JPH10156404A - Method for rolling hot rolled steel strip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To evade rolling failure caused by emergency stop by making rolling load and driving power for rolling at each stand of a finishing mill fall in the allowable values of equipment at the time of rolling a highly loaded material near the allowable value of the equipment. SOLUTION: In the rolling method of a hot rolled steel strip in which a rough bar is made by rolling a slab heated up to prescribed temp. into prescribed thickness with a roughing mill 2 and, next, a hot rolled steel strip having prescribed thickness is made by executing finish rolling to the rough bar with a finishing mill 3 consisting of plural stands, a rough bar heating device 6 for heating the rough bar throughout the width direction is provided on the inlet side of the finishing mill 3 and, based on the rolling load and measured value of the driving power for rolling at each stand of the finishing mill 3 and the measured value of temp. of the rough bar on the inlet side of the rough- bar heating device 6, the corresponding parts of the rough bar is beforehand heated up to required temp. with the rough-bar heating device 6 so that the rolling load and driving power for rolling at each stand of the finishing mill 3 are not more than the critical value of the emergency stop of the equipment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for rolling a hot-rolled steel strip using a continuous hot-rolling equipment, and more particularly to a method for pre-rolling a material to be rolled by a rough bar heating device installed on the entrance side of a finishing mill. , The rolling load and rolling power at each stand of the finishing mill are within the allowable value of the equipment (hereinafter referred to as equipment allowable value) so that the rolling failure due to the emergency stop of the equipment can be avoided. The present invention relates to a method for rolling a steel strip.

[0002]

2. Description of the Related Art Generally, a hot-rolled steel strip is obtained by heating a slab to be rolled to a predetermined temperature in a heating furnace, and roughly rolling the heated slab to a predetermined thickness by a rough rolling mill. Then, the rough bar is finish-rolled by a finishing mill comprising a plurality of stands to form a hot-rolled steel strip having a predetermined thickness, and the hot-rolled steel strip is cooled in a cooling stand on a run-out table, and then the coiler is used. It is manufactured by winding in.

[0003] In the process of producing such a hot-rolled steel strip, the rolling load and the rolling power, particularly in finish rolling, are not constant in the length direction of the material to be rolled. That is, the coarse bar has a long residence time on the entry side of the finishing mill. Therefore, the deformation resistance of the material to be rolled increases toward the tail end side where the temperature drop is large, and the rolling load and rolling power tend to increase.

[0004] At this time, if the rolling load and the rolling power are larger than the allowable values for equipment, the equipment may be damaged. Therefore, usually, as a protection measure, the operation value of the equipment emergency stop circuit (hereinafter referred to as the equipment emergency stop limit value) is set to a value that is 5 to 10% lower than the equipment allowable value. Many.

However, in this type of facility emergency stop circuit, although direct facility damage can be avoided,
When rolling high-load materials close to the equipment tolerance,
Due to fluctuations in the heating temperature, fluctuations in the temperature drop of the material to be rolled during rough rolling, fluctuations in the temperature conditions of the rough bar, etc., the equipment emergency stop circuit operates, and there is a high possibility that a rolling failure will occur.

[0006]

As described above, in the conventional method for rolling a hot-rolled steel strip, when rolling a high-load material close to the equipment allowable value, a rolling failure occurs due to an emergency stop of the equipment. There was a problem that the possibility was high.

An object of the present invention is to reduce the rolling load and the rolling power at each stand of a finishing mill within the equipment tolerance when rolling a high-load material close to the equipment tolerance, and to perform an emergency stop of the equipment. An object of the present invention is to provide a method for rolling a hot-rolled steel strip that can avoid rolling failure.

[0008]

In order to achieve the above object, according to the present invention, a slab heated to a predetermined temperature is rolled to a predetermined thickness by a rough rolling mill to form a coarse bar, and then the plurality of coarse bars are formed. In a method of rolling a hot-rolled steel strip so as to be a hot-rolled steel strip having a predetermined thickness by finish-rolling with a finishing rolling mill consisting of a stand, on the entry side of the finishing rolling mill, a coarse bar is formed over the entire width direction thereof. Install a coarse bar heating device for heating,
Based on the measured rolling load and rolling power at each stand of the finishing mill, and the measured temperature of the coarse bar at the entrance of the coarse bar heating device, the rolling load and rolling power at each stand of the finishing mill are emergency shut down. The corresponding portion of the coarse bar is preliminarily heated to a required temperature by a coarse bar heating device so as to be below the limit value.

Therefore, in the method for rolling a hot-rolled steel strip according to the present invention, after the start of rolling, the rolling load and rolling power at each stand of the finishing mill and the temperature of the coarse bar at the entrance side of the coarse bar heating device are measured. Then, based on these, the rolling load and rolling power at each part of the material to be rolled are estimated, and as a result, when it is determined that the estimated value reaches the equipment emergency stop limit value at one of the stands, that part is By heating the relevant portion of the coarse bar in advance to the required temperature with a coarse bar heating device so as not to reach the equipment emergency stop limit value, the deformation resistance of the material to be rolled is reduced, the rolling load during finish rolling, The rolling power can be reduced, and the failure of the rolling due to the operation of the equipment emergency stop circuit can be avoided.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the concept of the present invention will be described. In the continuous hot rolling equipment for hot-rolled steel strip, in the finishing mill, after starting rolling of the material to be rolled at each stand, the rolling load and rolling power are continuously measured during the rolling of the material to be rolled. Is possible.

Therefore, in the present invention, after the start of rolling, the measured rolling load and rolling power at each stand of the finishing mill, and the remaining rough bar length, rough bar temperature drop prediction formula, deformation resistance formula, and the like are used. The rolling load and rolling power at each part of the rolled material are estimated and calculated, and as a result, when it is determined that the equipment emergency stop limit value is reached at any one of the stands, that part does not reach the equipment emergency stop limit value. In advance, by heating the relevant portion of the coarse bar in advance to a required temperature with a coarse bar heating device installed on the entrance side of the finish rolling mill to reduce the deformation resistance of the material to be rolled, the rolling load during finish rolling, An attempt is made to reduce the rolling power to avoid a rolling failure due to the operation of the equipment emergency stop circuit.

Hereinafter, an embodiment of the present invention based on the above concept will be described in detail with reference to the drawings. FIG. 1 is a schematic view showing an embodiment of a continuous hot rolling facility to which a method for rolling a hot-rolled steel strip according to the present invention is applied.

Here, a heating furnace, a rough rolling mill (2 stands), a rough bar heating device, a finishing rolling mill (7 stands)
Is shown for a case where a hard high-tensile material is rolled for a hot rolling line composed of

In FIG. 1, a slab which is a material to be rolled is heated to a predetermined temperature in a heating furnace 1, and the heated slab is roughly rolled to a predetermined thickness by a rough rolling mill 2 to form a coarse bar.
Next, the rough bar is finish-rolled by a finishing mill 3 comprising a plurality of stands to form a hot-rolled steel strip having a predetermined thickness, and the hot-rolled steel strip is cooled in a cooling device 4 on a run-out table. (Winding machine) 5 is used for winding.

On the other hand, on the entry side of the finishing mill 3, a rough bar heating device 6 for heating the rough bar roughly rolled by the rough rolling machine 2 over its entire width direction is installed. A coarse bar heating device inlet thermometer 7 for measuring the temperature of the coarse bar passing therethrough is provided on the inlet side of the rough bar heating device 6.

Further, each stand of the finishing mill is provided with a rolling load detector 8 and a rolling power detector 9 for detecting a rolling load and a rolling power in the stand.

Further, a controller 10 for controlling heating in the rough bar heating device 6 is provided. That is, the controller 10 controls the rolling load at each stand of the finishing mill 3 by the rolling load detector 8 and the rolling power detector 9, the measured rolling power, and the coarse bar heating by the coarse bar heating device inlet thermometer 7. Based on the measured coarse bar temperature on the entry side of the device, the remaining coarse bar length, rough bar temperature drop prediction formula, deformation resistance formula, etc., the rolling load and rolling power at each part of the material to be rolled are estimated and calculated, As a result, when it is determined that the equipment emergency stop limit value is reached at any of the stands, the relevant portion of the coarse bar is set to the required temperature so that the rolling load and rolling power of that part do not reach the equipment emergency stop limit value. The coarse bar heating device 6 is controlled so as to heat up to the maximum.

As the rough bar heating device 6, a gas heating system, a current heating system, an induction heating system, or the like can be used. Are most preferred.

Next, a method of rolling a hot-rolled steel strip in the continuous hot-rolling equipment of the present embodiment configured as described above will be described with reference to FIGS. FIG. 2 is a characteristic diagram showing an example of a temperature transition from the heating furnace 1 at the tail end to the finishing mill 3 in the material to be rolled during rolling, and FIG. FIG. 4 is a conceptual diagram for explaining an example of the heating setting process by the rough bar heating device 6.

In FIG. 1, a slab is heated to a predetermined temperature by a heating furnace 1 and the heated slab is roughly rolled to a predetermined thickness by a rough rolling mill 2 to form a coarse bar. Next, the rough bar is finish-rolled by the finish rolling mill 3 to obtain a hot-rolled steel strip having a predetermined thickness.

Next, the hot-rolled steel strip is cooled by a cooling device 4 on a run-out table, and then wound up by a coiler 5. On the other hand, the temperature of the coarse bar passing through the inlet of the coarse bar heating device 6 is measured by the coarse bar heating device entrance thermometer 7.

A rolling load detector 8 and a rolling power detector 9 detect a rolling load and a rolling power at each stand of the finishing mill 3 respectively. Further, by controlling the coarse bar heating device 6 by the controller 10, the coarse bar rolled by the rough rolling machine 2 is heated by the heating device 3 over the entire width direction before entering the finishing mill 4.

That is, as shown in FIG. 3, the controller 10 detects the n-point rolling load at each stand of the finishing mill 3 detected by the rolling load detector 8 and the rolling power detector 9.
Based on the measured values of the rolling power and the measured values of the coarse bar heating device inlet coarse bar temperature at N points detected by the coarse bar heating device inlet thermometer 7, the remaining coarse bar length and rough bar temperature drop prediction formula The rolling load and rolling power at the N point of the material to be rolled at each stand of the finishing mill 3 are estimated and calculated from the deformation resistance formula and the like.

As a result, when it is determined that the equipment emergency stop limit value is reached at any of the stands,
The rough bar heating device 6 is controlled so as to heat the corresponding portion of the rough bar to a required temperature so that the rolling load and the rolling power of the portion do not reach the equipment emergency stop limit value.

In this case, specifically, as shown in FIG. 2, the temperature cycle at the leading end and the trailing end of the material to be rolled is changed mainly due to the difference in the residence time at the entrance to the finishing mill 3, and the coarse bar heating is performed. As a result of calculating the rolling load and the rolling power using the temperature of the coarse bar detected by the apparatus entrance thermometer 7, the tail end having a long residence time reaches the equipment emergency stop limit value in the finishing mill 3. It was estimated to fall to the value.

Therefore, the portion of the coarse bar that reaches the above-mentioned equipment emergency stop limit value is heated in advance by the coarse bar heating device 6 to a temperature that can avoid it. That is,
The calculation based on the flow as shown in FIG.
The heating temperature is calculated every several meters, the heating temperature required to avoid the equipment emergency stop limit value at each point is calculated, and the heating is performed to the target temperature value.

As a result, since the deformation resistance of the material to be rolled can be reduced, the rolling load and the rolling power at the time of finish rolling in the finishing mill 3 can be reduced to within the allowable values for equipment, and the above-described conventional technique can be achieved. Rolling failure due to operation of the equipment emergency stop circuit can be avoided.

FIG. 2 shows a comparison between a case where the tail end of the material to be rolled is heated in advance and a case where the tail end is not heated.
As described above, in the present embodiment, the rough bar heating device 6 for heating the rough bar over the entire width direction is installed on the entrance side of the finishing mill 3, and the rolling in each stand of the finishing mill 3 is performed. Based on the load, the rolling power measurement value, and the temperature measurement value of the coarse bar at the entrance side of the coarse bar heating device 6, the rolling load and the rolling power at each stand of the finishing mill 3 are equal to or less than the equipment emergency stop limit value. In addition, the corresponding portion of the coarse bar is heated in advance to a required temperature by the coarse bar heating device 6.

Therefore, when rolling a high-load material close to the equipment allowable value using the continuous hot rolling equipment, the rolling load and the rolling power at each stand of the finishing mill 3 are set within the equipment allowable value. In addition, it is possible to avoid a rolling failure due to an emergency stop of the equipment.

This not only contributes to the stabilization of the operation, but also takes into account the above-mentioned problem of the rolling failure, and sets the material to be rolled which has been rolled by shortening the slab length longer. Can be achieved, which can greatly contribute to improvement in efficiency and yield.

Since the rough bar heating device 6 employs an induction heating system having excellent control response, it is easy to adjust the output in the longitudinal direction of the rough bar.

[0032]

As described above, according to the present invention, a slab heated to a predetermined temperature is rolled to a predetermined thickness by a rough rolling mill to obtain a rough bar, and then the rough bar is finished with a plurality of stands. In a method of rolling a hot-rolled steel strip, which is finish-rolled into a hot-rolled steel strip having a predetermined thickness by a rolling mill, a rough bar for heating a rough bar over the entire width direction is provided on the entrance side of the finish rolling mill. A bar heating device is installed, and based on the rolling load at each stand of the finishing mill, the measured rolling power, and the measured temperature of the coarse bar at the entrance side of the coarse bar heating device, the rolling load at each stand of the finishing mill. In order to reduce the rolling power to the equipment emergency stop limit value or less, the coarse bar is heated in advance to the required temperature by the coarse bar heating device. When you finish Rolling load at each stand of the rolling mill, met with rolling power to features specific tolerance, rolling method facilities emergency hot rolled strip which can avoid the rolling failure due stop can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic view showing one embodiment of a continuous hot rolling facility to which a method for rolling a hot-rolled steel strip according to the present invention is applied.

FIG. 2 is a characteristic diagram showing an example of a temperature transition from a heating furnace 1 at a tail end to a finishing mill 3 in a material to be rolled during rolling by the continuous hot rolling equipment.

FIG. 3 is a conceptual diagram illustrating an example of a heating setting process performed by a rough bar heating device 6;

FIG. 4 is a flowchart showing an example of a heating setting process by a rough bar heating device 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Heating furnace, 2 ... Rough rolling mill, 3 ... Finish rolling mill, 4 ... Cooling device on a runout table, 5 ... Coiler (winding machine), 6 ... Coarse bar heating device, 7 ... Inlet side of coarse bar heating device Thermometer, 8: Rolling load detector, 9: Rolling power detector, 10: Controller.

Claims (1)

[Claims] 1. A slab heated to a predetermined temperature is rolled to a predetermined thickness by a rough rolling mill to form a coarse bar, and then the rough bar is finish-rolled by a finishing rolling mill comprising a plurality of stands to have a predetermined thickness. In the method for rolling a hot-rolled steel strip so as to be a hot-rolled steel strip, a coarse bar heating device for heating the coarse bar over the entire width direction thereof is installed on an entrance side of the finishing mill, Based on the rolling load at each stand of the rolling mill, the measured rolling power, and the measured temperature of the coarse bar at the entrance of the coarse bar heating device, the rolling load at each stand of the finishing rolling mill, the rolling power is installed. A method for rolling a hot-rolled steel strip, wherein a relevant portion of the rough bar is heated in advance to a required temperature by the rough bar heating device so as to be equal to or less than an emergency stop limit value.