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

Abstract

The present invention is provided with: a first temperature-raising device provided on a rolling line between a continuous casting machine 12 and a roughing mill 70; a second temperature-raising device provided on a temperature-raising line different from the rolling line; a first slab conveyance device 40 configured to be capable of moving a slab 100 between the outlet side for the slab 100 in the rolling line of the first temperature-raising device and the inlet side for the slab 100 in the temperature-raising line of the second temperature-raising device; and a second slab conveyance device 42 configured to be capable of moving the slab 100 between the inlet side for the slab 100 in the rolling line of the first temperature-raising device and the outlet side for the slab 100 in the temperature-raising line of the second temperature-raising device. The first temperature-raising device has a first induction heating slab heater 20, and the second temperature-raising device has a second induction heating slab heater 22. As a result, the present invention provides: a temperature-raising device with which it is possible to improve the temperature-raising efficiency before feeding a cast slab to the roughing mill as compared with the prior art; rolling equipment provided with the same; and a method for raising the temperature of the cast slab.

Description

Heating device, rolling equipment equipped with same, and method for raising the temperature of cast slab

[0001] The present invention relates to a heating device, a rolling facility equipped with the same, and a method for heating a slab.

[0002] Patent Document 1 describes a slab heating facility for direct rolling, which is installed on a slab transport line that transports steel slabs cast by a continuous casting machine to a rolling mill for direct rolling of the slabs, and which heats the slabs to an appropriate rolling temperature. The facility includes a heat retention chamber that temporarily accommodates multiple slabs in the order they arrive from the continuous casting machine, uses the heat contained in the slabs as a heat source, and has no other heat sources, and is surrounded by heat insulating material; a heating device that heats the slabs as they are drawn out of the heat retention chamber, and raises their temperature; and a heating device that is installed on the outlet side of the heat retention chamber, The document states that the apparatus is provided with a temperature measuring instrument that measures the temperature of the slab drawn out of the heat reserving chamber in order to determine whether the slab drawn out of the heat reserving chamber can be heated to the appropriate rolling temperature by passing it through the heating device once, and a reverse feed facility that, based on the measurement results from the temperature measuring instrument, returns the slab that has been heated in the heating device but has not yet reached the appropriate rolling temperature to the heat reserving chamber to be heated again by the heating device, and the slab that has been heated to the appropriate rolling temperature by the heating device is sent to the rolling mill.

[0003] Patent No. 5130139

[0004] In order to directly roll steel slabs (billets, slabs, etc.) cast by a continuous casting machine, the slabs from the continuous casting machine are sometimes heated to an appropriate rolling temperature before being sent to a rolling mill.

[0005] In this case, even if a slab having a temperature lower than normal is delivered from the continuous casting machine, the slab can be heated to an appropriate rolling temperature, and there is no need to reject (remove) the slab from the conveying line. For example, Patent Document 1 discloses a conventional technique for slab heating equipment in direct rolling.

[0006] However, the above technology has a problem in that the billet, which has been heated in the induction heating device but has not yet reached the appropriate rolling temperature, is returned to the heat retention chamber and then sent back to the induction heating device, whereupon the billet's temperature drops significantly.

[0007] The present invention provides a heating device capable of improving the efficiency of heating a slab before sending it to a roughing mill compared to conventional techniques, a rolling facility equipped with the same, and a method for heating a slab.

[0008] The present invention includes a plurality of means for solving the above-mentioned problems. One example is a heating device for heating a steel slab cast by a continuous casting machine, the heating device comprising: a first heating device provided in a rolling line between the continuous casting machine and a roughing mill; a second heating device provided in a heating line different from the rolling line; a first conveying device configured to be able to move the slab between the outlet side of the slab in the rolling line of the first heating device and the inlet side of the slab in the heating line of the second heating device; and a second conveying device configured to be able to move the slab between the inlet side of the slab in the rolling line of the first heating device and the outlet side of the slab in the heating line of the second heating device, wherein the first heating device and the second heating device have induction heating devices.

[0009] According to the present invention, the efficiency of heating the slab before sending it to the roughing mill can be improved compared to the conventional technology. Objects, configurations, and effects other than those described above will become clear from the following description of the embodiments.

[0010] 7 is a diagram showing an overview of rolling equipment of an embodiment. FIG. 1 is a diagram showing the temperature of a slab immediately before rough rolling when the slab is transported without heating. FIG. 2 is a diagram showing the temperature of a slab immediately before rough rolling when the slab is transported without heating. FIG. 3 is a diagram showing the temperature of a slab immediately before rough rolling when the slab is transported without heating. FIG. 4 is a diagram showing the flow when a slab is transported to rolling equipment using a slab heating device of an embodiment. FIG. 5 is a diagram showing the flow when a slab is transported to rolling equipment using a slab heating device of an embodiment. FIG. 6 is a diagram explaining a case where a slab is heated only by a first induction heating slab heater using the heating device of an embodiment to perform direct rolling. FIG. 7 is a diagram explaining a case where a slab is heated only by a second induction heating slab heater using the same equipment as in FIG. 8 is a diagram showing an example of a state where reject material is heated using a slab heating device of an embodiment. FIG. 8 is a diagram showing the relationship between the temperature change of the slab and the output of the induction heating slab heater when a heat retention device is not used in the heating device of an embodiment. FIG. 1 is a diagram showing the relationship between the temperature change of a slab and the output of an induction heating slab heater when a heat retention device is used in the heating apparatus of the embodiment. FIG. 2 is a diagram showing an example of an induction heating slab heater in the heating apparatus of the embodiment as viewed from the front. FIG. 3 is a diagram showing the difference in average temperature between the front and rear ends of a slab. FIG. 4 is a diagram explaining a method of eliminating the temperature difference between the front and rear ends of a slab using the heating apparatus of the embodiment. FIG. 5 is a diagram explaining a case where a slab is heated only by a first induction heating slab heater without using a second induction heating slab heater and direct rolling is performed using the heating apparatus of the embodiment. FIG. 6 is an example of a known facility in which a slab is inserted into a reheating furnace and heated. FIG. 7 is a diagram showing an example in which the slab heating apparatus of the present invention is installed in a facility in which a slab is inserted into a reheating furnace and heated. FIG. 8 is another example of an induction heating slab heater in the heating apparatus of the embodiment as viewed from the front. FIG. 9 is yet another example of an induction heating slab heater in the heating apparatus of the embodiment as viewed from the front. 13 is a diagram of an example of an induction heating slab heater in the temperature raising device of the embodiment as viewed from the front, and corresponds to the view of the arrows A-A in FIG. 12.

[0011] Hereinafter, embodiments of the heating device, the rolling equipment including the same, and the method for heating a slab according to the present invention will be described with reference to the drawings. In the drawings used in this specification, identical or similar reference numerals are used to designate identical or corresponding components, and repeated description of these components may be omitted.

[0012] 1 is a diagram showing an outline of a rolling facility of the present invention. The rolling facility 1 in FIG. 1 has a configuration in which a heating device for a slab 100 is disposed between a continuous casting machine 12 and a roughing mill 70.

[0013] A ladle turret 10 moves molten steel in a ladle (not shown) from the ladle to a position where it is poured into a continuous casting machine 12. The continuous casting machine 12 has two strands, and cast pieces are cast in two rows and then cut into slabs 100 of a desired length by a torch cutter 14 located on the outlet side of the continuous casting machine 12.

[0014] In this embodiment, the line that is the same as the rolling line is referred to as the first strand, and the line that is not the rolling line is referred to as the second strand. The slab 100 on the second strand is transported to the rolling line (first strand) by the continuous casting machine outlet slab transport device 48, and then transported in the direction of the roughing mill 70, etc.

[0015] If the cast slab 100 cannot be transported to the roughing mill 70 due to a malfunction in the rolling equipment or due to reasons related to the quality of the slab 100, the slab is transported as a reject material to a slab storage area 50 using a continuous casting machine outlet slab transport device 48. In the slab storage area 50, the reject material is stored and, if necessary, is treated.

[0016] The heating device of this embodiment shown in Figure 1 is a device for heating a steel slab 100 (see Figure 12, etc.) cast by a continuous casting machine 12, and is composed of a first induction heating slab heater 20, a first heat retention device 30, a first slab transport device 40, a second induction heating slab heater 22, a second heat retention device 32, a third heat retention device 34, a second slab transport device 42, a third slab transport device 44, a fourth slab transport device 46, a thermometer 201 in the first heating device, a thermometer 203 in the second heating device, a storage location thermometer 205, a control device 90, etc.

[0017] After heating in the heating device is completed, in the rolling facility 1, first, since oxide scale forms on the surface of the slab 100 due to high-temperature heating prior to rolling, the surface scale is removed by a scale breaker 60 that sprays high-pressure water onto the surface of the slab 100 before rolling to remove the scale, and then one roughing mill 70 performs reverse rolling, a row of multiple finishing mills 75 performs unidirectional rolling, strip cooling is performed on a run-out table 80, and the strip is coiled by a down coiler 85. It is also possible to arrange multiple roughing mills 70 in the rolling facility 1.

[0018] The first heating device is provided in the rolling line between the continuous casting machine 12 and the roughing mill 70, and includes a first induction heating slab heater 20, a first heat retention device 30, and the like.

[0019] The slab 100 transported from the continuous casting machine 12 in the direction of the rolling equipment is heated as desired by at least the first induction heating slab heater 20, and then transported to the first heat retention device 30, which is located on the outlet side of the slab 100 in the rolling line of the first induction heating slab heater 20 and uses the heat retained in the slab 100 as a heat source.In this first heat retention device 30, the temperature distribution within the cross section of the slab 100 is made uniform and the rolling timing is adjusted while suppressing heat radiation from the slab 100.

[0020] It takes time to raise the temperature of the slab 100 at the center of its thickness, which has dropped. However, when heating with the first induction slab heater 20, the surface heats up relatively quickly and reaches the upper limit of the surface temperature allowable. After that, heating must be continued within a range in which the surface temperature does not exceed the upper limit, but the supplied output (power) must be reduced.

[0021] Therefore, at that time, the slab 100 is transferred to the first heat retention device 30, and although the temperature of the surface of the slab 100 drops slightly, the temperature inside the slab 100 is increased, and by heating the other slabs 100 with an induction heating slab heater, it is possible to efficiently increase the central temperature of the slab 100 within the device.

[0022] In other words, by repeatedly heating the slab 100 multiple times using one induction heating slab heater and then soaking it in a heat retention device, it is possible to shorten the time that the slab 100 spends in the induction heating device compared to when the slab 100 is heated using induction heating alone, and the time interval until the induction heating device starts heating the next slab 100 can be shortened, making it possible to efficiently heat a large number of slabs 100 while ensuring time for the temperature at the center of the thickness to rise.

[0023] The second heating device is provided on a heating line different from the rolling line on which the first heating device is provided, and includes a second induction heating slab heater 22, a second heat retention device 32 provided on the inlet side of the slab 100 in the heating line of the second induction heating slab heater 22 and using the heat retained in the slab 100 as a heat source, and a third heat retention device 34 provided on the outlet side of the slab 100 in the heating line of the second induction heating slab heater 22 and using the heat retained in the slab 100 as a heat source.

[0024] This second heating device is provided to heat the slab 100 with the second induction heating slab heater 22 or to retain heat with the second heat retention device 32 or the third heat retention device 34 when the temperature of the slab 100 is insufficient with the first induction heating slab heater 20 of the first heating device. Note that although the second heating device has two heat retention devices, the second heat retention device 32 and the third heat retention device 34, it may have only one of them, or three or more.

[0025] In FIG. 1, the second induction heating slab heater 22, the second heat retaining device 32, and the third heat retaining device 34 are arranged as one set, but it is also possible to provide a plurality of sets.

[0026] The first induction heating slab heater 20, the second induction heating slab heater 22, the first heat retention device 30, the second heat retention device 32, and the third heat retention device 34 are provided with table rollers 130 (see Figure 12), which allow the slab 100 to move back and forth in the direction of travel.

[0027] The first induction slab heater 20 and the second induction slab heater 22 oscillate the slab 100 back and forth in the direction of travel, thereby achieving a uniform temperature rise in the longitudinal direction of the slab 100 and achieving uniform temperature distribution within the cross section. Details of the configuration will be described later using Figure 12, etc.

[0028] The first heat retention device 30, the second heat retention device 32, and the third heat retention device 34 can be configured to surround the periphery of the slab 100 with panels made up of reflectors and heat insulating material, thereby suppressing heat loss from the slab 100 placed inside and promoting uniform temperature distribution inside the slab 100. It is also possible to use a structure that combines heat insulating material such as refractory with a steel shell on the outside without providing a reflector. Also, placing a heating means inside and using that heating means to heat up the inside of the heat retention device at the start of operation is also effective in shortening the time required for temperature rise. Gas heating may be used as the internal heating means, but using an electric heater can prevent direct CO ２ Emissions can be reduced.

[0029] In these first heat retention device 30, second heat retention device 32, and third heat retention device 34, the slab 100 can be made to oscillate back and forth in the direction of travel to uniformly increase the temperature of the slab 100 in the longitudinal direction, while also achieving uniform temperature distribution within the cross section.

[0030] The first slab transport device 40 is configured to be able to move the slab 100 between the exit side of the slab 100 in the rolling line of the first heating device and the entrance side of the slab 100 in the heating line of the second heating device.

[0031] In contrast, the second slab transport device 42 is configured to be able to move the slab 100 between the entrance side of the slab 100 in the rolling line of the first heating device and the exit side of the slab 100 in the heating line of the second heating device.

[0032] The third slab transport device 44 is configured to be able to move the slab 100 between the slab storage location 50 where the slab 100 is stored and the inlet side of the slab 100 in the heating line of the second heating device. The fourth slab transport device 46 is configured to be able to move the slab 100 between the slab storage location 50 and the outlet side of the slab 100 in the heating line of the second heating device. Note that a configuration may be provided in which only either the third slab transport device 44 or the fourth slab transport device 46 is provided.

[0033] The first heating device internal thermometer 201 is provided in the first heating device and is a thermometer that measures the temperature of the slab 100. For example, it is configured to measure the surface temperature of the slab 100 in the first induction heating slab heater 20.

[0034] 1 and other figures show an example in which one thermometer 201 is provided in the first heating device, but two or more may be provided. Furthermore, the configuration is not limited to measuring the temperature of the slab 100 in the first induction heating slab heater 20, but may also be any of a configuration in which the temperature of the slab 100 is measured in the first heat retention device 30, a configuration in which the temperature of the slab 100 is measured before entering the first induction heating slab heater 20, after leaving the first induction heating slab heater 20, and after leaving the first heat retention device 30, or a configuration in which two or more of these are employed.

[0035] The second heating device internal thermometer 203 is provided in the second heating device and is a thermometer that measures the temperature of the slab 100 in the second heating device. For example, it is configured to measure the surface temperature of the slab 100 in the second induction heating slab heater 22.

[0036] Although one thermometer 203 in the second heating device is shown in the figure, two or more thermometers may be provided. Furthermore, the present invention is not limited to measuring the temperature of the slab 100 in the second induction heating slab heater 22, but may also measure the temperature of the slab 100 in the second heat retention device 32 or the third heat retention device 34, measure the temperature of the slab 100 before entering the second induction heating slab heater 22, after leaving the second induction heating slab heater 22, or before entering or leaving the second heat retention device 32 or the third heat retention device 34, or may employ two or more of these.

[0037] The storage location thermometer 205 is provided in the slab storage location 50 and is a thermometer that measures the temperature of the slabs 100 in the slab storage location 50. For example, it is configured to measure the surface temperature of the slabs 100.

[0038] Although one storage location thermometer 205 is shown in the figure, two or more may be used. Furthermore, the configuration is not limited to measuring the temperature of the slab 100 in the slab storage location 50, but may be one that measures the temperature of the slab 100 in the third slab transport device 44 or the fourth slab transport device 46, or may be a configuration that employs any two of these.

[0039] The control device 90 predicts the average temperature and the temperature at the center of the slab 100 based on the results of measuring the temperature of the slab 100 using one or more of the thermometers 201 in the first heating device, 203 in the second heating device, and 205 in the storage location, and determines the destination of the slab 100 based on the measured surface temperature and the predicted internal temperature. Details of this will be described later.

[0040] Figure 2 shows the temperature of a slab immediately before rough rolling when the slab is transported without heating, and shows the results of a simulation performed under the conditions of a casting speed Vc of 2.0 m / min, a slab thickness of 225 mm, and a slab width of 1300 mm. The horizontal axis of Figure 2 shows the position in the thickness direction, and the vertical axis shows the temperature at the center of the slab in the width direction.

[0041] The temperature immediately before rough rolling is set appropriately depending on the steel type, but the description here is for a case where the target temperature immediately before rough rolling is 1150°C. In this case, the required average temperature rise of the slab is 105°C.

[0042] Although the temperature of the slab at the position where it is heated by the induction heating slab heater is slightly higher than the temperature of the slab at the position immediately before rough rolling, the temperature rise amount by the induction heating slab heater is not significantly different from 105°C shown in Figure 2, so here, the temperature rise amount by the induction heating slab heater is set to 105°C.

[0043] Figure 3 also shows the temperature of a slab immediately before rough rolling when the slab is transported without heating, at a casting speed Vc of 1.2 m / min. The horizontal axis of Figure 3 represents the position in the thickness direction, and the vertical axis represents the temperature at the center of the slab width direction. In Figure 3, as in Figure 2, the required average temperature rise of the slab is 321°C.

[0044] Although the temperature of the slab at the position where it is heated by the induction heating slab heater is slightly higher than the temperature of the slab at the position immediately before rough rolling, the temperature rise by the induction heating slab heater is not significantly different from 321°C shown in Figure 3, so here, the temperature rise by the induction heating slab heater is set to 321°C.

[0045] FIG. 4 is a diagram showing the temperature of a slab immediately before rough rolling when the slab is transported without being heated. The horizontal axis shows the casting speed, and the vertical axis shows the temperature at the center of the slab in the width direction. The temperature at the center of the thickness direction, the average temperature in the thickness direction, and the surface temperature are used as parameters.

[0046] The temperature of the slab during transport is highest at the center and lowest at the surface. On the other hand, with induction heating slab heaters, heating near the surface can be done in a relatively short time, but heating the inside of the slab is done by thermal conduction, which takes time.

[0047] If the temperature at the center in the thickness direction is low, there is a problem that the rolling load becomes high, so the target temperature immediately before rough rolling is set to 1150°C (depending on the steel type). At the same time, if the temperature difference is large, the variation in the structure in the thickness direction increases, which can cause variations in the mechanical strength and elongation in the thickness direction, and can lead to problems such as not being able to obtain the desired toughness, so it is also a goal to bring the temperature at the center in the thickness direction close to the target temperature of 1150°C.

[0048] The surface can be heated to a high temperature using an induction heating slab heater, but the slab surface is descaled before rolling and the surface temperature drops during transportation, so the temperature is lowered.

[0049] Here, we will focus on the average temperature and the temperature at the center in the thickness direction, and describe a method of heating with an induction slab heater so that these temperatures become suitable for rolling.

[0050] 2 to 4 are simulation results for a slab supplied from a strand (second strand) that is not a rolling line parallel to the rolling line in Fig. 1. Slabs supplied from the same strand (first strand) as the rolling line tend to have a slightly higher temperature, but this is within a range that can be adjusted by heating with an induction slab heater.

[0051] The control device 90 also determines the transport speed of the slab 100 within each heating device and controls that speed.

[0052] 2 to 4 show the temperature at the front end of the slab 100. The temperature at the rear end of the slab 100 is slightly higher than that at the front end. The temperature difference between the front and rear ends of the slab 100 can be adjusted by heating the slab 100 as it is inserted into the induction heating slab heater. Therefore, when inserting the front end of the slab 100 into the induction heating slab heater, the control device 90 heats the slab 100 from the front end while inserting it into the induction heating slab heater, thereby making it possible to adjust the temperature so as to eliminate the temperature difference with the rear end, which is finally inserted into the induction heating slab heater.

[0053] 5 shows a flow in which a slab 100 is heated by a first induction heating slab heater 20, then kept at a temperature by a first heat retention device 30, and then transported to a rolling facility. In FIG. 5, the rounded letters indicate the processes corresponding to the numbers in parentheses below.

[0054] In this case, the control device 90 determines whether to transport the slab 100 to the roughing rolling mill 70 or the second heating device based on the temperature of the slab 100 measured by the thermometer 201 in the first heating device, and switches the transport direction of the slab 100. Here, an example is shown in which the average temperature and central temperature of the slab 100 have reached the target, and the slab 100 is transported to the roughing rolling mill 70.

[0055] As shown in Figure 5 (a), a slab 100 is cut into slabs 101 at a length of 12 m and transported in the direction of the rolling equipment, with each slab being cast at a casting speed of 2.0 m / min in a two-strand continuous casting machine 12. The first slab 101 arrives at the inlet side of the first induction heating slab heater 20.

[0056] The temperature of the first slab 101 immediately before rough rolling is 1120°C at the center of thickness, 1045°C on average, and 900°C at the surface. Therefore, in the following, the heating by the first induction heating slab heater 20 and the heat retention by the first heat retention device 30 on the outlet side are adjusted as shown in Figure 5b) so that the temperature during rough rolling is approximately 1150°C.

[0057] In Figure 5, b) (1) is the transport into the first induction heating slab heater 20. By utilizing this transport, the leading edge of the slab 100 is heated more by the first induction heating slab heater 20, while the trailing edge is heated less by the first induction heating slab heater 20. This phenomenon is utilized to reduce the temperature difference between the leading edge and the trailing edge. In this example, the average temperature difference between the leading edge and the trailing edge is 50°C, and the transport time is adjusted to 33 seconds to reduce this temperature difference.

[0058] 5 b) (2) shows the state in which the slab 100 is heated while oscillating (moving back and forth in the path direction) inside the first induction heating slab heater 20. Here, the upper limit of the surface temperature is set to 1300°C. After the surface temperature reaches 1300°C, the output (power) of the first induction heating slab heater 20 is reduced to prevent the surface temperature from exceeding 1300°C, while continuing to heat the entire slab 100.

[0059] After a heating time of 121 seconds (total 154 seconds), the temperatures reached the levels equivalent to 1170°C at the thickness center, 1230°C on average, and 1300°C on the surface, calculated as the temperatures immediately before rough rolling.

[0060] Since descaling is performed before rolling and the surface temperature and average temperature decrease during transportation to rough rolling, the temperature at the center of thickness hardly changes, so the center of thickness and average temperature can be maintained at around 1170°C when converted to the temperature immediately before rough rolling.

[0061] 5c) shows (3) 26 seconds of transport to the first heat retention device 30 (total 180 seconds) and (4) 33 seconds of heat retention while oscillating (total 213 seconds). The 12-m-long slab 100 is produced at a 6-minute interval, and because there are two strands, it arrives at the inlet side of the first induction heating slab heater 20 at a 3-minute interval. Therefore, the second slab 102 arrives at the inlet side of the first induction heating slab heater 20 at the timing when (3) transport is completed.

[0062] Thereafter, as shown in Figure 5(d), the rear end of the first slab 101 leaves the first heat retention device 30. The transport of (5) requires 19 seconds (a total of 232 seconds), so it takes a total of 232 seconds to pass through section L1. It takes 180 seconds (3 minutes) + 154 seconds = 334 seconds for the second slab 102 to complete (1) and (2), and because it took 213 seconds for the first slab 101 to complete (4), there is a margin of 121 seconds (= 334 - 213). It is possible to leave the slab 100 in the first heat retention device 30 for an additional 121 seconds.

[0063] 6 shows a flow in which the slab 100 is heated by both the first induction heating slab heater 20 and the second induction heating slab heater 22, and then transported to the rolling equipment. In FIG. 6, the rounded letters indicate the processes corresponding to the numbers in parentheses below.

[0064] In this case, the control device 90 determines the number of times the second induction heating slab heater 22, the second heat retention device 32, and the third heat retention device 34 have been used and the length of time the slab 100 has been in the second heat retention device based on the temperature measured by the thermometer 203 in the second heat retention device and the rolling status on the rolling line, and switches the transport direction of the slab 100. Here, the control device 90 determines in advance that the average temperature and central temperature of the slab 100 have not reached the target and therefore determines to transport the slab 100 to the second heat retention device.

[0065] In FIG. 6, a) shows the process from when the first slab 101 arrives at the first induction heating slab heater 20 until it is transported out of the rolling line by the first slab transport device 40.

[0066] The slabs 100 obtained by casting at a casting speed of 1.2 m / min on each strand of the two-strand continuous casting machine 12 are cut into lengths of 12 m each and transported in the direction of the rolling equipment, with the first slab 101 arriving at the inlet side of the first induction heating slab heater 20.

[0067] The temperature of the first slab 101 immediately before rough rolling is 870°C at the center of thickness, 829°C on average, and 750°C on the surface. Therefore, the heating is adjusted below so that the temperature immediately before rough rolling is approximately 1150°C. The temperature drop is greater than when the casting speed is 2.0 m / min in Figure 5. Therefore, as in Figure 5 (1), since the average temperature difference between the front and rear ends is 50°C, the transfer time is set to 33 seconds, and the slab is first transferred to the first induction heating slab heater 20 in (1), and the temperature difference is adjusted to be small.

[0068] Thereafter, as shown in (2), the slab 100 is heated while oscillating (moving back and forth in the path direction) inside the first induction heating slab heater 20. Here, the upper limit of the surface temperature is set to 1300°C. After the surface temperature reaches 1300°C, the output (power) of the first induction heating slab heater 20 is reduced to prevent the surface temperature from exceeding 1300°C, while continuing to heat the entire slab 100.

[0069] After 192 seconds of heating (225 seconds in total), the temperatures reached correspond to 985°C at the center of thickness, 1100°C on average, and 1300°C on the surface, converted to the temperatures immediately before rough rolling. However, heating by the first induction heating slab heater 20 alone did not result in the center of thickness or the average temperature reaching the target of 1150°C. Therefore, the control device 90 decided to transport the first slab 101 to the second heating device.

[0070] In FIG. 6, b) shows the process from when the first slab 101 is heated by the second induction slab heater 22 outside the rolling line until it is transported to the rolling line by the second slab transport device 42.

[0071] Until the slab is completely inserted into the second induction heating slab heater 22, 154 seconds (379 seconds in total) elapse for (3) transportation, (4) heat retention while oscillating inside the first heat retention device 30, and (5), (6), and (7) transportation, followed by (8) heating while oscillating (moving back and forth in the pass direction) inside the second induction heating slab heater 22. After 140 seconds of heating time (519 seconds in total), the slab reaches temperatures equivalent to 1080°C at the center of thickness, 1165°C on average, and 1300°C on the surface, calculated as the temperatures immediately before rough rolling. Heating by both the first induction heating slab heater 20 and the second induction heating slab heater 22 causes the average temperature to exceed the target temperature of 1150°C, but the temperature at the center of thickness does not reach the target temperature.

[0072] In FIG. 6, c) shows the state in which the first slab 101 has been reheated by the first induction heating slab heater 20 and has left the first heat retention device.

[0073] Since the heating power of both the first induction heating slab heater 20 and the second induction heating slab heater 22 is insufficient, 132 seconds (651 seconds in total) elapse before the slab is completely inserted into the first induction heating slab heater 20, including (9) transportation, (10) heat retention while oscillating inside the third heat retention device 34, (11), (12), and (13) transportation, and (14) heating while oscillating (moving back and forth in the path direction) inside the first induction heating slab heater 20.

[0074] After 140 seconds of heating (791 seconds in total), the temperature reaches a value equivalent to the temperature immediately before rough rolling of 1170°C at the thickness center, 1230°C on average, and 1300°C on the surface. Heating by the first induction heating slab heater 20, the second induction heating slab heater 22, and the second heating by the first induction heating slab heater 20 causes the temperature at the thickness center to exceed the target temperature of 1150°C.

[0075] Since descaling is performed before rolling and the surface temperature and average temperature decrease during transportation to rough rolling, the temperature at the center of thickness hardly changes, so the center of thickness and average temperature can be maintained at around 1170°C when converted to the temperature immediately before rough rolling.

[0076] Further, 79 seconds (870 seconds in total) pass during (15) conveyance, (16) heat retention while oscillating inside the first heat retention device 30, and (17) conveyance.

[0077] At a casting speed of 1.2 m / min, 12 m long slabs 100 are produced at 10 minute intervals, and because there are two strands, they arrive at the inlet side of the first induction heating slab heater 20 at 5 minute intervals. Therefore, the timing for returning the first slab 101 to the rolling line is after the second slab 102 and the third slab 103 have passed the inlet side of the first induction heating slab heater 20.

[0078] After the first slab 101 has been heated for the second time by the first induction heating slab heater 20, it is transported in the direction of the roughing mill 70. Similar to the first slab 101, the second slab 102, the third slab 103, and the subsequent fourth slab 104 and fifth slab 105 are also transported in the direction of the roughing mill 70 while being heated three times in total, by the first induction heating slab heater 20, the second induction heating slab heater 22, and the second first induction heating slab heater 20.

[0079] Here, in the case where it is determined that the slab should be heated further by the second induction slab heater 22 as shown in Fig. 6 rather than directly sent to the roughing mill 70 as shown in Fig. 5, and the number of times to heat and retain heat by the second induction slab heater 22, second heat retention device 32, and third heat retention device 34 is to be determined, the conditions for returning the slab to the rolling line (the timing of return and the temperature at that time) are first set, and the heating conditions for the second heating device (the number of heatings, the heating time for each, and the heat retention time for each) are then determined. The target slab 100 is then transported according to the determined conditions.

[0080] In this case, an upper limit temperature is set for each steel type because excessively high temperatures can cause problems such as excessive surface oxidation. For this reason, 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 induction heating device as efficiently as possible, make effective use of the heat retention device, and reduce electricity consumption.

[0081] FIG. 6 illustrates a method of increasing the temperature of the slab 100 by performing heating three times in total, first with the first induction heating slab heater 20, then with the second induction heating slab heater 22, and then with the first induction heating slab heater 20 again, but other methods are also possible.

[0082] For example, when the slab is returned from the heating line to the rolling line, it may be transported to the rolling equipment without being heated by the first induction heating slab heater 20 for the second time.

[0083] The timing for returning the first slab 101 to the rolling line is after the third slab 103 has passed. If the first slab 101 is returned to the middle between the third slab 103 and the fourth slab 104, it takes 5 minutes (passing the second slab 102) + 5 minutes (passing the third slab 103) + 2.5 minutes = 12.5 minutes to go from the state (1) in Figure 6 to the next state (1).

[0084] At this time, it is preferable that the third slab 103 has already completed its transport to the first heat retention device 30 (3). This prevents the third slab 103 from interfering with the second heating of the first slab 101 by the first induction slab heater 20. If the time required for the third slab 103 to go through (1), (2), and (3) is 2.5 minutes, the next first slab 101, which has made one turn, can begin its transport to the first induction slab heater 20 (1). Furthermore, 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.

[0085] In this way, by setting (1), (2), and (3) to half the pitch at which slabs 100 arrive, even if slabs 100 are returned from outside the rolling line in between slabs 100, the slabs 100 will not collide with each other or the heating conditions of the slabs 100 will not be mixed.

[0086] Furthermore, when the first and second heating times by the first induction slab heater 20 are shortened, it is possible to lengthen the heating time by the second induction slab heater 22. When the heating time by the second induction slab heater 22 is lengthened, it is also possible to perform heating by the second induction slab heater 22 and heat retention by the second heat retention device 32 or the third heat retention device 34 in multiple steps.

[0087] It takes time to raise the temperature at the center of the thickness, and by combining the first heating by the first induction heating slab heater 20, the second induction heating slab heater 22, and the second heating by the second induction heating slab heater with the heat retention by each heat retention device, the high temperature state of the slab 100 can be maintained as much as possible, thereby further raising the temperature at the center of the thickness.

[0088] In Figure 6, a total of 870 seconds (14.5 minutes) elapses from the start of transport at (1), the slab rotates once, returns to state (1), and then the slab is completed at state (17). For example, if section L1 is 56 m, the average passing speed of the slab 100 during this time is 3.86 m / min (= 56 / 14.5). Since each of the two strands of the continuous casting machine 12 continues casting at 1.2 m / min, the average passing speed of the slab 100 passing through the heating device after the heating device heats up is 3.86 m / min, which satisfies the relationship 3.86 > 2.4 (= 1.2 x 2). Therefore, the slab 100 supplied from the continuous casting machine 12 can be heated smoothly.

[0089] Here, the first slab is inserted into the first induction slab heater 20 after the third slab (3) is transported. However, the heating time in the first induction slab heater 20 can be extended by, for example, starting the insertion of the first slab when the rear end of the third slab leaves the first induction slab heater 20, or by starting the insertion of the fourth slab into the first induction slab heater 20 when the rear end of the first slab leaves the first induction slab heater after the first slab has been heated by the first induction slab heater 20 for the second time. Similarly, the heating time in the second induction slab heater 22 can be extended by inserting the subsequent slab into the second induction slab heater 22 without waiting for the completion of the (9) transport. The heating times in the first induction slab heater 20 and the second induction slab heater 22 can be adjusted within a range that does not cause interference between the slabs.

[0090] The flow of the slab when the slab does not move back and forth between the first heating device and the second heating device is not limited to the form shown in Fig. 5. Below, examples of different forms will be described using Fig. 7 and Fig. 8. Fig. 7 is a diagram illustrating a case where the slab is heated only by the first induction heating slab heater using a heating device and direct rolling is performed, and Fig. 8 is a diagram illustrating a case where the slab is heated only by the second induction heating slab heater and direct rolling is performed using the same equipment as Fig. 7.

[0091] As shown in Figures 7 and 8, after a slab (first slab) is transported to the first heating device of the rolling line, the next slab (second slab) is transported to the second heating device of the heating line through the second slab transport device 42. The second slab transport device 42 is formed by a transport table 301 and a transport table 304. When the second slab arrives at the transport table 301, the transport table 301 is rotated. At the same time, the transport table 304 is rotated to transport the second slab to the transport table 304.

[0092] The conveying table 304 then rotates and transports the slab to the second induction heating slab heater 22. After heating is complete, the slab is transported to the second heat retention device 32, where it is rotated while retaining the desired heat. The conveying table 302 also rotates, and the second heat retention device 32 and the conveying table 302 together form the first slab transport device 40.

[0093] That is, while a slab is heated by the first induction heating slab heater 20 and kept warm by the first heat retention device 30, the next slab is heated by the second induction heating slab heater and kept warm by the second heat retention device 32. In this case, while the second slab is being heated by the second heating device, the next slab is transported into the first heating device as soon as it becomes available and its temperature is increased.

[0094] In this way, the slabs are alternately supplied to the rolling equipment 1 by being heated only by the first heating device on the rolling line and then being supplied to the rolling equipment 1, such as the scale breaker 60 and roughing mill 70, or by passing through the second slab transport device 42 and being heated only by the second heating device, then being returned to the rolling line by the first slab transport device 40 and being supplied to the rolling equipment.

[0095] This allows the slabs to be transported to an available heating device, thereby reducing the waiting time of the slabs transported one after another from the continuous casting machine 12 and suppressing a drop in temperature.

[0096] Since the time until the next slab is transported to the same heating device is long, the slab can be heated over time using one heating device. If the supply pitch of slabs produced by the continuous casting machine 12 is the same as in Figures 7 and 8, the time required to heat the first slab using the first induction slab heater can be doubled compared to the case in Figure 5. Therefore, the slab can be heated sufficiently using one heating device.

[0097] In particular, when heating using the first heating device, the slab does not pass through the first slab transport device 40 or the second slab transport device 42, thereby suppressing a drop in temperature of the slab and enabling the slab to be heated efficiently.

[0098] FIG. 9 shows an example of the flow of heating the reject material.

[0099] When the slab 100 stored in the slab storage area 50 is ready to be rolled, it is heated by the second induction heating slab heater 22 and kept warm by the second heat retention device 32 and the third heat retention device 34 at least once, and then the slab 100 is transported to the rolling line by the second slab transport device 42, where it is further heated by the first induction heating slab heater 20 and kept warm by the first heat retention device 30, while the timing of rolling can be adjusted.

[0100] In this case, the control device 90 determines the number of times the second induction heating slab heater 22, the second heat retention device 32, and the third heat retention device 34 of the slab 100 are used and the length of time the slab 100 stays in the second heating device based on the temperature of the slab 100 measured by the thermometer 203 in the second heating device, the temperature of the slab 100 at the slab storage location 50 measured by the storage location thermometer 205, and the rolling conditions at the rolling line, and switches the transport direction of the slab 100.

[0101] Specifically, heating of the first slab 101 begins with heating while oscillating in the second induction heating slab heater 22, followed by "heating by the second induction heating slab heater 22 (first heating, first IH2 heating), heat retention by the second heat retention device 32 (SD2 heat retention), heating by the second induction heating slab heater 22 (second heating, second IH2 heating), heat retention by the third heat retention device 34 (SD3 heat retention), heating by the second induction heating slab heater 22 (third heating, third IH2 heating), and, although not shown in FIG. 11 , heat retention by the third heat retention device 34 (SD3 heat retention), heating by the first induction heating slab heater 20, and heat retention by the first heat retention device 30." However, the present invention is not limited to this.

[0102] As a result, heating is performed three times by the second induction heating slab heater 22 and once by the first induction heating slab heater 20, a total of four times, to obtain the desired temperature.

[0103] Here, when inserting the slab 100 from the slab storage location 50 into the second heating device, it is desirable that it be possible to move it to the second heating device from either the second heat retention device 32 side or the third heat retention device 34 side.

[0104] Furthermore, if the slab 100 is to be further heated by the first heating device after the second heating device, it is preferable to use the third slab transport device 44 so that it can be inserted from the inlet side of the second heating device. If heating is not to be performed by the first heating device, it is preferable to use the fourth slab transport device 46 to insert the slab from the discharge side of the second heating device. After heating is completed by the second heating device, the slab can also be transported to the rolling line using the first slab transport device 40.

[0105] FIG. 10 shows the relationship between the temperature change of the slab 100 and the output (power) of the first induction heating slab heater 20 and the second induction heating slab heater 22 when the rejected slab 100 is heated from room temperature without using a heat retention device.

[0106] If no heat retention device is provided, the condition for completing the heating in the shortest time is to continue heating continuously with the second induction heating slab heater 22 to complete the temperature rise.

[0107] On the other hand, since there is an upper limit temperature on the surface of the slab 100, the output of the second induction heating slab heater 22 is reduced midway. Figure 10 shows a case where the upper limit temperature on the surface is 1300°C. As the temperature of the surface of the slab 100 approaches the upper limit temperature, the output of the second induction heating slab heater 22 is reduced. Because there is heat conduction into the slab 100 and heat release from the surface of the slab 100, the output of the second induction heating slab heater 22 does not become 0. In this case, it is assumed that time t11 is required to heat to the desired temperature.

[0108] Here, when the slab 100 is transported from outside the rolling line to the rolling line, if a drop in temperature occurs, the slab is heated by the first induction heating slab heater 20 in the rolling line.

[0109] Fig. 11 shows the relationship between the temperature change of the slab 100 when a heat retention device is used and the output (power) of the first induction slab heater 20 and the second induction slab heater 22. Fig. 11 assumes a case in which a rejected slab 100 is heated three times from room temperature by the second induction slab heater 22 while using a heat retention device.

[0110] Heating of the first slab 101 begins with heating while oscillating within the second induction heating slab heater 22, and is carried out in the following flow: "heating by the second induction heating slab heater 22 (first heating, first IH2 heating), heat retention by the second heat retention device 32 (heat retention by SD2), heating by the second induction heating slab heater 22 (second heating, second IH2 heating), heat retention by the third heat retention device 34 (heat retention by SD3), heating by the second induction heating slab heater 22 (third heating, third IH2 heating), and, although not shown in Figure 11, heat retention by the third heat retention device 34 (heat retention by SD3), heating by the first induction heating slab heater 20, and heat retention by the first heat retention device 30."

[0111] In order to efficiently heat the multiple slabs 100, it is desirable to perform the first heating by placing the second slab 102 in the second induction heating slab heater 22 while the first slab 101 is being retained in the third heat retention device 34, as shown in Figure 11. Similarly, the third slab 103 can also be heated in the same manner as the second slab 102.

[0112] In the case of Figure 11, the surface temperature of the slab 100 does not reach the upper limit temperature until midway through the third heating cycle, and the maximum output of the second induction heating slab heater 22 can be used for most of the time. As a result, the time required to complete the three heating cycles with the second induction heating slab heater 22 has the relationship "t22 in Figure 11 < t11 in Figure 10 < t21 in Figure 11".

[0113] In the case of Figure 11, the first slab 100 requires a somewhat long time, t21, but from the second slab onwards, the slabs 100 can be supplied to the rolling line at a pitch of time t22. In other words, the greater the number of slabs 100 to be heated, the greater the difference. In this way, by efficiently using the heat retention device, it is possible to use the second induction heating slab heater 22 at maximum output, thereby shortening the heating time.

[0114] In this way, when the slabs 100 are kept warm by the second heat retention device 32 and the third heat retention device 34, it is desirable that the control device 90 control the transportation of the slabs 100 so that different slabs 100 are heated by the second induction slab heater 22. While Fig. 9 shows a case in which heating is performed three times by the second induction slab heater 22, it is also possible to heat the slab by the second induction slab heater 22, heat it by the first induction slab heater, transport the slab to the second induction slab heater 22 by the first slab transport device 40, heat it by the second induction slab heater 22, and then heat it by the first induction slab heater 20, thereby heating the slab from the second induction slab heater 22 to the first induction slab heater 20 in two rotations. Since it takes time to raise the temperature of the center of the slab in the thickness direction, by repeatedly heating with the slab heater and keeping the heat with the heat retention device to maintain the high temperature state of the slab 100 as much as possible, it is possible to use the slab heater efficiently without significantly reducing the output of the slab heater, and to heat multiple slabs and supply them to the rolling equipment in a short period of time.

[0115] Next, an example of the detailed configuration of the first induction heating slab heater 20 and the second induction heating slab heater 22 will be described using Fig. 12. Fig. 12 shows the first induction heating slab heater 20 as an example, but the second induction heating slab heater 22 can basically have approximately the same configuration. Fig. 12 shows a front view of the induction heating slab heater.

[0116] The first induction heating slab heater 20 shown in Figure 12 includes a side guide 110 and an in-device side guide 115, a slab width end heater 120, an entire slab heater 125, a table roller 130, a thermometer 201 inside the first heating device, and a first heating device inlet thermometer 202 that is provided on the inlet side of the slab 100 in the rolling line of the first heating device and measures the surface temperature of the slab 100.

[0117] 12, at least one whole slab heater 125 that heats the cross section of the slab 100 and at least one slab width end heater 120 that heats the end of the width direction of the slab 100 are arranged alternately. Here, the slab width end heater 120 provided on the most inlet side is provided closer to the inlet than the whole slab heater 125, but the arrangement order of the slab width end heater 120 and the whole slab heater 125 may be reversed.

[0118] As the whole slab heater 125, a longitudinal heating coil type, a transversal heating coil type, or the like is used.

[0119] The control device 90 further adjusts the output of the slab width end heater 120 and the entire slab heater 125 based on the temperature difference between the tip and rear end temperatures of the slab 100 measured by the first heating device inlet side thermometer 202 and the conveying speed of the slab 100.

[0120] For example, when the rear end of the slab 100 passes the slab width end heater 120 in the front row (the most upstream side in the conveying direction), the control device 90 switches the conveying direction of the slab 100 so that the slab 100 repeatedly moves back and forth between the slab entire heater 125 and the slab width end heater 120, and when the surface temperature measured by the thermometer 201 in the first heating device reaches a predetermined temperature or a predetermined time, the control device 90 completes the heating in the first induction heating slab heater 20 and conveys the slab 100 out of the first induction heating slab heater 20.

[0121] Here, in the first induction heating slab heater 20, the slab 100 is heated while oscillating (reciprocating) in the path direction. During the oscillation length L4, both the entire slab heater 125 and the slab width end heater 120 heat the slab. Each of the entire slab heater 125 and the slab 100 end heater heats its respective section, thereby enabling the entire length of the slab 100 to be heated evenly. The length L3 over which the slab 100 exists is the sum of the maximum slab length L2 and the oscillation length L4. Each of these lengths L2, L3, L4, and L5 is set appropriately according to the user's requirements.

[0122] Side guides 110 are provided on the inlet and outlet sides to determine the widthwise position of the slab 100, and in-apparatus side guides 115 are provided between the entire slab heater 125 and the slab width end heaters 120 to determine the widthwise position of the slab 100. The in-apparatus side guides 115 between each heater are set appropriately taking into consideration the minimum slab length, etc., and are not limited to those shown in Figure 12.

[0123] Figure 13 shows the difference in average temperature between the leading edge and trailing edge of the slab 100. The horizontal axis of Figure 13 represents the distance from the meniscus (the surface of the molten metal in the mold), and the vertical axis represents the temperature of the slab 100. The temperatures shown are the temperature at the center of the thickness of the slab, the average temperature, and the surface temperature. Here, solidification calculations are used, and it is assumed that the slab advances at the same speed. The distance from the meniscus represents the position of the slab, and indicates the temperature of the slab at that position.

[0124] After passing through the outlet of the continuous casting machine 12, the slab 100 advances at the casting speed until it is cut into slabs 100 by the torch cutter 14. When the rear end is cut by the torch cutter 14, the front end of the slab 100 advances at the casting speed for a distance equal to the length of the slab 100, so the temperature of the front end of the slab 100 is lower than that of the rear end.

[0125] When the length of the slab 100 was 12 m, the average temperature of the front end of the slab 100 after being cut by the torch cutter 14 was 1075°C, and the average temperature of the rear end of the slab 100 was 1125°C. In this case, the difference in average temperature between the front end and the rear end was 50°C.

[0126] 14 is a diagram illustrating a method for eliminating the temperature difference between the leading and trailing ends of the slab 100. Eliminating the temperature difference between the leading and trailing ends or achieving a desired temperature difference is called temperature difference compensation heating. This compensation heating may be performed by either the first heating device or the second heating device, and preferably by either.

[0127] If the moving length of the slab 100 is L6, after the leading end of the slab 100 arrives at the entrance of the induction heating slab heater, heating of the leading end of the slab 100 by the induction heating slab heater begins.

[0128] The slab 100 is transported at a speed Vs while continuing to be heated, and when the rear end reaches the entrance of the induction heating slab heater, the speed Vs and the output of each heater of the induction heating slab heater are adjusted to eliminate the temperature difference or to achieve the desired temperature difference.

[0129] Then, after the temperature difference between the leading end and the trailing end is eliminated or a desired temperature difference is achieved, the entire slab 100 is heated in the same manner while oscillating within the induction heating slab heater.

[0130] In Figure 13, if the slab 100 is 12 m long and the temperature difference between the front and rear ends is 50°C, by performing the above-mentioned temperature difference compensation heating, it is possible to eliminate or minimize this 50°C temperature difference.

[0131] FIG. 15 is a diagram for explaining a case where the slab 100 is heated only by the first induction slab heater 20 without using the second induction slab heater 22 and direct rolling is performed.

[0132] When the casting speed is a slow 1.2 m / min, the slab needs to be heated three times with the induction heating slab heater as shown in FIG.

[0133] According to the rolling equipment 1A in which at least three combinations of the first induction heating slab heater 20 and the first heat retention device 30 are arranged in series as shown in Figure 15, heating can be performed using only the first induction heating slab heater 20 in the rolling line, without using the second induction heating slab heater 22 and the second heat retention device 32 or the third heat retention device 34 outside the rolling line.

[0134] When the casting speed is faster than 1.2 m / min or depending on the capacity of the first induction slab heater 20, it is possible to use two first induction slab heaters 20.

[0135] Here, in FIG. 15, a total of four induction heating slab heaters are arranged, consisting of three first induction heating slab heaters 20 and one second induction heating slab heater 22. However, in the method described in FIG. 1 or FIG. 6, it is possible to use one first induction heating slab heater 20 and one second induction heating slab heater 22, for a total of two, which allows for a reduction in equipment costs.

[0136] 1 and 6, the overall length of the equipment from the continuous casting machine 12 to the down coiler 85 can be shortened compared to the embodiment of FIG. 15, making it possible to make the equipment more compact. Furthermore, when a large amount of slabs 100 is supplied from the continuous casting machine 12, two first induction slab heaters 20 and two second induction slab heaters 22 can be provided, and the slabs can be heated by both the first induction slab heater 20 and the second induction slab heater 22 using a first slab transport device 40 or the like, thereby making it possible to heat a large number of slabs to a desired temperature using a short facility. The number of first induction slab heaters 20 and second induction slab heaters 22 can be determined appropriately according to the user's production needs.

[0137] 16 is a diagram showing an example of a general facility in which a slab 100 is inserted into a reheating furnace for heating. Some rolling facilities have one reheating furnace 145, while others have multiple reheating furnaces.

[0138] 17 is a diagram showing the installation of the heating device for the slab 100 of the present invention in a general facility where the slab 100 is inserted into a reheating furnace and heated. The arrows in Fig. 17 indicate the flow of the slab after being heated by the second induction heating slab heater 22 and the first induction heating slab heater 20 and then sent to the rolling facility.

[0139] In a rolling facility equipped with the heating apparatus of the present invention as shown in Figure 17, when the temperature of the slab 100 is low, a large temperature increase can be achieved by heating the slab with the second induction slab heater 22 and the first induction slab heater 20, and then passing the slab again through the second induction slab heater 22 and the first induction slab heater 20. It is also possible to transport the slab along the route shown in Figure 9, heating it multiple times with the second induction slab heater 22, and then heating it with the first induction slab heater 20.

[0140] Although not shown, a method of placing the slab in a reheating furnace before or after heating with the first induction heating slab heater 20 and the second induction heating slab heater 22 may also be used.

[0141] Additionally, if the slab 100 needs to be maintained at an elevated temperature for a significant period of time, such as several hours, a reheat furnace may be utilized.

[0142] Generally, reheating furnaces use CO ２ In contrast, the temperature raising device of the present invention uses the first induction heating slab heater 20 and the second induction heating slab heater 22 for heating, which reduces direct CO ２ This reduces emissions and leads to the production of green steel.

[0143] In addition, the reheating furnace may be an electric furnace or a CO ２ By using a low-emissions furnace and combining the reheat furnace with the first induction slab heater 20 and the second induction slab heater 22, green steel can be produced.

[0144] Next, another example of the configuration of the first induction heating slab heater 20 and the second induction heating slab heater 22 will be described with reference to Figures 18 to 20. Figures 18 and 19 are front views of the induction heating slab heater, and Figure 20 is a view corresponding to the view seen from the arrow A-A in Figure 12, which is an example diagram.

[0145] In Figure 12, the slab width end heaters 120 are arranged within the length L3 in which the slab 100 exists, and the slab width end heaters 120 are arranged alternately with the entire slab heaters 125, but in Figure 18, the slab width end heaters 122 are arranged outside the length L3 in which the slab 100 exists, on the outlet side of the entire slab heater 125.

[0146] In this case, too, the control device 90 switches the transport direction of the slab 100 so that the slab 100 repeatedly moves back and forth inside the entire slab heater 125 until the surface temperature measured by the thermometer 201 in the first heating device reaches a predetermined temperature, and when the surface temperature measured by the thermometer 201 in the first heating device reaches a predetermined temperature or a predetermined time has passed, the slab 100 is transported to the slab width end heater 122.

[0147] When the slab 100 is heated while oscillating with the entire slab heater 125, the widthwise ends of the slab 100 are also heated, so that when the slab 100 is transported to the outlet side after the heating of the entire slab 100 is completed, the widthwise ends of the slab 100 are heated while transporting the slab 100 at an arbitrary speed.

[0148] The slab width end heater 122 in FIG. 18 has the same structure as the slab width end heater in FIG.

[0149] When the slab width edge heater 122 is arranged on the outlet side as shown in Figure 18, it is possible to compensate for the lack of heating at the width edge of the slab 100 caused by heating with the entire slab heater 125. Since the heating of the width edge of the slab 100 can be adjusted after the entire slab is heated, it is possible to heat the width edge of the slab 100 with high precision.

[0150] 12, the side guides are arranged above the table rollers 130, but it is possible to install them between the table rollers 130 without changing the oscillation length L4. If the side guides are installed above the table rollers 130, the equipment will overlap and the structure will become complicated, but by arranging the side guides between the table rollers 130, the equipment can be simplified.

[0151] Furthermore, as shown in FIG. 19, it is also possible to install a slab width edge heater 121 on the inlet side of the length L3 where the slab 100 exists, and heat the width edge before heating the entire slab 100.

[0152] When the slab width edge heater 121 is arranged on the inlet side as shown in Figure 19, the heating of the width edge of the slab 100 is completed before the heating of the entire cross section of the leading end of the slab 100 is completed. As shown in Figure 14, since the slab 100 is transported at a relatively low speed when performing temperature difference compensation heating, by also heating the width edge of the slab 100 under those conditions, there is no need to set aside a special time for heating the width edge of the slab 100.

[0153] Furthermore, if a heat retention device is placed on the outlet side of the induction heating slab heater (first heat retention device 30 or third heat retention device 34), this heat retention device can ensure uniform heating within the cross section of the slab 100 after overall heating and width end heating.

[0154] The arrangement of the in-apparatus side guides 115 between the entire slab heaters 125 is set appropriately taking into consideration the minimum slab length, etc., and is not limited to that shown in Fig. 18. In Figs. 18 and 19, the entire slab heaters 125 and the slab width end heaters 120 may be arranged alternately.

[0155] In Figure 20, a longitudinal heating coil type is used as the entire slab heater 125. The solid lines in Figure 20 indicate the positions of the slab width edge heaters when the slab is wide. The dashed lines indicate the positions of the slab width edge heaters when the slab is narrow. Here, the dashed lines only show the right side, but when the slab is narrow, the positions of the slab width edge heaters on the left side are the same as those on the right side.

[0156] The slab width edge heater 120 is capable of being moved in its position in the width direction so as to accommodate the wide slab 100A, which has the maximum width, and the narrow slab 100B, which has the minimum width, and can be set to a position suitable for heating the width edge of the slab 100 depending on the width of the slab 100. The positions of the slab width edge heaters 121 and 122 are also capable of being moved in the width direction in the same way.

[0157] The width of the slab 100 passing through the slab 100 varies over a wide range, for example, from 900 mm to 1600 mm. When the width of the slab 100 changes, the heating state of the width edge of the slab 100 by the whole slab heater 125 also changes. Therefore, the heating of the width edge of the slab 100 can be adjusted according to the width of the slab 100 by the slab width edge heaters 120, 121, and 122.

[0158] Furthermore, the in-apparatus side guide 115 can set the position at which the slab 100 passes in the width direction so that the width ends of the slab 100 do not interfere with the slab width end heaters 120 , 121 , and 122 .

[0159] Next, the effects of this embodiment will be described.

[0160] Conventionally, when a problem occurs after the roughing mill 70, the continuous casting machine 12 cannot be stopped immediately, and so it becomes necessary to discharge the cast slab 100 from the rolling line. In addition, depending on the slab 100, there are cases where surface treatment is required before rolling due to surface quality issues, and in such cases, the slab 100 also needs to be discharged from the rolling line.

[0161] The temperature of these rejected slabs 100 may drop to room temperature in the slab storage area 50 outside the rolling line. If the slabs 100 that have dropped to room temperature are reheated using only an induction slab heater, it would take a long time, and there would be insufficient capacity to reheat the rejected slabs 100 and return them to the rolling line. For this reason, a large number of induction slab heaters were required.

[0162] In contrast, the heating device for heating the steel slab 100 cast by the continuous casting machine 12 of the above-mentioned embodiment comprises a first heating device provided in a rolling line between the continuous casting machine 12 and the roughing mill 70, a second heating device provided in a heating line different from the rolling line, a first slab transport device 40 configured to be able to move the slab 100 between the outlet side of the slab 100 in the rolling line of the first heating device and the inlet side of the slab 100 in the heating line of the second heating device, and a second slab transport device 42 configured to be able to move the slab 100 between the inlet side of the slab 100 in the rolling line of the first heating device and the outlet side of the slab 100 in the heating line of the second heating device, and the first heating device has a first induction heating slab heater 20, and the second heating device has a second induction heating slab heater 22.

[0163] In addition, a method for heating a slab 100 of steel cast by a continuous casting machine 12 includes heating the slab 100 by induction heating in a rolling line between the continuous casting machine 12 and the roughing mill 70, heating the slab 100 by induction heating in a heating line different from the rolling line, moving the slab 100 between the post-heating side of the slab 100 in the rolling line and the pre-heating side of the slab 100 in the heating line, and moving the slab 100 between the pre-heating side of the slab 100 in the rolling line and the post-heating side of the slab 100 in the heating line.

[0164] By using induction heating slab heaters in combination in this way, if the temperature of the slab leaving the first heating device has not reached the desired temperature, the slab can be heated by the second heating device before being transported back to the first heating device via the transport device, so that the heating by the second heating device can compensate for the insufficient temperature rise by heating in the first heating device. This allows the temperature of the slab 100, even if the casting speed is slow, to be raised to the desired temperature, making direct rolling possible.

[0165] Furthermore, by using a combination of these induction heating slab heaters, it is possible to heat the rejected slab 100 from room temperature and roll it to the desired temperature using a small number of induction heating slab heaters.

[0166] Furthermore, the first heating device is provided on the exit side of the slab 100 in the rolling line of the first induction heating slab heater 20, and further includes a first heat retention device 30 that uses the heat retained in the slab 100 as a heat source, so it is possible to shorten the time that the slab 100 stays in the induction heating device compared to when the slab 100 is heated only by induction heating. This shortens the time interval until the induction heating device starts heating the next slab 100.

[0167] Furthermore, the second heating device is provided on at least one of the inlet and outlet sides of the slab 100 in the heating line of the second induction heating slab heater 22, and by further having a second heat retention device 32 and a third heat retention device 34 that use the heat retained in the slab 100 as a heat source, it is possible to shorten the time that the slab 100 stays in the induction heating device compared to when the slab 100 is similarly heated by induction heating alone.

[0168] In addition, by further providing at least one of a third slab transport device 44 configured to be able to move the slab 100 between the slab storage location 50 where the slab 100 is stored and the inlet side of the slab 100 in the heating line of the second heating device, and a fourth slab transport device 46 configured to be able to move the slab 100 between the slab storage location 50 and the outlet side of the slab 100 in the heating line of the second heating device, flexible transportation of the slab 100 between the slab storage location 50, the second heating device, and the first heating device can be realized depending on the rolling conditions in the rolling line.

[0169] Furthermore, by further providing a thermometer 201 in the first heating device that is provided in the first heating device and measures the temperature of the slab 100, and a control device 90 that determines whether to transport the slab 100 to either the roughing rolling mill 70 or the second heating device based on the temperature of the slab 100 measured by the thermometer 201 in the first heating device and switches the transport direction of the slab 100, it is possible to determine whether to transport the slab directly or to further heat it up using the second induction heating slab heater 22, thereby achieving more reliable heating.

[0170] In addition, the second heating device has a thermometer 203 inside the second heating device that measures the temperature of the slab 100, and a second heat retention device 32 and a third heat retention device 34 that are provided on at least one of the inlet and outlet sides of the slab 100 in the heating line of the second induction heating slab heater 22 and use the heat retained by the slab 100 as a heat source.The second heating device also has a control device 90 that determines the number of uses and residence time of the second induction heating slab heater 22, the second heat retention device 32, and the third heat retention device 34 of the slab 100 in the second heating device based on the temperature measured by the thermometer 203 inside the second heating device and the rolling status on the rolling line, and switches the transport direction of the slab 100, so that additional heating by the second induction heating slab heater 22 can be performed more efficiently.

[0171] Furthermore, the second heating device has a thermometer 203 in the second heating device that measures the temperature of the slab 100, and a second heat retention device 32 and a third heat retention device 34 that are provided at least on either the inlet side or outlet side of the slab 100 in the heating line of the second induction heating slab heater 22 and use the heat retained by the slab 100 as a heat source. A storage location thermometer 205 is provided in the slab storage location 50 where the slab 100 is stored and measures the temperature of the slab 100, and a storage location thermometer 205 measures the temperature of the slab 100. The control device 90 determines the number of times the second induction heating slab heater 22, the second heat retention device 32, and the third heat retention device 34 of the slab 100 are used and the length of time the slab 100 is in the second heating device based on the temperature of the slab 100, the temperature of the slab 100 at the slab storage location 50 measured by the storage location thermometer 205, and the rolling conditions at the rolling line, and switches the transport direction of the slab 100, thereby making it possible to more efficiently heat the slab 100 stored at the slab storage location 50.

[0172] In addition, the second heating device is provided on at least one of the inlet and outlet sides of the slab 100 in the heating line of the second induction heating slab heater 22, and has a second heat retention device 32 and a third heat retention device 34 that use the heat retained in the slab 100 as a heat source.When the slab 100 is kept warm by the second heat retention device 32 and the third heat retention device 34, a control device 90 is further provided that controls the transportation of the slab 100 so that different slabs 100 are heated by the second induction heating slab heater 22.This makes it possible to heat multiple slabs 100 efficiently and without waste, while minimizing the risk of exceeding the upper limit temperature.

[0173] Furthermore, the first induction heating slab heater 20 has at least one whole slab heater 125 that heats the cross section of the slab 100, or at least one slab width end heater 120 that heats the end of the width direction of the slab 100 and at least one whole slab heater 125 that heats the cross section of the slab 100, and is further equipped with a first heating device inlet thermometer 202 that is provided on the inlet side of the slab 100 in the rolling line of the first heating device and measures the surface temperature of the slab 100, and a control device 90 that adjusts the output of the slab width end heater 120 or the whole slab heater 125 based on the temperature difference between the front and rear end temperatures of the slab 100 measured by the first heating device inlet thermometer 202 and the conveying speed of the slab 100, thereby reducing the temperature difference between the front and rear ends of the slab 100 in the rolling direction, and thereby achieving more uniform heating of the slab 100.

[0174] The first heating device further includes a thermometer 201 inside the first heating device that measures the temperature of the slab 100, and the slab width end heaters 120 and the entire slab heaters 125 are arranged alternately. When the rear end of the slab 100 enters the first induction heating slab heater 20, the control device 90 switches the transport direction of the slab 100 so that the slab 100 moves back and forth repeatedly inside the first induction heating slab heater 20. When the surface temperature measured by the thermometer 201 inside the first heating device reaches a predetermined temperature or a predetermined time, the control device 90 completes the heating in the first induction heating slab heater 20 and transports the slab 100 out of the first induction heating slab heater 20, thereby allowing the slab 100 to be heated more uniformly in the rolling direction.

[0175] The apparatus further includes a thermometer 201 in the first heating device that is provided in the first heating device and that measures the temperature of the slab 100, and a slab width end heater 121 that is provided on the inlet side of the first induction heating slab heater 20. The control device 90 heats the width end of the slab 100 while the slab 100 is passing through the slab width end heater 121, and when the rear end of the slab 100 enters the first induction heating slab heater 20, controls the conveying direction of the slab 100 so that the slab 100 repeatedly reciprocates inside the first induction heating slab heater 20. By switching the direction and completing the heating in the first induction heating slab heater 20 and transporting the slab 100 out of the first induction heating slab heater 20 when the surface temperature measured by the thermometer 201 in the first heating device reaches a predetermined temperature or reaches a predetermined time, the slab width end heater 121 can compensate in advance for the lack of heating at the width end of the slab 100 caused by heating with the entire slab heater 125, and the heating of the entire cross section including the width end of the slab 100 can be adjusted during the entire heating.

[0176] The first heating device further includes a thermometer 201 inside the first heating device that measures the temperature of the slab 100, and a slab width end heater 122 provided on the outlet side of the first induction heating slab heater 20. The control device 90 switches the transport direction of the slab 100 so that the slab 100 repeatedly moves back and forth inside the first induction heating slab heater 20 until the surface temperature measured by the thermometer 201 inside the first heating device reaches a predetermined temperature or until a predetermined time has passed. When the surface temperature measured by the thermometer 201 inside the first heating device reaches the predetermined temperature or until the predetermined time has passed, the slab 100 is transported to the slab width end heater 122 provided on the outlet side of the first induction heating slab heater 20 to heat the width end of the slab 100. This allows the width end of the slab 100 to be heated after the entire slab has been heated, making it possible to heat the width end of the slab 100 with high accuracy.

[0177] <Others> The present invention is not limited to the above-described embodiments, and various modifications and applications are possible. The above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those having all of the described configurations.

[0178] For example, the slab transport device for transporting slabs 100 between rolling lines is shown in the figure as having the slab 100 move laterally, but other methods are also included in the present invention, such as a method of transporting the slab by rotating the transport table at any angle, or a method of transporting the slab using table rollers 130 after rotating it on a turntable. Furthermore, the present invention also includes a configuration in which a heat retention device is provided on the transport device or the rotating transport table to prevent the slab from cooling during transport. Furthermore, the present invention also includes a configuration in which the slab width end heater and the entire slab heater of the second heating device have the same configuration as the first heating device.

[0179] Furthermore, although the continuous casting machine 12 has been described as having two strands, the scope of the present invention also includes a single strand or a greater number of strands, such as by adding an additional continuous casting machine. If the production volume of the continuous casting machine 12 increases, the capacity of the first induction slab heater 20 and the second induction slab heater 22 may be increased in accordance with the production volume, or the number of induction slab heaters may be increased, all of which are within the scope of the present invention.

[0180] DESCRIPTION OF SYMBOLS 1, 1A... Rolling equipment 10... Ladle turret 12... Continuous casting machine 14... Torch cutter 20... First induction heating slab heater (induction heating device) 22... Second induction heating slab heater (induction heating device) 30... First heat retention device (heat retention device) 32... Second heat retention device (heat retention device) 34... Third heat retention device (heat retention device) 40... First slab transfer device (first transfer device) 42... Second slab transfer device (second transfer device) 44... Third slab transfer device (third transfer device) 46... Fourth slab transfer device (fourth transfer device) 48... Continuous casting machine outlet slab transfer device 50... Slab storage location 60... Scale breaker 70... Roughing mill 75... Finishing rolling mill train 80... Run-out table 85... Down coiler 90... Control device 100... Slab 100A... Wide slab 100B... Narrow slab 101... First slab 102... Second slab 103... Third slab 104... Fourth slab 105... Fifth slab 110... Side guide 115... Side guide inside the device 120... Slab width end heater (width end heater) 121... Slab width end heater (inlet side width end heater) 122... Slab width end heater (exit side width end heater) 125... Overall slab heater (overall heater) 130... Table roller 145... Reheating furnace 201... Thermometer inside first heating device 202... Thermometer on the inlet side of first heating device 203... Thermometer inside second heating device 205... Storage location thermometer 301... Transport table 302... Transport table 304... Transport table

Claims

1. A heating device for heating a steel slab cast by a continuous casting machine, a first heating device provided in a rolling line between the continuous casting machine and the roughing mill; A second heating device provided in a heating line different from the rolling line; a first conveying device configured to move the slab between an outlet side of the slab in the rolling line of the first heating device and an inlet side of the slab in the heating line of the second heating device; a second conveying device configured to move the slab between an inlet side of the slab in the rolling line of the first heating device and an outlet side of the slab in the heating line of the second heating device, The first heating device and the second heating device have induction heating devices. Heating device.

2. The temperature raising device according to claim 1, The first heating device is provided on the delivery side of the slab in the rolling line of the induction heating device, and further includes a heat retention device that uses the heat retained in the slab as a heat source. Heating device.

3. The temperature raising device according to claim 1, The second heating device is provided on at least one of the inlet side and the outlet side of the slab in the heating line of the induction heating device, and further includes a heat retention device that uses the heat retained in the slab as a heat source. Heating device.

4. The temperature raising device according to claim 1, The system further includes at least one of a third transport device configured to be able to move the slab between a storage location for storing the slab and an inlet side of the slab in the heating line of the second heating device, and a fourth transport device configured to be able to move the slab between the storage location and an outlet side of the slab in the heating line of the second heating device. Heating device.

5. The temperature raising device according to any one of claims 1 to 4, a thermometer provided in the first heating device and configured to measure the temperature of the slab; a control device that determines whether to transport the slab to the roughing mill or the second heating device based on the temperature of the slab measured by the thermometer in the first heating device and switches the transport direction of the slab. Heating device.

6. The temperature raising device according to any one of claims 1 to 4, the second heating device includes a thermometer in the second heating device that measures the temperature of the slab, and a heat retention device that is provided on at least one of an inlet side or an outlet side of the slab in the heating line of the induction heating device and uses the retained heat of the slab as a heat source; The rolling mill further includes a control device that determines the number of times the induction heating device and the heat retention device are used and the length of time the slab is in the second heating device based on the temperature measured by the thermometer in the second heating device and the rolling status in the rolling line, and switches the conveying direction of the slab. Heating device.

7. The temperature raising device according to claim 1 or 2, the second heating device includes a thermometer in the second heating device that measures the temperature of the slab, and a heat retention device that is provided on at least one of an inlet side or an outlet side of the slab in the heating line of the induction heating device and uses the retained heat of the slab as a heat source; a storage location thermometer provided in a storage location where the slabs are stored and measuring the temperature of the slabs; The apparatus further includes a control device that determines the number of times the induction heating device and the heat retention device of the slab are used and the residence time of the slab in the second heating device based on the temperature of the slab measured by the thermometer in the second heating device, the temperature of the slab at the storage location measured by the thermometer in the storage location, and the rolling status at the rolling line, and switches the conveying direction of the slab. Heating device.

8. The temperature raising device according to any one of claims 1 to 4, the second heating device is provided on at least one of an inlet side and an outlet side of the slab in the heating line of the induction heating device, and includes a heat retention device that uses the retained heat of the slab as a heat source; The apparatus further includes a control device that controls the conveyance of the slab so that a different slab is heated by the induction heating device when the slab is kept warm by the heat retention device. Heating device.

9. The temperature raising device according to any one of claims 1 to 4, the induction heating device has at least one whole heater that heats a cross section of the slab, or at least one width end heater that heats an end of the slab in a width direction and at least one whole heater that heats the cross section of the slab, a first heating device inlet side thermometer provided on an inlet side of the slab in the rolling line of the first heating device and configured to measure a surface temperature of the slab; a control device that adjusts the output of the width end heater or the entire heater based on the temperature difference between the front end temperature and the rear end temperature of the slab measured by the inlet side thermometer of the first heating device and the conveying speed of the slab. Heating device.

10. The temperature raising device according to claim 9, a thermometer provided in the first heating device for measuring the temperature of the slab; The width edge heaters and the overall heaters are arranged alternately, The control device When the rear end of the slab enters the induction heating device, the conveying direction of the slab is switched so that the slab repeatedly reciprocates inside the induction heating device; When the surface temperature measured by the thermometer in the first heating device reaches a preset temperature or reaches a preset time, the heating in the induction heating device is completed and the slab is transported out of the induction heating device. Heating device.

11. The temperature raising device according to claim 9, a thermometer provided in the first heating device and configured to measure the temperature of the slab; An inlet-side width end heater provided on the inlet side of the induction heating device, The control device heating the width end portions of the slab while the slab is passing through the inlet-side width end heater, and when the rear end of the slab enters the induction heating device, switching the conveying direction of the slab so that the slab repeatedly reciprocates inside the induction heating device; When the surface temperature measured by the thermometer in the first heating device reaches a preset temperature or reaches a preset time, the heating in the induction heating device is completed and the slab is transported out of the induction heating device. Heating device.

12. The temperature raising device according to claim 9, a thermometer provided in the first heating device and configured to measure the temperature of the slab; An outlet-side width end heater provided on the outlet side of the induction heating device, The control device switching the conveying direction of the slab so that the slab repeatedly reciprocates within the induction heating device until the surface temperature measured by the thermometer in the first heating device reaches a predetermined temperature or reaches a predetermined time; When the surface temperature measured by the thermometer in the first heating device reaches a preset temperature or reaches a preset time, the slab is transported to the outlet-side width end heater to heat the width end of the slab. Heating device.

13. the continuous casting machine; The temperature raising device according to any one of claims 1 to 4, The roughing mill is provided Rolling equipment.

14. A method for heating the slab using the heating device according to any one of claims 1 to 4, comprising: The temperature of the slab is increased by induction heating in the rolling line, The temperature of the slab is increased by induction heating in the temperature increasing line, The slab is moved between a post-heating side of the slab in the rolling line and a pre-heating side of the slab in the heating line; The slab is moved between a pre-heating side of the slab in the rolling line and a post-heating side of the slab in the heating line. Heating method.

15. A method for heating the slab using the heating device according to any one of claims 1 to 4, comprising: a first step of heating the slab by induction heating in the rolling line and then transporting the slab to the roughing mill; a second step of transporting different cast pieces to the heating line by the second transport device, heating the different cast pieces by induction heating in the heating line, and then transporting them to the rolling line by the first transport device, which are alternately performed. Heating method.