JP5418254B2 - Electric plating processing method - Google Patents

Description

  The present invention relates to a re-plating technique for performing re-plating by passing through a continuous processing line for performing electro-plating such as electrogalvanizing.

  In the case where a steel plate that has already been subjected to electroplating does not satisfy the target plating standard due to poor appearance such as uneven plating, conventionally, the plating that has already been applied is completely dropped and then replated. For example, Patent Document 1 and Patent Document 2 disclose a method of re-plating a zinc-nickel alloy plated steel sheet. In Patent Document 1, the plating is dissolved by pickling treatment with a high-concentration pickling treatment solution, and then the surface is ground with water washing and a brush roll to completely drop the plating, and then pickled again to perform plating. Yes. On the other hand, in Patent Document 2, after degreasing, pickling with weak hydrochloric acid is performed to dissolve the surface plating, and surface grinding is performed with a brush roll, and then re-plating is performed.

JP-A-60-141882 JP-A-64-83687

In the conventional technique in which the plating is completely removed after the plating is completely removed as in Patent Document 1, it takes time to remove the plating, surface grinding is required, and the pickling solution concentration and the number of times need to be changed a plurality of times. . For this reason, the subject that the line which drops the already applied plating is needed apart from the plating processing line occurs.
In addition, when the re-plating process is performed in the same line as a normal electric plating process line, when dropping the plating, for example, by passing the steel sheet through the plating process line with the electric plating part in a non-energized state, The plating will be gradually dropped in the washing tank. Even in this case, as described in the above-mentioned prior art, the plating cannot be completely removed by passing the pickling tank once. That is, in order to reduce the plating, it is necessary to pass through the plating processing line a plurality of times, which takes man-hours. Further, the surface of the steel sheet is dissolved non-uniformly by pickling, and the appearance is deteriorated. Furthermore, when the electroplating portion is passed through in a non-energized state, the appearance of the steel plate may be deteriorated even if the surface of the steel plate is roughened by sulfuric acid or the like in the plating solution. For this reason, the higher the appearance standard of the target plating is, the more difficult it is to deal with re-plating.

Also, usually, when re-plating is performed with the plating remaining, Pb contained in a small amount in the plating solution is preferentially precipitated, and blackening resistance tends to deteriorate, and the color tone of the appearance is emphasized. Problems arise in applications.
The present invention has been made in consideration of the above points, and an object of the present invention is to enable a re-plating process with reduced man-hours and excellent blackening resistance.

In order to solve the above-mentioned problem, the invention described in claim 1 of the present invention is a reference current which is a current density set in advance in a pickling treatment section and a steel plate portion which contains a plating solution and is immersed in the plating solution. By using an electroplating treatment facility that applies electroplating to a steel sheet by passing it through a continuous treatment line comprising an electroplating section equipped with a multi-stage electroplating treatment tank that conducts electricity at a density, It is an electroplating treatment method in which the applied steel plate is passed through the continuous treatment line and re-plating treatment is performed,
Among the plurality of electroplating treatment tanks, at least the current density in the first electroplating treatment tank to be energized was set to a high current density higher than the upper limit value of the reference current density, and the high current density was set. When the electroplating treatment tank is not the lowermost electroplating treatment tank, energization of all the lower electroplating treatment tanks at a current density lower than the above-mentioned high current density is performed. It is characterized by being set to a state.

Here, the “reference current density” is a current density that is set when an unplated steel sheet is plated.
The “upper limit value of the reference current density” refers to the reference current density having the largest value among the reference current densities set in each electroplating treatment tank.

Next, the invention described in claim 2 is characterized in that the high current density is 50 [A / dm ² ] or more with respect to the configuration described in claim 1.
Next, the invention described in claim 3 is the same as that described in claim 1 or claim 2 except that the electric plating treatment tank set at the high current density is not used as the lowest electric plating treatment tank. In this electroplating treatment tank, the current density is adjusted to 5 [A / dm ² ] or more and 20 [A / dm ² ] or less, and the electroplating for color tone adjustment is performed.

Next, the invention as set forth in claim 4 is a multi-stage electric circuit for conducting energization at a reference current density that is a preset current density in a pickling treatment section and a steel plate portion that contains the plating solution and is immersed in the plating solution. By using an electroplating treatment facility that applies electroplating to the steel sheet by passing it through a continuous treatment line having an electroplating unit equipped with a plating treatment tank, the steel plate that has already been electroplated is added to the continuous treatment line. An electric plating processing method for performing re-plating processing after passing through a plate,
Only the surface layer of the plating that has already been applied is activated by pickling in the pickling treatment section, and then the plating equivalent to or larger than the removal by pickling is performed in the electric plating section above the reference current density. It is characterized by carrying out electroplating at a high current density.
Next, the invention described in claim 5 is a coating process in which the continuous processing line is provided with a roll coater downstream of the electroplating portion with respect to the configuration described in any one of claims 1 to 4. It is characterized by providing a part.

According to the present invention, the re-plating process can be performed by passing through the plating process line once, and the blackening resistance is also good. For this reason, the man-hour for re-plating can be suppressed.
Moreover, by performing electroplating for re-plating at a high current density, precipitation of Pb from the plating solution is suppressed, and a high-quality plated steel sheet can be manufactured.

It is a conceptual diagram explaining the continuous processing line equipment which concerns on embodiment based on this invention. It is a figure explaining the structure of the electroplating processing tank which concerns on embodiment based on this invention. It is a figure explaining the coater apparatus main body which concerns on embodiment based on this invention. It is a figure which shows the result of 1st Example.

Next, an embodiment according to the present invention will be described with reference to the drawings.
FIG. 1 is a conceptual diagram showing a continuous processing line facility used in the present embodiment.
Here, in the continuous processing line equipment of the embodiment described below, an example in which the coating processing unit 7 is provided downstream of the electric plating unit 5 will be described. However, the electric plating unit 5 and the coating processing unit 7 may not be provided in one line. That is, it is not necessary to provide the coating processing unit 7 in a continuous processing line facility described later.

(Equipment configuration)
The continuous processing line equipment of this embodiment can use the usual electric plating equipment which has a pickling processing part and an electric plating processing part, the equipment which has a coating part, etc. further. An example is shown in FIG. As shown in FIG. 1, the following equipment is arranged in order from the upstream side. That is, the continuous processing line equipment of this embodiment includes an uncoiler 1, a welder 2, an entry side looper 3, a pickling treatment unit 4, an electric plating unit 5, a coating treatment unit 7, an exit side looper 8, a trimmer 9, and an inspection unit 10. And a coiler 11 in order.

The uncoiler 1 pays out the steel plate 12 to be plated. The welder 2 sequentially joins the discharged steel plates 12 by welding to enable continuous plating.
The pickling process part 4 is provided with the pickling tank which accommodated acids, such as a sulfuric acid. By passing the steel plate 12 through the pickling tank, the surface of the steel plate 12 is cleaned, that is, pretreatment for plating adhesion is performed.
The electroplating unit 5 is configured by arranging a plurality of stages, for example, seven stages of electroplating treatment tanks 6 in series. As shown in FIG. 2, each electroplating treatment tank 6 includes a plating tank 62 containing a plating solution 61, and an energizing device that energizes a steel plate portion in the plating tank 62 with a predetermined current density. The electrode 65 and the energizing roll 64 serve as an energizing device. Reference numeral 63 denotes a rubber roll.

  The coating processing unit 7 illustrated in FIG. 1 is a case where the coater device is configured by a pair of front and back sides and is a three-roll coater. FIG. 3 illustrates the three-roll coater. The coater device includes a coater device body, an oven, and a cooling zone. As shown in FIG. 3, the coater apparatus main body transfers the coating material 22 in the coater pan 21 onto the surface of the steel plate 12 that is continuously conveyed by the application roll 23.

  The trimmer 9 separates the steel plate 12 that has been processed. The inspection unit 10 inspects the surface quality of the steel plate 12. If it is determined that the appearance defect, that is, the preset target plating standard is not satisfied, it is subject to re-plating.

(Plating processing)
Using the above-mentioned continuous processing line equipment, electroplating and coating are continuously performed on the unplated steel sheet 12. The steel plate 12 is, for example, a cold rolled steel plate. The electroplating is, for example, electrogalvanizing.

Here, the current density at the time of energization in each electroplating treatment tank 6 for the unplated steel sheet 12, that is, the reference current density A0 depends on the target plating amount and the line speed, Usually, it is often set in the range of 35 [A / dm ² ] to 45 [A / dm ² ].
That is, when a normal unplated steel plate 12 is passed through the above-mentioned continuous processing line equipment, the surface of the steel plate is first cleaned in a pickling tank, and then sequentially plated in each electric plating treatment tank 6 of the electric plating section 5. Adheres to the desired amount of plating. Thereafter, a coating application process is performed in the coating processing unit 7. When the above process is completed, the coil is cut by the trimmer 9 and wound around the coiler 11 to form a coil again. At this time, if the quality of the steel plate 12 is inspected and it is determined that the appearance is poor, it is handled as a coil that requires re-plating.

  Next, the re-plating process for the steel plate 12 that has been subjected to the electro-plating and has been determined to be a coil that needs to be re-plated will be described. Here, the steel plate 12 to be re-plated may not be the steel plate 12 plated by the continuous processing line equipment.

  In the case of the re-plating treatment, only the lower two steps of the seven-stage electric plating treatment tank 6, in this embodiment, the lowermost stage and each of the electric plating treatment tanks 6 a and 6 b immediately before it are used. Perform re-payment. The other electroplating treatment tank 6 is in a non-energized state. The current density during energization in the two-stage electroplating treatment tanks 6a and 6b on the lower side is higher than the upper limit value of the reference current density A0 when normal electroplating is applied to the unplated steel sheet. Set to, and perform electric plating.

When the first plating process and the re-plating process are performed on the same line, the reference current density A0 may be considered as the highest value of the current density when the steel sheet 12 is subjected to the first plating process. In this embodiment, the plating process to the unplated steel sheet is performed at less than 50 [A / dm ² ], and the high current density AM is set to 50 [A / dm ² ] or more. The upper limit of the high current density AM is naturally determined due to the constraints of the equipment. For example, the upper limit value of the high current density AM is 100 [A / dm ² ]. The upper limit value is also determined by the re-plating amount with respect to the target plating amount.

When the above-described continuous processing line equipment is set for re-plating and the steel plate 12 that has already been plated is passed through, the surface layer of the plating of the steel plate 12 is first activated in the pickling section 4 and the surface layer is removed. Here, it is not possible to remove all the plating that has already been performed by simply passing the pickling treatment part 4 once.
Subsequently, the steel plate 12 after the pickling treatment is sent to the electroplating treatment unit, and re-electroplating is performed.

Usually, when the electroplating is carried out for the amount corresponding to the removal by pickling in the pickling processing section 4, the amount of plating applied may be small, so the current density may be set lower than the reference current density A0. In the present embodiment, conversely, it is set higher than the reference current density A0. For this reason, the electroplating treatment tank 6 to be energized is reduced.
The reason why blackening occurs is considered to be the impurity Pb. When re-plating is performed with the plating remaining after pickling, the lower the current density in the plating tank that starts energization, the more likely Pb will precipitate.

In this regard, in this embodiment, the current density during the re-plating process is set to the high current density AM, thereby suppressing the precipitation of Pb during the re-plating. This leads to suppressing blackening resistance deterioration due to re-plating.
Subsequently, a coating application process is performed in the coating processing unit 7.
Here, in the above-described embodiment, the case where the plating adhesion amount is the same before and after the re-plating is illustrated, but when the plating adhesion amount is changed by re-plating, for example, the activity of the plating in the pickling process You may set so that it may adhere more than the part removed by conversion. In this case, at least the current density in the first electroplating treatment tank to be energized may be set to a high current density higher than the reference current density.

(Effect of this embodiment)
In the present embodiment, at the time of re-plating, only the surface layer of the plating that has already been applied is removed by pickling as pre-treatment of electroplating, and then the necessary plating amount is re-plated. At this time, by setting the current density higher than the upper limit value of the current density for the unplated steel plate 12, precipitation of Pb from the plating solution 61 can be suppressed, and the plating can be performed even if the re-plating amount is small. Deterioration in appearance can be suppressed.

As described above, only by setting the electric plating unit 5 to a high current density for re-plating, it is possible to perform re-plating while ensuring a predetermined quality by passing through the continuous processing line equipment only once. It becomes possible.
At this time, it is possible to obtain excellent blackening resistance by setting the high current density AM at the time of re-plating to 50 [A / dm ² ] or more.

The higher current density AM is preferably higher, and is preferably set to 80 [A / dm ² ] or more. However, the upper limit of the high current density AM is also limited by the amount of plating deposited by re-plating, the number of electroplating treatment tanks used, the line speed, and the like.

(Modification)
(1) In the above embodiment, the case where two stages of the electric plating treatment tank 6 that is used for re-plating, that is, energized is illustrated, but one stage of the electric plating treatment tank 6 that is used for re-plating, that is, that is energized, is illustrated. Or three or more levels may be set.
(2) In the above embodiment, the electric plating treatment tank 6 used for re-plating is the lowermost stage and the preceding electric plating treatment tank 6a, 6b, and is not used for re-plating, that is, an electric plating treatment tank not energized. Is on the upper side of 6a and 6b. For this reason, there is no electric plating treatment tank 6 not used for re-plating on the lower side of the electric plating treatment tank 6 used for re-plating.
When the electric plating treatment tank 6 that is not used for re-plating is set on the lower side of the electric plating treatment tank 6 used for re-plating, the electric plating treatment tank 6 is not de-energized, and has a high current density AM. In addition, the energized state is set at a low current density. This is because the surface of the plating re-plated with the plating solution 61 may be roughened when the non-energized state is set.
Since the re-plating process is performed at a high current density AM, there are few cases where all the electric plating treatment tanks 6 are energized except for the case where the amount of plating is considerably thicker than the initial plating adhesion amount. It is preferable to arrange the plating treatment tank 6 on the lower side as much as possible.
(3) The electroplating treatment tank 6 used (energized) in the re-plating is set to other than the lowest level. For example, the electroplating treatment tank 6 used for the re-plating is set to the previous one and the previous electroplating treatment tank 6b, 6c.

The lowermost electroplating treatment tank 6a may be used for color tone adjustment. In this case, the current density in the lowermost electroplating treatment tank 6a is set in a range of 5 [A / dm ² ] to 20 [A / dm ² ]. That is, when there is a predetermined color tone for the plating surface, in order to secure the color tone, electroplating is performed at a low current to adjust the color tone of the plating surface.

(First embodiment)
An experiment of re-plating treatment was conducted using the above-mentioned continuous processing line equipment.
Here, as the steel plate 12 to be re-plated, an electrogalvanized steel plate in which 20 [g / m ² ] of electrogalvanized steel is formed on a cold-rolled steel plate (medium-low carbon steel) having a thickness of 0.4 mm and a plate width of 1250 mm. Was used. In this example, the line speed was 60 mpm.

The said pickling process part 4 was set as follows.
・ Pickling concentration: Acid (H ₂ SO ₄ ) concentration is 60-80 [g / l]
・ Pickling temperature: 15-40 [° C]
The electroplating treatment tank 6 used was a seven-stage electroplating treatment tank 6. Further, the current density of each electroplating treatment tank 6 with respect to the unplated steel plate was set to 35 [A / dm ² ].

However, at the time of re-plating, it is in a non-energized state except for the latter two stages, and the current density of the latter two stages is set to a high current density AM and is changed between 30 [A / dm ² ] to 100 [A / dm ² ]. And re-plated.
The experimental results are shown in FIG. FIG. 4 shows the relationship between the current density and the ΔL value related to blackening resistance evaluation during re-plating.
As can be seen from FIG. 4, the ΔL value improves as the current density increases. It can be seen that the ΔL values are set to −2.0 or more and −1.0 or more, respectively, by setting them to 50 [A / dm ² ] or more, preferably 80 [A / dm ² ] or more.

(Second embodiment)
A steel plate similar to that of the first example was used as the steel plate 12, and re-plating treatment was performed under the conditions shown in Table 1 to perform performance evaluation. The results are also shown in Table 1. For example, in Example 1 of Table 1, the amount of re-plating is set to 4 [g / m ² ], the second electroplating treatment tank 6 from the subsequent stage is set to high current density AM (50 [A / dm ² ]), The lowermost electric plating treatment tank 6 was set to a low current density for color tone adjustment. In addition, the former electroplating treatment tank 6 that is not used was not energized.

The line speed was 60 mpm.
Moreover, in the comparative example 1, the line is passed 4 times and the case where it re-plates after completely peeling off the old plating layer already performed by pickling is shown. In this case, the amount of re-plating was set to 20 [g / m ² ], and the plating process was performed under the current density conditions when not plating. In addition, in this case, it is a case where it passes 3 times for plating down, and it passes once for re-plating.

  The results are shown in Table 1.

As can be seen from Table 1, it can be seen that better re-plating can be achieved compared to the conventional case.
The quality performance was evaluated as follows.
(1) Appearance: Visual judgment of steel plate surface after re-plating Evaluation criteria ○: Uniform ×: Plating unevenness (2) Color tone L value (lightness) was measured with a gloss meter handy color tester HC1 manufactured by Suga Test Instruments Co., Ltd. .
Evaluation criteria ◎: L value 62.5 or more ○: L value 61 or more and less than 62.5 ×: L value 61 or less

(3) Blackening resistance The value obtained by subtracting (a) from the following (A) was defined as the ΔL value.
(A) Initial L value of steel sheet immediately after re-plating (a) After re-plating, the steel sheet is left in a constant temperature and humidity chamber at 80 ° C. and 95% RH for 5.5 hours after 5 days. L value Evaluation criteria A: ΔL value −1.0 or more ○: ΔL value −2.0 or more but less than −1.0 Δ: ΔL value −3.0 or more but less than −2.0 ×: ΔL value less than −3.0

(4) Corrosion resistance-Bare corrosion resistance The steel sheet after re-plating was evaluated by the appearance (white rust generation area ratio) after 72 hours of the salt spray test based on JIS-Z-2371.
-Corrosion resistance after alkaline degreasing After degreasing the steel plate after re-plating (CL-N364S manufactured by Nihon Parkerizing Co., Ltd.) at 60 ° C for 2 minutes, a salt spray test based on JIS-Z-2371 The appearance after 48 hours (white rust generation area ratio) was evaluated.
Evaluation criteria ○: White rust generation area ratio 10% or less △: White rust generation area ratio 10% or more 25% or less ×: White rust generation area ratio 25% or less

(5) Adhesion after painting After re-plating, the steel sheet was painted under the following conditions, and then a cross cut test and an Erichsen indentation test were performed.
Paint: Delicon No. 700 (Dainippon Paint Co., Ltd.), Film thickness: 30 μm
Heating: 130 ° C. × 30 minutes Evaluation criteria ○: Cross-cut test Peeling rate 20% or less and Erichsen indentation amount 5 mm or more, no peeling Δ: Cross-cut test Peeling rate 20% or more, 50% or less or Erichsen 3-5 mm Peeling ×: Cross cut test Peeling rate is over 50% or Erichsen is under 3mm

(6) Plating adhesion The steel plate after re-plating was evaluated in terms of peeling of the plating after Erichsen processing under the following conditions.
Test method: Eriksen tape test (a) Extrude the test object surface using an Erichsen tester until the substrate is cracked (do not make a grid).
(A) Adhesive tape is applied to the extruded convex part, and the tape is immediately peeled off and the plating peeling is visually observed. Evaluation standard ○: No peeling of the plating layer ×: Partial peeling of the plating layer

4 Pickling treatment part 5 Electroplating part 6 Electroplating treatment tank 7 Coating treatment part 12 Steel plate 61 Metal plating liquid 62 Metal plating tank A0 Reference current density AM High current density

Claims (5)

A pickling treatment unit, and an electric plating unit including a plurality of stages of an electric plating treatment tank that energizes at a reference current density that is a preset current density in a steel plate portion that contains the plating solution and is immersed in the plating solution. By passing through a continuous processing line, using an electroplating treatment facility that applies electroplating to the steel sheet,
An electric plating method for performing re-plating by passing a steel plate that has already been subjected to electro-plating through the continuous processing line,
Among the plurality of electroplating treatment tanks, at least the current density in the first electroplating treatment tank to be energized is set to a high current density higher than the upper limit value of the reference current density,
When the electroplating treatment tank set to the high current density is not the lowermost electroplating treatment tank, all the lower electroplating treatment tanks than the electroplating treatment tank set to the high current density are more than the above-mentioned high current density. An electroplating processing method characterized by setting the energized state at a low current density. 2. The electroplating method according to claim 1, wherein the high current density is 50 [A / dm ² ] or more. The electric plating treatment tank set to the above high current density is not used as the lowermost electric plating treatment tank, and the current density in the lowermost electric plating treatment tank is 5 [A / dm ² ] or more and 20 [A / dm ² ] or less. The electroplating processing method according to claim 1 or 2, wherein electroplating for color tone adjustment is performed as a range of the above. A pickling treatment unit, and an electric plating unit including a plurality of stages of an electric plating treatment tank that energizes at a reference current density that is a preset current density in a steel plate portion that contains the plating solution and is immersed in the plating solution. By passing through a continuous processing line, using an electroplating treatment facility that applies electroplating to the steel sheet,
An electric plating method for performing re-plating by passing a steel plate that has already been subjected to electro-plating through the continuous processing line,
Only the surface layer of the plating that has already been applied is activated by pickling in the pickling treatment section, and then the plating equivalent to or larger than the removal by pickling is performed in the electric plating section above the reference current density. An electroplating method characterized by performing electroplating at a high current density.   The said continuous processing line is provided with the coating process part provided with a roll coater downstream of the electric plating part, The electric plating processing method of any one of Claims 1-4 characterized by the above-mentioned.

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