JP2008303431A - Hot dip metal coating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hot dip metal coating apparatus with which bottom dross can be sufficiently removed even when a dam for an ingot is used and defects caused by swirling-up of the bottom dross can be reduced. <P>SOLUTION: The hot dip metal plating apparatus is equipped with a pump suction port arranged at the lower part of a dam, a molten metal pump for sucking dross together with molten metal in a molten metal bath from the pump suction port, and a removing means for separating and removing dross in the sucked molten metal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a molten metal plating apparatus that can efficiently remove dross in a molten metal plating bath and reduce adhesion of dross to a product.

As a typical hot-dip metal plating method for steel plates, after pre-treatment such as degreasing, the steel plates are heated with a predetermined heating pattern, cooled, and then immersed in a plating bath in which the metal to be plated is melted to adhere to the plating. After controlling the amount, there is a method of cooling to room temperature with a predetermined cooling pattern.

When an ingot for replenishing a consumable component due to plating into the bath is introduced into the molten metal plating bath, a low temperature ingot dissolving flow is generated along with the ingot melting, and the temperature is lowered around the ingot. In general, the composition of an ingot is different from that of a molten metal bath. Thus, when a sudden change in temperature and component concentration around the ingot occurs, metal compound fine particles called dross are likely to be generated.

For example, in the case of hot dip galvanization, which is a typical example of hot metal plating, dross is generated by the reaction of Fe in a steel plate with Zn in a zinc bath, Al added in the zinc bath, and the like. Of these, heavy dross composed mainly of FeZn ₇ is called bottom dross and is deposited at the bottom of the molten zinc pot. Since this bottom dross is as small as several tens of μm to 1 mm, it is easily wound up by molten zinc flow, and is likely to adhere to the steel sheet and cause defects.

In order to cope with this, for example, there is a method disclosed in Patent Document 1. In this method, weirs (hereinafter referred to as ingot weirs) that cover the ingot input region are provided to suppress rapid changes in temperature and components, thereby suppressing dross generation.
The prior patent documents are described below. Note that Patent Document 2 is referred to in the disclosure section below.
JP-A-5-186857 JP-A-7-207418

  The method disclosed in Patent Document 1 described above is excellent in that the ingot weir can suppress drastic changes in bath temperature and component concentration at the time of charging the ingot, thereby suppressing the generation of dross and producing a product with few defects. Although it is a method, however, dross generation cannot be completely stopped even if an ingot weir is used, and it is inevitable that a certain amount of bottom dross is generated.

  For example, in a molten metal plating apparatus having an ingot weir, bottom dross generated around the ingot when the ingot is melted accumulates in the lower part of the ingot weir. Further, when the steel plate is passed, bottom dross is inevitably generated by Fe eluted from the steel plate. When the ingot weir is arranged, the area under the weir becomes easy to stagnate, so these bottom drosses are most likely to accumulate at the bottom of the ingot weir. For the reasons described above, bottom dross is likely to be deposited in the lower portion of the ingot weir compared to other positions in the molten metal pot.

  In general, the bottom dross is removed by scraping periodically, but the quality requirements of products have become stricter in recent years, so it is difficult to satisfy the strict quality requirements even if only a few bottom dross accumulates. ing. Furthermore, in the molten metal plating apparatus provided with the ingot weir, the ingot weir becomes an obstacle, and the bottom dross scraping work itself under the ingot weir is difficult. For this reason, there is a problem that the lower part of the ingot weir tends to be insufficiently scraped, and can become a source of dross that is rolled up in the bath.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a molten metal plating apparatus that can sufficiently remove a bottom dross even when an ingot weir is used, and can reduce defects due to winding up the bottom dross.

  The invention according to claim 1 of the present invention is a molten metal plating apparatus comprising a weir covering an ingot charging region for replenishing a consumable component due to plating into a molten metal bath, and a pump suction port disposed below the weir. A molten metal plating apparatus comprising: a molten metal pump that sucks the dross in the molten metal bath together with the molten metal from the pump suction port; and a removing means that separates and removes the dross in the sucked molten metal. It is.

  The invention according to claim 2 of the present invention is the molten metal plating apparatus according to claim 1, further comprising a molten metal return port arranged at the rear of the snout for returning the clean molten metal after dross removal to the molten metal bath. This is a molten metal plating apparatus.

  In the present invention, a suction port of a molten metal pump is disposed under the ingot weir where the bottom dross concentrates and accumulates when the ingot weir is used, and after the bottom dross is sucked together with the molten metal, only the bottom dross is removed and clean molten metal is removed. Since it was made to return to the molten metal bath, the bottom dross in the pot could be removed efficiently. In addition, since the amount of bottom dross deposited on the pot bottom is reduced according to the present invention, it is possible to prevent trouble that the bottom dross is wound up by the flow of the molten metal bath and adheres to the product to cause defects.

  Hereinafter, the present invention will be specifically described with reference to the drawings. FIG. 1 is a view showing an example of a molten metal plating apparatus according to the present invention. In the figure, 1 is a melting pot, 2 is a molten metal bath, 3 is a material to be plated, 4 is a sink roll, 5 is a support roll, 6 is a snout, 7 is an ingot, 8 is a weir, 9 is a bottom dross, 10 is a pump suction Mouth, 11 is a molten metal pump, 12 is a removing means, 13 is a molten metal return port, and 14 is a spot.

  The material 3 to be plated is continuously introduced into the molten metal bath 2 in the melting pot 1 via the snout 6, turned upward by the sink roll 4, and drawn out of the bath via the support roll 5. .

  The present invention is directed to a molten metal plating apparatus having a weir 8 surrounding the charging portion of the ingot 7 for supplying a consumable component due to plating into the bath. As shown in FIG. 1, in the molten metal plating apparatus having an ingot weir, bottom dross 9 is concentrated on the bottom of the ingot weir.

  In the present invention, the pump suction port 10 for discharging the bottom dross 9 together with the molten metal to the outside of the pot system is disposed at the lower part of the ingot weir and is sucked by the molten metal pump 11. Further, the removing means 12 separates the bottom dross 9 and sends it to the dross spot 14, and returns the remaining clean molten metal to the molten metal bath 2. At this time, the molten metal return port 13 is disposed at the rear portion of the snout 6.

By arranging the pump suction port 10 in the lower part of the ingot weir, the bottom dross 9 concentrated in the lower part of the ingot weir can be efficiently discharged. In addition, since the bottom dross can be sucked and removed by a pump before being rolled up by the flow in the bath, the dross concentration in the vicinity of the steel sheet can be kept small, and dross defects can be reduced.

  Several methods have been proposed for sucking and removing the bottom dross by using a molten metal pump alone. For example, there is a technique disclosed in Patent Document 2. However, these technologies use only the pump under the condition that there is no ingot weir, and the dross generated when the ingot is charged may adhere to the steel plate before it accumulates on the bottom of the pot, resulting in a defect. In addition, in molten metal plating equipment that does not have an ingot weir, bottom dross accumulates on the entire pot bottom, and with the ability of a general pump, only the bottom dross near the suction port can be sucked. There is a problem that cannot be removed by suction. From the above, it is preferable that the pump suction port is disposed below the ingot weir.

  The molten metal discharged from the molten metal return port is a clean molten metal from which dross has been removed. Therefore, it is preferable to arrange the molten metal return port in the vicinity of the material to be plated, that is, in the rear portion of the snout so that the periphery of the material to be plated is filled with clean molten metal released from the molten metal return port.

  The molten metal pump may be any type of pump that can suck high-temperature molten metal. For example, a gas lift pump or a ceramic pump may be used. Moreover, as a removing means for separating dross, for example, sedimentation separation by a sedimentation tank, a porous filter, or the like may be used.

  Comparison was made between an example in which the molten metal plating apparatus according to the present invention was applied and two examples in which another molten metal plating apparatus was applied under the condition that the line speed was 150 mpm and dross was deposited most immediately before the bottom dross scraping operation. .

  As described above, the embodiment in which the present invention is applied to the hot dip galvanizing apparatus having the ingot weir on the steel sheet entrance side of the hot dip galvanizing pot, the pump suction port is at the lower part of the ingot weir and the molten metal return port is at the rear part of the snout. It is arranged. On the other hand, Comparative Example 1 is a condition in which no pump is used, that is, when dross removal is not performed, and Comparative Example 2 is a steel sheet outlet side as shown in FIG. 2 (the reference numerals in FIG. This is a condition in which the pump suction port 10 is arranged at the bottom of the pump, and only the arrangement position of the pump suction port is different from the embodiment to which the present invention is applied. In this example and comparative example 2, a gas lift pump of 400 L / min was used as the pump.

  FIG. 3 is a diagram illustrating an example of the comparison result. For each condition, a molten zinc bath at a position of 1000 mm under the snout was examined and evaluated by the dross mass concentration in the molten zinc bath. The results normalized by the dross concentration in the case of Comparative Example 1 are compared. Compared to Comparative Example 2 where the dross concentration is reduced by only 10% compared to Comparative Example 1, the present invention achieves a dross concentration reduction of as much as 70%. Thereby, the dross concentration reduction effect of the to-be-plated material vicinity by this invention and the raising suppression effect of bottom dross were confirmed.

It is a figure which shows an example of the molten metal plating apparatus which concerns on this invention. It is a figure which shows the molten metal plating apparatus which concerns on the comparative example 2. FIG. It is a figure which shows an example of a comparison result.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Melting pot 2 Molten metal bath 3 Material to be plated 4 Sink roll 5 Support roll 6 Snout 7 Ingot 8 Weir 9 Bottom dross 10 Pump suction port 11 Molten metal pump 12 Removal means 13 Molten metal return port 14 Dro spot

Claims (2)

In a molten metal plating apparatus provided with a weir covering an ingot charging area for replenishing a consumable component by plating into a molten metal bath,
A pump suction port disposed at the bottom of the weir;
A molten metal pump for sucking the dross in the molten metal bath together with the molten metal from the pump suction port;
A molten metal plating apparatus comprising: removal means for separating and removing dross in the sucked molten metal. In the molten metal plating apparatus according to claim 1,
A molten metal plating apparatus, comprising a molten metal return port arranged at the rear of the snout and configured to return clean molten metal after dross removal to a molten metal bath.

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