KR100419630B1 - System configuration methods for the optimized control of the radial conductor roll profile with the conductor roll cooling system - Google Patents

Abstract

The present invention is an electroplating roll to adjust the step of the conductor portion and the rubber coating on the surface of the conductor roll by changing the temperature of the roll cooling water according to the working conditions in the electroplating equipment using the cylindrical electroplating conductor roll using a mathematical model It relates to a step control apparatus and method of the. To this end, the present invention is the electroplating roll step control apparatus in the cooling system of the cylindrical electroplating roll, the central portion is made of a metal conductor and its peripheral portion is a rubber-coated ring,

When the electroplating roll is processed, the initial step of the metal part and the rubber coating part is calculated by a predetermined mathematical model, and after the electroplating roll processed with the calculated initial step is applied to the cooling system, the pressure between the steps of the electroplating roll is applied. Comprising a control model for varying the temperature of the cooling water for cooling the electroplating roll so that the difference is calculated by a predetermined mathematical model to maintain the pressure difference between the steps within a predetermined range.

Description

SYSTEM CONFIGURATION METHODS FOR THE OPTIMIZED CONTROL OF THE RADIAL CONDUCTOR ROLL PROFILE WITH THE CONDUCTOR ROLL COOLING SYSTEM}

The present invention relates to an apparatus and method for controlling a step of an electroplating roll, and more particularly, in an electroplating installation using a cylindrical electroplating conductor roll, by changing a temperature of a roll cooling water according to a working condition using a mathematical model. An apparatus and method for controlling a step of an electroplating roll adapted to adjust a step between a conductor part and a rubber coating part of a conductor roll surface.

Cylindrical electroplating apparatus has the advantage of reducing the voltage drop caused by the steel strip by minimizing the distance between the conductor roll and the strip (strip) flowing the plating current has a small power consumption to obtain the same plating amount. In addition, since only one side of the strip is plated at a time, it is easy to apply different plating conditions to both sides of the strip.

1 is a view showing a structure of such a general cylindrical electroplating apparatus and a conductor roll, Figure 2 is a cross-sectional view showing the configuration of the conductor roll of FIG. In general, such an electroplating apparatus is composed of a conductor roll (3) for applying electricity to the metal strip (2) to be plated in the electroplating tank (1) in which the plating solution circulates, and the plated metal opposite thereto. The anode 4 is placed, and the high-capacity roll 5 for assisting the running of the metal strip 2 is configured to be located outside the electroplating tank.

In such an electroplating apparatus, the conductor roll 3 is heated at the center of the roll 50-200 mm narrower than the minimum width of the steel strip to be plated with the conductor metal having corrosion resistance to the plating liquid on the general carbon steel SS41 of the base portion 33. It is composed of a structure that covers the remaining peripheral part with insulating rubber such as urethane. As a result, the plating current flows through the metal band in contact with the conductive portion of the conductor roll, and electricity can not flow through the remaining portions. In such a conductor roll, it is most ideal that the heights of the metal conductive portion 31 and the rubber insulation portion 32 in contact with the metal band are as equal as possible. However, since the metal conductive portion 31 and the rubber insulation portion 32 have a difference in thermal expansion rate, the relative height varies according to the change in operating temperature. Therefore, the metal conductive portion 31 and the rubber insulation portion 32 are processed to have a constant step in consideration of thermal expansion at the operating temperature during processing. . That is, since the thermal expansion rate of rubber is generally higher than that of metal and the usual plating operation temperature is higher than the normal temperature of the processing temperature, the (+) step processing is performed so that the height of the metal conductive portion 31 is slightly higher than that of the rubber insulation portion 32. It is common to carry out.

However, since the normal electroplating operation is performed in the range of 30 ° C. to 80 ° C. slightly higher than the normal temperature, the temperature profile of the inner and outer surfaces of the roll is different in the case of the conductor roll composed of metal and rubber whose surface is different in thermal conductivity and linear expansion rate. By forming differently, the step difference between the metal part and the rubber is changed depending on the operating conditions. Accordingly, when the metal ring part 31 rises higher than the rubber coating part 32 under a certain plating operation condition (+ step), the metal ring part 31 is pressed by the difference in the pressing pressure applied to the flexible plated surface wound on the conductor roll 3. The traces appear on board. On the contrary, when the rubber covering part 32 is raised higher than the metal ring part 31 (-step), an arc is likely to occur between the conductor roll and the plated surface.

In order to solve this problem, various methods for optimizing the shape and material of the stepped portion of the conductor roll of the cylindrical electroplating apparatus have been proposed. In addition, a method is also proposed in which hot water or the like is sprayed on the surface of the conductor roll to be heated to a temperature to be used and then subjected to step processing. However, this method can be applied by the + step and the arc due to the + step in all the step ranges that change according to the heat generation of the conductor roll, the change of the temperature of the plating solution, and the change of the coolant temperature inside the conductor roll. It does not provide a condition to prevent this.

As a more advanced active method, a method of controlling the temperature of a roll coolant by setting the level difference of a conductor roll surface and controlling the level to a set value has been proposed (Domestic Patent Publication No. 88-12800). This method uses a kind of sensor to measure the level on the surface of the conductor roll and, based on this information, adjusts the temperature of the coolant so that the level is equal to the set point. However, this method has the problem that it is extremely difficult to mount a device for directly measuring the step height of the conductor roll surface in a cylindrical electroplating bath in which a large amount of corrosive vapor is generated. In addition, the step information of the cylindrical conductor roll measured at the unsensed area does not provide enough information to adjust the pressure difference near the step boundary of the coiled area which causes the pressed plate of the actual plated steel strip. There is a problem that it is difficult to adjust the cooling conditions of the roll based on this information.

Accordingly, the present invention has been made to solve the above-mentioned conventional problems, the purpose of which is to improve the surface quality problems of plated steel, such as pressed marks, arcs caused by the step of the conductor roll in the cylindrical electroplating apparatus We propose a method of setting the appropriate initial step that is different from the material and thickness of the conductor roll, and present a predictable model for the step roll profile of the conductor roll that varies according to the initial step and operating conditions. It is an object of the present invention to provide an apparatus and a method for controlling the step of an electroplating roll to maintain an optimum step regardless of a change in operating conditions by controlling the coolant temperature and flow rate inside the conductor roll.

1 is a view showing the structure of such a general cylindrical electroplating apparatus and the conductor roll.

FIG. 2 illustrates a cross-sectional view of the conductive roll of FIG. 1.

Figure 3 shows an example of the step change of the electro-galvanized conductor roll according to the cooling water supply temperature.

Figure 4 is an exemplary view showing a change in the operating conditions of the pressure distribution of the conductor roll and the metal-to-contact portion.

Fig. 5 shows the correlation between the step difference profile and the pressure difference between the cylindrical electroplating conductor roll metal-to-contact portion and the occurrence of plated metal plate defects.

Figure 6 schematically shows a system configuration of the step control apparatus of the electroplating roll for implementing the present invention.

Explanation of symbols on the main parts of the drawings

1, electroplating bath, 2 ... metal strip,

3 ... conductor roll, 4 ... anode,

5 ... rubber roll, 6 ... cooling water circulation tank,

7 circulating pump, 8 filter,

9 ... heat exchanger, 10 ... control model,

21,22,23 ... temperature detector, 31 ... metal part,

32 ... rubber covering, 33 ... base.

In order to achieve the above object, the step control apparatus for electroplating rolls according to the present invention has a step of electroplating rolls in a cooling system of a cylindrical electroplating roll, in which a central portion is a metal conductor and a peripheral portion thereof is a rubber-coated ring. In the control unit,

When the electroplating roll is processed, the initial step of the metal part and the rubber coating part is calculated by a predetermined mathematical model, and after the electroplating roll processed with the calculated initial step is applied to the cooling system, the pressure between the steps of the electroplating roll is applied. It is characterized by having a control model for predicting and calculating the difference by a predetermined mathematical model and varying the temperature of the cooling water for cooling the electroplating roll so that the pressure difference between the steps is kept within a predetermined range.

Hereinafter will be described in detail with reference to the accompanying drawings the configuration and effect of the step control apparatus and method of the electroplating roll according to the present invention.

First, in order to implement the present invention, a step measurement system using a laser displacement sensor was constructed to directly investigate the profile change of the conductor roll, and as a result, the step profile of the metal part and the rubber coating of the conductor roll was sensitive to the temperature difference between the roll and the roll. It was confirmed that the change.

However, the measurement of the step profile by this direct method during plating operation has many limitations in terms of signal disturbance caused by the vapor generated in the plating bath, durability of the measurement system, etc. Is difficult. Therefore, through theoretical analysis and experimental means, it is possible to control the step difference by predicting the conductor roll profile of the cylindrical electroplating device from the information on the configuration and operating conditions of the initial conductor roll step. First of all, through theoretical analysis, the method of constructing the stepped portion and the change of conductor roll profile according to the operating conditions are investigated.

Figure 3 shows an example of the step change of the electro-galvanized conductor roll according to the cooling water supply temperature. As shown in FIG. 3, a condition (■, ●, ▲) where the metal strip is not in contact and thus no pressure is applied to the outside of the conductor roll 3 and a condition where the metal strip is in contact with the roll and a pressure is applied to the outside of the roll ( The thermal expansion amount of each of the conductive and insulating portions of the roll in □, ○, △) depends on the material properties and the coolant temperature conditions inside the roll. That is, when pressure is not applied to the outer surface of the roll, the coefficient of linear expansion becomes an important index, and as a rule, the coefficient of displacement tends to increase as the coefficient of linear expansion increases (Hastelloy-> Ebonite-> Multilastic-> Urethane).

On the other hand, when the pressure is applied to the outer surface of the roll, the final coefficient of displacement cannot be predicted only by the coefficient of linear expansion because the modulus of elasticity of the coating material has another influence in addition to the coefficient of linear expansion. In other words, based on the step information measured while the steel strip is not hung (without pressure on the outer surface of the roll), the part where the steel coil is wound to induce the appearance quality defect of the actual plating surface (when pressure is applied to the outer surface of the roll) It is not possible to maintain optimal conditions.

However, as can be seen in FIG. 3, the change in the coolant temperature on the inner surface of the roll becomes an important variable that can control the final displacement amount regardless of whether pressure is applied to the outer surface of the roll. In other words, when the center is made of metal ring and the periphery is made of rubber coating, such as the conductor roll of the cylindrical electroplating device, the initial step (when the metal is higher than the rubber coating) is greatly reduced by increasing the temperature of the cooling water. do. In addition, when pressure is applied to the roll surface, that is, when the steel strip surrounds the conductor roll, the rubber coating portion shrinks smaller as the cooling water temperature is increased. Accordingly, it is possible to maintain the proper step profile by predicting the surface step profile of the conductor roll composed of each material from the pressure, operating temperature, and coolant temperature of the roll surface and adjusting the temperature and flow rate of the coolant based on this information. .

On the other hand, Figure 4 is an exemplary view showing a change in the operating conditions of the pressure distribution of the conductor roll and the metal-to-contact portion. As shown in Fig. 4, the step between the metal conductor portion and the rubber coating portion at the portion where the tensioned metal band surrounds the conductor roll shows a value close to zero when properly set. For example, in FIG. 4, when the initial step of the metal conductor portion 31 and the rubber-coated insulation portion 32 is set to 0.3 mm, and the pressure applied to the metal stand 2 is 5.0 kgf / mm ² , the plating liquid temperature 60 The pressure difference applied to the metal strip 2 in which the metal conductive portion 31 and the rubber coating portion 32 are in contact with each other under the condition of 40 ° C. and a cooling water temperature of 40 ° C. indicates a value of 8 to 12 MPa depending on the material of the rubber.

These conditions also depend on the temperature of the plating liquid, the temperature of the conductor roll cooling water, and the magnitude of the tension applied to the metal band, and the pressure for zeroing the level difference between the metal part 31 and the rubber coating part 32 of the conductor roll metal band contact portion is zero. Depending on the difference, an arc or pressed mark is generated.

Fig. 5 shows the correlation between the step difference profile and the pressure difference between the cylindrical electroplating conductor roll metal-to-contact portion and the occurrence of plated metal plate defects. As shown in FIG. 5, the initial + step of the conductive roll metal conductive part and the rubber coating part decreases as the difference between the plating liquid temperature and the cooling water temperature increases, and when converted to − above a certain condition, an arc occurs on the surface of the plated metal plate. On the contrary, the pressure difference between the metal conductor portion of the metal band wrapped around the conductor roll and the rubber coating portion forms the plated layer press marks under the condition that the plating liquid temperature and the cooling water temperature are below a certain value. Thus, it can be seen that there are certain conditions for obtaining good plating surface quality at a given initial step and operating conditions.

Based on the theoretical and basic experimental results, numerical modeling and experiments were carried out to devise the initial step setting method of the conductor roll of the cylindrical electroplating apparatus and maintain the proper step profile by controlling the coolant temperature and flow rate. For this study, it was found that the thermal expansion amount of the metal part and the rubber coating part is proportional to the temperature difference, the linear expansion coefficient, and the thickness of the coating part inside and outside the conductor roll. That is, according to the study in the present invention, the difference δ of the thermal expansion amount of the metal part and the rubber coating part can be expressed as the following Equation 1 as a function thereof.

On the other hand, when the temperature of the cooling water and the plating solution of the conductor roll changes in a certain range, the maximum value δ _max of δ can be expressed by adding the following factors.

Accordingly, it is preferable that the initial step δ ₀ at the normal temperature processing of the conductor roll is designed as in Equation 3 below so as not to exceed the δ _max value given by Equation 2 in the operating range to be controlled.

In Equations 1,2,3 Allowable maximum and minimum temperature for each plating solution, Is the set maximum and minimum temperature of the conductor roll cooling water, T ₀ is the step machining temperature when manufacturing the conductor roll, α _m , α _r is the average linear expansion coefficient of the metal ring and the rubber-coated area, D is the average diameter of the conductor roll ring, Δt Is the thickness of the rubber-covered part, and C ₁ is experimentally determined by a constant ranging from 0.001 to 0.005.

On the other hand, the displacement of the outer periphery of the roll according to the pressure P applied to the metal ring and the rubber coating at the portion where the metal band surrounds the conductor roll can be modeled by the following equation.

The outer peripheral part displacement _{(mm) = C 2 + C} 3 · P (MPa)

In Equation 4, C ₂ is a factor depending on the plating liquid temperature and the roll cooling water temperature, and C ₃ is a factor depending on the material properties of the conductor roll coating, and C ₂ = 0.2 to 1.5 and C ₃ = 0.05 at normal operating conditions, respectively. It is a constant in the range of 0.15.

Accordingly, the condition that the outer periphery of the metal portion and the rubber coating portion in the portion of the conductor roll wrapped around the metal strip may be expressed as in Equation 5 below.

C2, r + C3, rPr = C2, m + C3, mPm + δ0

Therefore, the pressure difference (P _m -P _r ) between the steps of the metal part and the rubber coating part can be expressed by Equation 6 below.

In Equations 5 and 6, the subscripts r and m denote rubber coating portions and metal portions, respectively, and δ ₀ is an initial step.

On the other hand, when the pressure difference between the steps predicted using Equation 6 exceeds a certain threshold, it was possible to confirm the tendency of the pressing mark to be clear. In addition, the threshold value tends to decrease as the hardness of the plating layer decreases and the amount of plating increases. Therefore, the stable operating condition represented by Equation 6 may be expressed by Equation 7 below.

Pressure difference between steps (MPa) <C ₄ Plated layer Knoop hardness (Hk) / Plating amount (g / m2)

In Equation 7, C ₄ is an experimentally determined constant and is a value between 3.0 and 10.0.

Hereinafter, the operation and the effect of the step control apparatus and method of the electroplating roll according to the present invention based on the results obtained through the above-described mathematical model and experiment will be described with reference to the accompanying drawings.

Figure 6 schematically shows a system configuration of the step control apparatus of the electroplating roll for implementing the present invention. As shown in FIG. 6, in the step control apparatus of the electroplating roll for implementing the present invention, the coolant circulating in the conductor roll is exchanged with the filter 8 and the heat exchanger by the circulation pump 7 from the coolant circulation tank 6. It is supplied via group 9. The temperature of the conductor roll cooling water is configured to operate the heat exchanger to maintain the cooling water inlet temperature calculated by the control model 10 based on the initial step, the plating current, the plating liquid temperature, and the cooling water discharge temperature. The filter 8 is installed for the purpose of removing oxides and impurities generated inside the conductor roll, and a heater 11 as an example of a heater 11 inside or outside the cooling water circulation tank 6 for adjusting the initial cooling water temperature during operation. Is composed.

On the other hand, after cooling the electroplating roll, the cooling water output temperature detector 21 for detecting the temperature of the cooling water discharged to the cooling water circulation tank 6, and the plating liquid temperature detector for detecting the plating liquid temperature inside the electroplating tank 1 ( 22) and a coolant input temperature detector 23 for detecting a coolant input temperature supplied from the heat exchanger 9 to the electroplating roll 3 side. Therefore, the control model 10 receives the initial step value, the plating current, and the coolant temperature and the plating liquid temperature detected through the temperature detectors 21 to 23, calculates the pressure difference between the steps of the electroplating roll, and The cooling water temperature is controlled to maintain the pressure difference within a certain range. That is, the temperature of the cooling water supplied to the inside of the conductor roll through the heat exchanger 9 is controlled by controlling the driving of the heating medium so that the difference between the cooling water temperature and the plating liquid temperature is within a certain range, that is, the pressing marks and the step of generating the electroplating roll. Controlled to be maintained at a temperature within the range of no arcing.

On the other hand, the initial step input to the control model is the metal part of the electroplating roll corresponding to the initial step value calculated as calculated as a constant value in the machining step of the electroplating roll as described in Equation 1, 2, 3 above And after the step of the rubber coating is formed is put into the electroplating process.

After the electroplating process, as described above, the pressure difference between the steps is calculated, and the step of controlling the electroplating roll is performed by controlling the coolant temperature so that the pressure difference between the steps is maintained within a predetermined range.

Hereinafter, the step control method of the electroplating roll according to an embodiment of the present invention.

The initial step was set as shown in Table 1 by using Hastelloy as a metal ring of a conductor roll having a diameter of 2240 mm and having a carbon base of 60 mm in thickness, using urethane rubber and hydrogenated neobutyl rubber (H-NBR). Zinc plating was performed in a hydrochloric acid-based plating solution at a temperature of 60 to 70 ° C. using a conductive roll having. At this time, the coefficient of the model for controlling the internal temperature of the conductor roll was set as shown in Table 1, and the control was performed, and the degree of plating pressing mark and the occurrence of arc of the final product were evaluated.

Example Band thickness Step setting Plating condition Control constant quality Remarks Metal stand Rubber coating urethane HNBR Constant C1 Step (mm) Plating Bath (℃) Plating amount (g / m2) C2m C3m C2r C3r C4 pressed Arc One 24 20 - 0.003 0.25 60 30 0.28-0.32 0.07- 0.15 0.42- 0.50 0.10- 0.30 5.0 none none Inventive Example 2 24 20 - 0.003 0.38 65 30 0.28-0.32 0.07- 0.15 0.42- 0.50 0.10- 0.30 8.0 Minor none 3 24 20 - 0.003 0.38 70 30 0.28-0.32 0.07- 0.15 0.42- 0.50 0.10- 0.30 8.0 Minor none 4 24 - 20 0.003 0.19 60 30 0.28-0.32 0.07- 0.15 0.42- 0.50 0.10- 0.30 5.0 none none 5 24 - 20 0.003 0.28 65 30 0.28-0.32 0.07- 0.15 0.42- 0.50 0.10- 0.30 8.0 none none 6 24 - 20 0.003 0.28 70 30 0.28-0.32 0.07- 0.15 0.42- 0.50 0.10- 0.30 8.0 Minor none 7 24 20 - - 0.15 60 30 - - - - - Minor Occur Comparative example 8 24 20 - - 0.50 60 30 - - - - - Severe none 9 24 - 20 - 0.20 60 30 - - - - - Intermittent Intermittent

In the above embodiment, the constant C1 for setting the initial step was set to 0.003, and the appropriate step for each material was set by setting the normal operating temperature range of the plating solution to 5 to 10 ° C. In addition, the constant C4 necessary for setting the control target was experimentally set to a value between 5.0 and 8.0.

Examples 1, 2, and 3 were made of urethane rubber with rubber coating, and in case of plating solution temperature of 60 ° C, by applying a control model, galvanized products of good surface quality without plate traces and arc generation were obtained. Only slight pressing traces could be generated during 65 ~ 70 ℃ operation. In addition, in Examples 4, 5, and 6, the rubber coating part was composed of hydrogen-reinforced neobutyl rubber, and at the plating bath temperature of 60 to 65 ° C., a product having no traces of plating layer depression and arc generation was obtained by applying a control model. Only slight signs of depression occurred even at 70 ° C operation. On the other hand, Comparative Example 7, 8 is the case where the initial step setting is improperly set, the pressing trace and arc generation were a problem, and Comparative Example 9 is the case that the initial step setting is appropriate, but does not apply the control model of the present invention intermittently Press marks and arc generation occurred to obtain a good product.

Apparatus and method for controlling the step of the electroplating roll according to the present invention can be implemented in various modifications within the range allowed by the technical idea of the present invention without being limited to the above-described embodiment.

As described above, the apparatus and method for controlling the step of the electroplating roll according to the present invention is to improve the surface quality problems of the plated steel plate, such as pressing marks, arcs, etc. caused by the step of the conductor roll in the cylindrical electroplating apparatus. We present a method for setting the appropriate initial step, which is different from the material and thickness of the roll, and a predictable model without the direct measurement of the step profile of the conductor roll that varies according to the initial step and the operating conditions. Therefore, by calculating the pressure difference between the initial step and the step by the control model according to the present invention and by controlling the coolant temperature and flow rate inside the conductor roll according to the calculated result, the optimum step is always obtained regardless of the change in the operating conditions. It can maintain and obtain the effect of improving the surface quality of the plated steel sheet.

Claims (4)

In the electroplating roll step control apparatus in a cooling system of a cylindrical electroplating roll, the central portion of which is a metal conductor and its peripheral portion is a rubber-coated ring. When the electroplating roll is processed, the initial step of the metal part and the rubber coating part is calculated by a predetermined mathematical model, and after the electroplating roll processed with the calculated initial step is applied to the cooling system, the pressure between the steps of the electroplating roll is applied. Electroplating roll step control characterized in that it comprises a control model for predicting and calculating the difference by a predetermined formula model and varying the temperature of the coolant for cooling the electroplating roll so that the pressure difference between the steps is maintained within a predetermined range. Device. The method of claim 1, wherein the control model An apparatus for controlling a step of an electroplating roll, wherein an initial step δ ₀ of a metal conductor ring and a rubber-coated ring is calculated by the following equation during the processing of the electroplating roll. (One) (At this time, Allowable maximum and minimum temperature for each plating solution, Is the set maximum and minimum temperature of the conductor roll cooling water, T ₀ is the initial step machining temperature when manufacturing the conductor roll, α _m , α _r is the average linear expansion coefficient of the metal ring and the rubber coated area, D is the average diameter of the conductor roll ring, Δt is the thickness of the rubber-coated site, C ₁ is a constant in the range of 0.001 to 0.005). The method of claim 1, wherein the control model When the processed electroplating roll is applied to the electroplating apparatus and the electroplating is started, the pressure difference (MPa) between the steps of the conductor roll metal part and the rubber coating part is calculated by the following Equation 2, Step control apparatus for an electroplating roll, characterized in that the temperature of the plating liquid coolant is adjusted so that the calculated control target value satisfies the condition of Equation 3 below. --- (2) Pressure difference between steps (MPa) <C ₄ Plated layer Knoop hardness (Hk) / Plating amount (g / m ² ) --- (3) (However, Pm is the pressure applied to the surface of the conductor roll wrapped with metal, C ₂ is a constant value depending on the plating liquid temperature, roll cooling water temperature, C ₃ is a constant value depending on the material properties of the conductor roll coating, C ₄ is an experimentally determined constant, and the subscripts r and m represent rubber coating and metal parts. In the method of controlling the electroplating roll step in the cooling system of the cylindrical electroplating roll, the center portion of which is made of a metal conductor and its peripheral portion is made of a rubber-coated ring. When the electroplating roll is processed, the initial step of the metal part and the rubber coating part is calculated by Equation 1 below. --- (One) (At this time, Allowable maximum and minimum temperature for each plating solution, Is the set maximum and minimum temperature of the conductor roll cooling water, T ₀ is the initial step machining temperature when manufacturing the conductor roll, α _m , α _r is the average linear expansion coefficient of the metal ring and the rubber coated area, D is the average diameter of the conductor roll ring, Δt is the thickness of the rubber-covered part, C ₁ is a constant in the range of 0.001 to 0.005) After the electroplating roll processed to the calculated initial step is applied to the cooling system, the pressure difference between the steps of the electroplating roll is calculated by Equation 2 below. --- (2) Pressure difference between steps (MPa) <C ₄ Plated layer Knoop hardness (Hk) / Plating amount (g / m ² ) --- (3) (However, Pm is the pressure applied to the surface of the conductor roll wrapped with metal, C ₂ is a constant value depending on the plating liquid temperature, roll cooling water temperature, C ₃ is a constant value depending on the material properties of the conductor roll coating, C ₄ is an experimentally determined constant, and the subscripts r and m represent rubber coating and metal parts. Electroplating roll step control method characterized in that for varying the temperature of the cooling water for cooling the electroplating roll so that the pressure difference between the steps is maintained within the range calculated by the equation (3).