JPS6246640B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a method for controlling the concentration of plating solution in continuous electroplating of metal strips, and in particular to a method for controlling the concentration of plating solution in the continuous electroplating of metal strips. This invention relates to a method for controlling the amount of metal input into a melting tank.

(Prior art) Conventionally, plating solution concentration control in continuous electroplating of metal strips has been proposed, for example, in
As seen in Japanese Patent No. 24897, plating liquid is circulated between a plating liquid circulation tank and a metal dissolving tank, and the circulation flow rate is adjusted or turned on and off. The amount of metal ions supplied to the plating liquid circulation tank at this time is determined by calculating the amount of metal ions consumed by plating from the product of the plating current and time, and also calculating the target concentration of metal ions in the plating liquid circulation tank. The amount of plating liquid taken out by the metal strip was calculated from the difference between the two, and the flow rate regulating valve was controlled by setting the required amount of metal ions to be supplied in an amount commensurate with the consumption of these metal ions.

(Problems to be Solved by the Invention) By the way, this type of plating liquid concentration control requires time required for sampling measurements to measure metal ion concentration, delay time for flow rate adjustment, etc.
Naturally, sampling control is performed at fixed intervals, but in the conventional method described above, if the target plating amount is changed or the strip dimensions (width) or speed are changed, plating is controlled at regular intervals. The liquid concentration changes greatly, causing a phenomenon called hunting, where the concentration goes up and down around the target concentration.
The problem was that it was difficult to reach the target concentration. SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the conventional method and provide a method for controlling the concentration of the plating solution to a predetermined value while ensuring a predetermined plating quality.

(Means for Solving the Problems) The method of the present invention for achieving this object includes a plating tank, a plating liquid circulation tank, a metal dissolving tank, and a metal charging device to the metal dissolving tank, In strip electroplating in continuous electroplating equipment configured to circulate plating liquid between the liquid circulation tank and the metal dissolution tank and between the plating liquid circulation tank and the plating tank, the amount of metal in the metal dissolution tank, the metal dissolution rate, and The relational expression is determined in advance, and the amount of metal in the metal dissolution tank after a certain period of time is predicted and calculated from the current amount of metal and the metal dissolution rate, and the metal dissolution rate is calculated from this predicted amount of metal using the above relational expression. On the other hand, the target value and actual value of the metal ion concentration of the plating liquid in the plating liquid circulation tank, each factor of the plating speed defined by the product of the plating amount, the strip width and the stripping speed, and the metal dissolution rate are calculated. Find the relational expression in advance,
Using this relational expression, calculate the metal dissolution rate required to reach the target ion concentration after a certain period of time, and set the metal charging rate to the metal dissolution tank from the relationship between the required metal dissolution rate and the predicted metal dissolution rate. This is a plating solution concentration control method in continuous electroplating characterized by the following.

(Examples and effects of the invention) The present invention will be described in detail below based on examples.

FIG. 1 is a diagram showing the configuration of main parts of an apparatus in an embodiment in which the method of the present invention is applied to continuous electrogalvanizing of steel strip. In the figure, 1 is a zinc dissolving tank, 2 is a settling tank, 3 is a circulation tank, 4 is a plating tank, 5 is a zinc charging device, 6 is a level meter, 7 is a zinc charging amount control device, 8 is a speed meter, and 9 is a The setting device (or upper-level computer) 10 and 11 are arithmetic units.

In the above device configuration, zinc cut out from the cutting conveyor of the zinc feeding device 5 is fed into the zinc dissolving tank 1. The plating solution in the circulation tank 3 is fed into the zinc dissolving tank 1 by a pump _P1 , and the zinc introduced into the zinc dissolving tank 1 reacts with the plating solution to generate zinc ions.

This zinc ion solution is fed to the settling tank 2 to precipitate the zinc grains carried therewith, and then fed to the circulation tank 3 by the pump _P2 . A zinc ion solution is supplied from the circulation tank 3 to the plating tank 4, and the steel strip S passing through the plating tank 4 is plated with zinc. This plating reduces the zinc ion concentration in the plating tank 4, and the plating solution in the plating tank 4 with the reduced zinc ion concentration is sent to the circulation tank 3. In this way, the generation of zinc ions is carried out in the zinc dissolving tank 1, and the consumption of zinc ions by plating is carried out in the plating tank 4. In controlling the plating liquid concentration in such electroplating equipment, the present invention uses the following methods:
This method calculates the necessary zinc input speed from the zinc input device so that the zinc ion concentration in the circulation tank is within the target concentration range, and controls the amount of zinc cut out from the zinc input device so that the zinc input speed is achieved. be.

Here, the required zinc feeding rate is calculated as follows. Now, let the zinc ion concentration in the circulation tank be a _c [g/], the zinc dissolution rate in the zinc dissolution tank be WF [g/min], and the plating speed to the strip be MP [g/min], then the following will be obtained. The formula holds true.

a _c = a _cp -F・(MP-MP _p )-G・(WF-MP)・T-H・(WF-WF _p -MP+MP _p ) [g/]... Here, a _cp : Previous control Calculated zinc ion concentration (or measured value) [g/min] WF _p : Zinc dissolution rate during previous control [g/min] MP _p : Plating speed during previous control [g/min] T: Control time [g/min] min] F, G, H: coefficients. It is determined by the amount of liquid in the zinc dissolution tank, precipitation tank, circulation tank, plating tank, and the flow rate of liquid between the zinc dissolution tank and the circulation tank.

Also, the plating speed MP is as follows: MP=C・W・V [g/min] ...where, C: Target plating amount [g/m ² ] W: Strip width [m] V: Stripping speed [m/m2] It can be expressed as min].

Therefore, the zinc dissolution rate WF _t for making the zinc ion concentration in the circulation tank reach the target concentration a _ct after T minutes from the current time can be determined from the following equation, which is a modification of the above equation.

WF _t = _act -a _cp +MP・(G・T+F−H)−F・MP _p −H・(WF _p −MP _p )/G・T−H [g/min
]... Now, in actual operation, if the plating speed shown in the above formula changes, that is, if any one or more of the target plating amount, strip width, and strip speed changes, the required plating rate can be calculated using the above formula. Calculate the zinc dissolution rate WF _t . Also, measure the zinc ion concentration a _c in the circulation tank at regular intervals, and if it deviates significantly from the target concentration a _{c t} , replace a _cp on the right side of the above equation with the measured concentration a _c to determine the required zinc dissolution rate. Calculate WF _t . By the way, the dissolution rate of zinc in the zinc dissolving tank differs depending on the amount of zinc in the zinc dissolving tank. Therefore, in determining the required zinc dissolution rate based on the required zinc dissolution rate calculated as described above, the amount of zinc in the zinc dissolution tank and the zinc dissolution rate at that amount of zinc are predicted, and the predicted zinc dissolution rate is It is necessary to compare the speed with the required zinc dissolution rate WF calculated from the above formula.

In this example, the amount of zinc in the zinc dissolving tank is expressed as: W _p = W _p −WF _pp・DT + WF _s・DT where, W _p : Amount of zinc after DT minutes [g] W _p : Current amount Amount of zinc [g] WF _pp : Current zinc dissolution rate [g/min] WF _s : Current zinc input rate [g/min] Predicted as follows, and a relational expression determined in advance from this predicted zinc amount W _p is calculated. Using WF _p = f (W _p )..., the predicted value WF _p of the zinc dissolution rate is set at a constant period.
Calculate every DT minute (example: 1 minute). and WF _p ≦
In the case of WF _t , the amount of zinc cut out from the cutting conveyor is controlled so that the zinc input speed corresponds to WF _t . When WF _p > WF _t , zinc is not cut out, and when WF _p ≦ WF _t , as above,
The cutting amount should be equivalent to WF _t .

In predicting the zinc dissolution rate, if the amount of zinc in the zinc dissolution tank can be measured at short intervals with the level meter 6, the actual amount of zinc W _a may be used, but normally measurement using this type of measuring device is Since the period is long (more than 1 hour), it is necessary to predict it using a formula while it is not being measured.

FIG. 2 is a flowchart showing the calculation flow in the calculation unit 10 of FIG. 1, and FIG. 3 is a flowchart showing the calculation flow in the calculation unit 11 of FIG.

When calculating the amount of zinc in the zinc dissolving tank and the zinc dissolution rate after DT minutes (example: 1 minute), as shown in the flowchart in Figure 2, when the level measurement with the level meter 6 is completed, the zinc level Check the upper and lower limits of the measured value, then calculate the actual measured zinc amount W _a , and use this measured zinc amount W _a as the predicted zinc dissolution rate WF _p
Used for calculation. If the measurement by the level meter 6 has not been completed, the predicted zinc amount W _p is calculated using the formula. A predicted zinc dissolution rate WF _p is calculated by a formula using the measured zinc amount W _a or the predicted zinc amount W _p . and the next
The zinc amount and zinc dissolution rate are stored in memory as W _p and WF _pp for calculation after DT minutes. The zinc removal speed from the zinc charging device is calculated using the actual speed value V input from the speedometer 8 in FIG. 1 and the strip width input from the setting device 9, as shown in the flowchart in FIG. The plating speed MP is calculated from W and the target plating adhesion amount C using a formula. The zinc dissolution rate WF _t required to reach the target concentration is calculated from the elapsed time T since the previous zinc cutting speed setting output, the plating speed MP, and the target concentration a _ct input from the setting device 9 using a formula. Then, the predicted zinc dissolution rate WF _p calculated by the arithmetic circuit 10 is compared with the required zinc dissolution rate WF _t , and if WF _p ≦ WF _t , the zinc input corresponding to WF _t is set as the set zinc cutting rate WF _s . When WF _p > WF _t , the set zinc cutting speed WF _s is set to 0.
Next, the set cutting speed WF _s is set and outputted to the zinc input amount control device 7 shown in FIG. and the zinc ion concentration for calculation after a certain period of time (e.g. 15 minutes),
The plating rate and zinc dissolution rate are a _cp and
Store in memory as MP _p and WF _p . Calculation of the set zinc cutting rate is performed at regular intervals (for example, 15 minutes), when any one of the target plating amount, strip width, and strip speed changes, or every time the zinc ion concentration is measured.

In this way, the rate at which zinc is introduced into the zinc dissolving tank at which the zinc ion concentration in the plating liquid circulation tank should be set to the target value after a certain period of time is calculated, and the speed of the cutting conveyor is controlled in accordance with this zinc input rate. As a result, predictive control of the plating solution concentration is performed very effectively. In addition, by calculating (zinc feeding speed) x (cutting cycle) as the zinc cutting amount and setting this zinc cutting amount in the zinc feeding amount control device 7, predictive control of the plating solution concentration can be made extremely effective. It can also be done.

(Effects of the Invention) As described above, the method of the present invention can maintain the plating solution concentration within a predetermined concentration range during continuous electroplating of strips, and can also calculate and control the appropriate metal cutting speed.

Therefore, the basic unit of plating metal can be improved by cutting out the minimum amount of metal while ensuring a predetermined plating quality.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an apparatus configuration in an embodiment of the present invention, and FIGS. 2 and 3 are flowcharts showing an example of the calculation flow in the present invention. 1: Zinc dissolution tank, 2: Sedimentation tank, 3: Circulation tank, 4: Plating tank, 5: Zinc input device, 6: Level meter, 7: Zinc input amount control device, 8: Speed meter,
9: Setting device (or host computer), 10,1
1: Arithmetic unit.

Claims (1)

[Scope of Claims] 1 It has a plating tank, a plating liquid circulation tank, a metal dissolving tank, and a metal charging device to the metal dissolving tank, and has a plating liquid circulation tank and a metal dissolving tank, and a plating liquid circulation tank and a metal dissolving tank. When electroplating strips in continuous electroplating equipment configured to circulate plating liquid between the plating tanks, a relational expression between the amount of metal in the metal dissolving tank and the metal dissolution rate is determined in advance, and the current amount of metal and the metal dissolution rate are calculated in advance. The amount of metal in the metal dissolution tank after a certain period of time is calculated based on the dissolution rate, and the metal dissolution rate is predicted and calculated from this predicted amount of metal using the above relational expression. The relational expression between each factor of the plating speed defined by the product of the target value and measured value of ion concentration, the plating amount, the strip width and the stripping speed, and the metal dissolution rate is determined in advance.
Using this relational expression, calculate the metal dissolution rate required to reach the target ion concentration after a certain period of time, and set the metal charging rate to the metal dissolution tank from the relationship between the required metal dissolution rate and the predicted metal dissolution rate. A plating solution concentration control method in continuous electroplating, characterized in that: