JP2004068130A - Method for controlling coating weight in electroplating line - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for controlling the coating weight in an electroplating line by which plating can stably be applied so as to be a target coating weight even when a specified pass is stopped or a using rate is changed, or a line velocity is changed on the way. <P>SOLUTION: Plating efficiency is preliminarily set for individual pass in an electroplating line, and the coating weight is controlled for individual pass. In the control method, on the basis of the coating weight till the pass and the number of passes till a final pass, the individual coating weight to be applied in the pass is calculated, and further, an electric current required in the pass for attaining the above individual coating weight is calculated from the plating efficiency and line velocity in the pass, and conducting is performed. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for controlling a basis weight of an electroplating line such as a steel plate.
[0002]
[Prior art]
Conventionally, an electroplating line as shown in FIG. 3 has been used to apply electroplating such as tin or chrome to a metal strip such as a steel plate. In the electroplating tank 1 of the electroplating line, a number of paths 3 having electrodes 2 are provided in series. The metal strip is wound between the conductor roll 4 and the turn roll 5 in a zigzag manner, and travels continuously inside each pass 3. A current is supplied from the rectifier 6 to the electrode 2 of each path 3, and the metal strip running in each path 3 is electroplated.
[0003]
Conventionally, the control of the basis weight of the electroplating line has been exclusively performed by a total current control method. That is, conventionally, a necessary total current is calculated from a target basis weight (amount of plating), Coulomb equivalent, plating efficiency, and line speed, and the operator distributes the total current to each pass 3 to perform plating. Here, the plating efficiency means the ratio of the current that effectively contributes to the plating among the supplied current, and a part of the current is consumed for electrolysis of water, re-elution of the plating film, and the like, Unless a current equal to or greater than the theoretical current value calculated from the basis weight, Coulomb equivalent, and line speed is applied, the target basis weight cannot be obtained. This relationship can be expressed by an equation of (current to be supplied to obtain a target basis weight) = (theoretical current value) / (plating efficiency).
[0004]
In the conventional method, the plating efficiency is common to all the passes 3 and the total current according to the line speed is calculated. However, in practice, for example, there is a difference in plating efficiency between the pass 3 having a high usage rate and the pass 3 having a low usage rate. Therefore, when the specific path 3 is stopped or the usage rate is changed due to operational necessity such as failure of the electrode 2 or the like, the weight per unit area may vary even if the total current is correctly controlled. there were.
[0005]
Further, the conventional total current control method cannot cope with the case where the line speed is increased or decreased during plating. That is, the total current control method calculates the current on the premise that the metal strip travels all paths 3 at a constant line speed. However, if the line speed changes, the plating efficiency also changes. If it changes, the plating amount changes, and the final basis weight varies.
[0006]
As described above, in the conventional total current control method, it is difficult to control the basis weight with high accuracy as intended. If the weight per unit area is insufficient, the product becomes defective. Therefore, conventionally, the target weight per unit is set to be larger than the required weight per unit area, and there is a problem that the manufacturing cost is increased.
[0007]
[Problems to be solved by the invention]
The present invention solves the above-mentioned conventional problems, and stabilizes the target basis weight even when a specific path is stopped or the usage rate is changed, or when the line speed is changed halfway. The purpose of the present invention is to provide a method for controlling the basis weight of an electroplating line capable of performing plating.
[0008]
[Means for Solving the Problems]
The weight control method of the electroplating line of the present invention made in order to solve the above-mentioned problem, for each individual pass of the electroplating line having a large number of passes, the weight per unit weight up to the pass and the final pass. Calculate the individual basis weight to be deposited in the pass from the number of passes, calculate the current required in the pass to achieve the individual basis weight from the plating efficiency and the line speed in the pass, and apply the current. It is characterized in that the basis weight is controlled for each pass. As the plating efficiency for each individual pass, a value set in advance as a function of the current density and the line speed can be used. Further, a value that is automatically learned can be used as the plating efficiency for each individual pass.
[0009]
In the method of controlling the basis weight of the electroplating line of the present invention, by controlling the basis weight for each individual pass, even when a specific pass is stopped or the usage rate is changed, the line speed is also reduced. Even in the case of a change, plating can be performed accurately so as to achieve the target basis weight.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a schematic view of a plating facility composed of N passes, and a large number of passes 3 having electrodes 2 are provided in series in an electroplating tank 1 as in the prior art. The metal strip is wound between the conductor roll 4 and the turn roll 5 in a zigzag manner, and is electroplated while continuously running inside each pass 3. A current is supplied to the electrode 2 of each path 3 from the rectifier 6. As shown in FIG. 1, in the present invention, a current required in the path 3 is calculated and supplied for each individual path. The control method will be described below.
[0011]
In the present invention, first, the plating efficiency is set for each pass 3. The plating efficiency can be set in advance as a function of the current density of the electrode 2 and the line speed. In addition, this set value can be automatically learned online or offline, and can be corrected to a more accurate value according to the actual situation.
[0012]
In the present invention, the current value is controlled for each individual pass, and the plating adhesion amount can be obtained for each individual pass from the plating efficiency and the actual line speed set for each individual pass as described above. Although FIG. 1 shows the n-th pass, the plating weight at the time of passing the (n-1) -th pass is obtained by integrating the plating adhesion amount in each of the first to (n-1) -th passes. Then, the amount of plating required to be deposited in the remaining passes from the n-th pass to the final pass is obtained by subtracting the per-unit weight from the target plating amount.
[0013]
Next, from the number of passes up to the final pass, the individual basis weight to be attached in pass 3 is calculated. As described above, the current is not evenly distributed to all the paths, but a distribution ratio is set. For example, the distribution ratio at the entrance portion of the plating tank 1 is set low, and the distribution ratio at the central portion is set high. Therefore, as shown in FIG. 1, the sum of the allocation ratios of the respective paths from the n-th path to the final path is used as the denominator, and the allocation ratio of the n-th path is used as the numerator to attach the path (the n-th path). An individual weight per unit area is calculated.
[0014]
In this way, after calculating the individual areal weight to be deposited in the nth pass, the current required to achieve the individual areal weight is determined from the Coulomb equivalent, the plating efficiency and the line speed of the nth pass. Then, the current is supplied to the electrode 2 of the n-th path through the rectifier 6. As a result, it is possible to perform plating of an individual basis weight to be deposited in the n-th pass. Similar individual control is performed in the next (n + 1) th pass, and when the final pass is reached, plating of the target basis weight is performed. This relationship is shown in FIG.
[0015]
According to the method of the present invention described above, since the energization control is performed by calculating the plating adhesion amount and the current for each individual pass, even if the line speed is changed in the middle, for example, , The remaining weight required in the subsequent pass can be calculated and corrected to a current corresponding to the changed line speed. Also, even when the number of passes to be used is changed, the current can be controlled so that the target basis weight is obtained when the last pass is passed, and stable plating can be performed. For this reason, the variation in the basis weight is smaller than in the past. For example, when the method of the present invention was applied to a chrome plating line for container cans, the variation in the basis weight (maximum value−minimum value) of the plating was 30 mg / m ² conventionally. However, it could be reduced to 1/3 of 10 mg / m ² .
[0016]
【The invention's effect】
As described above, according to the method for controlling the basis weight of the electroplating line of the present invention, for each individual pass of the electroplating line having a large number of passes, the existing basis weight up to that pass and the pass up to the final pass are determined. Calculate the individual basis weight to be deposited in the pass from the number and then calculate the current required in that pass from the plating efficiency and the line speed in the pass to achieve the above individual basis weight, and energize the individual pass. Since the basis weight is controlled every time, even if a specific pass is stopped or the usage rate is changed, or if the line speed changes in the middle, plating is stably performed to reach the target basis weight. Can be applied. Therefore, according to the method for controlling the basis weight of the electroplating line of the present invention, since the basis weight does not become insufficient, there is no need to apply excessive plating as in the prior art, and the cost can be reduced while increasing the product yield. Can be.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a control method according to the present invention.
FIG. 2 is an explanatory diagram showing a change in a basis weight at the time of passing an individual pass in the present invention.
FIG. 3 is an explanatory diagram of a conventional control method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Electroplating tank 2 Electrode 3 Pass 4 Conductor roll 5 Turn roll 6 Rectifier

Claims (3)

For each individual pass of an electroplating line with a large number of passes, calculate the individual basis weight to be attached in that pass from the existing basis weight up to that pass and the number of passes up to the final pass, and then calculate the plating efficiency in that pass A method for controlling the basis weight of an electroplating line, comprising calculating a current required in the pass to achieve the above-mentioned basis weight from the line speed and applying the current, and controlling the basis weight for each individual pass. 2. The method according to claim 1, wherein a value preset as a function of the current density and the line speed is used as the plating efficiency for each individual pass. 2. The method according to claim 1, wherein a value learned automatically is used as the plating efficiency for each individual pass.

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