JPS63238911A - Method for rolling thick plate - Google Patents

Abstract

PURPOSE:To prevent thickness reduction in the plate biting end part by predicting a reducting amount of a work roll bender pressure at plate biting and correcting the bender pressure. CONSTITUTION:A draft schedule decided by a draft schedule calculation means 12 and a bender pressure correction amount decided by a bender pressure correction amount calculation means 13 are inputted to a draft schedule correction means 14. The draft schedule is corrected so that a bender pressure increased by the bender pressure correction amount from the bender pressure decided in the draft schedule is outputted for a prescribed period of time from a plate biting initiation. The bender pressure correction output is sent to an output device 10 to control respective bender pressures.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for rolling a thick plate, and particularly to prevention of reduction in plate thickness at the edge of the plate.

[Prior Art] Fig. 7 shows the direction in which the upper work roll 2 and the lower work roll 3 separate from each other (increase direction) when rolling the thick plate 1.
FIG. 2 is a schematic diagram showing a rolling mill equipped with work roll benders 4.5 that apply bending force Pa to the upper and lower work rolls 2.3 at both ends in the axial direction. Since the bending force PB can be increased, the ability to control the plate crown and plate flatness can be improved. In addition, in the figure, 6 is a backup roll.

In the rolling mill configured as described above, each pass rolling schedule in conventional thick plate rolling, that is, the rolling amount of each pass, the bending force P3 of work roll bender 4.5, etc., obtains a predetermined plate thickness and a good planar shape. The roll opening degree So (am) is determined based on the plate thickness h (
us), load P (Ton) and mill stiffness M (Ton
/i+m), the load P is the sum of the load P due to rolling down and the load increase 2P due to bending force PB, as shown in Figure 8, i.e. (Po+2PB). And this load P■P +2
This setting takes into consideration the fact that the mill housing will expand due to the reaction force of the PB.

[Problems to be Solved by the Invention] In the conventional rolling schedule setting method described above, the gap between the upper and lower chocks of the work roll opens due to the elongation of the mill housing 7 due to the sudden load rise when the plate is bitten, and the bending cylinder and the work roll chock are separated. A gap is created between the contact surfaces of the bender cylinder.

For this reason, as shown in Fig. 9, when the plate is bitten, ΔPB
This bender pressure attenuation amount Δ
There was a problem in that a reduction in plate thickness corresponding to PB occurred at the edge of the plate.

Furthermore, there is a problem in that a change in the ratio crown due to a change in the bender pressure, that is, generation of distortion, etc., occurs until the bender pressure that has attenuated at the time of biting is restored.

Furthermore, due to the difference in piping resistance etc. of each work roll bender 4, 5, the drive side bender pressure damping characteristic A as shown in FIG.
When a time difference Δt occurs between the bender pressure decay time t of B and the bender pressure decay time tV of the operating side bender pressure decay characteristic B, a difference occurs in the left and right roll openings of the upper and lower work rolls 2.3, and camber (board bending) occurs. ) occurred.

This invention was made to solve such problems, and the purpose is to propose a thick plate rolling method that can obtain a thick plate with a uniform thickness and shape from the time the plate is bitten. be.

[Means for Solving the Problems] The thick plate rolling method according to the present invention includes a rolling mill equipped with a work roll bender that applies a bending force to both axial ends of the work roll in a direction in which the upper and lower work rolls separate from each other. In plate rolling using a steel plate, the amount of work roll bender pressure attenuation due to elongation of the mill housing at the time of plate biting is predicted from the rolling schedule of each bus, and the amount of work roll bender pressure attenuation is calculated based on the predicted amount of work roll bender pressure attenuation. It is characterized by correcting the work roll bender pressure setting during loading.

[Function] In this invention, by reducing the amount of attenuation of the work roll bender pressure due to the elongation of the mill housing due to the sudden load rise when the board is caught, changes in the plate thickness and shape at the end of the board where the board is caught are prevented. do.

[Embodiment] FIG. 1 is a schematic diagram of a rolling mill according to an embodiment of the present invention, and in the figure, numerals 1 to 6 are exactly the same as the rolling mill shown in FIG. 7.

8 is an input device for inputting specifications such as target plate thickness, plate width, rolling load, etc.; 9 is an input device for inputting specifications input from input device 8, roll gap, bending force, shift amount, and thickness detector 1 during the previous pass;
10 is a calculation device 9 which determines the rolling schedule for each pass based on the rolling results such as plate thickness detected in step 1, and re-corrects the rolling schedule for the next pass and subsequent passes based on the rolling results of the previous pass between passes; This is an output device that outputs the roll gap, bend force, shift amount, etc. of each bus according to the determined reduction schedule.

As shown in FIG. 2, the calculation bag gIL9 includes a reduction schedule calculation means 12 and W for determining the reduction schedule of each bus.
The amount of bender pressure attenuation at the time of biting of the work roll benders 4 and 5 provided at both ends of the upper and lower work rolls 2.3 in the axial direction is predicted from the created rolling down schedule, and the bender pressure at the time of biting is corrected from this predicted value. It is provided with a bender pressure correction amount calculation means 13 for calculating the amount of bender pressure correction, and a reduction schedule correction means 14 for correcting the reduction schedule based on the calculated correction amount of the bender pressure.

The operation of rolling a thick plate using the rolling mill configured as described above will be described.

First, before rolling starts, the target thickness of plate 1 is set.

Specifications such as plate width 2 and rolling load are input from the input device 8 to the calculation device 9. Reduction schedule calculation means 12 of the calculation device 9
is the reduction schedule, that is, the amount of reduction, and the bender pressure PB based on the input conditions.

Roll opening degree S. etc., and sends the determined reduction schedule to the bender pressure correction amount calculation means 13.

The bender pressure correction amount calculation means 13 predicts and calculates the amount of attenuation of the bender pressure PB caused by the elongation of the mill housing due to the steep rise in load when the plate is bitten, based on the reduction schedule and the current thickness of the steel plate 1. A bender pressure correction amount ΔP at the time of biting is calculated from the bender pressure attenuation amount, and this bender pressure correction amount ΔP is sent to the reduction schedule correction means 14.

The reduction schedule correction means 14 inputs the reduction schedule determined by the reduction schedule calculation means 12 and the bender pressure correction amount ΔP calculated by the bender pressure correction amount calculation means 13, and creates the reduction schedule as shown in FIG. 3(b). The reduction schedule is corrected so that the bender pressure increased by the bender pressure correction amount ΔP from the bender pressure PB determined in is outputted for a predetermined time ΔT from the time of board biting, and this bender pressure correction output is sent to the output device 10, and each Control bender pressure. Incidentally, the time ΔT for correcting the bender pressure and the pressure correction amount ΔP are determined for each bender 4 and 5, taking into account the difference in pressure return characteristics determined by the piping resistance of each bender cylinder and the like.

Figure 3 (C) shows the bender pressure fluctuation when the bender pressure at the time of board biting is controlled by the bender pressure correction output corrected as above, and as shown in the figure, the bender pressure attenuation amount ΔPB at the time of board biting. was able to be significantly reduced. Furthermore, by optimizing the selection of the bender pressure attenuation amount ΔPB and the bender pressure correction time ΔT, the pressure return damping characteristics are made uniform, thereby preventing a difference between the drive side bender pressure damping special A and the operating side bender pressure damping characteristic B. be able to.
Also, between passes, the roll opening degree So for each pass.

Various results such as bender pressure P, shift amount, plate thickness, etc. are obtained, and the rolling schedule for the next pass and subsequent passes is corrected based on the various results, and rolling is performed by correcting the bender pressure at the time of plate biting in the same manner as above.

Figure 4 shows the change in thickness of the rolled thick plate 1 with respect to the longitudinal distance (mm) from the edge of the plate, and in the figure, C is the case where the bender pressure at the time of plate biting is corrected according to this embodiment. , D show the case of a conventional example in which no bender pressure correction is performed at the time of board biting.

As is clear from FIG. 4, this embodiment was able to significantly reduce the reduction in plate thickness at the end of the plate engagement compared to the conventional example.

In addition, in the above embodiment, the bender pressure P determined by the reduction schedule is used as the bender pressure correction output when the plate is bitten.
Although the case where the bender pressure correction amount ΔP is uniformly increased from a is shown, the fifth bender pressure correction output is
As shown in the figure, when the bender pressure correction amount ΔP is increased in accordance with the bender pressure attenuation amount after biting, and when the bender pressure correction amount ΔP is controlled to be decreased as the pressure is restored, or as shown in FIG. Even when the bender pressure correction amount ΔP is controlled to be gradually decreased after biting, the same effect as in the above embodiment can be achieved. @ [Effects of the Invention] As explained above, the present invention predicts the amount of attenuation of work roll bender pressure due to the elongation of the mill housing due to the steep rise in load when the plate is jammed, and reduces this amount of attenuation. Since the bender pressure at the time of board biting is corrected, it is possible to prevent a decrease in board thickness at the board biting end.

Further, by reducing the bender pressure attenuation amount when the plate is bitten, the bender pressure recovery time can be shortened, so that the change in the ratio crown due to the change in the bender pressure, that is, the distortion can be reduced.

Furthermore, by being able to reduce the difference between the left and right sides in terms of the bender pressure attenuation amount and the bender pressure return time, it is possible to prevent the occurrence of camber (board bending) without creating a difference in the left and right roll opening degrees.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a rolling mill according to an embodiment of the present invention;
Fig. 2 is a program diagram showing the arithmetic unit of the above embodiment, Fig. 3 is a characteristic diagram showing the bender pressure correction output and bender pressure fluctuation of the above embodiment, and Fig. 4 is a change in plate thickness with respect to the longitudinal distance of the plate. Characteristic diagram, Figure 5. FIG. 6 is a bender pressure correction output characteristic diagram according to other embodiments, FIG. 7 is a schematic diagram of a rolling mill equipped with a work roll bender that applies bender force in a direction in which upper and lower work rolls move away from each other, and FIG. 8 7 is a reaction force distribution diagram of the rolling mill shown in FIG. 7, and FIG. 9 is a bender pressure fluctuation characteristic diagram of a conventional rolling mill. 1... Thick plate, 2... Upper work roll, 3... Lower work roll, 4.5... Work roll bender, 6...
・Backup roll, 7... Mill housing, 8・
...Input device, 9... Arithmetic device, 10... Output device.

Claims (1)

[Claims] In plate rolling using a rolling mill equipped with a work roll bender that applies a bending force to both ends of the work roll in the direction in which the upper and lower work rolls move away from each other (increase direction), plate biting occurs. In advance, the amount of work roll bender pressure attenuation due to the elongation of the mill housing during biting is predicted from the reduction schedule of each pass, and the work roll bender pressure setting at the time of biting is corrected based on the predicted amount of work roll bender pressure attenuation. A thick plate rolling method characterized by: