JP2003088902A - Rolling method at great draft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling method at great draft by which at high rolling reduction for rapidly making a prescribed thickness can be performed by controlling the vibration of a hydraulic cylinder minimally while suppressing load at biting. SOLUTION: In the rolling method with a rolling mill provided with a hydraulic AGC, the opening degree of rolls before biting a material to be rolled is made larger than the set opening degree and the vibration of the opening degree of the rolls is suppressed while rapidly decreasing the opening degree of the rolls after biting the material to be rolled. When the top end of the material to be rolled abuts on work rolls, the abutment is detected with load cells or the like, a hydraulic screw-down device is operated with a control device on the basis of the detected signal and the opening degree of the rolls is rapidly controlled to the target opening degree while biting the top end of the material to be rolled between the rolls, thus the opening degree of the rolls is regulated to the preset opening degree.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a large rolling method for hot rolling of thin sheets. 2. Description of the Related Art Normally, the rolling reduction limit of a hot-rolled steel sheet is limited by the bite angle at the tip of a material to be rolled, the rolling torque, etc., for example, as disclosed in JP-A-63-238904. As a measure to improve the biting property during lubrication rolling, press the tip of the rolled material into the roll with a force that generates a specific compressive stress in the steel sheet using a pushing device until the rolling roll finishes biting the tip of the steel sheet. Thus, a method of rolling at a high bite angle has been proposed. Also, Japanese Patent Application Laid-Open No. 12-233203
In the publication, as a large rolling method, the roll opening is set to be larger than the set opening before the start of rolling, and the roll opening is gradually reduced after the material to be rolled has been bitten into the rolling rolls. A rolling method has been proposed in which the target opening is set when the leading end of the rolled material reaches a position immediately below the roll. [0003] Japanese Patent Application Laid-Open No. 63-2389
In the technology disclosed in the Japanese Patent Publication No. 04, a compressive force is applied at the time of biting to improve the biting performance. However, as the plate thickness increases, the necessary compressive force becomes excessive and the compressing force applying device becomes larger. There is a problem of doing. Further, since the compressive force is limited from the viewpoint of the facility capacity, there is also a problem in the effect of improving the biting property. Further, equipment such as a looper is installed on the entrance side of the rolling mill, and it is very difficult to provide a pushing device immediately near the rolling mill. [0004] Even if a pushing device can be provided on the entry side of a rolling mill, in the case of rolling a sheet material, there is a disadvantage that buckling is liable to occur at the time of pushing. Also, Japanese Patent Application Laid-Open
In the technique disclosed in Japanese Patent No. 233203, it is very difficult to measure the timing at which the leading end of the material to be rolled immediately below the roll after biting, and it is difficult to control the roll opening corresponding to the timing. Further, there is no mention of a method of controlling a hydraulic cylinder to quickly attenuate the impact at the time of biting. For this reason, mill vibration occurs when the material to be rolled is bitten, and it is very difficult to control the target thickness just below the rolling roll. FIG. 2 schematically shows the relationship between the roll opening degree and the time from the start of biting at this time. In this method, the roll opening oscillates according to the time from the start of biting due to the impact at the time of biting, and is controlled to a roll opening set value after a certain period of time. Therefore, it is very difficult to control the roll opening to a predetermined degree during a short time after the material to be rolled is bitten by the rolling roll and immediately below the rolling roll. The present invention has been made in view of such a technical background, and by controlling vibration of a hydraulic cylinder to a minimum while holding down a load at the time of biting, rolling at a high pressure reduction rate to quickly obtain a predetermined plate thickness. It is an object of the present invention to provide a large draft rolling method capable of achieving the following. [0006] In order to solve the above-mentioned problems, a large rolling reduction method according to the present invention is a method for rolling a rolling mill equipped with a hydraulic AGC, wherein the roll opening degree is reduced before the material to be rolled is bitten. When the roll opening is reduced immediately after the rolled material is bitten, the vibration of the roll opening is suppressed and the tip of the rolled material contacts the work roll. The contact is detected by a load cell, etc., and the control device operates the hydraulic pressure reduction device based on the detection signal, quickly controls the roll opening to the target opening while biting the tip of the material to be rolled between the rolls, and sets it in advance. It is characterized in that the roll opening degree is adjusted. An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, 1 is a work roll, and 2 is a material to be rolled. FIG. 1 (a) shows the roll opening set position and the material to be rolled before biting, and the roll opening at this time is set to be larger than the target roll setting opening. The angle is equal to or less than the limit bite angle. Writes engage the leading end of the rolled material at the rolled opening degree below the limit biting angle theta _f (Figure 1 (b)). At this time, the method of pushing the material to be rolled may be a method using a normal transport roll, a method of pushing the material to be rolled between the work rolls with a pinch roll, or a method of pushing the material to be rolled between the work rolls. Any method is acceptable. Further, in the present invention, since the bite is bitten at a bite angle smaller than the limit bite angle at the leading end of the material to be rolled, the impact at the time of biting is gentle. At this time, when the leading end of the material to be rolled comes into contact with the work roll, the contact is detected by a load cell or the like (not shown), and a control device (not shown) operates based on the detection signal. (Not shown), the roll opening is quickly controlled to the target opening while the tip of the material to be rolled is held between the rolls (FIG. 1 (c)), and the target set position (FIG. 1 (d) )). As described above, in the present invention, the roll opening is made larger than the set value in advance, so that the impact at the time of biting of the material to be rolled is small, and the roll opening is quickly reduced while suppressing the vibration of the hydraulic cylinder after biting. Since the opening is controlled to the set value, the time required to reach the target value is short. Since the limit bite angle of the steady portion of the material to be rolled is significantly larger than the bite angle of the tip of the material to be rolled, large bite rolling can be performed without any trouble after biting the tip of the material to be rolled. As is clear from the above description, in this embodiment, the degree of opening of the work roll is widened so that the leading end of the material to be rolled is bitten below the limit bite angle, and after biting, the rolled material is covered by the hydraulic pressure reduction device. Since the rolled material is pushed in and the tip of the material to be rolled is rolled, it is possible to perform a large reduction rolling while suppressing an impact load at the time of biting. FIG. 3 shows a rolling mill system having a hydraulic pressure reduction control system used for carrying out the method of the present invention. According to the present invention, a rolling mill having such a control system can realize large reduction rolling efficiently with a small load at the time of biting. In FIG. 3, a rolled material 2 is biting into a work roll 1, and a hydraulic pressure reduction device 4 is controlled by a pressure reduction controller 5, which performs a pressure reduction control according to a command from a host process control computer 6. is there. From the upper process computer 6, large roll angle S ₁ than the preset opening, giving roll target opening S ₀ to pressure controller 5, pressure controller 5 biting signal P _i and the hydraulic cylinder position P from the work roll 1 control _o . FIG. 4 shows the relationship between the position of the hydraulic cylinder and the biting time according to the conventional biting method in which the set opening is increased. FIG. 5 shows the relationship between the position of the hydraulic cylinder and the biting time in the biting method in which the set opening is increased according to the present invention. When the conventional method is applied, the position of the hydraulic cylinder vibrates and the time required to reach the set opening is long, whereas the control method according to the present invention can quickly reach the set opening, and the desired opening can be obtained. Large reduction rolling is possible. As is apparent from the above description, according to the present invention, it is possible to obtain the effect that it is possible to carry out a large rolling reduction while suppressing the load at the time of biting. It has a very useful effect.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing roll opening control in the present invention. FIG. 2 is a diagram showing a relationship between a hydraulic cylinder position and a time from the start of biting in a conventional method. FIG. 3 is a system diagram for implementing the method of the present invention. FIG. 4 shows the relationship between the position of a hydraulic cylinder and the time from the start of biting in the conventional method. FIG. 5 is a relationship between the position of the hydraulic cylinder and the time from the start of biting in the present invention. [Description of Signs] 1 ... Work roll 2 ... Rolled material 3 ... Backup roll 4 ... Hydraulic pressure reduction device 5 ... pressure controller 6 ...... upper process control computer P _i ...... biting signal P _o ...... hydraulic cylinder position command

Continuation of front page    (72) Inventor Hide Uchida             20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation             Company Technology Development Division (72) Inventor Shigeru Ogawa             20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation             Company Technology Development Division F term (reference) 4E002 AD01 BC05 CB05 CB06

Claims (1)

Claims: 1. In a rolling method for a rolling mill equipped with a hydraulic AGC, a roll opening is set larger than a set opening before biting of a material to be rolled, and the material to be rolled is bitten. After that, the roll opening is rapidly reduced, the vibration of the roll opening is suppressed, and when the leading end of the material to be rolled comes into contact with the work roll, the contact is detected by a load cell or the like, and the control device is controlled based on the detection signal. Operating the hydraulic pressure reduction device, quickly controlling the roll opening to the target opening while biting the tip of the material to be rolled between the rolls, and setting the roll opening to a preset roll opening, the large rolling reduction method .