JP2014181382A - Method of surface-treating metallic strip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a more effective technique for dissolving poor electric conduction caused by deposit adhered to a conduction roll.SOLUTION: A method of surface-treating a metallic strip includes a water scattering step of scattering water on a conduction roll which is arranged on the side of the inlet and/or the outlet of an electrolytic treatment tank of a surface treatment installation for carrying out surface treatment while carrying the metal strip and a surface treatment step of surface-treating the metal strip. The scattered water has a pH of 6.5-8.0. In the water scattering step, water is preferably scattered onto the metal strip so that the electrolyte concentration in recovered water is a half or lower of the electrolyte concentration in the electrolytic treatment tank, in recovering water adhered to the surface of the metal strip.

Description

  The present invention relates to a surface treatment method for treating the surface of a metal strip.

  In general, as one of the surface treatment methods for the metal strip, a method is used in which the metal strip is negatively charged via an energizing roll in an electrolytic treatment tank filled with an electrolyte solution, and the target metal is electrolytically deposited on the metal strip. ing.

  When the metal strip is surface-treated by such a method, there is a problem that the metal deposited on the surface of the metal strip adheres to and accumulates on the subsequent energizing roll, resulting in poor energization.

  Further, when the current density is increased in order to increase the processing speed, metal oxides are likely to be generated. Since this oxide has an electric resistance that is about 10 times larger than that of metal, there may be a case where an energization failure occurs when this oxide is deposited on a subsequent energizing roll.

  Patent Document 1 discloses a technique for eliminating the above-described energization failure in an energizing roll. Specifically, a method of spraying an acid or alkaline aqueous solution on at least one of the current-carrying roll and the metal strip is described.

Japanese Patent Laid-Open No. 04-17695

  Although the method described in Patent Document 1 can solve the problem of the above-described poor conduction, the method described in Patent Document 1 requires the installation of a shielding plate in the plating layer, which limits the installation space and the shielding plate. There is a problem of contact between the conductor roll and the metal strip, and there is a problem as an industrial manufacturing method. Therefore, it would be desirable if there was a more effective method that would not cause this problem.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a technique that is more effective than the conventional technique that eliminates a current-carrying failure caused by deposits adhering to a current-carrying roll.

  The inventors of the present invention have made extensive studies to solve the above problems. As a result, a water spraying step of spraying water on the energizing rolls arranged on the entry side and / or exit side of the electrolytic treatment tank of the surface treatment facility that carries out the surface treatment while conveying the metal strip, and the metal strip is surface treated It has been found that the above problems can be solved by a method having a surface treatment step, and the present invention has been completed. More specifically, the present invention provides the following.

  (1) A water spraying step of spraying water on energizing rolls arranged on the entry side and / or exit side of an electrolytic treatment tank of a surface treatment facility for carrying out a surface treatment while conveying the metal strip, and surface treating the metal strip A surface treatment method having a surface treatment step.

  (2) The water has a pH of 6.5 to 8.0, and when the water spraying step recovers the water adhering to the surface of the metal strip, the concentration of the electrolyte in the recovered water is the electrolytic treatment. The surface treatment method as described in (1) which is a process of spraying water on a metal strip so that it may become 1/2 or less of the electrolyte concentration in a tank.

  According to the method of the present invention, it is possible to produce a surface-treated metal strip that prevents the occurrence of energization failure in the energizing roll and has an overall good appearance.

It is a schematic diagram which shows an example of the surface treatment equipment which can be used for the surface treatment method of this invention. It is a schematic diagram which shows a mode that a spray apparatus sprays water on an electricity supply roll.

  Hereinafter, embodiments of the present invention will be described. In addition, this invention is not limited to the following embodiment.

  First, the surface treatment equipment used for the surface treatment method of the present invention will be described. FIG. 1 is a schematic view showing an example of surface treatment equipment that can be used in the surface treatment method of the present invention. The surface treatment facility shown in FIG. 1 is a horizontal electroplating facility for performing electroplating treatment on the surface of a steel strip. However, in the method of the present invention, a metal strip other than a steel strip can be used other than a horizontal electroplating facility. The method of processing using the surface treatment equipment is also included.

  A horizontal electroplating facility 1 shown in FIG. 1 is a facility for forming metal plating on the surface of a steel strip 2 using an electrolyte solution 3.

  As shown in FIG. 1, the horizontal electroplating equipment 1 includes an electrolytic treatment tank 11, an electrode 12, a support roll 13, a dam roll 14, an energizing roll 15, a backup roll 16, and an energizing roll polishing device 17 And a spray device 18.

  The electrolytic treatment tank 11 is a container for accommodating the electrolyte solution 3. The kind of the electrolyte solution 3 accommodated in the electrolytic treatment tank 11 is not particularly limited, and one that can form a desired metal plating on the surface of the steel strip 2 may be selected. For example, a sulfuric acid bath containing metal ions, a chloride bath, and a mixed bath thereof can be used.

  Since the surface treatment method of the present invention can be preferably applied to galvanization treatment, the electrolyte solution 3 preferably contains zinc ions in order to form galvanization on the surface of the steel strip 2.

  The electrode 12 is disposed at a position facing the front and back surfaces of the steel strip 2 that moves in the electrolytic treatment tank 11. In this embodiment, when the electrode 12 facing the front surface of the steel strip 2 and the electrode 12 facing the back surface are used as a pair of electrodes, the electrode 12 is composed of a front half portion and a rear half portion of the electrolytic treatment tank 11 (of the steel strip 2). Two sets are provided on the upstream side and the downstream side in the transport direction.

  The support roll 13 is a roll disposed between the pair of electrodes 12 in the front half and the pair of electrodes 12 in the rear half. The support roll 13 is composed of two rolls that sandwich the steel strip 2, and the two rolls prevent the steel strip 2 being conveyed from flapping or loosening.

  The dam roll 14 is disposed at the entrance end where the steel strip 2 enters the electrolytic treatment tank 11 and the exit end where the steel strip exits from the electrolytic treatment tank 11. The dam roll 14 is composed of two rolls each sandwiching the steel strip 2, and the roll prevents the electrolyte solution 3 from flowing out of the electrolytic treatment tank 11.

  The energizing roll 15 and the backup roll 16 are arranged in pairs near the upstream side of the incoming dam roll 14 and near the downstream side of the outgoing dam roll 14. The energizing roll 15 and the backup roll 16 sandwich the steel strip 2 so that the surface of the steel strip 2 is negatively charged by the energizing roll 15.

  In the present embodiment, the horizontal electroplating facility 1 includes a plurality of electrolytic treatment tanks 11. In this case, the steel strip 2 coming out of the upstream electrolytic treatment tank 11 passes between the energizing roll 15 and the backup roll 16 and is conveyed to the downstream electrolytic treatment tank 11. Here, the current-carrying roll 15 and the backup roll 16 are the current-carrying roll 15 and the backup roll 16 arranged on the outlet side when focusing on the upstream-side electrolytic treatment tank 11, and the downstream-side electrolytic treatment tank 11. If it does, it will become the electricity supply roll 15 and backup roll 16 which are arrange | positioned at the entrance side. Thus, whether it is arrange | positioned at the entrance side or what is arrange | positioned at the exit side changes with the electrolytic treatment tank 11 to which its attention is paid.

  The energizing roll polishing device 17 is disposed in the vicinity of the energizing roll 15 and removes metal plating attached to the energizing roll 15.

  The spray device 18 is disposed in the vicinity of the energizing roll 15 and sprays water on the energizing roll 15.

  FIG. 2 is a schematic diagram showing a state in which the spray device 18 sprays the water 4 on the energizing roll 15. As shown in FIG. 2, the spray device 18 has a cylindrical shape and has nine injection holes on the circumferential surface.

  The number of spray holes of the spray device is not particularly limited as long as water can be sprayed on the entire surface of the energizing roll 15. “Overall” includes the case where there is a region on the surface of the energizing roll 15 where the water from the spray holes does not directly hit.

  Further, the distance between the spray device 18 and the energizing roll 15 is not particularly limited, and may be adjusted as appropriate so as to achieve a desired effect. Since the desired effect can be obtained by adjusting the water pressure, the ratio of the area where the surface of the energizing roll 15 is exposed to water, the flow rate of water (L / min), etc., the above-mentioned distance can also be adjusted within the desired range. It may be adjusted according to the adjustment. In general, the distance from the tip of the injection hole closest to the surface of the energizing roll 15 to the surface of the energizing roll 15 is adjusted in the range of 20 to 100 cm.

  Then, the surface treatment method of this invention is demonstrated. The surface treatment method of the present invention includes a water spraying step and a surface treatment step. Hereinafter, each step will be described.

  A water spraying process is a process of spraying water on the energizing rolls arranged on the entry side and / or exit side of the electrolytic treatment tank.

  In the case of using the horizontal electroplating equipment shown in FIG. 1, the water spraying process is a spray device 18 on the surface of the energizing roll 15 while passing the steel strip 2 between the energizing roll 15 and the backup roll 16. Is a step of spraying water.

  In the water spraying step, the steel strip 2 is treated in the electrolytic treatment tank 11 upstream thereof. For this reason, the product produced by the surface treatment in the electrolytic treatment tank 11 immediately before is attached to the surface of the steel strip 2 before passing through the energizing roll 15 and the backup roll 16 in the water spraying step.

  The product refers to a metal and / or an oxide. The surface treatment method of the present invention can be applied to all surface treatments where the above-mentioned product may be generated. The product as described above is likely to deposit on the energizing roll 15 because the product may be easily deposited when the leakage current to the energizing roll increases. When the product accumulates, a problem of poor conduction occurs.

  In the present invention, since water is sprayed on the surface of the energizing roll 15, even if the product is likely to be deposited on the energizing roll 15, by spraying water, the electrolyte on the conductor roll is diluted, By making it difficult for Ni or the like to precipitate, accumulation of impurities can be suppressed. Further, even when the impurities temporarily exist on the energizing roll 15, the product tends to peel off from the energizing roll 15 immediately due to the action of water. In the present embodiment, the product falls from the energizing roll and is collected in the plating solution circulation tank.

  Moreover, since the electroplating performed in the electrolytic treatment tank 11 is performed using the steel strip 2 as a cathode, an oxide is generated during the treatment, and the oxide tends to adhere to the surface of the steel strip 2. Therefore, the oxide produced by the surface treatment in the immediately preceding electrolytic treatment tank 11 is attached to the surface of the steel strip 2 before passing between the energizing roll 15 and the backup roll 16 in the water spraying step. .

In the water spraying step, “water” to be sprayed is H ₂ O as a main component and is neutral. In the present invention, neutral means that the pH is in the range of 6.5 to 8.0.

  In the water spraying step, the amount of water sprayed by the spray device 18 is not particularly limited, but when the water adhering to the surface of the steel strip 2 is recovered, the recovered electrolyte concentration in the electrolytic treatment tank 11 is It is preferable that the spray device 18 sprays water on the surface of the energizing roll 15 so that the electrolyte concentration is ½ or less. Since the amount of water sprayed by the spray device 18 is in the above range, there is an effect that the amount of product produced can be minimized by diluting with water. The lower limit of the electrolyte concentration in the recovered water is not particularly limited, but is preferably 0.5 L / min or more.

  In the measurement of the electrolyte concentration in the recovered water, the recovery of the water adhering to the surface of the steel strip 2 is not particularly limited. For example, a liquid recovery pan and a buffer tank are placed under the energizing roll, and the liquid is plated. There is a method of providing a route for returning to the liquid circulation tank.

  In order to adjust the amount of water sprayed, it is preferable to adjust the flow rate from each injection hole in the range of 0.5 to 20 L / min. It is necessary to consider the ratio of the area where water hits the surface area, the total amount of water sprayed per unit time from all nozzles, and the like.

  A surface treatment process refers to the process of surface-treating a metal strip. As described above, since the present invention includes the water spraying step even when the surface treatment has the possibility that impurities and oxides accumulate on the current-carrying roll and cause a current-carrying failure, to the current-carrying roll of impurities and oxides. Accumulation of electricity is suppressed, and it becomes difficult for electric conduction failure to occur. As a result, in the surface treatment step, a surface-treated metal strip having good surface properties can be obtained.

  Hereinafter, the present invention will be described more specifically with reference to examples. The present invention is not limited to the following examples.

Invention Example The following surface treatment was performed using the equipment shown in FIG.

Electrolytic treatment containing an electrolyte solution (pH: 1.2, 50 ° C.) composed of 155 g / L of ZnSO ₄ .7H ₂ O, 23 g / L of NiSO ₄ .6H ₂ O ₃ and 55 g / L of Na ₂ SO ₄ in the bath, a Zn-Ni electroplating was applied to the steel strip under the conditions of cathode current density of 68A / dm ^2. The plating composition of the Zn—Ni electroplating is Ni: 12% by mass, the balance Zn and unavoidable impurities, and the plating adhesion amount is 30 g / m ² per side. And the steel strip sent out from the dam roll arrange | positioned at the edge of an electrolytic treatment tank was passed between the next electricity supply roll and the backup roll, and the steel belt was negatively charged with the electricity supply roll. At this time, water (pH 6.5 to 8.0, water amount 2.5 L / min) was sprayed from the spray device toward the surface of the energizing roll. The amount of water is the total amount of water coming out of all nozzles (all injection holes).

  In the above treatment, when the water adhering to the surface of the steel strip is collected, the amount of water is adjusted so that the electrolyte concentration in the collected water is 1/2 or less of the electrolyte concentration in the electrolytic treatment tank, Water was sprayed from the spray device.

  Moreover, the spray apparatus used by the Example and the following comparative example is specifically as follows. A spray device made of vinyl chloride, having a cylindrical shape with a total length of 2000 mm and a diameter of 22 mm, provided with 18 injection holes with a diameter of 18 mm, and an interval between the injection holes of 100 mm was used. The spray device for water was arrange | positioned so that water could be sprinkled from the seven spray devices to each of the seven energizing rolls (used only in the examples). Also, one spray device with the same shape was arranged for dilute sulfuric acid (used only in the comparative example). Moreover, it adjusted so that the distance from the front-end | tip of the injection hole nearest to the electricity supply roll surface to the electricity supply roll 15 surface might be in the range of 20-100 cm. In addition, a flow meter is provided in the edge part of a spray apparatus, and it can adjust to a desired flow volume by confirming a flow volume in this part.

  When the above treatment was carried out continuously for 12 hours, it was confirmed by visual observation that a surface-treated steel strip having a good surface property was obtained continuously.

Here, whether or not the surface properties were good was evaluated by visual observation according to the following criteria.
“◯ (good)”: When the deposit on the current roll does not transfer to the steel strip “× (bad)”: When the deposit on the current roll transfers to the steel strip Comparative Example Water contains 20% by mass of dilute sulfuric acid Surface treatment was performed in the same manner as in the inventive examples except that the solution was changed to an acidic solution (pH 0.5 to 1.5). When the above treatment was performed continuously for 12 hours, it was confirmed by visual observation that a surface-treated steel strip having poor surface properties was obtained. The evaluation method of the surface property is the same as in the case of the inventive examples.

DESCRIPTION OF SYMBOLS 1 Horizontal type electroplating equipment 11 Electrolytic processing tank 12 Electrode 13 Support roll 14 Dam roll 15 Current supply roll 16 Backup roll 17 Current supply roll polisher 18 Spray device 2 Steel strip 3 Electrolyte solution

Claims (2)

A water spraying step of spraying water on energizing rolls arranged on the entry side and / or exit side of the electrolytic treatment tank of the surface treatment facility for carrying out the surface treatment while conveying the metal strip;
A surface treatment method for a metal strip, comprising a surface treatment step for surface-treating the metal strip. The water has a pH of 6.5 to 8.0,
In the water spraying step, when water adhering to the surface of the metal strip is collected, the water is energized so that the electrolyte concentration in the collected water is ½ or less of the electrolyte concentration in the electrolytic treatment tank. The surface treatment method according to claim 1, wherein the surface treatment method is a step of spraying on a roll.

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