JPH1157989A - Plate brick - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the warp of a brick at the time of using and to reduce the surface wearing at a stroke position and the chip of a nozzle hole edge part by arranging a recessed surface surrounding the nozzle hole on the sliding surface of the brick. SOLUTION: The nozzle hole 2 is arranged on the sliding surface 1 of the plate brick 10, and the recessed surface 3 is arranged around this nozzle hole 2. In the case of being too shallow of the recessed surface 3, the relaxation of compressive stress caused by the thermal expansion at the time of using is unsufficient and the effect to achieve the target is reduced. The depth of the recessed surface 3 is desirable to be the depth, in which the stress developed to the surrounding of the nozzle hole is relaxed and gap between the surfaces is eliminated or reduced even in the case of expanding in the thickness direction at the surroundings of the inner hole in the plate at the time of using. This condition is decided with the coefficient of thermal expansion of a material used to the plate brick and the used temp., but the depth of the recessed surface is desirable to be 0.1-2% of the thickness of the plate brick from the coefficient of thermal expansion of alumina, zirconia, magnesia, silica or carbon, etc., as the material generally used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a plate brick used in a sliding nozzle device for controlling a flow rate of molten steel.

[0002]

2. Description of the Related Art In order to control the flow rate of molten steel, a sliding nozzle device is generally mounted on 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 overlapped and slid, thereby opening and closing by sliding the respective nozzle holes to control the flow rate of molten steel. . These plate bricks are clamped at a pressure of usually about 2 to 10 tons from above and below in order to prevent leakage of steel from between the surfaces.

[0004] The plate brick is easily damaged by the operation under squeezing pressure at a high temperature, and is usually replaced with a new one three to seven times. For the user, the complexity of replacement work,
It is an important issue to improve the durability of plate bricks from the viewpoint of reducing the cost of refractories or improving safety.

[0005] The state of damage to the plate brick includes enlargement of the hole diameter, surface wear at the stroke part, cracks, and chipping of the nozzle hole edge.

Conventionally, as a countermeasure against such damage to the plate brick, in addition to the improvement in terms of the material, in particular, as a countermeasure against surface wear at the stroke portion and chipping of the nozzle hole edge, Japanese Utility Model Application Laid-Open No. 50-83313 discloses a method. In addition, it is disclosed that a wear-resistant brick is mounted on or near a nozzle hole of a plate brick, but an effect sufficient to increase working costs and material costs is not obtained.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to effectively prevent surface wear of a stroke portion and chipping of a nozzle hole edge portion in a plate brick used in a sliding nozzle device.

[0008]

During use, the plate brick is heated by the heat from the inner hole surface due to the passage of molten steel through the nozzle hole, but the temperature around the inner hole becomes high. In order not to receive heat, the temperature decreases as the distance from the bore surface increases. FIG. 5 shows the result of calculating the temperature distribution of the plate brick during use by FEM analysis.
Shown in According to FIG. 5, the temperature around the inner hole is the highest,
The isotherm is concentric around the inner hole, and it can be seen that the closer to the inner hole, the narrower the width of the isotherm and the greater the temperature difference.

On the other hand, at the time of use, the plate brick a is mounted on the metal frame c as shown in FIG. 6 and slides while being sandwiched by a certain pressure.

Accordingly, during use, the plate brick expands in the thickness direction due to thermal expansion around the nozzle hole, and this expansion is larger than the end portion, so that the plate brick b as shown in FIG.
Will be in contact only around the nozzle hole D.

The state in which the plate brick warps during use can be confirmed by observing the actual use condition. When sliding in this warped state, pressure concentrates around the nozzle hole, so it is presumed that surface wear at the stroke portion is promoted or chipping of the nozzle hole edge occurs.

The present invention has been completed based on the elucidation of the mechanism of the surface wear at the stroke portion and the occurrence of chipping at the nozzle hole edge. A concave surface is provided on the sliding surface of the plate brick so as to surround the nozzle hole. This alleviates the compressive stress caused by the warpage of the plate brick caused by thermal expansion.

The depth of the concave surface to be provided is related to the area of the concave surface. If the concave surface area is small, the depth can be increased. Since a large amount of steel is penetrated, there are problems such as solidification of the molten steel to make it difficult to slide, a sliding surface to be rough, and steel leakage.

If the concave surface is too shallow, the relaxation of the compressive stress due to thermal expansion during use becomes insufficient, and the effect of suppressing surface wear at the stroke portion and chipping of the nozzle hole edge decreases.

The depth of the concave surface is such that even if the inner periphery of the plate expands in the thickness direction at the time of use, the stress generated around the nozzle hole is relieved, and there is no or small gap between the surfaces. Is preferred.

This state is determined by the coefficient of thermal expansion and the operating temperature of the material used for the plate brick, and is generally used, such as alumina, zirconia, magnesia, silica or carbon. From the coefficient of expansion, the depth of the concave surface is 0.1% of the thickness of the plate brick
~ 2% is preferred. The thickness of the plate brick as referred to herein means a thickness excluding a protrusion for joining to an upper nozzle, a lower nozzle, or the like.

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, the surface is flat. When the concave surface is large, it is possible to minimize the gap and maintain the sealing performance by providing a slope or a step according to the temperature distribution. Regarding the size of the concave surface, if it is too large, the sealing property is deteriorated. Therefore, the concave surface may be formed in an area of 2 mm or more and 70 mm or less from the inner surface of the nozzle hole and excluding a portion 10 mm from the end surface of the plate brick. preferable.

Since the temperature is higher near the nozzle hole and the temperature difference is large, the effect is effective even if the concave surface is considerably small, but at least 2 mm from the inner surface of the nozzle hole on the sliding surface is required. In addition, even if it is large, the depth may be changed according to the temperature distribution, but if it is too large, the sealing performance between the surfaces will be reduced, so it will be within 70 mm from the inner surface of the nozzle hole and from the end of the plate brick. It is preferable to form a concave surface in a region excluding a portion of 10 mm.

When only one side of the plates that are in sliding contact with each other is provided, the concave surface is formed on the plate on one side by forming a concave surface having a depth in consideration of the expansion of the mating plate brick. The effect is obtained.

If a sliding attachment is attached to the concave surface in advance at normal temperature before use, molten steel can be prevented from entering the concave portion when steel is passed.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be shown by the following examples.

Embodiment 1 FIG. 1 shows a plate brick 1 according to a first embodiment of the present invention.
FIG. 2 shows a cross section taken along line AA in FIG. This plate brick 10 has a total length of 400 mm,
A sliding surface 1 having a width of 200 mm and a thickness of 40 mm has a diameter of 60 mm.
mm nozzle hole 2 is provided, and a concave surface 3 having a diameter of 120 mm is provided around the nozzle hole 2. The depth of the concave surface 3 was 0.3 mm. The material of this plate brick is a sintering type of alumina and carbon, and the coefficient of thermal expansion is 1
1.2% at 500 ° C.

When 30 sets of this plate brick 10 were used in a set of two pieces in an actual molten steel pot of 250 t, the number of uses was 6.2 times on average. On the other hand, the same plate brick of the present invention without the concave surface 3 of the present invention could be used only 4.5 times on average because of the rough surface of the sliding surface. This indicates that the durability of the plate brick of the present invention has been greatly improved.

Embodiment 2 FIG. 3 shows a plate brick 20 according to a second embodiment of the present invention.
1 is an example in which the concave surface 3 is formed in an inclined shape.

The used plate brick 20 is the same material as in the first embodiment, and has the same dimensions except for the concave surface 3. The concave surface 3 is inclined at 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 warpage of the plate brick can be suppressed more effectively.

Embodiment 3 FIG. 4 shows a plate brick 30 according to a third embodiment of the present invention.
This is an example in which the concave surface 3 is formed into a curved surface. The material of the used plate brick 30 is the same as that of Example 1, and the dimensions except the concave surface 3 are also the same.

The concave surface 3 has a diameter of 120 mm, a depth of the nozzle hole 2 portion of 0.3 mm, and forms a curved surface closer to the expansion dimension in the thickness direction of the plate according to the temperature distribution. By forming the concave surface 3 so as to approach the expansion of the plate brick, the warpage 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, warpage of the plate brick during use is eliminated, and surface wear at the stroke portion and chipping of the nozzle hole edge are reduced. The durability of the plate brick is improved.

(2) By setting the depth of the concave surface to 0.1% to 2% of the thickness of the plate brick, it is possible to prevent surface wear at the stroke portion and chipping of the nozzle hole edge portion, and also to melt the concave surface. Trouble caused by metal penetration can be prevented.

(3) The concave surface is 2 mm or more and 70 mm or less from the inner surface of the nozzle hole and 10 mm from the end surface of the plate brick.
By forming the nozzle hole around the area excluding the part, in addition to reducing the surface wear at the stroke part and the chipping of the nozzle hole edge part, the sealing performance between the surfaces is secured and the air is sucked from between the surfaces To prevent

[Brief description of the drawings]

FIG. 1 is a plan view showing a first embodiment of the present invention.

FIG. 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, showing a temperature distribution of a plate brick in use.

FIG. 6 shows a sliding state of a plate brick.

FIG. 7 shows a warped state of a plate brick.

[Explanation of symbols]

 10, 20, 30 Plate brick 1 Sliding surface 2 Nozzle hole 3 Concave surface

Claims (3)

[Claims] 1. A plate brick characterized in that a sliding surface of the plate brick is provided with a concave surface surrounding the nozzle hole. 2. 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 concave surface is at least 2 mm from the inner surface of the nozzle hole.
Within 0mm and 10mm from the end of the plate brick
The plate brick according to claim 1, wherein the plate brick is formed so as to surround the nozzle hole in a region excluding the portion.