JPH1150139A - Production of galvanized steel sheet - Google Patents
Production of galvanized steel sheetInfo
- Publication number
- JPH1150139A JPH1150139A JP20170797A JP20170797A JPH1150139A JP H1150139 A JPH1150139 A JP H1150139A JP 20170797 A JP20170797 A JP 20170797A JP 20170797 A JP20170797 A JP 20170797A JP H1150139 A JPH1150139 A JP H1150139A
- Authority
- JP
- Japan
- Prior art keywords
- steel sheet
- annealing
- hot
- plating
- oxygen
- 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)
- Heat Treatment Of Strip Materials And Filament Materials (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、溶融亜鉛めっき鋼
板の不めっき、さざ波、アッシュ引き等の焼鈍後めっき
前の板表面に関わる格落ち欠陥が極めて少ない溶融亜鉛
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 method for producing a hot-dip galvanized steel sheet which has very few downgrade defects on the surface of the hot-dip galvanized steel sheet before annealing, such as non-plating, ripples, and ashing.
【０００２】[0002]
【従来の技術】溶融亜鉛めっき鋼板は他のめっき鋼板と
比較して、安価でかつ薄目付けが容易であることから、
自動車、建築、家電用に使用されている。溶融亜鉛めっ
きの種類としてはいわゆる溶融亜鉛めっき鋼板だけでは
なく、溶融亜鉛めっき直後に合金化処理を施した合金化
溶融亜鉛めっき鋼板や、溶融亜鉛めっきに比較的多量に
Ａｌを添加したいわゆるガルファン（５％Ａｌ）やガル
バリウム（５５％Ａｌ）などがある。いずれも溶融亜鉛
めっき浴に板を直接接触させることにより製造するため
に、焼鈍後のめっき前の板表面の性状が重要である。焼
鈍後めっき前の鋼板表面に関わる欠陥としては、不めっ
き、さざ波、アッシュ引きなどがある。不めっきはめっ
きの付着していない鋼板の露出した部分が生ずることで
あり、溶融亜鉛めっきとしては致命的な欠陥となる。さ
ざ波はさざ波状の白い色調欠陥であるが、酷い場合には
凹凸欠陥となり、この場合はプレス外板には致命的欠陥
である。アッシュ引きは溶融亜鉛浴表面の酸化膜引きで
ある。もちろん、大部分はこれらの欠陥の発生がないよ
うに操業するべきであり、例えば鋼板中への添加元素の
制限、侵入板温の上昇、浴温の上昇、ＮＯＦ（無酸化
炉）での酸化処理、焼鈍炉全体の水素濃度上昇などが比
較的効果的である。しかし、これらの欠陥は確率的に発
生し、全体に発生するのではなく、全体のごく一部にの
み局所的に発生するものである。そして、原因を特定で
きない以上、９９％は問題なくても、全生産量の内の格
落ち率が０．１〜０．５％、酷い場合には１％以下程度
の焼鈍後の表面に関わる欠陥は事実上避けがたいもので
あった。2. Description of the Related Art Hot-dip galvanized steel sheets are inexpensive and easy to make thinner than other coated steel sheets.
Used for automobiles, architecture, and home appliances. The types of hot-dip galvanized steel are not only so-called hot-dip galvanized steel sheets, but also alloyed hot-dip galvanized steel sheets that have been subjected to an alloying process immediately after hot-dip galvanizing, and so-called galvan ( 5% Al) and galvalume (55% Al). In any case, since the plate is manufactured by directly contacting the plate with the hot-dip galvanizing bath, the properties of the plate surface after the annealing and before the plating are important. Defects related to the steel sheet surface after annealing and before plating include non-plating, ripples, and ash pulling. Non-plating is the occurrence of an exposed portion of a steel plate to which no plating is attached, which is a fatal defect for hot-dip galvanizing. Ripple is a ripple-like white color defect, but if it is severe, it becomes a concave / convex defect, and in this case, it is a fatal defect in the press outer plate. The ash pull is an oxide film pull on the surface of the molten zinc bath. Of course, most should operate without these defects, such as limiting the elements added to the steel sheet, increasing the intrusion plate temperature, increasing the bath temperature, and oxidizing in a NOF (non-oxidizing furnace). Treatment, increase in hydrogen concentration in the entire annealing furnace, etc. are relatively effective. However, these defects occur stochastically and do not occur entirely but locally only in a small part of the whole. Since the cause cannot be specified, even if 99% is not a problem, the downgrade rate of the entire production is related to the annealed surface of about 0.1 to 0.5%, and in severe cases, about 1% or less. The flaw was virtually unavoidable.
【０００３】なお、焼鈍炉の雰囲気を規定した従来技術
は多数あり、例えば、特開平５−９６９３号公報、特開
平４−４８０６２号公報などがあるが、これらは焼鈍炉
も一般的条件であり、不めっき、さざ波、アッシュ引き
等の焼鈍後めっき前の欠陥を低減する観点からは、何の
知見も与えてくれない。また、特開平３−２５３５４８
号公報にはスナウト内の酸素濃度を２０〜２００ｐｐｍ
とすることが開示されているが、これはスナウト内のＺ
ｎ浴表面からのＺｎの蒸発を防止することを目的とし、
浴表面に酸化物を生成させるものである。[0003] There are many prior arts that define the atmosphere of an annealing furnace, for example, Japanese Patent Application Laid-Open Nos. 5-9693 and 4-48062, which are general conditions for an annealing furnace. It does not give any knowledge from the viewpoint of reducing defects before plating after annealing such as non-plating, ripples and ashing. Also, JP-A-3-253548
The publication discloses that the oxygen concentration in the snout is 20 to 200 ppm.
, But this is the Z in the snout.
The purpose is to prevent the evaporation of Zn from the n-bath surface,
An oxide is formed on the bath surface.
【０００４】[0004]
【発明が解決しようとする課題】本発明は溶融亜鉛めっ
き鋼板の、特に、不めっき、さざ波、アッシュ引き等の
焼鈍後めっき前の鋼板表面に関わる格落ち欠陥の極めて
少ない製造方法に関するものであり、これらの欠陥によ
る格落ち欠陥発生率が極めて少ない製造方法を提供する
ものである。SUMMARY OF THE INVENTION The present invention relates to a method for producing a hot-dip galvanized steel sheet, in particular, with extremely few downgrade defects relating to the steel sheet surface before annealing such as non-plating, ripples and ashing. An object of the present invention is to provide a manufacturing method in which the rate of occurrence of downgrade defects due to these defects is extremely small.
【０００５】[0005]
【課題を解決するための手段】本発明は、前記問題点を
解決するるためになされたもので、溶融亜鉛めっき浴に
先立つ連続焼鈍の再結晶焼鈍後の冷却から溶融亜鉛めっ
き浴に侵入するまでの過程において、水素濃度、酸素濃
度及び鋼板温度の関係が次式を満たすように制御するこ
とを特徴とする、焼鈍後めっき前の板表面に関わる欠陥
の少ない溶融亜鉛めっき鋼板の製造方法である。SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and enters the hot dip galvanizing bath from cooling after recrystallization annealing in continuous annealing prior to the hot dip galvanizing bath. In the process up to, characterized in that the relationship between the hydrogen concentration, oxygen concentration and the steel sheet temperature is controlled so as to satisfy the following equation, a method for producing a hot-dip galvanized steel sheet with few defects related to the sheet surface before plating after annealing. is there.
【０００６】１＜〔Ｏ〕＜（０．０００２５Ｔ2 −０．
２２５Ｔ＋５５）×〔Ｈ〕 ただし、〔Ｏ〕：酸素濃度（ｐｐｍ） Ｔ ：鋼板温度（℃） 〔Ｈ〕：水素濃度（％） とする。1 <[O] <(0.00025T 2 -0.
225T + 55) × [H] where [O]: oxygen concentration (ppm) T: steel sheet temperature (° C.) [H]: hydrogen concentration (%)
【０００７】[0007]
【発明の実施の形態】本発明者らは、よく知られている
不めっき現象を再確認し、例えば、（ａ）鋼中の易酸化
性元素（特にＳｉ、添加量が多ければＭｎ、Ｃｒ等）は
焼鈍時に表面濃化し、これがめっき性を阻害すること、
（ｂ）この対策としては、例えば焼鈍初期の酸化処理、
鋼中への添加量制限など、表面濃化の低減が有効である
こと、（ｃ）侵入板温や浴温度上昇により反応性がアッ
プし、改善される傾向にあること、（ｄ）スケール残り
や偏析等の原板欠陥原因もあること、等を再確認した。
しかし、同時に、不めっきの発生が確率的な現象である
こと、特に特徴のない軟鋼板やＰ添加３５キロクラスの
鋼板でも発生しうることに鑑み、上記の焼鈍時の表面濃
化のような原因のみでは説明しきれないことを知見し
た。そこで、その原因について鋭意検討した結果本発明
に至ったものである。DETAILED DESCRIPTION OF THE INVENTION The present inventors reconfirmed the well-known non-plating phenomenon, and found, for example, that (a) oxidizable elements (especially Si, Mn, Cr Etc.) are concentrated on the surface during annealing, which impairs the plating property.
(B) As a countermeasure, for example, oxidation treatment in the early stage of annealing,
(C) that the reactivity tends to be improved and improved by increasing the infiltration plate temperature or bath temperature, and (d) scale residue It was reconfirmed that there were also causes of defects in the original sheet, such as cracking and segregation.
However, at the same time, in view of the fact that the occurrence of non-plating is a stochastic phenomenon, especially in the case of mild steel sheets without special features and steel sheets with a P added of 35 kg class, it is possible to generate such a phenomenon as the above-described surface concentration during annealing. We found that it could not be explained by the cause alone. Then, as a result of diligent studies on the cause, the present invention has been achieved.
【０００８】また、同様に、さざ波やアッシュ引きに関
しても焼鈍後めっき前の鋼板表面の性状が大きく影響し
ていることを見出し、本発明に至ったものである。めっ
き前の連続焼鈍炉中には水素が添加され、露点（水蒸気
の結露温度）との比率Ｈ2 ／Ｈ2 Ｏで管理されるのが通
常である。加熱方式としてはＮＯＦ（無酸化炉）方式や
オールラジアントチューブ方式があり、前者では加熱工
程ではＦｅにとって酸化性である場合もあり、後者では
全て還元性である。加熱工程を経たごは、通常はＦｅに
とって還元性の雰囲気下であり、還元と再結晶が同時に
行われ、その後、およそ浴温度に近い温度まで冷却され
た後、溶融亜鉛めっき浴に導かれる。にもかかわらず、
軟鋼や３５キロクラスの鋼板でも不めっきが発生しうる
原因は、還元焼鈍終了後の還元された鋼板が、その後の
冷却時に酸化する現象によろものであり、微量酸素が原
因であることを見出した。[0008] Similarly, it has been found that the properties of the steel sheet surface after annealing and before plating are greatly affected also with respect to ripples and ash pulls, and the present invention has been accomplished. Normally, hydrogen is added to the continuous annealing furnace before plating, and is controlled by the ratio H 2 / H 2 O with respect to the dew point (condensation temperature of steam). As a heating method, there are a NOF (non-oxidizing furnace) method and an all-radiant tube method. In the former, Fe may be oxidizing in the heating step, and in the latter, all are reducing. After passing through the heating step, the slag is usually in a reducing atmosphere for Fe, and reduction and recrystallization are simultaneously performed. Thereafter, the slag is cooled to a temperature close to a bath temperature, and then led to a hot-dip galvanizing bath. in spite of,
The reason why non-plating can occur even in mild steel and steel sheets of 35 kg class is due to the phenomenon that the reduced steel sheet after the end of reduction annealing is oxidized during subsequent cooling, and it is found that trace oxygen is the cause. Was.
【０００９】還元焼鈍終了後の温度域における水素を含
有する雰囲気下での、酸素量が鋼板表面の酸化量に及ぼ
す影響を図１に示す。図１は４％Ｈ2 −Ｎ2 雰囲気で鋼
板温度５００℃における酸素濃度（Ｏ2 ｐｐｍ）と酸化
量（酸素のｍｇ／ｍ2 ）との関係を示すもので、鋼種は
３５キロクラスＰ添加ハイテンと極低炭素軟鋼について
示した。鋼板表面の酸化量は蛍光Ｘ線（ＬＳＡ結晶を使
用）の検量線法により定量化した。水素含有雰囲気下で
も雰囲気中に微量酸素が存在することにより、鋼板表面
が酸化されることがわかる。また、極低炭素軟鋼よりも
３５キロクラスの鋼の方が酸化されやすいことがわか
る。FIG. 1 shows the effect of the amount of oxygen on the amount of oxidation of the steel sheet surface in a hydrogen-containing atmosphere in the temperature range after the completion of the reduction annealing. FIG. 1 shows the relationship between the oxygen concentration (O 2 ppm) and the oxidation amount (mg / m 2 of oxygen) at a steel sheet temperature of 500 ° C. in a 4% H 2 —N 2 atmosphere. Hyten and ultra-low carbon mild steel are shown. The amount of oxidation on the surface of the steel sheet was quantified by a calibration curve method using fluorescent X-rays (using LSA crystals). It can be seen that even under a hydrogen-containing atmosphere, the presence of trace oxygen in the atmosphere oxidizes the steel sheet surface. In addition, it can be seen that 35 kg class steel is more easily oxidized than extremely low carbon mild steel.
【００１０】なお、この条件は、平衡論的には、エリン
ガムダイヤグラムから明らかなように、Ｈ2 ／Ｈ2 Ｏの
比率からはＦｅにとって還元性雰囲気である。酸素濃度
からはこのような微量であっても酸化性雰囲気である
が、焼鈍炉加熱帯から均熱帯にかけて微量酸素が含まれ
ていることはよくあり、その類推から、全体としては還
元性雰囲気と思われていた。例えば特開平３−２５３５
４８号公報も、Ｚｎ浴表面の酸化について述べている
が、鋼板表面の酸化については何の記載もない。Ｆｅよ
りも酸化されやすいＺｎがさほど酸化されていないので
あれば、Ｆｅはより酸化されないと考えられよう。ま
た、平衡論から考えて、焼鈍炉内で測定でされる酸素
は、計器の精度問題や雰囲気ガスのサンプリング問題と
も考えられる。In terms of equilibrium, this condition is a reducing atmosphere for Fe from the ratio of H 2 / H 2 O, as is clear from the Ellingham diagram. From the oxygen concentration, it is an oxidizing atmosphere even with such a small amount, but it is common for trace amounts of oxygen to be contained from the heating zone of the annealing furnace to the soaking tropics. Was thought. For example, JP-A-3-2535
Japanese Patent Publication No. 48 also describes oxidation of the surface of the Zn bath, but does not describe anything about oxidation of the surface of the steel sheet. If Zn, which is more likely to be oxidized than Fe, is not so oxidized, it will be considered that Fe is less oxidized. In addition, considering the equilibrium theory, oxygen measured in the annealing furnace is considered to be a problem of accuracy of the instrument and a problem of sampling of atmospheric gas.
【００１１】同様に、水素を含有する雰囲気下での酸素
量と鋼板温度が鋼板表面酸化量に及ぼす影響を図２に示
す。図２は４％Ｈ2 −Ｎ2 雰囲気中での極低炭素軟鋼の
鋼板温度（℃）と酸化量（酸素のｍｇ／ｍ2 ）との関係
をＯ2 濃度をパラメータとして示したものである。鋼板
温度が高温側では還元性の作用が大きく酸化量は少な
い。つまり、高温ではＦｅが酸化されにくく、低温ほど
酸化が進行することがわかる。すなわち、水素による還
元反応と酸素による酸化反応との競争反応であり、高温
域では水素による還元反応が優位であるが、低温域では
酸素による酸化反応が優位なのである。従って、高温域
では酸素のことを考慮する必要はほとんど無い。ところ
が、低温域ではこのように鋼板表面に酸化物がある場合
には不めっきが発生しうることは当然であり、図２の条
件でめっき実験を行った結果、鋼板表面の酸化量が酸素
として１０ｍｇ／ｍ2 以上の場合には実際に不めっき発
生を確認することができた。１０ｍｇ／ｍ2 未満であれ
ば不めっき等の発生を著しく抑制できた。そしてこのよ
うな板の表面状態にするためには焼鈍後の冷却時の板の
温度と酸素濃度、水素濃度を式のように制御すればよい
ことを見出した。Similarly, FIG. 2 shows the effect of the amount of oxygen and the temperature of the steel sheet in the atmosphere containing hydrogen on the amount of oxidation of the steel sheet surface. FIG. 2 shows the relationship between the steel sheet temperature (° C.) and the oxidation amount (mg / m 2 of oxygen) of the ultra-low carbon mild steel in a 4% H 2 —N 2 atmosphere, using the O 2 concentration as a parameter. . When the steel sheet temperature is high, the reducing action is large and the oxidation amount is small. That is, it is understood that Fe is hardly oxidized at a high temperature, and oxidation progresses at a low temperature. That is, it is a competitive reaction between the reduction reaction by hydrogen and the oxidation reaction by oxygen, and the reduction reaction by hydrogen is superior in a high temperature range, but the oxidation reaction by oxygen is superior in a low temperature range. Therefore, there is almost no need to consider oxygen in the high temperature range. However, it is natural that non-plating can occur when the oxide is present on the steel sheet surface in the low temperature range, and as a result of performing a plating experiment under the conditions of FIG. In the case of 10 mg / m 2 or more, occurrence of non-plating was actually confirmed. If it is less than 10 mg / m 2 , the occurrence of non-plating and the like can be suppressed remarkably. It has been found that in order to obtain such a surface state of the plate, the temperature, the oxygen concentration, and the hydrogen concentration of the plate at the time of cooling after annealing may be controlled as in the following equation.
【００１２】そこで、実際のＣＧＬ（連続溶融亜鉛めっ
きライン）での加熱帯、均熱帯、冷却帯、及び侵入前に
おける雰囲気条件を測定してみると、微量ではあるが酸
素が検出され、最高到達温度付近では十分に還元性であ
ったが、その後の冷却帯以降では、図２の結果から判断
すると、酸化されうることが判明した。そこで、冷却帯
以降での酸素濃度と鋼板温度を調整した結果、本発明の
範囲内であれば、不めっき欠陥を事実上皆無にすること
ができることを知見した。また、同時にさざ波やアッシ
ュ引きも減少することを知見した。これらの結果から、
本発明を完成したものである。[0012] Then, when the heating zone, the soaking zone, the cooling zone, and the atmospheric conditions before intrusion in the actual CGL (continuous hot-dip galvanizing line) were measured, oxygen was detected, albeit in a trace amount, and reached the maximum. Although it was sufficiently reducing around the temperature, it was found that it could be oxidized after the cooling zone, judging from the results of FIG. Then, as a result of adjusting the oxygen concentration and the steel sheet temperature after the cooling zone, it was found that non-plating defects could be virtually eliminated within the scope of the present invention. At the same time, they found that ripples and ash pulls also decreased. From these results,
The present invention has been completed.
【００１３】また、これらの結果より、不めっき、さざ
波、アッシュ引き等の欠陥が焼鈍後めっき前の鋼板表面
に関わる欠陥であることが明らかとなった。酸素濃度を
本発明の範囲内に制御するための手段としては、連続焼
鈍炉の後部からの水素含有投入ガス量増加、後部の炉圧
の上昇による酸素濃度の低減、焼鈍炉冷却帯以降での微
量酸素の導入による酸素濃度上昇等の手段が有効であ
る。Further, from these results, it has been clarified that defects such as non-plating, ripples, and ashing are defects relating to the steel sheet surface after annealing and before plating. Means for controlling the oxygen concentration within the scope of the present invention include: an increase in the amount of hydrogen-containing input gas from the rear of the continuous annealing furnace, a reduction in the oxygen concentration due to an increase in the furnace pressure in the rear, and the cooling zone after the annealing furnace cooling zone. Means of increasing the oxygen concentration by introducing a trace amount of oxygen are effective.
【００１４】なお、連続焼鈍炉には水素含有ガスは意図
的に導入しているが、酸素は特開平３−２５３５４８号
公報のように、意図的に導入する場合も稀にはあるが、
通常は、意図的に導入しているわけではなくまた、平衡
論からは酸素が検出できるはずがない。しかし、実際に
は酸素が検出され、これは炉壁やストリップ侵入口等の
わずかな隙間からの侵入であり、平衡に達する前の定常
状態なのであろうと考えられる。実際問題として、酸素
濃度を、平衡論のように、１ｐｐｍ以下を達成すること
は至難の業であり、膨大なコストがかかる。実用上は、
微量酸素を含有しても本発明範囲内では酸化反応はほと
んど起こらず、事実上全く問題ないので、１ｐｐｍより
大きい範囲とした。Although the hydrogen-containing gas is intentionally introduced into the continuous annealing furnace, oxygen is intentionally introduced rarely as in Japanese Patent Application Laid-Open No. 3-253548.
Usually, it is not introduced intentionally, and oxygen cannot be detected from equilibrium theory. However, actually, oxygen is detected, and this is an intrusion through a small gap such as a furnace wall or a strip entrance, and it is considered that this is a steady state before equilibrium is reached. As a practical matter, achieving an oxygen concentration of 1 ppm or less, as in the theory of equilibrium, is extremely difficult and requires enormous costs. In practice,
Even if a trace amount of oxygen is contained, the oxidation reaction hardly occurs within the scope of the present invention, and there is practically no problem.
【００１５】めっきのない連続焼鈍による焼鈍材製造の
場合には、テンパーカラーが発生すると、目視で判別す
ることができ、対応は容易である。しかし、めっき鋼板
製造の場合には、焼鈍後めっき前の鋼板表面をよく見る
ことはできず、仮に見えたしても、テンパーカラーがほ
とんど見えないほどの酸化量でも不めっき発生するほど
感受性が高いので溶融めっき鋼板製造の困難性がある。
実際にめっきのない焼鈍材製造のテンパーカラー解消の
知見をもってしても、不めっきを解消することはできな
かった。また、さざ波やアッシュ引きの場合には、焼鈍
後めっき前の鋼板板面がどれほど影響しているか、ほと
んど未知であった。In the case of producing an annealed material by continuous annealing without plating, when a temper color occurs, it can be visually identified, and the response is easy. However, in the case of plated steel sheet manufacturing, the steel sheet surface after annealing cannot be seen well before plating, and even if it is visible, even if the oxidation amount is such that the temper color is hardly visible, the sensitivity is so high that non-plating occurs. Since it is expensive, there is difficulty in manufacturing hot-dip coated steel sheets.
Even with the knowledge of eliminating temper color in the manufacture of annealed material without plating, non-plating could not be eliminated. In the case of ripples and ash pulls, it was almost unknown how much the surface of the steel sheet before annealing and before plating had an effect.
【００１６】本発明では焼鈍炉の冷却帯よりも前の均熱
帯又は加熱帯の雰囲気については特に規定しない。最高
到達板温時に還元されていれば十分であるためであり、
通常の連続焼鈍炉では還元されている。加熱方式として
はＮＯＦ（無酸化炉）であってもオールラジアント炉で
あってもよく、無関係である。めっき鋼板の種類として
は、溶融亜鉛めっき、合金化溶融亜鉛めっき、ガルファ
ン、ガルバリウムいずれにおいても同じことである。In the present invention, the atmosphere in the soaking zone or the heating zone before the cooling zone of the annealing furnace is not particularly specified. It is enough if it is reduced at the highest plate temperature,
It is reduced in a normal continuous annealing furnace. The heating method may be a NOF (non-oxidizing furnace) or an all-radiant furnace, which is irrelevant. The same applies to the types of galvanized steel sheets in hot-dip galvanizing, galvannealing, galvanizing, and galvalume.
【００１７】なお浴温度や侵入板温、Ａｌ濃度などのめ
っき条件、或いは原板の種類によって、不めっき、さざ
波又は、アッシュ引き欠陥に対する感受性がやや異なる
場合がある。そのために、本発明が規定した式の係数や
定数項はやや異なる場合があり得る。より安全には次式
のように狭くした範囲がより好ましい。 １＜〔Ｏ〕＜（０．０００１２５Ｔ2 −０．１１２５Ｔ
＋２７．５）×〔Ｈ〕 ただし、〔Ｏ〕：酸素濃度（ｐｐｍ） Ｔ ：板温度（℃） 〔Ｈ〕：水素濃度（％）The susceptibility to non-plating, ripples, or ash-pull defects may vary slightly depending on plating conditions such as bath temperature, penetration plate temperature, and Al concentration, or the type of original plate. Therefore, the coefficients and constant terms of the formula defined by the present invention may be slightly different. For more safety, a narrow range as shown in the following equation is more preferable. 1 <[O] <(0.000125T 2 -0.1125T
+27.5) × [H] where [O]: oxygen concentration (ppm) T: plate temperature (° C.) [H]: hydrogen concentration (%)
【００１８】[0018]
【実施例】以下に本発明の一例を示す。極低炭素鋼（供
試鋼Ａ）、低炭素鋼（供試鋼Ｂ）及びＰ添加３５キロク
ラス鋼（供試鋼Ｃ）の供試材を転炉にて溶製した後、連
続鋳造によりスラブとした。このスラブをスラブ加熱温
度（ＳＲＴ）１１５０〜１２００℃、仕上げ温度９００
〜９２０℃、コイル巻き取り温度５００〜８００℃にて
熱間圧延し３５ｍｍ厚とした。その後、酸洗によりスケ
ール層を除去し冷間圧延を行い０．７ｍｍ厚とした。こ
の冷間圧延板を連続溶融亜鉛めっきライン（ＣＧＬ）に
おいて、８００〜８５０℃で再結晶焼鈍を行った後、冷
却し、４７０℃で溶融亜鉛めっきを行った。この際、冷
却帯から溶融亜鉛めっきまでの板温度と雰囲気を制御し
た。An example of the present invention will be described below. Specimens of ultra-low carbon steel (test steel A), low carbon steel (test steel B) and P-added 35 kg class steel (test steel C) were melted in a converter, and then continuously cast. Slab. This slab is heated at a slab heating temperature (SRT) of 1150 to 1200 ° C. and a finishing temperature of 900.
It was hot-rolled at 920 ° C. and a coil winding temperature of 500-800 ° C. to a thickness of 35 mm. Thereafter, the scale layer was removed by pickling and cold rolling was performed to a thickness of 0.7 mm. This cold-rolled sheet was subjected to recrystallization annealing at 800 to 850 ° C in a continuous hot-dip galvanizing line (CGL), then cooled, and hot-dip galvanized at 470 ° C. At this time, the plate temperature and atmosphere from the cooling zone to the hot-dip galvanizing were controlled.
【００１９】なお、表１に記載した鋼板温度以外の温度
域の雰囲気は本発明で規定した範囲内の条件とした。大
部分は引き続き４６０〜５００℃で１０〜２５秒の合金
化処理を行った。不めっき、さざ波、アッシュ引き欠陥
はＲＣで静止検査し、目視およびプレス後砥石による凹
凸で格落ちした重量比で評価した。その結果を表１に示
す。比較例では、著しく欠陥発生率が高いが、本発明で
は欠陥発生率が低い。The atmosphere in the temperature range other than the steel plate temperature shown in Table 1 was set within the range specified in the present invention. Most of the alloys were continuously subjected to an alloying treatment at 460 to 500 ° C. for 10 to 25 seconds. Non-plating, ripples, and ash-pull defects were statically inspected by RC, and evaluated by visual inspection and by weight ratio degraded by unevenness due to the grindstone after pressing. Table 1 shows the results. In the comparative example, the defect occurrence rate is extremely high, but in the present invention, the defect occurrence rate is low.
【００２０】[0020]
【表１】 [Table 1]
【００２１】[0021]
【発明の効果】以上説明したように、本発明の開示する
溶融亜鉛めっき鋼板は不めっき、さざ波、アッシュ引き
等の焼鈍後めっき前の板性状に関わる欠陥発生率が小さ
く、高品質の溶融亜鉛めっき鋼板を得ることができる。As described above, the hot-dip galvanized steel sheet disclosed in the present invention has a low defect generation rate related to the sheet properties before annealing, such as unplating, ripples and ashing, and has a high quality hot-dip galvanized steel sheet. A plated steel sheet can be obtained.
【図面の簡単な説明】[Brief description of the drawings]
【図１】還元焼鈍終了後の温度域における、水素を含有
する雰囲気下での、酸素量が鋼板表面の酸化量に及ぼす
影響を示すグラフである。FIG. 1 is a graph showing the effect of the amount of oxygen on the amount of oxidation of the steel sheet surface in a hydrogen-containing atmosphere in a temperature range after the completion of reduction annealing.
【図２】水素を含有する雰囲気下での酸素量と鋼板温度
が鋼板表面酸化量に及ぼす影響を示すグラフである。FIG. 2 is a graph showing the influence of the amount of oxygen and the temperature of a steel sheet on the amount of oxidation of the steel sheet surface in an atmosphere containing hydrogen.
フロントページの続き (51)Int.Cl.6 識別記号 ＦＩ Ｃ２３Ｃ 2/06 Ｃ２３Ｃ 2/06 Continued on the front page (51) Int.Cl. 6 Identification code FI C23C 2/06 C23C 2/06
Claims (1)
晶焼鈍後の冷却から溶融亜鉛めっき浴に侵入するまでの
過程において、水素濃度、酸素濃度及び鋼板温度の関係
が次式を満たすように制御することを特徴とする、焼鈍
後めっき前の板表面に関わる欠陥の少ない溶融亜鉛めっ
き鋼板の製造方法。 １＜〔Ｏ〕＜（０．０００２５Ｔ2 −０．２２５Ｔ＋５
５）×〔Ｈ〕 〔Ｏ〕：酸素濃度（ｐｐｍ） Ｔ ：鋼板温度（℃） 〔Ｈ〕：水素濃度（％）1. In the process from cooling after recrystallization annealing in continuous annealing prior to hot-dip galvanizing to entering into a hot-dip galvanizing bath, the relationship between hydrogen concentration, oxygen concentration and steel sheet temperature is controlled so as to satisfy the following equation. A method for producing a hot-dip galvanized steel sheet having few defects relating to a sheet surface after annealing and before plating. 1 <[O] <(0.00025T 2 −0.225T + 5
5) × [H] [O]: Oxygen concentration (ppm) T: Steel sheet temperature (° C) [H]: Hydrogen concentration (%)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP20170797A JP3375520B2 (en) | 1997-07-28 | 1997-07-28 | Manufacturing method of hot-dip galvanized steel sheet |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP20170797A JP3375520B2 (en) | 1997-07-28 | 1997-07-28 | Manufacturing method of hot-dip galvanized steel sheet |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH1150139A true JPH1150139A (en) | 1999-02-23 |
| JP3375520B2 JP3375520B2 (en) | 2003-02-10 |
Family
ID=16445602
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP20170797A Expired - Fee Related JP3375520B2 (en) | 1997-07-28 | 1997-07-28 | Manufacturing method of hot-dip galvanized steel sheet |
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| Country | Link |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007262463A (en) * | 2006-03-28 | 2007-10-11 | Jfe Steel Kk | Method for producing hot dip galvanized steel sheet and alloyed hot dip galvanized steel sheet |
-
1997
- 1997-07-28 JP JP20170797A patent/JP3375520B2/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007262463A (en) * | 2006-03-28 | 2007-10-11 | Jfe Steel Kk | Method for producing hot dip galvanized steel sheet and alloyed hot dip galvanized steel sheet |
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| Publication number | Publication date |
|---|---|
| JP3375520B2 (en) | 2003-02-10 |
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