JP3530355B2 - High-strength hot-rolled steel sheet with high dynamic deformation resistance for impact absorption at the time of collision and manufacturing method thereof - Google Patents
High-strength hot-rolled steel sheet with high dynamic deformation resistance for impact absorption at the time of collision and manufacturing method thereofInfo
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- JP3530355B2 JP3530355B2 JP25888797A JP25888797A JP3530355B2 JP 3530355 B2 JP3530355 B2 JP 3530355B2 JP 25888797 A JP25888797 A JP 25888797A JP 25888797 A JP25888797 A JP 25888797A JP 3530355 B2 JP3530355 B2 JP 3530355B2
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- steel sheet
- rolled steel
- deformation resistance
- deformation
- Prior art date
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Classifications
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- 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
- Heat Treatment Of Steel (AREA)
- Heat Treatment Of Sheet Steel (AREA)
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、自動車部材等に使
用され、衝突時の衝撃エネルギーを効率よく吸収するこ
とによって乗員の安全性確保に寄与することの出来る高
い動的変形抵抗を示す衝突時衝撃吸収用高強度熱延鋼板
とその製造方法に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for automobile members and the like, and at the time of collision showing high dynamic deformation resistance which can contribute to ensuring safety of passengers by efficiently absorbing impact energy at the time of collision. The present invention relates to a high-strength hot-rolled steel sheet for impact absorption and a method for manufacturing the same.
【０００２】[0002]
【従来の技術】近年、自動車衝突時の乗員保護が自動車
の最重要性能として認識され、それに対応するための高
い高速変形抵抗を示す材料への期待が高まっている。例
えば乗用車の前面衝突においては、フロントサイドメン
バーと呼ばれる部材にこの様な材料を適用すれば、該部
材が圧潰することで衝撃のエネルギーが吸収され、乗員
にかかる衝撃を和らげることが出来る。2. Description of the Related Art In recent years, occupant protection in the event of an automobile collision has been recognized as the most important performance of an automobile, and there is an increasing expectation for a material having a high high-speed deformation resistance in order to cope with it. For example, in the case of a frontal collision of a passenger car, if such a material is applied to a member called a front side member, the energy of the shock is absorbed when the member is crushed, and the shock applied to the occupant can be softened.
【０００３】自動車の衝突時に各部位が受ける変形の歪
み速度は１０3 （１／ｓ）程度まで達するため、材料の
衝撃吸収性能を考える場合には、この様な高歪み速度領
域での動的変形特性の解明が必要である。また同時に、
省エネルギー、ＣＯ2 排出削減を目指して自動車車体の
軽量化を同時に達成することが必須と考えられ、このた
めに有効な高強度鋼板へのニーズが高まっている。Since the strain rate of deformation which each part receives at the time of a collision of an automobile reaches up to about 10 3 (1 / s), when considering the shock absorbing performance of a material, dynamic strain in such a high strain rate range is considered. It is necessary to clarify the deformation characteristics. At the same time,
At the same time, it is indispensable to achieve the weight reduction of the automobile body aiming at energy saving and reduction of CO 2 emission, and for this reason, there is a growing need for effective high strength steel sheets.
【０００４】例えば本発明者らは、CAMP-ISIJ Vol.9 (1
996) p.1112 〜1115に、高強度薄鋼板の高速変形特性と
衝撃エネルギー吸収能について報告し、その中で、１０
3 （１／ｓ）程度の高歪み速度領域での動的強度は、１
０-3（１／ｓ）の低歪み速度での静的強度と比較して大
きく上昇すること、材料の強化機構によって変形抵抗の
歪み速度依存性が変化すること、この中で、ＴＲＩＰ
（変態誘起塑性）型の鋼やＤＰ（フェライト／マルテン
サイト２相）型の鋼が他の高強度鋼板に比べて優れた成
形性と衝撃吸収能を兼ね備えていることを報告してい
る。For example, the present inventors have found that CAMP-ISIJ Vol.9 (1
996) p.1112 to 1115, we report high-speed deformation characteristics and impact energy absorption capacity of high strength thin steel sheets.
The dynamic strength in the high strain rate region of 3 (1 / s) is 1
A large increase compared to static strength at a low strain rate of 0 -3 (1 / s), and a strain rate dependence of deformation resistance changes due to the strengthening mechanism of the material.
It has been reported that the (transformation-induced plasticity) type steel and the DP (ferrite / martensite two-phase) type steel have both excellent formability and impact absorbing ability as compared with other high strength steel sheets.
【０００５】また、残留オーステナイトを含む耐衝撃特
性に優れた高強度鋼板とその製造方法を提供するものと
して、特開平７−１８３７２号公報には、衝撃吸収能を
変形速度の上昇に伴う降伏応力の上昇のみで解決できる
ことを開示しているが衝撃吸収能を向上させるために、
残留オーステナイトの量以外に残留オーステナイトの性
質をどのように制御すべきかは依然として明確にされて
いない。Further, Japanese Patent Laid-Open No. 7-18372 discloses a high-strength steel sheet containing retained austenite and excellent in impact resistance and a method for producing the same, in which a shock absorption capacity is increased and a yield stress is increased with an increase in deformation rate. Although it is disclosed that it can be solved only by raising, in order to improve shock absorption capacity,
It is still unclear how to control the properties of retained austenite other than the amount of retained austenite.
【０００６】[0006]
【発明が解決しようとする課題】このように、自動車衝
突時の衝撃エネルギーの吸収に及ぼす部材構成材料の動
的変形特性は少しづつ解明されつつあるものの、衝撃エ
ネルギー吸収能に優れた自動車部品用鋼材としてどのよ
うな特性に注目し、どのような基準に従って材料選定を
行うべきかは未だ明らかにされていない。また、自動車
用部品は、鋼材をプレス成形によって要求された部品形
状に成形され、その後、一般的には塗装焼き付けされた
後に自動車に組み込まれ、実際の衝突現象に直面する。
しかしながら、このような予変形＋焼き付け処理を行っ
た後の鋼材の衝突時の衝突エネルギー吸収能の向上にど
のような鋼材強化機構が適しているかも未だ明らかにさ
れていない。As described above, although the dynamic deformation characteristics of the material constituting the members that affect the absorption of impact energy in the event of an automobile collision are being elucidated little by little, it is for automobile parts having excellent impact energy absorption ability. It has not yet been clarified what characteristics should be paid attention to as a steel material and what criteria should be used for material selection. Further, automobile parts are formed into a required part shape by press forming a steel material, and then are generally baked in a paint and then incorporated into an automobile to face an actual collision phenomenon.
However, it has not yet been clarified what kind of steel material strengthening mechanism is suitable for improving the collision energy absorption capacity at the time of collision of steel materials after such pre-deformation + baking treatment.
【０００７】[0007]
【課題を解決するための手段】本発明は、フロントサイ
ドメンバー等の衝突時の衝撃エネルギー吸収を担う部品
に成形加工されて使用される鋼材で、高い衝撃エネルギ
ー吸収能を示す高強度鋼板とその製造方法を提供するこ
とを目的としている。その要旨は次のとおりである。DISCLOSURE OF THE INVENTION The present invention is a steel material that is used by being formed into a part that absorbs impact energy at the time of collision, such as a front side member, and a high-strength steel sheet that exhibits a high impact energy absorption capacity. It is intended to provide a manufacturing method. The summary is as follows.
【０００８】（１）重量％で、Ｃ：０．０４％以上０．
３％以下、ＳｉとＡｌの一方または双方を合計で０．５
％以上３．０％以下、Ｍｎ，Ｎｉ，Ｃｒ，Ｃｕ，Ｍｏの
１種または２種以上を合計で０．５％以上３．５％以下
含み、残部がＦｅ及び不可避的不純物からなり、最終的
に得られる冷延鋼板のミクロ組織がフェライトおよびベ
イナイトを含み、このいずれかを主相とし、体積分率で
３％以上の残留オーステナイトを含む第３相との複合組
織であり、残留オーステナイト中の固溶〔Ｃ〕量と鋼材
の平均Ｍｎ等量｛Ｍｎｅｑ＝Ｍｎ＋（Ｎｉ＋Ｃｒ＋Ｃｕ
＋Ｍｏ）／２｝によって決まる値（Ｍ＝６７８−４２８
×〔Ｃ〕−３３×Ｍｎｅｑ）が７０以上２５０以下で、
５９７ MPa 以上の引張り強度を有し、その鋼材に相当歪
みで０％超１０％以下の予変形を与えた後、５×１０2
〜５×１０3 （１／ｓ）の歪み速度範囲で変形した時の
３〜１０％の相当歪み範囲における変形応力の平均値：
σｄｙｎ（ＭＰａ）が予変形を与える前の５×１０-4〜
５×１０-3（１／ｓ）の歪み速度範囲で測定された静的
な引張り試験における最大応力ＴＳ(MPa) によって表現
される式：σdyn ≧０．７６６×ＴＳ＋２５０を特徴と
する高い動的変形抵抗を有する衝突時衝撃吸収用高強度
熱延鋼板。(1) C: 0.04% or more by weight%, 0.
3% or less, 0.5 of Si or Al or both in total
% Or more and 3.0% or less, and one or more of Mn, Ni, Cr, Cu, Mo in a total amount of 0.5% or more and 3.5% or less, and the balance consisting of Fe and inevitable impurities. The cold-rolled steel sheet thus obtained has a microstructure containing ferrite and bainite, which is a composite structure with a third phase containing either of them as a main phase and containing 3% or more of retained austenite by volume fraction. Amount of solid solution [C] and average Mn equivalent of steel material {Mneq = Mn + (Ni + Cr + Cu
+ Mo) / 2} (M = 678-428)
X [C] -33 x Mneq) is 70 or more and 250 or less,
After having a tensile strength of 597 MPa or more and subjecting the steel material to predeformation of more than 0% and 10% or less with equivalent strain, 5 × 10 2
Average value of deformation stress in the equivalent strain range of 3 to 10% when deformed in a strain rate range of up to 5 × 10 3 (1 / s):
5 × 10 −4 before σdyn (MPa) before pre-deformation
High dynamic characterized by the formula σdyn ≧ 0.766 × TS + 250 expressed by the maximum stress TS (MPa) in a static tensile test measured in a strain rate range of 5 × 10 −3 (1 / s) High-strength hot-rolled steel sheet with impact resistance at the time of collision with deformation resistance.
【０００９】（２）Ｎｂ，Ｔｉ，Ｖの１種又は２種以上
を合計で０．３重量％以下更に含むことを特徴とする
（１）記載の高い動的変形抵抗を有する衝突時衝撃吸収
用高強度熱延鋼板。
（３）Ｐを０．２重量％以下更に含むことを特徴とする
（１）または（２）記載の高い動的変形抵抗を有する衝
突時衝撃吸収用高強度熱延鋼板。
（４）Ｂを０．０１重量％以下更に含むことを特徴とす
る（１）〜（３）のいずれか１に記載の高い動的変形抵
抗を有する衝突時衝撃吸収用高強度熱延鋼板。(2) Absorption at impact with high dynamic deformation resistance as described in (1), further containing one or more of Nb, Ti and V in a total amount of 0.3% by weight or less.
Use high strength hot rolled steel sheet. (3) An impeller having a high dynamic deformation resistance as described in (1) or (2), which further contains 0.2% by weight or less of P.
High-strength hot-rolled steel sheet for impact shock absorption . (4) The high-strength hot-rolled steel sheet for impact shock absorption having a high dynamic deformation resistance according to any one of (1) to (3), further containing B in an amount of 0.01% by weight or less.
【００１０】（５）０％超１０％以下の予変形を与えた
後の鋼材の残留オーステナイト体積分率が２．５％超で
あり、かつ、予変形前の残留オーステナイト体積分率と
予変形後の残留オーステナイト体積分率の比が０．３以
上であることを特徴とする（１）〜（４）のいずれか１
に記載の高い動的変形抵抗を有する衝突時衝撃吸収用高
強度熱延鋼板。
（６）最終的に得られる熱延鋼板のミクロ組織中の残留
オーステナイトの平均粒径と、主相であるフェライトも
しくはベイナイトの平均粒径の比が０．６以下であるこ
とを特徴とする（１）〜（５）のいずれか１に記載の高
い動的変形抵抗を有する衝突時衝撃吸収用高強度熱延鋼
板。(5) The residual austenite volume fraction of the steel material after pre-deformation of more than 0% and less than 10% is more than 2.5%, and the retained austenite volume fraction and pre-deformation before pre-deformation Any one of (1) to (4), characterized in that the ratio of the residual austenite volume fraction after is 0.3 or more.
A high-strength hot-rolled steel sheet having high dynamic deformation resistance for impact absorption during collision . (6) the average particle size of the residual austenite in the microstructure of the finally obtained hot-rolled steel sheet, the ratio of the average particle size of the ferrite or bainite is the main phase is equal to or is more than 0.6 ( A high-strength hot-rolled steel sheet for impact shock absorption, which has the high dynamic deformation resistance according to any one of 1) to (5).
【００１１】（７）重量％で、Ｃ：０．０４％以上０．
３％以下、ＳｉとＡｌの一方または双方を合計で０．５
％以上３．０％以下、Ｍｎ，Ｎｉ，Ｃｒ，Ｃｕ，Ｍｏの
１種または２種以上を合計で０．５％以上３．５％以下
含み、残部がＦｅ及び不可避的不純物からなる鋳造スラ
ブを、鋳造ままで熱延工程へ直送し、もしくは一旦冷却
した後に１０００℃〜１３００℃の範囲に再度加熱した
後、熱延をＡｒ3 変態温度＋５０℃以上Ａｒ3 変態温度
＋１００℃以下の熱延仕上げ温度（ＦＴ）で完了し、そ
の後５℃／秒以上１００℃／秒以下の冷却速度で冷却
し、巻き取る際に、熱延仕上げ温度がＡｒ3 変態温度＋
５０℃以上の場合には２５０℃以上３８０℃未満の温度
で巻き取り、熱延仕上げ温度がＡｒ3 変態温度＋５０℃
未満の場合には２５０℃以上４２０℃未満の温度で巻き
取り、最終的に得られる熱延鋼板のミクロ組織がフェラ
イトおよびベイナイトを含み、このいずれかを主相と
し、体積分率で３％以上の残留オーステナイトを含む第
３相との複合組織であり、５９７ MPa 以上の引張り強度
を有し、残留オーステナイト中の固溶〔Ｃ〕量と鋼材の
平均Ｍｎ等量｛Ｍｎｅｑ＝Ｍｎ＋（Ｎｉ＋Ｃｒ＋Ｃｕ＋
Ｍｏ）／２｝によって決まる値（Ｍ＝６７８−４２８×
〔Ｃ〕−３３×Ｍｎｅｑ）が７０以上２５０以下で、そ
の鋼材に相当歪みで０％超１０％以下の予変形を与えた
後、５×１０2 〜５×１０3 （１／ｓ）の歪み速度範囲
で変形した時の３〜１０％の相当歪み範囲における変形
応力の平均値：σｄｙｎ（ＭＰａ）が予変形を与える前
の５×１０-4〜５×１０-3（１／ｓ）の歪み速度範囲で
測定された静的な引張り試験における最大応力ＴＳによ
って表現される式：σdyn ≧０．７６６×ＴＳ＋２５０
を満足することを特徴とする高い動的変形抵抗を有する
衝突時衝撃吸収用高強度熱延鋼板の製造方法。(7)%: C: 0.04% or more
3% or less, 0.5 of Si or Al or both in total
% Or more and 3.0% or less, one or two or more of Mn, Ni, Cr, Cu, Mo in total 0.5% or more and 3.5% or less, and the balance being Fe and inevitable impurities. and sent directly to the hot rolling step while casting, or once was heated again in the range of 1000 ° C. to 1300 ° C. after cooling, the hot rolled Ar 3 transformation temperature +50 ° C. or higher Ar 3 transformation temperature + 100 ° C. or less of the heat When it is completed at the rolling finish temperature (FT) and then cooled at a cooling rate of 5 ° C./sec or more and 100 ° C./sec or less and wound, the hot rolling finish temperature is the Ar 3 transformation temperature +
When the temperature is 50 ° C or higher, it is wound at a temperature of 250 ° C or higher and lower than 380 ° C, and the hot rolling finish temperature is Ar 3 transformation temperature + 50 ° C
Less than Ri winding <br/> taken at temperatures below 250 ° C. or higher 420 ° C. in the case, the microstructure of the finally obtained hot-rolled steel sheet includes ferrite and bainite, and this one with the main phase, the volume fraction Is a composite structure with a third phase containing retained austenite of 3% or more, and a tensile strength of 597 MPa or more.
It has an average of solute (C) the amount and the steel in the residual austenite Mn eq {Mneq = Mn + (Ni + Cr + Cu +
Mo) / 2} determined value (M = 678-428 ×
[C] -33 × Mneq) is 70 or more and 250 or less, and after subjecting the steel material to pre-deformation of more than 0% and 10% or less by equivalent strain, 5 × 10 2 to 5 × 10 3 (1 / s) of Mean value of the deformation stress in the equivalent strain range of 3 to 10% when deformed in the strain rate range: 5 × 10 −4 to 5 × 10 −3 (1 / s) before σdyn (MPa) gives pre-deformation The expression expressed by the maximum stress TS in a static tensile test measured in the strain rate range of: σ dyn ≧ 0.766 × TS + 250
Has a high dynamic deformation resistance characterized by satisfying
A method for manufacturing a high-strength hot-rolled steel sheet for shock absorption during a collision .
【００１２】（８）Ｎｂ，Ｔｉ，Ｖの１種又は２種以上
を合計で０．３重量％以下更に含むことを特徴とする
（７）記載の高い動的変形抵抗を有する衝突時衝撃吸収
用高強度熱延鋼板の製造方法。
（９）Ｐを０．２重量％以下更に含むことを特徴とする
（７）または（８）記載の高い動的変形抵抗を有する衝
突時衝撃吸収用高強度熱延鋼板の製造方法。(8) The impact absorption at the time of collision with high dynamic deformation resistance as described in (7), which further contains one or more of Nb, Ti and V in a total amount of 0.3% by weight or less.
For manufacturing high strength hot rolled steel sheet for automobiles. (9) The impact having a high dynamic deformation resistance according to (7) or (8), further containing 0.2% by weight or less of P.
A method for producing a high-strength hot-rolled steel sheet for impact shock absorption .
【００１３】（１０）Ｂを０．０１重量％以下更に含む
ことを特徴とする（７）〜（９）のいずれか１に記載の
高い動的変形抵抗を有する衝突時衝撃吸収用高強度熱延
鋼板の製造方法。(10) A high-strength heat for impact absorption during collision having a high dynamic deformation resistance as set forth in any one of (7) to (9), which further comprises 0.01% by weight or less of B. Manufacturing method of rolled steel sheet.
【００１４】[0014]
【発明の実施の形態】自動車のフロントサイドメンバー
等の衝突時の衝撃吸収用部材は、鋼板に曲げ加工やプレ
ス成形加工によって製造される。自動車の衝突時の衝撃
は、この様にして加工されて後に一般的には塗装焼き付
けされた後に加えられる。従って、この様に部材への加
工、処理が行われたのちに高い衝撃エネルギーの吸収能
を示す鋼板が必要となる。BEST MODE FOR CARRYING OUT THE INVENTION A shock absorbing member such as a front side member of an automobile at the time of collision is manufactured by bending or press forming a steel plate. The impact of a vehicle crash is applied after it has been processed in this way and is generally subsequently baked on. Therefore, a steel sheet that exhibits a high impact energy absorption capacity after being processed and treated as described above is required.
【００１５】本発明者らの研究の結果、このような成形
加工された実部材において、鋼板に適量の残留オーステ
ナイトを含むことが優れた衝撃吸収特性を示す高強度鋼
板を提供できることが判明した。すなわち、最終的に得
られる熱延鋼板中に存在する最適なミクロ組織は、種々
の置換型元素によって容易に固溶強化されるフェライト
およびベイナイトを含み、このいずれかを主相として、
塑性変形中に硬質のマルテンサイトに変態する残留オー
ステナイトを体積分率で３％以上含む場合に、高い動的
変形抵抗を示すことが判明した。また、初期ミクロ組織
の第３相にマルテンサイト粒子を含む場合にも、他の条
件が満足されれば、本発明の目的とする高い衝撃エネル
ギー吸収能を示す高強度鋼板の製造が可能となる。As a result of the research conducted by the present inventors, it has been found that, in such a formed and processed actual member, it is possible to provide a high strength steel plate exhibiting excellent shock absorption characteristics by containing an appropriate amount of retained austenite in the steel plate. That is, the optimal microstructure present in the finally obtained hot-rolled steel sheet contains ferrite and bainite that are easily solution-solution strengthened by various substitutional elements, with either of these as the main phase,
It has been found that when the retained austenite that transforms into hard martensite during plastic deformation is contained in a volume fraction of 3% or more, high dynamic deformation resistance is exhibited. Further, even when martensite particles are contained in the third phase of the initial microstructure, if other conditions are satisfied, it becomes possible to manufacture a high-strength steel sheet having a high impact energy absorption capacity, which is the object of the present invention. .
【００１６】本発明で規定する熱延鋼板の各成分の限定
理由は下記のとおりである。
Ｃ：Ｃはオーステナイトを室温で安定化させて残留させ
るために必要なオーステナイトの安定化に貢献する最も
安価な元素であるために、本発明において最も重要な元
素といえる。鋼材の平均Ｃ量は、室温で確保できる残留
オーステナイト体積分率に影響を及ぼすのみならず、製
造の加工熱処理中に未変態オーステナイト中に濃化する
ことで、残留オーステナイトの加工に対する安定性を向
上させることが出来る。しかしながら、この添加量が
０．０４重量％未満の場合には、最終的に得られる残留
オーステナイト体積分率が３％以上を確保することが出
来ないので０．０４％を下限とした。一方、鋼材の平均
Ｃ量が増加するに従って確保可能な残留オーステナイト
体積分率は増加し、残留オーステナイト体積率を確保し
つつ残留オーステナイトの安定性を確保することが可能
となる。しかしながら、鋼材のＣ添加量が過大になる
と、必要以上に鋼材の強度を上昇させ、プレス加工等の
成形性を阻害するのみならず、静的な強度上昇に比して
動的な応力上昇が阻害されると共に、溶接性を低下させ
ることによって成形された部品としての鋼材の利用が制
限されるようになる。従って鋼材のＣ重量％の上限を
０．３％とした。The reasons for limiting the components of the hot rolled steel sheet specified in the present invention are as follows. C: C is the most important element in the present invention because it is the cheapest element that contributes to the stabilization of austenite necessary for stabilizing and remaining austenite at room temperature. The average C content of steel not only affects the retained austenite volume fraction that can be secured at room temperature, but also improves the stability of retained austenite during processing by concentrating it in untransformed austenite during the manufacturing heat treatment. It can be done. However, if the added amount is less than 0.04% by weight, the finally obtained retained austenite volume fraction cannot be maintained at 3% or more, so 0.04% was made the lower limit. On the other hand, the retained austenite volume fraction that can be ensured increases as the average C content of the steel material increases, and it becomes possible to secure the stability of the retained austenite while securing the retained austenite volume ratio. However, if the amount of C added to the steel material becomes excessively large, the strength of the steel material is increased more than necessary, and not only the formability such as press working is hindered but also the dynamic stress increase is caused as compared with the static strength increase. In addition to being hindered, the decrease in weldability limits the use of steel as a molded part. Therefore, the upper limit of C weight% of the steel material is set to 0.3%.
【００１７】Ａｌ，Ｓｉ：ＡｌとＳｉは共にフェライト
の安定化元素であり、フェライト体積率を増加させるこ
とによって鋼材の加工性を向上させる働きがある。ま
た、Ａｌ，Ｓｉ共にセメンタイトの生成を抑制すること
から、効果的にオーステナイト中へのＣを濃化させるこ
とを可能とすることから、室温で適当な体積分率のオー
ステナイトを残留させるためには不可避的な添加元素で
ある。このようなセメンタイト生成抑制機能を持つ添加
元素としては、Ａｌ，Ｓｉ以外に、ＰやＣｕ，Ｃｒ，Ｍ
ｏ等が挙げられ、このような元素を適切に添加すること
も同様な効果が期待される。しかしながら、ＡｌとＳｉ
の一種もしくは双方の合計が０．５重量％未満の場合に
は、セメンタイト生成抑制の効果が十分でなく、オース
テナイトの安定化に最も効果的な添加されたＣの多くが
炭化物の形で浪費され、本発明に必要な残留オーステナ
イト体積率を確保することが出来ないか、もしくは残留
オーステナイトの確保に必要な製造条件が大量生産工程
の条件に適しないため下限を０．５重量％とした。ま
た、ＡｌとＳｉの一種もしくは双方の合計が３．０％を
越える場合には、母相であるフェライトもしくはベイナ
イトの硬質化や脆化を招き、歪み速度上昇による変形抵
抗の増加を阻害するばかりでなく、鋼材の加工性の低
下、靱性の低下、さらには鋼材コストの上昇を招き、ま
た化成処理性等の表面処理特性が著しく劣化するため
に、３．０重量％を上限値とした。Al, Si: Al and Si are both stabilizing elements of ferrite, and have the function of improving the workability of the steel material by increasing the ferrite volume ratio. Further, since both Al and Si suppress the formation of cementite, it is possible to effectively concentrate C in austenite. Therefore, in order to allow austenite to remain at an appropriate volume fraction at room temperature, It is an unavoidable additive element. As the additive element having such a cementite generation suppressing function, in addition to Al and Si, P, Cu, Cr and M
and the like, and the similar effect can be expected by appropriately adding such an element. However, Al and Si
If the content of one or both of the above is less than 0.5% by weight, the effect of suppressing the formation of cementite is not sufficient, and most of the added C that is most effective for stabilizing austenite is wasted in the form of carbide. The lower limit is set to 0.5% by weight because the volume ratio of the retained austenite required for the present invention cannot be secured or the manufacturing conditions required for securing the retained austenite are not suitable for the conditions of the mass production process. Further, if one or both of Al and Si exceed 3.0%, the ferrite or bainite as the matrix phase is hardened or embrittled, and the increase in deformation resistance due to an increase in strain rate is not only inhibited. However, the workability of the steel material is deteriorated, the toughness is decreased, the cost of the steel material is increased, and the surface treatment characteristics such as chemical conversion treatability are remarkably deteriorated. Therefore, the upper limit value is 3.0% by weight.
【００１８】Ｍｎ，Ｎｉ，Ｃｒ，Ｃｕ，Ｍｏ：Ｍｎ，Ｎ
ｉ，Ｃｒ，Ｃｕ，Ｍｏは全てオーステナイト安定化元素
であり、室温でオーステナイトを安定化させるためには
有効な元素である。特に、溶接性の観点からＣの添加量
が制限される場合には、この様なオーステナイト安定化
元素を適量添加することによって効果的にオーステナイ
トを残留させることが可能となる。また、これらの元素
はＡｌやＳｉ程ではないがセメンタイトの生成を抑制す
る効果があり、オーステナイトへのＣの濃化を助ける働
きもする。更に、これらの元素はＡｌ，Ｓｉと共にマト
リックスであるフェライトやベイナイトを固溶強化させ
ることによって、高速での動的変形抵抗を高める働きも
持つ。しかしながら、これらの元素の１種もしくは２種
以上の添加の合計が０．５重量％未満の場合には、必要
な残留オーステナイトの確保が出来なくなるとともに、
鋼材の強度が低くなり、有効な車体軽量化が達成できな
くなることから、下限を０．５重量％とした。一方、こ
れらの合計が３．５重量％を越える場合には、母相であ
るフェライトもしくはベイナイトの硬質化を招き、歪み
速度上昇による変形抵抗の増加を阻害するばかりでな
く、鋼材の加工性の低下、靱性の低下、さらには鋼材コ
ストの上昇を招くために、上限を３．５重量％とした。Mn, Ni, Cr, Cu, Mo: Mn, N
i, Cr, Cu and Mo are all austenite stabilizing elements and are effective elements for stabilizing austenite at room temperature. In particular, when the amount of C added is limited from the viewpoint of weldability, it becomes possible to effectively retain austenite by adding an appropriate amount of such an austenite stabilizing element. Further, these elements have an effect of suppressing the formation of cementite, though not so much as Al or Si, and also have a function of helping the concentration of C in austenite. Further, these elements also have a function of enhancing the dynamic deformation resistance at high speed by solid-solution strengthening the matrix ferrite or bainite together with Al and Si. However, if the total amount of one or more of these elements added is less than 0.5% by weight, the necessary retained austenite cannot be secured, and
The lower limit was set to 0.5% by weight because the strength of the steel material decreases and effective weight reduction of the vehicle body cannot be achieved. On the other hand, when the total amount of these exceeds 3.5% by weight, the matrix ferrite or bainite is hardened, which not only hinders the increase of the deformation resistance due to the increase of the strain rate, but also the workability of the steel material. The upper limit was set to 3.5% by weight in order to lower the toughness and the steel cost.
【００１９】Ｎｂ，Ｔｉ，Ｖ：また、必要に応じて添加
するＮｂ，Ｔｉ，Ｖは、炭化物、窒化物もしくは炭窒化
物を形成することによって鋼材を高強度化することが出
来るが、その合計が０．３％を越えた場合には母相であ
るフェライトやベイナイト粒内もしくは粒界に多量の炭
化物、窒化物もしくは炭窒化物として析出し、高速変形
時の可動転位発生源となって、高い動的変形抵抗を得る
ことが出来なくなる。また、炭化物の生成は、本発明に
とって最も重要な残留オーステナイト中へのＣの濃化を
阻害し、Ｃを浪費することから上限を０．３重量％とし
た。Nb, Ti, V: In addition, Nb, Ti, V added as necessary can strengthen the steel material by forming carbides, nitrides or carbonitrides, but the total of them. When the content exceeds 0.3%, a large amount of carbides, nitrides or carbonitrides are precipitated in the matrix of ferrite or bainite grains or at grain boundaries, and become a source of mobile dislocations during high-speed deformation, It becomes impossible to obtain high dynamic deformation resistance. Further, the formation of carbides impedes the concentration of C in the retained austenite, which is the most important for the present invention, and wastes C, so the upper limit was made 0.3% by weight.
【００２０】Ｐ：更に、必要に応じて添加するＰは、鋼
材の高強度化や前述のように残留オーステナイトの確保
に有効ではあるが、０．２重量％を越えて添加された場
合には鋼材のコストの上昇を招くばかりでなく、主相で
あるフェライトやベイナイトの変形抵抗を必要以上に高
め、かつ高速変形時の変形抵抗の上昇を阻害する。更
に、耐置き割れ性の劣化や疲労特性、靱性の劣化を招く
ことから、０．２重量％をその上限とした。P: Further, P added as necessary is effective for increasing the strength of the steel material and securing retained austenite as described above. However, when P is added in excess of 0.2% by weight, Not only does this lead to an increase in the cost of the steel material, but it also increases the deformation resistance of the main phase ferrite and bainite more than necessary, and hinders the increase of the deformation resistance during high-speed deformation. Further, 0.2 wt% is set as the upper limit because deterioration of resistance to cracking due to placement, deterioration of fatigue characteristics and deterioration of toughness are caused.
【００２１】Ｂ：また、必要に応じて添加するＢは、粒
界の強化や鋼材の高強度化に有効ではあるが、その添加
量が０．０１重量％を越えるとその効果が飽和するばか
りでなく、必要以上に鋼板強度を上昇させ、高速変形時
の変形抵抗の上昇を阻害すると共に、成形部品への加工
性も低下させることから、上限を０．０１重量％とし
た。B: B, which is added as necessary, is effective for strengthening grain boundaries and strengthening the steel material, but when the addition amount exceeds 0.01% by weight, the effect is saturated. Not only that, the steel plate strength is increased more than necessary, the increase of the deformation resistance during high-speed deformation is inhibited, and the workability of the formed part is also decreased. Therefore, the upper limit was made 0.01% by weight.
【００２２】次に、本発明者らの実験・検討の結果、フ
ロントサイドメンバー等の衝撃吸収用部材の成形加工に
相当する予変形の量は、部材中の部位によっては最大２
０％以上に達する場合もあるが、相当歪みとして０％超
１０％以下の部位が大半であり、また、この範囲の予変
形の効果を把握することで、部材全体としての予変形後
の挙動を推定することが可能であることを見いだした。
従って、本発明においては、部材への加工時に与えられ
る予変形量として相当歪みにして０％超１０％以下の変
形を選択した。Next, as a result of experiments and examinations conducted by the present inventors, the amount of pre-deformation corresponding to the forming process of the shock absorbing member such as the front side member is up to 2 depending on the part in the member.
Although it may reach 0% or more, most of the parts have an equivalent strain of more than 0% and 10% or less. Also, by grasping the effect of predeformation in this range, the behavior of the entire member after predeformation It has been found that it is possible to estimate.
Therefore, in the present invention, as the amount of pre-deformation given to the member during processing, a strain of not less than 0% and not more than 10% in equivalent strain is selected.
【００２３】また、フロントサイドメンバー等の衝撃吸
収用部材は、特徴的にハット型の断面形状をしており、
このような部材の高速での衝突圧潰時の変形を本発明者
らが解析した結果、最大では４０％以上の高い歪みまで
変形が進んでいるものの、吸収エネルギー全体の約７０
％以上が、高速の応力−歪み線図の１０％以下の歪み範
囲で吸収されていることを見いだした。従って、高速で
の衝突エネルギーの吸収能の指標として、１０％以下で
の高速変形時の動的変形抵抗を採用した。特に、歪み量
として３％〜１０％の範囲が最も重要であることから、
高速引張り変形時の相当歪みで３％〜１０％の範囲の平
均応力：σdyn をもって衝撃エネルギー吸収能の指標と
した。Further, the shock absorbing member such as the front side member characteristically has a hat-shaped cross section.
As a result of the analysis by the present inventors of the deformation at the time of high-speed collision crushing of such a member, the deformation has advanced to a high strain of 40% or more at the maximum, but about 70% of the total absorbed energy.
It has been found that% or more is absorbed in the strain range of 10% or less of the high-speed stress-strain diagram. Therefore, the dynamic deformation resistance during high-speed deformation at 10% or less was adopted as an index of the impact energy absorption capacity at high speed. Especially, since the range of 3% to 10% is the most important as the strain amount,
The equivalent strain during high-speed tensile deformation is an average stress in the range of 3% to 10%: σdyn was used as an index of impact energy absorption capacity.
【００２４】この高速変形時の３％〜１０％の平均応
力：σdyn (MPa) は、予変形や焼き付け処理が行われる
前の鋼材の静的な引張り強度（５×１０-4〜５×１０-3
（１／ｓ）の歪み速度範囲で測定された静的な引張り試
験における最大応力ＴＳの上昇に伴って大きくなること
が一般的である。従って鋼材の静的な引張り強度を増加
させることは部材の衝撃エネルギー吸収能の向上に直接
寄与する。しかしながら、鋼材の強度が上昇すると部材
への成形性が劣化し、必要な部材形状を得ることが困難
となる。従って、同一の最大応力で高いσdyn を持つ鋼
材が望ましい。この関係で、特にσdyn ≧０．７６６×
ＴＳ＋２５０の関係を満足する鋼材は、実部材としての
衝撃エネルギー吸収能が他の鋼材に比べて高く、部材の
総重量を増加させることなく衝撃エネルギー吸収能を向
上させることができることを見いだした。The average stress of 3% to 10% during high-speed deformation: σdyn (MPa) is the static tensile strength (5 × 10 −4 to 5 × 10) of the steel material before pre-deformation or baking treatment. -3
It generally increases as the maximum stress TS increases in the static tensile test measured in the strain rate range of (1 / s). Therefore, increasing the static tensile strength of the steel material directly contributes to the improvement of the impact energy absorption capacity of the member. However, if the strength of the steel material increases, the formability of the member deteriorates, and it becomes difficult to obtain the required member shape. Therefore, steel materials with the same maximum stress and high σdyn are desirable. In this relationship, in particular σdyn ≧ 0.766 ×
It has been found that a steel material satisfying the relationship of TS + 250 has a higher impact energy absorption capacity as an actual member than other steel materials, and can improve the impact energy absorption capacity without increasing the total weight of the member.
【００２５】本発明者らの実験・検討の結果、同一レベ
ルの最大応力に対して、σdyn は部材への加工が行われ
る以前の鋼板中に含まれる残留オーステナイト中の固溶
炭素量〔Ｃ〕（重量％）と鋼材の平均Ｍｎ等量（Ｍｎｅ
ｑ：重量％）｛Ｍｎｅｑ＝Ｍｎ＋（Ｎｉ＋Ｃｒ＋Ｃｕ＋
Ｍｏ）／２｝によって変化することが見いだされた。残
留オーステナイト中の炭素濃度は、Ｘ線解析やメスバウ
アー分光により実験的に求めることが出来、例えばＭｏ
のＫα線を用いたＸ線解析によりフェライトの（２０
０）面、（２１１）面及びオーステナイトの（２００）
面、（２２０）面、（３１１）面の積分反射強度をもち
いて、Journal of The Iron and Steel Institute, 206
(1968) p.60に示された方法にて算出できる。本発明者
らが行った実験結果から、この様にして得られた残留オ
ーステナイト中の固溶〔Ｃ〕と鋼材に添加されている置
換型合金元素から求められるＭｎｅｑを用いて計算され
る値（Ｍ＝６７８−４２８×〔Ｃ〕−３３×Ｍｎｅｑ）
が７０以上２５０以下の場合に、同一の静的な引張り強
度（ＴＳ）に対して大きなσdyn を示すことが見いださ
れた。このときＭ＞２５０では、実質的に変形中の残留
オーステナイトの変態による強度上昇の効果が極めて低
い歪み領域にのみ限られるために、部材への予変形時に
ほぼ全ての残留オーステナイトが浪費され、高速変形時
のσdyn の上昇に寄与しなくなることから、Ｍの上限を
２５０とした。また、Ｍが７０未満の場合には、変形途
中での残留オーステナイトの変態は進行するものの、変
態の進行が低歪み領域では十分に起こらないことから、
相当歪みで３％〜１０％の範囲での平均応力σdyn が低
いままに保たれ、静的な引張り強度（ＴＳ）に対してσ
dyn ≧０．７６６×ＴＳ＋２５０の関係を満足しなくな
るので、Ｍの下限を７０とした。As a result of experiments and examinations conducted by the present inventors, σdyn is the amount of solute carbon [C] in the retained austenite contained in the steel sheet before processing into a member for the same level of maximum stress. (Wt%) and average Mn equivalent of steel (Mne
q:% by weight {Mneq = Mn + (Ni + Cr + Cu +
Mo) / 2} was found to change. The carbon concentration in the retained austenite can be experimentally obtained by X-ray analysis or Moessbauer spectroscopy.
X-ray analysis using Kα ray of
0) plane, (211) plane and austenite (200) plane
Plane, (220) plane, (311) plane using the integrated reflection intensity, Journal of The Iron and Steel Institute, 206
(1968) It can be calculated by the method shown on p.60. From the results of experiments conducted by the present inventors, a value calculated using Mneq obtained from the solid solution [C] in the retained austenite thus obtained and the substitutional alloying elements added to the steel material ( M = 678-428 × [C] -33 × Mneq)
It was found that the value of 70 or more and 250 or less shows a large σdyn for the same static tensile strength (TS). At this time, when M> 250, the effect of increasing the strength due to the transformation of the retained austenite during deformation is substantially limited to the extremely low strain region, so that almost all of the retained austenite is wasted at the time of pre-deformation into a member, and high-speed Since it does not contribute to the increase of σdyn during deformation, the upper limit of M is set to 250. Further, when M is less than 70, the transformation of the retained austenite in the course of the transformation proceeds, but the transformation does not proceed sufficiently in the low strain region.
The average stress σdyn in the range of 3% to 10% at the equivalent strain is kept low, and σ is lower than the static tensile strength (TS).
Since the relationship of dyn ≧ 0.766 × TS + 250 is not satisfied, the lower limit of M is set to 70.
【００２６】熱延条件：熱延ままで本発明の鋼板を製造
する場合には、所定の成分に調整されたスラブを鋳造ま
まで熱延工程へ直送し、もしくは一旦冷却した後に１０
００℃〜１３００℃の範囲に再度加熱した後、熱間圧延
を行う。再加熱温度を１０００℃未満とする場合には、
スラブの均一加熱が困難となり、表面キズ発生等の問題
を生じるので、再加熱温度の下限を１０００℃とした。
また、再加熱温度が１３００℃超では、スラブの変形が
激しくなると同時にコスト高となることから、１３００
℃を上限とした。また、熱延仕上げ温度（ＦＴ）がＡｒ
3 変態温度＋５０℃未満である場合には、鋼板の表層部
及びその近傍に加工フェライト層が生成し、加工性を著
しく劣化させると同時に、動的な変形抵抗を下げる。従
って、熱延仕上げ温度の下限値をＡｒ3 変態温度＋５０
℃とする。また熱延仕上げ温度がＡｒ3＋１００℃超の
場合には、必要以上に鋼板の強度が上昇するのみなら
ず、組織の粗大化が起こり、鋼板動的変形抵抗の上昇を
阻害する。またこのような高温で熱延が完了された場合
には鋼板の表面粗度が大きくなり、表面品位を落とす。
従って、熱延仕上げ温度の上限値をＡｒ3 ＋１００℃以
下とする。Hot rolling condition: When the steel sheet of the present invention is produced by hot rolling, the slab adjusted to have a predetermined composition is directly sent to the hot rolling step as it is, or after cooling once, 10
After heating again in the range of 00 ° C to 1300 ° C, hot rolling is performed. When the reheating temperature is less than 1000 ° C,
Since it becomes difficult to uniformly heat the slab and problems such as surface scratches occur, the lower limit of the reheating temperature is set to 1000 ° C.
If the reheating temperature is higher than 1300 ° C, the slab becomes severely deformed and the cost becomes high.
The upper limit was ℃. Also, the hot rolling finish temperature (FT) is Ar
When the transformation temperature is less than + 50 ° C, a work ferrite layer is formed in the surface layer of the steel sheet and its vicinity, which significantly deteriorates the workability and lowers the dynamic deformation resistance. Therefore, the lower limit of the hot rolling finish temperature is set to the Ar 3 transformation temperature +50
℃. Further, when the hot rolling finishing temperature is higher than Ar 3 + 100 ° C. , not only the strength of the steel sheet is increased more than necessary, but also the structure is coarsened and the increase of the dynamic deformation resistance of the steel sheet is hindered. Further, when hot rolling is completed at such a high temperature, the surface roughness of the steel sheet increases, degrading the surface quality.
Therefore, the upper limit of the hot rolling finishing temperature is Ar 3 + 100 ° C or less.
Below .
【００２７】熱延完了後に鋼板は冷却されるが、このと
きの冷却速度を５℃／秒未満もしくは１００℃／秒超と
することは、大量生産の工程条件上困難であることか
ら、これを下限、上限とした。また冷却の方法は一定の
冷却速度で行っても、途中で低冷却速度の領域を含むよ
うな複数種類の冷却速度の組み合わせであってもよい。
冷却後鋼板は巻き取り処理が行われるが、この時の巻き
取り温度が２５０℃未満ではマルテンサイトの生成が過
多となって加工性を損なうので下限を２５０℃とした。
また、熱延仕上げ温度（ＦＴ）がＡｒ3 ＋５０℃以上の
場合には、３８０℃以上で巻き取ると静的強度（ＴＳ）
に対する動的な変形抵抗（σdyn ）の値が小さくなるこ
とから、熱延仕上げ温度（ＦＴ）がＡｒ3 ＋５０℃以上
の場合には巻き取り温度を３８０℃未満とした。また、
熱延仕上げ温度（ＦＴ）がＡｒ3＋５０℃未満の場合に
は、動的変形抵抗σdyn が低くなる巻き取り温度が４２
０℃以上であったため、熱延仕上げ温度（ＦＴ）がＡｒ
3 ＋５０℃未満の場合には巻き取り温度を４２０℃未満
とした。最終的な鋼板の動的変形抵抗をより高めるため
には巻き取り温度の下限を３００℃とすることが望まし
い。After the hot rolling is completed, the steel sheet is cooled, but it is difficult to set the cooling rate at this time to less than 5 ° C./sec or more than 100 ° C./sec because of the process conditions of mass production. The lower and upper limits were set. The cooling method may be a constant cooling rate or a combination of a plurality of types of cooling rates including a low cooling rate region in the middle.
After cooling, the steel sheet is wound up. However, if the winding temperature at this time is less than 250 ° C, martensite is excessively generated and workability is impaired, so the lower limit was set to 250 ° C.
When the hot rolling finish temperature (FT) is Ar 3 + 50 ° C or higher, the static strength (TS) is obtained when wound at 380 ° C or higher.
Since the value of the dynamic deformation resistance (σdyn) with respect to ( 3 ) becomes small, the coiling temperature was set to less than 380 ° C. when the hot rolling finishing temperature (FT) was Ar 3 + 50 ° C. or higher. Also,
When the hot rolling finishing temperature (FT) is less than Ar 3 + 50 ° C., the dynamic deformation resistance σdyn becomes low and the winding temperature is 42.
Since the temperature was 0 ° C or higher, the hot rolling finish temperature (FT) was Ar
When the temperature was less than 3 + 50 ° C, the winding temperature was less than 420 ° C. In order to further increase the final dynamic deformation resistance of the steel sheet, it is desirable to set the lower limit of the winding temperature to 300 ° C.
【００２８】[0028]
【実施例】〈実施例１〉
表１に示す２３種類の鋼材を１２００℃に加熱し、各鋼
の成分からＡｒ3 ＝９０１−３２５×％Ｃ＋３３×％Ｓ
ｉ−９２×％Ｍｎｅｑの式（％Ｍｎｅｑ＝％Ｍｎ＋％Ｎ
ｉ／２＋％Ｃｒ／２＋％Ｃｕ／２＋％Ｍｏ／２）で計算
されるＡｒ3 変態温度＋５０℃〜Ａｒ3 変態温度＋１０
０℃の範囲内で熱延を完了し、４５℃／秒の冷却速度で
冷却し、３５０℃〜３７０℃の範囲で巻き取った。なお
圧延完了後の板厚は３．０mmであった。このようにして
得られた熱延鋼板の熱延方向（Ｌ方向）とこれに直行す
る方向（Ｃ方向）に単軸引張りにより５％の予変形を付
加し、焼き付け処理を模擬するために１７０℃×２０分
の熱処理を行った後に鋼材の動的な特性を調査し、予変
形する前の静的な特性と比較した結果を表２に示した。
５９７ MPa 以上の引張り強度を有し、鋼の成分が本発明
の範囲内のものについては表中の＊１の欄に示した値が
正すなわち、目的通りσdyn が（０．７６６×ＴＳ＋２
５０）以上であることがわかる。
〈実施例２〉
表１に示した本発明の成分範囲内である鋼Ｐ２を用い
て、熱延条件、予変形条件及び熱処理条件、を変化させ
た場合の特性を調査した結果を表３および表４に示す。
Ｐ２鋼のＡｒ3 変態温度は上記の式から７６４℃と計算
された。加熱温度は１２００℃一定とした。熱延仕上げ
温度（ＦＴ）がＡｒ3 ＋５０℃以上の８３０℃の場合に
は、No. １，４、５では巻取り温度が本発明の範囲外で
あるために所定の動的変形抵抗σｄｙｎが得られていな
い。また、No. ６では、熱延仕上げ温度（ＦＴ）が本発
明の範囲外であるために結果的に残留オーステナイト粒
径とフェライト粒径の比が０．６よりも大きくなり、所
定の動的変形抵抗σｄｙｎが得られていない。他の例は
すべて本発明の例であり、熱延仕上げ温度、巻取り温
度、予変形量が本発明の範囲内であれば、予変形付与の
形態や予変形後の加工硬化処理（ＢＨ処理：１７０℃×
２０分の熱処理）の有無に関わらず表３中の＊１の欄の
値が正、すなわち所定の動的変形抵抗σｄｙｎが得られ
ることがわかる。ここで、Ｌ方向とは熱延と同一の方向
を指し、Ｃ方向はこれと直行する方向を指す。EXAMPLES Example 1 Twenty-three kinds of steel materials shown in Table 1 were heated to 1200 ° C., and Ar 3 = 901-325 ×% C + 33 ×% S was calculated from the components of each steel.
Formula of i-92 ×% Mneq (% Mneq =% Mn +% N
i / 2 +% Cr / 2 +% Cu / 2 +% Mo / 2) Ar 3 transformation temperature + 50 ° C. to Ar 3 transformation temperature +10
Hot rolling was completed within the range of 0 ° C, cooled at a cooling rate of 45 ° C / sec, and wound in the range of 350 ° C to 370 ° C. The plate thickness after completion of rolling was 3.0 mm. The hot-rolled steel sheet thus obtained was subjected to a uniaxial tension of 5% pre-deformation in the hot-rolling direction (L direction) and in the direction orthogonal thereto (C direction) to simulate the baking treatment. Table 2 shows the results of the examination of the dynamic properties of the steel material after heat treatment at 20 ° C. for 20 minutes and comparison with the static properties before pre-deformation.
For those having a tensile strength of 597 MPa or more and a steel composition within the range of the present invention, the value shown in the column of * 1 in the table is positive, that is, σdyn is (0.766 × TS + 2) as intended.
50) or more. <Example 2> The results of investigating the characteristics when the hot rolling conditions, the pre-deformation conditions and the heat treatment conditions were changed using the steel P2 within the composition range of the present invention shown in Table 1 are shown in Table 3 and It shows in Table 4.
The Ar 3 transformation temperature of P2 steel was calculated to be 764 ° C. from the above equation. The heating temperature was constant at 1200 ° C. When the hot rolling finishing temperature (FT) is 830 ° C., which is higher than Ar 3 + 50 ° C., in Nos. 1, 4 and 5, the winding temperature is out of the range of the present invention, so that the predetermined dynamic deformation resistance σdyn is Not obtained. Further, in No. 6, since the hot rolling finishing temperature (FT) is out of the range of the present invention, the ratio of the retained austenite grain size to the ferrite grain size is consequently larger than 0.6, and the predetermined dynamic The deformation resistance σdyn is not obtained. All other examples are examples of the present invention, and if the hot rolling finish temperature, the coiling temperature, and the amount of pre-deformation are within the scope of the present invention, the form of pre-deformation and work hardening treatment (BH treatment after pre-deformation) : 170 ℃ ×
It can be seen that the value in the column of * 1 in Table 3 is positive, that is, the predetermined dynamic deformation resistance σdyn is obtained regardless of the presence or absence of heat treatment for 20 minutes. Here, the L direction refers to the same direction as the hot rolling, and the C direction refers to the direction orthogonal to this.
【００２９】[0029]
【表１】 [Table 1]
【００３０】[0030]
【表２】 [Table 2]
【００３１】[0031]
【表３】 [Table 3]
【００３２】[0032]
【表４】 [Table 4]
【００３３】[0033]
【発明の効果】本発明により、自動車の軽量化と衝突安
全性の確保の要求に応えることのできる高い動的変形抵
抗を有する衝突時衝撃吸収用高強度熱延鋼板を確実に提
供することができる。According to the present invention, it is possible to reliably provide a high-strength hot-rolled steel sheet for impact shock absorption having a high dynamic deformation resistance, which can meet the demands for weight reduction of automobiles and securing of collision safety. it can.
【図面の簡単な説明】[Brief description of drawings]
【図１】本発明における、衝突時の衝撃エネルギー吸収
能の指標である、５×１０2 〜５×１０3 （１／ｓ）の
歪み速度範囲で変形した時の３〜１０％の相当歪み範囲
における変形応力の平均値σdyn と静的な素材強度との
関係を示す図である。FIG. 1 is an equivalent strain of 3 to 10% when deformed in a strain velocity range of 5 × 10 2 to 5 × 10 3 (1 / s), which is an index of impact energy absorption capacity during collision in the present invention. It is a figure which shows the relationship between the average value (sigma) dyn of the deformation stress in a range, and static material strength.
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 平９−241788（ＪＰ，Ａ) 特開 平７−62485（ＪＰ，Ａ) 特開 平７−252592（ＪＰ，Ａ) 特開 平７−207413（ＪＰ，Ａ) 特開 平１−184226（ＪＰ，Ａ) 特開 昭64−79345（ＪＰ，Ａ) 国際公開95／029268（ＷＯ，Ａ１) 三浦ら，自動車用衝撃吸収高張力鋼板 の開発，まてりあ ，1996年 ５月20 日，Ｖｏｌ．35 Ｎｏ．３， Ｐ，570 −572 板橋ら，予ひずみを与えられた建築構 造用圧延鋼材ＳＮ490Ｂの高速引張特性, 日本材料学会学術講演会講演論文集, 1997年 ５月22日，Ｖｏｌ．46ｔｈ , Ｐ．291−292 (58)調査した分野(Int.Cl.7，ＤＢ名) C22C 38/00 - 38/60 C21D 8/02 - 8/04 C21D 9/46 - 9/48 ─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-9-241788 (JP, A) JP-A-7-62485 (JP, A) JP-A-7-252592 (JP, A) JP-A-7- 207413 (JP, A) JP-A-1-184226 (JP, A) JP-A 64-79345 (JP, A) International Publication 95/029268 (WO, A1) Miura et al., Development of shock absorbing high-strength steel sheet for automobiles Materia, May 20, 1996, Vol. 35 No. 3, P, 570-572 Itabashi et al., High-speed tensile properties of prestrained rolled steel SN490B for building structures, Proc. Of the Japan Society of Materials Science, May 22, 1997, Vol. 46th, P. 291-292 (58) Fields surveyed (Int.Cl. 7 , DB name) C22C 38/00-38/60 C21D 8/02-8/04 C21D 9/46-9/48
Claims (10)
以下、ＳｉとＡｌの一方または双方を合計で０．５％以
上３．０％以下、Ｍｎ，Ｎｉ，Ｃｒ，Ｃｕ，Ｍｏの１種
または２種以上を合計で０．５％以上３．５％以下含
み、残部がＦｅ及び不可避的不純物からなり、最終的に
得られる冷延鋼板のミクロ組織がフェライトおよびベイ
ナイトを含み、このいずれかを主相とし、体積分率で３
％以上の残留オーステナイトを含む第３相との複合組織
であり、残留オーステナイト中の固溶〔Ｃ〕量と鋼材の
平均Ｍｎ等量｛Ｍｎｅｑ＝Ｍｎ＋（Ｎｉ＋Ｃｒ＋Ｃｕ＋
Ｍｏ）／２｝によって決まる値（Ｍ＝６７８−４２８×
〔Ｃ〕−３３×Ｍｎｅｑ）が７０以上２５０以下で、５
９７ MPa 以上の引張り強度を有し、その鋼材に相当歪み
で０％超１０％以下の予変形を与えた後、５×１０2 〜
５×１０3 （１／ｓ）の歪み速度範囲で変形した時の３
〜１０％の相当歪み範囲における変形応力の平均値σｄ
ｙｎ（ＭＰａ）が予変形を与える前の５×１０-4〜５×
１０-3（１／ｓ）の歪み速度範囲で測定された静的な引
張り試験における最大応力ＴＳ(MPa) によって表現され
る式：σdyn ≧０．７６６×ＴＳ＋２５０を特徴とする
高い動的変形抵抗を有する衝突時衝撃吸収用高強度熱延
鋼板。1. C: 0.04% or more and 0.3% by weight
Hereinafter, one or both of Si and Al are 0.5% or more and 3.0% or less in total, and one or more of Mn, Ni, Cr, Cu, and Mo are 0.5% or more and 3.5% or more in total. % Or less, the balance consisting of Fe and unavoidable impurities, and the microstructure of the finally obtained cold-rolled steel sheet contains ferrite and bainite. Either of them is the main phase and the volume fraction is 3
% Is a composite structure with a third phase containing at least% retained austenite, and the amount of solid solution [C] in the retained austenite and the average Mn equivalent of steel {Mneq = Mn + (Ni + Cr + Cu +
Mo) / 2} determined value (M = 678-428 ×
[C] -33 × Mneq) is 70 or more and 250 or less, 5
After having a tensile strength of 97 MPa or more and subjecting the steel material to pre-deformation of more than 0% and 10% or less with an equivalent strain, 5 × 10 2 to
3 when deformed within a strain rate range of 5 × 10 3 (1 / s)
Average value of deformation stress σd in the equivalent strain range of 10%
5 × 10 −4 to 5 × before yn (MPa) gives a pre-deformation
High dynamic deformation resistance characterized by the formula σdyn ≧ 0.766 × TS + 250 expressed by the maximum stress TS (MPa) in a static tensile test measured in the strain rate range of 10 −3 (1 / s) High-strength hot-rolled steel sheet for impact absorption during collision .
計で０．３重量％以下更に含むことを特徴とする請求項
１記載の高い動的変形抵抗を有する衝突時衝撃吸収用高
強度熱延鋼板。2. The impact-absorbing shock having high dynamic deformation resistance according to claim 1, further comprising one or more of Nb, Ti and V in a total amount of 0.3% by weight or less . High strength hot rolled steel sheet.
徴とする請求項１または２記載の高い動的変形抵抗を有
する衝突時衝撃吸収用高強度熱延鋼板。3. The high-strength hot-rolled steel sheet for impact shock absorption having high dynamic deformation resistance according to claim 1 or 2, further comprising P in an amount of 0.2% by weight or less.
特徴とする請求項１〜３のいずれか１項に記載の高い動
的変形抵抗を有する衝突時衝撃吸収用高強度熱延鋼板。4. A high-strength hot-rolled steel sheet for impact shock absorption having a high dynamic deformation resistance according to claim 1, further comprising B in an amount of 0.01% by weight or less. .
鋼材の残留オーステナイト体積分率が２．５％超であ
り、かつ、予変形前の残留オーステナイト体積分率と予
変形後の残留オーステナイト体積分率の比が０．３以上
であることを特徴とする請求項１〜４のいずれか１項に
記載の高い動的変形抵抗を有する衝突時衝撃吸収用高強
度熱延鋼板。5. The residual austenite volume fraction of the steel material after pre-deformation of more than 0% and 10% or more is more than 2.5%, and the residual austenite volume fraction before pre-deformation and after pre-deformation. The ratio of the retained austenite volume fraction of is 0.3 or more, The high strength hot rolled steel sheet for impact shock absorption having high dynamic deformation resistance according to any one of claims 1 to 4, .
中の残留オーステナイトの平均粒径と、主相であるフェ
ライトもしくはベイナイトの平均粒径の比が０．６以下
であることを特徴とする請求項１〜５のいずれか１項に
記載の高い動的変形抵抗を有する衝突時衝撃吸収用高強
度熱延鋼板。6. The ratio of the average grain size of retained austenite in the microstructure of the finally obtained hot rolled steel sheet to the average grain size of ferrite or bainite as a main phase is 0.6 or less. A high-strength hot-rolled steel sheet for impact shock absorption having high dynamic deformation resistance according to any one of claims 1 to 5.
以下、ＳｉとＡｌの一方または双方を合計で０．５％以
上３．０％以下、Ｍｎ，Ｎｉ，Ｃｒ，Ｃｕ，Ｍｏの１種
または２種以上を合計で０．５％以上３．５％以下含
み、残部がＦｅ及び不可避的不純物からなる鋳造スラブ
を、鋳造ままで熱延工程へ直送し、もしくは一旦冷却し
た後に１０００℃〜１３００℃の範囲に再度加熱した
後、熱延をＡｒ3 変態温度＋５０℃以上Ａｒ3 変態温度
＋１００℃以下の熱延仕上げ温度（ＦＴ）で完了し、そ
の後５℃／秒以上１００℃／秒以下の冷却速度で冷却
し、巻き取る際に、熱延仕上げ温度がＡｒ3 変態温度＋
５０℃以上の場合には２５０℃以上３８０℃未満の温度
で巻き取り、熱延仕上げ温度がＡｒ3 変態温度＋５０℃
未満の場合には２５０℃以上４２０℃未満の温度で巻き
取り、最終的に得られる熱延鋼板のミクロ組織がフェラ
イトおよびベイナイトを含み、このいずれかを主相と
し、体積分率で３％以上の残留オーステナイトを含む第
３相との複合組織であり、５９７ MPa 以上の引張り強度
を有し、残留オーステナイト中の固溶〔Ｃ〕量と鋼材の
平均Ｍｎ等量｛Ｍｎｅｑ＝Ｍｎ＋（Ｎｉ＋Ｃｒ＋Ｃｕ＋
Ｍｏ）／２｝によって決まる値（Ｍ＝６７８−４２８×
〔Ｃ〕−３３×Ｍｎｅｑ）が７０以上２５０以下で、そ
の鋼材に相当歪みで０％超１０％以下の予変形を与えた
後、５×１０2 〜５×１０3 （１／ｓ）の歪み速度範囲
で変形した時の３〜１０％の相当歪み範囲における変形
応力の平均値：σｄｙｎ（ＭＰａ）が予変形を与える前
の５×１０-4〜５×１０-3（１／ｓ）の歪み速度範囲で
測定された静的な引張り試験における最大応力ＴＳによ
って表現される式：σdyn ≧０．７６６×ＴＳ＋２５０
を満足することを特徴とする高い動的変形抵抗を有する
衝突時衝撃吸収用高強度熱延鋼板の製造方法。7. C: 0.04% or more and 0.3% by weight%
Hereinafter, one or both of Si and Al are 0.5% or more and 3.0% or less in total, and one or more of Mn, Ni, Cr, Cu, and Mo are 0.5% or more and 3.5% or more in total. % Or less, with the balance being Fe and unavoidable impurities, the cast slab is sent directly to the hot rolling process as it is, or once cooled and then heated again in the range of 1000 ° C. to 1300 ° C., the hot rolling is performed with Ar 3 Transformation temperature + 50 ℃ or more Ar 3 transformation temperature + 100 ℃ or less completed at the hot rolling finish temperature (FT), then cool at a cooling rate of 5 ℃ / s or more 100 ℃ / s or less, when hot rolling, Finishing temperature is Ar 3 transformation temperature +
When the temperature is 50 ° C or higher, it is wound at a temperature of 250 ° C or higher and lower than 380 ° C, and the hot rolling finish temperature is Ar 3 transformation temperature + 50 ° C
Less than Ri winding <br/> taken at temperatures below 250 ° C. or higher 420 ° C. in the case, the microstructure of the finally obtained hot-rolled steel sheet includes ferrite and bainite, and this one with the main phase, the volume fraction Is a composite structure with a third phase containing retained austenite of 3% or more, and a tensile strength of 597 MPa or more.
It has an average of solute (C) the amount and the steel in the residual austenite Mn eq {Mneq = Mn + (Ni + Cr + Cu +
Mo) / 2} determined value (M = 678-428 ×
[C] -33 × Mneq) is 70 or more and 250 or less, and after subjecting the steel material to pre-deformation of more than 0% and 10% or less by equivalent strain, 5 × 10 2 to 5 × 10 3 (1 / s) of Mean value of the deformation stress in the equivalent strain range of 3 to 10% when deformed in the strain rate range: 5 × 10 −4 to 5 × 10 −3 (1 / s) before σdyn (MPa) gives pre-deformation The expression expressed by the maximum stress TS in a static tensile test measured in the strain rate range of: σ dyn ≧ 0.766 × TS + 250
Has a high dynamic deformation resistance characterized by satisfying
A method for manufacturing a high-strength hot-rolled steel sheet for shock absorption during a collision .
計で０．３重量％以下更に含むことを特徴とする請求項
７記載の高い動的変形抵抗を有する衝突時衝撃吸収用高
強度熱延鋼板の製造方法。8. The impact-absorbing shock having high dynamic deformation resistance according to claim 7, further comprising one or more of Nb, Ti and V in a total amount of 0.3% by weight or less . Manufacturing method of high strength hot rolled steel sheet.
徴とする請求項７または８記載の高い動的変形抵抗を有
する衝突時衝撃吸収用高強度熱延鋼板の製造方法。9. The method for producing a high-strength hot-rolled steel sheet for impact shock absorption having high dynamic deformation resistance as set forth in claim 7, further containing 0.2 wt% or less of P.
を特徴とする請求項７〜９のいずれか１項に記載の高い
動的変形抵抗を有する衝突時衝撃吸収用高強度熱延鋼板
の製造方法。10. A high-strength hot-rolled steel sheet for impact shock absorption having a high dynamic deformation resistance according to claim 7, further comprising 0.01% by weight or less of B. Manufacturing method.
Priority Applications (17)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP25888797A JP3530355B2 (en) | 1997-09-24 | 1997-09-24 | High-strength hot-rolled steel sheet with high dynamic deformation resistance for impact absorption at the time of collision and manufacturing method thereof |
| CA002273334A CA2273334C (en) | 1996-11-28 | 1997-11-28 | High strength steels having high impact energy absorption properties and a method for producing the same |
| KR1019997004657A KR100318213B1 (en) | 1996-11-28 | 1997-11-28 | High-strength steel plate having high dynamic deformation resistance and method of manufacturing the same |
| TW086117962A TW384313B (en) | 1996-11-28 | 1997-11-28 | High strength steels having high impact energy absorption properties and a method for producing the same |
| CN97180921A CN1078623C (en) | 1996-11-28 | 1997-11-28 | High-strength steel having high impact energy absorption power and method for mfg. same |
| EP97913471.5A EP0952235B2 (en) | 1996-11-28 | 1997-11-28 | Method for producing high-strength steels having high impact energy absorption properties |
| AU50679/98A AU711873B2 (en) | 1996-11-28 | 1997-11-28 | High-strength steels having high impact energy absorption properties and a method for producing the same |
| EP10181458A EP2314730B1 (en) | 1996-11-28 | 1997-11-28 | High-strength steels having high impact energy absorption properties. |
| PCT/JP1997/004359 WO1998023785A1 (en) | 1996-11-28 | 1997-11-28 | High-strength steel plate having high dynamic deformation resistance and method of manufacturing the same |
| CA002278841A CA2278841C (en) | 1997-01-29 | 1998-01-23 | High strength steels having excellent formability and high impact energy absorption properties, and a method for producing the same |
| EP98900718.2A EP0974677B2 (en) | 1997-01-29 | 1998-01-23 | A method for producing high strength steels having excellent formability and high impact energy absorption properties |
| AU55767/98A AU716203B2 (en) | 1997-01-29 | 1998-01-23 | High strength steels having excellent formability and high impact energy absorption properties, and a method for production the same |
| PCT/JP1998/000272 WO1998032889A1 (en) | 1997-01-29 | 1998-01-23 | High-strength steel sheet highly resistant to dynamic deformation and excellent in workability and process for the production thereof |
| US09/355,435 US6544354B1 (en) | 1997-01-29 | 1998-01-23 | High-strength steel sheet highly resistant to dynamic deformation and excellent in workability and process for the production thereof |
| EP10181439A EP2312008B1 (en) | 1997-01-29 | 1998-01-23 | High-strength steels having high impact energy absorption properties. |
| CN98802157A CN1072272C (en) | 1997-01-29 | 1998-01-23 | High-strength steel sheet highly resistant to dynamic deformation and excellent in workability and process for production thereof |
| KR1019997006826A KR100334948B1 (en) | 1997-01-29 | 1998-01-23 | High-strength steel sheet highly resistant to dynamic deformation and excellent in workability and process for the production thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP25888797A JP3530355B2 (en) | 1997-09-24 | 1997-09-24 | High-strength hot-rolled steel sheet with high dynamic deformation resistance for impact absorption at the time of collision and manufacturing method thereof |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH11100640A JPH11100640A (en) | 1999-04-13 |
| JP3530355B2 true JP3530355B2 (en) | 2004-05-24 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP25888797A Expired - Fee Related JP3530355B2 (en) | 1996-11-28 | 1997-09-24 | High-strength hot-rolled steel sheet with high dynamic deformation resistance for impact absorption at the time of collision and manufacturing method thereof |
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| JP (1) | JP3530355B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH11189839A (en) * | 1997-12-26 | 1999-07-13 | Nippon Steel Corp | High strength steel plate with high dynamic deformation resistance, and its production |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5165236B2 (en) * | 2006-12-27 | 2013-03-21 | 新日鐵住金ステンレス株式会社 | Stainless steel plate for structural members with excellent shock absorption characteristics |
| EP2918868A4 (en) * | 2012-11-08 | 2016-07-13 | Jfe Steel Corp | Impact absorbing member |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6479345A (en) * | 1987-06-03 | 1989-03-24 | Nippon Steel Corp | High-strength hot rolled steel plate excellent in workability and its production |
| JPH0735536B2 (en) * | 1988-01-14 | 1995-04-19 | 株式会社神戸製鋼所 | Manufacturing method of high ductility and high strength composite structure steel sheet |
| JP3066689B2 (en) * | 1993-08-25 | 2000-07-17 | 新日本製鐵株式会社 | High-strength composite structure hot-rolled steel sheet excellent in workability and fatigue properties, and method for producing the same |
| JP3569307B2 (en) * | 1994-01-12 | 2004-09-22 | 新日本製鐵株式会社 | High strength composite structure cold rolled steel sheet having excellent workability and a tensile strength of 45 to 65 kgf / mm2, and a method for producing the same |
| JPH07252592A (en) * | 1994-03-15 | 1995-10-03 | Nippon Steel Corp | Hot rolled high strength steel sheet excellent in formability, low temperature toughness and fatigue property |
| TW363082B (en) * | 1994-04-26 | 1999-07-01 | Nippon Steel Corp | Steel sheet having high strength and being suited to deep drawing and process for producing the same |
| JPH09241788A (en) * | 1996-03-04 | 1997-09-16 | Kawasaki Steel Corp | High tensile strength steel plate excellent in impact resistance and its production |
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1997
- 1997-09-24 JP JP25888797A patent/JP3530355B2/en not_active Expired - Fee Related
Non-Patent Citations (2)
| Title |
|---|
| 三浦ら，自動車用衝撃吸収高張力鋼板の開発，まてりあ ，１９９６年 ５月２０日，Ｖｏｌ．３５ Ｎｏ．３， Ｐ，５７０−５７２ |
| 板橋ら，予ひずみを与えられた建築構造用圧延鋼材ＳＮ４９０Ｂの高速引張特性，日本材料学会学術講演会講演論文集，１９９７年 ５月２２日，Ｖｏｌ．４６ｔｈ ， Ｐ．２９１−２９２ |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH11189839A (en) * | 1997-12-26 | 1999-07-13 | Nippon Steel Corp | High strength steel plate with high dynamic deformation resistance, and its production |
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| Publication number | Publication date |
|---|---|
| JPH11100640A (en) | 1999-04-13 |
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