JP2000212710A - Production of galvanized steel sheet and apparatus thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a producing method of a galvanized steel sheet and an apparatus thereof, with which even in the case many welded points on the steel sheet exist, the galvanized steel sheet excellent in the quality can stably and continuously be produced. SOLUTION: In this producing method of a galvanized steel sheet, with which the steel sheets having different size are connected with welding and continuously supplied into galvanized bath 1 provided with a sink roll 5 for changing the advancing direction of the steel sheet to the vertical direction and one pair of support rolls 6 for sandwiching and supporting at the upper and the lower parts of the steel sheet vertically rising to apply the galvanizing on the surface of the steel sheet, just before passing the welded position of the steel sheets through the supporting rolls, the horizontal directional position of one pair of the support rolls is changed based on the equation pre-experimentally decided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for manufacturing a hot-dip galvanized steel sheet, and more particularly, to a method for preventing scratches and warpage of a steel strip caused by non-inversion of a support roll provided in a bath. To prevent the occurrence of splash caused by
This technology improves the quality of hot-dip coated steel sheets.

[0002]

2. Description of the Related Art Generally, a galvanizing apparatus as shown in FIG. 3 is used for producing a hot-dip galvanized steel sheet. It consists of a plating tank 2 for holding a molten zinc (plating bath 1) as a plating solution, and a cover 4 (referred to as a snout 4) for guiding the high-temperature steel strip 3 to the plating bath 1 while shielding it from the atmosphere.
A sink roll 5 for making the traveling direction of the steel strip 3 vertical in the plating bath 1, a pair of support rolls 6 for sandwiching and supporting the vertically rising steel strip 3, and passing through the support roll 6. A part of the plating solution adhering to the surface of the steel strip 3 that has escaped from the plating bath 1 is blown off with air to form a gas wiper 7 for adjusting the amount of adhesion. Usually, an alloying furnace 8 for heating and alloying the attached hot-dip galvanized steel strip 3 is often provided. The support rolls 6 are arranged vertically with the steel strip 3 interposed therebetween, and each roll 6 is movable in the surface direction of the steel strip 3 so that the distance from the steel strip surface can be changed. Has become.

In this plating apparatus, the steel plate 3 to be plated is used by unwinding a steel strip wound into a coil after rolling, and is operated continuously, so that steel strips of different sizes are used. They are connected to each other by welding to make them longer. Therefore, the welding point between the steel strips may have a great change in thickness or width, which causes disturbance in continuous operation. That is, when the welding point passes through the support roll 6, vibration of the steel strip 3 is promoted or splash is generated. Therefore, in the operation, when this welding point passes through the support roll 6, it is preferable to move the position of the support roll 6 according to the change in the thickness or the width, and to appropriately support the steel strip 3. .

Japanese Patent Application Laid-Open No. Hei 6-128711 discloses that, in order to make the width of the steel strip 3 and the amount of plating applied in the longitudinal direction uniform, the support roll 6 is not driven, and the sink roll 5 and the support roll 6 are not driven. It has been proposed that at least one of the support rolls 6 can be position-controlled in the horizontal direction.

However, usually, the steel strip 3 supplied to the plating bath 1 is covered with an annealing furnace 9 or the like (non-oxidizing furnace, reduction furnace) until just before the plating bath in order to prevent oxidation. Is not visible until it escapes from the plating bath. As a result, the movement of the position of the support roll in the plating bath 1 is delayed. Therefore, at the tip of the steel strip 3, there are many occurrences of scratches due to roll inversion, splash adhesion due to warpage of the steel sheet, or uneven plating adhesion amount. If the amount of movement of the support roll 6 is not changed in accordance with the temperature of the plating bath 1, the elongation change due to the temperature of the equipment members (that is, the support means of the support roll) existing in the bath is as follows. An error occurs in the amount of overlap between the left and right rolls (referred to as intermesh), and an appropriate amount of movement cannot be achieved. Further, in this technique, the position of the sink roll 5 or the support roll 6 is set each time the thickness of the steel strip 3 passing through the plating bath 1 is changed, and the position is set without stopping the movement of the steel strip 3. It does not operate continuously with changes.

[0006]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention provides a galvanized steel sheet capable of stably and continuously producing a high-quality coated steel sheet even if there are many welding points in the steel strip. It is an object of the present invention to provide a manufacturing method and apparatus.

[0007]

Means for Solving the Problems In order to achieve the above object, the inventor has further improved the technique described in Japanese Patent Application Laid-Open No. Hei 6-128711 and completed the present invention.

[0008] That is, the present invention provides a plating bath having a sink roll for making the traveling direction of a steel strip vertical, and a pair of support rolls for vertically sandwiching and supporting a vertically rising steel strip. In a method of manufacturing a hot-dip galvanized steel sheet in which different steel strips are connected to each other by welding and supplied continuously, and the surface of the steel strip is plated, the welding position between the steel strips is immediately before passing through a support roll. A horizontal position of the pair of support rolls is changed based on the following equation.

F = a1 · t + b1 · w + c1 · T + d1 (1) B = a2 · t + b2 · w + c2 · T + d2 (2) Here, the steel strip surface that is in contact with the sink roll is a back surface (Back) ), The opposite surface is defined as the front surface, and F and B are the movement amounts of the support roll contacting the front surface, and B is the movement amount of the support roll contacting the back surface. A1, a2, b1 (= α · L1), b
2 (= β, L2), c1, c2, d1, and d2 are constants specific to the equipment existing in the plating bath, t is the thickness of the steel strip on the downstream side of the welding position, and w is the value of the welding position. The width of the steel strip on the downstream side, T is the temperature of the plating bath, α and β are the coefficients of thermal expansion of the support roll supporting members, and L1 and L2 are the immersion depths of the respective support rolls in the bath.

[0010] The present invention also provides a plating method comprising, in a plating bath, a sink roll for making the traveling direction of a steel strip vertical, and a pair of support rolls for vertically sandwiching and supporting a vertically rising steel strip. In the apparatus for manufacturing a hot-dip galvanized steel sheet having a bath, a thermometer for measuring the temperature of the plating bath, and a position for detecting the welding position before the welding positions of steel strips of different sizes enter the plating bath. A sensor, a time calculator for calculating the time required for the detected welding position to reach the support roll, and receiving the size information of the steel strip before and after the welding position and the plating bath temperature information, and receiving the horizontal position of the support roll. And a support roll drive unit for receiving the determined horizontal position and the output signal of the time calculator and moving the support roll. An apparatus for manufacturing a molten zinc coated steel sheet, characterized in that there was e.

According to the present invention, even if the steel strip is welded at many positions, the position of the support roll is changed according to the size of the upstream and downstream sides of the welding position and the temperature of the plating bath. become able to. As a result, it becomes possible to stably and continuously produce plated steel sheets having excellent quality.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a view showing an example of an apparatus for producing a galvanized steel sheet according to the present invention. In this case, the following means are added to the above-described conventional manufacturing apparatus (see FIG. 3). That is, in the first, as shown in FIG. 1, a thermometer 10 was provided in the plating bath 1 and the temperature of the plating bath 1 was measured. by this,
Knowing the temperature change of the plating bath 1, when the welding position between the steel strips of different sizes passes through the support roll 6, the equipment member in the plating bath 1, in particular, due to the change in the length of the support member of the support roll 6. The horizontal position fluctuation of the support roll 6 can be corrected.

Second, a position sensor 11 for detecting the welding position of the steel strip 3 is mounted upstream of the plating tank 2 and the time required for the detected welding position to reach the support roll 6 is calculated. A time calculator 12 is provided.
This makes it possible to grasp the timing at which the horizontal position of the support roll 6 is moved before the welding position of the steel strip 3 passes through the support roll 6.

Third, there is provided a support roll position determiner 13 which receives the size information of the steel strip 3 before and after the welding position and the temperature information of the plating bath and calculates and determines the horizontal position of the support roll 6. . Here, the following equations for determining the horizontal position of the support roll are stored, and the horizontal position is calculated by inputting the plating bath temperature and the like obtained above into these equations.

F = a1 · t + b1 · w + c1 · T + d1 (1) B = a2 · t + b2 · w + c2 · T + d2 (2) Here, the steel strip surface in contact with the sink roll is a back surface (Back) ), The opposite surface is defined as the front surface, and F and B are the movement amounts of the support roll contacting the front surface, and B is the movement amount of the support roll contacting the back surface. A1, a2, b1 (= α · L1), b
2 (= β, L2), c1, c2, d1, and d2 are constants specific to equipment members existing in the plating bath, t is the thickness of the steel strip downstream from the welding position, and w is the welding position. The width of the steel strip on the downstream side, T is the temperature of the plating bath, α and β are the coefficients of thermal expansion of the support roll supporting members, and L1 and L2 are the immersion depths of the respective support rolls in the bath. The above equations (1) and (2) are obtained by conducting a test operation under various conditions in advance and obtaining a
1, a2, c1, c2, d1, d2 may be obtained,
Past operation data may be arranged.

Fourth, a support roll driving means 14 for receiving the horizontal position determined by the support roll position determiner 13 and the output signal of the time calculator 12 and moving the support roll 6 is provided. I did it. As a result, the support roll 6 can be moved to the horizontal position determined above.

Next, a scale for determining the horizontal position of the support roll 6 according to the present invention will be described. It is, as shown in Figure 2, one between the upper and lower support rolls.
Determine the coordinates of the dimension (X-axis only). The reference point (point 0) of the X axis is a position where the steel strip 3 is stretched vertically so as not to contact the support roll 6. Furthermore, on the X-axis on both sides of this reference position, the left side is minus (-),
The right side was set to plus (+), and the scale in mm was graduated. In addition, each support role 6
Is determined by the position where each roll 6 comes into contact with the steel strip 3 (one point on the outer periphery of the roll, symbol S). Thereby, even if the diameter of each support roll 6 changes variously, its horizontal position can be determined.

As for the thickness, it is preferable to use an actual value measured by a γ-ray thickness gauge. The time calculator 12
As the support roll position determiner 13, a process computer already used for operation management can be used. Further, as the support roll driving means 14, a known means such as a cylinder is sufficient.

[0020]

EXAMPLE A method for producing a hot-dip galvanized steel sheet according to the present invention was carried out using the plating apparatus shown in FIG. The material to be plated is a cold-rolled ultra low carbon steel strip, which is coiled for each size. The composition of the hot-dip galvanizing bath, the target temperature of the hot-dip galvanizing bath, and the like were determined under general operating conditions.

First, one of the coiled steel strips 3 is wound and bunched by an uncoiler (not shown), introduced into an annealing furnace 9 shown in FIG. And then passed through an alloying furnace 8 to obtain a product plated steel sheet. This steel strip is 1
When one coil was sent out, the ones having different sizes were sequentially connected by welding and supplied. At this time, in the manufacturing method according to the present invention, the size information before and after the welding position is input to the process computer 15 on the upstream side of the annealing furnace 9, and the welding position is detected, and the detected position is transmitted to the support roll 6. Is calculated by the time calculator 12. Subsequently, the information and the temperature separately measured in the plating bath 1 are sent to the support roll position determiner 13, and the support roll 6 is determined by the above equations (1) and (2).
The change in the horizontal position of was calculated. This change amount was executed by the support roll driving means 14 at a timing immediately before the welding position passed the support roll 6.

Table 1 shows the result of changing the support roll when the size of the steel strip is changed in three ways. Thus, even if there were many welding positions of the steel strip, smooth operation was possible. FIGS. 4 (a) and 4 (b) show how the support roll is changed according to the change in the plate thickness and the bath temperature.

Table 2 shows the quality results of the products obtained by this operation in comparison with the results obtained by the conventional method. From Table 2, it is clear that according to the method for producing a hot-dip galvanized steel sheet according to the present invention, not only scratches and splash adhesion of the product are reduced, but also the coating amount becomes uniform.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

As described above, according to the present invention, even if the steel strip is welded at many positions, the support can be adjusted according to the size of the upstream and downstream sides of the welding position and the temperature of the plating bath.・ Roll position can be changed. As a result, it has become possible to stably and continuously produce plated steel sheets having excellent quality.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an apparatus for manufacturing a galvanized steel sheet according to the present invention.

FIG. 2 is a diagram illustrating movement of a support roll.

FIG. 3 is a view illustrating a conventional apparatus for manufacturing a galvanized steel sheet.

FIGS. 4A and 4B are diagrams showing a change state of a support roll in the embodiment of the present invention, in which FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plating bath (hot-dip zinc) 2 Plating tank 3 Steel strip 4 Cover (snout) 5 Sink roll 6 Support roll 7 Gas wiper 8 Alloying furnace 9 Annealing furnace 10 Thermometer 11 Position sensor 12 hour calculator 13 Support Roll position determiner 14 Support roll driving means 15 Process computer

Claims (2)

[Claims] A steel strip having different sizes is provided in a plating bath having a sink roll for vertically moving a steel strip in a vertical direction and a pair of support rolls for vertically sandwiching and supporting a vertically rising steel strip. In a method of manufacturing a hot-dip galvanized steel sheet in which the steel strips are continuously supplied and plated on the surface of the steel strip, immediately before the welding position of the steel strips passes through a support roll, the pair of A method for manufacturing a hot-dip galvanized steel sheet, wherein a horizontal position of a support roll is changed based on the following equation. F = a1 · t + b1 · w + c1 · T + d1 (1) B = a2 · t + b2 · w + c2 · T + d2 (2) Here, the steel strip surface in contact with the sink roll is the back surface (Back), and the opposite surface is the back surface. Defined as the front,
F and B are the movement amounts of the support roll contacting the front surface, and B is the movement amount of the support roll contacting the back surface. Also, a1, a2, b1 (= α · L1), b2 (=
β, L2), c1, c2, d1, and d2 are constants specific to the equipment members existing in the plating bath, t is the thickness of the steel strip on the downstream side of the welding position, and w is the downstream of the welding position. , T is the temperature of the plating bath, α and β are the coefficients of thermal expansion of the support roll support members, and L1 and L2 are the immersion depths of the respective support rolls in the bath. 2. A melting bath having a plating bath including a sink roll for vertically moving a steel strip in a plating bath and a pair of support rolls for vertically sandwiching and supporting a vertically rising steel strip. In the apparatus for manufacturing a galvanized steel sheet, a thermometer that measures the temperature of the plating bath, a position sensor that detects the welding position before the welding position between the steel strips of different sizes enters the plating bath, A time calculator for calculating the time required for the welded position to reach the support roll, and the size information of the steel strip before and after the welding position and the temperature information of the plating bath, and calculate and determine the horizontal position of the support roll. A support roll position determiner, and a determined horizontal position and an output signal of the time calculator.
An apparatus for manufacturing a hot-dip galvanized steel sheet, comprising: a support roll driving means for moving a support roll.