JPH0129880B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] 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 a plating solution circulation tank to a predetermined concentration. The present invention relates to a method of keeping the metal ion concentration in a metal dissolving tank almost constant and controlling the time for feeding this metal ion solution at a constant flow rate to a plating liquid circulation tank.

[Conventional technology]

Conventionally, plating solution concentration control in continuous electroplating of metal strips has been proposed, for example, in
As seen in Japanese Patent No. 24897, the plating solution is circulated between the plating solution circulation tank and the metal dissolving tank, and the circulating 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.

[Problem that the invention seeks to solve]

By the way, this type of plating liquid concentration control requires time for sampling measurements to measure metal ion concentration, delay time for flow rate adjustment, etc.
Naturally, sampling is controlled at regular intervals, but
In the conventional method described above, when the target plating amount is changed or the strip dimensions (width) or speed are changed, the plating solution concentration changes greatly during the sampling period, resulting in a change in the target concentration. This causes a phenomenon called hunting that goes up and down around the
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 these conventional problems and to provide a method for controlling a plating solution to a predetermined concentration while ensuring a predetermined plating quality.

[Means for solving 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, and a When electroplating strips in continuous electroplating equipment configured to circulate the plating liquid between the plating liquid circulation tank and the plating tank, the metal is charged into the metal dissolving tank so that the metal ion concentration in the metal dissolving tank is almost constant. In addition to controlling the plating speed, the plating speed is defined as the target value and actual value of the metal ion concentration of the plating liquid in the plating liquid circulation tank, the plating speed defined by the product of the plating amount and the stripping speed, and the metal dissolution rate in the metal dissolving tank. A relational expression between each factor and the feeding time of the metal ion solution to the plating circulation tank is determined in advance, and using this relational expression, the metal ion concentration of the plating liquid in the plating liquid circulation tank is determined to be the target metal after a certain period of time. Continuous electroplating characterized by calculating the feeding time of the metal ion solution required to reach the ion concentration and controlling the feeding of the metal ion solution to the plating liquid circulation tank based on the calculated feeding time. This is a plating solution concentration control method.

[Effect]

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 control device, 8 is a speed meter, and 9 is a setting 10 and 11 are computing units, and 12 is a concentration meter.

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 liquid in the circulation tank 3 is fed into the zinc dissolving tank ₁ by a pump P1.
Zinc introduced into the zinc dissolving tank 1 reacts with the plating solution to generate zinc ions.

The zinc ion solution of No. 2 is sent to the settling tank No. 2, and after precipitating the zinc grains carried together, the zinc ion solution of No. 2 is sent to the settling tank No. _2.
It is fed to the circulation tank 3 by. Circulation tank 3
A zinc ion solution is supplied to the plating tank 4 from 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 solution concentration in such electroplating equipment, in the present invention, zinc is added so that the dissolution rate in the zinc dissolving tank is kept almost constant, that is, the amount of zinc in the zinc dissolving tank is kept almost constant. Zinc is extracted from the equipment and the zinc ion concentration in the zinc dissolving tank is controlled to be almost constant, and the zinc dissolution rate is calculated from the zinc ion concentration in the circulation tank, the strip plating speed, and the amount of zinc in the zinc dissolving tank. From this, calculate the required feeding time of the zinc ion solution from the zinc dissolving tank to the circulation tank in order for the zinc ion concentration in the circulation tank to fall within the target concentration range, and then calculate the required feeding time of the zinc ion solution from the zinc dissolving tank to the circulation tank, and then adjust pumps _P1 and P based on the feeding time. This controls the operation of _{step 2} .

Here, the required feeding time of the zinc ion solution to the circulation tank is calculated as follows. Now, let the zinc ion concentration in the circulation tank be Ac [g/],
The zinc dissolution rate in the zinc dissolution tank is expressed as WF [g/
min] and set the plating speed to the strip as MP
When it is [g/min], the following formula holds true.

Ac=Aco−F・(MP−MPo)+G・(WF−
MP)・T −H・(WF−WFo−MP+MPo) [g/
] … Where, Aco: Calculated value of zinc ion concentration (or measured value) during the previous control [g/] WFo: Zinc dissolution rate during the previous control [g/min] MPo: Plating speed during the previous control [g/min] min] T: Control time [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 [g/min] ] It can be expressed as

By the way, the dissolution rate of zinc in the zinc dissolving tank depends on the amount of zinc in the zinc dissolving tank. Therefore, in this example, the amount of zinc in the zinc dissolving tank is determined at regular intervals by using the current amount of zinc, the zinc dissolution rate at this zinc amount, and the zinc charging speed into the zinc dissolving tank. −WFpo・DT+WFs・DT … Where, Wp: Amount of zinc after DT minutes [g] Wo: Current amount of zinc [g] WFpo: Current zinc dissolution rate [g/min] WFpo: f (Wo) WFs is predicted as the current zinc input rate [g/min], and from this predicted zinc amount Wp, the predicted zinc dissolution rate WFp is calculated by using the predetermined relational expression WFp=f(Wp)... (Example: Every minute) When the target amount of zinc in the zinc dissolving tank is Wt, the target zinc dissolution rate WFt corresponding to Wt can be obtained from the formula. and,
If WFp≦WFt, target zinc dissolution rate WFt
The amount of zinc cut out from the cut-out conveyor is controlled so that the zinc input speed corresponds to .

In calculating the predicted 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 Wa may be used; The period is long (1
time), so it is necessary to predict using a formula while measurements are not being taken.

Then, using the predicted zinc dissolution rate WFp,
The required feeding time Ts of the zinc ion solution to the circulation tank in order to make the zinc ion concentration in the circulation tank reach the target concentration Act is calculated from the following equation, which is a modification of the above equation.

Ts=Act−Aco+F・(MP−MPo)+H・(WFp−WFo−MP
−MPo)/G・(WFp−MP) [g/min]… Now, in actual operation, if the plating speed shown by the above formula changes, that is, if any of the target plating amount, strip width, and strip speed changes. If more than one changes, the required zinc ion solution feeding time is determined by the above formula.
Calculate Tswa. In addition, the zinc ion concentration Ac in the circulation tank is measured at regular intervals, and if it deviates significantly from the target concentration Act, the right side of the above equation is calculated.
The required feeding time Ts is calculated by replacing Aco with the measured concentration Ac.

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 Wa, and use this actual measured zinc amount Wa as the predicted zinc dissolution rate WFp.
Used for calculation. If the measurement by the level meter 6 is not completed, the predicted zinc amount Wp is calculated using the formula. The predicted zinc dissolution rate WFp is calculated by the formula using the measured zinc amount Wa or the predicted zinc amount Wp. Then, the zinc amount and zinc dissolution rate are stored in memory as Wo and WFpo for calculation after the next DT minute.

The operating time of pumps P ₁ and P ₂ is the actual speed value (V) input from the speedometer 8 in Figure 1 and the strip width (W) input from the setting device 9 as shown in the flowchart in Figure 3. The plating speed (MP) is calculated from the target plating adhesion amount (C). Then, the target zinc dissolution rate (WFt) is calculated from the target zinc amount (Wt) in the zinc dissolution tank inputted from the setting device 9 using a formula.

Then, the predicted zinc dissolution rate (WFp) and the target zinc dissolution rate (WFt) calculated by the arithmetic circuit 10
When WFp≦WFt, the set zinc cutting speed (WFs) is adopted as the zinc feeding speed corresponding to WFt, and when WFp>WFt, the set zinc cutting speed (WFs) is adopted. (WFs) to 0.
Next, the set cutting speed (WFs) is set and outputted to the zinc input amount control device 7 shown in FIG.

Then, from the predicted zinc dissolution rate (WFp) calculated by the arithmetic circuit 10, the plating rate (MP), and the target concentration (Act) input from the setting device, the amount of zinc ion solution required to reach the target concentration is determined by a formula. Calculate pay hours (Ts).

When this calculated feeding time (Ts) is longer than the minimum pump operating time (TL) determined by the pump, pumps P ₁ and P ₂ are started to feed the zinc ion solution, and Ts Stop after (minutes). When the calculated feeding time (Ts) is smaller than the minimum operating time (TL), pumps P ₁ and P ₂ do not operate and feed is stopped. Then, the plating rate, zinc ion concentration, and predicted dissolution rate are stored in the memory as Aco, Mpo, and WFo, respectively, for calculation after the next fixed time (for example, 10 minutes). Calculation of the set zinc cutting rate is performed at regular intervals (for example, 10 minutes), at the time 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 of zinc injection into the zinc dissolving tank is set at a certain period, and after a certain period of time, the delivery time of the zinc ion solution to the circulation tank to bring the zinc ion concentration in the plating liquid circulation tank to the target value is set. is calculated, and the operation of the feed pump is controlled based on the operational time of the feed pump, and predictive control of the plating concentration is performed extremely effectively.

Although the above explanation was based on Zn plating, the method of the present invention can also be applied to Zn--Fe alloy plating, Zn--Ni alloy plating, and other metal plating other than Zn plating.

〔Effect of the invention〕

As described above, the method of the present invention can maintain the concentration of the plating solution 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 drawings]

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: Arithmetic unit, 11: Arithmetic unit, 12: Concentration meter.

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 a plating liquid circulation tank and a plating liquid circulation tank and a plating liquid circulation tank and a plating liquid circulation tank and a plating liquid circulation tank. During electroplating of strips in continuous electroplating equipment configured to circulate plating liquid between tanks, the rate of metal injection into the metal dissolution tank is controlled so that the metal ion concentration in the metal dissolution tank is approximately constant; The target value and actual value of the metal ion concentration of the plating liquid in the plating liquid circulation tank, the plating speed defined as the product of the plating amount, the strip width, and the strip speed, and each factor of the metal dissolution rate in the metal dissolution tank. A relational expression between the feeding time of the metal ion solution to the plating liquid circulation tank is determined in advance, and using this relational expression, the metal ion concentration of the plating liquid in the plating liquid circulation tank reaches the target metal ion concentration after a certain period of time. A plating liquid in continuous electroplating, characterized in that the necessary feeding time of the metal ion solution is calculated, and the feeding of the metal ion solution to a plating liquid circulation tank is controlled based on the calculated feeding time. Concentration control method.