JP4464789B2 - Refractory brick for steel making preheated before use and its heat insulation method - Google Patents

Description

  The present invention relates to a refractory brick for steel making that is preheated before use, such as a long nozzle, a submerged nozzle, or a stopper used in continuous casting of steel, and a method for keeping warm.

  Refractory bricks for steelmaking that are preheated before use, such as long nozzles, immersion nozzles or stoppers used for continuous casting of steel, are blocked to prevent damage due to thermal shock at the start of use, or the molten steel solidifies. In order to prevent this, it is preheated at 1000 ° C. or higher before use.

  For example, in the case of an immersion nozzle, a method of preheating with a burner simultaneously with the tundish while attached to the tundish, or a method of preheating with a burner in a preheating box and then attaching to the tundish is common.

  However, when preheating the submerged nozzle and tundish together, there is a step of moving the tundish onto the mold after the preheating is completed and injecting molten steel from the ladle. It takes 5 to 10 minutes to start passing. Also, when preheating the immersion nozzle with a gas burner in the preheating box, attach the molten steel from the preheating box to the tundish on the mold, and then inject the molten steel from the ladle until the molten steel actually starts to pass through the immersion nozzle. Takes 5 to 10 minutes. Furthermore, when troubles such as clogging of a molten steel flow rate control device such as a sliding nozzle device occur, more time is required.

  For this reason, a technique for preventing a temperature drop by winding a ceramic fiber heat insulating material around the entire circumference of the immersion nozzle is performed. However, even if a heat insulating material is used, a temperature decrease of 100 to 200 ° C. is unavoidable, and the preheating temperature is increased by that amount so that it is not damaged by spalling even if the temperature is decreased. However, there is a variation in the time until the start of use, and when time is required until the start of use, there is a problem that it may be damaged by a thermal shock when passing through the molten steel, or the life is shortened. In addition, there is a problem that the quality of brick is deteriorated due to excessive heat. Moreover, when the heat insulating material made of ceramic fiber enters the molten steel, it becomes an impurity and becomes a factor of deteriorating the quality of the steel.

Therefore, in order to preheat or keep warm until just before use, for example, it is conceivable to energize and heat the immersion nozzle. For example, Patent Document 1 discloses a method in which an immersion nozzle is made of a conductive refractory material, such as a graphite material, and is heated by energization. However, a special circuit made of a different material has to be made inside the immersion nozzle. For this reason, the physical properties of the immersion nozzle are changed, and there is a problem that the durability is lowered. Furthermore, there is a problem in that it takes time and effort to manufacture and is expensive. In addition, there is a problem that a special power supply facility with a low voltage and a high current is necessary, and it has not yet been put into practical use.
Japanese Utility Model Publication No. 6-552

  The problem to be solved by the present invention is that, in a refractory brick for steelmaking that is preheated before use, such as a submerged nozzle, long nozzle, stopper, etc., the time from preheating to contact with molten steel, the preheating temperature until then does not decrease. And it is providing the refractory brick for steel making preheated before use which can be heat-retained by a simple method, and its heat-retaining method.

  The present invention relates to a refractory brick for steel making that is preheated before use, such as an immersion nozzle, a long nozzle, a stopper, etc. By introducing combustion gas into the space formed by the cylinder with a burner, the decrease in the preheating temperature of the refractory brick is suppressed and the heat retention is further increased.

  Refractory bricks for steel making that are preheated before use, such as immersion nozzles, long nozzles, stoppers, etc., are kept warm after preheating, so that damage due to thermal shock and a decrease in life are suppressed, and the life is dramatically improved. . In addition, since a fiber-like heat insulating material is not used or the amount of use is very small as in the prior art, the working environment is improved and the contamination of molten steel is reduced.

  An example of a submerged nozzle is shown in FIG. 1 as an example of a refractory brick for steel making that is preheated before use of the present invention and a method for keeping it warm. FIG. 1 is a longitudinal sectional view of an immersion nozzle according to the present invention. The immersion nozzle 1 integrally has an iron outer cylinder 3 fixed to a metal case 4. That is, the jaw portion 5 of the immersion nozzle body 2 is covered with a metal case 4 in order to fix the iron outer cylinder 3, and the upper end portion of the cylindrical iron outer cylinder 3 is fixed to the lower portion of the metal case 4 by welding. ing. The iron outer cylinder 3 has an opening as a burner port 6 at the upper part and an opening as a gas discharge port 7 at the lower end. The iron outer cylinder 3 is slightly longer than the immersion nozzle body 2. The gap between the iron outer cylinder 3 and the immersion nozzle body 2 is 20 mm at the lower end. In the present embodiment, the metal case 4 is used to integrally fix the iron outer cylinder 3 to the submerged nozzle body 2, but other fixing methods such as a metal band can also be used without being limited to this method.

  The longer the length of the iron outer cylinder 3 is, the more preheating effect is obtained. However, the upper part of the immersion nozzle 1 is in contact with a support metal when attached to the tundish, and cannot be covered with the iron outer cylinder 3. For this reason, the iron outer cylinder 3 is provided so as to avoid a portion in contact with the support metal. Moreover, although the effect of a preheating is acquired by providing so that the lower end part of the iron outer cylinder 3 may be located below the lower end surface of the immersion nozzle 1, it is not necessary to cover the whole, for example, in the case of an immersion nozzle A sufficient heat-retaining effect can be obtained at the lower end of the cylinder 3 even near the upper part of the discharge port of the immersion nozzle.

  Since the iron outer cylinder 3 is used only once, there is no problem even if it is oxidized or slightly deformed during use. Although a thickness of 0.5 to 3 mm can be used, the thickness can be partially changed. For example, the vicinity of the discharge port can be made thin so as to be easily melted quickly. On the contrary, the non-immersed part may be thickened in order to increase the heat retention during use. Moreover, in order to improve the heat retaining property during the movement of the immersion nozzle after preheating, it is possible to further enhance the heat retaining property by providing a lid at the opening. Further, if a plurality of burner ports 6 are provided, a plurality of burner ports 6 may be provided because the temperature distribution becomes more uniform.

  In addition, although the conventional heat insulating material is unnecessary on the outer peripheral surface of the immersion nozzle 1, it is possible to further improve the heat insulating property by providing a small amount of heat insulating material as required.

  As for the clearance gap between the iron outer cylinder 3 and a refractory (immersion nozzle main body 2), 10-50 mm is more preferable. If it is less than 10 mm, it becomes difficult for the combustion gas to flow, and if it exceeds 50 mm, the outer diameter becomes too large, which hinders handling. For example, in the case of an immersion nozzle, if the outer diameter exceeds 50 mm on one side, it may not enter the mold.

  Next, an example of the immersion nozzle shown in FIG. 1 will be described with reference to FIG. 2 as an example of a method for keeping the refractory brick for steelmaking preheated before use.

  FIG. 2 is a longitudinal sectional view showing a state in which the immersion nozzle 1 of the present invention is set in a mold. Usually, the immersion nozzle 1 is preheated in another place while being attached to the preheating box or the tundish, and when the preheating is completed, it is moved together with the tundish and placed at a predetermined position in the mold 8. The immersion nozzle 1 is held by a holding device (not shown), and a portion of the support metal 10 is held, and is pressed against a lower nozzle attached to a sliding nozzle device provided at a lower portion of a tundish (not shown).

  In order to keep the immersion nozzle 1 warm, a burner 9 is inserted from the burner port 6 and heated. As the burner 9, a general burner using gas or liquid fuel as fuel is sufficient. In this case, a gas obtained by mixing air with a fuel gas such as LPG is discharged from the end of the pipe. The heating of the immersion nozzle 1 is preferably started as soon as possible after completion of preheating because the heat retention effect is higher as soon as possible, but it is sufficient even after being placed in the mold 8.

  After the immersion nozzle 1 is placed in the mold 8, molten steel is poured from the ladle into the tundish, and when a predetermined amount of molten steel has entered, the molten steel begins to pass through the immersion nozzle 1. The heating can be continued immediately before or after the molten steel passes through the immersion nozzle 1. At this time, the iron outer cylinder 3 is melted even if dipped in the molten steel together with the dipping nozzle 1 and is used without being adversely affected since it melts. Therefore, it can be preheated for a while after passing through the molten steel.

  During the casting, after the burner 9 is removed and the heating is stopped, if the burner port 6 is closed for the purpose of preventing the outer peripheral surface of the immersion nozzle 1 from being cooled and oxidized, a heat retaining effect can be obtained.

  In this way, since the immersion nozzle can be kept warm after the preheating is finished until the molten steel actually passes through the immersion nozzle, the damage of the immersion nozzle due to thermal shock can be greatly reduced, and the life of the immersion nozzle can be reduced. Is also extended significantly. Furthermore, since the heat can be kept sufficiently, troubles such as solidification of molten steel in the nozzle can be prevented.

  Moreover, since the iron outer cylinder 3 is provided integrally with the immersion nozzle 1, it is immersed by the air between the iron outer cylinder 3 and the radiant heat of the iron outer cylinder 3 while the preheating of the immersion nozzle 1 ends and moves. The effect which suppresses the temperature fall of the nozzle 1 is acquired.

  3 and 4 show a second embodiment.

  FIG. 3 is a vertical cross-sectional view of a support metal having a burner portion and an iron outer cylinder and an immersion nozzle, and FIG. 4 is a view of the burner portion as viewed from below.

  In FIG. 3, the immersion nozzle body 15 is supported by a support metal 10, and a donut-shaped burner portion 11 and an iron outer cylinder 3 are provided at the lower part of the support metal 10. The donut-type burner unit 11 includes a doughnut-type pipe 12 and a gas introduction pipe 13. The donut-shaped pipe 12 has a plurality of gas discharge ports 14. The donut-shaped burner portion 11 is fixed so as to be integrated with the support hardware 10. The iron outer cylinder 3 is suspended from the support metal 10 by a hook (not shown) and is detachably attached to the support metal 10.

  When heating is started, an air-fuel mixture of fuel gas and air is blown into the donut-type burner section 11 to ignite. Even in the state of FIG. 3, the preheating temperature of the submerged nozzle ignites without any problem, but from the viewpoint of safety, it is possible to confirm the occurrence of flame by igniting before mounting the iron outer cylinder 3. In this embodiment, since the gas discharge ports 14 are uniformly provided on the circumference of the donut-shaped pipe 12, the flame is generated uniformly, and the temperature of the space between the iron outer cylinder 3 and the submerged nozzle body 15 is further increased. There is a merit that can be made uniform.

  In addition, the first preheating can also be performed in the state of FIG. Furthermore, in this embodiment, the iron outer cylinder 3 is held by the support hardware 10, but there is no problem even if it is attached to the immersion nozzle integrally. For example, a metal band can be provided on the outer surface of the immersion nozzle body 15 and the metal band and the iron outer cylinder can be fixed to be integrated.

  FIG. 5 shows a case where it is applied to a stopper. In the case of the stopper 19, as in the case of the immersion nozzle, an iron outer cylinder 3 having a burner port 6 at the upper portion and a gas discharge port 7 at the lower portion is provided. The upper surface of the iron outer cylinder 3 has a through hole through which the bolt 17 penetrates, and the iron outer cylinder 3 is integrally attached to the stopper main body 18 with a nut 16 through the bolt 17 through the through hole. In the case of a stopper, it is used with an iron outer cylinder attached.

It is a longitudinal cross-sectional view of the immersion nozzle of this invention. It is a longitudinal cross-sectional view which shows the state which set the immersion nozzle of this invention to the mold. It is a longitudinal cross-sectional view of the support metal hardware which has a burner part and an iron outer cylinder, and an immersion nozzle. It is the figure which looked at the burner part from the bottom. It is the longitudinal cross-sectional view which applied this invention to the stopper.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Immersion nozzle 2 Immersion nozzle main body 3 Iron outer cylinder 4 Metal case 5 Jaw part of immersion nozzle main body 6 Burner port 7 Gas discharge port 8 Mold 9 Burner 10 Support metal 11 Burner unit 12 Pipe 13 Gas introduction pipe 14 Gas discharge port 15 Immersion nozzle body 16 Nut 17 Bolt 18 Stopper body 19 Stopper

Claims (4)

Long nozzle, the outer peripheral surface of the steelmaking refractory brick to be preheated before use, such as immersion nozzle or a stopper, provided with iron outer cylinder having a gas outlet to the burner mouth and bottom to top through the space, the steelmaking refractories In a state where the brick is attached to the molten metal container after preheating, at least until the refractory brick for steelmaking comes into contact with the molten steel, the combustion gas is blown from the burner port and kept warm, and the iron outer cylinder is attached to the refractory brick for steelmaking. A method of keeping warm a refractory brick for steelmaking preheated before use, characterized by immersing in molten steel together with a refractory brick for steelmaking. The heat-retaining method for a refractory brick for steel making according to claim 1, wherein the iron outer cylinder is fixed to the refractory brick side for steel making and integrated with the refractory brick for steel making. The heat-retaining method for refractory bricks for steel making according to claim 1 or 2, wherein the iron outer cylinder is disposed with a clearance of 10 to 50 mm from the outer peripheral surface of the refractory brick for steel making. Refractory bricks for steelmaking that are preheated before use, such as long nozzles, immersion nozzles, or stoppers, and are made of steel outer cylinders with a burner port on the top and a gas discharge port on the bottom. Refractory brick for steel making, preheated before use, characterized by being covered and integrated.

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