JPH05255877A - Method for controlling catenary in liquid immersing tank for band-shaped body to be transported - Google Patents

Abstract

PURPOSE:To automatically control the catenary curve of a long-sized steel strip in a pickling tank within a specified permissible range by adjusting the rotating speed of an upstream side bridle roll by the magnitude of the load current of the downstream side bridle roll of the pickling tank at the time of passing the steel strip in the pickling tank. CONSTITUTION:The long-sized steel strip 1 is passed in the pickling tank 6 to dissolve and remove the oxide film on the surface by an internal acid soln. 8. The driving current of the downstream side bridle roll 9 of the pickling tank 6 is detected in such a case. The tension of the steel strip in the pickling tank 6 is so large that the catenary curve of the steel strip 1 is raised upward and the pickling is insufficient when the detected value is larger than the prescribed value and, therefore, the rotating speed of the upstream side bridle roll 5 is increased by a control unit 10 to normalize the catenary curve of the steel strip 1. The tension of the steel strip 1 in the pickling tank 6 is so small that the catenary curve lowers to slide on the bottom and the steel strip 1 is flawed by the sliding on the bottom when the driving current of the upstream side bridle roll 9 is smaller than the prescribed value and, therefore, the rotating speed of the upstream side bridle roll 5 is lowered to normalize the catenary curve.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a catenary in a belt-like liquid immersion tank that is continuously conveyed such as a steel plate without using a catenary sensor.

[0002]

2. Description of the Related Art For example, as a pretreatment for cold rolling of a steel sheet, in order to remove an oxide film on the surface of the steel sheet, the steel sheet is continuously treated by passing through a pickling tank. Steel sheets are continuously conveyed in a pickling tank in a drooping curve called catenary.If the tension applied to the steel sheet is too high, the so-called catenary lifting is performed so that the steel sheet passes over the liquid surface. It will be in a state and cause poor pickling. Conversely, if the tension applied to the steel plate is too small,
The steel sheet is in a so-called catenary bottom-sliding state in which it comes into sliding contact with the bottom surface of the pickling tank, which may cause scratches on the surface of the steel sheet.

Therefore, it is conceivable to use a catenary sensor to adjust the rotational speed of the bridle roll upstream of the pickling tank so that the catenary curve of the steel sheet in the pickling tank is within the allowable range. It is necessary to install the sensor in a corrosive liquid such as hydrochloric acid, etc.
The labor and cost required to maintain the sensor becomes a problem.

[0004]

SUMMARY OF THE INVENTION In view of the problems of the prior art as described above, the main object of the present invention is to economically analyze the catenary curve in the liquid-immersion tank of the continuously conveyed strips. Moreover, it is to provide a method for automatically and reliably controlling within an allowable range.

[0005]

According to the present invention, the above-mentioned object is to realize the strip-shaped body in a liquid immersion tank provided between an upstream bridle roll and a downstream bridle roll for conveying the strip. A method of controlling a catenary, wherein the drive current of the downstream bridle roll is increased if the drive current of the downstream bridle roll is larger than a first predetermined value, and the drive current of the downstream bridle roll is the first It is achieved by providing a control method characterized in that the drive speed of the upstream bridle roll is reduced if it is smaller than a second predetermined value that is smaller than the predetermined value of.

[0006]

[Function] When the load current of the downstream bridle roll is excessive, the tension of the strip is excessive, so it is determined that the catenary is in a tensioned state, and when the load current of the downstream bridle roll is excessively small. Since the tension of the strip is insufficient, it can be judged that the catenary bottom slip state, the speed of the bridle roll on the upstream side is increased or decreased, and the catenary curve in the liquid immersion tank is automatically and constantly allowed to be constant. It can be controlled within the range.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a diagram showing a pickling process performed to remove an oxide film on a steel sheet prior to cold rolling the steel sheet. Steel plate 1 is bridle roll 2 at the inlet end
It is sent to the tension leveler 3 through the so as to be flattened and cracked in the oxide film so that the oxide film can be removed well by pickling. Next, the steel sheet 1 is fed into the pickling tank 6 via the two upstream bridle rolls 4 and 5 which are synchronized with each other, and is delivered to the next process (not shown) via the downstream bridle roll 9.

The pickling tank 6 is made of acid-resistant brick, and stores hydrochloric acid 8 and is provided with a plurality of cascades 7. The steel plates 1 conveyed in the pickling tank 6 are provided by these cascades 7. Each of the defined sections passes through a catenary.

According to the knowledge of the inventor, in such a pickling tank 6, the current of the downstream bridle roll 9 is controlled within a predetermined range according to the plate thickness T and the plate width B of the steel plate 6. By doing so, the catenary can be controlled within an allowable range. FIG. 2 shows such a relationship. When the load current of the downstream bridle roll 9 is equal to or higher than a first predetermined value determined according to the value of T ² × B, the steel sheet is pickled. When the load current of the downstream side bridle roll 9 is equal to or lower than the second predetermined value which is also determined according to the value of T ² × B, the steel sheet 1 is pickled. It is determined that the bottom of the tank is in sliding contact with the bottom of the tank.

Therefore, in this embodiment, if the data setting unit 11 inputs the plate thickness T and the plate width B given by the plate type and gives the data to the drive control unit 10, the downstream side When the load current value of the bridle roll 9 is given to the control unit 10 as an input, the control unit 10 increases or decreases the speed of the upstream bridle roll 4 based on the relationship shown in FIG. The value is kept within the range corresponding to the hatched portion in FIG. The bridle rolls 4 and 5 are synchronized with each other so that the bridle roll 5 rotates at the same rotational speed as the bridle roll 4.

FIG. 3 is a flow chart showing the operation of such a drive control unit. First, in step 1, the current I, the plate thickness T and the plate width B of the downstream bridle roll 9 are read into the data setting unit 11, and in step 2, the current I is read by the map showing the relationship shown in FIG. Is within a predetermined range. If the current value I is outside the predetermined range, the speed V of the bridle roll 4 is increased or decreased (step 3) so that the current I falls within the predetermined range. To do. If the current I is within the predetermined range, the process returns to step 1 again, and this process is repeated until the control process is completed (step 4).

[0013]

According to the present invention, only the bridle roll current is monitored without the durability and maintenance problems caused by the provision of the catenary sensor in the liquid immersion tank which is often in a corrosive atmosphere. It is possible to automatically control the catenary of the strip in the liquid immersion tank within a predetermined range.

[Brief description of drawings]

FIG. 1 is a diagram showing a pickling process of a steel plate to which a catenary control method according to the present invention is applied.

FIG. 2 is a graph showing the relationship between the plate type in the pickling process shown in FIG. 1 and the proper range of the current of the downstream bridle roll.

3 is a flowchart showing a control operation executed in a drive control unit 10 shown in FIG.

[Explanation of symbols]

 1 Steel plate 2, 4, 5, 9 Bridle roll 3 Tension leveler 6 Pickling tank 7 Cascade 8 Acid 10 Drive control unit 11 Data setting unit

Front Page Continuation (72) Inventor Masataka Kawamura 1 Kimitsu, Kimitsu City Nippon Steel Corporation Kimitsu Steel Works

Claims (1)

[Claims] 1. A method for controlling the catenary of the strip in a liquid immersion tank provided between an upstream bridle roll and a downstream bridle roll that convey the strip, the downstream bridle roll comprising: Is higher than the first predetermined value, the drive speed of the upstream bridle roll is increased, and the drive current of the downstream bridle roll is smaller than the second predetermined value which is smaller than the first predetermined value. For example, a control method characterized by lowering the drive speed of the upstream bridle roll.