JP2001025810A - Device for working and heat-treating thick steel plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a thick steel plate whose residual stress is lower at high efficiency in a device for working/heat-treating the thick steel plate without necessitating a wide space in order to remove the residual stress generated on the thick steel plate which is rolled with a hot rolling mill and, next, applied acceleration cooling with a cooling system and annealing for removing the residual stress is executed by sufficient heat insulating time. SOLUTION: In the device for working/heat-treating the thick steel plate which is provided with, on the outlet side of the rolling mill 1, the cooling system 2 for acceleratingly cooling the steel plate and heat insulating device 4 for executing the annealing for removing the residual stress to the steel plate cooled acceleratingly, the heat insulating device 4 is shifted and arranged along a rolling line by the side of the line. In the heat insulating device 4, a transporting mechanism for tranferring the steel plate in a direction orthogonally crossed with the rolling line is provided and, in the inlet side of the heat insulating device 4, a hot cutter 3 for cutting the thick steel plate into a prescribed size is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermomechanical processing apparatus for a steel plate for removing residual stress generated in a steel plate rolled by a hot rolling mill and then accelerated and cooled by a cooling device.

[0002]

2. Description of the Related Art A steel plate is manufactured by rolling a slab heated to a predetermined temperature in a heating furnace by a hot rolling mill, cooling the slab to room temperature, and cutting it to a predetermined size. In recent years, in order to increase the strength and toughness of thick steel plates, a cooling device is provided on the outlet side of the hot rolling mill, and accelerated cooling of the thick steel plate rolled by the hot rolling mill is performed. .
Such accelerated cooling by the cooling device makes it possible to reduce the alloying elements of the steel sheet, and to produce a thick steel sheet having excellent weldability and high strength and high toughness.

However, since the temperature of the thick steel plate after being accelerated and cooled by the cooling device is not always uniform, the steel plate is liable to undergo shape deterioration such as deformation. For this purpose, the steel plate after accelerated cooling is passed through a straightening machine or the like to correct its shape.However, in the shape correction by a straightening machine or the like, even if the shape of the steel plate can be improved. However, the residual stress caused by the thermal stress inside the steel sheet cannot be eliminated.

[0004] If residual stress is present inside the steel sheet, when the steel sheet is cut, the residual stress near the cut portion is released, but the steel sheet is deformed. The deformation of the steel sheet is particularly remarkable when the steel sheet is cut, and the cut steel sheet is bent laterally (bending in the sheet width direction, camber).

[0005] Therefore, attempts have been made to release the residual stress by subjecting the thick steel plate after accelerated cooling to stress relief annealing. Various methods for stress relief annealing of steel sheets after accelerated cooling have been studied in the past, and one of them is a method of performing annealing using an existing tempering furnace (hereinafter referred to as prior art). Technology 1) is known. Tempering furnaces are usually used to temper steel sheets after quenching, but stress relief annealing is generally performed at a temperature equal to or lower than the tempering temperature. A furnace can be utilized for residual stress relief annealing.

[0006] As a means for removing residual stress from a thick steel plate, there is known a method in which a slow cooling pit is used with a slow cooling cover (hereinafter referred to as prior art 2). In this method, a high-temperature steel plate immediately after rolling is stacked in a pit with a crane or the like, is annealed by covering it with a slow cooling cover and keeping it warm, and after a predetermined time has elapsed, removing the steel plate from the pit. Done.

[0007] Further, as means for fixing the slow cooling cover and gradually cooling the thick steel plate while transferring the same, annealing is performed.
For example, Japanese Patent Application Laid-Open No. 53-117609 (hereinafter referred to as Prior Art 3) discloses that the floor surface of a cooling floor is made of insulating brick.
There is disclosed a cooling floor for slow cooling of a thick steel plate having a structure in which a heat insulating ceiling is provided on an upper portion thereof. Inside the cooling floor, a carrier chain for transporting a steel sheet is installed, and at the front and rear entrances, a steel sheet curtain or an air curtain for preventing invasion of outside air is provided.

Japanese Patent Laid-Open Publication No. Hei 6-254615 discloses that an extension of a pass line on the outlet side of a cooling device is provided.
There is disclosed a technology (hereinafter, referred to as prior art 4) in which a heat retaining device is incorporated, a rolled steel sheet is cooled by a cooling device, and then the temperature is maintained at a constant temperature by the heat retaining device.

FIG. 5 is a schematic layout diagram of the prior art 4.
As shown in FIG. 5, along the rolling line, a rolling mill 1, a hot leveler 6, a cooling device 2 and a heat retaining device 4 are arranged in this order, and a temperature between the cooling device 2 and the heat retaining device 4 is set. A total of seven are provided. After the steel plate A rolled by the rolling mill 1 is cooled to a predetermined temperature by the cooling device 2, the steel plate A is charged into the heat retaining device 4, where the steel plate is kept at the predetermined temperature in the heat retaining device 4 and the temperature distribution is uniform. It is trying to make it.

[0010]

The method using the heat treatment furnace of the prior art 1 is satisfactory in terms of the uniformity and accuracy of the temperature of the thick steel plate, but the consistency between the rolling pitch and the processing time is not sufficient. There's a problem. That is, in recent years, the rolling pitch (time interval) of a thick steel plate in a rolling mill has been reduced to about 2.5 to 3 minutes in order to improve the rolling capacity of the rolling mill. On the other hand, about 10 minutes are required for the residual stress relief annealing performed in the heat treatment furnace. Since only one steel plate can be processed simultaneously in the normal-capacity tempering furnace, the processing time in the tempering furnace is limited until the next steel plate comes, that is, within the rolling pitch, Processing time is significantly short.

Another problem is that a heat treatment furnace installed for the purpose of material control is used for the purpose of removing stress, and it is originally necessary to manufacture a product whose material should be controlled in the heat treatment furnace. It becomes impossible, and loss of opportunity occurs, and it is not preferable from the viewpoint of process operation. In addition, it is necessary to transport the steel plate after being cooled in the cooling device to a place where the tempering furnace is installed, but the tempering furnace is usually installed in a different mill from the rolling mill. Therefore, a transport operation of transporting the cooled steel plate to the tempering furnace is required.

In the case of the method using the gradual cooling cover of the prior art 2, it is necessary to transport the cooled thick steel plate to the cooling floor provided with the gradual cooling cover. Further, in the case of this method, since a plurality of thick steel plates are stacked and kept warm, the heat retention time for each steel plate becomes uneven. In other words, the heat retention time of the thick steel plate after cooling is longer in the lower stage, that is, approximately one rolling pitch is longer each time the steel plate is lower by one stage, so that the heat retention time of the lower steel plate becomes too long. In addition, in the case of this method, it is necessary to carry the slow cooling cover by a crane or the like to open and close the slow cooling cover. For this carrying work, the slow cooling cover is temporarily placed near the cooling floor. It is necessary to secure a space for it.

In the case of the cooling floor for slow cooling according to the prior art 3, the work of transporting the slow cooling cover as in the prior art 2 becomes unnecessary, but merely the steel plate is retained in the slow cooling box. In this case, the steel plate can be maintained only at a temperature equal to or lower than the cooling stop temperature. Therefore, when a steel sheet having a different thickness or cooling stop temperature is inserted, it is difficult to control the holding temperature and the holding time of the steel sheet to desired values.

In the case of the method of prior art 4 in which the rolled thick steel plate is cooled and then kept in a heat retaining furnace, the heat retaining device is provided on an extension of the outlet side of the cooling device. It is not necessary to convey by a crane or the like, but there is a problem in the consistency between the rolling pitch and the processing time as in the case of using the tempering furnace. This problem can be solved by increasing the capacity of the heat retaining device so that a plurality of thick steel plates can be processed at the same time.
m, the length of the heat retention device should be at least 40-50m
Is required, and in order to process a plurality of thick steel plates, it is necessary to increase the length of the heat retaining device to several hundred meters.
Such a thing is difficult on a layout in a normal rolling mill.

Accordingly, an object of the present invention is to solve the above-mentioned problems, and requires a large amount of space to remove the residual stress generated in a steel plate rolled by a hot rolling mill and then accelerated and cooled by a cooling device. It is an object of the present invention to provide a thick steel plate thermomechanical treatment apparatus capable of performing residual stress removal annealing with a sufficient heat retention time and thereby producing a steel plate having a low residual stress with high efficiency.

[0016]

The invention as set forth in claim 1 is characterized in that a cooling device for accelerating cooling of a steel sheet is provided along a rolling line on an outlet side of a rolling mill, and a cooling device for accelerating cooling of the steel sheet is provided. In order to perform the residual stress removal annealing, a heat retaining device having a heating mechanism is provided, in a thermomechanical heat treatment device for a thick steel plate, the heat retaining device is displaced to the side along the rolling line. , Inside the heat retaining device,
A transport mechanism for transporting the steel sheet in a direction orthogonal to the rolling line is provided, and a hot-cutting machine for cutting a thick steel sheet to a predetermined size is provided on an entrance side of the heat retaining device. Is characterized by the fact that

According to a second aspect of the present invention, in the apparatus according to the first aspect, the transport mechanisms provided in the heat retaining device are two rows of parallel transport mechanisms each of which can be driven independently. It is characterized by having

According to a third aspect of the present invention, in the apparatus according to the first aspect, the transport mechanism provided in the heat retaining device transports the steel sheet in a direction orthogonal to the rolling line; And a mechanism for transferring the steel sheet in a direction parallel to the rolling line.

According to a fourth aspect of the present invention, in the apparatus according to any one of the first to third aspects, the heating mechanism provided in the heat retaining device supplies combustion air to the burner through the heat storage body and burns the combustion air from the burner. It is characterized by being composed of a regenerative alternating combustion burner system that discharges gas.

In the present invention, a hot-cutting machine is arranged on the inlet side of the heat retaining device, and the steel plate rolled by the rolling mill is cut by the hot-cutting machine to a length close to the length of the final product. After that, it is charged into the heat retention device. Therefore, the furnace width (length in the rolling line direction) of the heat retaining device can be reduced, and compact equipment can be provided.

[0021] The heat retaining device is arranged along the rolling line of the thick steel plate and shifted to the lateral side thereof. In the heat retaining device, a steel plate conveying mechanism for transporting the steel sheet in a direction perpendicular to the rolling line is provided. Is provided. Therefore, while transporting a plurality of thick steel plates in a direction orthogonal to the rolling line by the transport mechanism, it is possible to keep the temperature of the steel plates continuously. Also,
By making the furnace length of the heat retention device (the length in the direction of transport of the steel sheet perpendicular to the rolling line) several times the width of the thick steel plate, the heat retention time can be extended to several times the rolling pitch, and the heat retention time can be extended. Is no longer limited by the rolling pitch,
It does not hinder rolling efficiency.

Further, as described above, since the heat retaining device is displaced laterally along the rolling line as described above, a thick steel plate which does not require heat treatment can be directly sent to a hot leveler and a cooling floor. . Therefore, the rolling efficiency of a thick steel plate that does not require heat treatment is not hindered.

If the transport mechanism provided in the heat retaining device is a two-row parallel mechanism that can be driven independently, in the case of a thick steel plate having a long plate length, this is transferred to the heat retaining device one by one. In the case of thick steel plates with short plate length, two steel plates can be charged and extracted at the same time, so that the equipment capacity is maximized and the processing efficiency of the steel plates Can be improved.

Further, if the transport mechanism provided in the heat retaining device is a mechanism capable of transporting a steel sheet in two directions, that is, a direction perpendicular to the rolling line and a direction parallel to the rolling line, the thickness and the cooling stop can be improved. A plurality of thick steel plates having different temperatures are successively charged into the heat retaining device, and a thin steel plate or a high-temperature stopped steel plate can be extracted from the middle of the device. Therefore, the heat retention time can be kept constant irrespective of the sheet thickness and the cooling stop temperature, whereby sufficient stress relief annealing can be performed regardless of the sheet thickness, the cooling stop temperature, and the rolling pitch of the steel sheet.

If a heat storage type alternating combustion burner system for supplying combustion air to the burner through a heat storage body and discharging combustion gas from the burner is installed as a heating mechanism of the heat retaining device, each zone divided in the transport direction can be provided. Furthermore, fine combustion control becomes possible, and even if steel plates having different thicknesses and cooling stop temperatures are continuously loaded, the holding temperature and the holding time of the steel plates can be kept constant.

Depending on the thickness and chemical composition of the steel plate, quenching and tempering can be performed by this method.

[0027]

Next, a thermomechanical processing apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a layout diagram showing a first embodiment of the apparatus of the present invention. As shown in the drawing, a cooling device 2, a hot cutting device 3, a heat retaining device 4, a transfer 5, and a hot leveler 6 are arranged on a discharge side of a hot rolling mill 1 in this order along a rolling line a. .

The cooling device 2 is a device that accelerates and cools a thick steel plate by water spray or jet flow, and may use a usual device such as a roller quench or a pressure quench. A shape straightening device such as a hot leveler may be installed between the hot rolling mill 1 and the cooling device 2.

The type of the hot cutting machine 3 is not particularly limited as long as it does not affect the rolling pitch, and an ordinary shearing machine can be used. The position of the hot cutting machine 3 is not limited to the outlet side of the cooling device 2 as shown in the figure, but may be provided between the hot rolling mill 1 and the cooling device 2.

The heat retaining device 4 is composed of a heat retaining furnace having a heating mechanism surrounded by a side wall made of a heat insulating material, and is arranged along the rolling line a so as to be shifted laterally therefrom. In the apparatus, for example, a transport mechanism including a walking beam, a hearth roll, and the like for transporting the thick steel plate A in a direction orthogonal to the rolling line a is provided. Insulation device 4
As the heating mechanism provided in the above, in addition to a combustion burner and an induction heating device, a heat storage type alternating combustion burner system that supplies combustion air to the burner and discharges combustion gas from the burner through a heat storage body is used. .

Furnace length of heat retaining device 4 (length in the direction of transport of steel sheet)
Needs to be a length that does not hinder the rolling pitch. In the example of FIG. 2A described later, the length may be determined so as to satisfy the following expression.

L> nWth / tr, where L: furnace length of the heat retaining device (m) n: number of divisions of the thick steel plate by the cutting machine W: width of the steel plate (m) th: heat retaining time + heating time (min) tr: Rolling pitch (min) A transfer 5 for returning the thick steel plate A maintained at a constant temperature by the heat retaining device 4 to the rolling line a is provided adjacent to the heat retaining device 4 in a direction orthogonal to the rolling line a. ing. In addition, a transfer line b parallel to the rolling line a for transferring the thick steel plate A maintained at a constant temperature in the heat retaining device 4 to the transfer 5 between the outlet side of the heat retaining device 4 and the entrance side of the transfer 5. Is provided.

FIG. 2 shows an example of an embodiment of the heat retaining device according to the present invention. In the apparatus shown in FIG. 2A, the thick steel plate A sent from the rolling line a to the heat retaining device 4 by a transfer mechanism (not shown) passes through the heat retaining device 4 at right angles to the rolling line a as indicated by an arrow by a transport mechanism. To a constant temperature by a heating mechanism provided in the heat retaining device 4 during that time, and then extracted from the heat retaining device 4,
Next, the transfer line b is moved by a moving mechanism (not shown), sent to a transfer 5 provided adjacent to the heat retaining device 4, returned to the rolling line a by the transfer 5 as indicated by an arrow, and transferred to the next step. Is done.

When the inside of the heat retaining device 4 is divided into a plurality of heat retaining zones, and when thick steel plates having different thicknesses and cooling stop temperatures are loaded, the heating capacity is controlled for each of the heat retaining zones to keep the temperature. I just need.

In the apparatus shown in FIG. 2 (b), the steel plate transport mechanism provided in the heat retaining device 4 is composed of two rows of parallel transport mechanisms which can be driven independently. If the transport mechanism is configured as described above, in the case of a thick steel plate A having a long plate length, it is possible to move the inside of the heat retaining device 4 by using two rows of transport mechanisms together and synchronously driving them. On the other hand, in the case of thick steel plate A having a short plate length, two thick steel plates
Each of them can be sent to the transport mechanism of the row, and can be moved together in the heat retaining device 4. Therefore, the capacity of the heat retaining device can be effectively used without waste, and the processing capacity can be improved.

In the apparatus shown in FIG.
A horizontal transfer mechanism is provided at the intermediate position of the transfer mechanism toward the intermediate portion of the transfer 5 adjacent to the heat retaining device 4. According to this apparatus, in the case of a thick steel plate having a large thickness or a low steel plate having a low cooling stop temperature, the thick steel plate A is transferred into the heat retaining device 4 by the transfer mechanism in the same manner as the device shown in FIG. Is transported over its entire length, and then returned to the rolling line a by the transfer 5 provided adjacent to the heat retaining device 4. On the other hand, in the case of a thin steel plate or a steel plate having a high cooling stop temperature, the thick steel plate A is transferred to an intermediate portion of the transfer 5 by a lateral transfer mechanism provided at an intermediate position of the heat retaining device 4, and is transferred to the intermediate transfer portion. From rolling line a
Is returned to. Therefore, it is not necessary to perform fine heating capacity control in the heat retaining device 4, and the heat retaining time of the steel plate can be kept constant regardless of the thickness of the thick steel plate and the cooling stop temperature.

The horizontal transfer mechanism provided at the intermediate position of the transfer mechanism of the heat retaining device 4 toward the intermediate portion of the transfer 5 adjacent to the heat retaining device 4 may be provided at any position in the middle of the transfer mechanism. The number is not limited to one and may be plural.

As described above, the heating mechanism of the heat retaining device 4 includes, in addition to the combustion burner and the induction heating device, a heat storage type for supplying combustion air to the burner and discharging combustion gas from the burner through a heat storage body. An alternating combustion burner system is used. When such a heat storage type alternating combustion burner system is used, when steel plates having different plate thicknesses and different cooling stop temperatures are continuously loaded, it is possible to perform fine burning for each steel plate.

The thick steel plate to be kept warm in the warming device 4 is as follows:
Since the temperature is relatively high and there is no need to heat from room temperature, the heating capacity can be greatly reduced as compared with the case where a conventional refining furnace is used. By providing a margin for the heating capacity, the outer surface of the thick steel plate can be rapidly heated, and a thermal stress opposite to the residual stress can be generated. By generating a thermal stress opposite to the residual stress on the steel sheet, that is, by performing up-quench,
The residual stress inside the final thick steel plate can be reduced.

FIG. 3 is a layout diagram showing a second embodiment of the apparatus of the present invention. As shown in the drawing, in this embodiment, a transfer 5 is provided at right angles to the rolling line a after the hot cutting machine 3 following the cooling device 2, and a heat retaining device 4 is provided adjacent to the transfer 5. Is provided, and a hot leveler 6 is provided subsequent to the heat retaining device 4, which is different from the device of the first embodiment.

According to the apparatus of the second embodiment, the thick steel plate A cut to a predetermined size by the hot cutting machine 3 is transferred by the transfer 5 in the direction perpendicular to the rolling line as shown by the arrow, and then , Is transferred to the heat retaining device 4 by moving the transport line b parallel to the rolling line, and is maintained at a constant temperature by the heating mechanism before being returned to the rolling line a by the heat retaining device 4. Hot straightened. Therefore, since the thick steel plate A maintained at a constant temperature in the heat retaining device 4 is hot-corrected in the hot leveler 6 without lowering its temperature, the shape correcting effect can be improved.

FIG. 4 is a layout diagram showing a third embodiment of the apparatus of the present invention. As shown in the drawings, in this embodiment, a hot cutting machine 3 is provided between the rolling mill 1 and the cooling device 2, and a hot leveler 6 is provided on a transport line b parallel to the rolling line. Is different from the device of the first embodiment.

The steel plate A which does not require the stress relief annealing is:
After being cut to a predetermined size by a hot cutting machine 3 provided on the exit side of the rolling mill 1, the material is accelerated and cooled in the cooling device 2, and is sent from the rolling line a to the conveying line b by the transfer 5, and is transferred to the conveying line b. After the shape is corrected by the provided hot leveler 6, it is transferred to the next step.

On the other hand, a thick steel plate A requiring stress relief annealing
After being cut to a predetermined size by a hot cutting machine 3 provided on the exit side of the rolling mill 1, it is accelerated and cooled in the cooling device 2 and then sent to the heat retaining device 4. Then, after the stress relief annealing is performed in the heat retaining device 4, the wafer is sent to the transport line b, further subjected to shape correction by the hot leveler 6 provided in the transport line b, and transported to the next step.

According to the above-described apparatus, the thick steel plate cooled by the cooling device 4 is subjected to stress relief annealing in the heat retaining device 4 and then immediately hot-corrected by the hot leveler 6. In addition to reducing the heating capacity, the hot straightening effect is also improved.

[0046]

EXAMPLE Using a device according to the first embodiment of the present invention shown in FIG. 1, a thick steel plate was subjected to thermomechanical treatment. That is, a slab heated to a predetermined temperature by a heating furnace (not shown) is subjected to a reverse hot rolling mill 1 to have a thickness of 20 mm and a width of 2.
Ten sheets were continuously rolled on a 5 m thick steel plate having a length of 30 m. The rolled steel plate is cooled to 800 ° C. in the cooling device 2.
After cooling to 550 ° C., the hot cutting machine 3
It was cut and divided into two thick steel plates having a length of 15 m, and this was inserted into a heat retaining device 4 having a width of 20 m and a depth of 30 m.

The heating system of the heat retaining device 4 is a regenerative type alternating combustion burner system, in which a roof burner is mounted on the upper surface of the heat retaining device 4, a side burner is mounted on the lower surface, and the heat retaining device 4 is moved in the direction of conveying the steel sheet. It is divided into seven zones, and independent combustion control can be performed for each zone.

The thick steel plate charged into the heat retaining device 4 is transported through the heat retaining device 4 at a speed of 2.2 mpm while the steel plate is kept at a speed of 2.2 mpm.
By holding at a temperature of 40 ° C. for 10 minutes, annealing for removing residual stress was performed. The rolling pitch at this time is:
5 minutes. The steel plate subjected to the residual stress removal annealing in the heat retaining device 4 was then subjected to shape correction in the hot leveler 5 and then cooled to room temperature in the cooling floor.

After the steel plate cooled to room temperature was cut into a width of 500 mm, the lateral bending (camber) generated in the steel plate was examined.
mm or less, and the residual stress existing in the steel plate was surely removed.

[0050]

As described above, according to the thermomechanical treatment apparatus of the present invention, a hot cutting machine is provided on the exit side of a rolling mill, and a rolled steel plate is cut to a length close to a final product. In addition, since the heat insulation device is inserted into the heat insulation device, the length of the heat insulation device can be reduced. In addition, the heat retaining device is provided with a transfer mechanism that moves in a direction perpendicular to the rolling line, and the thick steel plate is kept warm while being transferred by the transfer mechanism, so that the heat keeping time can be extended to several times the rolling pitch. Therefore, it is possible to sufficiently maintain the temperature of the thick steel plate without impairing the rolling efficiency.

Therefore, according to the apparatus of the present invention, the residual stress generated in the steel plate rolled by the hot rolling mill and then accelerated and cooled by the cooling device can be sufficiently maintained by a compact facility without requiring a large space. It can be removed in a short time, which brings about an industrially useful effect that a steel plate with low residual stress can be manufactured with high efficiency.

[Brief description of the drawings]

FIG. 1 is a layout diagram showing a first embodiment of the apparatus of the present invention.

FIG. 2 is a plan view showing an example of an embodiment of a heat retaining device according to the present invention.

FIG. 3 is a layout diagram showing a second embodiment of the apparatus of the present invention.

FIG. 4 is a layout diagram showing a third embodiment of the apparatus of the present invention.

FIG. 5 is a schematic layout diagram showing a conventional slow cooling method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rolling machine 2 Cooling device 3 Hot cutting machine 4 Heat retention device 5 Transfer 6 Hot leveler 7 Thermometer A Steel plate

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akio Fujibayashi 1-2-1, Marunouchi, Chiyoda-ku, Tokyo, Japan Inside Nihon Kokan Co., Ltd. (72) Inventor Satoshi Ueoka 1-2-1, Marunouchi, Chiyoda-ku, Tokyo, Japan Honko Co., Ltd.

Claims (4)

[Claims] 1. An output side of a rolling mill, along a rolling line,
A cooling device for accelerating cooling of the steel plate, and a heat retaining device having a heating mechanism for performing residual stress relief annealing on the accelerated cooled steel plate, The apparatus is arranged along the rolling line and shifted laterally along the rolling line, and a transfer mechanism for transferring the steel sheet in a direction orthogonal to the rolling line is provided in the heat retaining device. And a hot-cutting machine for cutting a thick steel plate to a predetermined dimension is provided on an entrance side of the heat retaining device, wherein the thermomechanical heat treatment apparatus for a thick steel plate is provided. 2. The apparatus according to claim 1, wherein the transport mechanism provided in the heat retaining device comprises two rows of parallel transport mechanisms that can be driven independently of each other. 3. The transport mechanism provided in the heat retaining device includes: a mechanism that transports the steel sheet in a direction orthogonal to the rolling line; and a mechanism that transports the steel sheet in a direction parallel to the rolling line. The device of claim 1, wherein the device comprises: 4. The heat storage type alternating combustion burner system according to claim 1, wherein the heating mechanism of the heat retention device is a heat storage type alternating combustion burner system that supplies combustion air to a burner through a heat storage body and discharges combustion gas from the burner. An apparatus according to any one of the preceding claims.