JPH05222501A - Manufacture of galvannealed steel sheet - Google Patents
Manufacture of galvannealed steel sheetInfo
- Publication number
- JPH05222501A JPH05222501A JP2923092A JP2923092A JPH05222501A JP H05222501 A JPH05222501 A JP H05222501A JP 2923092 A JP2923092 A JP 2923092A JP 2923092 A JP2923092 A JP 2923092A JP H05222501 A JPH05222501 A JP H05222501A
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- JP
- Japan
- Prior art keywords
- steel sheet
- atmosphere
- steel
- temperature
- recrystallization
- 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.)
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- Coating With Molten Metal (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、めっき皮膜表面の平滑
性に優れた表面処理鋼板に関するもので、特に、自動車
外装用として好適な、ミクロ凹凸のない表面性状に優れ
た合金化溶融亜鉛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 surface-treated steel sheet having an excellent smoothness on the surface of a plated coating, and particularly to alloyed hot-dip galvanizing suitable for automobile exteriors and having excellent surface properties without micro unevenness. The present invention relates to a method for manufacturing a steel plate.
【０００２】[0002]
【従来の技術】合金化溶融亜鉛めっき鋼板は、溶接性、
塗装後の耐食性に比較的優れた防錆鋼板であり、近年に
おいては、自動車車体用、特に外装用の鋼板として需要
が拡大している。2. Description of the Related Art Alloyed hot-dip galvanized steel sheets have good weldability,
It is a rust-preventive steel plate that is relatively excellent in corrosion resistance after painting, and in recent years, demand is expanding as a steel plate for automobile bodies, especially for exteriors.
【０００３】自動車車体用として用いられる合金化溶融
亜鉛めっき鋼板は、一般に、低炭素低合金鋼、極低炭素
Ti添加IF(Interstitial Free) 鋼、あるいは、微量のS
i、Mn、Ｐを含有する高張力鋼を母材とし、通常は、こ
れら鋼種の鋼板を連続溶融亜鉛めっきラインで焼鈍およ
び溶融亜鉛めっきした後、合金化炉で合金化処理を施す
ことにより製造される。すなわち、まず最初に、鋼板を
酸化性雰囲気中で昇温させながら 500〜600 ℃で鋼板表
面に付着している圧延油を燃焼させ、次いで、鋼板の再
結晶温度よりも十分高い温度の還元性雰囲気中で加熱
し、先の加熱で生じた酸化物を還元すると同時に再結晶
を生じさせる。この焼鈍後の鋼板に溶融亜鉛めっき処理
を施し、さらに加熱して亜鉛めっき層を素地鋼と合金化
させる。Alloyed hot-dip galvanized steel sheets used for automobile bodies are generally low carbon low alloy steel and ultra low carbon.
Ti-added IF (Interstitial Free) steel or a small amount of S
Manufactured by using a high-strength steel containing i, Mn, and P as a base material, and usually by annealing and hot dip galvanizing steel sheets of these steel types in a continuous hot dip galvanizing line and then alloying them in an alloying furnace. To be done. That is, first, the rolling oil adhering to the surface of the steel sheet is burned at 500 to 600 ° C while the temperature of the steel sheet is raised in an oxidizing atmosphere, and then the reducibility at a temperature sufficiently higher than the recrystallization temperature of the steel sheet. By heating in an atmosphere, the oxide generated by the previous heating is reduced and at the same time recrystallization is caused. The annealed steel sheet is subjected to hot dip galvanizing treatment and further heated to alloy the galvanized layer with the base steel.
【０００４】ところが、この合金化過程では、母材の結
晶粒の内部よりも粒界部でFe−Zn合金化反応が促進され
るため、合金層の成長が不均一になり、得られるめっき
表面には母材表面の結晶粒界を反映した結晶粒単位の凹
凸、すなわち、ミクロ凹凸が生じる。この凹凸は、母材
表面の結晶粒が大きくなるほど、顕著にあらわれる。However, in this alloying process, the Fe-Zn alloying reaction is promoted at the grain boundary portion rather than inside the crystal grains of the base material, so that the growth of the alloy layer becomes non-uniform and the obtained plated surface Has irregularities in crystal grain units reflecting the crystal grain boundaries on the surface of the base material, that is, micro irregularities. The irregularities are more prominent as the crystal grains on the surface of the base material are larger.
【０００５】通常、溶融亜鉛めっき前の加熱、還元焼鈍
は母材鋼板の再結晶温度以上の温度域で行われるので結
晶粒が大きくなり、めっき表面の凹凸は一層顕著にな
る。めっき表面にこのような凹凸が存在すると、電着塗
装時に塗装ムラが発生したり、塗装後の外観に光沢ムラ
が発生するため、特に外装材として用いる場合には問題
となる。Usually, heating and reduction annealing before hot dip galvanizing are performed in a temperature range above the recrystallization temperature of the base steel sheet, so that the crystal grains become large and the irregularities on the plating surface become more prominent. The presence of such irregularities on the plating surface causes uneven coating during electrodeposition coating and uneven gloss on the appearance after coating, which is a problem particularly when used as an exterior material.
【０００６】この不均一な合金化に起因するめっき表面
の凹凸を抑制する方法として、本出願人は、溶融亜鉛め
っきを施す前の焼鈍工程で鋼板の表面にFe系酸化物を形
成させる方法を提案した（特開平３−134147号公報）。
この方法によると平滑性に優れた高品質の合金化溶融亜
鉛めっき鋼板を製造することができる。しかし、この方
法では加熱炉の雰囲気を制御しなければならず、実際の
操業においては必ずしも容易ではない。As a method for suppressing the unevenness of the plating surface due to this non-uniform alloying, the present applicant has proposed a method of forming an Fe-based oxide on the surface of the steel sheet in the annealing step before applying hot dip galvanizing. Proposed (JP-A-3-134147).
According to this method, a high-quality alloyed hot-dip galvanized steel sheet having excellent smoothness can be manufactured. However, this method requires controlling the atmosphere of the heating furnace, and is not always easy in actual operation.
【０００７】[0007]
【発明が解決しようとする課題】本発明は、上記の問題
を解決することを課題としてなされたものであって、特
に、自動車車体用として好適な、ミクロ凹凸のない表面
性状に優れた合金化溶融亜鉛めっき用鋼板の製造方法を
提供することを目的とする。DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and in particular, it is an alloying material which is suitable for automobile bodies and has an excellent surface property without micro unevenness. An object of the present invention is to provide a method for manufacturing a hot-dip galvanized steel sheet.
【０００８】[0008]
【課題を解決するための手段】本発明者らは、この加
熱、還元焼鈍について種々検討した結果、以下の知見を
得た。すなわち、母材鋼板を連続焼鈍またはバッチ焼鈍
する際、鉄に対して非酸化性の雰囲気中で、 550℃以上
で、かつ、その鋼板の再結晶温度より低い温度域で加熱
するか、あるいは、前記の加熱に続いてさらに再結晶温
度以上の温度域で加熱することにより、めっき表面にミ
クロ凹凸のない表面性状に優れた合金化溶融亜鉛めっき
鋼板を製造することができる。特に、後者のプロセスで
は、母材鋼板の機械的性質が損なわれることもない。As a result of various studies on the heating and reduction annealing, the present inventors have obtained the following findings. That is, when continuously annealing or batch annealing the base steel sheet, in an atmosphere non-oxidizing to iron, at 550 ℃ or more, and, in the temperature range lower than the recrystallization temperature of the steel sheet, or, Subsequent to the above heating, further heating in a temperature range equal to or higher than the recrystallization temperature makes it possible to produce an alloyed hot-dip galvanized steel sheet having excellent surface properties without micro unevenness on the plating surface. In particular, the latter process does not impair the mechanical properties of the base steel sheet.
【０００９】本発明は上記の知見に基づいてなされたも
ので、下記およびの合金化溶融亜鉛めっき鋼板の製
造方法を要旨とする。The present invention has been made based on the above findings, and has as its gist the following and the following method for producing a galvannealed steel sheet.
【００１０】 母材鋼板を、鉄に対して非酸化性の雰
囲気（以下、単に「非酸化性雰囲気」という）中で、 5
50℃以上でその鋼板の再結晶温度より低い温度域で加熱
して鋼板表面に鉄より酸化されやすい元素の選択酸化層
を形成させ、溶融亜鉛浴に浸漬して亜鉛めっきを施した
後、亜鉛めっき層を素地鋼と合金化させることを特徴と
する合金化溶融亜鉛めっき鋼板の製造方法。The base material steel sheet is placed in an atmosphere that is non-oxidizing with respect to iron (hereinafter, simply referred to as “non-oxidizing atmosphere”).
It is heated at a temperature lower than the recrystallization temperature of the steel sheet at 50 ° C or higher to form a selective oxidation layer of elements that are more easily oxidized than iron on the surface of the steel sheet. A method for producing an alloyed hot-dip galvanized steel sheet, which comprises alloying a plated layer with a base steel.
【００１１】 母材鋼板の表面に前記記載の選択酸
化層を形成させ、続いて再結晶温度以上の温度域で加熱
し、溶融亜鉛浴に浸漬して亜鉛めっきを施した後、亜鉛
めっき層を素地鋼と合金化させることを特徴とする合金
化溶融亜鉛めっき鋼板の製造方法。After forming the selective oxidation layer described above on the surface of the base material steel sheet, followed by heating in a temperature range of the recrystallization temperature or higher, dipping in a molten zinc bath to perform galvanizing, and then forming a galvanizing layer. A method for producing an alloyed hot-dip galvanized steel sheet, which comprises alloying with a base steel.
【００１２】前記の母材鋼板としては、Mn、Si、Al等の
合金元素を微量でも含む鋼種であればよく、一般に合金
化溶融亜鉛めっきに供される鋼板はいずれも本発明方法
の対象として用いることができる。The base steel sheet may be any steel type containing a small amount of alloying elements such as Mn, Si and Al. Generally, any steel sheet used for galvannealing is subject to the method of the present invention. Can be used.
【００１３】鉄より酸化されやすい元素の選択酸化層と
は、後述するように、合金元素として含まれるMn、Si、
Al等の酸化物層をいう。The selective oxidation layer of an element that is more easily oxidized than iron means Mn, Si, and
An oxide layer of Al or the like.
【００１４】[0014]
【作用】以下、本発明について詳細に説明する。The present invention will be described in detail below.
【００１５】本発明方法の特徴は、連続溶融亜鉛めっき
ラインにおいて、めっき処理の前に行う母材鋼板の焼鈍
を非酸化性雰囲気中で、その鋼板の再結晶温度より低い
温度で行い、Feは酸化させず、Feより酸化されやすいM
n、Si、Al等の酸化物層（選択酸化層）を鋼板表面に形
成させることにある。The feature of the method of the present invention is that, in a continuous hot-dip galvanizing line, the base material steel sheet is annealed before the plating treatment in a non-oxidizing atmosphere at a temperature lower than the recrystallization temperature of the steel sheet. M, which does not oxidize and is more easily oxidized than Fe
The purpose is to form an oxide layer (selective oxidation layer) of n, Si, Al, etc. on the steel sheet surface.
【００１６】図１は、本発明方法による合金化溶融亜鉛
めっき鋼板の製造プロセスにおける鋼板の温度変化の状
況を示す図であり、図２は、従来の製造プロセスにおけ
る鋼板の温度変化の状況を示す図である。これらの図に
おいて、めっき以降の工程は、本発明方法と従来法との
間に違いはない。両方法における相違は連続焼鈍または
バッチ焼鈍の際の雰囲気を含めたヒートパターンにあ
り、従来法では、母材鋼板をまず酸化性雰囲気中で昇温
させながら 500〜600 ℃で鋼板表面に付着している油等
を酸化除去した後、通常は 700〜850 ℃の還元性雰囲気
中で焼鈍するのに対し、本発明方法では、非酸化性雰囲
気中でその鋼板の再結晶温度より低い温度域で焼鈍する
か（前記の発明）、あるいは、その後さらに再結晶温
度以上の温度域で加熱する（の発明）。なお、本発明
方法において、鋼板表面に付着している圧延油は、非酸
化性雰囲気中での加熱でも雰囲気中に含まれる微量の水
分や酸素により燃焼もしくは気化するので、除去するこ
とが可能である。FIG. 1 is a diagram showing a temperature change situation of a steel sheet in a manufacturing process of a galvannealed steel sheet according to the method of the present invention, and FIG. 2 shows a temperature change situation of a steel sheet in a conventional production process. It is a figure. In these figures, there is no difference between the method of the present invention and the conventional method in the steps after plating. The difference between the two methods lies in the heat pattern that includes the atmosphere during continuous annealing or batch annealing.In the conventional method, the base steel sheet is first heated in an oxidizing atmosphere and adhered to the steel sheet surface at 500 to 600 ° C. After oxidizing and removing the oil etc. that are present, it is usually annealed in a reducing atmosphere at 700 to 850 ° C, whereas in the method of the present invention, in a temperature range lower than the recrystallization temperature of the steel sheet in a non-oxidizing atmosphere. Annealing is performed (invention described above) or heating is further performed in a temperature range higher than the recrystallization temperature (invention). In the method of the present invention, the rolling oil adhering to the surface of the steel sheet is burned or vaporized by a trace amount of water or oxygen contained in the atmosphere even when heated in a non-oxidizing atmosphere, so that it can be removed. is there.
【００１７】前記の選択酸化層は、図３に示すように、
鋼板表面の結晶粒２の表面、特にこの結晶粒２の結晶粒
界３に沿って形成されるので、その後の工程で再結晶温
度以上の還元性雰囲気中で焼鈍しても、前記の酸化層に
よって鋼板表面の結晶粒２の再結晶化が阻害されるた
め、鋼板表面の結晶粒２は細粒のまま保持される。従っ
て、合金化処理を行ってもミクロ凹凸が顕著にあらわれ
ることはない。The selective oxidation layer is formed as shown in FIG.
Since it is formed along the surface of the crystal grains 2 on the surface of the steel sheet, particularly along the crystal grain boundaries 3 of the crystal grains 2, even if annealed in a reducing atmosphere at a recrystallization temperature or higher in the subsequent step, the above-mentioned oxide layer is formed. As a result, the recrystallization of the crystal grains 2 on the surface of the steel sheet is hindered, so that the crystal grains 2 on the surface of the steel sheet are retained as fine grains. Therefore, even if the alloying treatment is performed, the micro unevenness does not significantly appear.
【００１８】図４(a) および図４(b) はAlキルド鋼を還
元性雰囲気（６体積％H2＋N2、露点−30℃、以下、雰囲
気ガスの組成を表す「％」は「体積％」を意味する）中
で、780℃で焼鈍したときの鋼表面の状態を示す図であ
る。(a) 図は走査型電子顕微鏡による観察結果で、結晶
粒界が示されている。また、(b) 図は(a) 図に対応する
部分（鋼表面からの深さが約 350Å）のMnの二次イオン
質量分析結果を示す図で、白色部分がMnが存在すること
を表しているが、結晶粒界に相当する部分にMnが多く存
在しており、結晶の粒界部で選択酸化層が形成され易い
ことがわかる。FIGS. 4 (a) and 4 (b) show an Al killed steel in a reducing atmosphere (6% by volume H 2 + N 2 , dew point −30 ° C., hereinafter, “%” representing the composition of the atmosphere gas is “volume”. % "), Showing the state of the steel surface when annealed at 780 ° C. Figure (a) shows the results of observation with a scanning electron microscope, showing the grain boundaries. Figure (b) shows the result of secondary ion mass spectrometry of Mn in the part corresponding to (a) (depth from the steel surface is about 350Å), and the white part shows the existence of Mn. However, a large amount of Mn is present in the portion corresponding to the crystal grain boundary, and it can be seen that the selective oxidation layer is easily formed at the grain boundary portion of the crystal.
【００１９】なお、結晶粒の表面にもMnの酸化物は形成
されているが、表面から 200Å程度の深さまでであり、
この(b) 図には現れていない。Although the oxide of Mn is also formed on the surface of the crystal grain, it is up to a depth of about 200 Å from the surface,
It does not appear in this figure (b).
【００２０】加熱雰囲気は、前記のように、Feに対して
非酸化性の雰囲気であればよく、Mn、Si、Al等を酸化す
るための酸化性ガスを含んでいることは必須ではない。
例えば、鋼板を還元性雰囲気中で加熱する場合でも、条
件によっては鋼中に含まれるMn、Si、Alなどの合金元素
が選択的に酸化され、選択酸化層が形成される。これ
は、加熱雰囲気中に含まれる微量の水分や酸素によるも
のと考えられており〔例えば、T.SHIRAIWA et.al.: Sec
ondary Ion Mass Spectrometry, SIMS-II,ed. byA.BENN
INGHOVEN et al.(1979)p167 (Springer Verlag). 参
照〕、Mn、Si、Alなどの含有量が微量であってもそれら
の酸化物層が生成する。すなわち、Feに対しては還元性
であるような雰囲気であっても、前記の合金元素を酸化
するのに十分な水分や酸素が含まれているためである。As described above, the heating atmosphere may be a non-oxidizing atmosphere with respect to Fe, and it is not essential that the heating atmosphere contains an oxidizing gas for oxidizing Mn, Si, Al and the like.
For example, even when the steel sheet is heated in a reducing atmosphere, alloy elements such as Mn, Si and Al contained in the steel are selectively oxidized depending on the conditions, and a selective oxidation layer is formed. It is considered that this is due to a small amount of water and oxygen contained in the heating atmosphere (for example, T.SHIRAIWA et.al .: Sec
ondary Ion Mass Spectrometry, SIMS-II, ed. by A.BENN
INGHOVEN et al. (1979) p167 (Springer Verlag).], Mn, Si, Al, etc., even if the contents thereof are minute, their oxide layers are formed. That is, even in an atmosphere that is reducing with respect to Fe, sufficient moisture and oxygen are included to oxidize the alloy elements.
【００２１】一般に加熱雰囲気の酸素ポテンシャルは、
H2/H2O比やCO/CO2比で表される。H2/H2O比の場合を例に
とると、Feが酸化されずに、Mn、Siなどが酸化される条
件は、酸化物の標準生成自由エネルギーの温度依存性を
表す図〔図は省略、例えば、第３版 鉄鋼便覧 第１巻
「基礎」（社）日本鉄鋼協会編 （丸善株式会社）等参
照〕から、H2/H2O比が５以上の領域であればよいことに
なる。Generally, the oxygen potential of the heating atmosphere is
It is represented by the H 2 / H 2 O ratio and the CO / CO 2 ratio. Taking the case of the H 2 / H 2 O ratio as an example, the conditions under which Fe is not oxidized and Mn, Si, etc. are oxidized are graphs showing the temperature dependence of the standard free energy of formation of oxides. Omission, for example, from the 3rd edition of the Iron and Steel Handbook Vol. 1 "Basics" (Company) edited by the Iron and Steel Institute of Japan (Maruzen Co., Ltd.)], it is sufficient if the H 2 / H 2 O ratio is 5 or more. Become.
【００２２】従来の還元焼鈍で使用されている雰囲気
（10〜40％H2＋N2）は、H2/H2Oの比が300 以上であり、
本発明方法を実施する際の非酸化性雰囲気として十分使
用できる。The atmosphere (10-40% H 2 + N 2 ) used in conventional reduction annealing has a H 2 / H 2 O ratio of 300 or more,
It can be sufficiently used as a non-oxidizing atmosphere when carrying out the method of the present invention.
【００２３】上記の非酸化性雰囲気中での加熱温度の上
限は、鋼板の再結晶温度より低い温度とする。これは、
再結晶による結晶の成長を抑え、細粒のまま保持するた
めである。また、加熱温度の下限は鋼板の表面に選択酸
化層を均一に生成させる必要があるため 550℃とする。The upper limit of the heating temperature in the above non-oxidizing atmosphere is lower than the recrystallization temperature of the steel sheet. this is,
This is because crystal growth due to recrystallization is suppressed and fine grains are maintained. The lower limit of the heating temperature is set to 550 ° C because it is necessary to uniformly generate the selective oxidation layer on the surface of the steel sheet.
【００２４】上記のように規定された条件下で焼鈍処理
を行えば（前記の発明）、結晶粒は細粒のまま保持さ
れるので、合金化処理をおこなってもミクロ凹凸が顕著
にあらわれることはない。When the annealing treatment is carried out under the conditions defined as described above (the invention described above), the crystal grains are kept as fine grains, so that even when the alloying treatment is carried out, the micro unevenness appears remarkably. There is no.
【００２５】の発明は非酸化性雰囲気中でその鋼板の
再結晶温度より低い温度で加熱して選択酸化層を形成さ
せた後、続いて再結晶温度以上で加熱する処理を施し、
めっき及び合金化処理する方法である。このときの加熱
の雰囲気は非酸化性雰囲気とする。これは、酸化性雰囲
気で加熱すると、鋼板表面に鉄の酸化物が形成され、溶
融亜鉛めっきに供すると、めっき付着がみられないか、
あるいは、付着してもめっき層が剥離してしまうためで
ある。According to the invention of (1), after heating at a temperature lower than the recrystallization temperature of the steel sheet in a non-oxidizing atmosphere to form a selective oxidation layer, a treatment of heating at a temperature higher than the recrystallization temperature is performed.
It is a method of plating and alloying treatment. The heating atmosphere at this time is a non-oxidizing atmosphere. This is because when heated in an oxidizing atmosphere, iron oxide is formed on the surface of the steel sheet, and when it is subjected to hot dip galvanizing, there is no plating adhesion,
Alternatively, it is because the plating layer is peeled off even if it is attached.
【００２６】また、加熱温度の上限は、機械的性質及び
加工性が劣化しないように、すなわち、鋼組織がα相か
らγ相へ変化しないように、実用鋼では 900〜950 ℃
（Ａ3変態点）とするのが好ましい。The upper limit of the heating temperature is 900 to 950 ° C. in practical steel so that the mechanical properties and workability are not deteriorated, that is, the steel structure does not change from α phase to γ phase.
(A 3 transformation point) is preferable.
【００２７】再結晶温度以上で加熱することにより従来
の焼鈍を施して得られる鋼板と同等の機械的性質を有す
る合金化溶融亜鉛めっき鋼板を得ることができる。これ
は、前記の図３に示したように、選択酸化層１は鋼板表
面から深さ0.1 μm 程度までしか生成していないから、
再結晶温度以上に加熱した場合には、鋼板表面の結晶粒
２はそのままで、鋼板の内部の結晶粒は再結晶により成
長し、従来の焼鈍で得られる鋼板と同様の結晶組織を有
するようになるからである。By heating above the recrystallization temperature, it is possible to obtain an alloyed hot dip galvanized steel sheet having the same mechanical properties as the steel sheet obtained by conventional annealing. This is because, as shown in FIG. 3, the selective oxidation layer 1 is formed only up to a depth of about 0.1 μm from the steel plate surface.
When heated above the recrystallization temperature, the crystal grains 2 on the surface of the steel sheet remain as they are, and the crystal grains inside the steel sheet grow by recrystallization so that they have the same crystal structure as the steel sheet obtained by conventional annealing. Because it will be.
【００２８】なお、溶融亜鉛めっきの前に行う焼鈍処理
は、連続焼鈍、バッチ焼鈍のいずれでもよい。The annealing treatment performed before hot dip galvanizing may be either continuous annealing or batch annealing.
【００２９】[0029]
【実施例１】母材鋼板として、表１に示す板厚 0.8mmの
冷延鋼板を用い、溶融亜鉛めっきおよび合金化処理を行
った後のめっき鋼板の表面性状を評価した。表１には、
これらの鋼板の再結晶温度も併せ示した。また、各鋼板
の化学組成を表２に示す。Example 1 As a base steel sheet, a cold-rolled steel sheet having a plate thickness of 0.8 mm shown in Table 1 was used, and the surface properties of the plated steel sheet after hot dip galvanizing and alloying treatment were evaluated. In Table 1,
The recrystallization temperatures of these steel sheets are also shown. Table 2 shows the chemical composition of each steel sheet.
【００３０】これらの供試材を 200mm×50mmに裁断し、
トリクロルエチレンで脱脂した後、溶融めっきシュミレ
ーターを用いて、下記の条件で、加熱、溶融めっきおよ
び合金化処理を行った。なお、加熱条件（ヒートパター
ン）は表３に示す通りであり、再結晶温度より低い温度
での加熱処理（選択酸化処理）に続いて、一部のものに
は再結晶温度以上での加熱処理（再結晶処理）を施し
た。These test materials were cut into 200 mm × 50 mm,
After degreasing with trichloroethylene, heating, hot dip coating and alloying treatment were performed under the following conditions using a hot dip plating simulator. The heating conditions (heat pattern) are as shown in Table 3, and the heating treatment (selective oxidation treatment) at a temperature lower than the recrystallization temperature is followed by some heating treatment at the recrystallization temperature or higher. (Recrystallization treatment) was performed.
【００３１】〔加熱条件〕 ・雰囲気 26％H2＋N2（H2/H2O比：３×1
04 ） 〔溶融亜鉛めっき条件〕 ・めっき浴中Al濃度 0.10重量％ ・めっき浴温度 460 ℃ ・浸漬時間 1 秒 〔合金化処理条件〕 ・処理時間 500 ℃ ・雰囲気 大気 合金化処理した後、めっき鋼板の表面および断面を走査
型電子顕微鏡で観察し、めっき鋼板の表面性状を評価し
た。評価基準は、ミクロ凹凸の発生度合に応じて表面性
状を３段階に分類し、ミクロ凹凸の発生がない場合をラ
ンク１、従来と同程度の場合をランク３、両者の中間
で、若干のミクロ凹凸がみられる場合をランク２とし
た。評価結果を表３に併せて示す。[Heating conditions] Atmosphere 26% H 2 + N 2 (H 2 / H 2 O ratio: 3 × 1
0 4 ) [Hot dip galvanizing conditions] ・ Al concentration in plating bath 0.10% by weight ・ Plating bath temperature 460 ℃ ・ Dip time 1 second [Alloying condition] ・ Treatment time 500 ℃ ・ Atmosphere Atmosphere After plating, plating The surface and cross section of the steel sheet were observed with a scanning electron microscope to evaluate the surface properties of the plated steel sheet. The evaluation criteria is to classify the surface texture into three levels according to the degree of occurrence of micro irregularities, rank 1 when no micro irregularities occur, rank 3 when the degree of micro irregularities is the same as the conventional level, and some micro in between. The case where unevenness was observed was ranked 2. The evaluation results are also shown in Table 3.
【００３２】表３の結果から明らかなように、本発明で
定めた条件で加熱した場合は、いずれも合金化後のめっ
き表面にミクロ凹凸の発生は認められない。これに対し
て本発明の規定から外れた条件で加熱した比較例では、
ミクロ凹凸が発生しており、特に、加熱温度が高いほど
多発している。As is clear from the results shown in Table 3, in the case of heating under the conditions defined in the present invention, no micro unevenness is observed on the plated surface after alloying. On the other hand, in the comparative example heated under conditions out of the definition of the present invention,
Micro unevenness is generated, and in particular, the higher the heating temperature is, the more frequently it occurs.
【００３３】[0033]
【表１】 [Table 1]
【００３４】[0034]
【表２】 [Table 2]
【００３５】[0035]
【表３】 [Table 3]
【００３６】[0036]
【実施例２】実施例１で用いた供試材（Ａ鋼）を実施例
１と同様に裁断し、脱脂した後、表４に示す条件（ヒー
トパターン）で加熱処理し、その後、実施例１と同じ条
件で溶融亜鉛めっきおよび合金化処理を行い、めっき鋼
板の表面性状を評価した。評価基準は実施例１の場合と
同じであるが、特に、めっき付着がみられない場合、あ
るいは、めっき層が剥離する場合は、×印で示した。評
価結果を表４に併せて示す。Example 2 The test material (A steel) used in Example 1 was cut and degreased in the same manner as in Example 1, and then heat-treated under the conditions (heat pattern) shown in Table 4, and then the example. Hot-dip galvanizing and alloying treatments were performed under the same conditions as in No. 1, and the surface properties of the plated steel sheet were evaluated. The evaluation criteria are the same as in Example 1, but in particular, when no adhesion of plating is observed or when the plating layer is peeled off, it is indicated by a cross. The evaluation results are also shown in Table 4.
【００３７】表４の結果にみられるように、選択酸化処
理をO2を含む酸化性雰囲気中で行うと、その後非酸化性
雰囲気中で再結晶処理をしてもミクロ凹凸の発生は避け
られず（No. 26）、また、O2を含む酸化性雰囲気中で選
択酸化処理のみを行った場合（No. 23）、あるいは、再
結晶処理をO2を含む酸化性雰囲気中で行った場合は（N
o. 25）、めっき付着不良あるいはめっき層の剥離が生
じ、正常なめっき層は得られなかった。As can be seen from the results in Table 4, when the selective oxidation treatment is carried out in an oxidizing atmosphere containing O 2 , even if recrystallization treatment is subsequently carried out in a non-oxidizing atmosphere, generation of micro unevenness can be avoided. No (No. 26), when only selective oxidation treatment was performed in an oxidizing atmosphere containing O 2 (No. 23), or when recrystallization treatment was performed in an oxidizing atmosphere containing O 2 Is (N
o.25), defective plating adhesion or peeling of the plating layer occurred, and a normal plating layer could not be obtained.
【００３８】[0038]
【表４】 [Table 4]
【００３９】[0039]
【発明の効果】本発明方法を適用することにより、自動
車車体用として好適な、ミクロ凹凸のない表面性状に優
れた合金化溶融亜鉛めっき鋼板を製造することができ
る。この方法は従来の還元焼鈍で使用されている雰囲気
中で、ヒートパターンを変えるだけで行うことができる
ので、実用上極めて有用である。By applying the method of the present invention, it is possible to produce an alloyed hot-dip galvanized steel sheet which is suitable for automobile bodies and has excellent surface properties without micro irregularities. This method is extremely useful in practice because it can be performed only by changing the heat pattern in the atmosphere used in conventional reduction annealing.
【図１】本発明方法による合金化溶融亜鉛めっき鋼板の
製造プロセスにおける鋼板の温度変化の状況を示す図で
ある。FIG. 1 is a diagram showing a situation of temperature change of a steel sheet in a manufacturing process of a galvannealed steel sheet according to the method of the present invention.
【図２】従来法による合金化溶融亜鉛めっき鋼板の製造
プロセスにおける鋼板の温度変化の状況を示す図であ
る。FIG. 2 is a diagram showing a situation of temperature change of a steel sheet in a manufacturing process of a galvannealed steel sheet by a conventional method.
【図３】本発明方法を適用することにより鋼板表面に生
成する選択酸化層の断面を示す模式図である。FIG. 3 is a schematic view showing a cross section of a selective oxidation layer formed on the surface of a steel sheet by applying the method of the present invention.
【図４】Alキルド鋼を本発明方法で規定する条件で焼鈍
した後の表面の状態を示す図で、(a) 図は走査型電子顕
微鏡で観察した結果を示す図、(b) 図は(a) に対応する
部分をＳＩＭＳ（二次イオン質量分析法）で分析した結
果を示す図である。FIG. 4 is a diagram showing a state of a surface of an Al killed steel after being annealed under a condition specified by the method of the present invention. (A) is a diagram showing a result observed by a scanning electron microscope, (b) is a diagram. It is a figure which shows the result of having analyzed the part corresponding to (a) by SIMS (secondary ion mass spectrometry).
Claims (2)
中で、 550℃以上でその鋼板の再結晶温度より低い温度
域で加熱して鋼板表面に鉄より酸化されやすい元素の選
択酸化層を形成させ、溶融亜鉛浴に浸漬して亜鉛めっき
を施した後、亜鉛めっき層を素地鋼と合金化させること
を特徴とする合金化溶融亜鉛めっき鋼板の製造方法。1. A base steel sheet is heated in a non-oxidizing atmosphere with respect to iron at a temperature range of 550 ° C. or higher and a temperature range lower than the recrystallization temperature of the steel sheet. A method for producing an alloyed hot-dip galvanized steel sheet, which comprises forming a selective oxidation layer, immersing it in a hot-dip galvanized bath for galvanizing, and then alloying the galvanized layer with a base steel.
中で、 550℃以上でその鋼板の再結晶温度より低い温度
域で加熱して鋼板表面に鉄より酸化されやすい元素の選
択酸化層を形成させ、続いて再結晶温度以上の温度域で
加熱し、溶融亜鉛浴に浸漬して亜鉛めっきを施した後、
亜鉛めっき層を素地鋼と合金化させることを特徴とする
合金化溶融亜鉛めっき鋼板の製造方法。2. A base material steel sheet is heated in an atmosphere non-oxidizing to iron at a temperature range of 550 ° C. or higher and lower than the recrystallization temperature of the steel sheet, so that the surface of the steel sheet contains elements that are more easily oxidized than iron. After forming a selective oxidation layer, followed by heating in a temperature range equal to or higher than the recrystallization temperature, and dipping in a molten zinc bath for galvanization,
A method for producing an alloyed hot-dip galvanized steel sheet, which comprises alloying a galvanized layer with a base steel.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2923092A JPH05222501A (en) | 1992-02-17 | 1992-02-17 | Manufacture of galvannealed steel sheet |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2923092A JPH05222501A (en) | 1992-02-17 | 1992-02-17 | Manufacture of galvannealed steel sheet |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH05222501A true JPH05222501A (en) | 1993-08-31 |
Family
ID=12270424
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2923092A Pending JPH05222501A (en) | 1992-02-17 | 1992-02-17 | Manufacture of galvannealed steel sheet |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH05222501A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2013007066A (en) * | 2011-06-22 | 2013-01-10 | Mitsubishi Cable Ind Ltd | Method and device for producing plated wire material |
-
1992
- 1992-02-17 JP JP2923092A patent/JPH05222501A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2013007066A (en) * | 2011-06-22 | 2013-01-10 | Mitsubishi Cable Ind Ltd | Method and device for producing plated wire material |
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