JP5000148B2 - Manufacturing method of welded steel pipe - Google Patents

Manufacturing method of welded steel pipe Download PDF

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JP5000148B2
JP5000148B2 JP2006035060A JP2006035060A JP5000148B2 JP 5000148 B2 JP5000148 B2 JP 5000148B2 JP 2006035060 A JP2006035060 A JP 2006035060A JP 2006035060 A JP2006035060 A JP 2006035060A JP 5000148 B2 JP5000148 B2 JP 5000148B2
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residual stress
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英司 津留
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Nippon Steel Corp
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本発明は、天然ガスまたは原油の輸送用ラインパイプ等に用いられる、母材およびアーク溶接によって形成された溶接金属の周方向の引張強度が850MPa以上である高強度溶接鋼管およびその製造方法に関する。   The present invention relates to a high-strength welded steel pipe in which the tensile strength in the circumferential direction of a base metal and a weld metal formed by arc welding used for a natural gas or crude oil transportation line pipe is 850 MPa or more, and a method for producing the same.

近年、天然ガスまたは原油を輸送する長距離パイプラインにおいて輸送の効率化、付帯設備のコスト削減の観点から引張強度が850MPa以上である高強度大径ラインパイプの敷設が検討され始めてきた。このようなラインパイプは通常、UOE方式、UOC方式、JOE方式やベンディングロール方式により、鋼板を筒状にして突合せ部をシーム溶接して造管される。この場合、つなぎ目となるシーム溶接部はサブマージアーク溶接により、通常、内面溶接、外面溶接の順で形成される。しかしながら、外面溶接後の非破壊検査でシーム溶接部に鋼管軸方向に直角方向の割れ、いわゆる横割れが散見される場合がある。   In recent years, laying of high-strength large-diameter line pipes having a tensile strength of 850 MPa or more has been studied from the viewpoints of efficient transportation and cost reduction of incidental facilities in long-distance pipelines that transport natural gas or crude oil. Such a line pipe is usually produced by UOE method, UOC method, JOE method or bending roll method by making a steel plate into a cylindrical shape and seam welding the butt portion. In this case, the seam welded portion serving as a joint is usually formed in the order of inner surface welding and outer surface welding by submerged arc welding. However, in the nondestructive inspection after outer surface welding, cracks in the direction perpendicular to the steel pipe axis direction, so-called transverse cracks, are sometimes found in the seam welds.

このような横割れが残存した鋼管を凍土地帯で使用すると、温度の季節変動によって、軸方向に管体の降伏強度を超えるような引張応力が負荷されて破壊する危険性や、繰り返しの応力負荷により割れが進展して輸送流体が漏洩し、大事故につながる危険性がある。このため製造時の割れ発生を未然に防ぐか、発生した割れを非破壊検査により確実に検出し、除去しなければならない。   When steel pipes with such transverse cracks are used in frozen land zones, there is a risk of breaking due to tensile stress exceeding the yield strength of the pipe in the axial direction due to seasonal fluctuations in temperature, and repeated stress loading There is a risk that the crack will develop and the transport fluid will leak, leading to a major accident. For this reason, it is necessary to prevent the occurrence of cracks during production or to reliably detect and remove the cracks that have occurred by nondestructive inspection.

シーム溶接部の横割れは、高強度材の脆化割れの一種である。この横割れは水素によるものが一般的であり、水素脆化割れとも呼ばれ、溶接金属の強度が低下すると発生しにくくなる。しかしながら、シーム溶接部の強度を低下させると脆化割れは起きにくくなるものの、内圧負荷時に選択的にシーム溶接部からの変形が促進され、溶接部からの破断に至る場合も想定される。したがって、溶接金属の強度を母材強度以上に保ちながら水素脆化割れを防止する方法が必要である。   A transverse crack in a seam weld is a kind of embrittlement crack in a high-strength material. This transverse crack is generally caused by hydrogen and is also called hydrogen embrittlement crack, and it is difficult to occur when the strength of the weld metal is lowered. However, if the strength of the seam welded portion is reduced, embrittlement cracks are less likely to occur, but it is also assumed that deformation from the seam welded portion is selectively promoted during internal pressure loading, leading to fracture from the welded portion. Therefore, there is a need for a method for preventing hydrogen embrittlement cracking while maintaining the strength of the weld metal at or above the base metal strength.

水素脆化割れは水素濃度、負荷応力、材料特性、特に強度に依存するため、複合的な効果によって水素脆化割れが発生しないように、これらを限界値以下に制御する必要がある。水素濃度を低下させる方法として、内外面からのシーム溶接後、100℃以上、好ましくは200℃以上に加温し、適切な時間だけ保持する方法がある。これは、いわゆる後熱であり、溶接金属を加熱して水素を拡散させ、横割れが発生する限界以下の水素濃度とする方法である。   Since hydrogen embrittlement cracks depend on the hydrogen concentration, load stress, material properties, and particularly strength, it is necessary to control these to below the limit value so that hydrogen embrittlement cracks do not occur due to complex effects. As a method for reducing the hydrogen concentration, there is a method in which after seam welding from the inner and outer surfaces, the temperature is raised to 100 ° C. or higher, preferably 200 ° C. or higher, and held for an appropriate time. This is so-called post-heating, in which the weld metal is heated to diffuse hydrogen to obtain a hydrogen concentration below the limit at which transverse cracking occurs.

このような観点から、UOE鋼管の溶接金属の強度、母材強度、溶接条件を複合的に抑えることで高強度材のシーム溶接部の水素脆化割れを防止する技術が特許文献1に開示されている。特許文献1には溶接部の横割れが先行するシーム溶接部で頻発することについては述べられているものの、水素濃度、溶接残留応力の抑制による横割れ防止について、具体的な条件は開示されていない。   From this point of view, Patent Document 1 discloses a technique for preventing hydrogen embrittlement cracking in a seam welded portion of a high-strength material by compositely suppressing the strength, base metal strength, and welding conditions of the weld metal of the UOE steel pipe. ing. Although Patent Document 1 describes that transverse cracks in welds occur frequently in the preceding seam welds, specific conditions are disclosed regarding prevention of transverse cracks by suppressing hydrogen concentration and welding residual stress. Absent.

また、溶接後、鋼管全体を焼入れ、焼戻しすることで靭性の低下、および凝固割れを防止する方法が特許文献2に提案されているが、水素濃度、溶接残留応力については触れられていない。同じく高強度のUOE鋼管の割れを防止する技術として、溶接の内外面高さ比を適切に制御し、水素脆化割れを誘起する要因となる残留応力を緩和させる方法が特許文献3に提案されている。   Moreover, although the method of preventing the toughness fall and solidification cracking by quenching and tempering the whole steel pipe after welding is proposed in Patent Document 2, the hydrogen concentration and welding residual stress are not mentioned. Similarly, as a technique for preventing cracking of a high-strength UOE steel pipe, Patent Document 3 proposes a method of appropriately controlling the height ratio of the inner and outer surfaces of the weld and relieving residual stress that causes hydrogen embrittlement cracking. ing.

特許文献3は内外面からサブマージアーク溶接したシーム溶接において、内面金属高さと外面金属高さの比を適切な範囲にし、水素割れが発生しないように残留応力を制御するものである。しかしながら、この方法によれば、シーム溶接におけるその他の課題、例えば溶接後の開先残り、アンダーカットなどの排除、止端角度の鈍角化のため、極めて狭い範囲に溶接条件を制御する必要があり、生産性を損なうことがある。   Japanese Patent Application Laid-Open No. 2003-228561 controls the residual stress so that hydrogen cracking does not occur in a seam welding in which submerged arc welding is performed from the inner and outer surfaces, with the ratio between the inner metal height and the outer metal height being in an appropriate range. However, according to this method, it is necessary to control the welding conditions within a very narrow range in order to eliminate other problems in seam welding, for example, removal of groove remaining after welding, undercut, etc., and blunting of the toe angle. , May impair productivity.

その他に水素脆化割れを誘起する要因である残留応力を緩和させる方法として、溶接後700℃程度まで加熱する、いわゆる応力除去焼純や、ハンマーピーニングによる殴打などで溶接部に塑性変形を与えることで残留応力を低下させる方法も提案されている。しかし、これらの方法は、水素濃度と残留応力の関係が横割れに及ぼす影響について考慮されていないため、耐水素脆化割れ性が確実に改善されているとはいえない。また、応力除去焼鈍は加熱冷却に過度な時間を要し、ハンマーピーニングは溶接後、直ちに行う必要があり、特別な加工装置が必要となる。したがって、これらの方法は、製造工程、製造コストを考慮すると必ずしもシーム溶接部への適用には適切な方法ではない。   In addition, as a method of relieving residual stress, which is a factor that induces hydrogen embrittlement cracking, plastic welding is applied to the welded part by so-called stress-relieving tempering, which is heated to about 700 ° C. after welding, or hammering. A method for reducing the residual stress is proposed. However, these methods do not take into account the influence of the relationship between the hydrogen concentration and the residual stress on the transverse cracking, and thus it cannot be said that the hydrogen embrittlement cracking resistance has been reliably improved. In addition, stress relief annealing requires an excessive amount of time for heating and cooling, and hammer peening needs to be performed immediately after welding, requiring a special processing device. Therefore, these methods are not necessarily appropriate methods for application to seam welds in consideration of the manufacturing process and manufacturing cost.

また、溶接材料の改良点として、水素トラップサイトとして作用する微細な析出物、例えば、VNなどを溶接金属に生成させて、横割れに有害な拡散性水素を低減させる方法や、低温変態溶材により常温での残留応力を低下させる方法がある。しかし、水素トラップサイトの活用は高強度材では必ずしも有用な方法でなく、また、低温変態溶材の使用は著しいコスト上昇を招く。   Also, as a refinement of the welding material, a fine precipitate that acts as a hydrogen trap site, such as VN, is generated in the weld metal to reduce diffusible hydrogen harmful to transverse cracks, There is a method of reducing the residual stress at room temperature. However, utilization of hydrogen trap sites is not always a useful method for high-strength materials, and the use of low-temperature transformation melts causes a significant cost increase.

特開2003−311321号公報JP 2003-313121 A 特開昭57−35636号公報JP 57-35636 A 特開2005−246403号公報JP 2005-246403 A

本発明は、内外面からシーム溶接を行う引張強度が850MPa以上である高強度溶接鋼管のシーム溶接部に生じる、水素起因の横割れの防止する溶接鋼管の製造方法を提供する。   The present invention provides a method for manufacturing a welded steel pipe that prevents hydrogen-induced lateral cracking that occurs in a seam welded portion of a high-strength welded steel pipe having a tensile strength of 850 MPa or more when performing seam welding from the inner and outer surfaces.

本発明は、上記課題を解決するためになされたもので、シーム溶接後、溶接金属の形状を変化させ、具体的には、溶接金属の肉厚方向の高さを圧縮変形または切除により減少させ、溶接金属の内部で先行して溶接した溶接金属に発生する残留応力を低減させ、水素誘起割れを防止する方法であり、その要旨は以下のとおりである。
(1)引張強度が850MPa以上の鋼板を筒状に成形し、突合せ部を内外面からサブマージアーク溶接する溶接鋼管の製造方法において、溶接方向の全長にわたり、常温での圧縮加工により、溶接金属の肉厚方向の高さを0.2〜1.8%減少させることを特徴とする溶接鋼管の製造方法。
The present invention has been made to solve the above-described problems. After seam welding, the shape of the weld metal is changed. Specifically, the height in the thickness direction of the weld metal is reduced by compressive deformation or cutting. This is a method for reducing the residual stress generated in the weld metal previously welded inside the weld metal and preventing hydrogen-induced cracking, and the gist thereof is as follows.
(1) In a method for manufacturing a welded steel pipe in which a steel sheet having a tensile strength of 850 MPa or more is formed into a cylindrical shape and the butt portion is submerged arc welded from the inner and outer surfaces, the weld metal is compressed by compression at room temperature over the entire length in the welding direction. A method for producing a welded steel pipe, characterized in that the height in the thickness direction is reduced by 0.2 to 1.8 %.

本発明によれば、天然ガス・原油輸送用ラインパイプ等に用いられる、引張強度が850MPa以上である高強度溶接鋼管の溶接部での水素脆化割れの発生を防止することが可能となる。   ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to prevent generation | occurrence | production of the hydrogen embrittlement crack in the weld part of the high intensity | strength welded steel pipe used for natural gas and a crude oil transportation line pipe etc. whose tensile strength is 850 MPa or more.

引張強度が850MPa以上である高強度溶接鋼管をUOE造管プロセスで製造する際には、Cプレスで鋼板の端部を曲げ、UプレスでU字形状に曲げ、次いでOプレスにより筒状に成形し、その後、通常、外面からの仮付け後、サブマージアーク溶接による内面溶接を行い、続いて外面溶接を行い、さらに拡管または縮管矯正により真円度を整える。   When manufacturing high-strength welded steel pipes with a tensile strength of 850 MPa or more by the UOE pipe making process, the end of the steel plate is bent by the C press, bent into a U shape by the U press, and then formed into a cylindrical shape by the O press. Thereafter, usually, after provisional attachment from the outer surface, inner surface welding by submerged arc welding is performed, then outer surface welding is performed, and roundness is adjusted by pipe expansion or contraction correction.

このUOE鋼管のシーム溶接部の欠陥を、JIS G 0584に準拠して、超音波探傷によって検出すると、頻度は少ないものの横割れが散見された。超音波探傷の結果によって、欠陥が検出された位置を特定すると、横割れは先行して溶接した内面の溶接金属に発生していることがわかった。また、横割れの破面を走査型電子顕微鏡で観察した結果、水素脆化割れ特有の破面を呈していることもわかった。   When a defect in the seam welded portion of this UOE steel pipe was detected by ultrasonic flaw detection in accordance with JIS G 058, transverse cracks were found infrequently. From the result of ultrasonic flaw detection, it was found that when the position where the defect was detected was specified, the transverse crack occurred in the weld metal on the inner surface welded in advance. Moreover, as a result of observing the fracture surface of the transverse crack with a scanning electron microscope, it was found that the fracture surface peculiar to hydrogen embrittlement crack was exhibited.

このことから高強度溶接鋼管のシーム溶接部に発生する横割れが、フラックス、開先の結露、大気中の水分などから溶接金属内に取り込まれた水素と溶接残留応力による水素脆化割れであると結論づけた。しかし、内面溶接を行った後、外面溶接を行わずに超音波探傷による欠陥の検出を試みたところ、内面溶接ままでは横割れが発生していないことがわかった。   As a result, transverse cracks that occur in seam welds of high-strength welded steel pipes are hydrogen embrittlement cracks caused by fluxes, groove condensation, moisture taken into the weld metal from the atmosphere, and hydrogen residual stress. It was concluded. However, after performing inner surface welding, an attempt was made to detect defects by ultrasonic flaw detection without performing outer surface welding, and it was found that transverse cracks did not occur with inner surface welding.

ここで述べるUOE鋼管の素材となる厚鋼板(母材)は、その鋼組成が、質量%で、C:0.02〜0.10%、Si:0.01〜0.6%、Mn:1.5〜2.5%、P:0.015%以下、S:0.003%以下、Ni:0.1〜2.0%、Mo:0.15〜0.60%、Nb:0.001〜0.10%、Ti:0.005〜0.030%、Al:0.06%以下を含有し、さらに、必要に応じてB:0.0001〜0.005%、N:0.0001〜0.006%、V:0.001〜0.10%、Cu:0.01〜1.0%、Cr:0.01〜1.0%、Zr:0.0001〜0.005%、Ta:0.0001〜0.005%、Ca:0.0001〜0.01%、REM:0.0001〜0.01%、Mg:0.0001〜0.006%の1種または2種類以上を含有し、残部Feおよび不可避的不純物からなる鋼を熱間制御圧延して得られたものである。   The steel plate (base material) used as the material of the UOE steel pipe described here has a steel composition of mass%, C: 0.02 to 0.10%, Si: 0.01 to 0.6%, Mn: 1.5 to 2.5%, P: 0.015% or less, S: 0.003% or less, Ni: 0.1 to 2.0%, Mo: 0.15 to 0.60%, Nb: 0 0.001 to 0.10%, Ti: 0.005 to 0.030%, Al: 0.06% or less, and B: 0.0001 to 0.005%, N: 0 as necessary. 0.0001-0.006%, V: 0.001-0.10%, Cu: 0.01-1.0%, Cr: 0.01-1.0%, Zr: 0.0001-0.005 %, Ta: 0.0001-0.005%, Ca: 0.0001-0.01%, REM: 0.0001-0.01%, Mg: 0.0001-0.00 % Of one or contain two or more types, in which the steel balance consisting of Fe and unavoidable impurities is obtained by hot controlled rolling.

上記UOE鋼管の製造に際しては、前述の鋼組成を有する厚鋼板(母材)を、質量%で、C:0.01〜0.12%、Si:0.3%以下、Mn:1.2〜2.4%、Ni:4.0〜8.5%、Cr+Mo+V:3.0〜5.0%、Ti:0.005〜0.15%、Al:0.02%以下を含有し、残部Feおよび不可避的不純物からなる溶接ワイヤーを用いて入熱:1.5kJ/mm〜6.3kJ/mmで溶接する。   In the production of the UOE steel pipe, the thick steel plate (base material) having the steel composition described above is, in mass%, C: 0.01 to 0.12%, Si: 0.3% or less, Mn: 1.2 -2.4%, Ni: 4.0-8.5%, Cr + Mo + V: 3.0-5.0%, Ti: 0.005-0.15%, Al: 0.02% or less, Welding is performed at a heat input of 1.5 kJ / mm to 6.3 kJ / mm using a welding wire composed of the remaining Fe and inevitable impurities.

このようにして得られた溶接金属については、成分が、質量%で、C:0.04〜0.14%、Si:0.05〜0.4%、Mn:1.2〜2.2%、P:0.01%以下、S:0.010%以下、Ni:1.3〜3.2%、Cr+Mo+V:1.0〜2.5%、Ti:0.003〜0.050%、Al:0.02%以下、B:0.005%以下、O:0.01〜0.03%を含有し、残部Feおよび不可避的不純物からなるものである。   About the weld metal obtained in this way, a component is the mass%, C: 0.04-0.14%, Si: 0.05-0.4%, Mn: 1.2-2.2 %, P: 0.01% or less, S: 0.010% or less, Ni: 1.3 to 3.2%, Cr + Mo + V: 1.0 to 2.5%, Ti: 0.003 to 0.050% Al: 0.02% or less, B: 0.005% or less, O: 0.01 to 0.03%, and the balance is Fe and inevitable impurities.

本発明者らは、UOE工程における拡管前の溶接金属部の残留応力を有限要素法(以下、FEAともいう。)による数値解析シミュレーションで求めた。これは、内外面からシーム溶接した溶接金属の内部の残留応力を非破壊で実測することが困難であるためである。   The present inventors obtained the residual stress of the weld metal part before pipe expansion in the UOE process by a numerical analysis simulation by a finite element method (hereinafter also referred to as FEA). This is because it is difficult to measure the residual stress inside the weld metal seam-welded from the inner and outer surfaces in a nondestructive manner.

本発明者らは、内面、外面の順でシーム溶接して引張強度が950MPaである溶接金属を形成し、拡管前の状態を仮定し、FEAによって、鋼管の周方向断面における溶接金属の中心線(溶接中心線、図1の一点鎖線)上での鋼管軸方向の残留応力を求め、その肉厚方向の分布を図2に示した。解析に必要な物性値である熱伝導率、比熱、密度は実測し、状態値である熱伝達係数は、外面溶接中の内面温度変化を実測して得た温度履歴と、FEAによる内面温度変化の解析値が一致する数値に設定した。   The inventors of the present invention formed a weld metal having a tensile strength of 950 MPa by seam welding in the order of the inner surface and the outer surface, and assumed a state before pipe expansion. By FEA, the center line of the weld metal in the circumferential section of the steel pipe The residual stress in the steel pipe axial direction on (welding center line, one-dot chain line in FIG. 1) was determined, and the distribution in the thickness direction is shown in FIG. Thermal conductivity, specific heat, and density, which are physical properties necessary for analysis, are measured, and heat transfer coefficient, which is a state value, is a temperature history obtained by actually measuring changes in internal temperature during external welding, and changes in internal temperature due to FEA. The analysis value was set to the same value.

図2の横軸は、溶接中心線上における鋼管の内面からの距離である。さらにX線回折により測定した、鋼管の内表面、外表面における溶接金属の残留応力も図2に示す。溶接金属の内表面および外表面の残留応力のFEAによる予測値とX線回折による測定値は良く一致している。このことから、図2に示した溶接金属の内部の残留応力のFEAによる予測値は、実際の溶接金属の残留応力を精度よく推定していると考えられる。   The horizontal axis in FIG. 2 is the distance from the inner surface of the steel pipe on the welding center line. Furthermore, the residual stress of the weld metal on the inner surface and outer surface of the steel pipe measured by X-ray diffraction is also shown in FIG. The predicted value by FEA of the residual stress on the inner and outer surfaces of the weld metal is in good agreement with the measured value by X-ray diffraction. From this, it is considered that the predicted value by FEA of the residual stress inside the weld metal shown in FIG. 2 accurately estimates the residual stress of the actual weld metal.

図2に示したように、残留応力は先行して溶接された内面溶接金属側で最大値を示し、その値は溶接金属の降伏強度、800MPaを超えている。また、残留応力が最大になる位置は、超音波探傷によって検出された横割れの発生個所と一致していることがわかった。したがって、残留応力を何らかの方法で低減すれば、水素脆化割れを防止することができると考えられる。   As shown in FIG. 2, the residual stress has a maximum value on the inner side weld metal side welded in advance, and the value exceeds the yield strength of the weld metal, 800 MPa. In addition, it was found that the position where the residual stress was maximized coincided with the occurrence of lateral cracking detected by ultrasonic flaw detection. Therefore, it is considered that hydrogen embrittlement cracking can be prevented if the residual stress is reduced by any method.

本発明者らは、次に水素濃度と横割れが発生する限界の残留応力との関係を把握するため、以下のようにして、引張強度が850MPa以上である溶接金属に水素脆化割れが発生する引張応力と水素濃度との関係を調査した。そこで、以下のようにして、引張強度が850MPa以上である高強度溶接鋼管の溶接金属の水素脆化割れが発生する応力と水素量の関係を調査した。溶接鋼管から内外面溶接金属を含むように、周方向と軸方向のサイズが200mm×200mmであるサンプルを採取し、直ちにドライアイスで冷却し、保存した。このサンプルの溶接金属から、長手方向が溶接方向と平行であり、平行部の直径が6mmである丸棒引張り試験片を採取した。これらの丸棒引張り試験片に、水素が逃散しないようにカドミウムめっきを施した。次に、この引張り試験片に一定荷重を240時間負荷し、破断の有無、すなわち水素脆化割れ発生の有無を調べた。更に、同様にして採取した平行部直径が6mmの丸棒引張り試験片を用いて、JIS Z 3118の鋼溶接部の水素測定方法で採用されているガスクロマトグラフ法に準拠して水素量を測定した。   In order to ascertain the relationship between the hydrogen concentration and the residual stress at which the lateral cracking is next generated, the present inventors generate hydrogen embrittlement cracking in a weld metal having a tensile strength of 850 MPa or more as follows. The relationship between tensile stress and hydrogen concentration was investigated. Therefore, the relationship between the stress at which hydrogen embrittlement cracking occurs in the weld metal of a high strength welded steel pipe having a tensile strength of 850 MPa or more and the amount of hydrogen was investigated as follows. A sample having a size of 200 mm × 200 mm in the circumferential direction and the axial direction was taken from the welded steel pipe so as to include the inner and outer surface weld metals, and immediately cooled with dry ice and stored. A round bar tensile test piece having a longitudinal direction parallel to the welding direction and a parallel part diameter of 6 mm was collected from the weld metal of this sample. These round bar tensile specimens were cadmium plated so that hydrogen would not escape. Next, a constant load was applied to the tensile test piece for 240 hours, and the presence or absence of breakage, that is, the occurrence of hydrogen embrittlement cracking was examined. Furthermore, the amount of hydrogen was measured in accordance with the gas chromatographic method employed in the hydrogen measurement method for steel welds of JIS Z 3118, using a round bar tensile test piece having a parallel part diameter of 6 mm that was collected in the same manner. .

結果を図3に示すが、水素量は、上記の測定方法によって測定した、即ち45℃で72時間保持して捕集した拡散性水素の量を、試験片100g当りに含まれる水素の体積[cc]で表したものである。図1の縦軸は、試験片に負荷した定荷重を試験片の平行部の断面積で除して、応力σ[MPa]で表したものである。   The results are shown in FIG. 3. The amount of hydrogen was measured by the above measurement method, that is, the amount of diffusible hydrogen collected by holding at 45 ° C. for 72 hours, and the volume of hydrogen contained per 100 g of test piece [ cc]. The vertical axis in FIG. 1 represents the constant load applied to the test piece divided by the cross-sectional area of the parallel part of the test piece and expressed as stress σ [MPa].

実機で測定される溶接金属における最大0.42cc/100gの水素量に対応する残留応力は、図3より680MPaであるから、残留応力が引張強度850MPaの80%未満であれば水素脆化割れは発生しないことになる。   Since the residual stress corresponding to the maximum amount of hydrogen of 0.42 cc / 100 g in the weld metal measured with an actual machine is 680 MPa from FIG. 3, if the residual stress is less than 80% of the tensile strength of 850 MPa, It will not occur.

つまり、図3より、溶接金属に発生する残留応力が、溶接金属の引張強度の80%未満である場合、水素割れは起こらないという指標を得た。   That is, from FIG. 3, an index was obtained that hydrogen cracking does not occur when the residual stress generated in the weld metal is less than 80% of the tensile strength of the weld metal.

また、水素濃度が溶接金属100g当り、0.2ccを超える場合には、水素量H[cc]と引張り応力σ[MPa]が、
(H−0.1)×(σ−550)≦45
を満足すれば、水素脆化割れは発生しないと推定できる。したがって、先行するシーム溶接によって形成された溶接金属に含有される水素量をH[cc]、該溶接金属に負荷される引張り残留応力を[MPa]が上記式の関係を満足すれば、高強度溶接鋼管の水素脆化割れを防止することができる。
When the hydrogen concentration exceeds 0.2 cc per 100 g of weld metal, the hydrogen amount H [cc] and the tensile stress σ [MPa]
(H−0.1) × (σ−550) ≦ 45
If it is satisfied, it can be estimated that hydrogen embrittlement cracking does not occur. Therefore, if the amount of hydrogen contained in the weld metal formed by the preceding seam welding is H [cc] and the tensile residual stress applied to the weld metal is [MPa] satisfies the relationship of the above formula, the strength is high. Hydrogen embrittlement cracking of the welded steel pipe can be prevented.

本発明者らは、溶接金属の形状を溶接ままの状態から変化させることにより、溶接金属の残留応力を再配分させて低減させる方法を検討した。溶接金属の形状を変化させることによって、溶接金属が本来有している性能、特に靭性を致命的に劣化させてはならない。本発明者らは、まず、溶接金属の内外面を圧縮して塑性変形させ、残留応力を低下させる方法を検討した。   The present inventors examined a method of reducing the residual stress of the weld metal by redistributing it by changing the shape of the weld metal from the as-welded state. By changing the shape of the weld metal, the performance inherent in the weld metal, particularly toughness, must not be critically degraded. The present inventors first studied a method for reducing the residual stress by compressing and plastically deforming the inner and outer surfaces of the weld metal.

内外面からサブマージアーク溶接され、溶接金属強度が950MPa、外径914mm、肉厚16mm、溶接金属高さ19.5mmのUOE鋼管から、シーム溶接部を中心に周方向300mm、軸方向100mmの試験片を切り出した。この試験片のシーム溶接部を内外面から挟み込む形で肉厚方向にプレスし(図4)、そのときの形状変化から、次式(1)によって加工割合を算出した。   Specimens with a welded metal strength of 950 MPa, an outer diameter of 914 mm, a wall thickness of 16 mm, and a weld metal height of 19.5 mm from a UOE steel pipe with inner and outer surfaces of 300 mm in the circumferential direction and 100 mm in the axial direction centered on the seam weld. Was cut out. The seam welded portion of this test piece was pressed in the thickness direction so as to be sandwiched from the inner and outer surfaces (FIG. 4), and the processing ratio was calculated by the following equation (1) from the shape change at that time.

加工後、電解研磨を行い、X線回折法により鋼管内面における溶接金属の表面の軸方向残留応力を測定した。結果を図5に示した。   After the processing, electrolytic polishing was performed, and the axial residual stress on the surface of the weld metal on the inner surface of the steel pipe was measured by an X-ray diffraction method. The results are shown in FIG.

また、実管の溶接金属を種々の加工割合で圧縮加工した場合を想定し、FEAによって求めた残留応力の推定値も同図にプロットした。FEA解析は、造管方法、物性値、状態値を図2を得た際の解析と同条件とし、更に、溶接金属の肉厚方向への圧縮変形を追加して行った。溶接金属をわずかに圧縮変形させることで、表層部の残留応力は大きく減少している。また、FEA値と実測値は一致していることから、FEAにより変形後の溶接金属内部の応力状態も予測できることを確認した。   In addition, assuming the case where the actual weld metal was compressed at various processing ratios, the estimated values of residual stress obtained by FEA were also plotted in the figure. The FEA analysis was performed by setting the pipe making method, physical property values, and state values to the same conditions as those in the analysis when FIG. 2 was obtained, and further adding compressive deformation in the thickness direction of the weld metal. By slightly compressing and deforming the weld metal, the residual stress in the surface layer portion is greatly reduced. Moreover, since the FEA value and the measured value were in agreement, it was confirmed that the stress state inside the weld metal after deformation could be predicted by FEA.

次に、加工度による溶接金属の軸方向の残留応力の変化をFEAによって解析し、図6に示した。これは、図2に示されている溶接金属の残留応力が最大になる位置を想定して求めた結果である。なお、FEA解析は、図5を得た際の解析と同様にして行った。溶接ままでは最大800MPaに達した残留応力は内表面同様に圧縮変形により激減する。わずか0.2%の圧縮塑性歪みを与えただけでも最大応力は割れを生じない750MPa以下に抑制できることがわかった。   Next, the change in the residual stress in the axial direction of the weld metal depending on the degree of processing was analyzed by FEA and shown in FIG. This is a result obtained by assuming a position where the residual stress of the weld metal shown in FIG. 2 is maximized. The FEA analysis was performed in the same manner as the analysis when obtaining FIG. The residual stress, which reaches a maximum of 800 MPa as welded, is drastically reduced by compressive deformation like the inner surface. It was found that the maximum stress can be suppressed to 750 MPa or less which does not cause cracking even by applying a compression plastic strain of only 0.2%.

次に、溶接金属に塑性変形を与えた際に劣化する機械特性のうち、靱性に着目した。内外面からサブマージアーク溶接が行われる場合、その会合面の靱性が最小になり、冷間成形により靱性が劣化することは以前から知られている。そこで、内面溶接金属と外面溶接金属の会合面における加工割合と塑性歪み量の関係を、図6を得た際と同様のFEA解析によって評価し、図7に示した。これより加工割合が3%を超えると会合面に歪みが集中し始めることが明らかになった。   Next, attention was focused on toughness among the mechanical properties that deteriorate when plastic deformation is applied to the weld metal. It has long been known that when submerged arc welding is performed from the inside and outside surfaces, the toughness of the meeting surface is minimized and the toughness is deteriorated by cold forming. Therefore, the relationship between the processing ratio and the plastic strain amount at the meeting surface of the inner surface weld metal and the outer surface weld metal was evaluated by the same FEA analysis as that in FIG. 6 and shown in FIG. From this, it became clear that when the processing ratio exceeds 3%, distortion starts to concentrate on the meeting surface.

次に、加工割合が0.1〜5%の範囲内の圧縮加工を加えた後、内外面の溶接会合部よりJIS Z 2202に準拠してVノッチシャルピー試験片を3本ずつ採取し、JIS Z 2242に準拠して室温で衝撃試験をおこなった結果を図8に示す。各加工割合ではシャルピー吸収エネルギーのばらつきは大きいものの、平均値で見ると、加工割合が3%を超えると次第に吸収エネルギーの劣化が顕著になることがわかる。したがって、本発明では圧縮加工の加工割合を3%以下にすることで靱性劣化を最小限に抑えることができる。   Next, after applying compression processing within a range of 0.1 to 5%, three V-notch Charpy specimens were collected from the welded joints on the inner and outer surfaces in accordance with JIS Z2202, FIG. 8 shows the result of an impact test conducted at room temperature in accordance with Z2242. Although the dispersion of Charpy absorbed energy is large at each processing ratio, it can be seen from an average value that when the processing ratio exceeds 3%, the deterioration of the absorbed energy gradually becomes remarkable. Therefore, in the present invention, deterioration in toughness can be minimized by setting the processing rate of compression processing to 3% or less.

以上から溶接金属に内外面から0.2%以上、3%以下の圧縮加工を加えることにより溶接金属の性能を著しく劣化させることなく、残留応力を低減させることが可能になり、水素脆化割れを防止できることがわかった。なお、上記の検討では、切り出しサンプルにプレス加工による塑性変形を加えたが、実管では溶接金属を内外面からプレス加工しても良く、圧延ロールにより圧縮加工しても良い。圧縮加工の加工割合の上限は、実施例に基づいて1.8%以下とする。
From the above, it is possible to reduce the residual stress without significantly degrading the performance of the weld metal by applying compression processing of 0.2% or more and 3% or less from the inner and outer surfaces to the weld metal, and hydrogen embrittlement cracking It was found that can be prevented. In the above examination, the cut sample is subjected to plastic deformation by press working. However, in an actual pipe, the weld metal may be pressed from the inner and outer surfaces, or may be compressed by a rolling roll. The upper limit of the processing ratio of compression processing is set to 1.8% or less based on the examples.

溶接金属の圧縮加工は形状変化と同時に塑性歪みを与え、降伏強度と同等の残留応力を最小の形状変化で解放することが可能であり、最も効率的な方法である。   The compression processing of the weld metal is the most efficient method because it gives plastic strain simultaneously with the shape change and can release the residual stress equivalent to the yield strength with the minimum shape change.

次に、本発明者は、塑性変形を与えることなく、溶接金属の形状変化のみによって残留応力を再配分させ、水素割れを防止する方法として、外面溶接金属の表層部を切除する方法を検討した。   Next, the present inventor examined a method of cutting off the surface layer portion of the outer surface weld metal as a method of redistributing residual stress only by a change in shape of the weld metal and preventing hydrogen cracking without giving plastic deformation. .

本発明者らはまず、図9に示すように、鋼管の外表面から、溶接金属の高さをH2だけ切削加工により除去し、そのときに変化する残留応力を測定した。図10に式2で示す切除割合による、鋼管内表面でX線回折で実測された内面溶接金属の残留応力変化とFEAにより求められた残留応力変化を示す。FEA解析は、造管方法、物性値、状態値を図2を得た際の解析と同条件とし、更に、外面溶接金属の表層を切削する加工を想定して行った。 First, as shown in FIG. 9, the present inventors removed the height of the weld metal by H 2 from the outer surface of the steel pipe by cutting, and measured the residual stress changing at that time. FIG. 10 shows the residual stress change of the inner surface weld metal measured by X-ray diffraction on the inner surface of the steel pipe and the residual stress change obtained by FEA according to the resection ratio shown by Formula 2. The FEA analysis was performed assuming that the pipe making method, physical property values, and state values were the same as those in the analysis when FIG. 2 was obtained, and that the surface layer of the outer surface weld metal was cut.

切除割合が増加するに従い、鋼管の内面における溶接金属の表面の残留応力は減少し、その傾向はFEAによる計算値ともよく一致する。切削したのは外面溶接金属側であるが、残留応力が再配分される結果、内面の残留応力も減少することがわかった。   As the cutting rate increases, the residual stress on the surface of the weld metal on the inner surface of the steel pipe decreases, and the tendency agrees well with the value calculated by FEA. Although it was cut on the outer surface weld metal side, it was found that the residual stress on the inner surface also decreased as a result of redistribution of the residual stress.

図11にはFEAで求めた溶接金属内部での最大軸方向残留応力の推移を示す。これは、図2に示されている溶接金属の残留応力が最大になる位置を想定し、図10を得た際と同様にFEA解析して求めた結果である。切除割合が溶接金属の肉厚方向の高さの2%を超えると最大応力の減少率が顕著になり、950MPaの強度に対して水素割れを発生させない限界残留応力、750MPaを下回ることが推定できた。   FIG. 11 shows the transition of the maximum axial direction residual stress inside the weld metal obtained by FEA. This is a result obtained by FEA analysis in the same manner as when FIG. 10 is obtained, assuming the position where the residual stress of the weld metal shown in FIG. 2 is maximized. If the cutting rate exceeds 2% of the weld metal height in the thickness direction, the reduction rate of the maximum stress becomes remarkable, and it can be estimated that it falls below 750 MPa, the residual residual stress that does not cause hydrogen cracking with respect to the strength of 950 MPa. It was.

溶接金属の切除量の上限については、少なくとも母材までの切り込みは溶接継手の強度を損なうため、外面余盛りを残す必要のあること、10%以上の切削割合では最大残留応力の低減効果が鈍化することから、実際の製造範囲においては切除割合は2%〜10%が好ましい。   As for the upper limit of the amount of cut of weld metal, at least the notch to the base metal impairs the strength of the welded joint. Therefore, it is necessary to leave the outer surface surplus. The cutting effect of 10% or more slows down the maximum residual stress reduction effect. Therefore, in the actual manufacturing range, the excision ratio is preferably 2% to 10%.

切除方法は、上記の検討において用いたフライス加工による切削以外に、グラインダーによる研削加工、更に、ガウジングまたは放電加工でも同様の効果が得られる。   As for the cutting method, the same effect can be obtained by grinding by a grinder, gouging or electric discharge machining, in addition to the cutting by milling used in the above examination.

切除する方法では外面の溶接金属を2%以上に切除したときの残留応力の再配分について示したが、同等以上の効果は内面の溶接金属を切除することによっても得られる。しかしながら、一般的には内面の溶接金属の余盛りは外面の溶接金属に比べて低く、また、鋼管内面の溶接金属の切除は外面溶接金属の切除に比較して容易ではないことから、工業的には外面溶接金属を切除することが好ましい。
In the cutting method , the redistribution of the residual stress when the weld metal on the outer surface is cut to 2% or more has been shown. However, the equivalent effect can be obtained by cutting the weld metal on the inner surface. However, in general, the weld metal on the inner surface is lower than the weld metal on the outer surface, and the cutting of the weld metal on the inner surface of the steel pipe is not easy compared to the cutting of the outer surface weld metal. For this, it is preferable to cut off the outer surface weld metal.

残留応力の実測は溶接金属の引張強度が950MPaのものについてのみ行ったが、溶接金属の強度が異なる場合にも同じ加工割合、または切除割合で限界応力以下の残留応力抑制ができるかどうかについてFEAにより検討した結果を図12に示す。水素割れ発生に対する限界応力は引張強度の約8割であり、0.2%の圧縮加工、2%の外面溶接金属の切除を行った場合、いずれの強度範囲においても限界応力を下回り、溶接金属の引張強度が850MPa以上であれば本発明の方法を適用できることが裏付けられた。   Residual stress was measured only for a weld metal with a tensile strength of 950 MPa, but whether the residual stress below the critical stress can be suppressed with the same processing rate or cutting rate even if the strength of the weld metal is different. The result of the examination is shown in FIG. The critical stress for hydrogen cracking is about 80% of the tensile strength. When 0.2% compression processing and 2% outer surface weld metal are cut, the weld metal is below the critical stress in any strength range. It was confirmed that the method of the present invention can be applied if the tensile strength of 850 MPa is 850 MPa or more.

強度が850MPa以上の超高強度ラインパイプは一般的にはUOE成形方式により造管されるが、ベンディングロールにより成形しても良い。   An ultra-high-strength line pipe having a strength of 850 MPa or more is generally formed by a UOE forming method, but may be formed by a bending roll.

以下に本発明例と比較例により本発明の実施による効果を説明する。   The effects of the implementation of the present invention will be described below with reference to the present invention examples and comparative examples.

鋼組成が、質量%で、C:0.02〜0.10%、Si:0.01〜0.6%、Mn:1.5〜2.5%、P:0.015%以下、S:0.003%以下、Ni:0.1〜2.0%、Mo:0.15〜0.60%、Nb:0.001〜0.10%、Ti:0.005〜0.030%、Al:0.06%以下を含有し、残部Feおよび不可避的不純物からなる鋼を熱間制御圧延して、UOE鋼管の素材となる厚鋼板を得た。一部の厚鋼板は、B:0.0001〜0.005%、N:0.0001〜0.006%、V:0.001〜0.10%、Cu:0.01〜1.0%、Cr:0.01〜1.0%、Zr:0.0001〜0.005%、Ta:0.0001〜0.005%、Ca:0.0001〜0.01%、REM:0.0001〜0.01%、Mg:0.0001〜0.006%の1種または2種類以上を含有している。これらの厚鋼板の引張強度は850〜1000MPaである。   Steel composition is mass%, C: 0.02-0.10%, Si: 0.01-0.6%, Mn: 1.5-2.5%, P: 0.015% or less, S : 0.003% or less, Ni: 0.1 to 2.0%, Mo: 0.15 to 0.60%, Nb: 0.001 to 0.10%, Ti: 0.005 to 0.030% , Al: steel containing 0.06% or less and the balance Fe and unavoidable impurities were hot-rolled to obtain a thick steel plate as a material for a UOE steel pipe. Some thick steel plates are: B: 0.0001 to 0.005%, N: 0.0001 to 0.006%, V: 0.001 to 0.10%, Cu: 0.01 to 1.0% Cr: 0.01-1.0%, Zr: 0.0001-0.005%, Ta: 0.0001-0.005%, Ca: 0.0001-0.01%, REM: 0.0001 -0.01%, Mg: 0.0001-0.006% of 1 type or 2 types or more are contained. The tensile strength of these thick steel plates is 850 to 1000 MPa.

これらの厚鋼板をCプレス、Uプレス、Oプレスの順で成形後、内面、外面の順番でサブマージアーク溶接した。内面溶接前の開先には霧吹きによる水滴を付着させたまま溶接を行った。これは実操業で起こりうる結露やフラックス等から不可避的に導入される水素を加速試験したものである。サブマージアーク溶接は、質量%で、C:0.01〜0.12%、Si:0.3%以下、Mn:1.2〜2.4%、Ni:4.0〜8.5%、Cr+Mo+V:3.0〜5.0%、Ti:0.005〜0.15%、Al:0.02%以下を含有し、残部Feおよび不可避的不純物からなる溶接ワイヤーを用いて、入熱を1.5〜6.3kJ/mmの範囲として行った。   After forming these thick steel plates in the order of C press, U press, and O press, submerged arc welding was performed in the order of inner surface and outer surface. Welding was performed with water droplets from the spray spray attached to the groove before the inner surface welding. This is an accelerated test of hydrogen that is inevitably introduced due to condensation and flux that can occur in actual operation. Submerged arc welding is mass%, C: 0.01-0.12%, Si: 0.3% or less, Mn: 1.2-2.4%, Ni: 4.0-8.5%, Cr + Mo + V: 3.0 to 5.0%, Ti: 0.005 to 0.15%, Al: 0.02% or less, and using a welding wire composed of the remainder Fe and inevitable impurities, heat input The measurement was performed in the range of 1.5 to 6.3 kJ / mm.

溶接金属は、成分が、質量%で、C:0.04〜0.14%、Si:0.05〜0.4%、Mn:1.2〜2.2%、P:0.01%以下、S:0.010%以下、Ni:1.3〜3.2%、Cr+Mo+V:1.0〜2.5%、Ti:0.003〜0.050%、Al:0.02%以下、B:0.005%以下、O:0.01〜0.03%を含有し、残部Feおよび不可避的不純物からなり、引張強度が850〜1000MPaであることを確認した。   The composition of the weld metal is mass%, C: 0.04 to 0.14%, Si: 0.05 to 0.4%, Mn: 1.2 to 2.2%, P: 0.01% Hereinafter, S: 0.010% or less, Ni: 1.3 to 3.2%, Cr + Mo + V: 1.0 to 2.5%, Ti: 0.003 to 0.050%, Al: 0.02% or less , B: 0.005% or less, O: 0.01-0.03%, consisting of the balance Fe and inevitable impurities, and confirming that the tensile strength is 850-1000 MPa.

外面溶接終了後、20分以内にシーム溶接部を含んだ200mm×200mmのサンプルを採取し、ドライアイス中に保存した。更に、常温に曝される時間を1時間以内にして、シーム溶接部を内外面から挟み込、プレスによる圧縮加工を行った。プレス前後の溶接金属の高さの変化から式1により加工割合を算出した。
A sample of 200 mm × 200 mm including the seam weld was collected within 20 minutes after the outer surface welding was completed, and stored in dry ice. Furthermore, the time of exposure to ambient temperature and within one hour, see write sandwiching the seam weld from inner and outer surfaces were subjected to compression processing by the press. From the change in the height of the weld metal before and after pressing, the processing ratio was calculated according to Equation 1.

溶接ままの試験片、およびプレス加工を行った試験片はともに常温で72時間以上放置し、JIS G 0584に準拠して、超音波探傷によりシーム溶接部に発生した割れの有無を検査した。ここで割れ発生個数とは、シーム溶接部の溶接方向の長さ1m当りに検出された割れの個数である。   Both the as-welded test piece and the pressed test piece were left at room temperature for 72 hours or more, and inspected for the presence or absence of cracks generated in the seam welded portion by ultrasonic flaw detection in accordance with JIS G 058. Here, the number of cracks generated is the number of cracks detected per 1 m in the welding direction of the seam weld.

一方、靭性を評価するために、内外面溶接会合面よりJIS Z 2202に準拠してVノッチシャルピー試験片、3本を採取し、JIS Z 2242に準拠して、−30℃で衝撃試験を行い、吸収エネルギーの3本の平均値を求めた。   On the other hand, in order to evaluate toughness, three V-notch Charpy specimens were collected from the inner and outer surface welding meeting surfaces in accordance with JIS Z 2202, and subjected to an impact test at −30 ° C. in accordance with JIS Z 2242. The average value of the three absorbed energy was determined.

また、FEAにより、各鋼管の製造方法、物性値、状態値に応じて、残留応力を解析によって求めた。この残留応力は、溶接金属の内部に生じる軸方向最大応力である。   Moreover, the residual stress was calculated | required by analysis according to the manufacturing method, physical-property value, and state value of each steel pipe by FEA. This residual stress is the maximum axial stress generated inside the weld metal.

表1に結果を示す。加工割合0.2%以上では残留応力が引張強度の80%未満であり、割れは皆無であった。一方、溶接まま、あるいは加工割合が0.2%に達しないものは割れが検出された。また、加工割合3%以下での吸収エネルギーは85Jを下回ることはなかった。   Table 1 shows the results. At a processing rate of 0.2% or more, the residual stress was less than 80% of the tensile strength, and there were no cracks. On the other hand, cracks were detected as welded or when the processing ratio did not reach 0.2%. Further, the absorbed energy at a processing rate of 3% or less did not fall below 85J.

次に、上記と同様の方法で成形、内外面からサブマージアーク溶接した後、フラックスを除去し、少なくとも20分以内に鋼管の外面から溶接金属をフライス加工により切除した。切除割合は切除前後の溶接金属の高さの変化から、式2により算出した。   Next, after forming and submerged arc welding from the inner and outer surfaces by the same method as described above, the flux was removed, and the weld metal was cut off from the outer surface of the steel pipe by milling within at least 20 minutes. The excision ratio was calculated by Equation 2 from the change in the height of the weld metal before and after excision.

溶接ままの鋼管、および切削加工を行った鋼管はともに常温で72時間以上経過した後、JIS G 0584に準拠して、超音波探傷によりシーム溶接部に発生した割れの有無を検査した。   Both the as-welded steel pipe and the steel pipe subjected to the cutting process were inspected for cracks generated in the seam welded part by ultrasonic flaw detection after lapse of 72 hours or more at room temperature in accordance with JIS G 058.

また、FEAにより各鋼管の製造方法、物性値、状態値に応じて、残留応力を解析によって求めた。この残留応力は、溶接金属の内部に生じる軸方向の最大応力である。   Moreover, the residual stress was calculated | required by analysis according to the manufacturing method, physical-property value, and state value of each steel pipe by FEA. This residual stress is the maximum axial stress generated inside the weld metal.

表2に結果を示す。加工割合2%以上では残留応力が引張強度の80%未満であり、割れは皆無であった。一方、溶接まま、あるいは加工割合が2%に達しないものは割れが検出された。   Table 2 shows the results. At a processing rate of 2% or more, the residual stress was less than 80% of the tensile strength, and there were no cracks. On the other hand, cracks were detected as-welded or when the processing ratio did not reach 2%.

残留応力のFEA解析を行った位置を示す図。The figure which shows the position which performed the FEA analysis of the residual stress. サイズφ1016x19mm、引張強度950MPaの拡管前のUOE鋼管のシーム溶接中心での軸方向残留応力分布を内面からの位置との関係で示した図。The figure which showed the axial direction residual stress distribution in the seam welding center of the UOE steel pipe before pipe expansion of size (phi) 1016x19mm and tensile strength 950MPa with respect to the position from an inner surface. 溶接金属における水素濃度と応力との関係を示す図。The figure which shows the relationship between the hydrogen concentration and stress in a weld metal. 加工割合を示す図。The figure which shows a process ratio. 加工割合と内面溶接金属表面の軸方向残留応力の関係を示す図。The figure which shows the relationship between a process ratio and the axial direction residual stress of an inner surface weld metal surface. 加工割合と溶接部最大軸方向応力の関係を示す図。The figure which shows the relationship between a process ratio and the welding part maximum axial direction stress. 加工割合と内外面溶接会合面での塑性歪み量の関係を示す図。The figure which shows the relationship between a processing ratio and the amount of plastic strain in an inner-outer surface welding meeting surface. 加工割合と会合面での吸収エネルギーの関係を示す図。The figure which shows the relationship between a processing ratio and the absorbed energy in an meeting surface. 切除割合を示す図。The figure which shows the resection ratio. 切除割合と内面溶接金属表面の軸方向残留応力の関係を示す図。The figure which shows the relationship between an excision ratio and the axial direction residual stress of an inner surface weld metal surface. 切除割合と溶接部最大軸方向応力の関係を示す図。The figure which shows the relationship between an excision ratio and a welding part maximum axial direction stress. 溶接金属の強度と限界応力、0.2%加工時、2%切除時の最大応力の関係を示す図。The figure which shows the relationship between the intensity | strength of a weld metal, limit stress, the maximum stress at the time of 0.2% processing, and 2% excision.

符号の説明Explanation of symbols

1 管体
2 外面金属
3 内面金属
4 加工工具
DESCRIPTION OF SYMBOLS 1 Tube 2 Outer surface metal 3 Inner surface metal 4 Processing tool

Claims (1)

引張強度が850MPa以上の鋼板を筒状に成形し、突合せ部を内外面からサブマージアーク溶接する溶接鋼管の製造方法において、溶接方向の全長にわたり、常温での圧縮加工により、溶接金属の肉厚方向の高さを0.2〜1.8%減少させることを特徴とする溶接鋼管の製造方法。 In a method for manufacturing a welded steel pipe, in which a steel sheet having a tensile strength of 850 MPa or more is formed into a cylindrical shape and the butt portion is submerged arc welded from the inner and outer surfaces, the weld metal thickness direction is obtained by compressing at normal temperature over the entire length in the welding direction. A method for producing a welded steel pipe, characterized in that the height of the steel is reduced by 0.2 to 1.8 %.
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