JPH05293542A - Necking prevention method for hot rolled steel sheet - Google Patents

Abstract

(57) [Summary] [Object] To provide a method for preventing necking of a hot rolled steel sheet in a winding device in hot rolling. [Structure] A method of preventing necking of a hot rolled steel sheet by controlling a pressing force of a wrapper roll that pushes the hot rolled steel sheet against a mandrel in a winding device in hot rolling.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of winding a steel sheet in hot rolling, which method prevents winding necking of the steel sheet.

[0002]

2. Description of the Related Art The structure of a hot rolling apparatus will be described with reference to FIGS. 4 and 5. The rolling apparatus is provided with a rolling mill 2 having a plurality of rolling rolls 2a, 2b, 2c, and is fed from the rolling mill 2. It is composed of a pinch roll 3 for sandwiching and feeding the rolled material 1 and a winding machine 4 for receiving and rolling the rolled material 1 fed from the pinch roll 3. In the winding machine 4, the winding cylinder called a mandrel 5 is usually speed-controlled by an electric motor at a so-called leading speed which is about 10 to 25% faster than the strip speed until the strip reaches the winding machine. Figure 5 after reaching the machine
As shown in FIG. 3, the mandrel is rotated with a constant torque, and the rolled material 1 is forcibly bent by the wrapper rolls (6a to 6d) arranged around the mandrel and wound around the mandrel. In a recent winding machine, the wrapper roll is normally driven by a hydraulic cylinder (7a-7d) electrically / hydraulic servo-controlled in order to prevent an impact between the step created by the strip tip and the wrapper roll (6a-6d). Sometimes the wrapper roll is pressed with a constant force, and the roll is pulled up only when passing the coil step (AJC: Aut
The Automatic Jumping Control) is performed.

An example of the operation at this time is shown in FIGS. 3 and 5.
When the rolled material 1 is wound with the rotating speed of the mandrel 5 as the leading speed, the rolled material becomes in a tensioned state at the time of winding, and the mandrel speed must be synchronized with the rolled material speed at that moment, so that the abrupt tension is increased. Occurs. This tension is an excessive tension to which the tension required for winding and the inertial force of the winder rotating at a higher reading speed than the rolling material speed are applied, and causes a width variation called necking. In order to prevent the above-mentioned necking, conventionally, the method of reducing the mandrel speed has been mainly devised. For example, as disclosed in JP-A-59-174217, after the rolled material 1 passes through the pinch roll 3, the pinch roll speed is made to match the rolled material speed, and the mandrel speed is slightly higher than the rolled material speed. By doing
Necking occurs between the pinch roll and mandrel,
The reduced width part is reduced. However, the excessive tension generated by necking sometimes occurs between the final stands (F6 and F7 when there are 7 finishing stands).
The above-mentioned method requires a large pinch roll comparable to that of a rolling mill, resulting in a large capital investment.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and provides a simple and effective method for preventing necking that does not require modification of a large facility.

[0005]

[Means for Solving the Problems] The fluctuation in tension caused by necking is due to the mandrel being decelerated to the rolling material speed due to the restraint of the rolling material in an instant, and the speed change of the mandrel is too fast. The mandrel cannot keep up with the rotation. Since the impact force generated by necking occurs due to the change in the momentum of the winder, the conventional control method reduces the change in the momentum of the winder, thereby reducing the impact force. The present invention has been made based on the knowledge that the impact force can be relaxed by gradually changing the momentum of the winder. That is, the present invention is a winding device in hot rolling, which is equipped with a controller for controlling the pressing force and position of the wrapper roll forcibly bending the rolled material tip and winding it around the mandrel. A method of preventing necking of hot-rolled steel sheet, wherein the pressing force is set to be smaller than the regular target value, and the wrapper roll pressing force is increased so as to reach the regular pressing force target value after rolling the rolled material several times, In and, after the rolled material reaches the mandrel, the necking of the hot-rolled steel plate is characterized by increasing the pressing force of the wrapper roll with the regular pressing force target value as the upper limit so that the mandrel torque becomes the set mandrel torque. It is a prevention method.

[0006]

According to the present invention, at the tip of the rolled material, the force of pressing the wrapper roll against the mandrel is reduced, and the mandrel restraining force by the rolled material is weakened. It is possible to suppress the occurrence of necking due to a large change in mandrel speed. Also, by gradually increasing the wrapper roll pressing force in the state where the mandrel speed is faster than the rolled material speed, the mandrel restraining force by the rolled material can be gradually strengthened and the rolled material can be wound with sufficient tension from the inner winding of the coil. it can.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. 1, 2, 3 and 5. Until the rolled material 1 reaches the mandrel 5, the wrapper rolls (6a to 6d) are controlled by the hydraulic cylinders (7a to 7d) to have a pressing force F ₀ . The rolled material tip reaches the mandrel 5,
When reaching the wrapper rolls (6a to 6d), the wrapper rolls (6a to 6d) are AJC controlled to avoid an impact by the rolled material tip, and after the rolled material tip passes, a pressing force F lower than the regular pressing force is applied. _{At 0} , the rolled material 1 is pressed against the mandrel 5. Then, the pressing force is increased as the mandrel rotates, and the mandrel restraining force by the rolled material is increased. The increase pattern of the wrapper roll pressing force may be a preset pattern, or may be controlled by the increase pattern of the mandrel torque increased by the restraint of the rolled material. The pressing force of the wrapper roll at the rolled material tip may be zero. At this time, as shown in FIG. 3, the wrapper roll is position-controlled so as to open a gap corresponding to the thickness of the rolled material with respect to the mandrel and always waits. , AJC control for changing the above pressing force target value.

Since the mandrel 5 is faster than the rolled material speed due to the influence of the reading speed which is set higher than that of the rolled material, before the relative speed between the rolled material 1 and the mandrel 5 is reached, the binding force is reached. It is desirable to reduce the mandrel speed to the rolling material speed. Therefore, it can be used together with the conventional control method for controlling the rotation of the mandrel. Further, since slippage occurs between the rolled material and the mandrel, it is possible to apply lubricating oil to the rolled material to prevent the occurrence of scratches and the like.

[0009]

According to the present invention, since a rapid change in mandrel speed due to restraint of the rolled material can be suppressed, excessive tension fluctuation does not occur and necking can be prevented.

[Brief description of drawings]

FIG. 1 is a control diagram of an embodiment according to the present invention.

FIG. 2 is a control diagram of an embodiment according to the present invention.

FIG. 3 is a control diagram showing an operation of a wrapper roll in AJC.

FIG. 4 is a layout diagram showing a configuration of rolling equipment.

FIG. 5 is a cross-sectional view of an example of a winding device.

[Explanation of symbols]

 1 rolling material 2a rolling mill 2b rolling mill 2c rolling mill 3 pinch roll 4 winder 5 mandrel 6a wrapper roll 6b wrapper roll 6c wrapper roll 6d wrapper roll 7a hydraulic cylinder 7b hydraulic cylinder 7c hydraulic cylinder 7d hydraulic cylinder

Claims (2)

[Claims] 1. A winding device for hot rolling, comprising a controller for controlling the pressing force and position of a wrapper roll forcibly bending the rolled material tip and winding the mandrel, and pressing the wrapper roll at the tip of the rolled material. A method for preventing necking of a hot-rolled steel sheet, comprising setting a force smaller than a regular target value, increasing the urging force of the wrapper roll so as to reach the regular pressing force target value after rolling the rolled material several times. 2. The pressing force of the wrapper roll is increased with the regular pressing force target value being the upper limit so that the mandrel torque becomes the set mandrel torque after the rolled material reaches the mandrel. A method for preventing necking of hot rolled steel sheet.