JP2002194503A - Steel tube with superior buckling resistance, and production method and evaluation system for the same - Google Patents
Steel tube with superior buckling resistance, and production method and evaluation system for the sameInfo
- Publication number
- JP2002194503A JP2002194503A JP2000400636A JP2000400636A JP2002194503A JP 2002194503 A JP2002194503 A JP 2002194503A JP 2000400636 A JP2000400636 A JP 2000400636A JP 2000400636 A JP2000400636 A JP 2000400636A JP 2002194503 A JP2002194503 A JP 2002194503A
- Authority
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- Japan
- Prior art keywords
- steel pipe
- stress
- ratio
- steel
- buckling resistance
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
Description
【0001】[0001]
【発明の属する技術分野】本発明は、ガスパイプライ
ン、水道配管、建築・土木用の柱などとして好適な鋼
管、その製造方法及びその評価方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel pipe suitable as a gas pipeline, a water supply pipe, a pillar for construction and civil engineering, a method for producing the same, and a method for evaluating the same.
【0002】[0002]
【従来の技術】UOE鋼管、電縫鋼管、スパイラル鋼
管、プレスベンド鋼管等の炭素鋼鋼管あるいは低合金鋼
鋼管は大量にかつ安定して製造出来るため、その優れた
経済性や溶接施工性とあいまって、ガスパイプラインや
水道配管等の流体の輸送用配管として広く用いられてい
る。2. Description of the Related Art Carbon steel pipes such as UOE steel pipes, electric resistance welded steel pipes, spiral steel pipes, and press-bend steel pipes and low alloy steel pipes can be manufactured in large quantities and in a stable manner. It is widely used as a pipe for transporting fluids such as gas pipelines and water pipes.
【0003】しかしながら、大地震が発生した場合や海
底管の敷設時に、上記鋼管の長手方向に引張あるいは圧
縮、曲げなどのの大きな力が加わり、局部座屈、場合に
よっては円周方向のき裂の発生や破断に至ることがあ
る。However, when a large earthquake occurs or when a submarine pipe is laid, a large force such as tension, compression, or bending is applied in the longitudinal direction of the steel pipe, causing local buckling and, in some cases, circumferential cracks. May result in breakage or breakage.
【0004】このような局部座屈への対策に対して、特
開平3−173719号公報、特開平5−65535号
公報、特開平5−117746号公報、特開平5−11
7747号公報、特開平5−156357号公報、特開
平6−49540号公報、特開平6−49541号公
報、特開平6−128641号公報、特開平6−264
143号公報、特開平6−264144号公報におい
て、耐座屈性能を向上させるため降伏応力と引張強さの
比である降伏比を小さくした鋼管の製造方法が開示され
ている。To cope with such measures against local buckling, Japanese Patent Application Laid-Open Nos. 3-173719, 5-65535, 5-117746, and 5-11
7747, JP-A-5-156357, JP-A-6-49540, JP-A-6-49541, JP-A-6-128641, JP-A-6-264
No. 143 and JP-A-6-264144 disclose a method of manufacturing a steel pipe in which the yield ratio, which is the ratio of yield stress to tensile strength, is reduced to improve buckling resistance.
【0005】また、特開平9−196243号公報、特
開平9−196244号公報、特開平9−316599
号公報においては、応力−ひずみ曲線の勾配、加工硬化
指数(n値)、降伏強さを引張り強さで除した降伏比
(YR)などの制御によるラインパイプの圧縮や曲げ変
形時の座屈性能を向上させる方法が開示されている。Further, Japanese Patent Application Laid-Open Nos. 9-196243, 9-196244 and 9-316599.
In the publication, buckling during compression or bending deformation of a line pipe is controlled by controlling a gradient of a stress-strain curve, a work hardening index (n value), and a yield ratio (YR) obtained by dividing a yield strength by a tensile strength. Methods for improving performance are disclosed.
【0006】[0006]
【発明が解決しようとする課題】しかしながら、特開平
3−173719号公報、特開平5−65535号公
報、特開平5−117746号公報、特開平5−117
747号公報、特開平5−156357号公報、特開平
6−49540号公報、特開平6−49541号公報、
特開平6−128641号公報、特開平6−26414
3号公報、特開平6−264144号公報に開示される
技術は、いずれも柱の曲げ応力に対する塑性変形吸収能
に関するもので、圧縮の軸力に対する局部座屈の発生を
防ぐための検討は行われていない。However, JP-A-3-173719, JP-A-5-65535, JP-A-5-117746, and JP-A-5-117.
747, JP-A-5-156357, JP-A-6-49540, JP-A-6-49541,
JP-A-6-128541, JP-A-6-26414
No. 3 and Japanese Patent Application Laid-Open No. 6-264144 each relate to the ability of a column to absorb plastic deformation against bending stress, and studies are being conducted to prevent the occurrence of local buckling due to the axial force of compression. Not done.
【0007】また、特開平9−196243号公報、特
開平9−196244号公報、特開平9−316599
号公報に開示される技術は、いずれも応力−ひずみ曲線
におけるひずみ範囲が明確ではない。Further, Japanese Patent Application Laid-Open Nos. 9-196243, 9-196244 and 9-316599.
In any of the techniques disclosed in Japanese Patent Application Laid-Open Publication No. H11-107, the strain range in the stress-strain curve is not clear.
【0008】このように、従来技術においてはラインパ
イプが座屈するような低ひずみ領域に注目して応力―ひ
ずみ関係を制御する方法は示されていない。さらに、鋼
管周方向ならびに長手方向の特性を制御し耐座屈性を向
上させる技術も開示されていない。As described above, the prior art does not show a method of controlling the stress-strain relationship by focusing on a low strain region where the line pipe buckles. Furthermore, there is no disclosure of a technique for controlling characteristics in the circumferential direction and the longitudinal direction of the steel pipe to improve buckling resistance.
【0009】本発明は、上記問題点に鑑みなされたもの
で、大地震や海底管の敷設の際に軸方向に作用する圧縮
や曲げ応力に対して、局部座屈を起こしにくく、ガスパ
イプライン、水道配管、建築・土木用の柱などに好適な
耐座屈性に優れた鋼管、その製造方法及びその評価方法
を提供することを目的とする。SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and is not liable to cause local buckling against a compressive or bending stress acting in an axial direction at the time of a large earthquake or laying a submarine pipe. An object of the present invention is to provide a steel pipe excellent in buckling resistance suitable for a water pipe, a pillar for construction and civil engineering, and the like, a manufacturing method thereof, and an evaluation method thereof.
【0010】[0010]
【課題を解決するための手段】上記目的を達成するた
め、本発明者らは、座屈性能について鋭意検討を行っ
た。その結果、耐座屈性能の向上は、圧縮による局部座
屈の防止が最も重要であること、そして、この圧縮によ
る局部座屈には鋼管管軸方向の降伏強さと公称歪み:
1.5%時の応力(σ1.5)との比である応力比
(σr-L)またはさらに鋼管周方向の降伏強さと公称歪
み:1.5%時の応力(σ1.5)との比である応力比
(σr-C)を適切な値に制御することが有効であること
を知見した。Means for Solving the Problems In order to achieve the above object, the present inventors have intensively studied the buckling performance. As a result, prevention of local buckling due to compression is of utmost importance in improving buckling resistance, and local buckling due to this compression involves yield strength and nominal strain in the axial direction of the steel pipe:
Stress ratio (σ rL ), which is the ratio to the stress at 1.5% (σ 1.5 ), or the ratio of the yield strength in the circumferential direction of the steel pipe to the nominal strain: stress at 1.5% (σ 1.5 ). It has been found that controlling the stress ratio (σ rC ) to an appropriate value is effective.
【0011】本発明はかかる知見に基づきなされたもの
で、以下のような構成を有する。The present invention has been made based on such findings, and has the following configuration.
【0012】[1]鋼管管軸方向の引張試験において降伏
強さと公称歪み:1.5%時の応力(σ1.5)との比で
ある応力比(σr-L)が1.05以上であることを特徴
とする耐座屈性に優れた鋼管。[1] In a tensile test in the axial direction of a steel pipe, a stress ratio (σ rL ) which is a ratio of a yield strength to a stress (σ 1.5 ) at 1.5% of nominal strain is 1.05 or more. A steel pipe with excellent buckling resistance characterized by the following.
【0013】[2]鋼管周方向の引張試験において降伏強
さと公称歪み:1.5%時の応力(σ1.5)との比であ
る応力比(σr-C)と鋼管管軸方向の引張試験において
降伏強さと公称歪み:1.5%時の応力(σ1.5)との
比である応力比(σr-L)がそれぞれ1.05以上であ
ることを特徴とする耐座屈性に優れた鋼管。[2] In the tensile test in the circumferential direction of the steel pipe, the stress ratio (σ rC ), which is the ratio between the yield strength and the stress (σ 1.5 ) at 1.5% of nominal strain, and the tensile test in the axial direction of the steel pipe A steel pipe excellent in buckling resistance, wherein a stress ratio (σ rL ) which is a ratio of a yield strength and a stress at 1.5% (σ 1.5 ) at each time is 1.05 or more.
【0014】[3]前記[1]または[2]において、mas
s%で、C:0.03〜0.1%、Si:0.05〜
0.5%、Mn:1〜2%を含有し、残部が実質的にF
eからなり、かつ下記式(1)で示されるPCMが0.1
0〜0.20を満足する成分組成を有することを特徴と
する耐座屈性に優れた鋼管。 PCM =C+Si/30+Mn/20+Cu/20+Ni/60+Cr/20+Mo /15+V/10+5xB (1) [4]前記[1]ないし[3]において、さらに、mass%
で、Cu:0.05〜0.5%、Ni:0.05〜0.
5%、Cr:0.05〜0.5%、及びMo:0.05
〜0.5%の群から選ばれた1種または2種以上を含有
することを特徴とする耐座屈性に優れた鋼管。[3] In the above [1] or [2], mas
s%, C: 0.03-0.1%, Si: 0.05-
0.5%, Mn: 1-2%, the balance being substantially F
consist e, and P CM represented by the following formula (1) is 0.1
A steel pipe excellent in buckling resistance, having a component composition satisfying 0 to 0.20. P CM = C + Si / 30 + Mn / 20 + Cu / 20 + Ni / 60 + Cr / 20 + Mo / 15 + V / 10 + 5 × B (1) [4] In the above [1] to [3], mass%
, Cu: 0.05-0.5%, Ni: 0.05-0.
5%, Cr: 0.05 to 0.5%, and Mo: 0.05
A steel pipe excellent in buckling resistance, comprising one or more selected from the group of ~ 0.5%.
【0015】[5]前記[1]ないし[4]において、さら
に、mass%で、Nb:0.005〜0.1%、V:
0.005〜0.1%、及びTi:0.005〜0.0
8%の群から選ばれた1種または2種以上を含有するこ
とを特徴とする耐座屈性に優れた鋼管。[5] In the above [1] to [4], further, in mass%, Nb: 0.005 to 0.1%, V:
0.005 to 0.1%, and Ti: 0.005 to 0.0
A steel pipe excellent in buckling resistance, comprising one or more selected from the group of 8%.
【0016】[6]前記[1]ないし[5]において、さら
に、mass%で、Ca:0.0005〜0.003
%、Mg:0.0005〜0.003%の群から選ばれ
た1種または2種を含有することを特徴とする耐座屈性
に優れた鋼管。[6] In the above items [1] to [5], Ca: 0.0005 to 0.003
%, Mg: one or two selected from the group of 0.0005 to 0.003%.
【0017】[7]mass%で、C:0.03〜0.1
%、Si:0.05〜0.5%、Mn:1〜2%を含有
し、残部が実質的にFeからなり、かつ下記式(1)で
示されるPCMが0.10〜0.20を満足する鋼を熱間
圧延した後、500℃以下の任意の温度まで冷却速度:
5℃/sec以上で加速冷却することにより得られた鋼
板を、冷間成形により造管することにより管軸方向にお
ける降伏強さと公称歪み:1.5%時の応力(σ1.5)
との比である応力比(σr-L)が1.05以上である鋼
管を得ることを特徴とする耐座屈性に優れた鋼管の製造
方法。 PCM =C+Si/30+Mn/20+Cu/20+Ni/60+Cr/20+M o/15+V/10+5xB (1) [8]mass%で、C:0.03〜0.1%、Si:
0.05〜0.5%、Mn:1〜2%を含有し、残部が
実質的にFeからなり、かつ下記式(1)で示されるP
CMが0.10〜0.20を満足する鋼を熱間圧延した
後、500℃以下の任意の温度まで冷却速度:5℃/s
ec以上で加速冷却することにより得られた鋼板を、拡
管率:1.4%以下で冷間成形により造管することによ
り鋼管周方向ならびに管軸方向における降伏強さと公称
歪み:1.5%時の応力(σ1.5)との比である応力比
(σr-C、σr-L)が1.05以上である鋼管を得ること
を特徴とする耐座屈性に優れた鋼管の製造方法。 PCM =C+Si/30+Mn/20+Cu/20+Ni/60+Cr/20+M o/15+V/10+5xB (1) [9]前記[7]または[8]において、さらに、mass%
で、Cu:0.05〜0.5%、Ni:0.05〜0.
5%、Cr:0.05〜0.5%、及びMo:0.05
〜0.5%の群から選ばれた1種または2種以上を含有
した鋼を用いることを特徴とする耐座屈性に優れた鋼管
の製造方法。[7] In mass%, C: 0.03 to 0.1
% Si: 0.05 to 0.5% Mn: it contains 1-2%, the balance being substantially Fe, and the P CM represented by the following formula (1) from 0.10 to 0. After hot rolling a steel satisfying No. 20, a cooling rate to an arbitrary temperature of 500 ° C. or less:
The steel sheet obtained by accelerated cooling at 5 ° C./sec or more is formed into a tube by cold forming, whereby the yield strength in the tube axis direction and the nominal strain: stress at 1.5% (σ 1.5 )
A method for producing a steel pipe having excellent buckling resistance, characterized by obtaining a steel pipe having a stress ratio (σ rL ) that is 1.05 or more. P CM = C + Si / 30 + Mn / 20 + Cu / 20 + Ni / 60 + Cr / 20 + Mo / 15 + V / 10 + 5 × B (1) [8] Mass%, C: 0.03-0.1%, Si:
0.05 to 0.5%, Mn: 1 to 2%, the balance substantially consisting of Fe, and P represented by the following formula (1)
After hot rolling a steel satisfying CM of 0.10 to 0.20, the cooling rate to an arbitrary temperature of 500 ° C. or less: 5 ° C./s
The steel sheet obtained by accelerated cooling at ec or more is formed by cold forming at a pipe expansion ratio of 1.4% or less, whereby the yield strength and nominal strain in the steel pipe circumferential direction and pipe axis direction are 1.5%. A method for producing a steel pipe having excellent buckling resistance, characterized by obtaining a steel pipe having a stress ratio (σ rC , σ rL ) which is a ratio with respect to a stress at the time (σ 1.5 ) of 1.05 or more. P CM = C + Si / 30 + Mn / 20 + Cu / 20 + Ni / 60 + Cr / 20 + Mo / 15 + V / 10 + 5 × B (1) [9] In the above [7] or [8], mass%
, Cu: 0.05-0.5%, Ni: 0.05-0.
5%, Cr: 0.05 to 0.5%, and Mo: 0.05
A method for producing a steel pipe excellent in buckling resistance, characterized by using steel containing one or more selected from the group of 0.5% to 0.5%.
【0018】[10]前記[7]ないし[9]において、さら
に、mass%で、Nb:0.005〜0.1%、V:
0.005〜0.1%、及びTi:0.005〜0.0
8%の群から選ばれた1種または2種以上を含有した鋼
を用いることを特徴とする耐座屈性に優れた鋼管の製造
方法。[10] In the above-mentioned [7] to [9], Nb: 0.005 to 0.1%, V:
0.005 to 0.1%, and Ti: 0.005 to 0.0
A method for producing a steel pipe having excellent buckling resistance, characterized by using a steel containing one or more selected from the group of 8%.
【0019】[11]前記[7]ないし[10]において、さ
らに、mass%で、Ca:0.0005〜0.003
%、Mg:0.0005〜0.003%の群から選ばれ
た1種または2種を含有した鋼を用いることを特徴とす
る耐座屈性に優れた鋼管の製造方法。[11] In the above items [7] to [10], further, by mass%, Ca: 0.0005 to 0.003
%, Mg: 0.0005 to 0.003%. A method for producing a steel pipe having excellent buckling resistance, characterized by using steel containing one or two kinds selected from the group of 0.0005 to 0.003%.
【0020】[12]鋼管管軸方向の引張試験における降
伏強さと公称歪み:1.5%時の応力(σ1.5)との比
である応力比(σr-L)を用いて、鋼管の耐座屈性を評
価することを特徴とする鋼管の耐座屈性評価方法。[12] Using a stress ratio (σ rL ) which is a ratio of a yield strength and a nominal strain: stress (σ 1.5 ) at 1.5% in a tensile test in the axial direction of the steel pipe, the seat resistance of the steel pipe is determined. A method for evaluating buckling resistance of a steel pipe, characterized by evaluating buckling property.
【0021】[13]鋼管周方向の引張試験における降伏
強さと公称歪み:1.5%時の応力(σ1.5)との比で
ある応力比(σr-C)と、鋼管管軸方向の引張試験にお
ける降伏強さと公称歪み:1.5%時の応力(σ1.5)
との比である応力比(σr-L)とを用いて、鋼管の耐座
屈性を評価することを特徴とする鋼管の耐座屈性評価方
法。[13] Stress ratio (σ rC ) which is a ratio of yield strength and nominal strain: stress (σ 1.5 ) at 1.5% in a tensile test in the circumferential direction of the steel pipe, and a tensile test in the axial direction of the steel pipe. Strength and nominal strain at 1.5% stress at 1.5% (σ 1.5 )
A method for evaluating buckling resistance of a steel pipe, wherein the buckling resistance of the steel pipe is evaluated using a stress ratio (σ rL ) which is a ratio of the buckling resistance to the steel pipe.
【0022】[14] 前記[12]または[13]におい
て、鋼管管軸方向における応力比(σr -L)またはさら
に鋼管周方向における応力比(σr-C)を1.05以上
とすることを特徴とする鋼管の耐座屈性評価方法。[14] In the above item [12] or [13], the stress ratio in the steel pipe axial direction (σ r -L ) or the stress ratio in the steel pipe circumferential direction (σ rC ) is 1.05 or more. Characteristic method for evaluating buckling resistance of steel pipes.
【0023】なお、これらの手段において、「残部実質
的にFe」とは、本発明の作用効果を無くさない限り、
不可避不純物をはじめ、他の微量元素を含有するものが
本発明の範囲に含まれ得ることを意味する。In these means, "substantially Fe" means, unless the effects of the present invention are lost.
It means that those containing other trace elements including unavoidable impurities can be included in the scope of the present invention.
【0024】また、本明細書において、鋼の成分を示す
%はすべてmass%である。Further, in this specification, all percentages indicating components of steel are mass%.
【0025】[0025]
【発明の実施の形態】以下に本発明に至った経緯とその
限定理由の詳細を述べる。DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention and the reasons for limiting the same will be described below.
【0026】まず、応力比(σr)について、限定理由
を説明する。First, the reason for limiting the stress ratio (σ r ) will be described.
【0027】本発明において、応力比(σr)とは、降
伏強さと公称歪み:1.5%時の応力(σ1.5)との比
であり、応力比(σr)が1.05以上であれば、圧縮
あるいは曲げひずみ付与時の耐座屈性が向上することか
ら、応力比(σr)は1.05以上とし、これが本発明
において最も重要な要件である。また、前記応力比(σ
r)は管軸方向の応力比(σr-L)のみ1.05以上とす
る場合と鋼管周方向ならびに管軸方向の応力比
(σr-C、σr-L)を1.05以上とする場合の2通りで
規定する。In the present invention, the stress ratio (σr) And descend
Yield strength and nominal strain: stress at 1.5% (σ1.5) And ratio
And the stress ratio (σr) Is greater than 1.05
Or is the buckling resistance at the time of applying bending strain improved?
From the stress ratio (σr) Is 1.05 or more, which is the present invention.
Is the most important requirement. Further, the stress ratio (σ
r) Is the stress ratio in the pipe axis direction (σrL) Only 1.05 or more
Ratio and stress ratio in steel pipe circumferential direction and pipe axis direction
(ΣrC, ΣrL) Is 1.05 or more.
Stipulate.
【0028】管軸方向の応力比(σr-L)を規定するこ
とにより、圧縮による局部座屈を防止することができ、
さらに、鋼管周方向の応力比(σr-C)を規定すること
により、曲げ歪みを付与し外圧時の局部座屈を防止する
ことができる。よって、例えば、陸上の耐震ラインパイ
プ等に用いる場合は管軸方向の応力比(σr-L)のみを
規定した本発明の鋼管を、敷設時に曲げと外圧がかかる
海底管等に用いる場合は鋼管周方向ならびに管軸方向の
応力比(σr-C、σr-L)を規定した本発明の鋼管をそれ
ぞれ用いる等、使用時の状況に合わせ適宜使い分けをす
ることが好ましい。By defining the stress ratio (σ rL ) in the tube axis direction, local buckling due to compression can be prevented.
Furthermore, by defining the stress ratio (σ rC ) in the circumferential direction of the steel pipe, it is possible to impart bending strain and prevent local buckling at the time of external pressure. Therefore, for example, when used for land-based seismic line pipes and the like, when the steel pipe of the present invention that defines only the stress ratio (σ rL ) in the pipe axis direction is used for submarine pipes that are subjected to bending and external pressure during laying, the steel pipe circumference is used. It is preferable to appropriately use the steel pipe according to the situation at the time of use, such as using the steel pipe of the present invention in which the stress ratio in the direction and the pipe axis direction (σ rC , σ rL ) is specified.
【0029】次に、成分組成範囲について、限定理由を
説明する。Next, the reasons for limiting the component composition range will be described.
【0030】C:0.03%未満もしくは0.1%を超
えてCを添加すると、安定して1.05以上の応力比
(σr)を得ることができず、さらに、溶接性も劣化す
る。よって、本発明において、C量は0.03%〜0.
1%とする。C: When C is added in less than 0.03% or more than 0.1%, a stress ratio (σ r ) of 1.05 or more cannot be obtained stably, and the weldability also deteriorates. I do. Therefore, in the present invention, the C content is 0.03% to 0.1%.
1%.
【0031】Si:構造用鋼としての充分な強度と靭性
を得るために、0.05%以上の添加が必要である。一
方、0.5%を超えて添加すると、溶接性の劣化をまね
く。よって、本発明において、Si量は0.05%〜
0.5%とする。Si: In order to obtain sufficient strength and toughness as structural steel, it is necessary to add 0.05% or more. On the other hand, if added over 0.5%, the weldability will be degraded. Therefore, in the present invention, the amount of Si is 0.05% to
0.5%.
【0032】Mn:構造用鋼としての充分な強度と靭性
を得るために、1%以上の添加が必要である。一方、2
%を超えて添加すると、溶接性の劣化をまねく。よっ
て、本発明において、Mn量は1〜2%とする。Mn: In order to obtain sufficient strength and toughness as a structural steel, 1% or more must be added. Meanwhile, 2
%, The weldability is degraded. Therefore, in the present invention, the amount of Mn is set to 1 to 2%.
【0033】Cu、Ni、Cr、Mo:強度の上昇に有
効な元素であり、Cu、Ni、Cr、及びMoの群から
選ばれた1種または2種以上を添加させることができ
る。ただし、強度を上昇させるためには各元素とも0.
05%以上の添加が必要であり、一方、0.5%を超え
て添加すると鋼管の母材部と溶接部の靭性や溶接性を劣
化させる。よって、本発明においては、Cu、Ni、C
r、Moの群から選択された1種または2種以上を添加
する場合、各成分を0.05〜0.5%で添加すること
が好ましい。Cu, Ni, Cr, Mo: an element effective for increasing the strength, one or more selected from the group consisting of Cu, Ni, Cr, and Mo can be added. However, in order to increase the strength, each of the elements has a content of 0.1.
Addition of not less than 0.5% is required, while addition of more than 0.5% deteriorates the toughness and weldability of the base material and the welded portion of the steel pipe. Therefore, in the present invention, Cu, Ni, C
When one or two or more selected from the group of r and Mo are added, it is preferable to add each component at 0.05 to 0.5%.
【0034】Nb、V、Ti:鋼板の靭性ならびに強度
の向上もしくくは鋳造時のスラブの傷防止に有効な元素
であり、Nb、V、Tiの群から選ばれた1種または2
種以上を添加させることができる。ただし、鋼板の靭性
と強度の向上させるためにはNb:0.005%以上、
V:0.005%以上の添加が必要であり、鋼板の靭性
の向上と鋳造時のスラブ傷防止のためにはTi:0.0
05%以上必要である。一方、Nb:0.1%超え、
V:0.1%超え、Ti:0.08%超えの添加は、溶
接性や溶接部の靭性を劣化させる。よって、本発明にお
いては、Nb、V、Tiの群から選択された1種または
2種以上を添加する場合、各成分をNb:0.005〜
0.1%、V:0.005〜0.1%、Ti:0.00
5〜0.08%で添加することが好ましい。Nb, V, Ti: elements that are effective for improving the toughness and strength of the steel sheet or for preventing damage to the slab during casting, and one or two elements selected from the group consisting of Nb, V, and Ti.
More than one species can be added. However, in order to improve the toughness and strength of the steel sheet, Nb: 0.005% or more,
V: 0.005% or more must be added. To improve the toughness of the steel sheet and to prevent slab damage during casting, Ti: 0.0
More than 05% is required. On the other hand, Nb: exceeds 0.1%,
Addition of V: more than 0.1% and Ti: more than 0.08% deteriorates weldability and toughness of a welded portion. Therefore, in the present invention, when one or more kinds selected from the group of Nb, V, and Ti are added, each component is Nb: 0.005 to 0.005.
0.1%, V: 0.005 to 0.1%, Ti: 0.00
It is preferable to add 5 to 0.08%.
【0035】Ca、Mg:硫化物系介在物の形態制御に
不可欠な元素であり、Ca、Mgの群から選ばれた1種
または2種を添加させることができる。ただし、各元素
とも硫化物系介在物の形態制御のためには0.0005
%以上必要であり、一方、0.003%を超えて添加す
ると効果が飽和し、逆に清浄度を低下させて耐座屈性を
劣化させる。よって、本発明においては、Ca、Mgの
群から選択された1種または2種を添加する場合、各成
分を0.0005〜0.003%で添加することが好ま
しい。Ca, Mg: Elements indispensable for controlling the form of sulfide inclusions, and one or two selected from the group consisting of Ca and Mg can be added. However, each element is 0.0005 in order to control the morphology of sulfide inclusions.
%, On the other hand, if it exceeds 0.003%, the effect is saturated, and conversely, the cleanliness is reduced and the buckling resistance is deteriorated. Therefore, in the present invention, when one or two kinds selected from the group of Ca and Mg are added, it is preferable to add each component at 0.0005 to 0.003%.
【0036】PCM:本発明において、PCMとはC+Si
/30+Mn/20+Cu/20+Ni/60+Cr/
20+Mo/15+V/10+5xB であり、鋼の強
度や靭性とよい相関関係を有する指標である。構造物と
して充分な強度を得て、良好な耐座屈性を得るるために
は0.10以上必要である。一方、0.20を超えると
耐座屈性と溶接性を劣化させる。よって、本発明におい
て、PCMは0.10〜0.20とする。[0036] P CM: In the present invention, the P CM C + Si
/ 30 + Mn / 20 + Cu / 20 + Ni / 60 + Cr /
20 + Mo / 15 + V / 10 + 5 × B, which is an index having a good correlation with the strength and toughness of steel. In order to obtain sufficient strength as a structure and to obtain good buckling resistance, 0.10 or more is required. On the other hand, when it exceeds 0.20, buckling resistance and weldability are deteriorated. Therefore, in the present invention, P CM is set to 0.10 to 0.20.
【0037】次に、鋼板製造工程について、限定理由を
説明する。Next, the reasons for limiting the steel sheet manufacturing process will be described.
【0038】本発明の鋼管に用いる鋼板は上記成分を有
する鋼を加熱し、例えば、加熱温度:1050℃〜12
50℃で熱間圧延した後、500℃以下の任意の温度ま
で冷却速度:5℃/sec以上で加速冷却することによ
り得られる。500℃よりも冷却停止温度が高いかある
いは5℃/sec未満の冷却速度で冷却すると、いずれ
の場合も安定して1.05以上の応力比(σr)が得ら
れず、耐座屈性に優れた鋼管が得られない。The steel sheet used for the steel pipe of the present invention is obtained by heating steel having the above-mentioned components, for example, at a heating temperature of 1050 ° C. to 12 ° C.
It is obtained by hot rolling at 50 ° C. and then accelerated cooling to an arbitrary temperature of 500 ° C. or less at a cooling rate of 5 ° C./sec or more. If the cooling stop temperature is higher than 500 ° C. or the cooling rate is lower than 5 ° C./sec, the stress ratio (σ r ) of 1.05 or more cannot be stably obtained in any case, and the buckling resistance Excellent steel pipe cannot be obtained.
【0039】次に、鋼管製造工程について、限定理由を
説明する。Next, the reasons for limiting the steel pipe manufacturing process will be described.
【0040】本発明の鋼管は、上記により得られた鋼板
を1.4%以下の拡管率で冷間成形することにより得ら
れる。拡管率が1.4%を超えると、鋼管周方向の応力
比の低下をもたらし、良好な耐座屈性が得られない。ま
た、冷間成形方法は特に限定されず、例えば、UOE、
ベンディングロール、プレスベンドなどにより冷間加工
して鋼管に成形される。The steel pipe of the present invention can be obtained by cold forming the steel sheet obtained as described above at a pipe expansion ratio of 1.4% or less. If the pipe expansion ratio exceeds 1.4%, the stress ratio in the circumferential direction of the steel pipe decreases, and good buckling resistance cannot be obtained. Further, the cold forming method is not particularly limited, for example, UOE,
It is formed into a steel pipe by cold working with a bending roll, press bend, or the like.
【0041】以上より、局部座屈を起こしにくく、耐座
屈性に優れた鋼管を得ることができ、鋼管の軸方向に作
用する応力による局部座屈の発生とそれに起因する脆性
的なき裂や破断の発生の防止、曲げ歪付与、及び外圧時
の局部座屈の防止ができる。As described above, it is possible to obtain a steel pipe which is less likely to cause local buckling and has excellent buckling resistance. The occurrence of local buckling due to the stress acting in the axial direction of the steel pipe and the brittle cracks and Breakage can be prevented, bending strain can be applied, and local buckling at the time of external pressure can be prevented.
【0042】[0042]
【実施例】(実施例1)外径と管厚の比(D/t)は3
5から60まで変化させた管外径600mmの鋼管に対
し、管軸方向における応力比(σr-L)、鋼管の座屈ひ
ずみを求めた。管軸方向における応力比(σr-L)を求
める際の管軸方向の引張試験は平行部幅38mm、標点
間距離50mmの全厚試験片によって行った。また、鋼
管の座屈ひずみは、実鋼管の圧縮試験により得られた座
屈ひずみを式:εb(座屈ひずみ)=35・t/Dで得
られる値で除した値とした。表1に性能評価結果を示
す。ここで、座屈ひずみの評価は1.2以上を良好とし
た。(Embodiment 1) The ratio (D / t) of the outer diameter to the tube thickness is 3
The stress ratio (σ rL ) in the pipe axis direction and the buckling strain of the steel pipe were determined for a steel pipe having a pipe outer diameter of 600 mm changed from 5 to 60. The tensile test in the tube axis direction for obtaining the stress ratio (σ rL ) in the tube axis direction was performed using a full-thickness test piece having a parallel portion width of 38 mm and a gauge length of 50 mm. The buckling strain of the steel pipe was a value obtained by dividing a buckling strain obtained by a compression test of an actual steel pipe by a value obtained by an equation: εb (buckling strain) = 35 · t / D. Table 1 shows the performance evaluation results. Here, the evaluation of the buckling strain was 1.2 or better.
【0043】[0043]
【表1】 [Table 1]
【0044】表1より、管軸方向における応力比(σ
r-L)が本発明範囲内にある鋼管No.1、2、3では
座屈ひずみが1.2倍以上で、耐座屈性に優れた鋼管が
得られているのがわかる。From Table 1, it can be seen that the stress ratio (σ
rL ) falls within the scope of the present invention. In the cases of 1, 2, and 3, the buckling strain is 1.2 times or more, and it can be seen that a steel pipe excellent in buckling resistance is obtained.
【0045】一方、管軸方向における応力比(σr-L)
が本発明範囲外である鋼管No.4では、座屈ひずみが
1.2未満であり、耐座屈性に劣っている。On the other hand, the stress ratio in the pipe axis direction (σ rL )
Is a steel pipe No. out of the scope of the present invention. In No. 4, the buckling strain was less than 1.2, and the buckling resistance was poor.
【0046】(実施例2)外径と管厚の比(D/t)は
35から60まで変化させた管外径600mmの鋼管に
対し、鋼管周方向ならびに管軸方向における応力比(σ
r-C、σr-L、)、鋼管の座屈ひずみを求めた。鋼管周方
向ならびに管軸方向における応力比(σr- C、σr-L)を
求めるにあたっての管周方向の引張試験は、矯正をして
いない鋼管の管周方向から採取した、平行部径6mm
φ、標点間距離25mmの丸棒試験片によって、管軸方
向の引張試験は平行部幅38mm、標点間距離50mm
の全厚試験片によって行った。また、鋼管の座屈ひずみ
は、実鋼管の圧縮試験(外圧あり)により得られた座屈
ひずみを式:εb(座屈ひずみ)=35・t/Dで得ら
れる値で除した値とした。表2に性能評価結果を示す。
ここで、座屈ひずみの評価は1.2以上を良好とした。(Example 2) The stress ratio (σ) in the steel pipe circumferential direction and the pipe axis direction was applied to a steel pipe having a pipe outer diameter of 600 mm in which the ratio of the outer diameter to the pipe thickness (D / t) was changed from 35 to 60.
rC , σ rL ) and the buckling strain of the steel pipe were determined. The tensile test in the circumferential direction of the pipe in determining the stress ratio ( σr - C , σrL ) in the circumferential direction of the steel pipe and in the axial direction of the pipe was performed using a straight pipe having a diameter of 6 mm taken from the circumferential direction of the uncorrected steel pipe.
Using a round bar test piece with φ, gauge length of 25 mm, the tensile test in the tube axis direction was parallel part width 38 mm, gauge length 50 mm
Was carried out by using a full thickness test piece. The buckling strain of the steel pipe was defined as a value obtained by dividing a buckling strain obtained by a compression test (with external pressure) of an actual steel pipe by a value obtained by an equation: εb (buckling strain) = 35 · t / D. . Table 2 shows the performance evaluation results.
Here, the evaluation of the buckling strain was 1.2 or better.
【0047】[0047]
【表2】 [Table 2]
【0048】表2より、鋼管周方向ならびに管軸方向に
おける応力比(σr-C、σr-L)が本発明範囲内にある鋼
管No.5、6、7では、座屈ひずみが1.2倍以上
で、耐座屈性に優れた鋼管が得られているのがわかる。From Table 2, it can be seen that the stress ratio (σ rC , σ rL ) in the circumferential direction and the axial direction of the steel pipe is within the range of the present invention. 5, 6, and 7, it can be seen that a buckling strain of 1.2 times or more and a steel pipe excellent in buckling resistance were obtained.
【0049】一方、鋼管周方向もしくは管軸方向におけ
る応力比(σr-C、σr-L)のいずれかが本発明範囲外で
ある鋼管No.8、9では、座屈ひずみが1.2未満と
低く、耐座屈性に劣っている。On the other hand, the steel pipe No. whose stress ratio (σ rC , σ rL ) in the circumferential direction or the axial direction of the steel pipe is out of the range of the present invention. In Examples 8 and 9, the buckling strain was as low as less than 1.2, and the buckling resistance was poor.
【0050】(実施例3)表3に示す成分を有し、外径
と管厚の比(D/t)は35から60まで変化させた管
外径600mmの鋼管に対し、管軸方向における応力比
(σr-L)、鋼管の座屈ひずみを求めた。管軸方向にお
ける応力比(σr-L)を求めるにあたっての管軸方向の
引張試験は平行部幅38mm、標点間距離50mmの全
厚試験片によって行った。また、鋼管の座屈ひずみは、
実鋼管の圧縮試験により得られた座屈ひずみを式:εb
(座屈ひずみ)=35・t/Dで得られる値で除した値
とした。表4に性能評価結果を示す。ここで、座屈ひず
みの評価は1.2以上を良好とした。また、溶接性は鋼
管成形後の縦シ−ム溶接部における溶接割れの有無を調
べ確認し、は溶接割れなし、×は溶接割れ有りとした。(Example 3) A steel pipe having a pipe outer diameter of 600 mm having the components shown in Table 3 and having an outer diameter to pipe thickness ratio (D / t) of 35 to 60 was used. The stress ratio (σ rL ) and the buckling strain of the steel pipe were determined. In determining the stress ratio (σ rL ) in the tube axis direction, a tensile test in the tube axis direction was performed using a full-thickness test piece having a parallel portion width of 38 mm and a gauge length of 50 mm. The buckling strain of the steel pipe is
The buckling strain obtained by the compression test of an actual steel pipe is expressed by the following equation:
(Buckling strain) = A value obtained by dividing by a value obtained at 35 · t / D. Table 4 shows the performance evaluation results. Here, the evaluation of the buckling strain was 1.2 or better. The weldability was checked by checking for the presence of weld cracks in the vertical seam weld after forming the steel pipe.
【0051】[0051]
【表3】 [Table 3]
【0052】[0052]
【表4】 [Table 4]
【0053】表4より、管軸方向における応力比(σ
r-L)が本発明範囲内にある鋼管No.10、14、1
5、16では、座屈ひずみが1.2倍以上でかつ溶接性
に優れ、耐座屈性に優れた鋼管が得られているのがわか
る。From Table 4, it can be seen that the stress ratio (σ
rL ) falls within the scope of the present invention. 10, 14, 1
5 and 16, it can be seen that a steel pipe having a buckling strain of 1.2 times or more, excellent weldability, and excellent buckling resistance was obtained.
【0054】一方、管軸方向における応力比(σr-L)
が本発明範囲外である鋼管No.11、12、13で
は、座屈ひずみが1.2未満と低く、耐座屈性に劣って
いる。特に鋼管No.12、13では、溶接性も劣って
いる。On the other hand, the stress ratio (σ rL ) in the pipe axis direction
Is a steel pipe No. out of the scope of the present invention. In 11, 12, and 13, the buckling strain was as low as less than 1.2, and the buckling resistance was poor. In particular, steel pipe No. In Nos. 12 and 13, the weldability is also poor.
【0055】(実施例4)表5に示す成分の鋼を加熱、
熱間圧延し、次いで表5に示す条件で加速冷却を行い、
得られた鋼板に冷間加工を施し、管外径600mmの鋼
管を得た。この時、外径と管厚の比(D/t)は35か
ら60まで変化させた。Example 4 Steel having the components shown in Table 5 was heated.
Hot rolling, then accelerated cooling under the conditions shown in Table 5,
The obtained steel sheet was subjected to cold working to obtain a steel pipe having a pipe outer diameter of 600 mm. At this time, the ratio (D / t) between the outer diameter and the tube thickness was changed from 35 to 60.
【0056】[0056]
【表5】 [Table 5]
【0057】得られた鋼管に対し、管軸方向における応
力比(σr-L)、鋼管の座屈ひずみを求めた。管軸方向
における応力比(σr-L)を求めるにあたっての管軸方
向の引張試験は平行部幅38mm、標点間距離50mm
の全厚試験片によって行った。また、鋼管の座屈ひずみ
は、実鋼管の圧縮試験により得られた座屈ひずみを式:
εb(座屈ひずみ)=35・t/Dで得られる値で除し
た値とした。表6に製造条件と併せて、性能評価結果を
示す。ここで、座屈ひずみの評価は1.2以上を良好と
した。また、溶接性は鋼管成形後の縦シ−ム溶接部にお
ける溶接割れの有無を調べ確認し、は溶接割れなし、×
は溶接割れ有りとした。With respect to the obtained steel pipe, the stress ratio (σ rL ) in the pipe axis direction and the buckling strain of the steel pipe were determined. In obtaining the stress ratio (σ rL ) in the pipe axis direction, a tensile test in the pipe axis direction was performed with a parallel part width of 38 mm and a gauge length of 50 mm.
Was carried out by using a full thickness test piece. The buckling strain of a steel pipe is calculated by using the buckling strain obtained by a compression test of an actual steel pipe as follows:
εb (buckling strain) = 35 · t / D divided by the value obtained. Table 6 shows the performance evaluation results together with the manufacturing conditions. Here, the evaluation of the buckling strain was 1.2 or better. The weldability was checked by checking for the presence of weld cracks in the vertical seam weld after forming the steel pipe.
Was determined to have weld cracks.
【0058】[0058]
【表6】 [Table 6]
【0059】表6より、加速冷却停止温度及び冷却速度
が本発明範囲内にある鋼管No.17、20、21では
管軸方向における応力比(σr-L)が1.05以上であ
り、座屈ひずみが1.2倍以上でかつ溶接性に優れ、耐
座屈性に優れた鋼管が得られているのがわかる。From Table 6, it can be seen that the steel pipe No. having the accelerated cooling stop temperature and the cooling rate falling within the range of the present invention. In 17, 20, and 21, a steel pipe having a stress ratio (σ rL ) in the pipe axis direction of 1.05 or more, a buckling strain of 1.2 times or more, excellent weldability, and excellent buckling resistance was obtained. You can see that it is done.
【0060】一方、加速冷却停止温度及び冷却速度が本
発明範囲外である鋼管No.18、19では、管軸方向
における応力比(σr-L)が1.05未満であり、座屈
ひずみも1.2未満と低く、耐座屈性に劣っている。On the other hand, in the case of steel pipe No. whose accelerated cooling stop temperature and cooling rate are outside the range of the present invention. In Nos. 18 and 19, the stress ratio (σ rL ) in the tube axis direction was less than 1.05, the buckling strain was as low as less than 1.2, and the buckling resistance was poor.
【0061】(実施例5)表6に示す成分の鋼を加熱、
熱間圧延し、次いで表7に示す条件で加速冷却を行い、
得られた鋼板に表8に示す拡管率で冷間加工を施し、管
外径600mmの鋼管を得た。この時、外径と管厚の比
(D/t)は35から60まで変化させた。(Example 5) Steel having the components shown in Table 6 was heated,
Hot rolling, then accelerated cooling under the conditions shown in Table 7,
The obtained steel plate was subjected to cold working at a pipe expansion ratio shown in Table 8 to obtain a steel pipe having a pipe outer diameter of 600 mm. At this time, the ratio (D / t) between the outer diameter and the tube thickness was changed from 35 to 60.
【0062】[0062]
【表7】 [Table 7]
【0063】得られた鋼管に対し、鋼管周方向ならびに
管軸方向における応力比(σr-C、σr-L)、鋼管の座屈
ひずみを求めた。鋼管周方向ならびに管軸方向における
応力比(σr-C、σr-L)を求めるにあたっての管周方向
の引張試験は、矯正をしていない鋼管の管周方向から採
取した、平行部径6mmφ、標点間距離25mmの丸棒
試験片によって、管軸方向の引張試験は平行部幅38m
m、標点間距離50mmの全厚試験片によって行った。
また、鋼管の座屈ひずみは、実鋼管の圧縮試験(外圧あ
り)により得られた座屈ひずみを式:εb(座屈ひず
み)=35・t/Dで得られる値で除した値とした。表
8に製造条件と併せて、性能評価結果を示す。ここで、
座屈ひずみの評価は1.2以上を良好とした。また、溶
接性は鋼管成形後の縦シ−ム溶接部における溶接割れの
有無を調べ確認し、は溶接割れなし、×は溶接割れ有り
とした。With respect to the obtained steel pipe, the stress ratio (σ rC , σ rL ) in the circumferential direction of the steel pipe and in the pipe axis direction, and the buckling strain of the steel pipe were determined. The tensile test in the circumferential direction of the pipe for determining the stress ratio (σ rC , σ rL ) in the circumferential direction of the steel pipe and in the axial direction of the pipe was performed using a straight section having a diameter of 6 mmφ and a gauge point taken from the circumferential direction of the uncorrected steel pipe. Using a round bar test piece with a distance of 25 mm, the tensile test in the tube axis direction was 38 m in parallel part width.
m, a test piece with a total thickness of 50 mm between gauge points.
The buckling strain of the steel pipe was defined as a value obtained by dividing a buckling strain obtained by a compression test (with external pressure) of an actual steel pipe by a value obtained by an equation: εb (buckling strain) = 35 · t / D. . Table 8 shows the performance evaluation results together with the manufacturing conditions. here,
The evaluation of buckling strain was 1.2 or better. The weldability was checked by checking for the presence of weld cracks in the vertical seam weld after forming the steel pipe.
【0064】[0064]
【表8】 [Table 8]
【0065】表8より、加速冷却停止温度、冷却速度及
び拡管率が本発明範囲内にある鋼管No.22、27、
28、29では鋼管周方向ならびに管軸方向における応
力比(σr-C、σr-L)が1.05以上であり、座屈ひず
みが1.2倍以上でかつ溶接性に優れ、耐座屈性に優れ
た鋼管が得られているのがわかる。From Table 8, it can be seen that the steel pipe No. having the accelerated cooling stop temperature, the cooling rate and the pipe expansion ratio within the range of the present invention. 22, 27,
In Nos . 28 and 29, the stress ratio (σ rC , σ rL ) in the steel pipe circumferential direction and pipe axis direction is 1.05 or more, the buckling strain is 1.2 times or more, and the weldability is excellent and the buckling resistance is excellent. It can be seen that an excellent steel pipe has been obtained.
【0066】一方、加速冷却停止温度、冷却速度及び拡
管率が本発明範囲外である鋼管No.23、24、2
5、26では、鋼管周方向もしくは管軸方向における応
力比(σr-C、σr-L、)のいずれかが1.05未満であ
り、座屈ひずみも1.2未満と低く、耐座屈性に劣って
いる。On the other hand, in the case of the steel pipe No. having the accelerated cooling stop temperature, the cooling rate and the expansion ratio outside the range of the present invention. 23, 24, 2
In Nos. 5 and 26 , either the stress ratio (σ rC , σ rL ) in the circumferential direction of the steel pipe or in the pipe axis direction is less than 1.05, the buckling strain is less than 1.2, and the buckling resistance is low. Inferior.
【0067】[0067]
【発明の効果】以上、本発明によれば、耐座屈性に優れ
た鋼管を得ることができる。本発明により得られる鋼管
は耐座屈性に優れているので、ガスパイプライン、水道
配管、建築・土木用の柱などに使用される鋼管として最
適である。As described above, according to the present invention, a steel pipe excellent in buckling resistance can be obtained. Since the steel pipe obtained by the present invention has excellent buckling resistance, it is most suitable as a steel pipe used for gas pipelines, water pipes, columns for construction and civil engineering, and the like.
【0068】また、本発明の鋼管は、大地震や海底管の
敷設の際に軸方向に作用する圧縮や曲げ応力に対して、
局部座屈を起こしにくいため、大地震が発生した際のガ
スパイプラインや水道配管の破損と内部流体の流出、あ
るいは高速道路の橋脚柱の破断による倒壊などの災害を
防ぐことができる。Further, the steel pipe of the present invention is resistant to compressive and bending stresses acting in the axial direction when a large earthquake or submarine pipe is laid.
Since local buckling is unlikely to occur, it is possible to prevent disasters such as damage to gas pipelines and water pipes and the outflow of internal fluid when a large earthquake occurs, or collapse due to breakage of pier pillars on a highway.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 鈴木 信久 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 近藤 丈 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 Fターム(参考) 2G061 AA01 AA02 BA01 BA03 BA20 CA02 CB04 CB19 EA02 EA03 EA04 EC02 4K032 AA04 AA08 AA11 AA14 AA16 AA19 AA22 AA23 AA31 AA35 AA36 BA03 CA02 CA03 CD02 CD03 CG01 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Nobuhisa Suzuki 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Takeshi Kondo 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Sun F-term (reference) in this steel pipe Co., Ltd.
Claims (14)
さと公称歪み:1.5%時の応力(σ1.5)との比であ
る応力比(σr-L)が1.05以上であることを特徴と
する耐座屈性に優れた鋼管。In a tensile test in the axial direction of a steel tube, a stress ratio (σ rL ) which is a ratio of a yield strength to a stress (σ 1.5 ) at 1.5% of nominal strain is 1.05 or more. A characteristic steel pipe with excellent buckling resistance.
と公称歪み:1.5%時の応力(σ1.5)との比である
応力比(σr-C)と鋼管管軸方向の引張試験において降
伏強さと公称歪み:1.5%時の応力(σ1.5)との比
である応力比(σr-L)がそれぞれ1.05以上である
ことを特徴とする耐座屈性に優れた鋼管。Wherein yield strength in a tensile test of the steel pipe circumferential direction and a nominal strain 1.5% when the stress (sigma 1.5) and which is the ratio stress ratio (sigma rC) and the yield in the tensile test of the steel pipe tube axis direction A steel pipe having excellent buckling resistance, wherein stress ratios (σ rL ), which are ratios between strength and nominal strain: stress (σ 1.5 ) at 1.5%, are each 1.05 or more.
%、Si:0.05〜0.5%、Mn:1〜2%を含有
し、残部が実質的にFeからなり、かつ下記式(1)で
示されるPCMが0.10〜0.20を満足する成分組成
を有することを特徴とする請求項1または2記載の耐座
屈性に優れた鋼管。 PCM =C+Si/30+Mn/20+Cu/20+Ni/60+Cr/20+Mo /15+V/10+5xB (1)3. Mass%, C: 0.03 to 0.1
% Si: 0.05 to 0.5% Mn: it contains 1-2%, the balance being substantially Fe, and the P CM represented by the following formula (1) from 0.10 to 0. The steel pipe having excellent buckling resistance according to claim 1 or 2, wherein the steel pipe has a component composition satisfying 20. P CM = C + Si / 30 + Mn / 20 + Cu / 20 + Ni / 60 + Cr / 20 + Mo / 15 + V / 10 + 5 × B (1)
〜0.5%、Ni:0.05〜0.5%、Cr:0.0
5〜0.5%、及びMo:0.05〜0.5%の群から
選ばれた1種または2種以上を含有することを特徴とす
る請求項1ないし3に記載の耐座屈性に優れた鋼管。4. Further, in mass%, Cu: 0.05
0.5%, Ni: 0.05 to 0.5%, Cr: 0.0
The buckling resistance according to any one of claims 1 to 3, wherein the buckling resistance is one or more selected from the group of 5 to 0.5% and Mo: 0.05 to 0.5%. Excellent steel pipe.
5〜0.1%、V:0.005〜0.1%、及びTi:
0.005〜0.08%の群から選ばれた1種または2
種以上を含有することを特徴とする請求項1ないし4に
記載の耐座屈性に優れた鋼管。5. The method according to claim 1, wherein the mass% is Nb: 0.005%.
5 to 0.1%, V: 0.005 to 0.1%, and Ti:
One or two selected from the group of 0.005 to 0.08%
The steel pipe excellent in buckling resistance according to claim 1, wherein the steel pipe contains at least one kind.
05〜0.003%、Mg:0.0005〜0.003
%の群から選ばれた1種または2種を含有することを特
徴とする請求項1ないし5に記載の耐座屈性に優れた鋼
管。6. Further, in mass%, Ca: 0.00
0.05 to 0.003%, Mg: 0.0005 to 0.003
The steel pipe excellent in buckling resistance according to claim 1, wherein the steel pipe contains one or two selected from the group of%.
%、Si:0.05〜0.5%、Mn:1〜2%を含有
し、残部が実質的にFeからなり、かつ下記式(1)で
示されるPCMが0.10〜0.20を満足する鋼を熱間
圧延した後、500℃以下の任意の温度まで冷却速度:
5℃/sec以上で加速冷却することにより得られた鋼
板を、冷間成形により造管することにより管軸方向にお
ける降伏強さと公称歪み:1.5%時の応力(σ1.5)
との比である応力比(σr-L)が1.05以上である鋼
管を得ることを特徴とする耐座屈性に優れた鋼管の製造
方法。 PCM =C+Si/30+Mn/20+Cu/20+Ni/60+Cr/20+M o/15+V/10+5xB (1)7. Mass%, C: 0.03 to 0.1
% Si: 0.05 to 0.5% Mn: it contains 1-2%, the balance being substantially Fe, and the P CM represented by the following formula (1) from 0.10 to 0. After hot rolling a steel satisfying No. 20, a cooling rate to an arbitrary temperature of 500 ° C. or less:
The steel sheet obtained by accelerated cooling at 5 ° C./sec or more is formed into a tube by cold forming, whereby the yield strength in the tube axis direction and the nominal strain: stress at 1.5% (σ 1.5 )
A method for producing a steel pipe having excellent buckling resistance, characterized by obtaining a steel pipe having a stress ratio (σ rL ) that is 1.05 or more. P CM = C + Si / 30 + Mn / 20 + Cu / 20 + Ni / 60 + Cr / 20 + Mo / 15 + V / 10 + 5 × B (1)
%、Si:0.05〜0.5%、Mn:1〜2%を含有
し、残部が実質的にFeからなり、かつ下記式(1)で
示されるPCMが0.10〜0.20を満足する鋼を熱間
圧延した後、500℃以下の任意の温度まで冷却速度:
5℃/sec以上で加速冷却することにより得られた鋼
板を、拡管率:1.4%以下で冷間成形により造管する
ことにより鋼管周方向ならびに管軸方向における降伏強
さと公称歪み:1.5%時の応力(σ1.5)との比であ
る応力比(σr-C、σr-L)が1.05以上である鋼管を
得ることを特徴とする耐座屈性に優れた鋼管の製造方
法。 PCM =C+Si/30+Mn/20+Cu/20+Ni/60+Cr/20+M o/15+V/10+5xB (1)8. Mass%, C: 0.03 to 0.1
% Si: 0.05 to 0.5% Mn: it contains 1-2%, the balance being substantially Fe, and the P CM represented by the following formula (1) from 0.10 to 0. After hot rolling a steel satisfying No. 20, a cooling rate to an arbitrary temperature of 500 ° C. or less:
A steel sheet obtained by accelerated cooling at 5 ° C./sec or more is subjected to cold forming at a pipe expansion ratio of 1.4% or less to yield yield strength and nominal distortion in the circumferential direction of the steel pipe and in the pipe axis direction: A method for producing a steel pipe having excellent buckling resistance, wherein a steel pipe having a stress ratio (σ rC , σ rL ) which is a ratio to a stress (σ 1.5 ) at 0.5% is 1.05 or more. . P CM = C + Si / 30 + Mn / 20 + Cu / 20 + Ni / 60 + Cr / 20 + Mo / 15 + V / 10 + 5 × B (1)
〜0.5%、Ni:0.05〜0.5%、Cr:0.0
5〜0.5%、及びMo:0.05〜0.5%の群から
選ばれた1種または2種以上を含有した鋼を用いること
を特徴とする請求項7または8に記載の耐座屈性に優れ
た鋼管の製造方法。9. Further, in mass%, Cu: 0.05
0.5%, Ni: 0.05 to 0.5%, Cr: 0.0
The steel according to claim 7 or 8, wherein a steel containing one or more selected from the group of 5 to 0.5% and Mo: 0.05 to 0.5% is used. A method for manufacturing steel pipes with excellent buckling properties.
05〜0.1%、V:0.005〜0.1%、及びT
i:0.005〜0.08%の群から選ばれた1種また
は2種以上を含有した鋼を用いることを特徴とする請求
項7ないし9に記載の耐座屈性に優れた鋼管の製造方
法。10. Further, in mass%, Nb: 0.0
05-0.1%, V: 0.005-0.1%, and T
10. The steel pipe having excellent buckling resistance according to claim 7, wherein a steel containing one or more kinds selected from the group of i: 0.005 to 0.08% is used. Production method.
005〜0.003%、Mg:0.0005〜0.00
3%の群から選ばれた1種または2種を含有した鋼を用
いることを特徴とする請求項7ないし10に記載の耐座
屈性に優れた鋼管の製造方法。11. Further, in mass%, Ca: 0.0
005 to 0.003%, Mg: 0.0005 to 0.00
11. The method for producing a steel pipe having excellent buckling resistance according to claim 7, wherein steel containing one or two selected from the group of 3% is used.
強さと公称歪み:1.5%時の応力(σ1.5)との比で
ある応力比(σr-L)を用いて、鋼管の耐座屈性を評価
することを特徴とする鋼管の耐座屈性評価方法。12. The buckling resistance of a steel pipe is determined by using a stress ratio (σ rL ) which is a ratio of a yield strength and a nominal strain: stress (σ 1.5 ) at 1.5% in a tensile test in an axial direction of the pipe. A method for evaluating buckling resistance of a steel pipe, characterized by evaluating the buckling resistance.
さと公称歪み:1.5%時の応力(σ1.5)との比であ
る応力比(σr-C)と、鋼管管軸方向の引張試験におけ
る降伏強さと公称歪み:1.5%時の応力(σ1.5)と
の比である応力比(σr-L)とを用いて、鋼管の耐座屈
性を評価することを特徴とする鋼管の耐座屈性評価方
法。13. A stress ratio (σ rC ) which is a ratio between a yield strength and a nominal strain: stress at 1.5% (σ 1.5 ) in a tensile test in the circumferential direction of a steel pipe, and a tensile test in an axial direction of the steel pipe. The buckling resistance of a steel pipe is evaluated using a stress ratio (σ rL ) which is a ratio of a yield strength and a nominal strain: stress (σ 1.5 ) at 1.5%. Buckling evaluation method.
(σr-L)またはさらに鋼管周方向における応力比(σ
r-C)を1.05以上とすることを特徴とする請求項1
2または13記載の鋼管の耐座屈性評価方法。14. A stress ratio (σ rL ) in the axial direction of the steel pipe or a stress ratio (σ rL ) in the circumferential direction of the steel pipe.
2. The method according to claim 1, wherein rC ) is 1.05 or more.
14. The method for evaluating buckling resistance of a steel pipe according to 2 or 13.
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