JP4762633B2 - Manufacturing method of hot dipped steel sheet - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a method for manufacturing a hot-dip galvanized steel sheet, a pretreatment cleaning apparatus, and a hot dip plating line equipment, and more particularly, a method for manufacturing a hot dip galvanized steel sheet, a pretreatment cleaning apparatus, and hot dip plating. It relates to line equipment.

  In the hot dip plated steel plate production line, in order to improve the wettability of the hot dip steel plate, the annealed steel plate is subjected to pre-plating by electric Ni plating (hereinafter referred to as “Ni pre-plating”) and then plated. A process for hot dip galvanizing in a bath is known. In such a process, it may be necessary to temporarily store the annealed steel sheet before performing these plating processes. The purpose of this storage is to supply the steel plate continuously to the hot dipping line even if the annealing equipment is stopped due to periodic repairs, maintenance work, etc. The purpose is to select and adjust the steel plate size.

  However, the annealed steel plate has a problem that it is easily oxidized and rusted. According to one theory, in order not to oxidize the steel sheet, it is considered appropriate to pass through the hot dipping line within about 8 hours after annealing the steel sheet. However, it is often difficult to store the annealed steel plate for a short period of time and let it pass through the hot dipping line because of the production schedule, and it is required to store the annealed steel plate for a certain period of time. The

  Therefore, conventionally, when an annealed steel sheet is stored for a predetermined period and passed through an electroplating line, temper rolling is performed after annealing, and a rust preventive is included in the temper rolling liquid used at this time. Or, by applying a rust preventive to the steel sheet after temper rolling, it has been practiced to prevent oxidation of the steel sheet stored.

  However, conventionally, when producing an electrogalvanized steel sheet, if the rust inhibitor applied on the surface of the steel sheet remains after annealing as described above, the plating adhesion may be uneven during electrogalvanization. Is known (see Patent Document 1). For this reason, in the conventional electroplating line, as a pretreatment for plating, the rust preventive agent adhering to the surface of the steel sheet was cleaned and removed using an alkaline spray, electrolytic degreasing tank, brush scrubber, etc. . In particular, Patent Document 1 discloses a method for improving the cleaning effect by performing electrolysis so as to finally become a cathode while switching the polarity of a steel plate in an alkaline solution in an electrolytic cleaning process as a cleaning process before electrogalvanization. Has been proposed.

JP 2005-2373 A JP 2004-124187 A Japanese Patent Publication No.46-19282 Japanese Patent No. 2725537

By the way, when performing Ni pre-plating in the hot dipping line, in order to exert its function, compared with a general electroplating plating amount (in the case of electrogalvanization, for example, about 30 g / m ² ). , The amount of Ni plating must be reduced (for example, about 0.2 g to 0.8 g / m ² ). Therefore, in Ni pre-plating, compared to conventional electroplating, it is necessary to strictly control the amount of plating deposited. For this purpose, the rust inhibitor adhering to the surface of the steel plate is preferably washed before plating. It is necessary to keep.

  However, in the past, there was some knowledge about the cleaning method before electrogalvanization, as described above. However, the cleaning method before Ni pre-plating is effective for removing the rust inhibitor attached to the steel plate. In addition, there was not enough knowledge about whether or not it could be cleaned sufficiently.

  For example, Patent Document 2 describes in paragraph [0043] that the surface of a steel sheet is Ni-plated and hot-dip galvanized after washing with an alkaline aqueous solution or the like. In [Example], NaOH is plated after Ni plating. It is also described that cleaning is performed with an aqueous solution, and a cleaning method suitable as a pretreatment for Ni pre-plating is not disclosed.

  Patent Document 3 describes in Example 1 that Ni is deposited on the surface of the steel sheet after pretreatment of the annealed steel sheet by electrolysis with soda solution, water washing, and pickling. In Example 2, it is described that the same effect was exhibited without performing the pretreatment of Example 1, and the effect of the cleaning treatment is not clear.

  Furthermore, in Patent Document 4, [0019] and [Example] describe that the steel sheet is cleaned by normal alkaline degreasing before the annealing process, but there is no description about the relationship with the removal of the rust inhibitor. It has not been.

  As described above, heretofore, there has not been sufficient knowledge about a method for cleaning and removing a rust inhibitor from a steel plate before Ni pre-plating for hot dipping. As described above, insufficient cleaning and removal of the rust inhibitor has the problem of unevenness in Ni plating with a small amount of adhesion. On the other hand, if the cleaning is performed more than necessary, the cleaning equipment becomes overspec. As a result, there is a problem that the equipment cost and the manufacturing cost are expensive and inefficient. Therefore, there has been a demand for a method capable of sufficiently and efficiently cleaning and removing the rust preventive agent adhering to the steel plate surface in the cleaning process before Ni pre-plating.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a rust preventive agent adhering to the surface of the steel sheet as necessary and sufficient and efficient as a pretreatment for pre-plating the steel sheet. It is an object of the present invention to provide a new and improved method for manufacturing a hot-dip galvanized steel sheet that can be cleaned and removed automatically .

  In order to solve the above-mentioned problems, the inventors of the present application diligently studied the cleaning effect of the pretreatment cleaning step when Ni pre-plating is performed before hot dipping.

  As a result, it has been found that if a water-soluble rust preventive agent is used, the electrolytic cleaning step conventionally used for cleaning the electroplating line can be omitted in the pretreatment cleaning step of Ni preplating. In other words, if the temper rolling ratio is adjusted using a water-soluble rust inhibitor, the water-soluble rust inhibitor attached to the steel sheet surface can be removed simply by washing with an alkaline solution without performing electrolytic cleaning. It has been found that it can be removed sufficiently and sufficiently to the extent that unevenness does not occur during Ni pre-plating. This is because Ni has a high precipitation overvoltage, so during Ni pre-plating, Ni precipitates on the steel sheet surface and hydrogen is likely to be generated at the same time. This hydrogen gas generation is effective in removing the rust inhibitor remaining on the steel sheet surface. It is thought that it originates in exhibiting.

Furthermore, when the electrolytic cleaning used in the conventional pretreatment cleaning is performed, for example, Fe-OH is dissolved in the cleaning solution or other metal impurities are mixed, so that metal impurity ions adhere to and precipitate on the surface. It has also been found that, on the contrary, it may adversely affect Ni pre-plating. That is, Ni pre-plating has a very low adhesion amount of, for example, 0.2 to 0.8 mg / cm ² and needs to be uniformly plated. It is necessary to avoid as much as possible. From this point of view, it was concluded that it is preferable to omit electrolytic cleaning in order to prevent metal impurity ions from adhering to and precipitating on the steel sheet surface in the cleaning process. Therefore, based on such knowledge, the inventors of the present application have come up with the following invention.

That is, in order to solve the above-described problems, according to one aspect of the present invention, an annealing process for annealing a steel sheet; and a rust inhibitor coating process for applying a water-soluble rust inhibitor to the annealed steel sheet; A cleaning process for cleaning the steel sheet coated with a rust preventive agent using an alkaline solution without electrolytic cleaning; a Ni pre-plating process for electro-Ni plating the cleaned steel sheet; and a steel sheet after Ni pre-plating; , hot dipping process and that hot dipping was immersed in molten coating metal containing molten Zn; the free Mutotomoni, wherein after the annealing process, temper rolling was the annealed steel sheet to temper rolling to temper with Further comprising a rolling step, wherein the rust preventive coating step is performed by adding the water-soluble rust preventive agent to the temper rolling solution in the temper rolling step. A method for manufacturing a steel sheet is provided.

According to this manufacturing method, in order to prevent rusting during storage of a steel plate after annealing and before plating treatment, when the steel plate after annealing is pre-plated with Ni and hot-plated to produce a hot-dip steel plate, A water-soluble rust preventive agent is applied to the annealed steel sheet, and as a pretreatment for the Ni pre-plating step, the steel sheet to which the rust preventive agent is attached is subjected to alkali cleaning without performing electrolytic cleaning. Since the water-soluble rust preventive agent is suitably removed from the alkali-washed steel plate in this way, it can exhibit the same wettability as when electrolytic cleaning is performed and can prevent the occurrence of unevenness during Ni pre-plating. . Further, the rust inhibitor remaining on the cleaned steel plate surface is peeled off and removed from the steel plate surface by the hydrogen gas generated at the same time as Ni deposition in the Ni pre-plating process in which electric Ni plating is performed. In this way, when Ni pre-plating is performed, even if some rust inhibitor remains on the surface of the steel sheet compared with the conventional electro-galvanization, the anti-rust is caused by the action of hydrogen gas during Ni plating. It is possible to remove the agent. Therefore, even with a cleaning method that does not perform electrolytic cleaning as described above, the rust inhibitor on the surface of the steel sheet can be cleaned and removed as necessary and sufficiently as pretreatment cleaning before Ni pre-plating. In addition, it includes a temper rolling process in which the steel sheet annealed with the temper rolling liquid is temper-rolled after the annealing process, and the rust preventive coating process is water-soluble in the temper rolling liquid in the temper rolling process. It is possible to apply the rust inhibitor to the annealed steel sheet during the temper rolling process, and it is necessary to provide a separate rust inhibitor application process. Because there is no, the manufacturing process becomes efficient.

  In addition, since electrolytic cleaning can be omitted, electrolytic cleaning equipment is unnecessary, which contributes to reduction in equipment cost and manufacturing cost. Furthermore, by performing electrolytic cleaning, it is possible to prevent metal impurity ions from adhering to and precipitating on the surface of the steel sheet, so that it is possible to further suppress the occurrence of unevenness in Ni plating that requires a strict plating adhesion amount.

  The cleaning process includes a spray cleaning process for cleaning a steel sheet coated with a rust inhibitor by spraying an alkaline liquid; a brush for cleaning the steel sheet after spray cleaning using a brush while supplying an alkaline liquid. And a washing step. Thus, by performing spray cleaning and brush cleaning, the water-soluble rust preventive agent adhering to the steel sheet surface is removed sufficiently and necessary to improve the wettability of the steel sheet surface without performing electrolytic cleaning, Generation of unevenness during Ni pre-plating can be prevented.

  Further, in the cleaning step, the electrolytic cleaning may not be performed in order to prevent metal impurity ions from adhering to and precipitating on the steel sheet surface by electrolytic cleaning. Thereby, the occurrence of unevenness during Ni pre-plating can be prevented.

Moreover, in the said washing | cleaning process, you may wash | clean so that the residual amount of a rust preventive agent in a steel plate surface may be 20 microgram / m < ² > or less. Thereby, in the Ni pre-plating step, the rust inhibitor can be cleaned and removed to such an extent that unevenness does not occur due to the rust inhibitor remaining on the steel sheet surface.

  In addition, it includes a temper rolling process in which the steel sheet annealed with the temper rolling liquid is temper-rolled after the annealing process, and the rust preventive coating process is water-soluble in the temper rolling liquid in the temper rolling process. It may be carried out by including a rust inhibitor. As a result, the rust preventive agent can be applied to the annealed steel sheet during the temper rolling process, and it is not necessary to provide a separate rust preventive agent applying process, so that the manufacturing process becomes efficient.

  Moreover, the temper rolling rate in the temper rolling process may be 0% or more and 0.4% or less. Thereby, the rust preventive agent on the steel sheet surface can be suitably removed in the cleaning process. In other words, the inventors of the present application have conducted intensive research and temper rolling using an aqueous temper rolling solution containing a rust preventive agent. During the temper rolling, the rust preventive agent is pushed into fine irregularities on the surface of the steel sheet. As a result, it has been found that uniform removal of the rust inhibitor may be difficult in the cleaning step before Ni pre-plating. Therefore, as a technique for solving such a problem, the inventors have come up with a technique for limiting the temper rolling ratio in the temper rolling process to 0.4% or less. Thereby, since it can suppress that a rust preventive agent is pushed into the steel plate surface at the time of temper rolling, a rust preventive agent can be easily and uniformly removed in a cleaning process.

  In addition, the method further includes a temper rolling step of temper-rolling the annealed steel sheet using the temper rolling solution that does not contain the water-soluble rust preventive agent. You may make it apply | coat a water-soluble rust preventive agent with respect to a steel plate. As a result, the water-soluble rust preventive agent is applied separately from the temper rolling step, and the rust preventive agent is pushed into the steel sheet surface by temper rolling as described above. There is no problem of end. Therefore, the rust inhibitor can be easily and uniformly removed in the cleaning process.

  In order to solve the above problems, according to another aspect of the present invention, a steel plate coated with a water-soluble rust preventive agent after annealing is subjected to Ni pre-plating by electric Ni plating and molten containing molten Zn. A pretreatment cleaning device for cleaning a steel sheet coated with a rust preventive agent is provided as a pretreatment for performing hot dipping immersed in a plated metal. This pretreatment cleaning apparatus is characterized in that a steel plate coated with a rust preventive agent is cleaned with an alkaline solution without performing electrolytic cleaning.

  The pretreatment cleaning device having such a configuration can be suitably applied to the cleaning process of the manufacturing method of the hot dip plated steel sheet. This pretreatment cleaning apparatus can remove the rust preventive agent sufficiently and sufficiently for the pretreatment cleaning of the Ni pre-plating without performing electrolytic cleaning, so that the cleaning processing can be made efficient. Furthermore, since it is not necessary to install an electrolytic cleaning device, overspecs can be avoided and the equipment cost can be reduced.

  In addition, the pretreatment cleaning device includes a spray cleaning device for cleaning a steel plate coated with a rust inhibitor by spraying an alkaline solution; and cleaning the steel plate after spray cleaning with a brush while supplying an alkaline solution. And a brush cleaning device. By performing spray cleaning and brush cleaning in this way, the water-soluble rust preventive agent adhering to the steel sheet surface is removed sufficiently and necessary without electrolytic cleaning, and the wettability of the steel sheet surface is improved. Generation of unevenness during pre-plating can be prevented.

  Further, in order to prevent metal impurity ions from adhering to and precipitating on the surface of the steel sheet by the electrolytic cleaning, the electrolytic cleaning may not be performed. Thereby, the occurrence of unevenness during Ni pre-plating can be prevented.

Moreover, you may make it wash | clean so that the residual amount of a rust preventive agent in the steel plate surface may be 20 microgram / m < ² > or less. Thereby, in the Ni pre-plating process, the rust preventive agent can be cleaned and removed to such an extent that unevenness does not occur due to the remaining rust preventive agent.

  In order to solve the above-described problems, according to another aspect of the present invention, the above-described pretreatment cleaning apparatus; an Ni preplating apparatus for electro-Ni plating a steel plate cleaned by the pretreatment cleaning apparatus; There is provided a hot dipping line facility comprising: a hot dipping apparatus for dipping hot dipped steel sheets in a hot dipped metal containing molten Zn and hot dipping. The hot dipping line equipment having such a configuration can be suitably applied to the method of manufacturing a hot dipped steel sheet as described above.

  As described above, according to the present invention, as a pretreatment for pre-plating a steel plate, the rust inhibitor adhering to the surface of the steel plate can be cleaned and removed sufficiently and efficiently.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

(First embodiment)
Below, the manufacturing method of the hot dipped steel plate concerning the 1st Embodiment of this invention and the manufacturing equipment of the hot dipped steel plate used for this are demonstrated.

  First, based on FIG. 1, the manufacturing equipment 1 of the hot dipped steel plate concerning this embodiment is demonstrated. FIG. 1 is a schematic diagram showing an outline of a production facility 1 for hot-dip plated steel sheets according to the present embodiment.

  The hot-dip plated steel sheet manufacturing equipment 1 includes, for example, a cold rolling / annealing building 10, a first adjusting building 11, a second adjusting building 12, a warehouse 13, and a hot dipping plating building 14. The cold rolling / annealing ridge 10, the first rectifying ridge 11, the second rectifying ridge 12, and the warehouse 13 are installed in a straight line in order in the X direction positive direction (right direction in FIG. 1). The hot dipping ridge 14 is installed on the positive side in the Y direction (downward in FIG. 1) of the second finishing ridge 12. The second finishing building 12 and the hot dipping plating building 14 are connected by a transfer passage 15.

  The cold rolling / annealing building 10 is formed with a cold rolling / annealing line facility 20 that continuously performs cold rolling and annealing of a steel strip. The cold rolling / annealing line equipment 20 is formed such that a steel plate is transferred from the X direction negative direction side (left direction side in FIG. 1) toward the first finishing building 11 side. The exit side of the cold rolling / annealing line facility 20 is installed, for example, in the first finishing building 11.

  For example, a relay line A for transferring a coiled steel plate is formed from the first adjustment building 11 to the second adjustment building 12. The relay line A is constituted by, for example, a roller conveyor. The entrance side of the relay line A is arranged in parallel with the exit side of the cold rolling / annealing line facility 20 in the first finishing building 11. The relay line A can transfer the steel plate on the exit side of the cold rolling / annealing line facility 20 into the second finishing building 12 in the X direction positive direction side.

  For example, a packaging line facility 21 for conveying and packing a coiled steel plate is formed from the second finishing building 12 to the warehouse 13. The entry side of the packing line facility 21 is installed in the second finishing building 12 and connected to the exit side of the relay line A. The packing line facility 21 is formed by, for example, a roller conveyor, and can transfer a coiled steel plate toward the positive side in the X direction, and the steel plate can be transferred by a packing machine (not shown) on the packing line facility 21 in the warehouse 13. Can be packed.

  In the hot dipping ridge 14, a hot dipping line facility 22 for plating a steel strip-like steel plate is formed. The hot dipping line equipment 22 is formed, for example, such that the longitudinal direction is in the X direction. That is, the hot dipping line equipment 22 is formed in parallel with the cold rolling / annealing line equipment 20 and the packing line equipment 21.

  For example, the first finishing building 11 is provided with a crane 30 that is a transfer device that can move in the Y direction above the exit side of the cold rolling / annealing line facility 20 and the entrance side of the relay line A. With this crane 30, the coil of the steel sheet that has been cold-rolled / annealed in the cold-rolling / annealing line equipment 20 can be conveyed to the entrance side of the relay line A.

  The second finishing building 12 is provided with a storage unit 31 that can temporarily store and store a plurality of coiled steel plates. The storage unit 31 is disposed, for example, between the packing line facility 21 and the relay line A and the conveyance path 15. In the second finishing building 12, for example, a crane 32, which is a transport device that can move in the Y direction above the packing line facility 21, the relay line A, and the storage unit 31, is provided. The crane 32 can transport and store the steel plate on the relay line A to the storage unit 31. Further, the steel plate of the storage unit 31 can be transported onto the packing line facility 21 by the crane 32. In addition, the transfer part which transfers the steel plate between the relay line A and the crane 32, and between the packing line equipment 21 and the crane 32 is provided in the connection part of the packing line equipment 21 and the relay line A. It may be.

  For example, the transport path 15 is provided with a crane 33 that is a transport device that can move in the Y direction from above the storage unit 31 into the transport path 15. In addition, a plurality of carriages 34 that are conveyance devices for conveying coiled steel plates are provided in the conveyance passage 15. The steel plate of the storage unit 31 of the second finishing building 12 can be transferred into the transfer passage 15 by the crane 33, and the steel plate of the transfer passage 15 can be transferred to the entrance side of the hot dipping line facility 22 of the hot dipping plate building 14 by the carriage 34. . In addition, the steel plate on the outlet side of the hot dipping line equipment 22 can be transported into the transport passage 15 by the carriage 34 and the steel plate can be transported to the storage unit 31 by the crane 33.

  Thus, for example, the crane 30, the relay line A, the cranes 32 and 33, and the carriage 34 convey the steel plate from the exit side of the cold rolling / annealing line facility 20 to the hot dipping line facility 22. Further, the steel plate is transported from the hot dipping line equipment 22 to the packing line equipment 21 by the carriage 34 and the cranes 33 and 32.

  Further, for example, a finishing line 36 for adjusting the length in the width direction of the steel plate is disposed from the second finishing tower 12 to the first finishing tower 11. The finishing line 36 is provided, for example, in the moving range of the crane 32 on the entry side, and is provided in the moving range of the crane 30 on the exit side. Therefore, for example, the steel plate that has been subjected to the hot dipping process can be transported to the finishing line 36 by the crane 32, and the steel sheet adjusted by the finishing line 36 can be returned to the entrance side of the relay line A by the crane 30. Note that the finishing line 36 may further have a function of removing and trimming a defective portion of the steel plate.

  With the above configuration, the steel sheet cold-rolled and annealed by the cold rolling / annealing line equipment 20 is transported to the hot dipping line equipment 22 and plated, and then the plated steel sheet is packed. It can be conveyed to the line equipment 21 and packed. During the transfer from the cold rolling / annealing line facility 20 to the hot dipping line equipment 22, a plurality of steel plates are temporarily stocked in the storage unit 31, thereby adjusting the steel sheet supply to the hot dipping line equipment 22. be able to. Thereby, even if the cold rolling / annealing line facility 20 is stopped for maintenance, the steel plate can be continuously supplied to the hot dipping line facility 22 to improve productivity. Further, by adjusting the size such as the width of the steel plate by the adjusting line 36, the efficiency of passing the steel plate in the hot dipping line equipment 22 can be improved.

  In order to prevent the steel sheet from rusting during temporary storage of the steel sheet in the storage unit 31 or when adjusting the size of the steel sheet using the finishing line 36, for example, in the cold rolling / annealing line equipment 20, the surface of the steel sheet after annealing A rust preventive is applied to the surface.

  Next, based on FIG. 2, the cold rolling / annealing line equipment 20 according to the present embodiment will be described in detail. FIG. 2 is a schematic diagram showing an outline of the cold rolling / annealing line facility 20 according to the present embodiment.

  As shown in FIG. 2, the cold rolling / annealing line equipment 20 includes, for example, a cold rolling device 40 that cold-rolls a steel strip-shaped steel plate H and an annealing device 50 that anneals the cold-rolled steel plate H. It is the structure formed continuously.

  The cold rolling apparatus 40 includes a rewinding machine 41 as a carrying-in apparatus, a welding machine 42, a tension bridle 43, a pickling basin 44 for pickling steel sheets, a deskelper 45, an entry side looper 46, and a steel sheet H. A cold rolling mill 47 for cold rolling, an intermediate welding machine 48, and a cleaning line 49 including an electrolytic cleaning device are provided in order from the upstream side to the downstream side. The steel sheet H cold-rolled by such a cold rolling device 40 is continuously supplied to the annealing device 50.

  The annealing apparatus 50 includes, for example, a center looper 51 that is a horizontal looper that expands and contracts in the horizontal direction, an annealing furnace 52 that anneals the steel sheet H, a post-processing apparatus 53 that pickles the annealed steel sheet, and a horizontal extension and contraction. An exit side looper 53 which is a horizontal looper, a temper rolling mill (skin pass mill) 55 for temper rolling the annealed steel sheet H, an exit side device 56 such as a trimmer and a shear, and a winder 57 as an unloading device. In order from the upstream side to the downstream side.

  The annealing furnace 52 anneals the steel sheet H, that is, heats the steel sheet H and performs soaking at a predetermined temperature (for example, 810 ° C., 400 ° C.), and then cools it in the furnace at a constant cooling rate. By this annealing treatment, the material of the steel plate H can be adjusted so as to remove strain inside the steel plate H due to work hardening, soften the structure, and improve the spreadability.

  The temper rolling machine 55 adjusts the thickness of the steel sheet H by temper rolling at a predetermined temper rolling rate while supplying a temper rolling liquid such as lubricating water to the annealed steel sheet H. In this embodiment, the temper rolling liquid used at the time of temper rolling contains a water-soluble rust preventive. Thereby, simultaneously with the temper rolling process, a water-soluble rust preventive agent is applied to the surface of the steel sheet H (rust preventive agent applying process), and the steel sheet H after annealing can be prevented from being oxidized and generating rust.

  Examples of the rust preventive include water-soluble rust preventives such as phenoxyalkylcarboxylate compounds (see Japanese Patent Publication No. 59-31594), 1-hydroxybenzotriazole compounds or salts thereof (Japanese Patent Publication No. 53-27694). Can be used. More specifically, for example, it is possible to use a rust inhibitor whose main component is Na salt of 1hydroxybenzotriazole and whose concentration is about 0.5%.

  Moreover, in this embodiment, the aqueous solution containing such a rust preventive agent is utilized as a temper rolling liquid. Such a water-soluble tempered rolling liquid has an advantage that the occurrence of contamination of the steel sheet H is less than that of an oil-soluble tempered rolling liquid (Non-patent document “Recent Cold Strip Equipment and Manufacturing Technology in Japan”). Progress, "page 160). In addition, by using a water-soluble rust preventive agent as described above instead of an oil-soluble rust preventive agent, the rust preventive agent can be used in a pretreatment cleaning device of the hot dipping line equipment 22 described later. Can be easily cleaned and removed.

  Further, from the viewpoint of facilitating the cleaning / removal treatment of the rust preventive agent in the subsequent process, the temper rolling ratio at the temper rolling by the temper rolling mill 55 is, for example, 0% to 0.4%. However, details will be described later.

  The steel sheet H is cold-rolled and annealed by the cold rolling / annealing line equipment 20 having the above-described configuration, and then a rust inhibitor is applied simultaneously with the temper rolling. The steel plate H to which the rust preventive agent is applied is stored in the storage unit 31 as shown in FIG. 1 or adjusted in size by the finishing line 36 and then transferred to the hot dipping line equipment 22. The

  As described above, the cold rolling / annealing line facility 20 according to the present embodiment has a facility configuration in which the cold rolling device 40 and the annealing device 50 are continuous, but the present invention is not limited to such an example. For example, a cold rolling device and an annealing device may be configured as separate and independent devices, and the steel sheet H after cold rolling by the cold rolling device may be transported to the annealing device and annealed.

  Next, the hot dipping line equipment 22 according to this embodiment will be described with reference to FIG. FIG. 3 is a schematic diagram showing an outline of the hot dipping line equipment 22 according to the present embodiment.

  As shown in FIG. 3, in the hot dipping line equipment 22, a rewinding machine 60 as a carry-in device and a winder 61 as a carry-out device are provided close to each other at the same height. The unwinder 60 and the winder 61 are provided on the same level as the cold rolling / annealing line equipment 20 and the packing line equipment 21 in the building, for example, and the steel sheet H can be easily carried in and out. It can be done.

  On the line from the unwinder 60 to the winder 61, an inlet side device 62 such as a shear or a welding machine, an inlet side looper 63, a pretreatment cleaning device 64 for preprocessing and cleaning the steel plate H, and a pretreatment A pre-plating device 65 for electro-Ni plating the washed steel plate H, a heating device 66 for heating the Ni pre-plated steel plate H immediately before hot dipping, a hot dipping device 67 for hot-plating the heated steel plate H, and hot dipping Alloying furnace equipment 68 for alloying steel plate H, temper rolling mill 69 for temper rolling steel plate H to adjust the thickness of steel plate H, and post-processing device for surface treatment of steel plate H 70, an exit side looper 71, and an exit side device 72 such as a trimmer, Euler, and shear are provided in order from the upstream side to the downstream side. The hot dipping line equipment 22 is formed in a substantially ring shape in a substantially vertical plane.

  For example, the entry-side looper 63 is a horizontal looper that expands and contracts in the horizontal direction, and is disposed above the rewinding machine 60 and the winding machine 61. The exit side looper 71 is also a horizontal looper and is disposed further above the entry side looper 63. In this way, the entrance side looper 63 and the exit side looper 71 are disposed so as to be stacked above the rewinding machine 60 and the winding machine 61. In the present embodiment, for example, the floor boundary is between the entrance side looper 63 and the exit side looper 71, the entrance side looper 63 side is the lower floor, and the exit side looper 71 side is the upper floor.

  The pretreatment cleaning device 64, the pre-plating device 65, the heating device 66, and the hot dipping device 67 on the exit side of the entry side looper 63 are provided at the same height on the same lower floor as the rewinding machine 60. Further, the rewinding machine 60, the pretreatment cleaning device 64, the pre-plating device 65, the heating device 66, and the hot dipping device 67 are arranged in a straight line when viewed from the plane. The hot dip plating apparatus 67 is disposed at a position farthest from the entry side looper 63 in the horizontal direction, and the path from the rewinding machine 60 to the hot dip plating apparatus 67 is the forward path of the substantially annular hot dip plating line equipment 22.

  The pretreatment cleaning device 64 is a pretreatment for performing Ni pre-plating and hot dip galvanizing on the steel sheet H, and cleans the steel sheet H to which a water-soluble rust preventive agent has been applied after the annealing. Remove unwanted material. Specifically, the pretreatment cleaning device 64 performs various processes such as spray cleaning using an alkaline liquid, brush cleaning, alkaline rinsing, and drying on the steel sheet H. The pretreatment cleaning device 64 is a characteristic component in the hot dipping line equipment 22 according to the present embodiment, and details will be described later.

As a pre-process of the hot dipping process, the pre-plating device 65 performs Ni pre-plating for applying electric Ni plating to the steel plate H cleaned by the pretreatment cleaning device 64 and activates the surface of the steel plate H. The pre-plating device 65 applies a current from a rectifier in a state where electrodes (anodes) are arranged on both sides of a steel plate H that passes through a plating solution (an aqueous solution containing Ni ions), and applies Ni as a plating metal to the steel plate H. It adheres to the surface (cathode). As a result, the steel plate H is electro Ni plated, and Ni thin films are formed on both surfaces of the steel plate H. The Ni plating adhesion amount in this Ni pre-plating is, for example, about 0.2 to 0.8 g / m ^2, which is much smaller than the adhesion amount of the hot dipping.

  The pre-plating device 65 performs, for example, pre-cleaning treatment, pickling treatment by horizontal pickling, pickle rinsing treatment, etc. on the steel plate H before Ni pre-plating, and the alkali adhering to the steel plate H. You may equip the apparatus which neutralizes a liquid.

  The heating device 66 heats the steel plate H immediately before hot dipping by causing a high current to flow through the Ni pre-plated steel plate H to generate heat by, for example, a heating method of a transformer effect type current heating method.

The hot dipping apparatus 67 performs hot dipping by attaching the plating metal to the surface of the steel plate H by immersing the hot steel plate H heated after the Ni pre-plating in the hot dipping metal stored in the hot dipping bath 67a. Here, the hot dip plating metal may be, for example, hot dip zinc or may be obtained by adding other metal such as aluminum or magnesium to hot dip zinc. In addition, the plating adhesion amount in this hot dipping is, for example, about 30 g / m ² .

  The alloying furnace equipment 68 is disposed, for example, above the hot dipping apparatus 67 and alloyes the metal hot-plated on the steel plate H. The alloying furnace equipment 68 includes, for example, an IH heating furnace, a heat retaining furnace capable of switching between hot air and cold air, a cooling device using an air-water cooling system, and the like.

  The temper rolling mill 69 and the post-processing device 70 are arranged on the exit side of the alloying furnace equipment 68, and are juxtaposed above the forward path to the hot dipping apparatus 67, for example, and the exit side looper 71 having the same height. Leads to. The temper rolling mill 69 temper-rolls the steel sheet H at a predetermined temper rolling rate for material adjustment and surface adjustment. Further, the post-processing device 70 performs an appropriate post-treatment such as chromate treatment, L treatment, Co plating treatment, etc. on the steel plate H according to the type of hot-dip plated steel plate.

  The exit side of the exit side looper 71 is provided on the opposite side of the post-processing device 70 and communicates with the lower exit side device 72. The delivery device 72 is installed at the same height on the same upper floor as the winder 61.

  The hot dipping line equipment 22 having the above-described structure is a hot dipped steel sheet by pre-washing the steel sheet H that has been carried out to remove unnecessary materials such as a rust inhibitor, and then performing Ni pre-plating and hot-dip galvanizing. Can be manufactured. As long as the hot dip galvanized steel sheet manufactured in this way is Ni pre-plated, not only GI (hot dip galvanized steel sheet), GA (alloyed galvanized steel sheet), but also Zn-0.5 % Mg-0.2% Al steel sheet, Zn-11% Al-3% Mg-0.2% Si steel sheet, Zn-5% Al-0.1% Mg steel sheet (hot-dip zinc-5% aluminum alloy plated steel sheet) , Any hot dip galvanized steel sheet such as galvalume steel sheet (hot dip-55% aluminum alloy plated steel sheet).

  Next, the pretreatment cleaning device 64 in the hot dipping line equipment 22 will be described in detail. The inventors of the present application conducted an earnest study and experiment on how to clean the rust preventive agent on the surface of the steel sheet H in a necessary and sufficient manner in the pre-treatment cleaning treatment before Ni pre-plating. It was. As a result, as shown in the following experimental results, spray cleaning using an alkaline solution and brush cleaning are sufficient to clean and remove the water-soluble rust preventive as pre-treatment cleaning for Ni pre-plating. Therefore, it was conceived that the conventional electrolytic cleaning can be omitted. Below, this experimental result and the structure of the pre-processing washing | cleaning apparatus 64 concerning this embodiment are demonstrated.

  First, in order to determine an efficient equipment specification of the pretreatment cleaning device 64, a cleaning evaluation experiment in which a test body of the steel plate H with the rust preventive agent is cleaned and the cleaning effect is evaluated will be described. Test conditions in this washing experiment are as follows.

Test material: A steel sheet coated with a water-soluble rust preventive (mainly 1-hydroxybenzotriazole Na salt) after annealing and temper rolling at a temper rolling rate of 0.4%.
Conditions of alkaline solution used for washing: NaOH solution of 5% by mass, temperature 60 ° C.
Plate speed during washing: 120m / min

  In this cleaning experiment, as shown in Table 1 below, the steel sheet was cleaned under four types of test conditions in which five types of cleaning methods were combined in various ways. For example, test condition 1 indicates that the steel sheet was cleaned by two cleaning methods of “electrolytic dip” and “alkali brush”.

The details of each cleaning method shown in Table 1 are as follows.
Electrolytic dip: Cleaning method in which steel plate is immersed in alkaline solution for electrolytic cleaning Prespray: Cleaning method in which alkaline solution is sprayed on the surface of the steel plate to clean Electrolytic spray: Electrolytic cleaning is performed while spraying alkaline solution on the surface of the steel plate Cleaning method Alkali brush: Cleaning method to wash with a nylon brush with abrasive grains while supplying alkaline liquid to the steel plate surface Hot water brush: Cleaning method to wash with a nylon brush with abrasive grains while spraying hot water on the steel plate surface

  The current densities of electrolytic cleaning in “electrolytic dip” and “electrolytic spray” were 33 A / dm and 67 A / dm, respectively. In addition, the brush rotation speed of the “alkali brush” and “warm water brush” was 900 rpm.

  The steel plate was washed under these four types of test conditions, and an experiment was conducted to evaluate the L value and water wettability of the steel plate surface after washing. The experimental results are shown in FIG. In addition, the original plate in FIG. 4 means an unwashed steel plate. Moreover, L value is the brightness of the steel plate surface, and shows a high numerical value, so that the steel plate is wash | cleaned suitably.

  As shown in FIG. 4A, the L value of the “original plate” was 85, whereas the L value of the steel plates after the cleaning under the test conditions 1 to 4 was 90. Further, as shown in FIG. 4B, the water wettability of the “original plate” was 0, whereas the L values of the steel plates after cleaning under the test conditions 1 to 4 were all 100.

  According to such experimental results, unnecessary materials adhering to the steel sheet surface by cleaning under the above test conditions 1 to 4 (such as rust preventives, rolling liquid, iron powder generated during rolling, dust in the atmosphere, etc.) However, it can be seen that it is suitably cleaned and removed. Further, it can be seen that the cleaning effects (L value, water wettability) under the respective test conditions 1 to 4 are comparable even though the cleaning methods are different.

  Therefore, if the cleaning effect is comparable, a cleaning method combining “Pre-spray” and “Alkaline cleaning” in test condition 4 is adopted from the viewpoint of reducing equipment and maintenance costs and improving cleaning efficiency. It can be said that it is preferable. That is, the cleaning method of test condition 4 does not perform electrolytic cleaning such as “electrolytic dip” and “electrolytic brush” and has a small number of cleaning steps, so that the equipment cost and maintenance cost required for the electrolytic cleaning apparatus can be reduced. At the same time, the steel sheet can be cleaned efficiently.

  Therefore, the pretreatment cleaning device 64 of the hot dipping line equipment 22 according to the present embodiment employs a cleaning method in which “pre-spray” and “alkaline brush” are combined in accordance with the example of the test condition 4 described above.

  Here, based on FIG. 5, the structure of the pre-processing washing | cleaning apparatus 64 of the hot dipping line equipment 22 concerning this embodiment is demonstrated in detail. FIG. 5 is a schematic diagram showing an outline of the pretreatment cleaning device 64 of the hot dipping line equipment 22 according to the present embodiment.

  The pretreatment cleaning device 64 according to this embodiment performs alkaline spray cleaning and alkaline brush cleaning while transferring the steel plate H from the entry side looper 63 at a predetermined feed rate (for example, 120 m / min), and the pre-plating. Send to device 65.

  Specifically, as shown in FIG. 5, the pretreatment cleaning device 64 includes a spray cleaning device 80 that sprays and cleans the steel plate H with an alkaline solution, and a brush cleaning of the sprayed steel plate H while supplying the alkaline solution. Brush cleaning device 81 for rinsing, rinse device 82 for rinsing by spraying a rinsing liquid onto brush-washed steel plate H, dryer 83 for drying the steel plate H after rinsing, and pickling for pickling the dried steel plate H A device 84, an alkaline solution circulation tank 85 for storing an alkaline solution (for example, 5% NaOH solution, solution temperature 60 ° C.) used in the spray cleaning device 80 and the brush cleaning device 81, and a rinse used in the rinse device 82 A rinsing liquid circulation tank 86 for storing a liquid (for example, water).

  The spray cleaning device 80 includes a pair of upper and lower feed rolls 91 that rotate in the feeding direction of the steel plate H to transfer the steel plate H to the downstream side, and a plurality of spraying sprays of alkaline liquid from above and below the surface of the steel plate H ( In the example of FIG. 5, a total of 6 nozzles 92 in the upper and lower pairs are provided.

Each spray nozzle 92 of the spray cleaning device 80 is continuously supplied with the alkaline liquid sent from the alkaline liquid circulation tank 85 by the pump 87, and each spray nozzle 92 supplies the alkaline liquid to, for example, 1.3 m ³ / min. Spray is sprayed on the surface of the steel plate H from above and below at a flow rate. The spray time (wet time) at this time is, for example, about 0.3 seconds or more, and the spray length is, for example, 1.4 m. The injected alkaline liquid is collected by the spray cleaning device 80, returned to the alkaline liquid circulation tank 85, and reused.

  The spray cleaning device 80 having such a configuration is adapted to clean and remove the temper rolling liquid, water-soluble rust preventive agent, etc. remaining on the surface of the steel sheet H by making them adapt to the alkaline liquid, and to raise the temperature of the steel sheet H. Can do.

  The brush cleaning device 81 is composed of, for example, a brush scrubber. The brush cleaning device 81 includes a plurality of brush rolls 93 (two in the vertical direction in the example of FIG. 5, four in total in the example shown in FIG. 5) arranged at equal intervals along the feeding direction of the steel plate H, and each brush. A plurality of backup rolls 94 (two in the upper and lower alternate in the example of FIG. 5, a total of four) arranged opposite to the roll 93 and the surface of the steel sheet H are alternately alkalinized from above and below. A plurality of spray nozzles 95 (six in the example of FIG. 5) for spraying the liquid and a pair of upper and lower feed rolls 96 that rotate in the feed direction of the steel plate H and transport the steel plate H downstream are provided.

  The brush roll 93 is made of, for example, a nylon brush containing abrasive grains, and rotates in a direction opposite to the feeding direction of the steel plate H (for example, 1200 rpm). On the other hand, the backup roll 94 is disposed so as to be paired with the brush roll 93 in the vertical direction, and rotates in the forward direction of the steel sheet H in the feed direction. The backup roll 94 has a function of transporting the steel plate H and a function of supporting the steel plate H from the opposite side of the brush roll 93 so that the steel plate H is not bent by the pressing force of the brush roll 93 during cleaning.

Further, each of the injection nozzles 95 is continuously supplied with the alkaline liquid sent from the alkaline liquid circulation tank 85 by the pump 87, and each of the injection nozzles 95 supplies the alkaline liquid at a flow rate of, for example, 0.6 m ³ / min. Spray spray onto the surface of the steel plate H. The injected alkaline liquid is recovered by the brush cleaning device 81, returned to the alkaline liquid circulation tank 85, and reused.

  The brush cleaning device 81 can mechanically and chemically brush clean the surface of the steel sheet H by rubbing the brush roll 93 against the surface of the steel sheet H while supplying an alkaline solution. As a result, the steel sheet H can be finished and cleaned, and rust preventives and the like that could not be removed by the rough cleaning by the spray cleaning device 80 can be cleaned and removed.

  The rinsing device 82 sprays a rinsing liquid (for example, hot water) from above and below the surface of the steel plate H, and two pairs of upper and lower feed rolls 97 that rotate in the feed direction of the steel plate H and transport the steel plate H downstream. And a plurality of jet nozzles 98 (6 in total in the upper and lower pairs in the example of FIG. 5).

The rinsing liquid sent out by the pump 88 from the rinsing liquid circulation tank 86 is continuously supplied to each spray nozzle 98 of the rinsing device 82, and each spray nozzle 98 supplies this rinsing liquid at a flow rate of, for example, 1.0 m ³ / min. Then, the surface of the steel plate H is sprayed from above and below. The injected rinse liquid is collected by the rinse device 82, returned to the rinse liquid circulation tank 86, and reused.

  The rinsing device 82 has a function of removing the alkaline liquid adhered to the steel sheet H by the spray cleaning device 80 and the brush cleaning device 81 by spraying the rinsing liquid.

  The dryer 83 dries the wet steel plate H that has been cleaned and rinsed as described above by, for example, a steam heat exchange method. The pickling device 84 cleans the steel sheet H after being dried by the dryer 83 with sulfuric acid, hydrochloric acid, or the like. The pickled steel plate H is transferred to the pre-plating device 65 and subjected to electro Ni plating.

  As described above, the pretreatment cleaning apparatus 64 according to the present embodiment includes only the spray cleaning apparatus 80 and the brush cleaning apparatus 81 as the cleaning means, and does not include the electrolytic cleaning apparatus. Is simple and has few installations. As a result, the equipment cost and maintenance cost required for the electrolytic cleaning apparatus can be reduced, and the cleaning can be efficiently performed by performing only the necessary and sufficient cleaning process for the steel plate H before Ni pre-plating.

  Next, in order to enhance the cleaning effect of the pretreatment cleaning device 64, the results of examination of a suitable temper rolling rate when temper rolling the steel plate H after the annealing will be described.

  As described above, in the temper rolling mill 55 of the cold rolling / annealing line facility 20 according to the present embodiment, the temper rolling is performed on the steel plate H after annealing. By adding a rust preventive agent, the rust preventive agent is applied simultaneously with temper rolling. However, as a result of intensive research by the inventors of the present application, if the temper rolling rate during temper rolling is too large, the rust preventive agent is pushed into the concave and convex portions on the surface of the steel sheet H during temper rolling. As a result, it has been found that it is difficult to remove the rust preventive agent uniformly during the pretreatment cleaning before the Ni pre-plating. Therefore, the inventors of the present application conducted an experiment on the correlation between the temper rolling rate of the steel plate H and the subsequent cleaning effect of the rust inhibitor on the surface of the steel plate H in order to find an appropriate temper rolling rate.

  In this experiment, temper rolling of the steel sheet H was performed by changing the temper rolling rate in multiple stages (5 stages of 0%, 0.2%, 0.4%, 0.6%, 0.8%) The surface of the steel sheet H temper-rolled at each temper rolling rate is washed with ethanol and ion-exchanged water, the cleaning solution is concentrated, and the rust inhibitor remains on the steel sheet H surface by high-performance liquid chromatography (HPLC). The amount was quantified. A hydroxybenzotriazole (HBT) aqueous solution was used as the rust inhibitor. FIG. 6 is a graph showing the results of such an experiment, where the horizontal axis is the cleaning time (defatting time), and the vertical axis is the residual HTB ion amount (residual amount of the rust inhibitor).

As shown in FIG. 6, it can be seen that the smaller the temper rolling ratio, the smaller the amount of rust inhibitor remaining on the surface of the steel plate H after cleaning, and the higher the cleaning effect. Generally, at the time of Ni pre-plating, if the remaining amount of the rust preventive agent on the surface of the steel sheet H is 20 μg / m ² , Ni pre-plating can be suitably performed without unevenness. Therefore, it can be seen from FIG. 6 that the temper rolling ratio needs to be 0 to 0.4% in order to achieve this target level of 20 μg / m ² or less.

  Based on the experimental results, in the temper rolling mill 55 of the cold rolling / annealing line facility 20 according to the present embodiment, the temper rolling rate of the steel sheet H is adjusted to be 0% or more and 0.4% or less. ing. By restricting the temper rolling rate to 0.4% or less in this way, it is possible to suppress the rust inhibitor from being pushed into the recesses on the surface of the steel sheet H during temper rolling, and therefore, during cleaning by the pretreatment cleaning device 46, The rust inhibitor can be easily and uniformly removed. Therefore, Ni pre-plating can be suitably performed without unevenness on the steel sheet H from which the rust preventive agent has been suitably removed. The same result can be obtained even when other water-soluble rust preventives described above are used.

  The configuration of the hot-dip plated steel sheet manufacturing facility 1 according to the present embodiment has been described above in detail. Next, based on FIG. 7, the manufacturing method of the hot dipped steel plate using this hot dipped steel plate manufacturing equipment 1 will be described. FIG. 7 is a flowchart showing a method for manufacturing a hot-dip galvanized steel sheet according to this embodiment.

  As shown in FIG. 7, first, in the cold rolling / annealing line facility 20, the steel sheet H is cold rolled by the cold rolling mill 47 and then annealed by the annealing furnace 52 (step S10: cold rolling / annealing step). ).

  Next, the steel plate H after annealing is temper-rolled by a temper rolling mill 55 using a temper rolling solution containing a water-soluble rust preventive agent, and the rust preventive agent is applied to the surface of the steel plate H. (Step S12: Temper rolling process and rust preventive coating process). The temper rolling ratio at the time of temper rolling is adjusted to be 0 to 0.4% so that the rust preventive agent is not pushed into the steel sheet H surface. When the temper rolling rate is 0%, the steel sheet H is passed through the temper rolling mill 55 and no reduction is performed.

  As described above, in this embodiment, the temper rolling process and the rust preventive coating process are simultaneously performed by adding the rust preventive agent to the temper rolling solution, thereby improving the production efficiency. However, the present invention is not limited to such an example. For example, the temper rolling process and the rust preventive coating process may be separate processes. Specifically, for example, a rust preventive coating device (not shown) that sprays a liquid containing a water-soluble rust preventive agent is installed, and the rust preventive coating device is used after the temper rolling. A rust inhibitor may be applied to the steel plate H. Further, the temper rolling step may be omitted, and a water-soluble rust preventive may be applied to the annealed steel sheet H without performing temper rolling. Also by these, the rust preventive agent can be prevented from being pushed into the surface of the steel sheet H, and the rust preventive agent can be easily and uniformly cleaned in the subsequent process.

  Thereafter, the steel plate H to which the rust preventive agent has been applied as described above is stored, for example, in the storage unit 31 of the second finishing building 12 for a predetermined period (step S14). Specifically, the coiled steel plate H on the exit side of the cold rolling / annealing line facility 20 is conveyed from the first adjustment building 11 to the second adjustment building 12 by the relay line A and relayed by the crane 32, for example. The product is transported from the exit side of the line A to the storage unit 31 and stored in the storage unit 31. If necessary, the steel plate H of the storage unit 31 may be transported to the finishing line 36 by the crane 32, and the width of the steel plate H and the like may be adjusted in the finishing line 36. Thereafter, the steel plate H stored in the storage unit 31 is transported into the transport passage 15 by the crane 33 and transported into the hot dipping ridge 14 by the carriage 34. Thus, the steel plate H is installed in the rewinding machine 60 of the hot dipping line equipment 22 shown in FIG.

  Next, the steel sheet H coated with the rust preventive agent is cleaned with an alkaline solution by the pretreatment washing machine 64 without performing electrolytic washing (step S16: pretreatment washing step). Specifically, the steel plate H installed in the unwinding machine 60 of the hot dipping line equipment 22 passes through the entry side device 62 and is sent to the upper entry side looper 63, and then to the pretreatment cleaning device 64. Be transported. In the pretreatment cleaning device 64, the transported steel plate H is roughly cleaned by the spray cleaning device 81 by spraying an alkaline solution, and then finished using a brush roll 93 while supplying the alkaline solution by the brush cleaning device 82. Further, the pretreatment cleaning is completed through the rinsing process by the rinsing apparatus 82, the drying process by the dryer 83, and the pickling process by the pickling apparatus 84.

  Thereafter, the cleaned steel plate H is electro Ni plated by the pre-plating device 65 (step S18: Ni pre-plating step). In such a Ni pre-plating process, hydrogen gas is generated along with Ni precipitation, so that this hydrogen gas has an effect of removing the rust preventive that remains slightly on the steel sheet H. As a result, the occurrence of unevenness in Ni plating can be suppressed.

  Further, the steel plate H after the Ni pre-plating is rapidly heated at a low temperature by energization by the heating device 66 and continuously dipped in the hot-dip metal containing molten Zn by the hot-dip plating device 67 to be hot-plated (step S20). : Hot dipping process). Thereafter, the hot-plated steel sheet H passes through the alloying furnace equipment 68, the temper rolling mill 69, and the post-processing device 70, and is sent to the exit side looper 71. Thereafter, the steel plate H passes through the delivery device 72 and is taken up by the winder 61.

  Next, the coiled steel sheet H wound up by the winder 61 is transported into the transport path 15 by the carriage 34 as shown in FIG. 1, for example, and is stored in the storage unit 31 of the second finishing building 12 by the crane 33. Is housed in. Thereafter, the steel plate H is transported onto the packaging line facility 21 by the crane 32. The steel plate H returned to the packing line facility 21 is transported to the warehouse 13 side by the packing line facility 21 and packed (step S22: packing step).

  As described above, in the method for manufacturing a hot-dip galvanized steel sheet according to this embodiment, a water-soluble rust inhibitor is applied to the annealed steel sheet H to prevent rust during storage, and this rust inhibitor is Prior to Ni pre-plating of the coated steel sheet H, the rust inhibitor can be removed sufficiently and sufficiently by alkaline cleaning without electrolytic cleaning.

As described above, when the electrolytic cleaning used in the conventional pretreatment cleaning is performed, for example, Fe—OH is dissolved in the cleaning liquid or other metal impurities are mixed, so that the metal impurity ions are converted into the steel plate H. It may adhere to and deposit on the surface. In Ni pre-plating, the amount of adhesion is very small, for example, 0.2 to 0.8 mg / cm ² , and it is necessary to be uniformly plated. There is a need to. For this reason, the pretreatment cleaning process according to the present embodiment is characterized in that electrolytic cleaning is omitted in order to prevent adhesion and deposition of metal impurity ions during cleaning.

  In addition, the conventional electrolytic cleaning apparatus has been mainly used for removing mineral oil, and oil-based rolling oil such as beef tallow and palm oil. However, like the above-described hot-plated steel sheet manufacturing equipment 1 according to the present embodiment, when the temper rolling ratio after annealing is limited and a water-soluble rust preventive agent is used, an electrolytic cleaning device is not required. With this, equipment costs and maintenance costs can be significantly reduced.

  Next, in the Ni pre-plating pretreatment cleaning step S16 as described above, even if the electrolytic cleaning required in the conventional electrogalvanization pretreatment is not performed, the Ni preplating pretreatment is sufficiently and sufficiently prevented. The reason why the rusting agent can be cleaned and removed will be described.

In the cleaning evaluation experiment results shown in FIG. 4, the L value and water wettability of the steel plates after cleaning were the same regardless of whether or not electrolytic cleaning was performed. From this result, it is concluded that the electrolytic cleaning may be omitted in the pretreatment cleaning device 64 before Ni pre-plating. Further, as described in the experiment of the temper rolling ratio in FIG. 6 above, it is preferable that the remaining amount of the rust inhibitor during Ni pre-plating is 20 μg / m ² or less. From these results, if the remaining amount of the rust inhibitor is 20 μg / m ² or less, the water wettability of the steel sheet H is good, and Ni pre-plating can be suitably performed.

  On the other hand, in general electrogalvanizing, as described in Patent Document 1 above, if even one atomic layer has a rust inhibitor remaining, plating unevenness may occur. Was necessary.

Considering all of the above, in the case of Ni pre-plating, plating can be performed if the remaining amount of the rust inhibitor is 20 μg / m ² or less without performing electrolytic cleaning. Electrolytic cleaning is also necessary. Therefore, it is considered that the residual level of the rust inhibitor required for electrolytic galvanization is even lower than 20 μg / m ² .

Therefore, the reason why electrolytic cleaning can be omitted in the case of Ni pre-plating is that the residual level of rust inhibitor required during Ni pre-plating (20 μg / m ² or less) is looser than the level required for electrogalvanizing. Furthermore, the reason why the remaining amount level is loose is considered to be that the rust preventive agent is easily removed from the surface of the steel sheet H at the time of Ni pre-plating compared to the case of electrogalvanizing.

  That is, in terms of ionization tendency, since it becomes difficult to ionize in the order of Zn, Fe, and Ni, Ni substitutes plating on Fe (Fe melts out and plating is performed without flowing electricity), but Zn is Fe. (Zn dissolves first. The principle of sacrificial corrosion protection of zinc plating). In general, Ni has a high precipitation overvoltage, and hydrogen generation tends to occur simultaneously. For this reason, at the time of Ni pre-plating, it is thought that this hydrogen gas generation also exhibits the dirt removing action on the surface of the steel sheet H. Therefore, at the time of Ni pre-plating, even if some rust preventive agent remains on the surface of the steel sheet H, the anti-rust agent can be easily removed by the action of removing the dirt of the hydrogen gas.

  Here, in order to explain the principle that the antirust agent can be easily removed from the steel plate H during Ni pre-plating, the adsorption mechanism of the antirust agent to the surface of the steel plate H will be described.

  The adsorption mechanism of the rust inhibitor on the surface of the steel sheet H includes physical adsorption and chemical adsorption, but in any of the adsorption mechanisms, as shown in FIG. A rust film is formed to rust prevent the surface of the steel plate H. The molecules of this rust preventive are not firmly bonded to the steel sheet H, but are attached to or separated from the surface of the steel sheet H, and a standby molecule that should be immediately adsorbed when separated is required. . Further, the atomic groups adsorbed on the surface of the steel plate H are easily dissolved in water (hydrophilic group), and enter the water film on the surface of the steel plate H to be adsorbed. As atoms having such adsorption ability, there are nitrogen N, oxygen O, phosphorus P, sulfur S, etc., but compounds actually having nitrogen atom N are actually used as water-soluble rust preventives. The representative is amine.

  Further, when the water-soluble rust preventive agent adheres to the surface of the steel plate H by about one atomic layer, a negative group is present on the steel plate H side and a positive group is present on the opposite side of the steel plate H as shown in FIG. It is thought that the rust preventive is oriented so that At this time, as other adsorbents existing on the surface of the steel sheet H, there are an adsorbed layer (water film) such as water, CO2 in the atmosphere, and dirt.

  Thus, when Ni pre-plating is performed with water-soluble rust inhibitor molecules adhering to the surface of the steel sheet H, hydrogen gas is generated as described above, and this hydrogen gas converts the rust inhibitor to the steel sheet. It has the effect of peeling off from the H surface. At this time, since the water-soluble rust inhibitor molecules are electrically oriented as described above, they are easily peeled off by the generated hydrogen gas. In addition, when an oil-based rust preventive agent is used, since the oil-based rust preventive agent which is a polymer adheres firmly to the surface of the steel sheet H, it seems that removal is difficult unless electrolytic cleaning is performed.

  For the reasons described above, if a water-soluble rust inhibitor with relatively low adhesion compared to an oil-based rust inhibitor is used, the conventional electrogalvanizing pre-treatment washing in the pre-treatment washing prior to Ni pre-plating Even if it does not perform the electrolytic cleaning performed in step 1, the water-soluble rust inhibitor is moderately applied from the surface of the steel plate H only by spray cleaning and brush cleaning like the pretreatment cleaning device 64 according to the present embodiment. It can be cleaned and removed, and uniform Ni pre-plating can be realized. Therefore, the electrolytic cleaning apparatus can be omitted, and the equipment cost and maintenance cost can be greatly reduced, and the cleaning process can be made more efficient.

  Furthermore, when electrolytic cleaning is performed, metal impurity ions may adhere to and precipitate on the surface of the steel sheet H, which may adversely affect Ni pre-plating. Therefore, from this point of view, it is preferable not to perform electrolytic cleaning. However, in this embodiment, since electrolytic cleaning is not performed, the adhesion and deposition of metal impurity ions as described above can be prevented, and Ni pre-plating can be performed uniformly. Can be executed.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

It is a schematic diagram which shows the outline of the manufacturing equipment of the hot dipped steel plate concerning the 1st Embodiment of this invention. It is a schematic diagram which shows the outline of the cold rolling and annealing line equipment concerning the embodiment. It is a schematic diagram which shows the outline of the hot dipping line equipment concerning the embodiment. It is a graph which shows the result of the washing | cleaning evaluation experiment by a multiple types of washing | cleaning system. It is a schematic diagram which shows the outline of the pre-processing washing | cleaning apparatus of the hot dipping line equipment concerning the embodiment. It is a graph which shows the experimental result about the correlation with the temper rolling rate of a steel plate, and the cleaning effect of a rust preventive agent. It is a flowchart which shows the manufacturing method of the hot dipped steel plate concerning the embodiment. It is explanatory drawing explaining the adsorption | suction mechanism to the steel plate surface of a rust preventive agent.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Manufacturing equipment of hot dip galvanized steel sheet 20 Cold rolling / annealing line equipment 21 Packing line equipment 22 Hot dip plating line equipment 40 Cold rolling equipment 47 Cold rolling mill 50 Annealing equipment 52 Annealing furnace 55 Temper rolling mill 64 Pretreatment washing equipment 65 Pre-plating device 66 Heating device 67 Hot dipping device 68 Alloying furnace equipment 80 Spray cleaning device 81 Brush cleaning device 82 Rinsing device 83 Dryer 84 Pickling device 85 Alkaline liquid circulation tank 86 Rinse liquid circulation tank 91 Feed roll 92 Injection nozzle 93 Brush roll 94 Backup roll 95 Injection nozzle 96 Feed roll H Steel plate

Claims (9)

An annealing process for annealing the steel sheet;
A rust preventive coating step of applying a water-soluble rust preventive to the annealed steel sheet;
A cleaning step of cleaning the steel sheet coated with the rust preventive agent using an alkaline solution without electrolytic cleaning;
A Ni pre-plating step of electro-Ni plating the cleaned steel plate;
A hot dipping process in which the steel plate after the Ni pre-plating is dipped in a hot dipped metal containing molten Zn and hot dipped;
Including
After the annealing step, further includes a temper rolling step of temper rolling the annealed steel sheet using a temper rolling solution,
The method for producing a hot-dip galvanized steel sheet, wherein the rust preventive coating step is performed by including the water-soluble rust preventive in the temper rolling solution in the temper rolling step . The washing step includes
A spray cleaning step of cleaning the steel sheet coated with the rust inhibitor by spraying an alkaline liquid;
A brush cleaning step of cleaning the steel plate after the spray cleaning with a brush while supplying an alkaline solution;
The manufacturing method of the hot dipped steel plate of Claim 1 characterized by the above-mentioned.   3. The hot-dip plated steel sheet according to claim 1, wherein, in the cleaning step, the electrolytic cleaning is not performed in order to prevent metal impurity ions from adhering to and precipitating on the surface of the steel sheet due to the electrolytic cleaning. Manufacturing method. In the said washing | cleaning process, it wash | cleans so that the residual amount of the said rust preventive agent in a steel plate surface may be 20 microgram / m < ² > or less, The manufacturing method of the hot dipped steel plate in any one of Claims 1-3 characterized by the above-mentioned. . The method for producing a hot-dip galvanized steel sheet according to any one of claims 1 to 4, wherein a temper rolling ratio in the temper rolling step is 0% or more and 0.4% or less. An annealing process for annealing the steel sheet;
A rust preventive coating step of applying a water-soluble rust preventive to the annealed steel sheet;
A cleaning step of cleaning the steel sheet coated with the rust preventive agent using an alkaline solution without electrolytic cleaning;
A Ni pre-plating step of electro-Ni plating the cleaned steel plate;
A hot dipping process in which the steel plate after the Ni pre-plating is dipped in a hot dipped metal containing molten Zn and hot dipped;
Including
Further comprising a temper rolling step of temper rolling the annealed steel sheet using the temper rolling liquid not containing the water-soluble rust inhibitor;
In the rust preventive agent coating step, the water-soluble rust preventive agent is applied to the steel sheet after the temper rolling .   The washing step includes
  A spray cleaning step of cleaning the steel sheet coated with the rust inhibitor by spraying an alkaline liquid;
  A brush cleaning step of cleaning the steel plate after the spray cleaning with a brush while supplying an alkaline solution;
The manufacturing method of the hot dipped steel plate of Claim 6 characterized by the above-mentioned.   The hot-dip galvanized steel sheet according to claim 6 or 7, wherein in the cleaning step, the electrolytic cleaning is not performed in order to prevent metal impurity ions from adhering to and precipitating on the surface of the steel sheet due to the electrolytic cleaning. Manufacturing method.   In the washing step, the residual amount of the rust inhibitor on the steel sheet surface is 20 μg / m. ² The method for producing a hot-dip galvanized steel sheet according to any one of claims 6 to 8, wherein the hot-dip steel sheet is washed so as to be as follows.

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