JPH0994605A - Cold rolling method for strip metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent edge crack breakage by adjusting a roll bending force applied to both end parts in the width direction of a strip metal held with a work roll so as to reduce the force along the increase of time used of the work roll based on the curve between continuous time used of the work roll and roll bending force set beforehand and constantly rolling in an edge buckling state. SOLUTION: A tendem mill having from a first to a forth stand is arranged between a payoff reel 1 and a coiling reel 2, roll benders 41-44 are arranged to work rolls 31-34 of each stand. Each roll bender is connected to a controller 5, movement of each roll bender 41-44 is controlled in response to an electrical signal from the controller 5, as a result, the roll bending force applied to both ends in the width direction of each stand is controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cold rolling a metal strip, and more particularly to a method capable of preventing breakage of a plate due to edge cracking (cracking of edge portions in the plate width direction) during rolling. .

[0002]

2. Description of the Related Art Generally, a tandem mill used for cold rolling a steel strip is equipped with roll benders at both ends in the width direction of a work roll in order to control the shape in the width direction of the strip. The roll bender controls so that the shape of the rolled steel sheet in the width direction becomes flat. However, according to such normal control, in the case of high-tensile rolling, there is a problem that if there are defects at both ends (ears) in the strip width direction, edge cracks tend to occur during rolling, and if this becomes large, the sheet breaks. .

A number of methods have been proposed in the past for preventing the rupture of the plate (ear crack rupture) due to such ear cracks.
For example, in Japanese Unexamined Patent Publication No. 4-200904, the length of the edge cracking portion is detected on the exit side of the first rolling stand, and when the detected value is equal to or more than a predetermined value, the rolling stand downstream of this lengthens. A method of adjusting a roll bender to be rolled into a state is disclosed.

[0004]

However, the control method in which the edge crack is detected and the rolling is performed in the edge-stretching state as described above has a problem that the control cannot be performed in time during high-speed rolling. In addition, the ear crack detector has not been sufficiently accurate, and in reality, a great effect could not be expected.

An object of the present invention is to solve the above-mentioned problems of the prior art, and to cool the metal strip capable of effectively preventing breakage of the edge crack even at high speed rolling without detecting the edge crack. A hot rolling method is provided.

[0006]

As a result of repeated studies to solve the above problems, the present inventors have found the following findings and completed the present invention. That is, when cold rolling a large-diameter coil at high speed, there is a tendency for a large amount of edge cracking to occur at the tail end side portion of the coil, but the cause is that the heat crown of the work roll increases as the rolling time increases. It turns out that it is because it grows. Therefore, if the roll bending force applied to both ends in the strip width direction is reduced in response to the increase in heat crown with the increase in the continuous use time of the work rolls, it is possible to carry out rolling with a proper edge extension state at all times. it can.

The present invention provides a cold rolling method for a metal strip, which rolls while controlling the shape in the sheet width direction by adjusting the roll bending force applied to both ends in the sheet width direction of the metal strip sandwiched by work rolls. Adjust the roll bending force so that the roll bending force decreases with the increase of the work roll continuous use time based on the preset work roll continuous use time-roll bending force curve, and the metal strip is always rolled in the edge extension state. A method for cold rolling a metal strip is provided.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. FIG. 1 is a schematic diagram showing a cold rolling apparatus capable of carrying out the method of the present invention. This rolling apparatus is a tandem mill having four stands, first to fourth, between a payoff reel 1 and a take-up reel (tension reel) 2, and roll roll benders 41 to 41 are provided on work rolls 31 to 34 of each stand. 44 are installed. Further, each roll bender 41 to 44 is connected to the controller 5, and the movement of each roll bender 41 to 44 is adjusted according to an electric signal from the controller 5, and as a result, both end portions in the plate width direction of each stand. The roll bending force exerted on the roller is controlled.

Here, as shown in FIG. 2, the roll bending force by the roll bender of each stand is changed for each number of continuous rolling coils. The continuous rolling coil number (work roll continuous use time) -work roll bending force curve of FIG. 2 corresponds to the case where the coil immediately after the work roll is replaced is the first coil and ten coils are continuously rolled. The amount of heat crown that increases with an increase in the number of rolling coils is calculated, and the roll bending force for achieving an appropriate edge-stretching state for each number of rolling coils is calculated from that value. For each stand, the roll bending force decreases as the number of continuous rolling coils increases. Also, as the number of continuous rolling coils increases, the difference in roll bending force between stands increases, and
The order is 1st stand, 3rd stand, 4th stand, 2nd stand.

With such a configuration, the pay-off reel 1
The steel strip (metal strip) S that has been unwound from the roll is rolled between the stands so as to have an appropriate edge extension state. That is, as the number of continuous rolling coils increases and the rolling time increases, the heat crown of the work roll increases, but the roll bending force applied to both ends in the strip width direction corresponds to the increase of the heat crown. Is reduced to a value that provides an appropriate edge extension state, so that the steel strip S is always rolled into an appropriate edge extension state. As a result, the tension applied to the widthwise end of the steel strip S is reduced, and ear cracks and accompanying cracks do not occur.

When the steel strip was actually cold-rolled by this method, the occurrence rate of edge crack fracture was reduced to 1/10 or less as compared with the case of normal control. Further, in this method, since it is not necessary to detect the edge crack, it is possible to effectively prevent the edge crack from breaking even during high speed rolling. Although the shape of the steel strip on the outgoing side is in a stretched state by such control, there is no particular problem because the end portion (end portion in the width direction) is usually removed to obtain a product. Further, in the final stand, by giving priority to the normal flat rolling control over the edge extension rolling control shown in FIG. 2, the delivery side shape can be improved.

In this embodiment, the number of continuous rolling coils is used as a unit of continuous use time of the work rolls, and the roll bending force is changed for each number of continuous rolling coils. The roll bending force may be changed for each stand according to the time, the length of the rolled steel strip, the cumulative weight (tonnage) of the rolled steel strip, and the like. Further, the metal strip to which the method of the present invention can be applied is not limited to the steel strip, but is applicable to all metal strips whose shape in the sheet width direction can be controlled by cold rolling.

[0013]

As described above, according to the method of the present invention, it is possible to prevent the cracking of the edge cracks by constantly performing the edge extension rolling without detecting the edge cracks. It is possible to prevent the ear crack from breaking.

[Brief description of drawings]

FIG. 1 is a schematic view showing a cold rolling apparatus capable of carrying out the method of the present invention.

FIG. 2 is a graph showing a number of continuously rolled coils (work roll continuous use time) -work roll bending force curve used in the embodiment.

[Explanation of symbols]

 S Steel strip (metal strip) 31-34 Work roll 41-44 Roll bender 5 Controller

Claims (1)

[Claims] 1. A cold-rolling method for a metal strip, wherein rolling is performed while controlling the shape in the sheet width direction by adjusting the roll bending force applied to both ends in the sheet width direction of the metal strip sandwiched by work rolls. Adjusting the roll bending force so that the roll bending force decreases as the work roll continuous use time increases based on the set work roll continuous use time-roll bending force curve, and the metal strip is always rolled in the edge-stretching state. A method for cold rolling a metal strip, comprising: