JP2732464B2 - Manufacturing method of continuous hot-dip galvanized steel strip - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a continuous hot-dip metal-plated steel strip, and more particularly to a method for manufacturing a hot-dip metal-plated steel strip while controlling meandering of the steel strip. It is.

[Prior Art] As an apparatus for producing a continuous hot-dip galvanized steel strip, there is one generally disclosed in Japanese Patent Publication No. 56-37302.
Here, as shown in FIG. 6, a tension adjusting device 1, a non-oxidizing preheating furnace 2, a heating equalizing furnace 3, a jet cooling furnace 4, a conditioning cooling furnace 5, a turndown roll 6, a melting pot 7, a sink roll 8, Nozzle 9, cooling device 10, teflector roll 1
1, cooling device 10, and tension bridle roll 12
Are sequentially arranged. In this case, the non-oxidizing preheating furnace 2, the heating equalizing furnace 3, the jet cooling furnace 4, the conditioning cooling furnace 5, and the like are generally referred to as a pretreatment furnace 21. Here, the steel strip 13 is held at a constant tension by the tension adjusting device 1 and the tension bridle roll 12, and first, the hot oil of incomplete combustion in the non-oxidizing preheating furnace 2 evaporates rolling oil or the like adhering to the steel strip. Remove by disassembly. Then, the surface of the steel strip 13 is reduced by a reducing atmosphere such as hydrogen at 900 to 1000 ° C. in a heating equalizing furnace 3 and cooled by a jet cooling furnace 4.
Further, it is kept in a reducing atmosphere in the conditioning cooling furnace 5 and overaged. Next, the molten metal is guided into the molten metal in the molten pot 7 by the turndown roll 6, the molten metal is adhered, the direction of the steel strip 13 is changed by the sink roll 8, and the basis weight of the molten metal adhered to the steel strip 13 by the nozzle 9. Is adjusted, and cooling after plating is performed by the cooling device 10. Here, it is important to make the basis weight of the molten metal of the steel strip uniform. Generally, the adjustment of the basis weight of the molten metal is performed by gas restriction by a nozzle 9 using an inert gas. In this method for adjusting the basis weight of the molten metal, the steel strip 13 in the nozzle 9 is used.
Swing is an important issue. In other words, a slit nozzle is generally used for the nozzle 9, and in order to obtain a uniform basis weight in the width direction of the steel strip, the shape of the slit width corresponding to the center and the end in the width direction of the steel strip is changed. In addition, the gas volume is adjusted by changing the gas pressure blown to the center and the end in the width direction of the steel strip. If the steel strip is severely meandering, it is difficult to center the steel strip with the slit nozzle, so that the coating weight in the width direction of the steel strip tends to be non-uniform. It can happen. If the runout of the steel strip 13 is excessive, not only the basis weight becomes unstable but also the nozzle 9 comes into contact with the steel strip 13,
This may lead to an accident that the nozzle 9 is clogged.

In recent years, the line speed increased to 200 due to the increase in size of plating equipment.
Higher speeds of up to 250 m / min have been required. In general, as the threading speed increases, the run-out of the steel strip 13 also increases. As a measure for preventing the run-out of the steel strip, a method of maintaining the tension of the steel strip at the nozzle portion high can be considered. However, in the above-described apparatus, the tension in the pretreatment furnace also increases. Since the atmosphere in the pretreatment furnace is a high-temperature atmosphere, if the tension of the steel strip is set too high, problems such as shrinkage of the sheet width and cutting of the sheet occur. For this reason, the tension in the pretreatment furnace is limited, and it is not possible to increase the entire tension to the tension required for the steel strip at the nozzle. To cope with this problem, Japanese Patent Publication No. 56-37302 discloses a motor driven bridle roll 14 at the rear of the pretreatment furnace, that is, at the place where the turndown roll is installed, as shown in FIG.
a and 14b are provided so that the tension of the steel strip at the nozzle can be increased irrespective of the tension of the steel strip in the pretreatment furnace.

However, it is difficult to prevent total runout only by tension, and while tension is effective for runout in the steel strip thickness direction, commonly called flapping, it is almost effective for runout or meandering in the steel strip width direction. There is no. In order to prevent the meandering of the steel strip 13, conventionally, the inclination of the axis of the sink roll 8 is changed so that the steel strip 13 does not meander near the nozzle 9.

[Problems to be Solved by the Invention] However, by adjusting the sink roll 8, the meandering of the steel strip 13 is prevented, the coating amount of the steel strip 13 in the width direction is made uniform, and the steel strip having no plating defect at the edge portion is formed. There were still many problems to make. The sink roll adheres the molten metal to the steel strip 13 in the melting pot 7 and the steel strip 13
The main purpose is to change the direction of the steel strip 13 and make the steel strip 13 travel to the next molten metal basis weight adjusting device. This sink roll is a steel strip
When used for steering control in order to prevent meandering of 13, one problem is that flaws occur on the surface of the plated steel strip 13. In addition, in order to properly prevent the meandering of the steel strip 13 by the sink roll 8, it is necessary to accurately detect the meandering state of the steel strip 13, but the place where the meandering state of the steel strip 13 is detected is limited. In addition, fumes such as zinc are generated at the location, and it is difficult to accurately detect the meandering of the steel sheet by using a usual steel strip meandering detection device such as a photoelectric sensor because the light receiving portion becomes cloudy. Further, the cause of meandering often occurs before the sink roll 8, and it is difficult to eliminate the cause only by the sink roll 8, and therefore, the production of a continuous hot-dip coated steel strip capable of preventing meandering. A method was strongly desired. The present invention has been made to solve the above-mentioned problems, and prevents meandering of the steel strip and does not cause unevenness in the coating amount of plating in the width direction of the steel strip or generation of plating defects at the edge of the steel strip. It is an object of the present invention to provide a method for producing a continuous hot-dip metal-plated steel strip.

[Means and Actions for Solving the Problems] To achieve the above object, the method of the present invention continuously melts in a molten metal plating apparatus equipped with a pretreatment furnace, a molten pot, and a molten metal basis weight adjusting device. In the method of manufacturing a metal-plated steel strip, a steering roll device and a steel strip meandering detection device are disposed at a rear side of the steel strip of the pretreatment furnace, and the meandering state of the traveling steel strip is continuously changed. By detecting the detected value and operating the plurality of rolls of the steering roll device as an integral body using an end pivot method in accordance with the detected value, the steel strip is subjected to steering control to produce a hot-dip coated steel strip.

Continuously detecting the meandering state of the steel strip traveling to the rear of the pretreatment furnace by the method of the present invention, and operating the plurality of rolls of the steering roll device as an integral unit using an end pivot method according to the detected value. Accordingly, the steering control of the steel strip is performed by correcting the meandering state of the steel strip before the steel strip is plated in the molten pot. Here, since the steel strip has not been plated yet, the quality of the plated steel strip is not affected. In addition to this, the end pivot method has a higher correction accuracy than the center pivot method, and it is possible to reduce the deformation amount of the steel strip and increase the correction amount by operating a plurality of rolls as one body. Easy. As a result, the meandering state can be accurately detected and corrected. Thereafter, the steel strip is plated in a molten pot, and then the molten metal weight per unit area is adjusted by a slit nozzle. Since the center ring is appropriate, the amount of plating applied in the width direction of the steel strip becomes uniform.

In the method of the present invention, an electromagnetic induction type sensor is used for the steel strip meandering detection device. The electromagnetic induction type sensor has a detection end including a transmission coil and a reception coil, and is arranged to face each other with a steel strip therebetween. A high-frequency current is applied to the transmission coil to generate an AC magnetic field, thereby inducing an electromotive voltage in the reception coil. When a steel strip exists between the transmission coil and the reception coil, the voltage of the reception coil changes to block a part of the magnetic field. The change is proportional to the movement of the steel strip. Therefore, the center position of the steel strip and the amount of movement from the center position are detected. In addition, the detection end has a robust structure, and the electromagnetic induction sensor can accurately detect the meandering state of the steel strip even when the location where the meandering state of the steel strip is detected is bad, for example, when fumes such as zinc are generated. Can be detected. Based on these characteristics of the electromagnetic induction type sensor, the present inventors made various trials in this limited place, and for the first time, enabled use of the steel strip meandering detection device in this limited place.

[Embodiment of the Invention] An embodiment of the method of the present invention will be described below with reference to the drawings. FIG. 1 shows a main part of an embodiment of a molten metal plating apparatus for performing the method of the present invention. In the figure, a steering roll device 23 is provided at a rear portion 22 of the pretreatment furnace 21 and a steel strip meandering detection device 24 is disposed on a steel strip exit side of the roll device, and the meandering state of the traveling steel strip 13 is continuously detected. The steel strip 13 is subjected to steering control by the steering roll device 23 according to the detected value. The steel strip 13 corrected by the steering roll device 23 is led to the melting pot 7 where the molten metal adheres to the sink roll 8.
Then, the vehicle travels with the basis weight adjusted by the molten metal basis weight adjusting device 9 provided immediately above the melting pot 7. As the molten metal weight control device 9, a slit nozzle using an inert gas or the like is used.

FIG. 2 is a diagram for explaining a center pivot method to be compared with the method of the present invention. Here, three rolls 20
Are united. These rolls are set on a gantry 25. Although a top view is shown with its position adjusted below the lateral view at the top of the figure, the gantry 25 is rotatable in the direction of the thick arrow by the fulcrum 26.

FIG. 3 is an explanatory view of an end pivot type steering roll device 23 of the molten metal plating device for performing the method of the present invention. Here, three rolls 20 are paired. These rolls are set on a gantry 27. This stand
Numeral 27 is rotatable in the direction of a thick arrow by a fulcrum 28 and is movable in the steel strip width direction. Here, it is preferable that a plurality of steering rolls of the steering roll device 23 be integrated. Thus, the winding angle between the steel strip and the steering roll can be increased, and slip of the steel strip on the steering roll can be prevented.
In this case, it is necessary to operate a plurality of steering rolls simultaneously in order to prevent deformation of the steel strip between the steering rolls. In the case of the end pivot method, the deformation of the steel strip before and after the steering roll can be minimized, the meandering correction amount can be increased, and high responsiveness can be obtained as compared with the case of the center pivot method. In the present invention, it is necessary to provide a steel strip meandering detection device on the steel strip exit side of the steering roll device 23. In this case, as a steel strip meandering detection device, as described above, a device using an electromagnetic induction type sensor is a steering roll device 23.
Suitable for installation in a limited place on the steel strip exit side.
FIG. 4 is a diagram for explaining meandering detection of a steel strip and its control. In the figure, the steel strip 13 by the steel strip meandering detection device 24 is shown.
The meandering state is continuously detected by a detection unit 29 using an electromagnetic induction sensor, and a signal is sent to a calculation unit 30 where the signal is converted into a meandering amount. When the meandering amount exceeds an allowable range, steering is performed by a command unit 32. An instruction is given to the device 31 to operate the steering roll device 23 in accordance with the meandering amount to control the steering of the steel strip 13.

Next, an example in which the method of the present invention is performed using the above-described apparatus will be specifically described.

(Example) A steel strip having an average plate width of 1000 mm is run using the above-described device, and the meandering state of the steel strip is continuously detected by an electromagnetic induction type sensor using an end pivot type steering roll device. When the steering was controlled by the steering roll device, the meandering state of the steel strip was continuously detected by the electromagnetic induction type sensor at the exit side of the steel strip of the melting pot, and the meandering amount was measured 500 times. As a comparison, when a conventional turndown roll without a steering roll function was used, the meandering state of the steel strip was continuously detected by the electromagnetic induction type sensor at the exit side of the steel strip of the melting pot, and the meandering amount was 500 times. It is a result of examining measured values. FIG. 5 shows the results of the relationship between the meandering amount of the steel strip and its frequency in that case.

Here, the solid line shows an example according to the method of the present invention,
The dotted line shows the case where a conventional turndown roll other than the steering roll is used. As is clear from this figure,
In the conventional method, the meandering amount of 20 mm to 50 mm was the most frequent, but in the case of the method of the present invention, 90% was within 10 mm, and the remaining 10% was within 20 mm, indicating that the meandering amount of the steel strip was greatly reduced. Recognize.

As described above, according to the method of the present invention, the meandering amount of the steel strip passing through the molten metal weight control device can be controlled to a value that does not affect the actual operation, so that the centering by the slit nozzle is appropriately performed, The plating amount in the width direction of the steel strip becomes uniform.

[Effects of the Invention] According to the method of the present invention, a steering roll device and a steel strip meandering detection device are provided at the rear of the pretreatment furnace at the exit side of the steel strip of the roll device. Since the meandering state can be continuously detected and the steel strip can be manufactured while steering the steel strip by an end pivot method with a steering roll device according to the detected value, a hot-dip coated steel strip can be manufactured. The basis weight is uniform in the width direction of the steel strip, and a stable hot-dip metal-plated steel strip can be produced without causing a defect in the plating amount at the edge thereof. As described above, the effect of the present invention that a high-quality hot-dip coated steel strip can be produced at a high yield is great.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a main part of an embodiment of a continuous hot-dip metal plating apparatus for performing the method of the present invention, and FIG. 2 is a side view and a plane for explaining a center pivot method which is compared with the method of the present invention. FIG. 3 is a side view and a plan view for explaining an end pivot method as a method of the present invention of a continuous hot-dip metal plating apparatus for performing the method of the present invention, and FIG. FIG. 5 is a diagram showing the meandering amount and its frequency of one embodiment according to the method of the present invention, FIG. 6 is a schematic diagram of a continuous hot-dip metal plating apparatus performing a conventional method, and FIG. FIG. 7 is a diagram showing that a bridle roll is used instead of the turndown roll in FIG. 6. 21 …… Pretreatment furnace, 22… Rear part, 23 …… Steering roll device, 24 …… Steel belt meandering detection device, 25,27 …… Base, 26,28… Support point, 29 …… Detector, 30… ... Calculation unit, 31 ... Steering roll drive unit, command unit.

Claims (2)

(57) [Claims] 1. A method for continuously producing a hot-dip metal-plated steel strip by a hot-dip metal plating apparatus having a pre-treatment furnace, a hot-dip pot, and a hot-dip metal plating apparatus, the method comprising: A steel strip meandering detector is disposed on the steel strip exit side of the roll apparatus, and the meandering state of the running steel strip is continuously detected, and a plurality of rolls of the steering roll apparatus according to the detected value. A method of manufacturing a continuous hot-dip metal-plated steel strip by operating the steel strip while steering-controlling the steel strip by operating the steel strip as an integral body using an end pivot method. 2. The method for producing a continuous hot-dip metal-plated steel strip according to claim 1, wherein the meandering detecting device detects the meandering in front of the melting pot by using an electromagnetic induction sensor.