EP4732971A1

EP4732971A1 - Temperature-raising device, rolling equipment provided with same, and method for raising temperature of cast slab

Info

Publication number: EP4732971A1
Application number: EP23954243.4A
Authority: EP
Inventors: Kenji Horii; Akio Kuroda; Toshihiro Usugi; Tatsunori Sugimoto; Stefan EBBING; Marco Rische; Andrej Umbrasko; Lukas PICHLER; Alois Seilinger
Original assignee: Primetals Technologies Austria GmbH; ABP Induction Systems GmbH; Primetals Technologies Japan Ltd
Current assignee: Primetals Technologies Austria GmbH; ABP Induction Systems GmbH; Primetals Technologies Japan Ltd
Priority date: 2023-09-27
Filing date: 2023-09-27
Publication date: 2026-04-29
Also published as: WO2025069267A1; CN121843776A; JPWO2025069267A1

Abstract

Provided are a first temperature raising device that is provided in a rolling line between a continuous casting machine 12 and a rough rolling mill 70, a second temperature raising device that is provided in a temperature raising line different from the rolling line, a first slab transportation device 40 that can move a slab 100 between the exit side of the slab 100 in the rolling line of the first temperature raising device and the entry side of the slab 100 in the temperature raising line of the second temperature raising device, and a second slab transportation device 42 that can move the slab 100 between the entry side of the slab 100 in the rolling line of the first temperature raising device and the exit side of the slab 100 in the temperature raising line of the second temperature raising device, and the first temperature raising device has a first IH slab heater 20 and the second temperature raising device has a second IH slab heater 22. Accordingly, it is possible to provide a temperature raising device, a rolling facility including the same, and a temperature raising method of a cast slab that can improve the temperature raising efficiency before sending the cast slab to a rough rolling mill as compared with the conventional technique.

Description

Technical Field

The present invention relates to a temperature raising device, a rolling facility including the same, and a temperature raising method of a cast slab.

Background Art

Patent Document 1 describes that in a cast slab heating facility in direct rolling that is installed in a cast slab transportation line for transporting a cast slab of steel cast by a continuous casting machine to a rolling mill to perform direct rolling of the cast slab and raises the temperature of the cast slab to a proper rolling temperature, provided are: a heat retaining chamber that temporarily accommodates a plurality of cast slabs from the continuous casting machine in the order of arrival, uses the retained heat itself of the cast slab as a heat source, does not have other heat sources, and is formed by being surrounded with an insulation material; a heating device that heats up and raises the temperature of the cast slab drawn from the heat retaining chamber while moving it; a thermometer that is installed on the exit side of the heat retaining chamber and measures the temperature of the cast slab drawn from the heat retaining chamber to know whether or not it is possible to raise the temperature to the proper rolling temperature by passing the cast slab drawn from the heat retaining chamber through the heating device once; and a reverse feed facility that returns the cast slab, whose temperature has been raised by the heating device and has not reached the proper rolling temperature, to the heat retaining chamber to raise the temperature again with the heating device on the basis of the measurement result by the thermometer, and the cast slab whose temperature has been raised to the proper rolling temperature by the heating device is sent to the rolling mill.

Prior Art Document

Patent Document

Patent Document 1: Patent No. 5130139

Summary of the Invention

Problem to be Solved by the Invention

In order to perform direct rolling of a cast slab (a billet, a slab, or the like) of steel cast by a continuous casting machine, the cast slab from the continuous casting machine is sent to a rolling mill after the temperature thereof is raised to a proper rolling temperature in some cases.
For example, there is a technique described in Patent Document 1 as a conventional technique of a cast slab heating facility in direct rolling, which can raise the temperature of the corresponding cast slab to a proper rolling temperature and requires no reject (removal) from a transportation line even in the case where a cast slab whose temperature is lower than usual is sent from a continuous casting machine at this time.
However, in the above technique, there is a problem that a billet, whose temperature has been raised by an induction heating device and has not reached the proper rolling temperature, is returned to the heat retaining chamber and the temperature of the billet significantly drops before being sent to the induction heating device again.
The present invention provides a temperature raising device, a rolling facility including the same, and a temperature raising method of a cast slab that can improve the temperature raising efficiency before sending the cast slab to a rough rolling mill as compared with the conventional technique.

Means for Solving the Problem

The present invention includes a plurality of means for solving the above problem, and provides, as an example, a temperature raising device for raising a temperature of a cast slab of steel cast by a continuous casting machine, the temperature raising device includes: a first temperature raising device that is provided in a rolling line between the continuous casting machine and a rough rolling mill; a second temperature raising device that is provided in a temperature raising line different from the rolling line; a first transportation device that can move the cast slab between an exit side of the cast slab in the rolling line of the first temperature raising device and an entry side of the cast slab in the temperature raising line of the second temperature raising device; and a second transportation device that can move the cast slab between an entry side of the cast slab in the rolling line of the first temperature raising device and an exit side of the cast slab in the temperature raising line of the second temperature raising device, and the first temperature raising device and the second temperature raising device each have an induction heating device.

Advantages of the Invention

According to the present invention, it is possible improve the temperature raising efficiency before sending a cast slab to a rough rolling mill as compared with the conventional technique. Problems, configurations, and effects other than those described above will be clarified by the description of the embodiment below.

Brief Description of the Drawings

FIG. 1 is a diagram for depicting an overview of a rolling facility of an embodiment.
FIG. 2 is a diagram for depicting the temperature of a slab immediately before rough rolling when the slab is transported without raising the temperature thereof.
FIG. 3 is a diagram for depicting the temperature of a slab immediately before rough rolling when the slab is transported without raising the temperature thereof.
FIG. 4 is a diagram for depicting the temperature of a slab immediately before rough rolling when the slab is transported without raising the temperature thereof.
FIG. 5 is a diagram for depicting a flow in the case where the slab is transported to the rolling facility by using a temperature raising device of the slab of the embodiment.
FIG. 6 is a diagram for depicting a flow in the case where the slab is transported to the rolling facility by using the temperature raising device of the slab of the embodiment.
FIG. 7 is a diagram for describing a case where the slab is heated up by only a first IH slab heater by using the temperature raising device of the embodiment and direct rolling is performed.
FIG. 8 is a diagram for describing a case where the slab is heated up by only a second IH slab heater by using the same facility as FIG. 7 and direct rolling is performed.
FIG. 9 is a diagram for depicting an example of a state in which a reject material is heated up by using the temperature raising device of the slab of the embodiment.
FIG. 10 is a diagram for depicting the relationship between the temperature change of the slab and the output power of an IH slab heater in the case of using no soaking device in the temperature raising device of the embodiment.
FIG. 11 is a diagram for depicting the relationship between the temperature change of the slab and the output power of the IH slab heater in the case of using a soaking device in the temperature raising device of the embodiment.
FIG. 12 is a diagram of an example in which the IH slab heater in the temperature raising device of the embodiment is viewed from the front.
FIG. 13 is a diagram for depicting a state of the difference in average temperature between the tip end and the rear end of the slab.
FIG. 14 is a diagram for describing a method of eliminating the temperature difference between the tip end and the rear end of the slab by using the temperature raising device of the embodiment.
FIG. 15 is a diagram for describing a case where the slab is heated up by only the first IH slab heater without using the second IH slab heater by using the temperature raising device of the embodiment and direct rolling is performed.
FIG. 16 is a diagram for depicting an example of a known facility that heats up the slab inserted into a reheating furnace.
FIG. 17 is a diagram for depicting an example in which the temperature raising device of slab of the present invention is installed in a facility that heats up the slab inserted into the reheating furnace.
FIG. 18 is a diagram of another example in which the IH slab heater in the temperature raising device of the embodiment is viewed from the front.
FIG. 19 is a diagram of still another example in which the IH slab heater in the temperature raising device of the embodiment is viewed from the front.
FIG. 20 is a diagram corresponding to the A-A arrow in FIG. 12 that is the diagram of an example in which the IH slab heater in the temperature raising device of the embodiment is viewed from the front.

Modes for Carrying Out the Invention

Hereinafter, an embodiment of a temperature raising device, a rolling facility including the same, and a temperature raising method of a cast slab of the present invention will be described by using the drawings. It should be noted that in the drawings used in the description, the same or corresponding constitutional elements will be given the same or similar signs, and repeated descriptions of these constitutional elements will be omitted in some cases.
FIG. 1 is a diagram for depicting an overview of a rolling facility of the present invention. A rolling facility 1 in FIG. 1 has a configuration in which a temperature raising device of a slab 100 is arranged between a continuous casting machine 12 and a rough rolling mill 70.
Molten steel in a ladle (omitted for the convenience of illustration) is moved from the ladle to an injection position into the continuous casting machine 12 by a ladle turret 10. The continuous casting machine 12 has two strands, and cast slabs are cast in two lines and divided into the slabs 100 having a desired length by a torch cutting machine 14 located on the exit side of the continuous casting machine 12.
Here, in the present embodiment, the same line as the rolling line is defined as a first strand, and the line side that is not the rolling line is defined as a second strand. The slab 100 of the second strand is transported to the rolling line (first strand) by a continuous casting machine exit-side slab transportation device 48, and then transported in the direction of the rough rolling mill 70 and the like.
In the case where the cast slab 100 cannot be transported to the rough rolling mill 70 due to troubles in the rolling facility or the quality of the slab 100, the continuous casting machine exit-side slab transportation device 48 is used to transport the slab as a rejected material to a storage yard for rejected slab 50. In the storage yard for rejected slab 50, the rejected material is stored, and repair and inspection of the rejected material are performed if necessary.
The temperature raising device of the present embodiment depicted in FIG. 1 is a device for raising the temperature of the steel slab 100 (see FIG. 12 and the like) cast by the continuous casting machine 12, and includes a first IH slab heater 20, a first soaking device 30, a first slab transportation device 40, a second IH slab heater 22, a second soaking device 32, a third soaking device 34, a second slab transportation device 42, a third slab transportation device 44, a fourth slab transportation device 46, a thermometer 201 in a first temperature raising device, a thermometer 203 in a second temperature raising device, a storage yard thermometer 205, a controller 90, and the like.
After finishing the heating up in the temperature raising device, at first, since an oxidation scale is generated on the surface of the slab 100 by high-temperature heating up prior to rolling in the rolling facility 1, the scale on the surface is removed by a scale breaker 60 that removes the scale by spraying high-pressure water on the surface of the slab 100 before rolling, reverse rolling is performed by a single rough rolling mill 70, unidirectional rolling is performed by a plurality of finishing rolling mill trains 75, strip cooling is performed by a run out table 80, and coiling is performed by a down coiler 85. In the rolling facility 1, it is possible to arrange a plurality of rough rolling mills 70.
The first temperature raising device is provided in the rolling line between the continuous casting machine 12 and the rough rolling mill 70, and has the first IH slab heater 20, the first soaking device 30, and the like.
The slab 100 transported from the continuous casting machine 12 to the direction of the rolling facility is heated up to a desired temperature by at least the first IH slab heater 20, and is then transported to the first soaking device 30 provided on the exit side of the slab 100 in the rolling line of the first IH slab heater 20 and using the retained heat of the slab 100 as a heat source, and in the first soaking device 30, the temperature distribution in the cross section of the slab 100 is uniformized and the rolling timing is adjusted while suppressing the heat radiation from the slab 100.
Time is required to raise the temperature at the thickness center of the slab 100 whose temperature has fallen. However, in the heating up by the first IH slab heater 20, the temperature of the surface becomes high relatively quickly, and reaches the upper-limit temperature allowed as the surface temperature. Thereafter, the heating up is continued within a range where the surface temperature does not exceed the upper-limit temperature, but the output (power) to be supplied needs to be reduced.
Therefore, the slab 100 is transferred to the first soaking device 30 at that time to increase the temperature inside the slab 100 although the temperature of the surface of the slab 100 falls more or less, and it becomes possible to efficiently increase the center temperature of the slab 100 in the device by heating up the other slabs 100 with the IH slab heater.
That is, by repeating the heating up a plurality of times in a single IH slab heater and the uniformizing of the temperature in the soaking device, it becomes possible to shorten the time for the slab 100 to stay in the induction heating device as compared with the case of heating up the slab 100 with induction heating alone, and it becomes possible to shorten the time interval until the induction heating device starts heating up the next slab 100, and thus it becomes possible to efficiently heat up a number of slabs 100 while ensuring the time until the temperature at the thickness center is raised.
The second temperature raising device is provided in a temperature raising line different from the rolling line where the first temperature raising device is provided has the second IH slab heater 22, the second soaking device 32 that is provided on the entry side of the slab 100 in the temperature raising line of the second IH slab heater 22 and uses the retained heat of the slab 100 as a heat source, the third soaking device 34 that is provided on the exit side of the slab 100 in the temperature raising line of the second IH slab heater 22 and uses the retained heat of the slab 100 as a heat source, and the like.
This second temperature raising device is provided to heat up in the second IH slab heater 22 and to retain the heat in the second soaking device 32, the third soaking device 34, and the like in the case where the temperature rise of the slab 100 is insufficient in the first IH slab heater 20 of the first temperature raising device. It should be noted that the configuration in which the second temperature raising device has two heat retaining devices such as the second soaking device 32 and the third soaking device 34 is depicted, but either one or three of more devices may be provided.
In FIG. 1, the second IH slab heater 22, the second soaking device 32, and the third soaking device 34 are defined as one set, but it is possible to provide a plurality of sets.
In the first IH slab heater 20, the second IH slab heater 22, the first soaking device 30, the second soaking device 32, and the third soaking device 34, a table roller 130 (see FIG. 12) is provided, and the slab 100 can be moved back and forth in the rolling direction.
The first IH slab heater 20 and the second IH slab heater 22 can uniformize the temperature in the cross section while uniformizing the temperature rise in the longitudinal direction of the slab 100 by reciprocating (oscillating) the slab 100 back and forth in the rolling direction. The details of the configuration thereof will be described later using FIG. 12 and the like.
The first soaking device 30, the second soaking device 32, and the third soaking device 34 can employ a configuration in which the slab 100 is surrounded with a panel configured using a reflector and an insulating material to suppress the escape of heat from the slab 100 arranged therein and to promote to uniformize the temperature inside the slab 100. It is also possible to have a structure in which an insulating material such as a refractory is combined with an iron shell on the outside without providing a reflector. In addition, it is also effective in shortening the time of the temperature rise to arrange heating means therein and use the heating means to raise the temperature inside the heat retaining device at the start of the operation. The internal heating means may use gas heating, but direct CO₂ emissions can be suppressed by using electric heaters.
Even in these first soaking device 30, second soaking device 32, and third soaking device 34, the temperature in the cross section can be uniformized while uniformizing the temperature rise in the longitudinal direction of the slab 100 by reciprocating (oscillating) the slab 100 back and forth in the rolling direction.
The first slab transportation device 40 is configured such that the slab 100 can be moved between the exit side of the slab 100 in the rolling line of the first temperature raising device and the entry side of the slab 100 in the temperature raising line of the second temperature raising device.
In contrast, the second slab transportation device 42 is configured such that the slab 100 can be moved between the entry side of the slab 100 in the rolling line of the first temperature raising device and the exit side of the slab 100 in the temperature raising line of the second temperature raising device.
The third slab transportation device 44 is configured such that the slab 100 can be moved between the storage yard for rejected slab 50 where the slab 100 is stored and the entry side of the slab 100 in the temperature raising line of the second temperature raising device. The fourth slab transportation device 46 is configured such that the slab 100 can be moved between the storage yard for rejected slab 50 and the exit side of the slab 100 in the temperature raising line of the second temperature raising device. It should be noted that a configuration in which either the third slab transportation device 44 or the fourth slab transportation device 46 is provided can be employed.
The thermometer 201 in the first temperature raising device is provided in the first temperature raising device and is a thermometer for measuring the temperature of the slab 100. For example, it is configured to measure the surface temperature of the slab 100 in the first IH slab heater 20.
It should be noted that although FIG. 1 and the like exemplify a case in which one thermometer 201 in the first temperature raising device is illustrated, the number can be two or more. In addition, it is not limited to the configuration of measuring the temperature of the slab 100 in the first IH slab heater 20, but it is possible to employ any of a configuration of measuring the temperature of the slab 100 in the first soaking device 30, a configuration of measuring the temperature of the slab 100 before entering the first IH slab heater 20, after exiting the first IH slab heater 20, or after exiting the first soaking device 30, and a configuration of employing any two or more of them.
The thermometer 203 in the second temperature raising device is provided in the second temperature raising device and is a thermometer for measuring the temperature of the slab 100 in the second temperature raising device. For example, it is configured to measure the surface temperature of the slab 100 in the second IH slab heater 22.
It should be noted that although a case in which one thermometer 203 in the second temperature raising device is also illustrated is exemplified, the number can be two or more. In addition, it is not limited to the configuration of measuring the temperature of the slab 100 in the second IH slab heater 22, but it is possible to employ any of a configuration of measuring the temperature of the slab 100 in the second soaking device 32 or the third soaking device 34, a configuration of measuring the temperature of the slab 100 before entering the second IH slab heater 22, after exiting the second IH slab heater 22, or before entering or after exiting the second soaking device 32 or the third soaking device 34, and a configuration of employing any two or more of them.
The storage yard thermometer 205 is provided in the storage yard for rejected slab 50 and is a thermometer for measuring the temperature of the slab 100 in the storage yard for rejected slab 50. For example, it is configured to measure the surface temperature of the slab 100.
It should be noted that although a case in which one storage yard thermometer 205 is also illustrated is exemplified, the number can be two or more. In addition, it is not limited to the configuration of measuring the temperature of the slab 100 in the storage yard for rejected slab 50, but it is possible to employ either a configuration of measuring the temperature of the slab 100 in the third slab transportation device 44 or the fourth slab transportation device 46 or a configuration of employing any two or more of them.
The controller 90 predicts the average temperature of the slab 100 and the temperature of the center of the slab 100 on the basis of the measurement result of the temperature of the slab 100 in one or more of the above-described thermometer 201 in the first temperature raising device, the thermometer 203 in the second temperature raising device, and the storage yard thermometer 205, and decides the transportation destination of the slab 100 on the basis of the measured surface temperature and the predicted internal temperature. The details thereof will be described later.
FIG. 2 is a diagram for depicting the temperature of the slab immediately before rough rolling when the slab is transported without raising the temperature, and depicts results obtained by performing a simulation under the conditions that the casting velocity Vc is 2.0 m/min, the thickness of the slab is 225 mm, and the width of the slab is 1300 mm. In FIG. 2, the horizontal axis depicts a position in the thickness direction, and the vertical axis depicts a temperature at the center in the width direction of the slab.
It should be noted that the temperature immediately before rough rolling is appropriately set according to the type of steel, but here a case in which the target temperature immediately before rough rolling is 1150°C is described. In this case, the average temperature raising amount of the slab to be required is 105°C.
Although the temperature of the slab at the position where it is heated up by the IH slab heater is slightly higher than that of the slab at the position immediately before rough rolling, the temperature raising amount heated up by the IH slab heater is not much different from 105°C depicted in FIG. 2, and thus the temperature raising amount in the IH slab heater is assumed to be 105°C here.
FIG. 3 is also a diagram for depicting the temperature of the slab immediately before rough rolling when the slab is transported without raising the temperature, and depicts a case when the casting velocity Vc is 1.2 m/min. In FIG. 3, the horizontal axis depicts a position in the thickness direction, and the vertical axis depicts a temperature at the center in the width direction of the slab. In FIG. 3, the average temperature raising amount of the slab to be required is 321°C as similar to FIG. 2.
Although the temperature of the slab at the position where it is heated up by the IH slab heater is slightly higher than that of the slab at the position immediately before rough rolling, the temperature raising amount heated up by the IH slab heater is not much different from 321°C depicted in FIG. 3, and thus the temperature raising amount in the IH slab heater is assumed to be 321°C here.
FIG. 4 is a diagram for depicting the temperature of the slab immediately before rough rolling when the slab is transported without raising the temperature, the horizontal axis depicts a casting velocity, the vertical axis depicts a temperature at the center in the width direction of the slab, and the temperature at the center in the thickness direction, the average temperature in the thickness direction, and the temperature of the surface are organized as parameters.
The temperature of the slab during transportation is the highest at the center and the lowest at the surface. On the other hand, in the heating up by the IH slab heater, the heating up near the surface can be performed in a relatively short time, but the heating up inside the slab is performed by heat conduction, and thus it takes time.
Since there is a problem that in the case where the temperature at the center in the thickness direction is low, the rolling load becomes high, it is necessary to set a goal that the average temperature is the target temperature of 1150°C (depending on the type of steel) immediately before rough rolling. At the same time, since there is a problem that when the temperature difference is large, a large variation in the thickness direction of the structure causes a variation in mechanical strength and elongation in the thickness direction, or the desired toughness cannot be obtained, it is also necessary to a goal that the temperature at the center in the thickness direction is brought closer to the target temperature of 1150°C.
The surface can be made a high temperature state by the IH slab heater, but the temperature falls because of the descaling of the slab surface before rolling and the temperature drop of the surface during transportation.
Here, by focusing the average temperature and the temperature at the center in the thickness direction, a method of heating up with the IH slab heater such that these temperatures become temperatures suitable for rolling will be described.
It should be noted that each data in FIG. 2 to FIG. 4 has been obtained by performing a simulation for the slab supplied from a strand (second strand) that is parallel to the rolling line in FIG. 1 and is not the rolling line. The slab supplied from the same strand (first strand) as the rolling line tends to be slightly higher in temperature, but the temperature can be adjusted by heating up with the IH slab heater.
In addition, the controller 90 decides a transportation velocity in each device within the temperature raising device of the slab 100 and controls the velocity thereof.
FIG. 2 to FIG. 4 show the temperature at the tip end of the slab 100. The temperature at the rear end of the slab 100 is slightly higher than that at the tip end. Since the temperature difference between the tip end and the rear end of slab 100 can be adjusted by the heating up when the slab 100 is inserted into the IH slab heater, the controller 90 can adjust the temperature difference to be eliminated from the rear end inserted into the IH slab heater last by inserting the slab 100 into the IH slab heater while heating up from the tip end when the tip end of the slab 100 is inserted into the IH slab heater.
FIG. 5 depicts a flow in the case where the slab 100 is heated up by the first IH slab heater 20, and the slab 100 is transported to the rolling facility after the temperature thereof is kept by the first soaking device 30. In FIG. 5, the circled letters indicate the processes matching the numbers in "()" below.
In this case, the controller 90 determines whether to transport the slab 100 to either the rough rolling mill 70 or the second temperature raising device on the basis of the temperature of the slab 100 measured by the thermometer 201 in the first temperature raising device, and switches the transportation direction of the slab 100. Here, a case in which the slab 100 is transported to the rough rolling mill 70 on the assumption that the average temperature and the center temperature of the slab 100 have reached the target is exemplified.
In FIG. 5, as depicted in a), a cast slab cast at a casting velocity of 2.0 m/min in each strand in the two-strand continuous casting machine 12 is transported in the direction of the rolling facility while being cut at a pitch of 12 m as the length of the slab 100, and a first slab 101 arrives at the entry side of the first IH slab heater 20.
Since the temperatures immediately before rough rolling of the first slab 101 correspond to 1120°C at the thickness center, 1045°C as the average, and 900°C on the surface, the heating up in the first IH slab heater 20 and the heat retention in the first soaking device 30 on the exit side thereof are adjusted as depicted in b) in FIG. 5 such that the temperature during rough rolling becomes approximately 1150°C later.
In FIG. 5, (1) of b) is the transportation to the inside of the first IH slab heater 20, and using this transportation, the tip end of the slab 100 is heated up more by the first IH slab heater 20, and the rear end is heated up less by the first IH slab heater 20. This phenomenon is used to reduce the temperature difference between the tip end and the rear end. Here, the temperature difference is adjusted to be small on the assumption that the temperature difference between the average temperatures of the tip end and the rear end is 50°C and the transportation time is 33 seconds.
In FIG. 5, (2) of b) depicts a state in which the slab 100 is heated up while being oscillated (reciprocated in the path direction) inside the first IH slab heater 20. Here, the upper limit of the surface temperature is set at 1300°C. After the surface temperature reaches 1300°C, the heating up of the entire slab 100 is continued such that the surface temperature does not exceed 1300°C by reducing the output (power) of the first IH slab heater 20.
After an elapse of a heating up time of 121 seconds (154 seconds in total), the converted temperatures immediately before rough rolling correspond to 1170°C at the thickness center, 1230°C as the average, and 1300°C on the surface.
The surface temperature falls due to the descaling performed before rolling and the transportation before rough rolling and the average temperature also falls, but the temperature at the thickness center hardly changes, and thus the temperature at the thickness center and the average temperature can be maintained at approximately 1170°C when converted to the temperatures immediately before rough rolling.
In FIG. 5, c) depicts (3) transportation to the first soaking device 30 for 26 seconds (180 seconds in total) and (4) heat retention while oscillating for 33 seconds (213 seconds in total). Since the slab 100 having a length of 12 m is produced at a 6-minute pitch, it arrives at the entry side of the first IH slab heater 20 at a 3-minute pitch due to two strands. Therefore, a second slab 102 arrives at the entry side of the first IH slab heater 20 at the timing when the transportation of (3) is completed.
Thereafter, as depicted in d) in FIG. 5, the rear end of the first slab 101 exits the first soaking device 30. 19 seconds (232 seconds in total) is required for the transportation of (5), and it passes through a section L1 for 232 seconds in total. Since "180 seconds (3 minutes) + 154 seconds = 334 seconds" is required for the second slab 102 to complete (1) and (2), and 213 seconds is required for the first slab 101 to complete (4), there is a margin of 121 seconds (= 334 - 213). It is possible to further keep the slab 100 inside the first soaking device 30 for 121 seconds longer.
FIG. 6 depicts a flow of heating up the slab 100 with both the first IH slab heater 20 and the second IH slab heater 22, and then transporting the slab 100 to the rolling facility. In FIG. 5, the circled letters indicate the processes matching the numbers in "()" below.
In this case, the controller 90 determines the number of times the second IH slab heater 22, the second soaking device 32, and the third soaking device 34 have been used for the slab 100 in the second temperature raising device and the staying time on the basis of the temperature measured by the thermometer 203 in the second temperature raising device and the rolling conditions in the rolling line, and switches the transportation direction of the slab 100. Here, the controller 90 determines in advance to transport the slab 100 to the second temperature raising device on the assumption that the average temperature and the center temperature of the slab 100 do not reach the target.
In FIG. 6, a) depicts that the first slab 101 arrives at the first IH slab heater 20 and is transported to the outside of the rolling line by the first slab transportation device 40.
The slab 100 obtained by cutting a cast slab, which has been cast at a casting velocity of 1.2 m/min in each strand in the two-strand continuous casting machine 12, at a pitch of 12 m length is transported in the direction of the rolling facility, and the first slab 101 arrives at the entry side of the first IH slab heater 20.
Since the temperatures of the first slab 101 immediately before rough rolling correspond to 870°C at the thickness center, 829°C as the average, and 750°C on the surface, the heating up is adjusted such that the temperature immediately before rough rolling becomes approximately 1150°C later. The temperature drop is larger than that in the case of a casting velocity of 2.0 m/min in FIG. 5. Therefore, as similar to (1) in FIG. 5, since the temperature difference between the average temperatures of the tip end and the rear end is 50°C, the slab is first transported to the first IH slab heater 20 in (1) by setting the transportation time at 33 seconds, and the temperature difference is adjusted to be small.
Thereafter, as in (2), the slab 100 is heated up while being oscillated (reciprocated in the path direction) inside the first IH slab heater 20. Here, the upper limit of the surface temperature is set at 1300°C. After the surface temperature reaches 1300°C, the heating up of the entire slab 100 is continued such that the surface temperature does not exceed 1300°C by reducing the output (power) of the first IH slab heater 20.
After an elapse of a heating up time of 192 seconds (225 seconds in total), the converted temperatures immediately before rough rolling correspond to 985°C at the thickness center, 1100°C as the average, and 1300°C on the surface. However, the thickness center and the average temperature do not reach the target of 1150°C only by the heating up of the first IH slab heater 20. Therefore, the controller 90 transports the first slab 101 to the second temperature raising device.
In FIG. 6, b) depicts that the first slab 101 is heated up by the second IH slab heater 22 outside the rolling line and is transported to the rolling line by the second slab transportation device 42.
Until the insertion into the second IH slab heater 22 is completed, 154 seconds (379 seconds in total) elapse in (3) transportation, (4) heat retention while oscillating inside the first soaking device 30, and the transportation of (5), (6), and (7), and the slab is heated up while (8) being oscillated (reciprocated in the path direction) inside the second IH slab heater 22. After an elapse of a heating up time of 140 seconds (519 seconds in total), the converted temperatures immediately before rough rolling correspond to 1080°C at the thickness center, 1165°C as the average, and 1300°C on the surface. By the heating up with both the first IH slab heater 20 and the second IH slab heater 22, the average temperature exceeds the target of 1150°C, but the temperature at the thickness center does not reach the target temperature.
In FIG. 6, c) depicts a state in which the first slab 101 is heated up again by the first IH slab heater 20 and exits the first heat retaining device.
Due to the insufficient heating up with the first IH slab heater 20 and the second IH slab heater 22, until the insertion into the first IH slab heater 20 is completed, 132 seconds (651 seconds in total) elapse in (9) transportation, (10) heat retention while oscillating inside the third soaking device 34, and the transportation of (11), (12), and (13), and the slab is heated up while (14) being oscillated (reciprocated in the path direction) inside the first IH slab heater 20.
After an elapse of a heating up time of 140 seconds (791 seconds in total), the converted temperatures immediately before rough rolling correspond to 1070°C at the thickness center, 1230°C as the average, and 1300°C on the surface. By the heating up with the first IH slab heater 20, the second IH slab heater 22, and the second heating up with the first IH slab heater 20, the temperature at the thickness center exceeds the target temperature of 1150°C.
The surface temperature falls due to the descaling performed before rolling and the transportation before rough rolling, and the average temperature also falls, but the temperature at the thickness center hardly changes, and thus the temperature at the thickness center and the average temperature can be maintained at approximately 1170°C when converted to the temperatures immediately before rough rolling.
Further, 79 seconds (870 seconds in total) elapse in (15) transportation, (16) heat retention while oscillating inside the first soaking device 30, and the transportation of (17).
Since the slab 100 having a length of 12 m is produced at a 10-minute pitch when the casting velocity is 1.2 m/min, it arrives at the entry side of the first IH slab heater 20 at a 5-minute pitch due to two strands. Therefore, the timing to return the first slab 101 to the rolling line is after the second slab 102 and a third slab 103 pass through the entry side of the first IH slab heater 20.
The first slab 101 is transported in the direction of the rough rolling mill 70 after the second heating up is completed by the first IH slab heater 20. As similar to the first slab 101, the second slab 102 and the third slab 103, and a fourth slab 104, a fifth slab 105, and the like that follow are transported in the direction of the rough rolling mill 70 while being heated up three times in total by the first heating up with the first IH slab heater 20 and the second IH slab heater 22, and the second heating up with the first IH slab heater 20.
When deciding how many times to heat up and retain the heat in the second IH slab heater 22, the second soaking device 32, and the third soaking device 34 in the case where it is determined that the temperature is additionally raised by the second IH slab heater 22 as depicted in FIG. 6 rather than direct transportation to the rough rolling mill 70 as depicted in FIG. 5, the conditions (the timing of return and the temperature at that time) for returning to the rolling line are set first, and the heating up conditions (the number of times of heating up, each heating up time, and each heat retention time) in the second temperature raising device are decided. The target slab 100 is then transported according to the decided conditions.
At this time, the upper-limit temperature is set for each steel type because there are problems such as excessive surface oxidation if the temperature is too high. Therefore, it is desirable that the temperature of the outer surface of the slab 100 does not exceed the limit value. It is desirable to use the soaking device as effectively as possible by efficiently using the induction heating device to suppress the consumption of electricity.
FIG. 6 describes that the temperature of the slab 100 is raised while being heated up three times in total by the first heating up with the first IH slab heater 20 and the second IH slab heater 22, and the second heating up with the first IH slab heater 20, but there are other methods.
For example, the slab can be transported to the rolling facility without the second heating up with the first IH slab heater 20 when returning from the temperature raising line to the rolling line.
The timing to return the first slab 101 to the rolling line is after the passage of the third slab 103. In the case where the first slab 101 is returned to the middle of the third slab 103 and the fourth slabs 104, "5 minutes (passage of the second slab 102) + 5 minutes (passage of the third slab 103) + 2.5 minutes = 12.5 minutes" elapse before becoming the next state of (1) from the state of (1) in FIG. 6.
At this time, it is preferable that the transportation of the third slab 103 to the transportation of the first soaking device 30 of (3) has been completed. This can prevent the third slab 103 from interfering with the second heating up of the first slab 101 in the first IH slab heater 20. If the time required by the third slab 103 for (1), (2), and (3) is 2.5 minutes, it is possible for the next first slab 101, which has been rotated once, to start (1) transportation to the first IH slab heater 20. Further, if this first slab 101 passes through (1), (2), and (3) in 2.5 minutes, the next fourth slab 104 can also pass through (1), (2), and (3) in 2.5 minutes.
Thus, by making (1), (2), and (3) half the pitch at which the slab 100 arrives, even if the slab 100 is returned from the outside of the rolling line in the middle of the slabs 100, the slabs 100 do not collide with each other or the heating up conditions of the slabs 100 are not mixed.
In addition, when the first heating up time and the second heating up time in the first IH slab heater 20 are shortened, the heating up time in the second IH slab heater 22 can be made longer. In the case where the heating up time in the second IH slab heater 22 is made longer, it is also possible to perform the heating up with the second IH slab heater 22 and the heat retention in the heat in the second soaking device 32 or the third soaking device 34 a plurality of times.
Since time is required to increase the temperature at the thickness center, and the high temperature state of the slab 100 can be maintained as much as possible by the combination of each heating up of the first heating up with the first IH slab heater 20 and the second IH slab heater 22 and the second heating up with the IH slab heater and the heat retention in each soaking device, the temperature at the thickness center can be increased more.
In FIG. 6, 870 seconds (14.5 minutes) elapse in total from the start of the transportation of (1) to the completion of the transportation of (17) next after becoming the state of (1) again. The average passing velocity of the slab 100 during this period is 3.86 m/min (= 56/14.5) in the case where the section L1 is, for example, 56 m. Since each of the two strands of the continuous casting machine 12 continues to cast at 1.2 m/min, the average passing velocity of 3.86 m/min at which the slab 100 passes through the temperature raising device after raising the temperature of the slab 100 in the temperature raising device has a relationship of 3.86 > 2.4 (= 1.2 × 2), it is possible to raise the temperature of the slab 100 supplied from the continuous casting machine 12 without delay.
Here, although it has been described that the first slab is inserted into the first IH slab heater 20 after the transportation of (3) for the third slab is completed, the heating up time in the first IH slab heater 20 can be made longer in such a manner that, for example, the insertion of the first slab is started when the rear end of the third slab exits the first IH slab heater 20, or the insertion of the fourth slab into the first IH slab heater 20 is started when the rear end of the first slab exits the first IH slab heater after the second hearting up of the first slab with the first IH slab heater 20. The heating up time in the second IH slab heater 22 can also be made longer than the above description by similarly inserting a subsequent slab into the second IH slab heater 22 without waiting for the completion of the transportation of (9). The heating up time in the first IH slab heater 20 and the second IH slab heater 22 can be adjusted within the range of the conditions that each slab does not interfere with the other slab.
It should be noted that the flow of the slab in the case where the slab is not moved back and forth between the first temperature raising device and the second temperature raising device is not limited to the configuration depicted in FIG. 5. Hereinafter, examples of different configurations will be described by using FIG. 7 and FIG. 8. FIG. 7 is a diagram for describing a case of performing direct rolling by heating up the slab with only the first IH slab heater by using the temperature raising device, and FIG. 8 is a diagram for describing a case of performing direct rolling by heating up the slab with only the second IH slab heater by using the same facility as FIG. 7.
As depicted in Fig. 7 and Fig. 8, after the slab (first slab) is transported to the first temperature raising device of the rolling line, the next slab (second slab) is transported to the second temperature raising device of the temperature raising line through the second slab transportation device 42. The second slab transportation device 42 is formed of a transportation table 301 and a transportation table 304. When the second slab arrives at the transportation table 301, the transportation table 301 is turned. At the same time, the transportation table 304 is turned to transport the second slab to the transportation table 304.
Thereafter, the transportation table 304 is turned to transport to the second IH slab heater 22. After the completion of the heating up, the slab is transported to the second soaking device 32, and the second soaking device is turned while performing desired heat retention in the second soaking device 32. The transportation table 302 is also turned to form the first slab transportation device 40 with the second soaking device 32 and the transportation table 302.
That is, while the slab is heated up by the first IH slab heater 20 and the temperature thereof is kept in the first soaking device 30, the next slab is heated up by the second IH slab heater and the temperature thereof is kept in the second soaking device 32. In this case, while the temperature of the second slab is raised by the second temperature raising device, the next slab is transported into the first temperature raising device and the temperature thereof is raised as soon as the first temperature raising device becomes available.
Thus, each slab is supplied to the rolling facility 1 by alternately performing the supply of the slab to the rolling facility 1 such as the scale breaker 60 or the rough rolling mill 70 after being heated up only by the first temperature raising device of the rolling line and the supply of the slab to the rolling facility after being heated up only by the second temperature raising device after passing through the second slab transportation device 42 and then being returned to the rolling line by the first slab transportation device 40.
Accordingly, since the slab can be transported to an available temperature raising device, the temperature drop can be suppressed by reducing the waiting time for the slabs to be transported one after another from the continuous casting machine 12.
Since the time required for the next slab to be transported to the same temperature raising device becomes long, one temperature raising device can raise the temperature of the slab over time. If the supply pitch of the slabs produced in the continuous casting machine 12 is the same as in FIG. 7 and FIG. 8, the time required to heat up the first slab with the first IH slab heater can be doubled as compared with the case in FIG. 5. Thus, even one temperature raising device can sufficiently raise the temperature of the slab.
In particular, in the case where the temperature is raised by the first temperature raising device, it is possible to suppress the temperature drop of the slab and efficiently raise the temperature of the slab by not passing through the first slab transportation device 40 and the second slab transportation device 42.
FIG. 9 depicts an example of a flow of heating up a rejected material.
When the slab 100 stored in the storage yard for rejected slab 50 can be rolled, it is possible to adjust the rolling timing by transporting the slab 100 to the rolling line by the second slab transportation device 42 after performing the heating up in the second IH slab heater 22 and the hear retention in the second soaking device 32 and the third soaking device 34 at least once, heating up the slab further in the first IH slab heater 20, and retaining the heat in the first soaking device 30.
In this case, the controller 90 determines the number of times the second IH slab heater 22, the second soaking device 32, and the third soaking device 34 have been used for the slab 100 in the second temperature raising device and the staying time on the basis of the temperature of the slab 100 measured by the thermometer 203 in the second temperature raising device, the temperature of the slab 100 in the storage yard for rejected slab 50 measured by the storage yard thermometer 205, and the rolling conditions in the rolling line, and switches the transportation direction of the slab 100.
Specifically, the heating up of the first slab 101 is started from heating up while being oscillated in the second IH slab heater 22, and is performed in a flow of "heating up with the second IH slab heater 22 (first heating up and first IH2 heating up), heat retention in the second soaking device 32 (SD2 heat retention), heating up with the second IH slab heater 22 (second heating up and second IH2 heating up), heat retention in the third soaking device 34 (SD3 heat retention), heating up with the second IH slab heater 22 (third heating up and third IH2 heating up), and further, not illustrated in FIG. 11, heat retention in the third soaking device 34 (SD3 heat retention), heating up with the first IH slab heater 20, and heat retention in the first soaking device 30." However, it is not limited to this.
Accordingly, the slab is heated up four times in total of three times by the second IH slab heater 22 and one time by the first IH slab heater 20 to obtain a desired temperature.
Here, when inserting the slab 100 from the storage yard for rejected slab 50 into the second temperature raising device, it is desirable to be movable to the second temperature raising device from both the second soaking device 32 side and the third soaking device 34 side.
In addition, in the case where the slab is further heated up by the first temperature raising device after the second temperature raising device, it is preferable that the slab 100 can be inserted from the entry side of the second temperature raising device by using the third slab transportation device 44. In the case where the slab is not heated up by the first temperature raising device, it is preferable to insert from the discharge side of the second temperature raising device by using the fourth slab transportation device 46. After the heating up with the second temperature raising device is completed, it can also be transported to the rolling line by using the first slab transportation device 40.
FIG. 10 depicts the relationship between the temperature change of the slab 100 without using the soaking device when heating up a rejected slab 100 from room temperature and the output (power) of the first IH slab heater 20 and the second IH slab heater 22.
In the case where there is no soaking device, the condition that allows the heating up to be completed in the shortest time is to continue the heating up continuously with the second IH slab heater 22 to complete the temperature rise.
On the other hand, since the upper-limit temperature exists on the surface of the slab 100, the output power of the second IH slab heater 22 is lowered in the middle. FIG. 10 depicts a case where the upper-limit temperature of the surface is 1300°C. As the temperature of the surface of the slab 100 approaches the upper-limit temperature, the output power of the second IH slab heater 22 is lowered. Because of the heat conduction into the inside of the slab 100 and the heat release from the surface of the slab 100, the output power of the second IH slab heater 22 does not become 0. In this case, it is assumed that time t11 is required to heat up to the desired temperature.
Here, in the case where a temperature drop occurs when the slab 100 is transported from the outside of the rolling line to the rolling line, the slab is heated up by the first IH slab heater 20 of the rolling line.
FIG. 11 depicts the relationship between the temperature change of the slab 100 in the case of using the soaking device and the output (power) of the first IH slab heater 20 and the second IH slab heater 22. In FIG. 11, it is assumed that the rejected slab 100 is heated up three times from room temperature by the second IH slab heater 22 while using the soaking device.
The heating up of the first slab 101 is started from heating up while being oscillated in the second IH slab heater 22, and is performed in a flow of "heating up with the second IH slab heater 22 (first heating up and first IH2 heating up), heat retention in the second soaking device 32 (SD2 heat retention), heating up with the second IH slab heater 22 (second heating up and second IH2 heating up), heat retention in the third soaking device 34 (SD3 heat retention), heating up with the second IH slab heater 22 (third heating up and third IH2 heating up), and further, not illustrated in FIG. 11, heat retention in the third soaking device 34 (SD3 heat retention), heating up with the first IH slab heater 20, and heat retention in the first soaking device 30."
Here, in order to efficiently heat up a plurality of slabs 100, it is desirable to perform the first heating up by putting the second slab 102 in the second IH slab heater 22 when the heat of the first slab 101 is kept by the third soaking device 34 as depicted in FIG. 11. Similarly, the third slab 103 can be also heated up as similar to the second slab 102.
In the case of FIG. 11, the surface temperature of the slab 100 becomes the upper-limit temperature from the middle of the third heating up, and the maximum output power of the second IH slab heater 22 can be used most of the time. As a result, the time taken to complete the third heating up in the second IH slab heater 22 has a relation of "t22 in FIG. 11 < t11 in FIG. 10 < t21 in FIG. 11."
In the case of FIG. 11, t21 for the first one takes slightly longer time, but the slab 100 can be supplied to the rolling line at a pitch of time t22 after the second one. That is, as the number of slabs 100 to be heated up is larger, the difference thereof becomes larger. Thus, by efficiently using the soaking device, it is possible to use the second IH slab heater 22 at the maximum output power and to shorten the heating up time.
Thus, it is desirable for the controller 90 to control the transportation of the slabs 100 such that when keeping the temperature of certain slabs 100 in the second soaking device 32 and the third soaking device 34, different slabs 100 are heated up by the second IH slab heater 22. Although FIG. 9 depicts the case of performing the heating up three times with the second IH slab heater 22, it is also possible to perform the heating up while performing the heating up from the second IH slab heater 22 to the first IH slab heater 20 in two rounds in such a manner that after the slab is heated up by the second IH slab heater 22 and then heated up by the first IH slab heater 20, the slab is transported to the second IH slab heater 22 by the first slab transportation device 40 and heated up by the second IH slab heater 22, and then the slab is heated up by the first IH slab heater 20. Since time is required to raise the temperature at the center of the slab in the thickness direction, by repeating the heating up by the slab heater and the heat retention by the heat retaining device, and by maintaining the high temperature state of the slab 100 as much as possible, it becomes possible to heat up a plurality of slabs and supply them to the rolling facility in a short time by efficiently using the slab heater without greatly reducing the output power of the slab heater.
Next, one example of the details of the configurations of the first IH slab heater 20 and the second IH slab heater 22 will be described by using FIG. 12. In FIG. 12, the first IH slab heater 20 is exemplified, but the second IH slab heater 22 can also have basically the same configuration. FIG. 12 depicts a front view of the IH slab heater.
The first IH slab heater 20 depicted in FIG. 12 has a side guide 110, a side guide 115 in the device, a slab width end heater 120, a slab whole area heater 125, a table roller 130, the thermometer 201 in the first temperature raising device, a thermometer 202 on the first temperature raising device entry side that is provided on the entry side of the slab 100 in the rolling line of the first temperature raising device and measures the surface temperature of the slab 100, and the like.
In the first IH slab heater 20 depicted in FIG. 12, at least one slab whole area heater 125 that raises the temperature of the cross section of the slab 100, and at least one slab width end heater 120 that raises the temperature of the end the slab 100 in the width direction are alternately arranged. Here, the slab width end heater 120 provided on the most entry side is provided closer to the entry side than the slab whole area heater 125, but the order of arrangement of the slab width end heater 120 and the slab whole area heater 125 may be reversed.
As the slab whole area heater 125, a longitudinal heating coil type or a transversal heating coil type is used.
The controller 90 further adjusts the output power of the slab width end heater 120 and the slab whole area heater 125 on the basis of the temperature difference between the tip end temperature and the rear end temperature of the slab 100 measured by the thermometer 202 on the first temperature raising device entry side and the transportation velocity of the slab 100.
For example, the controller 90 switches the transportation direction of the slab 100 such that when the rear end of the slab 100 passes through the slab width end heater 120 in the front row (the most upstream side of the transportation direction), the slab 100 is allowed to repeatedly reciprocate inside the slab whole area heater 125 and the slab width end heater 120, and transports the slab 100 to the outside of the first IH slab heater 20 by completing the temperature rise with the first IH slab heater 20 when the surface temperature measured by the thermometer 201 in the first temperature raising device reaches a preset temperature or when a preset time is reached.
Here, in the first IH slab heater 20, the slab 100 is heated up while being oscillated (reciprocated) in the path direction. In an oscillation length L4, the slab is heated up by both the slab whole area heater 125 and the slab width end heater 120, and each of the slab whole area heater 125 and the slab width end heater 120 can uniformly heat up the entire length of the slab 100 by heating up in the respective sections. A length L3 where the slab 100 exists is the total of the maximum slab length L2 and the oscillation length L4. Each of these lengths L2, L3, L4, and L5 is appropriately set according to requirements on the user side.
The side guides 110 are provided on the entry side and the exit side to define the position of the slab 100 in the width direction, and the side guide 115 in the device is provided between the slab whole area heater 125 and the slab width end heater 120 to define the position of the slab 100 in the width direction. The side guide 115 in the device between the heaters is appropriately set in consideration of the minimum slab length and the like, and is not limited to FIG. 12.
FIG. 13 depicts the difference in average temperature between the tip end and the rear end of the slab 100. In FIG. 13, the horizontal axis depicts a distance from the meniscus (the molten metal surface in the mold) and the vertical axis depicts the temperature of the slab 100. Each temperature of the temperature at the thickness center, the average temperature, and the surface temperature of a cast slab is described. Here, the solidification calculation is used, and the distance from the meniscus is the position of the cast slab, and the temperature of the cast slab at that position is depicted on the assumption that the cast slab advances at the same velocity.
After passing through the exit of the continuous casting machine 12, the slab 100 advances at the casting velocity until it is divided into the slabs 100 by the torch cutting machine 14. When cutting the rear end with the torch cutting machine 14, the tip end advances a distance equal to the length of the slab 100 at the casting velocity, and thus the temperature of the tip end of the slab 100 is lowered as compared with the rear end.
When the length of the slab 100 is 12 m, the average temperature at the tip end of the slab 100 after being divided by the torch cutting machine 14 is 1075°C, and the average temperature at the rear end of the slab 100 is 1125°C. In this case, the difference in average temperature between the tip end and the rear end is 50°C.
FIG. 14 is a diagram for describing a method of eliminating the temperature difference between the tip end and the rear end of the slab 100. Eliminating the temperature difference between the tip end and the rear end or making it a desired temperature difference is referred to as temperature difference compensation heating. This compensation heating may be executed in either the first temperature raising device or the second temperature raising device, and can be preferably executed in either one.
When the moving length of the slab 100 is L6, the heating up is started by the IH slab heater from the tip end of the slab 100 after the tip end of the slab 100 arrives at the entry of the IH slab heater.
When the heating up is continued while transporting the slab 100 at a velocity Vs and the rear end arrives at the entry of the IH slab heater, the velocity Vs and the output power of each heater of the IH slab heater are adjusted to eliminate the temperature difference or make it a desired temperature difference.
Then, after the temperature difference between the tip end and the rear end is eliminated or brought to the desired temperature difference, the entire slab 100 is similarly heated up while being oscillated in the IH slab heater.
In FIG. 13, in the case where the length of the slab 100 is 12 m and the temperature difference between the tip end and the rear end is 50°C, the temperature difference of 50°C can be eliminated or made as small as possible by performing the above temperature difference compensation heating.
FIG. 15 is a diagram for describing a case where the slab 100 is heated up by only the first IH slab heater 20 without using the second IH slab heater 22 and direct rolling is performed.
In the case where the casting velocity is a low velocity of 1.2 m/min, it is necessary to heat up three times with the IH slab heater as depicted in FIG. 6.
As depicted in FIG. 15, according to a rolling facility 1A in which at least three sets of combinations of the first IH slab heater 20 and the first soaking device 30 are arranged in series, the slab can be heated up only by the first IH slab heater 20 of the rolling line without using the second IH slab heater 22, the second soaking device 32, and the third soaking device 34 outside the rolling line.
In the case where the casting velocity is faster than 1.2 m/min or depending on the capability of the first IH slab heater 20, it is possible to use two first IH slab heaters 20.
Here, in FIG. 15, three first IH slab heaters 20 and one second IH slab heater 22, namely, four IH slab heaters in total are arranged, but two IH slab heaters in total such as one first IH slab heater 20 and one second IH slab heater 22 can be used in the system described in FIG. 1 and FIG. 6, and thus the facility costs can be reduced.
In addition, the configuration described in FIG. 1 and FIG. 6 can shorten the entire length of the facility from the continuous casting machine 12 to the down coiler 85, and can make the facility more compact as compared with the configuration in FIG. 15. Further, in the case where the continuous casting machine 12 supplies a large amount of slabs 100, it is possible to raise the temperature of a large number of slabs to a desired temperature with a short facility such that by using two first IH slab heaters 20 and two second IH slab heaters 22, the slabs can be heated up by both the first IH slab heaters 20 and the second IH slab heaters 22 using the first slab transportation device 40 and the like. The numbers of the first IH slab heaters 20 and the second IH slab heaters 22 are appropriately set according to the production needs of users.
FIG. 16 is a diagram for depicting an example of a general facility that heats up the slab 100 inserted into a reheating furnace. Some rolling facilities include one reheating furnace 145 or a plurality of reheating furnaces 145.
FIG. 17 is a diagram in which the temperature raising device of the slab 100 of the present invention is installed in a general facility that heats up the slab 100 inserted into the reheating furnace. The arrows in FIG. 17 show the flows of sending to the rolling facility after heating up with the second IH slab heater 22 and the first IH slab heater 20.
In the rolling facility including the temperature raising device of the present invention as in FIG. 17, in the case where the temperature of the slab 100 is low, a large amount of temperature rise can be obtained by heating up the slab with the second IH slab heater 22 and the first IH slab heater 20 and then passing it through the second IH slab heater 22 and the first IH slab heater 20 again. In addition, it is possible to transport the slab in the route depicted in FIG. 9 and heat it up with the first IH slab heater 20 after heating it up a plurality of times with the second IH slab heater 22 in the middle.
Although not illustrated, it is also possible to employ a method in which the slab is put in the reheating furnace before and after heating it up with the first IH slab heater 20 and the second IH slab heater 22.
In addition, in the case where it is necessary to maintain the slab 100 in a high temperature state for a considerable period of time such as several hours, the use of the reheating furnace may be chosen.
The reheating furnace generally emits more CO₂. On the contrary, in the temperature raising device of the present invention, direct CO₂ emissions can be reduced by heating up using the first IH slab heater 20 and the second IH slab heater 22, which leads to the production of green steel.
In addition, by using a reheating furnace that uses electricity or using a reheating furnace that emits less CO₂, green steel can be produced by combining the reheating furnace with the first IH slab heater 20 and the second IH slab heater 22.
Next, another example of the configurations of the first IH slab heater 20 and the second IH slab heater 22 will be described by using FIG. 18 to FIG. 20. FIG. 18 and FIG. 19 show front views of an IH slab heater, and FIG. 20 depicts an example view corresponding to the A-A arrow in FIG. 12.
Although the slab width end heaters 120 are arranged in the length L3 where the slab 100 exists and the slab width end heaters 120 are arranged alternately with the slab whole area heaters 125 in FIG. 12, the slab width end heater 122 is arranged outside the length L3 where the slab 100 exists on the exit side relative to the slab whole area heater 125 in FIG. 18.
Even in this case, the controller 90 switches the transportation direction of the slab 100 such that the slab 100 is allowed to repeatedly reciprocate inside the slab whole area heater 125 until the surface temperature measured by the thermometer 201 in the first temperature raising device reaches a preset temperature, and transports the slab 100 to the slab width end heater 122 when the surface temperature measured by the thermometer 201 in the first temperature raising device reaches a preset temperature or when a preset time is reached.
Since the width end of the slab 100 is also heated up when the slab 100 is heated up while being oscillated by the slab whole area heater 125, the width end of the slab 100 is heated up while transporting the slab 100 at an optional velocity when the slab 100 is transported to the exit side after the entire heating up of the slab 100 is completed.
The slab width end heater 122 in FIG. 18 has the structure similar to the slab width end heater in FIG. 12.
When the slab width end heater 122 is arranged on the exit side as depicted in FIG. 18, the lack of heating up of the width end of the slab 100 caused by heating up with the slab whole area heater 125 can be compensated. Since the heating up of the width end of the slab 100 can be adjusted after the entire heating up, it is possible to heat up the width end of the slab 100 with high accuracy.
In addition, although the side guide is arranged on the table rollers 130 in FIG. 12, it can be arranged between the table rollers 130 without changing the oscillation length L4. In the case where the side guide is installed on the table rollers 130, the facilities overlap each other and the structure becomes complicated, but the facility can be simplified by arranging the side guide between the table rollers 130.
Further, as depicted in FIG. 19, it is also possible to install the slab width end heater 121 on the entry side of the length L3 where the slab 100 exists to heat up the width end before the entire heating up of the slab 100.
When the slab width end heater 121 is arranged on the entry side as depicted in FIG. 19, the heating up of the width end of the slab 100 is finished before the heating up of the entire cross section of the tip end of the slab 100 is completed. As depicted in FIG. 14, since the slab 100 is transported at a relatively low velocity when the temperature difference compensation heating is performed, by heating up the width end of the slab 100 under that condition, no special time is needed for heating up the width end of the slab 100.
Further, in the case where the soaking device is arranged on the exit side of the IH slab heater (the first soaking device 30 or the third soaking device 34), this soaking device can uniformize the temperature in the cross section of the slab 100 after the entire heating up and the width end heating up.
In addition, the arrangement of the side guide 115 in the device between the slab whole area heaters 125 is appropriately set in consideration of the minimum slab length and the like, and is not limited to FIG. 18. In addition, the slab whole area heaters 125 and the slab width end heaters 120 may be alternately arranged in FIG. 18 and FIG. 19.
In FIG. 20, a longitudinal heating coil type is used as the slab whole area heater 125. The solid line in FIG. 20 depicts the position of the slab width end heater when the slab is wide. Although the dashed line depicts the position of the slab width end heater when the slab is narrow and the dashed line depicts only the right side in the drawing, the position of the slab width end heater is the same on the left side as on the right side when the slab is narrow.
The position of the slab width end heater 120 can be changed in the width direction so as to be able to handle the widest wide slab 100A and the narrowest slab 100B, and can be set at a position suitable for heating up the width end of the slab 100 according to the width of the slab 100. The positions of the slab width end heaters 121 and 122 can be similarly changed in the width direction.
The slab 100 in a wide range of, for example, 900 mm to 1600 mm passes through. When the width of the slab 100 is changed, the heating state of the width end of the slab 100 by the slab whole area heater 125 is also changed. Therefore, the heating up of the width end of the slab 100 can be adjusted according to the width of the slab 100 by the slab width end heaters 120, 121, and 122.
In addition, the side guide 115 in the device can set the passing position of the slab 100 in the width direction such that the width end of the slab 100 does not interfere with the slab width end heaters 120, 121, and 122.
Next, effects of the present embodiment will be described.
Conventionally, when a trouble occurs at or after the rough rolling mill 70, the continuous casting machine 12 cannot be immediately stopped, and thus it becomes necessary to discharge the cast slabs 100 outside the rolling line. In addition, there is a case where surface maintenance is necessary before rolling depending on the slabs 100 due to surface quality issues, and even in this case, the slabs 100 need to be discharged outside the rolling line.
The temperature of these discharged slabs 100 drop to room temperature in the storage yard for rejected slab 50 outside the rolling line in some cases. In the case where the slabs 100 whose temperature has dropped to room temperature are reheated up only by the IH slab heater, it takes a long time and the capability to reheat up the rejected slabs 100 and return them to the rolling line becomes insufficient. Therefore, a large number of IH slab heaters have been needed.
For this problem, the temperature raising device for raising the temperature of the slab 100 of steel cast by the continuous casting machine 12 of the above-described embodiment includes: the first temperature raising device that is provided in the rolling line between the continuous casting machine 12 and the rough rolling mill 70; the second temperature raising device that is provided in the temperature raising line different from the rolling line; the first slab transportation device 40 that can move the slab 100 between the exit side of the slab 100 in the rolling line of the first temperature raising device and the entry side of the slab 100 in the temperature raising line of the second temperature raising device; and the second slab transportation device 42 that can move the slab 100 between the entry side of the slab 100 in the rolling line of the first temperature raising device and the exit side of the slab 100 in the temperature raising line of the second temperature raising device, and the first temperature raising device has the first IH slab heater 20 and the second temperature raising device has the second IH slab heater 22.
In addition, in a method of raising the temperature of the slab 100 of steel cast by the continuous casting machine 12, the temperature of the slab 100 is raised by induction heating in the rolling line between the continuous casting machine 12 and the rough rolling mill 70, the temperature of the slab 100 is raised by induction heating in the temperature raising line different from the rolling line, the slab 100 is moved between the side after heating up the slab 100 in the rolling line and the side before heating up the slab 100 in the temperature raising line, and the slab 100 is moved between the side before heating up the slab 100 in the rolling line and the side after heating up the slab 100 in the temperature raising line.
As described above, by using a combination of IH slab heaters, in the case where the temperature of the cast slab exiting the first temperature raising device has not reached a desired temperature, the temperature of the cast slab can be raised by the second temperature raising device before being transported again to the first temperature raising device via the transportation device, and thus the lack of the temperature rise caused by the heating up with the first temperature raising device can be compensated by the heating up with the second temperature raising device. Accordingly, even the temperature of the slab 100 with a slow casting velocity can be raised to a desired temperature, and it is possible to perform direct rolling.
In addition, by using a combination of these IH slab heaters, even in the heating up of the rejected slab 100 from room temperature, it is possible to roll the slab 100 whose temperature has reached a desired temperature with a small number of IH slab heaters.
In addition, since the first temperature raising device further has the first soaking device 30 that is provided on the exit side of the slab 100 in the rolling line of the first IH slab heater 20 and uses the retained heat of the slab 100 as a heat source, it is possible to shorten the time of the slab 100 staying in the induction heating device as compared with the case where the slab 100 is heated up only by induction heating. Accordingly, it is possible to shorten the time interval before the start of heating up the next slab 100 with the induction heating device.
Further, the second temperature raising device further has the second soaking device 32 and the third soaking device 34 that are provided on at least one of the entry side and the exit side of the slab 100 in the temperature raising line of the second IH slab heater 22 and use the retained heat of the slab 100 as a heat source, and thus it is similarly possible to shorten the time of the slab 100 staying in the induction heating device as compared with the case where the slab 100 is heated up only by induction heating.
In addition, by further providing at least one of the third slab transportation device 44 that can move the slab 100 between the storage yard for rejected slab 50 for storing the slab 100 and the entry side of the slab 100 in the temperature raising line of the second temperature raising device, and the fourth slab transportation device 46 that can move the slab 100 between the storage yard for rejected slab 50 and the exit side of the slab 100 in the temperature raising line of the second temperature raising device, it is possible to realize the flexible transportation of the slab 100 among the storage yard for rejected slab 50, the second temperature raising device, and the first temperature raising device according to the rolling situation in the rolling line.
Further, by further providing the thermometer 201 in the first temperature raising device that is provided in the first temperature raising device and measures the temperature of the slab 100, and the controller 90 that determines whether to transport the slab 100 to either the rough rolling mill 70 or the second temperature raising device on the basis of the temperature of the slab 100 measured by the thermometer 201 in the first temperature raising device and switches the transportation direction of the slab 100, the direct rolling or the additional temperature rise with the second IH slab heater 22 is determined, and thus more reliable temperature rise can be realized.
In addition, the second temperature raising device has the thermometer 203 in the second temperature raising device that measures the temperature of the slab 100, and the second soaking device 32 and the third soaking device 34 that are provided on at least one of the entry side and the exit side of the slab 100 in the temperature raising line of the second IH slab heater 22 and use the retained heat of the slab 100 as a heat source, and the controller 90 that determines the number of times the second IH slab heater 22, the second soaking device 32, and the third soaking device 34 have been used for the slab 100 in the second temperature raising device and the staying time on the basis of the temperature measured by the thermometer 203 in the second temperature raising device and the rolling situation in the rolling line to switch the transportation direction of the slab 100 is further provided, and thus the additional temperature rise in the second IH slab heater 22 can be efficiently preformed.
Further, the second temperature raising device has the thermometer 203 in the second temperature raising device that measures the temperature of the slab 100, and the second soaking device 32 and the third soaking device 34 that are provided on at least one of the entry side and the exit side of the slab 100 in the temperature raising line of the second IH slab heater 22 and use the retained heat of the slab 100 as a heat source, the storage yard thermometer 205 that is provided in the storage yard for rejected slab 50 for storing the slab 100 to measure the temperature of the slab 100 and the controller 90 that determines the number of times the second IH slab heater 22, the second soaking device 32, and the third soaking device 34 have been used for the slab 100 in the second temperature raising device and the staying time on the basis of the temperature of the slab 100 measured by the thermometer 203 in the second temperature raising device, the temperature of the slab 100 in the storage yard for rejected slab 50 measured by the storage yard thermometer 205, and the rolling situation in the rolling line to switch the transportation direction of the slab 100 are further provided, and thus it is possible to more efficiently heat up the slab 100 stored in the storage yard for rejected slab 50.
In addition, the second temperature raising device has the second soaking device 32 and the third soaking device 34 that are provided on at least one of the entry side and the exit side of the slab 100 in the temperature raising line of the second IH slab heater 22 and use the retained heat of the slab 100 as a heat source, the controller 90 that controls, when the temperature of the slab 100 is kept in the second soaking device 32 and the third soaking device 34, the transportation of the slab 100 so as to heat up a different slab 100 with the second IH slab heater 22 is further provided, and thus a plurality of slabs 100 can be highly efficiently heated up without waste while minimizing the risk of exceeding the upper-limit temperature.
Further, the first IH slab heater 20 has at least one slab whole area heater 125 that raises the temperature of the cross section of the slab 100, or at least one slab width end heater 120 that raises the temperature of an end of the slab 100 in the width direction and at least one slab whole area heater 125 that raises the temperature of the cross section of the slab 100, the thermometer 202 on the first temperature raising device entry side that is provided on the entry side of the slab 100 in the rolling line of the first temperature raising device to measure the surface temperature of the slab 100, and the controller 90 that adjusts the output power of the slab width end heater 120 or the slab whole area heater 125 on the basis of the temperature difference between the tip-end temperature and the rear-end temperature of the slab 100 measured by the thermometer 202 on the first temperature raising device entry side and the transportation velocity of the slab 100 are further provided, and thus the temperature difference between the tip end and the rear end in the rolling direction of the slab 100 can be reduced, leading to realization of more uniform heating up of the slab 100.
Further, the thermometer 201 in the first temperature raising device that is provided in the first temperature raising device and measures the temperature of the slab 100 is further provided, the slab width end heaters 120 and the slab whole area heaters 125 are alternately arranged, the controller 90 switches the transportation direction of the slab 100 so as to repeatedly reciprocate the slab 100 inside the first IH slab heater 20 when the rear end of the slab 100 enters the first IH slab heater 20, and completes the temperature rise in the first IH slab heater 20 and transports the slab 100 outside the first IH slab heater 20 when the surface temperature measured by the thermometer 201 in the first temperature raising device reaches a preset temperature or when a preset time is reached, and thus it is possible to more uniformly heat up the slab 100 in the rolling direction.
In addition, the thermometer 201 in the first temperature raising device that is provided in the first temperature raising device and measures the temperature of the slab 100, and the slab width end heater 121 that is provided on the entry side of the first IH slab heater 20 are further provided, the controller 90 switches the transportation direction of the slab 100 so as to repeatedly reciprocate the slab 100 inside the first IH slab heater 20 when the width end of the slab 100 is heated up while the slab 100 passes through the slab width end heater 121 and the rear end of the slab 100 enters the first IH slab heater 20, and completes the temperature rise in the first IH slab heater 20 and transports the slab 100 outside the first IH slab heater 20 when the surface temperature measured by the thermometer 201 in the first temperature raising device reaches a preset temperature or when a preset time is reached, and thus the lack of the heating up of the width end of the slab 100 caused by heating up with the slab whole area heater 125 can be compensated in advance with the slab width end heater 121 and the heating up of the entire cross section including the width end of the slab 100 can be adjusted during the entire heating up.
Further, the thermometer 201 in the first temperature raising device that is provided in the first temperature raising device and measures the temperature of the slab 100, and the slab width end heater 122 that is provided on the exit side of the first IH slab heater 20 are further provided, the controller 90 switches the transportation direction of the slab 100 so as to repeatedly reciprocate the slab 100 inside the first IH slab heater 20 until the surface temperature measured by the thermometer 201 in the first temperature raising device reaches a preset temperature or until a preset time is reached, and transports the slab 100 to the slab width end heater 122 provided on the exit side of the first IH slab heater 20 to raise the temperature of the width end of the slab 100 when the surface temperature measured by the thermometer 201 in the first temperature raising device reaches a preset temperature or when a preset time is reached, and thus the heating up of the width end of the slab 100 can be performed after the entire heating up and accurate heating up of the width end of the slab 100 can be performed.

<Other>

It should be noted that the present invention is not limited to the above embodiment and can be modified and applied in various ways. The embodiment described above has been described in detail to clearly explain the present invention, and is not necessarily limited to those having all the described configurations.
For example, the slab transportation device that transports the slab 100 between the rolling line and the line different from the rolling line is depicted with the slab 100 traversing, but other methods, such as a method of transporting the slab by turning the transportation table at an optional angle or a method of transporting it with the table roller 130 after turning on the turntable, are also included in the present invention. In addition, a configuration in which the soaking device is added to the transportation device or the turning transportation table to suppress the temperature drop of the slab during transportation is also included in the present invention. In addition, it is also included in the present invention that the slab width end heater and the slab whole area heater of the second temperature raising device have the same configurations as the first temperature raising device.
In addition, although the continuous casting machine 12 has been described as two strands, the case of one strand or more strands by adding a continuous casting machine is also within the scope of the present invention. In the case where the amount of production on the continuous casting machine 12 side is increased, the capability of the first IH slab heater 20 and the second IH slab heater 22 is increased according to the amount of production, or the number of IH slab heaters is increased, both of which are within the scope of the present invention.

Description of Reference Characters

1, 1A: Rolling facility
10: Ladle turret
12: Continuous casting machine
14: Torch cutting machine
20: First IH slab heater (induction heating device)
22: Second IH slab heater (induction heating device)
30: First soaking device (soaking device)
32: Second soaking device (soaking device)
34: Third soaking device (soaking device)
40: First slab transportation device (first transportation device)
42: Second slab transportation device (second transportation device)
44: Third slab transportation device (third transportation device)
46: Fourth slab transportation device (fourth transportation device)
48: Continuous casting machine exit-side slab transportation device
50: Storage yard for rejected slab
60: Scale breaker
70: Rough rolling mill
75: Finishing rolling mill train
80: Run out table
85: Down coiler
90: Controller
100: Slab
100A: Wide-width slab
100B: Narrow-width slab
101: First slab
102: Second slab
103: Third slab
104: Fourth slab
105: Fifth slab
110: Side guide
115: Side guide in device
120: Slab width end heater (width end heater)
121: Slab width end heater (entry-side width end heater)
122: Slab width end heater (exit-side width end heater)
125: Slab whole area heater (whole area heater)
130: Table roller
145: Reheating furnace
201: Thermometer in first temperature raising device
202: Thermometer on first temperature raising device entry side
203: Thermometer in second temperature raising device
205: Storage yard thermometer
301: Transportation table
302: Transportation table
304: Transportation table

Claims

A temperature raising device for raising a temperature of a cast slab of steel cast by a continuous casting machine, the temperature raising device comprising:
a first temperature raising device that is provided in a rolling line between the continuous casting machine and a rough rolling mill;

a second temperature raising device that is provided in a temperature raising line different from the rolling line;

a first transportation device that can move the cast slab between an exit side of the cast slab in the rolling line of the first temperature raising device and an entry side of the cast slab in the temperature raising line of the second temperature raising device; and

a second transportation device that can move the cast slab between an entry side of the cast slab in the rolling line of the first temperature raising device and an exit side of the cast slab in the temperature raising line of the second temperature raising device, wherein

the first temperature raising device and the second temperature raising device each have an induction heating device.
The temperature raising device according to claim 1, wherein
the first temperature raising device further has a soaking device that is provided on the exit side of the cast slab in the rolling line of the induction heating device and uses retained heat of the cast slab as a heat source.
The temperature raising device according to claim 1, wherein
the second temperature raising device further has a soaking device that is provided on at least one of the entry side and the exit side of the cast slab in the temperature raising line of the induction heating device and uses retained heat of the cast slab as a heat source.
The temperature raising device according to claim 1, further comprising:
at least one of a third transportation device that can move the cast slab between a storage yard for storing the cast slab and the entry side of the cast slab in the temperature raising line of the second temperature raising device, and a fourth transportation device that can move the cast slab between the storage yard and the exit side of the cast slab in the temperature raising line of the second temperature raising device.
The temperature raising device according to any one of claims 1 to 4, further comprising:
a thermometer in the first temperature raising device that is provided in the first temperature raising device and measures a temperature of the cast slab; and

a controller that determines whether to transport the cast slab to either the rough rolling mill or the second temperature raising device on a basis of the temperature of the cast slab measured by the thermometer in the first temperature raising device, and switches a transportation direction of the cast slab.
The temperature raising device according to any one of claims 1, 2, and 4, wherein
the second temperature raising device has a thermometer in the second temperature raising device that measures a temperature of the cast slab, and a soaking device that is provided on at least one of the entry side and the exit side of the cast slab in the temperature raising line of the induction heating device and uses retained heat of the cast slab as a heat source, and

a controller that determines number of times the induction heating device and the soaking device have been used for the cast slab in the second temperature raising device and staying time on a basis of the temperature measured by the thermometer in the second temperature raising device and a rolling situation in the rolling line to switch a transportation direction of the cast slab is further provided.
The temperature raising device according to claim 1 or 2, wherein
the second temperature raising device has a thermometer in the second temperature raising device that measures a temperature of the cast slab, and a soaking device that is provided on at least one of the entry side and the exit side of the cast slab in the temperature raising line of the induction heating device and uses retained heat of the cast slab as a heat source,

a storage yard thermometer that is provided in a storage yard for storing the cast slab to measure a temperature of the cast slab is further provided, and

a controller that determines number of times the induction heating device and the soaking device have been used for the cast slab in the second temperature raising device and staying time on a basis of the temperature of the cast slab measured by the thermometer in the second temperature raising device, the temperature of the cast slab in the storage yard measured by the storage yard thermometer, and a rolling situation in the rolling line to switch a transportation direction of the cast slab is further provided.
The temperature raising device according to any one of claims 1, 2, and 4, wherein
the second temperature raising device has a soaking device that is provided on at least one of the entry side and the exit side of the cast slab in the temperature raising line of the induction heating device and uses retained heat of the cast slab as a heat source, and

a controller that controls, when the temperature of the cast slab is kept in the soaking device, transportation of the cast slab so as to heat up a different cast slab with the induction heating device is further provided.
The temperature raising device according to any one of claims 1 to 4, wherein
the induction heating device has at least one whole area heater that raises a temperature of a cross section of the cast slab, or at least one width end heater that raises a temperature of an end of the cast slab in a width direction and at least one whole area heater that raises a temperature of the cross section of the cast slab,

a thermometer on the first temperature raising device entry side that is provided on the entry side of the cast slab in the rolling line of the first temperature raising device to measure a surface temperature of the cast slab is further provided, and

a controller that adjusts output power of the width end heater or the whole area heater on a basis of a temperature difference between a tip-end temperature and a rear-end temperature of the cast slab measured by the thermometer on the first temperature raising device entry side and a transportation velocity of the cast slab is further provided.
The temperature raising device according to claim 9, further comprising:
a thermometer in the first temperature raising device that is provided in the first temperature raising device and measures a temperature of the cast slab, wherein

the width end heater and the whole area heater are alternately arranged, and

the controller
switches a transportation direction of the cast slab so as to repeatedly reciprocate the cast slab inside the induction heating device when a rear end of the cast slab enters the induction heating device, and

completes temperature rise in the induction heating device and transports the cast slab outside the induction heating device when the surface temperature measured by the thermometer in the first temperature raising device reaches a preset temperature or when a preset time is reached.
The temperature raising device according to claim 9, further comprising:
a thermometer in the first temperature raising device that is provided in the first temperature raising device and measures a temperature of the cast slab; and

an entry-side width end heater that is provided on the entry side of the induction heating device, wherein

the controller
switches a transportation direction of the cast slab so as to repeatedly reciprocate the cast slab inside the induction heating device when a width end of the cast slab is heated up while the cast slab passes through the entry-side width end heater and a rear end of the cast slab enters the induction heating device, and

completes temperature rise in the induction heating device and transports the cast slab outside the induction heating device when the surface temperature measured by the thermometer in the first temperature raising device reaches a preset temperature or when a preset time is reached.
The temperature raising device according to claim 9, further comprising:
a thermometer in the first temperature raising device that is provided in the first temperature raising device and measures a temperature of the cast slab; and

an exit-side width end heater that is provided on the exit side of the induction heating device, wherein

the controller
switches a transportation direction of the cast slab so as to repeatedly reciprocate the cast slab inside the induction heating device until the surface temperature measured by the thermometer in the first temperature raising device reaches a preset temperature or until a preset time is reached, and

transports the cast slab to the exit-side width end heater to raise a temperature of a width end of the cast slab when the surface temperature measured by the thermometer in the first temperature raising device reaches a preset temperature or when a preset time is reached.
A rolling facility comprising:
a continuous casting machine;

the temperature raising device according to any one of claims 1 to 4; and

a rough rolling mill.
A method of raising a temperature of a cast slab with the temperature raising device according to any one of claims 1 to 4, the method comprising:
raising the temperature of the cast slab by induction heating in the rolling line;

raising the temperature of the cast slab by induction heating in the temperature raising line;

moving the cast slab between a side after heating up the cast slab in the rolling line and a side before heating up the cast slab in the temperature raising line; and

moving the cast slab between a side before heating up the cast slab in the rolling line and a side after heating up the cast slab in the temperature raising line.
A method of raising a temperature of a cast slab with the temperature raising device according to any one of claims 1 to 4, the method comprising:
alternately performing

a first step of transporting the cast slab to the rough rolling mill after the temperature of the cast slab is raised by induction heating in the rolling line, and

a second step of transporting a different cast slab to the temperature raising line by the second transportation device, and transporting the different cast slab to the rolling line by the first transportation device after the temperature of the different cast slab is raised by induction heating in the temperature raising line.