JP3532041B2 - Preheating device for immersion nozzle for continuous casting - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a preheating device for a continuous casting immersion nozzle. More specifically, the present invention relates to a preheating device for a continuous casting immersion nozzle capable of preventing defective quality of a cast product in a continuous casting process.

[0002]

2. Description of the Related Art In the casting process of a continuous casting machine, there is a method of directly casting molten metal (molten steel) filled in a ladle, but as shown in FIG. It is temporarily stored in the tundish 51 for the purpose of adjusting the irregularity of the steel and distributing molten steel to each mold. In this case, when the molten steel is poured from the ladle 50 into the tundish 51, if the molten steel comes into contact with the atmosphere, oxidative pollution occurs,
It is supplied through a long nozzle 52 attached to the bottom of the ladle 50. Then, the molten steel clarified by the tundish 51 is poured into a mold (water-cooled mold) 54 through a submerged nozzle 53 attached to the bottom in order to obtain a stable molten steel flow, and is drawn downward with cooling. It is hardened continuously.

When the temperature of the inner wall of the tundish 51 is low, the molten steel poured into the tundish 51 is solidified. Therefore, the tundish 51 is usually preheated just before casting. Pre-heat the tundish 51 in anticipation of the ladle 50 reaching the casting process,
For example, if a trouble occurs in the previous process immediately before and the arrival of the ladle is delayed, the immersion nozzle 53 attached to the tundish 51 will stand by while being diffused into the atmosphere. In the tundish 51, the refractory material has a large thickness, and many lids are attached, so that the temperature drop does not have to be a concern for a short time. However, the immersion nozzle 53 has a small thickness and drops to a temperature that impairs casting in a short time.

Further, since the tundish 51 casts the molten steel amount of 5 to 10 ladle 50, when the ladle becomes empty, the next ladle is installed and the casting is continued again. Since it usually takes several tens of minutes to complete the preparation for casting, the tundish and the dipping nozzle stand by while releasing heat to the atmosphere. Then, this may cause defective quality of the slab.

Therefore, various methods for preheating the immersion nozzle have been conventionally proposed. For example, there is one in which a preheated gas for a tundish is flowed into an immersion nozzle to heat it (see JP-A-57-28659). Further, there is one in which the outer surface of the immersion nozzle is heated by the combustion gas injected by the burner, and the inner surface of the immersion nozzle is heated by forcibly sucking the preheating gas of the tundish into the immersion nozzle (Japanese Patent Laid-Open No. 61-60247). (See the official gazette). Further, there is one in which the immersion nozzle is heated by energization (see JP-A-59-127956).

[0006]

However, in the method described in Japanese Patent Laid-Open No. 57-28659, the gas heated to a high temperature easily rises, so that the gas is fed to the dipping nozzle attached to the bottom of the tundish. In order to guide, the tundish must be tightly sealed, so
There is a problem that the maintenance cost of the tundish increases. Further, since the internal atmospheric pressure of the tundish must be high, it is necessary to supply a large amount of fuel gas, which causes a problem of high cost.

Further, in the method described in JP-A-61-60247, since a preheated gas is forcibly sucked into the tundish, a larger amount of combustion is burned as compared with the method described in JP-A-57-28659. No need to supply gas. However, if the pressure in the tundish becomes negative due to forced suction, the temperature of the tundish will drop due to the outside air being drawn in.Therefore, it will be necessary to improve the airtightness or control the internal pressure, and a suction facility will be required. There is a problem that the casting cannot be started immediately because it is bulky and it takes time to remove the device after preheating.

Furthermore, the methods described in JP-A-57-28659 and JP-A-61-60247 are as follows.
When applied to a submerged nozzle that has been used more than once because it is heated by combustion gas, what adheres to the inner surface of the submerged nozzle is oxidized, which is not preferable in terms of quality.

On the other hand, in the method described in Japanese Patent Laid-Open No. 127956/1984, no oxide is used because no oxidizing gas is used. However, for uniform heating, there is a problem that it is necessary to keep the cross-sectional area in the length direction of the immersion nozzle constant, and the material of the immersion nozzle must be electrically conductive. In addition, a nozzle that has been used more than once may have local thinning due to contact with molten steel and slag, which may lead to variations in temperature rising characteristics and damage due to thermal stress.

In view of the above circumstances, it is an object of the present invention to provide a preheating device for a continuous casting immersion nozzle capable of improving the quality of a cast product.

[0011]

A preheating device for a continuous casting immersion nozzle according to the present invention is a continuous casting machine, in which a molten metal supplied from a ladle is heated after heating the immersion nozzle attached to a tundish. A preheating device for a dipping nozzle in a casting process adapted to be injected into a mold through the dipping nozzle, wherein the preheating device comprises a heating means surrounding the outside of the dipping nozzle and indirectly heating the dipping nozzle, It is characterized in that the heating means is a radiant tube burner device installed in plural around the immersion nozzle.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION A preheating apparatus for a continuous casting immersion nozzle according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is an explanatory view showing an embodiment of a preheating device for a continuous casting immersion nozzle according to the present invention, and FIGS. 2 to 3 are schematic views showing an example of using the preheating device in FIG.

The preheating device of the present invention is, for example, in a continuous casting machine, when initial preheating is performed and preparation for starting casting is made, if immediate casting is not possible, or a dipping nozzle that has been cast once or more is used again. In this case, heat is supplied from the outer surface of the standby immersion nozzle by indirect heating using an electric heater or a radiant tube device described later to prevent temperature drop.

As shown in FIG. 1, the preheating device comprises a heating means A surrounding the outer circumference of the immersion nozzle 1 and a power supply switch 2. As the heating means A, a ring-shaped electric heater 3 that indirectly (non-contactly) heats the immersion nozzle 1 can be used. This electric heater 3 has, for example, an inner diameter of 250 mm, an outer diameter of 450 mm and a height of 400 mm.
An embedded heating wire is installed on the inner surface of the refractory material 4, and a pair of terminals 5 and 6 are connected to the heating wire in order to pass an electric current. In this embodiment, the ring-shaped electric heater 3 is used as the heating means A, but the present invention is not limited to this. For example, a heat storage body and a burner are provided at both ends of a U-shaped radiant tube. A radiant tube burner device provided respectively can be used. When using such a radiant tube burner device, a plurality of radiant tube burner devices are installed around the dipping nozzle. The heating means A can also be arranged in the vicinity of the discharge hole 7 of the immersion nozzle 1.

In this embodiment, only the outer surface of the immersion nozzle 1 is heated by a heating means A such as an electric heater or a radiant tube device.
Since it is indirectly heated by, it can be a relatively simple facility. In addition, no gas is generated when using an electric heater, and gas can be easily recovered when using a radiant tube, so environmental measures are easy and there is no contact with oxidizing gas, resulting in poor quality due to oxide formation. Does not occur.
Furthermore, the airtightness of the tundish is not required, the maintenance cost of the tundish is not increased, and the device in which the internal pressure is difficult to control is also unnecessary.

Further, in this embodiment, it is easy to install and remove the preheating device, and the temperature drop can be prevented in a short time from the end of preheating to the start of casting. It is not necessary to limit the shape or physical properties of the immersion nozzle as in the case of electric heating. Further, in the conventional energization heating method, in order to energize the immersion nozzle used for casting once while preventing local heating, it is necessary to have a uniform cross-sectional area in the energizing direction, and at the time of energizing, the melted portion of the nozzle, etc. It needs to be repaired. Then, the adhered solidified iron itself may be energized, and it is necessary to remove the solidified iron in advance. On the other hand, the apparatus according to the present embodiment does not have these requirements at all.

Next, an example of use of the preheating device of this embodiment will be described. First, FIG. 2A shows an arrangement of the ladle 8, the tundish 9 and the mold 10 during casting.
(B) shows the state where the casting is completed. Next, Figure 2
As shown in (c), after the empty ladle is evacuated, it is removed from the mold 10 in order to make the tundish 9 stand by until the next ladle filled with molten steel arrives.
Then, as shown in FIG. 3A, the tundish 9 is slightly floated during standby and the electric heater 3 as the heating means A is installed.

Next, as shown in FIG. 3B, the tundish 9 is lowered so that the immersion nozzle 1 of the tundish 9 fits inside the electric heater 3, and then the immersion nozzle 1 is heated to the temperature at the start of heating. Although it is affected, it is usually heated for 5 to 15 minutes or more and heated up to about 1100 ° C, and kept warm until the next ladle comes. Then, during this period, the mold can be maintained.

When the next ladle comes, the tundish is removed from the electric heater, the electric heater is removed, and the casting process is repeated again. Since the electric heater 3 is lightweight, for example, one worker can install and remove it, and the time required for such installation and removal is 3-5.
It's about a minute.

In this embodiment, the immersion nozzle is heated during standby to prevent the temperature from dropping, so that no deposits are generated in the immersion nozzle and the discharge hole is not clogged.

In this embodiment, since the ring-shaped electric heater is used, it takes time to raise and lower the tundish at the time of installing and removing the electric heater. By adopting the type, work time can be improved by omitting the ascent and descent times.

[0023]

As described above, according to the present invention,
Since the immersion nozzle is indirectly heated by radiant heat, the deposit (oxide) is not generated, and the quality of the cast piece can be maintained.

Further, since it is a simple facility, it is very easy to install and remove, and since the work of loading and unloading is very small, the operating rate can be reduced and the temperature drop at the time of installation and removal can be prevented. it can.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of a preheating device for a continuous casting immersion nozzle of the present invention.

FIG. 2 is a schematic diagram showing an example of use of the preheating device in FIG.

FIG. 3 is a schematic diagram showing an example of use of the preheating device in FIG.

FIG. 4 is an explanatory view showing a casting process.

[Explanation of symbols]

1 immersion nozzle 2 power supply switch 3 electric heater 4 Fireproof material 5, 6 terminals 7 Discharge hole 8 ladle 9 Tundish 10 Mold A heating means

Front page continued (72) Inventor Yu Kitamura 1 Fuji-machi, Hirohata-ku, Himeji-shi, Hyogo Nippon Steel Corp. Hirohata Works (72) Inventor Akitori Wakaki Fuji-machi 1-cho, Hirohata, Himeji-shi Hyogo New (56) References JP-A-8-197208 (JP, A) JP-A-5-318055 (JP, A) JP-A-51-10129 (JP, A) JP-A-51-10129 Flat 1-170556 (JP, A) Actual Flat 1-189845 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) B22D 11/10 320 B22D 41/60

Claims (2)

(57) [Claims] 1. In a continuous casting machine, after heating an immersion nozzle attached to a tundish, the molten metal supplied from a ladle is poured into a mold through the immersion nozzle to preheat the immersion nozzle. An apparatus, wherein the preheating device comprises a heating means surrounding the outside of the immersion nozzle and indirectly heating the immersion nozzle, and the heating means is provided with a plurality of radiant tube burners installed around the immersion nozzle. A preheating device for a continuous casting immersion nozzle, which is a device. 2. The preheating device according to claim 1, wherein the heating means is arranged in the vicinity of the discharge hole of the immersion nozzle.