JP3672635B2 - Dipping tube for molten steel processing equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a structure of a dip tube for a molten steel processing apparatus.
[0002]
[Prior art]
Immersion pipes installed in molten steel processing equipment such as RH and DH vacuum degassing equipment and CAS equipment in the steel industry are affected by the flow of molten steel, reaction with slag floating on the molten steel, and peeling due to thermal cycling. Depending on the consumption. Then, the dip tube having a reduced consumption allowance is removed from the flange portion and replaced with a separately prepared dip tube.
[0003]
When the thickness of the slag adhering to the outer peripheral portion of the dip tube for molten steel processing equipment increases, for example, in the RH type vacuum degassing device in which the dip tubes are arranged in parallel, the dip tubes adhere to each other and the dip tube can be easily replaced. Not.
Further, the dip tube has a problem that the outer diameter increases due to the adhesion of the slag, and it becomes difficult to immerse in the ladle.
Therefore, as a means for preventing the slag from adhering to the outer peripheral portion, it has been proposed to dispose a carbon-containing refractory in the slag line portion as seen in, for example, JP-A-7-51821.
[0004]
[Problems to be solved by the invention]
The carbon-containing refractory is difficult to adhere to slag due to poor wettability of carbon to slag, and by arranging this in the slag line portion, the above-mentioned conventional slag adhesion problem can be solved. However, at the boundary between this carbon-containing refractory and the other refractories, molten steel penetrates into the joint opening caused by the difference in material, and damage to the metal cylinder and refractory support hardware inside the dip tube, Furthermore, there was a problem that the refractory below was dropped from the joint.
An object of the present invention is to solve the above-mentioned conventional problems in dip tubes.
[0005]
[Means for Solving the Problems]
The present invention relates to a dip tube for a molten steel processing apparatus in which a refractory layer is provided on an inner peripheral portion and an outer peripheral portion of a metal cylinder, and as a refractory layer on the outer peripheral portion, a slag line portion containing carbon of 3 to 50 wt. In addition to arranging the objects, the lower end portion of the above-mentioned regular refractory has an alternately long and short structure in the circumferential direction of the dip tube, and the outer portion other than the above-mentioned regular refractory is an irregular refractory. It is a dip tube for molten steel processing equipment. Moreover, in the above-mentioned dip tube structure, a dip tube for a molten steel processing apparatus in which a slag line part on the outer periphery and the upper side thereof are formed into a carbon-containing shaped refractory . Furthermore, it is the dip tube for molten steel processing apparatuses whose length difference in the height direction in the lower end part of the shaped refractories containing 3 to 50 wt% of carbon arranged in the slag line part is 20 to 60 mm .
[0006]
[Action]
Since the dip tube is used by being immersed in molten steel, the lower part expands due to thermal expansion, and the refractory layer does not follow this expansion.Therefore, in the structure in which the regular refractory is provided in the slag line part, A horizontal joint opening is generated at the boundary with the fixed refractory, and the joint opening width is large, and thus the refractory supporting metal is easily damaged and the refractory below is easily dropped from the joint. Moreover, the carbon-containing regular refractory has a small surface friction coefficient due to the carbon content, and is inferior in sinterability with other refractories, so that the refractory is particularly likely to fall off.
[0007]
On the other hand, the dip tube of the present invention has an uneven boundary between the regular refractory provided in the slag line part and the amorphous refractory below the refractory, so that the lower part of the dip tube expands due to thermal expansion. In this case, the horizontal joint opening generated at the boundary is alternately discontinuous up and down in the circumferential direction of the dip tube in accordance with the long and short structure of the regular refractory. Moreover, horizontal joint opening can be minimized by the frictional resistance of the vertical joint at the boundary. As a result, there are no accidents such as damage to the support metal due to the intrusion of molten steel from the joints, and dropping of the refractory under the dip tube.
[0008]
【Example】
The invention will be described in more detail on the basis of the embodiments shown in the drawings.
In the partial cross-sectional view of FIG. 1 (the right half is a cross section), the metal cylinder (1) serves as a skeleton of the outer and inner refractory layers (4) and (3). The upper end is generally provided with a flange (2) for making the dip tube detachable. The inner refractory layer (3) may be an irregular refractory, but a regular refractory is preferred from the standpoint of corrosion resistance.
[0009]
As the outer periphery refractory layer (4), carbon-containing shaped refractories (5) are arranged in the circumferential direction in the slag line portion. The support of the regular refractory (5) may depend on the lower amorphous refractory (6), but it is preferable to hold the upper and lower ends with the support hardware (7).
The number of the regular refractories (5) in the slag line portion is appropriately determined according to the size of the dip tube. Moreover, since the slag line changes according to the change of the height of the hot water surface, the size in the height direction takes a certain width with a margin.
[0010]
In the present invention, the lower end of the regular refractory (5) in the outer peripheral refractory layer (4) has a long and short structure alternately in the circumferential direction of the dip tube. The difference in length in the height direction at the lower end is preferably about 20 to 60 mm.
In the figure, the regular refractory (5) has a long and short structure alternately in the vertical direction of the outer periphery. However, the present invention is not limited to this, and the long or short length may be long or short, for example, every two pieces. . Further, the widths of the long and short shaped refractories may be different from each other.
[0011]
The carbon-containing shaped refractory (5) in the slag line portion contains carbon, for example, magnesia-carbon, spinel-carbon, magnesia-spinel-carbon, alumina-carbon, alumina-silicon carbide-carbon, etc. Fired product or non-fired product. The carbon content is 3 to 50 wt%, preferably 5 to 30 wt%, in order to obtain a sufficient slag adhesion preventing effect. If it is less than 3 wt%, the effect of preventing the adhesion of slag will be insufficient, and if it exceeds 50 wt%, the strength of the structure will be reduced by the oxidation of carbon.
[0012]
The specific material of the amorphous refractory (6) provided below the regular refractory (5) is not limited. For example, alumina, alumina-spinel, alumina-magnesia, alumina-magnesia-spinel , Castable refractories such as magnesia, magnesia-calcia. Although not shown in the figure, it is preferable that a stud is erected on the metal cylinder (1) in order to support the irregular refractory (6).
[0013]
FIG. 2 shows another embodiment, in which the length in the height direction of the regular refractory (5) in the outer peripheral refractory layer (4) is extended not only to the slag line portion but also to the upper side thereof.
Although not shown in the figure, the present invention can also be applied to a dip tube having a taper on its outer periphery as disclosed in, for example, Japanese Patent Laid-Open No. 6-145768.
[0014]
As an actual machine test, in an immersion pipe for an RH vacuum degassing apparatus having an inner diameter of 500 × an outer diameter of 1000 × a height of 1000 mm, the inner peripheral refractory is a fired magnesia-chromium shaped refractory, and the outer peripheral refractory has A non-fired magnesia-carbonaceous refractory containing 20% by weight of scaly graphite was provided, and the lower and upper portions thereof were alumina-magnesia castable refractories.
Further, the lower end of the unfired magnesia-carbon refractory was made to have a long and short structure alternately in the circumferential direction of the dip tube. The difference in length in the height direction between the long and short was 50 mm.
[0015]
The dip tube of the present invention example thus obtained was compared with a conventional dip tube having the same structure as that of the present invention example except that the lower end of the outer peripheral shaped refractory was aligned. As a result, in the conventional dip tube, as the lower part expands, a horizontally continuous joint opening occurs at the boundary between the outer peripheral shaped refractory and the lower shaped refractory, and the joint width is large. Due to the intrusion, after 33 charges were used, the service life was reached by dropping off the irregular refractory. In contrast, the dip tube according to the embodiment of the present invention has a discontinuous joint at the boundary between the outer periphery of the regular refractory and the amorphous refractory below it, and the joint width is small. In the meantime, the falling of the amorphous refractory below was not observed.
[0016]
【The invention's effect】
In the present invention, as described above, the lower end of the carbon-containing shaped refractory provided in the slag line portion has a long and short structure alternately in the circumferential direction of the dip tube, thereby opening joints along with the downward spread of the dip tube. Suppresses and prevents refractories from falling off. As a result, the slag adhesion preventing effect of the carbon-containing regular refractory in the slag line portion is exhibited and the durability of the entire dip tube is greatly improved.
[Brief description of the drawings]
FIG. 1 is a partial sectional view showing an embodiment of the present invention.
FIG. 2 is a partial cross-sectional view showing another embodiment of the present invention.
[Explanation of symbols]
1 Metal cylinder 2 Flange 3 Inner peripheral refractory layer 4 Outer peripheral refractory layer 5 Carbon-containing regular refractory 6 Amorphous refractory 7 Support metal

Claims (3)

In a dip tube for a molten steel processing apparatus provided with a refractory layer on the inner and outer peripheries of a metal cylinder, as a refractory layer on the outer periphery, a regular refractory containing 3 to 50 wt% carbon is arranged in the slag line portion. And the lower end portion of the above-mentioned regular refractory has an alternately long and short structure in the circumferential direction of the dip tube, and the outer portion other than the above-mentioned regular refractory is an irregular refractory. Immersion tube.   The dip tube for a molten steel processing apparatus according to claim 1, wherein the outer peripheral slag line part and the upper part thereof are carbon-containing shaped refractories. The dip tube for a molten steel processing apparatus according to claim 1 or 2, wherein the length difference in the height direction at the lower end portion of the shaped refractory containing 3 to 50 wt% of carbon arranged in the slag line portion is 20 to 60 mm.

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