increases. In this case, the possibility of molten steel flowing out from the tundish 1 in the non-steel bath section S1 is not as high as in the steel bath section S2, but it is desirable to prevent the occurrence of cracks.

The number of supports 40 to be installed satisfies the following relationship based on the balance of forces acting on the refractory material (wear material 30 and permanent material 20) when the tundish 1 is tilted.

Number of supports installed = (weight of refractory material loaded on the support) ÷ (load supported by one support)

From the above relationship, if the weight of the refractory loaded on the support 40 is reduced, the number of supports 40 installed can be reduced. Also, if the welding area between the support 40 and the steel shell 10 is increased, the load supported by each support 40 can be increased. Therefore, by fixing the support 40 to the steel shell 10 using a fixing member, the number of supports 40 installed can be reduced, and the occurrence of cracks in the wear material 30 can be further suppressed.

The support 40 according to this embodiment and the installation of the support 40 using the fixing member 50 will be described below with reference to Figures 5 and 6. Figure 5 is a schematic plan view showing an example of the support 40 fixed to the shell 10 using the fixing member 50, and shows the state as seen from the position of the D-D cutting line in Figure 6. Figure 6 is a partial cross-sectional view showing the state as seen from the position of the C-C cutting line in Figure 5 at room temperature. Figures 5 and 6 correspond to enlarged views of region Q in Figure 3.

The support 40 shown in Figures 5 and 6 is made of a rod-shaped member and has a base 41 that is fixed to the iron shell 10 and a support part 43 that extends from the base 41 toward the inner surface of the container.

The base 41 is fixed to the fixing member 50 by welding, which will be described later. The base 41 extends along the inner surface of the shell 10. For example, as shown in Figures 5 and 6, the base 41 extends in the longitudinal direction (Y direction) on the side walls 1a and 1b. The extension direction of the base 41 is not particularly limited as long as it is along the inner surface of the shell 10. The base 41 may extend in any direction that allows it to extend long so that the welding area with the fixing member 50 can be increased. By increasing the welding area with the fixing member 50, the base 41 and the fixing member 50 can be firmly fixed together.

The support part 43 has an axis part 43a, one end of which is located at the base part 41, extending from the base part 41 toward the inner surface side of the container, and tip parts 43b, 43c, which extend away from the other end of the axis part 43a. The support part 43 may be formed to have a Y-shape in plan view, as shown in FIG. 5. This allows the support part 43 to increase the support force of the wear material 30. The support part 43 may be disposed so that the tip is located at a position that is about 60% of the thickness t _w of the wear material 30, where t _w is the thickness of the wear material 30. In other words, the protruding length t _w2 of the support part 43 extending from the boundary position between the permanent material 20 and the wear material 30 toward the wear material 30 is about 60% of t _w . The thickness part of the wear material 30 where the support part 43 does not exist is the effective thickness t _w1 (=t _w -t _w2 ) of the wear material 30.

The fixing member 50 is a metal member and has an upper permanent material support member 51 and a lower permanent material support member 53. The fixing member 50 is fixed to the iron shell 10 after removing the permanent material 20.

The upper permanent material support member 51 is fixed to the steel shell 10 by welding, and supports the upper permanent material 20a located above the installation portion of the support 40 and the lower permanent material 20c located below. The upper permanent material support member 51 is an L-shaped member composed of a steel shell fixing portion 51a and an extension portion 51b. The steel shell fixing portion 51a corresponds to the first portion of the fixing member in the present invention, is fixed to the steel shell 10, and supports the support 40, the upper permanent material 20a, and the lower permanent material 20c. The extension portion 51b corresponds to the second portion of the fixing member in the present invention, and extends from the steel shell fixing portion 51a along the upper end surface of the lower permanent material 20c toward the inner surface of the container.

By fixing the support 40 to the shell 10 via the shell fixing portion 51a, the welding area can be made larger than if the base 41 of the support 40 were fixed directly to the shell 10. This allows the load supported by each support 40 to be increased. In addition, because the shell fixing portion 51a is a flat plate, it can be fixed to the shell 10 more easily than the support 40, which is a rod-shaped member.

In addition, as shown in FIG. 6, in the installation portion of the support 40, the permanent material 20 between the upper permanent material 20a on the upper side of the installation portion of the support 40 and the lower permanent material 20c on the lower side is partially removed. Therefore, the upper permanent material 20a is more likely to fall off than the other permanent materials 20. Here, the permanent material 20 is thermally expanded by the heat of the molten steel held during the preparation of the tundish 1. At this time, the upper permanent material 20a in the support installation portion expands downward, and the lower permanent material 20c expands upward. The iron shell fixing portion 51a provided between the upper permanent material 20a and the lower permanent material 20c functions to support the upper permanent material 20a from below and to support the lower permanent material 20c from above. In this way, by giving the fixing member 50 the function of supporting the permanent material 20 in the height direction, it is possible to compensate for the reduction in the support force of the refractory material caused by reducing the number of supports 40 installed.

As shown in FIG. 6, a gap is provided between the iron skin fixing part 51a and the upper permanent material 20a at room temperature. The wear material 30 flows into this gap. This reduces the load on the upper permanent material 20a. In other words, when the iron skin fixing part 51a thermally expands at high temperatures, the stress is dispersed to the wear material 30 between the iron skin fixing part 51a and the upper permanent material 20a and to the surrounding wear material 30, so that the thermally expanded iron skin fixing part 51a does not directly and locally apply stress to the upper permanent material 20a. Therefore, stress concentration on the permanent material 20 can be avoided, and the load on the permanent material 20 can be reduced.

The lower permanent material support member 53 is a member that supports the lower permanent material 20c from the inner surface side of the container. The lower permanent material support member 53 is an L-shaped member composed of an inner surface support portion 53a and an extension portion 53b. The inner surface support portion 53a corresponds to the third portion of the fixing member in this invention, and is a member that extends along the lower permanent material 20c toward the bottom surface 1e of the container. The extension portion 53b corresponds to the second portion of the fixing member in this invention, and is extended from the inner surface support portion 53a toward the iron shell 10 along the upper end surface of the lower permanent material 20c.

The inner support portion 53a supports the inner surface of the lower permanent material 20c in the height direction, thereby preventing the lower permanent material 20c from falling off when the tundish 1 is tilted. The length hs of the inner support portion 53a supporting the lower permanent material 20c in the height direction is not particularly limited, but it is sufficient that the length is about 1/3 of the thickness hp of the permanent material 20 to prevent the lower permanent material 20c from falling off. In addition, since the thermal expansion becomes significant when the inner support portion 53a is located in the steel bath portion S2, which can cause cracks in the wear material 30, the length hs of the inner support portion 53a should be long enough to prevent the lower permanent material 20c from falling off. The permanent material 20 on the bottom surface 1e side of the lower permanent material 20c is supported by the tension between the permanent materials 20, so support by the fixing member 50 is not necessary.

The fixing member 50 according to this embodiment is formed from two members, the upper permanent material support member 51 and the lower permanent material support member 53, but the present invention is not limited to this example. The fixing member 50 may be composed of a single member. For example, the extension portion 53b of the lower permanent material support member 53 shown in FIG. 6 may be integrated with the extension portion 51b of the upper permanent material support member 51, and a single member consisting of the iron shell fixing portion 51a, the extension portion 51b, and the inner surface support portion 53a may be used as the fixing member 50.

When the support 40 is fixed to the steel shell 10 via the fixing member 50 in this manner, in order to efficiently support the refractory bricks that are the permanent material 20 using the fixing member 50, the fixing member 50 may be provided on the tundish 1 so that the inner support portion 53a supports a pair of horizontally adjacent refractory bricks as shown in FIG. 7. In other words, the inner support portion 53a of one fixing member 50 is used for both a pair of refractory bricks and supports both refractory bricks. In this case, the support 40 and the fixing member 50 may be provided for every other refractory brick that constitutes the permanent material 20b in the installation portion of the support 40.

The above describes the tundish 1 according to one embodiment of the present invention. According to this embodiment, the supports 40 are provided on the inner surface of the side walls 1a to 1d so that the arrangement density decreases from the top to the bottom in the height direction of the vessel. As a result, fewer supports 40 are provided on the bottom side of the vessel where the molten steel is held than on the top side of the vessel, reducing the possibility of cracks occurring in the wear material 30 and preventing the molten steel from leaking out.

The above describes in detail preferred embodiments of the present invention with reference to the attached drawings, but the present invention is not limited to such examples. It is clear that a person with ordinary knowledge in the technical field to which the present invention pertains can conceive of various modified or revised examples within the scope of the technical ideas described in the claims, and it is understood that these also naturally fall within the technical scope of the present invention.

For example, in the above embodiment, the shape of the support portion 43 of the support 40 was Y-shaped, but the present invention is not limited to this example. For example, it may be V-shaped. Also, the base 41 of the support 40 is formed by bending the shaft portion 43a of the support portion 43 at a substantially right angle, but the present invention is not limited to this example. For example, the shaft portion 43a may be provided so as to extend from near the center of the extended base 41.

REFERENCE SIGNS LIST 1 Tundish 1a, 1b, 1c, 1d Side wall 1e Bottom surface 3a, 3b, 3c Nozzle 10 Iron shell 20 Permanent material 20a Upper permanent material 20c Lower permanent material 30 Wear material 40 Support 41 Base 43 Support portion 43a Shaft portion 43b, 43c Tip portion 50 Fixing member 51 Upper permanent material support member 51a Iron shell fixing portion 51b Extension portion 53 Lower permanent material support member 53a Inner surface support portion 53b Extension portion

Claims (6)

A shell that serves as the outer shell of a vessel that holds molten steel;
A wear material covering the inner surface of the iron shell;
A plurality of metal supports fixed to the inner surface of the shell and supporting the wear material;
having
The plurality of supports are provided such that their arrangement density decreases from the top side to the bottom side in a height direction of the container ,
A permanent material is provided between the iron shell and the wear material, except for a support installation portion where the support is provided on the iron shell,
Each of the supports is fixed to an inner surface of the shell via a fixing member fixed to the shell at a support installation portion corresponding to the support,
The fixing member is
a first portion for supporting the support, an upper permanent part located above the support installation portion, and a lower permanent part located below the support installation portion;
a second portion extending from the first portion toward an inner surface of the container along an upper end surface of the lower permanent member;
The tundish has In the height direction of the vessel, a portion from a set height position of the surface of the molten steel held in the vessel to a bottom side is defined as a steel bath portion, and a portion above the set height position of the surface of the molten steel is defined as a non-steel bath portion.
The tundish according to claim 1 , wherein the plurality of supports are provided only in the non-steel bath portion. The tundish according to claim 1 , wherein a gap is provided between the first portion and the upper permanent material at room temperature. The tundish according to any one of claims 1 to 3 , wherein the fixing member has a third portion extending from the second portion toward a bottom side of the container along the lower permanent material. The permanent material is a firebrick,
5. The tundish according to claim 4 , wherein the third portion is provided to serve a pair of horizontally adjacent refractory bricks and supports both of the pair of refractory bricks. The support is made of a rod-shaped member,
a base portion extending along an inner surface of the shell and fixed to the shell;
A support portion extending from the base portion toward an inner surface side of the container;
The tundish according to any one of claims 1 to 5 , comprising:

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