JP2014155949A - Welded steel pipe for line pipe with excellent low-temperature toughness, and method of manufacturing the same - Google Patents

Welded steel pipe for line pipe with excellent low-temperature toughness, and method of manufacturing the same Download PDF

Info

Publication number
JP2014155949A
JP2014155949A JP2013028146A JP2013028146A JP2014155949A JP 2014155949 A JP2014155949 A JP 2014155949A JP 2013028146 A JP2013028146 A JP 2013028146A JP 2013028146 A JP2013028146 A JP 2013028146A JP 2014155949 A JP2014155949 A JP 2014155949A
Authority
JP
Japan
Prior art keywords
welded
welding
steel pipe
weld metal
sectional area
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.)
Pending
Application number
JP2013028146A
Other languages
Japanese (ja)
Inventor
Yasushi Fujishiro
泰志 藤城
Takuya Hara
卓也 原
Yutaka Morimoto
裕 森本
Shuichi Nakamura
修一 中村
Koichi Shinada
功一 品田
Naoki Doi
直己 土井
Takashi Terasawa
崇 寺澤
Masashi Mogi
征史 茂木
Shinya Sakamoto
真也 坂本
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nippon Steel Corp
Original Assignee
Nippon Steel and Sumitomo Metal Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Nippon Steel and Sumitomo Metal Corp filed Critical Nippon Steel and Sumitomo Metal Corp
Priority to JP2013028146A priority Critical patent/JP2014155949A/en
Publication of JP2014155949A publication Critical patent/JP2014155949A/en
Pending legal-status Critical Current

Links

Images

Abstract

PROBLEM TO BE SOLVED: To provide a welded steel pipe for a line pipe with excellent low-temperature toughness, which is molded in a tubular shape in any one of UOE, JCO, bend roll and spiral steps, and a method of manufacturing the same.SOLUTION: When a butt part of a steel plate molded in a tubular shape has one layer of each of inner and outer surfaces welded by submerged arc welding, a weld metal sectional area S1 on an inner surface side and a weld metal sectional area S2 on an outer surface side in a weld zone are set to satisfy inequality (1): 0.5≤S2/S1≤1.0.

Description

本発明は、低温靭性に優れたラインパイプ用溶接鋼管並びにその製造方法に関する。特に、鋼材のサブマージアーク溶接方法に関し、UOE、JCO、ベンドロール、スパイラルいずれかの工程で管状に成形したラインパイプ用溶接鋼管の造管溶接に用いて好適なものに関する。   The present invention relates to a welded steel pipe for line pipe excellent in low temperature toughness and a method for producing the same. In particular, the present invention relates to a submerged arc welding method for steel materials, which is suitable for use in tube-forming welding of welded steel pipes for line pipes formed into a tubular shape by any one of UOE, JCO, bend roll, and spiral processes.

現在、原油および天然ガスの長距離輸送用幹線パイプライン素材として、米国石油協会(API)規格X70(引張強さ570MPa)以上、更にはX80(引張強さ625MPa以上)までのラインパイプ用溶接鋼管が実用化されている。
近年、更なる輸送効率向上のために、ラインパイプ用溶接鋼管の内圧の高圧化が検討されており、これに伴い、API規格X70(以下、X70という)以上、更にはAPI規格X80(以下、X80という)以上の高強度ラインパイプ用溶接鋼管の厚肉化が要求されている。また、今後の原油および天然ガスの掘削域は、北極圏などの極寒地まで及ぶことが予想され、高強度厚肉ラインパイプ用溶接鋼管には−40℃以下での低温靭性保証が要求されると予想される。特に鋼管を製造する際には、厚鋼板をUO、JCO、ベンドロールのいずれかの工程によって管状に成形した後、端部同士を突き合わせて、アーク溶接によるシーム部の溶接を行うが、板厚が厚肉化すると溶接による入熱が大入熱となり、溶接熱影響部(HAZ)の粒径が粗大化するため、低温靭性の低下が重要な問題となる。
Currently, the main pipeline material for long-distance transportation of crude oil and natural gas is the American Petroleum Institute (API) standard X70 (tensile strength of 570 MPa) or higher, and also X80 (tensile strength of 625 MPa or higher) welded steel pipes for line pipes. Has been put to practical use.
In recent years, in order to further improve transportation efficiency, increasing the internal pressure of welded steel pipes for line pipes has been studied. Accordingly, API standard X70 (hereinafter referred to as X70) or higher, further API standard X80 (hereinafter referred to as There is a demand for increasing the thickness of welded steel pipes for high-strength line pipes (referred to as X80). In addition, the future drilling area for crude oil and natural gas is expected to extend to extremely cold regions such as the Arctic Circle, and weld steel pipes for high-strength thick-walled line pipes are required to guarantee low temperature toughness at -40 ° C or lower. It is expected to be. In particular, when manufacturing a steel pipe, a thick steel plate is formed into a tubular shape by any one of UO, JCO, and bend rolls, then the ends are butted together and the seam is welded by arc welding. Since the heat input by welding becomes a large heat input and the particle size of the weld heat affected zone (HAZ) becomes coarse, a decrease in low temperature toughness becomes an important problem.

ラインパイプ用溶接鋼管の造管溶接(シーム溶接)には二電極以上のサブマージアーク溶接が適用され、パイプ生産能率向上の観点から内面側を1パス、外面側を1パスで溶接する両面一層盛り溶接とする、高能率な溶接施工がなされている(例えば特許文献1,2)。   Submerged arc welding with two or more electrodes is applied to pipe-forming welding (seam welding) of welded pipes for line pipes. From the viewpoint of improving pipe production efficiency, both inner and outer layers are welded with one pass on the inner side and one pass on the outer side. High-efficiency welding is performed (for example, Patent Documents 1 and 2).

両面一層溶接では、内面溶接金属と外面溶接金属が重なり、未溶融部がないように十分な溶け込み深さを確保する必要があり、このような欠陥の抑制を重視すると内外面の溶接入熱が高くなり、溶接熱影響部の靭性が劣化する傾向にある。また、溶接能率や施工性を考慮すると、サブマージアーク溶接する際の溶融金属の溶け落ち(メルトダウン)を回避するために、先に溶接する内面溶接金属の溶け込み深さを外面溶接金属の溶け込み深さよりも短くし、外面側の溶接入熱が内面側の溶接入熱よりも高くなるのが一般的である。さらに、一般的に入熱の大きい外面溶接熱影響部の靭性は内面溶接熱影響部の靭性よりも低くなるが、厚肉になると内面溶接熱影響部の靭性低下も顕著になる。   In double-sided single-layer welding, it is necessary to ensure a sufficient penetration depth so that the inner and outer weld metals overlap and there are no unmelted parts. It becomes high and the toughness of the heat affected zone tends to deteriorate. In consideration of welding efficiency and workability, the penetration depth of the inner weld metal to be welded first is set to the penetration depth of the outer weld metal in order to avoid melting down of the molten metal during submerged arc welding. The welding heat input on the outer surface side is generally higher than the welding heat input on the inner surface side. Furthermore, generally, the toughness of the outer surface heat affected zone having a large heat input is lower than the toughness of the inner surface heat affected zone.

溶接熱影響部の高靭性化には、溶接入熱を低減するのが有効であるが、通常行われているシーム溶接の入熱に対して大幅に入熱を低減させなければ、その靭性向上効果は明確とならない。しかしながら、大幅に入熱を低減させると溶着量も減少するため開先断面積を溶着量減少分に合わせて減らす必要が生じる。そのため、大きな溶接金属断面積を有する溶け込み溶接を行わなければ内外面の溶接金属は重ならず、溶け込み不足が生じる危険性が増大する。   To increase the toughness of the weld heat affected zone, it is effective to reduce the heat input of welding, but if the heat input is not significantly reduced compared to the heat input of the usual seam welding, the toughness is improved. The effect is not clear. However, if the heat input is significantly reduced, the welding amount is also reduced, so that it is necessary to reduce the groove cross-sectional area in accordance with the amount of welding reduction. Therefore, if penetration welding having a large weld metal cross-sectional area is not performed, the weld metals on the inner and outer surfaces do not overlap, increasing the risk of insufficient penetration.

したがって、溶接熱影響部の高靭性化は、投入入熱の大幅な低減と溶け込み深さの増大を両立させなければならず、従来より種々の提案がなされているがその達成は極めて困難である。また、厚肉になると通常外面溶接熱影響部よりも低入熱で溶接される内面溶接熱影響部の靭性低下も顕著になる。   Therefore, increasing the toughness of the weld heat-affected zone requires both a significant reduction in input heat input and an increase in penetration depth, and various proposals have been made so far, but this is extremely difficult to achieve. . In addition, when the thickness is increased, the toughness of the inner-surface weld heat-affected zone, which is welded with a lower heat input than that of the normal outer-surface weld heat-affected zone, becomes noticeable.

例えば、上記特許文献2では電極径に応じて電流密度を高め、溶け込み深さを増大させるサブマージアーク溶接方法が提案されているが、最近の仕様に対しては、電流および電流密度が不十分で入熱の大幅な低減と溶け込み深さの増大の両立は困難である。   For example, Patent Document 2 proposes a submerged arc welding method in which the current density is increased in accordance with the electrode diameter and the penetration depth is increased. However, the current and current density are insufficient for recent specifications. It is difficult to achieve both a significant reduction in heat input and an increase in penetration depth.

特許文献3には高電流で更なる高電流密度でのサブマージアーク溶接方法が提案されており、アークエネルギーをできるだけ板厚方向に投入することにより、必要な溶け込み深さだけを確保し、鋼材幅方向の母材の溶解を抑制することで過剰な溶接入熱を省いて、入熱低減と深溶け込みの両立が図られている。   Patent Document 3 proposes a submerged arc welding method with a high current and a further high current density. By supplying arc energy in the plate thickness direction as much as possible, only the necessary penetration depth is secured, and the steel width By suppressing the melting of the base material in the direction, excessive welding heat input is omitted, and both heat input reduction and deep penetration are achieved.

特許文献4ではサブマージアーク溶接時に使用するワイヤと電極への給電方法、電流密度を制御することで溶け込み深さを確保しながら溶接入熱を低減し、溶接熱影響部での靭性向上が図られている。   In Patent Document 4, the heat input method is reduced while securing the penetration depth by controlling the current density and the power supply method to the wires and electrodes used during submerged arc welding, and the toughness is improved at the weld heat affected zone. ing.

特許文献5、6では板厚表層のビード幅と溶け込み先端近傍でのビード幅、鋼板板厚との比を制御することで、スラグ巻き込みを抑制しつつ、溶接熱影響部での靭性向上が図られている。   In Patent Documents 5 and 6, by controlling the ratio of the bead width of the plate thickness surface layer to the bead width in the vicinity of the penetration tip and the steel plate thickness, it is possible to improve toughness in the heat affected zone while suppressing slag entrainment. It has been.

特許文献7、8では板厚に応じて内外面の溶接金属断面積を制御することで、十分な溶け込みを得ながら鋼板表面でのビード幅を広げ、溶接熱影響部での靭性向上が図られている。   In Patent Documents 7 and 8, by controlling the weld metal cross-sectional area of the inner and outer surfaces according to the plate thickness, the bead width on the steel plate surface is increased while obtaining sufficient penetration, and the toughness is improved in the weld heat affected zone. ing.

特開平11−138266号公報JP 11-138266 A 特開平10−109171号公報JP-A-10-109171 特開2006−272377号公報JP 2006-272377 A 特開2007−260684号公報JP 2007-260684 A 特開2009−214127号公報JP 2009-214127 A 特開2010−274276号公報JP 2010-274276 A 特開2009−233679号公報JP 2009-233679 A 特開2010−274275号公報JP 2010-274275 A

しかしながら、特許文献3記載のサブマージアーク溶接方法では、入熱低減と深溶け込みが両立できるものの、鋼板表面でのビード幅が小さくなって鋼板表面から溶け込み先端までほぼ一様なビード幅になりやすく、即ち、溶融線(Fusion Line,FLともいう。)が板厚方向に向くため板厚方向への脆性破壊が進展しやすくなり、低入熱溶接にもかかわらず靭性値が低くなりやすいという問題があった。   However, in the submerged arc welding method described in Patent Document 3, although both heat input reduction and deep penetration can be achieved, the bead width on the steel sheet surface is small and tends to be a substantially uniform bead width from the steel sheet surface to the penetration tip. That is, since the fusion line (also referred to as Fusion Line, FL) is oriented in the thickness direction, brittle fracture tends to progress in the thickness direction, and the toughness value tends to be lowered despite low heat input welding. there were.

また、特許文献4記載のサブマージアーク溶接方法では、入熱低減と深溶け込みが両立できるものの、内外面溶接金属の重なる位置近傍(会合部)でのビード幅が小さくなるため、内外面の溶接金属を重ねるためにはそれぞれの鋼管軸方向溶接位置が厳密に制御されなければならないという課題があった。
特許文献5〜8記載のサブマージアーク溶接方法では、板厚に対するビード幅、もしくは板厚に対するビード断面積については言及されているものの、内面側溶接部と外面側溶接部各々との相対的な形状関係については言及されておらず、さらに、主に溶接部全体の形状によって高靭性化を図っているため、特に外面溶接部では大幅な入熱低減効果が得られないという課題があった。
Further, in the submerged arc welding method described in Patent Document 4, although heat input reduction and deep penetration can be achieved at the same time, the bead width near the overlapping position (meeting portion) of the inner and outer surface weld metal is reduced, so that the weld metal on the inner and outer surfaces is reduced. In order to overlap, there has been a problem that each steel pipe axial welding position must be strictly controlled.
In the submerged arc welding methods described in Patent Documents 5 to 8, although the bead width with respect to the plate thickness or the bead cross-sectional area with respect to the plate thickness is mentioned, the relative shapes of the inner surface side welded portion and the outer surface side welded portion are referred to. There is no mention of the relationship, and furthermore, since a high toughness is achieved mainly by the shape of the entire welded part, there is a problem that a significant heat input reduction effect cannot be obtained particularly at the outer surface welded part.

本発明は、このような事情に鑑みてなされたものであり、内外面の溶接金属における断面積の比を適正に制御することにより、内外面両方の溶接熱影響部において優れた靭性が得られるものである。
特に、本発明では、管状に成形された鋼板の突合せ部を内外面からサブマージアーク溶接するに際し、外面入熱を大幅に低減して外面溶接熱影響部の低温靭性を向上させる。一方、内面入熱については、内外面溶接金属が十分重ねるために増加させるものの、内面溶接熱影響部の靭性は外面溶接時の焼き戻しによって向上させる。即ち、外面溶接熱影響部は低入熱化により向上させ、内面溶接熱影響部は外面溶接時の焼き戻しを利用して十分な溶け込みを得ながら内外面両方の溶接熱影響部で優れた低温靭性が得られるラインパイプ用溶接鋼管並びにそ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 such circumstances, and by controlling the ratio of the cross-sectional area of the weld metal on the inner and outer surfaces appropriately, excellent toughness can be obtained in the weld heat affected zone on both the inner and outer surfaces. Is.
In particular, in the present invention, when submerged arc welding is performed on the butt portion of the steel sheet formed into a tubular shape from the inner and outer surfaces, the heat input to the outer surface is greatly reduced and the low temperature toughness of the outer surface welding heat affected zone is improved. On the other hand, although the inner surface heat input is increased in order to sufficiently overlap the inner and outer surface weld metals, the toughness of the inner surface heat affected zone is improved by tempering during outer surface welding. In other words, the outer surface welding heat affected zone is improved by lowering heat input, and the inner surface welding heat affected zone uses tempering during outer surface welding to obtain sufficient penetration while obtaining excellent low temperature in both the inner and outer surface welding heat affected zones. It is an object of the present invention to provide a welded steel pipe for line pipe that can obtain toughness and a method for producing the same.

本発明者らは、サブマージアーク溶接で種々の溶接条件を用いて、鋼板の内外面溶接継手を有する溶接鋼管を作製し、溶接金属断面形状、入熱および溶接熱影響部の靭性について調査した。
その結果、内外面側それぞれの溶接金属断面積の比を適正に制御することで、外面溶接熱影響部の靭性が向上するとともに、内面溶接熱影響部の靭性は外面溶接時の焼き戻しによって向上した結果、十分な溶け込みを得ながら内外面両方の溶接熱影響部で優れた靭性が得られることを見出した。本発明は、得られた知見を基に更に検討を加えてなされたもので、その要旨は以下の通りである。
The present inventors produced welded steel pipes having inner and outer surface welded joints of steel plates using various welding conditions in submerged arc welding, and investigated the weld metal cross-sectional shape, heat input, and toughness of the weld heat affected zone.
As a result, by properly controlling the ratio of the weld metal cross-sectional area of each inner and outer surface side, the toughness of the heat-affected zone on the outer surface is improved and the toughness of the heat-affected zone on the inner surface is improved by tempering during outer surface welding. As a result, it has been found that excellent toughness can be obtained at the weld heat-affected zone on both the inner and outer surfaces while obtaining sufficient penetration. The present invention has been made by further study based on the obtained knowledge, and the gist thereof is as follows.

[1]管状に成形された鋼板を溶接した溶接鋼管であって、管状に成形された前記鋼板の突き合せ部をサブマージアーク溶接で内外面それぞれ一層溶接され、溶接部において、内面側の溶接金属断面積S1(mm)と外面側の溶接金属断面積S2(mm)が(1)式を満足することを特徴とする低温靭性に優れたラインパイプ用溶接鋼管。
0.5≦S2/S1≦1.0 ・・・ (1)
[2]前記鋼管の周方向を引張方向とした際、前記鋼板の引張強度が570〜825MPaであることを特徴とする上記[1]に記載の低温靭性に優れたラインパイプ用溶接鋼管。
[3]管状に成形された鋼板の突き合せ部をサブマージアーク溶接する際に、開先形状が、内面開先深さd1と外面開先深さd2が(2)式を満足するX開先となるよう加工を施し、得られた前記X開先をサブマージアーク溶接することを特徴とする上記[1]又は[2]に記載の低温靭性に優れたラインパイプ用溶接鋼管の製造方法。
d2/d1≦1.0 ・・・ (2)
[4]前記サブマージアーク溶接において、内面側の入熱λ1が3.5〜16.0kJ/mm、外面側の入熱λ2が2.5〜11.0kJ/mmであり、さらに、(3)式を満足することを特徴とする上記[3]に記載の低温靭性に優れたラインパイプ用溶接鋼管の製造方法。
0.1≦λ2/λ1≦2.5 ・・・ (3)
[1] A welded steel pipe welded to a steel plate formed into a tubular shape, and a butt portion of the steel plate formed into a tubular shape is welded to each of the inner and outer surfaces by submerged arc welding. A welded steel pipe for line pipes having excellent low-temperature toughness, characterized in that a cross-sectional area S1 (mm 2 ) and a weld metal cross-sectional area S2 (mm 2 ) on the outer surface side satisfy the formula (1).
0.5 ≦ S2 / S1 ≦ 1.0 (1)
[2] The welded steel pipe for line pipes with excellent low-temperature toughness according to [1] above, wherein the tensile strength of the steel sheet is 570 to 825 MPa when the circumferential direction of the steel pipe is the tensile direction.
[3] When submerged arc welding is performed on a butt portion of a steel sheet formed into a tubular shape, the groove shape is an X groove whose inner surface groove depth d1 and outer surface groove depth d2 satisfy the expression (2). The method for producing a welded steel pipe for a line pipe excellent in low temperature toughness according to the above [1] or [2], wherein the obtained X groove is subjected to submerged arc welding.
d2 / d1 ≦ 1.0 (2)
[4] In the submerged arc welding, the heat input λ1 on the inner surface side is 3.5 to 16.0 kJ / mm, the heat input λ2 on the outer surface side is 2.5 to 11.0 kJ / mm, and (3) The method for producing a welded steel pipe for line pipe excellent in low temperature toughness according to the above [3], wherein the formula is satisfied.
0.1 ≦ λ2 / λ1 ≦ 2.5 (3)

本発明によれば、内外面の溶接金属断面積の比を適正に制御することで、外面入熱を大幅に低減して外面溶接熱影響部の靭性を向上させ、さらに内面溶接熱影響部の靭性は外面溶接時の焼き戻しによって向上した結果、十分な溶け込みを得ながら内外面両方の溶接熱影響部で優れた低温靭性を有する溶接鋼管が得られるため、産業上極めて有用である。   According to the present invention, by appropriately controlling the ratio of the weld metal cross-sectional area of the inner and outer surfaces, the outer surface heat input is greatly reduced and the toughness of the outer surface weld heat affected zone is improved. As a result of improving the toughness by tempering during outer surface welding, a welded steel pipe having excellent low-temperature toughness in both the inner and outer surface of the heat affected zone can be obtained while obtaining sufficient penetration.

本実施形態における溶接部形状を説明する図である。It is a figure explaining the welding part shape in this embodiment. 本実施形態における開先形状を説明する図である。It is a figure explaining the groove shape in this embodiment. 本実施例におけるシャルピー衝撃試験片の採取位置を説明する図である。It is a figure explaining the sampling position of the Charpy impact test piece in a present Example. 本実施形態におけるシャルピー吸収エネルギーとS2/S1の関係を説明する図である。It is a figure explaining the relationship of Charpy absorbed energy and S2 / S1 in this embodiment.

以下、本発明のラインパイプ用溶接鋼管並びにその製造方法について説明する。
本発明に係るラインパイプ用溶接鋼管は、管状に成形された鋼板を溶接した溶接鋼管であって、管状に成形された前記鋼板の突き合せ部をサブマージアーク溶接で内外面それぞれ一層溶接され、溶接部において、内面側の溶接金属断面積S1と外面側の溶接金属断面積S2が(1)式を満足することを特徴とする。
本発明に係る鋼板のサブマージアーク溶接法では、鋼板をサブマージアーク溶接で内外面それぞれ一層溶接され、内面側の溶接金属断面積S1と外面側の溶接金属断面積S2が(1)式を満足するように溶接条件を選定する。
0.5≦S2/S1≦1.0 ・・・ (1)
ここで、S1:内面側の溶接金属断面積(mm)、S2:外面側の溶接金属断面積(mm)である。
Hereinafter, the welded steel pipe for line pipes of the present invention and the manufacturing method thereof will be described.
A welded steel pipe for a line pipe according to the present invention is a welded steel pipe welded to a steel plate formed into a tubular shape, and the butt portion of the steel plate formed into a tubular shape is welded to each inner and outer surfaces by submerged arc welding, and welded. The weld metal cross-sectional area S1 on the inner surface side and the weld metal cross-sectional area S2 on the outer surface side satisfy the expression (1).
In the submerged arc welding method for a steel sheet according to the present invention, the inner and outer surfaces of the steel sheet are each welded by submerged arc welding, and the weld metal cross-sectional area S1 on the inner surface side and the weld metal cross-sectional area S2 on the outer surface side satisfy the expression (1). Select welding conditions as follows.
0.5 ≦ S2 / S1 ≦ 1.0 (1)
Here, S1: weld metal cross-sectional area (mm 2 ) on the inner surface side, S2: weld metal cross-sectional area (mm 2 ) on the outer surface side.

前述したように、溶接能率や施工性を考慮すると、サブマージアーク溶接する際の溶融金属の溶け落ち(メルトダウン)を回避するために、先に溶接する内面側の溶接金属の溶け込み深さを、外面側の溶接金属の溶け込み深さよりも小さくし、外面側の溶接入熱が内面側の溶接入熱よりも高くなるのが一般的である。しかしながら、高靭性化を図るためには、溶接時に投入する入熱量の大幅な低減を達成しなければならないが、同時に、内外面それぞれの溶接金属が重なり、未溶融部が生じないように十分な溶け込み深さも確保しなければ健全な溶接継手と有する鋼管を得ることができなかった。
そこで本発明者らは、溶接鋼管における内外面それぞれの溶接金属の断面積の比を適正に制御することにより、内外面両方の溶接熱影響部の低温靭性を向上させうることを見出した。
つまり、本発明によれば、従来では困難とされていた外面側の溶接入熱を大幅に低減して外面側溶接熱影響部の低温靭性を向上させ、かつ、内面入熱については、内外面溶接金属が十分重ねるために増加させるものの、内面溶接熱影響部の靭性は外面溶接時の焼き戻しによって向上させることにより、溶接欠陥を生じさせることなく優れた低温靭性を得ることか可能となる。
As described above, in consideration of welding efficiency and workability, in order to avoid melting of the molten metal during melt welding (meltdown), the depth of penetration of the weld metal on the inner surface side to be welded first, In general, the depth is smaller than the penetration depth of the weld metal on the outer surface side, and the welding heat input on the outer surface side is higher than the welding heat input on the inner surface side. However, in order to achieve high toughness, it is necessary to achieve a significant reduction in the amount of heat input input during welding, but at the same time, it is sufficient that the weld metals on the inner and outer surfaces overlap and no unmelted part occurs. Unless the penetration depth was ensured, it was not possible to obtain a steel pipe having a sound welded joint.
Therefore, the present inventors have found that the low temperature toughness of the weld heat affected zone of both the inner and outer surfaces can be improved by appropriately controlling the ratio of the cross sectional areas of the weld metals on the inner and outer surfaces of the welded steel pipe.
That is, according to the present invention, the welding heat input on the outer surface side, which has been considered difficult in the past, is greatly reduced to improve the low temperature toughness of the outer surface side heat affected zone, and the inner surface heat input Although the weld metal is increased in order to overlap sufficiently, the toughness of the inner-surface weld heat-affected zone is improved by tempering during outer-surface welding, so that excellent low-temperature toughness can be obtained without causing weld defects.

以下、上記式(1)を限定した理由について詳細に説明する。
まず、シャルピー吸収エネルギーと(外面溶接金属S2)/(内面溶接金属S1)の関係について説明する。図4に−40℃で試験した際のシャルピー吸収エネルギーとS2/S1の関係を示す。S2/S1が大きくなると、外面入熱の増大により外面溶接熱影響部のシャルピー吸収エネルギーは低下した。一方、S2/S1が小さくなると、外面入熱の低減により外面溶接熱影響部のシャルピー吸収エネルギーは増加するものの、内面溶接熱影響部への焼きなまし効果が損なわれ、内面溶接熱影響部のシャルピー吸収エネルギーが低下した。
したがって、外面側の溶接金属(外面溶接金属)の断面積S2(mm)を内面側の溶接金属(内面溶接金属)の断面積S1(mm)で除した値(S2/S1)が大きくなる、つまり、外面側の溶接金属の溶け込み量が、内面側の溶接金属の溶け込み量よりも相対的に多くなると、外面入熱の大幅な低減効果が得られず、靭性が劣化してしまうため、S2/S1の上限を1.0とする。外面入熱の大幅な低減効果をより得るためには、上限を0.95とすることが好ましく、0.86とすることがさらに好ましい。
Hereinafter, the reason which limited the said Formula (1) is demonstrated in detail.
First, the relationship between Charpy absorbed energy and (outer surface weld metal S2) / (inner surface weld metal S1) will be described. FIG. 4 shows the relationship between Charpy absorbed energy and S2 / S1 when tested at −40 ° C. When S2 / S1 increased, the Charpy absorbed energy of the outer surface welding heat affected zone decreased due to an increase in outer surface heat input. On the other hand, when S2 / S1 is decreased, the Charpy absorbed energy of the outer surface welding heat affected zone is increased due to the reduction of the heat input to the outer surface, but the annealing effect on the inner surface weld heat affected zone is impaired, and the Charpy absorption of the inner surface weld heat affected zone is reduced. Energy decreased.
Therefore, the cross-sectional area S2 (mm 2) is larger divided by the (S2 / S1) by the cross-sectional area S1 of the weld metal of the inner surface side (inner surface weld metal) (mm 2) of the weld metal of the outer surface side (outer surface weld metal) In other words, if the penetration amount of the weld metal on the outer surface side is relatively larger than the penetration amount of the weld metal on the inner surface side, the effect of greatly reducing the heat input to the outer surface cannot be obtained, and the toughness deteriorates. The upper limit of S2 / S1 is 1.0. In order to further obtain a significant effect of reducing the heat input to the outer surface, the upper limit is preferably set to 0.95, and more preferably set to 0.86.

一方、S2/S1が小さいほど、外面入熱の低減効果が大きくなるが、0.5を下回ると外面溶接時に内面溶接熱影響部が焼きなまされて内面溶接熱影響部靭性が向上する効果が十分得られず、内面溶接熱影響部の靭性が劣化するため、下限を0.5とする。また、S2/S1が小さくなるほど過大な内面入熱を必要とし、溶接速度が低下するため、より好ましい下限は0.6とする。
このように、内外面それぞれの溶接金属の断面積比を規定して、外面入熱を大幅に低減させ、かつ内面溶接影響部は外面溶接時の焼き戻しを利用することにより、内外面両方の溶接熱影響部にて優れた低温靭性を得ることができる。
On the other hand, the smaller the S2 / S1, the greater the effect of reducing the heat input to the outer surface. However, when the ratio is less than 0.5, the effect of improving the toughness of the inner surface heat affected zone by annealing the inner surface heat affected zone during outer surface welding. Is not sufficiently obtained, and the toughness of the inner-surface weld heat-affected zone deteriorates, so the lower limit is made 0.5. Further, as S2 / S1 decreases, excessive inner surface heat input is required, and the welding speed decreases. Therefore, a more preferable lower limit is set to 0.6.
In this way, by defining the cross-sectional area ratio of the weld metal on each of the inner and outer surfaces, the heat input on the outer surface is greatly reduced, and the inner surface weld affected part uses tempering during outer surface welding, so Excellent low temperature toughness can be obtained at the weld heat affected zone.

ここで、本発明において内面側の溶接金属断面積S1は以下のように定義する。
通常、内面溶接を実施した後に外面溶接を実施するが、外面溶接の際に内面溶接金属の一部は溶融されるため、内外面溶接後に鋼管の内面溶接金属の断面積をそのまま測定することが不可能である。そのため、内面溶接金属のうち、外面溶接金属と重なる部分を除いた部分の面積を測定して内面溶接金属断面積S1とする。
Here, in the present invention, the weld metal cross-sectional area S1 on the inner surface side is defined as follows.
Usually, the outer surface welding is performed after the inner surface welding is performed, but since a part of the inner surface welding metal is melted during the outer surface welding, the cross-sectional area of the inner surface welding metal of the steel pipe can be measured as it is after the inner and outer surface welding. Impossible. Therefore, the area of the portion of the inner surface weld metal excluding the portion overlapping with the outer surface weld metal is measured as the inner surface weld metal cross-sectional area S1.

また、本発明に係る鋼管の周方向を引張方向とした際、母材とする鋼板の引張強度が570〜825MPaであることが好ましい。   Moreover, it is preferable that the tensile strength of the steel plate used as a base material is 570-825 MPa when the circumferential direction of the steel pipe which concerns on this invention is made into a tension direction.

また、本発明は、上述した溶接継手を含むラインパイプ用溶接鋼管であり、溶接鋼管における内外面それぞれの溶接金属の断面積の比を適正に制御することにより内外面両方の溶接熱影響部の低温靭性を向上させることができる。   Moreover, the present invention is a welded steel pipe for line pipes including the above-described welded joint, and by appropriately controlling the ratio of the cross-sectional area of the weld metal on the inner and outer surfaces of the welded steel pipe, Low temperature toughness can be improved.

次に、本発明に係るラインパイプ用溶接鋼管の製造方法について説明する。
本発明の溶接鋼管の製造方法は、管状に成形された鋼板の突き合せ部をサブマージアーク溶接で内外面一層溶接する際、開先形状は図2に示すようなX開先としても良い。X開先の形状は、内面側の溶接金属断面積よりも外面側の溶接金属断面積を小さくするために、図2中に示すような内面開先深さd1と外面開先深さd2が(2)式を満足する形状を採用しても良い。
d2/d1≦1.0 ・・・ (2)
このように、外面開先深さd2よりも内面開先深さd1が長いX開先をサブマージアーク溶接することにより、上述したようなS2/S1の関係をより満足させることができ、より靭性を向上させることができる。なお、d2/d1の下限値については特に限定しないが、0.2以上とすることが好ましい。
Next, the manufacturing method of the welded steel pipe for line pipes which concerns on this invention is demonstrated.
In the method for manufacturing a welded steel pipe according to the present invention, when the butt portion of a steel plate formed into a tubular shape is welded to the inner and outer surfaces by submerged arc welding, the groove shape may be an X groove as shown in FIG. The shape of the X groove has an inner groove depth d1 and an outer groove depth d2 as shown in FIG. 2 in order to make the weld metal sectional area on the outer surface side smaller than the weld metal sectional area on the inner surface side. You may employ | adopt the shape which satisfies (2) Formula.
d2 / d1 ≦ 1.0 (2)
Thus, by submerging arc welding the X groove having the inner groove depth d1 longer than the outer groove depth d2, it is possible to satisfy the relationship of S2 / S1 as described above, and tougher. Can be improved. In addition, although it does not specifically limit about the lower limit of d2 / d1, It is preferable to set it as 0.2 or more.

また、本発明において、鋼板を管状に成形した後に突合せ部を内外面からサブマージアーク溶接し溶接鋼管とするが、管状に成形する際の工程は、鋼板をCプレス、Uプレス、OプレスするUOE工程、JCO工程又はベンドロールのいずれかの工程としても良い。
また、本発明における上記サブマージアーク溶接において、内面側の入熱を3.5〜16.0kJ/mm、外面側の入熱が2.5〜11.0kJ/mmとすることが好ましく、さらに下記式(3)を満たすことがより好ましい。
0.1≦λ2/λ1≦2.5 ・・・ (3)
In the present invention, after the steel plate is formed into a tubular shape, the butt portion is subjected to submerged arc welding from the inner and outer surfaces to form a welded steel pipe. The process at the time of forming into a tubular shape is UOE in which the steel plate is C-pressed, U-pressed, and O-pressed. It may be a process, a JCO process, or a bend roll.
In the submerged arc welding according to the present invention, the heat input on the inner surface side is preferably 3.5 to 16.0 kJ / mm, and the heat input on the outer surface side is preferably 2.5 to 11.0 kJ / mm. It is more preferable to satisfy the formula (3).
0.1 ≦ λ2 / λ1 ≦ 2.5 (3)

また、鋼板板厚から内面開先深さd1および外面開先深さd2を差し引いた長さdn(ルート)は特に規定しないが、内面溶接時にメルトダウンを生じさせないためには、dnの下限を3mm、より好ましくは5mmとすることが好ましい。なお、dnの上限については、10mmとすることが好ましく、8mmとすることがより好ましい。   Further, a length dn (root) obtained by subtracting the inner surface groove depth d1 and the outer surface groove depth d2 from the steel plate thickness is not particularly defined. However, in order not to cause meltdown during inner surface welding, the lower limit of dn is set. The thickness is preferably 3 mm, more preferably 5 mm. In addition, about the upper limit of dn, it is preferable to set it as 10 mm, and it is more preferable to set it as 8 mm.

以下、実施例により本発明の効果を説明するが、本発明は、以下の実施例で用いた条件に限定されるものではない。   Hereinafter, the effects of the present invention will be described with reference to examples, but the present invention is not limited to the conditions used in the following examples.

本実施例においてサブマージアーク溶接する母材鋼板は引張強さ570〜625MPaの強度を有する板厚26mmのラインパイプ用鋼板を用いた。鋼板は、下記(式3)によって求められる炭素等量Ceqが0.39である。
次に、溶接する母材鋼板の突き合せ部に図2に示す開先形状の開先加工を施した後、管状に成形し、表2に示す溶接条件で内外面1層溶接の多電極サブマージアーク溶接を施して溶接継手を作製した。表1に開先寸法を示す。なお、管状に成形する際の工程は、UOE工程を採用した。
なお、表1中における母材鋼板の引張強度は、鋼管の周方向を引張方向とした際の引張強度である。製造No.1〜4いずれにおいても、引張強さ570〜625MPaであった。
Ceq=C+Mn/6+(Ni+Cu)/15+(Cr+Mo+V)/5
・・・(式3)
ここで、C、Mn、Ni、Cu、Cr、Mo、Vは各元素の含有量[質量%]である。
In this example, the base steel plate to be subjected to submerged arc welding was a steel plate for a line pipe having a tensile strength of 570 to 625 MPa and a thickness of 26 mm. The steel sheet has a carbon equivalent Ceq calculated by the following (formula 3) of 0.39.
Next, after the groove shape of the groove shape shown in FIG. 2 is applied to the butt portion of the base steel plate to be welded, it is formed into a tubular shape, and a multi-electrode submerged of inner and outer surface single layer welding under the welding conditions shown in Table 2 Arc welding was performed to produce a welded joint. Table 1 shows the groove dimensions. In addition, the UOE process was employ | adopted as the process at the time of shape | molding in a tubular shape.
In addition, the tensile strength of the base material steel plate in Table 1 is the tensile strength when the circumferential direction of the steel pipe is the tensile direction. Production No. In any of 1-4, the tensile strength was 570-625 MPa.
Ceq = C + Mn / 6 + (Ni + Cu) / 15 + (Cr + Mo + V) / 5
... (Formula 3)
Here, C, Mn, Ni, Cu, Cr, Mo, and V are contents [mass%] of each element.

作製した継手からシャルピー衝撃試験片2を採取し、JIS Z 2242の金属材料衝撃試験方法に準拠してシャルピー衝撃試験(切欠き位置:溶融線,試験温度:−40℃)を行い、HAZ部における吸収エネルギー(vE−40)を求めた。なお、表3中のHAZ靭性vE−40は、3本の試験片における吸収エネルギーの平均値である。また、HAZにおける低温靭性の評価については、HAZ靭性vE−40が100J以上を良好として評価した。 A Charpy impact test piece 2 is taken from the produced joint, and subjected to a Charpy impact test (notch position: melt line, test temperature: −40 ° C.) in accordance with the metal material impact test method of JIS Z 2242. Absorbed energy (vE- 40 ) was determined. In addition, HAZ toughness vE- 40 in Table 3 is an average value of absorbed energy in three test pieces. Moreover, about evaluation of the low temperature toughness in HAZ, HAZ toughness vE- 40 evaluated 100J or more as favorable.

図3に上記シャルピー衝撃試験片2の採取位置を示す。溶接部4の溶融線5を切欠き位置として、ノッチ3が板厚方向と平行でかつ内面溶接および外面溶接のそれぞれについて、母材鋼板1の表面下7mmの位置がシャルピー衝撃試験片2の中心となるように採取した。表4にシャルピー衝撃試験の結果得られたHAZ靭性vE−40(上段:内面側、下段:外面側)および溶接金属断面形状の観察結果、開先寸法を示す。 FIG. 3 shows the sampling position of the Charpy impact test piece 2. With the melt line 5 of the welded portion 4 as a notch position, the notch 3 is parallel to the plate thickness direction, and for each of the inner surface welding and the outer surface welding, the position 7 mm below the surface of the base steel plate 1 is the center of the Charpy impact test piece 2 It collected so that it might become. Table 4 shows the HAZ toughness vE- 40 (upper: inner surface, lower: outer surface) obtained as a result of the Charpy impact test, the observation results of the weld metal cross-sectional shape, and the groove dimensions.

本発明例(製造No.1〜3)は、外面溶接金属断面積S2を内面溶接金属断面積S1で除した値S2/S1が0.5〜1.0の範囲であり、外面溶接金属断面積S2を小さくしたことで外面入熱は大幅に低減され、特に外面側のHAZ靭性が大幅に改善し、−40℃でも100J以上の高いシャルピー吸収エネルギーを示した。また、内面溶接金属断面積S1を大きくすることで内外面の溶接金属は十分重なり、健全な溶接継手が得られている。さらに、内面側のHAZ靭性は入熱を大きくしても、外面溶接金属断面積S2を大きくすることで外面溶接時の焼きなまし効果により−40℃でも100J以上の高いシャルピー吸収エネルギーを保持しており、内外面両方の溶接熱影響部において優れた靭性を得ることが出来た。   In the present invention example (production Nos. 1 to 3), the value S2 / S1 obtained by dividing the outer surface weld metal cross-sectional area S2 by the inner surface weld metal cross-sectional area S1 is in the range of 0.5 to 1.0, and the outer surface weld metal breakage By reducing the area S2, the heat input to the outer surface was greatly reduced, and the HAZ toughness on the outer surface side was greatly improved, and a high Charpy absorbed energy of 100 J or more was exhibited even at −40 ° C. Further, by increasing the inner surface weld metal cross-sectional area S1, the weld metals on the inner and outer surfaces are sufficiently overlapped, and a sound welded joint is obtained. Furthermore, the HAZ toughness on the inner surface side maintains a high Charpy absorption energy of 100 J or more even at -40 ° C. due to the annealing effect during outer surface welding by increasing the outer surface weld metal cross-sectional area S2 even if the heat input is increased. Excellent toughness was obtained in the heat affected zone of both the inner and outer surfaces.

一方、比較例(製造No.4)は、上記特許文献7の範囲内だが、外面溶接金属断面積S2を大幅に低減したため外面溶接熱影響部の靭性は向上したものの、外面側の溶接金属断面積S2が小さ過ぎて内面溶接熱影響部での焼き戻し効果が十分得られず、内面溶接熱影響部の靭性が低下した例である。
また、比較例(条件No.5)も上記特許文献7の範囲内だが、外面溶接金属断面積S2が内面溶接金属S1よりも大きく、内面溶接熱影響部の靭性は良好であるものの、外面溶接金属断面積が大きすぎて外面溶接熱影響部の靭性が低下した例である。
On the other hand, the comparative example (Production No. 4) is within the range of the above-mentioned Patent Document 7, but the outer surface weld metal cross-sectional area S2 is greatly reduced. This is an example in which the area S2 is too small to sufficiently obtain the tempering effect in the inner surface welding heat affected zone and the toughness of the inner surface welding heat affected zone is lowered.
Further, the comparative example (condition No. 5) is also within the range of Patent Document 7, but the outer surface weld metal cross-sectional area S2 is larger than the inner surface weld metal S1 and the inner surface heat-affected zone has good toughness, but outer surface welding. This is an example in which the metal cross-sectional area is too large and the toughness of the heat-affected zone on the outer surface is reduced.

1 母材鋼板
2 シャルピー衝撃試験片
3 ノッチ
4 溶接部
5 溶融線
DESCRIPTION OF SYMBOLS 1 Base material steel plate 2 Charpy impact test piece 3 Notch 4 Welded part 5 Melt line

Claims (4)

管状に成形された鋼板を溶接した溶接鋼管であって、
管状に成形された前記鋼板の突き合せ部をサブマージアーク溶接で内外面それぞれ一層溶接され、
溶接部において、内面側の溶接金属断面積S1(mm)と外面側の溶接金属断面積S2(mm)が(1)式を満足することを特徴とする低温靭性に優れたラインパイプ用溶接鋼管。
0.5≦S2/S1≦1.0 ・・・ (1)
A welded steel pipe welded to a tubular steel plate,
The butt portion of the steel sheet formed into a tubular shape is welded to the inner and outer surfaces respectively by submerged arc welding,
In welds, for line pipe superior in low temperature toughness characterized by satisfying the weld metal cross sectional area S1 of the inner surface (mm 2) and the outer surface weld metal cross sectional area S2 (mm 2) is a (1) Welded steel pipe.
0.5 ≦ S2 / S1 ≦ 1.0 (1)
前記鋼管の周方向を引張方向とした際、前記鋼板の引張強度が570〜825MPaであることを特徴とする請求項1に記載の低温靭性に優れたラインパイプ用溶接鋼管。   The welded steel pipe for line pipe excellent in low temperature toughness according to claim 1, wherein the tensile strength of the steel sheet is 570 to 825 MPa when the circumferential direction of the steel pipe is a tensile direction. 管状に成形された鋼板の突き合せ部をサブマージアーク溶接する際に、開先形状が、内面開先深さd1と外面開先深さd2が(2)式を満足するX開先となるよう加工を施し、得られた前記X開先をサブマージアーク溶接することを特徴とする請求項1又は2に記載の低温靭性に優れたラインパイプ用溶接鋼管の製造方法。
d2/d1≦1.0 ・・・ (2)
When submerged arc welding is performed on a butt portion of a steel sheet formed into a tubular shape, the groove shape is an X groove where the inner surface groove depth d1 and the outer surface groove depth d2 satisfy the expression (2). The method for producing a welded steel pipe for a line pipe according to claim 1 or 2, wherein the X groove is processed and submerged arc welding is performed.
d2 / d1 ≦ 1.0 (2)
前記サブマージアーク溶接において、内面側の入熱λ1が3.5〜16.0kJ/mm、外面側の入熱λ2が2.5〜11.0kJ/mmであり、さらに、(3)式を満足することを特徴とする請求項3に記載の低温靭性に優れたラインパイプ用溶接鋼管の製造方法。
0.1≦λ2/λ1≦2.5 ・・・ (3)
In the submerged arc welding, the heat input λ1 on the inner surface side is 3.5 to 16.0 kJ / mm, the heat input λ2 on the outer surface side is 2.5 to 11.0 kJ / mm, and further satisfies Equation (3). The manufacturing method of the welded steel pipe for line pipes excellent in low-temperature toughness of Claim 3 characterized by performing.
0.1 ≦ λ2 / λ1 ≦ 2.5 (3)
JP2013028146A 2013-02-15 2013-02-15 Welded steel pipe for line pipe with excellent low-temperature toughness, and method of manufacturing the same Pending JP2014155949A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP2013028146A JP2014155949A (en) 2013-02-15 2013-02-15 Welded steel pipe for line pipe with excellent low-temperature toughness, and method of manufacturing the same

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP2013028146A JP2014155949A (en) 2013-02-15 2013-02-15 Welded steel pipe for line pipe with excellent low-temperature toughness, and method of manufacturing the same

Publications (1)

Publication Number Publication Date
JP2014155949A true JP2014155949A (en) 2014-08-28

Family

ID=51577205

Family Applications (1)

Application Number Title Priority Date Filing Date
JP2013028146A Pending JP2014155949A (en) 2013-02-15 2013-02-15 Welded steel pipe for line pipe with excellent low-temperature toughness, and method of manufacturing the same

Country Status (1)

Country Link
JP (1) JP2014155949A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104438436A (en) * 2014-12-03 2015-03-25 中冶辽宁德龙钢管有限公司 Reducing and rounding method for pipe end of helical weld pipe
CN105880809A (en) * 2014-11-14 2016-08-24 宋国栋 Online upward multi-wire submerged-arc welding process for medium longitudinally-welded steel pipe, and used welding pad roll

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2005288448A (en) * 2004-03-31 2005-10-20 Jfe Steel Kk Uoe steel tube manufacturing method
JP2007044710A (en) * 2005-08-08 2007-02-22 Nippon Steel Corp Method for manufacturing uo-formed steel pipe having excellent low temperature cracking resistance, and uo-formed steel pipe
JP2009233679A (en) * 2008-03-26 2009-10-15 Jfe Steel Corp Submerged arc welding method of steel material
JP2011212691A (en) * 2010-03-31 2011-10-27 Jfe Steel Corp Flux-cored welding wire for small diameter multi-electrode submerged arc welding

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2005288448A (en) * 2004-03-31 2005-10-20 Jfe Steel Kk Uoe steel tube manufacturing method
JP2007044710A (en) * 2005-08-08 2007-02-22 Nippon Steel Corp Method for manufacturing uo-formed steel pipe having excellent low temperature cracking resistance, and uo-formed steel pipe
JP2009233679A (en) * 2008-03-26 2009-10-15 Jfe Steel Corp Submerged arc welding method of steel material
JP2011212691A (en) * 2010-03-31 2011-10-27 Jfe Steel Corp Flux-cored welding wire for small diameter multi-electrode submerged arc welding

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105880809A (en) * 2014-11-14 2016-08-24 宋国栋 Online upward multi-wire submerged-arc welding process for medium longitudinally-welded steel pipe, and used welding pad roll
CN104438436A (en) * 2014-12-03 2015-03-25 中冶辽宁德龙钢管有限公司 Reducing and rounding method for pipe end of helical weld pipe
CN104438436B (en) * 2014-12-03 2016-03-02 中冶辽宁德龙钢管有限公司 A kind of end of spirial welded pipe undergauge full circle method

Similar Documents

Publication Publication Date Title
US9677692B2 (en) Welded steel pipe joined with high-energy-density beam and method for producing the same
CN102383049B (en) Method for manufacturing low-cost high-toughness X70 steel spiral submerged arc welded pipe
WO2010137186A1 (en) Submerged arc welding method for steel plate
JP5854145B2 (en) Submerged arc welding method, welded joint and steel pipe manufacturing method
WO2013051249A1 (en) Welded steel pipe with excellent welding heat-affected zone toughness, and process for producing same
WO2012019422A1 (en) Method for manufacturing continuous expansion pipe with high strength and ductility
CN104404299A (en) Titanium alloy continuous oil pipe and manufacturing method thereof
JP2006272377A (en) Submerged arc welding method of steel material
JP2015150597A (en) Submerged arc welding part excellent in low temperature toughness
JP2009214127A (en) Submerged arc welding method for steel material
JP6693688B2 (en) Welded steel pipe for line pipe excellent in low temperature toughness and method of manufacturing the same
JP5549176B2 (en) Method for producing martensitic stainless steel welded pipe with excellent intergranular stress corrosion cracking resistance
CN103194678B (en) A kind of UOE welded tube and manufacture method thereof
JP2009233679A (en) Submerged arc welding method of steel material
JP6579249B2 (en) Welded steel pipe for line pipe excellent in low temperature toughness and its manufacturing method
JP3702216B2 (en) Manufacturing method for inner and outer surface submerged arc welded steel pipes with excellent seam weld toughness
JP2014155949A (en) Welded steel pipe for line pipe with excellent low-temperature toughness, and method of manufacturing the same
JP2010172896A (en) Multi-electrode submerged arc welding method of steel material
JP4593399B2 (en) Manufacturing method of UO steel pipe excellent in low temperature crack resistance and UO steel pipe
JP5742090B2 (en) Submerged arc welding method for steel with excellent toughness of weld heat affected zone
JP3896031B2 (en) Manufacturing method of high strength UOE steel pipe
JP4482355B2 (en) Seam welding method for high strength UO steel pipe with excellent transverse cracking resistance
JP5742091B2 (en) Submerged arc welding method for steel with excellent toughness of weld heat affected zone
CN105886861A (en) Aluminum alloy coiled tubing and manufacturing method thereof
JP2013081985A (en) Submerged arc welding method for steel material

Legal Events

Date Code Title Description
A621 Written request for application examination

Free format text: JAPANESE INTERMEDIATE CODE: A621

Effective date: 20151005

A977 Report on retrieval

Free format text: JAPANESE INTERMEDIATE CODE: A971007

Effective date: 20161020

A131 Notification of reasons for refusal

Free format text: JAPANESE INTERMEDIATE CODE: A131

Effective date: 20161025

A02 Decision of refusal

Free format text: JAPANESE INTERMEDIATE CODE: A02

Effective date: 20170418