JPH09324297A - Method for estimating concentration of plating liquid for continuous electroplating equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To exactly estimate the average concn. over the entire part of a plating liquid necessary for adequately controlling the connection. of the plating liquid with continuous electroplating equipment. SOLUTION: The method for estimating the concns. of the plating liquid of the continuous electroplating equipment is constituted to have plating cells 1 to 3 for continuously plating a transported strip, circulating tanks 4 to 6 for replenishing these plating cells with plating liquid components while circulating the plating liquid to the cells and ancillary equipment 7 to 9 for supplying zinc, nickel and sulfuric acid respectively to the circulating tanks 4 to 6. In such a case, the continuous electroplating equipment is divided to nine pieces of equipment blocks. The concn. estimation models based on the material balance models taking the expenditure of the plating liquid components by plating and the income of the plating liquid component by the supply of the component materials into consideration are built for each of the respective equipment blocks. The plating liquid concns. of the respective equipment blocks are estimated by using these concn. estimation models.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for estimating the concentration of a plating solution in continuous electroplating, and particularly to a plating solution in continuous electroplating suitable for appropriately controlling the concentration of the plating solution in continuous electroplating equipment. Concerning the concentration estimation method.

[0002]

2. Description of the Related Art In order to plate a steel sheet with high precision in continuous electroplating equipment, the concentration of plating solution in the plating equipment must be
For example, it is extremely important to accurately control the pH (or H2 SO4 concentration) and the metal ion concentration to target values.

As a conventional plating solution concentration control method, for example, there is a technique of measuring pH (or H2 SO4 concentration) and introducing a metal chemical so that the pH (or H2 SO4 concentration) becomes constant. -97543, JP-A-58-12
3890 and JP-A-62-4900.

Further, Japanese Patent Laid-Open No. 60-48598 discloses a technique for measuring the metal ion concentration and introducing a metal chemical so that the metal ion concentration is constant.

Further, in order to control the metal ion to a target concentration, a technique of introducing an amount of a metal agent obtained from the sum of the predicted consumption and the deviation of the metal ion concentration is disclosed in JP-A-61-198.
00, JP-A-61-91396, JP-A-62-4664
0, JP-A-62-222099, JP-A-1-2988.
No. 0, disclosed in JP-A-1-234599.

Similarly, in order to control the metal ion to a target concentration, an amount of the metal agent obtained from the sum of the predicted consumption of the metal ion and the concentration deviation of the metal ion is added, and H 2 SO 4 is added.
A technique for adding a sulfuric acid chemical in an amount determined from the concentration (or pH) deviation is disclosed in JP-A-59-116400 and JP-B-61-1.
6440, JP-A-2-217499, JP-A-4-567
96.

Further, a technique for controlling the amount of metal drug input determined from the sum of the predicted consumption of metal ions, the metal ion concentration, and the metal ion concentration ratio deviation, by correcting from the measured value of the H2 SO4 concentration (or pH). JP-A-5-32099
7 is disclosed.

[0008]

However, in the above-mentioned conventional concentration control techniques, there is a difference whether or not the estimated consumption of the components of the plating solution is taken into consideration. Since the control is performed using the measured concentration value itself which is actually limited, there are the following problems.

Continuous electroplating equipment using an insoluble anode is generally a plating cell for electroplating a steel sheet, a circulation tank for circulating and supplying a plating solution to the plating cell, and a plating solution concentration (metal ion concentration). In the case of alloy plating, metal ion concentration ratio, H2 SO4 concentration or p
H) is included in the auxiliary equipment for adjusting.

Hereinafter, zinc carbonate (ZnCO) is used as a metal material.
3), Zn-Ni using nickel carbonate (NiCO3)
Plating in the above electroplating equipment will be described by taking the case of alloy-based electroplating as an example. In the plating cell,
The electroplating (electrodeposition) reaction on the steel sheet represented by the formulas (A) to (C) causes a decrease in metal ions and an increase in H2 SO4 (or a decrease in pH).

Electrodeposition reaction: Zn ² + 2e ⁻ → Zn ↓ (on the steel plate) (A) Ni ² + 2e ⁻ → Ni ↓ (on the steel plate) (B) H 2 O + SO 4 ^2- → H 2 SO 4 + O 2 ↑ + 2e ⁻ (anode Above) (C)

On the contrary, in the above-mentioned auxiliary equipment, the following (D),
Due to the dissolution reaction of the metal material represented by the formula (E), an increase in metal ions and a decrease in H2 SO4 (or an increase in pH)
Occurs.

Dissolution reaction: ZnCO3 + H2SO4 → ZnSO4 + H2O + CO2 ↑ (D) NiCO3 + H2SO4 → NiSO4 + H2O + CO2 ↑ (E)

Therefore, when the concentration measurement by the densitometer (metal ion concentration, H2 SO4 concentration or pH) is performed in the plating cell, the metal ion concentration is lower than the average concentration of the whole plating solution existing in the plating equipment. Becomes the measured value of H2
The SO4 concentration is a high (or pH is low) measurement value.
On the contrary, if the same concentration measurement is performed with the auxiliary equipment, the metal ion concentration becomes a higher measurement value and the H2 SO4 concentration becomes a lower measurement value (or the pH is higher) with respect to the average concentration of the entire plating solution. . Furthermore, in the case of continuous electroplating equipment, the degree of influence varies depending on the difference in the electrodeposition rate (line speed, amount of adhesion, plate width, etc.).

Therefore, in the continuous electroplating equipment, based on the measured values obtained at the limited positions as described above,
The plating solution concentration cannot be accurately controlled to the target value.

The present invention has been made to solve the above-mentioned conventional problems, and accurately estimates the average concentration of the entire plating solution necessary for appropriately controlling the concentration of the plating solution in continuous electroplating equipment. It is an object to provide a technology capable of doing so.

[0017]

SUMMARY OF THE INVENTION The present invention comprises one or more plating cells for continuously plating a strip to be conveyed.
In a plating solution concentration estimating method in a continuous electroplating equipment comprising auxiliary equipment for supplying a plating solution component while circulating the plating solution in the plating cell, the continuous electroplating equipment is divided into a plurality of equipment blocks, and each equipment block is divided. For each facility, a concentration estimation model based on a mass balance model that considers the effects of the plating solution component expenditure for plating and the income of the plating solution component due to the supply of component materials is constructed. The above problem is solved by estimating the plating solution concentration of the block.

That is, in the present invention, the continuous electroplating equipment is divided into a plurality of arbitrary equipment blocks, and the electrodeposition reaction in the plating cell and the dissolution reaction of the metal material (component material) in the auxiliary equipment are taken into consideration. With the concentration estimation model based on the material balance model described above, the concentration of each block can be continuously estimated. Therefore, even with one densitometer, the concentration balance of the entire facility can be constantly monitored. According to the third aspect, the average concentration of the entire facility can be estimated from the estimated concentration of each facility block and the bath amount thereof. Further, in the case of estimating the average concentration in this way, since it is not affected by the variation of the concentration measurement value depending on the measurement place, it becomes possible to perform the feedback (FB) control of the plating solution concentration with high accuracy.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of continuous electroplating equipment applied to one embodiment according to the present invention.

In this continuous electroplating equipment, three plating cells denoted by reference numerals 1 to 3 are arranged in one row, and the steel plate S is conveyed in the direction of the arrow in these plating cells 1 to 3 while continuously performing electroplating. Is to be done.

Further, the above-mentioned plating equipment is an accessory equipment for circulating a plating solution in the direction of the arrow 4, respectively.
6 to 6, and auxiliary equipments A to C having reference numerals 7 to 9 for supplying the material of the plating solution component are provided. The auxiliary equipment A7 corresponds to equipment for supplying zinc material as ZnCO3, the auxiliary equipment B8 corresponds to equipment for supplying nickel material as NiCO3, and the auxiliary equipment C9 corresponds to equipment for supplying sulfuric acid.

Further, in the above plating equipment, the circulation tanks 4 to
6, a level meter 10 is attached to each of the pipes 6, a supply pipe arranged between the plating cells 1 to 3 and the corresponding circulation tanks 4 to 6, and the circulation tank 4 to auxiliary equipment A7.
A flow meter 11 is attached to each of the feed pipes to C9, and a concentration meter 12 is attached only to the circulation tank 6.

In the present embodiment, the continuous electroplating equipment is divided into nine equipment blocks corresponding to the above-mentioned partial equipment with reference numerals 1 to 9, and the plating solution components for plating are provided for each equipment block. Of concentration and the concentration estimation model based on a mass balance model that takes into account the effects of the supply of component materials on the income of the components of the plating solution, and the concentration estimation model is used to estimate the concentration of the plating solution of each equipment block. To do.

First, in this concentration estimation model, the number of divisions of equipment blocks (hereinafter also simply referred to as blocks) is m.
Will be described below.

Zn concentration: CZ (t), Ni concentration: CN (t), H 2 SO of 1 to m blocks at time t calculated last time
4 Concentration: CA (t) is described by the following matrix. The matrix elements CZ1 (t) to CZm (t) and CN1 (t) to CNm
(t) and CA1 (t) to CAm (t) are the corresponding densities of 1 to m blocks at time t, and T represents the transposed matrix.

CZ (t) = (CZ1 (t), ..., CZm (t)) ^T ... (1) CN (t) = (CN1 (t), ..., CNm (t)) ^T. (2) CA (t) = (CA1 (t), ..., CAm (t)) ^T ... (3)

Further, the Zn balance amount: Uz, Ni balance amount: Un, H2 SO4 balance amount: Ua of the 1-m blocks from time t to time t + 1 are described by the following matrix. These matrices are
It corresponds to the mass balance model. Note that Uz1 which is an element of the matrix
˜Uzm, Un1 ˜Unm, Ua1 ˜Uam are t˜t
It is the income and expenditure amount corresponding to each of 1 to m blocks during +1 time.

Uz = (Uz1, ..., Uz1) ^T (4) Un = (Un1, ..., Unm) ^T (5) Ua = (Ua1, ..., Uam) ^T (6) )

As a result, Zn concentration of 1 to m blocks at time t + 1: CZ (t + 1), Ni concentration: CN (t + 1), H2
SO4 concentration: CA (t + 1) is the following (7), (8),
It can be obtained by the equation (9).

CZ (t + 1) = (IA−2) ⁻¹ × {(I + A / 2−VA) × CZ (t) + UZ} (7) CN (t + 1) = (IA / 2) ^-1 x {(I + A / 2-VA) x CN (t) + UN} (8) CA (t + 1) = (I-A / 2) ^-1 x {(I + A / 2-VA) × CA (t) + UA} (9) where I: m-th unit matrix A = V ⁻¹ × F × Δt V ⁻¹ : Block bath volume diagonal inverse matrix (m × m) F: Interblock liquid flow velocity Matrix (m × m) Δt: t to t + 1 elapsed time VA = V ⁻¹ × Vd Vd: block change bath amount diagonal matrix (m × m) between t and t + 1
m) UZ = V ⁻¹ × Uz × Δt UN = V ⁻¹ × Un × Δt NA = V ⁻¹ × Ua × Δt

When the number of blocks is m, as described above, the Zn ion concentration (Z) of each block (Z can be obtained by constructing the concentration estimation model consisting of the equations (7) to (9).
n concentration), Ni ion concentration (same as Ni concentration),
The distribution of H2 SO4 concentration can be predicted.

The method of deriving the concentration calculation model will be described in detail below. Here, in order to facilitate understanding, consider the case of a plating facility including three facility blocks, as shown in FIG.

The symbols in the blocks in FIG. 2 represent values at time t, and the symbols used in this figure have the following meanings.

That is, for i, j = 1, 2, 3, Vi [m ³ ]: bath amount of i block CZi [g / l]: Zn concentration of i block CNi [g / l]: Ni of i block Concentration CAi [g / l]: Concentration of H2SO4 in i block Usi [m ³ / h]: Water balance velocity of i block outside the circulation system Uzi [kg / h]: Zn of i block outside the circulation system Balance speed Uni [kg / l]: Ni balance speed of i-block outside the circulation system Uai [kg / l]: H2SO4 balance speed of i-block outside the circulation system Fij [m ³ / h]: From i block Liquid movement speed (flow velocity) to block j

For the sake of convenience, the Zn concentration change will be described as an example. The change amount (Δt (h)) of the bath amount (Δt (h)) between t and t + 1.
Vi [m ³ ]) can be described by the following equation in the case of one block.

ΔV1 = (F31−F12) × Δt + Us1 × Δt [m ³ ] (10)

In this equation, F31 × Δt is the amount flowing from 3 blocks to 1 block, F12 × Δt is the amount flowing from 1 block to 2 blocks, and Us1 × Δt is 1
This is the amount of water that flows into the block from outside the system.

Similarly, the following equations can be used for a few blocks.

[0040] ΔV2 = (F12-F23) × Δt + Us2 × Δt [m 3] ... (11) ΔV3 = (F23-F31) × Δt + Us3 × Δt [m 3] ... (12)

From the time t to the time t + 1 when the bath amount changes by ΔVi, the Zn between t and t + 1 time (Δt [h])
The Zn movement amount due to the change in concentration (ΔCZi [g / l]) can be described by the following equation in the case of one block.

(V1 + ΔV1) × (CZ1 (t) + ΔCZ1) −V1 × CZ1 (t) = (F31 × CZ3−F12 × CZ1) × Δt + Uz1 × Δt [kg] (13)

In this equation, the left side is obtained by subtracting the total amount of Zn at the time t + 1 from the total amount of Zn at the time t + 1, and the right side is F31 × CZ3 × Δt from 3 blocks to 1
Zn amount flowing into the block, F12 × CZ1 × Δt, Zn amount flowing out from one block to two blocks, Uz1 × Δt
Is the amount of Zn supplied to one block.

Similarly, the following equations can be used to describe a few blocks.

(V2 + ΔV2) × (CZ2 (t) + ΔCZ2) −V2 × CZ2 (t) = (F12 × CZ1−F23 × CZ2) × Δt + Uz2 × Δt [kg] (14) (V3 + ΔV3) × (CZ3 (t) + ΔCZ3) -V3 × CZ3 (t) = (F23 × CZ2−F31 × CZ3) × Δt + Uz3 × Δt [kg] (15)

However, CZi is an intermediate value between time t and time t + 1 (Equation (28) described later), and CZi (t) is a value at time t.

Therefore, from the equation (13), (V1 + ΔV1) × ΔCZ1 = (F31 × CZ3−F12 × CZ1 + Uz1) × Δt−ΔV1 × CZ1 (t) (16) From the equation (14), V2 + ΔV2) × ΔCZ2 = (F12 × CZ1−F23 × CZ2 + Uz2) × Δt−ΔV2 × CZ2 (t) (17) From the equation (15), (V3 + ΔV3) × ΔCZ3 = (F23 × CZ2−F31 ×) Each formula of CZ3 + Uz3) .times..DELTA.t-.DELTA.V3.times.CZ3 (t) (18) is obtained.

The above equations (16) to (18) can be summarized by matrix expression as the following equation (19).

[0049]

[Equation 1]

For this equation (3), a 3 × 3 matrix V,
When Vd, F and the three-column vectors CZ, Uz are set as in the following equations (20) to (24), the following equation (25) is obtained.

V = diag. (V1 + ΔV1, V2 + ΔV2, V3 + ΔV3) (20) Vd = diag. (ΔV1, ΔV2, ΔV3) (21) CZ = (CZ1, CZ2, CZ3) T (22) Uz = (Uz1, Uz2, Uz3) T (23)

[0052]

[Equation 2]

V · ΔCZ = F · CZ · Δt + Uz · Δt−Vd · CZ (t) (25)

The symbols in the equations (20) and (21) are A = diag. (A, b, c) has diagonal elements a,
b and c represent a diagonal matrix in which the other elements are 0. or,
The inverse matrix of A is A ⁻¹ = diag. (1 / a, 1 / b, 1
c).

In the above equation (22), CZ = (CZ1,
CZ2, CZ3) ^T is a transposed matrix,

(Equation 3) Is the meaning of.

Then, V ^-1 is applied to both sides of the equation (25) to obtain the following equation (26).

V ⁻¹ · V · ΔCZ = V ⁻¹ · F · CZ · Δt + V ⁻¹ · Uz · Δt −V ⁻¹ · Vd · CZ (t) (26)

When the left side of the above equation (26) is rearranged, the following equation (27) is obtained.

ΔCZ = V ⁻¹ · F · CZ · Δt + V ⁻¹ · Uz · Δt−V ⁻¹ · Vd · CZ (t) (27)

Then, the Zn concentration CZi (t +
1) and Zn concentration CZi (t) at time t, CZi, ΔCZ
To express i, we use discrete time representation by the trapezoidal method. In this trapezoidal method, the state variable x that changes from time t to time t + 1 is expressed as x = (x (t) + x (t + 1)) / 2.
It is a method of averaging numerical values. This is x = x (t + 1)
The method is an implicit function method and has high stability, and
Since an intermediate value between the time t and the time t + 1 is used, there is an advantage that the integration time t to t + 1 can be widened easily.

That is, using this discrete time expression, CZi = {CZi (t + 1) + CZi (t)} / 2 (28), and the change in the Zn concentration of the i block between time t and time t + 1. Since ΔCZi [g / l] is ΔCZi = CZi (t + 1) -CZi (t) (29), substituting the equations (28) and (29) into the equation (27) gives the following ( Equation (30) is obtained.

CZ (t + 1) −CZ (t) = V ⁻¹ · F · {(CZ (t + 1) + CZ (t)) / 2} · Δt + V ⁻¹ · Uz · Δt −V ⁻¹・ Vd ・ CZ (t) (30)

Here, the 3 × 3 matrices A, VA and the three-column vector UZ are respectively A = V ⁻¹ · F · Δt (31) UZ = V ⁻¹ · Uz · Δt (32) VA = V ^{When −1} · Vd (33), the equation (30) becomes the following equation (34).

CZ (t + 1) -CZ (t) = A. (CZ (t + 1) + CZ (t)) / 2 + UZ-VA.CZ (t) (34)

In the equation (34), if the terms of CZ (t + 1) are collected on the left side, (I−A / 2) · CZ (t + 1) = (I + A / 2−VA) · CZ (t ) + UZ (35) and the formula for obtaining CZ (t + 1) from CZ (t) is the following formula (36).

CZ (t + 1) = (IA−2) ⁻¹ · {(I + A / 2−VA) · CZ (t) + UZ} (36)

Up to now, a simple case where the number of equipment blocks is 3 has been described as an example, but this can be expressed as follows in a general case where the number of equipment blocks is m.

The bath volume of the i-th block at time t is Vi
[m ³ ], Zn concentration is CZi (t) [g / l], and the liquid flow rate from the i-th block to the j-th block is Fij [m ³ / h]
And

From time t to time t + 1 after Δt [h]
In the i-th block, (1) Uzi [kg / h] speed
There is a balance of Zn between the outside of the circulation system and (2) Usi
[m^Three/ h], there is a water balance between the outside and the circulation system,
(3) As a result, the bath volume Vi [m ^Three] Is ΔVi [m^Three] Increase
Zn concentration CZi (t + 1) [g / l] at time t + 1 when
It looks like this:

However, F, V, Vd, and
A, VA and I are m × m matrices, and CZ, Uz and UZ are
m-dimensional vector, except for the unit matrix I
It is represented by the formulas 7) to (44).

F = (fij) (37) (fij represents an element in the i-th row and j-th column of the matrix, and when i = j, fij = -ΣFik (sum of liquid flow velocities flowing out from the i block) i ≠ j , Fij = Fji (liquid flow velocity from the j block to the i block) (i = 1, ..., m; j = 1, ..., m; k = 1, ..., m)) V = diag. (V1 + ΔV1, ..., Vm + ΔVm) (38) Vd = diag. (ΔV1, ..., ΔVm) (39) A = V ⁻¹ · F · Δt = (aij) (40) (aij represents the i-th row and j-th column element of the matrix A, and aij = {f
ij / (Vi + ΔVi)} × Δt. ) VA = V ^-1 · Vd = diag. (ΔV1 / (V1 + ΔV1), ..., ΔVm / (Vm + ΔVm)) (41) CZ (t) = (CZ1 (t), ..., CZm (t)) ^T ... (42) Uz = (Uz1, ...) , Uzm) ^T (43) UZ = V ⁻¹ · Uz · Δt = ({Uz ¹ / (V 1 + ΔV 1)} × Δt, ..., {Uzm / (Vm + ΔVm)} × Δt) ^T (44)

Using the equations (37) to (44), the general form of the equation (34) becomes the following equation (45).

CZ (t + 1) −CZ (t) = A · (CZ (t + 1) + CZ (t) / 2 + UZ · Δt−VA · CZ (t) (45)

As in the case of the equation (34), the above (4
By collecting CZ (t + 1) on the left side of the equation (5), the Zn concentration estimation model represented by the equation (7) can be obtained. Therefore, the Zn concentration CZ (t + 1) [g / l] at the time t + 1 to be obtained is the Z concentration between the Zn concentration CZ (t) at the time t and the outside of the system between the times t and t + 1.
It can be obtained from the equation (7) from the balance Uz of n, the bath amount at the time t + 1, and the like.

The same calculation principle is applied to the Ni concentration CN [g / l], H
When applied to the 2 SO4 concentration CA [g / l], the respective concentration estimation models represented by the equations (8) and (9) can be obtained.

Next, the calculation procedure using the concentration estimation model consisting of the equations (7) to (9) will be described in detail with reference to FIG.

The calculation of the concentration estimation model is executed, for example, in a cycle of 30 seconds according to the flowchart shown in FIG.

First, in step 1, edit calculation of the block bath amount at time t + 1 is performed. In this step, in principle, the block bath volume at time t + 1 is
Each block of 1 to m that composes the model is aggregated and edited.

At this time, the bath amount of each block is measured by the level meter at the portion where the level meter can be measured. The amount of bath in the pipe can be changed by a predetermined constant according to the operating conditions, and the amount of bath in the pipe is included in the amount of bath in each equipment block.

Further, using the block bath amount at time t, the bath amount change speed for each block from time t to t + 1 is calculated. At that time, if there is a balance of water, it may be taken into consideration in the change in the bath volume of each block.

Next, in step 2, edit calculation of the liquid flow velocity between time t and time t + 1 is performed.

The calculation of the liquid flow velocity is executed for each block based on the liquid flow element calculation table prepared in advance. At that time, the inter-block liquid flow velocity is basically measured by a flow meter, but for a portion where there is no flow rate fluctuation, a constant switching that is determined in advance according to the operating condition may be used. By doing so, it is possible to reduce the equipment cost.

Then, in steps 3 to 6, the balance between t to t + 1 time is calculated for each of Zn, Ni and H2 SO4. This calculation is performed for each equipment block related to the balance.

An example of the basic Zn ion, Ni ion, and H 2 SO 4 balance calculation when calculating the balance for the components related to each block is shown below.

The balance in the plating cell is (A),
The expenditure of Zn ions by the electrodeposition reaction represented by the equation (B) is defined as G
Assuming that the expenditure of z and Ni ions is Gn and the income of H2 SO4 shown in the above equation (C) is Ga, the following can be obtained respectively.

Gz = J × (η / kF) × (1-εN) × (Mz / 2) × 3600 [kg / h] (46) Gn = J × (η / kF) × εN × (Mn / 2) × 3600 [kg / h] (47) Ga = J × (η / kF) × εA × (Ma / 2) × 3600 [kg / h] (48) where J: plating current [KA] η: Plating efficiency kF: Faraday constant εN: Ni content of the plating layer εA: Anode water decomposition rate Mz: Zn atomic weight Mn: Ni atomic weight Ma: H2 SO4 molecular weight

The balance of incidental equipment A (Zn supply equipment) is
Zn income from the Zn dissolution shown in the formula (D) is Sz,
If H2 SO4 expenditure is Daz, it becomes as follows.

Sz = Szc × λzc [kg / h] (49) Daz = (Sz / Mz) × Ma [kg / h] (50) However, Szc: ZnCO3 supply rate [kg / h] λzc: ZnCO3 Zn content of

The balance of incidental equipment B (Ni supply equipment) is
The Ni income by the Ni dissolution shown in the formula (E) is Sn,
If H2 SO4 expenditure is Dan, it becomes as follows respectively.

Sn = Snc × λnc [kg / h] (51) Dan = (Sn / Mn) × Ma [kg / h] (52) where Snc: NiCO3 supply rate [kg / h] λnc: NiCO3 Ni content of

The balance of the incidental equipment C (H2 SO4 supply equipment) is as follows, where H2 SO4 income from the supply of H2 SO4 is Sa.

Sa = Fa × λa [kg / h] (53) However, Fa: H 2 SO 4 supply rate [m ³ / h] λa: H 2 SO 4 concentration [g / l]

Then, in step 6, based on the calculation results executed in steps 1 to 5 described above, (7) to (9)
The calculation by the concentration estimation model of the formula is executed.

At this time, in the present embodiment, the concentration measurement is performed by a densitometer in an arbitrary section, and the following (5
By performing the filtering calculation by the equation 4),
It is possible to suppress the influence of the measurement error of the densitometer body and provide a stable predicted concentration.

That is, in the concentration measurement, a time difference generally occurs between the time when the plating solution is sampled and the time when the measurement is completed. Therefore, it is necessary to correct the error caused by this time difference based on the actual measurement value obtained for the measurement target. This correction is a filtering calculation, and for convenience sake, assuming that the block No. of the circulation tank to be measured is 3, the Zn ion concentration when the plating solution sampling time is t1 and the measurement completion time is t2 Will be described as an example.

Estimated value of Zn ion concentration at time t2 after filtering in three blocks (i = 3): CZCi (t
2) can be obtained by the following equation (54).

CZCi (t2) = CZi (t2) + kf (CZOi (t1) -CZi (t1)) (54) where CZOi (t1): Zn concentration measured value at time tCZi (t1): at time t1 Predicted Zn concentration according to formula (7) CZi (t2): Predicted Zn concentration according to formula (7) at time t2 (latest) kf: Filtering constant

Further, other blocks (j = 1, 2, 4,
... m) can be similarly obtained by the following equation (55) to which the correction value for the measurement target is applied.

CZCj (t2) = CZj (t2) + kf (CZOi (t1) -CZi (t1)) (55)

By doing so, the plating concentration after filtering can be obtained for each block based on the measured value of the zinc ion concentration at one location.

The above-mentioned constant kf used in this filtering calculation is a value of 0 to 1, and a value close to 1 is obtained as the actual concentration is stable and the model accuracy is poor, and on the contrary, the actual concentration is unstable,
The closer to 0 the better the model accuracy is set.

The Ni concentration and the H2 SO4 concentration can also be obtained by the same filtering method.

According to this embodiment described in detail above, based on the density value of each block of 1 to m estimated by the density estimation model of the above equations (7), (8) and (9), the above (54) ,
Zn ion, Ni ion, H 2 SO 4 obtained by using the equation (55) and the equations for the other two components corresponding thereto.
Each filtering calculation density of: CZCi, CNCi, C
Using ACi, the average concentration of the entire plating facility can be calculated by the following equations (56), (57), (58). Then, by determining the feedback (FB) control amount from the deviation between the average concentration value and the target value, the FB control operation that is erroneous from the concentration change unique to the measurement location is suppressed while considering the concentration change due to the reaction. It is possible to realize highly accurate concentration control at calculation cycle intervals.

[0104]

(Equation 4) However, Vall = sum of partial bath volumes V1 to Vm of each block

According to the present embodiment described in detail above, it is possible to suppress an erroneous control operation due to a change in concentration peculiar to the measurement location, suppress variation in the measurement values by the densitometer, and obtain a stable concentration measurement value. Can be used to control the plating concentration. Further, since the concentration of the plating solution can be controlled with high accuracy, the plating efficiency can be stabilized, and the quality of the deposited amount and the Ni content can be improved.

Further, according to the present embodiment, when the densitometer records an abnormal measured value, the densitometer compares with the predicted concentration,
It is possible to monitor abnormalities in concentration measurement values. Also, due to the prediction accuracy, the measurement cycle of the densitometer can be extended,
The running cost of the densitometer can also be reduced.

Although the present invention has been specifically described above, the present invention is not limited to the one shown in the above embodiment, and various modifications can be made without departing from the spirit of the invention.

For example, in the above-mentioned embodiment, a specific example of plating is Zn-Ni alloy plating, but the present invention is not limited to this, and pure Zn plating or iron-based plating is not particularly limited. Even in the case of Zn-Ni alloy plating,
The metal agents used are not limited to ZnCO3 and NiCO3,
It may be ZnO, metallic Zn, metallic Ni, or the like.

Further, as the concrete continuous electroplating equipment, although the equipment consisting of 9 blocks is shown in FIG. 1, it goes without saying that the equipment is not limited to this.

[0110]

As described above, according to the present invention,
It is possible to accurately estimate the average concentration of the entire plating solution necessary for appropriately controlling the concentration of the plating solution in the continuous electroplating equipment.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of continuous electroplating equipment applied to one embodiment according to the present invention.

FIG. 2 is an explanatory diagram used to derive a concentration estimation model.

FIG. 3 is a flowchart showing a calculation procedure based on a concentration estimation model.

[Explanation of symbols]

 1-3 ... Plating cell 4-6 ... Circulation tank 7 ... Ancillary equipment A 8 ... Ancillary equipment B 9 ... Ancillary equipment C 10 ... Level meter 11 ... Flowmeter 12 ... Concentration meter S ... Steel plate

Claims (4)

[Claims] 1. A plating in a continuous electroplating facility comprising one or more plating cells for continuously plating a conveyed strip, and ancillary equipment for supplying a plating solution component while circulating a plating solution in the plating cell. In the solution concentration estimation method, the continuous electroplating equipment is divided into multiple equipment blocks, and each equipment block considers the expenditure of plating solution components by plating and the substance balance considering the effect of the income of plating solution components due to the supply of component materials. A plating solution concentration estimation method for continuous electroplating equipment, characterized in that a concentration estimation model based on a model is constructed and the concentration estimation model is used to estimate the plating solution concentration of each equipment block. 2. When the continuous electroplating equipment is divided into m equipment blocks according to claim 1, Zn concentration of 1 to m blocks at time t of the previous calculation:
CZ (t), Ni concentration: CN (t), H2 SO4 concentration: CA
(t) is described by the following matrix having the density value in each block as an element, and CZ (t) = (CZ1 (t), ..., CZm (t)) ^T CN (t) = (CN1 (t), ..., CNm (t)) ^T CA (t) = (CA1 (t), ..., CAm (t)) ^T t-t + 1 Zn balance amount of 1 to m blocks during time: U
z, Ni balance amount: Un, H2 SO4 balance amount: Ua is described by the following matrix having the balance amount in each block as an element: Uz = (Uz1, ..., Uz1) ^T Un = ( Un1, ..., Unm) ^T Ua = (Ua1, ..., Uam) ^T t + 1 Zn concentration in 1 to m blocks at time: CZ (t + 1)
, Ni concentration: CN (t + 1), H2 SO4 concentration: CA (t + 1)
The concentration estimation model for estimating CZ (t + 1) = (IA−2) ⁻¹ × {(I + A / 2−VA) × CZ (t) + UZ} CN (t + 1) = (I− A / 2) ^-1 x {(I + A / 2-VA) x CN (t) + UN} CA (t + 1) = (I-A / 2) ^-1 x {(I + A / 2-VA) x CA ( t) + UA} where I: m-th order unit matrix A = V ⁻¹ × F × Δt V ⁻¹ : Block bath volume diagonal inverse matrix (m × m) F: Interblock liquid flow velocity matrix (m × m) Δt : T to t + 1 elapsed time VA = V ^-1 x Vd Vd: block change bath amount diagonal matrix (m x from t to t + 1)
m) UZ = V ⁻¹ × Uz × Δt UN = V ⁻¹ × Un × Δt NA = V ⁻¹ × Ua × Δt The plating solution concentration estimation method in continuous electroplating equipment. 3. When the concentration measurement of the plating solution is completed after a predetermined time has elapsed after sampling the plating solution in one or more arbitrary equipment blocks according to claim 1, A method for estimating the concentration of a plating solution in a continuous electroplating facility, characterized in that the estimated concentration is corrected by filtering calculation based on the difference between the actually measured concentration and the estimated concentration of the same model at the time of sampling. 4. The continuous electroplating according to claim 1, wherein the average concentration of the plating solution in the entire continuous electroplating equipment is estimated based on the estimated plating solution concentration of each equipment block and the bath amount in the block. Method for estimating plating solution concentration in equipment.