JPH09155402A - Process line operation method of steel strip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve productivity, lessening a reduction of production due to passing stoppage by carrying out roll change at skin pass rolling mill side during storing of a steel strip after heat treatment to a looper in a continuous process line of the steel strip. SOLUTION: In the process line of the steel strip carrying out a continuous heat treatment and skin-pass rolling continuously, the steel strip 1 at a skin-pass rolling mill 4 side is once stopped at the time of releasing roll reduction and after the releasing roll reduction, roll change is carried out while passing through the steel strip 1 at the skin-pass rolling mill 4 side and passing through of the steel sheet 1 at the skin-pass rolling mill 4 side is stopped only at the time of the roll reduction. While the passing through of this steel sheet 1 is stopped, the steel strip 1 after heat treatment is stored into the looper 3 with the continuous heat treatment equipment 2. While the steel strip 1 after the heat treatment is stored by the looper 3, the passing through of the steel strip 1 at the skin-pass rolling mill 4 side is stopped and the change of work rolls 5, 5a and intermediate rolls 6, 6a is terminated and the skin-pass rolling is started passing through the steel strip at once and gradually is shifted to maximum passing through speed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for operating a steel strip process line.

[0002]

2. Description of the Related Art As a process line for a steel strip, as shown in FIG. 1, a steel strip 1 is guided to a continuous heat treatment facility 2, and the steel strip 1 is annealed to provide workability, and then a looper 3 is used.
6 including upper and lower work rolls 5 and 5a, intermediate rolls 6 and 6a, and backup rolls 7 and 7a.
A Hi temper rolling mill 4 (which may be a 4Hi temper rolling mill) is rolled to a target plate thickness, and heat treatment and temper rolling of a steel strip are continuously performed. In such temper rolling, since line defects occur due to rolling in the cylinder circumferential direction at both ends of the rolled steel strip 1 of the upper and lower work rolls 5 and 5a and the upper and lower intermediate rolls 6 and 6a, the steel strip to be rolled next is formed. Becomes wider, transfer flaws continuously occur in the rolling direction on the front and back surfaces of both ends of the steel strip 1 after rolling. Therefore, when rolling the steel strip 1, scheduled rolling is performed in which the steel strip 1 having the largest width and the steel strip 1 having a narrow width are sequentially rolled to prevent the transfer flaw from occurring. Thus, after finishing rolling of the steel strip 1 of the minimum width, when changing to rolling of the steel strip 1 of the widest width, the rolls are changed to new upper and lower work rolls 5 and 5a and upper and lower intermediate rolls 6 and 6a, and then the maximum rolls are again changed. By rolling the wide steel strip 1 to the steel strip of the minimum width one by one, by repeating the schedule rolling, the line stop (stopping of the steel strip) due to roll change is avoided as much as possible.

When the line is stopped by changing the rolls as described above, the speed of the steel strip 1 after the heat treatment is reduced by the looper 3 while the steel strip 1 is stored in the looper 3 after being decelerated to about 1/2 the running speed. Stop steel strip 1 threading. That is, when the steel strip 1 passing through the continuous heat treatment equipment 2 is stopped, the steel strip 1 located inside the equipment 4 (in the furnace) is exposed to high temperature, and the material of the steel strip deteriorates. There is a risk of breakage when the plate is restarted. Therefore,
As described above, while the strip running on the temper rolling mill 4 side is stopped, the strip running speed in the continuous heat treatment facility 2 is reduced to heat treat the strip 1 and store it in the looper 3 for continuous operation. The work rolls 5, 5a, the upper and lower intermediate rolls 6, 6a of the temper rolling mill 4 are stopped by stopping the steel strip 1 threading on the temper rolling mill 4 side without stopping the steel strip 1 threading in the heat treatment facility 2. Is to be rearranged.

[0004]

As described above, the work rolls 5 and 5a and the upper and lower intermediate rolls 6 and 6 of the temper rolling mill 4 are as described above.
Since the reassembling of a generally requires about 2 minutes, the steel strip 1 running speed in the continuous heat treatment equipment 2 is reduced from about 800 m / min to about 400 m when the steel strip 1 running on the temper rolling mill 4 side is stopped.
It is designed and arranged in a looper 3 capacity that can be stored for about 2 minutes by decelerating to about half a minute. When the strip running speed of the steel strip 1 is reduced to about 1/2 in the continuous heat treatment equipment 2 in this way, the in-furnace time (heat treatment time) of the steel strip 1 in the continuous heat treatment equipment 2 is approximately doubled, and It will adversely affect the material. Therefore, when the furnace temperature is gradually lowered and the strip running speed of the steel strip 1 is also gradually reduced in proportion to the strip running speed of about 400 m / min, the storage in the looper 3 is started at the same time, After the steel strip 1 threading on the temper rolling mill 4 side was stopped and the work rolls 5 and 5a and the upper and lower intermediate rolls 6 and 6a were changed, the steel strip 1 threading on the temper rolling mill 4 side was restarted. The furnace temperature of the continuous heat treatment equipment 2 is gradually increased, and the strip running speed in the continuous heat treatment equipment 2 is gradually increased to about 800 m / min.
The strip running speed of the steel strip 1 on the temper rolling mill 4 side is also increased.

Thus, the speed of passing the steel sheet 1 in the continuous heat treatment equipment by changing the work rolls 5 and 5a and the upper and lower intermediate rolls 6 and 6a of the temper rolling mill 4 is reduced (from about 800 m / min to about 400 m / min). The amount of production reduction per 1 hour) is slightly different depending on the installed capacity, the size of the steel strip, etc., but can reach up to about 30 tons. It is about 50 times / month, although it varies slightly depending on the situation. Therefore, there is a problem that the amount of production reduction per month reaches about 1500 t, which is a major cause of remarkably reducing productivity. The method of the present invention has been made in order to advantageously solve such a problem, and reduces the amount of production reduction due to the stoppage of the steel strip 1 when the work rolls of the temper rolling mill are changed to improve the productivity. It is an object of the present invention to provide a method of operating a steel strip process line.

[0006]

A feature of the method of the present invention is that in a steel strip process line in which continuous heat treatment and temper rolling of a steel strip are continuously carried out, the steel strip is temper-rolled while passing through the steel strip. This is a method for operating a steel strip process line, which is characterized by changing the rolls of the machine.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The work of reassembling the work rolls 5 and 5a and the intermediate rolls 6 and 6a of the 6Hi temper rolling mill 4 is carried out by: a) rolling down the rolls (releasing the work rolls from the steel strip) for about 15 seconds; Approximately 6 roll replacements (roll replacements)
It is carried out for about 2 minutes in the procedure of 0 second, rolling down the roll (applying work roll to steel strip and applying rolling load) for about 40 seconds. Thus, in the method of the present invention, the steel strip 1 on the temper rolling mill 4 side is once stopped at the time of rolling reduction opening, and the steel strip 1 on the temper rolling mill 4 side is passed through after rolling reduction opening,
b The rolls are replaced, and the steel strip 1 threading on the temper rolling mill 4 side is stopped only when the rolls are rolled down. That is, if a reduction is applied to the steel strip 1 in the threading, the steel strip 1 may be broken, and during roll reassembling work, a maximum of about 4
The steel strip 1 threading on the temper rolling mill 4 side is stopped for 0 seconds. This steel strip 1 Steel strip 1 after heat treatment in continuous heat treatment equipment 2 while strip running
Is stored in the looper 3 for about 40 seconds, and the looper 3 of the existing equipment can be surely stored without reducing the strip running speed in the continuous heat treatment equipment 2. As described above, while the steel strip 1 after heat treatment is stored in the looper 3, the strip 1 on the temper rolling mill 4 side is stopped to change the work rolls 5, 5a and the intermediate rolls 6, 6a. Immediately after the completion, the steel strip is passed through the steel strip to start temper rolling, and the steel sheet is gradually moved to the maximum strip-passing speed.

In such a roll change, there is a steel strip that cannot be rolled by the temper rolling mill 4 during the roll change, and in order to minimize this unrollable steel strip,
For example, when the width is expanded from the minimum width to the maximum width, the width is rapidly expanded and the steel strip may be narrowed in the furnace, and the steel strip may be broken in the furnace. Therefore, in general, when the width of the steel strip is expanded from the minimum width to the maximum width, a connecting material for connecting the steel strips of the intermediate width is applied. By using the unrolled steel strip as the tie material, the steel strip on the temper rolling mill 4 side at the time of roll reshuffling 1 stoppage of the strip and continuous heat treatment equipment 2
It is possible to avoid a large reduction in the steel strip threading speed on the side, and it is possible to significantly reduce the production reduction amount of the steel strip process line due to the roll rearrangement. Further, the tie material (steel strip) that could not be rolled can be prevented from being reduced in yield by transferring it to an offline temper rolling mill to be rolled into a product.

As described above, when the work rolls 5 and 5a and the intermediate rolls 6 and 6a are recombined, the work rolls 5 and 5a are replaced.
When the steel strip 1 on the temper rolling mill 4 side is stopped at the time of rolling down the intermediate rolls 6 and 6a and the steel strip 1 after the heat treatment is stored in the continuous heat treatment equipment 2 at high speed for about 40 seconds, When the looper 3 having a large capacity is arranged, for example, the strip running speed of the steel strip 1 on the continuous heat treatment equipment 2 side is reduced to such an extent that the material of the steel strip 1 is not adversely affected, so that the strip running is surely stopped. It can be stored in the looper 3. Further, as described above, the work rolls of the temper rolling mill 4 and the upper and lower work rolls 5 are moved to the passing position of the steel strip 1 after replacement of the intermediate rolls.
When the reduction of 5a is applied, the upper work roll 5, the upper intermediate roll 6 and the upper backup roll 7 are as shown in FIG.
Can be shifted to the steel strip 1 threading position in a short time by a pass line adjusting mechanism (not shown), but the lower work roll 5a can be moved up through the lower backup roll 7a and the intermediate roll 6a by jacking up. The vicinity of the position of the steel strip 1 is rapidly approached, and then the distance θ to the position of the passage of the steel plate 1 is stopped at a low speed to prevent the lower work roll 5a from being damaged due to a collision. Therefore, it takes a long time to reduce the work roll pressure after changing the work rolls.
The stoppage time of the steel strip 1 also becomes long. Therefore, immediately after changing the lower work roll 5a, the jack 8
And the lower work roll 5a is preliminarily positioned within a distance θ of 100 mm between the steel strip 1 threading position and the outer circumference of the lower work roll 5a. Simultaneously with the movement to the plate position, the lower work roll 5a is moved upward to apply the reduction,
Since the reduction of the upper and lower work rolls 5 and 5a can be shortened for several seconds, the amount of steel strip stored in the looper 3 can be reduced, and the upper and lower work rolls 5 on the temper rolling mill 4 side can be reduced.
The high-speed steel strip 1 of the continuous heat treatment equipment 2 can be reliably stored even in the small-capacity looper 3 of the existing equipment when the steel strip 1 is stopped at the steel strip passage position when the reduction is applied to 5a.

Next, examples of the method of the present invention will be given together with comparative examples.

[Table 1]

Note 1: A continuous strip heat treatment facility having a maximum striping speed of about 800 m / min and a steel strip process line consisting of a temper rolling mill were used. Note 2: WR is a work roll, IMR is an intermediate roll, and BUR is a backup roll. Note 3: Rolled steel strip size of temper rolling mill is 600mm in width,
Plate thickness 0.22 mm. Note 4: In Examples 1 and 2, immediately after the work rolls were recombined, the lower work roll was positioned at the steel strip passing position of the temper rolling mill and the outer circumference of the lower work roll was 90 mm, and at the same time when the upper work roll was lowered. Then, the lower work roll was moved upward and pressed down for a short time. Note 5: The strip speed of continuous heat treatment in the comparative example was gradually reduced from 800 m / min to 380 m / min over 57 minutes while lowering the furnace temperature, and immediately when storage in the looper was started,
At the same time, the strip running on the temper rolling mill side was stopped and the upper and lower work rolls were recombined. Note 6: The strip passing speed on the temper rolling mill side was set to be approximately the same when the work rolls were reassembled and during the steady rolling operation. Note 7: The strip running on the temper rolling mill side is stopped at the time of rolling down and rolling down. Was passed at a higher speed than the continuous heat treatment side. Therefore, Examples 1 and 2
However, even if the strip running on the temper rolling mill side was temporarily stopped, the production did not decrease, so the production reduction amount was 0t. In addition, Example 3 is
Since the looper storage amount of the steel strip is smaller than in Examples 1 and 2, if the strip running speed on the temper rolling mill side is increased at the start of strip running, the strip running speed on the continuous heat treatment side may have to be reduced. Therefore, the speed increase at the start of strip running was suppressed, and the production cut due to the suspension of strip running on the temper rolling mill side could not be covered, resulting in a 4t reduction in production.

[0012]

According to the method of the present invention, it is possible to remarkably reduce the amount of production reduction at the time of roll changing of the temper rolling mill in the process line of the steel strip, and to remarkably improve the productivity. In addition, it can be carried out without facility modification and new operation load, and excellent effects such as a great industrial effect can be obtained.

[Brief description of the drawings]

FIG. 1 is a flow chart showing an example of a process line for a steel strip.

FIG. 2 is a side view showing how work rolls are changed in the temper rolling mill.

Claims (2)

[Claims] 1. A steel strip process in which a steel strip is subjected to continuous heat treatment and temper rolling in a continuous process line, in which rolls of a temper rolling mill are recombined while the steel strip is passed through. Line operation method. 2. Rolls are exchanged while passing through a steel strip,
2. The method of operating a steel strip process line according to claim 1, wherein the strip running is stopped when the roll is released and when the roll is rolled after the roll is replaced.