JPH0538515A - Method and device for forced cooling for thick steel plate - Google Patents

Abstract

PURPOSE:To offer the method and the device for forced cooling for a thick steel plate by executing acceleration and forced cooling with respect to a thick steel plate of a high temperature rolled by a hot rolling mill by on-line without generating a distortion. CONSTITUTION:The forced cooling device is positioned in the upper part and the lower part of a thick steel plate S of a high temperature moving between the upper roll 2 and the lower roll 3 and provided with a cooling injection nozzle 1, and in this forced cooling device for a thick steel plate, pressing mechanisms 4 are provided, the upper roll 2 being ascendable/descendable, and the lower roll 3 are placed zigzag, and also, pinch rolls 5, 6 are provided as tension adding mechanisms on the upstream and the downstream sides of said forced cooling device. By using said device, forced cooling and straightening of a thick steel plate can be executed enough.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for forcibly cooling a thick steel plate hot rolled by a hot rolling mill for accelerating and forcibly cooling it online without causing distortion.

[0002]

2. Description of the Related Art In the production of thick steel plates, the method of forced cooling using an on-line forced cooling device is high strength,
In order to obtain a thick steel sheet with high toughness and weld crack resistance,
It is indispensable.

However, since this forced cooling device is generally arranged after the hot rolling mill to cool the thick steel plate after hot rolling with water, uneven cooling rate is unavoidable, and strain or residual stress is generated. Outbreak is a big problem.

As a method for reducing or eliminating this residual stress, the following methods have been conventionally known. Restricting the cooling conditions; by restricting the upper limit and the lower limit of the cooling rate and the cooling stop temperature, the strain and the residual stress are reduced to a range that does not adversely affect the practical use. Performing tempering; this is to remove strain and residual stress by utilizing the creep phenomenon by tempering heating to a temperature of 550 ° C. or higher. Correcting; a method of removing the residual stress caused by rolling by a hot leveler immediately after rolling (JP-A-48-46554).

Further, a method has been proposed in which water is cooled immediately after rolling and then strain is removed by a hot leveler.
Further, as a new method different from the above, it has been proposed to apply a leveler during forced cooling (JP-A-54-4212 and JP-A-61-231124).

[0006]

However, the above-mentioned technique has the following problems.

Regarding the method of regulating the cooling condition,
It sacrifices the strength increase effect of forced cooling,
There are inherent problems.

Regarding the means for performing the tempering process, a heat treatment step is required, which causes an increase in manufacturing cost.
Further, the tempering treatment has a drawback that the strength is lowered.

[0009] As one of means for correcting, Japanese Patent Laid-Open No. 4
According to the technique disclosed in Japanese Patent Laid-Open No. 8-46554, it is difficult to make a steel plate uniform even if the steel plate entering the cooling device has no strain or residual stress, and it is difficult to remove the strain by water cooling. Have difficulty.

Further, the method of removing the strain by water cooling immediately after rolling and then by a hot leveler is such that the strain of rolling and the strain of water cooling are superposed and the deformation resistance of the material increases, so that the hot leveler is used for straightening. To do that, you need a super powerful straightening machine.

The method using the device disclosed in Japanese Patent Laid-Open No. 54-4112 is to apply a leveler during forced cooling, but the effect is not sufficient.

That is, the cooling rate has unevenness in the plate thickness, the plate width, and the longitudinal direction, respectively, which causes strain and residual stress. In this device and method, although a large warp in the plate longitudinal direction due to the uneven cooling rate in the plate thickness direction, a warp in the plate width direction, and an uneven distribution of residual stress in the plate thickness direction can be corrected,
The main component of the strain caused by the nonuniformity of the plate width and the cooling rate in the longitudinal direction is the nonuniform strain in the plate longitudinal direction (so-called shape disorder).
Therefore, non-uniform residual stress in the plate longitudinal direction cannot be corrected with these devices.

The technique disclosed in Japanese Patent Laid-Open No. 61-23112 is intended to improve the non-uniform cooling as described above, but it is difficult to control the amount of cooling water flowing in the plate width direction.
In practice, it is difficult to sufficiently correct the uneven cooling.

The present invention is intended to solve the above problems, and in principle, quenching is performed while correcting distortion, but a thick steel plate capable of uniformly cooling in the plate width direction. It is an object of the present invention to provide a forced cooling method and apparatus therefor.

[0015]

In order to achieve the above object, the present invention provides a method for forcibly cooling a thick steel plate by a forced cooling device equipped with upper and lower rolls and a cooling jet nozzle, wherein the thick steel plate is cooled. However, the method for forced cooling of a thick steel plate is characterized by repeatedly bending and simultaneously applying tension to the thick steel plate.

Further, as an apparatus suitable for performing the above method,
The present invention is a forced cooling device having cooling jet nozzles positioned above and below a high-temperature thick steel plate that moves between upper and lower rolls, and includes a pressing mechanism and staggers an upper roll and a lower roll that can be raised and lowered. And a tension applying mechanism on the upstream and downstream sides of the forced cooling device.

In the apparatus of the present invention, it is necessary to provide a pressing mechanism and arrange the upper roll and the lower roll which can be moved up and down in a staggered manner. By these, the high temperature thick steel plate moving between the upper and lower rolls can be accurately and repeatedly bent. Furthermore, in addition to the above, the device of the present invention requires the provision of a tensioning mechanism on the upstream and downstream sides of the forced cooling device. High flatness can be imparted to high-temperature thick steel plates that move between the upper and lower rolls.

That is, since the thick steel sheet is repeatedly bent and simultaneously applied with tension, even if there is uneven cooling, the deformation resistance of the material is low, so that it can be effectively corrected with a small amount of power, and Since the correction is performed at the time when the strain is generated, it is possible to prevent the promotion of the non-uniform cooling due to the generation of the strain.

[0019]

Embodiments of the present invention will be shown below with reference to the drawings. FIG. 1 is a diagram showing an embodiment of the device of the present invention, and FIG. 2 is a diagram showing the essential parts of the present invention. In the figure, 1 is a cooling jet nozzle, 2 is an upper roll, 3 is a lower roll, 4 is a pressing mechanism, and 5 and 6 are pinch rolls for tension application.

The forced cooling device of the present invention comprises cooling jet nozzles 1 located above and below a high temperature steel material S moving between an upper roll 2 and a lower roll 3, and a pressing mechanism 4 is provided. In addition, the upper roll 2 and the lower roll 3 which can be moved up and down are arranged in a staggered manner, and the pinch rolls 5 and 6 as a tension applying mechanism are provided on the upstream and downstream sides of the forced cooling device.

The forced cooling device of the present invention is installed on the downstream side of the hot rolling mill 7, and the high temperature steel material S exiting from the hot rolling mill 7 is installed.
Is moved by the upper rolls 2 and the lower rolls 3 arranged in a staggered manner while being cooled by the cooling water sprayed from the cooling spray nozzles 1 in a plurality of rows, and repeatedly bent between them, and at the same time, Tension is applied by changing the peripheral speeds of the pinch rolls 5 and 6. Since the pressing mechanism 4 is provided and the upper roll 2 and the lower roll that can be raised and lowered are arranged in a zigzag manner, it has the same function as a so-called roller leveler.

That is, the upper roll is supported by bearings so that the pressing force can be applied to the thick steel plate, the bearings are fixed, and an elevating mechanism is provided on the housing itself. It is designed so that it can freely contact the steel plate. The raising and lowering may be simultaneously movable as described above, or may be individually movable for each roll. In this case, in order to effectively correct the shape, it is possible to provide a support roll capable of controlling the axial deflection of the roll.

The tensioning pinch rolls 5 and 6 generate tension by frictional force while rotating in synchronization with the plate speed. In the above embodiment, the pinch rolls 5 and 6 were provided on the upstream and downstream sides of the forced cooling device as tension applying mechanisms to apply tension to the thick steel plate, but the method of the present invention is not limited to this.

Instead of the tensioning pinch rolls 5 and 6, the upper roll 2 and the lower roll 3 may be provided with a tensioning mechanism. Upper roll 2 and lower roll 3 arranged continuously
It is possible to apply a tension to a thick steel plate moving between them by providing a driving mechanism as a tension applying mechanism for each of the upper roll 2 and the lower roll 3 which are paired with each other and providing a pair of them. Also, by arranging a plurality of forced cooling devices and installing a tensioning pinch roll between them,
Tension can be applied to the thick steel plate passing through each forced cooling device.

FIG. 3 shows a state where the plate shape is corrected by the method of the present invention. In FIG. 3, a steel plate S having a defective shape is formed.
By holding down multiple upper and lower rolls,
The thick steel plate goes in a direction in which the lengths thereof are aligned in the longitudinal direction, and a compressive force acts on the portion having a distorted shape, that is, the compression portion 8, and a tensile force acts on the other portion, that is, the tension portion 9.

If bending is performed in this state, stress distribution in the plate thickness direction is added. And the compression part 11 and the tension part 12
Cause At this time, when tension is applied, the plate surface portion 10 of the portion having a short elongation reaches the plastic region, this portion is stretched, the lengths in the plate longitudinal direction are aligned, and the shape is corrected. The elastic range is shown between the dotted lines in the figure.

Further, in the forced cooling method of the present invention, in addition to the above-described forced cooling method of forced cooling, high-temperature thick steel plates rolled by a hot rolling mill are used in the present invention one by one. It is also possible to adopt a simultaneous simultaneous forced cooling method in which water is sprayed onto the entire surface of the thick steel plate to cool it by introducing it into a forced cooling device. In the case of the simultaneous forced cooling method, the rolls are reciprocated so that the forced cooling and the correction are performed simultaneously.

As described above, by using the forced cooling method and the apparatus thereof according to the present invention, it is possible to reduce the turbulence of the shape of the thick steel plate and the unevenness of the residual stress, which have been inevitable until now.

The results of the experiment in which the thick steel plate was forcibly cooled using the apparatus shown in FIG. 1 will be described in detail. Here, the thick steel plate shown in Table 1 is forcibly cooled from 900 ° C to 300 ° C,
The shape was investigated. The specifications of the roll group at this time are shown in Table 2, and the operating conditions thereof are shown in Table 3.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

Table 4 shows the effect of the present invention. Here, the effect is expressed by the steepness of the auricular wave of the thick steel plate that is usually performed. As a comparison, Comparative Example (1) uses a conventional cooling device that moves while moving on a lower roll, and Comparative Example (2) shows a downstream side of the cooling device of Comparative Example (1). In the case of using the apparatus combined with the 400 ° C. hot leveler arranged in the above, in Comparative Example (3), only the leveler was applied in the forced cooling apparatus. As is clear from the experimental results shown in Table 4, the effect of the present invention was excellent.

[0034]

[Table 4]

[0035]

EFFECTS OF THE INVENTION By using the method of the present invention and the cooling apparatus therefor, the thick steel plate can be cooled and sufficiently straightened at the same time. It is an invention that has an extremely large effect.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a main part of the present invention.

FIG. 3 is a diagram showing a state of the shape of a thick steel plate when the present invention is used.

[Explanation of symbols]

 1 Cooling injection nozzle 2 Upper roll 3 Lower roll 4 Pressing mechanism 5, 6 Pinch roll for applying tension

Claims (2)

[Claims] 1. A method for forcibly cooling a thick steel sheet by a forced cooling device comprising upper and lower rolls and a cooling jet nozzle,
A method for forcibly cooling a thick steel sheet, which comprises repeatedly bending while simultaneously cooling the thick steel sheet, and simultaneously applying tension to the thick steel sheet. 2. A forced cooling device having cooling jet nozzles located above and below a high-temperature thick steel plate that moves between upper and lower rolls, the upper roll being equipped with a pressing mechanism, and the lower roll being movable up and down. And a tension applying mechanism provided on the upstream and downstream sides of the forced cooling device.