JPH0816260B2 - Method for producing galvannealed steel sheet having excellent press formability and powdering resistance - Google Patents
Method for producing galvannealed steel sheet having excellent press formability and powdering resistanceInfo
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- JPH0816260B2 JPH0816260B2 JP2302626A JP30262690A JPH0816260B2 JP H0816260 B2 JPH0816260 B2 JP H0816260B2 JP 2302626 A JP2302626 A JP 2302626A JP 30262690 A JP30262690 A JP 30262690A JP H0816260 B2 JPH0816260 B2 JP H0816260B2
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- plating
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- alloying
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Description
【発明の詳細な説明】 〔産業上の利用分野〕 この発明は、自動車の車体、足回り部品等に用いられ
る合金化溶融亜鉛めっき鋼板、特にプレス成形時に要求
される耐パウダリング性に優れ、しかも摩擦特性がコイ
ル内で安定した合金化溶融亜鉛めっき鋼板の製造方法に
関する。DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention provides an alloyed hot-dip galvanized steel sheet used for automobile body parts, underbody parts, etc., particularly excellent in powdering resistance required at the time of press forming, Moreover, the present invention relates to a method for producing an alloyed hot-dip galvanized steel sheet whose frictional characteristics are stable in the coil.
合金化溶融亜鉛めっき鋼板は優れた塗装後耐食性や溶
接性を有するため、自動車用防錆鋼板としてその需要が
近年増加しており、特に最近では、耐食性を確保するた
めめっき皮膜が厚目付化する傾向にある。Since the galvannealed steel sheet has excellent corrosion resistance and weldability after painting, its demand as an anticorrosion steel sheet for automobiles has been increasing in recent years.In particular, recently, the plating film is thickened to secure the corrosion resistance. There is a tendency.
この種のめっき鋼板には、優れたプレス成形性とプレ
ス成形時の耐皮膜剥離性、所謂耐パウダリング性が要求
される。特に最近ではこれらについてより厳しい性能が
求められ、とりわけ上記のような皮膜の厚目付化に伴
い、耐パウダリング性の確保が大きな課題となりつつあ
る。This type of plated steel sheet is required to have excellent press formability, film peeling resistance during press forming, and so-called powdering resistance. Particularly recently, more severe performances have been demanded for these materials, and particularly with the increase in the coating weight of the film as described above, securing powdering resistance is becoming a major issue.
このような耐パウダリング性を改善する方法として、
例えば、特公昭59−14541号公報等に示されるように、
めっき鋼板を急速加熱で１次加熱して皮膜の一部を合金
化させた後、バッチ焼鈍で２次加熱を行うという技術が
知られているが、この方法は耐パウダリング性の改善に
は有効であるものの、製造コストが高いという欠点があ
る。As a method of improving such powdering resistance,
For example, as shown in Japanese Patent Publication No. 59-14541,
A technique is known in which a plated steel sheet is primarily heated by rapid heating to partially alloy the coating, and then secondary annealing is performed by batch annealing, but this method is effective for improving powdering resistance. Although effective, it has the drawback of high manufacturing costs.
一方、インラインにおいて耐パウダリング性を改善す
る技術として、特開昭64−17843号公報において、Al:0.
003〜0.13％めっき浴でめっき後、低温（520〜470℃の
範囲で且つAl％が低いほど低温側）で合金化処理を施す
ことにより、めっき表層に耐パウダリング性に有効なζ
相を残留させるという技術が開示されている。On the other hand, as a technique for improving the powdering resistance in-line, in JP-A 64-17843, Al: 0.
After plating with a 003 to 0.13% plating bath, alloying treatment is performed at a low temperature (in the range of 520 to 470 ° C and the lower the Al%, the lower the temperature), so that the plating surface layer is effective for powdering resistance ζ.
A technique of leaving a phase is disclosed.
しかし、この方法は低温で合金化処理するため、処理
時間が長くなり、ライン速度を遅くするか、設備を大型
化することが必要となり、いずれにしても生産性の低下
や設備コストの増大が避けられない。However, since this method performs alloying treatment at a low temperature, the treatment time becomes long, and it is necessary to slow down the line speed or enlarge the equipment, and in any case, the productivity is lowered and the equipment cost is increased. Unavoidable.
さらに、通常用いられているガス直火加熱方式の合金
炉では、ストリップ幅方向及び長さ方向での板温の変動
が起りやすいため、上述したような皮膜構造の厳密な制
御は困難であり、得られるめっき皮膜は部分的に過合金
或いはη相（純亜鉛相）が残留したものとなってしま
う。したがって、得られるめっき鋼板は場所によってζ
相の量が不均一な、すなわち、鋼板の各部で耐パウダリ
ング性が不均一なものとなってしまう。Furthermore, in the alloy furnace of the gas direct-fired heating method which is usually used, since the variation of the strip temperature in the strip width direction and the length direction is likely to occur, it is difficult to strictly control the coating structure as described above. The obtained plating film partially becomes a superalloy or an η phase (pure zinc phase) remains. Therefore, the obtained plated steel sheet may be ζ depending on the location.
The amount of phases is non-uniform, that is, the powdering resistance is non-uniform in each part of the steel sheet.
また、上記のような合金化めっき層上に上層めっきを
施すことにより摩擦係数を減少させ、プレス成形性を改
善することができるが、上記のようにζ相の量が不均一
な状態では、そのプレス成形性も不安定なものとなって
しまう。Further, by applying the upper layer plating on the alloyed plating layer as described above, the friction coefficient can be reduced and the press formability can be improved, but in the state where the amount of ζ phase is non-uniform as described above, The press formability also becomes unstable.
以上のような従来の問題に対し、本発明者らは、ま
ず、溶融亜鉛めっき鋼板の合金化反応に関して検討を行
い、その結果、ｉ）ζ相は495℃以下の反応により発生
し、それ以上では発生しないこと、ii）したがって、49
5℃以下で主要な反応（溶融亜鉛相がなくなるまでの反
応）を起し、その後冷却すれば、ζ相が残留した皮膜を
形成することができること、が明らかとなった。第１図
（ａ）、（ｂ）は溶融亜鉛めっき鋼板の450℃、500℃で
の恒温合金化反応による相変化の一例を示すもので、45
0℃での合金化ではζ相が発生するのに対し、500℃での
合金化ではζ相はほとんど発生しない。With respect to the conventional problems as described above, the present inventors first investigated the alloying reaction of hot-dip galvanized steel sheet, and as a result, i) ζ phase was generated by the reaction at 495 ° C. or lower, and further Ii) Therefore, 49
It was clarified that a major reaction (reaction until the molten zinc phase disappears) occurs at 5 ° C or lower, and then the film is cooled to form a film in which the ζ phase remains. FIGS. 1 (a) and 1 (b) show an example of the phase change of the galvanized steel sheet at 450 ° C. and 500 ° C. due to the isothermal alloying reaction.
In the alloying at 0 ° C, the ζ phase is generated, whereas in the alloying at 500 ° C, the ζ phase is hardly generated.
しかし上述したように、このように低温で合金化する
方法では合金化完了までに長時間を要するため、ライン
スピードの低下、設備の大型化を余儀なくされる。さら
に、通常の直火加熱方式の合金化炉を用いて上記条件で
合金化すると、焼きムラが発生し易く、不均一な合金層
が形成されてしまう。このような焼きムラを防止しよう
とすると炉温を上げて合金化する必要があるが、高温で
の合金化処理ではζ相が残留せず、耐パウダリング性の
劣ったものとなる。However, as described above, in such a method of alloying at a low temperature, it takes a long time to complete the alloying, so that the line speed is lowered and the equipment is inevitably enlarged. Furthermore, when alloying is performed under the above conditions using a normal direct-fired heating type alloying furnace, uneven baking is likely to occur and a non-uniform alloy layer is formed. In order to prevent such burning unevenness, it is necessary to raise the furnace temperature for alloying, but in the alloying treatment at a high temperature, the ζ phase does not remain, and the powdering resistance becomes poor.
このようなことから、耐パウダリング性とプレス成形
性の両者を安定的に得る方法について検討を重ねた結
果、以下のような知見を得た。From the above, as a result of repeated studies on a method for stably obtaining both powdering resistance and press formability, the following findings were obtained.
めっき浴中で積極的に合金化反応（ζ相の生成）を
起し、しかもその後の合金化処理を高周波誘導加熱方式
の加熱炉を用いて行うことにより、ストリップの幅方
向、長手方向で均一な量のζ相が残留した皮膜を短時間
の合金化処理で得られること、 また、このようにして得られる合金化めっき皮膜
は、上述したようなマクロ的な均一性のみならず、ミク
ロ的にも合金化反応が均一に起きるため、この面からも
優れた耐パウダリング性が得られること、 浴条件と高周波誘導加熱方式の加熱炉出側板温条件
を規定することにより、厳密な皮膜の制御が可能である
こと、 具体的には、低Al浴で且つ浴中Al量との関係で規定
される高めの侵入板温でめっきを施すことにより、浴中
で積極的に合金化反応（ζ相の発生）を起こすことが可
能であり、さらに、このようなめっき鋼板に対する高周
波誘導加熱方式の加熱炉を用いた合金化処理を、加熱炉
出側での板温を495℃以下に管理して行うことにより、
上記、で述べたような皮膜を得られること、 上記のようにして合金化されためっき皮膜に上層め
っきを施すことにより、少ない付着量で良好且つ均一な
プレス成形性が得られること 本発明はこのような知見に基づきなされたもので、そ
の特徴とするところは、Alを含有し、残部Znおよび不可
避的不純物からなる亜鉛めっき浴でめっきを施した後、
目付量調整を行い、加熱炉で皮膜中のFe含有量が８〜12
％となるように合金化処理を行う合金化溶融亜鉛めっき
鋼板の製造方法において、浴中Al量:0.05％以上、0.13
％未満、鋼板のめっき浴中への侵入板温:495℃以下、浴
温度:470℃以下で、且つ、浴中Al量と侵入板温とが、 437.5×〔Al％〕＋448≧Ｔ≧437.5×〔Al％〕＋428 但し、〔Al％〕：浴中Al量（％） T:侵入板温（℃） を満足する条件でめっきを行うことにより、浴中でζ相
を形成する合金化反応を積極的に起こし、めっき後、高
周波誘導加熱炉で加熱炉出側の板温が495℃以下となる
ように加熱し、所定時間保持後冷却し、次いで、上層め
っきとしてFe含有量が50％以上のFe系めっきを1g/m2以
上施すようにしたことにある。The alloying reaction (formation of ζ phase) is positively caused in the plating bath, and the subsequent alloying treatment is performed using a high frequency induction heating type heating furnace, so that the strip is uniform in the width direction and the longitudinal direction. It is possible to obtain a film in which a large amount of ζ phase remains by a short-time alloying treatment. Moreover, the alloyed plating film obtained in this way has not only the above-mentioned macroscopic uniformity but also a microscopic Since the alloying reaction occurs uniformly even in this case, excellent powdering resistance can be obtained from this aspect as well, and by stipulating the bath conditions and the heating furnace outlet side plate temperature conditions of the high frequency induction heating system, strict coating It is possible to control, specifically, by plating in a low Al bath and at a higher penetration plate temperature defined by the relationship with the amount of Al in the bath, the alloying reaction ( (generation of ζ phase) The alloying treatment using a high-frequency induction heating type heating furnace for such plated steel sheet is performed by controlling the plate temperature on the outlet side of the heating furnace to 495 ° C or less,
The above-described film can be obtained, and by applying the upper layer plating to the plating film alloyed as described above, good and uniform press formability can be obtained with a small adhesion amount. What was made based on such knowledge, the characteristic is that after containing the Al, after plating with a zinc plating bath consisting of the balance Zn and unavoidable impurities,
After adjusting the basis weight, the Fe content in the coating is 8-12 in the heating furnace.
In the method for producing an alloyed hot-dip galvanized steel sheet in which an alloying treatment is performed so that the content of Al in the bath is 0.05% or more, 0.13 or more.
%, The plate temperature of the steel plate invading the plating bath: 495 ° C. or lower, the bath temperature: 470 ° C. or lower, and the amount of Al in the bath and the plate temperature are 437.5 × [Al%] + 448 ≧ T ≧ 437.5 × [Al%] + 428 However, [Al%]: Al content in bath (%) T: Alloying reaction to form ζ phase in the bath by plating under conditions that satisfy the penetration plate temperature (° C) Positively, after heating, heating in a high-frequency induction heating furnace so that the plate temperature on the heating furnace outlet side is 495 ° C or less, holding for a predetermined time and cooling, and then Fe content of 50% as upper layer plating The above Fe-based plating is applied at a rate of 1 g / m 2 or more.
従来、めっき鋼板の合金化処理を高周波誘導加熱によ
り行うという技術は、例えば、特公昭60−8289号公報、
特開平２−37425号公報等において知られている。しか
し、これらに開示された技術は、高周波誘導加熱を単に
急速加熱の一手段として用いているに過ぎない。Conventionally, a technique of performing alloying treatment of a plated steel sheet by high frequency induction heating is disclosed in, for example, Japanese Patent Publication No. 60-8289.
It is known from JP-A-2-37425. However, the techniques disclosed therein merely use high-frequency induction heating as a means of rapid heating.
これに対して本発明は、浴中でζ相を形成する合金化
反応を積極的に起こし、且つこのようにして形成された
めっき皮膜に対し、高周波誘導加熱による合金化処理を
特定の条件で実施することにより、マクロ的にζ相が非
常に均一に形成され、しかも皮膜構造のミクロ的な均一
性によって全体としてより耐パウダリング性が改善され
ためっき鋼板が得られることを見出したものである。On the other hand, the present invention positively causes an alloying reaction to form a ζ phase in the bath, and the plating film thus formed is subjected to alloying treatment by high frequency induction heating under specific conditions. It was found that by carrying out the method, a ζ phase is formed very uniformly macroscopically, and further, the plated steel sheet with improved powdering resistance as a whole is obtained due to the microscopic uniformity of the film structure. is there.
本発明の製造法において、上述のような優れた特性の
めっき鋼板が得られるのは次のような理由によるものと
推定される。In the production method of the present invention, it is presumed that the reason why the plated steel sheet having the above excellent properties is obtained is as follows.
まず、第１に、合金化処理において高周波誘導加熱方
式を用いることにより、鋼板自体を直接加熱することが
でき、しかも、めっき皮膜に接する界面が最も加熱され
るため、雰囲気加熱方式に較べ界面におけるFe−Zn反応
が短時間でしかもストリップ上の位置に無関係に均一に
起き、このため、鋼板各部で均一な量のζ相が残留し、
均一な耐パウダリング性が得られるものと推定される。First, by using the high frequency induction heating method in the alloying process, the steel sheet itself can be directly heated, and the interface in contact with the plating film is heated most, so that the interface heating in the interface is higher than that in the atmosphere heating method. The Fe-Zn reaction takes place uniformly in a short time regardless of the position on the strip.Therefore, a uniform amount of ζ phase remains in each part of the steel sheet,
It is estimated that uniform powdering resistance can be obtained.
第２に、高周波誘導加熱は上記のように鋼板側からの
加熱であるため、微視的にも均一な合金化反応が生じる
ことによるものと推定される。すなわち、従来一般に行
われているガス加熱による合金化処理では、皮膜の外側
から熱が加えられるため加熱が不均一となり易く、この
ため合金化反応が微視的に不均一に生じ易い。特に結晶
粒界は反応性に富むため、所謂アウトバースト反応が生
じ易く、このようにアウトバースト組織が発生すると、
この部分からΓ相が成長し始め、このΓ相の形成により
耐パウダリング性が劣化する。これに対し、高周波誘導
加熱は鋼板側からの加熱であるため、上記のような合金
化の局部的なバラツキが少なく、また、鋼板面の酸化物
や浴中で生じた合金化抑制物質（Fe2Al5）も容易に拡散
するため、ミクロ的にも均一な合金化皮膜が得られるも
のと思われる。Secondly, since the high-frequency induction heating is heating from the steel sheet side as described above, it is presumed that a uniform alloying reaction occurs microscopically. That is, in the conventional alloying treatment by gas heating, which is generally performed, heat is applied from the outside of the film, so that the heating is likely to be nonuniform, and thus the alloying reaction is likely to be microscopically nonuniform. In particular, since the crystal grain boundaries are rich in reactivity, so-called outburst reaction is likely to occur, and when such an outburst structure occurs,
The Γ phase begins to grow from this portion, and the powdering resistance deteriorates due to the formation of the Γ phase. On the other hand, since high-frequency induction heating is heating from the steel sheet side, there are few local variations in alloying as described above, and the oxides on the steel sheet surface and the alloying-suppressing substances (Fe) 2 Al 5 ) also diffuses easily, and it is thought that a microscopically uniform alloyed film can be obtained.
第３に、本発明では浴中での合金化反応により大部分
のζ相が生じているため、続く高周波誘導加熱による合
金化処理において合金化抑制相であるFe2Al5の影響を受
けにくく、これがミクロ的な均一性とこれによる耐パウ
ダリング性の改善に寄与しているものと考えられる。す
なわち、本発明において浴中で発生するζ相は、浴中で
初期に生成するFe2Al5中でFeが拡散することにより生じ
る。つまり浴中で既にFeの拡散が生じているということ
である。したがって、続く合金化加熱では合金化抑制物
質であるFe2Al5の量が少なく、特に上記したように高周
波誘導加熱は鋼板側からの加熱であるため、残った合金
化抑制物質を容易に拡散できるものである。これに対
し、浴中で積極的にζ相を形成させることがない従来の
方法では、Feの拡散は炉内での加熱によりはじめて且つ
急速に生じるものであるため、ガス加熱はもとより、合
金化処理を高周波誘導加熱で行っても、Fe2Al5の厚い部
分は合金化が送れ易く、この結果ミクロ的に不均一な合
金皮膜となり、耐パウダリング性が劣るものとなる。Thirdly, in the present invention, most of the ζ phase is generated by the alloying reaction in the bath, so that it is less susceptible to the alloying suppressing phase Fe 2 Al 5 in the subsequent alloying treatment by high frequency induction heating. However, it is considered that this contributes to the improvement of the microscopic uniformity and the powdering resistance. That is, in the present invention, the ζ phase generated in the bath is generated by diffusion of Fe in Fe 2 Al 5 which is initially formed in the bath. This means that Fe has already diffused in the bath. Therefore, in the subsequent alloying heating, the amount of Fe 2 Al 5 which is an alloying suppressing substance is small, and since the high frequency induction heating is heating from the steel sheet side as described above, the remaining alloying suppressing substance is easily diffused. It is possible. On the other hand, in the conventional method in which the ζ phase is not positively formed in the bath, the diffusion of Fe occurs only rapidly when it is heated in the furnace. Even if the treatment is carried out by high-frequency induction heating, alloying is likely to be sent to a thick portion of Fe 2 Al 5 , resulting in a microscopically non-uniform alloy film and poor powdering resistance.
また、プレス成形性に関しても、上記したように合金
化がマクロ、ミクロに均一になされる結果、安定的且つ
均一なプレス成形性が得られ、しかも溶融めっき後の加
熱を高周波誘導加熱で行うと、めっき表面が酸化されな
いため、合金化めっき層上に上層めっきを適切に付着さ
せることができ、このためガス加熱で合金化処理した場
合に較べ少ない付着量の上層めっきにより安定したプレ
ス成形性が得られるものと考えられる。。As for the press formability, as described above, the alloying is made macroscopically and microscopically uniform, so that stable and uniform press formability can be obtained, and if the heating after hot dip coating is performed by high frequency induction heating. Since the plating surface is not oxidized, the upper layer plating can be properly adhered to the alloyed plating layer. Therefore, a smaller amount of the upper layer plating than that in the case of alloying treatment by gas heating provides stable press formability. It is thought to be obtained. .
以下、本発明の構成とその限定理由について説明す
る。Hereinafter, the configuration of the present invention and the reason for the limitation will be described.
本発明では、めっき浴中でζ相を形成する合金化反応
を積極的に起こすため、めっき浴中のAl量、めっき浴に
侵入する際の鋼板の板温及び浴温度が規定される。In the present invention, the amount of Al in the plating bath, the plate temperature of the steel sheet when entering the plating bath, and the bath temperature are defined in order to positively cause the alloying reaction that forms the ζ phase in the plating bath.
Alは浴中でのFe−Zn反応を抑制するために添加される
が、本発明では浴中で積極的に合金化反応（ζ相の形
成）を起こさせること重要であり、したがって浴中Alは
低めの含有量とする。しかし、Al量が低すぎると浴中で
アウトバースト反応と呼ばれる局部的な合金化反応が発
生し、最終的にΓ相が厚く形成され、耐パウダリング性
の劣る皮膜となる。このためAl量の下限を0.05％とす
る。一方、Al量が0.13％以上であると浴中でのζ相形成
反応が起りにくくなる。このためAl量は0.13％未満とす
る。Al is added to suppress the Fe-Zn reaction in the bath, but in the present invention, it is important to positively cause the alloying reaction (formation of ζ phase) in the bath. Is a low content. However, if the amount of Al is too low, a local alloying reaction called an outburst reaction occurs in the bath, and the Γ phase is finally formed thick, resulting in a film with poor powdering resistance. Therefore, the lower limit of the amount of Al is set to 0.05%. On the other hand, when the amount of Al is 0.13% or more, the ζ-phase forming reaction in the bath becomes difficult to occur. Therefore, the Al content is less than 0.13%.
浴中でζ相を形成させためには浴中への侵入板温の管
理が重要である。この侵入板温は下記するように浴中Al
量との関係でもその上限および下限が規定されるが、い
ずれにしても495℃を超えるとζ相が形成されず、した
がって、その絶対的な上限を495℃とする。In order to form the ζ phase in the bath, it is important to control the temperature of the plate entering the bath. This penetration plate temperature is
The upper limit and the lower limit are also defined in relation to the amount, but in any case, when the temperature exceeds 495 ° C, the ζ phase is not formed, and therefore the absolute upper limit is 495 ° C.
また、侵入板温は浴中Al量との関係で下記関係式の条
件を満足する必要がある。In addition, the intrusion plate temperature needs to satisfy the condition of the following relational expression in relation to the amount of Al in the bath.
437.5×〔Al％〕＋448≧Ｔ≧437.5×〔Al％〕＋428 但し、〔Al％〕：浴中Al量（％） T:侵入板温（℃） 侵入板温が495℃以下でも、浴中Al量との関係で上記
上限を超えるとζ相の形成が十分でなく、また、アウト
バーストを生じ、Γ相が生じ易くなる。一方、侵入板温
が上記下限を下回ると合金化が起りにくくなり、浴中で
のζ相の積極的な形成を利用することによる本発明の作
用効果が期待できない。上記に規定する範囲において侵
入板温が高いほど、浴中でのζ相の形成量が多く、した
がって最終的な皮膜中のζ相も多くなる。437.5 × [Al%] + 448 ≧ T ≧ 437.5 × [Al%] + 428 However, [Al%]: Al amount in bath (%) T: Penetration plate temperature (° C) Even if penetration plate temperature is 495 ° C or less, in bath If the upper limit is exceeded in relation to the amount of Al, the formation of the ζ phase is not sufficient, and outburst occurs, and the Γ phase is likely to occur. On the other hand, if the penetration plate temperature is lower than the above lower limit, alloying is less likely to occur, and the action and effect of the present invention due to the positive formation of the ζ phase in the bath cannot be expected. The higher the penetration plate temperature in the range defined above, the larger the amount of ζ phase formed in the bath, and thus the more ζ phase in the final film.
なお、侵入板温が495℃を超えると、上記のようにζ
相が形成されないばかりでなく、ポットへの入熱量増加
により浴温冷却手段等の付加的設備が必要になり、さら
に、浴中でのドロス発生量が増加し、表面欠陥が多発す
る等の問題を生じる。In addition, if the intrusion plate temperature exceeds 495 ° C,
Not only the phase is not formed, but additional equipment such as bath temperature cooling means is required due to the increase in heat input to the pot, and further, the amount of dross generated in the bath increases and many surface defects occur. Cause
めっき浴温度が高いと浴中における合金化反応（ζ相
の形成）が促進されるが、浴温度が高過ぎると浴中に浸
漬された構造物が侵食され、ドロスが発生するなどの問
題を生じる。このため、浴温は470℃以下とする。If the plating bath temperature is high, the alloying reaction (formation of ζ phase) in the bath is promoted, but if the bath temperature is too high, the structure immersed in the bath will be eroded, causing problems such as dross. Occurs. Therefore, the bath temperature should be 470 ° C or lower.
めっきされた鋼板は、高周波誘導加熱炉において合金
化のための加熱処理される。本発明では、上記のような
浴条件の規定に加え、この高周波誘導加熱炉による加熱
処理が大きな特徴であり、上述したように通常行なわれ
ているガス加熱では、本発明が目的とするような合金化
めっき皮膜は全く得られない。この合金化処理では、炉
出側の板温が495℃以下となるように加熱し、所定時間
保持後冷却する。上述したようにζ相を形成させるため
には495℃以下での加熱が必要であり、本発明において
は高周波誘導加熱炉出側の板温を管理する理由は、その
部分が合金化熱サイクルでの最高板温となるためであ
る。また、合金相の成長速度はこの付近で最大となるた
め、出側板温を管理することにより、その温度での合金
化反応を起すことが可能になる。The plated steel sheet is heat-treated for alloying in a high frequency induction heating furnace. In the present invention, in addition to the stipulation of bath conditions as described above, the heat treatment by this high-frequency induction heating furnace is a major feature, and in the gas heating that is usually performed as described above, the object of the present invention is No alloyed plating film is obtained. In this alloying treatment, heating is performed so that the plate temperature on the exit side of the furnace is 495 ° C. or lower, and after holding for a predetermined time, it is cooled. As described above, heating at 495 ° C. or lower is necessary to form the ζ phase, and the reason for controlling the plate temperature on the exit side of the high-frequency induction heating furnace in the present invention is that that part is an alloying heat cycle. This is because the maximum plate temperature of Further, since the growth rate of the alloy phase becomes maximum around this, it becomes possible to cause the alloying reaction at that temperature by controlling the outlet plate temperature.
本発明は皮膜中のFe含有量が８〜12％の合金化溶融亜
鉛めっき鋼板の製造を目的としている。皮膜中のFe含有
量が12％を超えると、皮膜が硬質になり、耐パウダリン
グ性が劣化する。高周波誘導加熱炉出側以降合金化を進
めると固体内拡散反応により皮膜中のFe含有量が上昇し
てしまう。一方、Fe含有量が８％未満では、η相（純亜
鉛相）が表面に残留するため、プレス成形時に焼付け
（フレーキング）と呼ばれる現象が起り好ましくない。The present invention aims to produce an alloyed hot-dip galvanized steel sheet having a Fe content of 8 to 12% in the coating. If the Fe content in the coating exceeds 12%, the coating becomes hard and the powdering resistance deteriorates. If alloying proceeds from the high-frequency induction heating furnace exit side, the Fe content in the coating will increase due to the diffusion reaction in the solid. On the other hand, when the Fe content is less than 8%, the η phase (pure zinc phase) remains on the surface, which is not preferable because a phenomenon called baking (flaking) occurs during press molding.
従来では、皮膜中のFe含有量により皮膜構造が一義的
に決まると考えられていたが、本発明のように浴条件を
適当に選択し、しかも合金化処理を高周波誘導加熱で行
うことにより、皮膜中のFe含有量にかかわらず、本発明
が目的とするような特定の皮膜構造が得られる。Conventionally, it was thought that the film structure is uniquely determined by the Fe content in the film, but by appropriately selecting the bath conditions as in the present invention, and by performing the alloying treatment by high frequency induction heating, Regardless of the Fe content in the coating, a specific coating structure as intended by the invention is obtained.
このようにして得られた合金化めっき皮膜は、表層側
から均一なζ相、δ１相、および極く薄いΓ相が存在す
る構造となる。The alloyed plating film thus obtained has a structure in which a uniform ζ phase, a δ 1 phase, and an extremely thin Γ phase are present from the surface layer side.
以上のような合金化処理後、摩擦係数を減少させプレ
ス成形性を改善するために、上層めっきとしてFe含有量
が50％以上のFe系めっきを1g/m2以上施す。摩擦係数を
低下させるには上層めっきをα単相とすることが好まし
く、Fe系めっきでは、第２図に示すようにFe含有量がほ
ぼ50％以上でα単相となる。After the alloying treatment as described above, in order to reduce the friction coefficient and improve the press formability, 1 g / m 2 or more of Fe-based plating having an Fe content of 50% or more is applied as the upper layer plating. In order to reduce the friction coefficient, it is preferable that the upper layer plating is α single phase, and in Fe-based plating, as shown in FIG. 2, when the Fe content is approximately 50% or more, it becomes α single phase.
また、上層めっきの付着量が1g/m2未満では摩擦係数
の低減が十分ではない。第３図は上層めっき量と摩擦係
数との関係を示すもので、めっき量を1g/m2以上とする
ことにより、0.13以下の摩擦係数が得られていることが
判る。また、このめっき付着量に特に上限はないが、コ
スト面から3g/m2以下とすることが好ましい。本発明の
ように溶融めっき後の加熱を高周波誘導加熱で行うと、
めっき表面が酸化されないため、合金化めっき層上に上
層めっきを適切に付着させることができ、このためガス
加熱で合金化処理した場合に較べ上層めっきの付着量を
少なくすることができる。Further, if the amount of the upper layer plating deposited is less than 1 g / m 2 , the friction coefficient is not sufficiently reduced. FIG. 3 shows the relationship between the upper layer plating amount and the friction coefficient. It can be seen that a friction coefficient of 0.13 or less is obtained by setting the plating amount to 1 g / m 2 or more. Further, although there is no particular upper limit to the coating amount, it is preferably 3 g / m 2 or less in terms of cost. When the heating after hot dip plating is performed by high frequency induction heating as in the present invention,
Since the plating surface is not oxidized, the upper layer plating can be properly adhered to the alloyed plating layer, and thus the amount of the upper layer plating adhered can be reduced as compared with the case where the alloying treatment is performed by gas heating.
なお、同図によれば、上層めっきを施した鋼板と上層
めっきを施さない鋼板（付着量:0g/m2）とを較べると、
後者ではζ相の形成量の多少によって摩擦係数に大きな
差があるのに対し、前者ではζ相の形成量が摩擦係数に
及ぼす影響は後者ほどではなく、上層めっきの形成によ
り、ζ相の形成量が多くても摩擦係数の低減化が効果的
になされていることが判る。According to the figure, comparing the steel plate with the upper layer plating with the steel plate without the upper layer plating (adhesion amount: 0 g / m 2 ),
In the latter, there is a large difference in the friction coefficient depending on the amount of ζ-phase formation, whereas in the former, the effect of the amount of ζ-phase formation on the friction coefficient is not as great as in the latter. It can be seen that the friction coefficient is effectively reduced even if the amount is large.
本発明の実施例を第１表に示す。 Examples of the present invention are shown in Table 1.
この実施例では、Alキルド鋼およびTi添加IF鋼から製
造された冷延鋼板を素材とし、第１表に示される条件で
溶融亜鉛めっき、加熱処理および上層めっきを行った。
この上層めっきはライン出側に設置された電気めっき設
備で実施した。また、上記加熱処理はガス加熱方式およ
び高周波誘導加熱方式を用いた。In this example, cold-rolled steel sheets manufactured from Al-killed steel and Ti-added IF steel were used as raw materials, and hot dip galvanizing, heat treatment, and upper layer plating were performed under the conditions shown in Table 1.
This upper layer plating was carried out in an electroplating facility installed on the outlet side of the line. Moreover, the said heat processing used the gas heating system and the high frequency induction heating system.
本実施例において、鋼板のめっき浴中への侵入温度は
放射型温度計で測定した浸漬直前の鋼板の表面温度であ
る。また、加熱炉出側の板温は放射型温度計で測定した
鋼板の表面温度である。In this example, the temperature at which the steel sheet penetrates into the plating bath is the surface temperature of the steel sheet immediately before immersion measured by a radiation thermometer. The plate temperature on the outlet side of the heating furnace is the surface temperature of the steel plate measured by a radiation thermometer.
また、めっき浴中Alは下式に定義される有効Al濃度で
ある。Further, Al in the plating bath has an effective Al concentration defined by the following formula.
〔有効Al濃度〕＝〔浴中全Al濃度〕−〔浴中鉄濃度〕 ＋0.03 皮膜中Fe％は浴条件、加熱条件および冷却条件に依存
する。冷却条件は本発明の特徴の一つである皮膜構造の
マクロ或いはミクロな均一性にほとんど影響を及ぼさな
いが、合金化度（皮膜中Fe％）を変化させることにより
特性に影響を及ぼす。したがって、本実施例では冷却用
のブロアの風量、ミストの量を調整し、皮膜中のFe％を
制御した。[Effective Al concentration] = [Total Al concentration in bath]-[Iron concentration in bath] +0.03 Fe% in the coating depends on bath conditions, heating conditions and cooling conditions. The cooling conditions have almost no effect on the macro- or micro-uniformity of the film structure, which is one of the features of the present invention, but affect the properties by changing the alloying degree (Fe% in the film). Therefore, in this example, the air amount of the cooling blower and the amount of mist were adjusted to control the Fe% in the film.
また、製品のζ相の測定方法および各特性に関する試
験、評価方法は以下の通りである。Further, the method for measuring the ζ phase of the product and the test and evaluation method for each characteristic are as follows.
○製品皮膜中ζ相の量： 得られた皮膜をＸ線回折し、ζ相についてはｄ＝1.90
0のピーク強度Ｉζ（421）を、またδ１相についてはｄ
＝1.990のピーク強度Ｉδ１（249）をそれぞれ取り、下
式で示すピーク強度比をもって皮膜中のζ相の量を表し
た。なお、IBGはバックグランドであり、Z/Dが20以下な
らば実質的にζ相は存在しない。○ Amount of ζ phase in the product film: The obtained film was subjected to X-ray diffraction, and d = 1.90 for the ζ phase.
A peak intensity I ζ (421) of 0 and d for the δ 1 phase
The peak intensity I δ1 (249) of = 1.990 was taken, and the amount of ζ phase in the film was expressed by the peak intensity ratio shown by the following formula. Note that I BG is the background, and if Z / D is 20 or less, the ζ phase does not substantially exist.
Z/D＝（Ｉζ（421）−IBG）／（Ｉδ１（249）−IBG）
×100 ○耐パウダリング性： 試験片に防錆油（パーカー興産（株）製ノックスラス
ト530F）を1g/m2塗布した後、ビード半径R:0.5mm、押し
付け荷重P:500kg、押し込み深さh:4mmでビード引き抜き
試験を行い、テープ剥離後、成形前後の重量変化から剥
離量を算出した。なお、表中の数値は複数の測定値（５
×５＝25個）の平均値である。Z / D = (I ζ (421) −I BG ) / (I δ1 (249) −I BG ).
× 100 ○ Powdering resistance: After applying 1g / m 2 of rust preventive oil (Noxlast 530F manufactured by Parker Kosan Co., Ltd.) to the test piece, bead radius R: 0.5mm, pressing load P: 500kg, indentation depth A bead pull-out test was performed at h: 4 mm, and after peeling the tape, the peeling amount was calculated from the weight change before and after molding. The values in the table are for multiple measured values (5
× 5 = 25 pieces).
○耐パウダリング性の板幅方向最大偏差： 操業条件が安定した箇所で、鋼板長さ方向５点、鋼板
幅方向５点（両エッジ、1/4の位置およびセンター部）
で上記耐パウダリング性をそれぞれ測定し、最大値と最
小値の差をとった。○ Maximum deviation of powdering resistance in the plate width direction: 5 points in the steel plate length direction, 5 points in the steel plate width direction (both edges, 1/4 position and center part) where the operating conditions are stable.
The above powdering resistance was measured and the difference between the maximum value and the minimum value was taken.
○摩擦係数： 試験片に防錆油（パーカー興産（株）製ノックスラス
ト530F）を1g/m2塗布した後、工具鋼SKD11製の圧子を荷
重400kgで押し付け、1m/minの引き抜き速度で引き抜き
を行い、引き抜き荷重と押し付け荷重との比を摩擦係数
とした。なお、表中の数値は複数の測定値（５×５＝25
個）の平均値である。○ Friction coefficient: After applying 1g / m 2 of rust preventive oil (Knox Thrust 530F manufactured by Parker Kosan Co., Ltd.) to the test piece, press an indenter made of tool steel SKD11 with a load of 400kg and pull out at a pulling speed of 1m / min. Then, the ratio between the pulling load and the pressing load was taken as the friction coefficient. The values in the table are for multiple measured values (5 x 5 = 25
The average value of
○摩擦係数の板幅方向最大偏差： 耐パウダリング性と同一箇所で摩擦係数をそれぞれ測
定し、最大値と最小値の差をとった。○ Maximum deviation of friction coefficient in the plate width direction: The friction coefficient was measured at the same location as the powdering resistance, and the difference between the maximum value and the minimum value was taken.
第１表において、比較例１および比較例２は侵入板温
が高過ぎるために浴中でζ相が形成されず、合金化加熱
を高周波誘導加熱で行っても製品皮膜中にはζ相がまっ
たく存在していない。このため耐パウダリング性が劣っ
ている。In Table 1, in Comparative Example 1 and Comparative Example 2, since the penetration plate temperature is too high, the ζ phase is not formed in the bath, and even if the alloying heating is performed by the high frequency induction heating, the ζ phase is present in the product film. It doesn't exist at all. Therefore, the powdering resistance is inferior.
比較例３、比較例４および比較例11は、侵入板温が低
いためにめっき浴中でζ相を形成するような合金化反応
が生じていない例である。これらの比較例では、加熱を
495℃以下で行っているため製品皮膜中にはζ相は存在
するものの、浴中でのζ相の形成がなかったため、合金
化反応のミクロ的な不均一性により耐パウダリング性が
劣っており、またそのバラツキも大きい。Comparative Examples 3, 4, and 11 are examples in which the alloying reaction that forms the ζ phase in the plating bath does not occur because the intrusion plate temperature is low. In these comparative examples, heating
Although the ζ phase is present in the product coating because it is performed at 495 ° C or lower, the ζ phase was not formed in the bath, so the powdering resistance was poor due to the microscopic non-uniformity of the alloying reaction. There are also large variations.
比較例５および比較例６は上層めっきの付着量に関す
る比較例である。Comparative examples 5 and 6 are comparative examples relating to the amount of the upper layer plating deposited.
比較例７はめっき浴中ではζ相が形成されているもの
の、高周波誘導加熱での加熱温度が高過ぎるため製品皮
膜中にはζ相は存在していない。このため耐パウダリン
グ性が劣っている。In Comparative Example 7, the ζ phase is formed in the plating bath, but the heating temperature in the high frequency induction heating is too high, and the ζ phase is not present in the product film. Therefore, the powdering resistance is inferior.
比較例８〜比較例10、比較例12は、浴中でζ相が形成
させた後、加熱をガス加熱で行なった例である。このう
ち比較例８は加熱温度で高過ぎるため製品皮膜中にはζ
相は存在しておらず、また、焼きムラのため局部的に厚
いΓ相が形成されているため、耐パウダリング性が極め
て悪く、また、そのバラツキも大きい。比較例９および
比較例10は、加熱温度が低いため製品皮膜中にはζ相は
存在しているものの、焼きムラにより局部的にΓ相が厚
く形成されたり、或いはη相が局部的に残留し、このた
め耐パウダリング性、プレス成形性とも板幅方向で大き
なバラツキを生じており、したがって、これら特性値自
体も悪い。また、合金化相のミクロ的な均一性にも劣っ
ており、この面からも耐パウダリング性に劣っている。
比較例12も焼きムラによって特性のバラツキが大きく、
また、上記と同様の理由により特性値自体も悪い。Comparative Examples 8 to 10 and Comparative Example 12 are examples in which heating was performed by gas heating after the ζ phase was formed in the bath. Of these, Comparative Example 8 was too high at the heating temperature, and therefore ζ was contained in the product film.
Since there is no phase and a thick Γ phase is locally formed due to uneven burning, the powdering resistance is extremely poor and the variation is large. In Comparative Example 9 and Comparative Example 10, since the heating temperature is low, the ζ phase is present in the product film, but the Γ phase is locally formed thick due to uneven baking, or the η phase locally remains. However, for this reason, both the powdering resistance and the press formability have large variations in the plate width direction, and therefore these characteristic values themselves are also poor. In addition, the microscopic uniformity of the alloying phase is also inferior and the powdering resistance is also inferior in this respect.
Comparative Example 12 also has a large variation in characteristics due to uneven baking,
Further, the characteristic value itself is also bad for the same reason as above.
従来例１〜従来例４は、浴中でζ相が形成されておら
ず、特に、従来例３は加熱を高周波誘導加熱で行なって
いるにもかかわらず、比較例２と同様合金化反応のミク
ロ的な不均一性により耐パウダリング性が劣り、またそ
のバラツキも大きい。In Conventional Example 1 to Conventional Example 4, the ζ phase was not formed in the bath, and in particular, in Comparative Example 3, although the heating was performed by high frequency induction heating, the alloying reaction similar to Comparative Example 2 was performed. Due to microscopic non-uniformity, powdering resistance is inferior and its variation is large.
第１図（ａ）、（ｂ）は、溶融亜鉛めっき鋼板の450
℃、500℃での恒温合金化反応による相変化の一例を示
すものである。第２図は電着Zn−Fe合金の相構成を示す
ものである。第３図は上層めっき量と摩擦係数との関係
を示すものである。1 (a) and 1 (b) show 450 of hot dip galvanized steel sheet.
It shows an example of a phase change due to an isothermal alloying reaction at ℃ and 500 ℃. FIG. 2 shows the phase constitution of the electrodeposited Zn-Fe alloy. FIG. 3 shows the relationship between the upper layer plating amount and the friction coefficient.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 平谷 晃 東京都千代田区丸の内１丁目１番２号 日 本鋼管株式会社内 (72)発明者 森田 正哉 東京都千代田区丸の内１丁目１番２号 日 本鋼管株式会社内 (56)参考文献 特開 平２−173250（ＪＰ，Ａ) 特開 平２−254146（ＪＰ，Ａ) 特開 平２−66148（ＪＰ，Ａ) ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Akira Hiratani Akira Marunouchi 1-2-2, Chiyoda-ku, Tokyo Japan Steel Pipe Co., Ltd. (72) Masaya Morita 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Date (56) References JP-A-2-173250 (JP, A) JP-A-2-254146 (JP, A) JP-A-2-66148 (JP, A)
Claims (1)
からなる亜鉛めっき浴でめっきを施した後、目付量調整
を行い、加熱炉で皮膜中のFe含有量が８〜12％となるよ
うに合金化処理を行う合金化溶融亜鉛めっき鋼板の製造
方法において、浴中Al量:0.05％以上、0.13％未満、鋼
板のめっき浴中の侵入板温:495℃以下、浴温度:470℃以
下で、且つ、浴中Al量と侵入板温とが、 437.5×〔Al％〕＋448≧Ｔ≧437.5×〔Al％〕＋428 但し、〔Al％〕：浴中Al量（％） T:侵入板温（℃） を満足する条件でめっきを行うことにより、浴中でζ相
を形成する合金化反応を積極的に起こし、めっき後、高
周波誘導加熱炉で加熱炉出側の板温が495℃以下となる
ように加熱し、所定時間保持後冷却し、次いで、上層め
っきとしてFe含有量が50％以上のFe系めっきを1g/m2以
上施すことを特徴とするプレス成形性および耐パウダリ
ング性の優れた合金化溶融亜鉛めっき鋼板の製造方法。1. A Fe content in the coating is adjusted to 8 to 12% in a heating furnace after plating with a zinc plating bath containing Al and the balance Zn and unavoidable impurities, and then adjusting the basis weight. In the method for producing alloyed hot-dip galvanized steel sheet, which is subjected to alloying treatment, the amount of Al in the bath: 0.05% or more and less than 0.13%, the plate temperature of the steel sheet in the plating bath: 495 ° C or less, the bath temperature: 470 ° C Below, and the amount of Al in the bath and the penetration plate temperature are 437.5 x [Al%] + 448 ≥ T ≥ 437.5 x [Al%] + 428, however, [Al%]: Al amount in the bath (%) T: Penetration By plating under conditions that satisfy the plate temperature (° C), the alloying reaction that forms the ζ phase in the bath positively occurs, and after plating, the plate temperature on the exit side of the heating furnace is 495 in the high-frequency induction heating furnace. ℃ heated to be equal to or less than, cooled after a predetermined time holding, then that Fe content as an upper layer plating subjected to Fe-based plating over 50% 1g / m 2 or more Method for producing a press-formability and powdering resistance superior galvannealed steel sheet according to symptoms.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2302626A JPH0816260B2 (en) | 1990-11-09 | 1990-11-09 | Method for producing galvannealed steel sheet having excellent press formability and powdering resistance |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2302626A JPH0816260B2 (en) | 1990-11-09 | 1990-11-09 | Method for producing galvannealed steel sheet having excellent press formability and powdering resistance |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH04176853A JPH04176853A (en) | 1992-06-24 |
| JPH0816260B2 true JPH0816260B2 (en) | 1996-02-21 |
Family
ID=17911248
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2302626A Expired - Fee Related JPH0816260B2 (en) | 1990-11-09 | 1990-11-09 | Method for producing galvannealed steel sheet having excellent press formability and powdering resistance |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0816260B2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100910451B1 (en) * | 2002-12-28 | 2009-08-04 | 주식회사 포스코 | Hot?dip galvannealed steel sheet having superior flaking resistance and method for manufacturing thereof |
| JP2006104503A (en) * | 2004-10-01 | 2006-04-20 | Ntn Corp | Press pulley |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0266148A (en) * | 1988-08-30 | 1990-03-06 | Sumitomo Metal Ind Ltd | Multi-layer played steel sheet excellent in flaking resistance |
| JPH02173250A (en) * | 1988-12-26 | 1990-07-04 | Sumitomo Metal Ind Ltd | Alloyed hot dip galvanizing steel sheet and production thereof |
| JPH02254146A (en) * | 1989-03-27 | 1990-10-12 | Nkk Corp | Induction heating device, induction heating-type alloying furnace, and alloying method |
-
1990
- 1990-11-09 JP JP2302626A patent/JPH0816260B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH04176853A (en) | 1992-06-24 |
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