JP4653664B2 - Preheating method and apparatus for immersion nozzle for continuous casting - Google Patents

Description

The present invention relates to a preheating method and a preheating device for a continuous casting immersion nozzle used when pouring molten steel in a tundish into a mold in continuous casting.

In continuous casting, molten steel at approximately 1500 to 1530 ° C. supplied from a ladle into a tundish is poured into a mold via a continuous casting immersion nozzle (hereinafter also simply referred to as “immersion nozzle”). At this time, since a severe heat load is applied to the immersion nozzle and cracks and breakage may occur, the immersion nozzle is preheated to prevent breakage. This makes it difficult for the temperature of the molten steel passing through the immersion nozzle to decrease, and can prevent deterioration in the quality of the cast product.

Here, as a conventional preheating method for the immersion nozzle, there is known a method of heating to 1000 to 1200 ° C. using a burner capable of supplying fuel gas and oxygen from an upper pouring port or a lower discharge hole of the immersion nozzle. (For example, refer to Patent Document 1). Further, a method of performing induction heating by inserting a cylindrical induction coil inside the immersion nozzle (see, for example, Patent Document 2), or a cylindrical induction coil arranged outside the immersion nozzle to induce the immersion nozzle A method of heating is also known.

Japanese Patent Laid-Open No. 61-262455 JP-A-9-122901

However, the conventional preheating method and preheating apparatus for the continuous casting immersion nozzle still have the following problems to be solved.
In the method of Patent Document 1, heating takes time, and the refractory constituting the immersion nozzle is deteriorated during heating, so that troubles such as spalling are likely to occur during actual operation. Moreover, since the heating temperature by a burner is lower (1000-1200 degreeC) than the temperature (1500-1530 degreeC) of molten steel normally, when an immersion nozzle contacts molten steel at the time of an actual operation, troubles, such as a spalling, were easy to generate | occur | produce. .

In the method of Patent Document 2, the immersion nozzle can be heated to a high temperature of about 1400 ° C. in a short time. However, since the induction coil is inserted into the immersion nozzle, the refractory of the immersion nozzle and the induction coil come into contact with each other. When the induction coil is damaged and its life is shortened, carbon and antioxidants mixed in the refractory of the immersion nozzle are removed by contact, and troubles such as spalling and excessive melting occur during actual operation was there. In addition, a mechanism for inserting the induction coil into the immersion nozzle is necessary, and installation is expensive. In addition, it is necessary to prepare a large number of induction coils having different outer diameters in accordance with immersion nozzles having different inner diameters.

Furthermore, when a cylindrical induction coil is disposed outside the immersion nozzle and heated, a magnetic field is generated parallel to the outer surface of the immersion nozzle, that is, parallel to the axis of the immersion nozzle, and uneven The outer surface of an immersion nozzle with a certain thickness could not be heated uniformly, and in particular, the slag line portion protruding compared with other portions was excessively heated. In addition, it is necessary to prepare a plurality of induction coils having different inner diameters in accordance with immersion nozzles having different outer diameters.

The present invention has been made in view of such circumstances, and preheating a continuous casting immersion nozzle that can heat an immersion nozzle having various inner diameters and outer diameters at a uniform temperature with a long coil life, little deterioration of the immersion nozzle. It is an object to provide a method and a preheating device.

A method for preheating a continuous casting immersion nozzle according to the present invention in accordance with the above object is an induction coil in which an immersion nozzle for pouring molten steel from a tundish of a continuous casting facility into a mold is disposed along the outer peripheral surface of the immersion nozzle. By the preheating method of the immersion nozzle that is preheated before pouring,
The induction coil is arranged so that the winding center direction of the induction coil intersects the immersion nozzle, and the immersion nozzle is induction-heated by the induction coil.

The induction coil is formed by forming a metal, for example, a copper tube in a ring shape or a spiral shape around the center of the core, and causes a current to flow through the metal to generate lines of magnetic force. Here, the spiral shape means a state that is formed by one or both of a curved line and a straight line that rotate around a central point and away from the center point, and is substantially planar. The induction coil is preferably curved along the outer surface of the immersion nozzle. When the induction coil is formed of a tubular body, the induction coil can be prevented from being heated by the radiant heat and resistance heating of the heated immersion nozzle by supplying cooling water (for example, tap water) into the pipe. .

What is necessary is just to arrange | position an immersion nozzle so that the winding center direction of an induction coil may cross | intersect with respect to the immersion nozzle side surface. In this case, it is preferable that the direction of the winding core of the induction coil passes through the immersion nozzle (for example, the axis) when the immersion nozzle is viewed in plan. Moreover, you may arrange | position so that the surface of an induction coil may incline more than 0 degree and 30 degree | times with respect to an immersion nozzle, for example. By arranging the induction coil along the outer peripheral surface of the immersion nozzle in this way, the magnetic field lines along the length direction of the immersion nozzle generated when the cylindrical induction coil described in Patent Document 2 is used are reduced. Instead, the lines of magnetic force generated in the direction intersecting the immersion nozzle are increased, and these lines of magnetic force pass through the immersion nozzle to generate an eddy current in the immersion nozzle, and the immersion nozzle is heated by the eddy current.

Moreover, the lower limit of the heating temperature of the immersion nozzle is 1200 ° C., preferably 1300 ° C., more preferably 1350 ° C., and the upper limit is about 1530 ° C. which is the temperature of the molten steel. In addition, since the temperature of an immersion nozzle falls after completion | finish of heating of an immersion nozzle until the pouring of molten steel, it is good also as a heating of an immersion nozzle higher than the temperature of molten steel, for example, about 1600 degreeC. The immersion nozzle is formed of a conductor such as alumina graphite (AG), and when the preheating temperature is about the temperature of molten steel (approximately 1500 to 1530 ° C.), there is little temperature change when pouring the molten steel into the immersion nozzle. Since it becomes difficult to receive an impact, a high-strength material containing zirconia or the like that is susceptible to thermal shock can also be used.

In the preheating method of the continuous casting immersion nozzle according to the present invention, it is preferable that the induction coil is divided into a plurality (for example, two).
For example, two induction coils may be arranged in a double door shape that is connected to one end in the circumferential direction of adjacent induction coils and opened from the center to both sides. You may arrange. In addition, when a plurality of induction coils are arranged at a predetermined interval on the immersion nozzle, a part of the induction coils may be overlapped (wrapped).

In the preheating method for a continuous casting immersion nozzle according to the present invention, the induction coil may be disposed at least near one or both of a discharge hole and a slag line portion of the immersion nozzle.
Since the discharge hole of the immersion nozzle is easily cooled, it is easy to spall, and the slag line part is easy to spall because it is in contact with the high temperature slag. Can be suppressed.

In the method for preheating a continuous casting immersion nozzle according to the present invention, after the immersion nozzle is attached to the tundish, the immersion nozzle is heated together with induction heating by the induction coil and further using a high-temperature gas. Is preferred.
The present invention includes an immersion nozzle attached directly to the tundish and an immersion nozzle attached via a sliding nozzle. The high-temperature gas can heat a part that is difficult to heat by induction heating, for example, one or both of the inner surface and the upper part of the immersion nozzle. In particular, the immersion nozzle attached via the sliding nozzle is integrally provided with a metal trunnion or the like for attaching the immersion nozzle to the tundish at the upper end, and the size is larger than that of the immersion nozzle. Since it may not enter the coil and induction heating is difficult, for example, heating is performed with a high-temperature gas from a preheating burner arranged in a through-hole of a tundish cover installed at the top of the tundish. The preheating burner can preheat auxiliary equipment such as a sliding nozzle device located above the immersion nozzle and an upper nozzle attached to the tundish. Thus, the immersion nozzle including the incidental equipment can be heated more uniformly using the high temperature gas, and troubles during actual operation such as spalling of the refractory can be suppressed.

Here, the high temperature gas can be obtained, for example, by burning coke oven gas (COG). In order to heat the inner surface of the immersion nozzle, COG serving as gas preheating fuel is supplied from the discharge hole of the immersion nozzle, air serving as primary air for gas preheating is supplied from below the immersion nozzle, and air is ejected by the ejector effect. You may draw in the inside of an immersion nozzle and generate | occur | produce a hot gas inside an immersion nozzle. Further, COG may be supplied from the lower part of the immersion nozzle, and air may be supplied from the discharge hole of the immersion nozzle to obtain a high temperature gas. Furthermore, when heating the upper part of an immersion nozzle, the preheating burner for tundish can be used.

In the method for preheating a continuous casting immersion nozzle according to the present invention, it is preferable to perform induction heating with the induction coil in a temperature range where the temperature of the immersion nozzle is at least 700 ° C. or higher.
Assuming that the immersion nozzle is preheated in the atmosphere, an antioxidant is generally applied to the surface of the refractory provided inside the immersion nozzle. When this antioxidant exceeds 700 ° C., oxidation is promoted and the protective function of the refractory tends to be lowered. Therefore, it is necessary to shorten the time that the immersion nozzle is exposed to 700 ° C. or higher during preheating. Since the induction coil can be rapidly heated, the time for exposing the immersion nozzle to 700 ° C. or more can be shortened by induction heating with the induction coil in a region of at least 700 ° C. or more. In addition, in the temperature range below 700 degreeC, you may carry out induction heating with an induction coil, but an electricity bill becomes high. Moreover, in a temperature range of 700 ° C. or higher, high-temperature gas may be used in combination with induction heating.

In the method for preheating a continuous casting immersion nozzle according to the present invention, the immersion nozzle may be rotated relative to the induction coil around the axis of the immersion nozzle.
If there is a temperature difference in the circumferential direction of the immersion nozzle depending on the location of the induction coil, rotate the immersion nozzle relative to the induction coil relative to the axis of the immersion nozzle to determine the temperature in the circumferential direction of the immersion nozzle. The difference can be reduced.

A preheating device for a continuous casting immersion nozzle according to the present invention is a preheating device for an immersion nozzle that preheats an immersion nozzle for pouring molten steel into a mold from a tundish of a continuous casting facility,
An induction coil divided into a plurality of parts is arranged along the outer peripheral surface of the immersion nozzle, and the winding center direction of each induction coil intersects the immersion nozzle.

In the preheating device for a continuous casting immersion nozzle according to the present invention, the induction coil is preferably formed to be curved along the outer surface of the immersion nozzle.
In the preheating device for continuous casting immersion nozzle according to the present invention, it is preferable that gas heating means for heating the immersion nozzle with a high-temperature gas is further provided.

In the preheating method of the immersion nozzle for continuous casting of Claims 1-6, it arrange | positions so that an induction coil may be along the outer peripheral surface of an immersion nozzle, and the winding core direction of an induction coil may cross | intersect with an immersion nozzle. Therefore, a large magnetic field can be generated in a direction intersecting the outer surface of the immersion nozzle, and the outer surface of the immersion nozzle can be uniformly heated with little influence of the unevenness.

Particularly, in the method for preheating a submerged nozzle for continuous casting according to claim 2, since the induction coil is divided into a plurality of parts, the induction coil can be easily detached from the vicinity of the outer surface of the submerged nozzle. At the time of attaching and detaching, the immersion nozzle and the induction coil do not slide or come into contact with each other, and the deterioration of the immersion nozzle and the induction coil can be prevented. In addition, since a plurality of induction coils can be arranged according to the outer diameter of the immersion nozzle, various induction coils are not required according to the outer diameter of the immersion nozzle as in the prior art, and the number of spare parts for non-operational induction coils is reduced. it can.

4. The method for preheating a continuous casting immersion nozzle according to claim 3, wherein the induction coil is disposed at least in the vicinity of either one or both of the discharge hole and the slag line portion of the immersion nozzle, so that it is easy to spall. Can be heated uniformly, and breakage of the immersion nozzle can be prevented.
In the preheating method of the continuous casting immersion nozzle according to claim 4, since the immersion nozzle is heated together with the induction heating by the induction coil and the high temperature gas is used together, the portion difficult to be heated by the induction coil can be heated by the high temperature gas, The immersion nozzle can be heated more uniformly.

In the preheating method of the immersion nozzle for continuous casting according to claim 5, since the induction heating is performed by the induction coil in a temperature range where the temperature of the immersion nozzle is at least 700 ° C or higher, the time for exposing the immersion nozzle to 700 ° C or higher is shortened. And the deterioration of the antioxidant applied to the immersion nozzle can be prevented.
In the method for preheating a continuous casting immersion nozzle according to claim 6, since the immersion nozzle is rotated relative to the induction coil around the axis of the immersion nozzle, the immersion nozzle can be heated more uniformly.

In the preheating device for continuous casting immersion nozzles according to claims 7 to 9, since the induction coil divided into a plurality of parts is disposed along the outer peripheral surface of the immersion nozzle, it can be easily obtained from the vicinity of the outer surface of the immersion nozzle. In addition to being detachable, the immersion nozzle and the induction coil do not slide or come into contact with each other when the induction coil is attached / detached, and deterioration of the immersion nozzle and the induction coil can be prevented. Since the winding core direction of each induction coil intersects the immersion nozzle, a large amount of magnetic field is generated in the direction intersecting the outer surface of the immersion nozzle by the induction coil, and the influence of unevenness on the outer surface is small. The immersion nozzle can be heated uniformly. In addition, since a plurality of induction coils can be arranged according to the outer diameter of the immersion nozzle, various induction coils are not required according to the outer diameter of the immersion nozzle as in the prior art, and the number of spare parts for non-operational induction coils is reduced. it can.

Particularly, in the preheating device for continuous casting immersion nozzle according to claim 8, since the induction coil is formed to be curved along the outer surface of the immersion nozzle, it is easy to make the distance between the induction coil and the immersion nozzle constant. The immersion nozzle can be heated more uniformly.
In the preheating device for the continuous casting immersion nozzle according to claim 9, since the gas heating means for heating the immersion nozzle with a high-temperature gas is further provided, it is possible to heat a portion that is difficult to heat with the induction coil, Heat more uniformly.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
Here, FIG. 1 is an explanatory view showing a use state of a preheating device for a continuous casting immersion nozzle according to an embodiment of the present invention, FIG. 2 is a sectional view of the immersion nozzle heated by the preheating device, and FIGS. FIG. 5 is a front view, a side view, and a plan view of the preheating device, FIG. 6 is an explanatory diagram of the induction coil of the preheating device, and FIG. 7 is a graph showing the relationship between the preheating time and the preheating temperature of the immersion nozzle.

With reference to FIGS. 1-6, the preheating apparatus 10 of the immersion nozzle for continuous casting which concerns on one embodiment of this invention is demonstrated.
As shown in FIG. 1, a continuous casting immersion nozzle preheating device (hereinafter also simply referred to as “preheating device”) 10 uses a tundish of molten steel supplied from a ladle (not shown) in a continuous casting facility 11. This is a device for heating a continuous casting immersion nozzle (hereinafter, also simply referred to as “immersion nozzle”) 13 attached to the tundish 12 before pouring from 12 into a mold (not shown). For example, the tundish 12 is provided with a sliding nozzle 14, and the immersion nozzle 13 is attached to the tundish 12 via the sliding nozzle 14.

The immersion nozzle 13 is formed of a conductive material such as alumina graphite containing carbon for the purpose of preventing oxidation of molten steel poured from the tundish 12 into the mold. As shown in FIG. 2, the shape of the immersion nozzle 13 is substantially a cylindrical shape with the bottom portion closed, and includes a pouring port 15 where molten steel is poured into the upper portion and two holes facing the lower side surface. The provided discharge hole 16 is provided, and a thick slag line portion 17 is formed at the center in the height direction. A refractory 18 coated with an antioxidant is provided inside the immersion nozzle 13. Further, an argon gas supply hole 19 for supplying argon gas from the outer surface side to the inner side of the immersion nozzle 13 is provided in the upper part of the immersion nozzle 13. A stainless trunnion (not shown) provided with a bar-like horizontal member (not shown) for installing the immersion nozzle 13 on the tundish 12 is integrally formed on the outer side of the upper end of the immersion nozzle 13. Installed.

As shown in FIGS. 3 to 5, the preheating device 10 includes a plurality of, for example, two divided induction coils 20 and 21 arranged along the outer peripheral surface of the immersion nozzle 13. The induction coils 20 and 21 are, for example, formed by welding a copper tube having a rectangular cross section into a spiral shape, and then bending it along the outer surface of the immersion nozzle 13, as shown in FIG. (It is a curved plane). The two induction coils 20 and 21 are opposed to each other with the immersion nozzle 13 in the center, and the winding cores of the induction coils 20 and 21 are arranged in the vicinity of the thick slag line portion 17. .

In addition, one end side of the center of each of the spirals of the induction coils 20 and 21 is connected via a connection fitting 22 by a connection pipe 25 formed by a copper tube 24 having a circular cross section whose outer side is covered with a heat insulating material 23. The other end sides of the induction coils 20 and 21 are paired and connected to a power source (not shown) to form one circuit. The power source is, for example, AC 200/220 V, 60 Hz, and 26 KvA, the output of the induction coils 20 and 21 is 20 kW at maximum, the frequency is 5 to 40 kHz, for example, 20 kHz, and the immersion nozzle 13 is, for example, 1200 to 1530 ° C. Heat. Further, in order to prevent heating of the induction coils 20 and 21 due to radiant heat and resistance heating when the immersion nozzle 13 is heated, for example, the induction coil 20 is connected to the other end side of the induction coil 20 connected to the induction coil 21. , 21 is connected to a tap water supply pipe (not shown) for supplying tap water.

Here, as shown in FIG. 6, the winding directions of the induction coils 20, 21 arranged opposite to each other are arranged, for example, with the induction coil 20 on the front side of the immersion nozzle 13 and the induction coil 21 on the back side of the immersion nozzle 13. Assuming that the current flows from the induction coil 20 side to the induction coil 21 side via the connecting tube 25, the current flows clockwise through the induction coil 20 and the induction coil 21 as viewed from the front. The winding direction of the induction coils 20 and 21 is counterclockwise when the current is passed from the induction coil 20 side to the induction coil 21 side through the connecting tube 25 when viewed in front from the induction coil 20 and the induction coil 21. A current may flow through the induction coils 20, 21 and the current flowing through the induction coils 20, 21 may be in the reverse direction.

The induction coils 20 and 21 have a plan view of the immersion nozzle 13, and the winding core direction of the induction coils 20 and 21 intersects with the immersion nozzle 13 (for example, the axial center 26 or the hollow portion of the immersion nozzle 13). When the nozzle 13 is viewed from the side, the surfaces of the induction coils 20 and 21 are arranged so that the surfaces of the induction coils 20 and 21 are parallel to the immersion nozzle 13, that is, parallel to the immersion nozzle 13. Since the angle is 90 degrees, many lines of magnetic force (not shown) intersect with the immersion nozzle 13 are generated, and these lines of magnetic force pass through the immersion nozzle 13 to cause an eddy current (not shown) in the immersion nozzle 13. The immersion nozzle 13 is heated by this eddy current. As a result, the outer surface of the immersion nozzle 13 can be heated uniformly with little influence of the unevenness. The induction coils 20 and 21 may be arranged so that the surfaces of the induction coils 20 and 21 are inclined with respect to the immersion nozzle 13 at, for example, more than 0 degree and 30 degrees or less. For example, it is possible to uniformly heat the immersion nozzle 13 by changing the distance between the portions having different thicknesses, particularly the distance between the slag line portion 17 and the induction coils 20 and 21 and the distance between the discharge hole 16 and the induction coils 20 and 21. .

Furthermore, the preheating device 10 has a gas heating means 30 for heating the immersion nozzle 13 with a high temperature gas. The gas heating means 30 is disposed below the immersion nozzle 13 by being inserted into the immersion nozzle 13 through the discharge hole 16 of the immersion nozzle 13 and the immersion nozzle 13, and the coke oven is provided in the immersion nozzle 13 by the ejector effect. It has a COG gas supply pipe 32 that supplies gas (COG), and the inner surface of the immersion nozzle 13 can be heated by a high-temperature gas generated by burning COG. Further, as shown in FIG. 1, the gas heating means 30 has a preheating burner 42 disposed in a through hole 41 of a tundish cover 40 installed at the upper part of the tundish 12, and the tundish 12 is provided by the preheating burner 42. The inside can be heated at the same time. In the preheating burner 42, a molten steel stopper 43 disposed in the tundish 12, an upper nozzle 45 and a lower nozzle 46 provided in a molten steel discharge port 44 at the bottom of the tundish 12, the sliding nozzle 14, and the immersion nozzle 13. The upper part can be heated. In the preheating device 10, the immersion nozzle 13 can be heated by induction heating by the induction coils 20 and 21 and high-temperature gas by the gas heating means 30.

Next, a method for preheating the continuous casting immersion nozzle 13 using the continuous casting immersion nozzle preheating device 10 will be described.
Before injecting molten steel from the tundish 12 of the continuous casting equipment 11 into the mold, the two induction coils 20, 21 curved along the outer peripheral surface of the immersion nozzle 13 attached to the tundish 12 via the sliding nozzle 14. Are arranged in the vicinity of the discharge hole 16 of the immersion nozzle 13 and the outer surface of the slag line portion 17 so that the winding center direction of each induction coil 20, 21 intersects the immersion nozzle 13. Further, the air supply pipe 31 is disposed inside the immersion nozzle 13 from the discharge hole 16 of the immersion nozzle 13, and the COG gas supply pipe 32 is disposed below the immersion nozzle 13. Further, the tundish cover 40 is disposed on the tundish 12, and the preheating burner 42 is disposed in the through hole 41 of the tundish cover 40.

First, the gas heating means 30 heats the inner surface and upper part of the immersion nozzle 13 to a temperature range of about 700 ° C. or higher (about 700 to 1100 ° C.), for example, 1000 ° C. At this time, the inner surface of the immersion nozzle 13 is heated by the high temperature gas from the air supply pipe 31 and the COG gas supply pipe 32, and the upper part of the immersion nozzle 13 and the inside of the tundish 12 are heated by the preheating burner 42.

After the temperature of the immersion nozzle 13 reaches, for example, about 1000 ° C., the power supply connected to the induction coils 20 and 21 has a maximum output of 20 kW to the induction coils 20 and 21, and the frequency is 5 to 40 kHz. The immersion nozzle 13 is heated to 1200 to 1530 ° C., for example, 1400 ° C. by applying a current of 20 kHz. Since induction heating by the induction coils 20 and 21 is performed in a temperature range where the temperature of the immersion nozzle 13 is 700 ° C. or higher, the time during which the immersion nozzle 13 is exposed to 700 ° C. or more is shortened, and the refractory 18 of the immersion nozzle 13 is attached to the refractory 18. Degradation of the applied antioxidant can be prevented. Induction heating may be performed by the induction coils 20 and 21 when the temperature of the immersion nozzle is less than 700 ° C. However, since the electricity bill becomes high, the induction heating by the induction coils 20 and 21 is performed at the temperature of the immersion nozzle 13. It is preferable to carry out in a temperature range of 700 ° C. or higher. Further, at the time of induction heating by the induction coils 20 and 21, heating with a high temperature gas by the gas heating means 30 may or may not be performed.

In addition, since the temperature of the immersion nozzle 13 falls after completion | finish of the heating of the immersion nozzle 13 to the pouring of molten steel, it is preferable to make the heating temperature of the immersion nozzle 13 higher than the temperature of molten steel (about 1600 degreeC). Further, during heating, tap water is supplied into the induction coils 20 and 21 at, for example, 4 liters / minute to prevent the induction coils 20 and 21 from being heated by radiant heat and resistance heating of the immersion nozzle 13.

As described above, the induction coils 20 and 21 reduce the influence of the unevenness on the outer surface of the immersion nozzle 13 by generating a large magnetic field in the direction intersecting the outer surface of the immersion nozzle 13, so that the immersion coil 13 is immersed. The nozzle 13 is heated uniformly. Further, the induction coils 20 and 21 are curved along the outer surface of the immersion nozzle 13 so that the distance between the induction coils 20 and 21 and the immersion nozzle 13 is constant, and the immersion nozzle 13 is heated more uniformly.

In addition, the induction coils 20 and 21 are divided into a plurality of parts so that the induction coils 20 and 21 can be easily attached to and detached from the immersion nozzle 13. In particular, when the induction coils 20 and 21 are attached to and detached from the immersion nozzle 13, Are not slid and contacted, and the deterioration of the immersion nozzle 13 and the induction coils 20 and 21 is prevented. Further, since the plurality of induction coils 20 and 21 can be adjusted and arranged according to the outer diameter of the immersion nozzle 13, cylindrical induction coils having various inner diameters matched to the outer diameter of the immersion nozzle 13 as in the past. The number of spare parts for non-operating induction coils can be reduced.

In addition, the induction coils 20 and 21 are arranged in the vicinity of the discharge hole 16 of the immersion nozzle 13 and the outer surface of the slag line portion 17 to uniformly heat a portion that is easily spalled, thereby preventing the immersion nozzle 13 from being damaged. Yes. Furthermore, since the part which is difficult to heat in the induction coils 20 and 21 is heated by the gas heating means 30, the immersion nozzle 13 can be heated more uniformly.

Next, a simulation was performed in order to confirm the effect of the present invention.
(Simulation 1)
Two induction coils curved along the outer surface of the immersion nozzle are placed along the entire outer peripheral surface of the immersion nozzle so that the winding core direction of the induction coil intersects perpendicularly to the immersion nozzle and induction heating After preheating with, continuous casting was performed.

(Simulation 2)
Four induction coils that are curved with respect to the outer surface of the submerged nozzle are placed two by two near the outer surface of the discharge hole of the submerged nozzle and the slug line part, and the winding core direction of the pair of induction coils is immersed in each part. The coils were arranged so as to intersect perpendicularly with respect to the nozzles, and the winding core directions of the induction coils were the same, and after preheating by induction heating, continuous casting was performed.
(Comparative Example 1)
A conventionally used cylindrical induction coil was placed outside the immersion nozzle and preheated by induction heating, and then continuous casting was performed.

About the simulation 1 and the comparative example 1, the lifetime (number ratio which can be used for continuous casting) index | exponent of an induction coil was compared. Assuming that the life index (usable number of times) of the induction coil of Comparative Example 1 is 1, in Simulation 1, the life is considerably long as 4. This is because in Comparative Example 1 using a conventional cylindrical coil, a heat insulating material for protecting the induction coil when the immersion nozzle is attached to and detached from the induction coil, particularly when the immersion nozzle is taken out of the induction coil after heating. In the simulation 1, the induction coil is divided into two parts and can be detached and attached, so that the induction coil and the immersion nozzle are in contact with each other while sliding. This is because the deterioration of the immersion nozzle and the induction coil can be prevented.

Moreover, about the simulation 1 and the comparative example 1, each trial calculation was performed about the installation cost in the case of performing continuous casting. Here, when the equipment cost index of the induction coil in the comparative example 1 is 1, in the simulation 1, it is considerably low as 0.2. In Comparative Example 1, induction coils with various inner diameters are required in accordance with the outer diameter of the immersion nozzle. The number of induction coils increases, and the immersion nozzle, the induction coil lifting device, and the non-operational induction coil are installed. Incidental facilities such as pits for storage are required, and the facility costs are increasing. In addition, in the simulation 1, since the induction coil divided into two can be arranged according to the outer diameter of the immersion nozzle, the number of spare parts for the non-operational induction coil can be reduced, and the above-mentioned incidental equipment is not necessary, It is understood that the cost can be kept low.

Furthermore, the difference of the surface temperature of the immersion nozzle heated by the simulation 1 and the comparative example 1 was compared. The difference in the surface temperature of the immersion nozzle was about 450 ° C. in Comparative Example 1, but was considerably small, about 160 ° C. in Simulation 1. This is because in Comparative Example 1, since the induction coil is cylindrical, the interval between the immersion nozzle and the induction coil cannot be made constant, and in particular, the slag line part and the discharge hole are easily heated, In the simulation 1, the distance between the induction coil and the immersion nozzle can be freely changed, and the surface temperature of the immersion nozzle is made uniform by suppressing the temperature rise near the discharge hole without arranging the induction coil particularly in the discharge hole. It is understood that it was made.

Moreover, about simulation 1, 2, and the comparative example 1, the trial calculation of the trouble at the time of the casting | casting which generate | occur | produced in multiple times casting, ie, the generation | occurrence | production index of the crack of a submerged nozzle, and a failure | damage, was performed. The index of occurrence of cracks and breakage of the immersion nozzle was considerably low at 0.1 for simulations 1 and 2 when Comparative Example 1 was set to 1. This is because, in Comparative Example 1, the surface temperature difference of the immersion nozzle is large as described above, and the antioxidant applied to the refractory of the immersion nozzle is partially peeled off or dissolved to oxidize the immersion nozzle. In the simulations 1 and 2, the surface of the immersion nozzle is made uniform, although it cannot be prevented and strength reduction or abnormal melting damage occurs due to partial abnormal oxidation of the immersion nozzle, causing cracks or breakage of the immersion nozzle in the initial stage of casting. Since it can be heated, it is understood that the abnormal oxidation of the immersion nozzle does not occur and the trouble during casting is reduced.

Further, when the immersion nozzle is heated using only the induction coil used in the simulation 1 (simulation 1), and after being heated to 700 ° C. or higher and 1100 ° C. or lower by a gas heating means using high-temperature gas, the same as in the simulation 1 The case where the induction coil was used in combination (Simulation 3) and the case where the induction coil was heated only (Comparative Example 2) were compared.
As shown in FIG. 7, in Comparative Example 2, the immersion nozzle could only be heated to about 1100 ° C. in 60 minutes. Moreover, the temperature of the immersion nozzle fell to about 700 ° C. from the end of preheating to the start of pouring (about 10 minutes), and the immersion nozzle could be damaged due to a temperature difference from the hot molten steel.

In simulation 1, the immersion nozzle could be heated to 1400 ° C. in about 13 minutes from the start of heating. However, in normal continuous casting operation, preheating of the immersion nozzle starts about 70 minutes before pouring, so The holding time at 1400 ° C. becomes longer, peeling or dissolution of the antioxidant of the immersion nozzle occurs, and the immersion nozzle is easily cracked or broken. In addition, when the start of preheating is delayed, preheating may not be in time for emergency pouring.

In the simulation 3, the immersion nozzle is heated to 1000 ° C. by the gas heating means, and induction heating is performed by the induction coil before the operation is started, so that the immersion nozzle is set to 1400 ° C. In addition, since the temperature of the immersion nozzle at the start of pouring is about 1100 ° C. and exposure time of 700 ° C. or more is shorter than that in the simulation 1, the immersion nozzle can be prevented from being damaged and stably continuous. Casting can be performed. Further, since the temperature difference between the immersion nozzle and the molten steel can be reduced, the immersion nozzle can be changed to a material having high strength and high corrosion resistance, and the immersion nozzle can be reduced in weight.

The present invention is not limited to the above-described embodiment, and can be changed without changing the gist of the present invention. For example, some or all of the above-described embodiments and modifications are possible. The case where the continuous casting immersion nozzle preheating method and the preheating apparatus of the present invention are configured in combination is also included in the scope of the present invention.
For example, in the preheating method and the preheating device for the continuous casting immersion nozzle of the above embodiment, the immersion nozzle detachably attached to the tundish is heated, but the immersion nozzle integrally provided in the tundish is heated. You can also. Further, the immersion nozzle may be removed from the tundish and heated.

Furthermore, in the said embodiment, although the two induction coils were arrange | positioned outside the immersion nozzle, you may arrange | position one or three or more induction coils. Moreover, you may provide the rotation means which rotates an induction coil relatively centering on the axis center of an immersion nozzle with respect to an immersion nozzle, and this can heat an immersion nozzle more uniformly. Furthermore, you may arrange | position an induction coil in the outer surface vicinity of any one of the discharge hole of a submerged nozzle, or a slag line part. Alternatively, high temperature gas may be obtained by supplying air from the lower part of the immersion nozzle and supplying COG from the discharge hole of the immersion nozzle.

It is explanatory drawing which shows the use condition of the preheating apparatus of the immersion nozzle for continuous casting which concerns on one embodiment of this invention. It is sectional drawing of the immersion nozzle heated with the same preheating apparatus. It is a front view of the preheating device. It is a side view of the preheating device. It is a top view of the preheating device. It is explanatory drawing of the induction coil of the preheating apparatus. It is a graph which shows the relationship between the preheating time of an immersion nozzle, and preheating temperature.

Explanation of symbols

10: Preheating device for continuous casting immersion nozzle, 11: Continuous casting equipment, 12: Tundish, 13: Continuous casting immersion nozzle, 14: Sliding nozzle, 15: Pouring port, 16: Discharge hole, 17: Slag line section , 18: refractory material, 19: argon gas supply hole, 20, 21: induction coil, 22: connecting metal fitting, 23: heat insulating material, 24: copper pipe, 25: connecting pipe, 26: axial center, 30: gas heating means , 31: air supply pipe, 32: COG gas supply pipe, 40: tundish cover, 41: through hole, 42: preheating burner, 43: stopper, 44: molten steel discharge port, 45: upper nozzle, 46: lower nozzle

Claims (9)

In the preheating method of the immersion nozzle in which the immersion nozzle for pouring molten steel into the mold from the tundish of the continuous casting facility is preheated before pouring by an induction coil arranged along the outer peripheral surface of the immersion nozzle.
A method for preheating an immersion nozzle for continuous casting, wherein the induction coil is disposed so that a winding center direction of the induction coil intersects the immersion nozzle, and the immersion nozzle is induction-heated by the induction coil. . 2. The method for preheating a continuous casting immersion nozzle according to claim 1, wherein the induction coil is divided into a plurality of pieces. 3. The method for preheating a continuous casting immersion nozzle according to claim 1, wherein the induction coil is disposed at least in the vicinity of one or both of a discharge hole and a slag line portion of the immersion nozzle. A preheating method for an immersion nozzle for continuous casting. The preheating method of the continuous casting immersion nozzle according to any one of claims 1 to 3, wherein after the immersion nozzle is attached to the tundish, in addition to induction heating by the induction coil, a high-temperature gas is further used in combination. And the preheating method of the immersion nozzle for continuous casting, wherein the immersion nozzle is heated. The preheating method for the continuous casting immersion nozzle according to claim 4, wherein the induction heating is performed by the induction coil in a temperature range where the temperature of the immersion nozzle is at least 700 ° C or higher. Method. The preheating method for a continuous casting immersion nozzle according to any one of claims 1 to 5, wherein the immersion nozzle is rotated relative to the induction coil around an axis of the immersion nozzle. A preheating method for a continuous casting immersion nozzle. In the preheating device of the immersion nozzle that preheats the immersion nozzle for pouring molten steel into the mold from the tundish of the continuous casting equipment,
For continuous casting, wherein an induction coil divided into a plurality of portions is arranged along the outer peripheral surface of the immersion nozzle, and the winding core direction of each induction coil intersects the immersion nozzle. Preheating device for immersion nozzle. 8. The preheating device for a continuous casting immersion nozzle according to claim 7, wherein the induction coil is formed to be curved along an outer surface of the immersion nozzle. 9. The continuous casting immersion nozzle preheating device according to claim 7, further comprising a gas heating means for heating the immersion nozzle with a high-temperature gas. Preheating device for immersion nozzle.

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