JP7282709B2 - PREHEATING DEVICE AND PREHEATING METHOD OF UPPER NOZZLE THAT BECOMES A PATH FOR MOLTEN STEEL SUPPLIED FROM TUNDISH TO MOLD - Google Patents

Description

The present invention is a preheating device for preheating an upper nozzle (a so-called tundish nozzle) and a lower nozzle, which form a flow path for molten steel when supplying molten steel from a tundish to a mold in continuous casting. and preheating method.

Steel products such as steel plates, bars, and bars are manufactured through a process of adjusting the composition of the molten steel, a process of pouring the molten steel into a mold and solidifying it, and a process of rolling and other processing to finish it into the desired shape and dimensions. be done. In the process of solidifying molten steel, continuous casting is widely used from the viewpoint of productivity improvement, and the technology of storing molten steel with adjusted components in a tundish and supplying it to the mold through a nozzle is widespread. . FIG. 4 is a cross-sectional view schematically showing an example of a tundish and nozzle during continuous casting operation. In addition, the mold is omitted from the drawing. As shown in FIG. 4 , the nozzle serving as the flow path for the molten steel 4 is composed of an upper nozzle 2 embedded in the tundish 1 and a lower nozzle 3 extending downward from the tundish 1 .

Before the continuous casting operation is started, the molten steel 4 is not stored inside the tundish 1, and the tundish 1 and the nozzles (that is, the upper nozzle 2 and the lower nozzle 3) are kept at ambient temperature. When the molten steel 4 is stored in the tundish 1 at the start of operation, the temperature of the molten steel 4 drops and solidifies inside the nozzle, causing clogging (so-called clogging) of the upper nozzle 2 and the lower nozzle 3. As a result, the operation rate of continuous casting is lowered and the productivity is lowered.

Furthermore, since the temperature of the molten steel 4 in the tundish 1 inevitably drops during restoration work of the clogged nozzle, the molten steel 4 must be disposed of as scrap, resulting in a decrease in the yield of the molten steel 4. There is also the issue of inviting.

Continuous casting equipment has conventionally been equipped with a replacement device (not shown) for replacing the lower nozzle 3, so when the lower nozzle 3 is clogged, it is heated in advance to raise the temperature. If the lower nozzle 3 is replaced with a (hereinafter referred to as preheated) lower nozzle 3, the operation can be restarted in a short period of time.

However, since the upper nozzle 2 is embedded in the refractory brick wall at the bottom of the tundish 1, it cannot be easily replaced. Therefore, techniques for preventing clogging of the upper nozzle 2 are being studied.

For example, before the molten steel 4 is stored in the tundish 1 in advance, a technique of preheating the upper nozzle 2 by heating the upper nozzle 2 from above (that is, from inside the tundish 1) with a burner has been studied. In this technique, the worker manually preheats using a burner, which not only takes a long time, but also requires ancillary equipment to ensure the safety of the worker, which increases the preheating cost. is unavoidable, resulting in an increase in continuous casting costs.

Further, Japanese Patent Application Laid-Open No. 2002-200002 discloses an upper nozzle that incorporates a heating element that generates heat when energized. This technique inevitably increases the manufacturing cost of the upper nozzle, resulting in an increase in the continuous casting cost. Furthermore, there is also the problem that the wiring that supplies current to the heating element is likely to break when exposed to the high temperature radiated from the molten steel. Since the upper nozzle is embedded in the refractory brick wall at the bottom of the tundish 1 as already explained, it is difficult to newly install the wiring. In other words, since preheating cannot be performed if the wiring is disconnected, the upper nozzle is likely to be clogged.

JP-A-2000-153347

An object of the present invention is to solve the problems of the prior art and to preheat an upper nozzle, which serves as a flow path for molten steel supplied from a tundish to a mold in continuous casting, in a short time and at a low cost using a simple means. It is an object of the present invention to provide a preheating apparatus and a preheating method capable of suppressing a decrease in the yield of molten steel.

In studying a technique for preheating the upper nozzle with a simple means, the present inventor focused on a lower nozzle replacement device that has conventionally been installed as ancillary equipment of the tundish. That is, if a heating element is attached to the exchanging device and the temperature of the upper nozzle is raised from below, it becomes possible to preheat the upper nozzle using a simple means. In addition, since there is no need for manual preheating by an operator, the time required for preheating can be shortened. Furthermore, by utilizing conventional equipment, preheating can be performed by developing only the heating element and its pedestal, so the introduction cost of new equipment can be suppressed.

The present invention has been made based on such findings.
That is, the present invention is attached to a replacement device for replacing the lower nozzle in order to preheat the upper nozzle of the upper nozzle and the lower nozzle, which form the flow path of the molten steel supplied from the tundish to the mold in continuous casting. A preheating device,
a plate-shaped heating element serving as a heat source for preheating the upper nozzle and provided with a first screw hole to be screwed with the heating element fixing bolt;
A plate-like heating element is placed on the upper side, and a second screw hole for screwing with a heating element fixing bolt is provided at a position opposite to the first screw hole, and a third screw hole for screwing with a pedestal connection bolt is provided on the upper side. a pedestal;
A collar sliding hole for inserting a combination collar through which a pedestal fixing bolt is screwed is provided at a position facing the third screw hole, and a fourth screw hole for screwing a height adjustment bolt is provided at the center. a lower pedestal;
It is a preheating device with

The preheating device of the present invention is
a plurality of washers sandwiched between the plate-shaped heating element and the upper pedestal and between the upper pedestal and the head of the heating element fixing bolt;
a plurality of washers sandwiched between the upper pedestal and the combination collar and between the combination collar and the head of the pedestal connecting bolt;
It is preferred to have

Further, the present invention provides a preheating method for preheating an upper nozzle out of an upper nozzle and a lower nozzle, which form a flow path for molten steel supplied from a tundish to a mold in continuous casting,
a plate-shaped heating element serving as a heat source for preheating the upper nozzle and provided with a first screw hole to be screwed with the heating element fixing bolt;
A plate-shaped heating element is placed thereon, and a second screw hole for screwing with a heating element fixing bolt is provided at a position opposite to the first screw hole, and a third screw hole for screwing with a pedestal fixing bolt is provided. an upper pedestal;
A collar slide hole for inserting a combination collar through which a pedestal fixing bolt is screwed is provided at a position facing the third screw hole, and a fourth screw hole for screwing a height adjustment bolt is provided at the center. a lower pedestal;
to the replacement device of the lower nozzle, rotate the height adjustment bolt and screw it into the fourth screw hole to adjust the distance between the lower end surface of the lower pedestal and the upper end surface of the plate-shaped heating element In this preheating method, the lower end surface of the upper nozzle and the upper end surface of the plate-shaped heating element are brought into close contact with each other to preheat the upper nozzle.

In the preheating method of the present invention,
a plurality of washers sandwiched between the plate-shaped heating element and the upper pedestal and between the upper pedestal and the head of the heating element fixing bolt;
a plurality of washers sandwiched between the upper pedestal and the combination collar and between the combination collar and the head of the pedestal connecting bolt;
It is preferred to use a preheating device with

According to the present invention, it is possible to preheat the upper nozzle, which is the flow path of molten steel supplied from the tundish to the mold in continuous casting, in a short time and at low cost using a simple means. Since it is possible to suppress the decrease and to improve the productivity and operating rate of continuous casting, it is possible to achieve a remarkable industrial effect.

FIG. 4 is a cross-sectional view schematically showing an example of preheating an upper nozzle using a preheating device according to the present invention; 2 is a cross-sectional view showing a mechanism for adjusting the distance between the upper end surface of the plate-shaped heating element and the lower end surface of the upper nozzle of the preheating device shown in FIG. 1; FIG. FIG. 3 is a cross-sectional view schematically showing an example of a plate-shaped heating element; FIG. 4 is a cross-sectional view schematically showing an example of a tundish and a nozzle;

FIG. 1 is a cross-sectional view schematically showing an example of preheating an upper nozzle 2 using a preheating device 6 according to the present invention. Note that the illustration of the tundish is omitted. FIG. 2 is a sectional view showing a mechanism for adjusting the distance (hereafter referred to as height adjustment) between the upper end surface of the plate-shaped heating element 7 and the lower end surface of the upper nozzle 2 of the preheating device 6 shown in FIG.

The preheating device 6 according to the present invention uses one height adjusting bolt 12, but the number of heating element fixing bolts 10 and pedestal connection bolts 11 and the shapes of the plate-shaped heating element 7, upper pedestal 8, and lower pedestal 9 are determined. (For example, circular, hexagonal, rectangular, etc.) are not particularly limited. As an example, an example in which four rectangular plate-shaped heating elements 7, upper pedestals 8, lower pedestals 9, four heating element fixing bolts 10, and four pedestal connecting bolts 11 are used in combination will be described below.

First, the configuration of the preheating device 6 will be described with reference to FIG. 2(a). In the preheating device 6 according to the present invention, the plate-shaped heating element 7 and the upper pedestal 8 are connected and fixed via the heating element fixing bolt 10 . First screw holes 21 are provided at the corners (four places) of the rectangular plate-shaped heating element 7 for screwing the heating element fixing bolts 10 thereon. Second screw holes 22 are provided in the corners (four places) of the rectangular upper pedestal 8 so as to face the first screw holes 21, and the heating element fixing bolts 10 pass through the second screw holes 22. , and further engages within the first screw hole 21 .

In this way, in order to prevent loosening of the heating element fixing bolts 10 that connect and fix the plate-shaped heating element 7 and the upper pedestal 8, and to prevent damage to the plate-shaped heating element 7 and the upper pedestal 8, the plate-shaped heating element 7 and the upper end surface of the upper pedestal 8, and between the lower end surface of the upper pedestal 8 and the head of the heating element fixing bolt 10. It is preferable to insert a washer 20 (so-called washer) appropriately.

Furthermore, the upper pedestal 8 and the lower pedestal 9 are connected via a pedestal connecting bolt 11 . The upper pedestal 8 is provided with four third screw holes 23 for screwing the pedestal connecting bolts 11 . Four collar sliding holes 25 are provided in the rectangular lower pedestal 9 so as to face the third screw holes 23 . The inner surface of the collar sliding hole 25 is not provided with a screw to be screwed with the pedestal connecting bolt 11, and the combination collar 26 is slidably inserted therethrough. The inner surface of the combination collar 26 is provided with a screw that engages with the pedestal connection bolt 11 . That is, the pedestal connecting bolt 11 passes through the combination collar 26 and is locked in the third screw hole 23 .

In order to prevent loosening of the pedestal connection bolt 11 that connects the upper pedestal 8 and the lower pedestal 9 and to prevent damage to the upper pedestal 8, the lower pedestal 9, and the combination collar 26, the lower end surface of the upper pedestal 8 and It is preferable to sandwich the washer 20 appropriately between the upper end of the combination collar 26 and between the head of the base connecting bolt 11 and the lower end of the combination collar 26 .

A fourth screw hole 24 into which the height adjusting bolt 12 is screwed is provided in the central portion (one place) of the lower pedestal 9 . A threaded hole for screwing the height adjustment bolt 12 is not provided in the central portion of the upper base 8 .

Next, with reference to FIGS. 2(a) to 2(c), adjustment of the distance between the upper end surface of the plate-shaped heating element 7 and the lower end surface of the lower pedestal 9 will be described. The adjustment of the distance between the upper end surface of the plate-shaped heating element 7 and the lower end surface of the lower pedestal 9 corresponds to the adjustment of the height of the plate-shaped heating element 7, as will be described later.

As shown in FIG. 2(a), the height adjusting bolt 12 is screwed into the fourth screw hole 24 of the lower base 9 and penetrated. By subsequently screwing in the height adjusting bolt 12 and raising it, the tip of the height adjusting bolt 12 is brought into contact with the lower end surface of the upper pedestal 8 as shown in FIG. 2(b). When the height adjusting bolt 12 is further rotated, a force is applied to raise the upper pedestal 8 together with the plate-like heating element 7 . Alternatively, the upper pedestal 8 prevents the height adjustment bolt 12 from rising, and a force acts to push down the lower pedestal 9 through the fourth screw hole 24 . As a result, as shown in FIG. 2(c), while the inner surface of the collar slide hole 25 and the outer surface of the combination collar 26 slide, the distance between the upper end surface of the lower pedestal 9 and the lower end surface of the upper pedestal 8 is increased. Expanding.

That is, in the preheating device 6 according to the present invention, the distance between the upper end surface of the plate-shaped heating element 7 and the lower end surface of the upper nozzle 2 is adjusted by rotating the height adjustment bolt 12 and screwing it into the fourth screw hole 24 . can be adjusted.

Such a preheating device 6 is attached to the exchange device 5 as shown in FIG. At this time, the plate-shaped heating element 7 is positioned upward and the lower pedestal 9 is positioned downward. Then, by screwing the height adjusting bolt 12 into the fourth screw hole 24 and raising the plate-shaped heating element 7 together with the upper base 8, the lower end surface of the upper nozzle 2 and the upper end surface of the plate-shaped heating element 7 are brought into close contact. (illustration omitted).

In the present invention, the means for attaching the preheating device 6 to the exchange device 5 is not limited. For example, preheating can be easily performed by placing the preheating device 6 utilizing the shape (for example, projection) of the exchanging device 5 (see FIG. 1). Furthermore, by using pins, bolts, etc. together, it is possible to prevent the preheating device 6 from being dislocated or falling off.

Although the configuration of the plate-shaped heating element 7 is not particularly limited, FIG. 3 schematically shows an example of the plate-shaped heating element 7 as a cross-sectional view.

The plate-shaped heating element 7 shown in FIG. 3 has a heater 14 with a built-in heating wire embedded inside a rectangular metal plate-shaped outer shell 13 . This plate-shaped heating element 7 is supplied with electric current through the current supply wiring 15, and the heat generated from the heating wire built-in heater 14 passes through the metal plate-shaped outer shell 13, and heats up the upper nozzle 2 from below by thermal conduction. heat is stored in Therefore, it is preferable to use a material having excellent thermal conductivity (for example, oxygen-free copper, etc.) for the metal plate-shaped outer shell 13 .

No molten steel is stored in the tundish 1 when the upper nozzle 2 is preheated using the preheating device 6 according to the present invention. After preheating is completed, the height adjusting bolt 12 is operated to remove the plate-shaped heating element 7 from the upper nozzle 2 , and then the preheating device 6 is removed from the exchanging device 5 . Then, the replacement device 5 is used to attach the lower nozzle 3 below the upper nozzle 2, the molten steel is stored in the tundish 1, and the continuous casting operation is started (see FIG. 4). Therefore, since the preheating device 6 is not likely to be exposed to excessive high temperature from the molten steel 4, it is possible to prevent deformation and failure due to high heat.

As described above, according to the present invention, the upper nozzle can be preheated using a simple means. In addition, since there is no need for manual preheating by an operator, the time required for preheating can be shortened. Furthermore, by utilizing the existing exchange device 5, preheating can be performed by developing only the heating element and its pedestal, so the introduction cost of new equipment can be suppressed.

Before starting a test operation of preheating the upper nozzle 2 and performing continuous casting by applying the present invention, first, a plate-shaped heating element 7 shown in FIG. 3 was manufactured. The square metallic plate-shaped outer shell 13 made of oxygen-free copper had dimensions of 120 mm in length and width and 12 mm in thickness, and four heaters 14 with built-in heating wires were arranged in parallel and buried. The capacity of each heating wire built-in heater 14 was 1200 W (specified voltage 220 V, weight 1.4 kg).

When the plate-shaped heating element 7 was manufactured in this way and a temperature rise test was performed by supplying current from the current supply wiring 15, the maximum temperature reached by the plate-shaped heating element 7 was 600° C., and the upper nozzle 2 was preheated. It has been found that the upper nozzle 2 can be preheated by setting the distance between the upper end surface of the plate-shaped heating element 7 and the lower end surface of the upper nozzle 2 to 0 mm (that is, they are in close contact).

Next, the preheating device 6 shown in FIG. 2 was manufactured and attached to the exchange device 5 (see FIG. 1). Subsequently, the height adjusting bolt 12 was operated to bring the plate-shaped heating element 7 into close contact with the upper nozzle 2 .

After heating the upper nozzle 2 from below using the preheating device 6 (energization time: 2 hours), the height adjustment bolt 12 is operated to remove the plate-shaped heating element 7 from the upper nozzle 2 and replace it. Removed from device 5. Then, the lower nozzle 3 was attached below the upper nozzle 2 using the exchange device 5, and molten steel was stored in the tundish 1 to start the continuous casting operation. occlusion did not occur.

When the continuous casting operation was continued using the preheating device 6 for 6 months, there was no clogging of the nozzle, which contributed to the improvement of the yield of molten steel. Further, since the nozzle was not clogged, the operation could be performed without any trouble even if the temperature of the molten steel stored in the tundish 1 was lowered by 5°C. As a result, it became possible to lower the temperature of the molten steel in the refining process for adjusting the components of the molten steel, and an effect of contributing to energy saving in the refining process was obtained.

REFERENCE SIGNS LIST 1 tundish 2 upper nozzle 3 lower nozzle 4 molten steel 5 exchange device 6 preheating device 7 plate-shaped heating element 8 upper pedestal 9 lower pedestal
10 Heating element fixing bolt
11 Pedestal connection bolt
12 Height adjustment bolt
13 Metal plate shell
14 Heater with built-in heating wire
15 Current supply wiring
20 washer
21 1st screw hole
22 Second screw hole
23 3rd screw hole
24 4th screw hole
25 Collar slide hole
26 combination colors

Claims (4)

A preheating device attached to an exchanging device for exchanging the lower nozzle in order to preheat the upper nozzle out of the upper nozzle and the lower nozzle, which form the flow path of the molten steel supplied from the tundish to the mold in continuous casting. There is
a plate-shaped heating element serving as a heat source for preheating the upper nozzle and provided with a first screw hole to be screwed with a heating element fixing bolt;
A second screw hole for mounting the plate-shaped heating element and screwed with the heating element fixing bolt is provided at a position opposite to the first screw hole, and a third screw hole is provided for screwing with the pedestal connection bolt. The upper pedestal provided,
A collar slide hole for inserting a combination collar through which the pedestal connection bolt is screwed is provided at a position opposite to the third screw hole, and is centered around the fourth screw hole for screwing the height adjustment bolt. A lower pedestal provided,
A preheating device comprising: a plurality of washers sandwiched between the plate-shaped heating element and the upper pedestal and between the upper pedestal and the head of the heating element fixing bolt;
a plurality of washers sandwiched between the upper pedestal and the combination collar and between the combination collar and the head of the pedestal connecting bolt;
The preheating device according to claim 1, characterized by comprising: In a preheating method for preheating the upper nozzle out of the upper nozzle and the lower nozzle that serve as a flow path for molten steel supplied from the tundish to the mold in continuous casting,
a plate-shaped heating element serving as a heat source for preheating the upper nozzle and provided with a first screw hole to be screwed with a heating element fixing bolt;
A second screw hole for mounting the plate-shaped heating element and screwed with the heating element fixing bolt is provided at a position opposite to the first screw hole, and a third screw hole is provided for screwing with the pedestal connection bolt. The upper pedestal provided,
A collar slide hole for inserting a combination collar through which the pedestal connection bolt is screwed is provided at a position opposite to the third screw hole, and is centered around the fourth screw hole for screwing the height adjustment bolt. A lower pedestal provided,
to the lower nozzle replacement device, and then rotate the height adjustment bolt and screw it into the fourth screw hole so that the lower end surface of the lower pedestal and the plate-shaped heating element A preheating method, wherein the upper nozzle is preheated by adjusting the distance from the upper end surface so that the lower end surface of the upper nozzle and the upper end surface of the plate-shaped heating element are brought into close contact with each other. The preheating device
a plurality of washers sandwiched between the plate-shaped heating element and the upper pedestal and between the upper pedestal and the head of the heating element fixing bolt;
a plurality of washers sandwiched between the upper pedestal and the combination collar and between the combination collar and the head of the pedestal connecting bolt;
The preheating method according to claim 3, characterized by comprising:

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