JP4427416B2 - Large heat input submerged arc welding method with excellent weld metal toughness. - Google Patents

Large heat input submerged arc welding method with excellent weld metal toughness. Download PDF

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JP4427416B2
JP4427416B2 JP2004233783A JP2004233783A JP4427416B2 JP 4427416 B2 JP4427416 B2 JP 4427416B2 JP 2004233783 A JP2004233783 A JP 2004233783A JP 2004233783 A JP2004233783 A JP 2004233783A JP 4427416 B2 JP4427416 B2 JP 4427416B2
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俊永 長谷川
茂 大北
繁男 大山
博志 中澤
隆一 元松
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Nippon Steel Corp
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Description

本発明は、特に、建築、造船、橋梁、海洋構造物などの高い安全性が要求される溶接構造物を建造する際に用いられる大入熱サブマージアーク溶接方法に関し、特に、良好な靭性を有する溶接金属が得られる高張力鋼板の大入熱サブマージアーク溶接方法に関する。   The present invention particularly relates to a large heat input submerged arc welding method used when building a welded structure requiring high safety such as a building, shipbuilding, bridge, and marine structure, and particularly has good toughness. The present invention relates to a high heat input submerged arc welding method for a high-tensile steel sheet from which a weld metal is obtained.

建築分野、造船分野等において、大型溶接構造物を建造する際には溶接施工能率を高めるために溶接時の大入熱化が要求され、アーク溶接の中でも溶接入熱が高いサブマージアーク溶接が多く用いられている。一方、建築、造船等では、同時に溶接構造物に対して高い安全性が要求され、特に溶接部に高い靭性が要求される。特に、建築構造物では、地震時の脆性破壊を防止する観点から溶接部、特に溶接金属の高靭性化に対する社会的要請が極めて大きくなってきている。   When building large welded structures in the construction field, shipbuilding field, etc., it is required to increase the heat input during welding in order to increase the welding work efficiency. Among arc welding, there are many submerged arc weldings with high welding heat input. It is used. On the other hand, in construction, shipbuilding, etc., high safety is required for the welded structure at the same time, and particularly high toughness is required for the welded portion. In particular, in a building structure, a social demand for increasing the toughness of a welded portion, particularly a weld metal, has been extremely increased from the viewpoint of preventing brittle fracture during an earthquake.

近年の建築構造物の大型化に伴い、板厚が５０ｍｍ以上の厚鋼板を溶接してボックス柱を製造する際に、溶接能率を向上させるために、多電極を用いた片面１パス大入熱サブマージアーク溶接の適用が増加している。このような厚鋼板の大入熱サブマージアーク溶接では、溶接入熱が４００ｋＪ／ｃｍ以上になり、溶接部に形成される溶接金属の冷却速度が遅くなるため、冷却過程でオーステナイト（γ）粒界から靭性に有害な粗大な初析フェライト（α）が生成されやすく、溶接金属の靭性が低下する問題が生じる。   Along with the recent increase in size of building structures, when manufacturing box columns by welding thick steel plates with a thickness of 50 mm or more, single-sided single-pass heat input using multiple electrodes is used to improve welding efficiency. The application of submerged arc welding is increasing. In such a large heat input submerged arc welding of a thick steel plate, the welding heat input is 400 kJ / cm or more, and the cooling rate of the weld metal formed in the welded portion is slowed down. Therefore, the austenite (γ) grain boundary in the cooling process Therefore, coarse pro-eutectoid ferrite (α) which is harmful to toughness is easily generated, and the toughness of the weld metal is lowered.

また、鋼板板厚が厚く、溶接入熱がさらに高くなる場合には、溶接金属の厚み範囲において、溶融金属が最初に凝固する溶接ルート部側（以降、溶接裏面側とも言う）の溶接金属がより厳しい熱履歴となるため靭性劣化が著しく、その結果、厚み方向の中心部や表面側の溶接金属と同等の良好な靭性を確保することが困難となる。
比較的入熱が大きい溶接時の溶接金属靭性を確保する方法として、一般に溶接材料を用いて溶接金属中に合金元素を多く添加し焼入性を高めることで組織微細化を図ることが知られている。 In addition, when the steel plate thickness is thick and the welding heat input is further increased, the weld metal on the weld root side where the molten metal first solidifies (hereinafter also referred to as the weld back side) in the thickness range of the weld metal is As the heat history becomes more severe, the toughness deteriorates remarkably, and as a result, it becomes difficult to ensure good toughness equivalent to the center part in the thickness direction and the weld metal on the surface side.
As a method to ensure weld metal toughness during welding with relatively high heat input, it is generally known to refine the structure by increasing the hardenability by adding a lot of alloying elements to the weld metal using welding materials. ing.

しかし、板厚が５０ｍｍ以上の厚鋼板を溶接入熱が４００ｋＪ／ｃｍ以上で１パス片面サブマージ溶接する場合には、溶接材料を用いて溶接金属中に合金元素量を増加させると、溶接表面側の溶接金属の焼入性が過大となって逆に靭性が劣化する問題が生じるようになる。   However, when one-pass single-sided submerged welding is performed on a thick steel plate having a thickness of 50 mm or more at a welding heat input of 400 kJ / cm or more, if the amount of alloy elements is increased in the weld metal using a welding material, However, the hardenability of the weld metal becomes excessive, and the problem arises that the toughness deteriorates.

上記厚鋼板の大入熱サブマージ溶接時の溶接金属厚み範囲における靭性の不均一性は、２電極以上を用いて溶接する多電極サブマージアーク溶接、および、板厚が５０ｍｍ以上の厚鋼の場合にその問題が顕在化しやすい。   The non-uniformity of toughness in the weld metal thickness range at the time of large heat input submerged welding of the above-mentioned thick steel plate is in the case of multi-electrode submerged arc welding in which welding is performed using two or more electrodes and thick steel having a plate thickness of 50 mm or more. The problem is easy to manifest.

従来、ボックス柱角継手の大入熱サブマージアーク溶接時に溶接金属靭性を向上させる方法として、ボンドフラックスおよび溶接ワイヤを用いて、溶接金属中のＴｉ、Ｂ、Ｍｏの複合添加により焼き入れ性を向上し、溶接金属靭性を改善する方法が開示されている（例えば、特許文献１参照）。   Conventionally, as a method to improve weld metal toughness at the time of submerged arc welding with large heat input of box column corner joint, hardenability is improved by combined addition of Ti, B and Mo in weld metal using bond flux and welding wire And the method of improving weld metal toughness is disclosed (for example, refer patent document 1).

しかし、この方法では溶接金属の靭性は０℃でのシャルピー衝撃値で４７Ｊ以上までの改善はできるが、１００Ｊ以上、さらには、１５０Ｊ以上の靭性向上は難しい。   However, with this method, the toughness of the weld metal can be improved to 47 J or more with the Charpy impact value at 0 ° C., but it is difficult to improve the toughness of 100 J or more, and further 150 J or more.

また、従来から、溶接時に溶接金属にＴｉを添加することによりＴｉ酸化物を生成させ、これを核として微細なアシキュラーフェライトを生成させることで溶接金属を高靭化させる方法が知られている。しかしながら、ボックス柱角継手の大入熱サブマージアーク溶接のように大入熱溶接の中でも入熱の極めて大きい溶接方法においては、一般のアーク溶接に比べて、溶融金属プールが長時間維持されるので、溶接金属中にＴｉを相当量添加しても、Ｔｉ酸化物はスラグ浴中に移行して溶融金属と分離してしまう部分が多い。このため、溶接金属中のＴｉ酸化物をアシキュラーフェライトの核生成サイトとして十分に機能させ、溶接金属の靭性を十分に改善することは困難である。また、大入熱サブマージアーク溶接では冷却速度が極めて小さいため、溶接金属中に粒界フェライトが多く生成し、かつ粗大化しやすいため、アシキュラーフェライト生成により十分な靭性改善は得られ難いという問題もある。   Further, conventionally, a method is known in which Ti oxide is generated by adding Ti to the weld metal during welding, and fine acicular ferrite is generated using this as a nucleus to make the weld metal tough. . However, in a welding method with extremely high heat input, such as high heat input submerged arc welding of box column corner joints, the molten metal pool is maintained for a long time compared to general arc welding. Even if a considerable amount of Ti is added to the weld metal, the Ti oxide often moves into the slag bath and separates from the molten metal. For this reason, it is difficult to sufficiently improve the toughness of the weld metal by sufficiently functioning the Ti oxide in the weld metal as a nucleation site of acicular ferrite. In addition, since the cooling rate is very low in high heat input submerged arc welding, a lot of grain boundary ferrite is generated in the weld metal and it is easy to coarsen, so it is difficult to achieve sufficient toughness improvement by generating acicular ferrite. is there.

また、最近では、δフェライト相を安定化させて凝固オーステナイト粒径の微細化を図り、その結果として変態組織を微細化させる技術も提案されている（例えば、特許文献２参照）。しかし、板厚が５０ｍｍ以上の厚手鋼板の１パス大入熱サブマージアーク溶接では、溶接金属全体を均一に高靭化することは難しい。   Recently, a technique has also been proposed in which the δ ferrite phase is stabilized to refine the solidified austenite grain size, and as a result, the transformation structure is refined (see, for example, Patent Document 2). However, in one-pass large heat input submerged arc welding of a thick steel plate having a thickness of 50 mm or more, it is difficult to make the entire weld metal uniform and tough.

以上のように、溶接金属の靭性向上を図るための従来技術は、厚手鋼板の１パス大入熱サブマージアーク溶接時に溶接金属厚み範囲における靭性のばらつきを充分に改善することは困難である。   As described above, it is difficult for the conventional technique for improving the toughness of the weld metal to sufficiently improve the toughness variation in the weld metal thickness range at the time of one-pass large heat input submerged arc welding of the thick steel plate.

したがって、厚手鋼板の１パス大入熱サブマージアーク溶接において溶接金属中心部だけでなく、溶接金属の表面側から裏面側までの厚み範囲全体における靭性を均一に向上させる技術が望まれている。   Therefore, in 1-pass large heat input submerged arc welding of thick steel plates, there is a demand for a technique that uniformly improves toughness not only in the weld metal center but also in the entire thickness range from the front side to the back side of the weld metal.

特開平１１−１７００８５号公報Japanese Patent Laid-Open No. 11-170085 特開２００４−１０２８号公報JP 2004-1028 A

本発明は、上記の従来技術の問題点に鑑みて、５００〜６００ＭＰａ級の引張強度の鋼板を溶接入熱が４００ｋＪ／ｃｍ以上での片面１パス大入熱サブマージアーク溶接時に溶接金属の表面側から裏面側までの全厚み範囲で靭性が均一であり、かつ０℃における２ｍｍＶノッチシャルピー吸収エネルギーが１００Ｊ以上の高い靭性が得られる溶接方法を提供することを目的とする。   In view of the above-mentioned problems of the prior art, the present invention provides a surface of the weld metal during one-sided one-pass large heat input submerged arc welding of a steel sheet having a tensile strength of 500 to 600 MPa class with a heat input of 400 kJ / cm or more. An object of the present invention is to provide a welding method in which the toughness is uniform in the entire thickness range from the rear surface side to the back surface, and a high toughness with a 2 mmV notch Charpy absorbed energy at 0 ° C. of 100 J or more is obtained.

上記課題を解決するために、本発明者らはサブマージアーク溶接において、溶接金属の厚み方向での変態挙動、組織と靱性との関係から、変態前のオーステナイト組織や厚み方向での冷却速度の違いに大きな影響を受けずに微細アシキュラーフェライトの生成、粒界フェライトの抑制ができる溶接金属の成分組成を検討した。その結果、ＴｉとＢの複合添加による微細アシキュラーフェライト生成の促進と共に、焼入性元素であるＮｉ及びＭｏの適量添加、及びＢ添加量の制限による粗大粒界フェライトの抑制と上部ベイナイトの抑制または微細化の作用効果を有効活用することにより、溶接金属の全厚み範囲における靭性向上が可能となることを見いだした。本発明は、これらの知見に基づきなされたものであり、その要旨とするところは以下の通りである。   In order to solve the above-mentioned problems, the present inventors, in submerged arc welding, in the transformation behavior in the thickness direction of the weld metal, the relationship between the structure and toughness, the difference in the austenite structure before transformation and the cooling rate in the thickness direction. We investigated the composition of weld metal components that can produce fine acicular ferrite and suppress intergranular ferrite without being greatly affected by the above. As a result, the formation of fine acicular ferrite by the combined addition of Ti and B, the addition of appropriate amounts of hardenable elements Ni and Mo, and the suppression of coarse grain boundary ferrite and the suppression of upper bainite by limiting the amount of B addition Alternatively, it has been found that the toughness can be improved in the entire thickness range of the weld metal by effectively utilizing the effect of miniaturization. The present invention has been made based on these findings, and the gist thereof is as follows.

（１）板厚が５０ｍｍ以上の鋼板を４００ｋＪ／ｃｍ以上の溶接入熱で片面１パス溶接するサブマージアーク溶接方法において、質量％で、Ｃ：０．０２〜０．２％、Ｓｉ：０．０１〜１％、Ｍｎ：０．１〜２．５％、Ａｌ：０．００２〜０．１％、Ｎ：０．００１〜０．０１５％を含有し、Ｐ：０．０２％以下、Ｓ：０．０１％以下、Ｏ：０．０１％以下に制限し、残部がＦｅ及び不可避不純物からなる鋼板を、質量％で、ＳｉＯ2：１０〜２５％、ＭｇＯ：５〜２０％、ＣａＯ：５〜１５％、ＣａＦ2：１〜１０％、Ａｌ2Ｏ3：５〜２５％、ＴｉＯ2：２〜２０％、Ｆｅ：１０〜２５％、Ｂ2Ｏ3：０．６１％〜２．５％を含有するフラックスと、質量％で、Ｃ：０．０２〜０．２％、Ｓｉ：０．０１〜１％、Ｍｎ：０．５〜２．５％、Ｍｏ：０．１〜３％、Ｎｉ：１〜６％、Ａｌ：０．００２〜０．１％、Ｔｉ：０．００５〜０．３％、Ｎ：０．００１〜０．０１５％含有し、Ｐ：０．０２％以下、Ｓ：０．０１％以下、Ｏ：０．０１％以下に制限し、残部がＦｅ及び不可避不純物からなる溶接ワイヤを用いてサブマージアーク溶接することを特徴とする溶接金属の靱性に優れた大入熱サブマージアーク溶接方法。 (1) In a submerged arc welding method in which a steel sheet having a thickness of 50 mm or more is welded on one side with a welding heat input of 400 kJ / cm or more, the mass is C: 0.02 to 0.2%, Si: 0.00. 01 to 1%, Mn: 0.1 to 2.5%, Al: 0.002 to 0.1%, N: 0.001 to 0.015%, P: 0.02% or less, S 0.01% or less, O: limited to 0.01% or less, the steel sheet balance of Fe and inevitable impurities, in mass%, SiO 2: 10~25%, MgO: 5~20%, CaO: 5~15%, CaF 2: 1~10% , Al 2 O 3: 5~25%, TiO 2: 2~20%, Fe: 10~25%, B 2 O 3: 0.61% ~2. 5% flux and mass%, C: 0.02-0.2%, Si: 0.01-1%, Mn: 0.5-2.5% Mo: 0.1 to 3%, Ni: 1 to 6%, Al: 0.002 to 0.1%, Ti: 0.005 to 0.3%, N: 0.001 to 0.015% , P: 0.02% or less, S: 0.01% or less, O: 0.01% or less, submerged arc welding using a welding wire with the balance being Fe and inevitable impurities Large heat input submerged arc welding method with excellent weld metal toughness.

（２）前記サブマージアーク溶接によって、質量％で、Ｃ：０．０３〜０．２％、Ｓｉ：０．１〜１％、Ｍｎ：０．７〜２％、Ａｌ：０．００１〜０．０７％、Ｍｏ：０．１〜１％、Ｎｉ：０．７５〜３％、Ｔｉ：０．００５〜０．１％、Ｂ：０．００１〜０．０１％、Ｎ：０．００１〜０．０１％、Ｏ：０．０１〜０．０５％を含有し、Ｐ：０．０２％以下、Ｓ：０．０１％以下に制限した溶接金属を形成することを特徴とする上記（１）記載の溶接金属の靱性に優れた大入熱サブマージアーク溶接方法。   (2) By the submerged arc welding, C: 0.03-0.2%, Si: 0.1-1%, Mn: 0.7-2%, Al: 0.001-0. 07%, Mo: 0.1 to 1%, Ni: 0.75 to 3%, Ti: 0.005 to 0.1%, B: 0.001 to 0.01%, N: 0.001 to 0 (1) characterized by forming a weld metal containing 0.01%, O: 0.01 to 0.05%, P: 0.02% or less, and S: 0.01% or less Large heat input submerged arc welding method with excellent toughness of the described weld metal.

（３）前記鋼板が、質量％で、さらに、Ｔｉ：０．００２〜０．０５％、Ｂ：０．０００３〜０．０１５％、Ｍｏ：０．０１〜１．５％、Ｃｒ：０．０１〜１．５％、Ｗ：０．０１〜１．５％、Ｃｕ：０．０１〜１．５％、Ｎｉ：０．０１〜６％、Ｎｂ：０．００２〜０．１％、Ｖ：０．００２〜０．５％、および、Ｔａ：０．００２〜０．５％の１種または２種以上を含有することを特徴とする上記（１）または（２）に記載の溶接金属の靱性に優れた大入熱サブマージアーク溶接方法。   (3) The said steel plate is the mass%, and also Ti: 0.002-0.05%, B: 0.0003-0.015%, Mo: 0.01-1.5%, Cr: 0.00. 01 to 1.5%, W: 0.01 to 1.5%, Cu: 0.01 to 1.5%, Ni: 0.01 to 6%, Nb: 0.002 to 0.1%, V The weld metal according to (1) or (2) above, which contains one or more of 0.002 to 0.5% and Ta of 0.002 to 0.5% Large heat input submerged arc welding method with excellent toughness.

（４）上記フラックスが、質量％で、さらに、Ｍｏ：１〜５％、および、Ｎｉ：１〜５％の１種または２種を含有することを特徴とする上記（１）〜（３）の何れかに記載の溶接金属の靱性に優れた大入熱サブマージアーク溶接方法。   (4) The above-described flux (1) to (3), wherein the flux contains 1% or 2% of Mo: 1 to 5% and Ni: 1 to 5%. A high heat input submerged arc welding method excellent in toughness of the weld metal according to any one of the above.

（５）上記溶接ワイヤが、質量％で、さらに、Ｃｕ：０．０１〜１．５％、Ｃｒ：０．０１〜１．５％、Ｗ：０．０１〜２％、Ｎｂ：０．００２〜０．０５％、Ｖ：０．００５〜０．５％、Ｔａ：０．００２〜０．２％、および、Ｂ：０．００１〜０．０５％の１種または２種以上を含有することを特徴とする上記（１）〜（４）の何れかに記載の溶接金属の靱性に優れた大入熱サブマージアーク溶接方法。   (5) The welding wire is in% by mass, further Cu: 0.01 to 1.5%, Cr: 0.01 to 1.5%, W: 0.01 to 2%, Nb: 0.002. -0.05%, V: 0.005-0.5%, Ta: 0.002-0.2%, and B: contain 0.001-0.05% of 1 type or 2 types or more The high heat input submerged arc welding method excellent in toughness of the weld metal according to any one of the above (1) to (4).

（６）前記溶接金属がサブマージアーク溶接によって、質量％で、Ｃ：０．０３〜０．２％、Ｓｉ：０．１〜１％、Ｍｎ：０．７〜２％、Ａｌ：０．００１〜０．０７％、Ｍｏ：０．１〜１％、Ｎｉ：０．７５〜３％、Ｔｉ：０．００５〜０．１％、Ｂ：０．００１〜０．０１％、Ｎ：０．００１〜０．０１％、Ｏ：０．０１〜０．０５％を含有し、Ｐ：０．０２％以下、Ｓ：０．０１％以下に制限し、さらに、Ｃｕ：０．０１〜１．５％、Ｃｒ：０．０１〜０．５％、Ｗ：０．０１〜０．５％、Ｎｂ：０．００２〜０．０５％、Ｖ：０．００５〜０．５％、および、Ｔａ：０．００５〜０．５％の１種または２種以上を含有した溶接金属を形成することを特徴とする上記（３）〜（５）の何れかに記載の溶接金属の靱性に優れた大入熱サブマージアーク溶接方法。   (6) The weld metal is obtained by submerged arc welding in mass%, C: 0.03 to 0.2%, Si: 0.1 to 1%, Mn: 0.7 to 2%, Al: 0.001. -0.07%, Mo: 0.1-1%, Ni: 0.75-3%, Ti: 0.005-0.1%, B: 0.001-0.01%, N: 0.00. 001 to 0.01%, O: 0.01 to 0.05%, P: 0.02% or less, S: 0.01% or less, and Cu: 0.01 to 1.%. 5%, Cr: 0.01-0.5%, W: 0.01-0.5%, Nb: 0.002-0.05%, V: 0.005-0.5%, and Ta : It is excellent in the toughness of the weld metal according to any one of the above (3) to (5), wherein a weld metal containing one or more of 0.005 to 0.5% is formed. Large heat input sub Jiaku welding method.

（７）前記鋼板が、質量％で、さらに、Ｃａ、ＭｇおよびＲＥＭの１種または２種以上を０．０００２〜０．０１％含有することを特徴とする上記（１）〜（６）の何れかに記載の溶接金属の靱性に優れた大入熱サブマージアーク溶接方法。   (7) In the above (1) to (6), the steel sheet further contains 0.0002 to 0.01% of one or more of Ca, Mg and REM in mass%. A high heat input submerged arc welding method excellent in toughness of the weld metal according to any one of the above.

（８）上記溶接ワイヤが、質量％で、さらに、Ｃａ、ＭｇおよびＲＥＭの１種または２種以上を０．０００２〜０．０１％含有することを特徴とする上記（１）〜（７）の何れかに記載の溶接金属の靱性に優れた大入熱サブマージアーク溶接方法。   (8) The above-mentioned (1) to (7), wherein the welding wire contains 0.0002 to 0.01% of one or more of Ca, Mg and REM in mass%. A high heat input submerged arc welding method excellent in toughness of the weld metal according to any one of the above.

（９）前記溶接金属がサブマージアーク溶接によって、質量％で、Ｃ：０．０３〜０．２％、Ｓｉ：０．１〜１％、Ｍｎ：０．７〜２％、Ａｌ：０．００１〜０．０７％、Ｍｏ：０．１〜１％、Ｎｉ：０．７５〜３％、Ｔｉ：０．００５〜０．１％、Ｂ：０．００１〜０．０１％、Ｎ：０．００１〜０．０１％、Ｏ：０．０１〜０．０５％を含有し、Ｐ：０．０２％以下、Ｓ：０．０１％以下に制限し、Ｃｕ：０．０１〜１．５％、Ｃｒ：０．０１〜０．５％、Ｗ：０．０１〜０．５％、Ｎｂ：０．００２〜０．０５％、Ｖ：０．００５〜０．５％、および、Ｔａ：０．００５〜０．５％の１種または２種以上を含有し、さらに、Ｃａ、ＭｇおよびＲＥＭの１種または２種以上を０．０００１〜０．００５％含有した溶接金属を形成することを特徴とする上記（７）または（８）に記載の溶接金属の靱性に優れた大入熱サブマージアーク溶接方法。   (9) The weld metal is obtained by submerged arc welding in mass%, C: 0.03 to 0.2%, Si: 0.1 to 1%, Mn: 0.7 to 2%, Al: 0.001. -0.07%, Mo: 0.1-1%, Ni: 0.75-3%, Ti: 0.005-0.1%, B: 0.001-0.01%, N: 0.00. 001 to 0.01%, O: 0.01 to 0.05%, P: 0.02% or less, S: 0.01% or less, Cu: 0.01 to 1.5% Cr: 0.01-0.5%, W: 0.01-0.5%, Nb: 0.002-0.05%, V: 0.005-0.5%, and Ta: 0 Forming a weld metal containing 0.005 to 0.5% of one or more, and further containing 0.0001 to 0.005% of one or more of Ca, Mg and REM Excellent high heat input submerged arc welding method in toughness of the weld metal according to (7) or (8), characterized.

本発明によれば、板厚が５０ｍｍ以上の引張強度が５００〜６００ＭＰａ級の高張力鋼板を溶接入熱が４００ｋＪ／ｃｍ以上の片面１パス溶接する大入熱サブマージアーク溶接において、溶接金属の表面から裏面までの全厚み範囲で靭性を均一にでき、かつ０℃での２ｍｍＶノッチシャルピー吸収エネルギーが１００Ｊ以上、さらには、１５０Ｊ以上の高い靭性が得られる。したがって、本発明の適用により、建築、造船、橋梁、海洋構造物などの溶接構造物の溶接施工効率を向上し、かつその安全性を高めることができるため、産業上の非常に利用価値が高いものである。   According to the present invention, in a large heat input submerged arc welding in which a high-tensile steel plate having a thickness of 50 mm or more and a tensile strength of 500 to 600 MPa class is subjected to one-pass one-pass welding with a heat input of 400 kJ / cm or more, the surface of the weld metal Toughness can be made uniform over the entire thickness range from the back surface to the back surface, and a high toughness of 2 mmV notch Charpy absorbed energy at 0 ° C. of 100 J or more, and further 150 J or more can be obtained. Therefore, by applying the present invention, it is possible to improve the welding construction efficiency of welded structures such as buildings, shipbuilding, bridges, marine structures and the like, and increase the safety thereof, so that the industrial utility value is very high. Is.

本発明の詳細について以下に説明する。   Details of the present invention will be described below.

先ず、本発明の技術的課題とこれを解決するための技術思想について説明する。   First, a technical problem of the present invention and a technical idea for solving the technical problem will be described.

本発明は、板厚が５０ｍｍ以上の高張力鋼板を４００ｋＪ／ｃｍ以上の溶接入熱で片面１パス溶接するサブマージアーク溶接方法を前提とする。前述したように、板厚が厚い鋼板の大入熱サブマージアーク溶接では、溶融金属の厚み方向の各位置によって熱履歴や冷却速度が異なり、特に溶接裏面側の溶接金属は、溶接表面側および中心部の溶接金属に比べて熱履歴や冷却速度がより厳しいため靭性が著しく劣化することが問題となる。   The present invention is premised on a submerged arc welding method in which a high-strength steel plate having a thickness of 50 mm or more is welded on one side by one pass with welding heat input of 400 kJ / cm or more. As described above, in high heat input submerged arc welding of a steel plate with a large thickness, the heat history and cooling rate differ depending on the position in the thickness direction of the molten metal. Since the heat history and cooling rate are more severe than those of the weld metal, the toughness is significantly deteriorated.

そこで、本発明者らは、板厚が５０ｍｍ以上の高張力鋼板を溶接入熱が４００ｋＪ／ｃｍ以上での片面１パス大入熱サブマージアーク溶接を前提とし、溶融金属の表面側から裏面側まで全厚み範囲における靭性が０℃における２ｍｍＶノッチシャルピー吸収エネルギーで１００Ｊ以上、好ましくは１５０Ｊ以上の高い靱性を確保することを目標とし、溶接試験等からこれを達成するための溶接金属の成分組成と溶接金属組織の検討を行った。その結果、以下の知見が得られた。   Therefore, the present inventors presuppose one-sided single-pass large heat input submerged arc welding of a high-strength steel plate having a thickness of 50 mm or more and a welding heat input of 400 kJ / cm or more, from the surface side to the back side of the molten metal. The aim is to ensure a high toughness of 100 J or more, preferably 150 J or more with a 2 mmV notch Charpy absorbed energy at 0 ° C. in the entire thickness range. The metal structure was examined. As a result, the following knowledge was obtained.

ａ） Ｔｉ及びＢ複合添加（複合析出物による微細アシキュラーフェライト生成促進）
一般に溶接金属中のＴｉ酸化物は微細アシキュラーフェライトの生成核として作用することが知られている。しかし、本発明が前提とする厚鋼板の１パス大入熱サブマージアーク溶接では、溶融金属プールが長時間維持されるため、溶接材料により溶接金属中に添加されたＴｉの大部分はスラグ浴中に移行し、排出され、その機能を十分に発揮することはできない。また，Ｔｉ酸化物によるアシキュラーフェライト生成能が同じでも溶接入熱が大きくなって冷却速度が小さくなるとアシキュラーフェライト１個１個のサイズが粗大化するため，４００ｋＪ／ｃｍ以上の溶接入熱で良好な靭性を得るためにはＴｉ酸化物のアシキュラーフェライト生成能だけでは不十分である。 a) Addition of Ti and B composites (acceleration of fine acicular ferrite formation by composite precipitates)
In general, it is known that Ti oxide in a weld metal acts as a production nucleus of fine acicular ferrite. However, in the one-pass large heat input submerged arc welding of thick steel plate, which is a premise of the present invention, the molten metal pool is maintained for a long time, so most of the Ti added to the weld metal by the welding material is in the slag bath. It will not be able to fully perform its functions. Moreover, even if the acicular ferrite generation ability by the Ti oxide is the same, if the welding heat input increases and the cooling rate decreases, the size of each acicular ferrite becomes coarse, so that the welding heat input is 400 kJ / cm or more. In order to obtain good toughness, the ability of Ti oxide to form acicular ferrite is not sufficient.

これに対して、本発明者らは、溶接材料によりＴｉと共にＢを溶接金属中に複合添加すると、凝固後の溶接金属の冷却過程でＴｉ酸化物界面にＢＮおよびＦｅ２３（Ｃ、Ｂ）６などのＢ化合物が析出し、Ｔｉ酸化物の微細アシキュラーフェライト生成能を向上させ、Ｔｉの単独添加に比べて微細アシキュラーフェライトの生成が促進されることを確認した。   On the other hand, when the present inventors compositely add B together with Ti into the weld metal using a welding material, BN and Fe23 (C, B) 6 etc. are formed at the Ti oxide interface during the cooling process of the weld metal after solidification. It was confirmed that the B compound was precipitated and the fine acicular ferrite formation ability of the Ti oxide was improved, and the production of fine acicular ferrite was promoted as compared with the addition of Ti alone.

ｂ） Ｎｉ、Ｍｏ添加（焼入れ性向上による粒界フェライト抑制かつ上部ベイナイト抑制・微細化）
一般に溶接金属中に合金元素を添加し焼入性を高めると、溶接金属の靭性に有害な粗大粒界フェライトの生成は抑制され、溶接金属組織が微細化され、靭性が向上することが知られている。しかし、本発明が前提とする厚板鋼板の１パス大入熱サブマージアーク溶接では、溶接金属の厚み方向での冷却速度差が大きく、冷却速度が遅い裏面側溶接金属で粒界フェライトが顕著に生成する。したがって、合金元素の添加量を裏面側溶接金属に合わせて多く添加すると、表面側溶接金属の焼入性が過大となり硬質かつ粗大な上部ベイナイト組織が生成する結果、逆に靱性が劣化するため、溶接金属の厚み方向で均一な靭性を得ることは困難であった。 b) Addition of Ni and Mo (suppression of grain boundary ferrite and suppression of upper bainite and refinement by improving hardenability)
In general, adding alloying elements to the weld metal to increase the hardenability suppresses the formation of coarse grain boundary ferrite that is harmful to the toughness of the weld metal, refines the weld metal structure, and improves toughness. ing. However, in the 1-pass large heat input submerged arc welding of thick steel plates, the premise of the present invention, the difference in cooling rate in the thickness direction of the weld metal is large, and the grain boundary ferrite is prominent in the back side weld metal with a slow cooling rate Generate. Therefore, if the addition amount of the alloy element is increased in accordance with the back surface side weld metal, the hardenability of the surface side weld metal becomes excessive and a hard and coarse upper bainite structure is generated. It was difficult to obtain uniform toughness in the thickness direction of the weld metal.

これに対して、本発明者らは焼入れ性の高い合金元素の中でも、ＮｉとＭｏは溶接金属を多く添加しても上部ベイナイトの生成を抑制または上部ベイナイトの有効結晶粒径を微細化する作用効果を有し、ＮｉとＭｏの添加により溶接金属厚み方向における靭性の冷却速度依存性を小さくし、均一化できることを確認した。   On the other hand, among the highly hardenable alloy elements, the present inventors suppress the formation of upper bainite or refine the effective crystal grain size of the upper bainite even if a large amount of weld metal is added to Ni and Mo. It was confirmed that by adding Ni and Mo, the cooling rate dependence of toughness in the weld metal thickness direction can be reduced and uniformized.

ｃ） Ｂの固溶作用（粒界偏析による粒界フェライト抑制）
一般に溶接金属中でＢはオーステナイト相中に固溶状態で存在すると、オーステナイト粒界に偏析して粒界焼入性を高め、靱性に有害な粗大粒界フェライト生成を抑制する作用があることが知られている。しかし、本発明が前提とする厚板鋼板の１パス大入熱サブマージアーク溶接のように，、溶接金属の厚み方向での冷却速度差が大きくなってくると，単にＢを含有させただけでは粒界フェライトの生成抑制効果が十分でない場合が生じる。これに対して，本発明者らは，冷却速度の広い範囲で粒界フェライトを抑制し，かつ靭性に好ましくない上部ベイナイトの生成も抑制するにはＢが最も好適ではあるが，その含有量範囲を厳密に規定し，さらにＮｉ，Ｍｏと合わせて用いる必要があることを確認した。 c) B solid solution action (suppression of grain boundary ferrite by grain boundary segregation)
In general, when B exists in the austenite phase in the weld metal in a solid solution state, it segregates at the austenite grain boundaries to increase grain boundary hardenability and to suppress the formation of coarse grain boundary ferrite harmful to toughness. Are known. However, when the difference in cooling rate in the thickness direction of the weld metal becomes large as in the one-pass large heat input submerged arc welding of the thick steel plate that the present invention presupposes, simply adding B is sufficient. There are cases where the effect of suppressing the formation of grain boundary ferrite is not sufficient. On the other hand, the present inventors are most suitable for suppressing the intergranular ferrite in a wide range of the cooling rate and also suppressing the formation of upper bainite which is not preferable for toughness, but the content range thereof. Was strictly defined, and it was confirmed that it should be used together with Ni and Mo.

本発明は、以上の知見を基になされたものであり、上記ａ）からｃ）の相乗効果により、図１に示すように、従来のＴｉ添加による溶接金属中の微細アシキュラーフェライト生成（図１のａ、参照）、合金元素添加による溶接金属の焼入性向上（図１のｂ１およびｂ２、参照）では困難であった、厚鋼板の片面１パス大入熱サブマージアーク溶接における溶融金属の全厚み範囲での靭性の均一化を達成することを技術思想とするものである。   The present invention has been made on the basis of the above knowledge, and, as shown in FIG. 1, due to the synergistic effect of a) to c), as shown in FIG. 1 a), which is difficult to improve the hardenability of the weld metal by adding alloying elements (see b1 and b2 in FIG. 1). The technical idea is to achieve uniform toughness over the entire thickness range.

以下に本発明における鋼板、フラックスおよび溶接ワイヤの限定理由について説明する。   The reasons for limiting the steel plate, flux and welding wire in the present invention will be described below.

なお、以下の説明において「％」は特に説明がない限りは、「質量％」を意味するものとする。   In the following description, “%” means “% by mass” unless otherwise specified.

先ず、本発明の目的を達成するために必要とする鋼板の基本成分の限定理由につい説明する。   First, the reason for limiting the basic components of the steel sheet necessary to achieve the object of the present invention will be described.

本発明において、鋼板成分は、溶接構造用鋼板としての機械的特性を維持するとともに、大入熱サブマージアーク溶接における鋼板の溶融により溶接金属中への鋼板成分の希釈による溶接金属中の成分組成および機械的特性、特に靭性を維持するために以下のように限定するものである。   In the present invention, the steel plate component maintains the mechanical properties as a welded structural steel plate, and the component composition in the weld metal due to dilution of the steel plate component into the weld metal by melting the steel plate in high heat input submerged arc welding, and In order to maintain mechanical properties, particularly toughness, the following limitations are imposed.

Ｃ：Ｃは、鋼板の強度を確保する上で０．０２％以上含有させる必要がある。一方、鋼板中に０．２％超含有させると、鋼板の靱性や溶接熱影響部靱性、さらには耐溶接割れ性の劣化が大きくなって構造用鋼としての安全性が損なわれることと、溶接による鋼板溶融、成分希釈によって溶接金属のＣ含有量が過大となって溶接金属の靱性も劣化させる懸念があるため、本発明においては鋼板のＣ含有量の上限を０．２％とする。   C: C needs to be contained by 0.02% or more in order to secure the strength of the steel sheet. On the other hand, if more than 0.2% is contained in the steel plate, the toughness of the steel plate and the weld heat-affected zone toughness, as well as the deterioration of the weld crack resistance, increase the safety as structural steel, and welding. In the present invention, the upper limit of the C content of the steel sheet is set to 0.2% because there is a concern that the C content of the weld metal becomes excessive due to the melting and dilution of the steel sheet due to the steel sheet, and the toughness of the weld metal is deteriorated.

Ｓｉ：Ｓｉは、脱酸元素として、また、鋼板の強度確保に有効な元素である。０．０１％未満の含有では脱酸が不十分となり、また強度確保に不利である。逆に１％を超える過剰の含有は粗大な酸化物を形成して鋼板の延性や靭性劣化を招く。また、溶接による鋼板溶融、成分希釈によって溶接金属中のＳｉ含有量も過大となって溶接金属の靱性を損ねる恐れがある。そこで、鋼板におけるＳｉ含有量の範囲は０．０１〜１％とした。   Si: Si is an element effective as a deoxidizing element and for securing the strength of the steel sheet. If the content is less than 0.01%, deoxidation becomes insufficient and it is disadvantageous for securing the strength. On the other hand, an excessive content exceeding 1% forms a coarse oxide and causes the ductility and toughness of the steel sheet to deteriorate. Moreover, there is a risk that the Si content in the weld metal becomes excessive due to steel plate melting and component dilution by welding, and the toughness of the weld metal is impaired. Then, the range of Si content in a steel plate was 0.01 to 1%.

Ｍｎ：Ｍｎは、鋼板の焼入性を高めて強度、靭性の確保に必要な元素であり、最低限０．１％以上含有させる必要がある。しかし、２．５％を超える過剰な含有は、過剰なＣ含有と同様、鋼板の靭性を著しく劣化させ、かつ、溶接熱影響部の靭性、割れ性なども劣化させる。さらに溶接による鋼板溶融、成分希釈によって溶接金属靱性にも悪影響を及ぼすようになるため、上限を２．５％とした。   Mn: Mn is an element necessary for enhancing the hardenability of the steel sheet and ensuring strength and toughness, and it is necessary to contain at least 0.1% or more. However, an excessive content exceeding 2.5%, as with an excessive C content, significantly deteriorates the toughness of the steel sheet, and also deteriorates the toughness and cracking properties of the weld heat affected zone. Furthermore, the upper limit was set to 2.5% because the weld metal toughness would be adversely affected by steel plate melting and component dilution by welding.

Ａｌ：Ａｌは鋼板の脱酸、溶接熱影響部の加熱オーステナイト粒径の微細化等に有効な元素であり、これらの効果を発揮するために０．００２％以上含有する。一方、０．１％を超えて過剰に鋼板にＡｌを含有させると、粗大な酸化物を形成して鋼板の靭性、延性を極端に劣化させる。また、溶接による鋼板溶融、成分希釈によって溶接金属中のＡｌ量が過大となって、靱性に有害な上部ベイナイトが形成されて溶接金属の靱性が劣化する恐れがあるため、本発明においては、鋼板のＡｌ含有量を０．００２％〜０．１％の範囲に限定する。   Al: Al is an element effective for deoxidation of the steel sheet, refinement of the heated austenite grain size in the weld heat affected zone, and the like. On the other hand, when Al is excessively contained in excess of 0.1%, a coarse oxide is formed, and the toughness and ductility of the steel plate are extremely deteriorated. In addition, in the present invention, there is a risk that the amount of Al in the weld metal becomes excessive due to steel plate melting and component dilution due to welding, and upper bainite that is harmful to toughness is formed and the toughness of the weld metal deteriorates. The Al content is limited to the range of 0.002% to 0.1%.

Ｎ：Ｎは鋼板中でＡｌやＴｉと結びついてオーステナイト粒微細化に有効に働いて鋼板の靱性向上に寄与し、その効果が十分に得るために０．００１％以上含有させる。一方、Ｎが鋼板中に過剰に含有すると固溶Ｎが増加して鋼板の靭性の劣化を招く。また、鋼板中のＮ含有量が０．０１５％を超えて過度に高くなると、溶接による鋼板溶融、成分希釈によって溶接金属のＮ量も過大となって、Ｂと窒化物を形成して組織微細化に有効な固溶Ｂ量を減少させ、粒内、粒界とも溶接金属組織を粗大化するため、好ましくない。このため、本発明では鋼板中のＮ含有量の上限を０．０１５％とする。   N: N is combined with Al and Ti in the steel sheet, effectively works to refine the austenite grains, contributes to improvement of the toughness of the steel sheet, and is contained in an amount of 0.001% or more in order to obtain the effect sufficiently. On the other hand, when N is excessively contained in the steel sheet, the solute N increases and the toughness of the steel sheet is deteriorated. In addition, if the N content in the steel sheet exceeds 0.015% and becomes excessively high, the N content of the weld metal becomes excessive due to steel sheet melting and component dilution by welding, forming B and nitrides and forming a fine structure. This is not preferable because the amount of solute B effective for the reduction is reduced and the weld metal structure is coarsened in the grains and at the grain boundaries. For this reason, in this invention, the upper limit of N content in a steel plate shall be 0.015%.

Ｐ：Ｐは不純物元素であり、鋼板の特性、溶接金属の特性に対してともに、極力低減することが好ましいが、靭性確保の点から許容できる量として上限を０．０２％とした。   P: P is an impurity element, and it is preferable to reduce both the characteristics of the steel plate and the weld metal as much as possible. However, the upper limit is set to 0.02% as an allowable amount from the viewpoint of securing toughness.

Ｓ：Ｓも不純物元素で、鋼板及び溶接金属の延性、靭性をともに劣化させるため、低減が必要である。延性、靭性の劣化が大きくなく、実用的に許容できる上限として、その含有量を０．０１％以下とする。   S: S is also an impurity element and needs to be reduced because both the ductility and toughness of the steel plate and weld metal are deteriorated. As the upper limit that is practically acceptable without significant deterioration in ductility and toughness, the content is 0.01% or less.

Ｏ：Ｏは、鋼板においては不可避的不純物元素であり、酸化物を形成し鋼板の延性、靱性に悪影響を与えるため好ましくない。また、溶接による鋼板溶融、成分希釈によって溶接金属のＯ量を過度に高めて、同様に溶接金属の延性、靱性を劣化させることも懸念されるため、Ｏ含有量を０．０１％以下に制限する。   O: O is an unavoidable impurity element in a steel sheet, and is not preferable because it forms an oxide and adversely affects the ductility and toughness of the steel sheet. In addition, there is a concern about excessively increasing the amount of O of the weld metal by melting the steel plate by welding and diluting the components, and similarly degrading the ductility and toughness of the weld metal, so the O content is limited to 0.01% or less. To do.

本発明において上記鋼板の基本成分の他に、さらに鋼板および溶接金属の機械的特性、特に強度、靭性を調整するために、選択成分として、さらに、Ｔｉ、Ｂ、Ｍｏ、Ｎｉ、Ｃｒ、Ｗ、Ｃｕ、Ｎｂ、Ｖ、Ｔａの１種または２種以上を以下の所定範囲で鋼板中に添加しても良い。   In the present invention, in addition to the basic components of the steel plate, in order to further adjust the mechanical properties of the steel plate and the weld metal, particularly strength and toughness, as optional components, Ti, B, Mo, Ni, Cr, W, You may add 1 type (s) or 2 or more types of Cu, Nb, V, Ta in the steel plate in the following predetermined ranges.

Ｔｉ：ＴｉはＴｉＮの形成によりオーステナイト粒を微細化して鋼板の靭性向上に有効な元素である。   Ti: Ti is an effective element for improving the toughness of a steel sheet by refining austenite grains by forming TiN.

また、溶接による鋼板溶融、成分希釈によって溶接金属中にＴｉを含有させ、Ｔｉ酸化物の形成により微細アシキュラーフェライトの生成核として作用し、溶接金属の組織微細化にも効果を発揮する。これらの効果を発揮させるためには鋼板中にＴｉを０．００２％以上含有させることが好ましい。一方、鋼板中のＴｉ含有量が０．０５％を超えると、粗大な酸化物や窒化物を形成して鋼板の靭性や延性を劣化さる。また、溶接材料の組成によっては溶接による鋼板溶融、成分希釈で溶接金属中のＴｉ量を過剰にして、溶接金属の強度を過度に高める恐れがあるため、Ｔｉ含有量の上限を０．０５％とするのが好ましい。   Further, Ti is contained in the weld metal by melting the steel plate by welding and dilution of the components, and it acts as a production nucleus of fine acicular ferrite by the formation of the Ti oxide, and is effective in refining the structure of the weld metal. In order to exert these effects, it is preferable to contain 0.002% or more of Ti in the steel sheet. On the other hand, when the Ti content in the steel sheet exceeds 0.05%, coarse oxides and nitrides are formed, and the toughness and ductility of the steel sheet are deteriorated. Also, depending on the composition of the welding material, there is a risk of excessively increasing the amount of Ti in the weld metal by melting the steel sheet by welding and diluting the component, and thus excessively increasing the strength of the weld metal, so the upper limit of the Ti content is 0.05%. Is preferable.

Ｂ：Ｂは極微量で焼入性を高める元素であり、鋼板の高強度化に有効な元素である。また、溶接による鋼板溶融、成分希釈によって溶接金属中にＢを含有させ、溶接金属で固溶Ｂの結晶粒界偏析による粒界フェライト抑制、およびＴｉ酸化物でのＢＮ等のＢ化合物析出による微細アシキュラーフェライト生成促進の作用効果を有する。これらの効果を発揮するためには、Ｂは鋼板中に０．０００３％以上含有するのが好ましい。一方、０．０１５％を超えて鋼板中にＢを含有させると、鋼板製造時に加熱段階で粗大な析出物を形成し、鋼板の焼入性向上効果が不十分となり、かつ、鋼片の割れや析出物に起因した靭性劣化を招くため、鋼板のＢ含有量の上限を０．０１５％とするのが好ましい。   B: B is an element that enhances hardenability with a very small amount, and is an element effective for increasing the strength of a steel sheet. In addition, steel is melted by welding, B is contained in the weld metal by dilution of components, grain boundary ferrite is suppressed by grain boundary segregation of solute B in the weld metal, and fineness is caused by precipitation of B compounds such as BN in Ti oxide. Has the effect of promoting the formation of acicular ferrite. In order to exhibit these effects, B is preferably contained in the steel sheet in an amount of 0.0003% or more. On the other hand, if B is contained in the steel plate exceeding 0.015%, coarse precipitates are formed in the heating stage during the steel plate production, the effect of improving the hardenability of the steel plate is insufficient, and cracking of the steel slab is caused. In addition, the upper limit of the B content of the steel sheet is preferably set to 0.015% in order to cause deterioration of toughness due to precipitates.

Ｍｏ：Ｍｏは、焼入性向上と析出強化とによって鋼板の強度向上に有効な元素である。また、溶接による鋼板溶融、成分希釈によって溶接金属中にＭｏを含有させ、溶接金属の焼入性を高めて粒界フェライト抑制し、また、アシキュラーフェライトやベイナイトの有効結晶粒径を微細化し、溶接金属組織の微細化の作用効果がある。これらの効果を生じさせるためには、鋼板のＭｏ含有量を０．０１％以上とするのが好ましい。一方、Ｍｏが１．５％を超えて過剰に鋼板に含有されると、強度が過度に高くなって鋼板の靭性を劣化させるため、鋼板中のＭｏ含有量の上限を１．５％とするのが好ましい。   Mo: Mo is an element effective for improving the strength of a steel sheet by improving hardenability and precipitation strengthening. In addition, steel is melted by welding, Mo is contained in the weld metal by dilution of components, the hardenability of the weld metal is increased to suppress grain boundary ferrite, and the effective crystal grain size of acicular ferrite and bainite is refined, There is an effect of refinement of the weld metal structure. In order to produce these effects, it is preferable that the Mo content of the steel sheet is 0.01% or more. On the other hand, if Mo exceeds 1.5% and is excessively contained in the steel sheet, the strength is excessively increased and the toughness of the steel sheet is deteriorated, so the upper limit of the Mo content in the steel sheet is 1.5%. Is preferred.

Ｎｉ：Ｎｉは、本質的に鋼板マトリクスの靭性を高める作用を有する元素であり、ミクロ組織に大きく依存せず強度と靭性を同時に向上できるため、鋼板、溶接金属いずれにおいても非常に有効な元素である。これらの効果を発揮するためには鋼板中にＮｉを０．０１％以上含有させるのが好ましい。一方、Ｎｉ含有量が６％を超えて含有させると、鋼板、溶接金属の強度、靭性の向上効果は飽和するため、経済性も考慮して、Ｎｉ含有量の上限を６％とするのが好ましい。   Ni: Ni is an element that essentially has the effect of increasing the toughness of the steel sheet matrix, and can be improved at the same time in strength and toughness without greatly depending on the microstructure, so it is a very effective element in both steel sheets and weld metals. is there. In order to exhibit these effects, it is preferable to contain 0.01% or more of Ni in the steel sheet. On the other hand, if the Ni content exceeds 6%, the effect of improving the strength and toughness of the steel sheet and weld metal is saturated, so the upper limit of the Ni content should be 6% in consideration of economy. preferable.

Ｃｒ：Ｃｒは、Ｍｏとほぼ同様の焼入性を有し、鋼板の強度向上に有効な元素である。また、溶接による鋼板溶融、成分希釈によって溶接金属中にＣｒを含有させ、溶接金属の焼入性を高めて粒界フェライト抑制し、溶接金属組織の微細化の効果がある。これらの効果を生じさせるためには、鋼板のＣｒ含有量を０．０１％以上とするのが好ましい。一方、Ｃｒが１．５％を超えて過剰に鋼板に含有されると、強度が過度に高くなって鋼板の靭性を劣化させるため、鋼板中のＣｒ含有量の上限を１．５％とするのが好ましい。   Cr: Cr has substantially the same hardenability as Mo and is an element effective for improving the strength of the steel sheet. In addition, Cr is contained in the weld metal by melting the steel plate and diluting the components by welding, thereby improving the hardenability of the weld metal and suppressing the grain boundary ferrite, and having the effect of refining the weld metal structure. In order to produce these effects, the Cr content of the steel sheet is preferably 0.01% or more. On the other hand, if Cr exceeds 1.5% and is excessively contained in the steel sheet, the strength becomes excessively high and the toughness of the steel sheet is deteriorated, so the upper limit of the Cr content in the steel sheet is 1.5%. Is preferred.

Ｗ：Ｗは、Ｍｏ、Ｃｒと同様の焼入性を有し、鋼板の強度向上に有効な元素である。また、溶接による鋼板溶融、成分希釈によって溶接金属中にＷを含有させ、溶接金属の焼入性を高めて粒界フェライト抑制し、溶接金属組織の微細化の効果がある。これらの効果を生じさせるためには、鋼板のＷ含有量を０．０１％以上とするのが好ましい。一方、Ｗが１．５％を超えて過剰に鋼板に含有されると、強度が過度に高くなって鋼板の靭性を劣化させるため、鋼板中のＷ含有量の上限を１．５％とするのが好ましい。   W: W is an element having the same hardenability as Mo and Cr and effective in improving the strength of the steel sheet. Further, W is contained in the weld metal by melting the steel plate and diluting the components by welding, thereby improving the hardenability of the weld metal and suppressing the grain boundary ferrite, and having the effect of refining the weld metal structure. In order to produce these effects, it is preferable that the W content of the steel sheet is 0.01% or more. On the other hand, if W exceeds 1.5% and is excessively contained in the steel sheet, the strength becomes excessively high and the toughness of the steel sheet is deteriorated, so the upper limit of the W content in the steel sheet is 1.5%. Is preferred.

Ｃｕ：Ｃｕは、主として焼入性向上効果と固溶強化により鋼板の強度向上に有効な元素であり、これらの効果を発揮するためには、鋼板にＣｕを０．０１％以上含有させるのが好ましい。一方、鋼板にＣｕを１．５％超含有させると、鋼板の熱間加工性が劣化し、また、溶接による鋼板溶融、成分希釈によって溶接金属のＣｕ含有量が増加し、耐高温割れ性を劣化させるため、鋼板中のＣｕ含有量の上限は１．５％とするのが好ましい。   Cu: Cu is an element effective for improving the strength of the steel sheet mainly by improving the hardenability and strengthening the solid solution. In order to exert these effects, the steel sheet should contain 0.01% or more of Cu. preferable. On the other hand, when the steel sheet contains Cu over 1.5%, the hot workability of the steel sheet deteriorates, and the Cu content of the weld metal increases due to the steel sheet melting and component dilution by welding, thereby increasing the hot crack resistance. In order to cause deterioration, the upper limit of the Cu content in the steel sheet is preferably 1.5%.

Ｎｂ：Ｎｂは、析出強化及び変態強化により微量で鋼板の高強度化に有効な元素であり、また、加熱オーステナイト粒径微細化によって鋼板の靭性向上にも有効である。これらの効果を発揮するためには、Ｎｂ含有量を０．００２％以上とするのが好ましい。一方、０．１％を超えてＮｂを過剰に含有させると、鋼板の靭性を劣化させ、かつ、溶接による鋼板溶融、成分希釈によって溶接金属中に過剰なＮｂが含有され、溶接金属の靭性を劣化させる懸念も生じるため、本発明においては、鋼板中のＮｂ含有量の上限を０．１％とするのが好ましい。   Nb: Nb is an element effective for increasing the strength of a steel sheet in a small amount by precipitation strengthening and transformation strengthening, and is also effective for improving the toughness of the steel sheet by refining the heated austenite grain size. In order to exhibit these effects, the Nb content is preferably 0.002% or more. On the other hand, when Nb is excessively contained exceeding 0.1%, the toughness of the steel sheet is deteriorated, and the weld metal is excessively contained by melting and dilution of the steel sheet by welding, so that the toughness of the weld metal is reduced. Since there is a concern of deterioration, in the present invention, the upper limit of the Nb content in the steel sheet is preferably set to 0.1%.

Ｖ：Ｖは主として析出強化により微量で鋼板の高強度化に有効な元素であり、効果を発揮するためには、Ｖを０．００２％以上含有させるのが好ましい。一方、０．５％を超えてＶを鋼板に過剰に含有させると、粗大な析出物を形成して鋼板の靭性を劣化させ、かつ、溶接による鋼板溶融、成分希釈によって溶接金属中にも過剰なＶが含有され、溶接金属の靭性を劣化させる懸念も生じるため、本発明においては、鋼板中のＶ含有量の上限は０．５％とするのが好ましい。   V: V is an element that is effective for increasing the strength of a steel sheet in a small amount mainly by precipitation strengthening. In order to exert the effect, it is preferable to contain V by 0.002% or more. On the other hand, when V is excessively contained in the steel sheet exceeding 0.5%, coarse precipitates are formed to deteriorate the toughness of the steel sheet, and the weld metal is excessively melted by melting and dilution of components by welding. In the present invention, the upper limit of the V content in the steel sheet is preferably set to 0.5%.

Ｔａ：Ｔａは、主として析出強化により微量で鋼板の高強度化に有効な元素であり、この効果を発揮するためには、Ｔａ含有量を０．００２％以上とするのが好ましい。一方、０．５％を超えてＴａを鋼板に過剰に含有させると、粗大な析出物を形成して鋼板の靭性を劣化させ、かつ、溶接による鋼板溶融、成分希釈によって溶接金属中にも過剰なＴａが含有されて溶接金属の靭性を劣化させる懸念も生じるため、本発明においては、鋼板中のＴａ含有量の上限は０．５％とするのが好ましい。   Ta: Ta is an element that is effective for increasing the strength of a steel sheet in a small amount mainly by precipitation strengthening. To exhibit this effect, the Ta content is preferably 0.002% or more. On the other hand, if Ta is excessively contained in the steel sheet exceeding 0.5%, coarse precipitates are formed to deteriorate the toughness of the steel sheet, and the weld metal is excessively melted by welding and dilution of components. In the present invention, the upper limit of the Ta content in the steel sheet is preferably set to 0.5%.

本発明において、上記鋼板の基本成分および選択成分の他に、鋼板の機械特性、特に延性を改善するために、さらにＣａ、Ｍｇ、ＲＥＭの１種または２種以上を鋼板中に含有させることができる。   In the present invention, in addition to the basic components and selected components of the steel plate, in order to improve mechanical properties of the steel plate, particularly ductility, one or more of Ca, Mg, and REM may be further contained in the steel plate. it can.

Ｃａ、Ｍｇ、ＲＥＭ：Ｃａ、Ｍｇ、ＲＥＭは、いずれも硫化物の熱間圧延中の展伸を抑制して延性特性向上に有効である。また、酸化物を微細化させて溶接熱影響部の靭性向上にも有効な元素である。これらの効果を発揮するためには、鋼板中のＣａ、Ｍｇ、ＲＥＭの１種または２種以上の含有量の下限を０．０００２％とするのが好ましい。一方、鋼板中のＣａ、Ｍｇ、ＲＥＭの１種または２種以上の含有量が０．０１％を超えると、硫化物や酸化物の粗大化を生じ、鋼板の延性、靭性、さらに疲労特性の劣化を招く。また、溶接による鋼板溶融、成分希釈によって溶接金属中にＣａ、Ｍｇ、ＲＥＭが過剰に含有されると、溶接性も阻害する可能性があるため、鋼板中の鋼板中のＣａ、Ｍｇ、ＲＥＭの１種または２種以上の含有量の上限を０．０１％とするのが好ましい。   Ca, Mg, REM: Ca, Mg, and REM are all effective in improving ductility characteristics by suppressing extension during hot rolling of sulfides. In addition, it is an element effective for improving the toughness of the weld heat affected zone by refining the oxide. In order to exhibit these effects, it is preferable that the lower limit of the content of one or more of Ca, Mg, and REM in the steel plate is 0.0002%. On the other hand, if the content of one or more of Ca, Mg, and REM in the steel sheet exceeds 0.01%, it causes the coarsening of sulfides and oxides, and the ductility, toughness, and fatigue characteristics of the steel sheet. It causes deterioration. In addition, when Ca, Mg, and REM are excessively contained in the weld metal due to steel plate melting and component dilution by welding, weldability may be hindered, so the Ca, Mg, and REM in the steel plate in the steel plate The upper limit of the content of one or more types is preferably 0.01%.

次に、本発明の目的を達成するために必要とするフラックスの基本成分の限定理由を説明する。   Next, the reasons for limiting the basic components of the flux required to achieve the object of the present invention will be described.

厚鋼板の大入熱サブマージアーク溶接では、溶接ワイヤとともにフラックスの成分組成による溶接金属の組織および機械的特性への寄与が大きい。このため、本発明が目的とする溶接金属の全厚み範囲における機械的特性、特に均一にかつ高い靱性を達成するためには、溶接ワイヤや鋼板だけでなく、フラックスの成分組成を以下のように適正化する必要がある。   In the high heat input submerged arc welding of thick steel plates, the contribution to the structure and mechanical properties of the weld metal by the component composition of the flux together with the welding wire is large. For this reason, in order to achieve mechanical properties in the entire thickness range of the weld metal targeted by the present invention, particularly uniform and high toughness, not only the welding wire and steel plate, but also the composition of the flux as follows: It needs to be optimized.

ＳｉＯ２：ＳｉＯ２は大入熱サブマージアーク溶接においてビード止端部のなじみ性を改善し、良好な溶接ビードを形成するために最も重要な成分であり、この効果を得るためにフラックス中にＳｉＯ２を１０％以上含有する。一方、フラックス中のＳｉＯ２含有量が２５％を超えると溶接金属の酸素やＳｉが増加し、靭性が劣化するため、その含有量の上限を２５％に規定する。   SiO2: SiO2 is the most important component for improving the conformability of the bead toe at high heat input submerged arc welding and forming a good weld bead. To obtain this effect, 10% of SiO2 is added to the flux. % Or more. On the other hand, if the SiO2 content in the flux exceeds 25%, oxygen and Si in the weld metal increase and the toughness deteriorates, so the upper limit of the content is specified to 25%.

ＭｇＯ：ＭｇＯはサブマージアーク溶接のような入熱の大きい溶接においてスラグの耐火性を向上させ、ビード形状を良好とするためにフラックス中に５％以上含有する。一方、ＭｇＯ含有量が２０％を超えるとビード表面に突起物が発生してビード形状が劣化するため、フラックス中のＭｇＯ含有量の上限は２０％とする。   MgO: MgO is contained in the flux in an amount of 5% or more in order to improve the slag fire resistance and improve the bead shape in welding with high heat input such as submerged arc welding. On the other hand, if the MgO content exceeds 20%, protrusions are generated on the bead surface and the bead shape deteriorates, so the upper limit of the MgO content in the flux is 20%.

ＣａＯ：ＣａＯはスラグの融点及び流動性を調整し、ビード止端部のなじみ性を改善するために重要な成分であり、この効果を得るためにフラックス中にＣａＯを５％以上含有する。一方、フラックス中のＣａＯ含有量が１５％を超えると、スラグ流動性が不良となり、ビード高さが不均一になるため、フラックス中のＣａＯ含有量の上限を１５％とした。   CaO: CaO is an important component for adjusting the melting point and fluidity of the slag and improving the conformability of the bead toe. To obtain this effect, the flux contains 5% or more of CaO. On the other hand, when the CaO content in the flux exceeds 15%, the slag fluidity becomes poor and the bead height becomes non-uniform, so the upper limit of the CaO content in the flux is set to 15%.

ＣａＦ２：ＣａＦ２は靭性改善に効果があり、この効果を得るためフラックス中にＣａＦ２を１％以上含有する。一方、ＣａＦ２は融点が低いため１０％を超えて過多に含有すると大入熱サブマージアーク溶接では、ビードの平滑性が損なわれ、ビード不良となるため、フラックス中のＣａＦ２含有量の上限を１０％とした。   CaF2: CaF2 is effective in improving toughness. To obtain this effect, the flux contains 1% or more of CaF2. On the other hand, since CaF2 has a low melting point and excessively exceeds 10%, the high heat input submerged arc welding impairs the smoothness of the beads and results in poor beads. Therefore, the upper limit of the CaF2 content in the flux is 10%. It was.

Ａｌ２Ｏ３：Ａｌ２Ｏ３はスラグ剥離性を良好にする効果があり、この効果を得るためフラックス中にＡｌ２Ｏ３を５％以上含有する。一方、Ａｌ２Ｏ３含有量が２５％を超えると凸ビードになり、ビード形状不良となるため、フラックス中のＡｌ２Ｏ３含有量の上限を２５％とした。   Al2O3: Al2O3 has an effect of improving the slag releasability, and in order to obtain this effect, the flux contains 5% or more of Al2O3. On the other hand, when the Al2O3 content exceeds 25%, a convex bead is formed and the bead shape is poor. Therefore, the upper limit of the Al2O3 content in the flux is set to 25%.

ＴｉＯ２：ＴｉＯ２はビード表面の平滑性向上および靭性向上に効果があり、これらの効果を得るためフラックス中にＴｉＯ２を２％以上含有する。一方、ＴｉＯ２含有量が２０％を超えるとビード止端部の立ち上がり角度が大きくなってビード形状を悪化させるため、また、溶接金属中にＴｉＯ２が過度に存在し、靱性に悪影響を及ぼすようになるため、フラックス中のＴｉＯ２含有量の上限を２０％とした。   TiO2: TiO2 is effective in improving the smoothness and toughness of the bead surface. In order to obtain these effects, the flux contains 2% or more of TiO2. On the other hand, if the TiO2 content exceeds 20%, the rising angle of the bead toe portion becomes large and the bead shape is deteriorated. In addition, TiO2 is excessively present in the weld metal and adversely affects toughness. Therefore, the upper limit of the TiO2 content in the flux is set to 20%.

Ｆｅ：Ｆｅは溶着効率の向上及び溶接入熱の低減に効果があり、これらの効果を得るためフラックス中のＦｅを１０％以上含有する。一方、Ｆｅ含有量が２５％を超えるとビード表面に突起物が発生するため、フラックス中のＦｅ含有量の上限を２５％とした。なお、本発明において、Ｆｅは純Ｆｅの他、例えば、Ｍｎ、ＳｉとのＦｅ合金であっても良く、フラックス中のＦｅの合計含有量が上記範囲内であれば効果を発揮する。   Fe: Fe is effective in improving the welding efficiency and reducing the welding heat input. In order to obtain these effects, it contains 10% or more of Fe in the flux. On the other hand, if the Fe content exceeds 25%, protrusions are generated on the bead surface, so the upper limit of the Fe content in the flux was set to 25%. In the present invention, Fe may be pure Fe, for example, an Fe alloy with Mn or Si, and the effect is exhibited if the total content of Fe in the flux is within the above range.

Ｂ２Ｏ３：Ｂ２Ｏ３は溶接金属中で生成したＴｉ酸化物の界面にＢＮなどのＢ化合物を析出し、Ｔｉ酸化物の微細アシキュラーフェライト生成能をさらに促進させ、また、溶接勤続中で固溶Ｂとしてオーステナイト結晶粒界に偏析し、粗大な粒界フェライトの生成を抑制する作用を有する。これらの作用を利用し、溶接金属組織を微細化するためには、フラックス中にＢ２Ｏ３を０．６１％以上含有する必要がある。なお、後述するようにＢを溶接ワイヤから溶接金属に添加することも可能であるが、溶接ワイヤ中のＢ含有量の増加は、溶接ワイヤ製造時の加工性を劣化させるため好ましくない。このため、本発明では、Ｂの溶接金属への添加は、基本的にフラックスからＢ２Ｏ３の形態で添加し、これに加えて、後述する必要に応じて補助的に溶接ワイヤからＢを溶接金属に添加する。   B2O3: B2O3 precipitates B compounds such as BN at the interface of the Ti oxide generated in the weld metal, further promotes the ability of the Ti oxide to form fine acicular ferrite, and as a solute B during the welding process It segregates at austenite grain boundaries and has the effect of suppressing the formation of coarse grain boundary ferrite. In order to use these functions to refine the weld metal structure, it is necessary to contain B2O3 in the flux at 0.61% or more. As will be described later, it is possible to add B from the welding wire to the weld metal, but an increase in the B content in the welding wire is not preferable because it deteriorates workability at the time of manufacturing the welding wire. For this reason, in the present invention, B is added to the weld metal basically from the flux in the form of B2O3, and in addition to this, B is added from the welding wire to the weld metal as needed. Added.

一方、フラックス中のＢ２Ｏ３含有量が２．５％を超えると、大入熱サブマージアーク溶接における溶接金属の厚み方向の靭性を高いレベルで均一化する場合に、表面側溶接金属の焼入れ性が過度に増加し、硬質で粗大な上部ベイナイト組織の生成が顕著となり、逆に靭性の劣化を招く。このため、フラックス中のＢ２Ｏ３含有量の上限を２．５％と規定した。   On the other hand, if the B2O3 content in the flux exceeds 2.5%, the hardenability of the surface side weld metal is excessive when the toughness in the thickness direction of the weld metal in high heat input submerged arc welding is made uniform at a high level. The formation of a hard and coarse upper bainite structure becomes remarkable, and conversely, the toughness is deteriorated. For this reason, the upper limit of B2O3 content in a flux was prescribed | regulated as 2.5%.

なお、本発明において、フラックス中のＢの形態をＢ２Ｏ３とした理由は、Ｂ２Ｏ３は、金属Ｂやその他のＢ化合物の形態に比べて溶接金属中のＢの歩留まりが良いためである。本発明では上記のフラックス成分を基本成分として含有するが、これら成分を結合させるための水ガラス等のバインダー（Ｎａ2Ｏ、Ｋ2Ｏ）等を常法通り含有させてもよい。 In the present invention, the reason why the form of B in the flux is B2O3 is that B2O3 has a better yield of B in the weld metal than the form of metal B or other B compounds. In the present invention, the above-described flux component is contained as a basic component, but a binder (Na 2 O, K 2 O) or the like such as water glass for binding these components may be contained as usual.

本発明において上記フラックスの基本成分の他に、さらに溶接金属の機械的特性、特に靱性を安定して向上させるために、選択成分として、以下の範囲でＭｏ、Ｎｉを添加しても良い。   In the present invention, in addition to the above basic components of the flux, in order to stably improve the mechanical properties of the weld metal, particularly toughness, Mo and Ni may be added as optional components in the following ranges.

Ｍｏ、Ｎｉ：Ｍｏは、他の焼入れ性元素に比べて、溶接金属のアシキュラーフェライトやベイナイトの有効結晶粒径を微細化する作用が高い元素である。特に大入熱サブマージアーク溶接における溶接金属の厚み方向での熱履歴や冷却速度の違いより、溶接金属の全厚み範囲の焼き入性を向上させる場合に靭性に有害な上部ベイナイトが生成しやすい表層側溶接金属において、上部ベイナイト結晶粒径を微細化し、靭性劣化を抑制できるため、溶接金属の全範囲の靭性を均一化するために有効な元素である。また、Ｎｉは、焼入れ性元素中で、唯一固溶靭化効果を有して本質的に靱性を向上でき、Ｎｉ量が多い方が靱性は良好となる。Ｎｉは、他のオーステナイト安定化元素に比べて、ＣＣＴ図でのベイナイトノーズを広げる効果が大きいため、溶接金属中のＮｉにより、大入熱サブマージアーク溶接時の溶接金属厚み方向での冷却速度の違いよる表面側と裏面側との組織変化およびそれによる靭性差を小さくでき、溶接金属の全範囲の靭性を均一化するために有効な元素である。   Mo, Ni: Mo is an element that has a higher effect of refining the effective crystal grain size of acicular ferrite or bainite of the weld metal than other hardenable elements. In particular, due to the difference in heat history and cooling rate in the thickness direction of the weld metal in high heat input submerged arc welding, the surface layer is likely to generate upper bainite that is harmful to toughness when improving the hardenability of the entire thickness range of the weld metal. In the side weld metal, the upper bainite crystal grain size can be refined and toughness deterioration can be suppressed, so that it is an effective element for uniformizing the toughness of the entire range of the weld metal. In addition, Ni is the only hardenable element that has the only solid solution toughening effect and can essentially improve toughness. The higher the amount of Ni, the better the toughness. Compared with other austenite stabilizing elements, Ni has a greater effect of expanding the bainite nose in the CCT diagram. Therefore, Ni in the weld metal has a cooling rate in the weld metal thickness direction during high heat input submerged arc welding. It is an effective element for uniformizing the toughness of the entire range of the weld metal because the difference in structure between the front side and the back side due to the difference and the difference in toughness due to the change can be reduced.

本発明では、基本的にワイヤからＭｏ、Ｎｉを溶接金属中に添加するが、これに加えて、補助的にフラックスからＭｏ、Ｎｉを溶接金属中に添加し、後述するＭｏ、Ｎｉの作用により溶接金属の組織微細化、靱性向上の効果をより安定して得るために、フラックス中にＭｏおよびＮｉの1種または２種を含有させる場合は、それぞれの含有量の下限を１％とすることが好ましい。一方、ＭｏおよびＮｉのそれぞれの含有量が５％超になると、溶接ワイヤ組成や鋼板組成によっては溶接金属の硬さが過大となって靱性を劣化させる懸念があるため、フラックス中にＭｏおよびＮｉの1種または２種を含有させる場合は、それぞれの含有量の上限は５％とするのが好ましい。   In the present invention, Mo and Ni are basically added from the wire into the weld metal, but in addition to this, Mo and Ni are added from the flux to the weld metal as a result of the action of Mo and Ni described later. In order to obtain the effects of refinement of the microstructure of the weld metal and improvement of toughness more stably, when containing one or two of Mo and Ni in the flux, the lower limit of each content should be 1%. Is preferred. On the other hand, if the content of each of Mo and Ni exceeds 5%, depending on the welding wire composition and the steel sheet composition, there is a concern that the hardness of the weld metal becomes excessive and the toughness is deteriorated. When one or two of these are contained, the upper limit of each content is preferably 5%.

なお、フラックス中のＭｏ、Ｎｉの形態は、ＭｏおよびＮｉの含有量が上記範囲内であれば、純金属、合金、酸化物、いずれの形態でも構わない。溶接金属中の酸素量を低減するためには金属Ｍｏ、金属ＮｉまたはＭｏ、Ｎｉを含有する合金で含有させるのがより好ましい。   The form of Mo and Ni in the flux may be any form of pure metal, alloy, and oxide as long as the contents of Mo and Ni are within the above ranges. In order to reduce the amount of oxygen in the weld metal, it is more preferable to contain metal Mo, metal Ni, or an alloy containing Mo and Ni.

以上が本発明における目的および技術思想を達成するためのフラックスの主要な成分組成の限定理由であるが、本発明の目的および技術思想から逸脱せず、溶接金属の機械的特性を害さない範囲において、上記フラックス成分の他の成分や、バインダー成分を含有することができる。   The above is the reason for limiting the main component composition of the flux for achieving the purpose and technical idea of the present invention, but does not depart from the purpose and technical idea of the present invention and does not impair the mechanical properties of the weld metal. In addition, other components of the flux component and a binder component can be contained.

次に、本発明の目的を達成するために必要とする溶接ワイヤの基本成分組成の限定理由を説明する。   Next, the reasons for limiting the basic component composition of the welding wire necessary to achieve the object of the present invention will be described.

厚鋼板の大入熱サブマージアーク溶接では、フラックスとともに溶接ワイヤの成分組成による溶接金属の組織および機械的特性への寄与が大きい。このため、本発明が目的とする溶接金属の全厚み範囲における機械的特性、特に均一にかつ高い靱性を達成するためには、フラックスや鋼板だけでなく、溶接ワイヤの成分組成を以下のように適正化する必要がある。   In high heat input submerged arc welding of thick steel plates, the contribution to the structure and mechanical properties of the weld metal due to the composition of the welding wire as well as the flux is large. For this reason, in order to achieve the mechanical properties in the entire thickness range of the weld metal targeted by the present invention, particularly uniform and high toughness, not only the flux and the steel plate, but also the composition of the components of the welding wire is as follows: It needs to be optimized.

Ｃ：Ｃは、溶接金属の強度を向上させる成分であり、特に高張力鋼用溶接金属として引張強度５００〜８００ＭＰａを確保するために、溶接ワイヤ中に０．０２％以上含有させる。一方、溶接ワイヤ中のＣが０．２％を超えて含有されると、溶接金属中のＣ量が過剰となり、溶接金属の靭性が劣化するため、好ましくない。従って、本発明において溶接ワイヤ中のＣ含有量は０．０２〜０．２％に限定する。   C: C is a component that improves the strength of the weld metal, and is contained in the welding wire in an amount of 0.02% or more in order to ensure a tensile strength of 500 to 800 MPa, particularly as a weld metal for high-tensile steel. On the other hand, if the content of C in the welding wire exceeds 0.2%, the amount of C in the weld metal becomes excessive and the toughness of the weld metal deteriorates, which is not preferable. Therefore, in the present invention, the C content in the welding wire is limited to 0.02 to 0.2%.

Ｓｉ：Ｓｉは、脱酸元素であり、溶接金属中の酸素量を減少させ、溶接金属の介在物による欠陥を抑制し、酸素による材質劣化を抑制する。これらの効果を発揮するためには溶接ワイヤ中にＳｉを０．０１％以上含有させる。しかしながら、１％を超えてワイヤ中にＳｉを含有すると、溶接金属の硬さが過剰に高まり、靭性を劣化させるので、ワイヤ中のＳｉ含有量の上限を１％とした。   Si: Si is a deoxidizing element, reduces the amount of oxygen in the weld metal, suppresses defects due to inclusions in the weld metal, and suppresses material deterioration due to oxygen. In order to exert these effects, 0.01% or more of Si is contained in the welding wire. However, if Si is contained in the wire exceeding 1%, the hardness of the weld metal is excessively increased and the toughness is deteriorated, so the upper limit of the Si content in the wire is set to 1%.

Ｍｎ：Ｍｎは、溶接金属の強度向上及び脱酸作用を有し、その溶接ワイヤ中の含有量が０．１％を下回ると、十分な脱酸作用と溶接金属の十分な強度が得られず、また、溶接金属の酸素量が高くなるために、溶接金属の靭性を劣化させる。そのため、ワイヤ中のＭｎ含有量の下限を０．１％とした。一方ワイヤ中のＭｎ含有量が２．５％を超えると、溶接金属組織が粗大なベイナイト組織となって靭性が劣化する可能性が高くなるため、本発明においては、溶接ワイヤ中のＭｎ含有量の上限を２．５％とする。   Mn: Mn has an effect of improving the strength and deoxidizing of the weld metal. If the content in the welding wire is less than 0.1%, sufficient deoxidation and sufficient strength of the weld metal cannot be obtained. Moreover, since the oxygen content of the weld metal becomes high, the toughness of the weld metal is deteriorated. Therefore, the lower limit of the Mn content in the wire is set to 0.1%. On the other hand, if the Mn content in the wire exceeds 2.5%, the weld metal structure becomes a coarse bainite structure and the toughness is likely to deteriorate. Therefore, in the present invention, the Mn content in the welding wire Is set to 2.5%.

Ｍｏ：Ｍｏは、他の焼入れ性元素に比べて、溶接金属のアシキュラーフェライトやベイナイトの有効結晶粒径を微細化する作用を有する元素である。特に大入熱サブマージアーク溶接における溶接金属の厚み方向での熱履歴や冷却速度の違いより、溶接金属の全厚み範囲の焼き入性を向上させる場合に靭性に有害な上部ベイナイトが生成しやすい表層側溶接金属において、上部ベイナイト結晶粒径を微細化し、靭性劣化を抑制できるため、溶接金属の全範囲の靭性を均一化するために特に重要な元素である。これらの作用効果により、溶接金属の表側から裏側の全厚み範囲にわたって均一に、かつ安定的に高い靭性を保持するためには、溶接ワイヤ中にＭｏを０．１％以上含有させる必要がある。しかしながら、３％を超えて溶接金属中にＭｏを過剰に含有させると溶接金属が過剰に硬化し、溶接金属の靭性を著しく劣化させるので、本発明では溶接ワイヤ中のＭｏ含有量の上限を３％とした。
なお、サブマージアーク溶接では、Ｍｏをフラックスから溶接金属中に添加できるが、溶接ワイヤからＭｏを添加する方がより溶接金属でのＭｏの歩留まりがより安定するため、本発明においては、基本的にはＭｏを溶接ワイヤから添加し、後述する必要に応じてＭｏをフラックスから補助的に添加する。 Mo: Mo is an element having an effect of refining the effective crystal grain size of the acicular ferrite or bainite of the weld metal as compared with other hardenable elements. In particular, due to the difference in heat history and cooling rate in the thickness direction of the weld metal in high heat input submerged arc welding, the surface layer is likely to generate upper bainite that is harmful to toughness when improving the hardenability of the entire thickness range of the weld metal. In the side weld metal, since the upper bainite crystal grain size can be refined and toughness deterioration can be suppressed, it is an especially important element for making the toughness of the entire range of the weld metal uniform. Due to these effects, in order to maintain high toughness uniformly and stably over the entire thickness range from the front side to the back side of the weld metal, it is necessary to contain 0.1% or more of Mo in the welding wire. However, if Mo is excessively contained in the weld metal exceeding 3%, the weld metal is excessively hardened and the toughness of the weld metal is remarkably deteriorated. Therefore, in the present invention, the upper limit of the Mo content in the weld wire is 3%. %.
In submerged arc welding, Mo can be added from the flux into the weld metal, but adding Mo from the welding wire makes the Mo yield in the weld metal more stable, so in the present invention, basically, Adds Mo from the welding wire, and supplementarily adds Mo from the flux if necessary.

Ｎｉ：Ｎｉは、焼入れ性元素中で唯一固溶靭化効果を有して本質的に靱性を向上でき、Ｎｉ量が多い方が靱性は良好となる。また、Ｎｉは、他のオーステナイト安定化元素に比べて、ＣＣＴ図でのベイナイトノーズを広げる効果が大きい。このため、溶接金属中のＮｉは、厚鋼板の１パス大入熱サブマージアーク溶接時に溶接金属の厚み方向における冷却速度差に起因する表面側と裏面側との溶接金属組織の変化を小さくし、その結果、溶接金属の全厚み範囲における靭性の均一化を達成するために特に重要な元素である。これらの作用効果を充分に発現するためには、Ｎｉは溶接ワイヤ中に１％以上含有させる必要がある。特に、低温での溶接金属靱性を確実に確保するためには、溶接ワイヤ中のＮｉ含有量を２．１％以上とするのが好ましい。   Ni: Ni has the only solid solution toughening effect among the hardenable elements and can essentially improve toughness. The higher the amount of Ni, the better the toughness. Further, Ni has a greater effect of expanding the bainite nose in the CCT diagram than other austenite stabilizing elements. For this reason, Ni in the weld metal reduces the change in the weld metal structure between the front side and the back side due to the cooling rate difference in the thickness direction of the weld metal during the one-pass large heat input submerged arc welding of the thick steel plate, As a result, it is a particularly important element for achieving uniform toughness in the entire thickness range of the weld metal. In order to fully express these effects, Ni must be contained in the welding wire by 1% or more. In particular, in order to ensure weld metal toughness at a low temperature, it is preferable that the Ni content in the welding wire is 2.1% or more.

一方、６％を超えてＮｉを溶接ワイヤ中に含有しても効果が飽和する一方で、溶接金属の焼入性が過剰となり、強度が過大となって靱性を劣化させる可能性が生じるため、本発明においては溶接ワイヤ中のＮｉ含有量の上限を６％に限定する。   On the other hand, even if Ni is included in the welding wire in excess of 6%, the effect is saturated, but the hardenability of the weld metal becomes excessive, and there is a possibility that the strength becomes excessive and deteriorates the toughness. In the present invention, the upper limit of the Ni content in the welding wire is limited to 6%.

なお、サブマージアーク溶接では、Ｎｉをフラックスから溶接金属中に添加できるが、溶接ワイヤからＮｉを添加する方がより溶接金属でのＮｉの歩留まりがより安定するため、本発明においては、基本的にはＮｉを溶接ワイヤから添加し、後述する必要に応じてＮｉをフラックスから補助的に添加する。   In submerged arc welding, Ni can be added from the flux into the weld metal, but adding Ni from the welding wire makes the yield of Ni in the weld metal more stable. Ni is added from the welding wire, and Ni is supplementarily added from the flux as necessary, which will be described later.

Ａｌ：Ａｌは、脱酸元素として働き、溶接金属中の酸素量制御に有効な元素であり、溶接金属の脱酸に有効に寄与するために溶接ワイヤ中にＡｌを０．００２％以上含有させる。一方、溶接金属中にＡｌが過剰に含有されると微細アシキュラーフェライトの生成が抑制され、溶接金属組織が粗大化し、靭性が劣化するため、溶接ワイヤ中のＡｌ含有量の上限は０．１％とする。   Al: Al acts as a deoxidizing element and is an effective element for controlling the amount of oxygen in the weld metal. In order to effectively contribute to the deoxidation of the weld metal, Al is contained in the welding wire in an amount of 0.002% or more. . On the other hand, if Al is excessively contained in the weld metal, the formation of fine acicular ferrite is suppressed, the weld metal structure is coarsened, and the toughness is deteriorated. Therefore, the upper limit of the Al content in the weld wire is 0.1. %.

Ｔｉ：Ｔｉは、溶接金属においてＴｉ酸化物を形成して微細アシキュラーフェライトの生成核として作用し、溶接金属組織の微細化に寄与する本発明において重要な元素である。本発明では、溶融金属プールが長時間維持されるような大入熱サブマージアーク溶接でも、後述するフラックスから溶接金属中に添加するＢがＢＮおよびＦｅ２３（Ｃ、Ｂ）６などのＢ化合物としてＴｉ酸化物界面に析出し、微細アシキュラーフェライト生成能を高めることが可能となる。本発明では、これらの効果を充分に確保するため、溶接ワイヤ中にＴｉを０．００５％以上含有させる。一方、溶接ワイヤ中のＴｉ含有量が０．３％を超えると、溶接金属中に脆性破壊の起点となるような粗大なＴｉを含む酸化物や窒化物を形成して溶接金属の靭性を劣化させるため、本発明においては、溶接ワイヤ中のＴｉ含有量の上限は０．３％とした。   Ti: Ti is an important element in the present invention that forms a Ti oxide in a weld metal and acts as a production nucleus of fine acicular ferrite, thereby contributing to refinement of the weld metal structure. In the present invention, even in high heat input submerged arc welding in which the molten metal pool is maintained for a long time, B added to the weld metal from the flux described later is Ti as a B compound such as BN and Fe23 (C, B) 6. Precipitation at the oxide interface makes it possible to increase the fine acicular ferrite generation ability. In the present invention, in order to sufficiently secure these effects, 0.005% or more of Ti is contained in the welding wire. On the other hand, if the Ti content in the welding wire exceeds 0.3%, the weld metal deteriorates the toughness of the weld metal by forming coarse Ti-containing oxides and nitrides that can cause brittle fracture. Therefore, in the present invention, the upper limit of the Ti content in the welding wire is set to 0.3%.

Ｎ：Ｎは、溶接ワイヤ中の不可避的不純物元素であるが、Ｎは溶接金属中でＴｉ、Ｂと窒化物を形成して、オーステナイト微細化や微細アシキュラーフェライト生成には有益な元素である。これらの効果をえるためにはＮ含有量を０．００１％以上とする必要がある。一方、溶接ワイヤのＮ含有量が０．０１５％を超えて多くなると、溶接金属におけるＮ含有量を増加させ、該溶接金属中のＮが固溶状態でフェライトマトリクスの靭性を劣化させる。また、Ｂを窒化物として固定してしまい、固溶Ｂの粒界偏析によるオーステナイト粒界での初析フェライト（粒界フェライト）変態の抑止、およびそれによる靭性効果を阻害する。そこで、本発明では、その溶接ワイヤ中の含有量の上限を０．０１５％とした。   N: N is an inevitable impurity element in the welding wire, but N is a useful element for forming austenite and fine acicular ferrite by forming nitrides with Ti and B in the weld metal. . In order to obtain these effects, the N content needs to be 0.001% or more. On the other hand, when the N content of the welding wire exceeds 0.015%, the N content in the weld metal is increased, and the toughness of the ferrite matrix is deteriorated when N in the weld metal is in a solid solution state. Further, B is fixed as a nitride, which inhibits the transformation of proeutectoid ferrite (grain boundary ferrite) at the austenite grain boundary due to the grain boundary segregation of the solid solution B and the toughness effect thereby. Therefore, in the present invention, the upper limit of the content in the welding wire is set to 0.015%.

Ｐ：Ｐは不可避的不純物元素であり、溶接金属中のＰは溶接金属の靭性を劣化させるため、溶接ワイヤ中のＰ含有量は極力低減することが好ましい。本発明では、溶接金属の靭性確保の点から許容できる上限量として溶接ワイヤ中のＰ含有量の上限を０．０２％とした。   P: P is an unavoidable impurity element, and P in the weld metal deteriorates the toughness of the weld metal. Therefore, it is preferable to reduce the P content in the weld wire as much as possible. In the present invention, the upper limit of the P content in the welding wire is set to 0.02% as an allowable upper limit from the viewpoint of ensuring the toughness of the weld metal.

Ｓ：Ｓは不可避的不純物元素であり、溶接金属の延性、靭性をともに劣化させるため、溶接ワイヤ中のＳ含有量は極力低減する必要がある。本発明では、溶接金属の延性、靭性の確保の観点から実用的に許容できる上限として、溶接ワイヤ中のＳ含有量の上限を０．０１％とした。   S: S is an inevitable impurity element, and both the ductility and toughness of the weld metal are deteriorated. Therefore, the S content in the welding wire needs to be reduced as much as possible. In the present invention, the upper limit of the S content in the welding wire is set to 0.01% as an upper limit that is practically acceptable from the viewpoint of ensuring the ductility and toughness of the weld metal.

Ｏ：酸素（Ｏ）は、溶接ワイヤ中の不可避的不純物元素であり、Ｏ含有量が過大であると、溶接ワイヤの製造性を阻害し、また、溶接金属中のＯ含有量を増加させて、溶接金属の延性、靱性を劣化させるため好ましくない。本発明においては、溶接ワイヤの製造性を良好にし、溶接金属の延性、靱性の劣化させないために、溶接ワイヤ中のＯ含有量の上限を０．０１％とする。   O: Oxygen (O) is an unavoidable impurity element in the welding wire, and if the O content is excessive, the manufacturability of the welding wire is hindered, and the O content in the weld metal is increased. This is not preferable because it deteriorates the ductility and toughness of the weld metal. In the present invention, the upper limit of the O content in the welding wire is set to 0.01% in order to improve the manufacturability of the welding wire and not deteriorate the ductility and toughness of the weld metal.

本発明において上記溶接ワイヤの基本成分の他に、溶接金属の機械的特性、特に強度、靭性を調整するために、さらにＣｕ、Ｃｒ、Ｗ、Ｎｂ、Ｖ、Ｔａ、Ｂの１種または２種以上を所定範囲で溶接ワイヤ中に含有させることができる。   In the present invention, in addition to the basic components of the welding wire, one or two of Cu, Cr, W, Nb, V, Ta, and B are further added to adjust the mechanical properties of the weld metal, particularly strength and toughness. The above can be contained in the welding wire within a predetermined range.

Ｃｕ：Ｃｕは、オーステナイト安定化元素であり、溶接金属の焼入性を高めることにより、粗大粒界フェライト生成を抑制し、溶接金属組織の微細化および強度・靱性向上に有効な元素である。これらの効果を得るためには溶接ワイヤ中のＣｕ含有量を０．０１％以上とするのが好ましい。一方、溶接ワイヤ中のＣｕ含有量が １．５％超であると、高温割れを生じやすくなり、溶接ワイヤの製造性が劣化するため、Ｃｕ含有量の上限を１．５％とするのが好ましい。なお、Ｃｕは溶接ワイヤ中に含有させても、ワイヤ表面にメッキしてもその実質的効果は変わらない。   Cu: Cu is an austenite stabilizing element, and is an element effective in suppressing the formation of coarse grain boundary ferrite by increasing the hardenability of the weld metal, and making the weld metal structure finer and improving the strength and toughness. In order to obtain these effects, the Cu content in the welding wire is preferably 0.01% or more. On the other hand, if the Cu content in the welding wire is more than 1.5%, hot cracking is likely to occur and the weld wire manufacturability deteriorates, so the upper limit of the Cu content should be 1.5%. preferable. Even if Cu is contained in the welding wire or plated on the surface of the wire, the substantial effect does not change.

Ｃｒ：Ｃｒは、Ｍｏと同等の焼入性を有する元素であり、溶接金属の強度向上のために溶接ワイヤ中にＣｒを０．０１％以上含有する。一方、溶接ワイヤ中のＣｒ含有量が １．５％超であると、溶接金属の靱性劣化が顕著に生じるため、Ｃｒ含有量の上限は１．５％とするのが好ましい。   Cr: Cr is an element having a hardenability equivalent to Mo and contains 0.01% or more of Cr in the welding wire in order to improve the strength of the weld metal. On the other hand, if the Cr content in the welding wire is more than 1.5%, the toughness of the weld metal is significantly deteriorated, so the upper limit of the Cr content is preferably 1.5%.

Ｗ：Ｗは、定性的にはＣｒと同様の作用効果を有する元素であり、溶接金属の強度向上のために溶接ワイヤ中にＷを０．０１％以上含有するのが好ましい。一方、溶接ワイヤ中のＷ含有量が２％超であると、溶接金属の靱性劣化が顕著に生じるため、Ｗ含有量の上限は２％とするのが好ましい。   W: W is qualitatively an element having the same effect as Cr, and it is preferable to contain 0.01% or more of W in the welding wire in order to improve the strength of the weld metal. On the other hand, if the W content in the welding wire is more than 2%, the toughness of the weld metal is remarkably deteriorated, so the upper limit of the W content is preferably 2%.

Ｎｂ：Ｎｂは、溶接金属の焼入性向上および析出強化により、溶接金属の強度向上に有効な元素である。この効果を確実に発揮するためには、溶接ワイヤ中のＮｂ含有量は０．００２％以上とするのが好ましい。一方、溶接ワイヤ中のＮｂ含有量が０．０５％を超えると、溶接金属の強度が過大となり、また、粗大なＮｂ析出物が形成されるために、溶接金属の靭性劣化が著しくなるため、好ましくない。そのため、溶接ワイヤ中のＮｂ含有量の上限を０．０５％とするのが好ましい。   Nb: Nb is an element effective for improving the strength of the weld metal by improving the hardenability and precipitation strengthening of the weld metal. In order to exhibit this effect reliably, the Nb content in the welding wire is preferably 0.002% or more. On the other hand, if the Nb content in the welding wire exceeds 0.05%, the strength of the weld metal becomes excessive, and because coarse Nb precipitates are formed, the toughness deterioration of the weld metal becomes significant. It is not preferable. Therefore, it is preferable that the upper limit of the Nb content in the welding wire is 0.05%.

Ｖ：Ｖは、溶接金属の析出強化により、溶接金属の強度向上に有効な元素である。この効果を確実に発揮するためには、溶接ワイヤ中のＶ含有量は０．００５％以上とするのが好ましい。一方、溶接ワイヤ中のＶ含有量が０．５％を超えると、溶接金属の強度が過大となり、溶接金属の靭性劣化が著しくなるため、好ましくない。そのため、溶接ワイヤ中のＶ含有量の上限を０．５％とするのが好ましい。   V: V is an element effective for improving the strength of weld metal by precipitation strengthening of the weld metal. In order to exhibit this effect reliably, the V content in the welding wire is preferably 0.005% or more. On the other hand, if the V content in the welding wire exceeds 0.5%, the strength of the weld metal becomes excessive, and the toughness of the weld metal becomes significantly deteriorated. Therefore, the upper limit of the V content in the welding wire is preferably 0.5%.

Ｔａ：Ｔａは、Ｖとほぼ同様の作用を有する元素であり、溶接金属の析出強化により、溶接金属の強度向上に有効な元素である。この効果を確実に発揮するためには、溶接ワイヤ中のＴａ含有量は０．００２％以上とするのが好ましい。一方、溶接ワイヤ中のＴａ含有量が０．２％を超えると、溶接金属の強度が過大となり、溶接金属の靭性劣化が著しくなるため、好ましくない。そのため、溶接ワイヤ中のＴａ含有量の上限を０．２％とするのが好ましい。   Ta: Ta is an element having substantially the same action as V, and is an element effective for improving the strength of the weld metal by precipitation strengthening of the weld metal. In order to exhibit this effect reliably, the Ta content in the welding wire is preferably 0.002% or more. On the other hand, if the Ta content in the welding wire exceeds 0.2%, the strength of the weld metal becomes excessive and the toughness of the weld metal is significantly deteriorated, which is not preferable. Therefore, the upper limit of the Ta content in the welding wire is preferably 0.2%.

Ｂ：Ｂは、溶接金属中で固溶Ｂとしてオーステナイト結晶粒界に偏析し、粗大粒界フェライトの生成を抑制し、Ｔｉ酸化物と同時にＢＮなどのＢ化合物として析出し、Ｔｉ酸化物との相互作用により微細アシキュラーフェライト生成を促進させる作用をもつ。これらの作用を利用し、溶接金属の組織を微細化し、大入熱サブマージアーク溶接における溶接金属の表側から裏側までの全厚み範囲の靭性を均一に向上させるために、Ｂは溶接金属中で必須元素である。本発明では、Ｂは基本的にフラックスから添加し、さらにＢの作用効果を安定して得るために補助的にＢを溶接ワイヤから溶接金属中に添加する場合は、溶接ワイヤ中のＢ含有量を０．００１％以上とするのが好ましい。   B: B segregates at the austenite grain boundary as a solid solution B in the weld metal, suppresses the formation of coarse grain boundary ferrite, precipitates as a B compound such as BN simultaneously with the Ti oxide, It has the effect of promoting the formation of fine acicular ferrite by interaction. Using these actions, B is essential in the weld metal in order to refine the weld metal structure and to uniformly improve the toughness of the entire thickness range from the front side to the back side of the weld metal in high heat input submerged arc welding. It is an element. In the present invention, B is basically added from the flux, and in addition, in order to supplementarily add B from the welding wire to the weld metal in order to obtain the effect of B stably, the B content in the welding wire Is preferably 0.001% or more.

一方、溶接ワイヤ中のＢ含有量が０．０５％超になると、溶接金属中に粗大な上部ベイナイト組織が生成され、溶接金属の靱性が劣化し、さらに、ワイヤ製造時の加工性が劣化するため、好ましくない。そこで、溶接ワイヤ中にＢを含有する場合は、Ｂ含有量の上限を０．０５％とするのが好ましい。   On the other hand, when the B content in the welding wire exceeds 0.05%, a coarse upper bainite structure is generated in the weld metal, the toughness of the weld metal is deteriorated, and the workability at the time of manufacturing the wire is deteriorated. Therefore, it is not preferable. Therefore, when B is contained in the welding wire, the upper limit of the B content is preferably 0.05%.

本発明において上記溶接ワイヤの基本成分および選択成分の他に、溶接金属の機械的特性、特に延性、靭性を改善するために、さらにＣａ、Ｍｇ、ＲＥＭの１種または２種以上を溶接ワイヤ中に所定範囲で含有させることができる。   In the present invention, in addition to the basic component and the selective component of the welding wire, in order to improve the mechanical properties of the weld metal, particularly ductility and toughness, one or more of Ca, Mg, and REM are further contained in the welding wire. In a predetermined range.

Ｃａ、Ｍｇ、ＲＥＭ：Ｃａ、Ｍｇ、ＲＥＭはいずれも、溶接金属において硫化物の構造を変化させ、また硫化物、酸化物のサイズを微細化し、溶接金属の延性及び靭性を向上するために有効な元素である。これらの効果を発揮するためには、溶接ワイヤ中のＣａ、ＭｇおよびＲＥＭの１種または２種以上の含有量は、０．０００２％とすることが好ましい。一方、Ｃａ、ＭｇおよびＲＥＭの１種または２種以上の含有量が０．０１％を超える過剰な添加は、溶接金属中の硫化物や酸化物を粗大化させ、溶接金属の延性、靭性の劣化を招き、また、溶接ビード形状の劣化、溶接性の劣化の可能性も生じるため、溶接ワイヤ中のＣａ、ＭｇおよびＲＥＭの１種または２種以上の含有量の上限を０．０１％とする。   Ca, Mg, REM: Ca, Mg, and REM are all effective in changing the structure of sulfides in weld metals, reducing the size of sulfides and oxides, and improving the ductility and toughness of weld metals. Element. In order to exhibit these effects, the content of one or more of Ca, Mg and REM in the welding wire is preferably 0.0002%. On the other hand, excessive addition of one or more of Ca, Mg, and REM exceeding 0.01% coarsens sulfides and oxides in the weld metal, and improves the ductility and toughness of the weld metal. Deterioration of the weld bead shape and weldability may occur, so the upper limit of the content of one or more of Ca, Mg and REM in the welding wire is 0.01%. To do.

以上が本発明における鋼板、フラックス、溶接ワイヤの成分組成の限定理由である。本発明では、本発明の目的を達成するために必要とする、鋼板、溶接ワイヤ、フラックスによりサブマージ溶接して形成される溶接金属の基本成分組成を以下のように限定される。
Ｃ：Ｃは、溶接金属の強度を向上させる成分であり、５００ＭＰａ以上の高張力鋼用溶接金属の引張強度を確保するために、Ｃは溶接金属中に０．０３％以上含有させる。しかしながらＣは、オーステナイトの安定化元素であるために溶接金属に過剰に含有すると溶接金属の硬さが過剰となり、かつ、靭性に有害な粗大なセメンタイト（Ｆｅ３Ｃ）や島状マルテンサイトが多く生成するため、溶接金属の靭性を確保する必要性から溶接金属中のＣ含有量の上限は０．２％とした。 The above is the reason for limiting the component compositions of the steel plate, flux, and welding wire in the present invention. In the present invention, the basic component composition of a weld metal formed by submerged welding using a steel plate, a welding wire, and a flux, which is necessary to achieve the object of the present invention, is limited as follows.
C: C is a component that improves the strength of the weld metal. In order to ensure the tensile strength of the weld metal for high-tensile steel of 500 MPa or more, C is contained in the weld metal by 0.03% or more. However, since C is an austenite stabilizing element, if contained excessively in the weld metal, the hardness of the weld metal becomes excessive, and a large amount of coarse cementite (Fe3C) and island martensite harmful to toughness are generated. Therefore, the upper limit of the C content in the weld metal is set to 0.2% because of the need to ensure the toughness of the weld metal.

Ｓｉ：Ｓｉは、溶接金属中の脱酸元素として働き、溶接金属の酸素量を減少させることで溶接金属の靱性、延性を向上できる成分であり、効果を発揮するために溶接金属中のＳｉ含有量を０．１％以上とする。ただし、１％を超えてＳｉを過剰に含有すると、溶接金属の硬さを過剰に高め、また島状マルテンサイト生成を促進して靭性を劣化させるので、溶接金属中のＳｉ含有量の上限を１％とした。   Si: Si is a component that acts as a deoxidizing element in the weld metal and can improve the toughness and ductility of the weld metal by reducing the oxygen content of the weld metal. The amount is 0.1% or more. However, if Si is contained excessively exceeding 1%, the hardness of the weld metal is excessively increased, and the martensite formation is promoted to deteriorate the toughness, so the upper limit of the Si content in the weld metal is limited. 1%.

Ｍｎ：Ｍｎは、溶接金属の強度の向上及び脱酸作用を有し、その含有量が０．７％を下回ると溶接金属の十分な強度が得られず、また、溶接金属の酸素量が高くなり、溶接金属の靭性を劣化させるため好ましくない。このため、溶接金属中のＭｎ含有量の下限を０．７％とした。しかしながらＭｎは２％を超えて含有すると焼入性が過剰となって溶接金属の強度が過大となって靱性を劣化させるため、溶接金属中のＭｎ含有量の上限は２％とした。   Mn: Mn has the effect of improving the strength of the weld metal and deoxidizing, and if its content is less than 0.7%, sufficient strength of the weld metal cannot be obtained, and the oxygen content of the weld metal is high. This is not preferable because it deteriorates the toughness of the weld metal. For this reason, the minimum of Mn content in a weld metal was made into 0.7%. However, if Mn exceeds 2%, the hardenability becomes excessive and the strength of the weld metal becomes excessive and the toughness is deteriorated, so the upper limit of the Mn content in the weld metal is 2%.

Ａｌ：Ａｌは、溶接金属中のＮを固定し、固溶Ｎ低減によって靱性向上に寄与する他、ＢＮの生成を抑制し固溶Ｂを確保する作用を有する。これらの効果を得るために溶接金属中にＡｌを０．００１％以上含有させる。一方、０．０７％を超えて過剰にＡｌを溶接金属中に含有すると、ＢＮの生成を極度に抑制し、本発明のＴｉ酸化物粒界に析出するＢＮが減少し、微細アシキュラーフェライトの生成促進による靭性向上効果を阻害するため、本発明において溶接金属中のＡｌ含有量の上限を０．０７％とした。   Al: Al fixes N in the weld metal and contributes to the improvement of toughness by reducing the solid solution N, and also has the effect of suppressing the generation of BN and ensuring the solid solution B. In order to obtain these effects, 0.001% or more of Al is contained in the weld metal. On the other hand, if the Al content exceeds 0.07%, the formation of BN is extremely suppressed, BN precipitated at the Ti oxide grain boundaries of the present invention is reduced, and the fine acicular ferrite is reduced. In order to inhibit the effect of improving toughness due to the promotion of formation, the upper limit of the Al content in the weld metal is set to 0.07% in the present invention.

Ｍｏ：Ｍｏは、他の焼入れ性元素に比べて、溶接金属のアシキュラーフェライトやベイナイトの有効結晶粒径を微細化する効果を有する元素である。特に大入熱サブマージアーク溶接における溶接金属の厚み方向での熱履歴や冷却速度の違いより、溶接金属の全厚み範囲の焼き入性を向上させる場合に靭性に有害な上部ベイナイトが生成しやすい表層側溶接金属において、上部ベイナイト結晶粒径を微細化し、靭性劣化を抑制できるため、溶接金属の全範囲の靭性を均一化するために特に重要な元素である。これらの作用効果により、溶接金属の表側から裏側の全厚み範囲にわたって均一に、かつ安定的に高い靭性を保持するためには、溶接金属中にＭｏを０．１％以上含有させる必要がある。しかしながら、１％を超えて溶接金属中にＭｏを過剰に含有させると溶接金属が過剰に硬化し、溶接金属の靭性を著しく劣化させるので、本発明では、溶接金属中のＭｏ含有量の上限を１％とした。   Mo: Mo is an element having an effect of refining the effective crystal grain size of acicular ferrite or bainite of a weld metal as compared with other hardenability elements. In particular, due to the difference in heat history and cooling rate in the thickness direction of the weld metal in high heat input submerged arc welding, the surface layer is likely to generate upper bainite that is harmful to toughness when improving the hardenability of the entire thickness range of the weld metal. In the side weld metal, since the upper bainite crystal grain size can be refined and toughness deterioration can be suppressed, it is an especially important element for making the toughness of the entire range of the weld metal uniform. Due to these effects, in order to maintain high toughness uniformly and stably over the entire thickness range from the front side to the back side of the weld metal, it is necessary to contain 0.1% or more of Mo in the weld metal. However, if Mo is excessively contained in the weld metal in excess of 1%, the weld metal is excessively cured and the toughness of the weld metal is remarkably deteriorated. Therefore, in the present invention, the upper limit of the Mo content in the weld metal is limited. 1%.

Ｎｉ：Ｎｉは、焼入れ性元素中で唯一固溶靭化効果を有して本質的に靱性を向上でき、Ｎｉ量が多い方が靱性は良好となる。また、Ｎｉは、他のオーステナイト安定化元素に比べて、ＣＣＴ図でのベイナイトノーズを広げる効果が大きい。このため、溶接金属中のＮｉは、厚鋼板の１パス大入熱サブマージアーク溶接時に溶接金属の厚み方向における冷却速度差に起因する表面側と裏面側との溶接金属組織の変化を小さくし、その結果、溶接金属の全厚み範囲における靭性の均一化を達成するために特に重要な元素である。これらの作用効果を充分に発現するためには、Ｎｉは溶接金属中に０．７５％以上含有させる必要がある。一方、３％を超えてＮｉを溶接金属中に含有しても効果が飽和する一方で、溶接金属の焼入性が過剰となり、強度が過大となって靱性を劣化させる可能性が生じるため、本発明においては溶接金属中のＮｉ含有量の上限を３％に限定する。   Ni: Ni has the only solid solution toughening effect among the hardenable elements and can essentially improve toughness. The higher the amount of Ni, the better the toughness. Further, Ni has a greater effect of expanding the bainite nose in the CCT diagram than other austenite stabilizing elements. For this reason, Ni in the weld metal reduces the change in the weld metal structure between the front side and the back side due to the cooling rate difference in the thickness direction of the weld metal during the one-pass large heat input submerged arc welding of the thick steel plate, As a result, it is a particularly important element for achieving uniform toughness in the entire thickness range of the weld metal. In order to fully express these effects, Ni needs to be contained in the weld metal by 0.75% or more. On the other hand, even if Ni is included in the weld metal in excess of 3%, the effect is saturated, but the hardenability of the weld metal becomes excessive, and the strength may be excessively increased to deteriorate toughness. In the present invention, the upper limit of the Ni content in the weld metal is limited to 3%.

Ｔｉ：Ｔｉは溶接金属中でＴｉを含有する酸化物を形成して微細アシキュラーフェライトの核となり、溶接金属組織を微細化ずるために有効な元素である。本発明では、溶接金属中にＴｉはＢとともに複合添加することにより、Ｔｉが酸素と優先的に結合してＴｉ酸化物を生成し、そのＴｉ酸化物界面にＢＮおよびＦｅ２３（Ｃ、Ｂ）６などのＢ化合物を析出し、微細アシキュラーフェライトの生成能を格段に向上する。これらのＴｉの効果を発揮するためには、Ｔｉは溶接金属中に０．００５％以上含有させる必要がある。ただし、０．１％を超えて溶接金属中に過剰に含有させると、粗大なＴｉ酸化物、Ｔｉ窒化物が増加して靱性に悪影響を及ぼすため、本発明においては溶接金属中のＴｉ含有量の上限を０．１％とした。   Ti: Ti is an effective element for forming an oxide containing Ti in the weld metal to become the core of fine acicular ferrite, and for reducing the weld metal structure. In the present invention, Ti is added together with B in the weld metal, so that Ti preferentially bonds with oxygen to form Ti oxide, and BN and Fe23 (C, B) 6 are formed at the Ti oxide interface. B compounds such as these are precipitated, and the ability to produce fine acicular ferrite is significantly improved. In order to exhibit these effects of Ti, it is necessary to contain Ti in the weld metal by 0.005% or more. However, if it exceeds 0.1% and is excessively contained in the weld metal, coarse Ti oxide and Ti nitride increase and adversely affect toughness. Therefore, in the present invention, the Ti content in the weld metal The upper limit was set to 0.1%.

Ｂ：Ｂは、溶接金属中に生成したＴｉ酸化物界面にＢＮなどのＢ化合物を複合析出し、Ｔｉ酸化物の微細アシキュラーフェライト生成能を向上させ、溶接金属組織の微細化に必須の元素である。また、溶接金属中で固溶Ｂとしてオーステナイト結晶粒界に偏析し、粒界の焼入れ性を高め、靭性に有害な粗大粒界フェライトの生成を抑制する作用効果も有する。これらの効果を発揮するためには、Ｂは溶接金属中に０．００１％以上含有させる必要がある。特に、溶接金属の表面から裏面側の溶接金属組織の変化を最小限に止めるためには、溶接金属中のＢ含有量の下限は０．００１５％とすることがより好ましい。一方、０．０１％を超えて過剰にＢを溶接金属中に含有させると、大入熱サブマージアーク溶接における溶接金属の厚み方向の靭性を高いレベルで均一化する場合に、表面側溶接金属の焼入れ性が過度に増加し、硬質で粗大な上部ベイナイト組織の生成が顕著となり、逆に靭性の劣化を招く。また、高温割れの危険性も増大して好ましくない。このため、本発明においては、溶接金属中のＢ含有量の上限を０．０１％とした。   B: B is an element indispensable for refining the weld metal structure by compound-depositing B compounds such as BN on the Ti oxide interface formed in the weld metal, improving the fine acicular ferrite formation ability of the Ti oxide. It is. Moreover, it has the effect of suppressing the production | generation of the coarse grain boundary ferrite which segregates in the austenite crystal grain boundary as solid solution B in a weld metal, raises the hardenability of a grain boundary, and is harmful to toughness. In order to exert these effects, B must be contained in the weld metal in an amount of 0.001% or more. In particular, in order to minimize the change in the weld metal structure from the front surface to the back surface of the weld metal, the lower limit of the B content in the weld metal is more preferably 0.0015%. On the other hand, when B is excessively contained in the weld metal exceeding 0.01%, the toughness in the thickness direction of the weld metal in the high heat input submerged arc welding is made uniform at a high level. The hardenability increases excessively, the formation of a hard and coarse upper bainite structure becomes remarkable, and conversely, the toughness is deteriorated. Further, the risk of hot cracking is increased, which is not preferable. For this reason, in the present invention, the upper limit of the B content in the weld metal is set to 0.01%.

Ｎ：Ｎは溶接金属中でＴｉ、Ｂと窒化物を形成して、オーステナイト微細化や微細アシキュラーフェライト生成には有益な元素であるため、溶接金属組織の微細化効果を発揮するためにはＮ含有量を０．００１％以上とする必要がある。一方、０．０１％を超えてＮを溶接金属中に過剰に含有させると、溶接金属中の固溶Ｎ量が増加してフェライトマトリクスの靭性を劣化する。また、ＢＮが過剰に生成して前記固溶Ｂの粒界偏析による粗大粒界フェライト抑制およびこれによる靭性向上効果を阻害しする。このため、本発明においては、溶接金属中のＮ含有量の上限を０．０１％とした。   N: N is a useful element for forming austenite and fine acicular ferrite by forming nitrides with Ti and B in the weld metal. The N content needs to be 0.001% or more. On the other hand, if the N content exceeds 0.01% and excessively contained in the weld metal, the amount of solute N in the weld metal increases and the toughness of the ferrite matrix deteriorates. Moreover, BN produces | generates excessively and the coarse grain boundary ferrite suppression by the grain boundary segregation of the said solid solution B and the toughness improvement effect by this are inhibited. For this reason, in the present invention, the upper limit of the N content in the weld metal is set to 0.01%.

Ｏ：酸素（Ｏ）は、ＴｉとＴｉ酸化物を形成し、溶接金属中のアシキュラーフェライト生成核として作用し溶接金属の微細化にするために溶接金属中に０．０１％以上含有する必要がある。しかし、それ以外には有益な効果は示さず、過剰に含有させると溶接金属の延性及び靭性を劣化させるのでＯ含有量の上限を０．０５％とした。   O: Oxygen (O) forms Ti and Ti oxide, and acts as acicular ferrite formation nuclei in the weld metal, and it is necessary to contain 0.01% or more in the weld metal in order to make the weld metal finer There is. However, other than that, no beneficial effect is shown, and if contained excessively, the ductility and toughness of the weld metal are deteriorated, so the upper limit of the O content was set to 0.05%.

Ｐ、Ｓ：Ｐ、Ｓは不可避的不純物元素であり、溶接金属中のこれらの含有量は少ないほど好ましい。本発明では、溶接金属の靭性確保の点から許容できる上限量としてＰ含有量の上限を０．０２％、Ｓ含有量の上限を０．０１％とした。   P, S: P and S are unavoidable impurity elements, and the content thereof in the weld metal is preferably as small as possible. In the present invention, the upper limit of the P content is set to 0.02% and the upper limit of the S content is set to 0.01% as the upper limit allowable from the viewpoint of ensuring the toughness of the weld metal.

以上が本発明の目的を達成するために必要とする、本発明の溶接金属の基本成分及び不可避的不純物元素の限定理由である。なお、本発明においては、上記溶接金属の基本成分の他に、さらに溶接金属の機械的特性、特に強度や靱性の調整のために、選択成分として、Ｃｕ、Ｃｒ、Ｗ、Ｎｂ、Ｖ、Ｔａの１種または２種以上を所定範囲で溶接金属中に含有させることができる。   The above is the reason for limiting the basic components and unavoidable impurity elements of the weld metal of the present invention that are necessary to achieve the object of the present invention. In the present invention, in addition to the basic components of the weld metal, Cu, Cr, W, Nb, V, and Ta are selected as optional components for adjusting the mechanical properties of the weld metal, particularly strength and toughness. 1 type or 2 types or more can be contained in a weld metal in a predetermined range.

Ｃｕ：Ｃｕは、オーステナイト安定化元素であり、溶接金属中に適正量含有させると焼入性を高めて溶接金属の高強度化、さらに、粗大粒界フェライト生成の抑制による組織微細化による靱性向上に有効である。これらの効果を発揮するためにはＣｕは０．０１％以上溶接金属中に含有させるのが好ましい。一方、溶接金属中のＣｕ含有量が１．５％を超えて過剰に含有されると、溶接金属の耐高温割れ性を劣化させ、また、溶接機金属強度が過大となって靱性も劣化するようになるため好ましくない。そのため、溶接金属中のＣｕ含有量の上限を１．５％とするのが好ましい。   Cu: Cu is an austenite stabilizing element. When an appropriate amount is contained in the weld metal, the hardenability is increased to increase the strength of the weld metal, and the toughness is improved by refining the structure by suppressing the formation of coarse grain boundary ferrite. It is effective for. In order to exert these effects, Cu is preferably contained in the weld metal in an amount of 0.01% or more. On the other hand, if the Cu content in the weld metal exceeds 1.5%, the hot crack resistance of the weld metal deteriorates, and the welder metal strength becomes excessive and the toughness also deteriorates. This is not preferable. Therefore, it is preferable that the upper limit of the Cu content in the weld metal is 1.5%.

Ｃｒ：Ｃｒは、弱いながらＭｏと類似の焼入性を高めて溶接金属組織のベイナイト化あるいはアシキュラーフェライトの微細化により靱性向上の作用を有する元素であり、かつ、固溶強化、析出強化により強度向上にも有効な元素である。この効果を得るためには、溶接金属中のＣｒ含有量は０．０１％以上とするのが好ましい。しかしながら、０．５％を超えてＣｒを溶接金属中に過剰に含有されると溶接金属を過剰に硬化させ、溶接金属の靭性を著しく劣化させるので、溶接金属中のＣｒ含有量の上限を０．５％とするのが好ましい。   Cr: Cr is an element that has the effect of improving the toughness by weakening the hardenability similar to Mo and improving the toughness by making the weld metal structure bainite or refining the acicular ferrite, but also by solid solution strengthening and precipitation strengthening. It is an effective element for improving strength. In order to obtain this effect, the Cr content in the weld metal is preferably 0.01% or more. However, if Cr is excessively contained in the weld metal exceeding 0.5%, the weld metal is excessively hardened and the toughness of the weld metal is remarkably deteriorated, so the upper limit of the Cr content in the weld metal is set to 0. .5% is preferable.

Ｗ：Ｗは、溶接金属の強度を高めるのに有効な元素であり、また、弱いながらＭｏと類似の組織微細化効果を有する。これらの効果を発揮するためには溶接金属中のＷ含有量を０．０１％とすることが好ましい。一方、０．５％を超えてＷを溶接金属中に含有させると溶接金属を過剰に硬化させ、溶接金属の靭性を著しく劣化させるので、溶接金属中のＷ含有量の上限を０．５％とするのが好ましい。   W: W is an element effective for increasing the strength of the weld metal, and has a structure refining effect similar to that of Mo although being weak. In order to exhibit these effects, the W content in the weld metal is preferably set to 0.01%. On the other hand, if W is included in the weld metal in excess of 0.5%, the weld metal is excessively cured and the toughness of the weld metal is remarkably deteriorated, so the upper limit of the W content in the weld metal is 0.5%. Is preferable.

Ｎｂ：Ｎｂは、焼入性向上効果と析出強化により溶接金属の高強度化に有効な元素である。この溶接金属の高強度化の効果を得るためには、Ｎｂは溶接金属中に０．００２％以上含有させることが好ましい。一方、０．０５％を超えてＮｂを溶接金属中に含有させると析出脆化を生じて溶接金属の靱性を著しく損ねるため、溶接金属中のＮｂ含有量の上限は０．０５％とするのが好ましい。   Nb: Nb is an element effective for increasing the strength of the weld metal due to the effect of improving hardenability and precipitation strengthening. In order to obtain the effect of increasing the strength of the weld metal, Nb is preferably contained in the weld metal by 0.002% or more. On the other hand, if Nb is contained in the weld metal in excess of 0.05%, precipitation embrittlement occurs and the toughness of the weld metal is remarkably impaired, so the upper limit of the Nb content in the weld metal is 0.05%. Is preferred.

Ｖ、Ｔａ：Ｖ、ＴａもＮｂと定性的にほぼ同様の作用を有し、溶接金属の高強度化の効果を明確に発揮するためにはＶ、Ｔａは何れも０．００５％以上含有するのが好ましい。一方、Ｖ、Ｔａは何れも０．５％を超えて溶接金属中に含有させると溶接金属の靱性劣化が大きくなるため、溶接金属中のＶ、Ｔａの含有量の上限は、いずれも０．５％とするのが好ましい。   V, Ta: V and Ta also have almost the same qualitative action as Nb, and in order to clearly demonstrate the effect of increasing the strength of the weld metal, both V and Ta contain 0.005% or more. Is preferred. On the other hand, if both V and Ta exceed 0.5% and are contained in the weld metal, the toughness deterioration of the weld metal increases, so the upper limit of the content of V and Ta in the weld metal is 0. 5% is preferable.

本発明において上記溶接金属の基本成分および選択成分の他に、溶接金属の機械的特性、特に延性、靭性を改善するために、さらに、Ｃａ、Ｍｇ、ＲＥＭの１種または２種以上を所定範囲で溶接金属中に含有させることができる。   In the present invention, in addition to the above-mentioned basic components and selected components of the weld metal, in order to improve the mechanical properties of the weld metal, particularly ductility and toughness, one or more of Ca, Mg, and REM are further added within a predetermined range. And can be contained in the weld metal.

Ｃａ、Ｍｇ、ＲＥＭ：Ｃａ、Ｍｇ、ＲＥＭはいずれも、溶接金属において硫化物の構造を変化させ、また硫化物、酸化物のサイズを微細化し、溶接金属の延性及び靭性向上に有効な元素である。   Ca, Mg, and REM: Ca, Mg, and REM are effective elements for improving the ductility and toughness of weld metal by changing the structure of sulfide in weld metal and reducing the size of sulfide and oxide. is there.

また、Ｔｉとの複合酸化物を形成して酸化物の微細化、分散密度増加を介してアシキュラーフェライト生成能を高める効果を有する。これらの効果を発揮するためには、Ｃａ、Ｍｇ、ＲＥＭのいずれも含有量を０．０００１％以上とするのが好ましい。一方、Ｃａ、Ｍｇ、ＲＥＭのいずれも０．００５％を超えて溶接金属中に過剰に含有すると、硫化物や酸化物の粗大化を生じ、溶接金属の延性、靭性の劣化を招く。また、溶接ビード形状の劣化、溶接性の劣化の可能性も生じる。このため、Ｃａ、Ｍｇ、ＲＥＭの含有量の上限はいずれも上０．００５％とするのが好ましい。   Moreover, it has the effect of forming a complex oxide with Ti and increasing the acicular ferrite forming ability through refinement of the oxide and increase in the dispersion density. In order to exhibit these effects, it is preferable that the content of Ca, Mg, and REM is 0.0001% or more. On the other hand, if any of Ca, Mg, and REM exceeds 0.005% and is contained excessively in the weld metal, the sulfide and oxide are coarsened and the ductility and toughness of the weld metal are deteriorated. In addition, there is a possibility of deterioration of the weld bead shape and weldability. For this reason, it is preferable that the upper limit of Ca, Mg, and REM content is 0.005%.

以下に、実施例により本発明の効果を説明する。   The effects of the present invention will be described below with reference to examples.

図２に示すように予め鋼板端部に開先加工した表１に示す板厚と成分組成の鋼板を突合せて継手を形成し、この開先部を表２に示す成分組成の焼成型フラックスと、表３に示す成分組成の溶接ワイヤを用いて、表４に示す溶接条件で１パス、入熱５６１ＫＪ／ｃｍでの大入熱サブマージアーク溶接を行った。その後、溶接継手において、図２に示す溶接部中央の鋼板表面下７ｍｍ、板厚中心部、裏面上７ｍｍの３箇所から２ｍｍＶノッチシャルピー衝撃試験片を採取し、機械試験を実施した。溶接金属の靭性は０℃におけるシャルピー衝撃試験を行い、各々繰返し数：３本の測定値の平均値で評価した。なお、表１において、鋼板１〜９が本発明範囲内の化学組成を有する鋼板、鋼板１０〜１４が本発明範囲から外れる化学組成を有する鋼板である。また、表２において、フラックス１〜１０が本発明範囲内の化学組成を有するフラックスであり、フラックス１１〜１５が本発明の範囲外の化学組成を有するフラックスである。さらに、表３において、ワイヤ１〜９が本発明範囲内の化学組成を有するワイヤ、鋼板１０〜１６が本発明範囲から外れる化学組成を有するワイヤである。   As shown in FIG. 2, a joint is formed by abutting the plate thickness shown in Table 1 on the end of the steel plate in advance with the steel plate having the component composition shown in FIG. Using the welding wires having the component compositions shown in Table 3, one-pass, large heat input submerged arc welding was performed at a heat input of 561 KJ / cm under the welding conditions shown in Table 4. Thereafter, in the welded joint, 2 mm V-notch Charpy impact test specimens were collected from three locations, 7 mm below the surface of the steel sheet at the center of the welded portion shown in FIG. The toughness of the weld metal was evaluated by a Charpy impact test at 0 ° C., and the number of repetitions: the average value of three measured values. In Table 1, steel plates 1 to 9 are steel plates having a chemical composition within the range of the present invention, and steel plates 10 to 14 are steel plates having a chemical composition outside the range of the present invention. In Table 2, fluxes 1 to 10 are fluxes having a chemical composition within the scope of the present invention, and fluxes 11 to 15 are fluxes having a chemical composition outside the scope of the present invention. Furthermore, in Table 3, wires 1-9 are wires having a chemical composition within the scope of the present invention, and steel plates 10-16 are wires having a chemical composition outside the scope of the present invention.

表５は各鋼板、フラックス、溶接ワイヤを用いて作製した溶接継手における溶接金属の化学組成と靱性値を示す。表５の中で継手Ａ１〜Ａ２４は鋼板、フラックスおよび溶接ワイヤが発明で規定する成分組成の範囲を満足するため、サブマージアーク溶接で得られた溶接金属の各成分組成も本発明で規定する範囲内である発明例を示す。また、継手Ｂ１〜Ｂ１７は鋼板、フラックスおよび溶接ワイヤの少なくともいずれかが発明で規定する成分組成の範囲から外れているため、その結果、サブマージアーク溶接で得られた溶接金属の各成分組成も本発明で規定する範囲から外れた比較例を示す。   Table 5 shows the chemical composition and toughness value of the weld metal in a welded joint produced using each steel plate, flux, and welding wire. In Table 5, since the joints A1 to A24 satisfy the range of the component composition specified by the invention for the steel plate, the flux and the welding wire, the range of each component composition of the weld metal obtained by submerged arc welding is also specified by the present invention. The invention example which is inside is shown. Further, since at least one of the steel plate, the flux, and the welding wire is out of the range of the component composition specified in the invention, the joints B1 to B17 are also each of the component compositions of the weld metal obtained by the submerged arc welding. The comparative example which deviated from the range prescribed | regulated by invention is shown.

表５に示すとおり、継手Ａ１〜Ａ２４の本発明例はいずれも、溶接金属の靱性が溶接金属の表面下７ｍｍから裏面上７ｍｍの全厚み範囲にわたって安定的に１７０Ｊ以上の吸収エネルギーが得られ、極めて良好な溶接金属靱性を達成した。   As shown in Table 5, in all of the inventive examples of the joints A1 to A24, the toughness of the weld metal stably obtained an absorbed energy of 170 J or more over the entire thickness range from 7 mm below the surface of the weld metal to 7 mm above the back surface. Very good weld metal toughness was achieved.

一方、継手Ｂ１〜Ｂ１７の比較例では、本発明で規定する要件の少なくとも何れかを満足していないために、溶接金属の靱性が劣るか、あるいは、厚み方向の特定測定位置では比較的良好な靱性が得られても、厚み方向の別の測定位置では極端に靱性が劣る、すなわち、溶接金属の厚み方向で均一な高靱性が得られない結果となった。   On the other hand, in the comparative examples of the joints B1 to B17, since at least one of the requirements defined in the present invention is not satisfied, the toughness of the weld metal is inferior, or is relatively good at a specific measurement position in the thickness direction. Even if toughness was obtained, the toughness was extremely poor at another measurement position in the thickness direction, that is, a uniform high toughness was not obtained in the thickness direction of the weld metal.

すなわち、継手Ｂ１は、鋼板のＣ量が過大であるために、溶接金属のＣ量も過大で、溶接金属の硬さが過剰となり、かつ、靭性に有害な粗大なセメンタイト（Ｆｅ３Ｃ）や島状マルテンサイトが多く生成するため、溶接金属の靱性が溶接金属の位置によらず劣る。   That is, in the joint B1, since the C amount of the steel plate is excessive, the C amount of the weld metal is also excessive, the hardness of the weld metal is excessive, and coarse cementite (Fe3C) or island-like that is harmful to toughness. Since a lot of martensite is generated, the toughness of the weld metal is inferior regardless of the position of the weld metal.

継手Ｂ２は、鋼板のＢ量が過大であるために、溶接金属のＢ量も過大で、溶接金属の焼入性が過剰になって強度が過大になり、また粗大な析出物が形成されるため、溶接金属の靱性が溶接金属の位置によらず劣る。   In the joint B2, since the B amount of the steel plate is excessive, the B amount of the weld metal is also excessive, the hardenability of the weld metal is excessive, the strength is excessive, and coarse precipitates are formed. Therefore, the toughness of the weld metal is inferior regardless of the position of the weld metal.

継手Ｂ３は、鋼板のＰ量が過大であるために、溶接金属のＰ量も過大で、そのため、溶接金属の靱性が溶接金属の位置によらず劣る。   In the joint B3, since the P amount of the steel plate is excessive, the P amount of the weld metal is also excessive. Therefore, the toughness of the weld metal is inferior regardless of the position of the weld metal.

継手Ｂ４は、鋼板のＳ量が過大であるために、溶接金属のＳ量も過大で、そのため、溶接金属の靱性が溶接金属の位置によらず劣る。   In the joint B4, since the S amount of the steel plate is excessive, the S amount of the weld metal is also excessive, so that the toughness of the weld metal is inferior regardless of the position of the weld metal.

継手Ｂ５は、鋼板のＮ量が過大であるために、溶接金属のＮ量も過大で、そのため、固溶Ｂ量が確保できず、合金組成の調整により表面下７ｍｍでは良好な靱性が得られているものの、板厚中心部から裏面上７ｍｍでは組織微細化が十分でなく、表面下７ｍｍに比べて靱性が大きく劣化している。すなわち、溶接金属全体で高靱性を達成する目的からは不十分な達成レベルとなっている。   In the joint B5, since the N amount of the steel sheet is excessive, the N amount of the weld metal is also excessive. Therefore, the solid solution B amount cannot be secured, and good toughness can be obtained at 7 mm below the surface by adjusting the alloy composition. However, when the thickness is 7 mm from the center of the plate thickness on the back surface, the structure is not sufficiently refined, and the toughness is greatly deteriorated as compared with 7 mm below the surface. That is, it is an insufficient achievement level for the purpose of achieving high toughness in the entire weld metal.

継手Ｂ６は、フラックスの組成のうち、Ｂ２Ｏ３が含有されていないため、溶接金属中のＢ量が過小となり、そのため、溶接金属組織において、アシキュラーフェライトの生成が十分でなく、また、粒界フェライトの抑制効果が不十分なため、本発明に比べて全体的に靱性は低位であり、かつ、粒界フェライト生成挙動の冷却速度依存性が大きいために、表面下７ｍｍと裏面上７ｍｍとの靱性差も大きく、好ましくない。   Since the joint B6 does not contain B2O3 in the flux composition, the amount of B in the weld metal is too small. Therefore, in the weld metal structure, the generation of acicular ferrite is not sufficient, and the grain boundary ferrite The toughness is low as compared with the present invention and the toughness of the grain boundary ferrite formation behavior is largely dependent on the cooling rate. The difference is also large and undesirable.

継手Ｂ７は、フラックスの組成のうち、Ｂ２Ｏ３が過剰に含有されているため、溶接金属中のＢ量も過大となり、溶接金属の焼入性が過剰になって強度が過大になり、また粗大な析出物が形成されるため、溶接金属の靱性が溶接金属の位置によらず劣る。   In the joint B7, since B2O3 is excessively contained in the flux composition, the amount of B in the weld metal is excessive, the hardenability of the weld metal is excessive, the strength is excessive, and the joint is coarse. Since precipitates are formed, the toughness of the weld metal is inferior regardless of the position of the weld metal.

継手Ｂ８は、フラックス中のＭｏ量が過大であるために、溶接金属中のＭｏ量も過大となり、そのため、溶接金属が過剰に硬化するため、溶接金属の靭性劣化が著しい。   In the joint B8, since the amount of Mo in the flux is excessive, the amount of Mo in the weld metal also becomes excessive. Therefore, the weld metal is hardened excessively, and thus the toughness of the weld metal is significantly deteriorated.

継手Ｂ９は、Ｍｏに加えてＮｉもフラックス中の含有量が過大であるため、溶接金属中のＭｏ、Ｎｉ量とも過大となり、その結果、溶接金属強度が過度に高くなり、溶接金属の靭性劣化が著しい。   In the joint B9, since the content of Ni in the flux in addition to Mo is excessive, both the amount of Mo and Ni in the weld metal are excessive. As a result, the weld metal strength is excessively increased, and the toughness of the weld metal is deteriorated. Is remarkable.

継手Ｂ１０は、フラックス中のＴｉＯ２量が過大なため、ビード止端部の立ち上がり角度が大きくなってビード形状を悪化させて好ましくない、また、溶接金属の靱性も位置によらず劣化している。   In the joint B10, since the amount of TiO2 in the flux is excessive, the rising angle of the bead toe portion is increased to deteriorate the bead shape, and the toughness of the weld metal is also deteriorated regardless of the position.

継手Ｂ１１は、溶接ワイヤのＣ含有量が過大であるため、溶接金属のＣ量も過大で、溶接金属の硬さが過剰となり、かつ、靭性に有害な粗大なセメンタイト（Ｆｅ３Ｃ）や島状マルテンサイトが多く生成するため、溶接金属の靱性が溶接金属の位置によらず劣る。   In the joint B11, since the C content of the welding wire is excessive, the C amount of the weld metal is excessive, the hardness of the weld metal is excessive, and coarse cementite (Fe3C) or island martens which are harmful to toughness. Since many sites are generated, the toughness of the weld metal is inferior regardless of the position of the weld metal.

継手Ｂ１２は、溶接ワイヤのＮｉ、Ｍｏ含有量が過小なために、溶接金属中のＮｉ、Ｍｏ量が過小となり、そのため、靱性レベルが若干劣るとともに、粒界フェライト生成の冷却速度依存性が抑制されておらず、そのため、溶接金属中の靱性変動が大きく、特に裏面上７ｍｍの靱性劣化が著しく、好ましくない。   In the joint B12, since the Ni and Mo contents of the welding wire are too small, the amounts of Ni and Mo in the weld metal are too small. Therefore, the toughness level is slightly inferior and the dependency on the cooling rate of the formation of grain boundary ferrite is suppressed. For this reason, the toughness variation in the weld metal is large, and the toughness deterioration particularly on the back surface of 7 mm is remarkable, which is not preferable.

継手Ｂ１３は、溶接ワイヤのＮ含有量が過大なために溶接金属中のＮ含有量も過大となり、そのため、固溶Ｂ量が確保できず、靱性変動が大きく、特に裏面上７ｍｍの靱性が著しく劣る。   In the joint B13, since the N content of the welding wire is excessive, the N content in the weld metal is also excessive. Therefore, the amount of solute B cannot be secured, the toughness fluctuation is large, and particularly the toughness of 7 mm on the back surface is remarkable. Inferior.

継手Ｂ１４は、溶接ワイヤのＰ量が過大であるために、溶接金属のＰ量も過大で、そのため、溶接金属の靱性が溶接金属の位置によらず劣る。   In the joint B14, since the P amount of the welding wire is excessive, the P amount of the weld metal is also excessive. Therefore, the toughness of the weld metal is inferior regardless of the position of the weld metal.

継手Ｂ１５は、溶接ワイヤのＭｏ含有量が過大であるために、溶接金属中のＭｏ量も過大となり、そのため、溶接金属が過剰に硬化するため、溶接金属の靭性劣化が著しい。   In the joint B15, since the Mo content in the welding wire is excessive, the amount of Mo in the weld metal also becomes excessive. Therefore, the weld metal is hardened excessively, so that the toughness of the weld metal is significantly deteriorated.

継手Ｂ１６は、溶接ワイヤのＴｉ含有量が過小であるため、溶接金属組織のアシキュラーフェライト生成が十分でなく、組織が粗大となる。そのため、靱性が溶接金属位置によらず大きく劣る。   In the joint B16, since the Ti content of the welding wire is excessively small, the generation of acicular ferrite in the weld metal structure is not sufficient, and the structure becomes coarse. Therefore, the toughness is greatly inferior regardless of the position of the weld metal.

継手Ｂ１７は、溶接ワイヤのＢ含有量が過大であるため、溶接金属中のＢ量も過大となり、そのため、溶接金属が過剰に硬化するため、溶接金属の靭性劣化が著しい。   In the joint B17, since the B content of the welding wire is excessive, the amount of B in the weld metal also becomes excessive. As a result, the weld metal is hardened excessively, so that the toughness of the weld metal is significantly deteriorated.

以上の実施例の結果から、本発明によれば、板厚が５０ｍｍ以上の鋼板を４００ｋＪ／ｃｍ以上の溶接入熱で片面１パスの大入熱サブマージアーク溶接する際に、溶接金属の表面側から裏面側までの全厚み範囲にわたって均一にかつ２ｍｍＶノッチシャルピー吸収エネルギーで１００Ｊ以上の優れた靭性が得られることは明らかである。   From the results of the above examples, according to the present invention, when a steel sheet having a thickness of 50 mm or more is welded with a heat input of 400 kJ / cm or more and one-side high-pass submerged arc welding on one side, the surface side of the weld metal It is clear that excellent toughness of 100 J or more can be obtained uniformly over the entire thickness range from the back surface to the back surface with 2 mmV notch Charpy absorbed energy.

Figure 0004427416
Figure 0004427416

Figure 0004427416
Figure 0004427416

Figure 0004427416
Figure 0004427416

Figure 0004427416
Figure 0004427416

Figure 0004427416
Figure 0004427416

片面１パス大入熱サブマージアーク溶接における靱性分布と溶接金属組成との関係を模式的に示す図である。It is a figure which shows typically the relationship between the toughness distribution and weld metal composition in single-sided one-pass large heat input submerged arc welding. 本発明の実施例に用いた溶接開先形状と２ｍｍＶノッチシャルピー衝撃試験片の採取位置、方向を示す図である。It is a figure which shows the collection position and direction of the welding groove shape used for the Example of this invention, and a 2 mmV notch Charpy impact test piece.

Claims (9)

板厚が５０ｍｍ以上の鋼板を４００ｋＪ／ｃｍ以上の溶接入熱で片面１パス溶接するサブマージアーク溶接方法において、質量％で、Ｃ ：０．０２〜０．２％、Ｓｉ：０．０１〜１％、Ｍｎ：０．１〜２．５％、Ａｌ：０．００２〜０．１％、Ｎ：０．００１〜０．０１５％を含有し、Ｐ：０．０２％以下、Ｓ：０．０１％以下、Ｏ：０．０１％以下に制限し、残部がＦｅ及び不可避不純物からなる鋼板を、質量％で、ＳｉＯ２：１０〜２５％、ＭｇＯ：５〜２０％、ＣａＯ：５〜１５％、ＣａＦ２：１〜１０％、Ａｌ２Ｏ３：５〜２５％、ＴｉＯ２：２〜２０％、Ｆｅ：１０〜２５％、Ｂ２Ｏ３：０．６１％〜２．５％を含有するフラックスと、質量％で、Ｃ：０．０２〜０．２％、Ｓｉ：０．０１〜１％、Ｍｎ：０．５〜２．５％、Ｍｏ：０．１〜３％、Ｎｉ：１〜６％、Ａｌ：０．００２〜０．１％、Ｔｉ：０．００５〜０．３％、Ｎ：０．００１〜０．０１５％含有し、Ｐ：０．０２％以下、Ｓ：０．０１％以下、Ｏ：０．０１％以下に制限し、残部がＦｅ及び不可避不純物からなる溶接ワイヤを用いてサブマージアーク溶接することを特徴とする溶接金属の靱性に優れた大入熱サブマージアーク溶接方法。 In a submerged arc welding method in which a steel plate having a thickness of 50 mm or more is welded on one side by one pass with a welding heat input of 400 kJ / cm or more, C: 0.02 to 0.2%, Si: 0.01 to 1 in mass%. %, Mn: 0.1 to 2.5%, Al: 0.002 to 0.1%, N: 0.001 to 0.015%, P: 0.02% or less, S: 0.0. 0.1% or less, O: limited to 0.01% or less, the steel sheet balance of Fe and inevitable impurities, in mass%, SiO 2: 10~25%, MgO: 5~20%, CaO: 5~15 %, CaF 2: 1~10%, Al 2 O 3: 5~25%, TiO 2: 2~20%, Fe: 10~25%, B 2 O 3: 0.61% to 2.5% The flux and the mass%, C: 0.02-0.2%, Si: 0.01-1%, Mn: 0.5-2. %, Mo: 0.1-3%, Ni: 1-6%, Al: 0.002-0.1%, Ti: 0.005-0.3%, N: 0.001-0.015% It is contained, P: 0.02% or less, S: 0.01% or less, O: 0.01% or less, submerged arc welding using a welding wire consisting of Fe and inevitable impurities as the remainder Large heat input submerged arc welding method with excellent toughness of weld metal. 前記サブマージアーク溶接によって、質量％で、Ｃ：０．０３〜０．２％、Ｓｉ：０．１〜１％、Ｍｎ：０．７〜２％、Ａｌ：０．００１〜０．０７％、Ｍｏ：０．１〜１％、Ｎｉ：０．７５〜３％、Ｔｉ：０．００５〜０．１％、Ｂ：０．００１〜０．０１％、Ｎ：０．００１〜０．０１％、Ｏ：０．０１〜０．０５％を含有し、Ｐ：０．０２％以下、Ｓ：０．０１％以下に制限した溶接金属を形成することを特徴とする請求項１記載の溶接金属の靱性に優れた大入熱サブマージアーク溶接方法。   By the submerged arc welding, C: 0.03-0.2%, Si: 0.1-1%, Mn: 0.7-2%, Al: 0.001-0.07% by mass% Mo: 0.1 to 1%, Ni: 0.75 to 3%, Ti: 0.005 to 0.1%, B: 0.001 to 0.01%, N: 0.001 to 0.01% The weld metal according to claim 1, wherein the weld metal contains O: 0.01 to 0.05%, P: 0.02% or less, and S: 0.01% or less. Large heat input submerged arc welding method with excellent toughness. 前記鋼板が、質量％で、さらに、Ｔｉ：０．００２〜０．０５％、Ｂ：０．０００３〜０．０１５％、Ｍｏ：０．０１〜１．５％、Ｎｉ：０．０１〜６％、Ｃｒ：０．０１〜１．５％、Ｗ：０．０１〜１．５％、Ｃｕ：０．０１〜１．５％、Ｎｂ：０．００２〜０．１％、Ｖ：０．００２〜０．５％、および、Ｔａ：０．００２〜０．５％の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または２に記載の溶接金属の靱性に優れた大入熱サブマージアーク溶接方法。   The said steel plate is the mass%, and also Ti: 0.002-0.05%, B: 0.0003-0.015%, Mo: 0.01-1.5%, Ni: 0.01-6 %, Cr: 0.01 to 1.5%, W: 0.01 to 1.5%, Cu: 0.01 to 1.5%, Nb: 0.002 to 0.1%, V: 0.00. It has one or more of 002 to 0.5% and Ta: 0.002 to 0.5%, and has high toughness of weld metal according to claim 1 or 2. Heat input submerged arc welding method. 上記フラックスが、質量％で、さらに、Ｍｏ：１〜５％、および、Ｎｉ：１〜５％の１種または２種を含有することを特徴とする請求項１〜３の何れかに記載の溶接金属の靱性に優れた大入熱サブマージアーク溶接方法。   The said flux contains the 1 type (s) or 2 types of Mo: 1-5% and Ni: 1-5% by the mass%, The any one of Claims 1-3 characterized by the above-mentioned. Large heat input submerged arc welding method with excellent weld metal toughness. 上記溶接ワイヤが、質量％で、さらに、Ｃｕ：０．０１〜１．５％、Ｃｒ：０．０１〜１．５％、Ｗ：０．０１〜２％、Ｎｂ：０．００２〜０．０５％、Ｖ：０．００５〜０．５％、Ｔａ：０．００２〜０．２％、および、Ｂ：０．００１〜０．０５％の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１〜４の何れかに記載の溶接金属の靱性に優れた大入熱サブマージアーク溶接方法。   The said welding wire is the mass%, and also Cu: 0.01-1.5%, Cr: 0.01-1.5%, W: 0.01-2%, Nb: 0.002-0. It contains one or more of 05%, V: 0.005 to 0.5%, Ta: 0.002 to 0.2%, and B: 0.001 to 0.05%. A high heat input submerged arc welding method excellent in toughness of the weld metal according to any one of claims 1 to 4. 前記溶接金属がサブマージアーク溶接によって、質量％で、Ｃ：０．０３〜０．２％、Ｓｉ：０．１〜１％、Ｍｎ：０．７〜２％、Ａｌ：０．００１〜０．０７％、Ｍｏ：０．１〜１％、Ｎｉ：０．７５〜３％、Ｔｉ：０．００５〜０．１％、Ｂ：０．００１〜０．０１％、Ｎ：０．００１〜０．０１％、Ｏ：０．０１〜０．０５％を含有し、Ｐ：０．０２％以下、Ｓ：０．０１％以下に制限し、さらに、Ｃｕ：０．０１〜１．５％、Ｃｒ：０．０１〜０．５％、Ｗ：０．０１〜０．５％、Ｎｂ：０．００２〜０．０５％、Ｖ：０．００５〜０．５％、および、Ｔａ：０．００５〜０．５％の１種または２種以上を含有した溶接金属を形成することを特徴とする請求項３〜５の何れかに記載の溶接金属の靱性に優れた大入熱サブマージアーク溶接方法。   The weld metal is obtained by submerged arc welding in mass%, C: 0.03 to 0.2%, Si: 0.1 to 1%, Mn: 0.7 to 2%, Al: 0.001 to 0.00. 07%, Mo: 0.1 to 1%, Ni: 0.75 to 3%, Ti: 0.005 to 0.1%, B: 0.001 to 0.01%, N: 0.001 to 0 0.01%, O: 0.01 to 0.05%, P: 0.02% or less, S: 0.01% or less, further Cu: 0.01 to 1.5%, Cr: 0.01-0.5%, W: 0.01-0.5%, Nb: 0.002-0.05%, V: 0.005-0.5%, and Ta: 0.0. A high heat input submerged arc excellent in weld metal toughness according to any one of claims 3 to 5, wherein a weld metal containing one or more of 005 to 0.5% is formed. Contact method. 前記鋼板が、質量％で、さらに、Ｃａ、ＭｇおよびＲＥＭの１種または２種以上を０．０００２〜０．０１％含有することを特徴とする請求項１〜６の何れかに記載の溶接金属の靱性に優れた大入熱サブマージアーク溶接方法。   The welding according to any one of claims 1 to 6, wherein the steel sheet further contains 0.0002 to 0.01% of one or more of Ca, Mg, and REM in mass%. Large heat input submerged arc welding method with excellent metal toughness. 上記溶接ワイヤが、質量％で、さらに、Ｃａ、ＭｇおよびＲＥＭの１種または２種以上を０．０００２〜０．０１％含有することを特徴とする請求項１〜７の何れかに記載の溶接金属の靱性に優れた大入熱サブマージアーク溶接方法。   8. The welding wire according to claim 1, wherein the welding wire further contains 0.0002 to 0.01% of one or more of Ca, Mg, and REM in mass%. Large heat input submerged arc welding method with excellent weld metal toughness. 前記溶接金属がサブマージアーク溶接によって、質量％で、Ｃ：０．０３〜０．２％、Ｓｉ：０．１〜１％、Ｍｎ：０．７〜２％、Ａｌ：０．００１〜０．０７％、Ｍｏ：０．１〜１％、Ｎｉ：０．７５〜３％、Ｔｉ：０．００５〜０．１％、Ｂ：０．００１〜０．０１％、Ｎ：０．００１〜０．０１％、Ｏ：０．０１〜０．０５％を含有し、Ｐ：０．０２％以下、Ｓ：０．０１％以下に制限し、Ｃｕ：０．０１〜１．５％、Ｃｒ：０．０１〜０．５％、Ｗ：０．０１〜０．５％、Ｎｂ：０．００２〜０．０５％、Ｖ：０．００５〜０．５％、および、Ｔａ：０．００５〜０．５％の１種または２種以上を含有し、さらに、Ｃａ、ＭｇおよびＲＥＭの１種または２種以上を０．０００１〜０．００５％含有した溶接金属を形成することを特徴とする請求項７または８に記載の溶接金属の靱性に優れた大入熱サブマージアーク溶接方法。   The weld metal is obtained by submerged arc welding in mass%, C: 0.03 to 0.2%, Si: 0.1 to 1%, Mn: 0.7 to 2%, Al: 0.001 to 0.00. 07%, Mo: 0.1 to 1%, Ni: 0.75 to 3%, Ti: 0.005 to 0.1%, B: 0.001 to 0.01%, N: 0.001 to 0 0.01%, O: 0.01 to 0.05%, P: 0.02% or less, S: 0.01% or less, Cu: 0.01 to 1.5%, Cr: 0.01 to 0.5%, W: 0.01 to 0.5%, Nb: 0.002 to 0.05%, V: 0.005 to 0.5%, and Ta: 0.005 It is characterized by forming a weld metal containing 0.5% of one or more, and further containing 0.0001 to 0.005% of one or more of Ca, Mg and REM. Excellent high heat input submerged arc welding method in toughness of the weld metal according to claim 7 or 8.
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