JP3287251B2 - Steel sheets and steel pipes excellent in high fatigue strength characteristics by arc local heating, and methods for producing them - Google Patents
Steel sheets and steel pipes excellent in high fatigue strength characteristics by arc local heating, and methods for producing themInfo
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- JP3287251B2 JP3287251B2 JP01324197A JP1324197A JP3287251B2 JP 3287251 B2 JP3287251 B2 JP 3287251B2 JP 01324197 A JP01324197 A JP 01324197A JP 1324197 A JP1324197 A JP 1324197A JP 3287251 B2 JP3287251 B2 JP 3287251B2
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- fatigue strength
- steel
- heating
- arc
- steel sheet
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- Heat Treatment Of Sheet Steel (AREA)
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、アーム、メンバ
ー、フレーム等の自動車構造部材のような疲労強度が要
求される用途に適用される、アーク局部加熱による高疲
労強度化特性に優れた鋼板および鋼管、ならびにそれら
の製造方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel sheet which is applied to applications requiring fatigue strength such as automobile structural members such as arms, members, frames, etc., and which is excellent in characteristics of increasing fatigue strength by local heating of an arc. The present invention relates to steel pipes and a method for producing them.
【０００２】[0002]
【従来の技術】近年、自動車分野では、衝突安全性への
対応のためのゲージアップや新たなリーンフォースメン
トの追加など、ボディー部材の車両重量増加要因が増え
てきている。このために、アーム、メンバー、フレーム
等の構造部材には、さらなる軽量化が求められている。
剛性や疲労強度の低下をともなわず軽量化を図るために
は、材料の高張力化が必要であるが、これらの部材は成
形性が良好なことが必要であり、そのため高張力化が困
難であった。2. Description of the Related Art In recent years, in the field of automobiles, factors for increasing vehicle weight of body members have been increasing, such as increasing gauges for collision safety and adding new reinforcements. For this reason, structural members such as arms, members, and frames are required to be further reduced in weight.
In order to reduce the weight without lowering the rigidity and fatigue strength, it is necessary to increase the tension of the material.However, these members need to have good formability, and it is difficult to increase the tension. there were.
【０００３】そこで、低強度の素材を用いて優れた成形
性を確保しつつ、必要な部分のみ高強度化する技術が、
特開平４−７２０１０号公報、特開平６−７３４３８号
公報に開示されている。これらはいずれも鋼板にレーザ
ービームを照射し、板厚方向の全厚を溶融・凝固させる
ことで鋼板の高強度化を図る技術である。これらのうち
特開平６−７３４３８号公報には照射条件に加え、対象
鋼の組織についての知見も記載されている。そして、こ
れらの技術によって局部的に１００ＭＰａ程度の強度上
昇が得られている。[0003] Therefore, a technique of using a low-strength material to ensure excellent moldability and increase the strength of only necessary parts has been developed.
It is disclosed in JP-A-4-72010 and JP-A-6-73438. These are all techniques for increasing the strength of a steel sheet by irradiating the steel sheet with a laser beam and melting and solidifying the entire thickness in the thickness direction. Among them, Japanese Patent Application Laid-Open No. Hei 6-73438 describes knowledge about the structure of the target steel in addition to the irradiation conditions. These techniques have locally increased the strength by about 100 MPa.
【０００４】[0004]
【発明が解決しようとする課題】しかしながら、このよ
うな方法により局部的な強化を行うと、耐久疲労試験を
行った場合、静的強度の上昇にもかかわらず、疲労強度
が向上しないという問題点がある。これは、レーザー加
熱のような極めてエネルギー密度の高い入熱を行うと、
板厚全厚に亘って高強度化を図ることができる反面、隣
接する非加熱部との変形抵抗の差によって、繰り返し変
形時に歪の集中が生じるためであると考えられる。However, when the local strengthening is performed by such a method, the fatigue strength is not improved in the durability fatigue test despite the increase in the static strength. There is. This is because heat input with extremely high energy density, such as laser heating,
It is considered that the strength can be increased over the entire thickness of the sheet, but the difference in deformation resistance between the adjacent non-heated portions causes concentration of strain during repeated deformation.
【０００５】そこで、レーザー加熱のように全厚に亘っ
て高強度化を図るのではなく、よりエネルギー密度の低
いアーク加熱によって表面部分のみ硬度を上昇させ、高
疲労強度を達成することが考えられるが、このような高
疲労強度化に適した材料については未だ検討されていな
い。Therefore, it is conceivable to achieve high fatigue strength by increasing the hardness of only the surface portion by arc heating with a lower energy density, instead of increasing the strength over the entire thickness unlike laser heating. However, materials suitable for such high fatigue strength have not yet been studied.
【０００６】本発明は、かかる事情に鑑みてなされたも
のであって、アーク局部加熱を用いて疲労強度を高める
のに好適な鋼板および鋼管、ならびにそれらの製造方法
を提供することを目的とする。The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a steel sheet and a steel pipe suitable for enhancing fatigue strength by using local heating of an arc, and a method of manufacturing the same. .
【０００７】[0007]
【課題を解決するための手段】本発明者らは、疲労強度
向上という観点から鋭意検討を重ねた結果、まず局部加
熱方法と被加熱材の加熱−冷却挙動について検討し、ア
ーク加熱により鋼板の全厚ではなく表面部のみの硬度を
上昇させることで高疲労強度化が達成されることを確認
した。また、このようなアーク局部加熱を前提にして、
鋼板材質と疲労強度上昇効果との関係について実験的検
討を重ねた結果、特定の組成の材料を用いることで耐久
疲労強度比が１．１以上の高疲労強度化特性が得られる
ことを知見し、本発明を完成するに至ったものである。
局部加熱により耐久疲労強度比を１．１以上とすること
で、１グレード強度の高い鋼と同等の疲労強度が得られ
る。Means for Solving the Problems The present inventors have conducted intensive studies from the viewpoint of improving fatigue strength. As a result, first, the local heating method and the heating-cooling behavior of the material to be heated are examined, and the steel sheet is heated by arc heating. It was confirmed that high fatigue strength was achieved by increasing the hardness of only the surface portion, not the entire thickness. Also, on the premise of such arc local heating,
As a result of repeated experimental studies on the relationship between the steel sheet material and the effect of increasing the fatigue strength, it was found that high fatigue strength characteristics with a durability fatigue strength ratio of 1.1 or more can be obtained by using a material of a specific composition. Thus, the present invention has been completed.
By setting the durability fatigue strength ratio to 1.1 or more by local heating, a fatigue strength equivalent to that of steel having a high grade strength can be obtained.
【０００８】本発明はこのような知見に基づいてなされ
たものであり、以下の（１）〜（５）を提供するもので
ある。 （１）アーク加熱により表面部のみを局部的に加熱し、
疲労強度を高めて使用する鋼板であって、重量％で、
Ｃ：０．０１〜０．３５％、Ｓｉ：２．０％以下、Ｍ
ｎ：０．１〜２．０％を含有し、以下の（Ａ）式で示す
パラメータξが ０．３≦ξ≦１０ を満たすことを特徴とする、アーク局部加熱による高疲
労強度化特性に優れた鋼板。[0008] The present invention has been made based on such findings, and provides the following (1) to (5). (1) Only the surface is locally heated by arc heating,
A steel plate used to increase fatigue strength.
C: 0.01 to 0.35%, Si: 2.0% or less, M
n: 0.1 to 2.0%, and the parameter ξ represented by the following formula (A) satisfies 0.3 ≦ ξ ≦ 10. Excellent steel plate.
【０００９】（２）上記鋼板を造管して得られるアーク
局部加熱による高疲労強度化特性に優れた鋼管。(2) A steel pipe obtained by forming the above-mentioned steel sheet into a pipe and having an excellent property of increasing fatigue strength by local heating of an arc.
【００１０】（３）重量％で、Ｃ：０．０１〜０．３５
％、Ｓｉ：２．０％以下、Ｍｎ：０．１〜２．０％を含
有し、以下の（Ａ）式で示すパラメータξが ０．３≦ξ≦１０ を満たす鋼スラブを連続鋳造後、１２００℃を超える温
度に再加熱することなく熱間圧延を行うことを特徴とす
る、アーク局部加熱による高疲労強度化特性に優れた鋼
板の製造方法。(3) C: 0.01-0.35% by weight
%, Si: 2.0% or less, Mn: 0.1 to 2.0%, and after continuously casting a steel slab in which the parameter で represented by the following formula (A) satisfies 0.3 ≦ ξ ≦ 10: 1. A method for producing a steel sheet excellent in high fatigue strength characteristics by local heating of an arc, wherein hot rolling is performed without reheating to a temperature exceeding 1200 ° C.
【００１１】（４）重量％で、Ｃ：０．０１〜０．３５
％、Ｓｉ：２．０％以下、Ｍｎ：０．１〜２．０％を含
有し、以下の（Ａ）式で示すパラメータξが ０．３≦ξ≦１０ を満たす鋼スラブを連続鋳造後、１１００℃を超える温
度に再加熱することなく熱間圧延し、５８０℃以下の温
度で巻取ることを特徴とする、アーク局部加熱による高
疲労強度化特性に優れた鋼板の製造方法。(4) C: 0.01 to 0.35% by weight
%, Si: 2.0% or less, Mn: 0.1 to 2.0%, and after continuously casting a steel slab in which the parameter で represented by the following formula (A) satisfies 0.3 ≦ ξ ≦ 10: 1. A method for producing a steel sheet excellent in high fatigue strength characteristics by local heating of an arc, comprising hot rolling without reheating to a temperature exceeding 1100 ° C. and winding at a temperature of 580 ° C. or less.
【００１２】（５）（１）の鋼板、または（２）もしく
は（３）の方法で得られた鋼板を幅絞り率１〜１０％の
範囲で造管して、電縫鋼管を得ることを特徴とする、高
疲労強度化特性に優れた鋼管の製造方法。(5) An electric resistance welded steel pipe is obtained by forming the steel sheet of (1) or the steel sheet obtained by the method of (2) or (3) in a range of a width reduction ratio of 1 to 10%. A method for producing a steel pipe characterized by high fatigue strength characteristics.
【００１３】 ξ＝Ｃ／（２Ｔｉ*＋Ｖ＋０．５Ｎｂ） ……（Ａ） ただし、 Ｔｉ＞３．４２Ｎの時 Ｔｉ*＝Ｔｉ−３．４２Ｎ Ｔｉ≦３．４２Ｎの時 Ｔｉ*＝０Ξ = C / (2Ti * + V + 0.5Nb) (A) where Ti> 3.42N Ti * = Ti−3.42N Ti ≦ 3.42N Ti * = 0
【００１４】[0014]
【発明の実施の形態】本発明は鋼板および鋼管、ならび
にそれらの製造方法に係るものであり、鋼組成、または
それに加えて熱間圧延条件もしくは造管条件を適正に制
御してはじめて達成されるものである。以下、本発明に
ついて（１）鋼組成、（２）熱間圧延条件、（３）造管
条件に分けて説明する。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a steel sheet and a steel pipe, and a method for producing the same, and is achieved only by appropriately controlling the steel composition or, in addition, hot rolling conditions or pipe forming conditions. Things. Hereinafter, the present invention will be described by dividing into (1) steel composition, (2) hot rolling conditions, and (3) tube forming conditions.
【００１５】（１）鋼組成 本発明に係る鋼板および鋼管は、重量％で、Ｃ：０．０
１〜０．３５％、Ｓｉ：２．０％以下、Ｍｎ：０．１〜
２．０％を含有し、パラメータξが０．３≦ξ≦１０を
満たす化学組成を有する。(1) Steel Composition The steel sheet and the steel pipe according to the present invention have a C content of 0.0% by weight.
1 to 0.35%, Si: 2.0% or less, Mn: 0.1 to
2.0%, and has a chemical composition in which the parameter を 満 た す satisfies 0.3 ≦ ξ ≦ 10.
【００１６】Ｃ：Ｃは加熱前に固溶元素あるいは炭化物
として存在し、アーク加熱−冷却により存在形態を変え
ることで局部高疲労強度に寄与する。しかし、その含有
量が０．０１％未満では所望の高疲労強度化を達成する
ことができず、一方、０．３５％を超えると加熱部と非
加熱部の硬度比が大きくなり、非加熱部分に歪の集中が
生じ、疲労強度がかえって低下する。したがって、Ｃ含
有量を０．０１〜０．３５％の範囲とする。C: C exists as a solid solution element or carbide before heating, and contributes to local high fatigue strength by changing its form by arc heating-cooling. However, if the content is less than 0.01%, the desired high fatigue strength cannot be achieved, while if it exceeds 0.35%, the hardness ratio between the heated portion and the non-heated portion increases, and Concentration of strain occurs in the portion, and fatigue strength is rather reduced. Therefore, the C content is in the range of 0.01 to 0.35%.
【００１７】Ｓｉ：Ｓｉは加熱部と非加熱部の硬度比を
小さくし、非加熱部への応力集中を抑制することで高疲
労強度化に寄与する。しかし、２．０％を超えると非加
熱部が高強度化し、局部加熱による高疲労強度化の効果
が得られなくなる。したがって、Ｓｉ含有量を２．０％
以下とする。Si: Si contributes to high fatigue strength by reducing the hardness ratio between the heated portion and the non-heated portion and suppressing the concentration of stress on the non-heated portion. However, if it exceeds 2.0%, the strength of the non-heated portion increases, and the effect of increasing the fatigue strength by local heating cannot be obtained. Therefore, the Si content is set to 2.0%
The following is assumed.
【００１８】Ｍｎ：Ｍｎは加熱部と非加熱部の硬度比を
小さくし、非加熱部への応力集中を抑制することで高疲
労強度化に寄与する。しかし、０．１％未満では所望の
高疲労強度化が達成されず、一方、２．０％を超えると
加熱部が著しく高強度化し、かえって疲労強度が低下す
る。したがって、Ｍｎ含有量を０．１〜２．０％の範囲
とする。Mn: Mn contributes to high fatigue strength by reducing the hardness ratio between the heated part and the non-heated part and suppressing stress concentration on the non-heated part. However, if it is less than 0.1%, the desired high fatigue strength cannot be achieved, while if it exceeds 2.0%, the heating part has a remarkably high strength, and on the contrary, the fatigue strength decreases. Therefore, the Mn content is set in the range of 0.1 to 2.0%.
【００１９】Ｔｉ、Ｖ、Ｎｂ：Ｔｉ、Ｖ、Ｎｂは加熱部
に炭化物として析出し、高疲労強度化特性を向上させる
効果を有する。これらの含有量は、以下に説明するパラ
メータξで規定される。なお、Ｚｒ、Ｗ、Ｔａも同様の
効果を有する。Ti, V, Nb: Ti, V, and Nb precipitate as carbides in the heated portion and have an effect of improving the high fatigue strength characteristics. These contents are defined by the parameter す る described below. Note that Zr, W, and Ta have the same effect.
【００２０】パラメータξ：パラメータξは以下の
（Ａ）式で表され、Ｃ、Ｔｉ、Ｖ、Ｎｂ量を規定するも
のであり、アーク加熱による高疲労強度化特性と対応関
係がある。このξが１０を超えると加熱部と非加熱部の
硬度比が４を超え、非加熱部に歪の集中が生じ、耐久疲
労強度比が１．１未満となる。一方、ξが０．３未満で
あると加熱部と非加熱部の硬度比が１．３未満と加熱に
よる硬度上昇が小さく、やはり耐久疲労強度比１．１以
上が得られない。したがって、０．３≦ξ≦１０の範囲
とする。 ξ＝Ｃ／（２Ｔｉ*＋Ｖ＋０．５Ｎｂ） ……（Ａ） ただし、 Ｔｉ＞３．４２Ｎの時 Ｔｉ*＝Ｔｉ−３．４２Ｎ Ｔｉ≦３．４２Ｎの時 Ｔｉ*＝０ なお、Ｔｉ*はＮに固定されていないＴｉを示す。Parameter ξ: Parameter さ れ is expressed by the following equation (A) and defines the amounts of C, Ti, V, and Nb, and has a relationship with the high fatigue strength characteristics by arc heating. If the value of ξ exceeds 10, the hardness ratio between the heated portion and the non-heated portion exceeds 4, the concentration of strain occurs in the non-heated portion, and the durability fatigue strength ratio becomes less than 1.1. On the other hand, when ξ is less than 0.3, the hardness ratio between the heated part and the non-heated part is less than 1.3, the increase in hardness due to heating is small, and a durability fatigue strength ratio of 1.1 or more cannot be obtained. Therefore, the range is 0.3 ≦ ξ ≦ 10. ξ = C / (2Ti * + V + 0.5Nb) (A) where Ti> 3.42N Ti * = Ti-3.42N Ti ≦ 3.42N Ti * = 0 Note that Ti * is N Shows the Ti not fixed to.
【００２１】図１はξと加熱部と非加熱部の硬度比との
関係を示す図、図２は加熱部と非加熱部の硬度比と素材
とアーク加熱材の耐久疲労強度比との関係を示す図であ
る。これらの図から、ξが０．３〜１０の間で加熱部と
非加熱部の硬度比が１．３〜４の間となり、この時耐久
疲労強度比が１．１以上の高疲労強度化特性が得られる
ことが確認される。FIG. 1 is a diagram showing the relationship between Δ and the hardness ratio between the heated portion and the non-heated portion, and FIG. 2 is the relationship between the hardness ratio between the heated portion and the non-heated portion and the durability fatigue strength ratio between the material and the arc-heated material. FIG. From these figures, it can be seen that when ξ is between 0.3 and 10, the hardness ratio between the heated part and the non-heated part is between 1.3 and 4, and at this time, the fatigue strength ratio is at least 1.1. It is confirmed that characteristics can be obtained.
【００２２】なお、ここでの実験条件は次の通りであ
る。板厚２．６ｍｍの熱延鋼板に、電流１００Ａ、電圧
１０Ｖ、アーク走査速度１００ｃｍ／ｍｉｎ、走査ピッ
チ５ｍｍ、大気中放冷の条件で片面ずつ両面のＴＩＧア
ーク加熱を行った。これよりアーク走査方向に疲労試験
片を採取し、サイクル数２５Ｈｚで、歪一定、両振りに
て平面曲げ疲労試験を実施した。１０7サイクルの破断
限界応力を耐久疲労強度とし、これと非加熱材の耐久疲
労強度の比を耐久疲労強度比とした。なお、片面のみ加
熱を行い片振り条件で疲労試験を行っても、同様の耐久
疲労強度比が得られることを確認している。アーク加熱
中心部の破断硬度を板厚方向に０．１ｍｍピッチで測定
し、この時の最大硬度を加熱部の破断硬度として、これ
と非加熱部の断面硬度の比を硬度比のパラメータとし
た。The experimental conditions here are as follows. TIG arc heating was performed on both sides of a hot-rolled steel sheet having a thickness of 2.6 mm one by one under the conditions of a current of 100 A, a voltage of 10 V, an arc scanning speed of 100 cm / min, a scanning pitch of 5 mm, and cooling in the air. From this, a fatigue test piece was sampled in the arc scanning direction, and a plane bending fatigue test was performed at a cycle number of 25 Hz with constant strain and swinging. The fracture limit stress of 10 7 cycles and endurance fatigue strength, it the ratio of the endurance fatigue strength of non-heated material was durable and fatigue strength ratio. In addition, it has been confirmed that the same durability fatigue strength ratio can be obtained even when heating is performed on only one side and a fatigue test is performed under oscillating conditions. The breaking hardness of the arc heating center portion was measured at a pitch of 0.1 mm in the thickness direction, and the maximum hardness at this time was taken as the breaking hardness of the heating portion, and the ratio of this to the cross-sectional hardness of the non-heating portion was used as a parameter of the hardness ratio. .
【００２３】なお、本発明で規定する元素以外の元素
は、本発明が意図している高疲労強度化特性に対する影
響はほとんど認められず、これらの元素は別の目的で適
宜添加しても構わない。It should be noted that elements other than the elements specified in the present invention hardly affect the high fatigue strength characteristics intended by the present invention, and these elements may be appropriately added for another purpose. Absent.
【００２４】（２）熱間圧延条件 上記鋼組成の熱延スラブを連続鋳造後、１２００℃を超
える温度に再加熱することなく熱間圧延する。スラブ加
熱温度が１２００℃以下の場合には比較的大きなＴｉ、
Ｖ、Ｎｂ炭窒化物組織となり、熱延のままで成形性が良
好な鋼板、鋼管が得られ、このような鋼板、鋼管を部材
に成形後、アーク加熱処理を施すことにより高疲労強度
化特性を得ることができる。スラブ加熱温度が１２００
℃を超えると、熱延ままで微細な炭窒化物が析出し、鋼
板、鋼管の成形性が劣化し、かつ高疲労強度化特性が低
下する。(2) Hot Rolling Conditions The hot-rolled slab having the above-mentioned steel composition is continuously rolled after continuous casting without reheating to a temperature exceeding 1200 ° C. When the slab heating temperature is 1200 ° C. or less, relatively large Ti,
V and Nb carbonitride structure, steel sheet and steel pipe with good formability as hot rolled are obtained, and after forming such steel sheet and steel pipe into a member, arc heating treatment is applied to increase fatigue strength. Can be obtained. Slab heating temperature is 1200
When the temperature exceeds ℃, fine carbonitride precipitates as it is hot-rolled, the formability of a steel sheet or a steel pipe is deteriorated, and the high fatigue strength property is deteriorated.
【００２５】図３および図４に、それぞれスラブ再加熱
温度と成形性との関係、およびスラブ再加熱温度と耐久
疲労強度比との関係を示す。これらの図から、再加熱温
度１１００℃以下で限界板厚歪０．２以上の優れた成形
性と、耐久疲労強度比１．１以上の高い疲労強度化特性
が得られることが確認される。スラブを連続鋳造後直ち
に熱間圧延を行う直接圧延の場合には、１２００℃以上
に再加熱することなく熱間圧延し、５８０℃以下で巻取
ることにより同様の特性が得られる。FIGS. 3 and 4 show the relationship between the slab reheating temperature and the formability, and the relationship between the slab reheating temperature and the endurance fatigue strength ratio, respectively. From these figures, it is confirmed that excellent formability with a critical thickness strain of 0.2 or more and high fatigue strength characteristics with a durability fatigue strength ratio of 1.1 or more can be obtained at a reheating temperature of 1100 ° C. or less. In the case of direct rolling in which hot rolling is performed immediately after continuous casting of a slab, similar characteristics can be obtained by hot rolling without reheating to 1200 ° C or higher and winding at 580 ° C or lower.
【００２６】（３）造管条件 上記鋼組成を有する本発明の鋼板を用いて電縫鋼管を製
造する場合、その幅絞り率を１〜１０％とする。幅絞り
率が１０％を超えると、加熱による加工軟化が顕著とな
り、疲労強度はかえって低下するので１０％を上限とす
る。一方、幅絞り率が１％未満であると、周方向での疲
労強度特性が不均一となり、特定の部位に歪が集中し、
高い疲労強度が得られない。なお、幅絞り率は以下の式
で求められる。 ｛スリットコイル幅−π（外径−板厚）｝／π（外径−
板厚）×１００％(3) Pipe Making Conditions When an ERW pipe is manufactured using the steel sheet of the present invention having the above steel composition, the width reduction ratio is set to 1 to 10%. When the width reduction ratio exceeds 10%, the softening of the work due to heating becomes remarkable, and the fatigue strength is rather reduced. Therefore, the upper limit is 10%. On the other hand, if the width reduction ratio is less than 1%, the fatigue strength characteristics in the circumferential direction become non-uniform, and strain concentrates on a specific portion,
High fatigue strength cannot be obtained. The width reduction ratio is obtained by the following equation. {Slit coil width-π (outer diameter-plate thickness)} / π (outer diameter-
Board thickness) x 100%
【００２７】[0027]
【実施例】以下、本発明の実施例について説明する。 （実施例１）表１に示す１５種類の鋼を溶製し、表１に
示すような熱延条件にて板厚２．６ｍｍの熱延鋼板を作
成した。熱延鋼板に対して前述した条件でＴＩＧアーク
加熱を行った後、プレス成形性、硬度比、耐久疲労強度
比を求めた。さらに、走査方向に平行に採取したＪＩＳ
５号引張試験片で引張試験を行い、アーク加熱による引
張強度（ＴＳ）上昇量を評価した。その結果を表２に示
す。Embodiments of the present invention will be described below. (Example 1) Fifteen kinds of steels shown in Table 1 were melted and hot-rolled steel sheets having a thickness of 2.6 mm were prepared under the hot-rolling conditions shown in Table 1. After performing TIG arc heating on the hot-rolled steel sheet under the conditions described above, press formability, hardness ratio, and durability fatigue strength ratio were determined. Furthermore, JIS sampled in parallel to the scanning direction
A tensile test was performed on a No. 5 tensile test piece to evaluate the amount of increase in tensile strength (TS) due to arc heating. Table 2 shows the results.
【００２８】表２に示すように、本発明を満足する組成
の鋼Ａ〜Ｅ、Ｊ〜Ｏについて、スラブ加熱温度を１１０
０℃以下とした場合に、アーク加熱により耐久疲労強度
比が１．１以上となり、良好な高疲労強度化特性が得ら
れることが確認された。As shown in Table 2, for steels A to E and J to O having compositions satisfying the present invention, the slab heating temperature was set at 110.
When the temperature was set to 0 ° C. or lower, it was confirmed that the durability ratio of the fatigue strength became 1.1 or more due to the arc heating, and good high fatigue strength characteristics were obtained.
【００２９】[0029]
【表１】 [Table 1]
【００３０】[0030]
【表２】 [Table 2]
【００３１】（実施例２）本発明の組成を満足する鋼Ａ
〜Ｃ、Ｅ、Ｊ、Ｌ、Ｏを用いて、表３に示すように、熱
間圧延条件、造管条件を種々変化させて製造した鋼板、
あるいは鋼管について、実施例１と同様に硬度比、耐久
疲労強度比、ＴＳ上昇量を求めた。なお、鋼管の場合
は、外径６０．５ｍｍφに電縫造管したものに、前述し
た条件で外側片面のＴＩＧアーク加熱を行った。鋼管の
耐久疲労強度比は、小野式回転曲げ試験によって求め
た。鋼管の引張試験はＪＩＳ１２号Ａ試験片で行った。(Example 2) Steel A satisfying the composition of the present invention
~ C, E, J, L, O, as shown in Table 3, hot-rolling conditions, steel plate manufactured by variously changing the pipe-forming conditions,
Alternatively, for the steel pipe, the hardness ratio, the durability fatigue strength ratio, and the TS increase were determined in the same manner as in Example 1. In the case of a steel pipe, one side of the outside was subjected to TIG arc heating under the above-described conditions on an electric resistance welded pipe having an outer diameter of 60.5 mmφ. The durability fatigue strength ratio of the steel pipe was determined by an Ono-type rotary bending test. The tensile test of the steel pipe was performed using a JIS No. 12A test piece.
【００３２】表３に示すように、鋼組成が本発明の範囲
を満足する場合、熱間圧延条件、造管条件が本発明を満
足する鋼板および鋼管について、アーク加熱により耐久
疲労強度比が１．１以上となり、良好な高疲労強度化特
性が得られることが確認された。As shown in Table 3, when the steel composition satisfies the range of the present invention, the steel sheet and the steel pipe having the hot rolling conditions and the pipe forming conditions satisfying the present invention have a durability fatigue strength ratio of 1 by arc heating. .1 or more, and it was confirmed that good high fatigue strength characteristics were obtained.
【００３３】[0033]
【表３】 [Table 3]
【００３４】[0034]
【発明の効果】以上説明したように、本発明によれば、
アーク局部加熱により疲労強度を高めるのに好適な鋼板
および鋼管、ならびにそれらの製造方法を得ることがで
きる。したがって、本発明により自動車構造部材等の素
材のゲージダウンが可能となる。As described above, according to the present invention,
It is possible to obtain a steel sheet and a steel pipe suitable for increasing the fatigue strength by local heating of the arc, and a method for producing the same. Therefore, according to the present invention, it is possible to reduce the gauge of a material such as an automobile structural member.
【図面の簡単な説明】[Brief description of the drawings]
【図１】パラメータξと加熱部と非加熱部の硬度比との
関係を示す図。FIG. 1 is a diagram showing a relationship between a parameter ξ and a hardness ratio between a heated portion and a non-heated portion.
【図２】加熱部と非加熱部の硬度比と耐久疲労強度比と
の関係を示す図。FIG. 2 is a diagram showing a relationship between a hardness ratio of a heated portion and a non-heated portion and a durability fatigue strength ratio.
【図３】スラブ再加熱温度と成形性との関係を示す図。FIG. 3 is a diagram showing a relationship between slab reheating temperature and formability.
【図４】スラブ再加熱温度と耐久疲労強度比との関係を
示す図。FIG. 4 is a diagram showing a relationship between a slab reheating temperature and a durability fatigue strength ratio.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 真保 幸雄 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 大村 雅紀 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 占部 俊明 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 平５−51692（ＪＰ，Ａ) 特開 平７−62489（ＪＰ，Ａ) 特開 平10−195595（ＪＰ，Ａ) 特開 昭54−65107（ＪＰ，Ａ) 特開 平10−193164（ＪＰ，Ａ) 特開 昭61−110721（ＪＰ，Ａ) 特開 昭60−204823（ＪＰ，Ａ) 特開 昭60−234919（ＪＰ，Ａ) (58)調査した分野(Int.Cl.7，ＤＢ名) C22C 38/00 - 38/60 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yukio Maho 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Masaki Omura 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Inside (72) Inventor Toshiaki Urabe 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (56) References JP-A-5-51692 (JP, A) JP-A-7-62489 ( JP, A) JP-A-10-195595 (JP, A) JP-A-54-65107 (JP, A) JP-A-10-193164 (JP, A) JP-A-61-110721 (JP, A) 60-204823 (JP, A) JP-A-60-234919 (JP, A) (58) Fields investigated (Int. Cl. 7 , DB name) C22C 38/00-38/60
Claims (5)
加熱し、疲労強度を高めて使用する鋼板であって、 重量％で、Ｃ：０．０１〜０．３５％、 Ｓｉ：２．０％以下、 Ｍｎ：０．１〜２．０％ を含有し、以下の式で示すパラメータξが ０．３≦ξ≦１０ を満たすことを特徴とする、アーク局部加熱による高疲
労強度化特性に優れた鋼板。 ξ＝Ｃ／（２Ｔｉ*＋Ｖ＋０．５Ｎｂ） ただし、 Ｔｉ＞３．４２Ｎの時 Ｔｉ*＝Ｔｉ−３．４２Ｎ Ｔｉ≦３．４２Ｎの時 Ｔｉ*＝０1. A steel sheet which is used by locally heating only a surface portion by arc heating to increase fatigue strength, wherein C: 0.01 to 0.35%, and Si: 2.0% by weight. % Or less, Mn: 0.1 to 2.0%, and the parameter 示 す represented by the following formula satisfies 0.3 ≦ ξ ≦ 10. Excellent steel plate. ξ = C / (2Ti * + V + 0.5Nb) where Ti> 3.42N Ti * = Ti−3.42N Ti ≦ 3.42N Ti * = 0
ク局部加熱による高疲労強度化特性に優れた鋼管。2. A steel pipe obtained by pipe-forming the steel sheet according to claim 1 and having an excellent property of increasing fatigue strength by local heating of an arc.
度に再加熱することなく熱間圧延を行うことを特徴とす
る、アーク局部加熱による高疲労強度化特性に優れた鋼
板の製造方法。 ξ＝Ｃ／（２Ｔｉ*＋Ｖ＋０．５Ｎｂ） ただし、 Ｔｉ＞３．４２Ｎの時 Ｔｉ*＝Ｔｉ−３．４２Ｎ Ｔｉ≦３．４２Ｎの時 Ｔｉ*＝０3. The method according to claim 1, wherein C: 0.01 to 0.35%, Si: 2.0% or less, and Mn: 0.1 to 2.0% by weight. It is characterized by performing hot rolling without reheating to a temperature exceeding 1200 ° C. after continuous casting of a steel slab satisfying 0.3 ≦ ξ ≦ 10, and excellent in high fatigue strength characteristics by local heating of an arc. Steel plate manufacturing method. ξ = C / (2Ti * + V + 0.5Nb) where Ti> 3.42N Ti * = Ti−3.42N Ti ≦ 3.42N Ti * = 0
度に再加熱することなく熱間圧延し、５８０℃以下の温
度で巻取ることを特徴とする、アーク局部加熱による高
疲労強度化特性に優れた鋼板の製造方法。 ξ＝Ｃ／（２Ｔｉ*＋Ｖ＋０．５Ｎｂ） ただし、 Ｔｉ＞３．４２Ｎの時 Ｔｉ*＝Ｔｉ−３．４２Ｎ Ｔｉ≦３．４２Ｎの時 Ｔｉ*＝０4. The method according to claim 1, wherein C: 0.01 to 0.35%, Si: 2.0% or less, and Mn: 0.1 to 2.0% by weight%, and the parameter ξ represented by the following formula: After continuous casting of a steel slab satisfying 0.3 ≦ ξ ≦ 10, hot rolling without reheating to a temperature exceeding 1200 ° C., and winding at a temperature of 580 ° C. or less, characterized by local arc heating A method for producing steel sheets with excellent fatigue strength characteristics. ξ = C / (2Ti * + V + 0.5Nb) where Ti> 3.42N Ti * = Ti−3.42N Ti ≦ 3.42N Ti * = 0
は請求項３の方法で得られた鋼板を幅絞り率１〜１０％
の範囲で造管して、電縫鋼管を得ることを特徴とする、
高疲労強度化特性に優れた鋼管の製造方法。5. The steel sheet according to claim 1, or the steel sheet obtained by the method according to claim 2 or 3, wherein the width reduction ratio is 1 to 10%.
Characterized by obtaining an ERW steel pipe in the range of
A method for manufacturing steel pipes with excellent fatigue strength characteristics.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP01324197A JP3287251B2 (en) | 1997-01-10 | 1997-01-10 | Steel sheets and steel pipes excellent in high fatigue strength characteristics by arc local heating, and methods for producing them |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP01324197A JP3287251B2 (en) | 1997-01-10 | 1997-01-10 | Steel sheets and steel pipes excellent in high fatigue strength characteristics by arc local heating, and methods for producing them |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH10195594A JPH10195594A (en) | 1998-07-28 |
| JP3287251B2 true JP3287251B2 (en) | 2002-06-04 |
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ID=11827713
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
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| WO2012133558A1 (en) * | 2011-03-30 | 2012-10-04 | 新日本製鐵株式会社 | Electroseamed steel pipe and process for producing same |
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|---|---|
| JPH10195594A (en) | 1998-07-28 |
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