JP2003055791A - Electroplating method of steel strip - Google Patents

Abstract

(57) [Abstract] [Problem] In an electroplating of a steel strip by a horizontal type continuous plating equipment, a power supply unit is used while appropriately energizing the steel strip without making a significant change to the conventional electroplating equipment. To provide an electroplating method capable of appropriately suppressing the generated C warpage. SOLUTION: In a method of electroplating a steel strip by a horizontal continuous plating equipment provided with a power supply unit including a power supply roll and a backup roll, a steel strip whose warp in the width direction has been corrected in advance is passed through a plating line. The steel generated when passing the energizing unit by sandwiching the steel strip between a pair of upper and lower rolls having different contact lengths with respect to the steel strip on the upstream side and / or the downstream side of part or all of the energizing unit. A steel strip electroplating method is used, which corrects the warpage of the steel strip by giving a warp in the opposite direction to the warp of the strip. It is effective to use a pair of upper and lower rolls having different contact lengths with the steel strip as draining rolls provided in the plating tank.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for electroplating a steel strip by horizontal continuous plating equipment.

[0002]

2. Description of the Related Art FIG. 1 is an explanatory view showing an example of a method for electroplating a steel strip using a horizontal type continuous plating equipment. Generally, the horizontal type continuous plating equipment is provided with a plurality of plating tanks 7 having upper and lower electrodes 4a and 4b (only one plating tank is shown in FIG. 1), and usually between each plating tank 7 (and the first plating tank 7). At each position (on the inlet side of the tank and on the outlet side of the last plating tank), there is provided a steel strip energizing means called an energizing unit consisting of a pair of upper and lower rolls. This energizing unit is composed of an energizing roll 1 and a backup roll 2, and a steel strip to be passed is sandwiched by a pair of upper and lower rolls and is energized by applying a predetermined pressing load. The energizing roll 1 is a metal roll, and the backup roll 2 is a metal roll whose surface is coated with a viscoelastic material such as urethane rubber.

The plating layer formed on the steel strip surface by such a plating method is preferably uniform over the entire plate surface,
By ensuring the uniformity of the plating layer thickness, the quality of the plated steel strip becomes stable, and it becomes possible to reduce the plating unit.
However, in general, steel strips are caused by residual stress due to deformation given in the preceding step of plating such as rolling or continuous annealing, and bending deformation given by a transfer roll in the process line up to the plating step. A warp (C warpage) occurs in the width direction. When such a steel strip is passed through the plating tank, the distance between the upper and lower surfaces of the steel strip and the upper and lower electrodes in the plating tank is It becomes uneven. As a result, the formed plating layer has a non-uniform layer thickness in the plate width direction. In an extreme case, a steel strip having a C warp may come into contact with the electrode, and when the steel strip comes into contact with the electrode, a spark is generated, which damages the surface of the steel strip and the current-carrying roll. I will end up. Therefore, when plating a steel strip having a large amount of C warp, it is necessary to sufficiently increase the distance between the electrodes, and there is a problem that the power cost increases accordingly.

As a means for preventing the above-mentioned problem due to the C warp of the steel strip, Japanese Patent Laid-Open No. 9-316691 discloses a sensor for detecting the shape of the steel strip on the inlet side of the plating tank and the shape of the steel strip. There is disclosed a method of arranging a straightening roll for straightening and performing up-and-down control of the straightening roll based on a signal detected by a sensor to straighten the shape of the steel strip and then perform electroplating.

However, the method disclosed in Japanese Patent Laid-Open No. 9-316691 can suppress the C warp on the entrance side of the plating equipment, but cannot suppress the C warp generated in the energizing unit. There is a problem. The occurrence of C warpage in the energization unit is due to the following mechanism. When the steel strip is electroplated, the larger the pressing load of the energizing roll is, the smaller the energizing resistance becomes, which is preferable.However, when the pressing load acts between the energizing roll and the backup roll, rubber or the like is applied to the metal energizing roll. Since the amount of surface deformation of the coated backup roll is large, the contact length with the roll is different above and below the steel strip, and a bending moment acts on the steel strip. As a result, a warp (L warp) that winds around the energizing roll occurs in the steel strip, and this L warp is constrained by the line tension, so that the steel strip warps in the width direction (C
(Warpage) occurs. The occurrence of such a C warp is a problem in terms of non-uniformity of plating thickness and power cost as described above.

As a measure for preventing C warpage that occurs in the energizing unit as described above, Japanese Patent Laid-Open No. 63-210294 discloses a method in which the hardness of the rubber covering the backup roll is increased and the amount of deformation on the rubber side is reduced. It is disclosed. Further, in Japanese Patent Laid-Open No. 64-36790, the distribution of the plating amount in the plate width direction and the warp amount in the plate width direction are detected, and the backup roll is pressed according to the deviation of the plating thickness or the warp in the plate width direction. A method for adjusting the load (pressing force) is disclosed. Further, Japanese Patent Application Laid-Open No. 10-68098 discloses a method of reducing the diameter of the backup roll and arranging the backup roll in an offset arrangement with respect to the energizing roll.

[0007]

Problems to be Solved by the Invention JP-A-63-2102
If the method described in Japanese Patent Publication No. 94 is used, the amount of C warpage that occurs in the energizing unit can be reduced, but if the rubber hardness that coats the backup roll is increased, the contact length with the steel strip on the energizing roll side becomes smaller. Therefore, the contact state between the energizing roll and the steel strip becomes unstable. In particular, at the time of passing through a welding point where the plate thickness fluctuates, sparks may occur due to insufficient contact between the energizing roll and the steel strip in the energizing unit.

Further, when the method described in Japanese Patent Laid-Open No. 64-36790 is used, when the warp amount is large, pressing by the energizing unit is performed in order to reduce the difference in contact length between the energizing roll and the backup roll. It is necessary to control to reduce the load. In this case as well, the contact length with the steel strip on the energizing roll side becomes small and the contact state becomes unstable, so sparks may occur when passing through the welding point.

Further, in the method described in Japanese Patent Laid-Open No. 10-68098, the diameter of the backup roll is reduced so that the difference between the contact length with the steel strip on the energizing roll side and the contact length on the backup roll side is reduced. As a result of the reduction, the C warpage becomes smaller. However, in order to eliminate the C warp only by reducing the diameter of the backup roll, it is necessary to extremely reduce the diameter of the backup roll. This is a technology that reduces warpage. In this method, the optimum offset amount is calculated according to the plate thickness of the steel strip, the plate width, the material, or the initial plate shape,
It is necessary to change the roll arrangement to have the offset amount, but in order to change the offset amount, a roll shaft moving mechanism is required, and a large capital investment is required.

The object of the present invention is to solve the problems of the prior art as described above, and in the electroplating of a steel strip by the horizontal type continuous plating equipment, the steel strip can be formed without making a big change to the conventional electroplating equipment. An object of the present invention is to provide an electroplating method capable of appropriately suppressing C warpage that occurs in an energizing unit while properly ensuring energization.

[0011]

The features of the present invention for solving the above problems are as follows.

(1) In the method of electroplating a steel strip by a horizontal continuous plating equipment equipped with an energization unit consisting of an energization roll and a backup roll, a steel strip whose warp in the width direction has been corrected in advance is passed through the plating equipment. When the energizing unit is passed through the plate by sandwiching the steel strip with a pair of upper and lower rolls having different contact lengths to the steel strip on the upstream side and / or the downstream side of part or all of the energizing unit A method for electroplating a steel strip, characterized in that the warp of the steel strip is corrected by giving the steel strip a warp in the opposite direction to that of the steel strip.

(2) The method of electroplating a steel strip according to (1), characterized in that the pair of upper and lower rolls having different contact lengths with respect to the steel strip are draining rolls provided in a plating tank.

(3) It is characterized in that the shape of the steel strip on the side of the plating equipment is detected, and the straightening amount of the steel strip to be passed through the plating equipment is controlled based on the shape detection. The method for electroplating a steel strip according to (2).

(4) The method of electroplating a steel strip according to any one of (1) to (3), characterized in that the pressing loads of a pair of upper and lower rolls having different contact lengths to the steel strip are controlled.

(5) It is characterized in that the shape of the steel strip on the delivery side of the plating equipment is detected, and the pressing loads of a pair of upper and lower rolls having different contact lengths to the steel strip are feedback-controlled based on the shape detection. The method for electroplating a steel strip according to (4).

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION In the electroplating of a steel strip by a horizontal type continuous plating facility equipped with a current-carrying unit consisting of a current-carrying roll and a backup roll, the occurrence of C-warping in the current-carrying unit is suppressed or the C-warping caused To correct
In the present invention, a steel strip whose widthwise warp has been corrected in advance is passed through a plating facility, and a part or all of the current-carrying unit upstream and / or downstream has different contact lengths with respect to the steel strip. By sandwiching the steel strip with a pair of rolls, the warp of the steel strip is corrected by giving the steel strip a warp in a direction opposite to that of the steel strip generated when the current-carrying unit is passed.

The electroplating method of the present invention will be described in detail below.

The energizing roll constituting the energizing unit is made of metal, while the backup roll is covered with a viscoelastic material such as rubber. Therefore, the steel strip is sandwiched between the energizing roll and the backup roll in the energizing unit,
When a pressing load is applied between both rolls, C warpage occurs in the steel strip due to the difference in roll contact length between the upper and lower portions of the steel strip. Therefore, if the pressing load is reduced to reduce the difference in contact length between each roll and the steel strip, the C warpage can be reduced. However, if the pressing load is reduced, the contact state on the side of the current-carrying roll becomes insufficient and sparks are generated. There is a risk. That is, it is difficult to achieve stable energization and prevention of C-curvature at the same time in the energizing unit.

In order to correct such a problem, the present inventors have the same principle as the bending deformation applied to the steel strip by the current-carrying unit in the vicinity of the current-carrying unit in order to correct the C warpage that occurs in the current-carrying unit. Is applied in the opposite direction (that is, a bending deformation in the opposite direction to the bending deformation in the energizing unit is applied), and the C warping caused by this bending deformation cancels out the C warping in the energizing unit. I devised a method to virtually eliminate C warpage. That is, this method is an electroplating method for a steel strip by a horizontal type continuous plating equipment provided with an energization unit consisting of an energizing roll and a backup roll, in which a pre-rectified steel strip is passed through the plating equipment and the energization is performed. On the upstream side and / or the downstream side of a part or all of the unit, by bending the steel strip by a pair of upper and lower rolls having different contact lengths to the steel strip, the warpage of the steel strip generated when the current-carrying unit is threaded The warp of the steel strip is corrected by giving the steel strip a warp in the opposite direction.

This principle will be described with reference to FIG. By a pair of upper and lower rolls (hereinafter referred to as warp straightening rolls) having different contact lengths to the steel strip near the upstream side or the downstream side (or both) of the current-carrying unit including the current-carrying roll 1 and the backup roll 2 By sandwiching the steel strip, the warp of the steel strip is corrected by giving the steel strip a warp in the opposite direction to the warp of the steel strip generated when the energizing unit is passed through. Here, as shown in FIG. 2, if the upper roll of the energizing unit is the energizing roll 1, a C-warp having a downward convex shape is generated in the steel strip, so that the steel strip 3 with respect to the lower warp straightening roll 17b is formed. The warp straightening rolls 17a and 17b whose contact length is longer than the contact length of the steel strip 3 to the upper warp straightening roll 17a gives the steel strip a warp in the opposite direction to the energizing unit. As described above, the warpage imparted to the steel strip cancels out the C warpage occurring in the energizing unit, so that the C warping in the energizing unit can be substantially eliminated.

Here, when the warp straightening rolls 17a and 17b apply the warp to the steel strip on the downstream side of the energizing unit as shown in FIG. 2, the C warp generated in the energizing unit is energized. The bending deformation opposite to the bending applied to the steel strip by the unit is applied by a warpage correction roll to correct it.

When the warp straightening rolls 17a and 17b apply the warp to the steel strip on the upstream side of the energizing unit, the warp straightening rolls have a C warp in the opposite direction to that generated in advance in the energizing unit. Is given, and the C-curve is subsequently generated in the energizing unit portion, so that the warp is eliminated.

Further, in the case where the warp straightening rolls 17a and 17b apply the warp to the steel strip on the downstream side and the upstream side of the energization unit, a C warp in the opposite direction to that generated in the energization unit section, The warp of the steel strip is straightened by applying the warping straightening rolls on the downstream side and the upstream side to the steel strip. The upstream side warp straightening roll imparts a C warp in the opposite direction to that generated in the energization unit in advance, and subsequently the C warpage generated in the energization unit is further corrected by the downstream side warp straightening roll. In this case, the warp straightening roll 17a is provided on either the upstream side or the downstream side,
With 17b, the warp can be corrected with a smaller pressing load than in the case where the warp is applied to the steel strip.

Contrary to FIG. 2, when the lower roll of the energizing unit is the energizing roll and the upper roll is the backup roll, a C-warp which is convex upward is generated in the steel strip, so The contact length of the steel strip 3 with respect to the warp straightening roll 17b is equal to that of the steel strip 3 with respect to the lower warp straightening roll 17a.
Warp straightening roll 17 that is longer than the contact length of
At a and 17b, the steel strip is warped in the opposite direction to the current-carrying unit.

In order to make the contact length to the steel strip different between the upper and lower warp correction rolls 17a and 17b, for example,
The surface hardness of one warp straightening roll 17a is made lower than the surface hardness of the other warp straightening roll 17b, or the diameter of one warp straightening roll 17b is made larger than the diameter of the other warp straightening roll 17a.

The amount of warp applied to the steel strip by the warp straightening rolls 17a and 17b can be adjusted by controlling the pressing load of the warp straightening rolls 17a and 17b. The amount of warp of the steel strip 3 changes depending on the type of steel strip, the plate thickness, the plate width, etc. Therefore, depending on the amount of C warpage that occurs in the energizing unit, the amount of warp that can eliminate the warp is given to the steel strip 3. The pressing load of the straightening rolls 17a and 17b is controlled.

By the above, the C warp generated in the energizing unit can be almost corrected, but the C warp generated before the plating process is corrected in advance and then the above-mentioned correction is performed, whereby the C warp generated in the energizing unit is corrected. The warp can be corrected more effectively. If the initial amount of C warp of the steel strip (the amount of C warp on the entrance side of the plating equipment) is large, the C warp on the exit side of the plating equipment may not be satisfactorily corrected by the warp straightening roll used in the present invention. By passing a steel strip, whose warpage has been corrected in advance, through a plating facility, it is possible to correct the C-warp that occurs in the energizing unit without being affected by the initial C-warp shape of the steel strip, resulting in a flatter surface. It is possible to obtain various steel strips.
For this purpose, it is preferable to arrange an initial straightening roll on the entrance side of the plating equipment. As the initial straightening roll, it is possible to use a pair of rolls having a structure capable of moving up and down.

In carrying out the method of the present invention, the vicinity of the energizing unit in the plating equipment (upstream side and / or downstream side)
Although it is possible to arrange a dedicated warp straightening roll, the liquid draining roll provided in the plating tank can be used as the warp straightening roll, which eliminates the need to provide a dedicated warp straightening roll It is very effective in suppressing C warpage. Draining rolls, also called dam rolls, are usually placed on the inlet and outlet sides of the plating tank to prevent the plating liquid from flowing into the energizing unit, and as a result, are placed upstream and downstream of the energizing unit. It will be. Since the liquid draining roll is composed of a pair of upper and lower rolls covered with a viscoelastic material such as rubber, the surface hardness can be easily changed. Therefore, for this draining roll, the surface hardness of the draining roll on the backup roll contact surface side of the energizing unit in the vicinity of the draining roll is made larger than the surface hardness of the draining roll on the contacting side of the energizing roll. By applying a pressing load to the steel strip using the above, the difference in the contact length with the steel strip between the upper and lower draining rolls can be applied to the steel strip in the direction opposite to the bending that occurs in the energizing unit. It is possible to correct the C warpage that occurs in the energizing unit.

As described above, generally, the energization unit is arranged between each of the plurality of plating tanks, the entrance side of the first plating tank, and the exit side of the final plating tank. Therefore, when the liquid draining roll of the plating tank is used as the warp straightening roll, the liquid draining roll is present on both the upstream side and the downstream side of the energization unit arranged between the plating tanks. In this case, both the liquid draining rolls on the upstream side and the downstream side may be the warp straightening rolls, or one of the liquid draining rolls may be the warp straightening rolls. When both draining rolls are used as warp straightening rolls, the C warp in the opposite direction to that generated in the energizing unit portion is divided by the warp straightening rolls on the downstream side and the upstream side as described above. By giving the steel strip, the warp of the steel strip is corrected.

FIG. 3 shows an embodiment of the horizontal continuous plating equipment and the method of the present invention using the same equipment. The horizontal continuous plating equipment comprises a plurality of horizontal plating tanks 7 arranged in series. ,
Each of these plating tanks 7, an entrance side of the first plating tank 7, an energization roll 1 which is an energization unit arranged on the exit side of the last plating tank 7, and a backup roll 2 are configured. The plurality of plating tanks 7 are provided with upper and lower electrodes 4a and 4b. In the present embodiment, the plating apparatus for plating both sides of the steel strip has been described, but when plating is performed on only one side of the steel strip, the electrodes may be arranged on only one of 4a and 4b. The steel strip to be threaded is sandwiched by a pair of upper and lower rolls of the current-carrying unit, and a predetermined pressing load is applied to the steel strip to be energized. The energizing roll 1 is a metal roll, and the backup roll 2 is a metal roll whose surface is coated with a viscoelastic material such as urethane rubber. A liquid draining roll (dam roll) 10 is arranged on the inlet side and the outlet side of each plating tank 7. The liquid draining rolls 10 are arranged on the inlet side and the outlet side of each plating tank 7 for the purpose of preventing the plating liquid 11 from flowing into the energization unit. A coated roll is used. The number of plating tanks 7 is 15 in FIG. 3, but can be set arbitrarily.

After cold rolling, continuous annealing, etc., the steel strip 3 having a predetermined plate thickness and mechanical characteristics is dispensed from the payoff reel 5 and attached to the steel strip surface by the electrolytic degreasing device 6. The oil content is washed away. Initial straightening rolls 8a and 8b are arranged on the entrance side of the horizontal continuous plating equipment, whereby the steel strip 3 is straightened in shape and then conveyed to the horizontal continuous plating equipment for plating. At this time, the draining roll 1
0 is used as a warp straightening roll and is generated in the energizing unit C
Correct the warp. Any liquid draining roll 10 can be used as a warp straightening roll. By controlling the pressing load of the warp straightening roll, the amount of warp of the steel strip can be adjusted.
2 shows a case where the drainage roll 10 on the downstream side of the energization unit is used as a warp straightening roll to control the pressing load and straighten the C warp. The detailed control method will be described later. For the current-carrying unit arranged without the liquid-cutting roll 10 on the downstream side of the current-carrying unit and arranged on the outlet side of the last plating tank 7, the liquid-cutting roll on the upstream side is used as the warp correction roll.

When the shape of the steel strip 3 is straightened by the initial straightening rolls 8a, 8b, the shape of the steel strip on the side of the plating equipment is detected, and the straightening amount of the steel strip to be passed through the plating equipment is detected by the shape detection. It is preferable to control based on The straightening of the initial shape of the steel strip that is passed through the plating equipment is performed by a structure in which the initial straightening rolls 8a and 8b for vertically correcting the shape of the steel strip that are vertically arranged on the entrance side of the plating equipment in FIG. By changing the pushing amount of the initial straightening roll, it is possible to control by changing the curvature given to the steel strip. A shape measuring device 9a for detecting the shape of the steel strip is installed downstream of the initial straightening rolls 8a and 8b. As the shape measuring device 9a, for example, a laser displacement meter can be used. If the laser displacement meter is installed so as to be movable in the width direction of the steel strip, the shape of the steel strip can be obtained based on the detected value of the distance to the surface of the steel strip. At this time, the detection signal obtained from the shape measuring device 9a is set to the initial straightening roll 8a,
8b is used as a control signal for the initial straightening rolls 8a, 8b.
It is preferable that the ascending / descending control of b is performed and the straightening amount of the steel strip to be passed through the plating equipment is feedback-controlled. When it is determined from the detection signal obtained from the shape measuring device 9 that the steel strip has the upwardly convex C-warp, the initial straightening roll 8a is lowered so that the pushing amount of the initial straightening roll 8a becomes large. However, the shape of the steel strip is corrected by giving a working curvature opposite to the curvature of the steel strip. When it is determined from the detection signal obtained from the shape measuring device 9 that the steel strip has a downwardly convex warp, the initial straightening roll 8b is raised so that the pushing amount of the initial straightening roll 8b becomes large. Let By the elevation control of the initial straightening roll, the flattened steel strip is passed through the plating line.
In the present embodiment, the case where the shape measuring device is located downstream of the initial straightening roll has been described, but it is also possible to arrange the shape measuring device upstream of the initial straightening roll to perform feedforward control.

Further, it is preferable that the shape of the steel strip on the delivery side of the plating equipment is detected and the pressing load of the warp straightening roll is feedback-controlled based on the shape detection. The amount of correction of C-warp generated in the energizing unit is measured by the above-described electroplating method by a device 9 for measuring the shape of the steel strip on the outlet side of the plating equipment.
It is possible to adjust by arranging b and performing feedback control of the pressing load of the warp straightening roll according to the detected shape of the steel strip. Hereinafter, a specific method of controlling the pressing load will be described. In the energizing unit, it is necessary to apply a sufficient pressing load for stable energization. With the load per unit width
If you apply a pressing load of 29 to 49 N / mm (3 to 5 kg / mm),
Stable energization is possible. At this time, the C warp generated in the energizing unit changes depending on the material, the plate thickness, and the plate width of the steel strip being conveyed. Fig. 4 shows an energizing unit in which the energizing roll is made of metal with a roll diameter of φ350 mm and the backup roll has a surface hardness of type A durometer hardness of 90 degrees (JIS
K 6253) rubber coated with 20 mm diameter φ300 mm roll, using a steel strip 1.0 mm in width and 1200 mm in width, width pressing load 34.
The figure shows the change in the amount of C warp with respect to the material of the steel strip when electricity is applied at 3 N / mm (3.5 kg / mm). Steel strips having different yield stresses were used as the material of the steel strip, and the amount of C warpage was measured with the upward warpage as a positive value. From FIG. 4, it can be seen that the smaller the yield stress of the steel strip, the larger the amount of C warp, and the amount of C warp changes depending on the material of the steel strip. Since the amount of C-warp generated in the energizing unit changes depending on the manufacturing conditions as described above, by changing the pressing load of the liquid draining roll which is the warp straightening roll, such a change in the amount of C-warp can be dealt with. Figure 5
In addition, using the same energization unit as that used in Fig. 4, thickness 0.8mm, width 1600mm, yield stress 196N / mm ² (20kg /
mm ² ) steel after passing through the liquid cutting roll when the pressing load of 49000N (5000kg) is applied to the steel strip and the pressing load of the liquid cutting roll (warp straightening roll) arranged behind it is changed. The amount of C warpage of the belt is shown. This draining roll has a difference in upper and lower surface hardness.
Using a coated φ300 mm roll, the drainage roll surface hardness of the energizing roll side of the steel strip is 75 degrees (JIS K 6253),
The surface hardness of the backup roll side is 100 degrees (JIS K 625
3) The pressing load of the draining roll is 30000N (300
The amount of C warp is about 5 mm or less at about 0 kg), and it can be understood that the C warp generated in the energizing unit can be corrected by optimizing the pressing load of the liquid cutting roll. Therefore, in order to control the amount of C warpage, as described above, the material of the steel strip,
The relationship between the pressing load of the liquid cutting roll and the amount of C warp according to the plate thickness and the plate width is obtained in advance, and the data is used as the control arithmetic unit 1
3, the information of the material, plate thickness, and plate width of the steel strip to be threaded is input to the control calculation device 13 from the input device 12 to optimize the pressing load of the liquid cutting roll. Further, it is more effective to input the shape of the steel strip obtained by the shape measuring device 9b installed on the downstream side of the plating equipment to the control calculation device 13 to perform the feedback control. A shape measuring device 9b for detecting the shape of the steel strip is arranged on the downstream side of the plating equipment. When the detected steel strip shape is different from the target shape, the warp straightening roll is a warp straightening roll so as to be close to the target shape. By feedback controlling the pressing load, it is possible to stably and highly accurately correct the C warp of the steel strip.

As described above, by using the electroplating method of the present invention, stable energization and reduction of C warp can be achieved at the same time.
Further, by controlling the pressing loads of the initial straightening roll and the warp forced roll, the shape of the steel strip can be stably flattened with high accuracy.

[0036]

[Example] Zinc plating was carried out in a horizontal continuous electroplating facility under the following conditions to produce a zinc-plated steel strip. Using the electroplating equipment shown in Fig. 3, a steel strip with a strip width of 1600 mm, a strip thickness of 0.8 mm and a yield stress of 196 N / mm ² (20 kg / mm ² ) has a line speed of 150 mpm.
It was made to pass through the plate and electroplated with zinc. As the initial straightening rolls 8a and 8b, metal rolls having a roll diameter of 300 mm and a body length of 2150 mm were used, and a laser-type steel strip shape measuring device 9a was installed downstream thereof. Based on the signal from the shape measuring device, the pushing amount of the initial straightening roll was controlled so that the shape of the steel strip was flat. A metal roll having a roll diameter of φ350 mm and a body length of 2150 mm was used as the energizing roll 1, and a roll having a roll diameter of φ300 mm and a body length of 2150 mm coated with 20 mm of rubber was used as the backup roll 2. The surface hardness of the backup roll was 90 degrees (JIS K 6253). Fifteen plating tanks were continuously arranged in the steel strip conveying direction. At this time, the width pressing load of the energizing unit was operated at 29.4 N / mm (3 kg / mm), which allows stable energization in all energizing units. Draining roll 1
For 0, use a roll of φ300 mm coated with 20 mm of rubber,
The roll length was 2150 mm. In order to use the liquid draining roll on the downstream side of the energizing unit as a warp straightening roll, the surface hardness of the liquid draining roll on the energizing roll side (upper side) is set to 75 degrees (JIS K 6253) with respect to the steel strip, and the backup roll side The surface hardness of the liquid draining roll (lower side) is 98 degrees (JIS K 625
3) For the current-carrying unit arranged on the outlet side of the last plating tank 7, the liquid draining roll on the upstream side was a warp straightening roll. The liquid draining rolls other than the straightening rolls have a surface hardness of 75 degrees both up and down (JIS K 6253).
In addition, the pressing load of the liquid cutting roll was controlled to 29400N (3000 kg) at the start of the threading by the control arithmetic unit 13 based on the steel strip data (plate width, plate thickness, yield stress) input from the input device 12. Further, on the downstream side of the final plating tank, a shape measuring device 9b for detecting the shape of the steel strip by a laser displacement detection method and an adhesion amount measuring device 14 for measuring the plating adhesion amount of the steel strip by using fluorescent X-rays are arranged. did. Shape measuring device 9
The pressing load of the liquid cutting roll was feedback-controlled by inputting the steel strip shape obtained from b into the control arithmetic unit 13. The electrogalvanized steel strip was subjected to chemical conversion treatment in the chemical conversion treatment tank 15 and then wound up by the tension reel 16.

The steel strip plated as described above is referred to as steel strip A. In addition to the steel strip A, electrozinc plating was performed under the same conditions as the steel strip A (steel strip B), except that the initial straightening rolls 8a and 8b on the inlet side of the plating equipment were not used (surface strip hardness). The same as steel strip A (steel strip C), except that the upper and lower sides are set to 75 degrees (JIS K 6253), the surface hardness of the liquid cutting roll is the same as steel strip C. A method of controlling the pushing load of the energizing unit according to the warp amount of the steel strip detected from the shape measuring device 9b using the same plating equipment as the steel strip A except that the same 75 degrees (JIS K6253) is used. An electrozinc plated product (steel strip D) was manufactured. In the production of the steel strip D, the width pressing load in the energizing unit was controlled to 21.6 N / mm (2.2 kg / mm), and the steel strip was electroplated with zinc.

FIG. 6 shows the results of measuring the shapes of the steel strips A to D in the case where the electroplating was performed by the above-mentioned respective methods by the shape measuring device 9a on the entry side. In the steel strip B that did not use the initial straightening roll, a C warp of up to about 10 mm occurred, whereas in the steel strips A, C, and D that used the initial straightening roll, the initial warpage at the entrance side of the plating equipment The C warpage was almost corrected.

FIG. 7 shows the results of measuring the shapes of the steel strips A to D when electroplating was performed by each method, using the shape measuring device 9b on the outlet side of the plating equipment. In steel strip B, the influence of the initial shape remains, so that C warpage of about 10 mm remains. Since the steel strip C cannot correct the C warp generated in the energizing unit, a large C warp of 20 mm or more occurred. In steel strip A and steel strip D, C warpage did not occur.

In Tables 1 to D, variations in the plating amount in the width direction obtained from the results of measuring the zinc plating amount in the width direction of the steel strip by using the plating amount measuring device 14 in the steel strips A to D, Indicates the status of spark occurrence. As shown in FIG.
Table 1 also shows the amount of C warpage measured by the shape measuring device 9b on the delivery side.

[0041]

[Table 1]

Regarding the variation in the amount of plating applied, in the steel strips B and C having C warpage, there is a large variation in the deposition amount in the width direction, whereas in the steel strips A and D, the variation in the adhesion amount within ± 4%. Met. Steel strip D had a small C warp and a small variation in the adhered amount, but because the width pressing load of the energizing unit was small, stable energization was not performed and sparking occurred.

As described above, it was found that in the steel strip A, the correction of the C warpage that occurs in the energizing unit and the stable energization can both be achieved. Therefore, even if there is an initial C warp that has occurred before the plating process, it is possible to manufacture a flat plated steel strip with little variation in the amount of C warp and the amount of plating adhered in the width direction by using the correction with the initial straightening roll together. I understood.

[0044]

As described above, according to the present invention, it is possible to reduce the C warpage that occurs in the plating step when performing electroplating on a steel strip that is continuously conveyed horizontally.
As a result, it is possible to obtain a plated steel strip having a uniform amount of plating applied in the plate width direction, and the quality and yield are improved. Further, since it is possible to prevent the occurrence of sparks due to the contact between the electrodes and the steel strip, it is possible to reduce the power cost by narrowing the space between the electrodes, and it is possible to reduce the production cost.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of a method for electroplating a steel strip using a horizontal continuous plating facility.

FIG. 2 is a principle diagram of the present invention.

FIG. 3 is a diagram showing an embodiment of the method of the present invention using the horizontal type continuous plating equipment and the same equipment.

FIG. 4 is a graph showing the amount of C warpage with respect to the yield stress of a steel strip.

FIG. 5 is a graph showing the amount of C-warp with respect to the pressing force applied to the liquid cutting roll.

FIG. 6 is a graph showing the amount of C warpage with respect to the position in the plate width direction of the steel strip after the initial correction.

FIG. 7 is a graph showing the amount of C warpage with respect to the position in the plate width direction of the steel strip after the plating process.

[Explanation of symbols]

1: energizing roll 2: Backup roll 3: Steel strip 4a, 4b: electrodes 5: Payoff reel 6: Electrolytic degreasing device 7: Plating tank 8a, 8b: Initial straightening roll 9a, 9b: Shape measuring device 10: Draining roll 11: Plating liquid 12: Input device 13: Control arithmetic unit 14: Adhesion amount measuring device 15: Chemical conversion treatment tank 16: Tension reel 17a, 17b: Warp straightening roll

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Munehiro Ishioka             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. F-term (reference) 4K024 BA03 BC01 CB10 CB19 CB24                       CB26 EA02

Claims (5)

[Claims] 1. A method for electroplating a steel strip by a horizontal continuous plating facility equipped with a current-carrying unit composed of a current-carrying roll and a backup roll, in which a steel strip whose warp in the width direction has been corrected is passed through the plating facility. At the same time, when a steel strip is sandwiched by a pair of upper and lower rolls having different contact lengths to the steel strip on the upstream side and / or the downstream side of a part or all of the energization unit, it occurs when the energization unit is threaded. Characterizing the warp of the steel strip by giving the steel strip a warp in the opposite direction to the warp of the steel strip,
Method of electroplating steel strip. 2. The method for electroplating a steel strip according to claim 1, wherein a pair of upper and lower rolls having different contact lengths with respect to the steel strip are liquid draining rolls provided in a plating tank. 3. The method according to claim 1, wherein the shape of the steel strip on the entrance side of the plating equipment is detected, and the correction amount of the steel strip to be passed through the plating equipment is controlled based on the shape detection. Two
The method of electroplating a steel strip according to. 4. The pressing load of a pair of upper and lower rolls having different contact lengths with respect to the steel strip is controlled.
The method for electroplating a steel strip according to claim 3. 5. The shape of the steel strip on the delivery side of the plating facility is detected, and the pressing load of a pair of upper and lower rolls having different contact lengths to the steel strip is feedback-controlled based on the shape detection. 4. The method for electroplating a steel strip according to item 4.