JPH0361723B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a porous plug whose usage limit can be detected. [Conventional technology] To improve the quality of steel, gas such as argon gas is injected into molten steel through a porous plug, stirred,
Decarburization, removal of non-metallic inclusions, etc. are widely practiced. The porous plug used for this purpose is generally placed at the bottom of the pot, so it is very important to judge the amount of wear and tear, that is, to detect the usage limit.If used beyond the limit, hot water may leak, etc. may lead to serious accidents. For this reason, various considerations have been made to determine the limits of use, but the reality is that they have both advantages and disadvantages, and must be used with excessive consideration given to safety in terms of accuracy, ease, etc. For example, (1) the shape of the gas blowing part changes as the number of times it is used increases, and (2) the ability to read temperature changes has been adopted or proposed. [Problems to be solved by the invention] The above-mentioned conventional method is effective to some extent, but (1) has the disadvantage that depending on the operating time or operating conditions, there is a risk of using more than the allowable size. , (2) is not sufficient in that it is expensive because several temperature sensors (thermocouples, etc.) are embedded in the porous plug, and equipment accompanying the temperature sensor is required. It was wanted. The present invention was discovered as a result of various studies from these viewpoints. [Means for Solving the Problems] The porous plug of the present invention has a porous plug that follows the gas introduction pipe, and a gas permeable refractory B is arranged next to the gas introduction pipe, and the air permeable refractory B is smaller than the gas permeable refractory B. Surround the breathable refractory B with a truncated cone-shaped breathable refractory A having a truncated cone shape, and intersect with the axis of the truncated cone-shaped breathable refractory A in the joining part of the breathable refractories A and B. The thickness of the surface part is 0.3 to 8 mm.
It is characterized by having an empty space. The porous plug of the present invention will be explained below with reference to the drawings. Figure 1 shows a typical example. (1) is a sleeve brick, (2) is an iron shell, 3 is a gas introduction pipe, 4 is a permeable refractory A, 5 is a permeable refractory B, and 6 is a permeable refractory B. It is empty. Here, the porous plug of the present invention basically consists of breathable refractories A and B, and the permeability of the breathable refractory B located in the gas introduction part following the gas introduction pipe is lower than that of the surrounding cone. It is larger than the trapezoidal air-permeable refractory A, and has a thickness of 0.3 to 8 mm on the surface perpendicular to the axis of the truncated cone-shaped air-permeable refractory A in the joint between both air-permeable refractories.
It has an empty space. The porous plug of the present invention is thus a makeshift part between two types of breathable refractories having different permeability, and the surface facing the surface of the breathable refractory B to which the gas introduction pipe is attached. When cutting the porous plug in a plane perpendicular to the axis of the truncated cone-shaped breathable refractory A, the hollow part is surrounded by the breathable refractory A. It should be a cross section. Therefore, the interface between the air-permeable refractory B and the cavity provided at the joining part of the air-permeable refractories A and B is slightly inclined from perpendicular to the axis of the truncated cone-shaped air-permeable refractory A. Even if they intersect, they are orthogonal in the sense of the present invention, and in this case, of course, a porous plug having the same detection effect can be obtained. As the material of the breathable refractory constituting the porous plug, those normally used for porous plugs, such as alumina, mullite, and chromia, can be used as is. In the porous plug of the present invention, for example, an air-permeable refractory B having a high air permeability is arranged in the gas introduction part of the porous plug following the gas introduction pipe, and a truncated cone-shaped air-permeable refractory having a smaller air permeability is placed around it. A is placed and integrally cast so as to form a hollow part in the vicinity of the plane perpendicular to the axis of the truncated cone-shaped breathable refractory A in the joint between the breathable refractories A and B. You can make it together. To explain the air permeability here, the air permeability of the two types of breathable refractories must be different, and preferably the difference is 0.05 or more as a value measured at room temperature in cm ² /sec cmH ₂ O, More preferably, the air permeability of the air-permeable refractory B in the gas introduction section is 1.05 times or more that of the air-permeable refractory A. The preferable difference in air permeability is 1.0 or less as measured in units of cm ² /sec·cmH ₂ O, and desirably about 0.1 to 0.5. In addition, the air permeability of breathable refractories A and B is generally
It is preferably about 0.5 to 2.0 cm ² /cmH ₂ O. In the porous plug of the present invention, the hollow part is the joint between the air-permeable refractory B of the gas introduction part with a high permeability and the truncated cone-shaped air-permeable refractory A surrounding it (the part installed at the bottom of the pot). The basic form is as shown in Figure 1, between the air-permeable refractory B and the air-permeable refractory A, which has a high air permeability. Among the mating parts, the entire surface perpendicular to the axis of the truncated cone-shaped breathable refractory A should be formed, but as shown in Fig. 3, even if it is formed in a part thereof. Of course it's good. It is desirable that the effective area of the empty space be as large as possible, but even in the embodiment shown in FIG. 3, it is generally desirable to secure approximately 7 cm ² or more. In addition, the thickness d of the hollow part is desirably larger from the point of view of the desired detection effect, but if it is too large, the durability of the porous plug will be reduced, so it is limited to 0.3 to 8 mm, and preferably 0.5
~5mm. [Function] The usability limit detection function of the porous plug of the present invention is as explained below. Taking the case of steelmaking as an example, a porous plug is usually placed at the bottom of a refining vessel called a ladle. After each refining session, steel is tapped and the inside of the furnace is observed when the ladle is empty. At this time, the porous plug is observed to be red hot at the bottom of the furnace. However, due to the double structure shown in the present invention, as the breathable refractory A begins to wear out, the center part becomes darkened at some point as shown in Figure 2. It is detected that the remaining thickness of the breathable refractory material A is small, and the usage limit can be known. The reason for this is that the air-permeable refractory B, which has a higher permeability than the surrounding area, is placed in the gas introduction part of the porous plug, so the introduced gas mainly passes through the air-permeable refractory B and into the air-permeable refractory A. For this reason, the breathable refractory B is cooled more than the breathable refractory A, and as the remaining thickness of the breathable refractory A decreases, the breathable refractory B and the breathable refractory A are The temperature of the center part, which corresponds to the part of the plane perpendicular to the axis of the gas introduction tube where the hollow part exists, is lower than that of the surrounding area, and it appears darker than the surrounding area. In order to maximize this detection effect, an empty space is provided at the joint between the breathable refractories A and B. In addition, the air permeability of breathable refractory B is the same as that of breathable refractory A.
The fact that it is larger than that contributes to increasing the detection effect. [Example] Table 1 shows the results of using a porous plug as shown in FIG. 1 made of breathable alumina refractory in a 60-ton LF pot.

[Table] Among these, sample 1 did not have a hollow part, and even though the remaining thickness of breathable refractory A was small, the darkening in the center was not very obvious. In No. 2, air-permeable refractories A and B having the same air permeability were used and a hollow space was provided between them, but the darkening in the center was not clear. On the other hand, in Samples 3 and 4, which are porous plugs of the present invention, the darkening in the center was clearly visible, and it was confirmed that the remaining breathable refractory material A could be detected extremely easily and accurately. It was also confirmed that the durability of Sample 4 was not necessarily sufficient. [Effects of the Invention] In the porous plug of the present invention, when the air-permeable refractory A is consumed in this way and approaches the minimum usable remaining size, the remaining size can be easily and accurately detected by the color change in the central part. Therefore, steel leakage can be reliably prevented and safety is high, and if the thickness of the hollow part is specified, the durability is sufficient, and its practical value is great.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an example showing the basic structure of the porous plug of the present invention. Fig. 2 is an explanatory diagram showing the observation situation at the time of pouring the porous plug of the present invention attached to the bottom of the ladle;
Figures a and b are cross-sectional views showing an application example of the porous plug of the present invention. In the figure, 1 is a sleeve brick, 2 is an iron shell,
3 is a gas introduction pipe, 4 is a breathable refractory A, 5 is a breathable refractory B, 6 is a hollow part, 7 is a part of the breathable refractory A that is visible when the porous plug is observed from outside the furnace, 8 indicates the blackened area in the center.

Claims (1)

[Claims] 1. In the porous plug following the gas introduction pipe,
A breathable refractory B is placed next to the gas inlet pipe, and a truncated cone-shaped breathable refractory A having a smaller air permeability than the breathable refractory B surrounds the breathable refractory B. Among the joint parts of refractories A and B,
A porous plug characterized in that a hollow part with a thickness of 0.3 to 8 mm is provided on a surface perpendicular to the axis of a truncated cone-shaped breathable refractory A. 2 The difference in air permeability between refractory A and refractory B is 0.05.
cm ² /sec・cmH ₂ O or more Claim 1
The porous plug described in section.