JP2003117782A - Polishing method and polishing device for top roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing method and a polishing device for a top roll capable of reducing push flaws generated on a steel strip surface due to foreign matter sticking on the top roller less than a conventional top roller in a continuous molten metal plating line. SOLUTION: When polishing a surface of the top roller arranged in the continuous molten metal plating line by a polishing roller, a pushing-in quantity of the polishing roller to the top roller is adjusted according to a load of a motor for rotating the polishing roller.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing method and a polishing apparatus for a top roll, and more specifically, a so-called "top roll" provided for changing the direction of a steel strip running on a continuous hot-dip galvanizing line. The present invention relates to a technique for polishing and cleaning the surface.

[0002]

2. Description of the Related Art For example, in order to manufacture an alloyed hot-dip galvanized steel sheet, a continuous hot-dip galvanizing apparatus (referred to as a line) as shown in FIG. 2 is used. The steel strip 2 heated in the annealing furnace 1 is continuously supplied into a bath 4 holding a molten metal plating (hereinafter referred to as a plating bath 3), and the steel strip 2 is provided by a dipping roll 5 provided in the plating bath 3. The molten metal plating is adhered to the surface of the steel strip 2 by vertically raising the traveling direction of the steel strip 2. For the steel strip to which the plating has adhered and which has come out of the bath, the coating adhesion amount is adjusted by blowing a gas called wiping, and then heated by a heating device 6 to alloy the plating layer, if necessary. Then, it is cooled by the cooling device 7, passed through a skin pass rolling device (not shown) and the like, and taken up by a tension reel (not shown). In such a continuous hot-dip galvanizing line, the vertically rising steel strip 2 advances with two rolls (which are called top rolls 8 because they are located at the highest position in the process) provided above and separated from each other. It reverses the direction and descends. It should be noted that the cooling device 7 is usually installed in two separate locations on the ascending side and the descending side of the steel strip 2 due to the height of the building. By the way, even if the cooling device 7 as described above is provided, the top roll 8 comes into contact with the steel strip 2 having a temperature of 300 ° C. to 400 ° C. during operation. Therefore, there has been a problem that foreign matter such as zinc powder adheres to the surface of the top roll 8 and deteriorates the quality of the hot-dip galvanized steel sheet as a product. Therefore, Japanese Patent Application Laid-Open No. 5-320844 discloses
It has been proposed to dispose a polishing roll 9 for polishing the surface of the top roll 8 immediately online. As shown in FIG. 2, it is provided at a position substantially horizontal to the height of the top roll 8 and is in contact with the surface of the top roll while rotating to polish the surface (hereinafter referred to as polishing roll 9). A trolley that supports the polishing roll 9 and is movable along the axial direction of the top roll 8, a vertical traveling device that mounts these and moves forward and backward toward the top roll, and a drive unit that drives the vertical traveling device. It is composed of and. Then, when polishing the surface of the top roll, the polishing roll made of an abrasive is pressed against the surface of the top roll and rotated, but how much the polishing roll is pressed against the top roll is important. The pushing amount (distance to move the position of the polishing roll to the top roll side) is determined by placing the support member of the polishing roll on the guide rail as described above and mechanically pushing it to the stopper position with a hydraulic or pneumatic cylinder. The top is pushed in using a pull handle or a motor. However, in such a conventional technique, when the polishing roll is moved along the axial direction of the top roll (this movement is orthogonal to the moving direction for pushing, it is called lateral movement), the pushing amount is constant. Then,
There are the following problems.

(A) The top roll usually has a convex swelling shape (referred to as a thermal crown) as shown in FIG.
The contact condition of the polishing roll 9 changes at some position in the axial direction, and the foreign matter adhering to the top roll 8 cannot be removed at a place where the contact is small, so that the surface of the hot-dipped metal strip 2 is removed. The foreign matter is transferred to cause a defect that the surface of the steel strip is dented (this is called a push defect). In this case, if the pushing amount of the polishing roll 9 is adjusted on the basis of a place with less contact, the polishing roll 9 will be damaged at the place with strong contact.

(B) Further, even when the polishing roll 9 is worn and the diameter of the roll is reduced, the removal force of the foreign matter is reduced and the foreign matter remains on the surface of the top roll 8 to push the steel strip. Generate defects.

In FIG. 3, the operator side means that the operator passes by the side of the top roll and the side where the operator works is the drive side, and the drive side means the top roll drive means. Means the side.

[0006]

SUMMARY OF THE INVENTION In view of such circumstances, the present invention is to polish a top roll in a continuous hot-dip galvanizing line capable of reducing the push defects generated in the product due to the foreign matter adhering to the top roll as compared with the prior art. It is an object to provide a method and a polishing device.

[0007]

[Means for Solving the Problems] The inventors of the present invention have made extensive studies in order to achieve the above object, and have realized the results in the present invention.

That is, according to the present invention, when the surface of the top roll provided in the continuous hot-dip galvanizing line is polished by the polishing roll, the top roll of the polishing roll is adjusted according to the load of the motor for rotating the polishing roll. The method for polishing a top roll is characterized by adjusting the amount of pushing into the top roll.

The present invention also provides a polishing roll which is provided at a position substantially horizontal to the height of the top roll of the continuous hot-dip galvanizing line, contacts the surface of the top roll while rotating, and polishes the surface, and the polishing roll. A trolley that supports the rolls and is movable along the axial direction of the top roll, a vertical traveling device that mounts these and moves forward and backward toward the top roll, and a drive unit that moves the vertical traveling device. In a top roll polishing device provided with a sensor for detecting the load of a motor for rotating the polishing roll, and comparing the detected value with a threshold value, and a control device for changing the pushing amount of the polishing roll to the top roll. A top roll polishing apparatus comprising: In this case, the sensor is preferably an ammeter.

According to the present invention, the polishing roll comes into contact with the entire top roll in the axial direction with an appropriate force, and the foreign matter adhering to the surface of the top roll can be almost completely removed. As a result, the flaws caused by the foreign matter do not occur on the surface of the steel strip that has been subjected to the hot dip metal plating, and it becomes possible to manufacture a hot dip galvanized steel sheet having a better plating quality than before.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

First, the inventors thought that, in order to solve the above-mentioned problems of the prior art, it was necessary to bring the polishing roll into contact with the entire top roll in the axial direction with an appropriate force. Then, for that purpose, a place where the contact force is abnormally large or a place where the contact force is abnormally small is detected, and a measure for preventing such a place from occurring is examined. As a result, the present invention has conceived a polishing method in which the magnitude of the contact force is determined by the load of a motor that rotates the polishing roll and the amount of pushing of the polishing roll with respect to the top roll is adjusted. Specifically, the position of the polishing roll with respect to the top roll is moved according to the load of the motor that rotates the polishing roll.

In the present invention, the magnitude of the contact force is
The motor load when a good polishing state is obtained is obtained in advance, and the threshold is used as the threshold. In this case, the value of the motor load can be obtained by torque, current, etc., but it is preferable to use the current from the economical point of view.

Next, the polishing apparatus according to the present invention will be described with reference to the side view of FIG.

As shown in FIG. 2, the polishing apparatus is provided at a position substantially horizontal to the height of the top roll 8 of the continuous molten metal plating line. Then, the main part thereof is in contact with the surface of the top roll 8 while rotating, and a roll 9 for polishing the surface, and a trolley that supports the polishing roll 9 and is movable along the axial direction of the top roll 8. 10 (hereinafter, referred to as a lateral traveling device), and these are placed on the top roll 8
And a vertical traveling device 11 that moves forward and backward toward
And a drive means 12 for moving. In this case, various types of driving means 12 can be considered, but a cylinder utilizing hydraulic pressure or pneumatic pressure is preferable. FIG. 1 shows a motor 13 that generates hydraulic pressure.

In contrast to such a polishing apparatus, the present invention newly compares the sensor 15 for detecting the load of the motor 14 for rotating the polishing roll 9 with the detected value and comparing the detected value with a threshold value. The controller 16 is modified so as to include a controller 16 for changing the amount of pushing into the roll 8. With this configuration, the carriage that makes the position of the polishing roll 9 with respect to the top roll 8, that is, the pushing amount, movable along the axial direction of the top roll 8 according to the load of the motor 14 that rotates the polishing roll 9. This is because it can be carried out by moving 10 and the vertical traveling device 11 which is mounted on these and moves forward and backward toward the top roll 8. In this example, as the load, the current value detected by the ammeter is used.

Generally, the amount of movement of the polishing roll 9 toward the top roll 8 and the current value of the motor 14 for rotating the polishing roll 9 have the relationship shown in FIG. That is, FIG.
As shown in, when the amount of movement of the polishing roll 9 toward the top roll 8 increases, so-called "polishing resistance" increases, so that the current value of the motor 14 that rotates the polishing roll 9 increases. Therefore, in the present invention, the amount of movement that makes polishing appropriate is set in advance as a threshold value, and the corresponding current value and the current value actually measured by the sensor 15 are compared by the control device 16, and based on the output thereof. Drive means 12 (Fig. 1
Then, the output of the hydraulic motor 13) may be adjusted.

[0018]

EXAMPLE A hot-rolled metal-plated steel sheet was manufactured by applying the top roll polishing method and polishing apparatus according to the present invention to the hot-rolled metal plating line of FIG. At that time, the top roll 8
120 μm WC (tungsten carbide) on the surface
A thick sprayed layer is used and its surface is J
Surface roughness (Ram) of IS standard (JIS B 0601)
It is mirror-finished to 0.4 μm corresponding to the ax) value.
The polishing roll 9 has an alumina-based polishing agent applied to the surface thereof.

First, in both the polishing roll 9 and the top roll 8, when the outer diameter of each roll does not change due to use, the current value shown in FIG. 4 and the amount of movement of the polishing roll to the top roll (position) are shown. ) Created a relationship with. At that time, the position where the current value was 11 amperes (A) was the origin, and the rotation speed of the polishing roll 9 was constant at 1200 rpm. As a result, when the current value is in the range of 11 to 15 A, the time required for polishing and the polishing finish condition of the top roll are compared, and the current value is 1
It was judged that the optimum current value (threshold value) was 4A.

Next, this current value is stored in the control device 16 shown in FIG. 1, and the current value which is the load of the motor 15 for rotating the polishing roll 9 is measured by the control device 16, and the measured value is the above-mentioned value. The operation was performed while adjusting the position of the vertical traveling device 11 so as to approach the stored optimum current value.

FIG. 5 shows the operation results when the top roll 8 having the thermal crown shown in FIG. Further, FIG. 6 shows the adjustment state of the moving amount of the polishing roll 9 to the top roll 8 measured at the same time. The thermal crown of FIG. 3 indicates that the roll diameter is large near the center of the top roll 8 in the axial direction.
As shown in FIG. 6, it is clear that the polishing roll 9 is moving away from the top roll 8 near the axial center of the top roll 8. That is, as shown in FIG. 5, the current value can be made substantially constant near the threshold value, and the top roll 8 can be optimally polished.

Further, in order to confirm the polishing result, the inventors compared the occurrence frequency of the flaw defect of the product before and after applying the present invention. In making this comparison, hot-dip galvanized steel sheets (those not alloyed) were manufactured at 350 tons each by the operation to which the present invention was applied and the conventional operation to which the present invention was not applied, and the total amount thereof was visually inspected to see if there were any flaws. investigated. As a result, in the operation to which the present invention was not applied, 253 defects were generated, but in the operation to which the present invention was applied, 1
The number of defects was extremely reduced to 2 points. It should be noted that the number of the scratches was only the scratches that can be judged to be caused by the foreign matter adhering to the top roll.

[0023]

As described above, according to the present invention, in a continuous hot-dip galvanizing line, the frequency of occurrence of flaws on the product due to foreign matter adhering to the top roll is significantly reduced as compared with the conventional case. That is, the present invention greatly contributes to the production of hot-dip galvanized steel sheets for automobiles, building materials and the like that require strict surface quality.

[Brief description of drawings]

FIG. 1 is a side view showing a polishing apparatus for a top roll according to the present invention.

FIG. 2 is a flow chart showing steps of a continuous hot-dip metal plating line.

FIG. 3 is an explanatory diagram of a thermal crown generated on a top roll.

FIG. 4 is a diagram showing a relationship between a current value of a motor that rotates a polishing roll and a movement amount in a direction of a top roll.

FIG. 5 is a diagram showing a current value adjustment state of a polishing roll according to an embodiment of the present invention.

FIG. 6 is a diagram showing a movement situation in a direction of a top roll according to an embodiment of the present invention.

[Explanation of symbols]

1 Annealing furnace 2 steel strip 3 plating bath 4 tanks 5 dipping roll 6 heating device 7 Cooling device 8 top rolls 9 polishing roll 10 carts (traverse device) 11 Vertical traveling device 12 Drive means 13 Hydraulic pressure generation motor 14 Polishing roll rotation motor 15 sensors 16 Control device

Claims (3)

[Claims] 1. When polishing the surface of a top roll provided in a continuous molten metal plating line with a polishing roll, depending on the load of a motor that rotates the polishing roll,
A method for polishing a top roll, comprising adjusting the amount of the polishing roll pushed into the top roll. 2. A polishing roll which is provided at a position substantially horizontal to the height of the top roll of a continuous hot-dip metal plating line, contacts the surface of the top roll while rotating, and polishes the surface, and supports the polishing roll. A top roll provided with a carriage that is movable along the axial direction of the top roll, a vertical traveling device that mounts these and moves forward and backward toward the top roll, and a drive unit that moves the vertical traveling device. In the polishing apparatus, a sensor that detects a load of a motor that rotates the polishing roll, and a control device that compares the detected value with a threshold value and changes the pushing amount of the polishing roll to the top roll are provided. Top roll polishing device. 3. The top roll polishing apparatus according to claim 2, wherein the sensor is an ammeter.