JP2004218057A - Method of producing plated steel sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing a plated steel sheet where the suppression of winding in hot dip zinc-55% aluminum alloy plating which has not been sufficient only by using an apparatus coated with a cermet alloy in a bath, and stable operation is made possible. <P>SOLUTION: An apparatus 10 in a bath is treated with an acid liquid before plating, and is used so as to be brought into contact with a scraper 13 in a plating bath 100. Further, the apparatus 10 is taken up from the plating bath 100, and is thereafter reused after treatment with 5 to 20% hydrochloric acid. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００３９】
上記結果より、「研磨のみ」（表１における「名称」で表示する。以下同様である。）では、めっき表面が侵食され合金層が形成された。一方、「塩酸酸洗処理」または「クロム酸処理」では、それらの処理を施すことで、合金層の形成が抑制される効果が認められた。特に塩酸に浸漬処理を施したもの（「塩酸酸洗処理」）は、めっき浴に長時間（９６時間）浸漬しても合金層の形成が抑制されており、めっき浴中での耐食性が向上していることが確認された。
【００４０】
２．基体表面被覆、酸洗処理、及びスクレーパ使用の効果
表２に示す仕様の連続溶融めっきラインにおいて、シンクロールにスクレーパを適用した場合の、絞込み発生までの操業時間を調査した。シンクロールの基体材質、ライニング（被覆処理）、研磨仕上げ粗さ、めっき条件、及びスクレーパ使用の有無を表３に示す。なお、スクレーパを使用する場合、操業開始時点から、図１に示す方法で、スクレーパ１３（材質：ＳＵＳ３１６、板厚：２５ｍｍ）をシンクロール１０に接触させた。押し付け力は５００ｋｇとした。
【表２】

【表３】

上記各比較例１及び２、並びに実施例１〜３の各条件における絞込み発生までの時間を表４に示す。
【表４】

【００４１】
この結果より、シンクロール研磨後に酸洗処理をしていない比較例２では、ライニングをしていない比較例１より良好であるが、比較的短時間で絞込みが発生した。一方、シンクロール研磨後に酸洗処理を施した実施例１〜３では、絞込み発生がさらに抑制されることが確認された。特にシンクロール研磨後に塩酸浸漬処理した実施例３では、スクレーパ使用の効果と相まって絞込みの発生が長時間にわたって抑制されることが確認された。
【００４２】
３．使用済み浴中機器の酸洗処理の効果
使用済み浴中機器の付着金属除去の効果を調査するため、めっき浴から採取したドロス（鋳型で直径約３０ｍｍ、厚さ５ｍｍのコイン形状に凝固させたもの。主成分はＡ１−Ｆｅ合金）および表１の「研磨のみ」試験片を、１０％塩酸、１０％硫酸、及び１０％リン酸の各種酸液（各濃度は容量％）に２４時間浸漬して影響を調査した。その結果を表５に示す。
【表５】

上記表５に示される結果から、１０％塩酸浸漬処理によって、使用後のロールにほとんどダメージを与えることなくドロスを溶解することができることが確認された。
【００４３】
以上、現時点において、もっとも、実践的であり、かつ、好ましいと思われる実施形態に関連して本発明を説明したが、本発明は、本願明細書中に開示された実施形態に限定されるものではなく、請求の範囲および明細書全体から読み取れる発明の要旨或いは思想に反しない範囲で適宜変更可能であり、そのような変更を伴うめっき鋼板の製造方法もまた本発明の技術的範囲に包含されるものとして理解されなければならない。
【００４４】
【発明の効果】
以上に説明したように、本発明のめっき鋼板の製造方法によれば、溶融亜鉛−５５％アルミニウムめっきで問題とされていた浴中機器への巻きつきに起因する問題（たとえばシンクロールに巻きついた場合の絞込み発生）を抑制でき、安定した連続操業性が得られる。
【図面の簡単な説明】
【図１】シンクロールにスクレーパを適用した場合の一例を模式的に示す図である。
【図２】研磨後に酸洗処理を実施した試験片と実施していない試験片とを９６時間めっき浴に浸漬した後の断面の顕微鏡写真である。
【図３】シンクロール表面にドロスが巻きついて鋼帯に絞込みが発生している状態を示す概略斜視図である。
【符号の説明】
１０ シンクロール（浴中機器）
１３ スクレーパ
１００ めっき浴[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a plated steel sheet.
[0002]
[Prior art]
In a continuous hot-dip metal plating line (CGL), devices such as sink rolls, snap rolls, and bearings immersed in a molten metal bath of zinc (Zn) or a zinc-aluminum-based alloy (Zn-Al) For example, stainless steels such as SUS316 and carbon steels such as S55C have been widely used as the materials used for the “in-bath equipment”.
[0003]
On the other hand, in recent years, a zinc-55% aluminum alloy has been widely used as a metal to be plated on a steel sheet surface for the purpose of improving corrosion resistance. When the above-mentioned equipment in a bath using a material such as stainless steel or carbon steel is used in the above-described zinc-55% aluminum alloy plating bath, dross in the plating bath causes the steel running in the bath. When it is caught in the belt and adheres and accumulates on the surface of the sink roll (hereinafter, this phenomenon is referred to as "winding"), if the operation is continued as it is, the profile of the sink roll will have a shape with a bulged center or a stepped shape. , Uneven stress is applied in the width direction of the steel strip, and a shape defect called “squeezing” may occur.
[0004]
FIG. 3 is a diagram showing an outline of a situation in which narrowing down occurs. In the molten metal bath 100, the running direction of the steel strip 31 traveling from above to below is reversed by the sink roll 30 and travels from below to above. At the center of the surface of the sink roll 30, dross wound by the steel strip 31 has already been deposited. Therefore, when the running direction is reversed by the sink roll 30, an uneven force is applied in the width direction of the steel strip 31, and the narrowing 33 is generated in the steel strip 31.
[0005]
In particular, when the operation is continued under the condition that the penetration temperature of the steel strip 31 into the plating bath 100 is low,
As the bath temperature decreases in the vicinity of the steel sheet, the saturated Fe concentration decreases, so that dross is likely to occur and narrowing is apt to occur. When the sheet thickness is small, the steel strip itself is easily deformed, and the steel sheet is often operated at a low sheet temperature, so that the occurrence of narrowing is often a problem.
[0006]
Winding is also related to the corrosion resistance of the bath equipment, and using a bath equipment with good corrosion resistance was considered effective as a measure against winding. As a technique for improving the corrosion resistance of the bath equipment, for example, Patent Document 1, a method of lining a cermet alloy in which dispersed was the Co-Cr-Fe alloy as the matrix W _{2 C} or the like have been disclosed. Further, Patent Documents 2 and 3 propose a technique in which a chromium oxide ceramic coating layer is further formed after spraying ceramic on the surface of an immersion member in a hot-dip galvanizing bath. Furthermore, Patent Document 4 discloses a technique of operating while mechanically removing the "winding" on the premise of "winding", specifically, operating while removing dross and a metal layer attached to a hot-dip plating sink roll with a scraper. Technology has been proposed.
[0007]
Patent Document 5 discloses a method in which dross adhered to a sink roll in a hot-dip galvanizing bath is pickled with a pickling solution to which an oxidizing agent has been added.
[Patent Document 1]
Japanese Patent No. 3291128 [Patent Document 2]
Published Japanese Utility Model Application No. 3-63565 [Patent Document 3]
JP-A-5-106015 [Patent Document 4]
JP-A-6-83762 [Patent Document 5]
JP-A-11-236656 [0008]
[Problems to be solved by the invention]
The present inventors first studied a technique using a scraper. In the case of a conventional roll of SUS316 or the like, particularly in a Zn-Al plating bath, the deposit adheres firmly. Therefore, in order to remove the deposit, the pressing force of the scraper had to be increased. In this case, since the scraper itself is also immersed in the plating bath, the same material such as SUS316 as used in the conventional bath equipment is used. As a result, the surface of the roll is roughened, thereby causing a vicious cycle in which winding is more likely to occur.
[0009]
Next, from the viewpoint of improving the corrosion resistance of the sink roll itself, the applicability of a sink roll in which the surface of SUS316 was lined with the cermet alloy described in Patent Document 1 was investigated. However, although the winding state is improved from the conventional state, it is narrowed down in a short period of operation contrary to expectations, and the practicality is insufficient.
[0010]
Accordingly, the present invention provides a method for producing a plated steel sheet that suppresses winding in hot-dip zinc-55% aluminum alloy plating and enables stable operation, which was not sufficient only by using bath equipment coated with a cermet alloy. The task is to provide
[0011]
[Means for Solving the Problems]
In order to solve the above problems, the present invention is not limited to using bath equipment coated with a cermet alloy, and further applies the following technology.
[0012]
The invention of claim 1 is a method for producing a hot-dip zinc-55% aluminum-plated steel sheet using a bath equipment (10) whose surface is coated with a cermet alloy, wherein the bath equipment is acidified before plating. The above-mentioned problem is solved by a method for producing a plated steel sheet to be used after the treatment. Here, "in-bath equipment" means a sink roll that is immersed in a molten metal bath such as zinc (Zn) or a zinc-aluminum alloy (Zn-Al) in a continuous molten metal plating line (CGL). Equipment such as snap rolls and bearings.
[0013]
According to this invention, the corrosion resistance of the equipment can be improved by treating the equipment in the bath with an acid solution before using the equipment in the plating step. Thereby, the effect of suppressing winding can be obtained.
[0014]
The invention according to claim 2 is a method for producing a hot-dip zinc-55% aluminum-plated steel sheet using an in-bath apparatus (10) whose surface is coated with a cermet alloy. The object is achieved by providing a method for producing a plated steel sheet which is used by bringing an apparatus into contact with a scraper (13).
[0015]
According to the present invention, it is possible to remove the wrap around the equipment surface in the bath by the scraper.
[0016]
The invention according to claim 3 is a method for producing a hot-dip zinc-55% aluminum-plated steel sheet using a bath equipment (10) whose surface is coated with a cermet alloy, wherein the bath equipment is acidified before plating. The above object is solved by a method for producing a plated steel sheet which is used by contacting the in-bath equipment with the scraper (13) in the plating bath (100).
[0017]
According to the present invention, the pickling improves the corrosion resistance of the equipment surface in the bath and suppresses winding. Further, even if winding occurs, it can be removed by a scraper.
[0018]
According to a fourth aspect of the present invention, in the method for producing a plated steel sheet according to the first or third aspect, the acid solution is a 5 to 20% hydrochloric acid aqueous solution.
[0019]
In conventional bath equipment made of stainless steel such as SUS316 or carbon steel such as S55C, the roll surface is corroded by hydrochloric acid. Therefore, the use of hydrochloric acid as an acid solution is hardly considered. Was. However, since the surface of the bath equipment according to the present invention is covered with cermet, the surface is not damaged by hydrochloric acid, and hydrochloric acid can be used without any problem.
[0020]
The invention of claim 5 is a method for producing a hot-dip zinc-55% aluminum-plated steel sheet by reusing an in-bath apparatus (10) whose surface is coated with a cermet alloy from a plating bath and then reusing the apparatus. The above problem is solved by a method of manufacturing a plated steel sheet in which the steel sheet is pulled up from the plating bath (100), treated with 5 to 20% hydrochloric acid, and then reused.
[0021]
According to the present invention, dross adhering to the surface of the equipment in the bath after use can be easily removed with hydrochloric acid. Moreover, since the material of the roll that appears on the surface after dross removal is cermet, it is not corroded by hydrochloric acid.
[0022]
The invention of claim 6 is the method for producing a plated steel sheet according to any one of claims 1 to 5, wherein the cermet alloy has W ₂ C dispersed in a Co—Cr—Fe alloy matrix. I do.
[0023]
ADVANTAGE OF THE INVENTION According to this invention, it is excellent in corrosion resistance and can provide the apparatus in a bath which has corrosion resistance also to hydrochloric acid.
[0024]
According to a seventh aspect of the present invention, in the method for producing a plated steel sheet according to any one of the first to sixth aspects, the in-bath equipment is a sink roll (10).
[0025]
According to the present invention, each of the above-described inventions can be applied to a sink roll as an in-bath apparatus.
[0026]
Such actions and advantages of the present invention will be apparent from embodiments described below.
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
<1> Base of bath equipment and surface coating In the present invention, stainless steel such as SUS316, which is widely used as a base of bath equipment of a plating apparatus for coating a steel strip with molten zinc-55% aluminum alloy, Carbon steel such as S55C can be used. The surface of a substrate such as a sink roll is coated with a cermet alloy in which a single metal such as Co or Cr or an alloy thereof is used as a matrix and an oxide or carbide is dispersed therein. Preferably, use those surface-coated with Cr-Co-Fe alloy matrix _{W 2} C or cermet alloy which contains about 30～60Vo1% carbides such as Cr ₂ C. Further, as a coating method, ordinary thermal spraying or the like may be used, but it is preferable to use a powder welding method from the viewpoint of improving the adhesion to a roll.
[0028]
<2> Pickling treatment (1)
As one embodiment of the present invention, the above-mentioned surface-coated in-bath equipment is treated with an acid solution (hereinafter, referred to as “pickling treatment”) before being immersed in the plating bath. As will be described later, a cermet alloy-coated roll which is polished only has insufficient corrosion resistance when immersed in a plating bath. As pickling, corrosion resistance of bath equipment is improved and immersed in Cr ₂ 0 ₃ solution and hydrochloric acid. A preferred pickling solution is 5 to 20% hydrochloric acid. After pickling, the equipment in oil is washed with water and dried before use.
[0029]
<3> Pickling treatment (2)
In the present invention, the treatment with hydrochloric acid is also effective when the used in-bath equipment used in the plating operation is pulled up from the bath and reused. In the case of this reuse, it is necessary to dissolve metals, especially dross components, attached to the equipment in the bath. In the case of ordinary hot-dip galvanizing, sulfuric acid or phosphoric acid is often used to dissolve metal (including dross) attached to equipment in a bath. However, in the case of hot-dip zinc-55% aluminum plating, the deposit is hardly dissolved in sulfuric acid or phosphoric acid. On the other hand, in the conventional SUS316 roll and the ceramic sprayed layer, since the roll surface is corroded by hydrochloric acid, application of hydrochloric acid has hardly been studied. In the present invention, the surface of a device in a bath such as a roll coated with a cermet alloy is hardly corroded by hydrochloric acid, and therefore, it is possible to perform pickling treatment using hydrochloric acid. This also makes it possible to achieve the above-described effect of improving winding. As the treatment with the acid solution, it is easiest to immerse the equipment in the bath in the acid solution, but a spray treatment or the like may be used as long as a similar effect can be obtained.
[0030]
<4> Use of Scraper Furthermore, in the method for producing a plated steel sheet of the present invention, operation can be performed while using a scraper. Of course, the pickling and the scraper may be used in combination. As described above, use of a scraper is particularly significant when the wrapping cannot be completely suppressed by pickling the sink roll surface-coated with the cermet alloy.
[0031]
The material of the scraper is not particularly limited as long as the winding can be removed. For example, the same material as the material used for the base of the in-bath equipment such as SUS316 described above can be used. However, if the material is too hard, there is a danger that the surface coating layer of the equipment in the bath may be damaged. Therefore, it is desirable to select the material in consideration of the hardness of the surface coating layer.
[0032]
It is preferable that the use of the scraper during operation is started before a product defect due to winding such as narrowing occurs. It is not always necessary to start using the scraper from the start of operation, and it is not necessary to always use the scraper if the winding can be removed. In the present invention, since the hard cermet alloy is coated on the surface of the in-bath equipment, the use of a scraper causes less damage to the roll surface. Therefore, the scraper may be used continuously from the start of operation.
[0033]
The method of applying the scraper to the roll (angle, load) is not particularly limited as long as the winding can be removed. For example, a SUS316 plate having a thickness of 20 to 30 mm and the same width as the roll can be used in contact with the sink roll with a load of 300 to 800 kg.
[0034]
FIG. 1 is a diagram schematically illustrating an example in which a scraper is applied to a sink roll. The steel strip 16 a is guided from the inside of the snout 12 to the hot-dip zinc-55% aluminum plating bath 100. The steel strip 16a is turned upward by a sink roll 10 disposed in a state of being immersed in the plating bath 100, and is guided out of the plating bath 100 by being guided by a pair of snap rolls 11a and 11b. . The steel strip 16b led out of the plating bath 100 is turned at a substantially right angle by the guide roll 14, and is led to a winding device (not shown).
[0035]
In the plating bath 100, Fe ions eluted from the steel strip 16a subjected to the continuous hot-dip plating react with a plating component present in the plating bath 100 to form a dross alloy compound. The dross alloy compound adheres to the surface of the sink roll 10 or is sandwiched between the steel strip 16a and is transferred to the steel strip 16a, resulting in a push-in scratch or a wrinkling phenomenon caused by wrinkling of the steel strip. (See FIG. 3). In order to prevent such inconvenience from occurring, a scraper 13 is provided for the purpose of removing dross adhering to the surface of the sink roll 10.
[0036]
The scraper 13 is slightly larger than the maximum width of the steel strip 16a to be passed, and is brought into contact with the sink roll 10 at a position where the scraper 13 does not hinder plating production. A pressing force (arrow indicated by reference numeral 15 in the drawing) is applied to the scraper 13 by air pressure. The use conditions of the scraper 13 may be appropriately selected and changed according to the use environment. For example, in FIG. 1, a single scraper 13 is brought into contact with the sink roll 10 at a substantially right angle, but a scraper divided in the width direction may be used, or the contact angle to the roll may be changed. . Furthermore, by using the above-mentioned pickling treatment before immersion in the plating bath and the application of a scraper during operation, winding and narrowing can be greatly suppressed.
[0037]
The sink roll has been described as an example of the in-bath apparatus, but the present invention can also be applied to other in-bath apparatuses such as a snap roll and a bearing.
[0038]
【Example】
1. Effect SUS316 (dimensions: 15mm × 50mm × 15mm) of the pickling treatment to the surface of, Co-Cr-Fe was used as a binder _{W 2} C-cermet alloy in which dispersed lining (lining thickness: 1.5 mm) was subjected to the test Multiple pieces were created. These test pieces were polished so as to have a surface roughness Ra of 0.7 μm, and then subjected to the treatment shown in Table 1. These test pieces were placed in a hot-dip Zn-55% Al plating bath (bath composition (weight ratio) A1: Zn: Si = 55: 43.4: 1.6, bath temperature 600 ° C.) for a predetermined time (10, 48, After immersion for 96 hours), a cross section near the surface of the test piece was observed with a microscope. The results are shown in FIG. 2 (after immersion for 96 hours) and in Table 1.
[Table 1]

[0039]
From the above results, in the case of "polishing only" (indicated by "name" in Table 1; the same applies hereinafter), the plating surface was eroded and an alloy layer was formed. On the other hand, in the “hydrochloric acid pickling treatment” or “chromic acid treatment”, the effect of suppressing the formation of the alloy layer was recognized by performing those treatments. In particular, those subjected to immersion treatment in hydrochloric acid ("hydrochloric acid pickling treatment") suppress formation of an alloy layer even when immersed in a plating bath for a long time (96 hours), thereby improving corrosion resistance in the plating bath. It was confirmed that.
[0040]
2. Effects of Substrate Surface Coating, Pickling Treatment, and Use of Scraper In a continuous hot-dip galvanizing line having the specifications shown in Table 2, when a scraper was applied to a sink roll, the operation time until narrowing occurred was investigated. Table 3 shows the base material of the sink roll, lining (coating treatment), polishing finish roughness, plating conditions, and whether or not a scraper was used. When a scraper was used, the scraper 13 (material: SUS316, plate thickness: 25 mm) was brought into contact with the sink roll 10 by the method shown in FIG. The pressing force was 500 kg.
[Table 2]

[Table 3]

Table 4 shows the time until the narrowing-down occurs under the respective conditions of Comparative Examples 1 and 2 and Examples 1 to 3.
[Table 4]

[0041]
From this result, in Comparative Example 2 in which the pickling treatment was not performed after the polishing of the sink roll, although better than Comparative Example 1 in which no lining was performed, narrowing was performed in a relatively short time. On the other hand, in Examples 1 to 3 where the pickling treatment was performed after the polishing of the sink roll, it was confirmed that the occurrence of narrowing was further suppressed. In particular, in Example 3 in which hydrochloric acid immersion treatment was performed after sink roll polishing, it was confirmed that the occurrence of narrowing was suppressed for a long time in combination with the effect of using the scraper.
[0042]
3. Effect of pickling treatment on used bath equipment In order to investigate the effect of removing adhering metal on used bath equipment, dross collected from a plating bath (solidified into a coin shape having a diameter of about 30 mm and a thickness of 5 mm using a mold). The main component is A1-Fe alloy) and the "polished only" test pieces in Table 1 are immersed in various acid solutions of 10% hydrochloric acid, 10% sulfuric acid, and 10% phosphoric acid (each concentration is volume%) for 24 hours. And investigated the effects. Table 5 shows the results.
[Table 5]

From the results shown in Table 5 above, it was confirmed that dross could be dissolved by the 10% hydrochloric acid immersion treatment without substantially damaging the used roll.
[0043]
Although the present invention has been described in connection with the most practical and preferred embodiments at this time, the present invention is not limited to the embodiments disclosed herein. Instead, the present invention can be appropriately changed without departing from the spirit or spirit of the invention which can be read from the claims and the entire specification, and a method of manufacturing a plated steel sheet with such a change is also included in the technical scope of the present invention. Must be understood.
[0044]
【The invention's effect】
As described above, according to the method for manufacturing a plated steel sheet of the present invention, a problem (for example, winding around a sink roll) caused by winding around bath equipment, which has been a problem with hot-dip zinc-55% aluminum plating, has been considered. Can be suppressed, and stable continuous operability can be obtained.
[Brief description of the drawings]
FIG. 1 is a diagram schematically illustrating an example in which a scraper is applied to a sink roll.
FIG. 2 is a photomicrograph of a cross section of a test piece that has been subjected to an acid washing treatment after polishing and a test piece that has not been subjected to polishing, after being immersed in a plating bath for 96 hours.
FIG. 3 is a schematic perspective view showing a state in which dross is wound around the surface of a sink roll and a steel strip is narrowed.
[Explanation of symbols]
10 sink rolls (bathroom equipment)
13 Scraper 100 Plating bath

Claims (7)

A method for producing a hot-dip zinc-55% aluminum-plated steel sheet using a bath equipment whose surface is coated with a cermet alloy, wherein the bath equipment is treated with an acid solution before plating and then used. Manufacturing method. A method for producing a hot-dip zinc-55% aluminum-plated steel sheet using an in-bath equipment whose surface is coated with a cermet alloy, comprising the steps of: Production method. A method for producing a hot-dip zinc-55% aluminum-plated steel sheet by using a bath equipment whose surface is coated with a cermet alloy, wherein the bath equipment is treated with an acid solution before plating, and A method for producing a plated steel sheet, wherein the in-bath equipment is used in contact with a scraper. The method for producing a plated steel sheet according to claim 1 or 3, wherein the acid solution is a 5 to 20% hydrochloric acid aqueous solution. A method of manufacturing a hot-dip zinc-55% aluminum-plated steel sheet by raising and lowering an in-bath equipment having a surface coated with a cermet alloy and then reusing the same, wherein the in-bath equipment is pulled up from the plating bath. A method for producing a plated steel sheet to be reused after being treated with about 20% hydrochloric acid. The cermet alloy, a manufacturing method of a plated steel sheet according to claim 1, W _{2 C} in Co-Cr-Fe alloy matrix are dispersed. The method according to any one of claims 1 to 6, wherein the in-bath equipment is a sink roll.

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