JP3814170B2 - Method and apparatus for cooling hot dipped steel sheet - Google Patents

Description

【００３０】
表１に示す結果から、水準１及び２のようにスリットノズル吐出流速が大きい場合にはメッキ付着量のバラツキが大きく、また水準５及び６のように丸ノズル吐出流速が大きい場合には風紋の発生があり、これら両者の吐出流速を適正な範囲で組み合わせることにより水準３及び４のようにメッキ外観良好な製品を製造することができた。
【００３１】
【発明の効果】
本発明によれば、連続溶融メッキ工程において、メッキ鋼板を冷却する際に、メッキ鋼板のバタツキを防止でき、かつメッキ鋼板の通板方向のメッキ付着量差のバラツキによるメッキ外観不良を効果的に防止できるという顕著な効果を奏する。
【図面の簡単な説明】
【図１】本発明の溶融メッキ鋼板の冷却装置の概要を示す図である。
【図２】ノズル吐出流速と板幅方向の吐出流速バラツキとの関係により風紋が発生することを示す図である。
【符号の説明】
１ メッキ浴
２ エアーナイフ
３ 第１の冷却帯域
４ 板温計
５ メッキ鋼板
６ 第２の冷却帯域
７ 水平スリットノズル
８ 丸ノズル
９ 吐出口[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for cooling a hot-dip plated steel sheet in a continuous hot-dip plating process, and in particular, prevents the plating steel sheet from fluttering during cooling, and the amount of plating adhesion in the plate-passing direction of the plated steel sheet. The present invention relates to a cooling method and apparatus for preventing poor plating appearance due to variation in difference.
[0002]
[Prior art]
In a hot dip plating process such as hot dip galvanization or hot dip zinc alloy plating, a method of cooling gas or water as a refrigerant after plating is common. The cooling methods can be roughly divided into two cooling methods: a cooling method for cooling the plated steel plate after the plating has solidified after the hot dipping, and a cooling method for cooling before the solidification of the plating. The cooling method for cooling the plated steel sheet after the plating has solidified hardly affects the appearance of the plated surface, and even if the cooling rate in the width direction of the steel sheet fluctuates relatively, it does not cause a product problem. However, the cooling method of cooling before plating solidification tends to affect the appearance of the plating surface. For example, as described in Japanese Patent Application Laid-Open No. 08-269664, the basis weight of the hot dip plated steel sheet pulled up from the hot dip bath is reduced. Immediately after adjustment, the hot dip plated steel sheet is cooled in the cooling device, and the cooling rate is controlled along the steel plate traveling direction of the cooling device, and the hot dip plated steel plate is rapidly cooled at the start of cooling by the cooling device, so that the zero spangle appearance A cooling method for controlling the temperature, and a nozzle assembly that sprays a refrigerant fluid on a plated steel sheet led out onto a plating bath as described in Japanese Patent Application Laid-Open No. 11-106881 Cooling method comprising a fluid blowing zone and adjusting the air volume by providing a refrigerant discharge amount regulator in each of the refrigerant supply ducts A. These disclose a cooling method for cooling a plated steel sheet after performing a basis weight control after plating.
[0003]
[Problems to be solved by the invention]
However, in recent years, there has been a demand for highly corrosion-resistant plated steel sheets, and plated products with a wide plating solidification range have begun to be developed. In that case, the cooling amount after plating needs to be significantly cooled compared to the conventional case. Conventionally, for example, as described in Japanese Patent Application Laid-Open No. 08-269664, when cooling is performed only with a slit nozzle, the slit nozzle has good uniformity in the cooling rate in the width direction, but the cooling efficiency is the length in the width direction. Worse than nozzles installed at a uniform pitch in the direction. For this reason, in order to increase the cooling efficiency, it is necessary to greatly increase the discharge flow rate of the slit nozzle. However, when the discharge flow rate is increased, the steel plate collision flow rate becomes very large, so that the fluttering of the plated steel plate becomes severe, resulting in a variation in the amount of plating adhesion in the plate passing direction, resulting in a defective plating appearance. .
[0004]
Accordingly, in view of the above problems, the present invention has an object to solve the problem of preventing the appearance of the plated steel sheet from fluctuating and the plating appearance defect due to the difference in the amount of plating adhesion when cooling the plated steel sheet. is there.
[0005]
[Means for Solving the Problems]
The inventor has studied the prevention of plating appearance defects of the plated steel sheet during cooling in the continuous hot dipping process. That is, if the plated steel sheet is cooled by greatly increasing the refrigerant discharge flow rate of the horizontal slit nozzle, the plated steel sheet flutters and the appearance of the plating deteriorates. Therefore, research has been conducted on a technique for preventing the plated steel sheet flutter. As a result, the cooling by the cooling zone of the horizontal slit nozzle and the cooling by the cooling zone of the nozzle provided with the coolant discharge ports at equal pitches in the width and length direction of the plated steel plate can be used together to prevent fluttering of the plated steel plate. It has been found that poor plating appearance due to variations in the amount of plating adhesion in the sheet passing direction can be prevented. The present invention has been completed based on this finding, and the gist of the invention is as follows.
[0006]
(1) After the annealed steel sheet is immersed in a hot dipping bath and hot-dip plated, when the plated steel sheet is cooled, it is first cooled in the cooling zone of a multi-stage horizontal slit nozzle extending in the plate width direction of the plated steel sheet. And then cooling in a cooling zone of a nozzle provided with coolant discharge ports at equal pitches in the plate width and length direction of the plated steel plate.
[0007]
(2) Plate thermometers are installed at at least two locations on the cooling zone entry side of the slit nozzle and on the cooling zone exit side of the nozzle where the refrigerant discharge ports are installed at equal pitches in the width and length direction of the steel plate. The method for cooling a hot dipped steel sheet according to (1) above, wherein the refrigerant discharge amount of each nozzle cooling zone is adjusted according to the detected plate temperature and through plate size.
[0008]
(3) When cooling is performed at a nozzle discharge flow rate of 20 m / s or more in the cooling zone of the nozzle in which the refrigerant discharge ports are provided at equal pitches in the plate width and length direction of the plated steel plate, the temperature of the hot-dip steel plate is plated. The method for cooling a hot-dip plated steel sheet according to (1) or (2) above, wherein the solidification temperature + 30 ° C. to the plating solidification temperature is adjusted so that the nozzle discharge variation is ± 20% or less.
[0009]
(4) In a cooling device that cools a plated steel sheet after the annealed steel sheet is immersed in a hot dipping bath and hot-dip plated, the cooling zone of a multi-stage horizontal slit nozzle extending in the plate width direction of the plated steel sheet, A cooling apparatus for a hot-dip plated steel sheet, comprising a cooling zone for a nozzle provided with coolant discharge ports at equal pitches in the plate width and length direction of the plated steel plate after the cooling zone of the horizontal slit nozzle.
[0010]
(5) The thermometer according to (4) above, wherein plate thermometers are installed at at least two locations on the cooling zone entry side of the slit nozzle and on the cooling zone exit side of the nozzle where the equal pitch is installed on the refrigerant discharge port. Cooling equipment for hot dipped steel sheet.
[0011]
(6) The cooling apparatus for a hot-dip galvanized steel sheet according to (4) or (5) above, comprising a refrigerant discharge amount adjusting device for adjusting a refrigerant discharge amount discharged from a nozzle in each cooling zone.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings.
[0013]
FIG. 1 is a diagram showing an outline of a cooling apparatus for hot-dip galvanized steel sheets such as hot dip galvanizing and hot dip zinc alloy plating according to the present invention.
[0014]
As shown in FIG. 1, the annealed steel sheet is immersed in a hot dipping bath 1 in a continuous hot dipping process. The plated steel sheet 5 plated by hot dip plating and pulled up vertically around the sink roll is adjusted by the air knife 2 so that the plating adhesion amount is a predetermined adhesion amount. Thereafter, the steel plate 5 having an unsolidified plating film in a molten state or a semi-molten state is cooled in the first cooling zone 3 in which a multi-stage horizontal slit nozzle 7 extending in the plate width direction of the plated steel plate is disposed, and then plated. It cools with the 2nd cooling zone 6 of the nozzle 8 in which the refrigerant | coolant discharge port was provided in the board width and length direction of the steel plate at equal pitches.
[0015]
In the first cooling zone, a multistage horizontal slit nozzle is formed at a substantially constant pitch in the moving direction (pass line direction) of the steel plate, and a refrigerant discharge amount adjusting device capable of adjusting the refrigerant discharge amount discharged from the slit nozzle is provided. Is provided.
[0016]
Also, in the second cooling zone of the nozzle in which the refrigerant discharge ports are provided at equal pitches in the plate width and length direction of the plated steel plate, the refrigerant discharge amount discharged from the nozzle is adjusted similarly to the first cooling zone. A refrigerant discharge amount adjusting device capable of performing the operation is provided.
[0017]
As the cooling medium, gas (air), a mixture of gas and liquid, or the like can be used, and there is no particular limitation.
[0018]
In the adjustment of the refrigerant discharge amount, as shown in FIG. 1, the second cooling zone 6 of the nozzle in which the outlets are installed at equal pitches in the first cooling zone 3 entrance side and the steel plate width and length direction of the slit nozzle. A plate thermometer 4 is installed at two locations on the side, and the plate temperature of the plated steel plate is measured by this plate thermometer 4. The relationship between the plate temperature of the plated steel sheet and the refrigerant discharge amount is determined in advance, and the refrigerant discharge amount is adjusted according to the measured plate temperature. Adjustment of the refrigerant discharge amount can be performed by providing a flow rate regulator such as a control damper in a refrigerant supply duct that supplies refrigerant to the nozzle outlet and controlling the degree of opening and closing thereof. Further, since the cooling heat capacity varies depending on the size of the plated steel plate, it is necessary to adjust the refrigerant discharge amount according to the size of the plated steel plate. Therefore, in this invention, the refrigerant | coolant discharge amount of each nozzle cooling zone is adjusted with the plate | board temperature and plate | board size of a plated steel plate.
[0019]
In the example of FIG. 1, the plate thermometers 4 are provided at two locations. However, if a plate thermometer is further installed between the two cooling zones, the refrigerant discharge amount can be adjusted with better cooling accuracy. .
[0020]
In the present invention, by providing two cooling zones with different nozzle shapes, it is not clear why the plated steel sheet can be prevented from fluttering during cooling, but the nozzle shape is different, depending on the cooling medium that collides with the plated steel sheet. It is considered that the induced vibration is mitigated and flutter can be prevented. As a result, it is possible to prevent variations in the amount of plating attached in the steel plate passing direction.
[0021]
In addition, as the hot dipping in the present invention, it can be applied to conventionally used hot dipping such as zinc, zinc alloy, aluminum, aluminum alloy and tin, tin alloy.
[0022]
Further, when examining the cooling conditions of the steel sheet having an unsolidified plating layer in the second cooling zone, it can be seen that a plating appearance defect called a wind ripple occurs depending on the conditions of the nozzle discharge flow rate and the discharge flow rate variation in the plate width direction. It was issued.
[0023]
FIG. 2 is a diagram showing that a wind pattern is generated due to the relationship between the nozzle discharge flow rate and the discharge flow rate variation in the plate width direction.
[0024]
As shown in FIG. 2, it can be seen that, as a cooling condition for a steel sheet having an unsolidified plated layer, a wind ripple occurs when the discharge flow rate is 20 m / s or more and the nozzle discharge variation exceeds ± 20%. In FIG. 2, a circle mark indicates that no wind pattern has occurred, and a x mark indicates that a wind pattern has occurred.
[0025]
Therefore, in the present invention, in the second cooling zone, as the optimum condition for cooling the steel sheet having the unsolidified plating layer from the plating solidification temperature + 30 ° C. to the plating solidification temperature, the nozzle discharge flow rate is 20 m / s or more, Nozzle discharge variation ± 20% or less.
[0026]
【Example】
Examples are shown below.
[0027]
Using the apparatus shown in FIG. 1, a cooling test was performed on a molten Zn-11% Al-based plated steel sheet.
[0028]
A horizontal slit nozzle 7 is arranged in the first cooling zone 3, and a round nozzle 8 is arranged in the second cooling zone 6. As cooling conditions, the cooling plate 3 inlet plate temperature and the outlet plate temperature of the cooling zone 6 were made constant, and the steel plate vibration state and the presence or absence of wind ripples were investigated when the discharge wind speeds of the cooling zones 3 and 6 were changed. The results are shown in Table 1. Here, the wind ripple is a defective plating appearance caused by the discharge flow rate variation of the steel plate 5 in the width direction of the second cooling zone 6.
[0029]
[Table 1]

[0030]
From the results shown in Table 1, when the slit nozzle discharge flow rate is high as in levels 1 and 2, the amount of plating adhesion is large, and when the round nozzle discharge flow rate is high as in levels 5 and 6, wind ripples are generated. A product with a good plating appearance like Levels 3 and 4 could be produced by combining the discharge flow rates of both of these in an appropriate range.
[0031]
【The invention's effect】
According to the present invention, in the continuous hot dipping process, when the plated steel sheet is cooled, it is possible to prevent the plated steel sheet from fluctuating, and to effectively prevent the plating appearance defect due to the variation in the plating adhesion amount in the plate passing direction of the plated steel sheet. There is a remarkable effect that it can be prevented.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of a cooling apparatus for hot-dip plated steel sheets according to the present invention.
FIG. 2 is a diagram showing that a wind pattern is generated due to the relationship between the nozzle discharge flow rate and the discharge flow rate variation in the plate width direction.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Plating bath 2 Air knife 3 1st cooling zone 4 Plate thermometer 5 Plated steel plate 6 2nd cooling zone 7 Horizontal slit nozzle 8 Round nozzle 9 Discharge port

Claims (6)

After the annealed steel sheet is immersed in a hot dipping bath and hot-dip plated, when the plated steel sheet is cooled, it is first cooled in a cooling zone of a multi-stage horizontal slit nozzle extending in the plate width direction of the plated steel sheet, and then A method for cooling a hot-dip plated steel sheet, wherein cooling is performed in a cooling zone of a nozzle provided with coolant discharge ports at equal pitches in the plate width and length direction of the plated steel sheet. Plate thermometers installed at at least two locations on the inlet side of the cooling zone of the slit nozzle and on the outlet side of the cooling zone of the nozzle where the refrigerant outlets are installed at equal pitches in the width and length direction of the steel plate, and detected by the plate thermometer The method for cooling a hot-dip plated steel sheet according to claim 1, wherein the refrigerant discharge amount of each nozzle cooling zone is adjusted according to the temperature and the plate size. When cooling is performed at a nozzle discharge flow rate of 20 m / s or more in a nozzle cooling zone in which refrigerant discharge ports are provided at equal pitches in the plate width and length direction of the plated steel plate, the temperature of the hot-dip steel plate is the plating solidification temperature +30. 3. The method for cooling a hot-dip plated steel sheet according to claim 1, wherein the temperature is adjusted so that the nozzle discharge variation is ± 20% or less from 0 ° C. to the plating solidification temperature. In a cooling device for cooling a plated steel sheet after the annealed steel sheet is immersed in a hot dipping bath and hot-dip plated, the cooling zone of the multi-stage horizontal slit nozzle extending in the plate width direction of the plated steel sheet, the horizontal slit nozzle A cooling apparatus for a hot-dip plated steel sheet, comprising a cooling zone for a nozzle provided with coolant discharge ports at equal pitches in the plate width and length direction of the plated steel plate after the cooling zone. The hot-dip galvanized steel sheet according to claim 4, wherein plate thermometers are installed at at least two locations on the cooling zone entry side of the slit nozzle and on the cooling zone exit side of the nozzle where the equal pitch is provided with the refrigerant discharge port. Cooling system. The apparatus for cooling a hot-dip plated steel sheet according to claim 4 or 5, further comprising a refrigerant discharge amount adjusting device for adjusting a refrigerant discharge amount discharged from a nozzle in each cooling zone.

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