JP3751421B2 - Plate brick - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plate brick used in a sliding nozzle device for controlling the flow rate of molten steel.
[0002]
[Prior art]
In order to control the flow rate of molten steel, a sliding nozzle device is generally attached to the bottom of a molten metal container such as a ladle or a tundish.
[0003]
In this sliding nozzle device, two or three plate bricks each having a nozzle hole are slid and overlapped to open and close by sliding the nozzle holes to control the flow rate of the molten steel. And these plate bricks are clamped by the pressure which usually reaches about 2-10 tons from the upper and lower sides, in order to prevent the leakage steel from between each surface.
[0004]
This plate brick is easily damaged by operation under a pinching pressure at a high temperature, and is usually replaced with a new one 3 to 7 times.
For the user, it is an important issue to improve the durability of the plate brick from the viewpoint of complexity of the replacement work, cost reduction of the refractory or improvement of safety.
[0005]
Examples of the state of damage to the plate brick include enlargement of the hole diameter, surface wear at the stroke portion, cracks, and chipping at the nozzle hole edge.
[0006]
Conventionally, as a countermeasure against damage to such a plate brick, in addition to the improvement from the material surface, in particular, as a countermeasure against the surface wear of the stroke portion and the chipping of the nozzle hole edge portion, Japanese Utility Model Laid-Open No. 50-83313 discloses a plate Although it is disclosed that a wear-resistant brick is attached to the nozzle hole portion of the brick or the vicinity thereof, an effect that is commensurate with an increase in work cost and material cost has not been obtained.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to effectively prevent occurrence of surface wear at a stroke portion and chipping at a nozzle hole edge portion in a plate brick used in a sliding nozzle device.
[0008]
[Means for Solving the Problems]
During use, the plate brick is heated around the inner hole due to the passage of the molten steel in the nozzle hole, but the inner hole is not heated from the inner hole surface. The temperature decreases as you move away from the surface. FIG. 5 shows the result of FEM analysis for the temperature distribution of the plate brick in use. According to FIG. 5, the temperature around the inner hole is the highest, and the isotherm is concentric around the inner hole. The closer to the inner hole, the narrower the isotherm, the greater the temperature difference.
[0009]
On the other hand, the plate brick a is mounted on the metal frame c as shown in FIG.
[0010]
Accordingly, during use, the plate brick expands in the thickness direction due to thermal expansion around the nozzle hole, and since this expansion is larger than the end portion, the plate brick b warps as shown in FIG. 7 and contacts only around the nozzle hole D. It will be.
[0011]
The state in which the plate brick is warped during use can be confirmed by observing the situation where it is actually used. When sliding in this warped state, the pressure is concentrated around the nozzle hole, so that it is estimated that the surface wear of the stroke portion is promoted or the nozzle hole edge portion is chipped.
[0012]
The present invention has been completed based on elucidation of chipping occurrence mechanisms in surface wear and the nozzle hole edge portion of the stroke part, within 2mm or 70mm from the nozzle hole bore surface, and, 10 mm from the end surface of the plate brick It is characterized by forming a circular concave surface that is circular when viewed from the plane and concave when viewed from the cross section in the area around the nozzle hole excluding the part up to this point. Compressive stress due to warping of the plate brick is reduced.
[0013]
The depth of the concave surface to be provided is related to the area of the concave surface, and if the concave surface area is small, it can be deepened, but if the concave surface area is wide, if it is too deep, molten steel will infiltrate into the concave surface during use. Therefore, there is a problem that the molten steel is solidified and difficult to slide, the sliding surface is rough, or the steel leaks.
[0014]
If the concave surface is too shallow, the relaxation of the compressive stress due to thermal expansion during use will be insufficient, and the effect of suppressing surface wear at the stroke site and chipping at the nozzle hole edge will be reduced.
[0015]
The depth of the concave surface is preferably a depth that relaxes the stress generated around the nozzle hole even when the periphery of the inner hole of the plate expands in the thickness direction during use, and further, there is no gap between the surfaces.
[0016]
This state is determined by the coefficient of thermal expansion of the material used for the plate brick and the operating temperature, but is based on the coefficient of expansion of commonly used materials such as alumina, zirconia, magnesia, silica or carbon. The depth of the concave surface is preferably 0.1% to 2% of the thickness of the plate brick. The thickness of the play brick here refers to the thickness excluding the protruding portion for joining with the upper nozzle, the lower nozzle and the like.
[0017]
The concave surface may be an inclined surface, a flat surface, a step surface, or a curved surface. When the concave surface is relatively small, it is a flat surface. When the concave surface is large, it is possible to minimize the gap and maintain the sealing performance by providing an inclination or a step according to the temperature distribution. As for the size of the concave surface, if it is too large, the sealing performance deteriorates. Therefore, the concave surface is formed in a region excluding a portion of 2 mm or more and 70 mm from the inner surface of the nozzle hole and 10 mm from the end of the plate brick .
[0018]
The closer the nozzle hole is, the higher the temperature is and the larger the temperature difference is. Therefore, even if the concave surface is considerably small, it is effective, but at least 2 mm or more from the inner surface of the nozzle hole is required on the sliding surface. Even if it is large, the depth may be changed according to the temperature distribution. However, if it becomes too large, the sealing performance between the surfaces will deteriorate, so that it is within 70 mm from the inner surface of the nozzle hole and from the end face of the plate brick. It is preferable to form a concave surface in a region excluding the 10 mm portion.
[0019]
When this concave surface is provided on only one side of the plates that are in sliding contact with each other, a sufficient effect can be obtained by forming the concave surface with a depth that takes into account the expansion of the other plate brick. It is done.
[0020]
Moreover, when a sliding attachment material is attached to the concave surface in advance in a normal temperature state before use, molten steel intrusion into the concave portion during steel passing can be suppressed.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Specific embodiments of the present invention are illustrated by the following examples.
[0022]
Example 1
FIG. 1 shows a plate brick 10 according to a first embodiment of the present invention, and FIG. 2 shows a cross section taken along line AA of FIG. This plate brick 10 is provided with a nozzle hole 2 having a diameter of 60 mm on a sliding surface 1 having a total length of 400 mm, a width of 200 mm, and a thickness of 40 mm, and a concave surface 3 having a diameter of 120 mm around the nozzle hole 2. The depth of the concave surface 3 was 0.3 mm. The material of this plate brick is an alumina-carbonaceous fired type, and its coefficient of thermal expansion is 1.2% at 1500 ° C.
[0023]
When this plate brick 10 was used in a set of 2 pieces and 30 sets were used in an actual 250t molten steel pan, the number of uses was 6.2 on average. On the other hand, the same conventional plate brick not forming the concave surface 3 of the present invention can be used only 4.5 times on average mainly due to the rough surface of the sliding surface. Thereby, it turns out that the durability of the plate brick of this invention improved significantly.
[0024]
Example 2
FIG. 3 shows a cross section of a plate brick 20 according to the second embodiment of the present invention, which is an example in which the concave surface 3 is formed in an inclined shape.
[0025]
The used plate brick 20 is made of the same material as that of the first embodiment, and the same size as that of the plate brick except for the concave surface 3 is used. The concave surface 3 is inclined with a diameter of 120 mm and a depth of the nozzle hole 2 of 0.5 mm. By inclining the concave surface 3 in a shape close to the temperature distribution, the concave surface 3 can be formed on a wider surface, and the warp of the plate brick can be more effectively suppressed.
[0026]
Example 3
FIG. 4 shows a cross section of a plate brick 30 according to a third embodiment of the present invention, which is an example in which the concave surface 3 is formed in a curved surface shape. The material of the used plate brick 30 is the same material as in Example 1, and the dimensions excluding the concave surface 3 are the same.
[0027]
The concave surface 3 has a diameter of 120 mm, the depth of the nozzle hole 2 part is 0.3 mm, and further forms a curved surface close to the expansion dimension in the thickness direction of the plate according to the temperature distribution. By thus forming the concave surface 3 close to the expansion of the plate brick, the warp of the plate brick can be more effectively suppressed.
[0028]
【The invention's effect】
(1) By providing a concave surface on the sliding surface of the plate brick so as to surround the nozzle hole, there is no warping of the plate brick during use, and it is possible to reduce surface wear at the stroke site and chipping at the nozzle hole edge. This improves the durability of plate bricks.
[0029]
(2) By setting the depth of the concave surface to 0.1% to 2% of the thickness of the plate brick, in addition to preventing surface wear at the stroke portion and chipping at the nozzle hole edge, molten metal permeation into the concave surface is achieved. Trouble caused by it can be prevented.
[0030]
(3) The concave surface is formed to surround the nozzle hole in a region that is 2 mm or more and 70 mm or less from the inner surface of the nozzle hole and excluding the 10 mm portion from the end surface of the plate brick. In addition to reducing the air pressure, the seal between the surfaces is secured to prevent air from being sucked in between the surfaces.
[Brief description of the drawings]
FIG. 1 is a plan view showing a first embodiment of the present invention.
2 shows a cross section taken along line AA of FIG.
FIG. 3 shows a cross section of a second embodiment of the present invention.
FIG. 4 shows a cross section of a third embodiment of the present invention.
FIG. 5 is a diagram for explaining the background of the present invention and showing a temperature distribution of a plate brick in use.
FIG. 6 shows a sliding state of a plate brick.
FIG. 7 shows the state of warping of a plate brick.
[Explanation of symbols]
10, 20, 30 Plate brick 1 Sliding surface 2 Nozzle hole 3 Concave surface

Claims (4)

In plate brick for use in a sliding nozzle device having a nozzle hole in the sliding sliding surface, surrounding within 70mm above 2mm from the nozzle hole bore surface, and nozzle holes excluding the portion from the end face of the plate brick to 10mm In this area, the plate brick is formed with a circular concave surface whose outer periphery is circular when viewed from a plane and concave when viewed from a cross section .   The plate brick according to claim 1, wherein the depth of the concave surface is 0.1% to 2% of the thickness of the plate brick. 3. The plate brick according to claim 1, wherein the concave surface forms an inclined surface whose depth is reduced in the direction of the nozzle hole when viewed from a vertical section passing through the center of the nozzle hole . The plate brick according to claim 3 , wherein the concave inclined surface is curved .

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