JP2014136247A - Preheating method and preheating device of immersion nozzle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a preheating method and a preheating device of an immersion nozzle capable of sufficiently preheating the immersion nozzle to a desired degree.SOLUTION: In the preheating method of the immersion nozzle 30 installed on an under surface of a tundish 20 of a continuous casting machine, the preheating method of the immersion nozzle is composed of a first step of arranging a pipe 2 fluidly communicating with a fluid discharge device 1 existing on the outside of the tundish 20 on the inside from an inlet end 30b of the immersion nozzle 30 via the inside of the tundish 20, by installing the inlet end 30b of the immersion nozzle 30 on the under surface of the tundish 20, before preheating the tundish 20 and a second step of preheating an inner surface of at least the immersion nozzle 30 by taking high temperature exhaust gas existing inside the tundish 20 in the immersion nozzle 30, by forming a negative pressure area in the immersion nozzle 30 by providing this high pressure fluid, by providing the high pressure fluid in the immersion nozzle 30, by preheating the tundish 20, and then, operating the fluid discharge device 1.

Description

  The present invention relates to a preheating method and a preheating apparatus for an immersion nozzle attached to the lower surface of a tundish of a continuous casting machine.

  The reason is that the immersion nozzle (tundish nozzle) for pouring into the mold (mold) is not sufficiently preheated or the temperature drop after completion of preheating is large at the start of pouring with the stopper or sliding nozzle of the continuous casting machine As a problem, alumina in the molten steel is deposited around the inlet end of the immersion nozzle attached to the lower surface of the tundish, and the immersion nozzle is clogged. This clogging of the immersion nozzle may occur about once a day. However, due to the clogging of the immersion nozzle, the amount of pouring from the immersion nozzle to the mold is extremely reduced and the auto start cannot be started. It is necessary to continue the hot water. Here, the manual intervention is to forcibly discharge the deposit around the inlet end of the immersion nozzle by continuous opening and closing of the stopper and sliding nozzle.

  Moreover, when the immersion nozzle is completely blocked, the strand must be stopped from casting, leading to a decrease in productivity. In addition, the casting stop of this strand may occur about once a week.

  Here, in Patent Document 1, the outer side of the immersion nozzle is preheated by a burner in the second furnace body, and the preheating of the inner wall of the immersion nozzle that affects the clogging of the immersion nozzle is applied to the exhaust port of the second furnace body. For the tundish that preheats by sucking out the atmosphere in the second furnace body by making the ejector effect by blowing the driving gas to make the second furnace body negative pressure and sucking the preheated hot air in the tundish through the inside of the immersion nozzle An immersion nozzle preheating device is disclosed.

  However, when the preheating device disclosed in Patent Document 1 is actually applied, there is a gap between the upper opening that is opened in the second furnace body and through which the immersion nozzle passes and the immersion nozzle that passes through this opening. The present inventor is that a large amount of ambient air at normal temperature is sucked into the second furnace body, and thus the preheated hot air in the tundish is not sufficiently sucked and the inner surface of the immersion nozzle cannot be sufficiently preheated. It is specified by verification. This will be described with reference to FIG.

  FIG. 7 shows a state in which the immersion nozzle is preheated in a posture in which the inlet end DNa of the immersion nozzle DN is attached to the lower surface of the tundish TD. In the illustrated example, the tundish TD is equipped with two burners Ba, and a single stopper S that can be raised and lowered inside the tundish is attached to the outer plate of the tundish TD. The number of stoppers varies. For example, when two strands are formed from one tundish, there is a stopper unique to each strand, and an immersion nozzle is disposed below each stopper. Become.

  In the preheating of the immersion nozzle DN shown in the figure, the main body of the immersion nozzle DN is surrounded by a first furnace body R1, and a second furnace body R2 is disposed below the main body, and an outlet of the immersion nozzle DN is provided at the second furnace body R2. Accommodates a portion of the body including the ends.

  A burner Bb is attached to the first furnace body R1, and an ejector E provided with high-pressure air is attached to the first furnace body R1 and the second furnace body R2 in a posture in fluid communication with both furnace bodies. Yes.

  When the burner Bb and the ejector E are driven in preheating the immersion nozzle DN, a negative pressure region is formed in the ejector E by the high-pressure air that is the driving gas provided (Y1 direction). The high-temperature exhaust gas that heated the tundish TD enters the immersion nozzle DN from the tundish TD (Y2 direction) by the suction force of the negative pressure region in the ejector E, and is immersed while heating the upper region of the immersion nozzle DN. It passes through the nozzle DN, is injected into the second furnace body R2 through the opening DNb at the tip (Y3 direction), and is sucked into the ejector E (Y4 direction). At the same time, the exhaust gas that has heated the main body of the immersion nozzle DN in the first furnace body R1 is also sucked into the ejector E by the suction force of the negative pressure region in the ejector E (Y5 direction).

  Thus, according to the immersion nozzle preheating device disclosed in Patent Document 1, high-temperature exhaust gas in the tundish TD is caused to enter the immersion nozzle DN by the so-called ejector effect caused by the negative pressure region generated in the ejector E. While being provided and heating the inside, the tip of the immersion nozzle DN can also be heated by heating the main body with the exhaust gas from the burner Bb.

  However, according to the verification by the present inventors using a preheating device similar to this, as shown in the figure, the exhaust gas in the tundish TD is actually generated by the negative pressure region generated in the ejector E. When the air is about to be sucked into the immersion nozzle DN, external air passes through the first furnace body R1 and further through a gap at the attachment interface between the immersion nozzle DN and the first furnace body R1 attached therearound. It has been found that the high-temperature exhaust gas in the tundish TD that is sucked into the second furnace body R2 cannot be sufficiently sucked. The fact that the exhaust gas cannot be sufficiently sucked into the immersion nozzle DN means that the inner surface of the immersion nozzle DN cannot be heated to a desired level without being recovered.

  Therefore, even when trying to increase the supply of driving gas to the ejector E in order to enhance the preheating effect, the surrounding atmosphere just leaks from the gaps and the like this time, and the inside of the tundish TD Exhaust gas inhalation does not increase.

  As for the preheating of the immersion nozzle, after the immersion nozzle is preheated in the preheating region as shown in the figure, the tundish TD provided with the immersion nozzle is moved in the horizontal direction and positioned at the casting position. A ladle nozzle (not shown) is attached to the tundish TD at the casting position. The ladle contains molten steel made in a blast furnace after secondary refining. In addition, as for the molten steel poured into the tundish TD below the ladle from the bottom of the ladle, some of the inclusions contained in the tundish TD are removed by floating separation.

  In the conventional preheating apparatus shown in the figure, since the submersible nozzle during transfer in which the tundish is transferred from the preheating region to the casting region cannot be preheated, and preheating during the transfer is not assumed in this way, the submersible nozzle When it takes time from the end of preheating to the time when molten steel is injected from the ladle at the casting position (when the sliding nozzle of the ladle fails to open and performs unsteady operations such as oxygen opening), it is heated. There was a problem that the temperature of the immersion nozzle was lowered.

Japanese Utility Model Publication No. 64-10359

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a preheating method and a preheating apparatus for an immersion nozzle that can sufficiently preheat the immersion nozzle to a desired degree.

  In order to achieve the above object, a preheating method for an immersion nozzle according to the present invention is a preheating method for an immersion nozzle attached to the lower surface of a tundish of a continuous casting machine, and is applied to the lower surface of the tundish before the preheating of the tundish. A first step of attaching the inlet end of the immersion nozzle and disposing a pipe in fluid communication with a fluid discharge device outside the tundish from the inlet end of the immersion nozzle to the inside of the immersion nozzle through the inside of the tundish; The dish is preheated, and then the fluid discharge device is operated to provide high-pressure fluid in the immersion nozzle. By providing this high-pressure fluid, a negative pressure region is formed in the immersion nozzle, and high-temperature exhaust gas inside the tundish is immersed. It comprises a second step of taking in the nozzle and preheating at least the inner surface of the immersion nozzle.

  In the preheating method of the immersion nozzle according to the present invention, the pipe connected to the fluid discharge device arranged outside the tundish is connected to the inlet of the immersion nozzle through the inside of the tundish with respect to the immersion nozzle attached to the lower surface of the tundish. Inserting from the end and providing a driving gas such as high-pressure air from the fluid discharge device into the immersion nozzle to form a negative pressure area in the immersion nozzle, so that the hot exhaust gas in the tundish is immersed in the immersion nozzle by the ejector effect It is to be provided within.

  By applying the preheating method of the present invention, external air is sucked into the ejector from the gap between the immersion nozzle and the furnace body attached to the outer periphery thereof, and the high-temperature exhaust gas in the tundish is sufficiently contained in the immersion nozzle. The problem of not being provided is solved.

  In addition, the preheating method of the present invention is arranged such that a pipe that leads to a fluid discharge device that provides driving gas in the immersion nozzle is disposed in the immersion nozzle through the inside of the tundish, so that the immersion nozzle is provided as in the prior art. There is no need for a device having a complicated structure that is surrounded by one or more furnace bodies and that the ejector is mounted in fluid communication with the furnace body.

  According to a preferred embodiment of the preheating method for an immersion nozzle according to the present invention, in the first step, the inlet end of the immersion nozzle is attached to the lower surface of the tundish and a part of the main body including the outlet end of the immersion nozzle is hollowed. It is housed inside the furnace body.

  According to the present embodiment, since a part of the main body of the immersion nozzle is accommodated in the hollow furnace body, the high-temperature exhaust gas discharged from the tip of the immersion nozzle is reflected inside the furnace body and Provided on the outer surface, not only the inner surface of the immersion nozzle but also its outer surface can be heated effectively.

  In this way, the outer surface of the immersion nozzle, a part of which is immersed in the mold, is heated, so that the molten steel surface in the mold is cured by the outer surface of the cooled immersion nozzle and is fixed between the outer surface and the mold copper plate. The problem disappears.

  Further, in a preferred embodiment of the preheating method of the immersion nozzle according to the present invention, the tundish is provided with a rod-like stopper for adjusting the opening degree of the immersion nozzle at a position above the immersion nozzle so as to be movable up and down. In the first step, when the tip of the pipe is inserted into the immersion nozzle from the inlet end of the immersion nozzle, the pipe is sent out along the stopper and inserted into the immersion nozzle.

  In the present embodiment, a bar-shaped stopper for adjusting the opening of an immersion nozzle that is originally provided in a tundish is applied as a pipe guide member. Is inserted from the inlet end of the immersion nozzle into the inside, so that the pipe can be easily disposed and fixed in the tundish, and the tip can be precisely fed into the immersion nozzle.

  In a preferred embodiment of the method for preheating an immersion nozzle according to the present invention, the tundish is transferred between a casting position below the ladle and a preheating position different from the casting position. The second step is executed not only before the transfer but also when the tundish is transferred.

  In the preheating method of the present invention, for example, even when the tundish is mounted on a tundish car and the tundish is transferred from the preheating region to the casting region by this tundish car, the fluid discharge device is driven to drive the driving gas into the tundish. The inside of the immersion nozzle can continue to be heated even during the transfer by continuing to feed it to the immersion nozzle attached to the lower surface thereof. Therefore, the problem that the immersion nozzle cools before the molten steel is poured into the tundish from the ladle in the casting region can be effectively solved.

  Furthermore, in another embodiment of the preheating method of the immersion nozzle according to the present invention, the preheating of the tundish is performed until the temperature of the refractory disposed inside the tundish exceeds 1000 ° C., The fluid discharge device is operated when the temperature of the refractory reaches 600 to 800 ° C., and preheating of the inner surface of the immersion nozzle is started.

  A refractory made of, for example, alumina or silica is usually attached to the inside of the tundish. According to the verification by the present inventors, when the temperature of the refractory reaches 600 to 800 ° C., the fluid discharge device is driven to start preheating inside the immersion nozzle based on the ejector effect, and the temperature of the refractory By providing the driving gas until the temperature exceeds 1000 ° C., the upper region of the immersion nozzle can be made 600 to 800 ° C. or more in as short a time as possible. It has been identified that oxidation of objects can be effectively prevented.

  Further, the present invention extends to a preheating device for a submerged nozzle, which is a preheating device for a submerged nozzle attached to the lower surface of a tundish of a continuous casting machine, and a fluid located outside the tundish. A discharge device, and a pipe that is in fluid communication with the fluid discharge device and is disposed inside the submersible nozzle from the inlet end of the submersible nozzle that is attached to the lower surface of the tundish via the tundish. The dish is preheated, and then the fluid discharge device is operated to provide high-pressure fluid in the immersion nozzle. By providing this high-pressure fluid, a negative pressure region is formed in the immersion nozzle, and high-temperature exhaust gas inside the tundish is immersed. The control which takes in in a nozzle and preheats at least the inner surface of an immersion nozzle is performed.

  The preheating device of the present invention has an improved configuration in which a pipe that leads to a fluid discharge device that provides driving gas into the immersion nozzle is disposed in the immersion nozzle through the inside of the tundish, compared to a preheating device having a conventional structure. The structure is simple and the cost for manufacturing the device is low.

  Further, as a preferred embodiment of the preheating device for an immersion nozzle according to the present invention, an embodiment further comprising a hollow furnace body that accommodates a part of the main body including the outlet end of the immersion nozzle can be mentioned.

  Further, as a preferred embodiment of the preheating device for the immersion nozzle according to the present invention, when the tip of the pipe is inserted into the immersion nozzle from the inlet end of the immersion nozzle, it is attached to the upper position of the tundish immersion nozzle so as to be movable up and down. In this case, a rod-shaped stopper for adjusting the opening degree of the immersion nozzle is applied as a guide member for feeding the pipe and inserting it into the immersion nozzle.

  As can be understood from the above description, according to the preheating method and the preheating device of the submerged nozzle of the present invention, the fluid discharge device disposed outside the tundish is connected to the submerged nozzle attached to the lower surface of the tundish. By inserting the pipe to be connected from the inlet end of the immersion nozzle through the inside of the tundish and providing the driving gas from the fluid discharge device into the immersion nozzle to form a negative pressure region in the immersion nozzle. High-temperature exhaust gas in the tundish can be effectively provided in the immersion nozzle, and at least the inside of the immersion nozzle can be sufficiently preheated.

It is the schematic diagram which simulated the continuous casting machine which comprises the preheating apparatus of the immersion nozzle of this invention. It is the longitudinal cross-sectional view which showed Embodiment 1 of the preheating apparatus of the immersion nozzle of this invention, and is the figure explaining the preheating method of the immersion nozzle. It is the longitudinal cross-sectional view which showed Embodiment 2 of the preheating apparatus of the immersion nozzle of this invention, and is the figure explaining the preheating method of the immersion nozzle. It is the figure explaining one Embodiment of the drive control by a fluid discharge apparatus. It is the figure which showed the experimental result regarding the relationship between the amount of drive gas, and the inlet-end inner surface temperature of an immersion nozzle. It is the figure which showed the verification result regarding the production amount per month by a strand. It is the longitudinal cross-sectional view which showed embodiment of the preheating apparatus of the conventional immersion nozzle, and is the figure explaining the preheating method of the immersion nozzle.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a preheating device and a preheating method for an immersion nozzle according to the present invention will be described with reference to the drawings. In the example shown in the figure, the tundish is equipped with two burners, and the tundish outer plate is attached with one stopper that can be raised and lowered inside the tundish, but the number of burners and stoppers is For example, when two strands are formed from one tundish, there is a stopper unique to each strand, and an immersion nozzle is disposed below each stopper.

(Embodiment 1 of preheating device and preheating method for immersion nozzle)
FIG. 1 is a schematic view simulating a continuous casting machine equipped with a preheating device for an immersion nozzle according to the present invention, and FIG. 2 is a longitudinal sectional view showing Embodiment 1 of the preheating device for an immersion nozzle according to the present invention. And it is the figure explaining the preheating method of the immersion nozzle.

  First, the continuous casting machine will be outlined with reference to FIG. As shown in FIG. 1, the continuous casting machine is equipped with a ladle 60 at the uppermost portion into which molten steel is poured and a tundish 20 on the operation floor frame 50, and is movable from the preheating area YA to the casting area CA. (T1 direction) (not shown) tundish car, mold 70 in which molten steel is injected from the tundish 20 positioned in the casting area CA through the immersion nozzle 30, and steel manufactured by rapid solidification in the mold 70 It is mainly composed of a roll 80 for conveying the piece ST.

  Molten steel made in the blast furnace is poured into the ladle 60 through secondary refining. And after the ladle 60 is installed in the uppermost part of a continuous casting machine, the molten steel accommodated in the ladle 60 is inject | poured into the lower tundish 20 from the bottom part of the ladle 60 (Q2 direction), This tundish Even 20, some of the inclusions in the molten steel are removed by floating separation.

  The molten steel accommodated in the tundish 20 is then poured into the mold 70 from the immersion nozzle 30 at the bottom thereof. The mold 70 is generally made of copper and is always water-cooled, and the molten steel in contact with the mold 70 is cooled while precisely adjusting the temperature. In the mold 70, the molten steel begins to form a thin solidified shell made of fine crystals from the outside, and the fine crystals are connected to grow into large dendritic crystals, which are transferred to the steel piece ST from below the mold 70. Is done.

  The steel slab ST begins to solidify from the outside while being conveyed by the roll 80, and when the steel slab ST is a large slab called slab or bloom, an appropriate length is obtained by a gas cutting machine (not shown) at the end of the roll row. Disconnected. On the other hand, when the steel piece ST is a small slab called billet, it is cut by a shear (not shown) and adjusted to an appropriate length.

  Next, Embodiment 1 of the preheating device and preheating method for the immersion nozzle will be described with reference to FIGS. First, in the preheating area YA of the operation floor frame 50, an inlet end 30b of a cylindrical immersion nozzle 30 is attached to the lower surface of the tundish 20 as shown in FIG. Further, on the outer plate of the tundish 20, a rod-like stopper 3 for adjusting the opening degree of the immersion nozzle 30 at a position above the immersion nozzle 30 is attached so as to be movable up and down (X1 direction). In contrast to the immersion nozzle 30 attached to the lower surface of the tundish 20, a pipe 2 connected to the fluid discharge device 1 disposed outside the tundish 20 is provided along the stopper 3 via the inside of the tundish 20 through the immersion nozzle 30. Is inserted from the inlet end 30b and temporarily fixed at the midpoint of the main body 30a (first step).

  In addition, the preheating apparatus 10 of an immersion nozzle is comprised from the stopper 3 used as the guide member at the time of inserting the fluid discharge apparatus 1 and the pipe 2 and the pipe 2 which are fluidly connected to this into the immersion nozzle 30. FIG.

  The insertion length of the pipe 2 inserted into the immersion nozzle 30 is preferably adjusted to 50 to 70 mm from the inlet end 30b. As for the pipe 2, a pipe having a diameter of 6A and a material of SGP can be applied.

  In this way, the pipe 2 in the tundish 20 is arranged by applying the bar-shaped stopper 3 for adjusting the opening of the submerged nozzle 30 originally provided in the tundish 20 as a guide member of the pipe 2. It is easy to fix and the tip can be precisely fed into the immersion nozzle 30.

  Next, the burner 21 attached to the upper plate of the tundish 20 is operated, and the refractory (not shown) attached to the inner surface of the tundish 20 is heated by the high-temperature exhaust gas from the burner 21 to heat the tundish 20. Perform preheating.

After a certain period of time has elapsed from the operation of the burner 21, the fluid discharge device 1 is operated and a driving gas such as high-pressure air is supplied into the immersion nozzle 30 via the pipe 2, whereby a negative pressure region is generated in the immersion nozzle 30. The hot exhaust gas in the tundish 20 is taken into the main body 30a of the immersion nozzle 30 by the ejector effect (W1 direction), and the hot exhaust gas is circulated inside the immersion nozzle 30 and flows out from the outlet end 30c. By doing so (W2 direction), at least the inner surface of the immersion nozzle 30 is preheated (second step). As the driving gas, pressure air of about 0.2 to 0.6 N / mm ² can be applied.

  By applying the preheating method shown in the figure, external air is sucked into the ejector from the gap between the immersion nozzle and the furnace body attached to the outer periphery, and the hot exhaust gas in the tundish is sufficiently provided in the immersion nozzle. The problem of the conventional preheating device that is not performed is solved. The immersion nozzle 30 can be sufficiently preheated, and the problem of nozzle clogging that tends to occur near the inlet end 30b of the immersion nozzle 30 is also eliminated.

  Further, in the second step, the tundish 20 and the immersion nozzle 30 are not only preheated in the preheating area YA, but also during the transfer from the preheating area YA to the casting area CA below the ladle 60. Preheating is performed continuously.

  Even during the transfer of the tundish 20 from the preheating area YA to the casting area CA, the fluid discharge device 1 is driven to continuously send the driving gas to the immersion nozzle 30 attached to the lower surface thereof through the inside of the tundish 20. During the transfer, the inside of the immersion nozzle 30 can continue to be heated. Therefore, the problem that the immersion nozzle cools before the molten steel is poured into the tundish from the ladle 60 in the casting area CA can be effectively solved.

(Embodiment 2 of preheating device and preheating method for immersion nozzle)
FIG. 3 is a longitudinal sectional view showing Embodiment 2 of the preheating device for an immersion nozzle according to the present invention, and is a diagram for explaining a method for preheating the immersion nozzle.

  A preheating device 10A shown in the figure includes a fluid discharge device 1, a pipe 2 in fluid communication with the fluid discharge device 1, a stopper 3 serving as a guide member when the pipe 2 is inserted into the immersion nozzle 30, and an outlet end 30c of the immersion nozzle. It is comprised from the hollow furnace body 40 which accommodates a part of main body 30a to contain.

  In the first step of the preheating method, the preheating device 10A shown in the preheating area YA is formed, and in the second step, the fluid discharge device 1 is operated after preheating the tundish 20 by burner heating, Hot exhaust gas in the tundish 20 is taken into the immersion nozzle 30 (W1 direction), circulated through the immersion nozzle 30, and discharged from the outlet end 30c (W2 direction).

  The high temperature exhaust gas exhausted from the outlet end 30c of the immersion nozzle 30 is reflected in the surrounding furnace body 40 (W3 direction) and provided on the outer surface of the main body 30a of the immersion nozzle 30 (W3 direction). Not only the inner surface of 30 but also its outer surface is effectively heated.

  As described above, the outer surface of the immersion nozzle 30 that is partially immersed in the mold 70 is heated, so that the molten steel surface in the mold is cured by the outer surface of the cooled immersion nozzle, and the outer surface and the mold copper plate are interposed between the outer surface and the mold copper plate. The problem of sticking is eliminated.

[Example of drive control by fluid ejection device]
The inventors of the present invention have carried out one example relating to the preheating pattern of the submerged nozzle and verified the antioxidant effect of the refractory in the upper part of the submerged nozzle and in the tundish near the upper part.

  First, when the tundish was cold, a pipe with a material of SGP and a diameter of 6A was installed, and temporarily fixed with the end of the pipe entering the immersion nozzle in the range of 50 to 70 mm.

  Next, preheating of the immersion nozzle was performed with the preheating pattern shown in FIG. Specifically, the inside of the tundish was heated with a burner, and the fluid discharge device was operated when the inner surface temperature of the tundish reached 600 to 800 ° C. after 2 hours. Due to the operation of this fluid discharge device, the hot exhaust gas in the tundish is sucked into the immersion nozzle due to the ejector effect, the temperature in the immersion nozzle rises rapidly in a short time, and the temperature of the tundish and the temperature in the immersion nozzle are reduced. Both reached 1200 ° C 3 hours after the start of tundish heating.

  The temperature of 1200 ° C. is a temperature at which nozzle clogging does not occur in the immersion nozzle, and is a target temperature for preheating the immersion nozzle.

  In this way, when the temperature in the tundish (refractory) reaches 600 to 800 ° C, the fluid discharge device is operated to start preheating the inside of the immersion nozzle based on the ejector effect, and the temperature of the refractory is 1000 ° C. By providing the driving gas until the temperature exceeds the upper limit, the upper region of the immersion nozzle can be brought to 600 to 800 ° C. or more in as short a time as possible, and the inner surface of the upper region and the refractory in the vicinity thereof are oxidized. It was found that can be effectively prevented.

[Experiments and results on the relationship between the amount of driving gas and the temperature at the inlet end of the immersion nozzle]
The inventors of the present invention used a three-strand tundish equipped with two immersion nozzles having the conventional structure shown in FIG. 7 and one immersion nozzle according to the present invention shown in FIG. An experiment was conducted to preheat for a time and then measure the inner surface temperature of the inlet end of each immersion nozzle.

  Here, regarding the immersion nozzle of the present invention, an immersion nozzle having an overall length of 740 mm, an outer diameter of the nozzle of φ135 mm, an inner diameter of φ70 mm, and four outlets of φ40 mm on the side surface below the main body was used.

  Various changes were made in the amount of driving gas, and the temperature of the inner surface of the inlet end for each driving gas amount of each immersion nozzle in the examples and comparative examples was measured to verify the correlation. The verification result is shown in FIG.

From the figure, the immersion nozzle was driven gas amount embodiment is 3m ³ / min, to achieve 1050 ° C. target at 1 hour of the ejector drive, it was found that reach 1200 ° C. in 5 m ³ / min.

On the other hand, it was found that the immersion nozzle of the comparative example saturates at a temperature of less than 1000 ° C. with a driving gas amount of about 3 m ³ / min and does not reach the target of 1050 ° C. even if the driving gas amount is increased. As described above with reference to FIG. 7, the reason is that when ejecting high-temperature exhaust gas into the immersion nozzle with an ejector, external air is sucked from the gap between the immersion nozzle and the surrounding furnace body. This is because the exhaust gas cannot be sufficiently sucked.

[Verification and result of monthly production by Strand]
The inventors further verified the production per month by the strands. In the conventional method, since the immersion nozzle cannot be preheated to the target temperature, the immersion nozzle is clogged once / day and manual intervention is required. Moreover, the immersion nozzle is completely closed once a week, and casting stops. Thus, since the strand which stopped casting cannot be produced, productivity falls large. For example, in the case of 3 strands, if the casting stops with 1 strand, the remaining 2 strands will be produced and the productivity will be 2/3.

  Here, the production amount per month was compared between the conventional preheating method and the preheating method of the present invention. With regard to the production volume for one month, if the ladle capacity is Qton in the case of a 3-strand machine and 10 pans are cast continuously per day, it will be 1 time / day x 3 strands at the start of casting. And when 100% casting start is successful as in the embodiment, 10 pans / day × 30 days × Qton = 300 Qton / month.

  On the other hand, when the casting is stopped once / week as in the comparative example, the number of times of casting stop is 1 time / week × 4 weeks × 3 strands = 12 times, the number of casting times = 1 time / day × 30 days × 3 strands = 90 times, success rate = (90-12) / 90 × 100 = 87%, production failure amount = 12 times × 10 pans × Qton × 1/3 strand = 40 Qton / month. Therefore, the production amount of the comparative example is 300 Qton / month−40 Qton / month = 260 Qton / month.

  By substituting a certain Q value into the above formula, the production amounts per month of both the comparative example and the example are obtained, and the value of the example is expressed as a ratio relative to the value of the comparative example, which is shown in FIG.

  From the figure, it was found that the production amount of the example was improved by 15% compared to the comparative example. Many steel mills operate day and night continuously, and a 15% increase in production is a significant operational effect.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. They are also included in the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Fluid discharge apparatus, 2 ... Pipe, 3 ... Stopper, 10, 10A ... Preheating apparatus, 20 ... Tundish, 21 ... Burner, 30 ... Dipping nozzle, 30a ... Main body, 30b ... Inlet end, 30c ... Outlet end, 40 ... Furnace body, 50 ... Operating floor frame, 60 ... Ladle, 70 ... Mould, 80 ... Roll, YA ... Preheating area, CA ... Casting area, ST ... Slab

Claims (8)

A preheating method for an immersion nozzle attached to the lower surface of a tundish of a continuous casting machine,
Before pre-heating the tundish, attach the inlet end of the immersion nozzle to the bottom of the tundish,
A first step of disposing a pipe in fluid communication with a fluid ejection device outside the tundish from the inlet end of the immersion nozzle through the inside of the tundish to the inside of the immersion nozzle;
The tundish is preheated, and then the fluid discharge device is operated to provide a high-pressure fluid in the immersion nozzle. By providing this high-pressure fluid, a negative pressure region is formed in the immersion nozzle, and the hot exhaust gas inside the tundish is removed. A preheating method for an immersion nozzle comprising a second step of taking in the immersion nozzle and preheating at least the inner surface of the immersion nozzle.   2. The immersion nozzle according to claim 1, wherein in the first step, the inlet end of the immersion nozzle is attached to the lower surface of the tundish, and a part of the main body including the outlet end of the immersion nozzle is accommodated in the hollow furnace body. Preheating method. In the tundish, a rod-like stopper for adjusting the opening degree of the immersion nozzle is attached to the upper position of the immersion nozzle so as to be movable up and down.
3. The immersion according to claim 1, wherein in the first step, when the tip of the pipe is inserted from the inlet end of the immersion nozzle into the immersion nozzle, the pipe is sent out along the stopper and inserted into the immersion nozzle. Nozzle preheating method. The tundish is transferred between a casting position below the ladle and a preheating position different from the casting position.
The preheating method for an immersion nozzle according to any one of claims 1 to 3, wherein the second step is executed not only before the transfer of the tundish but also when the tundish is transferred. Tundish preheating is performed until the temperature of the refractory disposed inside the tundish exceeds 1000 ° C.
The method for preheating an immersion nozzle according to any one of claims 1 to 4, wherein the fluid discharge device is operated when the temperature of the refractory reaches 600 to 800 ° C, and preheating of the inner surface of the immersion nozzle is started. A preheating device for an immersion nozzle attached to the lower surface of a tundish of a continuous casting machine,
A fluid ejection device outside the tundish;
A fluid communicating with the fluid ejection device, and a pipe disposed inside the immersion nozzle from the inlet end of the immersion nozzle attached to the lower surface of the tundish via the inside of the tundish,
The tundish is preheated, and then the fluid discharge device is operated to provide a high-pressure fluid in the immersion nozzle. By providing this high-pressure fluid, a negative pressure region is formed in the immersion nozzle, and the hot exhaust gas inside the tundish is removed. A preheating device for an immersion nozzle in which control is performed to take in the immersion nozzle and preheat at least the inner surface of the immersion nozzle.   The preheating device for an immersion nozzle according to claim 6, further comprising a hollow furnace body that accommodates a part of the main body including the outlet end of the immersion nozzle.   When the tip of the pipe is inserted into the immersion nozzle from the inlet end of the immersion nozzle, a rod-like stopper for adjusting the opening degree of the immersion nozzle is attached to the position above the immersion nozzle of the tundish so as to be movable up and down. The preheating device for an immersion nozzle according to claim 6 or 7, which is applied as a guide member for pipe feeding and insertion into the immersion nozzle.

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