JP4710619B2 - Method for producing tin-plated steel strip and tin-plating cell - Google Patents

Description

  The present invention relates to a method for producing a tin-plated steel strip and a tin-plating cell, and in particular, a method for producing a tin-plated steel strip for continuously tin-plating a steel strip to be plated using a horizontal plating cell, and its The present invention relates to a horizontal tin plating cell used for manufacturing.

  There are roughly two types of electrotin plating equipment: vertical plating equipment using a vertical plating cell and horizontal plating equipment using a horizontal plating cell. Furthermore, the electrotin plating equipment using a horizontal plating cell has a stannous chloride bath (halogen bath) having a pH of 3 to 4, depending on the type of plating solution, an alkanol sulfonic acid bath (ASA bath) having a pH of 1 or less, Similarly, it is divided into a methanesulfonic acid bath (MSA bath) having a pH of 1 or less. Each facility usually has a three-stage plating section, with a plurality of horizontal plating cells arranged horizontally in the lower two stages, and a drag-out tank and a water washing device arranged in the uppermost stage. ing.

  When manufacturing a tin-plated steel strip using the above horizontal plating cell, the steel strip activated by degreasing, pickling and activating at the entry side of the equipment is first placed in the horizontal plating cell row at the bottom. Transport and apply tin plating only to the lower surface of the steel strip, then change the direction of the steel strip by 180 ° and transport it from the opposite direction to the middle horizontal plating cell row to transport the lower surface of the steel strip In other words, tin plating is applied only to the upper surface at the bottom, and then the direction of the steel strip is further changed by 180 ° to be transported to the top dragout tank and washing tank for cleaning, and then as necessary. Reflow treatment and chemical treatment to produce a tin-plated product.

  As shown in the schematic cross-sectional view shown in FIG. 1, the horizontal type tin plating cell is disposed on the plating tank 1 and on the front and rear sides of the steel strip S (that is, on the entry / exit side) of the plating tank. It consists of a pair of rolls of an energizing roll 2 and a back-up roll 3. The plating tank 1 has a rubber lining on the surface, and the inside thereof is filled with a plating solution 4, and the plating solution 4 is circulated. Inside the plating tank 1, a tin anode (soluble anode) 5 made of metallic tin is placed on a carbon or titanium clad anode bed (conducting support base) 6 with a uniform length in the longitudinal direction of the coil. They are placed side by side. The anode bed 6 is installed so that the upper surface has a gradient in the plate width direction so that a constant distance of 25 to 30 mm is always maintained between the steel strip S and the anode 5 even if the anode is gradually melted during plating. . The used anode 5 is pushed out in the plate width direction and taken out, and a new anode is supplied from the other end.

  Tin plating using this horizontal plating cell is performed as follows. The steel strip S degreased and pickled on the entry side of the plating facility is guided by the energizing roll 2 and the backup roll 3 and carried into the plating tank 1 (from right to left in FIG. 1). The plating tank 1 is filled with a plating solution 4, and the liquid level is controlled so that the plating solution 4 is always in contact with the lower surface of the steel strip S while the steel strip S passes through the plating cell. On the other hand, the tin anode 5 and the energizing roll 2 are energized through a direct current power source 7 and a conductor 8, and steel is eluted from a soluble tin anode made of metallic tin and becomes a cathode (cathode). Tin plating is performed by depositing metallic tin on the lower surface of the band S.

  By the way, when electrotin plating is performed using a horizontal type plating cell as shown in FIG. 1, as shown in FIG. 2, as the steel strip advances, the plating solution in contact with the lower surface of the steel strip is changed. While moving together with the steel strip, it also moves around the upper surface of the steel strip to cause liquid covering, and forms a large liquid pool on the front surface of the current-carrying roll on the downstream side of the plating tank. As a result, there is a problem that metal tin is deposited on the upper surface of the steel strip, which is a non-plated surface, and causes overcoating of the edge portion. In addition, this edge overcoating not only causes a decrease in current efficiency in tin plating and a reduction in tin basic unit, but also causes a build-up when a tin-plated steel strip is wound around a coil. .

  Furthermore, the flow of the plating solution accompanying the progress of the steel strip causes the concentration of the plating solution downstream of the plating tank and hinders the smooth liquid flow, thereby causing the plating solution to stay. When the plating solution stays, the temperature of the solution rises and exceeds the allowable range of the brightener contained in the plating solution. As a result, there is a problem that the surface of the tin-plated surface after reflow causes a gloss failure.

As a countermeasure against such a problem, for example, Patent Document 1 discloses a technique for preventing liquid covering by installing a roll pair with a steel strip sandwiched upstream of an energizing roll.
JP-A-2005-307250

  The technique of the said patent document 1 exhibits a moderate effect in reducing the precipitation of metallic tin to a non-plating surface at the point which suppresses the liquid covering to the steel strip upper surface in the electricity supply roll front surface of an exit side. . However, the actual situation is that it is far from simply preventing the deposition of metallic tin on the non-plated surface and the deterioration of the surface quality due to the retention of the plating solution simply by suppressing the liquid covering.

  Therefore, an object of the present invention is to provide a method for producing a tin-plated steel strip that prevents edge overcoating and is excellent in surface quality, and a horizontal tin-plating cell used for the production.

  The inventors have intensively studied in order to solve the above-described problems of the prior art. As a result, in the horizontal tin plating cell, if the plating solution discharge port is provided on the outlet side of the plating tank and the plating solution moving with the progress of the steel strip is discharged, the flow of the plating solution will be smooth. The liquid pool on the front surface of the energizing roll can be eliminated, and the retention of the plating solution is also eliminated. As a result, it has been found that the deposition of metallic tin on the non-plated surface and the deterioration of the surface quality can be effectively suppressed, and the present invention has been completed. .

That is, the present invention relates to a plating tank having a soluble tin anode and a plating solution, and an energizing roll and a backup roll that are arranged on each of the inlet side and the outlet side of the plating tank and continuously convey the steel strip to be plated. In a method for producing a tin-plated steel strip by energizing between the tin anode and the steel strip to be plated using a horizontal tin plating cell comprising a pair of rolls, a plating solution is discharged on the outlet side of the plating tank. A method for producing a tin-plated steel strip characterized by using a horizontal tin-plating cell of a methanesulfonic acid bath provided with an outlet.

The present invention also provides a plating tank having a soluble tin anode and a plating solution, and an energizing roll and a backup roll that are disposed on each of the entry side and the exit side of the plating tank and continuously convey the steel strip to be plated. A horizontal tin plating cell for a methanesulfonic acid bath , wherein a plating solution discharge port is provided on the outlet side of the plating tank.

  According to the present invention, since the flow of the plating solution in the plating tank in the horizontal tin plating cell can be made smooth, the liquid pool on the front surface of the energizing roll and the stay of the plating solution on the downstream side of the plating tank can be eliminated. Precipitation of metallic tin on the surface can be greatly reduced, and surface quality can be improved. In addition, by reducing the deposition of metallic tin on the non-plated surface, it is possible to improve the current efficiency in tin plating and reduce the tin basic unit.

  The inventors examined the cause of metal tin deposition on the non-plated surface and the stagnation of the plating solution and the preventive measures thereof in the prior art. As a result, both of the two problems are caused by the downstream flow of the plating solution that occurs as the steel strip progresses during the plating process. Therefore, if the flow of the plating solution is controlled, I came up with a good thing.

  The flow of the liquid in the plating tank in the conventional horizontal tin plating cell is indicated by black arrows in FIG. In the conventional cell, the plating solution is supplied from the bottom on the entry side of the plating tank, and the plating solution that circulates in the plating tank overflows from the entry side upper portion of the plating tank and is discharged. On the other hand, during plating, a flow of the plating solution that occurs with the progress of the steel strip, which is different from the flow of the plating solution, occurred, and the flow directly hit the front surface of the delivery-side energizing roll. Moreover, since there is no discharge port for the plating solution on the outlet side of the plating tank, a large liquid pool is generated on the front surface of the energizing roll, and the liquid level of the plating solution is increased. ). Furthermore, since the plating solution moved to the outlet side of the plating tank had no place to go, it was estimated that the plating solution stayed on the outlet side of the plating tank and caused an increase in the temperature of the plating solution.

  Therefore, the inventors conceived of modifying the structure of the plating cell and providing a discharge port for discharging the plating solution on the outlet side of the plating tank, thereby completing the present invention.

  FIG. 3 shows an example of the plating cell according to the present invention, which is for modifying the downstream side (exit side) of the plating cell where the plating solution concentrates as the steel strip progresses, and for discharging the plating solution. A plating solution discharge port 9 is newly installed. Further, in the figure, the flow of the plating solution changed by the installation of the plating solution discharge port 9 is indicated by a black arrow. From this, in the conventional plating cell, the plating solution that reached the outlet energizing roll formed a large liquid pool, but in the plating cell of the present invention, plating was performed from the plating solution discharge port installed immediately before the energizing roll. As a result of discharging the liquid, the liquid pool formed immediately before the outlet-side energizing roll becomes very small. Furthermore, since the liquid level of the plating tank is lowered as the liquid pool is reduced, an effect of reducing the liquid covering formed on the upper surface of the steel strip is also obtained. In addition, as a result of the plating solution being discharged from the plating solution discharge port, the retention of the plating solution generated downstream of the plating bath is eliminated, and the temperature of the plating solution in the plating bath is also made uniform.

  As a result, when the tin-plated steel strip is manufactured using the plating cell of the present invention, the deposition of metallic tin on the non-plated surface is reduced, not only the defects due to edge overcoating are reduced, but also the plating solution Gloss defects due to temperature rise can also be reduced. Furthermore, as a result of the decrease in the deposition of metallic tin on the non-plated surface, it is possible to achieve an improvement in the basic unit of tin as a plating raw material and an improvement in current efficiency. In addition, when the plating cell of the present invention is used, it is possible to suppress the accumulation of liquid on the front surface of the energizing roll and to prevent the deposition of metallic tin on the energizing roll. It is also effective in reducing defects caused by surface defects such as adhesion of tin powder and squeezing.

  In addition, it is preferable to provide the plating solution discharge port installed in the plating tank of the present invention at positions symmetrical with respect to the center in the plate width direction at both ends in the plate width direction where the steel strip does not pass on the plating tank exit side. . It is preferable that this plating solution discharge port can adjust the opening area so that the discharge amount of the plating solution can be adjusted. Furthermore, it is preferable to provide a shielding dam (weir) on the upstream side of the plating solution outlet of the plating tank. This dam can block the flow of the plating solution accompanying the progress of the steel strip, increase the effect of suppressing the liquid covering, and can effectively prevent the precipitation of metallic tin on the energizing roll. FIG. 4 shows an example of another plating cell of the present invention provided with a shielding dam.

  Moreover, the tin plating tank of the present invention can be applied to any electroplating equipment that uses a horizontal tin plating cell, regardless of the type of plating tank, but plating using a methanesulfonic acid bath It is preferable to apply to equipment. This is because the methanesulfonic acid bath has a low pH and the elution of Fe from the steel strip is likely to occur, so that the plating cell of the present invention having a liquid covering suppression effect has a large effect of suppressing an increase in Fe concentration. .

In an electric tin plating facility in which horizontal tin plating cells of a methanesulfonic acid bath are arranged at 10 cells at the bottom and 10 cells at the middle, the conventional type plating cell shown in FIG. 2 and the book shown in FIG. 3 and FIG. Using the plating cell having the plating solution discharge port according to the invention, tin-plated steel is applied under the plating conditions shown in Table 1 for a process material having a tin adhesion amount of 1.12 / 1.12 (g / m ² ). 100 coils and 50 coils were manufactured for each band, and the following items were compared.
a. Edge overcoating amount:
Measure the amount of tin adhered to the total of four locations on both sides of the front and back using the electrolytic stripping method specified in JIS G3303; The adhesion amount of tin in the conventional plating cell was 1.0, and the edge overcoating amount in the cell of the present invention was relatively compared.
b. Incidence of metal tin deposition on current rolls:
In the tin plating facility, the current-carrying roll is visually observed once every 5 coils, and when metal tin is deposited on the current-carrying roll even in one cell, it is evaluated that metal tin is deposited on the current-carrying roll. The occurrence rate in the conventional plating cell was 1.0, and the occurrence rate in the cell of the present invention was relatively compared.
c. Variation in plating solution temperature in plating tank:
Measure the temperature of the plating solution at three locations in the plating tank (plating solution inlet and plating solution outlet 2 locations) in any one cell at a frequency of once every 5 coils. (Maximum temperature-Minimum temperature) Was determined as a variation in liquid temperature.

  The results of the measurement are shown together in Table 1. From Table 1, when using the plating cell of the present invention, compared to the conventional type of plating cell, not only can the amount of edge overcoating and the occurrence rate of metal tin deposition on the energizing roll be significantly reduced, Uniformity of the plating solution temperature in the plating tank can be achieved. Furthermore, it was also found in a separate investigation that the amount of Fe elution in the methanesulfonic acid bath can be reduced by about 20% when the plating cell of the present invention is used.

It is a figure explaining the structure of a horizontal type plating cell. It is a figure explaining the conventional horizontal type plating cell. It is a figure explaining the horizontal type plating cell of the present invention. It is a figure explaining the other example of the horizontal type plating cell of this invention.

Explanation of symbols

S: steel strip 1: plating tank 2: energizing roll 3: backup roll 4: plating solution 5: tin anode (soluble anode)
6: Anode bed (energizing support)
7: DC power supply 8: Conductor 9: Plating solution outlet 10: Shielding dam

Claims (2)

A plating tank comprising a soluble tin anode and a plating solution, and a pair of rolls of an energizing roll and a backup roll that are disposed on the entry side and the exit side of the plating tank and continuously convey the steel strip to be plated. In a method for producing a tin-plated steel strip by energizing between the tin anode and the steel strip to be plated using a horizontal tin plating cell, methanesulfone provided with a plating solution outlet on the outlet side of the plating tank A method for producing a tin-plated steel strip, characterized by using an acid bath horizontal tin-plating cell. A plating tank comprising a soluble tin anode and a plating solution, and a pair of rolls of an energizing roll and a backup roll that are disposed on the entry side and the exit side of the plating tank and continuously convey the steel strip to be plated. A horizontal tin plating cell for a methanesulfonic acid bath, characterized in that a plating solution discharge port is provided on the outlet side of the plating tank .

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