JP2014201798A - Method for manufacturing galvanized steel strip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a galvanized steel strip, capable of preventing a steel strip from being contacted to a facility by a warp and vibration of the steel strip to be flawed and preventing a plating coating weight of the steel strip from being shifted from a target value even when a steel strip welding connection part connected by welding in order to continuously manufacture two kinds of steel strips having different widths and/or thicknesses is entered in a range controlled by an electromagnet.SOLUTION: Two or more sets of electromagnet units 6-12 having a pair of electromagnets 6a and 6b faced and provided so as to sandwich the front and rear of the steel strip 1 and a displacement sensor 6c for measuring a surface outside direction displacement of the steel strip 1 are arranged in a steel strip width direction. In steel strip control means 5 for controlling a warp in a width direction of the steel strip in non-contact by controlling the outputs of the electromagnets on the basis of information on the displacement sensor, a warp in a pass line and in a steel strip width direction is reformed in non-contact using only certain sets of electromagnet units processed in the line only while the steel strip welding connection part and the vicinity thereof pass through a control range of the control means.

Description

  The present invention relates to a method for producing a hot dip galvanized steel strip or a hot dip galvanized steel strip, and in particular, a warp in the width direction of the steel strip in a gas wiping portion (hereinafter sometimes simply referred to as “warp”) or out of plane. The present invention relates to a method for preventing directional vibrations (hereinafter, simply referred to as “vibration”), suppressing uneven plating adhesion, and preventing wrinkling due to contact of a steel strip with a gas wiping device.

In a line for producing a hot dip galvanized steel strip, the suppression of warpage and vibration of the plated steel strip in the gas wiping section is an important factor that determines the plating quality and production efficiency of the steel strip.
For example, in a production line for a hot dip galvanized steel strip, a steel strip that has been cold-rolled or a steel strip from which surface oxide scale has been removed after hot rolling is immersed in a hot-dip zinc bath, After adhering the molten zinc to the surface, the amount of plating adhesion is adjusted by scraping off the excess molten zinc adhering to the surface of the steel strip to the target adhesion amount using a gas wiping device. If the steel strip is warped, the plating adhesion amount is non-uniform in the plate width direction, and if it is vibrating, the plating adhesion amount is non-uniform in the sheet passing direction. Further, when the warp or vibration of the steel strip is large, the steel strip comes into contact with the gas wiping device and wrinkles are generated on the surface of the steel strip.

Conventionally, with respect to the problem of the warp in the plate width direction of the steel strip and the vibration in the out-of-plane direction in such a wiping portion, as shown in Patent Documents 1 to 3, for example, an electromagnet and a displacement are located immediately above the wiping portion. A method of suppressing warpage in the plate width direction and vibration in the out-of-plane direction of a steel strip is performed by arranging a plate-passing stabilization device equipped with a sensor and appropriately controlling the attractive force of the electromagnet.
In any of the above methods, a plurality of electromagnet pairs, which are sets of electromagnets arranged opposite to each other in the thickness direction of the traveling steel strip, are arranged in the width direction of the steel strip, and the electromagnet to be used is switched according to the plate width. The position of the steel strip is controlled by changing the output of the electromagnet corresponding to the position, shape and vibration of the steel.

JP 2009-179834 A JP 2010-156023 A JP 2011-214146 A

  However, in the above-described conventional technology, a steel strip welded joint joined by welding to continuously produce two types of steel strips having the same width and / or thickness has entered the control range of the electromagnet. In some cases, the steel strip is greatly deviated from the target position, warpage is increased, vibration is increased, and as a result, the steel strip comes into contact with equipment to become wrinkles, or the steel strip is attached to the plating. There was a problem that the amount deviated from the target value.

  This is because, when the width of the steel strip passing through the control range by the electromagnet greatly fluctuates in the steel strip weld joint, the electromagnetic force per unit area of the steel strip end portion changes temporarily, and the electromagnetic force and the steel This is because the balance with the reaction force of the belt occurs due to momentary collapse.

The present invention has been made by extensive research to solve the above-described problems, and has the following configuration.
(1) A pair of electromagnets provided facing each other so as to sandwich the front and back of a running steel strip that has left the hot dip galvanizing bath or hot dip zinc alloy plating bath, and a displacement sensor that measures the out-of-plane displacement of the steel strip Of a hot dip galvanized steel strip or a hot dip galvanized steel strip provided with a steel strip position control device in which a plurality of electromagnet units having a plurality of positions are arranged in the width direction of the steel strip and a pair of gas wiping nozzles for adjusting the amount of plating adhered In production equipment,
While adjusting the output of the electromagnet based on the information of the displacement sensor to control at least the pass line of the steel strip and the warp in the width direction of the steel strip in a non-contact manner, continuous hot dip galvanization or hot dip zinc alloy plating is performed. A method of manufacturing a steel strip,
The steel strip is fixed to a certain number of sets of electromagnet units only while the steel strip welded joint connecting steel strips having different widths and / or thicknesses passes through the control range of the steel strip position control device. A method for producing a hot dip galvanized steel strip characterized by correcting the warp in the width direction of the steel strip in a non-contact manner.

(2) Only when the steel strip welding joint and its vicinity pass through the control range of the steel strip position control device, it is fixed only to the electromagnet unit used when passing the steel strip with the minimum width processed in the line. The method of manufacturing a hot-dip galvanized steel strip according to (1), wherein the warp in the steel strip pass line and the strip width direction is corrected without contact.
(3) The steel strip welding joint and its vicinity are continuously used as a constant output without changing the output of the exciting electromagnet only while passing through the control range of the steel strip position control device. The method for producing a hot-dip galvanized steel strip according to (1) or (2), wherein the position control of the band weld joint is performed.

  (4) The output of the electromagnet per set to be excited only when the steel strip weld joint and its vicinity pass through the control range of the steel strip position control device, and the output before passing the steel strip weld joint is If it is below a predetermined upper limit value, it is used continuously at the output before passing through the steel strip weld joint, and if it exceeds a predetermined upper limit value, it is used at a constant output equal to the predetermined upper limit value, The method of manufacturing a hot dip galvanized steel strip according to any one of (1) to (3), wherein the position control of the steel strip weld joint is performed.

  According to the present invention, since the steel strip position can be accurately controlled in the same manner as the stationary portion even in the vicinity of the steel strip welded portion connecting steel strips having different widths and / or thicknesses, the steel strip welded connecting portion can be obtained. Stable galvanized steel strip can be manufactured by suppressing the vibration and displacement of the steel strip in the vicinity, and as a result, uniform plating is possible even in the vicinity of the weld zone of the steel strip. It can also prevent wrinkles caused by contact.

It is the schematic which shows the structure of the hot dip galvanization equipment in the hot dip galvanization steel strip production line seen from the side surface direction. It is the schematic which shows the structure of the steel strip position control apparatus 5 seen from the upper surface direction.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
Incidentally, the vicinity of the welded zone of the steel strip indicates a range of 10 meters before and after the place where the preceding steel strip and the subsequent steel strip are welded at the maximum. The range is usually 5 meters in front and back.
FIG. 1 shows a schematic configuration of a hot dip galvanizing facility in a hot dip galvanized steel strip production line as viewed from the side. 1 is a steel strip, 2 is a molten zinc bath, and 3 is a sink roll in a molten zinc pot. Reference numerals 4a and 4b denote a pair of gas wiping nozzles, which adjust the adhesion amount of molten zinc by injecting gas onto both surfaces of the steel strip 1 exiting the molten zinc bath 2. Reference numeral 5 denotes a non-contact steel strip position control device installed in the vicinity of the gas wiping nozzles 4a and 4b.

  FIG. 2 is a view of an example of the configuration of the steel strip position control device 5 using the electromagnet unit installed in the hot dip galvanized steel strip production line, as viewed from the top. The steel strip 1 is represented by a cross section in the width direction and runs in a direction perpendicular to the paper surface. The steel strip position control device 5 is composed of seven sets of electromagnet units 6 to 12 arranged in the width direction, and each unit attracts the steel strip by electromagnetic force to correct the position, and the front electromagnets 6a to 12a and the back electromagnets 6b to 6 12b and non-contact displacement sensors 6c to 12c for measuring the distance.

  The electromagnet unit used for the steel strip position control is switched depending on the plate width of the steel strip 1. In this line, the electromagnet units 8 to 10 are used when the steel strip of the minimum width passes through, and the electromagnet units 6 to 12 are used when the steel strip of the maximum plate width passes through. Each electromagnet unit controls the position of the steel strip by adjusting the output of the electromagnet according to the displacement of the steel strip measured by the displacement sensor. Thereby, the fluctuation | variation of the space | interval of the steel strip and a gas wiping nozzle by the curvature and vibration of a steel strip is suppressed, and adjustment of the molten zinc adhesion amount by a gas wiping apparatus is stabilized. As a result, deviation of the plating thickness from the target value is suppressed.

However, when a steel strip welded joint that connects two types of steel strips that do not have the same width passes through the control range of the steel strip position control device, the electromagnetic force per unit area of the steel strip end portion changes greatly. However, the balance between the electromagnetic force and the reaction force of the steel strip momentarily collapses, and the steel strip vibrates and the displacement of the steel strip increases instantaneously.
Therefore, the control method of temporarily stopping the steel strip position control device by cutting off the power supply of the electromagnet only while the steel strip welding joint and its vicinity pass, but when switching control from movable to stop The vibration / displacement of the steel strip suddenly increased, resulting in a non-uniform plating adhesion (conventional example).

  Therefore, for the electromagnet unit used when the steel strip welding joint passes through the control range of the steel strip position control device, a method of fixing the electromagnet to a certain number while utilizing the electromagnet was implemented (example of the present invention). . With this method, fluctuations in the attractive force of the electromagnet could be suppressed even if the width and / or thickness of the steel strip passing through it changed. Further, when the above-described steel strip welding joint passes through the control range of the steel strip position control device, the electromagnet unit used for the steel strip having the minimum width to be processed in the line further fixes the fluctuation. Could be suppressed.

That is, immediately before the steel strip welding joint passes, by switching to only the electromagnet unit arranged at the minimum width of the steel strip, the overall position control of the steel strip is continued and the electromagnetic at the end of the steel strip is continued. It has been clarified that it is possible to prevent the adverse effect that the balance between the suction force due to the force and the reaction force of the steel strip collapses rapidly due to the change in the steel strip width.
In addition, the output of the electromagnet is further preferably set to a constant output without changing the output until the vicinity of the steel strip welding joint passes through the control range of the steel strip position control device. Moreover, the upper limit value of the output of the electromagnet per set that allows the steel strip to pass stably is obtained in advance, and if the output before the vicinity of the steel strip weld joint passes is equal to or lower than the upper limit value, the output is determined. If it continues and it is more than the upper limit, it is more preferable that the output of the electromagnet when the vicinity of the welded portion of the steel strip passes is the same constant output as the upper limit.

  A conventional method for temporarily stopping the steel strip position control device using an electromagnet only during the passage of the above-described steel strip weld joint and its vicinity under the same conditions of steel strip tension, steel strip speed, and gas wiping pressure. Method 1 of the present invention in which the steel strip position control device is used by fixing to only three central electromagnet units corresponding to the steel strip having the minimum line width as a number, the width of the steel strip before and after the steel strip weld joint, and / or Method 2 of the present invention in which the final output of the preceding steel strip is maintained regardless of the thickness change and attracted with an electromagnet, and the output before passing through the steel strip weld joint is set in advance for the output of the electromagnet per set Table 1 shows the results of carrying out the method 3 of the present invention in which the output is constant when the upper limit is exceeded.

  When the preceding steel strip of the same size and the succeeding steel strip of the same size are plated, the variation range of the steel strip is significantly less than 1/2 compared with the conventional example, and the steel strip and the electromagnet It was confirmed that the present invention was effective without generation of wrinkles due to contact.

DESCRIPTION OF SYMBOLS 1 Steel strip 2 Molten zinc bath 3 Sink roll 4a, 4b Gas wiping nozzle 5 Steel strip position control apparatus 6-12 using an electromagnet unit Electromagnet units 6a-12a Surface electromagnet 6b-12b Back surface electromagnet 6c-12c Non-contact displacement sensor

Claims (4)

An electromagnet having a pair of electromagnets provided facing each other so as to sandwich the front and back of a running steel strip that has left the hot dip galvanizing bath or hot dip zinc alloy plating bath, and a displacement sensor that measures the out-of-plane displacement of the steel strip In a production facility for a hot dip galvanized steel strip or a hot dip galvanized steel strip, comprising a steel strip position control device in which a plurality of units are arranged in the width direction of the steel strip and a pair of gas wiping nozzles for adjusting the amount of plating applied ,
While adjusting the output of the electromagnet based on the information of the displacement sensor to control at least the pass line of the steel strip and the warp in the width direction of the steel strip in a non-contact manner, continuous hot dip galvanization or hot dip zinc alloy plating is performed. A method of manufacturing a steel strip,
The steel strip is fixed to a certain number of sets of electromagnet units only while the steel strip welded joint connecting steel strips having different widths and / or thicknesses passes through the control range of the steel strip position control device. A method for producing a hot dip galvanized steel strip characterized by correcting the warp in the width direction of the steel strip in a non-contact manner.   Only while the steel strip welded joint and its vicinity pass through the control range of the steel strip position control device, the steel strip is fixed only to the electromagnet unit used when passing the steel strip with the minimum width processed in the line. The method for producing a hot dip galvanized steel strip according to claim 1, wherein the warp in the strip pass line and the strip width direction is corrected without contact.   Only while the steel strip welding joint and its vicinity pass through the control range of the steel strip position control device, it is continuously used as a constant output without changing the output of the electromagnet to be excited. The method for producing a hot-dip galvanized steel strip according to claim 1 or 2, wherein position control of the part is performed.   The output of the electromagnet per set to be excited only when the steel strip weld joint and its vicinity pass through the control range of the steel strip position control device, and the output before passing the steel strip weld joint is a predetermined upper limit. If it is less than the value, it is continuously used at the output before passing through the weld zone of the steel strip, and if it exceeds a predetermined upper limit value, it is used at a constant output that is the same value as the predetermined upper limit value. The method for manufacturing a hot dip galvanized steel strip according to any one of claims 1 to 3, wherein the position of the joint portion is controlled.

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