JPH09227929A - Immersion tube for molten steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the development of crack and the fall-down of a shaped refractory at the outer periphery, in a refractory coating structure of an immersion tube for molten steel arranged with the shaped refractory at the outer periphery. SOLUTION: In the immersion tube for molten steel obtained by coating the outer periphery and an inner periphery of a cylindrical core metal 5 with the refractory, the refractory in at least below the molten steel surface 3 of the outer periphery of the immersion tube is formed by surrounding arrangement of the plural shaped refractories 6 and a bored hole 12 inclined upward is arranged on the back surface of the each shaped refractory 6. Further, a supporting rod 11 inclined upward is projected at the outer periphery of the core metal 5 and inserted into the bored hole 12 on the back surface of the shaped refractory.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a molten steel immersion pipe having excellent durability.

[0002]

2. Description of the Related Art In steelmaking equipment, various dipping pipes are used for circulating molten steel with the lower end immersed in the molten steel. For example, it is a dip tube attached to a vacuum degassing device called RH or DH or a simple degassing device called PI or CAS. The one-sided structure of these dip tubes is
Description will be given by taking an immersion pipe of an H vacuum degassing device as an example. FIG.
Is a sectional view thereof. (1) is a dip tube, (2) is a vacuum tank, and (3) is a molten steel level. During operation of the vacuum degassing apparatus, molten steel is sucked into the vacuum tank (2) or discharged from the vacuum tank (2) through the dip pipe (1), whereby the molten steel is degassed.

The dip tube (1) has a cylindrical cored bar (5) having a flange (4) at its upper end, and the outer and inner peripheries thereof are covered with a refractory material. When the damage to the refractory progresses, the dip pipe (1) is removed from the flange (4) and replaced with a new one.

Since the regular refractory is manufactured by pressure molding, it has a superior structure strength as compared with the cast irregular refractory. The refractory to be coated on the dip pipe (1) is preferably a regular refractory on both the inner and outer sides in consideration of durability. However, unlike the outer circumference, the inner circumference refractory cannot obtain a pressing force in the circumferential direction, and unlike the irregular-shaped refractory, it cannot be supported by studs. Therefore, the conventional covering structure of the refractory material is generally a regular refractory material on the inner circumference and an irregular refractory material on the outer circumference.

In recent years, in order to improve the durability of the immersion pipe, a structure has been proposed in which a fixed refractory is also used on the outer periphery of the immersion pipe as disclosed in, for example, Japanese Patent Laid-Open No. 7-341119. FIG. 5 is a partial sectional view thereof. The figure is a partially enlarged view of the immersion pipe corresponding to the portion surrounded by the alternate long and short dash line in FIG.

In this example, the regular refractory material (6) on the outer periphery is provided at the contact portion with the molten steel surface (3). Further, the fixed refractory (6) has its upper and lower surfaces diverged toward the inside of the dip tube, and the upper and lower sides of the fixed refractory (6) are gripped and fixed by a holding metal fitting (7) and a receiving metal fitting (8). The molten steel surface (3) is also a so-called slag line in which slag floats, and is a place where the wear rate is particularly high. Therefore, the durability of the peripheral refractory is improved by providing the fixed refractory in this portion.

[0007]

However, in the above-mentioned conventional structure, the molten steel surface (3) and the contact portion are the regular refractory, but the lower portion is the irregular refractory (9). Irregular refractories are inferior in corrosion resistance to regular refractory materials. Also,
Due to the thermal expansion and contraction of the refractory during use of the dip tube, the regular refractory (6) on the outer periphery and the irregular refractory (9) located below it
There is a concern that a void will be generated at the interface with and the molten metal intrudes into this portion, damaging the receiving metal fitting (8) and dropping off the fixed refractory (6) on the outer periphery.

In order to improve the life of the immersion pipe, it is necessary that the regular refractory material is provided not only on the molten steel surface but also on the entire molten steel immersion area below that. Providing the outer peripheral fixed refractory material (6) up to the lower end of the dip pipe causes a problem of supporting the lower end of the fixed refractory material. That is, when the standard refractory material reaches the lower end, the position of the receiving metal fitting (8) is exposed from the refractory material and is immediately melted by contact with the molten steel.

Therefore, as shown in FIG. 6, a step (13) is provided on the back surface of the fixed refractory (6), and a receiving metal fitting (8) is provided on this step, so that the fixed refractory (6) is attached to the dip pipe. It extends to the lower end and does not expose the receiving fitting (8). However, the regular shaped refractory (6) on the outer circumference has a step (1
By providing 3), there is a problem that cracks are likely to occur at the step portion during manufacturing or use thereof. Step (1
It is even more so when 2) is made into an acute angle as shown in the figure.

When the step (13) of the regular shaped refractory (6) on the outer circumference is cracked during use of the dip pipe, the lower part falls off from this crack part, and further, the receiving metal fitting (8) is melted by the exposure to cause damage to the receiving metal fitting. Refractories above (8) will also fall off. The present invention is intended to solve the above-mentioned problems in a refractory coating structure of a dip tube in which a fixed refractory is provided on the outer periphery.

[0011]

Means for Solving the Problems The present inventors first thought of using a support rod instead of a metal fitting for supporting the lower part of the regular refractory material on the outer periphery. By supporting the regular shaped refractory on the outer periphery with the support rod inserted into the perforation formed on the back surface,
Even when the outer peripheral fixed refractory reaches the lower end of the dip pipe, the supporting member is not exposed from the refractory portion. In addition, the perforations formed on the back surface of the regular refractory material are structurally unlikely to cause cracks, unlike steps. Further, it is easy to form the perforations, which is extremely preferable from the viewpoint of the productivity of the dip tube.

However, in the structure in which the back surface of the standard refractory material is simply supported by the supporting rod, a gap is created between the standard refractory material on the outer periphery and the core metal, and molten steel penetrates into the gap to melt the core metal. There is a problem of losing. The gap is created because the lower part of the dip pipe is immersed in the molten steel when it is used, and the lower part of the dip pipe expands under the heat of the molten steel. Is the cause. Therefore, as a result of further studies by the present inventors, in a structure in which the back surface of a fixed refractory material on the outer periphery is supported by a support rod, when the support rod is tilted upward, the fixed shape refractory material on the outer periphery and the core metal are The present inventors have completed the present invention by knowing that voids can be prevented from being generated between them.

The present invention relates to a molten steel dip tube in which a cylindrical cored bar is coated with a refractory material on the outer and inner circumferences thereof. The fixed refractory material is provided with a perforated hole that is inclined upward, and a supporting rod that is inclined upward is provided on the outer periphery of the core bar, and the supporting rod is formed into the fixed refractory material. It is a molten steel dip tube characterized by being inserted into a back hole.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS. 2, 3 and 4. 2 and 3 are partially enlarged views of the immersion pipe corresponding to the portion surrounded by the alternate long and short dash line in FIG. 4 is a sectional view taken along the line AA of FIG.

In FIGS. 2 and 4, the inner peripheral refractory of the core metal (5) may be either a regular refractory or an irregular refractory, but as is conventional, the regular refractory is preferred. Here, the standard shaped refractory (10) on the inner circumference is 3 up and down.
Although provided in steps, a plurality of steps other than three steps or an integrated one in the top and bottom may be used. It is preferable that the fixed refractory material (10) on the inner circumference is divided into a plurality of pieces in the circumferential direction. Further, it is preferable to fill the space between the core metal (5) and the fixed refractory material (10) on the inner circumference with an irregular refractory material as shown in the figure.

The support structure for the regular refractory material (10) on the inner circumference is not particularly limited. As shown in the same figure, in addition to inserting and supporting the support rod (12) in the perforation (11) provided in the back surface of the fixed refractory (10), the metal fitting (8) may be used as shown in FIG. When an irregular refractory is provided on the inner circumference, a stud (not shown) is erected on the core metal (5) to support the irregular refractory.

The standard refractory material is pressure molded into an arbitrary shape,
After drying, it is baked if necessary. On the other hand, amorphous refractories use alumina cement as a binder,
It is constructed by pouring. Irregular refractories can be quickly and easily constructed by pouring them directly into a mold that fits the shape of the dipping pipe, but a large amount of construction water is used and pressure molding is not performed, so compared to regular refractories. Poor tissue strength.

The greatest feature of the present invention is the supporting structure for the regular refractory material (6) on the outer periphery. In the present invention, the core metal (5) is provided in the perforation (11) provided on the back surface of the regular refractory material (6) on the outer periphery.
The support bar (12) protruding from the outer periphery of the is inserted. The support rod (12) is fixed by, for example, passing the support rod (12) through a through hole provided in the cored bar (11) and welding the base end portion to the cored bar (5). As a matter of course, the material of the support rod (12) is made of metal. Further, it is preferable to fill the space between the core metal (5) and the regular refractory material (6) with an irregular refractory material as shown in the figure.

Regarding the perforation (11) and the support rod (12),
The cross-sectional shape at right angles to the length direction may be circular, elliptical, or polygonal, but the circular shape is the most preferable from the viewpoint of easy perforation (11) and strength of the support rod (12). Also, the perforations (11) and the support rods (12) need to have at least their upper surfaces inclined, for example, for the perforations (11), the upper surfaces are inclined and the lower surfaces are horizontal. Even a shape is included in the inclined perforation referred to in the present invention.

The perforations (11) and the support rods (12) are preferably provided on all of the fixed refractory materials (6) on the outer periphery, but if sufficient pressure can be applied between the fixed refractory materials (6) to support each other, It may be provided at intervals in the circumferential direction. Further, the positions of the perforations (11) and the supporting rods (12) inserted through the perforations in the height direction with respect to the dip pipe may be changed in the circumferential direction within the range of the height of the fixed refractory (6) on the outer circumference. Good.

Support rods (12) and regular shaped refractory materials (6) on the periphery
The holes (11) provided in the both are inclined upward.
The inclination angle θ is, for example, 15 to 65 ° with respect to the horizontal plane.
Is preferred. If the angle of inclination is too small, the effect of the present invention cannot be obtained, and conversely if too large, the regular refractory (6) on the outer periphery is likely to be damaged.

The support rod (12) pulls the fixed refractory (6) on the outer periphery by the friction due to this inclination. As a result, the formation of voids between the fixed refractory (6) and the cored bar (5) on the outer circumference due to expansion and contraction below the dip tube is prevented. The perforation (11) provided on the back surface of the fixed refractory (6) can be easily perforated by a boring machine or the like.

The fixed refractory material (6) on the outer periphery is provided at least below the molten steel surface (3). Since the height of the molten steel molten metal surface (3) changes during use, the fixed refractory (6) on the outer periphery is provided with a margin in the height direction so as to correspond to the change of the molten steel molten metal surface (3). The upper end of the fixed refractory (6) on the outer periphery may be supported in the same manner as in the conventional case. For example, as shown in the figure, the holding metal fitting (7) whose base end is fixed to the core metal (5) is used. Further, it is preferable that the upper end (3) of the regular shaped refractory material on the outer periphery is inclined downward as shown in the figure.

FIG. 3 shows another embodiment. Here, as a configuration other than that shown in FIG. 2, the entire outer circumference of the dip tube is a standard refractory material (6). Although the position of the holding metal fitting (7) is not particularly limited, it is provided on the lower surface of the flange (4) here. Further, in both of the embodiments shown in FIGS. 2 and 3, a taper (14) is provided so that the outer peripheral surface of the outer peripheral fixed refractory (6) is inclined downward toward the inside of the dip tube. Due to this taper (14), the buoyancy force that the outer peripheral fixed refractory (6) receives from the molten steel acts toward the inside of the dip pipe, and the gap between the outer peripheral fixed refractory (6) and the core metal (5). Prevention of generation becomes more effective. In addition, in order to suppress the expansion of the cored bar (5) due to thermal expansion, it goes without saying that, for example, ribs (not shown) may be provided on the inner and outer circumferences of the cored bar (5).

[0025]

EXAMPLES The present invention was carried out in a dipping tube of a 230 t capacity RH vacuum degasser. The dip tube has an inner diameter of 65
The diameter is 0 mm, the outer diameter is 1220 mm, and the height is 800 mm. The inner circumference is lined with a fired fixed refractory of magnesia-chromium mineral, and the refractory of the outer circumference is provided with a non-fired fixed refractory of magnesia-carbonaceous material below the molten steel surface, and the upper part of it is cast with alumina-magnesia Filled with standard refractory.
The height of the regular refractory on the outer circumference is 600 from the lower end of the dip pipe.
The thickness was 80 mm and the thickness was 80 mm.

The regular refractory material on the outer periphery was formed with a boring machine having a hole having a diameter of 20 mm on the back surface, and a steel support rod having a diameter of 16 mm and a length of 60 mm, the base end of which was welded to a core metal, was inserted.
Further, the perforations on the rear surface of the regular refractory material and the support rods inserted through the perforations were both tilted at 30 ° with respect to the horizontal plane.

The example of FIG. 5 in which the outer peripheral fixed refractory is provided only on the molten steel surface, the outer peripheral fixed refractory is extended to the lower end of the dipping pipe, but a step is provided on the rear surface of the outer peripheral fixed refractory. The example of FIG. 6 and the example which was the same as the example of the present invention except that the perforations on the back surface of the fixed refractory for inserting the supporting rod and the same were made horizontal were compared and tested with the example of the present invention. The dimensions of the immersion pipe, the conditions of use, the material of the refractory material, etc. were the same as those of the examples of the present invention and comparative examples.

In each of the examples, the irregular refractory layer was supported by the studs erected on the core bar in the portion to be constructed with the irregular refractory material in the usual manner. In the example of FIG. 5, the lower part of the outer periphery was inferior in corrosion resistance due to the irregular-shaped refractory, and had a service life of 10 charges. In the example of FIG. 6, cracks were formed on the stepped portion on the back surface of the regular refractory material, and the service life was 10 charges. In addition, in the example in which the support rod and the perforation on the back surface of the fixed refractory that penetrates it are made horizontal, molten steel penetrates into the gap formed between the fixed refractory on the outer periphery and the core metal, which is the main cause. The service life was 10 charges.

On the other hand, in the examples of the present invention, there were no defects found in the comparative examples, and the effect of corrosion resistance due to the fact that the entire molten steel dipping portion was made into a regular refractory was sufficiently exhibited.
A service life longer than the charge was obtained. The above examples are RH
Although it is a dipping tube for a vacuum degassing device, the same result is obtained for dipping pipes such as a DH vacuum degassing device or a simple degassing device called PI or CAS. .

[0030]

As described above, the immersion pipe of the present invention has excellent durability. As a result, according to the vacuum degassing apparatus using the immersion pipe of the present invention, the effects such as reduction of the man-hours for exchanging the immersion pipe and improvement of the operation rate of the vacuum degassing device are extremely large.

[Brief description of drawings]

FIG. 1 is a sectional view showing the entire structure of a molten steel immersion pipe.

FIG. 2 is a partially enlarged cross-sectional view of an embodiment of an immersion pipe according to an embodiment of the present invention.

FIG. 3 is a partially enlarged cross-sectional view of an embodiment of an immersion pipe according to an embodiment of the present invention.

FIG. 4 is a sectional view taken along line AA of FIG. 2;

FIG. 5 is a partially enlarged sectional view of a conventional immersion tube.

FIG. 6 is a partially enlarged cross-sectional view of a dip tube of a comparative example.

[Explanation of symbols]

 1 Immersion pipe 2 Vacuum tank 3 Molten steel surface 4 Flange 5 Core bar 6 Perimeter fixed refractory 7 Holding metal 8 Receiving metal 9 Irregular refractory 10 Perforation 11 Support rod 12 Support rod 13 Step 14 14 Taper

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeo Nakamura 1-3-1, Niihama, Arai-cho, Takasago, Hyogo Prefecture Harima Ceramics Co., Ltd.

Claims (2)

[Claims] 1. A molten steel dip tube in which a cylindrical cored bar is coated with a refractory material on the outer and inner circumferences thereof. And a perforation inclined upward is provided on the back surface of the standard refractory, and a support bar inclined upward is provided on the outer periphery of the core metal, and the support bar is provided on the rear surface of the standard refractory. An immersion pipe for molten steel, characterized by being inserted into a hole. 2. The immersion pipe for molten steel according to claim 1, wherein the outer peripheral surface of the fixed refractory material on the outer periphery of the immersion pipe has a taper inclined downward toward the inside of the immersion pipe.