JP2003277908A - Continuous galvanizing method - Google Patents
Continuous galvanizing methodInfo
- Publication number
- JP2003277908A JP2003277908A JP2002085936A JP2002085936A JP2003277908A JP 2003277908 A JP2003277908 A JP 2003277908A JP 2002085936 A JP2002085936 A JP 2002085936A JP 2002085936 A JP2002085936 A JP 2002085936A JP 2003277908 A JP2003277908 A JP 2003277908A
- Authority
- JP
- Japan
- Prior art keywords
- wiping
- gas
- bath
- nozzle
- hood
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Landscapes
- Coating With Molten Metal (AREA)
Abstract
Description
【発明の詳細な説明】
【0001】
【発明の属する技術分野】本発明は、連続溶融亜鉛めっ
き方法に関し、特に、ガスワイピング工程でのめっき面
への亜鉛粉付着による製品表面欠陥の発生を防止するた
めの連続溶融亜鉛めっき方法に関する。
【0002】
【従来の技術】従来、帯鋼に連続的に溶融亜鉛めっきを
施す場合、帯鋼を一旦浴中(浴=溶融亜鉛浴)に引き入
れた後に、浴中のシンクロールで鉛直上方に変向して浴
外に引き上げていき、帯鋼表面に付着して上がってきた
溶融亜鉛の余剰分を、浴面上方に相互対向配置した1対
のワイピングノズルからのガス吹付けにより払拭し、め
っき厚を所定要求値に制御する。しかし、このとき帯鋼
表面から払拭された亜鉛が帯鋼の板面や板端から飛散
し、亜鉛粉の飛沫(スプラッシュ)となってガス流に乗
り、めっき後の帯鋼表面に再付着し、浴上サポートロー
ル等のロールで圧着されてめっき面にまだら模様をつく
るという問題があった。
【0003】この問題の解決策として、特開昭57−1982
53号公報(公報Aと称する)では、浴面およびワイピン
グ機器付近をシールボックスで囲い、このボックス内を
不活性ガスでシールするためのガスをワイピングノズル
の上方から同ボックス内に吐出させ、あるいはさらに、
該シールガスが帯鋼に直接当るのを防止する遮蔽板をワ
イピングノズル背面に取り付ける方法が開示されてい
る。
【0004】また、特開平4−231148号公報(公報Bと
称する)では、ワイピングノズル上方をシールボックス
で囲い、このボックス内のガスをワイピングノズル直上
付近の吸出し管から吸出すとともに、その上方の加圧管
からこのボックス内にガスを圧入するようにした装置が
開示されている。
【0005】
【発明が解決しようとする課題】しかしながら、上記公
報A記載の技術では、ワイピング地点での帯鋼めっき面
への亜鉛粉付着による製品表面欠陥(亜鉛粉欠陥)の発
生を十分な程度には防止できないという問題があった。
また、上記公報B記載の技術では、加圧と吸引のバラン
スをとることが困難であるという問題や、吸出し管に亜
鉛粉が詰まり易く、メンテナンス負荷が大きいという問
題があった。本発明の目的は、これらの問題点を解決
し、亜鉛粉欠陥の発生を容易かつ有効に防止しうる連続
溶融亜鉛めっき方法を提供することにある。
【0006】
【課題を解決するための手段】本発明者は、上記問題を
解決するために、鋭意検討した結果、亜鉛粉欠陥の発生
機構に関し、以下の知見を得た。すなわち、ワイピング
地点では、図3に示すように、ワイピング機器3のノズ
ル(ワイピングノズル)3Aから吐出したワイピングガ
ス5は帯鋼1に当った後同符号矢示方向(上下左右の各
方向)に流出する。この流出に伴ってワイピング地点に
は周囲のガスが流入する。この周囲からの流入ガス6の
主流方向は同符号矢示方向(帯鋼1板面に向かって直進
する方向)であるがその流速(風力)は一定ではなくそ
の強弱が時期的に不規則に大きく変化する。一方、ワイ
ピングガスの衝突によって上方に飛散した亜鉛粉は、空
中を不規則に漂流し、主に流入ガス6が弱風の時期に、
ワイピング機器3に付着、堆積する。上記公報A記載の
技術では、この付着、堆積を防止することはできない。
【0007】めっき面から飛散後漂流中の亜鉛粉はニー
ドル形をしていて、長い方で30μm程度の微粒であり、
この微粒亜鉛がめっき面に再付着しても実害はない。し
かし、ワイピング機器3に付着、堆積して、ある程度の
大きさに成長した亜鉛堆積物10は、流入ガス6の強風を
受けると、そこから粒径2000μm 程度以上の粗粒亜鉛11
が分離、飛散しやすく、この飛散した粗粒亜鉛11がめっ
き面に再付着して、亜鉛粉欠陥の原因となる。
【0008】本発明は、かかる知見に基づいて、ワイピ
ング機器への亜鉛粉の付着、堆積およびそこからの粗粒
亜鉛の分離を阻止する手段を検討した結果完成されたも
のであり、その要旨は、溶融亜鉛浴から引き上げた帯鋼
にワイピングノズルからワイピングガスを吹付けてめっ
き厚制御を行う連続溶融亜鉛めっき方法において、ワイ
ピング機器のノズル上部からその上方の浴上サポートロ
ール付近までをフードで覆い、該フード内にワイピング
ガス吹出し流量を超える流量でパージガスを吹込むこと
を特徴とする連続溶融亜鉛めっき方法にある。
【0009】
【発明の実施の形態】本発明では、例えば図1に示すよ
うに、浴2から引き上げた帯鋼1にワイピングノズル3
Aからワイピングガス5を吹付けてめっき厚制御を行う
連続溶融亜鉛めっき方法において、ワイピング機器3の
ノズル上部からその上方の浴上サポートロール4付近ま
でを、好ましくは同ワイピング機器の背面側から、フー
ド7で覆い、該フード7内に、例えば送気ダクト8を介
して、ワイピングガス5の吹出し流量を超える流量で、
パージガス9を吹込みながら、ガスワイピングによるめ
っき厚制御を実行する。吹込まれたパージガス9は同符
号矢示方向の定常的な主流を形成する。パージガスとし
ては窒素ガス等の非酸化性ガスまたは不活性ガスを用い
るのが好ましい。
【0010】フード7内へのパージガス9の吹込み流量
W1をワイピングガスの吹出し流量W2よりも大きくす
る(W1>W2)ことにより、フード7内からその開口
前方の帯鋼1パスライン近くまでの領域を正圧(該領域
の外側よりも高圧)に保つことができ、この正圧領域内
へのその外側からのガスの流入が阻止される。帯鋼1板
面に当った後のワイピングガス5の上昇流も同様に阻止
される。
【0011】ワイピング機器3のノズル3A上方部分が
正圧領域内となることにより、ワイピングにより飛散し
た亜鉛粉はこの正圧領域内へ入り難くなって、ワイピン
グ機器3への付着、堆積が起こり難くなる。また、万一
何らかの加減で図3に示したような亜鉛堆積物10がある
程度まで成長したとしても、この正圧領域内へその外側
から図3の流入ガス6のような強風が不規則に吹込むこ
とはないから、亜鉛堆積物10から粗粒亜鉛11が分離、飛
散して帯鋼1めっき面に付着するおそれはない。
【0012】よって、本発明によれば、めっき鋼板製品
の亜鉛粉欠陥発生を有効に防止することができる。ま
た、フードからのガス吸出しを行わないから、前記公報
Bにおけるような運転面やメンテナンス面での問題はな
い。
【0013】
【実施例】ガスワイピングによりめっき厚を制御する連
続溶融亜鉛めっきラインでの操業において、浴上のワイ
ピング機器に図1のような形態でフードおよび送気ダク
トを取付け、該フード内にパージガスとして窒素ガスを
吹込みながらガスワイピングを行うものとし、その際、
ワイピングガス吹出し流量W2を略一定(帯鋼単位幅1
mあたり約4000m3/h )としてパージガス吹込み流量W
1を種々変更し、得られためっき製品の亜鉛粉欠陥発生
数を調査した。なお、流量W1、W2としては、送気駆
動源(ポンプ、ブロワ等)の吐出流量から、ノズル先端
(または送気ダクト先端開口)に至るまでの配管抵抗
(設計値)によるロス分を差し引いたものを用いた。ま
た、亜鉛粉欠陥の発生数は、1200mm幅の帯鋼を処理した
際の、帯鋼100 m当たりの欠陥個数で評価した。
【0014】調査結果を図2に示す。同図に示す通り、
本発明に該当するW1>W2の条件で操業したもの(実
施例)は、本発明を外れるもの(比較例)に比べ、亜鉛
粉欠陥発生率が格段に低減し、本発明の効果が顕現し
た。
【0015】
【発明の効果】かくして本発明によれば、ワイピング地
点でのめっき面への粗粒亜鉛付着を有効に防止でき、連
続溶融亜鉛めっき製品の亜鉛粉欠陥発生率が格段に低減
するという効果を奏する。Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous hot-dip galvanizing method and, more particularly, to the prevention of the occurrence of a product surface defect due to the adhesion of zinc powder to a plating surface in a gas wiping process. The present invention relates to a continuous hot-dip galvanizing method. 2. Description of the Related Art Conventionally, when a steel strip is continuously hot-dip galvanized, the steel strip is once drawn into a bath (bath = hot-dip zinc bath), and then vertically drawn by a sink roll in the bath. Deflected and pulled out of the bath, the excess amount of molten zinc adhering to the steel strip surface and rising was wiped off by gas blowing from a pair of wiping nozzles arranged opposite each other above the bath surface, The plating thickness is controlled to a predetermined required value. However, at this time, the zinc that has been wiped from the surface of the steel strip scatters from the steel sheet surface and the edge of the steel strip, forming a splash (splash) of zinc powder on the gas flow and re-adhering to the steel strip surface after plating. However, there is a problem that a mottled pattern is formed on the plating surface by being pressed by a roll such as a support roll on the bath. As a solution to this problem, Japanese Patent Application Laid-Open No. 57-1982
In Japanese Patent Publication No. 53 (referred to as Publication A), the bath surface and the vicinity of the wiping device are surrounded by a seal box, and a gas for sealing the inside of the box with an inert gas is discharged from above the wiping nozzle into the box, or further,
A method is disclosed in which a shielding plate for preventing the sealing gas from directly hitting the steel strip is attached to the back surface of the wiping nozzle. In Japanese Unexamined Patent Publication No. 4-231148 (hereinafter referred to as "publication B"), the upper portion of the wiping nozzle is enclosed by a seal box, and gas in this box is sucked out from a suction pipe near immediately above the wiping nozzle, and the gas above the wiping nozzle is sucked. An apparatus is disclosed in which gas is press-fitted into the box from a pressurized tube. [0005] However, in the technique described in the above-mentioned publication A, the occurrence of product surface defects (zinc powder defects) due to the adhesion of zinc powder to the steel strip plating surface at the wiping point is sufficiently reduced. Had a problem that it could not be prevented.
Further, the technique described in the above publication B has a problem that it is difficult to balance the pressurization and the suction, and a problem that the zinc dust is easily clogged in the suction pipe and a maintenance load is large. An object of the present invention is to solve these problems and to provide a continuous hot-dip galvanizing method capable of easily and effectively preventing the occurrence of zinc powder defects. Means for Solving the Problems The present inventors have conducted intensive studies to solve the above problems, and as a result, have obtained the following knowledge on the mechanism of zinc powder defect generation. That is, at the wiping point, as shown in FIG. 3, the wiping gas 5 discharged from the nozzle (wiping nozzle) 3 </ b> A of the wiping device 3 hits the steel strip 1 and then moves in the same arrow direction (up, down, left and right directions). leak. With this outflow, surrounding gas flows into the wiping point. The main flow direction of the inflowing gas 6 from the surroundings is the direction indicated by the same reference numeral (the direction in which the gas advances straight toward the surface of the steel strip 1), but the flow velocity (wind force) is not constant, and the strength is irregular at times. It changes greatly. On the other hand, the zinc powder scattered upward due to the collision of the wiping gas drifts irregularly in the air, and mainly when the inflow gas 6 is in a weak wind,
It adheres and deposits on the wiping device 3. The technique described in the above publication A cannot prevent this adhesion and deposition. [0007] The zinc powder that is drifting after being scattered from the plating surface is in the form of a needle, and is a fine particle having a length of about 30 μm.
There is no actual harm even if this fine zinc adheres to the plating surface. However, when the zinc deposit 10 attached to and deposited on the wiping device 3 and grown to a certain size receives the strong wind of the inflow gas 6, the zinc deposit 10 having a particle size of about 2000 μm or more is received therefrom.
Are easily separated and scattered, and the scattered coarse-grained zinc 11 is re-adhered to the plated surface, causing zinc powder defects. The present invention has been completed based on such findings, as a result of studying means for preventing adhesion and deposition of zinc powder on a wiping device and separation of coarse zinc from the zinc powder. In a continuous hot-dip galvanizing method in which a wiping gas is sprayed from a wiping nozzle onto a steel strip pulled up from a hot-dip zinc bath to control plating thickness, a hood covers the upper portion of the nozzle of the wiping device and the vicinity of a support roll on the bath above the nozzle. A continuous hot-dip galvanizing method characterized in that a purge gas is blown into the hood at a flow rate exceeding a wiping gas blowing flow rate. In the present invention, for example, as shown in FIG. 1, a wiping nozzle 3 is attached to a steel strip 1 pulled up from a bath 2.
In the continuous hot-dip galvanizing method in which the wiping gas 5 is sprayed from A to control the plating thickness, from the upper part of the nozzle of the wiping device 3 to the vicinity of the support roll 4 above the bath, preferably from the back side of the wiping device, Covered with a hood 7, and in the hood 7, for example, via an air supply duct 8, at a flow rate exceeding the blowing flow rate of the wiping gas 5,
The plating thickness control by gas wiping is executed while blowing the purge gas 9. The blown purge gas 9 forms a steady mainstream in the direction indicated by the same arrow. It is preferable to use a non-oxidizing gas such as a nitrogen gas or an inert gas as the purge gas. By making the flow rate W1 of the purge gas 9 into the hood 7 larger than the flow rate W2 of the wiping gas (W1> W2), the flow rate from the inside of the hood 7 to the vicinity of the strip 1 pass line in front of the opening thereof is increased. The zone can be maintained at a positive pressure (higher than outside the zone), and the inflow of gas from outside into this zone is prevented. Similarly, the upward flow of the wiping gas 5 after hitting the strip 1 is also prevented. Since the upper portion of the nozzle 3A of the wiping device 3 is in the positive pressure region, the zinc powder scattered by the wiping is less likely to enter the positive pressure region, and is less likely to adhere and deposit on the wiping device 3. Become. Also, even if the zinc deposit 10 as shown in FIG. 3 grows to some extent due to some adjustment, a strong wind such as the inflow gas 6 in FIG. 3 blows into this positive pressure region from outside. Therefore, there is no possibility that the coarse zinc 11 is separated and scattered from the zinc deposit 10 and adheres to the plated surface of the steel strip 1. Thus, according to the present invention, it is possible to effectively prevent zinc powder defects from occurring in a plated steel sheet product. Further, since gas is not sucked out from the hood, there is no problem in terms of operation and maintenance as described in the above publication. [0013] In operation in a continuous hot-dip galvanizing line in which the plating thickness is controlled by gas wiping, a hood and an air duct are attached to the wiping equipment on the bath in the form shown in FIG. Gas wiping shall be performed while blowing nitrogen gas as a purge gas.
The wiping gas blowing flow rate W2 is approximately constant (unit width of steel strip 1).
about 4000 m 3 / h) and the purge gas injection flow rate W
1 was changed variously, and the number of generated zinc powder defects in the obtained plated product was investigated. As the flow rates W1 and W2, a loss due to a pipe resistance (design value) from the discharge flow rate of the air supply drive source (pump, blower, etc.) to the nozzle tip (or the air supply duct tip opening) is subtracted. Was used. The number of zinc powder defects was evaluated based on the number of defects per 100 m of steel strip when a steel strip having a width of 1200 mm was treated. FIG. 2 shows the results of the investigation. As shown in the figure,
In the case of operating under the condition of W1> W2, which corresponds to the present invention (Example), the zinc powder defect occurrence rate was remarkably reduced as compared with the case of deviating from the present invention (Comparative Example), and the effect of the present invention became apparent. . As described above, according to the present invention, it is possible to effectively prevent coarse zinc from adhering to the galvanized surface at the wiping point, and to significantly reduce the zinc powder defect occurrence rate of the continuous galvanized product. It works.
【図面の簡単な説明】
【図1】本発明の1実施形態を示す説明図(a:側面
視、b:正面視)である。
【図2】W1/W2と亜鉛粉欠陥発生率との関係を示す
グラフである。
【図3】亜鉛粉欠陥の発生機構を示す説明図(a:側面
視、b:正面視)である。
【符号の説明】
1 帯鋼
2 浴(溶融亜鉛浴)
3 ワイピング機器
3A ノズル(ワイピングノズル)
4 サポートロール
5 ワイピングガス
6 周囲からの流入ガス
7 フード
8 送気ダクト
9 パージガス
10 亜鉛堆積物
11 粗粒亜鉛BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view (a: side view, b: front view) showing an embodiment of the present invention. FIG. 2 is a graph showing a relationship between W1 / W2 and a zinc powder defect occurrence rate. FIG. 3 is an explanatory view (a: side view, b: front view) showing a mechanism of generating zinc powder defects. [Description of Signs] 1 Strip steel 2 Bath (molten zinc bath) 3 Wiping equipment 3A Nozzle (wiping nozzle) 4 Support roll 5 Wiping gas 6 Inflow gas 7 from surroundings Food 8 Air supply duct 9 Purge gas 10 Zinc deposit 11 Coarse Grain zinc
Claims (1)
ングノズルからワイピングガスを吹付けてめっき厚制御
を行う連続溶融亜鉛めっき方法において、ワイピング機
器のノズル上部から浴上のサポートロール付近までをフ
ードで覆い、該フード内にワイピングガス吹出し流量を
超える流量でパージガスを吹込むことを特徴とする連続
溶融亜鉛めっき方法。Claims: 1. A continuous hot-dip galvanizing method in which a wiping gas is blown from a wiping nozzle onto a steel strip pulled up from a hot-dip galvanizing bath to control a plating thickness. A continuous hot-dip galvanizing method comprising covering a portion near a support roll with a hood, and blowing a purge gas into the hood at a flow rate exceeding a wiping gas blowing flow rate.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2002085936A JP2003277908A (en) | 2002-03-26 | 2002-03-26 | Continuous galvanizing method |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2002085936A JP2003277908A (en) | 2002-03-26 | 2002-03-26 | Continuous galvanizing method |
Publications (1)
Publication Number | Publication Date |
---|---|
JP2003277908A true JP2003277908A (en) | 2003-10-02 |
Family
ID=29232710
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP2002085936A Pending JP2003277908A (en) | 2002-03-26 | 2002-03-26 | Continuous galvanizing method |
Country Status (1)
Country | Link |
---|---|
JP (1) | JP2003277908A (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN103572189A (en) * | 2012-08-01 | 2014-02-12 | 联合铁钢株式会社 | Method and apparatus for producing zinc-aluminum alloy-coated steel sheet with superior workability and corrosion resistance |
US9598756B2 (en) | 2008-10-01 | 2017-03-21 | Nippon Steel & Sumitomo Metal Corporation | Method for producing hot dip plated steel sheet and apparatus for hot dip plating |
-
2002
- 2002-03-26 JP JP2002085936A patent/JP2003277908A/en active Pending
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US9598756B2 (en) | 2008-10-01 | 2017-03-21 | Nippon Steel & Sumitomo Metal Corporation | Method for producing hot dip plated steel sheet and apparatus for hot dip plating |
CN103572189A (en) * | 2012-08-01 | 2014-02-12 | 联合铁钢株式会社 | Method and apparatus for producing zinc-aluminum alloy-coated steel sheet with superior workability and corrosion resistance |
CN103572189B (en) * | 2012-08-01 | 2015-11-18 | 联合铁钢株式会社 | The production method of the Zn-Al alloy plated steel sheet of workability and excellent corrosion resistance and device |
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