JP5877123B2 - Degassing equipment dip tube - Google Patents

Description

  The present invention relates to a dip tube of a degassing apparatus used in a melting step of an iron making process.

The molten steel that has undergone primary refining in the converter is degassed using vacuum degassing equipment (also simply referred to as degassing equipment or degassing equipment) for decarburization and for the purpose of removing dissolved gases such as hydrogen and nitrogen. Gas treatment is performed. Examples of the degassing method include a DH (Dortmount-Horde) method and a RH (Ruhrstahl-Heraus) method.
The degassing equipment used for this degassing process has a vacuum degassing tank and a dip tube provided in the lower part thereof. In addition, the dip tube generally has a configuration in which refractories are provided on the inner peripheral side and the outer peripheral side of the cylindrical metal core, and the degassing treatment is performed by taking the tip (lower end) of the dip tube into the ladle. The molten steel is immersed in the molten steel, and the molten steel is sucked into a vacuum degassing tank and simultaneously refluxed.
However, as described above, the degassing treatment is performed in a state where the tip of the dip tube is immersed in the molten steel in the ladle, so that the refractory at the tip (immersed part) is damaged, In addition, since the core metal is deformed by heat, the life of the dip tube cannot be extended.
Thus, for example, Patent Document 1 discloses a dip tube in which a heat insulating mortar is disposed between a cylindrical cored bar (core tube) and a refractory (refractory material).

JP 2010-168600 A

However, when the thermal conductivity of the heat insulating mortar used in Patent Document 1 is estimated from FIG. 3 of Patent Document 1, it is approximately 0.1 W / (m · K), and the heat insulating property is insufficient. The core metal cannot be prevented from being deformed.
Further, when the heat-insulating mortar is sintered due to heat received by the operation of the dip tube, the shrinkage occurs. For this reason, when the thickness of the heat insulating mortar is increased in order to improve the heat insulating effect, a gap generated on the back side of the wear refractory due to the shrinkage allowance of the heat insulating mortar becomes large. It becomes unstable, causing problems such as opening of brick joints and cracking of irregular shaped refractories (castable, etc.), and in extreme cases, wear refractories may fall off.
Furthermore, since the dip tube is operated at a high temperature, it is conceivable that the thermal conductivity is greatly increased due to the shrinkage of the heat insulating mortar. In particular, with the increase in the number of times of use (treatment) of the dip tube, it is conceivable that the decrease in the heat insulation property becomes significant when the sintering (sintering) of the heat insulating mortar proceeds and the structure becomes dense.
In this case, thermal deformation (expansion) occurs in the metal core exposed to high temperature, joint opening occurs in the brick that cannot follow the deformation, and cracks occur in the amorphous refractory, which are immersed in the dip tube. There is a risk that the life of the dip tube will be limited and the life of the dip tube cannot be extended.

  The present invention has been made in view of such circumstances, and provides a dip tube for a degassing apparatus capable of extending the life of a refractory very easily without significantly changing the conventional dip tube structure. The purpose is to do.

The dip tube of the degassing apparatus according to the present invention in accordance with the above object is a degassing apparatus immersing the inner peripheral refractory and the outer peripheral refractory on the inner peripheral side and outer peripheral side of the cylindrical cored bar, respectively. In the tube
Heat at an ambient temperature of 500 ° C. between the inner peripheral refractory and the core metal, and between or both of the outer peripheral refractory and the core metal, with a thickness of 1 mm to 5 mm. A heat insulating material having a conductivity of 0.05 W / (m · K) or less is disposed.

  In the dip tube of the degassing apparatus according to the present invention, the heat insulating material is preferably microporous.

  In the dip tube of the degassing apparatus according to the present invention, the heat insulating material is disposed between the inner peripheral refractory and the cored bar, and the inner peripheral refractory has a porosity of 8% by volume or more and 15 volumes. % Of magnesia-chromia bricks, the effect of arranging the heat insulating material becomes more remarkable.

  In the dip tube of the degassing apparatus according to the present invention, the heat insulating material is disposed between the inner peripheral refractory and the core metal, and the inner peripheral refractory is reduced and fired at 1400 ° C. for 3 hours. The effect of arranging the heat insulating material becomes more remarkable by constituting the carbon amount of magnesia-carbonaceous brick with 2% by mass or more and 9% by mass or less of carbon.

  In the dip tube of the degassing apparatus according to the present invention, it is preferable to provide a plurality of studs having adjacent intervals of 80 mm or more and 250 mm or less on the outer peripheral surface of the cored bar.

In the dip tube of the degassing apparatus according to the present invention, since a heat insulating material is disposed between the core metal (particularly, air-cooled core metal) and the refractory, the thickness direction of the refractory, that is, the working surface (molten steel contact surface side). It is possible to make the temperature gradient between the refractory and the back surface (insulating material side) gentle, and to reduce the rapid temperature change of the refractory (rapid cooling due to heat removal). Thereby, since the spalling damage (peeling damage) of the refractory can be reduced, the life of the refractory can be improved.
In particular, by making the thermal conductivity of the heat insulating material 0.05 W / (m · K) or less, heat input from the surrounding molten steel is avoided by heat insulation when using the dip tube (dipping in molten steel), The core metal temperature can be reduced. Furthermore, by setting the thickness of the heat insulating material to 1 mm or more and 5 mm or less, the heat insulating property of the heat insulating material can be maintained, and the joint opening of the brick and the cracking of the irregular refractory material due to the shrinkage of the heat insulating material can be prevented.
Even if the core metal is air-cooled, since the dip tube is used by immersing it in the molten steel being processed, the heat input from the molten steel is large and the temperature of the core metal becomes high. Expansion causes the opening of brick joints and the cracking of irregular refractories. For this reason, the ingot enters into the refractory through the open joints and cracks, leading to a further increase in the core metal temperature, and damage that determines the life of the dip tube, resulting in a short life of the dip tube. Therefore, by disposing the above-described heat insulating material between the core metal and the refractory, deformation of the core metal is suppressed, and the life of the refractory can be extended.
From the above, the dip tube of the degassing apparatus of the present invention can easily extend the life of the refractory simply by heat insulation in the vicinity of the core metal without significantly changing the conventional dip tube structure. It is.

  Moreover, when a heat insulating material is microporous, the heat insulating material of predetermined | prescribed heat conductivity can be obtained easily.

  And when a heat insulating material is arranged between the inner periphery side refractory and the metal core, since the spall damage of the inner peripheral side refractory can be reduced by the heat insulating material, spall damage occurs in the inner peripheral side refractory. It is possible to use a magnesia-chromia brick with reduced porosity. Thereby, since the loss resistance of the inner periphery side refractory can be improved by reducing the porosity, the life of the dip tube can be extended.

  In addition, when the insulation is placed between the inner refractory and the metal core, the insulation can reduce spalling damage of the inner refractory, so that spalling damage occurs on the inner refractory. It is possible to use magnesia-carbon bricks with reduced carbon content. Thereby, since the erosion resistance of the inner periphery side refractory can be improved by reducing the amount of carbon, it is possible to extend the life of the dip tube.

  Furthermore, when a plurality of studs having an interval of 80 mm or more and 250 mm or less adjacent to each other are provided on the outer peripheral surface of the cored bar, there is insufficient holding power of the outer peripheral refractory due to the studs, and the number of micro cracks generated from the stud Since the reduction can be achieved, the life of the dip tube can be extended.

It is a partial front sectional view of a dip tube of a degassing apparatus according to an embodiment of the present invention.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
As shown in FIG. 1, a dip tube (hereinafter also simply referred to as a dip tube) 10 of a degassing apparatus according to an embodiment of the present invention is a wear refractory on the inner peripheral side of a cylindrical cored bar 11. A certain brick (an example of an inner peripheral refractory) 12 is provided, and an irregular refractory (an example of an outer peripheral refractory) 13 that is a wear refractory is provided on the outer peripheral side. The life of the refractory can be easily extended without significantly changing the tube structure. This will be described in detail below.

  The dip tube 10 can be used for the purpose of decarburization and degassing of molten steel using vacuum (reduced pressure). The dip tube is not particularly limited as long as it is used for the above-described decarburization and degassing refining. For example, the DH method, the RH method, and further CAS (Composition Adjustment by Sealed Argon Bubbling). It may be used for law.

The cored bar 11 of the dip tube 10 has a cylindrical shape made of iron (metal), and its upper end is connected to a vacuum degassing tank (not shown). A support metal 14 for supporting the bricks 12 arranged on is fixed. The cored bar 11 is cylindrical here, but is not particularly limited as long as it is cylindrical.
Further, the cored bar 11 has a structure having a hollow portion 15 whose inside is shielded from the outside air, and has a configuration capable of cooling the cored bar 11 from the inside (a configuration capable of air cooling), depending on use conditions. For example, it can also be set as the structure (solid plate shape) which does not have a hollow part.

As described above, the brick (brick) 12 is installed on the inner peripheral side of the core metal 11, but an irregular refractory can also be installed according to the use application of the dip tube. Further, as described above, the amorphous refractory 13 is mainly used on the outer peripheral side of the core metal 11 as described above. However, the amorphous refractory and brick may be used in combination.
The thickness of the brick 12 is, for example, about 70 to 300 mm, and the thickness of the amorphous refractory 13 is, for example, about 70 to 200 mm.

Moreover, conventionally well-known refractory materials can be used for the brick 12 and the indeterminate refractory 13 that cover the core metal 11. Examples of the refractory material include magnesia-chromia (also referred to as magnesia-chromium, magchrom), magnesia-carbon, alumina-chromia (also referred to as alumina-chromia), alumina-carbon, alumina- Examples include magnesia, alumina-magnesia-carbon, alumina-spinel-carbon.
It should be noted that gas supply pipes are respectively arranged inside the brick 12 and the irregular refractory 13, and purge Ar (argon gas) used for preventing the outside air from entering the dip tube 10 is replaced with brick. It can also be supplied into the inside 12 and into the irregular refractory 13.

Between the radial inner surface of the core metal 11 and the radial outer surface of the brick 12, and between the radial outer surface of the core metal 11 and the radial inner surface of the amorphous refractory 13, a heat insulating material 16 is provided. Has been placed. Thereby, when the cored bar 11 is air-cooled due to the heat insulating effect of the heat insulating material 16, it is possible to suppress the deformation of the cored bar 11 due to heat by the effect of maintaining the cooling function of the cored bar 11. And can contribute to extending the life of the irregular refractory 13.
The heat insulating material 16 is disposed directly on the inner surface and the outer surface of the core metal 11, but the heat insulating material 16 is disposed between the core metal 11 and the brick 12 and between the core metal 11 and the amorphous refractory 13. If it is arranged, it is not limited to this. For example, if the heat insulating material 16 is disposed adjacent to the metal core 11 (arranged at a position where the heat insulating function can be exhibited), the heat insulating material 16 is fixed (adhered) to the surface of the metal core 11. A refractory material (adhesive material) such as a thin mortar can be installed between the materials 16.

As described above, when an irregular refractory is installed on the core metal, for example, a plurality of studs are installed (planted) on the outer peripheral portion (outer peripheral surface) of the core metal to support the irregular refractory. In this case, the stud is installed avoiding the above-mentioned heat insulating material.
Moreover, although the heat insulating material 16 is installed in both the inner peripheral side and outer peripheral side of the metal core 11, even when arrange | positioned only in any one of an inner peripheral side and an outer peripheral side (especially only inner peripheral side). The deformation of the metal core 11 due to heat can be suppressed to some extent, and can contribute to the extension of the life of the brick 12 or the irregular refractory 13. However, as described above, it is more desirable to arrange the heat insulating material 16 on both the inner peripheral side and the outer peripheral side of the core metal 11.

The above-mentioned plurality of studs can be reduced in heat transfer from the molten steel to the core metal when the adjacent interval is set as wide as 300 to 400 mm, for example, but the holding power of the irregular refractory on the outer periphery of the core metal is insufficient. In the degassing process, fine cracks may be formed in the irregular refractory on the outer periphery of the cored bar. Although this fine crack does not lead to defects such as peeling off of the irregular refractory, the temperature of the core metal becomes high, the heat insulation effect is reduced, and it may be difficult to extend the life of the dip tube.
On the other hand, if the distance between the studs is set as narrow as 50 mm, for example, the heat of the molten steel is easily transmitted to the cored bar through the studs, and the number of fine cracks starting from the studs increases, so the heat insulation effect decreases. However, it may be difficult to extend the life of the dip tube.

For this reason, it is desirable to provide an interval between adjacent studs at an appropriate interval of about 80 mm to 250 mm.
Conventionally, when studs are provided at the intervals described above, the heat of the molten steel is transmitted to the cored bar through the studs, and it has been difficult to extend the life of the dip tube. However, by installing a heat insulating material between the cored bar and the irregular refractory, the heat of the molten steel is transferred to the cored bar in the area where the stud is installed, but in the area where the stud is not installed, the molten steel Since heat is insulated by the effect of the heat insulating material, the heat insulating effect is not impaired.

As the above-described heat insulating material, one having a thermal conductivity of 0.05 W / (m · K) or less at an atmospheric temperature of 500 ° C. is used.
Here, the reason why the thermal conductivity of the heat insulating material is defined at an ambient temperature of 500 ° C. is that the use environment of the dip tube in which the heat insulating material is installed is taken into consideration. The reason why the thermal conductivity is specified to be 0.05 W / (m · K) or less is that heat input from the molten steel must be avoided by heat insulation, and the core metal temperature of the dip tube must be reduced. This is because it is desirable to be conductive.
Therefore, although a heat insulating material having a thermal conductivity of 0.05 W / (m · K) or less at an atmospheric temperature of 500 ° C. was used, the thermal conductivity was 0.04 W / (m · K) or less, and further 0.035 W. It is preferable to use a heat insulating material of / (m · K) or less.
On the other hand, for the reasons described above, the lower limit value of the thermal conductivity of the heat insulating material is not stipulated, but considering the low heat conductive heat insulating material existing in the world, for example, 0.01 W / (m · K) It is.

The type of the heat insulating material to be used is not particularly limited as long as it has the above-described thermal conductivity, but a microporous heat insulating material having a low thermal conductivity and a cell structure is preferable.
Moreover, the thickness of a heat insulating material shall be 1 mm or more and 5 mm or less.
The reason why the lower limit of the thickness of the heat insulating material is set to 1 mm is that the heat insulating material (particularly a microporous heat insulating material) takes into consideration the thickness that can be manufactured while maintaining the heat insulating property. On the other hand, the reason why the upper limit value of the thickness is set to 5 mm is that consideration is given to the thickness at which the joints of the bricks (joint breaks) and cracks of the irregular refractory do not occur due to the shrinkage of the heat insulating material.
Therefore, by setting the thickness of the heat insulating material to 1 mm or more and 5 mm or less, it is possible to further extend the life of the dip tube in the second half of the operation (after the deterioration of the performance of the heat insulating material) and to avoid sudden troubles due to sudden refractory peeling. However, it is preferable that the lower limit is 1.5 mm, more preferably 2 mm, and the upper limit is 4 mm, further 3 mm.

The size (scale) of the dip tube 10 of the degassing apparatus described above is not particularly limited, but the effect of the present invention is more remarkable when the inner diameter of the dip tube 10 (the brick 12). In this case, the inner width is set to 300 mm or more.
When the inner diameter of the dip tube is less than 300 mm, the refractory provided on the inner peripheral side of the metal core is structurally stabilized. Specifically, even if joint opening occurs in the brick, it becomes an irregular refractory. Even if cracks occur, the inner diameter of the dip tube is small, so that adjacent refractories compete with each other in the circumferential direction of the dip tube, making it difficult to fall (peel). Accordingly, it becomes difficult to cause damage such as joint opening or cracking of the refractory material due to the life of the dip tube.
On the other hand, the upper limit value is not particularly defined for the reasons described above, but is generally said to be about 2500 mm.

Then, the degassing method using the dip tube 10 of the degassing apparatus which concerns on one embodiment of this invention is demonstrated.
First, as shown in FIG. 1, between the metal core 11, the brick 12 and the amorphous refractory 13, the thickness is 1 mm or more and 5 mm or less, and the thermal conductivity at an ambient temperature of 500 ° C. is 0.05 W / (m K) Prepare the dip tube 10 in which the following heat insulating material 16 is arranged. And the front-end | tip part of this dip tube 10 is immersed in the molten steel in a ladle (not shown), and a degassing process is performed.

In general, the life of a refractory is determined by the remaining state of the refractory due to the wear of the refractory due to wear or melting caused by molten steel or slag. However, other than that, the life of refractories used in the dip tube of the degassing device is greatly affected by cracks and delamination caused by thermal deformation of the core metal of the dip tube, resulting in cracks and joint openings. Therefore, there is a rate-determining factor other than the remaining thickness of the refractory.
That is, since the thermal deformation of the core metal of the dip tube is prevented due to the heat insulation effect, the size of the heat insulation is a factor that determines the deformation of the core metal and further determines the life of the dip tube. Furthermore, in the latter half of the operation of the dip tube, the heat insulating property of the heat insulating material is reduced due to the shrinkage due to heat reception, and conversely, cracks due to the size of the voids due to the shrinkage of the heat insulating material occur, so the heat insulating material shrinks. It is a factor that determines the life of the tube.

Then, like the above-mentioned dip tube 10, the heat insulation of the heat insulating material 16 is provided by arranging the heat insulating material 16 defining the thermal conductivity between the core metal 11, the brick 12 and the amorphous refractory 13. It can be maintained, deformation of the cored bar can be suppressed, and the life of the refractory can be extended. Furthermore, by defining the thickness of the heat insulating material 16, it is possible to maintain the heat insulating property of the heat insulating material 16 in the latter half of the operation of the dip tube 10, and to suppress the opening of brick joints and the cracking of the irregular refractory material. It is possible to extend the life of things.
Therefore, by using the dip tube of the degassing apparatus of the present invention, it is possible to easily extend the life of the refractory simply by heat insulation in the vicinity of the core metal without significantly changing the conventional dip tube structure.

Next, examples carried out for confirming the effects of the present invention will be described.
Here, the dip tube of the degassing apparatus of DH method was used. In addition, magnesia-chromia (porosity: 8 volume% or more and 23 volume% or less) brick was mainly used as the ware refractory on the inner circumference side of the dip pipe (brick on the inner circumference side of the dip pipe). Carbon bricks (carbon amount after reduction firing at 1400 ° C. for 3 hours was 2% by mass to 15% by mass) were also used. Further, an alumina-magnesia amorphous refractory was used as the outer refractory. Furthermore, the thickness of this brick was 260 mm, the thickness of the amorphous refractory was 175 mm, and the inner diameter of the dip tube was 2000 mm. The above-described reduction firing at 1400 ° C. for 3 hours is a pre-heat treatment that is commonly used for measuring the carbon content of magnesia-carbonaceous bricks.

Table 1 shows the type of heat insulating material used for the dip tube, the thermal conductivity, the thickness, and the damage status of the refractory under each condition. In addition, “MgCr1” described in the column of the dip pipe inner peripheral brick in Table 1 means a brick made of a magnesia-chromia material and having a porosity changed in the range of 16% by volume to 23% by volume. and also "MgCr2" is made of a material described above, which means the bricks changing the porosity in the range of 15 vol% 8 vol% or more. In addition, “MgC1” described in the column of the inner periphery of the dip tube is made of magnesia-carbon material, and the carbon amount after reduction firing at 1400 ° C. for 3 hours is changed within a range of 10 mass% to 15 mass%. means the bricks, also "MgC2" is made of a material described above, which means the bricks its carbon content was changed in the range of 9 wt% or more 2%

“WDS” as a type of heat insulating material described in Table 1 is “Porethertherm WDS (registered trademark)” manufactured by Porextherm Damstoff GmbH, and the material thereof is a microporous molded body mainly made of fumed silica. (Microporous heat insulating material). “C.F.” means ceramic fiber.
The said heat insulating material was installed in three kinds of both the outer peripheral surface and inner peripheral surface of a metal core shown in FIG. 1, and the inner peripheral surface or outer peripheral surface of a metal core. In addition, for the construction of the irregular refractory material on the outer peripheral side of the cored bar, a plurality of studs whose tip side provided on the outer peripheral surface of the cored bar branches in a Y shape is used, and the installation interval between adjacent studs is 80 to 300 mm. It changed in the range of.

  The average wear rate of the brick is the amount of wear per charge of the brick installed on the inner peripheral side of the core metal of the dip tube. This average wear rate is determined by the amount of indented refractory that was pressed into the inner periphery of the core during the first repair of the brick installed on the inner periphery of the core (after 80 to 100 charges from the start of operation). By measuring, the amount of wear of the brick was obtained and calculated from the result. Specifically, a cylindrical core with a constant inner diameter is set in the dip tube (degassing tank), and the gap between the core and the brick is closed between the core and the lower end of the dip tube. Then, an irregular refractory was press-fitted to the height of the dip tube, and the repair thickness was determined from the height of the dip tube and the measured amount (volume) of the irregular refractory.

Furthermore, the evaluation was performed by comprehensive evaluation including both the effect of suppressing wear and defects at the end of operation.
In addition, the effect of wear suppression is an evaluation showing the durability of the brick, and is a result obtained from the average wear rate of the brick. Here, the average wear rate is 1.0 (mm / ch) or less as “」 ”, 1.0 (mm / ch) and 1.5 (mm / ch) or less as“ ◯ ”, 1.5 (mm / ch). ch) “×” was defined as “super”.
Further, the defect at the end of operation was an evaluation showing the stability of operation (whether or not a sudden trouble occurred), and the presence or absence of joint opening or crack generation was visually monitored.

In Examples 1 and 2, as shown in FIG. 1, the position of the heat insulating material is both the inner peripheral surface and the outer peripheral surface (both sides) of the cored bar, and the heat conductivity and the thickness are within the appropriate ranges as the heat insulating material ( This is a result of using WDS having a thermal conductivity of 0.05 W / (m · K) or less, a thickness of 1 mm or more and 5 mm or less) (immersion brick on the inner peripheral side of the dip tube: MgCr1).
As shown in Examples 1 and 2, it was confirmed that the effect of reducing the average wear rate of the brick was obtained by improving the heat insulation (decreasing the thermal conductivity). In particular, as shown in Example 2, the effect of further reducing the average wear rate was obtained by increasing the thickness of the heat insulating material within an appropriate range (Example 1: 1.15 mm / ch, Example 2). : 0.98 mm / ch).
In Example 2, by increasing the thickness of the heat insulating material, cracks and joint openings were more likely to occur at the end of operation than in Example 1, but the thickness of the heat insulating material was adjusted within an appropriate range. The use was not hindered (overall evaluation: ○).

In Examples 3 and 4, Examples 5 to 8, and Reference Examples 9 and 10, the arrangement positions of the heat insulating materials are the inner peripheral surface or the outer peripheral surface (only one surface) of the core metal (inner pipe inner periphery) Side brick: MgCr1).
When the heat insulating material is disposed only on the inner peripheral surface or only the outer peripheral surface of the core metal, the average wear rate is increased as compared with the case where the heat insulating material is disposed on both the inner peripheral surface and the outer peripheral surface of the core metal. Compared to the case where no material was used (Comparative Example 4), the effect of reducing the average wear rate was obtained, and the average wear rate was more than 1.0 (mm / ch) and 1.5 (mm / ch) or less. Obtained. Moreover, when arrange | positioning a heat insulating material only to the internal peripheral surface or only the outer peripheral surface of a metal core, the reduction effect of the average wear rate was acquired by thickening a heat insulating material in any case. However, the effect of reducing the average wear rate is greater when the heat insulating material is disposed only on the inner peripheral surface of the core metal than when it is disposed only on the outer peripheral surface of the core metal.

In Examples 7 and 8, as compared with Examples 1 to 6, the stud interval was narrowed to 80 mm. Moreover, the reference examples 9 and 10 make the space | interval of a stud wide with 300 mm compared with Examples 1-6 (immersion pipe inner peripheral side brick: MgCr1).
In the narrowing of the interval as described above, an increase in the average wear rate that causes a problem as compared with Comparative Example 4 is not recognized, but rather, the occurrence of fine cracks in the irregular refractory on the outer peripheral side of the metal core is suppressed. Thus, it is considered that the heat insulation effect could be maintained. However, there is an optimum value for the interval between adjacent studs, and 80 mm or more and 250 mm or less were the best results in this experiment.

On the other hand, Comparative Examples 1-3 are the results of using a heat insulating material in which either or both of the thermal conductivity and thickness of the heat insulating material are outside the proper range, and Comparative Example 4 is the inner peripheral surface of the cored bar. It is a result when a heat insulating material is not arrange | positioned in any of an outer peripheral surface (immersion pipe inner peripheral side brick: MgCr1).
First, as in Comparative Examples 1 and 3, when the thermal conductivity of the heat insulating material was set high (over 0.05 W / (m · K)), the average wear rate of the brick increased. In particular, as shown in Comparative Example 1, the average wear rate significantly increased by increasing the thermal conductivity of the heat insulating material to 0.30 W / (m · K) (Comparative Example 1: 2.00 mm / ch, Comparative Example 3: 1.98 mm / ch).
Further, as in Comparative Examples 1 and 2, when the thickness of the heat insulating material is set to be thick (8 mm or more), the remaining thickness of the refractory material such as cracks and joint openings is not increased after about 300 charges at the end of the operation of the dip tube. It was confirmed that there was a reason for replacing the dip tube. Then, when the dismantling investigation of the refractory was performed after the operation of the dip tube, all of the heat insulating materials initially applied were contracted by 5 mm or more at the maximum. For this reason, it is considered that the gap between the refractory and the cored bar generated by the shrinkage is caused by the joint opening of the brick and the crack of the irregular refractory.

Moreover, also in the comparative example 4 which did not use a heat insulating material for both the inner peripheral surface and the outer peripheral surface of the cored bar, the average wear rate is 1.95 (mm / ch), which is the same as the comparative examples 1 and 3. Rose.
In Comparative Example 4, although cracking and joint opening due to thermal deformation of the core metal occurred, the joint thickness between the core metal was only the thickness corresponding to the refractory mortar (about 1 to 3 mm) filled in the gap. It can be inferred that cracks and joint openings due to the shrinkage hardly occurred.

From the above, Comparative Examples 1 and 3 were not able to obtain the effect of suppressing the wear of bricks, and both Comparative Examples 1 and 2 were defective at the end of operation.
Thus, in Comparative Example 1, since the effect of suppressing the wear of the brick was not obtained and a defect occurred at the end of operation, the overall evaluation was “x”.
In Comparative Example 2, although the effect of suppressing the wear of the brick was obtained, the thickness of the heat insulating material was too thick and a defect occurred at the end of the operation, which hindered the use of the dip tube. × ”.
Furthermore, although the comparative example 3 was able to eliminate the defect at the end of operation, the heat conductivity of the heat insulating material was too high, and the effect of suppressing the wear of the brick was not obtained, which hindered the use of the dip tube. The overall evaluation was “x”.

Next, with respect to the conditions of Example 3, MgCr1 whose magnesia-chromia brick, which is a wear refractory on the inner peripheral side of the core metal, was changed in a range of 16% by volume to 23% by volume. The brick was changed to an MgCr2 brick that was changed in the range of 8% by volume to 15% by volume. The results are shown in Example 11.
In general, when the porosity of the brick is lowered, the melt resistance is improved, but the spalling resistance is deteriorated and the brick tends to be easily cracked. The occurrence of the spalling is explained by the internal stress generated by the temperature difference between the working surface side (molten steel contact surface side) and the back surface side of the brick, but by arranging the heat insulating material as in the present invention, The temperature difference is reduced.
Therefore, compared with Example 3, Example 11 was able to improve the average wear rate of bricks without noticeable wear due to spalling, and no deterioration of defects at the end of operation was observed.

Moreover, when using a magnesia-carbon brick for the wear refractory on the inner peripheral side of the cored bar, as shown in Example 12, the amount of carbon (carbon composition) after reduction firing at 1400 ° C. for 3 hours, When it was changed in the range of 10% by mass or more and 15% by mass or less where wear due to spalling is less likely to occur, good results were obtained with the average wear rate and defects at the end of operation due to the effects of the present invention.
On the other hand, as shown in Example 13, when the amount of carbon after reduction firing at 1400 ° C. for 3 hours was changed in the range of 2% by mass or more and 9% by mass or less, which is likely to cause wear due to spalling, the spalling was further performed. The average wear rate could be improved in a range where the above-mentioned phenomenon was not significant, and the deterioration of defects at the end of the operation, which would easily occur if a heat insulating material was not arranged, was not seen.

From the above, by using the dip tube of the degassing apparatus of the present invention, the long life of the refractory can be very easily achieved by only heat insulation in the vicinity of the core metal without significantly changing the conventional dip tube structure. We were able to confirm that
In addition, due to the effect of the heat insulating material, although the spalling is generally inferior, it is possible to extend the life of the refractory by using a low-porosity dense refractory brick with a higher resistance to erosion and a brick with a low carbon content. I was able to confirm that it was possible.

  As described above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the configuration described in the above embodiment, and the matters described in the scope of claims. Other embodiments and modifications conceivable within the scope are also included. For example, the case where the dip tube of the degassing apparatus of the present invention is configured by combining some or all of the above-described embodiments and modifications is also included in the scope of the right of the present invention.

10: Degassing device dip tube, 11: Metal core, 12: Brick (inner refractory), 13: Indeterminate refractory (outer refractory), 14: Support metal, 15: Hollow part, 16: Insulation

Claims (5)

In the dip tube of the degassing apparatus in which the inner peripheral side refractory and the outer peripheral side refractory are provided on the inner peripheral side and the outer peripheral side of the cylindrical metal core, respectively.
A heat insulating material having a thickness of 1 mm or more and 5 mm or less and a thermal conductivity of 0.05 W / (m · K) or less at an ambient temperature of 500 ° C. is disposed between the inner peripheral refractory and the cored bar. ,
A dip tube for a degassing apparatus, wherein the inner peripheral refractory is made of magnesia-chromia brick having a porosity of 8% by volume to 15% by volume . In the dip tube of the degassing apparatus in which the inner peripheral side refractory and the outer peripheral side refractory are provided on the inner peripheral side and the outer peripheral side of the cylindrical metal core, respectively.
A heat insulating material having a thickness of 1 mm or more and 5 mm or less and a thermal conductivity of 0.05 W / (m · K) or less at an ambient temperature of 500 ° C. is disposed between the inner peripheral refractory and the cored bar. ,
A dip tube for a degassing apparatus, characterized in that the inner circumferential refractory is composed of magnesia-carbon bricks having a carbon content of 2% by mass or more and 9% by mass or less after reducing and firing at 1400 ° C. for 3 hours. . In the dip tube of the degassing apparatus in which the inner peripheral side refractory and the outer peripheral side refractory are provided on the inner peripheral side and the outer peripheral side of the cylindrical metal core, respectively.
Heat at an ambient temperature of 500 ° C. between the inner peripheral refractory and the core metal, and between or both of the outer peripheral refractory and the core metal, with a thickness of 1 mm to 5 mm. A heat insulating material having a conductivity of 0.05 W / (m · K) or less is disposed,
A dip tube for a degassing apparatus, wherein a plurality of studs having an interval of 80 mm or more and 250 mm or less are provided on an outer peripheral surface of the cored bar . The dip tube of the degassing apparatus according to claim 1 or 2, wherein a plurality of studs having adjacent intervals of 80 mm or more and 250 mm or less are provided on the outer peripheral surface of the cored bar. . The dip tube of the degassing apparatus of any one of Claims 1-4 WHEREIN: The said heat insulating material is microporous , The dip tube of the degassing apparatus characterized by the above-mentioned .

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