JPH1046307A - Production of hot dipped steel plate - Google Patents
Production of hot dipped steel plateInfo
- Publication number
- JPH1046307A JPH1046307A JP22057996A JP22057996A JPH1046307A JP H1046307 A JPH1046307 A JP H1046307A JP 22057996 A JP22057996 A JP 22057996A JP 22057996 A JP22057996 A JP 22057996A JP H1046307 A JPH1046307 A JP H1046307A
- Authority
- JP
- Japan
- Prior art keywords
- hot
- steel sheet
- dip
- plating
- heat treatment
- 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.)
- Granted
Links
Landscapes
- Coating With Molten Metal (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術野】この発明は、酸洗処理を施さな
い熱延鋼板を素材とし、Ａｌを２０〜９５重量％含有す
る溶融Ａｌ−Ｚｎ系合金めっき層を有する溶融めっき鋼
板の製造方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a hot-dip coated steel sheet having a hot-dip Al-Zn-based alloy coating layer containing 20 to 95% by weight of Al by using a hot-rolled steel sheet which is not subjected to pickling treatment. .
【０００２】[0002]
【従来の技術】従来、連続溶融めっき設備で製造される
溶融Ａｌ−Ｚｎ系合金めっき鋼板は、熱延鋼板の表面に
生成している酸化膜（スケール）を予め酸洗工程で除去
し、めっき設備において還元処理を経た後、溶融めっき
することにより製造されてきた。このように溶融めっき
前に酸洗によるスケール除去を行うのは、鋼板のめっき
浴浸漬時にスケールがめっき金属をはじくことよって不
メッキを生じさせたり、鋼板とめっき金属との反応が妨
げられることによりめっき密着性が劣化するためであ
り、このため従来の溶融Ａｌ−Ｚｎ系合金めっき鋼板の
製造ではめっき前に鋼板を酸洗処理し、スケールを完全
に除去することが不可欠であるとされてきた。しかし、
酸洗工程を設置するには莫大な設備コストがかかり、ま
た酸洗を行うことは操業コストの増大につながるため、
酸洗工程の簡略化若しくは工程そのものを省略できる技
術の開発が望まれていた。2. Description of the Related Art Conventionally, in a hot-dip Al-Zn alloy-plated steel sheet manufactured by a continuous hot-dip coating apparatus, an oxide film (scale) generated on the surface of a hot-rolled steel sheet is removed in advance by a pickling process, and plating is performed. It has been manufactured by hot-dip plating after reduction treatment in equipment. The scale removal by pickling before hot-dip plating is performed because the scale repels the plating metal during immersion in the plating bath of the steel sheet, thereby causing non-plating or hindering the reaction between the steel sheet and the plating metal. This is because the plating adhesion is deteriorated. For this reason, in the production of conventional hot-dip Al-Zn-based alloy-plated steel sheets, it has been considered that it is essential to completely remove scale by performing pickling treatment before plating. . But,
Since the installation of the pickling process requires enormous equipment costs, and the pickling leads to an increase in operating costs,
It has been desired to develop a technology that can simplify the pickling process or omit the process itself.
【０００３】このような背景の下で、特開昭５４−１４
７１２５号や特開平６−２７９９６７号等では、酸洗工
程を省略するための熱延鋼板の処理方法ないしは溶融め
っき鋼板の製造法が提案されている。これらのうち、特
開昭５４−１４７１２５号が提案する熱延鋼帯の処理方
法は、熱間圧延されたスケール付着量１ｍｇ／ｃｍ2以
下の鋼帯を、還元性ガス雰囲気の連続焼鈍炉において５
００℃以上で６０秒以上保持して焼鈍することによりス
ケール除去を行う方法である。また、特開平６−２７９
９６７号が提案する溶融めっき鋼帯の製造方法は、熱延
鋼帯を酸洗処理することなく、還元性ガス雰囲気中にお
いて還元温度、還元時間及び水素濃度をスケール厚さに
応じて制御した還元処理を行った後、連続的に溶融めっ
きを行う製造法である。Under such a background, Japanese Patent Application Laid-Open No. 54-14 / 1979
No. 7125 and Japanese Patent Application Laid-Open No. 6-279967 propose a method for treating a hot-rolled steel sheet or a method for producing a hot-dip coated steel sheet in order to omit the pickling step. Among these, a method for treating a hot-rolled steel strip proposed in Japanese Patent Application Laid-Open No. 54-147125 is a method in which a hot-rolled steel strip having a coating weight of 1 mg / cm 2 or less is subjected to continuous annealing in a reducing gas atmosphere. 5
In this method, scale is removed by annealing at a temperature of 00 ° C. or more for 60 seconds or more. Also, Japanese Patent Application Laid-Open No. 6-279
No. 967 proposes a method of manufacturing a hot-dip coated steel strip, in which a hot-rolled steel strip is not pickled, and the reduction temperature, the reduction time and the hydrogen concentration are controlled in a reducing gas atmosphere according to the scale thickness. This is a manufacturing method in which hot-dip plating is performed continuously after processing.
【０００４】[0004]
【発明が解決しようとする課題】しかし、これらのうち
前者の処理法はスケール付着量が１ｍｇ／ｃｍ2以下と
極めて薄い場合にのみ適用可能であり、したがって、通
常得られる３〜５ｍｇ／ｃｍ2（スケール厚で５．７〜
９．５μｍ）程度のスケール付着量の熱延鋼板にそのま
ま適用することは不可能であり、あえて適用しようとす
ると薄スケール化のための付帯設備が必要となり、コス
トの増大を招く。また、後者の製造法は通常のスケール
厚さを有する熱延鋼板にも適用可能な方法であるが、ス
ケールを還元処理するために必要とされる温度、時間、
水素濃度が増すため、操業コストや設備コストが増大す
るという欠点がある。However, the former treatment method among these methods is applicable only when the amount of scale adhesion is extremely thin, that is, 1 mg / cm 2 or less, and therefore, 3 to 5 mg / cm 2 which is usually obtained. (5.7 ~
It is impossible to apply it as it is to a hot-rolled steel sheet having a scale adhesion amount of about 9.5 μm), and if it is attempted to do so, an additional facility for thinning the scale is required, resulting in an increase in cost. In addition, the latter manufacturing method is a method applicable to a hot-rolled steel sheet having a normal scale thickness, but the temperature, time, and
Since the hydrogen concentration increases, there is a disadvantage that operating costs and equipment costs increase.
【０００５】したがって本発明の目的は、通常の工程で
得られる熱延鋼板を素材とし、酸洗等の脱スケール処理
工程を経ることなく且つ操業コストや設備コストを増大
させることなく、不めっき等のない良好な表面外観を有
する溶融Ａｌ−Ｚｎ系合金めっき鋼板の製造方法を提供
することにある。また、本発明の他の目的は、良好な表
面外観のみならず、めっき密着性にも優れた溶融Ａｌ−
Ｚｎ系合金めっき鋼板の製造方法を提供することにあ
る。Accordingly, an object of the present invention is to use a hot-rolled steel sheet obtained in a usual process as a raw material without passing through a descaling process such as pickling, and without increasing operating costs and equipment costs. It is an object of the present invention to provide a method for producing a hot-dip Al-Zn-based alloy-plated steel sheet having a good surface appearance without defects. Another object of the present invention is to provide not only a good surface appearance but also a molten Al-
An object of the present invention is to provide a method for producing a Zn-based alloy-plated steel sheet.
【０００６】[0006]
【課題を解決するための手段】本発明者らは、上記のよ
うな課題を解決するため種々の実験と検討を行い、その
結果、以下に述べるような知見を得た。まず、表面にス
ケールが生成した熱延鋼板を還元性ガス雰囲気中で熱処
理した場合、スケール表層から還元が進行し、鋼板面に
還元Ｆｅ層が形成されるが、通常行われるような操業条
件での還元処理では、スケールを完全に還元することは
難しい。しかしながら、このように未還元スケールが残
存した状態でも、還元処理条件によって不めっき等に対
する特性やめっき密着性が大きく左右され、還元処理条
件を適切に制御することにより、不めっき等のない良好
な表面外観と優れためっき密着性が得られることが判っ
た。Means for Solving the Problems The present inventors conducted various experiments and studies in order to solve the above-mentioned problems, and as a result, obtained the following findings. First, when a hot-rolled steel sheet with scale generated on its surface is heat-treated in a reducing gas atmosphere, reduction proceeds from the scale surface layer, and a reduced Fe layer is formed on the steel sheet surface. It is difficult to completely reduce the scale in the reduction treatment of. However, even in a state in which the unreduced scale remains, the properties for non-plating and the like and the plating adhesion are greatly affected by the reducing treatment conditions, and by appropriately controlling the reducing treatment conditions, a good condition without non-plating and the like is obtained. It was found that surface appearance and excellent plating adhesion were obtained.
【０００７】また、特にめっき密着性については、未還
元スケール層に生じているクラック（微細な割れ）がそ
の特性の向上に大きく寄与していることが判明した。す
なわち、熱延鋼板表面に生成したスケールは母材鋼板と
は異なる物理的性質（密度）を有するため、熱間圧延→
巻取→冷却の過程において鋼板に機械的加工や冷却など
による変形応力が加わるとスケールは微細に破壊し、無
数のクラックを有するようになる。このようなスケール
層を有する鋼板を連続溶融めっきラインで還元処理する
と、スケール層の表層側から還元が進行するだけでなく
クラックに沿って還元が進行し、還元されたＦｅが母材
鋼板（地鉄）とスケール表層とを連絡（連結）する還元
Ｆｅの連絡路を形成することが判った。そして、この鋼
板が溶融めっき浴に浸漬されると、還元Ｆｅの連絡路が
合金相を介して地鉄とめっき皮膜とを連絡（連結）する
ことになるため、優れためっき密着性が得られることが
判った。またこの還元Ｆｅの連絡路は、より高密度に形
成されるほど母材鋼板とめっき皮膜との密着性が高まる
こと、そして、還元処理条件により還元Ｆｅの連絡路の
形成密度を制御できることが判った。[0007] In particular, it has been found that cracks (fine cracks) generated in the unreduced scale layer greatly contribute to the improvement of the plating adhesion. In other words, the scale formed on the surface of the hot-rolled steel sheet has different physical properties (density) from the base steel sheet.
When a deformation stress is applied to the steel sheet by mechanical processing, cooling, or the like in the process from winding to cooling, the scale is finely broken and has numerous countless cracks. When a steel sheet having such a scale layer is subjected to a reduction treatment in a continuous hot-dip galvanizing line, the reduction proceeds not only from the surface layer side of the scale layer but also along cracks, and the reduced Fe becomes a base steel sheet (ground metal). It was found that a reduced iron (Fe) connecting path (iron) and the scale surface layer were formed (connected). When the steel sheet is immersed in the hot-dip plating bath, the connection path of the reduced Fe connects (connects) the ground iron and the plating film via the alloy phase, so that excellent plating adhesion is obtained. It turns out. In addition, it was found that the higher the density of the reduced Fe communication channel, the higher the adhesion between the base steel sheet and the plating film, and that the density of the reduced Fe communication channel could be controlled by the reduction treatment conditions. Was.
【０００８】そして、以上の知見事実に基づきさらに検
討を重ねた結果、還元処理後に未還元スケール層が残存
した状態でも不めっき等のない優れた表面外観性と優れ
ためっき密着性を得るには、連続溶融めっきラインの熱
処理炉で還元処理する際に、還元帯での最高到達板温を
還元帯の長さ及びライン速度に応じて特定の範囲に制御
することが有効であることが判明した。また、還元Ｆｅ
の連絡路が形成されるスケール層のクラックをより積極
的に導入するには、熱間圧延を特定の条件で実施するこ
と、具体的には熱延仕上げ最終圧延スタンドにおける圧
下率と熱延仕上温度及び熱延巻取温度を特定の関係に規
制することが特に有効であることが判った。As a result of further studies based on the above findings, it has been found that even in a state where the unreduced scale layer remains after the reduction treatment, it is possible to obtain excellent surface appearance without non-plating and excellent plating adhesion. It has been found that it is effective to control the maximum plate temperature in the reduction zone to a specific range according to the length of the reduction zone and the line speed when performing the reduction treatment in the heat treatment furnace of the continuous hot-dip plating line. . In addition, reduced Fe
In order to more actively introduce the cracks in the scale layer where the communication path is formed, hot rolling should be performed under specific conditions, specifically, the rolling reduction and the hot rolling finish in the final rolling stand for hot rolling finishing. It has been found to be particularly effective to regulate the temperature and the hot rolling temperature in a specific relationship.
【０００９】本発明はこのような知見に基づきなされた
もので、その特徴とする構成は以下の通りである。 [1] 連続溶融めっきラインにおいて熱延鋼板にＡｌを２
０〜９５重量％含有する溶融Ａｌ−Ｚｎ系合金めっきを
施すに当り、表面にスケール層を有する熱延鋼板を脱ス
ケール処理することなく連続溶融めっきラインに装入
し、熱処理炉の還元性ガス雰囲気中において下記(1)式
を満足する条件で還元処理した後、溶融めっきを施すこ
とを特徴とする溶融めっき鋼板の製造方法。 （６０×ＲＬ）／ＬＳ＋０．６×ＲＴ≧５３０ … (1) 但し ＲＴ：熱処理炉の還元帯での最高到達板温（℃） ＲＬ：熱処理炉の還元帯の長さ（ｍ） ＬＳ：ライン速度（ｍｐｍ）The present invention has been made on the basis of such knowledge, and the characteristic configuration thereof is as follows. [1] In a continuous hot-dip galvanizing line, 2
In applying a hot-dip Al-Zn-based alloy plating containing 0 to 95% by weight, a hot-rolled steel sheet having a scale layer on its surface is charged into a continuous hot-dip plating line without descaling, and a reducing gas in a heat treatment furnace is used. A method for producing a hot-dip coated steel sheet, comprising subjecting a hot-dip coating to a reduction treatment in an atmosphere under conditions satisfying the following expression (1). (60 × RL) /LS+0.6×RT≧530 (1) where, RT: maximum plate temperature in reduction zone of heat treatment furnace (° C.) RL: length of reduction zone of heat treatment furnace (m) LS: line Speed (mpm)
【００１０】[2] 連続溶融めっきラインにおいて熱延鋼
板にＡｌを２０〜９５重量％含有する溶融Ａｌ−Ｚｎ系
合金めっきを施すに当り、表面にスケール層を有する熱
延鋼板を脱スケール処理することなく連続溶融めっきラ
インに装入し、熱処理炉の還元性ガス雰囲気中において
下記(2)式を満足する条件で還元処理した後、溶融めっ
きを施すことを特徴とする溶融めっき鋼板の製造方法。 （６０×ＲＬ）／ＬＳ＋０．６×ＲＴ≧５８０ … (2) 但し ＲＴ：熱処理炉の還元帯での最高到達板温（℃） ＲＬ：熱処理炉の還元帯の長さ（ｍ） ＬＳ：ライン速度（ｍｐｍ）[2] When a hot-rolled steel sheet is subjected to hot-dip Al—Zn-based alloy plating containing 20 to 95% by weight of Al in a continuous hot-dip coating line, the hot-rolled steel sheet having a scale layer on its surface is descaled. A method for producing a hot-dip coated steel sheet which is charged into a continuous hot-dip coating line without reduction, reduced in a reducing gas atmosphere of a heat treatment furnace under conditions satisfying the following expression (2), and then hot-dip coated. . (60 × RL) /LS+0.6×RT≧580 (2) where, RT: maximum plate temperature at the reduction zone of the heat treatment furnace (° C.) RL: length of the reduction zone of the heat treatment furnace (m) LS: line Speed (mpm)
【００１１】[3] 上記[1]または[2]の製造方法におい
て、熱処理炉の還元性ガス雰囲気中において、地鉄表面
の未還元スケール層の平均厚さが３．５μｍ以下になる
まで処理することを特徴とする溶融めっき鋼板の製造方
法。 [4] 上記[1]、[2]または[3]の製造方法において、還元
性ガス雰囲気中で還元されるスケールの平均厚さが０．
５μｍ以上であることを特徴とする溶融めっき鋼板の製
造方法。 [5] 上記[1]、[2]、[3]または[4]の製造方法において、
スラブを下記(3)式を満足する条件で熱間圧延し、該熱
延鋼板を脱スケール処理することなく連続溶融めっきラ
インに装入し、還元性ガス雰囲気中で熱処理した後、溶
融めっきを施すことを特徴とする溶融めっき鋼板の製造
方法。[3] In the manufacturing method of the above [1] or [2], the treatment is carried out in a reducing gas atmosphere of a heat treatment furnace until the average thickness of the unreduced scale layer on the surface of the iron base becomes 3.5 μm or less. A method for producing a hot-dip coated steel sheet. [4] In the method of [1], [2] or [3], the average thickness of the scale reduced in a reducing gas atmosphere is 0.
A method for producing a hot-dip coated steel sheet, which is not less than 5 μm. [5] The method according to the above [1], [2], [3] or [4],
The slab is hot-rolled under the conditions satisfying the following formula (3), the hot-rolled steel sheet is charged into a continuous hot-dip galvanizing line without descaling, and heat-treated in a reducing gas atmosphere. A method for producing a hot-dip coated steel sheet, comprising:
【数２】 (Equation 2)
【００１２】[0012]
【発明の実施の形態】本発明が製造の対象とする溶融め
っき鋼板は、Ａｌを２０〜９５重量％含有する溶融Ａｌ
−Ｚｎ系合金めっき層を有する溶融Ａｌ−Ｚｎ系合金め
っき鋼板であり、所謂５５％Ａｌ−Ｚｎ合金めっき鋼板
が最も代表的なものとして知られている。通常、溶融Ａ
ｌ−Ｚｎ系合金めっき層は１．２〜２．０重量％程度の
Ｓｉを含有している。本発明の製造法では、連続溶融め
っきラインにおいて熱延鋼板にＡｌを２０〜９５重量％
含有する溶融Ａｌ−Ｚｎ系合金めっきを施すに当り、表
面にスケール層を有する熱延鋼板を脱スケール処理する
ことなく連続溶融めっきラインに装入し、ライン内熱処
理炉の還元性ガス雰囲気中において、以下に述べるよう
な条件で還元処理し、引き続き溶融めっきを施す。BEST MODE FOR CARRYING OUT THE INVENTION A hot-dip coated steel sheet manufactured by the present invention is a hot-dip Al-containing steel sheet containing 20 to 95% by weight of Al.
It is a hot-dip Al-Zn alloy plated steel sheet having a Zn-based alloy plated layer, and a so-called 55% Al-Zn alloy plated steel sheet is known as the most typical one. Usually, melting A
The l-Zn-based alloy plating layer contains about 1.2 to 2.0% by weight of Si. In the production method of the present invention, 20 to 95% by weight of Al is added to a hot-rolled steel sheet in a continuous hot-dip galvanizing line.
In applying the hot-dip Al-Zn-based alloy plating containing, a hot-rolled steel sheet having a scale layer on its surface is charged into a continuous hot-dip plating line without descaling treatment, and in a reducing gas atmosphere of a heat treatment furnace in the line. Then, a reduction treatment is performed under the following conditions, followed by hot-dip plating.
【００１３】熱処理炉での還元処理条件については、引
続いて行われる溶融めっきにおける不めっきを防止する
ためには下記(1)式を満足する条件で、またこれに加え
て優れためっき密着性を得るためには下記(2)式を満足
する条件で、それぞれ還元処理を行う必要がある。 （６０×ＲＬ）／ＬＳ＋０．６×ＲＴ≧５３０ … (1) （６０×ＲＬ）／ＬＳ＋０．６×ＲＴ≧５８０ … (2) 但し ＲＴ：熱処理炉の還元帯での最高到達板温（℃） ＲＬ：熱処理炉の還元帯の長さ（ｍ） ＬＳ：ライン速度（ｍｐｍ）Regarding the conditions of the reduction treatment in the heat treatment furnace, in order to prevent non-plating in the subsequent hot-dip plating, the conditions satisfying the following formula (1) are satisfied. In order to obtain, it is necessary to perform reduction treatment under the conditions satisfying the following equation (2). (60 × RL) /LS+0.6×RT≧530 (1) (60 × RL) /LS+0.6×RT≧580 (2) where RT is the highest attained sheet temperature in the reduction zone of the heat treatment furnace (° C.) ) RL: Length of reduction zone of heat treatment furnace (m) LS: Line speed (mpm)
【００１４】先に述べたようにスケールの還元により生
じた還元Ｆｅ層は還元処理条件によってめっきはじきや
不めっきに対する特性が大きく左右される。図１は、ス
ケール層が付着したままの熱延鋼板を熱処理炉の還元帯
の長さが１００ｍの連続溶融めっきラインに装入し、還
元性ガス雰囲気（５％Ｈ2−Ｎ2）中で還元処理を行った
後、溶融Ａｌ−Ｚｎ合金めっき（５５％Ａｌ−１．５％
Ｓｉ−Ｚｎ）を施して製造された溶融Ａｌ−Ｚｎ系合金
めっき鋼板について、その表面外観性を還元帯での最高
到達板温とライン速度で整理して示したものであり、上
記(1)式を満足しない条件で還元処理を実施した場合に
は不めっき等による外観不良を生じていることが判る。As described above, the characteristics of the reduced Fe layer generated by the reduction of the scale to plating repellency and non-plating greatly depend on the conditions of the reduction treatment. FIG. 1 shows that a hot-rolled steel sheet with a scale layer attached thereto is charged into a continuous hot-dip galvanizing line having a reduction zone of 100 m in a heat treatment furnace, and is placed in a reducing gas atmosphere (5% H 2 -N 2 ). After performing the reduction treatment, hot-dip Al-Zn alloy plating (55% Al-1.5%
(A) shows the surface appearance of a hot-dip Al-Zn-based alloy-plated steel sheet produced by applying (Si-Zn), organized by the highest attained sheet temperature in the reduction zone and the line speed. It can be seen that when the reduction treatment was performed under conditions that did not satisfy the expression, poor appearance due to non-plating or the like occurred.
【００１５】また、優れためっき密着性を得るために
は、還元処理条件を制御することにより、未還スケール
層に生成しているクラックを利用して地鉄とめっき皮膜
を連絡する還元Ｆｅの連絡路を適切に形成させる必要が
ある。図２は、スケール層が付着したままの熱延鋼板を
熱処理炉の還元帯の長さが１００ｍの連続溶融めっきラ
インに装入し、還元性ガス雰囲気（５％Ｈ2−Ｎ2）中で
還元処理を行った後、溶融Ａｌ−Ｚｎ合金めっき（５５
％Ａｌ−１．５％Ｓｉ−Ｚｎ）を施して製造された溶融
Ａｌ−Ｚｎ系合金めっき鋼板について、そのめっき密着
性を還元帯での最高到達板温とライン速度で整理して示
したものであり、上記(2)式を満足しない条件で還元処
理を実施した場合にはめっき密着不良を生じていること
が判る。また、より高度なめっき密着性を確保するため
には、還元処理後の未還元スケール層の平均厚さを３．
５μｍ以下に制御することが好ましい。未還元スケール
層の平均厚さが３．５μｍを超えると、鋼板に曲げ歪み
を与えた場合にスケール−地鉄界面に割れが発生し、容
易にめっき剥離を生じる。Further, in order to obtain excellent plating adhesion, by controlling the conditions of the reduction treatment, it is possible to utilize the cracks generated in the unreduced scale layer to reduce the amount of reduced Fe that connects the ground iron and the plating film. It is necessary to form a communication channel appropriately. FIG. 2 shows that the hot-rolled steel sheet with the scale layer adhered was charged into a continuous hot-dip galvanizing line having a reduction zone of 100 m in a heat treatment furnace, and was placed in a reducing gas atmosphere (5% H 2 -N 2 ). After performing the reduction treatment, the molten Al-Zn alloy plating (55
% Al-1.5% Si-Zn), which shows the plating adhesion of the hot-dip Al-Zn-based alloy-plated steel sheet, organized by the maximum temperature and line speed in the reduction zone. It can be seen that when the reduction treatment was performed under the condition not satisfying the above expression (2), poor plating adhesion occurred. In order to ensure higher plating adhesion, the average thickness of the unreduced scale layer after the reduction treatment is set to 3.
It is preferable to control it to 5 μm or less. If the average thickness of the unreduced scale layer exceeds 3.5 μm, when a bending strain is applied to the steel sheet, cracks occur at the scale-base iron interface, and the plating easily peels off.
【００１６】連続溶融めっきラインに装入する原板（熱
延鋼板）としては、スケール層の平均厚さが２．０〜
７．０μｍの熱延鋼板を用いることが好ましい。原板の
スケール層の平均厚さが７．０μｍを超えると、未還元
スケール層の厚さを上述した３．５μｍ以下とするため
に連続溶融めっきライン内で還元しなければならないス
ケール厚が３．５μｍを超え、これを実現するためには
長時間の還元処理が必要となる等、設備や製造上のコス
トが大幅に増大するため好ましくない。一方、スケール
層の平均厚さが２．０μｍ未満の熱延鋼板を得るには、
熱間圧延およびコイル巻取りを非酸化雰囲気で行ったり
或いは巻取り後の鋼板スケールを研削する等の特別な処
理が必要になり、これも設備は製造上のコスト増大を招
く。As a raw sheet (hot-rolled steel sheet) to be charged into the continuous hot-dip plating line, the average thickness of the scale layer is 2.0 to 2.0.
It is preferable to use a hot-rolled steel sheet of 7.0 μm. When the average thickness of the scale layer of the original plate exceeds 7.0 μm, the scale thickness that must be reduced in the continuous hot-dip plating line to reduce the thickness of the unreduced scale layer to the above-mentioned 3.5 μm or less is 3. It exceeds 5 μm, and it is not preferable because the cost for equipment and production is greatly increased, such as a long-time reduction treatment is required to realize this. On the other hand, in order to obtain a hot-rolled steel sheet in which the average thickness of the scale layer is less than 2.0 μm,
Hot rolling and coil winding need to be performed in a non-oxidizing atmosphere, or special processing such as grinding the scale of the steel sheet after winding is required, which also causes an increase in manufacturing cost of the equipment.
【００１７】また本発明では、原板である熱延鋼板が還
元処理された状態で、表層にスケールの還元によるＦｅ
層が生成していることが必要であるが、このＦｅ層の厚
さ、すなわち還元されるスケールの平均厚さが０．５μ
ｍを下回ると不めっきが発生するおそれがあり、このた
め、還元されるスケールの平均厚さは０．５μｍ以上と
することが好ましい。Further, in the present invention, in the state where the hot-rolled steel sheet as the original sheet is subjected to the reduction treatment, the surface layer is made of Fe by reducing the scale.
It is necessary that a layer is formed, and the thickness of the Fe layer, that is, the average thickness of the scale to be reduced is 0.5 μm.
If it is less than m, non-plating may occur, so that the average thickness of the scale to be reduced is preferably 0.5 μm or more.
【００１８】上述したように通常の操業条件（還元温
度、還元時間、還元ガス濃度）による還元処理では熱延
鋼板のスケール層の全部を完全に還元することは難し
く、本発明の製造法も還元処理後に未還元スケール層が
不可避的に残存することを前提としている。したがっ
て、本発明の製造法では還元ガス濃度や還元時間及び温
度等の操業条件は特別なものとする必要はない。還元温
度は、還元時間との関係で処理効率を考慮して決められ
るが、一般にはめっき浴温度との関係から６００℃以上
とされる。また、還元性ガス雰囲気中の還元性ガス濃度
もあまり高くする必要はなく、Ｈ2の場合で５〜３０ｖ
ｏｌ％程度の濃度で十分である。また、このような還元
性ガス雰囲気中における上記還元温度での処理時間（還
元時間）は５０〜１００秒程度とすることが適当であ
る。As described above, it is difficult to completely reduce the entire scale layer of the hot-rolled steel sheet by the reduction treatment under normal operating conditions (reduction temperature, reduction time, reduction gas concentration). It is assumed that an unreduced scale layer will inevitably remain after the treatment. Therefore, in the production method of the present invention, the operating conditions such as the reducing gas concentration, the reducing time and the temperature do not need to be special. The reduction temperature is determined in consideration of the processing efficiency in relation to the reduction time, but is generally set to 600 ° C. or higher in relation to the plating bath temperature. Further, the concentration of the reducing gas in the reducing gas atmosphere does not need to be too high, and is 5 to 30 V in the case of H 2.
A concentration of about ol% is sufficient. Further, the treatment time (reduction time) at the above-mentioned reduction temperature in such a reducing gas atmosphere is suitably about 50 to 100 seconds.
【００１９】優れためっき密着性を得るためには、未還
元スケール層中のクラック内に生じる還元Ｆｅの連絡路
がなるべく高密度に形成されることが好ましい。このた
めにはめっき原板である熱延鋼板のスケール層に、上記
還元Ｆｅの連絡路を形成し得るようなクラックをなるべ
く高密度に生じさせておく必要がある。具体的には、ク
ラック（特に好ましくは、スケール層の表面から地鉄ま
で達するようなクラック）をスケール層表面の合計長さ
で５００ｃｍ／ｃｍ2以上の密度で形成させることが好
ましい。In order to obtain excellent plating adhesion, it is preferable that the connection paths of reduced Fe generated in cracks in the unreduced scale layer are formed as densely as possible. For this purpose, it is necessary to generate cracks as high as possible in the scale layer of the hot-rolled steel sheet, which is the original plating sheet, so as to form the above-described communication path for reduced Fe. Specifically, it is preferable to form cracks (particularly preferably cracks extending from the surface of the scale layer to the ground iron) at a density of 500 cm / cm 2 or more in total length of the surface of the scale layer.
【００２０】先に述べたように、通常の条件で製造され
る熱延鋼板に生成するスケール層にも、製造時及び製造
後に作用する変形応力によって多数のクラックが生じて
いるが、このようなクラックをより確実且つ高密度に形
成するためには、下記(3)式の条件を満足するよう熱間
圧延を実施することが好ましく、これにより、スケール
層に高い形成密度（５００ｃｍ／ｃｍ2以上）でクラッ
ク、それもスケール層を厚さ方向で貫通して地鉄まで達
するようなクラックを適切に形成させることができる。As described above, a large number of cracks are also generated in the scale layer generated in the hot-rolled steel sheet manufactured under ordinary conditions due to deformation stress acting during and after the manufacturing. In order to form cracks more reliably and at a high density, it is preferable to perform hot rolling so as to satisfy the condition of the following formula (3), whereby the scale layer has a high formation density (500 cm / cm 2 or more). ), Cracks can be appropriately formed that penetrate the scale layer in the thickness direction and reach the ground iron.
【数３】 熱延仕上げ最終圧延スタンドにおける圧下率Ｒ（％）と
熱延仕上温度ＦＴ（℃）及び熱延巻取温度ＣＴ（℃）が
上記(3)式の条件を満足しないと、スケール層に導入さ
れるクラックの高密度化が十分でない。(Equation 3) If the rolling reduction R (%), the hot rolling finishing temperature FT (° C.) and the hot rolling winding temperature CT (° C.) in the final rolling stand at the hot rolling finish do not satisfy the condition of the above formula (3), they are introduced into the scale layer. Crack density is not sufficient.
【００２１】[0021]
［実施例１］低炭素Ａｌキルド鋼を転炉にて精錬した
後、連続鋳造してスラブとし、これを再加熱後、熱間圧
延した。この熱間圧延における上記(3)式の左辺の値は
０．８５〜０．９５の範囲とした。熱延巻取り後の鋼板
を常温まで冷却した後、酸洗処理し若しくは酸洗処理す
ることなく連続溶融めっきラインに装入した。この連続
溶融めっきラインでは、熱処理元炉の還元性ガス雰囲気
（Ｎ2−１０％Ｈ2）中で鋼板の還元処理を行い、引き続
き溶融Ａｌ−Ｚｎ系合金めっきを施した。溶融めっき条
件は、浴組成：５５％Ａｌ−１．５％Ｓｉ−Ｚｎ、浴
温：６００℃、浸入板温：６００℃、めっき付着量（両
面の合計付着量）：１５０ｇ／ｍ2とした。また、本実
施例で用いた連続溶融めっきラインの熱処理炉還元帯の
長さ（ＲＬ）は１００ｍであった。なお、他の製造条件
は連続溶融めっき設備で通常採用される標準的な条件と
した。得られた溶融Ａｌ−Ｚｎ系合金めっき鋼板につい
て、表面外観及びめっき密着性の評価を行った。その結
果を、酸洗処理工程の有無、溶融めっき条件、還元処理
前後のスケール層の厚さ等とともに表１及び表２に示
す。Example 1 A low-carbon Al-killed steel was refined in a converter, continuously cast into a slab, reheated, and then hot-rolled. The value on the left side of the above equation (3) in this hot rolling was in the range of 0.85 to 0.95. After the steel sheet after hot rolling and winding was cooled to room temperature, it was pickled or charged into a continuous hot dipping line without pickling. In this continuous hot-dip galvanizing line, the steel sheet was reduced in a reducing gas atmosphere (N 2 -10% H 2 ) in a heat treatment source furnace, and subsequently, hot-dip Al—Zn-based alloy plating was performed. The hot-dip plating conditions were as follows: bath composition: 55% Al-1.5% Si-Zn, bath temperature: 600 ° C., infiltration plate temperature: 600 ° C., and coating weight (total coating weight on both sides): 150 g / m 2 . . Further, the length (RL) of the reduction zone of the heat treatment furnace of the continuous hot-dip plating line used in this example was 100 m. The other manufacturing conditions were standard conditions usually employed in continuous hot-dip plating equipment. The surface appearance and plating adhesion of the obtained hot-dip Al-Zn alloy-plated steel sheet were evaluated. The results are shown in Tables 1 and 2, together with the presence or absence of a pickling treatment step, hot-dip plating conditions, and the thickness of the scale layer before and after the reduction treatment.
【００２２】なお、めっき表面外観性の評価は、めっき
後の外観を観察し、外観の美麗さ及び不めっきの有無等
を評価することにより行った。その評価基準は以下の通
りである。 ○：不めっきは皆無で、均一な外観を有する △：不めっきが１〜５個／ｍ2で、外観の一部にムラが
有る ×：不めっきが６個／ｍ2以上で、外観の一部にムラが
目立つ また、めっき密着性の評価は、めっき鋼板に０Ｔの１８
０°の曲げを加え、曲げを加えた面でのクラック発生の
有無を調べるとともに、その面にテープ剥離試験を実施
することにより行った。その評価基準（但し、ｔ：板厚
［ｍｍ］）は以下の通りである。 ◎：曲げ先端部のめっき表面のクラックは皆無で、めっ
き剥離も無し ○：曲げ先端部のめっき表面にクラックが１〜５本／π
ｔ（ｍｍ）生じたが、めっき剥離は無し △：曲げ先端部のめっき表面にクラックが６〜１０本／
πｔ（ｍｍ）生じ、めっき剥離も若干有り ×：曲げ先端部のめっき表面にクラックが１１本／πｔ
（ｍｍ）以上生じ、顕著なめっき剥離を生じたThe plating surface appearance was evaluated by observing the appearance after plating and evaluating the beauty of the appearance and the presence or absence of non-plating. The evaluation criteria are as follows. ○: non-coating is none, △ has a uniform appearance: In non-plated 1-5 / m 2, × unevenness is in the part of Appearance: non-plated six / m 2 or more, the appearance The unevenness is conspicuous in some areas. The plating adhesion was evaluated as 0T of 18
The test was performed by applying a 0 ° bend, examining the presence or absence of cracks on the bent surface, and performing a tape peeling test on the surface. The evaluation criteria (where t: plate thickness [mm]) are as follows. ◎: No crack on the plating surface at the tip of the bend, and no peeling of the plating. ○: 1 to 5 cracks / π on the plating surface at the tip of the bend.
t (mm) occurred, but there was no plating peeling Δ: 6 to 10 cracks /
πt (mm) occurred and plating peeling was slightly observed. ×: 11 cracks / πt on plating surface at bending tip
(Mm) or more, resulting in remarkable plating peeling
【００２３】[0023]
【表１】 [Table 1]
【００２４】[0024]
【表２】 [Table 2]
【００２５】［実施例２］実施例１と同じ組成のスラブ
を熱延条件を変化させて熱間圧延し、この熱延鋼板を酸
洗処理を施すことなく実施例１と同じ連続溶融めっきラ
インに装入して還元処理し、引き続き実施例１と同じ条
件で溶融めっきを実施した。得られた溶融Ａｌ−Ｚｎ系
合金めっき鋼板について、実施例１と同様の方法及び評
価基準により表面外観及びめっき密着性の評価を行っ
た。その結果を、熱延条件、溶融めっき条件、還元処理
前後のスケール層の平均厚さ等とともに表３に示す。Example 2 A slab having the same composition as in Example 1 was hot-rolled while changing the hot-rolling conditions, and the hot-rolled steel sheet was subjected to the same continuous hot-dip coating line as in Example 1 without performing pickling treatment. , And subjected to a reduction treatment. Subsequently, hot-dip plating was performed under the same conditions as in Example 1. The surface appearance and plating adhesion of the obtained hot-dip Al-Zn-based alloy-plated steel sheet were evaluated by the same method and evaluation criteria as in Example 1. The results are shown in Table 3 together with hot rolling conditions, hot-dip plating conditions, the average thickness of the scale layer before and after the reduction treatment, and the like.
【００２６】[0026]
【表３】 [Table 3]
【００２７】[0027]
【発明の効果】以上述べたように本願の請求項１に係る
発明によれば、通常の工程で得られる熱延鋼板を素材と
して、酸洗工程を経ることなく且つ操業コストや設備コ
ストを増大させることなく、優れた表面外観を有する溶
融Ａｌ−Ｚｎ系合金めっき鋼板を製造することができ
る。また、本願の請求項２に係る発明によれば、通常の
工程で得られる熱延鋼板を素材として、酸洗工程を経る
ことなく且つ操業コストや設備コストを増大させること
なく、表面外観とめっき密着性がともに優れた溶融Ａｌ
−Ｚｎ系合金めっき鋼板を製造することができる。As described above, according to the invention of claim 1 of the present application, a hot-rolled steel sheet obtained in a normal process is used as a raw material, and the operating cost and the equipment cost are increased without going through a pickling process. A hot-dip Al-Zn-based alloy-plated steel sheet having an excellent surface appearance can be produced without causing the surface appearance. According to the invention of claim 2 of the present application, a hot-rolled steel sheet obtained in a normal process is used as a raw material, without going through a pickling process and without increasing operating costs and equipment costs, and improving surface appearance and plating. Molten Al with excellent adhesion
-A Zn-based alloy plated steel sheet can be manufactured.
【図１】スケール層が付着したままの熱延鋼板を素材と
して製造された溶融Ａｌ−Ｚｎ系合金めっき鋼板の表面
外観性を、還元帯での最高到達板温とライン速度との関
係で示すグラフFIG. 1 shows the surface appearance of a hot-rolled Al—Zn-based alloy-coated steel sheet manufactured using a hot-rolled steel sheet with a scale layer adhered as a relationship between the maximum reached sheet temperature in the reduction zone and the line speed. Graph
【図２】スケール層が付着したままの熱延鋼板を素材と
して製造された溶融Ａｌ−Ｚｎ系合金めっき鋼板のめっ
き密着性を、還元帯での最高到達板温とライン速度との
関係で示すグラフFIG. 2 shows the plating adhesion of a hot-rolled Al—Zn-based alloy-coated steel sheet manufactured using a hot-rolled steel sheet with a scale layer adhered as a relationship between the maximum reached sheet temperature in the reduction zone and the line speed. Graph
───────────────────────────────────────────────────── フロントページの続き (72)発明者 鷺山 勝 東京都千代田区丸の内一丁目１番２号 日 本鋼管株式会社内 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masaru Sagiyama 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd.
Claims (5)
にＡｌを２０〜９５重量％含有する溶融Ａｌ−Ｚｎ系合
金めっきを施すに当り、表面にスケール層を有する熱延
鋼板を脱スケール処理することなく連続溶融めっきライ
ンに装入し、熱処理炉の還元性ガス雰囲気中において下
記(1)式を満足する条件で還元処理した後、溶融めっき
を施すことを特徴とする溶融めっき鋼板の製造方法。 （６０×ＲＬ）／ＬＳ＋０．６×ＲＴ≧５３０ … (1) 但し ＲＴ：熱処理炉の還元帯での最高到達板温（℃） ＲＬ：熱処理炉の還元帯の長さ（ｍ） ＬＳ：ライン速度（ｍｐｍ）When a hot-rolled steel sheet is subjected to hot-dip Al-Zn-based alloy plating containing 20 to 95% by weight of Al in a continuous hot-dip coating line, the hot-rolled steel sheet having a scale layer on its surface is descaled. A method for producing a hot-dip coated steel sheet, wherein the hot-dip steel sheet is charged into a continuous hot-dip galvanizing line, subjected to reduction treatment in a reducing gas atmosphere of a heat treatment furnace under conditions satisfying the following expression (1), and then hot-dip coated. (60 × RL) /LS+0.6×RT≧530 (1) where, RT: maximum plate temperature in reduction zone of heat treatment furnace (° C.) RL: length of reduction zone of heat treatment furnace (m) LS: line Speed (mpm)
にＡｌを２０〜９５重量％含有する溶融Ａｌ−Ｚｎ系合
金めっきを施すに当り、表面にスケール層を有する熱延
鋼板を脱スケール処理することなく連続溶融めっきライ
ンに装入し、熱処理炉の還元性ガス雰囲気中において下
記(2)式を満足する条件で還元処理した後、溶融めっき
を施すことを特徴とする溶融めっき鋼板の製造方法。 （６０×ＲＬ）／ＬＳ＋０．６×ＲＴ≧５８０ … (2) 但し ＲＴ：熱処理炉の還元帯での最高到達板温（℃） ＲＬ：熱処理炉の還元帯の長さ（ｍ） ＬＳ：ライン速度（ｍｐｍ）2. A hot-rolled steel sheet having a scale layer on its surface is subjected to descaling when hot-rolled steel sheet is subjected to hot-dip Al-Zn-based alloy plating containing 20 to 95% by weight of Al in a continuous hot-dip coating line. A method for producing a hot-dip coated steel sheet, wherein the hot-dip coated steel sheet is charged into a continuous hot-dip galvanizing line, subjected to reduction treatment in a reducing gas atmosphere of a heat treatment furnace under conditions satisfying the following expression (2), and then hot-dip coated. (60 × RL) /LS+0.6×RT≧580 (2) where, RT: maximum plate temperature at the reduction zone of the heat treatment furnace (° C.) RL: length of the reduction zone of the heat treatment furnace (m) LS: line Speed (mpm)
て、地鉄表面の未還元スケール層の平均厚さが３．５μ
ｍ以下になるまで還元処理することを特徴とする請求項
１または２に記載の溶融めっき鋼板の製造方法。3. An average thickness of an unreduced scale layer on a surface of a base iron in a reducing gas atmosphere of a heat treatment furnace is 3.5 μm.
m. The method for producing a hot-dip coated steel sheet according to claim 1, wherein the reduction treatment is performed until the value becomes m or less.
ルの平均厚さが０．５μｍ以上であることを特徴とする
請求項１、２または３に記載の溶融めっき鋼板の製造方
法。4. The method for producing a hot-dip coated steel sheet according to claim 1, wherein the average thickness of the scale reduced in the reducing gas atmosphere is 0.5 μm or more.
間圧延し、該熱延鋼板を脱スケール処理することなく連
続溶融めっきラインに装入し、還元性ガス雰囲気中で還
元処理した後、溶融めっきを施すことを特徴とする請求
項１、２、３または４に記載の溶融めっき鋼板の製造方
法。 【数１】 5. A slab is hot-rolled under the conditions satisfying the following expression (3), and the hot-rolled steel sheet is charged into a continuous hot-dip galvanizing line without descaling, and subjected to a reduction treatment in a reducing gas atmosphere. The method for producing a hot-dip coated steel sheet according to claim 1, wherein hot-dip coating is performed after the hot-dip coating. (Equation 1)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP22057996A JP3248431B2 (en) | 1996-08-02 | 1996-08-02 | Manufacturing method of hot-dip coated steel sheet |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP22057996A JP3248431B2 (en) | 1996-08-02 | 1996-08-02 | Manufacturing method of hot-dip coated steel sheet |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH1046307A true JPH1046307A (en) | 1998-02-17 |
| JP3248431B2 JP3248431B2 (en) | 2002-01-21 |
Family
ID=16753192
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP22057996A Expired - Fee Related JP3248431B2 (en) | 1996-08-02 | 1996-08-02 | Manufacturing method of hot-dip coated steel sheet |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3248431B2 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101190489B1 (en) | 2010-06-29 | 2012-10-12 | 현대하이스코 주식회사 | Method for manufacturing high tensile strength steel with excellent plating adhesion |
| CN106466697A (en) * | 2016-08-12 | 2017-03-01 | 宝山钢铁股份有限公司 | A kind of steel drop stamping product with aluminum or aluminum alloy coating and its manufacture method |
-
1996
- 1996-08-02 JP JP22057996A patent/JP3248431B2/en not_active Expired - Fee Related
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101190489B1 (en) | 2010-06-29 | 2012-10-12 | 현대하이스코 주식회사 | Method for manufacturing high tensile strength steel with excellent plating adhesion |
| CN106466697A (en) * | 2016-08-12 | 2017-03-01 | 宝山钢铁股份有限公司 | A kind of steel drop stamping product with aluminum or aluminum alloy coating and its manufacture method |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3248431B2 (en) | 2002-01-21 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP2007277652A (en) | Manufacturing method of galvannealed sheet steel having good workability, powdering resistance and sliding property | |
| JP2000309824A (en) | Cold rolled steel sheet, hot dip plated steel sheet and their production | |
| JP3468004B2 (en) | High strength hot-dip galvanized steel sheet | |
| KR19990043945A (en) | Manufacturing Method of Plated Steel Sheet | |
| JP3248431B2 (en) | Manufacturing method of hot-dip coated steel sheet | |
| JPH02285057A (en) | Method for continuously annealing steel sheet to be galvanized | |
| JP2661409B2 (en) | Cold-rolled steel sheet for deep drawing, its galvanized product, and method for producing them | |
| JP3248432B2 (en) | Manufacturing method of hot-dip coated steel sheet | |
| JP2787371B2 (en) | Manufacturing method of aluminum plated steel sheet with excellent plating adhesion and appearance | |
| JPH11140587A (en) | Galvannealed steel sheet excellent in plating adhesion | |
| JP3581862B2 (en) | Method for producing hot-dip Al-Zn-based plated steel sheet | |
| JPH06116653A (en) | Production of low cost type hot rolled and hot dip plated steel strip excellent in plating surface property and plating adhesion and device therefor | |
| JP2997971B2 (en) | Method and apparatus for producing hot-rolled hot-dip galvanized steel strip with excellent plating adhesion | |
| JP3020846B2 (en) | Manufacturing method of high-strength hot-dip galvanized steel sheet | |
| JP3580541B2 (en) | Surface-treated steel sheet excellent in workability and corrosion resistance of processed part and method for producing the same | |
| JP3233045B2 (en) | Manufacturing method of hot-dip galvanized steel sheet | |
| JP2000309847A (en) | Hot rolled steel sheet, hot-dip metal coated hot rolled steel sheet, and their manufacture | |
| JPH1088307A (en) | Production of hot dip plated steel sheet excellent in plating adhesion | |
| JP2978096B2 (en) | High strength hot-dip galvanized steel sheet with excellent plating properties | |
| JPH1060613A (en) | Galvannealed steel sheet excellent in powdering resistance and plating adhesion and its production | |
| JP3221331B2 (en) | Hot-dip coated steel sheet with excellent plating adhesion | |
| JPH09217160A (en) | Production of galvanized steel sheet | |
| JP3233043B2 (en) | Manufacturing method of hot-dip galvanized steel sheet | |
| JPH09143662A (en) | Hot dip galvanized steel sheet | |
| JP4131577B2 (en) | Manufacturing method of plated steel sheet |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| LAPS | Cancellation because of no payment of annual fees |