JP3376590B2 - Method for producing high tensile alloyed hot-dip galvanized steel sheet with excellent stretch flangeability - Google Patents
Method for producing high tensile alloyed hot-dip galvanized steel sheet with excellent stretch flangeabilityInfo
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- JP3376590B2 JP3376590B2 JP23688291A JP23688291A JP3376590B2 JP 3376590 B2 JP3376590 B2 JP 3376590B2 JP 23688291 A JP23688291 A JP 23688291A JP 23688291 A JP23688291 A JP 23688291A JP 3376590 B2 JP3376590 B2 JP 3376590B2
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Description
【０００１】[0001]
【産業上の利用分野】本発明は、ロアアームなどの自動
車足廻り部品等に好適に使用される成形性（とくに伸び
フランジ性）・耐食性に優れる高張力合金化溶融亜鉛メ
ッキ鋼板の製造方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high-strength alloy hot-dip galvanized steel sheet having excellent formability (especially stretch flangeability) and corrosion resistance, which is preferably used for automobile underbody parts such as lower arms.
【０００２】[0002]
【従来の技術】近年、地球環境保護の機運が高まる中、
自動車にはCO2ガス排出量低減のために燃費低減が強く
求められている。そのための有力な対策の一つとして車
体の軽量化があり、使用する鋼板を高強度化、薄肉化す
る努力が続けられている。その中でも、ロアアームなど
の自動車足廻り部品に使用される熱延鋼板は、伸びフラ
ンジ成形を主体とする過酷な成形を受けるために、高張
力でかつ優れたプレス成形性、とくに良好な伸びフラン
ジ性を有することが必要とされる。加えて、足廻り部品
は重要保安部品であるため、薄肉化には錆しろの低減に
見合う耐食性の向上が必須となる。また、車体の保証期
間に対する要求も年々長期化しており、この意味でも足
廻り部品への高耐食鋼板の要求が高まっている。このよ
うに、加工性が良好で且つ耐食性に優れた熱延高強度鋼
板が強く求められている。2. Description of the Related Art In recent years, as the momentum for protecting the global environment has increased,
There is a strong demand for automobiles to reduce fuel consumption in order to reduce CO 2 gas emissions. One of the effective measures for this is to reduce the weight of the vehicle body, and efforts are being made to increase the strength and thickness of the steel sheet used. Among them, hot-rolled steel sheets used for undercarriage parts of automobiles such as lower arms are subject to severe forming mainly by stretch flange forming, and therefore have high tensile strength and excellent press formability, particularly good stretch flange forming property. Is required to have. In addition, since the underbody parts are important safety parts, it is essential to improve the corrosion resistance in order to reduce the rust margin in order to reduce the wall thickness. In addition, the demand for the warranty period of the vehicle body is increasing year by year, and in this sense, the demand for highly corrosion-resistant steel sheets for suspension parts is increasing. Thus, there is a strong demand for hot-rolled high-strength steel sheets that have good workability and excellent corrosion resistance.
【０００３】これらの要求に対して、これまでにも耐食
性に優れる高張力合金化溶融亜鉛メッキ熱延鋼板に加工
性を付与する技術が提案されている。即ち、特開昭６３
−１４９３２１号ではＣＧＬ前の熱延条件を規制し、加
工性を付与する技術の開示がなされている。一方、特公
昭６０−４９６９８号でも、ＣＧＬでの加熱温度、冷却
速度を限定することにより高張力合金化溶融亜鉛メッキ
熱延鋼板に加工性を付与する技術の提案が行なわれてい
る。To meet these demands, there have been proposed techniques for imparting workability to high-strength hot-dip galvanized hot-rolled steel sheets having excellent corrosion resistance. That is, JP-A-63
No. 149321 discloses a technique of restricting hot rolling conditions before CGL and imparting workability. On the other hand, Japanese Patent Publication No. 60-49698 also proposes a technique for imparting workability to a high-strength hot-dip galvanized hot-rolled steel sheet by limiting the heating temperature and cooling rate in CGL.
【０００４】[0004]
【発明が解決しようとする課題】前者の方法ではメッキ
性を劣化させるSiを抑制することに伴う強度の低下を、
P添加によって補っているが、P添加は合金化を困難にす
る問題がある。In the former method, the decrease in strength caused by suppressing Si, which deteriorates the plating property, is
Although supplemented by P addition, P addition has a problem that alloying becomes difficult.
【０００５】又後者の方法ではプレス成形性を確保する
ためにＣＧＬ熱履歴を限定し、さらにMoを添加すること
によりフェライト＋マルテンサイト組織としている。し
かし、マルテンサイト相を得るために高価な添加元素を
必要としておりコスト的に不利である。また、フェライ
ト＋マルテンサイト組織は良好な強度−延性バランスを
示すが、伸びフランジ性には有利な組織とは言えない。In the latter method, the CGL heat history is limited in order to secure press formability, and Mo is added to form a ferrite + martensite structure. However, an expensive additional element is required to obtain the martensite phase, which is disadvantageous in cost. Further, the ferrite + martensite structure shows a good strength-ductility balance, but it cannot be said that it is an advantageous structure for stretch flangeability.
【０００６】以上のように、高張力合金化溶融亜鉛メッ
キ鋼板に良好な加工性を付与する目的で、ＣＧＬ熱履歴
を限定し組織を制御する試みがいくつかなされてきた
が、ＣＧＬでは亜鉛メッキを施すという制約のために、
その熱履歴には自ずと制限が存在し、十分な加工性を付
与するに至っていない。As described above, several attempts have been made to limit the thermal history of CGL and control the microstructure for the purpose of imparting good workability to the high-strength hot-dip galvanized steel sheet. Because of the constraint that
The thermal history is naturally limited, and sufficient workability has not been imparted.
【０００７】本発明は従来技術の以上の様な問題に鑑み
創案されたもので、良好な加工性、特に高伸びフランジ
性を有する高張力合金化溶融亜鉛メッキ鋼板を低コスト
で、且つ安定して製造する方法を提供せんとするもので
ある。The present invention was devised in view of the above problems of the prior art, and it is a low-cost, stable, and high-strength galvannealed steel sheet having good workability, particularly high stretch flangeability. It is intended to provide a manufacturing method.
【０００８】[0008]
【課題を解決するための手段】そのため、発明者等はＣ
ＧＬ前組織と高張力合金化溶融亜鉛メッキ鋼板の加工性
との関係を鋭意検討し、その結果ＣＧＬ前組織を特定の
組織とすることによりＣＧＬ後の鋼板の加工性を従来の
それよりも向上させ、合金化溶融亜鉛メッキ処理に伴う
加工性の劣化という問題を有利に解決する方法を発明し
た。Therefore, the inventor et al.
The relationship between the pre-GL structure and the workability of the high-strength hot-dip galvanized steel sheet has been rigorously studied, and as a result, the pre-CGL structure has a specific structure, which improves the workability of the post-CGL steel plate over that of the conventional one. Thus, the inventors have invented a method for advantageously solving the problem of workability deterioration associated with the galvannealing treatment.
【０００９】即ち本発明法は、熱延条件を限定しＣＧＬ
前組織を調整することにより、合金化溶融亜鉛メッキ鋼
板の製造にあたって不可避的に加えられるＣＧＬ熱履歴
を経た後に優れた加工性、特に優れた伸びフランジ性を
有する高張力合金化溶融亜鉛メッキ鋼板を製造する方法
を提供するものであって、次の様な構成を有している。That is, the method of the present invention limits the hot rolling conditions to CGL.
By adjusting the pre-structure, a high-strength galvannealed steel sheet having excellent workability, particularly excellent stretch flangeability after undergoing CGL heat history that is inevitably added in the production of galvannealed steel sheet is produced. The present invention provides a manufacturing method, and has the following configuration.
【００１０】重量％でC：0.04〜0.10％、Si：0.005〜0.
15％、Mn：1.0〜2.0％、S：0.0002〜0.0010％、Sol.A
l：0.005〜0.050％、N：0.0010〜0.0030％を含有し、残
部Fe及び他の不可避的不純物からなる鋼に対し、Ar3〜
(Ar3＋50℃)を仕上げ温度として熱延を行ない、続いて
直ちに50〜200℃／sの冷却速度で620〜680℃の温度域に
冷却すると共に、その後3〜7秒保持し又は空冷し、次い
で50〜150℃／sの冷却速度で350〜450℃の温度に冷却し
て巻取り、酸洗後、Ac1〜（Ac1＋70℃）の（α＋γ）２
相共存域温度に5秒〜1分加熱均熱し、メッキ温度まで冷
却し溶融亜鉛メッキを施し、その後470〜550℃で合金化
処理し、冷却し、更に伸長率0.5〜3.0％の範囲でスキン
パスを行なう。これらの工程を経て、極めて微細なフェ
ライト相と低温変態相の複合組織からなる伸びフランジ
性に優れた高張力合金化溶融亜鉛メッキ鋼板が得られ
る。% By weight C: 0.04 to 0.10%, Si: 0.005 to 0.
15%, Mn: 1.0 to 2.0%, S: 0.0002 to 0.0010%, Sol.A
l: 0.005 to 0.050%, N: 0.0010 to 0.0030%, with the balance Ar 3 ~ against steel consisting of balance Fe and other unavoidable impurities
(Ar 3 + 50 ° C) is used as the finishing temperature for hot rolling, followed by immediate cooling to a temperature range of 620 to 680 ° C at a cooling rate of 50 to 200 ° C / s, followed by holding for 3 to 7 seconds or air cooling. Then, it is cooled to a temperature of 350 to 450 ° C. at a cooling rate of 50 to 150 ° C./s, wound up, pickled, and then (α + γ) 2 of Ac 1 to (Ac 1 + 70 ° C.).
Heat soak for 5 seconds to 1 minute at the phase coexistence zone, cool to the plating temperature, apply hot dip galvanizing, then alloy at 470 to 550 ° C, cool, and further skin pass in the range of 0.5 to 3.0% elongation. Do. Through these steps, a high-strength hot-dip galvanized steel sheet having an excellent stretch flangeability, which is composed of an extremely fine composite structure of a ferrite phase and a low temperature transformation phase, can be obtained.
【００１１】又、第２発明では上記構成に加えて添加元
素としてNbを含むもので、上記第１発明の鋼成分を有す
る他、Nb：0.005〜0.030wt％を含むものである。In addition, in the second invention, in addition to the above-mentioned constitution, Nb is contained as an additional element, and in addition to the steel component of the first invention, Nb: 0.005 to 0.030 wt% is contained.
【００１２】更に、第３発明では上記第１発明の構成に
於ける合金化処理の工程を誘導加熱により行なうもので
ある。Further, in the third invention, the step of alloying treatment in the constitution of the first invention is carried out by induction heating.
【００１３】一方、第４発明では上記第２発明の構成に
於ける合金化処理の工程を誘導加熱により行なうもので
ある。On the other hand, in the fourth invention, the alloying process in the structure of the second invention is carried out by induction heating.
【００１４】本発明は、熱延条件を限定しＣＧＬ前組織
を微細なフェライト＋ベイナイトの複合組織に作り込む
ことによって、ＣＧＬ後も良好な加工性、特に高伸びフ
ランジ性を有する鋼板が製造されるということを最大の
特徴としている。そこで、本発明を組織形成の観点から
説明する。According to the present invention, a steel sheet having good workability even after CGL, particularly high stretch flangeability, is manufactured by limiting hot rolling conditions and incorporating a pre-CGL structure into a fine ferrite + bainite composite structure. The biggest feature is that Therefore, the present invention will be described from the viewpoint of tissue formation.
【００１５】仕上げ圧延終了直後の急冷、中間温度での
保持又は空冷によって微細なオーステナイト相から微細
なフェライト相が生成する。この時の高い冷却速度は、
フェライト相の核生成を促進し、微細なフェライト相を
得るために重要である。又短時間の中間温度保持によっ
て、パーライトを生成させることなく、適量のフェライ
ト相を析出させることができる。そして巻取温度を350
〜450℃の間にすることで、微細なベイナイト相を第二
相とする複合組織を得ることができる。A fine ferrite phase is produced from a fine austenite phase by quenching immediately after finishing rolling, holding at an intermediate temperature or air cooling. The high cooling rate at this time is
It is important for promoting nucleation of the ferrite phase and obtaining a fine ferrite phase. Further, by maintaining the intermediate temperature for a short time, an appropriate amount of ferrite phase can be precipitated without generating pearlite. And the winding temperature is 350
By setting the temperature to be in the range of to 450 ° C, it is possible to obtain a composite structure having a fine bainite phase as the second phase.
【００１６】熱延後の組織をこのような微細なフェライ
ト＋ベイナイトの複合組織とすることにより、次なるＣ
ＧＬでのメッキ前焼鈍加熱時に微細なオーステナイト相
が生成し、このオーステナイト相は、メッキ浴、合金化
炉での熱履歴を経た後、微細な低温変態相を形成し、微
細なフェライト＋低温変態相の複合組織を持つ加工性、
特に伸びフランジ性の良好な、合金化溶融亜鉛メッキ鋼
板を得ることができる。しかし、仮にＣＧＬ前組織がパ
ーライトを含むと、再加熱後に微細な低温変態相が得ら
れず、加工性の良好な合金化溶融亜鉛メッキ鋼板を得る
ことができない。又ＣＧＬ前組織をマルテンサイトを含
む組織とすると、鋼板の形状制御性が悪くなりＣＧＬ通
板時に問題が生じることになる。By making the structure after hot rolling into such a fine ferrite + bainite composite structure, the following C
A fine austenite phase is generated during pre-plating annealing heating in GL, and this austenite phase forms a fine low-temperature transformation phase after passing through a heat history in a plating bath and an alloying furnace, and a fine ferrite + low-temperature transformation Workability with a composite structure of phases,
It is possible to obtain an alloyed hot-dip galvanized steel sheet having particularly good stretch flangeability. However, if the pre-CGL structure contains pearlite, a fine low-temperature transformation phase cannot be obtained after reheating, and a galvannealed steel sheet with good workability cannot be obtained. Further, when the pre-CGL structure is a structure containing martensite, the shape controllability of the steel sheet is deteriorated, which causes a problem during CGL passing.
【００１７】以下、本発明における構成要件の限定理由
を説明する。The reasons for limiting the constituents of the present invention will be described below.
【００１８】先ず、本発明による鋼板の化学成分範囲の
限定理由を説明する。First, the reason for limiting the chemical composition range of the steel sheet according to the present invention will be described.
【００１９】C：Cはベイナイトを生成させ、目標とする
強度を確保するために必須な元素である。本発明で対象
とする50〜60Kgf／mm2の強度を得るには、0.04％以上が
必要でありこれを下限とする。一方0.10％を超えると加
工性、溶接性が悪化するのでこれを上限とする。C: C is an essential element for forming bainite and securing a target strength. In order to obtain the strength of 50 to 60 Kgf / mm 2 targeted by the present invention, 0.04% or more is necessary, and this is the lower limit. On the other hand, if it exceeds 0.10%, the workability and weldability deteriorate, so this is the upper limit.
【００２０】Si：Siは0.15％を超えるとメッキ付着性が
悪化するので極力低減する。一方、製鋼での経済性を考
慮して0.005％を下限とした。Si: When Si exceeds 0.15%, the adhesion of the plating is deteriorated, so the content is reduced as much as possible. On the other hand, 0.005% was made the lower limit in consideration of economic efficiency in steelmaking.
【００２１】Mn：Mnはベイナイト組織形成に不可欠の元
素であり、固溶強化をもたらし、必要な強度と所望の組
織を得るためには少なくとも1.0％必要でありこれを下
限とする。一方、2.0％を超えると溶接性、加工性が悪
化するのでこれを上限とする。Mn: Mn is an indispensable element for bainite structure formation, and it is necessary to be at least 1.0% in order to bring about solid solution strengthening and to obtain necessary strength and a desired structure, and this is the lower limit. On the other hand, if it exceeds 2.0%, the weldability and workability deteriorate, so this is made the upper limit.
【００２２】S：SはMnとA系介在物を作り、伸びフラン
ジ性を低下させる不純物元素であるので、極力低減する
ことが望ましい。S量が0.0010％を超えた場合穴拡げ性
は悪化するのでこれを上限とした。一方製鋼での経済性
を考慮して0.0002％を下限とした。S: S is an impurity element that forms Mn and A type inclusions and deteriorates stretch flangeability, so it is desirable to reduce it as much as possible. If the S content exceeds 0.0010%, the hole expandability deteriorates, so this was made the upper limit. On the other hand, 0.0002% was made the lower limit in consideration of economic efficiency in steelmaking.
【００２３】Sol.Al：Sol.Alはその脱酸作用で鋼の清浄
度を高める効果が期待できる。添加量が0.005％に満た
ないとその添加効果に乏しいのでこれを下限とした。一
方0.050％を超えて添加してもその効果は飽和し、又メ
ッキ付着性が悪化するのでこれを上限とする。Sol.Al: Sol.Al can be expected to have the effect of increasing the cleanliness of steel by its deoxidizing action. If the addition amount is less than 0.005%, the effect of the addition is poor, so this was made the lower limit. On the other hand, even if added over 0.050%, the effect is saturated and the adhesion of the plating deteriorates, so this is the upper limit.
【００２４】N：Nは伸びフランジ性を劣化させる不純物
であるので、悪影響が顕著となる0.0030％を上限とし
た。一方、製鋼での経済性から0.0010％を下限とする。N: N is an impurity that deteriorates stretch-flange formability, so 0.0030% at which adverse effects are significant is set as the upper limit. On the other hand, 0.0010% is the lower limit because of the economics of steelmaking.
【００２５】Nb：Nbはその炭窒化物を析出させることに
より組織の微細化、析出強化が期待できる。添加量が0.
005％に満たないとその添加効果に乏しいのでこれを下
限とした。一方、0.030％を超えて添加してもその効果
は飽和し、又延性が悪化するのでこれを上限とした。Nb: Nb can be expected to have a finer structure and precipitation strengthening by precipitating its carbonitride. Addition amount is 0.
If less than 005%, the effect of addition is poor, so this was made the lower limit. On the other hand, even if added over 0.030%, the effect is saturated and the ductility deteriorates, so this was made the upper limit.
【００２６】次に、熱延条件及びＣＧＬ条件の限定理由
を説明する。Next, the reasons for limiting the hot rolling conditions and the CGL conditions will be described.
【００２７】仕上げ圧延温度：熱延終了後の組織を微細
なフェライト相とベイナイト相からなる複合組織とする
ためにオーステナイト相の微細化を図る必要がある。そ
のためにはAr3〜（Ar3＋50℃）の温度範囲で仕上げ圧延
を行なう必要がある。仕上げ圧延温度が（Ar3＋50℃）
を超えるとオーステナイト粒が粗大となり微細なフェラ
イトとベイナイトの複合組織が得られなくなり、加工性
が低下する。一方、仕上げ圧延温度がAr3未満ではフェ
ライト粒内に圧延歪が蓄積され加工性が劣化する。Finishing rolling temperature: It is necessary to refine the austenite phase in order to make the structure after the hot rolling a composite structure composed of a fine ferrite phase and a bainite phase. For that purpose, it is necessary to carry out finish rolling in the temperature range of Ar 3 to (Ar 3 + 50 ° C). Finish rolling temperature is (Ar 3 + 50 ℃)
If it exceeds, the austenite grains become coarse, and it becomes impossible to obtain a fine composite structure of ferrite and bainite, and the workability deteriorates. On the other hand, when the finish rolling temperature is less than Ar 3 , rolling strain is accumulated in the ferrite grains and workability deteriorates.
【００２８】本発明者らは、下記表１に示すＡ鋼を用い
て仕上げ温度〜（仕上げ温度＋50℃）の温度範囲での圧
下率と合金化溶融亜鉛メッキ鋼板の穴拡げ（λ値）の関
係を調査（他の条件は本発明条件として）し、図１に示
す結果を得た。The inventors of the present invention used the steel A shown in Table 1 below to determine the reduction ratio and the hole expansion (λ value) of the galvannealed steel sheet in the temperature range of finishing temperature to (finishing temperature + 50 ° C.). The relationship was investigated (other conditions are the conditions of the present invention), and the results shown in FIG. 1 were obtained.
【００２９】[0029]
【表１】 [Table 1]
【００３０】同図から明らかなように70％以上の圧下率
でλ値は非常に優れた値となるが、これは仕上げ圧延終
了直後の組織が十分に微細なオーステナイト相となるた
めと考えられる。ここで、90％を超える圧下はミル能力
からみて困難である。従って、仕上げ温度〜（仕上げ温
度＋50℃）の温度範囲で合計70〜90％の圧下率を採るこ
とが望ましい。As is clear from the figure, the λ value becomes extremely excellent at a rolling reduction of 70% or more, which is considered to be because the structure immediately after the finish rolling is a fine austenite phase. . Here, reduction of more than 90% is difficult from the viewpoint of mill capacity. Therefore, it is desirable to adopt a reduction rate of 70 to 90% in total in the temperature range of finishing temperature to (finishing temperature + 50 ° C).
【００３１】仕上げ圧延終了直後の急冷条件：本発明者
らは、前記表１に示すＡ鋼を用いて仕上げ圧延直後の冷
却速度と合金化溶融亜鉛メッキ鋼板の穴拡げ率（λ値）
の関係を調査（他の条件は本発明条件として）し、図２
に示す結果を得た。同図から明らかなように冷却速度が
50〜200℃／sの範囲のときλ値は良好な値を示す。しか
し冷却速度が50℃／s未満あるいは、200℃／sを超える
とλ値は低下する。これは冷却速度が50℃／sに満たな
いと、Ar3温度直上の仕上げ圧延で生じたオーステナイ
ト相から生成するフェライト相が十分に微細な状態とな
らないためと考えられる。また、冷却速度が200℃／sを
超えると次の中間保持温度の制御性が悪化するためλ値
が低下すると考えられる。以上の理由により、仕上げ圧
延直後の冷却速度を50℃／s〜200℃／sに限定する。Quenching conditions immediately after finish rolling: The inventors of the present invention used the A steels shown in Table 1 above to cool the steel sheet immediately after finish rolling and the hole expansion ratio (λ value) of the galvannealed steel sheet.
2 was investigated (other conditions are conditions of the present invention), and FIG.
The results shown in are obtained. As is clear from the figure, the cooling rate
In the range of 50 to 200 ° C / s, the λ value shows a good value. However, when the cooling rate is less than 50 ° C / s or more than 200 ° C / s, the λ value decreases. This is considered to be because if the cooling rate is less than 50 ° C / s, the ferrite phase generated from the austenite phase generated in the finish rolling just above the Ar 3 temperature will not be in a sufficiently fine state. Further, when the cooling rate exceeds 200 ° C./s, the controllability of the next intermediate holding temperature deteriorates, and it is considered that the λ value decreases. For the above reasons, the cooling rate immediately after finish rolling is limited to 50 ° C / s to 200 ° C / s.
【００３２】中間温度域での保持又は空冷条件：適量の
フェライト相を生成させるためには620〜680℃の温度域
で3〜7秒の保持が必要不可欠である。これは保持又は空
冷時間が3秒未満では必要なフェライト量が得られな
い。一方、実機での操業性、生産性を考慮して7秒をそ
の上限とした。Holding in the intermediate temperature range or air cooling conditions: In order to generate an appropriate amount of ferrite phase, it is essential to hold for 3 to 7 seconds in the temperature range of 620 to 680 ° C. If the holding or air cooling time is less than 3 seconds, the required amount of ferrite cannot be obtained. On the other hand, 7 seconds was set as the upper limit in consideration of operability and productivity on an actual machine.
【００３３】保持又は空冷から巻取温度までの冷却速
度：この工程の急冷速度の下限はパーライトの生成を避
けることから規定される。つまり冷却速度が50℃／s未
満ではパーライトノーズにかかり、適正な複合組織とな
らないため優れた伸びフランジ性が達成できない。一
方、150℃／sを超えると次の巻取温度の制御性が低下し
材質の安定性を低下させるためこれを上限とする。Cooling rate from holding or air cooling to coiling temperature: The lower limit of the quenching rate in this step is defined by avoiding the formation of pearlite. That is, when the cooling rate is less than 50 ° C / s, the pearlite nose is applied and an appropriate composite structure is not formed, so that excellent stretch flangeability cannot be achieved. On the other hand, if it exceeds 150 ° C / s, the controllability of the next winding temperature is lowered and the stability of the material is lowered, so this is made the upper limit.
【００３４】巻取温度：適正なＣＧＬ前組織、すなわち
微細なフェライト相とベイナイト相からなる複合組織を
得るために、巻取温度は350〜450℃としなければならな
い。巻取温度が450℃を超えるとパーライト相が生成
し、伸びフランジ性が低下する。一方、巻取温度が350
℃を下回るとマルテンサイト相が生成し、鋼板の形状制
御性が悪化する。Winding temperature: In order to obtain a proper CGL pre-structure, that is, a composite structure composed of a fine ferrite phase and a bainite phase, the winding temperature must be 350 to 450 ° C. When the coiling temperature exceeds 450 ° C, a pearlite phase is generated and stretch flangeability is deteriorated. On the other hand, the winding temperature is 350
When the temperature is lower than 0 ° C, a martensite phase is generated and the shape controllability of the steel sheet deteriorates.
【００３５】メッキ前焼鈍条件：本発明者らは、前記表
１に示すＡ鋼を用いてＣＧＬ焼鈍温度と合金化溶融亜鉛
メッキ鋼板の（TS×λ）の値との関係を調査（他の条件
は本発明条件として）し、図３に示す結果を得た。ここ
で（TS×λ）値は鋼板の強度−伸びフランジ性バランス
を示す。同図から明らかなように、焼鈍温度がAc1〜（A
c1＋70℃）の温度範囲のとき鋼板の強度−伸びフランジ
性バランスは最良となる。これは、熱延巻取後に微細な
フェライト相とベイナイト相の複合組織とした鋼板をAc
1〜（Ac1＋70℃）の温度範囲に加熱すると、微細なベイ
ナイト相より優先的にC濃度の高い微細なオーステナイ
ト相が形成され、これが冷却時に微細な低温変態相とな
り強度−伸びフランジ性バランスを良好にするためと考
えられる。一方、加熱温度がAc1温度より低いとオース
テナイト相が形成されず、ＣＧＬ後の組織に微細な低温
変態相が得られず強度が低下し、強度−伸びフランジ性
バランスは劣化するのでこの温度を下限とする。また、
加熱温度が（Ac1＋70℃）を超えると、オーステナイト
相中のC濃度が低下し、またオーステナイト相が粗大化
し、ＣＧＬ後の組織にパーライト相が形成され強度が低
下し、強度−伸びフランジ性バランスは劣化するのでこ
の温度を上限とする。さらに、Ac1〜（Ac1＋70℃）での
加熱時間が5秒〜1分のときにC濃度の高い微細なオース
テナイト相が形成される。加熱時間が5秒に満たない
と、十分なオーステナイト相が形成されずＣＧＬ後の強
度が低下するのでこれを下限とした。一方、加熱時間が
1分を超えるとオーステナイト相中のC濃度が低下し、ま
た微細なオーステナイト相が得られず、ＣＧＬ後の伸び
フランジ性が低下するのでこれを上限とした。Pre-plating annealing conditions: The present inventors investigated the relationship between the CGL annealing temperature and the value of (TS × λ) of the galvannealed steel sheet using the A steel shown in Table 1 (other The conditions were the conditions of the present invention), and the results shown in FIG. 3 were obtained. Here, the (TS × λ) value indicates the balance between strength and stretch flangeability of the steel sheet. As is clear from the figure, the annealing temperature is Ac 1 ~ (A
In the temperature range of c 1 + 70 ° C, the steel plate has the best balance of strength and stretch flangeability. This is a steel sheet having a composite structure of fine ferrite phase and bainite phase after hot rolling.
When heated to a temperature range of 1 to (Ac 1 + 70 ° C), a fine austenite phase with a higher C concentration is formed preferentially than a fine bainite phase, which becomes a fine low-temperature transformation phase during cooling, and strength-stretch flangeability balance. It is thought to be for improving. On the other hand, if the heating temperature is lower than the Ac 1 temperature, an austenite phase is not formed, a fine low-temperature transformation phase is not obtained in the structure after CGL, the strength decreases, and the strength-stretch flangeability balance deteriorates. The lower limit. Also,
When the heating temperature exceeds (Ac 1 + 70 ° C), the C concentration in the austenite phase decreases, the austenite phase becomes coarse, and the pearlite phase is formed in the structure after CGL, resulting in a decrease in strength and strength-stretch flangeability. Since the balance deteriorates, this temperature is set as the upper limit. Furthermore, a fine austenite phase having a high C concentration is formed when the heating time at Ac 1 to (Ac 1 + 70 ° C.) is 5 seconds to 1 minute. If the heating time is less than 5 seconds, a sufficient austenite phase is not formed and the strength after CGL decreases, so this was made the lower limit. On the other hand, the heating time
If it exceeds 1 minute, the C concentration in the austenite phase will decrease, and a fine austenite phase will not be obtained, and the stretch flangeability after CGL will decrease, so this was made the upper limit.
【００３６】合金化温度：メッキ後の合金化温度は470
〜550℃とする。合金化温度が470℃より低いと短時間に
十分な合金化が進まないためこの温度を下限とする。一
方、合金化温度が550℃を超えると合金化相中のFe％が
高くなり、加工性、耐食性が劣化するためこの温度を上
限とする。Alloying temperature: The alloying temperature after plating is 470.
~ 550 ℃ If the alloying temperature is lower than 470 ° C, sufficient alloying does not proceed in a short time, so this temperature is made the lower limit. On the other hand, if the alloying temperature exceeds 550 ° C, the Fe% in the alloying phase becomes high, and the workability and corrosion resistance deteriorate, so this temperature is made the upper limit.
【００３７】誘導加熱による合金化：図４は、前記表１
中のＡ鋼及びＥ鋼を用いて、合金化をガスバーナ加熱炉
と誘導加熱炉で行い、（他の条件は本発明条件として）
合金化溶融亜鉛メッキ鋼板の穴拡げ率（λ値）を比較し
たものである。同図から、合金化処理を誘導加熱で行な
うことによりより優れたλ値が得られることがわかる。
これは、誘導加熱炉では鋼板表面だけを加熱できるため
鋼板の加工性がさらに向上するものと考えられる。Alloying by induction heating: FIG.
Alloying was carried out in the gas burner heating furnace and the induction heating furnace by using the A steel and the E steel in the inside (other conditions are the conditions of the present invention).
It is a comparison of the hole expansion ratios (λ values) of alloyed hot-dip galvanized steel sheets. From the figure, it is understood that a better λ value can be obtained by performing the alloying treatment by induction heating.
It is considered that this is because the workability of the steel sheet is further improved because only the surface of the steel sheet can be heated in the induction heating furnace.
【００３８】スキンパス伸長率：図５に、前記表１に示
された本発明のＡ鋼を用いて、本発明の熱延条件及びＣ
ＧＬ条件で製造した板厚2.6mmの合金化溶融亜鉛メッキ
鋼板にスキンパスを行ったときの穴拡げ率に及ぼすスキ
ンパス伸長率の影響を示した。この図より、合金化溶融
亜鉛メッキを施した鋼板に伸長率0.5〜3.0％のスキンパ
スを施すと、伸びフランジ性がさらに向上することがわ
かる。このスキンパスによる伸びフランジ性の改善効果
の原因は必ずしも明確でないが、表面粗さの低下が伸び
フランジ成形に良好に作用するためであろうと考えられ
る。伸長率が0.5％未満であると伸びフランジ性の改善
効果は小さくこれを下限とした。一方、伸長率が3.0％
を超えると伸びフランジ性は劣化するのでこれを上限と
した。Skin pass elongation: In FIG. 5, using the A steel of the present invention shown in Table 1 above, the hot rolling conditions and C of the present invention were used.
The influence of the skin pass elongation rate on the hole expansion rate when skin passing was performed on a 2.6 mm thick galvannealed steel sheet produced under the GL condition was shown. From this figure, it can be seen that stretch flangeability is further improved by applying a skin pass having an elongation rate of 0.5 to 3.0% to a steel sheet that has undergone galvannealing. The cause of the improvement effect of stretch flangeability due to this skin pass is not always clear, but it is considered that the decrease in surface roughness is likely to work well for stretch flange forming. If the elongation rate is less than 0.5%, the effect of improving the stretch flangeability is small, and this was made the lower limit. On the other hand, the growth rate is 3.0%
If it exceeds, the stretch flangeability deteriorates, so this was made the upper limit.
【００３９】[0039]
【実施例】以下本発明法の具体的実施例につき詳述す
る。EXAMPLES Hereinafter, specific examples of the method of the present invention will be described in detail.
【００４０】＜実施例 １＞発明者等は、まず前記表１
に示す成分組成を有する１０種の鋼を溶製した。このう
ち鋼Ａ〜Ｅが本発明規定成分を満足する鋼であり、鋼Ｆ
〜Ｊは比較鋼である。このＡ〜Ｊの鋼を表２の条件（本
発明で規定された範囲内）で熱延・酸洗・メッキ・合金
化・スキンパスを行い、板厚2.6mmの合金化溶融亜鉛メ
ッキ鋼板を製造した。<Example 1> The inventors of the present invention first set out Table 1 above.
Ten kinds of steel having the composition shown in Table 1 were melted. Of these, Steels A to E are steels satisfying the composition stipulated in the present invention and Steel F
~ J are comparative steels. The steels A to J are hot-rolled, pickled, plated, alloyed, and skin-passed under the conditions shown in Table 2 (within the range specified in the present invention) to produce an alloyed hot-dip galvanized steel sheet having a plate thickness of 2.6 mm. did.
【００４１】[0041]
【表２】 [Table 2]
【００４２】これらの鋼板の機械的性質を調べるために
引張試験、穴拡げ試験を行い、その結果を表３に示し
た。なお、同表では穴拡げ試験で伸びフランジ性を評価
している。Tensile tests and hole expansion tests were carried out in order to investigate the mechanical properties of these steel sheets, and the results are shown in Table 3. In addition, in the same table, the stretch flangeability is evaluated by the hole expansion test.
【００４３】[0043]
【表３】 [Table 3]
【００４４】ここで、穴拡げ率(λ)とは前記合金化溶融
亜鉛メッキ鋼板に直径10mmの円形の穴を打抜き、この穴
に60゜円錐ポンチを押し当て穴拡げ加工を行い、穴縁に
亀裂を生じた時点での穴の拡大率のことであり、次式に
よって計算した。
λ(％)＝｛(ｄb−ｄi)／ｄi｝×100
但し、ｄiは初期穴径(mm)、ｄbは亀裂発生時穴径(mm)を
それぞれ表す。Here, the hole expansion ratio (λ) means that a circular hole having a diameter of 10 mm is punched out from the above-mentioned galvannealed steel sheet, and a 60 ° conical punch is pressed against this hole to expand the hole. It is the expansion ratio of the hole at the time when a crack was generated, and was calculated by the following formula. λ (%) = {(d b −d i ) / d i } × 100, where d i is the initial hole diameter (mm) and d b is the hole diameter (mm) at the time of crack initiation.
【００４５】同表から本発明で規定された成分組成を有
するＡ〜Ｅの鋼では、強度−延性バランスを示す(TS×E
l)の値が1700Kgf／mm2・％以上で且つ強度−伸びフラン
ジ性バランスを示す(TS×λ)の値が6000Kgf／mm2・％以
上の高い値を有する50〜60Kgf／mm2級の強度レベルの伸
びフランジ性に優れた合金化溶融亜鉛メッキ鋼板が得ら
れることがわかる。特に、鋼ＥのNb添加鋼を用いた実施
例５によって得られた鋼板は、より優れた伸びフランジ
性を示すことがわかる。From the table, the steels A to E having the composition defined in the present invention show a strength-ductility balance (TS × E).
l) value of 1700 Kgf / mm 2 ·% or more and strength-stretch flangeability balance (TS × λ) value of 6000 Kgf / mm 2 ·% or more high value of 50-60 Kgf / mm 2 class It can be seen that an alloyed hot-dip galvanized steel sheet excellent in strength level stretch flangeability is obtained. In particular, it can be seen that the steel sheet obtained in Example 5 using Nb-added steel of Steel E exhibits more excellent stretch flangeability.
【００４６】これに対して、鋼の組成が本発明から外れ
ている鋼Ｆ、Ｉ、Ｊの比較例６、９、１０の合金化溶融
メッキ鋼板は、(TS×λ)が5000Kgf／mm2・％程度であっ
て伸びフランジ性が低い。これは微細なフェライトと低
温変態相よりなる最適な複合組織が得られていないため
である。Mn含有量の低い鋼Ｈの比較例８では、強度が不
足し、伸びフランジ性も劣る。また、Si含有量の高い鋼
Ｇの比較例７では、機械特性は良好であるがメッキ付着
性が不良となる。On the other hand, the alloyed hot-dip plated steel sheets of Comparative Examples 6, 9 and 10 of Steels F, I and J whose steel compositions are out of the present invention have (TS × λ) of 5000 Kgf / mm 2・ It is about% and stretch flangeability is low. This is because the optimum composite structure consisting of fine ferrite and low temperature transformation phase has not been obtained. In Comparative Example 8 of Steel H having a low Mn content, the strength is insufficient and the stretch flangeability is poor. Further, in Comparative Example 7 of Steel G having a high Si content, the mechanical properties are good, but the plating adhesion is poor.
【００４７】＜実施例 ２＞前記した表１のＡ〜Ｄ鋼を
用いて表４に示すように熱延、焼鈍、合金化、スキンパ
スの各条件を種々変化させて板厚2.6mmの合金化溶融亜
鉛メッキ鋼板を製造した。このようにして得られた鋼板
の機械試験値を表５に示す。<Example 2> Using the steels A to D shown in Table 1, as shown in Table 4, various conditions such as hot rolling, annealing, alloying, and skin pass were variously changed to form an alloy having a plate thickness of 2.6 mm. A galvanized steel sheet was manufactured. Table 5 shows the mechanical test values of the steel sheet thus obtained.
【００４８】[0048]
【表４】 [Table 4]
【００４９】[0049]
【表５】 [Table 5]
【００５０】本発明で規定された範囲内の条件で製造さ
れた本発明例１１〜１８では、強度−延性バランスを示
す（TS×El）の値が1700Kgf／mm2・％以上で且つ強度−
伸びフランジ性バランスを示す（TS×λ）の値が6000Kg
f／mm2・％以上の高い値を有する50〜60Kgf／mm2級の強
度レベルの伸びフランジ性に優れた合金化溶融亜鉛メッ
キ鋼板が得られている。一方本発明法の熱延、焼鈍、合
金化、スキンパスの各条件のいずれかを満足していない
比較例１９〜２１、２４〜３３、３５、３６では、（TS
×λ）の値は6000Kgf／mm2・％以下で、本発明例に比べ
て強度−伸びフランジ性バランスが劣る。これは、比較
例では本発明でいう組織の適正化が達成されていないた
めであると考えられる。また、中間保持温度の低い比較
例２２、２３では伸びフランジ性は良好であるが、（TS
×El）の値が1600Kgf／mm2・％以下で、強度−延性バラ
ンスが劣る。また、合金化処理温度の低い比較例３４で
は合金化不良となる。In Examples 11 to 18 of the present invention produced under the conditions within the range specified in the present invention, the value of (TS × El) indicating the strength-ductility balance was 1700 Kgf / mm 2 ·% or more and the strength-
The value of (TS x λ) showing stretch flangeability balance is 6000 kg
An alloyed hot-dip galvanized steel sheet having a high value of f / mm 2 ·% or more and a strength level of 50 to 60 kgf / mm 2 grade and excellent stretch flangeability has been obtained. On the other hand, in Comparative Examples 19 to 21, 24 to 33, 35 and 36 which do not satisfy any of the conditions of hot rolling, annealing, alloying and skin pass of the method of the present invention, (TS
The value of x λ) is 6000 Kgf / mm 2 ·% or less, and the strength-stretch flangeability balance is inferior as compared with the inventive examples. This is considered to be because the optimization of the structure referred to in the present invention has not been achieved in the comparative example. Further, in Comparative Examples 22 and 23 having a low intermediate holding temperature, the stretch flangeability is good, but (TS
XEl) is 1600 Kgf / mm 2 ·% or less, the strength-ductility balance is poor. Further, in Comparative Example 34 in which the alloying treatment temperature is low, alloying fails.
【００５１】[0051]
【発明の効果】以上説明したように、この本発明によれ
ば、現行の熱間圧延工程、連続合金化溶融亜鉛メッキ工
程に格別な変更を加えることなく、しかも格別に高価な
素材を使用せずに加工性、特に伸びフランジ性に優れた
高張力合金化溶融亜鉛メッキ鋼板を低コストで、且つ安
定して製造することができるようになる。As described above, according to the present invention, it is possible to use a particularly expensive material without making any special changes to the existing hot rolling process and continuous galvannealing process. It becomes possible to stably manufacture a high-strength alloyed hot-dip galvanized steel sheet excellent in workability, especially stretch flangeability, at low cost.
【図１】仕上げ温度〜（仕上げ温度＋50℃）の温度範囲
での圧下率と伸びフランジ性（穴拡げ率）の関係を示す
グラフである。FIG. 1 is a graph showing a relationship between a rolling reduction and a stretch flangeability (hole expansion rate) in a temperature range of finishing temperature to (finishing temperature + 50 ° C.).
【図２】仕上げ圧延直後の冷却速度と伸びフランジ性
（穴拡げ率）の関係を示すグラフである。FIG. 2 is a graph showing the relationship between the cooling rate immediately after finish rolling and the stretch flangeability (hole expansion rate).
【図３】ＣＧＬ焼鈍温度と強度−伸びフランジ性バラン
ス（TS×λ）の関係を示すグラフである。FIG. 3 is a graph showing the relationship between CGL annealing temperature and strength-stretch flangeability balance (TS × λ).
【図４】合金化処理の加熱方法と伸びフランジ性（穴拡
げ率）の関係を示すグラフである。FIG. 4 is a graph showing a relationship between a heating method of alloying treatment and stretch flangeability (hole expansion rate).
【図５】スキンパス伸長率と伸びフランジ性（穴拡げ
率）の関係を示すグラフである。FIG. 5 is a graph showing the relationship between the skin pass expansion ratio and the stretch flangeability (hole expansion ratio).
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.7 識別記号 ＦＩ Ｃ２２Ｃ 38/06 Ｃ２２Ｃ 38/06 Ｃ２３Ｃ 2/06 Ｃ２３Ｃ 2/06 2/28 2/28 (72)発明者 木下 正行 東京都千代田区丸の内一丁目１番２号 日本鋼管株式会社内 (72)発明者 大北 智良 東京都千代田区丸の内一丁目１番２号 日本鋼管株式会社内 (56)参考文献 特開 昭56−136928（ＪＰ，Ａ) 特開 昭57−145925（ＪＰ，Ａ) 特開 昭56−133424（ＪＰ，Ａ) 特開 昭60−184629（ＪＰ，Ａ) 特開 昭57−116767（ＪＰ，Ａ) (58)調査した分野(Int.Cl.7，ＤＢ名) C21D 9/46 C21D 8/02 C22C 38/00 301 C22C 38/06 C23C 2/06 C23C 2/28 ─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. 7 Identification Code FI C22C 38/06 C22C 38/06 C23C 2/06 C23C 2/06 2/28 2/28 (72) Inventor Masayuki Kinoshita Chiyoda, Tokyo Marunouchi 1-2-2 Nippon Steel Pipe Co., Ltd. (72) Inventor Tomoyoshi Okita 1-2-12 Marunouchi Marunouchi, Tokyo Chiyoda-ku Nippon Steel Pipe Co., Ltd. (56) Reference JP-A-56-136928 (JP , A) JP 57-145925 (JP, A) JP 56-133424 (JP, A) JP 60-184629 (JP, A) JP 57-116767 (JP, A) (58) Fields investigated (Int.Cl. 7 , DB name) C21D 9/46 C21D 8/02 C22C 38/00 301 C22C 38/06 C23C 2/06 C23C 2/28
Claims (4)
0.15％、Mn：1.0〜2.0％、S：0.0002〜0.0010％、Sol.A
l：0.005〜0.050％、N：0.0010〜0.0030％を含有し、残
部Fe及び他の不可避的不純物からなる鋼に対し、Ar3〜
(Ar3＋50℃)を仕上げ温度として熱延を行ない、続いて
直ちに50〜200℃／sの冷却速度で620〜680℃の温度域に
冷却すると共に、その後3〜7秒保持し又は空冷し、次い
で50〜150℃／sの冷却速度で350〜450℃の温度に冷却し
て巻取り、酸洗後、Ac1〜（Ac1＋70℃）の（α＋γ）２
相共存域温度に5秒〜1分加熱均熱し、メッキ温度まで冷
却し溶融亜鉛メッキを施し、その後470〜550℃で合金化
処理し、冷却し、更に伸長率0.5〜3.0％の範囲でスキン
パスを行なうことを特徴とする伸びフランジ性に優れた
高張力合金化溶融亜鉛メッキ鋼板の製造方法。1. C: 0.04 to 0.10% by weight%, Si: 0.005 to
0.15%, Mn: 1.0 to 2.0%, S: 0.0002 to 0.0010%, Sol.A
l: 0.005 to 0.050%, N: 0.0010 to 0.0030%, with the balance Ar 3 ~ against steel consisting of balance Fe and other unavoidable impurities
(Ar 3 + 50 ° C) is used as the finishing temperature for hot rolling, followed by immediate cooling to a temperature range of 620 to 680 ° C at a cooling rate of 50 to 200 ° C / s, followed by holding for 3 to 7 seconds or air cooling. Then, it is cooled to a temperature of 350 to 450 ° C. at a cooling rate of 50 to 150 ° C./s, wound up, pickled, and then (α + γ) 2 of Ac 1 to (Ac 1 + 70 ° C.).
Heat soak for 5 seconds to 1 minute at the phase coexistence zone, cool to the plating temperature, apply hot dip galvanizing, then alloy at 470 to 550 ° C, cool, and further skin pass in the range of 0.5 to 3.0% elongation. A method for producing a high-strength galvannealed steel sheet having excellent stretch flangeability, which comprises performing
0.15％、Mn：1.0〜2.0％、S：0.0002〜0.0010％、Sol.A
l：0.005〜0.050％、N：0.0010〜0.0030％、Nb:0.005〜
0.030％を含有し、残部Fe及び他の不可避的不純物から
なる鋼に対し、Ar3〜(Ar3＋50℃)を仕上げ温度として熱
延を行ない、続いて直ちに50〜200℃／sの冷却速度で62
0〜680℃の温度域に冷却すると共に、その後3〜7秒保持
し又は空冷し、次いで50〜150℃／sの冷却速度で350〜4
50℃の温度に冷却して巻取り、酸洗後、Ac1〜（Ac1＋70
℃）の（α＋γ）２相共存域温度に5秒〜1分加熱均熱
し、メッキ温度まで冷却し溶融亜鉛メッキを施し、その
後470〜550℃で合金化処理し、冷却し、更に伸長率0.5
〜3.0％の範囲でスキンパスを行なうことを特徴とする
伸びフランジ性に優れた高張力合金化溶融亜鉛メッキ鋼
板の製造方法。2. C: 0.04 to 0.10% by weight%, Si: 0.005 to
0.15%, Mn: 1.0 to 2.0%, S: 0.0002 to 0.0010%, Sol.A
l: 0.005 to 0.050%, N: 0.0010 to 0.0030%, Nb: 0.005 to
For steel containing 0.030% and balance Fe and other unavoidable impurities, hot rolling is performed with Ar 3 ~ (Ar 3 + 50 ° C) as finishing temperature, and then immediately cooling rate of 50 ~ 200 ° C / s. At 62
While cooling in the temperature range of 0 ~ 680 ℃, then hold or air cooling for 3 ~ 7 seconds, then 350 ~ 4 at a cooling rate of 50 ~ 150 ℃ / s.
After cooling to a temperature of 50 ° C, winding and pickling, Ac 1 to (Ac 1 +70
℃) (α + γ) two-phase coexistence zone temperature soaking for 5 seconds to 1 minute, cooling to the plating temperature and hot dip galvanizing, then alloying at 470 to 550 ℃, cooling, and elongation 0.5
A method for producing a high-strength galvannealed steel sheet with excellent stretch-flangeability, characterized by performing skin pass in the range of up to 3.0%.
0.15％、Mn：1.0〜2.0％、S：0.0002〜0.0010％、Sol.A
l：0.005〜0.050％、N：0.0010〜0.0030％を含有し、残
部Fe及び他の不可避的不純物からなる鋼に対し、Ar3〜
(Ar3＋50℃)を仕上げ温度として熱延を行ない、続いて
直ちに50〜200℃／sの冷却速度で620〜680℃の温度域に
冷却すると共に、その後3〜7秒保持し又は空冷し、次い
で50〜150℃／sの冷却速度で350〜450℃の温度に冷却し
て巻取り、酸洗後、Ac1〜（Ac1＋70℃）の（α＋γ）２
相共存域温度に5秒〜1分加熱均熱し、メッキ温度まで冷
却し溶融亜鉛メッキを施し、その後470〜550℃で誘導加
熱を行なって合金化処理し、冷却し、更に伸長率0.5〜
3.0％の範囲でスキンパスを行なうことを特徴とする伸
びフランジ性に優れた高張力合金化溶融亜鉛メッキ鋼板
の製造方法。3. C: 0.04 to 0.10% by weight%, Si: 0.005 to
0.15%, Mn: 1.0 to 2.0%, S: 0.0002 to 0.0010%, Sol.A
l: 0.005 to 0.050%, N: 0.0010 to 0.0030%, with the balance Ar 3 ~ against steel consisting of balance Fe and other unavoidable impurities
(Ar 3 + 50 ° C) is used as the finishing temperature for hot rolling, followed by immediate cooling to a temperature range of 620 to 680 ° C at a cooling rate of 50 to 200 ° C / s, followed by holding for 3 to 7 seconds or air cooling. Then, it is cooled to a temperature of 350 to 450 ° C. at a cooling rate of 50 to 150 ° C./s, wound up, pickled, and then (α + γ) 2 of Ac 1 to (Ac 1 + 70 ° C.).
Heat soak for 5 seconds to 1 minute at the phase coexisting zone temperature, cool to the plating temperature and apply hot dip galvanizing, then induction heat at 470 to 550 ° C for alloying, cooling, and elongation 0.5 to
A method for producing a high-strength hot-dip galvanized steel sheet having excellent stretch-flangeability, which comprises performing a skin pass in a range of 3.0%.
0.15％、Mn：1.0〜2.0％、S：0.0002〜0.0010％、Sol.A
l：0.005〜0.050％、N：0.0010〜0.0030％、Nb:0.005〜
0.030％を含有し、残部Fe及び他の不可避的不純物から
なる鋼に対し、Ar3〜(Ar3＋50℃)を仕上げ温度として熱
延を行ない、続いて直ちに50〜200℃／sの冷却速度で62
0〜680℃の温度域に冷却すると共に、その後3〜7秒保持
し又は空冷し、次いで50〜150℃／sの冷却速度で350〜4
50℃の温度に冷却して巻取り、酸洗後、Ac1〜（Ac1＋70
℃）の（α＋γ）２相共存域温度に5秒〜1分加熱均熱
し、メッキ温度まで冷却し溶融亜鉛メッキを施し、その
後470〜550℃で誘導加熱を行なって合金化処理し、冷却
し、更に伸長率0.5〜3.0％の範囲でスキンパスを行なう
ことを特徴とする伸びフランジ性に優れた高張力合金化
溶融亜鉛メッキ鋼板の製造方法。4. C: 0.04 to 0.10% by weight%, Si: 0.005 to
0.15%, Mn: 1.0 to 2.0%, S: 0.0002 to 0.0010%, Sol.A
l: 0.005 to 0.050%, N: 0.0010 to 0.0030%, Nb: 0.005 to
For steel containing 0.030% and balance Fe and other unavoidable impurities, hot rolling is performed with Ar 3 ~ (Ar 3 + 50 ° C) as finishing temperature, and then immediately cooling rate of 50 ~ 200 ° C / s. At 62
While cooling in the temperature range of 0 ~ 680 ℃, then hold or air cooling for 3 ~ 7 seconds, then 350 ~ 4 at a cooling rate of 50 ~ 150 ℃ / s.
After cooling to a temperature of 50 ° C, winding and pickling, Ac 1 to (Ac 1 +70
℃) (α + γ) two-phase coexisting zone temperature soaking for 5 seconds to 1 minute, cooling to the plating temperature and hot dip galvanizing, and then induction heating at 470 to 550 ° C for alloying and cooling. And a method for producing a high-strength hot-dip galvanized steel sheet having excellent stretch-flange formability, which is characterized by further performing a skin pass in the range of an elongation rate of 0.5 to 3.0%.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP23688291A JP3376590B2 (en) | 1991-08-26 | 1991-08-26 | Method for producing high tensile alloyed hot-dip galvanized steel sheet with excellent stretch flangeability |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP23688291A JP3376590B2 (en) | 1991-08-26 | 1991-08-26 | Method for producing high tensile alloyed hot-dip galvanized steel sheet with excellent stretch flangeability |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0551647A JPH0551647A (en) | 1993-03-02 |
| JP3376590B2 true JP3376590B2 (en) | 2003-02-10 |
Family
ID=17007185
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP23688291A Expired - Fee Related JP3376590B2 (en) | 1991-08-26 | 1991-08-26 | Method for producing high tensile alloyed hot-dip galvanized steel sheet with excellent stretch flangeability |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3376590B2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| TW504519B (en) | 1999-11-08 | 2002-10-01 | Kawasaki Steel Co | Hot dip galvanized steel plate excellent in balance of strength and ductility and in adhesiveness between steel and plating layer, and method for producing the same |
| CN105543682A (en) * | 2015-12-22 | 2016-05-04 | 本钢板材股份有限公司 | Hot-rolled pickled plate used for automobile structure |
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1991
- 1991-08-26 JP JP23688291A patent/JP3376590B2/en not_active Expired - Fee Related
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| Publication number | Publication date |
|---|---|
| JPH0551647A (en) | 1993-03-02 |
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