JP5348713B2 - Dip tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stably usable immersion tube with which the break-down and the fall-down of an outside fixed-form refractory disposed at the outermost circumference are restrained. <P>SOLUTION: In the immersion tube provided with a flange 1, a cylindrical core metal 2 fixed to the flange and the refractories disposed at the outer circumferential side and the inner circumferential side of the core metal 2, and disposing the outside fixed-form refractory 6 as the refractory at the outermost circumference; on the inner circumferential face of the outside fixed-form refractory 6, a recessed part 7 inclining this upper face upward in the range from this lower-end to 10-30% of the total length of this outside fixed-form refractory is arranged, and on the outer circumferential face of the core metal 2, a projected part 8 inclining this upper face upward with the same angle as the upper face of the recessed part in the outside fixed-form refractory is arranged. The outside fixed-form refractory 6 is supported from the lower part by supporting the upper face of the recessed part 7 in the outside fixed-form refractory 6 with the upper face of the projected part 8 in the core metal 2, and the upper-end part of the outside fixed-form refractory 6 is abutted to a supporting plate 9 arranged in the flange 1 and a monolithic refractory 5 is arranged on the whole circumference at the lower part of the outside fixed-form refractory 6. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a dip tube attached to a molten steel processing apparatus such as an RH type or DH type vacuum degassing apparatus or a CAS apparatus in the steel industry.

  The dip tube is composed of a flange, a cylindrical cored bar fixed to the flange, and a refractory disposed on the outer peripheral side and the inner peripheral side of the cored bar. And as a refractory of the outermost periphery of a dip tube, in order to prevent adhesion of slag, outer shape refractories, such as a magnesia carbon brick, are arranged in many cases.

  As this outer fixed refractory, generally a long fixed refractory having a length of 400 to 900 mm is used, and this is arranged in the circumferential direction on the outer peripheral side of the core bar in the vertical direction, and above and below it. It is a common configuration to arrange an irregular refractory.

  However, in the dip tube having such a configuration, since the outer regular refractory easily falls off, various support structures have been conventionally proposed in order to prevent the outer regular refractory from dropping off.

  For example, Patent Document 1 proposes a structure in which an upper end and a lower end of an outer fixed refractory are respectively supported by upper and lower support hardware provided on a core metal.

In Patent Document 2, long bricks extending to the lower end of the dip tube and short bricks held to the vicinity of the lower end of the core metal are alternately arranged as outer-shaped refractories. In addition, a structure has been proposed that is supported by a support metal provided on the core at an upper portion of 100 mm or more from the lower end.
JP-A-9-67612 Japanese Patent Laid-Open No. 10-60520

  In the support structure of Patent Document 1, since the upper end and the lower end of the outer fixed refractory are supported and fixed, a large bending stress is generated in the outer fixed refractory itself due to the thermal expansion of the outer fixed refractory, and from the vicinity of the center portion. Trouble that breaks easily occurs. In this breakage, the outer fixed refractory breaks and jumps out toward the outside, so that molten steel enters the back side of the outer fixed refractory or the broken outer fixed refractory comes out. Also, when the molten steel enters the joint between the lower end of the outer fixed refractory and the irregular refractory, the lower support metal supporting the lower end of the outer fixed refractory is melted and the outer fixed refractory loses its support. Things may fall off.

  On the other hand, in the support structure of the long brick in Patent Document 2, since the lower support hardware is positioned above the lower end of the long brick, the molten steel is less likely to enter the position of the lower support hardware, The melting of the lower support metal is suppressed. Moreover, compared with the case where the upper end and lower end of an external fixed refractory are supported and fixed like patent document 1, the bending stress concerning an external fixed refractory by thermal expansion can also be reduced.

  However, in the support structure of Patent Document 2, the force to support the brick does not act below the support position by the lower support hardware of the long brick, and the lower portion is not restrained. There is a problem that stress concentrates on the support position by the support metal, and cracks are easily generated in the horizontal direction starting from the stress. And since the downward direction of a long brick is not supported at all, once a crack generate | occur | produces, it will lead to falling off quickly.

  Therefore, a problem to be solved by the present invention is to provide a dip tube that can be stably used by suppressing breakage and dropout of the outer fixed refractory disposed on the outermost periphery.

  The present invention comprises a flange, a cylindrical cored bar fixed to the flange, and a refractory disposed on the outer peripheral side and the inner peripheral side of the cored bar, and an outer fixed refractory disposed as an outermost refractory In the pipe, the outer peripheral surface of the core metal is provided with a recess whose upper surface is inclined upward in the range of 10% to 30% with respect to the entire length of the outer fixed refractory on the inner peripheral surface of the outer fixed refractory. Provided with a convex portion whose upper surface is inclined upward at the same angle as the upper surface of the concave portion of the outer fixed refractory, and the upper surface of the concave portion of the outer fixed refractory is supported by the upper surface of the convex portion of the core metal Is supported from below, the upper end of the outer shaped refractory is brought into contact with a support plate provided on the core metal or the flange, and the irregular shaped refractory is arranged on the entire circumference below the outer shaped refractory.

  As described above, in the present invention, the outer fixed refractory is supported from below on the upper surface of the recess provided above the lower end of the outer fixed refractory. Therefore, the distance between the upper and lower support positions (span) is smaller than when the outer fixed refractory is supported at the lower end, and the bending stress applied to the outer fixed refractory is reduced. Therefore, the breakage from the central portion of the outer fixed refractory hardly occurs.

  In addition, the position of a convex part such as a support metal provided on the core metal to support the concave part of the outer fixed refractory (hereinafter referred to as “lower support metal”) is a position away from the lower end of the outer fixed refractory. Therefore, even if molten steel permeates into the joint between the lower end of the outer shaped refractory and the irregular shaped refractory, the lower supporting hardware does not melt, and the outer shaped refractory does not easily fall off.

  In addition, it is possible to join the lower support metal piece to the core metal upward as compared with the conventional dip tube that supports the lower end of the outer fixed refractory. For this reason, the strength of the lower support metal is increased, and the dropout of the outer fixed refractory due to the deformation of the lower support metal is also suppressed.

  Furthermore, in the present invention, the load in the portion below the support position by the lower support metal is supported by the irregular refractory, so that it is difficult for horizontal cracks to occur at the support position by the lower support metal, and the horizontal cracks are temporarily generated. Even if it breaks, dropping is suppressed.

  Here, in the present invention, the position of the upper surface of the concave portion provided in the outer fixed refractory is specifically in the range of 10% to 30% with respect to the total length of the outer fixed refractory from the lower end of the outer fixed refractory. . If it is less than 10% of the total length, the distance (span) between the upper and lower support positions of the outer fixed refractory is not sufficiently shortened, so that the effect of suppressing breakage of the outer fixed refractory cannot be sufficiently obtained. On the other hand, if it exceeds 30%, the mass of the portion located below the lower support metal of the outer fixed refractory becomes too large, so that the downward tensile stress applied to the concave portion of the outer fixed refractory becomes excessive. For this reason, it becomes easy to generate | occur | produce the crack which makes a recessed part the starting point.

  Moreover, as a material of the outside fixed refractory, a carbon-containing refractory, particularly magnesia carbon, is preferable from the viewpoint of slag resistance. Since magnesia carbon has a large coefficient of thermal expansion and poor adhesion to an irregular refractory, the above improvement effect by applying the structure of the dip tube of the present invention is great. Further, the outer periphery-shaped refractory can be a long object having a length of 400 to 900 mm. Long objects do not have joints on the way, so their durability is very good.

  ADVANTAGE OF THE INVENTION According to this invention, the trouble generation | occurrence | production of the breakage | failure of an external fixed refractory and the accompanying pullout etc. can be suppressed, and the dip tube which can be used stably can be provided. Therefore, sudden replacement of the dip tube which becomes a production obstacle can be avoided, which can contribute to improvement of productivity.

  Embodiments of the present invention will be described below based on examples shown in the drawings.

  FIG. 1 is a cross-sectional view showing a dip tube of the present invention, and FIG. 2 is an enlarged cross-sectional view showing a lower support portion of an outer shaped refractory in the dip tube shown in FIG.

  The dip tube shown in FIG. 1 has a refractory disposed on the outer peripheral side and the inner peripheral side of a cylindrical cored bar 2 fixed to a metal flange 1, and has a substantially cylindrical shape as a whole. In addition, an Ar gas pipe 10 is embedded in the dip tube for blowing Ar gas, and the tip of the Ar gas pipe 10 opens as a gas blow-in port 10a on the inner peripheral surface of the dip pipe.

  A magnesia chrome brick 3 is disposed on the innermost periphery of the dip tube as an inner fixed refractory. The magnesia chrome brick 3 is supported from below by a lower end support metal 4 fixed to the lower end of the inner peripheral surface of the core metal 2. In addition, an amorphous refractory 5 is disposed on the entire circumference between the magnesia chrome brick 3 and the core metal 2 and below the magnesia chrome brick 3.

  On the outermost periphery of the dip tube, magnesia carbon brick 6 is arranged as an outer fixed refractory. In addition, an amorphous refractory 5 is disposed on the entire circumference between the magnesia carbon brick 6 and the core metal 2 and below the magnesia carbon brick 6.

At the lower end of the magnesia carbon brick 6, a recess 7 is provided as shown in FIG. The recess 7 is open at two sides of the surface facing the lower end surface to the core metal 2 of the magnesia carbon bricks 6, the upper surface 7a of the recess 7 is upwardly inclined at an inclination angle theta _1. According to the present invention, the upper surface 7a of the recess 7 is provided so as to be located within a range of 10% or more and 30% or less from the lower end of the magnesia carbon brick 6 with respect to its entire length L (see FIG. 1).

In the embodiment, 70 mm distance alpha ₁ from the lower end of the magnesia carbon bricks 6 to the lower end of the upper surface 7a of the recess 7, the distance alpha ₂ to the upper end of the upper surface 7a of the recess 7 and 90 mm, the total length of the magnesia carbon bricks 6 L ( 500 mm), the upper surface 7a of the recess 7 was provided in a range of 14 to 18% from the lower end. The inclination angle θ ₁ was 25 °. The inclination angle θ ₁ can be arbitrarily set in the range of 10 ° to 60 °.

On the other hand, a lower support metal 8 is provided below the outer peripheral surface of the cored bar 2. The upper surface 8 a of the lower support metal 8 is inclined upward at the same inclination angle θ ₁ as the upper surface 7 a of the recess 7 of the magnesia carbon brick 6. Then, the magnesia carbon brick 6 is supported from below by supporting the upper surface 7a of the concave portion 7 of the magnesia carbon brick 6 with the upper surface 8a of the lower support hardware 8.

  Further, the upper end of the magnesia carbon brick 6 is brought into contact with the upper support metal 9 provided on the flange 1 as shown in FIG. 1, and the magnesia carbon brick 6 is supported from above by the upper support metal 9. Thus, the magnesia carbon brick 6 is securely held and fixed from above and below by the lower support metal 8 and the upper support metal 9. The upper support metal 9 may be provided on the outer peripheral surface of the core metal 2 instead of the flange 1. Further, a mortar, a sealing material, or a ceramic fiber can be disposed between the upper support metal 9 and the magnesia carbon brick 6 as an expansion absorption allowance. The thickness of the expansion absorption allowance can be 0.1 to 1% of the total length of the magnesia carbon brick 6.

Furthermore, the upper end surface and the lower end surface of the magnesia carbon brick 6 are formed in a tapered shape that expands toward the inner peripheral side, thereby preventing breakage. In the embodiment, the inclination angle θ ₂ of the upper end surface and the lower end surface of the magnesia carbon brick 6 is set to 35 °, but the inclination angle θ ₂ can be arbitrarily set in the range of 20 ° to 70 °.

  Next, Table 1 shows the test results in the actual furnace of the dip tube of the present invention. The dip tube used in Table 1 is obtained by changing only the position of the concave portion 7 provided on the inner peripheral surface of the outer regular refractory (magnesia carbon brick 6) in the dip tube of FIG. The number of uses in Table 1 shows an average value of N = 3.

  The dip tubes in the range of the present invention in Examples 1 to 3 were used well with almost no breakage (they were replaced due to damage of the inner regular refractory (magnesia chrome brick 3)). On the other hand, in the dip tube of Comparative Example 1, breakage occurred at the center of the outer shaped refractory (magnesia carbon brick 6) in one of the three dip tubes, and the outer shaped refractory came out in the middle. It became an exchange. In addition, the remaining two folds were seen in the center of the outer fixed refractory after use. About the comparative examples 2 and 3, since the crack generate | occur | produced in the lower part of the outside fixed refractory material, it was replaced | exchanged on the way.

It is sectional drawing which shows the dip tube of this invention. It is an expanded sectional view which shows the lower side support part of the outside fixed form refractory in the dip tube shown in FIG.

Explanation of symbols

1 Flange 2 Core 3 Magnesia Chrome Brick (Inside Refractory)
4 Lower end support metal 5 Unshaped refractory 6 Magnesia carbon brick (outside shaped refractory)
7 Concave portion 7a Top surface of the concave portion 8 Lower support hardware (convex portion)
8a Upper surface of lower support hardware (convex portion) 9 Upper support hardware (support plate)
10 Ar gas piping 10a Gas inlet

Claims (1)

In a dip tube comprising a flange, a cylindrical cored bar fixed to the flange, and a refractory disposed on the outer peripheral side and inner peripheral side of the cored bar, and an outer shaped refractory disposed as the outermost refractory,
On the inner peripheral surface of the outer fixed refractory, a concave portion whose upper surface is inclined upward in the range of 10% to 30% with respect to the entire length of the outer fixed refractory from the lower end thereof is provided.
On the outer peripheral surface of the cored bar, a convex portion that is inclined upward at the same angle as the upper surface of the concave portion of the outer shaped refractory is provided,
Supporting the outer shaped refractory from below by supporting the upper surface of the concave portion of the outer shaped refractory with the upper surface of the convex portion of the core metal,
The upper end of the outer shaped refractory is brought into contact with a support plate provided on the core metal or flange,
A dip tube in which an irregular shaped refractory is placed all around the outer regular refractory.

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