JP2004115843A - High tensile hot dip galvannealed steel sheet and its manufacturing method - Google Patents
High tensile hot dip galvannealed steel sheet and its manufacturing method Download PDFInfo
- Publication number
- JP2004115843A JP2004115843A JP2002278521A JP2002278521A JP2004115843A JP 2004115843 A JP2004115843 A JP 2004115843A JP 2002278521 A JP2002278521 A JP 2002278521A JP 2002278521 A JP2002278521 A JP 2002278521A JP 2004115843 A JP2004115843 A JP 2004115843A
- Authority
- JP
- Japan
- Prior art keywords
- less
- steel sheet
- martensite
- mass
- impurities
- 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
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Landscapes
- Coating With Molten Metal (AREA)
- Heat Treatment Of Sheet Steel (AREA)
Abstract
Description
【0001】
【発明の属する技術分野】
本発明は、自動車、建築、電気機器等に用いられる部材として有用な高張力合金化溶融亜鉛めっき鋼板、およびその製造方法に関する。
【0002】
【従来の技術】
近年、自動車においては、環境への影響の観点から燃費の向上が望まれており、そのために車体の軽量化が進んでいる。また、車体を軽量化しても安全性を維持できるように、車体を構成する様々な部材において、従来用いられてきた鋼板より強度が高い鋼板(高張力鋼板)への需要が高まっている。しかしながら、強度が高くなると延性の低下および形状凍結性の低下が起こりやすいため、強度が高くかつ、形状凍結性および延性の良好な鋼板が必要とされている。
【0003】
強度と延性のバランスを向上させるために、鋼へのSiの添加が非常に有効であることが知られている。さらに、フェライト生成元素のSiまたはAlとオーステナイト生成元素のMnを多量に含有し、残留オーステナイトの歪み誘起変態による大きな伸び(TRIP効果)を利用した高延性の高張力鋼板(以下、「残留オーステナイト型高張力鋼板」または単に「残留オーステナイト型鋼板」という)等の開発がなされている。しかしながら、この残留オーステナイト型高張力鋼板は降伏比(YR)が高く、成形後の弾性回復による形状変化が大きいため、形状凍結性の観点からは十分の性能を有しているとはいえない。
【0004】
この残留オーステナイト型高張力鋼板を製造するためには、焼鈍処理後、350〜600℃の温度域での保持時間(以下、この温度域での保持を「低温保持」、そのときの保持時間を「低温保持時間」という)を長くしてベイナイト変態を促進させ、オーステナイトにCを濃縮させて安定化し、室温までオーステナイトを残留させることが重要である。このとき、SiまたはAlの含有量が少ないと、べイナイト変態中にセメンタイトが析出してしまい、オーステナイト中にCが濃縮されず、安定にならない。また、低温保持時間が短い場合にもべイナイト変態が十分でなく、やはりオーステナイトが安定にならない。オーステナイトが安定化しない場合、冷却中にオーステナイトの一部がマルテンサイト変態を起こしてしまい、TRIP効果が得られにくくなり、延性が低下する。
【0005】
また、強度が同じでも、YRが低いフェライトとマルテンサイトの複合組織を持つDual phase鋼(以下、「DP鋼」という)の鋼板の開発も進んでいる。この鋼板は、残留オーステナイト型鋼板と比較して、形状凍結性においては優れているが、延性については残留オーステナイト型鋼板より低くなっている。なお、この鋼板においても、一般的に、延性確保のためにSiが添加されることが多い。
【0006】
一方、耐食性および外観の向上という観点から、自動車用部材としてめっき材の適用が進んでおり、現在では、多くの部材に溶融亜鉛めっき鋼板が用いられている。しかし、既設の溶融亜鉛めっき設備では、低温保持ライン長が短いものが多く、母材鋼板がSi含有量の多い残留オーステナイト型鋼板の場合には、還元焼鈍処理後、溶融亜鉛めっきを施す前の低温保持時間を長くしなければならないため、既存の設備では、ライン速度が低下し、生産性が著しく低下する。さらに、低温保持時間を長くすると、還元性雰囲気下であっても、鋼板表面にSiの酸化物が濃化するため、めっき濡れ性およびめっき密着性が低下する。以上のことから、Siを添加した鋼を母材鋼板として用いる場合は、生産性の低下およびめっき密着性の劣化が懸念される。
【0007】
前記Siを多量に含有した残留オーステナイト型鋼板およびその製造方法は、例えば、特許文献1〜特許文献5で開示されている。しかし、そのような鋼板を得るためには、前述したように、低温保持時間を長くとることが必要で、生産性が著しく低下するだけでなく、形状凍結性、めっき濡れ性およびめっき密着性にも問題がある。
【0008】
特許文献6では、SiおよびAlの含有量の少ないめっき密着性に優れた溶融亜鉛めっき鋼板とその製造方法が開示されており、その鋼板組織はベイナイトとフェライト、またはベイナイトとフェライトとマルテンサイトである。また、特許文献7では、Si含有量は少ないが、Al:0.07〜0.7%を含有する鋼板およびその製造方法が開示されており、その鋼板組織はフェライトと、残留オーステナイトを含むマルテンサイトである。そのような鋼板は、形状凍結性とめっき密着性には優れているものの、延性が十分ではない。
【0009】
特許文献8には、Si含有量が少なく、Al含有量が多い残留オーステナイト型の鋼板が開示されているが、先に述べたように、残留オーステナイト型鋼板は形状凍結性が悪いだけでなく、成分および製造条件(特に、低温保持時間と最終冷却条件)により特性が大きく変わるため好ましくない。
【0010】
前記の残留オーステナイト型鋼とDP鋼の問題点を整理すると、以下のようになる。
〔残留オーステナイト型鋼〕
(イ)降伏比(YR)が高いため、形状凍結性が悪い。
【0011】
(ロ)製造するに際し、オーステナイトを安定化させ、室温までオーステナイトを残留させるために低温保持時間を長時間とする必要があるので、めっき密着性と生産性が悪い。一方、残留オーステナイトのTRIP効果により延性が良好となる。これに対し、低温保持時間を短時間とすると、マルテンサイトが一部混在するようになり、TRIP効果が発現しにくくなって延性が低下する。
〔DP鋼〕
(イ)降伏比が低く、形状凍結性は優れるが、残留オーステナイト型鋼に比べて延性が劣る。
【0012】
以上述べたように、Si添加量が少なく、製造条件で低温保持時間が短くても、優れた形状凍結性とめっき密着性を有し、かつ、延性の優れた高張力溶融亜鉛めっき鋼板は実用化されていないのが現状であり、高張力鋼板の適用を推進する上で、これらの課題の解決が求められている。
【0013】
【特許文献1】
特開平05−70886号公報
【特許文献2】
特開平06−145788号公報
【特許文献3】
特開平11−131145号公報
【特許文献4】
特開2001−140022号公報
【特許文献5】
特開2001−303229号公報
【特許文献6】
特開平05−125485号公報
【特許文献7】
特開2000−345288号公報
【特許文献8】
特開平05−247586号公報
【0014】
【発明が解決しようとする課題】
本発明はこのような状況に鑑みなされたもので、その目的は、形状凍結性、めっき密着性および延性に優れた、引張強さが450MPa以上の高張力合金化溶融亜鉛めっき鋼板、およびその製造方法を提供することにある。
【0015】
【課題を解決するための手段】
本発明者らは、上記問題点を解決するため、成分および焼鈍条件が鋼板の材質に及ぼす影響を詳細に調査した結果、以下の知見を得た。
【0016】
(a)母材鋼板は、焼鈍処理後の低温保持時間が短くマルテンサイトが生成する場合には、残留オーステナイトが存在していても、TRIP効果を示しにくい。しかし、低温短時間保持中にベイナイト変態させ、さらに、SiとAlによるオーステナイトへのCの濃縮度とMn含有量とをバランスさせることにより、オーステナイトの安定度を調整し、オーステナイトの残留を抑制してCを多く含むマルテンサイト(以下、「高Cマルテンサイト」という)の生成を促進させることにより、フェライト+マルテンサイト組織鋼(DP鋼)よりも良好な延性を確保することができる。しかも、降伏比(YR)を低く抑えることができるので、形状凍結性も良好である。理想的な金属組織はフェライト+ベイナイト+高Cマルテンサイトである。この時、残留オーステナイトは少ない方がよい。
【0017】
(b)高Cマルテンサイトの生成には、低温保持温度と低温保持時間、および、合金化処理後の冷却速度が重要である。
【0018】
(c)AlはSiと同様に酸化されやすい元素であるが、SiよりもAlの方がAc3変態点を上昇させるので、同じ焼鈍温度と焼鈍時間でもオーステナイトヘのC濃縮が進みやすい。そのため、焼鈍処理後の低温保持時間を短くすることができ、酸化物の生成を抑制することが可能となるので、めっき密着性の低下を回避することができる。Siを添加した場合は、低温保持を長時間行わねばならず、酸化物生成によるめっき密着性の劣化が起こる。
【0019】
(d)形状凍結性および延性に優れるという母材特性と、めっき密着性とを同時に満たすためには、Alを積極的に添加するのがよい。
【0020】
(e)前処理としてNiを鋼板表面に付着させると、めっき密着性は向上する。
【0021】
本発明は、上記知見に基づいて完成されたもので、その要旨は、下記(1)の高張力合金化溶融亜鉛めっき鋼板、および(2)のその鋼板の製造方法にある。
【0022】
(1)質量%で、C:0.10〜0.30%、Si:0.2%以下、Mn:1.0〜3.0%、Al:0.5〜2.0%を含有し、かつ、Si、AlおよびMnが下記▲1▼式を満足し、残部はFeおよび不純物からなり、不純物中のPが0.1%以下、Sが0.1%以下、Nが0.020%以下であり、さらに体積%でマルテンサイトを3〜50%含有する鋼板(母材鋼板)の上に、質量%でFe:7〜15%を含有する亜鉛合金めっき層を備える高張力合金化溶融亜鉛めっき鋼板。なお、▲1▼式におけるSi(%)、Al(%)およびMn(%)は、それぞれ前記母材鋼板のSi、AlおよびMnの含有量(質量%)を表す。
【0023】
2≦Si(%)+Al(%)+Mn(%)≦4 ・・・▲1▼
前記(1)に記載の鋼板は、さらに、質量%で、Ni:2.0%未満、Co:2.0%未満およびCu:1.0%未満(これらを「第1群の成分」という)のうちの何れか1種以上、Ti:0.1%未満、Nb:0.1%未満およびV:0.2%未満(これらを「第2群の成分」という)のうちの何れか1種以上、および、Mo:1.0%未満、Cr:1.0%未満およびB:0.01%未満(これらを「第3群の成分」という)のうちの何れか1種以上、の三つのグループの何れか一以上のグループに属する元素を含むものであってもよい。
【0024】
(2)前記(1)に記載の化学組成を有する鋼板に、下記(A)〜(F)の処理を順次施す高張力合金化溶融亜鉛めっき鋼板の製造方法。
【0025】
(A)700〜900℃の二相共存温度域で30〜600秒焼鈍する処理
(B)3〜200℃/秒の冷却速度で350〜550℃の温度域まで冷却する処理
(C)前記温度域で10〜90秒間保持する処理
(D)溶融亜鉛めっき浴に浸漬する処理
(E)470〜600℃の温度域に5〜180秒間保持する処理
(F)4℃/秒以上の冷却速度で250℃以下まで冷却する処理
前記(A)の処理の前に、鋼板表面にNiを付着させる処理を施せば、めっき密着性が向上する。
【0026】
【発明の実施の形態】
以下、本発明の高張力合金化溶融亜鉛めっき鋼板(上記(1)の発明)およびその製造方法(上記(2)の発明)について詳細に説明する。なお、母材鋼板の化学成分含有量の「%」、めっき皮膜中のFe含有量の「%」およびめっき浴中のAl濃度の「%」は、いずれも「質量%」を意味する。
【0027】
本発明の高張力合金化溶融亜鉛めっき鋼板において、母材鋼板の化学組成を上記のように規定するのは以下の理由による。
【0028】
C:0.10〜0.30%
本発明の高張力合金化溶融亜鉛めっき鋼板の母材鋼板においては、Cを多く含むマルテンサイトを生成させることによって延性を高め、強度と延性のバランスをDP鋼よりも向上させる。そのため、Cは必須の元素である。Cの含有量は目標とする鋼板強度に応じて適宜定めればよいが、本発明が狙いとする450MPa以上の引張強さを達成し、かつ、DP鋼より延性を向上させるためには、0.10%以上含有させることが必要である。C含有量の上限は、良好なスポット溶接性を確保するために、0.30%とする。
【0029】
Si:0.2%以下
Siはセメンタイトに固溶せず、セメンタイトの析出を抑制する。上述したように、低温保持中にセメンタイトが生成しにくいベイナイト変態を促進させ、オーステナイト中にCを濃縮させてオーステナイトの安定度を調整するために重要な元素である。しかし、Si含有量が増加すると低温保持を長時間行わねばならず、めっき密着性が低下するので、その含有量は0.2%以下とする。Si含有量の下限は、Si単独では規定せず、後述するように、AlおよびMnを含めた合計の含有量で規定する。
【0030】
Mn:1.0〜3.0%
Mnは鋼板の強度を高めるだけでなく、オーステナイト生成元素で、オーステナイトの安定度に直接作用する重要な元素である。また、高温からの冷却中におけるパーライトの生成を抑制する効果も有している。これらの効果を得るためには、少なくとも1.0%含有させることが必要であり、その範囲内で、狙いとする母材鋼板の引張強さに応じてMn含有量を適宜調整すればよい。Mn含有量の上限は、コストおよび転炉での溶製の観点から3.0%とする。
【0031】
Al:0.5〜2.0%
Alは脱酸材としても用いられると同時に、Siと同じように、低温保持中にセメンタイトが生成しにくいベイナイト変態を促進させ、オーステナイト中にCを濃縮させてオーステナイトの安定度を調整するために重要な元素である。低温保持時間を短くできるため、Siを含有させる場合に比べてめつき密着性を高めることができることから、本発明ではAlを積極的に利用する。
【0032】
最終的に高Cのマルテンサイトを得るためには、0.5%以上含有させる必要がある。ただし、過剰の添加はめっきの密着性および溶接性を悪化させるので、上限は、2.0%とする。
【0033】
2≦Si(%)+Al(%)+Mn(%)≦4(上記▲1▼式)
SiとAlによるオーステナイトへのCの濃縮度とMn含有量とをバランスさせることにより、オーステナイトの安定度を調整し、オーステナイトの残留を抑制して高Cのマルテンサイトの生成を促進することができる。
【0034】
Si(%)+Al(%)+Mn(%)の値が2を下回る場合、オーステナイトの安定度が低くなり、焼鈍処理時の高温からの冷却中および低温保持中にオーステナイトからパーライトが生成するか、またはオーステナイトがフェライトとセメンタイトに分解し、所望の組織が得られない。一方、4を上回る場合、オーステナイトの安定度が高くなりすぎて、オーステナイトが残留し、マルテンサイト量が減少して所望量(体積%で、3〜50%)が得られなくなるため、延性が低下するだけでなく、YR(降伏比)が高くなって形状凍結性が劣化する。したがって、Si、AlおよびMnの含有量は、2≦Si(%)+Al(%)+Mn(%)≦4の関係を満たすように調整することが必要である。望ましくは、2.5≦Si(%)+Al(%)+Mn(%)≦3.5である。
【0035】
本発明の高張力合金化溶融亜鉛めっき鋼板の母材鋼板は、上述した成分以外、残部がFeと不純物からなるものである。不純物としては、P、SおよびNの上限を抑えることが必要である。
【0036】
P:0.1%以下
Pは不純物として鋼中に不可避的に含まれる元素であって、できるだけ低い方が望ましい。特に、0.1%を超えて含まれると鋼板の延性劣化が顕著になることから、P含有量は0.1%以下とする。
【0037】
S:0.1%以下
Sも不純物として綱中に不可避的に含有される元素であって、やはり低い方が望ましい。特に、0.1%を超えて含まれると、MnSの析出が顕著になり、鋼板の延性が阻害されるのみならず、オーステナイトの安定化元素として添加されるMnがMnSとして消費されるので、S含有量は0.1%以下とする。
【0038】
N:0.020%以下
Nも不純物として綱中に不可避的に含有される元素であり、その含有量は低い方が望ましい。N含有量が0.020%を超えるとAlNとして消費されるAlの量が多く、Alの効果が減殺されるばかりでなく、AlNによる延性の劣化が顕著になるので、N含有量の上限は0.020%とする。
【0039】
上記(1)の高張力合金化溶融亜鉛めっき鋼板の母材鋼板は、さらに、前記第1群の成分(Ni:2.0%未満、Co:2.0%未満およびCu:1.0%未満)のうちの何れか1種以上、前記第2群の成分(Ti:0.1%未満、Nb:0.1%未満およびV:0.2%未満)のうちの何れか1種以上、および、前記第3群の成分(Mo:1.0%未満、Cr:1.0%未満およびB:0.01%未満)のうちの何れか1種以上、の三つのグループの何れか一以上のグループに属する元素を含むものであってもよい。これらの成分の作用効果と含有量の適正範囲は下記のとおりである。
【0040】
Ni:2.0%未満
Co:2.0%未満
Cu:1.0%未満
Ni、CoおよびCuは、Mnと同じように、オーステナイト生成元素であると同時に、鋼板の強度を向上させる元素である。また、いずれもFeよりも酸化されにくいので、鋼板表面に濃化し、SiやAlの酸化によるめっき密着性の低下を防止する効果を有するので、必要に応じて添加してもよい。添加する場合、過剰の添加はコストの上昇を招くので、Ni、Coについては、含有量は、それぞれ2.0%未満とする。Cuについては、熱間割れの防止の観点から、1.0%未満とする。含有量の下限は特に定めないが、添加による顕著な効果を得るためには、Ni、CoおよびCuの何れについても0.1%以上含有させるのが望ましい。
【0041】
Ti:0.1%未満
Nb:0.1%未満
V:0.2%未満
Ti、NbおよびVは、鋼板の強度を向上させるだけでなく、亜鉛めっきの合金化処理を行う場合には、合金化速度を向上させる有効な元素であり、必要に応じて添加してもよい。添加する場合、過剰の添加は延性の劣化をもたらすだけでなく、降伏比(YR)も上昇させ、形状凍結性を劣化させるので、Ti、Nbについては、その含有量は、それぞれ0.1%未満とする。Vについては、Ti、Nbと比較して添加の効果が小さいので、その含有量は0.2%未満とする。含有量の下限は特に定めないが、添加による顕著な効果を得るためには、Ti、Nbについては、それぞれ0.005%以上、Vについては0.01%以上含有させるのが望ましい。
【0042】
Mo:1.0%未満
Cr:1.0%未満
B:0.01%未満
Mo、CrおよびBは、焼鈍処理時の高温からの冷却中におけるパーライトの生成を抑制し、マルテンサイトの生成を促進する有効な元素であり、必要に応じて添加してもよい。添加する場合、MoおよびCrについては1.0%以上、Bについては0.01%以上添加してもその効果が飽和するだけでなく、コスト高になるので、その含有量は、MoおよびCrについてはそれぞれ1.0%未満、Bについては0.01%未満とする。含有量の下限は特に定めないが、添加による顕著な効果を得るためには、Mo、Crについては、それぞれ0.1%以上、Bについては0.0005%以上含有させるのが望ましい。
【0043】
本発明の高張力合金化溶融亜鉛めっき鋼板の母材鋼板は、さらに、体積%でマルテンサイトを3〜50%含有するものとする。形状凍結性と延性の双方を同時に満足するためには、高Cマルテンサイトが母材中に存在することが重要であり、そのためには、体積%でマルテンサイトが3%以上含まれることが必要である。しかし、含有量が50%を超えると、強度が高くなりすぎ、延性が劣化するばかりか、高Cマルテンサイトが少なくなる。マルテンサイトの望ましい含有量は、5〜35%である。なお、ここでいうマルテンサイトの含有量(存在量)は、4%ピクリン酸エチルアルコール溶液と、1%ピロ亜硫酸ナトリウム水溶液とによるレペラ法により着色エッチングを行い、光学顕微鏡観察によって体積率を測定することにより求めた値である。
【0044】
本発明の高張力合金化溶融亜鉛めっき鋼板は、上記の鋼板の上に7〜15%のFeを含有する亜鉛合金めっき層を備える鋼板である。めっき層中のFeの含有量を前記の範囲に規定するのは、Fe含有量が15%を超えるとめっき密着性や加工性の確保が困難になり、また、7%に満たない場合は良好なスポット溶接性が確保できなくなるからである。
【0045】
次に、本発明の高張力合金化溶融亜鉛めっき鋼板の製造方法(上記(2)の発明)について説明する。
【0046】
まず、母材鋼板としては、上記の化学組成を有する冷間圧延鋼板(冷延鋼板)を用いる。この鋼板を得るための熱間圧延、冷間圧延は公知の方法で行えばよいが、母材の粒径が大きくなりすぎたり、小さくなりすぎると母材鋼板としての所望の特性が得られないので、熱間圧延工程における巻取り温度は700℃以下、冷延率は40〜80%の範囲内にするのが望ましい。
【0047】
この母材鋼板に、その表面を溶融めっきに適する状態にするために、アルカリ水溶液での洗浄や、ナイロンブラシ等での表面研削等、公知の方法で前処理を施す。
【0048】
この前処理時において、鋼板表面にNiを付着させる処理を施せば、めっき密着性が著しく向上する。この場合、鋼板表面へのNiの付着量は、経済性の観点から、1g/m2以下とするのが望ましい。
【0049】
続いて、母材鋼板を700〜900℃の二相(フェライト相+オーステナイト相)共存温度域に加熱して、30〜600秒間焼鈍する(上記(A)の処理)。この焼鈍処理は、通常、還元性雰囲気中で行う。
【0050】
還元性雰囲気としては、水素を5〜30体積%含有し、残部が窒素からなり、露点が−60〜0℃の範囲にあるガス雰囲気が好適である。なお、材料特性を向上させるために、冷間圧延後に、連続焼鈍ラインまたはバッチ式焼鈍により予備焼鈍を施してもよい。
【0051】
前記の焼鈍処理において、焼鈍温度が700℃未満であったり、焼鈍時間が30秒未満であったりすると、再結晶が起こりにくく、かつセメンタイトが固溶しないため、鋼板の特性が劣化する。一方、焼鈍温度が900℃を超えると、結晶粒が粗大化するだけでなく、焼鈍中のオーステナイトの体積率が増大し、最終的に生成するマルテンサイト中のC含有量が低くなるだけでなく、炉温の上昇による製造コストの増大が避けられない。また、焼鈍時間が600秒を超える場合には、結晶粒が粗大化するほか、ライン速度が低下し、生産性が低下するので、好ましくない。
【0052】
焼鈍処理後の母材鋼板を、めっき浴温近傍の350〜550℃の温度域(すなわち、低温保持温度域)まで3〜200℃/秒の冷却速度で冷却し(上記(B)の処理)、その温度域で10〜90秒間保持(低温保持)する(上記(C)の処理)。
【0053】
焼鈍処理後の冷却速度が3℃/秒より低い場合には、冷却中にオーステナイトからパーライトまたはセメンタイトが生成し、所望の金属組織が得られない。冷却速度が200℃/秒より速い場合には、冷却速度の制御が困難になり、均一な組織が得られない。
【0054】
低温保持温度が350℃未満では、焼鈍後の冷却中に低Cのマルテンサイトが生成し、低温保持温度が550℃より高い場合には、ベイナイト変態が起こらず、オーステナイトがパーライトに変態するため、所望の材料特性が得られない。
【0055】
低温保持時間が10秒未満の場合には、ベイナイト変態が起こらず、オーステナイトへのCの濃縮が進まないため、低Cのマルテンサイトとなり、延性が低下する。低温保持時間が90秒を超える場合には、先に述べたように、生産性が低下するだけでなく、酸化物の生成によるめっき密着性の劣化を招くほか、本発明の理想組織である高Cマルテンサイトの生成が抑制されて、延性の低下と形状凍結性不良を招く。
【0056】
前記所定の低温保持を行った後の母材鋼板を溶融亜鉛めっき浴に浸漬する処理を行って、鋼板表面に亜鉛めっき層を形成させる(上記(D)の処理)。
【0057】
めっき浴温度は、めっき付着量の調整を容易にするために430℃以上とし、Znの蒸発を避けてめっき浴の維持を容易にするために550℃以下とする。めっき浴から引き上げた後のめっき付着量の調整は、気体絞り法等、通常用いられている方法により行えばよい。
【0058】
その後、470〜600℃の温度域に5〜180秒間保持する合金化処理を行った後(上記(E)の処理)、250℃以下の温度に4℃/秒以上の冷却速度で冷却する(上記(F)の処理)。
【0059】
合金化処理温度が470℃未満では、合金化が起こらず、600℃を超えると、オーステナイトがセメンタイトとフェライトに分解して特性が劣化する。
【0060】
合金化処理時間が5秒未満では、合金化が起こらず、めっき密着性が劣化する。一方、合金化処理時間が180秒を超えると、オーステナイトがセメンタイトとフェライトに分解して特性が劣化するだけでなく、前記の低温保持時間が規定範囲を超えた場合と同様、ライン速度が低下し、生産性が低下する。
【0061】
合金化処理後の冷却速度が4℃/秒未満では、冷却中にマルテンサイトが生成しにくく、ベイナイトまたはフェライトとセメンタイトが生成する。そのため、合金化処理後の冷却速度は4℃/秒以上とする。この冷却は、窒素および工業用ガス(空気)を用いて行う。さらに通常のミスト冷却を行ってもよい。
【0062】
上記本発明の高張力合金化溶融亜鉛めっき鋼板は、高い強度を有し、形状凍結性および延性が良好で、めっき密着性にも優れているので、家電製品、建材、自動車車体用などの素材として好適である。特に、建築分野で鋼板を塗装して使用する場合等において、本発明の高張力合金化溶融亜鉛めっき鋼板は優れた性能および経済性を発揮することができる。
【0063】
【実施例】
表1に示す鋼種を真空溶解炉で溶製し、鍛造を施した鋳塊(厚さ:20mm)を仕上げ温度850℃で板厚4.0mmまで熱間圧延した。その後、650℃で30分間保持し、20℃/hの冷却速度で室温まで炉冷した。この熱延鋼板を酸洗し、冷間圧延を施して板厚1.2mmの溶融亜鉛めっき用冷延鋼板を得た。
【0064】
【表1】
【0065】
この冷延鋼板を母材鋼板として、これに縦型溶融めっきシミュレータを用いて、めっき付着量が60mg/m2になるように溶融亜鉛めっきを施し、その後、ソルトバスを用いて合金化処理を施し、種々の合金化溶融亜鉛めっき鋼板を作製した。
【0066】
溶融亜鉛めっきの各工程における条件を表2に示す。表2において、「還元焼鈍処理」の欄の冷却速度(すなわち、還元焼鈍処理後の冷却速度)を「冷却速度CR1」と、「合金化処理」の欄の冷却速度を「冷却速度CR2」と記す。
【0067】
【表2】
【0068】
これらの合金化溶融亜鉛めっき鋼板について、マルテンサイトの体積率を求め、引張試験を行って、引張強さ(TS)、伸び(El)を測定し、また、形状凍結性およびめっき密着性を調査した。
【0069】
マルテンサイトの体積率は、先に述べた方法により求めた。
【0070】
形状凍結性の調査では、下記の試験条件でハット型成形試験を行い、パンチ肩部のスプリングバック量(角度)を測定した。
〔試験条件〕
サンプルサイズ:幅50mm×長さ250mm
パンチ肩部半径:10mm
ダイス肩部半径:10mm
パンチ幅 :50mm
成形高さ :60mm
成形速度 :60mm/min
めっき密着性の調査は、前記の形状凍結性の調査後のサンプルのダイス肩部外側でテープ剥離試験を行い、剥離したテープをルーペにより観察し、下記の判断基準で評価した。
◎印:めっき剥離が認められず、極めて良好
○印:若干のめっき剥離が認められるが、めっき密着性に問題なく、良好×印:多量の剥離が認められ、不良
調査結果を表3に示す。なお、表2に示した溶融亜鉛めっき条件のうちの変化させた条件(還元焼鈍温度および冷却速度CR1、低温保持温度および時間、合金化処理後の冷却速度CR2)も、表3に併せて示した。
【0071】
【表3】
【0072】
表3に示したように、本発明の合金化溶融亜鉛めっき鋼板は、強度が高く、延性も良好で、強度・延性バランスの指標としての「TS(引張強さ)×El(伸び)」が高い値を示している。形状凍結性も良好で、めっき密着性にも優れている。また、めっき前処理で鋼板表面にNiを付着させた本発明例のNo.4および14では、めっき密着性の向上が認められた。
【0073】
これに対し、母材鋼板のSi含有量を本発明の規定(0.2%以下)を超えて0.63%、1.00%とした比較例のNo.22、23では、引張特性は優れているが、Siの酸化物が鋼板表面に濃化しているため、めっき密着性が不良であった。
【0074】
焼鈍温度を本発明の規定(700〜900℃)より低い650℃とした比較例のNo.9では、再結晶および変態が起こらず、引張特性が劣化しただけでなく、形状凍結性も悪かった。
【0075】
焼鈍処理後の冷却速度CR1を本発明の規定(3〜200℃/s)より低い1℃/sとした比較例のNo.6、および低温保持温度を本発明の規定(350〜550℃)より高い650℃とした比較例のNo.2では、冷却中または低温保持中にパーライト変態が起こり、引張特性が劣化した。
【0076】
低温保持時間を本発明の規定(10〜90秒)より短い1秒とした比較例のNo.12では、低温保持中のベイナイト変態がほとんど起こらず、オーステナイトのほとんどがマルテンサイト変態を起こし、引張特性が劣化した。
【0077】
合金化処理後の冷却速度CR2を本発明の規定(4℃/s以上)より低い1℃/sとした比較例のNo.15では、冷却中にオーステナイトがフェライトとセメンタイトに分解し、マルテンサイトが生成せず、引張特性が劣化した。
【0078】
【発明の効果】
本発明の高張力合金化溶融亜鉛めっき鋼板は、形状凍結性、めっき密着性および延性に優れ、高い強度を有する鋼板で、自動車、建築、電気機器等に用いられる部材として好適である。この鋼板は、本発明の方法により容易に製造することができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a high-tensile alloyed hot-dip galvanized steel sheet useful as a member used for automobiles, buildings, electric devices, and the like, and a method for producing the same.
[0002]
[Prior art]
2. Description of the Related Art In recent years, automobiles have been demanded to improve fuel efficiency from the viewpoint of environmental impact, and accordingly, the weight of vehicle bodies has been reduced. Further, in order to maintain safety even when the vehicle body is reduced in weight, there is an increasing demand for steel sheets (high-tensile steel sheets) having higher strength than conventionally used steel sheets in various members constituting the vehicle body. However, when the strength is increased, the ductility and the shape freezing property are likely to decrease. Therefore, a steel sheet having high strength and good shape freezing property and ductility is required.
[0003]
It is known that the addition of Si to steel is very effective in improving the balance between strength and ductility. Furthermore, a high ductility, high tensile strength steel sheet (hereinafter, referred to as “residual austenite type”) containing a large amount of Si or Al as a ferrite forming element and Mn as an austenite forming element and utilizing large elongation (TRIP effect) due to strain-induced transformation of retained austenite. High-tensile steel sheets ”or simply“ retained austenitic steel sheets ”have been developed. However, since the retained austenite-type high-tensile steel sheet has a high yield ratio (YR) and a large change in shape due to elastic recovery after forming, it cannot be said that it has sufficient performance from the viewpoint of shape freezing.
[0004]
In order to produce this retained austenite type high-strength steel sheet, after the annealing treatment, a holding time in a temperature range of 350 to 600 ° C. (hereinafter, holding in this temperature range is referred to as “low temperature holding”, It is important to increase the "low-temperature holding time" to promote the bainite transformation, to concentrate C in austenite to stabilize it, and to leave the austenite up to room temperature. At this time, if the content of Si or Al is small, cementite will precipitate during the transformation of bainite, and C will not be concentrated in austenite and will not be stable. Further, even when the low-temperature holding time is short, bainite transformation is not sufficient, and austenite does not become stable. If the austenite is not stabilized, part of the austenite undergoes martensitic transformation during cooling, making it difficult to obtain the TRIP effect and reducing ductility.
[0005]
Further, development of a dual-phase steel (hereinafter, referred to as "DP steel") steel sheet having a composite structure of ferrite and martensite having a low YR even with the same strength is also progressing. This steel sheet is superior in the shape freezing property as compared with the retained austenite type steel sheet, but is lower in ductility than the retained austenite type steel sheet. In addition, also in this steel sheet, generally, Si is often added for ensuring ductility.
[0006]
On the other hand, from the viewpoint of improving corrosion resistance and appearance, plating materials have been increasingly used as automotive members, and at present, hot-dip galvanized steel sheets are used for many members. However, in the existing hot-dip galvanizing equipment, the low-temperature holding line length is often short, and when the base steel sheet is a residual austenite type steel sheet with a large Si content, after reduction annealing treatment and before hot-dip galvanizing. Because of the need to extend the low-temperature holding time, existing equipment reduces the line speed and significantly reduces productivity. Further, if the low-temperature holding time is increased, even in a reducing atmosphere, the oxide of Si is concentrated on the surface of the steel sheet, so that the plating wettability and the plating adhesion are reduced. From the above, when steel to which Si is added is used as a base steel sheet, there is a concern that productivity may be reduced and plating adhesion may be deteriorated.
[0007]
The residual austenitic steel sheet containing a large amount of Si and a method for manufacturing the same are disclosed in Patent Documents 1 to 5, for example. However, in order to obtain such a steel sheet, as described above, it is necessary to increase the low-temperature holding time, which not only significantly reduces the productivity but also reduces the shape freezing property, plating wettability and plating adhesion. There is also a problem.
[0008]
Patent Document 6 discloses a hot-dip galvanized steel sheet having a low content of Si and Al and excellent in plating adhesion and a method for producing the same, and the steel sheet structure is bainite and ferrite or bainite, ferrite, and martensite. . Patent Document 7 discloses a steel sheet having a low Si content but containing Al: 0.07 to 0.7% and a method for producing the steel sheet. The steel sheet structure has a ferrite and a marten containing residual austenite. Site. Such a steel sheet is excellent in shape freezing property and plating adhesion, but is insufficient in ductility.
[0009]
Patent Document 8 discloses a residual austenitic steel sheet having a low Si content and a large Al content. However, as described above, the residual austenitic steel sheet has not only poor shape freezing properties, It is not preferable because the characteristics greatly change depending on the components and the production conditions (particularly, low-temperature holding time and final cooling conditions).
[0010]
The problems of the residual austenitic steel and DP steel are summarized as follows.
(Retained austenitic steel)
(A) Since the yield ratio (YR) is high, the shape freezing property is poor.
[0011]
(B) In the production, the long-term low-temperature holding time is required to stabilize austenite and allow austenite to remain at room temperature, so that plating adhesion and productivity are poor. On the other hand, ductility is improved by the TRIP effect of retained austenite. On the other hand, when the low-temperature holding time is short, martensite is partially mixed, and the TRIP effect is less likely to be exhibited, and ductility is reduced.
[DP steel]
(A) Although the yield ratio is low and the shape freezing property is excellent, the ductility is inferior to that of the retained austenitic steel.
[0012]
As described above, a high tensile galvanized steel sheet having excellent shape freezing properties and plating adhesion and excellent ductility even when the amount of Si added is small and the low-temperature holding time is short under the manufacturing conditions is practical. At present, these problems have not been developed, and there is a need to solve these problems in promoting the application of high-tensile steel sheets.
[0013]
[Patent Document 1]
JP 05-70886 A
[Patent Document 2]
JP 06-145788 A
[Patent Document 3]
JP-A-11-131145
[Patent Document 4]
JP 2001-140022 A
[Patent Document 5]
JP 2001-303229 A
[Patent Document 6]
JP-A-05-125485
[Patent Document 7]
JP 2000-345288 A
[Patent Document 8]
JP 05-247586 A
[0014]
[Problems to be solved by the invention]
The present invention has been made in view of such circumstances, and its object is to provide a high-tensile alloyed hot-dip galvanized steel sheet having excellent shape freezing properties, excellent plating adhesion and ductility, and a tensile strength of 450 MPa or more, and production thereof. It is to provide a method.
[0015]
[Means for Solving the Problems]
The present inventors have investigated the effects of the components and annealing conditions on the material of the steel sheet in detail in order to solve the above problems, and have obtained the following knowledge.
[0016]
(A) In the case where the low-temperature holding time after the annealing treatment is short and martensite is generated, the base steel sheet is unlikely to exhibit the TRIP effect even if residual austenite is present. However, by transforming bainite during holding at low temperature for a short time, and by further balancing the enrichment of C into austenite by Si and Al and the Mn content, the stability of austenite is adjusted, and the retention of austenite is suppressed. By promoting the formation of martensite containing a large amount of C (hereinafter referred to as “high C martensite”), it is possible to secure better ductility than ferrite + martensitic structure steel (DP steel). Moreover, since the yield ratio (YR) can be kept low, the shape freezing property is also good. The ideal metallographic structure is ferrite + bainite + high C martensite. At this time, it is better that the retained austenite is small.
[0017]
(B) For the generation of high C martensite, the low-temperature holding temperature and low-temperature holding time, and the cooling rate after the alloying treatment are important.
[0018]
(C) Al is an element that is easily oxidized like Si, but Al is more Ac than Si. 3 Since the transformation point is raised, even at the same annealing temperature and annealing time, C enrichment in austenite tends to proceed. Therefore, the low-temperature holding time after the annealing treatment can be shortened, and the generation of oxides can be suppressed, so that a decrease in plating adhesion can be avoided. When Si is added, the low-temperature holding must be performed for a long time, and the adhesion of the plating deteriorates due to the formation of oxide.
[0019]
(D) In order to simultaneously satisfy the base material characteristics of excellent shape freezing property and ductility and the plating adhesion, it is preferable to positively add Al.
[0020]
(E) When Ni is adhered to the surface of the steel sheet as a pretreatment, plating adhesion is improved.
[0021]
The present invention has been completed based on the above findings, and the gist of the present invention lies in the following (1) high-tensile alloyed hot-dip galvanized steel sheet and (2) a method for producing the steel sheet.
[0022]
(1) In mass%, C: 0.10 to 0.30%, Si: 0.2% or less, Mn: 1.0 to 3.0%, Al: 0.5 to 2.0% And Si, Al and Mn satisfy the following formula (1), the balance being Fe and impurities, P in the impurities is 0.1% or less, S is 0.1% or less, and N is 0.020%. % Or less, further comprising a zinc alloy plating layer containing 7 to 15% by mass of Fe on a steel plate (base material steel plate) containing 3 to 50% of martensite by volume. Hot-dip galvanized steel sheet. In the formula (1), Si (%), Al (%) and Mn (%) represent the contents (% by mass) of Si, Al and Mn of the base steel sheet, respectively.
[0023]
2 ≦ Si (%) + Al (%) + Mn (%) ≦ 4 (1)
The steel sheet according to (1) further includes, by mass%, Ni: less than 2.0%, Co: less than 2.0%, and Cu: less than 1.0% (these are referred to as “first group components”). ), Ti: less than 0.1%, Nb: less than 0.1%, and V: less than 0.2% (these are referred to as “second group components”). One or more, and any one or more of Mo: less than 1.0%, Cr: less than 1.0%, and B: less than 0.01% (these are referred to as “components of the third group”); May include elements belonging to any one or more of the three groups.
[0024]
(2) A method for producing a high-tensile alloyed hot-dip galvanized steel sheet in which the steel sheet having the chemical composition described in (1) is sequentially subjected to the following processes (A) to (F).
[0025]
(A) Annealing treatment in a two-phase coexisting temperature range of 700 to 900 ° C for 30 to 600 seconds
(B) A process of cooling to a temperature range of 350 to 550 ° C. at a cooling rate of 3 to 200 ° C./sec.
(C) a process of maintaining the temperature range for 10 to 90 seconds
(D) Treatment immersed in hot-dip galvanizing bath
(E) A process of maintaining the temperature in a temperature range of 470 to 600 ° C. for 5 to 180 seconds.
(F) A process of cooling at a cooling rate of 4 ° C./sec or more to 250 ° C. or less
If the treatment for adhering Ni to the steel sheet surface is performed before the treatment (A), the plating adhesion is improved.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the high tensile alloyed hot-dip galvanized steel sheet of the present invention (the invention of the above (1)) and the method for producing the same (the invention of the above (2)) will be described in detail. Note that “%” of the chemical component content of the base steel sheet, “%” of the Fe content in the plating film, and “%” of the Al concentration in the plating bath all mean “% by mass”.
[0027]
In the high tensile alloyed hot-dip galvanized steel sheet of the present invention, the chemical composition of the base steel sheet is specified as described above for the following reasons.
[0028]
C: 0.10 to 0.30%
In the base steel sheet of the high-tensile alloyed hot-dip galvanized steel sheet of the present invention, the ductility is increased by generating martensite containing a large amount of C, and the balance between strength and ductility is improved as compared with the DP steel. Therefore, C is an essential element. The content of C may be appropriately determined according to the target steel sheet strength. However, in order to achieve a tensile strength of 450 MPa or more, which is the target of the present invention, and to improve ductility more than DP steel, 0% is required. It is necessary that the content be 10% or more. The upper limit of the C content is set to 0.30% in order to secure good spot weldability.
[0029]
Si: 0.2% or less
Si does not form a solid solution in cementite and suppresses precipitation of cementite. As described above, it is an important element for promoting bainite transformation in which cementite is hardly generated during low-temperature holding, and for enriching C in austenite to adjust the stability of austenite. However, when the Si content increases, the low-temperature holding must be performed for a long time, and the plating adhesion decreases, so the content is set to 0.2% or less. The lower limit of the Si content is not defined by Si alone, but is defined by the total content including Al and Mn as described later.
[0030]
Mn: 1.0-3.0%
Mn not only increases the strength of the steel sheet but also is an austenite-forming element, and is an important element that directly affects the stability of austenite. It also has the effect of suppressing the generation of pearlite during cooling from high temperatures. In order to obtain these effects, it is necessary to contain at least 1.0%, and within that range, the Mn content may be appropriately adjusted according to the target tensile strength of the base steel sheet. The upper limit of the Mn content is 3.0% from the viewpoint of cost and melting in a converter.
[0031]
Al: 0.5 to 2.0%
Al is also used as a deoxidizing material, and at the same time, like Si, to promote bainite transformation in which cementite is hardly generated during low-temperature holding, and to concentrate C in austenite to adjust the stability of austenite. It is an important element. Since the low-temperature holding time can be shortened and the adhesion can be improved as compared with the case where Si is contained, Al is positively used in the present invention.
[0032]
In order to finally obtain high C martensite, it is necessary to contain 0.5% or more. However, since excessive addition deteriorates the adhesion and the weldability of the plating, the upper limit is made 2.0%.
[0033]
2 ≦ Si (%) + Al (%) + Mn (%) ≦ 4 (Formula (1))
By balancing the concentration of C in austenite and the Mn content in austenite by Si and Al, it is possible to adjust the stability of austenite, suppress the retention of austenite, and promote the generation of high-C martensite. .
[0034]
When the value of Si (%) + Al (%) + Mn (%) is less than 2, the stability of austenite becomes low, and pearlite is generated from austenite during cooling from a high temperature during annealing and during holding at a low temperature, Alternatively, austenite is decomposed into ferrite and cementite, and a desired structure cannot be obtained. On the other hand, if it exceeds 4, the stability of austenite becomes too high, austenite remains, the amount of martensite decreases, and the desired amount (3 to 50% by volume) cannot be obtained, and the ductility decreases. In addition, the YR (yield ratio) is increased and the shape freezing property is deteriorated. Therefore, it is necessary to adjust the contents of Si, Al and Mn so as to satisfy the relationship of 2 ≦ Si (%) + Al (%) + Mn (%) ≦ 4. Desirably, 2.5 ≦ Si (%) + Al (%) + Mn (%) ≦ 3.5.
[0035]
The base steel sheet of the high-tensile alloyed hot-dip galvanized steel sheet of the present invention has the balance of Fe and impurities other than the components described above. As impurities, it is necessary to suppress the upper limits of P, S, and N.
[0036]
P: 0.1% or less
P is an element inevitably contained in steel as an impurity, and is preferably as low as possible. In particular, when the content exceeds 0.1%, the ductility of the steel sheet deteriorates remarkably, so the P content is set to 0.1% or less.
[0037]
S: 0.1% or less
S is also an element inevitably contained in the class as an impurity, and it is desirable that S is also lower. In particular, when the content exceeds 0.1%, precipitation of MnS becomes remarkable, not only hinders the ductility of the steel sheet, but also consumes Mn added as an austenite stabilizing element as MnS. The S content is set to 0.1% or less.
[0038]
N: 0.020% or less
N is also an element inevitably contained in the class as an impurity, and its content is preferably low. When the N content exceeds 0.020%, the amount of Al consumed as AlN is large, and not only the effect of Al is reduced, but also the ductility is significantly deteriorated by AlN. 0.020%.
[0039]
The base steel sheet of the high-tensile alloyed hot-dip galvanized steel sheet of the above (1) further includes the components of the first group (Ni: less than 2.0%, Co: less than 2.0%, and Cu: 1.0%). ), And at least one of the components of the second group (Ti: less than 0.1%, Nb: less than 0.1%, and V: less than 0.2%). And any one or more of the components of the third group (Mo: less than 1.0%, Cr: less than 1.0%, and B: less than 0.01%) It may contain an element belonging to one or more groups. The effects and the appropriate ranges of the contents of these components are as follows.
[0040]
Ni: less than 2.0%
Co: less than 2.0%
Cu: less than 1.0%
Ni, Co and Cu, like Mn, are austenite-forming elements and also elements that improve the strength of the steel sheet. In addition, since all are less oxidized than Fe, they are concentrated on the surface of the steel sheet and have an effect of preventing a reduction in plating adhesion due to oxidation of Si or Al. Therefore, they may be added as necessary. In the case of adding, since excessive addition causes an increase in cost, the contents of Ni and Co are each set to less than 2.0%. Cu is set to less than 1.0% from the viewpoint of preventing hot cracking. The lower limit of the content is not particularly defined, but in order to obtain a remarkable effect by the addition, it is desirable to make Ni, Co and Cu all contain 0.1% or more.
[0041]
Ti: less than 0.1%
Nb: less than 0.1%
V: less than 0.2%
Ti, Nb, and V are effective elements that not only improve the strength of the steel sheet but also increase the alloying speed when performing galvanizing alloying treatment, and may be added as necessary. . In the case of adding, excessive addition not only causes deterioration of ductility, but also increases the yield ratio (YR) and deteriorates the shape freezing property. Therefore, the contents of Ti and Nb are each 0.1%. Less than Since the effect of addition of V is smaller than that of Ti and Nb, its content is set to less than 0.2%. The lower limit of the content is not particularly defined, but in order to obtain a remarkable effect by the addition, it is preferable that each of Ti and Nb be contained at 0.005% or more, and V is contained at 0.01% or more.
[0042]
Mo: less than 1.0%
Cr: less than 1.0%
B: less than 0.01%
Mo, Cr and B are effective elements that suppress the formation of pearlite during cooling from a high temperature during the annealing treatment and promote the formation of martensite, and may be added as necessary. In the case of adding Mo and Cr, 1.0% or more of B and 0.01% or more of B not only saturates the effect but also increases the cost. Is less than 1.0%, and B is less than 0.01%. The lower limit of the content is not particularly defined, but in order to obtain a remarkable effect by the addition, it is preferable that Mo and Cr are contained in 0.1% or more, respectively, and B is contained in 0.0005% or more.
[0043]
The base steel sheet of the high tensile alloyed hot-dip galvanized steel sheet of the present invention further contains 3 to 50% of martensite by volume%. In order to simultaneously satisfy both the shape freezing property and the ductility, it is important that high C martensite is present in the base material, and for that purpose, it is necessary that martensite be contained by 3% or more by volume%. It is. However, when the content exceeds 50%, the strength becomes too high, ductility is deteriorated, and high C martensite is reduced. A desirable content of martensite is 5-35%. The content (abundance) of martensite referred to here is measured by performing color etching by a repeller method using a 4% ethyl picrate phosphoric acid solution and a 1% aqueous sodium pyrosulfite solution, and measuring the volume ratio by observation with an optical microscope. This is the value obtained from the above.
[0044]
The high-tensile alloyed hot-dip galvanized steel sheet of the present invention is a steel sheet provided with a zinc alloy plating layer containing 7 to 15% Fe on the above-mentioned steel sheet. The reason why the content of Fe in the plating layer is defined in the above range is that if the content of Fe exceeds 15%, it becomes difficult to secure the plating adhesion and workability, and if the content of Fe is less than 7%, it is good. This is because it becomes impossible to secure a high spot weldability.
[0045]
Next, the method for producing a high-tensile alloyed hot-dip galvanized steel sheet of the present invention (the invention of (2) above) will be described.
[0046]
First, a cold-rolled steel sheet (cold-rolled steel sheet) having the above chemical composition is used as the base steel sheet. Hot rolling and cold rolling for obtaining this steel sheet may be performed by a known method, but if the particle size of the base material is too large or too small, desired characteristics as the base material steel plate cannot be obtained. Therefore, it is desirable that the winding temperature in the hot rolling step is 700 ° C. or less and the cold rolling reduction is in the range of 40 to 80%.
[0047]
The base steel sheet is subjected to a pretreatment by a known method such as washing with an alkaline aqueous solution or surface grinding with a nylon brush or the like in order to make the surface suitable for hot-dip plating.
[0048]
At the time of this pretreatment, if a treatment for attaching Ni to the steel sheet surface is performed, the plating adhesion is significantly improved. In this case, the amount of Ni attached to the steel sheet surface is 1 g / m 2 from the viewpoint of economy. 2 It is desirable to do the following.
[0049]
Subsequently, the base steel sheet is heated to a temperature range of coexistence of two phases (ferrite phase + austenite phase) at 700 to 900 ° C., and is annealed for 30 to 600 seconds (the process (A)). This annealing treatment is usually performed in a reducing atmosphere.
[0050]
As the reducing atmosphere, a gas atmosphere containing 5 to 30% by volume of hydrogen, the balance being nitrogen, and having a dew point in the range of −60 to 0 ° C. is preferable. In addition, in order to improve material characteristics, preliminary annealing may be performed by a continuous annealing line or batch annealing after cold rolling.
[0051]
In the above annealing treatment, if the annealing temperature is less than 700 ° C. or the annealing time is less than 30 seconds, recrystallization is unlikely to occur and cementite does not form a solid solution, so that the properties of the steel sheet deteriorate. On the other hand, when the annealing temperature exceeds 900 ° C., not only the crystal grains become coarse, but also the volume fraction of austenite during annealing increases, and not only the C content in the finally generated martensite decreases, but also In addition, an increase in manufacturing cost due to an increase in furnace temperature is inevitable. On the other hand, if the annealing time exceeds 600 seconds, the crystal grains become coarse, the line speed decreases, and the productivity decreases, which is not preferable.
[0052]
The base steel sheet after the annealing treatment is cooled at a cooling rate of 3 to 200 ° C./sec to a temperature range of 350 to 550 ° C. (that is, a low temperature holding temperature range) near the plating bath temperature (the process (B)). Then, the temperature is held (low temperature holding) for 10 to 90 seconds in the temperature range (the process (C)).
[0053]
If the cooling rate after the annealing treatment is lower than 3 ° C./sec, pearlite or cementite is generated from austenite during cooling, and a desired metal structure cannot be obtained. If the cooling rate is higher than 200 ° C./sec, it becomes difficult to control the cooling rate, and a uniform structure cannot be obtained.
[0054]
When the low-temperature is lower than 350 ° C, low-C martensite is generated during cooling after annealing, and when the low-temperature is higher than 550 ° C, bainite transformation does not occur and austenite is transformed into pearlite. Desired material properties cannot be obtained.
[0055]
If the low-temperature holding time is less than 10 seconds, bainite transformation does not occur, and the concentration of C in austenite does not proceed, resulting in low C martensite and reduced ductility. When the low-temperature holding time is longer than 90 seconds, as described above, not only the productivity is lowered, but also the adhesion of the plating is deteriorated due to the generation of oxides, and the ideal structure of the present invention, ie, The formation of C martensite is suppressed, leading to a decrease in ductility and a poor shape freezing property.
[0056]
The base steel sheet after the predetermined low-temperature holding is immersed in a hot-dip galvanizing bath to form a galvanized layer on the steel sheet surface (processing (D) above).
[0057]
The plating bath temperature is set to 430 ° C. or higher in order to facilitate the adjustment of the coating weight, and to 550 ° C. or lower in order to avoid the evaporation of Zn and facilitate the maintenance of the plating bath. Adjustment of the amount of plating after pulling up from the plating bath may be performed by a commonly used method such as a gas squeezing method.
[0058]
Then, after performing an alloying process in which the temperature is maintained in a temperature range of 470 to 600 ° C. for 5 to 180 seconds (the process (E)), it is cooled to a temperature of 250 ° C. or less at a cooling rate of 4 ° C./sec or more ( (Process of the above (F)).
[0059]
If the alloying treatment temperature is lower than 470 ° C., alloying does not occur. If the temperature exceeds 600 ° C., austenite is decomposed into cementite and ferrite, and the characteristics are deteriorated.
[0060]
If the alloying time is less than 5 seconds, alloying does not occur, and the plating adhesion deteriorates. On the other hand, when the alloying treatment time exceeds 180 seconds, not only does austenite decompose into cementite and ferrite and the properties deteriorate, but also as in the case where the low-temperature holding time exceeds the specified range, the line speed decreases. , Lowering productivity.
[0061]
If the cooling rate after the alloying treatment is less than 4 ° C./sec, martensite is hardly generated during cooling, and bainite or ferrite and cementite are generated. Therefore, the cooling rate after the alloying treatment is set to 4 ° C./sec or more. This cooling is performed using nitrogen and industrial gas (air). Further, normal mist cooling may be performed.
[0062]
The high-tensile alloyed hot-dip galvanized steel sheet of the present invention has high strength, good shape freezing property and ductility, and excellent plating adhesion. It is suitable as. In particular, when a steel sheet is painted and used in the construction field, the high-tensile alloyed hot-dip galvanized steel sheet of the present invention can exhibit excellent performance and economic efficiency.
[0063]
【Example】
The steel types shown in Table 1 were melted in a vacuum melting furnace, and a forged ingot (thickness: 20 mm) was hot-rolled to a sheet thickness of 4.0 mm at a finishing temperature of 850 ° C. Thereafter, the temperature was maintained at 650 ° C. for 30 minutes, and the furnace was cooled to room temperature at a cooling rate of 20 ° C./h. The hot-rolled steel sheet was pickled and cold-rolled to obtain a 1.2 mm-thick cold-rolled steel sheet for galvanizing.
[0064]
[Table 1]
[0065]
This cold-rolled steel sheet was used as a base steel sheet, and the coating weight was 60 mg / m2 using a vertical hot-dip coating simulator. 2 , And then subjected to alloying treatment using a salt bath to produce various alloyed hot-dip galvanized steel sheets.
[0066]
Table 2 shows the conditions in each step of the hot-dip galvanizing. In Table 2, the cooling rate in the column of “reduction annealing” (that is, the cooling rate after reduction annealing) is “cooling rate CR1”, and the cooling rate in the section of “alloying” is “cooling rate CR2”. Write.
[0067]
[Table 2]
[0068]
For these alloyed hot-dip galvanized steel sheets, the volume fraction of martensite is determined, a tensile test is performed, the tensile strength (TS) and the elongation (El) are measured, and the shape freezing property and plating adhesion are investigated. did.
[0069]
The volume fraction of martensite was determined by the method described above.
[0070]
In the investigation of the shape freezing property, a hat-shaped molding test was performed under the following test conditions, and the springback amount (angle) of the punch shoulder was measured.
〔Test condition〕
Sample size: width 50mm x length 250mm
Punch shoulder radius: 10mm
Die shoulder radius: 10mm
Punch width: 50mm
Molding height: 60mm
Molding speed: 60 mm / min
For the examination of plating adhesion, a tape peeling test was performed on the outer side of the die shoulder of the sample after the shape freezing property was examined, and the peeled tape was observed with a loupe, and evaluated according to the following criteria.
◎ mark: no exfoliation of plating was observed, very good
印: slight plating peeling was observed, but there was no problem in plating adhesion, and good x: large amount of peeling was observed and defective
Table 3 shows the results of the survey. The changed conditions (reduction annealing temperature and cooling rate CR1, low-temperature holding temperature and time, cooling rate after alloying treatment CR2) among the hot-dip galvanizing conditions shown in Table 2 are also shown in Table 3. Was.
[0071]
[Table 3]
[0072]
As shown in Table 3, the galvannealed steel sheet of the present invention has high strength and good ductility, and “TS (tensile strength) × El (elongation)” as an index of strength-ductility balance. It shows a high value. Good shape freezing property and excellent plating adhesion. In addition, in the case of No. 1 of the present invention in which Ni was adhered to the surface of the steel sheet by plating pretreatment. In Nos. 4 and 14, improvement in plating adhesion was observed.
[0073]
On the other hand, the Si content of the base steel sheet exceeded the regulation of the present invention (0.2% or less) and was 0.63% and 1.00%. In Nos. 22 and 23, the tensile properties were excellent, but the adhesion of plating was poor because the oxide of Si was concentrated on the steel sheet surface.
[0074]
The annealing temperature was set to 650 ° C. lower than the specified value (700 to 900 ° C.) of the present invention. In No. 9, recrystallization and transformation did not occur, and not only the tensile properties were deteriorated, but also the shape freezing property was poor.
[0075]
The cooling rate CR1 after the annealing treatment was set to 1 ° C./s which was lower than the regulation (3 to 200 ° C./s) of the present invention. No. 6 and Comparative Example No. 6 in which the low-temperature holding temperature was set to 650 ° C. which was higher than the prescribed value (350 to 550 ° C.) of the present invention. In No. 2, pearlite transformation occurred during cooling or holding at low temperature, and the tensile properties deteriorated.
[0076]
In Comparative Example No. 1 in which the low-temperature holding time was 1 second shorter than the specified value (10 to 90 seconds) of the present invention. In No. 12, bainite transformation hardly occurred during low-temperature holding, most of austenite underwent martensitic transformation, and tensile properties deteriorated.
[0077]
The cooling rate CR2 after the alloying treatment was set to 1 ° C./s which was lower than the specified value (4 ° C./s or more) of the present invention. In No. 15, austenite was decomposed into ferrite and cementite during cooling, no martensite was formed, and the tensile properties were deteriorated.
[0078]
【The invention's effect】
The high-tensile alloyed hot-dip galvanized steel sheet of the present invention has excellent shape freezing property, plating adhesion and ductility, and has high strength, and is suitable as a member used for automobiles, buildings, electric appliances and the like. This steel sheet can be easily manufactured by the method of the present invention.
Claims (6)
2≦Si(%)+Al(%)+Mn(%)≦4 ・・・▲1▼In mass%, C: 0.10 to 0.30%, Si: 0.2% or less, Mn: 1.0 to 3.0%, Al: 0.5 to 2.0%, and Si, Al and Mn satisfy the following formula (1), and the balance consists of Fe and impurities. P in the impurities is 0.1% or less, S is 0.1% or less, and N is 0.020% or less. High-tensile alloyed hot-dip galvanizing characterized by comprising a zinc alloy plating layer containing 7 to 15% by mass of Fe on a steel plate containing 3 to 50% of martensite by volume. steel sheet.
2 ≦ Si (%) + Al (%) + Mn (%) ≦ 4 (1)
2≦Si(%)+Al(%)+Mn(%)≦4 ・・・▲1▼2. In addition to the component according to claim 1, further contains at least one of Ni: less than 2.0%, Co: less than 2.0%, and Cu: less than 1.0% by mass%. And Si, Al and Mn satisfy the following formula (1), the balance being Fe and impurities, P in the impurities is 0.1% or less, S is 0.1% or less, and N is 0.1% or less. 020% or less, and further comprising a zinc alloy plating layer containing 7 to 15% by mass Fe on a steel plate containing 3 to 50% martensite by volume. Galvanized steel sheet.
2 ≦ Si (%) + Al (%) + Mn (%) ≦ 4 (1)
2≦Si(%)+Al(%)+Mn(%)≦4 ・・・▲1▼In addition to the components according to claim 1 or 2, further, in mass%, at least one of Ti: less than 0.1%, Nb: less than 0.1%, and V: less than 0.2%. , And Si, Al and Mn satisfy the following formula (1), with the balance being Fe and impurities, where P in the impurities is 0.1% or less, S is 0.1% or less, and N is 0.020% or less, and further comprising a zinc alloy plating layer containing 7 to 15% by mass of Fe on a steel plate containing 3 to 50% of martensite by volume. Tension galvannealed steel sheet.
2 ≦ Si (%) + Al (%) + Mn (%) ≦ 4 (1)
2≦Si(%)+Al(%)+Mn(%)≦4 ・・・▲1▼In addition to the component according to any one of claims 1 to 3, any one of Mo: less than 1.0%, Cr: less than 1.0%, and B: less than 0.01% by mass%. At least one element is contained, and Si, Al and Mn satisfy the following formula (1), and the balance consists of Fe and impurities. P in the impurities is 0.1% or less and S is 0.1% or less. , N is 0.020% or less, and a zinc alloy plating layer containing 7 to 15% by mass Fe on a steel plate containing 3 to 50% martensite by volume. High tensile alloyed hot-dip galvanized steel sheet.
2 ≦ Si (%) + Al (%) + Mn (%) ≦ 4 (1)
(A)700〜900℃の二相共存温度域で30〜600秒間焼鈍する処理
(B)3〜200℃/秒の冷却速度で350〜550℃の温度域まで冷却する処理
(C)前記温度域で10〜90秒間保持する処理
(D)溶融亜鉛めっき浴に浸漬する処理
(E)470〜600℃の温度域に5〜180秒間保持する処理
(F)4℃/秒以上の冷却速度で250℃以下まで冷却する処理A method for producing a high-tensile alloyed hot-dip galvanized steel sheet, comprising sequentially performing the following processes (A) to (F) on a steel sheet having the chemical composition according to claim 1.
(A) a process of annealing for 30 to 600 seconds in a two-phase coexisting temperature range of 700 to 900 ° C (B) a process of cooling to a temperature range of 350 to 550 ° C at a cooling rate of 3 to 200 ° C / sec (C) the temperature (D) Dipping in a hot-dip galvanizing bath (E) Treatment in a temperature range of 470 to 600 ° C. for 5 to 180 seconds (F) At a cooling rate of 4 ° C./sec or more Processing to cool to 250 ° C or less
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2002278521A JP4000974B2 (en) | 2002-09-25 | 2002-09-25 | High tensile alloyed hot dip galvanized steel sheet and method for producing the same |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2002278521A JP4000974B2 (en) | 2002-09-25 | 2002-09-25 | High tensile alloyed hot dip galvanized steel sheet and method for producing the same |
Related Child Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP2006271050A Division JP4975406B2 (en) | 2006-10-02 | 2006-10-02 | High-strength galvannealed steel sheet and method for producing the same |
Publications (2)
Publication Number | Publication Date |
---|---|
JP2004115843A true JP2004115843A (en) | 2004-04-15 |
JP4000974B2 JP4000974B2 (en) | 2007-10-31 |
Family
ID=32273781
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP2002278521A Expired - Fee Related JP4000974B2 (en) | 2002-09-25 | 2002-09-25 | High tensile alloyed hot dip galvanized steel sheet and method for producing the same |
Country Status (1)
Country | Link |
---|---|
JP (1) | JP4000974B2 (en) |
Cited By (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2006097063A (en) * | 2004-09-29 | 2006-04-13 | Nisshin Steel Co Ltd | METHOD FOR PRODUCING HIGH STRENGTH HOT DIP Zn-Al-Mg ALLOY PLATED STEEL SHEET |
WO2006104282A1 (en) * | 2005-03-31 | 2006-10-05 | Jfe Steel Corporation | Alloyed hot-dip galvanized steel sheet and method for producing same |
WO2006104275A1 (en) * | 2005-03-31 | 2006-10-05 | Jfe Steel Corporation | Alloyed hot-dip galvanized steel sheet and method for producing same |
JP2006299349A (en) * | 2005-04-20 | 2006-11-02 | Jfe Steel Kk | Method for producing high tensile strength hot-dip galvanized steel sheet, and method for producing high tensile strength hot dip galvannealed steel sheet |
JP2006307326A (en) * | 2005-03-31 | 2006-11-09 | Jfe Steel Kk | High ductility and high strength alloyed hot-dip galvanized steel sheet having excellent surface property and method for producing same |
JP2007327123A (en) * | 2006-06-09 | 2007-12-20 | Kobe Steel Ltd | Method for improving variation of strength-ductility balance of galvannealed steel sheet |
US20080175743A1 (en) * | 2005-03-31 | 2008-07-24 | Jfr Steel Corporation, A Corporation Of Japan | Alloyed Hot-Dip Galvanized Steel Sheet and Method of Producing the Same |
WO2008123561A1 (en) | 2007-03-30 | 2008-10-16 | Jfe Steel Corporation | High-strength hot-dip zinc-coated steel sheet |
WO2009081997A1 (en) | 2007-12-20 | 2009-07-02 | Jfe Steel Corporation | Processes for producing high-strength hot-dip galvanized steel sheet and high-strength galvannealed steel sheet |
WO2013037485A1 (en) * | 2011-09-13 | 2013-03-21 | Tata Steel Ijmuiden B.V. | High strength hot dip galvanised steel strip |
WO2014139625A1 (en) * | 2013-03-11 | 2014-09-18 | Tata Steel Ijmuiden Bv | High strength hot dip galvanised complex phase steel strip |
-
2002
- 2002-09-25 JP JP2002278521A patent/JP4000974B2/en not_active Expired - Fee Related
Cited By (23)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2006097063A (en) * | 2004-09-29 | 2006-04-13 | Nisshin Steel Co Ltd | METHOD FOR PRODUCING HIGH STRENGTH HOT DIP Zn-Al-Mg ALLOY PLATED STEEL SHEET |
JP4544579B2 (en) * | 2004-09-29 | 2010-09-15 | 日新製鋼株式会社 | Manufacturing method of high strength molten Zn-Al-Mg alloy plated steel sheet |
US20080175743A1 (en) * | 2005-03-31 | 2008-07-24 | Jfr Steel Corporation, A Corporation Of Japan | Alloyed Hot-Dip Galvanized Steel Sheet and Method of Producing the Same |
EP1867747A4 (en) * | 2005-03-31 | 2009-09-09 | Jfe Steel Corp | Alloyed hot-dip galvanized steel sheet and method for producing same |
JP2006307326A (en) * | 2005-03-31 | 2006-11-09 | Jfe Steel Kk | High ductility and high strength alloyed hot-dip galvanized steel sheet having excellent surface property and method for producing same |
JP2006307327A (en) * | 2005-03-31 | 2006-11-09 | Jfe Steel Kk | High ductility and high strength alloyed hot-dip galvanized steel sheet having excellent surface property and brittle resistance to secondary processing and method for producing same |
JP2006307325A (en) * | 2005-03-31 | 2006-11-09 | Jfe Steel Kk | Low yield ratio type high strength alloyed hot-dip galvanized steel sheet having excellent ductility and method for producing same |
EP1867747A1 (en) * | 2005-03-31 | 2007-12-19 | JFE Steel Corporation | Alloyed hot-dip galvanized steel sheet and method for producing same |
EP1867746A1 (en) * | 2005-03-31 | 2007-12-19 | JFE Steel Corporation | Alloyed hot-dip galvanized steel sheet and method for producing same |
EP1867746A4 (en) * | 2005-03-31 | 2014-06-11 | Jfe Steel Corp | Alloyed hot-dip galvanized steel sheet and method for producing same |
WO2006104275A1 (en) * | 2005-03-31 | 2006-10-05 | Jfe Steel Corporation | Alloyed hot-dip galvanized steel sheet and method for producing same |
WO2006104282A1 (en) * | 2005-03-31 | 2006-10-05 | Jfe Steel Corporation | Alloyed hot-dip galvanized steel sheet and method for producing same |
KR100932828B1 (en) * | 2005-03-31 | 2009-12-21 | 제이에프이 스틸 가부시키가이샤 | Alloyed hot dip galvanized steel sheet and manufacturing method thereof |
KR100918549B1 (en) * | 2005-03-31 | 2009-09-21 | 제이에프이 스틸 가부시키가이샤 | Galvannealed steel sheet and method for producing the same |
JP2006299349A (en) * | 2005-04-20 | 2006-11-02 | Jfe Steel Kk | Method for producing high tensile strength hot-dip galvanized steel sheet, and method for producing high tensile strength hot dip galvannealed steel sheet |
JP4732962B2 (en) * | 2006-06-09 | 2011-07-27 | 株式会社神戸製鋼所 | Method for improving variation in strength-ductility balance of galvannealed steel sheet |
JP2007327123A (en) * | 2006-06-09 | 2007-12-20 | Kobe Steel Ltd | Method for improving variation of strength-ductility balance of galvannealed steel sheet |
WO2008123561A1 (en) | 2007-03-30 | 2008-10-16 | Jfe Steel Corporation | High-strength hot-dip zinc-coated steel sheet |
US8076008B2 (en) | 2007-03-30 | 2011-12-13 | Jfe Steel Corporation | Galvanized high strength steel sheet |
WO2009081997A1 (en) | 2007-12-20 | 2009-07-02 | Jfe Steel Corporation | Processes for producing high-strength hot-dip galvanized steel sheet and high-strength galvannealed steel sheet |
WO2013037485A1 (en) * | 2011-09-13 | 2013-03-21 | Tata Steel Ijmuiden B.V. | High strength hot dip galvanised steel strip |
WO2014139625A1 (en) * | 2013-03-11 | 2014-09-18 | Tata Steel Ijmuiden Bv | High strength hot dip galvanised complex phase steel strip |
CN105247089A (en) * | 2013-03-11 | 2016-01-13 | 塔塔钢铁艾默伊登有限责任公司 | High strength hot dip galvanised complex phase steel strip |
Also Published As
Publication number | Publication date |
---|---|
JP4000974B2 (en) | 2007-10-31 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US11035021B2 (en) | High-strength steel sheet and high-strength galvanized steel sheet | |
JP5834717B2 (en) | Hot-dip galvanized steel sheet having a high yield ratio and method for producing the same | |
CN109072380B (en) | Steel sheet, plated steel sheet, and method for producing same | |
CN108291283B (en) | High-strength hot-dip galvanized steel sheet, hot-rolled steel sheet and cold-rolled steel sheet used for same, and method for producing high-strength hot-dip galvanized steel sheet | |
JP5092507B2 (en) | High tensile alloyed hot dip galvanized steel sheet and its manufacturing method | |
CN108474095B (en) | High-strength hot-dip galvanized steel material having excellent plating properties and method for producing same | |
JP6249113B2 (en) | High yield ratio type high strength galvanized steel sheet and method for producing the same | |
JP2013163827A (en) | High-strength cold-rolled steel sheet, high-strength galvanized steel sheet, and high-strength alloying hot-dip galvanized steel sheet, excellent in bendability, and method for manufacturing the same | |
CN103764864B (en) | Cold-rolled steel sheet hot rolled steel plate, hot-dip galvanizing sheet steel hot rolled steel plate and manufacture method thereof | |
CN109154045A (en) | Coated steel sheet and its manufacturing method | |
JP4631241B2 (en) | High-tensile hot-dip galvanized steel sheet and high-tensile alloyed hot-dip galvanized steel sheet with excellent strength ductility balance, plating adhesion and corrosion resistance | |
JP7164024B2 (en) | High-strength steel plate and its manufacturing method | |
CN113122772A (en) | Thin steel sheet and plated steel sheet, and method for producing thin steel sheet and plated steel sheet | |
WO2017131055A1 (en) | High-yield ratio high-strength galvanized steel sheet, and method for producing same | |
JP6249140B1 (en) | High yield ratio type high strength galvanized steel sheet and method for producing the same | |
CN114981457A (en) | High-strength galvanized steel sheet and method for producing same | |
KR101647223B1 (en) | Method for manufacturing high strength galvanized steel sheet having excellent surface property and coating adhesion | |
JP2011231377A (en) | High strength steel sheet | |
CN109642280B (en) | High-strength steel sheet and method for producing same | |
KR20180087435A (en) | Austenitic molten aluminum-plated steel sheet excellent in plating property and weldability and method for manufacturing the same | |
JP4000974B2 (en) | High tensile alloyed hot dip galvanized steel sheet and method for producing the same | |
CN114555845B (en) | High-strength steel sheet and method for producing same | |
JP2002309358A (en) | Galvannealed steel sheet with excellent workability | |
JP4940813B2 (en) | Method for producing hot-dip galvanized steel sheet having a value of TS × El of 21000 MPa ·% or more | |
JP2006274378A (en) | High yield ratio high strength cold rolled steel sheet, high yield ratio high strength hot dip galvanized steel sheet, high yield ratio high strength alloyed hot dip galvanized steel sheet, and method for producing them |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20041018 |
|
A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20060721 |
|
A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20060801 |
|
A521 | Request for written amendment filed |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20061002 |
|
A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20070123 |
|
A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20070424 |
|
A521 | Request for written amendment filed |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20070621 |
|
TRDD | Decision of grant or rejection written | ||
A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 20070724 |
|
A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20070806 |
|
FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20100824 Year of fee payment: 3 |
|
R150 | Certificate of patent or registration of utility model |
Ref document number: 4000974 Country of ref document: JP Free format text: JAPANESE INTERMEDIATE CODE: R150 Free format text: JAPANESE INTERMEDIATE CODE: R150 |
|
FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20110824 Year of fee payment: 4 |
|
FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20110824 Year of fee payment: 4 |
|
FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20120824 Year of fee payment: 5 |
|
FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20120824 Year of fee payment: 5 |
|
FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20130824 Year of fee payment: 6 |
|
FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20130824 Year of fee payment: 6 |
|
S111 | Request for change of ownership or part of ownership |
Free format text: JAPANESE INTERMEDIATE CODE: R313111 |
|
FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20130824 Year of fee payment: 6 |
|
R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |
|
S533 | Written request for registration of change of name |
Free format text: JAPANESE INTERMEDIATE CODE: R313533 |
|
R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |
|
LAPS | Cancellation because of no payment of annual fees |