JP2004059944A - Apparatus and method for cooling hot-dipped steel sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for cooling a hot-dipped steel sheet, which maintains a surface quality, maximizes a coolability of the cooling apparatus and increases an efficiency of a productivity in manufacturing the plated steel sheet, in a cooling process after hot-dipping a steel sheet, and to provide a cooling method. <P>SOLUTION: In the apparatus for cooling the hot-dipped steel sheet by spraying a coolant gas onto the hot-dipped surface of the steel sheet, this apparatus has a gas knife for diagonally spraying a gas onto the surface of the steel sheet (preferably at a flow velocity of the coolant gas or higher) from the bottom side of the cooling apparatus to intercept the coolant gas. <P>COPYRIGHT: (C)2004,JPO

Description

ライン速度は３０〜６０ｍｐｍとし、ガスナイフを設置しない比較例について冷却ガスの吐出流速を６０ｍ／秒から０ｍ／秒まで変化させた。
その結果、冷却ガスの吐出流速が４０ｍ／秒以上ではめっき表面に半月模様が発生し、めっき外観の評価は×（不良）であった。
【００１３】
比較例において冷却ガスの吐出流速を２０／秒、０ｍ／秒と低下させれば、めっきの表面外観は徐々に改善され△（良好）乃至○（優秀）の評価となった。
表１に実施例として表示した本発明例においては、冷却ガスの流速が６０ｍ／秒においてもめっきの表面外観は○（優秀）〜△（良好）と比較的よい結果を示している。
特に、ガスナイフの吐出流速を冷却ガスの吐出流速以上とした場合には冷却ガスの吐出流速が６０ｍ／秒であっても、めっきの表面外観は○（優秀）となり、ガスナイフの著しい効果が確認できた。
【００１４】
【発明の効果】
本発明によれば、ガス冷却装置の直前（下側）にガスナイフを設けることにより、ガス冷却装置から下方に吹出すガスを遮断することにより、溶融めっき鋼板のめっき後の冷却過程において、めっきの凝固線による半月模様の発生を防止することができる溶融めっき鋼板の冷却装置および冷却方法を提供することができる。
また、ガス冷却装置の吐出流速を下げなくてもめっきの表面性状を維持することができるので、冷却装置の冷却能力を最大限とし、めっき鋼板製造の生産性を効率化することができるなど、産業上有用な著しい効果を奏する。
【図面の簡単な説明】
【図１】本発明における溶融めっき鋼板の冷却装置の全体構成を示す図である。
【図２】本発明におけるガス冷却装置の側面図である。
【図３】従来のめっき鋼板の冷却装置を示す図である。
【符号の説明】
１：鋼板、
２：スナウト、
３：ガスワイピングノズル、
４：浴中支持ロール、
５：溶融めっきポット、
６：溶融めっき浴、
７：浴中折返しロール、
８：ガス冷却装置、
９：スリットノズル、
１０：ガスナイフ、
１１：不均一ガス流[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a cooling apparatus and a cooling method for a hot-dip coated steel sheet that cools the hot-dip coated steel sheet by blowing a cooling gas onto the surface thereof.
Specifically, in the cooling process after hot-dip galvanized steel sheet, the surface quality is maintained, and the cooling capacity of the cooling device is maximized, so that the productivity of the hot-dip coated steel sheet manufacturing can be made more efficient. A cooling device and a cooling method.
[0002]
[Prior art]
Various proposals have hitherto been made regarding a cooling apparatus and a cooling method for a hot-dip coated steel sheet for cooling the steel sheet by blowing a cooling gas onto the surface of the hot-dip coated steel sheet.
[0003]
For example, Japanese Patent Application Laid-Open No. H11-106881 discloses a method of controlling a cooling gas flow rate in a cooling process after plating according to a solidification state of a plated steel sheet.
In this conventional technique, the required quality of the plated steel sheet is ensured by adjusting the flow rate of the cooling gas according to the temperature or the solidification state of the plated steel sheet in the cooling device.
However, such a conventional cooling device has the following problems.
FIG. 3 is a view showing a conventional apparatus for cooling a plated steel sheet.
In FIG. 3, a cooling gas is sprayed by a gas cooling device 8 on the surface of the plated steel sheet 1.
[0004]
At this time, a gas flow is generated from the gas cooling device 8 to the outside as shown by an arrow in the frame of the dotted line in FIG. 3, which may affect the surface properties of the plated steel sheet.
That is, the cooling gas blown from the gas cooling device 8 and onto the surface of the steel plate is blown out of the gas cooling device 8 as shown by an arrow.
Since the flow rate of the blown gas is early in the central portion of the steel sheet 1 and slow in the end portion, a non-uniform gas flow 11 is generated, and a semilunar pattern due to a solidification line may be generated on the plating surface. In particular, it was remarkable when the solidification temperature range of hot-dip plating was wide such as multi-component alloy plating containing Zn-Al-Mg-Si.
As a means for avoiding this, it is conceivable to reduce the flow rate of the cooling gas. However, this would significantly reduce the capacity of the gas cooling device itself, causing a reduction in productivity in the production of plated steel sheets. was there.
[0005]
[Problems to be solved by the invention]
The present invention solves the problems of the prior art as described above, and in the cooling process after plating of a hot-dip coated steel sheet, maintains the surface texture, and maximizes the cooling capacity of the cooling device, and manufactures a coated steel sheet. An object of the present invention is to provide a cooling apparatus and a cooling method for a hot-dip coated steel sheet that can improve productivity.
[0006]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned problems, the present invention maintains a surface property by installing a gas knife that shuts off a cooling gas below the gas cooling device, and increases the cooling capacity of the cooling device. It is intended to provide a cooling apparatus and a cooling method for a hot-dip coated steel sheet which can maximize the productivity of the production of a coated steel sheet, and the gist thereof is as described in the claims below. It is.
[0007]
(1) In a cooling apparatus for a hot-dip coated steel sheet, which cools the steel sheet by spraying a cooling gas onto the surface of the hot-dip coated steel sheet, a gas is blown obliquely to the surface of the steel sheet from below the cooling apparatus. An apparatus for cooling a hot-dip coated steel sheet, comprising a gas knife for shutting off cooling gas.
(2) A method of cooling a hot-dip coated steel sheet according to (1), wherein the flow rate of the gas blown by the gas knife is equal to or higher than the flow rate of the cooling gas. .
(3) The method for cooling a hot-dip coated steel sheet according to (2), wherein the flow rate of the gas blown by the gas knife is 20 to 80 m / sec.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described in detail with reference to FIGS.
FIG. 1 is a diagram showing the overall configuration of a hot-dip coated steel sheet cooling apparatus according to the present invention.
In FIG. 1, a cold-rolled and annealed steel strip 1 is immersed in a hot-dip plating bath 6 in a hot-dip plating pot 5 through a snout 2, plated, and passed through a wrapping roll 7 in a bath and a supporting roll 4 in a bath. After the amount of plating is controlled by spraying N ₂ gas or the like with the gas wiping nozzle 3, the gas is cooled by blowing a gas such as air onto the surface by the gas cooling device 8.
[0009]
The gas cooling device 8 is a device that discharges a cooling gas from a plurality of arranged slit nozzles toward the steel sheet 1, and the gas that has collided with the steel sheet 1 becomes a non-uniform gas flow from the gas cooling device 7 through the steel sheet 1. Is discharged out of the device.
On the other hand, one gas knife 10 for each of the front and back surfaces of the steel plate 1 is provided immediately before (below) the gas cooling device 8 in the present invention.
[0010]
This gas knife 10 has a slit-shaped nozzle in the width direction of the steel plate,
By blowing a gas, such as air, obliquely upward from the lower side of the gas cooling device 8 onto the surface of the steel plate, it is possible to prevent the cooling gas from blowing downward from the gas cooling device 8. Thereby, it is possible to prevent a half-moon pattern from being generated on the surface of the steel sheet 1 in the conventional gas cooling device.
In order to prevent the cooling gas from blowing downward, it is preferable that the flow rate of the gas blown from the gas knife 10 to the steel sheet surface be equal to or higher than the flow rate of the cooling gas.
[0011]
The flow rate of the gas blown from the gas knife 10 to the surface of the steel sheet is preferably 20 to 80 m / sec. If the length is less than 20 m, the effect of blocking the cooling gas is not recognized. If the length is more than 80 m, the gas may be blown into the cooling gas device.
FIG. 2 is a side view of the gas cooling device according to the present invention.
In FIG. 2, a slit nozzle 9 is provided on the entire surface of the gas cooling device 8. By discharging the cooling gas from the slit nozzle 9, the gas can be uniformly sprayed on the surface of the steel plate.
[0012]
【Example】
Table 1 shows the results of applying the present invention to hot-dip coated steel sheets of Zn-11% Al-3% Mg-0.2% Si using the hot-dip steel sheet cooling apparatus of the present invention.
The specifications of the gas knife used were as follows: nozzle slit thickness: 2 mm, slit width: 1700 mm, distance between nozzle and steel plate: 100 mm, spray angle: 60 degrees.
[Table 1]

The line speed was 30 to 60 mpm, and the discharge speed of the cooling gas was changed from 60 m / sec to 0 m / sec for the comparative example in which the gas knife was not installed.
As a result, when the cooling gas discharge flow rate was 40 m / sec or more, a half-moon pattern was generated on the plating surface, and the plating appearance was evaluated as poor (poor).
[0013]
In the comparative example, when the discharge flow rate of the cooling gas was reduced to 20 / sec and 0 m / sec, the surface appearance of the plating was gradually improved, and was evaluated as Δ (good) to ○ (excellent).
In the examples of the present invention shown as examples in Table 1, even when the flow rate of the cooling gas is 60 m / sec, the surface appearance of the plating shows a relatively good result of （(excellent) to Δ (good).
In particular, when the discharge velocity of the gas knife is equal to or higher than the discharge velocity of the cooling gas, even if the discharge velocity of the cooling gas is 60 m / sec, the surface appearance of the plating becomes ○ (excellent), and the remarkable effect of the gas knife can be confirmed. Was.
[0014]
【The invention's effect】
According to the present invention, a gas knife is provided immediately before (below) the gas cooling device to shut off gas blown downward from the gas cooling device. A cooling device and a cooling method for a hot-dip coated steel sheet that can prevent a meniscus pattern from occurring due to a solidification line can be provided.
In addition, since the surface properties of the plating can be maintained without lowering the discharge flow rate of the gas cooling device, the cooling capacity of the cooling device can be maximized, and the productivity of the production of plated steel sheets can be increased, and the like. It has significant industrially useful effects.
[Brief description of the drawings]
FIG. 1 is a diagram showing the overall configuration of a hot-dip steel sheet cooling device according to the present invention.
FIG. 2 is a side view of the gas cooling device according to the present invention.
FIG. 3 is a view showing a conventional cooling apparatus for a plated steel sheet.
[Explanation of symbols]
1: steel plate,
2: Snout,
3: gas wiping nozzle
4: Support roll in bath
5: hot-dip plating pot,
6: hot-dip bath
7: Folding roll in bath,
8: gas cooling device,
9: slit nozzle,
10: Gas knife,
11: Non-uniform gas flow

Claims (3)

In a cooling apparatus for a hot-dip coated steel sheet, which cools the steel sheet by spraying a cooling gas on the surface of the hot-dip coated steel sheet, the cooling gas is blown obliquely to the steel sheet surface from below the cooling apparatus. A cooling device for a hot-dip coated steel sheet, comprising a gas knife for shutting off. A method for cooling a hot-dip coated steel sheet according to claim 1, wherein a flow rate of the gas blown by the gas knife is equal to or higher than a flow rate of a cooling gas. The method for cooling a hot-dip coated steel sheet according to claim 2, wherein the flow rate of the gas blown by the gas knife is 20 to 80 m / sec.

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