JP3262635B2 - Supply method of zinc ion to plating solution - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of supplying zinc ions for replenishing consumed zinc ions in a plating solution in a continuous electrogalvanizing equipment for metal strips such as steel strips using an insoluble anode.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for improved corrosion resistance in automobiles, home electric appliances and the like, and the demand for galvanized steel sheets has also increased remarkably. To cope with such an increase in demand, a high-speed plating method with a high current density that enables high-efficiency production has been adopted.However, in the high-speed plating method, the anode replacement is more required than in the soluble anode method in which anode replacement must be performed frequently. It goes without saying that a system in which an unnecessary insoluble anode such as an iridium-based one is used and metal ions are continuously supplied is more advantageous.

As a plating solution, a sulfuric acid-based electrolytic solution is usually used. In addition, as a method of replenishing zinc ions in the plating solution, there are a method of dissolving metal zinc by directly contacting the plating solution and a method of dissolving a metal compound such as zinc oxide. The method of directly dissolving granular or massive metallic zinc has a low dissolution rate, and it seems seemingly more efficient to dissolve the powdered metallic compound.However, such metallic compound powder is generally introduced into a liquid. When the method is adopted, it is easy to agglomerate (block) due to the reaction heat generated on the powder surface, and the agglomerated material hardly dissolves. There are many.

In this case, the concentration of the plating solution is controlled by, for example, circulating the plating solution between a plating solution circulation tank and a metal zinc dissolving tank as described in Japanese Patent Publication No. 53-24897. It is performed by turning on / off the circulation pump of the solution or adjusting the circulation flow rate according to the upper and lower limits of the plating solution concentration in the circulation tank. In this case, the supply amount of metal ions to the circulation tank is calculated by calculating the consumption amount of metal ions by plating from the product of the plating current and time, and measuring the target value of the metal ion concentration in the plating solution circulation tank and the target value. The amount taken out by the metal strip was calculated from the difference from the concentration, and the consumption of these metal ions was regarded as the required supply.

[0005] However, this method is poor in follow-up with respect to the timing shift between the concentration measurement and the action such as flow rate adjustment, and the change of the target concentration accompanying the change of the plating condition. There was a problem of being large. In order to improve these points,
The plating solution concentration control method described in JP-B-62-46640 will be briefly described with reference to FIG. Fig. 3
1 shows a zinc storage hopper, 2 shows a raw material cutting device, 3 shows a zinc dissolving tank,
31 is a level meter, 4 is a circulation tank, 6 is a plating tank in the line, 8 is a sedimentation tank, 9 is a speedometer, 10 is a setter, 11 is a calculator, 12 is a controller, and S is a strip.

[0006] In the above configuration, the zinc charging speed into the zinc dissolving tank 3 is calculated and calculated at predetermined intervals so that the zinc ion concentration in the plating solution circulation tank 4 after the predetermined time has reached the target value. By controlling the raw material cutting device 2 corresponding to the zinc feeding speed, the prediction control of the plating solution concentration is effectively performed. However, in this method, it is difficult to respond quickly when the operating conditions of the plating tank 6 in the line greatly change. In that case,
If the capacity of the circulation tank 4 is increased, it can be dealt with to some extent, but it is uneconomical.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide a method for precisely controlling the concentration of zinc ions by extremely easy and reliable means.

[0008]

The present invention comprises a plating tank,
Circulation tank that circulates plating solution with this plating tank
And the zinc solution that circulates the plating solution with this circulation tank.
In a continuous electrogalvanizing equipment for metal strips using a dissolving tank and using an insoluble anode, when replenishing zinc ions by dissolving metallic zinc in the plating solution, the basis weight of the material to be plated, width, line speed While calculating the required zinc supply rate, separately determining the zinc dissolution tank feed plating solution flow rate corresponding to the zinc supply rate from the pH value of the plating solution,
A method for supplying zinc ions to a plating solution, wherein the flow rate of the plating solution from the circulation tank to the zinc dissolving tank at the outlet of the liquid sending pump is controlled to be the determined value.

[0009]

[Operation] The basis weight of the material to be plated is G (g / m ² ), the plate width is W (m), the line speed is S (m / min), and the zinc ion concentration in the plating solution is α (g / l). ), Assuming that the amount of the plating solution carried out by the material to be plated is β (l / m ² ), the consumption rate Z (g / min) of zinc ion is as follows: Z = G · W · S + α · β · WS・ It is determined by (1). It should be noted that among the quantities in the formula, G and S have a substantially corresponding relationship, and α may be treated as a constant since the operation is performed so as to maintain the target value. β is a value obtained empirically and is treated as a constant.

On the other hand, when the relationship between the flow rate of the dissolving apparatus and the amount of zinc dissolved is determined for each pH of the plating solution, a graph as shown in FIG. 2 is obtained. The abscissa represents the flow rate of the plating solution fed to the zinc dissolving tank in which the flow rate for dissolving 1.0 g / l at pH = 2.0 is set to 1 and the ordinate represents the dissolution amount of zinc metal. According to the equation (1), the consumption rate Z of the zinc ion is calculated from the operating conditions of the line.
If the solution flow rate of the dissolving device is determined from the graph of FIG. 2 according to the pH of the plating solution, the consumption rate Z of zinc ions matches the dissolution rate of zinc, and the zinc ion concentration is kept constant. Will be.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic diagram showing a part of a steel strip continuous electrogalvanizing line according to an embodiment of the present invention. Figure 3 above
The same reference numerals are used for the same components. 5a is a circulation tank
Pump for feeding liquid from 4 to zinc dissolving tank 3 , 5b for circulation tank 4
A pump for feeding a liquid to the in- line plating tank 6 and a plating solution analyzer 7.

The zinc ion consumption rate Z is calculated from the operating conditions such as the sheet width and the basis weight according to the above equation (1), and the feed rate is adjusted to the zinc ion consumption rate Z calculated by controlling the raw material cutting device 2. Dissolve zinc. On the other hand, the flow rate of the plating solution flowing into the zinc dissolution tank is determined from the target pH of the plating solution, and the flow rate of the plating solution from the circulation tank 4 to the zinc dissolution tank 3 is determined.
The flow rate on the outlet side of the liquid pump 5a is controlled to be this value. In this embodiment, the pump is of a variable flow rate type , and the number of revolutions of the pump is controlled by electric means such as VVVF control.
A flow control valve may be provided on the pump outlet side to control the flow rate.

Thus, starting with the calculated values,
The plating solution analyzer 7 monitors the pH and the zinc ion concentration, and feeds back the data to the calculator 11. However, since the accuracy of the initially calculated values is high, the operation can be performed with almost no fluctuation in the concentration.

[0014]

According to the present invention, the amount of zinc dissolved is controlled so as to match the amount of zinc consumed (taken out) by the strip, so that the zinc concentration is small and plating of consistent quality is always performed. It has an excellent effect.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the amount of zinc dissolved and the flow rate of a plating solution in a melting tank.

FIG. 3 is a configuration diagram showing a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Zinc storage hopper 2 Raw material extraction device 3 Zinc dissolution tank 4 Circulation tank 5a, 5b Liquid feed pump 6 Plating tank 7 Plating solution analyzer 8 Sedimentation tank 9 Speedometer 10 Setting device 11 Computing device 12 Controller

Claims (1)

(57) [Claims] A plating tank is provided between the plating tank and the plating tank.
Between the circulation tank that circulates the liquid
With a zinc dissolving tank that circulates the plating solution, in a continuous electrogalvanizing equipment of a metal strip using an insoluble anode, when replenishing zinc ions by dissolving metallic zinc in the plating solution, the basis weight of the material to be plated, Calculate the required zinc supply speed from the width dimension and the line speed, and separately determine the zinc dissolution tank feeding plating solution flow rate corresponding to the zinc supply speed from the pH value of the plating solution, and determine the plating solution flow rate from the circulation tank. Zinc solution
A method for supplying zinc ions to a plating solution, wherein the flow rate of the plating solution on the outlet side of the liquid sending pump to the decomposing tank is controlled to be the determined value.