JP4775035B2 - Metal strip hot dip plating method and hot dip plating equipment - Google Patents

Description

  The present invention relates to a hot dip plating method and hot dip plating equipment for a metal strip.

As a method for continuously plating a metal strip such as a steel strip, a hot dipping method is known in which the metal strip is immersed in a molten metal such as zinc or aluminum and the surface of the metal strip is plated.
In the hot dipping method, the metal strip that has been rolled in the cold rolling process and then cleaned in the cleaning process is annealed in an annealing furnace maintained at a non-oxidizing or reducing atmosphere (at this time, the surface oxide film After being removed), it is cooled to approximately the same temperature as the molten metal temperature, and is formed into a substantially V-shaped path having a sink roll disposed in a bath (referring to a molten metal bath or a plating bath) as a turning point. It is made to pass along and is immersed in a bath, and a molten metal is made to adhere to the surface of a metal belt. Further, the wiping gas is sprayed on the front and back surfaces of the metal strip drawn from the bath so as to face each other with the path surface interposed therebetween to wipe away excess molten metal, thereby adjusting the amount of metal adhesion.

This hot dipping method has features such as the ability to produce a plated metal strip at a lower cost and the ability to easily produce a thick plated metal strip than the electroplating method.
The metal strip generates warpage (C warpage) convex in the width direction on the side opposite to the sink roll by bending and unbending at the sink roll when passing through the bath. In order to correct this C warp, a pair of support rolls provided on the sink roll outlet side is used. If the shape of the metal strip can be made flat by this correction, the adhesion amount distribution can be made fairly uniform.

However, normally, due to the width direction component of the three-dimensional flow of wiping gas from the gas wiping nozzle, a difference in the amount of adhesion tends to occur between the center and the end in the width direction, and it is difficult to obtain a uniform amount distribution. In addition, foreign matters such as molten metal droplets adhere to the gas wiping nozzle, and the nozzle gap is likely to be clogged, which hinders stable operation of molten metal plating.
As a means for solving these problems, there is known a variable gap type gas wiping nozzle disclosed in Patent Document 1 that includes a strain induction type actuator (for example, a piezoelectric element) that adjusts the opening degree of a nozzle gap for blowing wiping gas. It has been. A plurality of strain-inducing actuators are arranged in the nozzle width direction (parallel to the metal band width direction), and are interposed between the upper lip and the lower lip forming the nozzle gap in each arrangement portion, or the upper lip and the lower lip And the opening degree of the nozzle gap is adjusted by the expansion and contraction.

Multiple strain-inducing actuators arranged in the nozzle width direction are compact and excellent in responsiveness, and individually adjust the nozzle gap of each arrangement part according to the output of the adhesion meter etc. arranged on the downstream side of the path Therefore, the uniform distribution of the amount of adhesion is achieved. Further, by causing the strain-inducing actuator to vibrate continuously or intermittently (small high-speed vibration having a vibration amplitude of 0.1 mm or less and a vibration frequency of 10 Hz or more), adhesion of foreign matter to the nozzle can be suppressed. In addition, since the strain-inducing actuator is built in the nozzle and has no protruding portion outside the nozzle, the wiping gas blowing air current is not disturbed, and a stable adhesion amount distribution can be obtained.
JP-A-2005-133208

  However, when using the gap variable gas wiping nozzle in the production line of continuous hot dip galvanized steel sheet, it is built into the nozzle during continuous hot dip galvanizing operation in order to suppress foreign matter adhesion to the nozzle. The strain induction type actuator was vibrated almost always. For this reason, coupled with the fact that the usage environment is severe at high temperatures, the life of the strain-inducing actuator is short, and it is necessary to replace it frequently, and there is a problem that the productivity of the hot dip galvanized steel sheet is hindered. In addition, since the strain induction type actuators are quite expensive and a plurality of strain induction type actuators are used, the short replacement cycle has been an obstacle to reducing the running cost.

  In view of the above-described circumstances, the present invention maintains the quality of plated products when using a gas wiping nozzle (referred to as a vibration nozzle) with a built-in strain induction actuator in the molten metal plating technology field of a metal strip. However, an object of the present invention is to provide a means capable of extending the replacement period of the strain induction type actuator.

  In order to achieve the above object, the inventors conducted an experiment to grasp the occurrence of foreign matter adhesion to the nozzle in a continuous hot dip galvanizing line that targets a steel strip as a metal strip. Got. That is, the occurrence of foreign matter adhesion to the vibration nozzle is determined by the location where the leading end and the trailing end of the steel strip to be plated are connected by welding (referred to as the welding point). It has been found that it occurs in a time zone from when it passes through until a short time elapses. This is because the vicinity of the welding point is an unsteady part where the steel strip material, thickness and width change. In such unsteady part, the banding state becomes unstable, and warping and slackening occur. This is thought to be related to the fact that shape disturbance is likely to occur. Therefore, if the vibration nozzle is vibrated only for a short time based on the timing at which the welding point passes the vibration nozzle position, foreign matter adhesion to the vibration nozzle can be efficiently suppressed.

The present invention has been made based on these findings and further studies. That is, the present invention is as follows.
(1) Hot-dip plating that removes excess metal adhering from the surface of the metal strip pulled up after being immersed in a molten metal bath with a vibration nozzle while continuously passing a metal strip having a welding point in the longitudinal direction A hot dipping method, wherein the vibration nozzle is vibrated based on a tracking position of a welding point.

(2) Hot-dip plating that continuously wipes a metal strip having a welding point in the longitudinal direction while wiping gas from the surface of the metal strip pulled up after being immersed in a molten metal bath with a vibration nozzle. In the method, the hot-dip plating method is characterized in that the vibration nozzle is vibrated based on the tracking position of the welding point and the amount of warpage of the metal band measured on the downstream side of the vibration nozzle position.
(3) Hot-dip plating that continuously wipes a metal strip having a welding point in the longitudinal direction while wiping gas from the surface of the metal strip pulled up after being immersed in a molten metal bath with a vibration nozzle. In the equipment, a welding point detector that detects the passage of the welding point upstream of the molten metal bath, a movement amount measuring device that measures the movement amount of the metal band in the molten plating equipment, and a detected value and a movement amount of the welding point detector. A hot dipping plating facility comprising a tracking calculator that calculates a tracking position of a welding point from a measurement value of a measuring instrument, and nozzle vibration control means that vibrates a vibration nozzle based on the calculation result of the tracking calculator .

  (4) Hot-dip plating that continuously wipes a metal strip having a welding point in the longitudinal direction while wiping gas from the surface of the metal strip pulled up after being immersed in a molten metal bath with a vibration nozzle. In the equipment, a welding point detector that detects the passage of the welding point upstream of the molten metal bath, a movement amount measuring device that measures the movement amount of the metal band in the molten plating equipment, and a detected value and a movement amount of the welding point detector. A tracking calculator that calculates the tracking position of the welding point from the measurement value of the measuring instrument, a warp measuring means that measures the amount of metal band warping downstream from the vibration nozzle position based on the calculation result of the tracking calculator, and warp measurement A hot dipping apparatus comprising nozzle vibration control means for vibrating the vibration nozzle based on the measurement result of the means.

  According to the present invention, the vibration-inducing actuator can be vibrated at an optimal timing, and the distortion-inducing actuator incorporated in the vibration nozzle while suppressing the adhesion of foreign matter to the vibration nozzle and maintaining the quality of the plated product. The replacement cycle can be extended.

Hereinafter, an embodiment of the present invention will be described by taking a hot dip galvanizing method of a steel strip as an example, but the present invention is not limited to this example, and a metal strip other than the steel strip, or a melt other than the molten zinc The present invention can also be applied to a hot dipping method using metal.
FIG. 1 is a schematic view showing an example of a hot dip galvanizing line for steel strip to which the present invention is applied. FIG. The steel strip 20 is coiled out in two strips 11 alternately, and the leading end of the preceding material and the leading end of the succeeding material are cut by the entrance-side cutting machine 13, and the cutting ends are separated from each other. Those having welding points formed by welding and joining are welded in the direction indicated by the arrow 10. After passing through various pretreatments (not shown), the steel strip 20 in the continuous zone is annealed in the annealing furnace 2 and subsequently immersed in the molten zinc bath 1, and obliquely from below to above by the sink roll 5 in the bath. After the direction is changed and the shape is corrected by the support roll 6 in the bath, it is pulled up on the bath, and then the molten zinc adhering excessively on both surfaces of the steel strip 20 is wiped off by blowing the gas from the vibration nozzle 3. After that, it is guided by the bath support roll 7 and the like, and after various post-processing (not shown), finally, the welding point is cut and removed by the exit side cutting machine 14, and two winders It is wound up in a coil shape alternately at 12.

A punch hole is opened at the welding point, and this installation position is welded by a light emitting / receiving type welding point detector 8 installed on the upstream side of the molten zinc bath 1 (the entrance side of the annealing furnace 2 in FIG. 1). The event that the point has passed can be detected. In the annealing furnace 2, a moving amount measuring device 9 made of PLD or the like for measuring the moving amount of the steel strip 20 is installed.
Further, on the downstream side of the vibration nozzle 3, a plurality of distance meters forming a sensor part 4A of the warp measuring means 4 for measuring the warp amount of the steel strip 20 are arranged in a direction parallel to the steel strip passage width direction. .

  The vibration nozzle 3 is a gas wiping nozzle having a built-in strain induction actuator, and an example thereof is shown in FIG. In these examples, the piezoelectric element 16 is used as a strain-inducing actuator. In FIG. 3A, the upper and lower lips 81 and 82 forming the nozzle tip are connected to the gas outlet of the original header 80, and the piezoelectric element 16 crosses the gas flow flowing in the gas flow direction 18 indicated by the arrow. The upper and lower lips 81 and 82 are mounted in a cross-linking manner. In FIG. 3B, the gas outlet of the original header portion (not shown) is connected to a gas passage penetrating the thickness of the upper lip 81, and the piezoelectric element 16 connects the root portions of the upper and lower lips 81 and 82 to each other. It is mounted in a shape that does not interfere with the gas flow. In FIG. 3C, the upper and lower lips 81 and 82 forming the nozzle tip are connected to the gas outlet of the original header 80, and the piezoelectric element 16 is separately provided on the inner surface side of the upper and lower lips 81 and 82. It is installed.

  A plurality of piezoelectric elements 16 are arranged in the width direction of the vibration nozzle 3, and some of the piezoelectric elements are used for vibration, and each vibrate in the arrow vibration direction 17 </ b> A by a vibration control signal from the signal line 30. In accordance with this vibration, the upper and lower lips 81 and 82 vibrate in the arrow vibration direction 17. Due to this vibration, foreign matter adhering to the vibration nozzle 3 is eliminated. The frequency of the vibration of the vibration nozzle is preferably 10 to 1000 Hz, and the amplitude is preferably 10 to 100 μm. The piezoelectric elements other than those for vibration are used for adjusting the nozzle gap distribution in the width direction, and are individually controlled to expand or contract by a predetermined amount.

  In the present invention, the vibration of the vibration nozzle is controlled based on the tracking position of the welding point. Specifically, the vibration nozzle is vibrated from the time when the tracking position of the welding point coincides with the vibration nozzle position. Here, after the foreign matter has been sufficiently removed, the vibration in a time zone in which new foreign matter hardly adheres is wasted. Therefore, the vibration nozzle is vibrated for a necessary time after the welding point passes the vibration nozzle position, and then stopped.

A preferred control system for carrying out this method is shown in FIG. This control system includes a tracking calculator 19 for calculating the tracking position of the welding point from the detected value of the welding point detector 8 and the measured value of the movement amount measuring unit 9, and the excitation nozzle based on the calculation result of the tracking calculator 19. And nozzle vibration control means 21 for vibrating 3.
In the present invention, it is preferable to vibrate the vibration nozzle not only based on the tracking position of the welding point but also on the amount of warpage of the steel strip measured downstream from the vibration nozzle position. Specifically, the amount of warpage of the steel strip is measured from the time when the tracking position of the welding point coincides with the position of the vibration nozzle, and the vibration nozzle is vibrated from the time when this measured value is equal to or less than the target value. According to this, the time from when the tracking position of the welding point passes through the vibration nozzle position until the steel strip warpage is stabilized does not vibrate the vibration nozzle, leaving the foreign matter to adhere, By simply vibrating from the time when the warpage of the steel strip is stabilized, the adhered foreign matter can be removed sufficiently and efficiently, compared to the case where vibration is started from the point where the welding point passes through the vibration nozzle position. Also, the vibration time can be shortened.

  A preferred control system for carrying out this method is shown in FIG. This control system includes a tracking calculator 19 for calculating the tracking position of the welding point from the detected value of the welding point detector 8 and the measured value of the movement amount measuring unit 9, and the excitation nozzle based on the calculation result of the tracking calculator 19. A warp measuring means 4 for measuring the amount of metal band warpage downstream from the position and a nozzle vibration control means 22 for vibrating the vibration nozzle 3 based on the measurement result of the warp measuring means 4 are provided.

The hot dip galvanization of the steel strip was performed on the conditions of following AD using the hot dipping equipment shown in FIG.
A (comparative example): The vibration nozzle is not vibrated at all.
B (comparative example): The vibration nozzle is constantly vibrated.
C (Example of the present invention): Using the control system of FIG. 4A, the vibration nozzle is vibrated at a frequency of 850 Hz and an amplitude of 20 μm for 30 seconds from the time when the welding point passes the vibration nozzle position.

D (example of the present invention): Using the control system of FIG. 4B, the amount of warpage of the steel strip was measured from the time when the welding point passed through the vibration nozzle position, and the measured value was below the target value. The excitation nozzle is vibrated at a frequency of 850 Hz and an amplitude of 20 μm only for 25 seconds.
FIG. 5A and FIG. 5B show a comparison between the nozzle clogging defect rate (product defect occurrence rate due to nozzle clogging) and the piezoelectric element life in the plating operation under these conditions. The nozzle clogging failure rate is shown as a relative value when the condition A is 100, and the life of the piezoelectric element is shown as a relative value when the condition B is 1. The nozzle clogging failure rate was obtained from the number of coils in which 1000 coils were processed under each condition and a defect occurred.

  As shown in the figure, according to the present invention, nozzle clogging can be effectively suppressed, and the life of the piezoelectric element can be significantly extended while maintaining the quality of the plated product.

It is the schematic which shows one example of the hot dip galvanizing line of a steel strip. FIG. 2 is a detailed view of a G part in FIG. 1. It is sectional drawing which shows the example of a vibration nozzle. It is a block diagram which shows the example of the vibration control system of a vibration nozzle. It is a graph which shows the nozzle clogging defective rate (a) and piezoelectric element lifetime (b) of an Example (C, D) and a comparative example (A, B).

Explanation of symbols

1 Molten metal bath (molten zinc bath)
2 Annealing furnace 3 Gas wiping nozzle (vibration nozzle) with built-in strain induction actuator
4 Warp measurement means
4A Sensor part (distance meter) of warp measuring means
5 sink roll 6 support roll in bath 7 support roll on bath 8 welding point detector 9 travel meter
10 Arrow indication method
11 Dispenser
12 Winder
13 Entry side cutting machine
14 Outlet cutting machine
15 Welding machine
16 Strain-induced actuator (piezoelectric element)
17, 17A Arrow vibration direction
18 Arrow gas flow direction
19 Tracking calculator
20 Metal strip (steel strip)
21 Nozzle vibration control means
22 Nozzle vibration control means
30 signal lines
80 original header
81 upper lip
82 Lower lip

Claims (4)

  In the hot dip plating method in which a metal strip having a welding point in the longitudinal direction is continuously passed, and the excess adhesion of the molten metal is wiped off with a vibration nozzle from the surface of the metal strip pulled up after being immersed in the molten metal bath, A hot dipping method, wherein the vibration nozzle is vibrated based on the tracking position of the welding point.   In the hot dip plating method in which a metal strip having a welding point in the longitudinal direction is continuously passed, and the excess adhesion of the molten metal is wiped off with a vibration nozzle from the surface of the metal strip pulled up after being immersed in the molten metal bath, A hot dipping method, wherein the vibration nozzle is vibrated based on the tracking position of the welding point and the amount of warpage of the metal band measured on the downstream side of the vibration nozzle position.   In the hot dip plating facility that continuously wipes the metal strip having the welding point in the longitudinal direction, and wipes off the excess adhesion of the molten metal from the surface of the metal strip pulled up after being immersed in the molten metal bath with a vibration nozzle, A welding point detector that detects the passage of a welding point upstream of the molten metal bath, a movement amount measuring device that measures the movement of the metal band in the hot dipping equipment, and a detection value and a movement amount measuring device of the welding point detector. A hot dipping apparatus comprising: a tracking calculator that calculates a tracking position of a welding point from a measurement value; and nozzle vibration control means that vibrates a vibration nozzle based on a calculation result of the tracking calculator.   In the hot dip plating facility that continuously wipes the metal strip having the welding point in the longitudinal direction, and wipes off the excess adhesion of the molten metal from the surface of the metal strip pulled up after being immersed in the molten metal bath with a vibration nozzle, A welding point detector that detects the passage of a welding point upstream of the molten metal bath, a movement amount measuring device that measures the movement of the metal band in the hot dipping equipment, and a detection value and a movement amount measuring device of the welding point detector. A tracking calculator that calculates the tracking position of the welding point from the measured value, a warp measuring means that measures the amount of metal band warping downstream from the vibration nozzle position based on the calculation result of the tracking calculator, and a measurement by the warp measuring means A hot dipping apparatus comprising nozzle vibration control means for vibrating the vibration nozzle based on the result.

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