JP2000109966A - Production of hot dip galvanized high tensile strength steel sheet excellent in workability - Google Patents
Production of hot dip galvanized high tensile strength steel sheet excellent in workabilityInfo
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- JP2000109966A JP2000109966A JP10281530A JP28153098A JP2000109966A JP 2000109966 A JP2000109966 A JP 2000109966A JP 10281530 A JP10281530 A JP 10281530A JP 28153098 A JP28153098 A JP 28153098A JP 2000109966 A JP2000109966 A JP 2000109966A
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Abstract
Description
【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION
【０００１】[0001]
【発明の属する技術分野】本発明は、自動車車体などに
用いられる、加工性に優れた溶融亜鉛めっき高張力鋼板
（合金化したものを含む）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 high-strength steel sheet (including an alloyed steel sheet) having excellent workability and used for an automobile body or the like.
【０００２】[0002]
【従来の技術】自動車用の鋼板には、一般に、耐食性と
加工性が必要であるため、種々の表面処理鋼板が用いら
れている。なかでも、溶融亜鉛めっき鋼板は、高度な耐
食性を有しているとともに、再結晶焼鈍および亜鉛めっ
きを同一ラインで処理できる連続溶融亜鉛めっきライン
（ＣＧＬ）により、極めて安価に製造できるという利点
を具えている。また、前記亜鉛めっきの後、引き続いて
合金化処理を行った溶融亜鉛めっき鋼板は、とりわけ耐
食性に優れ、溶接性やプレス成形性にも優れている。一
方、近年、地球環境の改善を目指した燃費向上のための
自動車の軽量化が迫られ、また、安全性向上のための衝
突時の安全規制の強化が要請されるようになって、溶融
亜鉛めっき鋼板にも高強度化（高張力化）が必要になっ
てきた。2. Description of the Related Art Generally, various surface-treated steel sheets are used for steel sheets for automobiles because corrosion resistance and workability are required. Among them, hot-dip galvanized steel sheet has high corrosion resistance and has the advantage that it can be manufactured at extremely low cost by continuous hot-dip galvanizing line (CGL) that can process recrystallization annealing and galvanizing on the same line. I have. The galvanized steel sheet which has been subjected to an alloying treatment after the galvanization is particularly excellent in corrosion resistance and also excellent in weldability and press formability. On the other hand, in recent years, there has been a pressing need to reduce the weight of automobiles to improve fuel efficiency with the aim of improving the global environment. High strength (high tension) has also been required for plated steel sheets.
【０００３】ところで、高張力鋼板には種々の強化機構
を利用したものが開発されているが、とりわけ、自動車
の耐衝突特性に優れた鋼板として複合組織鋼板が挙げら
れる。複合組織鋼板は、フェライト相に、第２相とし
て、主にマルテンサイト相を複合させた鋼板であり、こ
の硬質な第２相を分散させることによって、組織強化に
よる高強度化を図ったものである。複合組織鋼板の一般
的な製造方法は、低炭素材にMnなどの合金元素を添加
し、フェライトとオーステナイトの２相領域に加熱した
のち、冷却し、オーステナイト相をマルテンサイトに低
温変態させるものである。このマルテンサイト変態時
に、マルテンサイトの周囲のフェライトに可動転位が導
入され、降伏比（ＹＲ＝降伏強さ／引張強さ）が低くな
る。このように降伏比が低い材料では、プレス成形時の
しわの発生が抑えられるので、プレス成形に有利であ
る。また、複合組織鋼板には、加工硬化（ｎ値）が高
く、均一伸びが高いという利点もある。[0003] By the way, high-strength steel sheets utilizing various strengthening mechanisms have been developed. Among them, a steel sheet having a composite structure is mentioned as a steel sheet having excellent crash resistance characteristics of an automobile. The composite structure steel sheet is a steel sheet in which a ferrite phase is mainly combined with a martensite phase as a second phase. By dispersing this hard second phase, high strength is achieved by strengthening the structure. is there. A common method of manufacturing a multi-structure steel sheet is to add an alloying element such as Mn to a low-carbon material, heat it to a two-phase region of ferrite and austenite, cool it, and transform the austenite phase to martensite at a low temperature. is there. During this martensitic transformation, mobile dislocations are introduced into the ferrite around the martensite, and the yield ratio (YR = yield strength / tensile strength) decreases. Such a material having a low yield ratio is advantageous for press molding because the generation of wrinkles during press molding is suppressed. In addition, the composite structure steel sheet also has the advantages of high work hardening (n value) and high uniform elongation.
【０００４】上述した２相域焼鈍において、オーステナ
イト相をマルテンサイト相に変態させるためには、合金
元素の添加が必要である。例えば、特開昭57−152421号
公報には、焼鈍後の冷却速度に応じて合金元素の添加量
を規定する技術が提案されている。この開示技術のよう
に、焼き入れ性を向上させるためには、Mn、Mo、Crなど
の合金元素を添加する必要がある。ここで、Moはめっき
性への影響が小さいものの、コストアップを招き、多量
に添加することは難しい。このため、高強度化を図るた
めの合金添加は、主としてMnあるいはCrを添加すること
によって対処していた。[0004] In the two-phase annealing described above, it is necessary to add an alloying element in order to transform the austenite phase into the martensite phase. For example, Japanese Patent Laying-Open No. 57-152421 proposes a technique for defining the amount of an alloy element to be added according to the cooling rate after annealing. In order to improve the hardenability as in the disclosed technology, it is necessary to add alloy elements such as Mn, Mo, and Cr. Here, Mo has little effect on the plating property, but causes an increase in cost, and it is difficult to add a large amount of Mo. For this reason, alloy addition for achieving high strength has been dealt with mainly by adding Mn or Cr.
【０００５】しかし、このMn、Crは、一般に、焼鈍の過
程で鋼板の表面に濃化して (表面濃化層の形成) 、めっ
き性、とくに溶融亜鉛めっきする際の濡れ性を悪くし不
めっきをもたらすことが知られているので、極力低減す
ることが望ましい元素であるといえる。一方、溶融亜鉛
めっき後に合金化処理する場合には、通常の連続焼鈍ラ
イン（ＣＡＬ）の場合に比べて冷却速度が遅くなるの
で、マルテンサイトを確保するためには、より多くの合
金元素の添加が避けられなくなるという側面がある。こ
のため、溶融亜鉛めっき後、合金化処理した溶融亜鉛め
っき高張力鋼板で、低降伏比の特性が得られる程度に合
金元素を添加すると、他方で不めっきが発生し、外観を
問題視する自動車用の部品への適用が困難になるという
問題があった。[0005] However, Mn and Cr are generally concentrated on the surface of the steel sheet during the annealing process (formation of a surface-concentrated layer), thereby deteriorating the plating property, particularly the wettability during hot-dip galvanizing, and causing unplating. Therefore, it can be said that it is an element to be reduced as much as possible. On the other hand, when alloying is performed after hot-dip galvanizing, the cooling rate is slower than in the case of a normal continuous annealing line (CAL). Therefore, in order to secure martensite, more alloying elements must be added. There is an aspect that becomes inevitable. For this reason, if the alloying element is added to such an extent that a low yield ratio characteristic can be obtained in a hot-dip galvanized high-strength steel sheet that has been subjected to alloying after hot-dip galvanizing, non-plating will occur on the other hand, and automobiles with a problematic appearance There is a problem that it becomes difficult to apply to parts for use.
【０００６】これらの問題に対する従来の方策として
は、めっき濡れ性の改善について、例えば、鋼板を連続
亜鉛めっきラインに導入するに先立って、電気めっきを
行う方法（特開平２−194156号公報）、クラッド法によ
りSi、Mnなどの含有量の少ない組成の鋼を表層にする方
法（特開平３−199363号公報）が提案されている。しか
し、これらの方法では、コストがかかり、生産性も悪い
工程を新たに経る必要があるなどの問題が生じてしま
う。[0006] As a conventional measure against these problems, for example, a method of improving the plating wettability by performing electroplating before introducing a steel sheet into a continuous galvanizing line (Japanese Patent Laid-Open No. 2-194156), A method has been proposed in which a steel having a low content of Si, Mn, or the like is made into a surface layer by a cladding method (JP-A-3-199363). However, these methods have problems such as the necessity of a new process which is costly and has poor productivity.
【０００７】[0007]
【発明が解決しようとする課題】上述したように、溶融
亜鉛めっき高張力鋼板を製造するに当たって、従来の既
知技術は、不めっきの発生、密着性の低下、降伏比の上
昇（加工性の低下）などを招き、また、過度の合金添加
や新たな附帯設備の増設などに伴って、生産性の低下や
コストの上昇をもたらしていた。本発明は、従来技術が
抱えていたこのような問題を解消した溶融亜鉛めっき高
張力鋼板を製造するための新規な製造方法を提案するこ
とを目的とする。また、本発明の目的は、とくに不めっ
きがなく、密着性に優れ、しかも降伏比が低く、良好な
加工性を有する溶融亜鉛めっき高張力鋼板の新規な製造
方法を提案することにある。さらに、本発明の他の目的
は、具体的な特性として、引張強さが380 〜1000ＭPa、
とりわけ440 〜580 ＭPaで、降伏比が55％以下を満た
し、めっき性がよい溶融亜鉛めっき高張力鋼板の製造方
法を提案することにある。As described above, in producing a hot-dip galvanized high-strength steel sheet, the conventional techniques described in the prior art include the occurrence of non-plating, a decrease in adhesion, and an increase in yield ratio (a decrease in workability). ), And the excessive addition of alloys and the addition of new auxiliary equipment have led to a decrease in productivity and an increase in cost. An object of the present invention is to propose a new manufacturing method for manufacturing a hot-dip galvanized high-strength steel sheet that solves such a problem that the conventional technology has. Another object of the present invention is to propose a novel method for producing a hot-dip galvanized high-strength steel sheet having no non-plating, excellent adhesion, low yield ratio, and good workability. Still another object of the present invention is to provide, as specific properties, a tensile strength of 380 to 1000 MPa,
In particular, it is an object of the present invention to propose a method for producing a hot-dip galvanized high-strength steel sheet having a yield ratio of 440 to 580 MPa and a yield ratio of 55% or less and having good plating properties.
【０００８】[0008]
【課題を解決するための手段】発明者らは、めっき性と
加工性を両立させるための溶融亜鉛めっき鋼板の製造方
法について、鋭意研究した。その結果、合金元素を適正
に添加したうえ、鋼板表面における成分濃化を抑制し、
かつ、所望の複合組織を得るために適した、熱処理工程
を採用することによって、上記の目的を達成できるとの
知見を得て本発明を完成するに至った。その要旨構成は
以下のとおりである。Means for Solving the Problems The present inventors have intensively studied a method for producing a hot-dip galvanized steel sheet in order to achieve both plating properties and workability. As a result, in addition to properly adding alloying elements, component concentration on the steel sheet surface is suppressed,
Further, the present inventors have found that the above object can be achieved by adopting a heat treatment step suitable for obtaining a desired composite structure, and have completed the present invention. The summary configuration is as follows.
【０００９】(1) Ｃ：0.005 〜0.15wt％、Mn：0.3 〜3.
0 wt％、Mo：0.05〜1.0 wt％を含有するめっき母板を、
Ａc1変態点以上、Ａr3変態点以下の温度で少なくとも１
回は焼鈍し、冷却後に、酸洗して表面濃化層を除去し、
次いで、Ａc1変態点〜Ａc3変態点の温度範囲に加熱し、
この加熱温度から少なくともめっき浴温度までの温度域
を、Ｂ含有量に応じて下記 (1)式または (2)式で表され
る臨界冷却速度以上の速度で冷却して、必要に応じて
(すなわち、前記冷却においてめっき浴温度未満まで鋼
板を冷却した場合は) 少なくともめっき浴温度まで加熱
し、次いで (前記めっき浴温度までの加熱の有無にかか
わらず) 溶融亜鉛めっきを施し、めっき後300 ℃までの
温度域を、Ｂ含有量に応じて下記 (1)式または (2)式で
表される臨界冷却速度以上の速度で冷却することを特徴
とする、加工性に優れた溶融亜鉛めっき高張力鋼板の製
造方法。 記 Ｂ≦0.0006wt％のとき、 log ＣＲ＝−3.50（Mowt％）−1.20（Mnwt％）−0.16（Siwt％）− 2.0（Crwt ％）−0.08（Niwt％＋Cuwt％）−0.32（Ｐwt％）＋3.50 ……… (1) Ｂ＞0.0006wt％のとき、 log ＣＲ＝−3.50（Mowt％）−1.20（Mnwt％）−0.16（Siwt％）− 2.0（Crwt ％）−0.08（Niwt％＋Cuwt％）−0.32（Ｐwt％）＋3.20 ……… (2) ただし、ＣＲ：臨界冷却速度（℃／sec)(1) C: 0.005 to 0.15 wt%, Mn: 0.3 to 3.
A plating mother plate containing 0 wt% and Mo: 0.05 to 1.0 wt%
At least 1 at a temperature between the Ac 1 transformation point and the Ar 3 transformation point
Annealing and cooling, after pickling, to remove the surface concentrated layer,
Next, heating to a temperature range from the Ac 1 transformation point to the Ac 3 transformation point,
The temperature range from the heating temperature to at least the plating bath temperature is cooled at a rate equal to or higher than the critical cooling rate represented by the following equation (1) or (2) according to the B content.
(I.e., when the steel sheet is cooled to a temperature lower than the plating bath temperature in the cooling), it is heated to at least the plating bath temperature, and then hot-dip galvanized (with or without heating to the plating bath temperature), and after plating, Hot-dip galvanizing with excellent workability, characterized in that the temperature range up to ℃ is cooled at a rate higher than the critical cooling rate represented by the following formula (1) or (2) according to the B content. Manufacturing method of high strength steel sheet. When B ≤ 0.0006 wt%, log CR = -3.50 (Mowt%)-1.20 (Mnwt%)-0.16 (Siwt%)-2.0 (Crwt%)-0.08 (Niwt% + Cuwt%)-0.32 (Pwt%) +3.50 ... (1) When B> 0.0006 wt%, log CR = -3.50 (Mowt%)-1.20 (Mnwt%)-0.16 (Siwt%)-2.0 (Crwt%)-0.08 (Niwt% + Cuwt %)-0.32 (Pwt%) + 3.20 (2) where CR is the critical cooling rate (° C / sec)
【００１０】(2) Ｃ：0.005 〜0.15wt％、Mn：0.3 〜3.
0 wt％、Mo：0.05〜1.0 wt％を含有するめっき母板を、
Ａc1変態点以上、Ａr3変態点以下の温度で少なくとも１
回は焼鈍し、冷却後に、酸洗して表面濃化層を除去し、
次いで、Ａc1変態点〜Ａc3変態点の温度範囲に加熱し、
この加熱温度から少なくともめっき浴温度までの温度域
を、Ｂ含有量に応じて下記 (1)式または (2)式で表され
る臨界冷却速度以上の速度で冷却して、必要に応じて
(すなわち、前記冷却においてめっき浴温度未満まで鋼
板を冷却した場合は) 少なくともめっき浴温度まで加熱
し、次いで (前記めっき浴温度までの加熱の有無にかか
わらず) 溶融亜鉛めっきを施し、引き続いて、合金化処
理を行い、合金化処理後300 ℃までの温度域を、Ｂ含有
量に応じて下記 (1)式または (2)式で表される臨界冷却
速度以上の速度で冷却することを特徴とする、加工性に
優れた溶融亜鉛めっき高張力鋼板の製造方法。 記 Ｂ≦0.0006wt％のとき、 log ＣＲ＝−3.50（Mowt％）−1.20（Mnwt％）−0.16（Siwt％）− 2.0（Crwt ％）−0.08（Niwt％＋Cuwt％）−0.32（Ｐwt％）＋3.50 ……… (1) Ｂ＞0.0006wt％のとき、 log ＣＲ＝−3.50（Mowt％）−1.20（Mnwt％）−0.16（Siwt％）− 2.0（Crwt ％）−0.08（Niwt％＋Cuwt％）−0.32（Ｐwt％）＋3.20 ……… (2) ただし、ＣＲ：臨界冷却速度（℃／sec)(2) C: 0.005 to 0.15 wt%, Mn: 0.3 to 3.
A plating mother plate containing 0 wt% and Mo: 0.05 to 1.0 wt%
At least 1 at a temperature between the Ac 1 transformation point and the Ar 3 transformation point
Annealing and cooling, after pickling, to remove the surface concentrated layer,
Next, heating to a temperature range from the Ac 1 transformation point to the Ac 3 transformation point,
The temperature range from the heating temperature to at least the plating bath temperature is cooled at a rate equal to or higher than the critical cooling rate represented by the following equation (1) or (2) according to the B content.
(I.e., when the steel sheet is cooled to below the plating bath temperature in the cooling), at least heat up to the plating bath temperature, then perform hot-dip galvanizing (with or without heating to the plating bath temperature), and subsequently, It is characterized by performing alloying treatment and cooling the temperature range up to 300 ° C after alloying treatment at a rate higher than the critical cooling rate represented by the following formula (1) or (2) depending on the B content. A method for producing a hot-dip galvanized high-strength steel sheet having excellent workability. When B ≤ 0.0006 wt%, log CR = -3.50 (Mowt%)-1.20 (Mnwt%)-0.16 (Siwt%)-2.0 (Crwt%)-0.08 (Niwt% + Cuwt%)-0.32 (Pwt%) +3.50 ... (1) When B> 0.0006 wt%, log CR = -3.50 (Mowt%)-1.20 (Mnwt%)-0.16 (Siwt%)-2.0 (Crwt%)-0.08 (Niwt% + Cuwt %)-0.32 (Pwt%) + 3.20 (2) where CR is the critical cooling rate (° C / sec)
【００１１】(3) 上記 (1)または (2)において、めっき
用母板の成分組成が、 Ｃ：0.005 〜0.15wtwt％、 Mn：0.3 〜3.0 wt％、 Mo：0.05〜1.0 wt％ を含み、かつ Si：0.05〜0.5 wt％、 Cr：0.05〜1.0 wt％、 Ｐ：0.02〜0.1 wt％、 Ｂ：0.0003〜0.01wt％、 Ni：0.05〜1.5 wt％、 Cu：0.05〜1.5 wt％、 Nb：0.3 wt％以下、 Ti ：0.3 wt％以下、および Ｖ：0.3 wt％以下 から選ばれるいずれか１種または２種以上を含有し、残
部はFeおよび不可避的からなることを特徴とする、加工
性に優れた溶融亜鉛めっき高張力鋼板の製造方法。(3) In the above (1) or (2), the component composition of the base plate for plating includes: C: 0.005 to 0.15 wt%, Mn: 0.3 to 3.0 wt%, Mo: 0.05 to 1.0 wt%. And Si: 0.05-0.5 wt%, Cr: 0.05-1.0 wt%, P: 0.02-0.1 wt%, B: 0.0003-0.01 wt%, Ni: 0.05-1.5 wt%, Cu: 0.05-1.5 wt%, Nb: 0.3 wt% or less, Ti: 0.3 wt% or less, V: 0.3 wt% or less, and the balance is Fe and inevitable. A method for producing hot-dip galvanized high-strength steel sheets with excellent workability.
【００１２】[0012]
【発明の実施の形態】まず、本発明の成分組成を上記範
囲に限定理由したについて説明する。 Ｃ：0.005 〜0.15wt％ Ｃは、第２相をマルテンサイト化し、また、そのマルテ
ンサイト相の強度を確保するために必要な元素である。
Ｃ量が0.005 wt％未満では、マルテンサイト化しにく
く、複合組織を安定して得ることが困難となる。一方、
0.15wt％を超えて添加するとマルテンサイトへの変態温
度が低下し、マルテンサイト化しにくくなる。このた
め、Ｃ量は0.005 〜0.15wt％、好ましくは0.02〜0.10wt
％とする。First, the reasons for limiting the composition of the present invention to the above ranges will be described. C: 0.005 to 0.15 wt% C is an element necessary for converting the second phase into martensite and ensuring the strength of the martensite phase.
If the C content is less than 0.005 wt%, it is difficult to form martensite, and it is difficult to stably obtain a composite structure. on the other hand,
When added in excess of 0.15 wt%, the transformation temperature to martensite decreases, and it becomes difficult to form martensite. Therefore, the C content is 0.005 to 0.15 wt%, preferably 0.02 to 0.10 wt%.
%.
【００１３】Mn：0.3 〜3.0 wt Mnは、焼き入れ性を向上させる元素として有効な元素で
あり、安定した複合組織を得るためには、少なくとも0.
3 wt％は添加する必要がある。一方、Mn含有量が3.0 wt
％を超えると、加工性が低下し、また、めっき性が本発
明工程によっても改善できなくなる。このため、Mn量
は、0.3 〜3.0 wt％、好ましくは 1.0〜2.4 wt％とす
る。Mn: 0.3 to 3.0 wt. Mn is an element effective as an element for improving hardenability.
3 wt% must be added. On the other hand, when the Mn content is 3.0 wt.
%, The workability is reduced, and the plating property cannot be improved by the process of the present invention. Therefore, the amount of Mn is set to 0.3 to 3.0 wt%, preferably 1.0 to 2.4 wt%.
【００１４】Mo：0.05〜1.0 wt％ Moは、焼き入れ性を向上させるが、めっき性への悪影響
が少ないので、強度確保の上で極めて有用な元素であ
る。このような効果を発揮させるためには、0.05wt％以
上の添加が必要である。一方、1.0 wt％を超える添加
は、合金化の遅延を招くほか、コスト上昇にもつながる
ので、Mo添加量は0.05〜1.0 wt％、好ましくは0.10〜0.
50wt％の範囲とする。本発明の鋼板は、上記組成を基本
成分として、残部はFeおよび不可避的不純物とすればよ
い。Mo: 0.05 to 1.0 wt% Mo improves the hardenability, but has a small adverse effect on the plating property, and is therefore an extremely useful element for securing strength. In order to exert such effects, it is necessary to add 0.05 wt% or more. On the other hand, if the addition exceeds 1.0 wt%, it causes delay in alloying and also leads to an increase in cost. Therefore, the Mo addition amount is 0.05 to 1.0 wt%, preferably 0.10 to 0.1.
The range is 50 wt%. The steel sheet of the present invention may have the above composition as a basic component, and the balance may be Fe and inevitable impurities.
【００１５】以上の基本成分に加えて、高張力鋼板のさ
らなる材質改善をはかるために、焼入性改善元素として
Si, Cr, Ｐ, Ｂ, Ni, Cuのうち１種以上を、また、局部
延性改善元素としてTi, Nb, Ｖのうち１種以上を、それ
ぞれ添加してよい。[0015] In addition to the above basic components, in order to further improve the quality of the high-tensile steel sheet, as a hardenability improving element
One or more of Si, Cr, P, B, Ni and Cu may be added, and one or more of Ti, Nb and V may be added as a local ductility improving element.
【００１６】Si：0.05〜0.5 wt％ Siは、鋼の強化と強度−伸びバランスに有用な元素であ
る。その効果は0.05wt％以上の添加で得られるが、0.5
wt％を超えて添加すると、めっき性、とくに濡れ性を阻
害する。このため、Si量は0.05〜0.5 wt％とする。Si: 0.05-0.5 wt% Si is an element useful for strengthening steel and balancing strength-elongation. The effect can be obtained by adding 0.05 wt% or more.
If added in excess of wt%, plating properties, especially wettability, are impaired. For this reason, the amount of Si is set to 0.05 to 0.5 wt%.
【００１７】Cr：0.05〜1.0 wt％ Crは、マルテンサイト化を促進するとともに、マルテン
サイトの分布状態を制御し、低降伏比化に有利な元素で
ある。この効果は0.05wt％以上の添加で発現するが、1.
0 wt％を超えて添加すると濡れ性を阻害する。よって、
Cr量は、0.05〜1.0 wt％の範囲で添加する。Cr: 0.05-1.0 wt% Cr is an element that promotes the formation of martensite, controls the distribution state of martensite, and is advantageous for lowering the yield ratio. This effect is manifested when 0.05 wt% or more is added.
Addition of more than 0 wt% impairs wettability. Therefore,
The Cr content is added in the range of 0.05 to 1.0 wt%.
【００１８】Ｐ：0.02〜0.1 wt％ Ｐは、強度向上のほか、伸びやｒ値の改善に有効な元素
である。これらの効果は0.02wt％以上で得られるが、0.
1 wt％を超えての添加は、加工性の低下、靭性の低下を
もたらすので、0.02〜0.1 wt％の範囲とする。P: 0.02 to 0.1 wt% P is an element effective for improving strength, elongation and r-value. These effects can be obtained at 0.02 wt% or more,
Addition exceeding 1 wt% causes a reduction in workability and a decrease in toughness, so the content is set in the range of 0.02 to 0.1 wt%.
【００１９】Ｂ：0.0003〜0.01wt％ Ｂは、焼き入れ性を改善するほか、伸びの改善に有効な
元素である。この効果は0.0003wt％以上で得られるが、
0.01wt％％を超えて添加すると析出による加工性の低下
をきたす。よって、Ｂは0.0003〜0.01wt％の範囲で添加
する。B: 0.0003 to 0.01 wt% B is an element effective for improving hardenability and elongation. This effect can be obtained at 0.0003 wt% or more,
If it is added in excess of 0.01% by weight, the workability is reduced due to precipitation. Therefore, B is added in the range of 0.0003 to 0.01 wt%.
【００２０】Ni：0.05〜1.5 wt％ Niは、焼き入れ性の向上に有効であり、めっき性への悪
影響が少ない元素であるが、1.5 wt％を超えて添加する
と伸びなどの加工特性を低下させるので、0.05〜1.5 wt
％の範囲で添加する。Ni: 0.05 to 1.5 wt% Ni is effective for improving the hardenability and is an element having little adverse effect on the plating property. However, when added in excess of 1.5 wt%, the processing characteristics such as elongation are deteriorated. 0.05-1.5 wt
%.
【００２１】Cu：0.05〜1.5 wt％ Cuは、焼き入れ性を向上させる元素である。この効果を
発揮させるためには、0.05wt％以上の添加が必要である
が、1.5 wt％を超えて添加すると、熱間圧延におけるス
ケール疵の原因になりやすいので、0.05〜1.5 wt％の範
囲で添加する。Cu: 0.05-1.5 wt% Cu is an element for improving hardenability. In order to exhibit this effect, it is necessary to add 0.05 wt% or more. However, if it exceeds 1.5 wt%, it tends to cause scale flaws in hot rolling. Add in.
【００２２】Nb：0.3 wt％以下、Ti：0.3 wt％以下、
Ｖ：0.3 wt％以下 Nb, Ti, Ｖは、微細な炭化物をフェライトへ析出させる
ことによりフェライトの強度を上昇させ、伸びフランジ
性などの局部延性を向上させるのに有効な元素である。
但し、0.3 wt％を超えての添加は析出物が多くなりすぎ
て伸びの低下をまねくので、0.3 wt％を上限とする。な
お、Nb、TiおよびＶの３元素は、同等の効果をもち、0.
3 wt％超の添加は伸びの低下をまねくので、合計量 (Nb
＋Ti＋Ｖ量) で0.3 wt％以下の範囲で添加するのが望ま
しい。Nb: 0.3 wt% or less, Ti: 0.3 wt% or less,
V: 0.3 wt% or less Nb, Ti, and V are elements effective for increasing the strength of ferrite by precipitating fine carbides into ferrite and improving local ductility such as stretch flangeability.
However, if the addition exceeds 0.3 wt%, the amount of precipitates becomes too large and the elongation is reduced, so the upper limit is 0.3 wt%. Note that the three elements Nb, Ti and V have the same effect, and
Since the addition of more than 3 wt% leads to a decrease in elongation, the total amount (Nb
(+ Ti + V amount) in a range of 0.3 wt% or less.
【００２３】次に、溶融亜鉛めっき高張力鋼板の製造条
件について説明する。上述した成分を有するスラブを溶
製し、熱間圧延を行う。熱間圧延は、オーステナイト域
で終了させることが好ましい。その後、表面の酸化スケ
ールを酸洗により除去したのち、冷間圧延を行い、所定
の板厚に調整する。これをＡc1変態点以上、Ａc3変態点
以下の２相域温度に加熱（焼鈍）する。焼鈍は連続焼鈍
ライン(以下、単に「ＣＡＬ」と略記する) が好ましい
が、バッチ焼鈍でもよい。上記ＣＡＬでの加熱の目的
は、鋼板表面に成分の濃化を促すとともに、鋼板を複合
組織形成条件におき第２相に合金元素を濃化させること
によって、めっき性を改善し、降伏比を低下させること
にある。なお、表面直下３〜30μｍ程度の深さに粒界酸
化物が少量形成すると、めっき性にはなおよい。このよ
うなＣＡＬでの加熱によって得られる効果は、１回の加
熱で十分得られるが、複数回繰り返せば一層大きな効果
が期待される。焼鈍時間はＣＡＬの場合、積算で30秒〜
15分が好ましい。Next, the manufacturing conditions for the hot-dip galvanized high-strength steel sheet will be described. A slab having the above components is melted and hot-rolled. The hot rolling is preferably terminated in the austenite region. Then, after removing the oxide scale on the surface by pickling, cold rolling is performed to adjust the thickness to a predetermined thickness. This is heated (annealed) to a two-phase region temperature equal to or higher than the Ac 1 transformation point and equal to or lower than the Ac 3 transformation point. Annealing is preferably a continuous annealing line (hereinafter simply referred to as "CAL"), but may be batch annealing. The purpose of the heating in the above CAL is to promote the concentration of components on the steel sheet surface, to improve the plating property and to increase the yield ratio by enriching the alloy element in the second phase by placing the steel sheet under the conditions for forming the composite structure. To lower it. In addition, when a small amount of the grain boundary oxide is formed at a depth of about 3 to 30 μm just below the surface, the plating property is further improved. The effect obtained by such heating with CAL can be sufficiently obtained by one heating, but a larger effect can be expected by repeating a plurality of times. Annealing time is 30 seconds or more for CAL
15 minutes is preferred.
【００２４】図１は、溶融亜鉛めっき鋼板のめっき性と
降伏比に及ぼすＣＡＬ加熱温度の影響を示したものであ
る。ここに、溶融亜鉛めっき鋼板は、表１の鋼13（Ａc1
＝710 ℃、Ａc3＝850 ℃）を種々のＣＡＬ温度で加熱し
た後、連続溶融亜鉛めっきライン（以下単に「ＣＧＬ」
と略記）の加熱温度を760 ℃、保持時間を60秒とし、め
っき前（ＣＧＬ加熱終了からめっき浴浸入まで）および
めっき後300 ℃までを、それぞれ15℃／秒、20℃／秒と
する速度で冷却して製造したものである。図１から、め
っき性、降伏比とも良好な加熱温度は、Ａc1変態点以上
の温度範囲であるといえる。しかし、加熱温度がＡc3を
超えるγ単相域になると、降伏比は高くなり、また、表
面濃化に起因してめっき性も悪化する。これらの結果を
もとに、本発明における焼鈍 (ＣＡＬ) での鋼板の到達
温度は、鋼成分によって定まるＡc1変態点以上、Ａc3変
態点以下 (好ましくは950 ℃以下) とする必要がある。
なお、ＣＡＬの雰囲気は、スケールの発生を抑制するた
めに、鋼板に対し還元性とすることが必要であり、一般
には、数％のＨ2 を含むＮ2 ガスを用いればよい。FIG. 1 shows the effect of the CAL heating temperature on the plating properties and the yield ratio of a hot-dip galvanized steel sheet. Here, the hot-dip galvanized steel sheet is steel 13 (Ac 1
= 710 ° C, Ac 3 = 850 ° C) at various CAL temperatures and then a continuous hot-dip galvanizing line (hereinafter simply “CGL”).
Abbreviated as the heating temperature of 760 ° C., the holding time of 60 seconds, and the rates of 15 ° C./sec and 20 ° C./sec before plating (from the end of CGL heating to plating bath immersion) and up to 300 ° C. after plating, respectively. It was manufactured by cooling at From FIG. 1, it can be said that the heating temperature in which both the plating property and the yield ratio are good is in the temperature range of the Ac 1 transformation point or higher. However, when the heating temperature is in the γ single phase region exceeding Ac 3 , the yield ratio increases, and the plating properties deteriorate due to the surface concentration. Based on these results, the ultimate temperature of the steel sheet during annealing (CAL) in the present invention must be not less than the Ac 1 transformation point and not more than the Ac 3 transformation point (preferably 950 ° C. or less) determined by the steel composition. .
The atmosphere of CAL needs to be reducible to the steel sheet in order to suppress the generation of scale, and in general, N 2 gas containing several% of H 2 may be used.
【００２５】通常、ＣＡＬの還元雰囲気では、鉄は酸化
されず、Mnなどが外部酸化層として現れる。ただしミク
ロ的にみると、粒界にそってMnの内部酸化物が存在する
ことがあり、これが酸洗でもとれずに残る。また、ＣＡ
Ｌで二相組織にすることは、フェライトの粒界にMnなど
の元素が濃化した第２相を存在させることになるので、
次工程でのＣＧＬのサイクルで、それらの元素の表面へ
の濃化が抑制できる。Normally, in a reducing atmosphere of CAL, iron is not oxidized, and Mn and the like appear as an external oxide layer. However, from a microscopic point of view, an internal oxide of Mn may be present along the grain boundaries, and this remains without being removed by pickling. Also, CA
Making a two-phase structure with L means that a second phase in which elements such as Mn are concentrated exists at the grain boundaries of ferrite,
In the CGL cycle in the next step, the concentration of those elements on the surface can be suppressed.
【００２６】上記加熱によって、鋼板表面には、鋼中の
Ｐが析出し、Si、Mn、Crなどが酸化物として濃化する。
これらの濃化成分は、めっき性に対して悪影響を及ぼす
ので、この表面濃化層を除去する。このとき、内部酸化
物は除去せず残すことが好ましいが、酸洗等の通常の工
業的除去手段であれば、内部酸化物は除去されずに鋼板
の表層部直下に残る。By the above heating, P in the steel precipitates on the surface of the steel sheet, and Si, Mn, Cr, etc. are concentrated as oxides.
These thickening components have an adverse effect on the plating properties, so that this surface thickening layer is removed. At this time, the internal oxide is preferably left without being removed, but if it is a usual industrial removing means such as pickling, the internal oxide is not removed but remains immediately below the surface layer of the steel sheet.
【００２７】酸洗に続いて、ＣＧＬの還元雰囲気の下で
加熱（焼鈍）を行う。このときの温度は、めっき濡れ性
や合金化速度の点からは650 ℃以上あればよいが、複合
組織の形成を考えてＡc1変態点〜Ａr3変態点の２相域温
度とする必要がある。ＣＧＬにて、Ａc1変態点〜Ａc3変
態点の温度に加熱することによって、合金元素がさらに
第２相つまりγ相へと濃化する。そして、この濃化部分
は、その後に所定速度で冷却したとき、マルテンサイト
相となって複合組織の形成に寄与する。ここでいう合金
元素とは、Mn、Moなどの置換型の合金元素であり、前述
したＣＡＬ加熱やＣＧＬでの加熱の温度域では、比較的
拡散しにくい元素をいう。これらの合金元素は、かかる
温度域における加熱をＣＡＬおよびＣＧＬで繰り返すこ
とによって、より局所的に濃化し、複合組織がより理想
的に安定して形成される。ここで、ＣＡＬでの加熱の役
割は、一旦、フェライトと第２相との複合組織となし、
ＣＧＬにおけるめっき前の加熱 (焼鈍) の際に、第２相
にさらに合金元素を濃化させることにより、フェライト
および第２相がより安定して形成されるようにすること
にある。このとき、最終製品と同じ複合組織が得られれ
ばもちろんよいが、そうでなくとも、少なくとも粒界の
３重点付近に合金元素が濃化するため、最終製品での複
合組織形成が安定化する。Subsequent to the pickling, heating (annealing) is performed in a reducing atmosphere of CGL. The temperature at this time may be 650 ° C. or more from the viewpoint of plating wettability and alloying speed, but it is necessary to set the temperature in the two-phase region from the Ac 1 transformation point to the Ar 3 transformation point in consideration of the formation of a composite structure. is there. By heating to a temperature between the Ac 1 transformation point and the Ac 3 transformation point by CGL, the alloy element is further concentrated to the second phase, that is, the γ phase. Then, when the concentrated portion is subsequently cooled at a predetermined rate, it becomes a martensite phase and contributes to the formation of a composite structure. The alloy element referred to here is a substitutional alloy element such as Mn or Mo, and is an element that is relatively difficult to diffuse in the above-described CAL heating or CGL heating temperature range. By repeating heating in such a temperature range with CAL and CGL, these alloy elements are more locally concentrated, and a composite structure is more ideally and stably formed. Here, the role of heating in CAL is once a composite structure of ferrite and the second phase,
In heating (annealing) before plating in CGL, an alloy element is further concentrated in the second phase so that ferrite and the second phase are formed more stably. At this time, it is sufficient that the same composite structure as that of the final product is obtained. However, otherwise, the formation of the composite structure in the final product is stabilized because the alloy element is concentrated at least in the vicinity of the triple point of the grain boundary.
【００２８】このように、ＣＡＬおよびＣＧＬの２工程
で加熱すれば、内部酸化層の形成により、めっき性の上
からも極めて望ましい表面状態が得られる。すなわち、
ＣＡＬでの加熱、酸洗による表面濃化層の除去を終える
と、表面にミクロ的な内部酸化層が形成された鋼板とな
る。これを、ＣＧＬで加熱すると、めっき性に不利なSi
やMnなどの合金元素は、粒界にそって表面に濃化しよう
とするが、これら合金元素は上記内部酸化物にトラップ
されて表面には移動できなくなる。一方で、鋼板表面で
は、還元雰囲気により、還元されたFe層が形成され、め
っき性に好ましい表面になる。これらの相乗効果によっ
て、めっき性が著しく向上するのである。As described above, if the heating is performed in two steps of CAL and CGL, a very desirable surface state can be obtained from the viewpoint of plating properties due to the formation of the internal oxide layer. That is,
When the removal of the surface-concentrated layer by heating and pickling in CAL is completed, a steel sheet having a micro internal oxide layer formed on the surface is obtained. When this is heated by CGL, Si which is disadvantageous for plating
Alloying elements such as Al and Mn tend to concentrate on the surface along the grain boundaries, but these alloying elements are trapped by the internal oxide and cannot move to the surface. On the other hand, on the steel sheet surface, a reduced Fe layer is formed by the reducing atmosphere, which makes the surface preferable for plating. Due to these synergistic effects, the plating properties are significantly improved.
【００２９】ＣＧＬにおいて加熱した後に、溶融亜鉛め
っき、あるいはさらに合金化処理を施して、最終的に複
合組織からなる溶融亜鉛めっき高張力鋼板とするために
は、ＣＧＬでの加熱温度から少なくともめっき浴温度ま
で、およびめっき浴温度から(あるいは合金化処理温度
から) 300 ℃までの各温度域における冷却速度を以下の
条件とすることが必要である。まず、ＣＧＬでの加熱温
度からめっき浴温度（通常、 550〜450 ℃）までの温度
域では、Ｂ含有量に応じて下記式で表される臨界冷却速
度ＣＲ（℃／sec)以上の速度で冷却する。Ｂ≦0.0006wt
％のとき、 log ＣＲ＝−3.50（Mowt％）−1.20（Mnwt％）−0.16
（Siwt％）− 2.0（Crwt％）−0.08（Niwt％＋Cuwt％）
−0.32（Ｐwt％）＋3.50 Ｂ＞0.0006wt％のとき、 log ＣＲ＝−3.50（Mowt％）−1.20（Mnwt％）−0.16
（Siwt％）− 2.0（Crwt％）−0.08（Niwt％＋Cuwt％）
−0.32（Ｐwt％）＋3.20 上記各式で冷却することによって、合金元素の濃化部は
マルテンサイトに変態し、降伏比が低い複合組織鋼板を
製造できる。なお、上式は、合金元素の含有量により、
冷却過程でのパーライトの晶出曲線が変化するため、パ
ーライトノーズにかからないよう合金元素の量に応じて
冷却速度を制御しなければならないことを意味してい
る。上記の冷却はめっき浴温度で終えて、そのまま溶融
亜鉛めっきを施してもよい。また、めっき浴温度未満ま
で冷却した後、少なくともめっき浴温度まで加熱して溶
融亜鉛めっきを施してもよい。In order to obtain a hot-dip galvanized high-strength steel sheet having a composite structure after being subjected to hot-dip galvanizing or further alloying after heating in the CGL, at least the plating bath must be heated from the heating temperature in the CGL. The cooling rate in each temperature range from the plating bath temperature to 300 ° C. from the plating bath temperature (or from the alloying treatment temperature) needs to be as follows. First, in the temperature range from the heating temperature in CGL to the plating bath temperature (normally, 550 to 450 ° C.), the temperature is higher than the critical cooling rate CR (° C./sec) represented by the following equation according to the B content. Cooling. B ≦ 0.0006wt
%, Log CR = -3.50 (Mowt%)-1.20 (Mnwt%)-0.16
(Siwt%)-2.0 (Crwt%)-0.08 (Niwt% + Cuwt%)
−0.32 (Pwt%) + 3.50 When B> 0.0006 wt%, log CR = −3.50 (Mowt%) − 1.20 (Mnwt%) − 0.16
(Siwt%)-2.0 (Crwt%)-0.08 (Niwt% + Cuwt%)
−0.32 (Pwt%) + 3.20 By cooling according to the above equations, the concentrated portion of the alloy element is transformed into martensite, and a composite structure steel sheet having a low yield ratio can be manufactured. The above equation is based on the content of the alloying element.
Since the crystallization curve of pearlite changes during the cooling process, it means that the cooling rate must be controlled according to the amount of the alloying element so as not to cover the pearlite nose. The above cooling may be finished at the plating bath temperature, and then hot-dip galvanized may be applied as it is. Further, after cooling to a temperature lower than the plating bath temperature, hot-dip galvanizing may be performed by heating to at least the plating bath temperature.
【００３０】また、溶融亜鉛めっきを施した後、めっき
温度から (さらに合金化処理を行う場合には、合金化処
理温度（通常、 470℃〜Ａc1）から) 300 ℃までの温度
域をも、上述した方法と同様にして、Ｂ含有量に応じて
次式で表される臨界冷却速度以上の速度で冷却する。Ｂ
≦0.0006wt％のとき、 log ＣＲ＝−3.50（Mowt％）−1.20（Mnwt％）−0.16
（Siwt％）− 2.0（Crwt％）−0.08（Niwt％＋Cuwt％）
−0.32（Ｐwt％）＋3.50 Ｂ＞0.0006wt％のとき、 log ＣＲ＝−3.50（Mowt％）−1.20（Mnwt％）−0.16
（Siwt％）− 2.0（Crwt％）−0.08（Niwt％＋Cuwt％）
−0.32（Ｐwt％）＋3.20 冷却速度が上記速度より小さいと、オーステナイト相が
マルテンサイトになる前にベイナイト変態してしまい、
製品の降伏比が上昇する。After the hot-dip galvanizing, the temperature range from the plating temperature to 300 ° C. (or from the alloying temperature (normally 470 ° C. to Ac 1 ) when further alloying is performed) is also required. In the same manner as in the above-described method, cooling is performed at a rate equal to or higher than the critical cooling rate represented by the following equation according to the B content. B
When ≦ 0.0006 wt%, log CR = −3.50 (Mowt%) − 1.20 (Mnwt%) − 0.16
(Siwt%)-2.0 (Crwt%)-0.08 (Niwt% + Cuwt%)
−0.32 (Pwt%) + 3.50 When B> 0.0006 wt%, log CR = −3.50 (Mowt%) − 1.20 (Mnwt%) − 0.16
(Siwt%)-2.0 (Crwt%)-0.08 (Niwt% + Cuwt%)
-0.32 (Pwt%) + 3.20 If the cooling rate is lower than the above rate, bainite transformation occurs before the austenite phase becomes martensite,
The yield ratio of the product increases.
【００３１】[0031]
【実施例】以下に、実施例に基づき本発明について説明
する。表１に示す組成の鋼スラブを、1150℃に加熱した
のち、仕上げ温度 900〜 850℃で熱問圧延した。この熱
延板を酸洗したあと冷間圧延し、この冷延板をめっき用
母板とした。これらの母板をＣＡＬで加熱（焼鈍）し、
ＣＧＬにて、めっき前の加熱（焼鈍）を行い、めっきし
て、溶融亜鉛めっき鋼板とした。また、めっき後さらに
合金化処理を行ったものも製造した。これら工程におけ
る、ＣＡＬでの加熱、ＣＧＬでの加熱、めっき、合金化
などの処理条件を、表２および以下に示す。The present invention will be described below with reference to examples. A steel slab having the composition shown in Table 1 was heated to 1150 ° C, and then hot-rolled at a finishing temperature of 900 to 850 ° C. The hot-rolled sheet was pickled and then cold-rolled, and this cold-rolled sheet was used as a mother plate for plating. These mother plates are heated (annealed) with CAL,
Heating (annealing) before plating was performed by CGL, followed by plating to obtain a hot-dip galvanized steel sheet. In addition, a product subjected to an alloying treatment after plating was also manufactured. The processing conditions such as CAL heating, CGL heating, plating, and alloying in these steps are shown in Table 2 and below.
【００３２】[0032]
【表１】 [Table 1]
【００３３】[0033]
【表２】 [Table 2]
【００３４】 ・ＣＡＬ、ＣＧＬでの加熱（焼鈍・めっき前加熱） 雰囲気：５％Ｈ2 ＋Ｎ2 ガス（露点−20℃） ・表面濃化層の除去 塩酸酸洗（濃度：５％Ｈclの水溶液） 温度：60℃ 浸漬時間：６秒 ・めっき めっき浴のAl濃度：0.13wt％ 浴温：475 ℃ 板温：475 ℃ 浸漬時間：３秒 目付け量：45ｇ／ｍ2 なお、表２中、No.13 の鋼は、ＣＧＬにおいてめっき前
加熱後350 ℃まで冷却し、その後475 ℃まで加熱してめ
っきを施した。他の鋼は、ＣＧＬにおいてめっき前加熱
後475 ℃まで冷却し、引き続きめっきを施した。 ・合金化 処理温度： 470〜550 ℃ 合金化後のFe濃度目標：10wt％ (Ｘ線を使ったオンライ
ン制御を行った)Heating by CAL, CGL (heating before annealing / plating) Atmosphere: 5% H 2 + N 2 gas (dew point −20 ° C.) ・ Removal of surface concentrated layer Hydrochloric acid pickling (concentration: 5% Hcl aqueous solution) ) Temperature: 60 ° C Immersion time: 6 seconds ・ Plating Plating bath Al concentration: 0.13wt% Bath temperature: 475 ° C Plate temperature: 475 ° C Immersion time: 3 seconds Weight per unit area: 45g / m 2 In Table 2, No. The .13 steel was plated at CGL, cooled to 350 ° C after pre-plating, then heated to 475 ° C. The other steels were cooled to 475 ° C. after heating before plating in the CGL and subsequently plated.・ Alloying treatment temperature: 470-550 ° C Target of Fe concentration after alloying: 10wt% (On-line control using X-ray was performed)
【００３５】得られた供試鋼板について、引張特性（降
伏強さＹＳ，引張強さＴＳ，伸びＥｌ，降伏伸びＹＥ
ｌ，降伏比ＹＲ）、めっき性（不めっきの程度）および
パウダリング性を調査した。 ・めっき性およびパウダリング性の評価方法 不めっき欠陥の判定は、目視により、不めっき欠陥が全
くないものを「１」、もっとも不めっきの多いものを
「５」とする５段階で評価した。耐パウダリング性は90
°曲げ戻しの後、セロテープに付着した亜鉛粉を蛍光Ｘ
線にて測定した。蛍光Ｘ線は、亜鉛粉の亜鉛の蛍光Ｘ線
を計数管で２分カウントした。セロテープにうっすらと
亜鉛粉が付着した状態が2000cps であり、2500cps 以下
であれば、自動車などのプレス成形に耐えうるものとな
る。これらの測定結果を併せて表２に示す。なお、めっ
き層中Fe含有量は、硫酸によりめつき層を溶解し、原子
吸光にて測定した。The tensile properties (yield strength YS, tensile strength TS, elongation El, yield elongation YE) of the obtained test steel sheet were measured.
1, yield ratio YR), plating properties (degree of non-plating) and powdering properties were investigated. Method of evaluating plating property and powdering property Non-plating defects were visually evaluated on a scale of 1 to 1 when there were no non-plating defects, and 5 when most non-plating defects were present. 90 powdering resistance
° After bending back, the zinc powder adhering to the
It was measured with a line. Regarding the fluorescent X-ray, the fluorescent X-ray of zinc in the zinc powder was counted for 2 minutes by a counter tube. The state where the zinc powder is slightly adhered to the cellophane tape is 2000 cps, and if it is 2500 cps or less, it can withstand the press forming of automobiles and the like. Table 2 also shows these measurement results. In addition, the Fe content in the plating layer was measured by dissolving the plating layer with sulfuric acid and performing atomic absorption.
【００３６】表２から、本発明によって製造した溶融亜
鉛めっき高張力鋼板は、いずれも、合金化処理の有無に
かかわらず、めっき性、耐パウダリング性が良好である
とともに、降伏比が54.0以下の低い値が得られることが
わかる。From Table 2, it can be seen that the hot-dip galvanized high-strength steel sheets produced according to the present invention have good plating properties and powdering resistance and a yield ratio of 54.0 or less regardless of the presence or absence of alloying treatment. It can be seen that a low value of is obtained.
【００３７】[0037]
【発明の効果】以上説明したように、本発明によれば、
表面濃化層の除去、内部酸化層の形成、複合組織の形成
が有効に作用して、優れためっき性と耐パウダリング
性、低降伏比を共に満たした、溶融亜鉛めっき高張力鋼
板を提供することが可能になる。したがって、本発明
は、耐食性と加工性が求められる自動車の車体などの品
質向上や生産性の向上に寄与するところが極めて大き
い。As described above, according to the present invention,
Removal of surface thickened layer, formation of internal oxide layer, formation of composite structure work effectively to provide hot-dip galvanized high-strength steel sheet that satisfies both excellent plating properties, powdering resistance and low yield ratio. It becomes possible to do. Therefore, the present invention greatly contributes to improving the quality and productivity of automobile bodies and the like that require corrosion resistance and workability.
【図１】溶融亜鉛めっき鋼板のメッキ性と降伏比に及ぼ
すＣＡＬ加熱温度の影響を示すグラフである。FIG. 1 is a graph showing the effect of CAL heating temperature on the plating properties and yield ratio of a hot-dip galvanized steel sheet.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 古君 修 千葉県千葉市中央区川崎町１番地 川崎製 鉄株式会社技術研究所内 (72)発明者 磯部 誠 千葉県千葉市中央区川崎町１番地 川崎製 鉄株式会社技術研究所内 Ｆターム(参考） 4K027 AA02 AA23 AB02 AB28 AC02 AC12 AC73 AE12 AE18 4K037 EA02 EA04 EA05 EA15 EA16 EA17 EB06 FJ05 FJ06 GA05 GA08 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Osamu Furukun 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Inside the Technical Research Institute of Kawasaki Steel Co., Ltd. (72) Makoto Isobe 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture 4K027 AA02 AA23 AB02 AB28 AC02 AC12 AC73 AE12 AE18 4K037 EA02 EA04 EA05 EA15 EA16 EA17 EB06 FJ05 FJ06 GA05 GA08
Claims (3)
点以下の温度で少なくとも１回は焼鈍し、冷却後に、酸
洗して表面濃化層を除去し、次いでＡc1変態点〜Ａc3変
態点の温度範囲に加熱し、この加熱温度から少なくとも
めっき浴温度までの温度域を、Ｂ含有量に応じて下記
(1)式または (2)式で表される臨界冷却速度以上の速度
で冷却して、必要に応じて少なくともめっき浴温度まで
加熱し、次いで溶融亜鉛めっきを施し、めっき後300 ℃
までの温度域を、Ｂ含有量に応じて下記 (1)式または
(2)式で表される臨界冷却速度以上の速度で冷却するこ
とを特徴とする、加工性に優れた溶融亜鉛めっき高張力
鋼板の製造方法。 記 Ｂ≦0.0006wt％のとき、 log ＣＲ＝−3.50（Mowt％）−1.20（Mnwt％）−0.16（Siwt％）− 2.0（Crwt ％）−0.08（Niwt％＋Cuwt％）−0.32（Ｐwt％）＋3.50 ……… (1) Ｂ＞0.0006wt％のとき、 log ＣＲ＝−3.50（Mowt％）−1.20（Mnwt％）−0.16（Siwt％）− 2.0（Crwt ％）−0.08（Niwt％＋Cuwt％）−0.32（Ｐwt％）＋3.20 ……… (2) ただし、ＣＲ：臨界冷却速度（℃／sec)1. A plating base plate containing C: 0.005 to 0.15 wt%, Mn: 0.3 to 3.0 wt%, and Mo: 0.05 to 1.0 wt% is heated to a temperature between the Ac 1 transformation point and the Ar 3 transformation point. At least once, after cooling, pickling to remove the surface-concentrated layer, and then heating to a temperature range from the Ac 1 transformation point to the Ac 3 transformation point, from the heating temperature to at least the plating bath temperature. The temperature range is as follows according to the B content
Cool at a rate higher than the critical cooling rate represented by the formula (1) or (2), heat to at least the plating bath temperature as needed, then apply hot-dip galvanizing, and after plating 300 ℃
Temperature range up to the following (1) or
A method for producing a hot-dip galvanized high-strength steel sheet excellent in workability, characterized by cooling at a rate higher than the critical cooling rate represented by the formula (2). When B ≤ 0.0006 wt%, log CR = -3.50 (Mowt%)-1.20 (Mnwt%)-0.16 (Siwt%)-2.0 (Crwt%)-0.08 (Niwt% + Cuwt%)-0.32 (Pwt%) +3.50 ... (1) When B> 0.0006 wt%, log CR = -3.50 (Mowt%)-1.20 (Mnwt%)-0.16 (Siwt%)-2.0 (Crwt%)-0.08 (Niwt% + Cuwt %)-0.32 (Pwt%) + 3.20 (2) where CR is the critical cooling rate (° C / sec)
点以下の温度で少なくとも１回は焼鈍し、冷却後に、酸
洗して表面濃化層を除去し、次いで、Ａc1変態点〜Ａc3
変態点の温度範囲に加熱し、この加熱温度から少なくと
もめっき浴温度までの温度域を、Ｂ含有量に応じて下記
(1)式または (2)式で表される臨界冷却速度以上の速度
で冷却して、必要に応じて少なくともめっき浴温度まで
加熱し、次いで溶融亜鉛めっきを施し、引き続いて、合
金化処理を行い、合金化処理後300℃までの温度域を、
Ｂ含有量に応じて下記 (1)式または (2)式で表される臨
界冷却速度以上の速度で冷却することを特徴とする、加
工性に優れた溶融亜鉛めっき高張力鋼板の製造方法。 記 Ｂ≦0.0006wt％のとき、 log ＣＲ＝−3.50（Mowt％）−1.20（Mnwt％）−0.16（Siwt％）− 2.0（Crwt ％）−0.08（Niwt％＋Cuwt％）−0.32（Ｐwt％）＋3.50 ……… (1) Ｂ＞0.0006wt％のとき、 log ＣＲ＝−3.50（Mowt％）−1.20（Mnwt％）−0.16（Siwt％）− 2.0（Crwt ％）−0.08（Niwt％＋Cuwt％）−0.32（Ｐwt％）＋3.20 ……… (2) ただし、ＣＲ：臨界冷却速度（℃／sec)2. A plating base plate containing C: 0.005 to 0.15 wt%, Mn: 0.3 to 3.0 wt%, and Mo: 0.05 to 1.0 wt% is heated to a temperature between the Ac 1 transformation point and the Ar 3 transformation point. At least once, and after cooling, pickling to remove the surface thickened layer. Then, from the Ac 1 transformation point to Ac 3
Heating to the temperature range of the transformation point, the temperature range from this heating temperature to at least the plating bath temperature, depending on the B content,
Cool at a rate higher than the critical cooling rate represented by the formula (1) or (2), heat to at least the plating bath temperature if necessary, apply hot-dip galvanizing, and subsequently perform alloying treatment. The temperature range up to 300 ° C after alloying
A method for producing a hot-dip galvanized high-strength steel sheet excellent in workability, characterized by cooling at a rate higher than the critical cooling rate represented by the following formula (1) or (2) according to the B content. When B ≤ 0.0006 wt%, log CR = -3.50 (Mowt%)-1.20 (Mnwt%)-0.16 (Siwt%)-2.0 (Crwt%)-0.08 (Niwt% + Cuwt%)-0.32 (Pwt%) +3.50 ... (1) When B> 0.0006 wt%, log CR = -3.50 (Mowt%)-1.20 (Mnwt%)-0.16 (Siwt%)-2.0 (Crwt%)-0.08 (Niwt% + Cuwt %)-0.32 (Pwt%) + 3.20 (2) where CR is the critical cooling rate (° C / sec)
用母板の成分組成が、 Ｃ：0.005 〜0.15wt％、 Mn：0.3 〜3.0 wt％、 Mo：0.05〜1.0 wt％、 を含み、かつ Si：0.05〜0.5 wt％、 Cr：0.05〜1.0 wt％、 Ｐ：0.02〜0.1 wt％、 Ｂ：0.0003〜0.01wt％、 Ni：0.05〜1.5 wt％、 Cu：0.05〜1.5 wt％、 Nb：0.3 wt％以下、 Ti：0.3 wt％以下、および Ｖ：0.3 wt％以下 から選ばれるいずれか１種または２種以上を含有し、残
部はFeおよび不可避的からなることを特徴とする、加工
性に優れた溶融亜鉛めっき高張力鋼板の製造方法。3. The plating composition according to claim 1, wherein the component composition of the plating base plate comprises: C: 0.005 to 0.15% by weight, Mn: 0.3 to 3.0% by weight, Mo: 0.05 to 1.0% by weight, And Si: 0.05-0.5 wt%, Cr: 0.05-1.0 wt%, P: 0.02-0.1 wt%, B: 0.0003-0.01 wt%, Ni: 0.05-1.5 wt%, Cu: 0.05-1.5 wt%, Nb : 0.3 wt% or less, Ti: 0.3 wt% or less, and V: 0.3 wt% or less, and the remainder is composed of Fe and unavoidable. Of hot-dip galvanized high-strength steel sheet with excellent heat resistance.
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| JP28153098A JP3646539B2 (en) | 1998-10-02 | 1998-10-02 | Manufacturing method of hot-dip galvanized high-tensile steel sheet with excellent workability |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2002022893A1 (en) * | 2000-09-12 | 2002-03-21 | Kawasaki Steel Corporation | High tensile strength hot dip plated steel sheet and method for production thereof |
| WO2002044434A1 (en) * | 2000-11-28 | 2002-06-06 | Kawasaki Steel Corporation | Composite structure type high tensile strength steel plate, plated plate of composite structure type high tensile strength steel and method for their production |
| EP1666622A1 (en) * | 2003-09-26 | 2006-06-07 | JFE Steel Corporation | High strength steel sheet excellent in deep drawing characteristics and method for production thereof |
-
1998
- 1998-10-02 JP JP28153098A patent/JP3646539B2/en not_active Expired - Fee Related
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6797410B2 (en) | 2000-09-11 | 2004-09-28 | Jfe Steel Corporation | High tensile strength hot dip plated steel and method for production thereof |
| WO2002022893A1 (en) * | 2000-09-12 | 2002-03-21 | Kawasaki Steel Corporation | High tensile strength hot dip plated steel sheet and method for production thereof |
| KR100786052B1 (en) * | 2000-09-12 | 2007-12-17 | 제이에프이 스틸 가부시키가이샤 | High tensile strength hot dip plated steel sheet and method for production thereof |
| WO2002044434A1 (en) * | 2000-11-28 | 2002-06-06 | Kawasaki Steel Corporation | Composite structure type high tensile strength steel plate, plated plate of composite structure type high tensile strength steel and method for their production |
| EP1338667A1 (en) * | 2000-11-28 | 2003-08-27 | Kawasaki Steel Corporation | Composite structure type high tensile strength steel plate, plated plate of composite structure type high tensile strength steel and method for their production |
| EP1338667A4 (en) * | 2000-11-28 | 2005-08-17 | Jfe Steel Corp | Composite structure type high tensile strength steel plate, plated plate of composite structure type high tensile strength steel and method for their production |
| EP1666622A1 (en) * | 2003-09-26 | 2006-06-07 | JFE Steel Corporation | High strength steel sheet excellent in deep drawing characteristics and method for production thereof |
| EP1666622A4 (en) * | 2003-09-26 | 2006-11-29 | Jfe Steel Corp | High strength steel sheet excellent in deep drawing characteristics and method for production thereof |
| US7686896B2 (en) | 2003-09-26 | 2010-03-30 | Jfe Steel Corporation | High-strength steel sheet excellent in deep drawing characteristics and method for production thereof |
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