JP4673710B2 - Two-electrode single-sided one-pass large heat input submerged arc welding method with excellent weld metal toughness - Google Patents
Two-electrode single-sided one-pass large heat input submerged arc welding method with excellent weld metal toughness Download PDFInfo
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本発明は、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2電極片面1パス大入熱サブマージアーク溶接方法に関する。 The present invention relates to a high 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 more particularly, a weld metal having good toughness. The present invention relates to a two-electrode single-sided one-pass large heat input submerged arc welding method of a high-tensile steel plate from which high temperature steel 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。とりわけ、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 become extremely large from the viewpoint of preventing brittle fracture during an earthquake.
近年の建築構造物の大型化にともない、板厚が40mm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、1〜2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、溶接金属の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 the size of building structures, when manufacturing box columns by welding thick steel plates with a thickness of 40 mm or more, one-sided large pass using one or two electrodes to improve the welding efficiency The application of heat input submerged arc welding is increasing. In such a large heat input submerged arc welding of such 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, austenite (γ ) Coarse pro-eutectoid ferrite (α) harmful to toughness tends to be generated from the grain boundary, resulting in a problem that 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(以下、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。 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 (hereinafter also referred to as the weld back side) where the molten metal first solidifies in the thickness range of the weld metal 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.
一般に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、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 general, as a method to ensure weld metal toughness during welding with relatively high heat input, it is known to refine the structure by adding a lot of alloying elements to the weld metal using a welding material to improve hardenability. ing.
しかし、板厚が40mm以上の厚鋼板を溶接入熱が400kJ/cm以上で片面1パス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 a thick steel plate having a thickness of 40 mm or more is welded with a heat input of 400 kJ / cm or more and single-sided one-pass submerged welding, 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電極以上の多電極サブマージアーク溶接方法を用い、板厚が40mm以上の厚鋼を溶接する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 obtained when using a multi-electrode submerged arc welding method with two or more electrodes and welding a thick steel with a plate thickness of 40 mm or more. Problems are likely 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、ボンドフラックス及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入性を向上し、溶接金属靭性を改善する方法が提案されている(例えば、特許文献1参照)。 Conventionally, as a method of improving weld metal toughness at the time of submerged arc welding with large heat input for box column corner joints, bond flux and welding wire are used, and hardenability is improved by combined addition of Ti, B, and Mo in the weld metal. And the method of improving weld metal toughness is proposed (for example, refer patent document 1).
しかし、この方法により溶接金属の靭性は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、70J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 70 J or more.
また、従来から、大入熱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極めて入熱量の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、粒内に微細なアシキュラーフェライトを生成させても粗大な粒界フェライトが靭性に支配的な影響を及ぼすため、十分な靭性改善は得られ難いという問題もある。 In addition, a method has been conventionally known in which Ti is added to a weld metal during high heat input welding to produce Ti oxide, and fine acicular ferrite is produced using this as a core to make the weld metal tough. It has been. However, in a welding method with a very large heat input, such as a large heat input submerged arc welding of a box column corner joint, 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 large amount of intergranular ferrite is generated in the weld metal, and it is easy to coarsen. Therefore, even if fine acicular ferrite is generated in the grains, coarse grains are produced. There is also a problem that it is difficult to obtain sufficient toughness improvement because the boundary ferrite has a dominant influence on the toughness.
また、最近では、溶接金属の凝固後に生成される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、その結果として溶接金属の変態組織を微細化させて靭性を向上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40mm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, there is also a technology that stabilizes the δ ferrite phase generated after solidification of the weld metal to refine the solidified austenite grain size and, as a result, refines the transformation structure of the weld metal to improve toughness. It has been proposed (see, for example, Patent Document 2). However, in 1-pass large heat input submerged arc welding of a thick steel plate having a thickness of 40 mm or more, it is difficult to make the entire weld metal uniform and tough.
以上のように、溶接材料の工夫により溶接金属組織改善を通して溶接金属の靭性向上を図る従来技術には限界があり、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十分に改善することは困難である。従って、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新しい技術が望まれている。 As described above, there is a limit to the conventional technology for improving the toughness of the weld metal by improving the weld metal structure by devising the weld material, and the toughness variation in the weld metal thickness range during one-pass large heat input submerged arc welding of thick steel plates It is difficult to improve sufficiently. Therefore, there is a demand for a new technique for uniformly improving the toughness not only in the weld metal center portion but also in the entire thickness range from the front surface side to the back surface side of the weld metal in one-pass large heat input submerged arc welding of thick steel plates.
本発明は、上記の従来技術の問題点に鑑みて、板厚が40mm以上、引張強度が490MPa級以上の厚手高張力鋼板を溶接入熱が400kJ/cm以上での2電極片面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70J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 high-strength steel plate having a thickness of 40 mm or more and a tensile strength of 490 MPa class or more. To provide a welding method in which the toughness is uniform over the entire thickness range from the front surface side to the back surface side of the weld metal during thermal submerged arc welding, and a high toughness with a 2 mmV notch Charpy absorbed energy at 0 ° C. of 70 J or more is obtained. Objective.
前記課題を解決するため、本発明者らは、溶接材料による溶接金属組成の最適化をベースとした上で、通常、厚手鋼板における2電極片面1パスサブマージアーク溶接では不可避的に生じる溶接金属の溶接表面側と裏面側との間の温度履歴の差を溶接条件によって可能な限り小さくし、溶接金属の合金成分の含有量を過度に高めずに、溶接金属の表面側から裏面側にわたって均一に高靭性が得られる新たな方法を考究した。 In order to solve the above-mentioned problems, the inventors of the present invention based on the optimization of the weld metal composition by the welding material, and usually the weld metal that inevitably occurs in the two-electrode single-sided one-pass submerged arc welding on the thick steel plate. The difference in temperature history between the welding surface side and the back surface side is made as small as possible depending on the welding conditions, and it is uniform from the surface side to the back side of the weld metal without excessively increasing the alloy content of the weld metal. A new method for obtaining high toughness was studied.
その結果、2電極片面1パスサブマージアーク溶接に用いる溶接ワイヤとフラックスの組成を適正範囲とした上で、第1電極(先行極)と第2電極(後行極)の溶接ワイヤの直径とその断面積の比率を適正化することによって、溶接金属裏側の冷却速度を制御し、高温割れを回避しつつ、裏面側の冷却速度をほぼ表面側と同程度にすることが可能となることを知見した。 As a result, the welding wire used for two-electrode single-sided one-pass submerged arc welding and the composition of the flux are within an appropriate range, and the welding wire diameter of the first electrode (leading electrode) and the second electrode (following electrode) and its Knowledge that the ratio of the cross-sectional area can be optimized to control the cooling rate on the back side of the weld metal and avoid high-temperature cracking, while making the cooling rate on the back side almost the same as that on the front side. did.
本発明はかかる新知見に基づいて発明されたものであり、その発明の要旨とするところは以下の通りである。 The present invention has been invented based on such new findings, and the gist of the invention is as follows.
(1)板厚が40mm以上の鋼板を2電極サブマージアーク溶接で片面1パス溶接するに際して、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%、
B2O3:0.1%〜2.5%からなるフラックスと、
質量%で、
C:0.02〜0.2%、
Si:0.01〜1%、
Mn:0.5〜2.5%、
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第1電極および第2電極の溶接ワイヤを用い、第2電極の溶接ワイヤの直径が6〜8mmであり、かつ第2電極の溶接ワイヤの断面積に対する第1電極の溶接ワイヤの断面積の比率が35〜75%である条件で溶接することを特徴とする溶接金属の靱性に優れた2電極片面1パス大入熱サブマージアーク溶接方法。
(1) When a steel plate having a thickness of 40 mm or more is subjected to one-pass one-pass welding by two-electrode submerged arc welding,
C: 0.02 to 0.2%,
Si: 0.01 to 1%,
Mn: 0.1 to 2.5%
Al: 0.002 to 0.1%,
N: 0.001 to 0.015% is contained,
P: 0.02% or less,
S: 0.01% or less,
O: limited to 0.01% or less,
A steel plate with the balance being Fe and inevitable impurities,
% By mass
SiO 2 : 10 to 25%,
MgO: 5 to 20%,
CaO: 5 to 15%,
CaF 2 : 1 to 10%,
Al 2 O 3 : 5 to 25%,
TiO 2 : 2 to 20%,
Fe: 10 to 25%,
B 2 O 3 : a flux composed of 0.1% to 2.5%,
% By mass
C: 0.02 to 0.2%,
Si: 0.01 to 1%,
Mn: 0.5 to 2.5%
Al: 0.002 to 0.1%,
Ti: 0.005 to 0.3%,
N: 0.001 to 0.015% contained,
P: 0.02% or less,
S: 0.01% or less,
O: Limiting to 0.01% or less, using the welding wire of the first electrode and the second electrode, the balance being Fe and inevitable impurities, the diameter of the welding wire of the second electrode is 6 to 8 mm, and the second Welding is performed under the condition that the ratio of the cross-sectional area of the welding wire of the first electrode to the cross-sectional area of the welding wire of the electrode is 35 to 75%. Submerged arc welding method.
(2)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%、
Ni:0.01〜6%、
Cu:0.01〜1.5%、
Nb:0.002〜0.1%、
V:0.002〜0.5%、及び、
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前記(1)に記載の溶接金属の靱性に優れた2電極片面1パス大入熱サブマージアーク溶接方法。
(2) The steel sheet is mass%,
Ti: 0.002 to 0.05%,
B: 0.0003 to 0.015%,
Mo: 0.01 to 1.5%,
Cr: 0.01 to 1.5%
W: 0.01 to 1.5%
Ni: 0.01-6%,
Cu: 0.01 to 1.5%,
Nb: 0.002 to 0.1%,
V: 0.002-0.5% and
Ta: 0.002 to 0.5% of one type or two or more types, the two-electrode single-sided one-pass high-heat-input submerged arc welding excellent in toughness of the weld metal according to (1) above Method.
(3)前記鋼板が、質量%で、さらに、
Ca:0.0002〜0.01%
Mg:0.0002〜0.01%、及び、
REM:0.0002〜0.01%の1種または2種以上を含有することを特徴とする前記(1)または(2)に記載の溶接金属の靱性に優れた2電極片面1パス大入熱サブマージアーク溶接方法。
(3) The steel sheet is in mass%, and
Ca: 0.0002 to 0.01%
Mg: 0.0002 to 0.01%, and
REM: 0.0002 to 0.01% of 1 type or 2 types or more, 2 electrode single sided 1 pass large insertion with excellent toughness of weld metal according to (1) or (2) Thermal submerged arc welding method.
(4)前記フラックスが、質量%で、さらに、
Mo:1〜5%、及び、
Ni:1〜5%の1種または2種を含有することを特徴とする前記(1)〜(3)の何れかに記載の溶接金属の靱性に優れた2電極片面1パス大入熱サブマージアーク溶接方法。
(4) The flux is mass%,
Mo: 1-5%, and
Ni: 1 to 5% of 1 type or 2 types, The two-electrode single-sided one-pass large heat input submerged excellent in toughness of the weld metal according to any one of the above (1) to (3) Arc welding method.
(5)前記溶接ワイヤが、質量%で、さらに、
Ni:0.1〜6%、
Cu:0.01〜1.5%、
Cr:0.01〜1.5%、
Mo:0.1〜3%、
W:0.01〜2%、
Nb:0.002〜0.05%、
V:0.005〜0.5%、
Ta:0.002〜0.2%、及び、
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前記(1)〜(4)の何れかに記載の溶接金属の靱性に優れた2電極片面1パス大入熱サブマージアーク溶接方法。
(5) The welding wire is in% by mass, and
Ni: 0.1 to 6%,
Cu: 0.01 to 1.5%,
Cr: 0.01 to 1.5%
Mo: 0.1 to 3%,
W: 0.01-2%
Nb: 0.002 to 0.05%,
V: 0.005 to 0.5%,
Ta: 0.002 to 0.2%, and
B: One
(6)前記溶接ワイヤが、質量%で、さらに、
Ca:0.0002〜0.01%、
Mg:0.0002〜0.01%、及び、
REM:0.0002〜0.01%の1種または2種以上を含有することを特徴とする前記(1)〜(5)の何れかに記載の溶接金属の靱性に優れた2電極片面1パス大入熱サブマージアーク溶接方法。
(6) The welding wire is in% by mass, and
Ca: 0.0002 to 0.01%,
Mg: 0.0002 to 0.01%, and
REM: 1 type or 2 types or more of 0.0002-0.01% 2 electrode single side |
本発明によれば、板厚が40mm以上の引張強度が500〜600MPa級の厚手高張力鋼板を溶接入熱が400kJ/cm以上の2電極片面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70J以上の高い靭性が得られる。従って、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 high heat input submerged arc welding in which a thick high strength steel plate having a plate thickness of 40 mm or more and a tensile strength of 500 to 600 MPa class is welded by two-pass single-sided one-pass welding with a heat input of 400 kJ / cm or more. The toughness can be made uniform in the entire thickness range from the front surface to the back surface of the metal, and high toughness with 2 mmV notch Charpy absorbed energy at 70 ° C. of 70 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 to increase the safety thereof, so that the industrial utility value is very high. Is.
通常、2電極片面1パスサブマージアーク溶接をするに際に、第1電極(先行極)と第2電極(後行極)とに同一ワイヤを用い、同一入熱条件で溶接すると、溶接金属の裏面側は第1電極(先行極)による溶接入熱に加えて、さらに第2電極(後行極)による溶接入熱の影響を受けるため、溶接後の溶接金属裏面側の冷却速度は表面側に比べて不可避的に遅くなる。特に、溶接金属の組織を左右する、溶接金属の裏側の800℃から500℃までの冷却速度が表面側に比べて遅くなるため、溶接金属の裏側に変態点の高い組織が形成されやすくなる。実際に、溶接金属の裏面側の組織は、表面側に比べて粒界フェライトの割合が多くなり、靭性が低下しやすい傾向にある。 Normally, when performing two-electrode single-sided one-pass submerged arc welding, using the same wire for the first electrode (leading electrode) and the second electrode (following electrode) and welding under the same heat input conditions, Since the back side is affected by the welding heat input by the second electrode (following electrode) in addition to the welding heat input by the first electrode (leading electrode), the cooling rate on the back side of the weld metal after welding is on the front side. Compared with inevitably slow. In particular, since the cooling rate from 800 ° C. to 500 ° C. on the back side of the weld metal, which influences the structure of the weld metal, is slower than that on the surface side, a structure having a high transformation point is likely to be formed on the back side of the weld metal. Actually, the structure on the back surface side of the weld metal has a higher proportion of intergranular ferrite than the front surface side, and the toughness tends to decrease.
板厚が限定された鋼板を2電極片面1パスサブマージアーク溶接をする場合には、溶接材料を選定し、溶接金属の化学組成を非常に厳密に一定範囲に収めることにより表面側と裏面側の溶接金属の組織差を極力小さくし、厚み範囲で均一に高い靭性を保持することも可能ではある。しかし、特殊な溶接材料を使用し、対象となる鋼板板厚も制限されるため、実用面で問題がある。 When two-electrode single-sided one-pass submerged arc welding is performed on a steel plate with a limited thickness, the welding material is selected, and the chemical composition of the weld metal is kept within a certain range very strictly. It is also possible to minimize the difference in the structure of the weld metal and maintain high toughness uniformly in the thickness range. However, since a special welding material is used and the target steel plate thickness is limited, there is a problem in practical use.
また、冷却速度が遅くなる溶接金属の裏面側の焼入れ性を高めるために、第1電極(先行極)のワイヤの合金成分を第2電極(後行極)に比べて多くする方法も考えられる。しかし、本発明者らの検討によれば、板厚が40mm以上の厚手鋼板を溶接する場合には、ワイヤの合金成分の制御だけでは、第1電極(先行極)で形成された溶接金属と第2電極(後行極)で形成された溶接金属とが溶融状態で混合され、溶接金属の表面側と裏面側の成分組成の差による大きな効果は期待できないことを確認している。 Moreover, in order to improve the hardenability of the back surface side of the weld metal whose cooling rate becomes slow, a method of increasing the alloy component of the wire of the first electrode (leading electrode) compared to the second electrode (following electrode) is also conceivable. . However, according to the study by the present inventors, when a thick steel plate having a thickness of 40 mm or more is welded, the welding metal formed by the first electrode (leading electrode) can be obtained only by controlling the alloy component of the wire. It has been confirmed that the weld metal formed by the second electrode (following electrode) is mixed in a molten state, and a great effect due to the difference in the component composition between the front surface side and the back surface side of the weld metal cannot be expected.
さらに、第1電極(先行極)と第2電極(後行極)の溶接入熱量に差をつけ、溶接金属の表面側と裏面側での冷却速度の差を小さくすることにより、冷却速度に起因する溶接金属の表面側と裏面側の靱性差を小さくする方法も考えられるが、溶接入熱の制御は、溶接の安定性およびビード形状確保の点から好ましい方法とは言えない。 Furthermore, by making a difference in the amount of welding heat input between the first electrode (leading electrode) and the second electrode (following electrode), and reducing the difference in cooling rate between the front side and the back side of the weld metal, the cooling rate can be reduced. Although a method of reducing the difference in toughness between the front side and the back side of the weld metal can be considered, control of welding heat input cannot be said to be a preferable method from the viewpoint of welding stability and ensuring the bead shape.
そこで、本発明者らは、板厚が40mm以上の厚手鋼板を2電極片面1パスサブマージアーク溶接する際に、溶接安定性及びビード形状を良好に維持しつつ、溶接金属の表面側から裏面側までの厚み範囲で均一で、かつ高い靭性が得られるための、溶接ワイヤ、フラックスおよび鋼板の成分組成制御と、第1電極(先行極)と第2電極(後行極)のワイヤによる溶接金属裏面側の実効的な入熱制御方法について検討した。 Therefore, the present inventors have maintained the welding stability and the bead shape well when the thick steel plate having a thickness of 40 mm or more is subjected to the two-electrode single-sided one-pass submerged arc welding, while maintaining the welding stability and the bead shape from the back side to the back side. Metal composition control of welding wire, flux and steel plate to obtain uniform and high toughness up to the thickness range up to, and weld metal by wire of first electrode (leading electrode) and second electrode (following electrode) The effective heat input control method on the back side was studied.
その結果、溶接電流などによる溶接入力は変化させずに、両者のワイヤ断面積の比率が所定範囲内となるように第1電極(先行極)のワイヤの直径を第2電極(後行極)のワイヤに比べて細くすることにより、溶接金属の裏面側のビード幅を許容範囲内で狭くすることができ、その結果、裏面側の冷却速度を表面側と同程度まで高められることを確認した。また、この溶接金属の裏面側の実効的な入熱制御に加え、溶接ワイヤ、フラックスおよび鋼板の成分組成制御により、溶接安定性及びビード形状を良好に維持しつつ、溶接金属の表面側から裏面側までの厚み範囲で均一で、かつ高い靭性を得ることができることを確認した。 As a result, the diameter of the wire of the first electrode (leading electrode) is changed to the second electrode (following electrode) so that the ratio of the wire cross-sectional areas of both is within a predetermined range without changing the welding input due to the welding current or the like. It was confirmed that the bead width on the back surface side of the weld metal can be narrowed within an allowable range by making it thinner than the wire of this type, and as a result, the cooling rate on the back surface side can be increased to the same level as the front surface side. . In addition to effective heat input control on the back side of the weld metal, the composition of the welding wire, flux, and steel sheet controls the weld stability and bead shape, while maintaining good weld stability and bead shape. It was confirmed that uniform and high toughness can be obtained in the thickness range up to the side.
本発明は、以上の知見および技術思想の基になされたものである。 The present invention has been made based on the above knowledge and technical idea.
以下に、上記技術思想の基に目的とする効果を達成するために必要な本発明の技術事項の限定理由について説明する。 The reasons for limiting the technical matters of the present invention necessary to achieve the intended effect based on the above technical idea will be described below.
本発明では、上記のとおり、溶接電流などによる溶接入力は変化させずに、第1電極(先行極)のワイヤの直径を第2電極(後行極)のワイヤに比べて細くすることにより、溶接金属の裏面側のビード幅を狭くし、裏面側の冷却速度を表面側と同程度まで高められることを技術思想とする。 In the present invention, as described above, by changing the diameter of the wire of the first electrode (leading electrode) compared to the wire of the second electrode (following electrode) without changing the welding input due to the welding current or the like, The technical idea is to reduce the bead width on the back side of the weld metal and increase the cooling rate on the back side to the same level as the front side.
しかし、第1電極(先行極)のワイヤの直径の低下により、溶接金属の裏面側のビード幅が過度に狭くなると、高温割れや融合不良が生じたり、溶接能率も低下する可能性が高くなる。このため、このような問題が生じないように、2電極片面1パスサブマージアーク溶接に用いる、第1電極(先行極)の溶接ワイヤと第2電極(後行極)の溶接ワイヤとの断面積比率を35〜75%とし、かつ第2電極(後行極)の溶接ワイヤの直径を6〜8mmとする両者を適正化する必要がある。 However, if the bead width on the back surface side of the weld metal becomes excessively narrow due to a decrease in the diameter of the wire of the first electrode (leading electrode), there is a high possibility that hot cracking or poor fusion will occur or the welding efficiency will decrease. . Therefore, the cross-sectional area of the welding wire of the first electrode (leading electrode) and the welding wire of the second electrode (following electrode) used in the two-electrode single-sided one-pass submerged arc welding so that such a problem does not occur. It is necessary to optimize both the ratio of 35 to 75% and the diameter of the welding wire of the second electrode (following electrode) of 6 to 8 mm.
該ワイヤ径が6mm未満となると、全体的にビード幅が過度に小さくなってビード形状が縦長(なし形)となる結果、高温割れが生じやすくなり、溶接欠陥を抑制する点から好ましくない。一方、ワイヤ径が8mmより大きくなると、溶接機の能力限定から電流密度が過小となってアークが不安定になるなどの溶接作業性が劣化し、また、溶接金属組成が鋼材組成の影響を過度に受けて材質を安定的に確保することが困難になる。 When the wire diameter is less than 6 mm, the bead width becomes excessively small as a whole and the bead shape becomes vertically long (none). As a result, high temperature cracking is likely to occur, which is not preferable from the viewpoint of suppressing welding defects. On the other hand, if the wire diameter is larger than 8 mm, the welding workability such as the current density becomes excessive due to the limited capacity of the welding machine and the arc becomes unstable is deteriorated, and the weld metal composition excessively influences the steel composition. Therefore, it becomes difficult to secure a stable material.
このような理由から、本発明では、第2電極の溶接ワイヤの直径を6〜8mmとする。 For this reason, in the present invention, the diameter of the welding wire of the second electrode is set to 6 to 8 mm.
本発明では、第2電極(後行極)の溶接ワイヤの直径を上記範囲に限定するとともに、以下の検討結果を基に、第2電極(後行極)の溶接ワイヤの断面積と第1電極(先行極)の溶接ワイヤの断面積との比率を35〜75%とする。 In the present invention, the diameter of the welding wire of the second electrode (following electrode) is limited to the above range, and the cross-sectional area of the welding wire of the second electrode (following electrode) and the first are based on the following examination results. The ratio of the electrode (leading electrode) to the cross-sectional area of the welding wire is set to 35 to 75%.
本発明者らは、板厚が40mm未満の比較的薄い鋼板を2電極片面1パス大入熱サブマージアーク溶接する際に、良好な靭性の溶接金属を形成できることを確認した、溶接ワイヤ、フラックスおよび鋼板の成分組成の条件で、第1電極及び第2電極の溶接入熱を変えずに、第1電極と第2電極のそれぞれの溶接ワイヤの直径を変化させ、溶接後の溶接金属の厚み範囲の靭性を測定した。
すなわち、化学組成が、0.12%C−0.25%Si−1.41%Mn−0.009%P−0.004%S−0.016%Al−0.0035%N−0.0029%O−0.007%Nb−0.011%Ti−0.0020%Caで、板厚が55mmの鋼板を、化学組成がSiO2:18%、MgO:12.3%、CaO:11.8%、CaF2:3.7%、Al2O3:12%、TiO2:11%、Fe:18.5%、B2O3:0.8%、Ni:1.5%からなるフラックスと、化学組成が0.06%C−0.15%Si−2.0%Mn−0.01%P−0.004%S−0.006%Al−0.0051%N−0.95%Ni−0.46%Mo−0.023%Ti−0.0031%Oからなる溶接ワイヤを用い、2電極片面1パスサブマージアーク溶接を行う際に、溶接入熱は、約540〜550kJ/cm程度でほぼ一定とし、第1電極(先行極)と第2電極(後行極)の各溶接ワイヤの直径を種々変えた条件で、溶接継手を作成した。また、得られた溶接継手について、図1に示す、溶接金属の種々位置から2mmVノッチシャルピー衝撃試験片を採取し、溶接金属の厚み範囲の靭性分布を測定し評価した。なお、第2電極(後行極)の溶接ワイヤの直径を8mm、7mm、6.4mmの3種類とし、各第2電極の溶接ワイヤ径毎に、ワイヤ直径の異なる第1電極(先行極)の溶接ワイヤを数種類のずつ組み合わせて継手を作成した。
The present inventors have confirmed that when a relatively thin steel plate having a thickness of less than 40 mm is subjected to two-electrode single-sided one-pass large heat input submerged arc welding, a weld metal with good toughness can be formed. The thickness range of the weld metal after welding is changed by changing the diameters of the welding wires of the first electrode and the second electrode without changing the welding heat input of the first electrode and the second electrode under the conditions of the component composition of the steel plate. The toughness was measured.
That is, the chemical composition is 0.12% C-0.25% Si-1.41% Mn-0.009% P-0.004% S-0.016% Al-0.0035% N-0. A steel plate having a plate thickness of 55 mm with 0029% O-0.007% Nb-0.011% Ti-0.0020% Ca and a chemical composition of SiO 2 : 18%, MgO: 12.3%, CaO: 11 .8%, CaF 2 : 3.7%, Al 2 O 3 : 12%, TiO 2 : 11%, Fe: 18.5%, B 2 O 3 : 0.8%, Ni: 1.5% And a chemical composition of 0.06% C-0.15% Si-2.0% Mn-0.01% P-0.004% S-0.006% Al-0.0051% N-0 .Use of welding wire made of 95% Ni-0.46% Mo-0.023% Ti-0.0031% O When performing merge arc welding, the welding heat input is approximately constant at about 540 to 550 kJ / cm, and the diameters of the welding wires of the first electrode (leading electrode) and the second electrode (following electrode) are variously changed. Welded joints were created under the above conditions. Moreover, about the obtained welded joint, 2 mmV notch Charpy impact test pieces shown in FIG. 1 were collected from various positions of the weld metal, and the toughness distribution in the thickness range of the weld metal was measured and evaluated. The diameter of the welding wire of the second electrode (following electrode) is three types of 8 mm, 7 mm, and 6.4 mm, and the first electrode (leading electrode) having a different wire diameter for each welding wire diameter of each second electrode. A joint was made by combining several types of welding wires.
図2に、溶接金属の裏面上7mm位置での0℃吸収エネルギーと溶接金属の表面下7mm位置での0℃吸収エネルギーとの差を求め、この0℃吸収エネルギーの差と、第1電極(先行極)と第2電極(後行極)との溶接ワイヤ断面積の比率との関係を整理した結果を示す。 FIG. 2 shows the difference between the 0 ° C. absorbed energy at the 7 mm position on the back surface of the weld metal and the 0 ° C. absorbed energy at the 7 mm position below the surface of the weld metal, and the difference between this 0 ° C. absorbed energy and the first electrode ( The result which arranged the relationship between the ratio of the welding wire cross-sectional area of a 2nd electrode (following electrode) and a 2nd electrode (following electrode) is shown.
なお、本実験で使用した鋼板をフラック及び溶接ワイヤで溶接した場合は、溶接金属の表面下7mm位置での0℃吸収エネルギーは、全て100J以上の良好な靭性が得られている。 In addition, when the steel plate used in this experiment was welded with a flack and a welding wire, good toughness of 100 J or more was obtained for all 0 ° C. absorbed energy at a position 7 mm below the surface of the weld metal.
図2から明らかなように以上から、第2電極(後行極)の溶接ワイヤ径が6〜8mmの前提条件で、第2電極(後行極)のワイヤ断面積に対する第1電極(先行極)のワイヤ断面積の比が0.35〜0.75の範囲内にある場合に、高温割れや融合不良の溶接欠陥は発生せず、かつ溶接金属の裏面側の靭性は、ほぼ表面側と同等程度に高めることが可能となる。また、この条件では、溶接作業性の劣化もなかった。 As apparent from FIG. 2, the first electrode (leading electrode) with respect to the wire cross-sectional area of the second electrode (following electrode) on the precondition that the welding wire diameter of the second electrode (following electrode) is 6 to 8 mm. ) Is within the range of 0.35 to 0.75, no hot cracks or poor weld defects occur, and the toughness of the back side of the weld metal is almost the same as the surface side. It can be increased to the same extent. Under these conditions, there was no deterioration in welding workability.
一方、第2電極(後行極)のワイヤ断面積に対する第1電極(先行極)のワイヤ断面積の比が0.75超であると、溶接金属の裏面側での焼入性不足を解消できず、裏面側の冷却速度が表面側に比べて遅くなるため、靭性を劣化させる粒界フェライトの生成、或いは、粒成長による結晶粒の粗大化の結果、裏面上7mmでの靭性劣化が著しい。 On the other hand, if the ratio of the wire cross-sectional area of the first electrode (leading electrode) to the wire cross-sectional area of the second electrode (following electrode) is more than 0.75, the lack of hardenability on the back side of the weld metal is resolved. Since the cooling rate on the back surface side becomes slower than that on the front surface side, the toughness deterioration at 7 mm on the back surface is remarkable as a result of the formation of grain boundary ferrite that deteriorates toughness or the coarsening of crystal grains due to grain growth. .
また、第2電極(後行極)のワイヤ断面積に対する第1電極(先行極)のワイヤ断面積の比が0.35未満になると、溶接金属の裏面上7mmの組織は表面下7mmとほぼ同等に微細化されるが、溶接金属の裏面側の冷却速度が過度に速くなるため、拡散性水素の偏析、或いは、裏面側ビード幅が狭くなることにより、高温割れ(ビード幅が狭い場合に溶接金属の凝固組織の成長や凝固収縮に起因して発生する割れ)、融合不良などの溶接欠陥が生じやすくなる。これらの欠陥の存在によって、溶接金属の裏面上7mmの吸収エネルギーは、ワイヤ断面積の比が適正範囲(0.35〜0.75)の場合に比べて若干低めとなる。 Further, when the ratio of the wire cross-sectional area of the first electrode (leading electrode) to the wire cross-sectional area of the second electrode (following electrode) becomes less than 0.35, the structure of 7 mm above the back surface of the weld metal is almost 7 mm below the surface. Although it is refined equally, the cooling rate on the back side of the weld metal becomes excessively high, so segregation of diffusible hydrogen, or the back side bead width becomes narrow, resulting in hot cracking (when the bead width is narrow). Cracks caused by solidification structure growth and solidification shrinkage of the weld metal) and welding defects such as poor fusion are likely to occur. Due to the presence of these defects, the absorbed energy of 7 mm on the back surface of the weld metal is slightly lower than when the ratio of the wire cross-sectional areas is in the proper range (0.35 to 0.75).
以上の検討結果を基に、本発明では、高温割れ及び融合不良などの溶接欠陥を生じさせず、かつ、溶接作業性の劣化等をともなわずに、溶接金属の裏面側の靭性を表面側と同等程度に高めるために、第2電極(後行極)の溶接ワイヤの直径6〜8mmを前提とし、かつ、第2電極(後行極)の溶接ワイヤの断面積に対する第1電極(先行極)の溶接ワイヤの断面積の比率を35〜75%とする。ことが可能となる。 Based on the above investigation results, in the present invention, the toughness on the back side of the weld metal is defined as the front side without causing welding defects such as hot cracks and poor fusion and without deteriorating welding workability. In order to increase to the same extent, the diameter of the welding wire of the second electrode (following electrode) is assumed to be 6 to 8 mm, and the first electrode (leading electrode) with respect to the cross-sectional area of the welding wire of the second electrode (following electrode) ) Welding wire cross-sectional area ratio is 35 to 75%. It becomes possible.
本発明では、上記第1電極(先行極)および第2電極(後行極)の溶接ワイヤの条件を適正に制御することに加え、溶接金属全体の靱性を目的とするレベルに高めるためには、溶接金属組成を適正に制御するため、鋼板、フラックスおよび溶接ワイヤのそれぞれの成分組成を以下のように限定する必要がある。 In the present invention, in addition to appropriately controlling the welding wire conditions of the first electrode (leading electrode) and the second electrode (following electrode), in order to increase the overall toughness of the weld metal to a target level. In order to appropriately control the weld metal composition, it is necessary to limit the respective component compositions of the steel plate, the flux and the welding wire as follows.
2電極片面1パス大入熱サブマージアーク溶接方法では、通常のアーク溶接に比べて溶接入熱量が高いため、溶接時に形成させる溶接金属の成分組成は、鋼板の成分が一部溶融して混入する比率、つまり、鋼板の希釈率が大きくなるため、溶接金属組成に対する鋼板組成の寄与を無視できない。
そのため、本発明においては、鋼板は質量%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、必要に応じて、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%、Ni:0.01〜6%、Cu:0.01〜1.5%、Nb:0.002〜0.1%、V:0.002〜0.5%、及び、Ta:0.002〜0.5%、の1種または2種以上を含有し、さらに必要に応じて、Ca:0.0002〜0.01%、Mg:0.0002〜0.01%、及び、REM:0.0002〜0.01%、の1種または2種以上を含有する。
In the two-electrode single-sided one-pass large heat input submerged arc welding method, the amount of welding heat input is higher than that of ordinary arc welding, so the component composition of the weld metal formed during welding is partially mixed with the steel plate components. Since the ratio, that is, the dilution ratio of the steel sheet increases, the contribution of the steel sheet composition to the weld metal composition cannot be ignored.
Therefore, in this invention, a steel plate is the mass%, C: 0.02-0.2%, Si: 0.01-1%, Mn: 0.1-2.5%, Al: 0.002- 0.1%, N: 0.001 to 0.015%, P: 0.02% or less, S: 0.01% or less, O: 0.01% or less, as required , Ti: 0.002 to 0.05%, B: 0.0003 to 0.015%, Mo: 0.01 to 1.5%, Cr: 0.01 to 1.5%, W: 0.01 -1.5%, Ni: 0.01-6%, Cu: 0.01-1.5%, Nb: 0.002-0.1%, V: 0.002-0.5%, and Ta: 0.002 to 0.5%, or one or more of them, and if necessary, Ca: 0.0002 to 0.01%, Mg: 0.0002 to 0.01%, And REM: 0 From 0,002 to 0.01%, containing one or more.
先ず、鋼板中の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、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。
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。
First, C in the steel plate needs to be contained by 0.02% or more in order to secure the strength of the steel plate. On the other hand, if more than 0.2% is contained in the steel sheet, the deterioration of the toughness of the steel sheet, the weld heat affected zone toughness, and further the resistance to weld cracking will be impaired, and the safety as structural steel will be impaired. Therefore, the upper limit of the C content of the steel sheet is set to 0.2% in the present invention.
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. In addition, the Si content in the weld metal may be excessive and the toughness of the weld metal may be impaired. Then, the range of Si content in a steel plate was 0.01 to 1%.
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 is an element necessary for enhancing the hardenability of the steel sheet and ensuring strength and toughness, and it is necessary to contain Mn at least 0.1%. 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. Further, since the weld metal toughness is also adversely affected, the upper limit is set to 2.5%.
Alは鋼板の脱酸、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、効果を発揮するためには0.002%以上含有する必要があるが、0.1%を超えて過剰に含有させると、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ため、また、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量を0.002%〜0.1%の範囲に限定する。 Al is an element effective for deoxidation of steel sheets, refinement of the grain size of heated austenite, etc., and in order to exert the effect, it is necessary to contain 0.002% or more, but exceeding 0.1% excessively If it is included, a coarse oxide is formed and the toughness and ductility of the steel sheet are extremely deteriorated. Also, the amount of Al in the weld metal becomes excessive, and upper bainite that is harmful to toughness is formed, resulting in weld metal. In the present invention, the amount of Al in the steel sheet is limited to a range of 0.002% to 0.1%.
Nは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するが、その効果が明確になるためには0.001%以上含有させる必要がある一方、過剰に含有させると固溶Nが増加して鋼板の靭性の劣化につながる。また、鋼板のN量が過度に高いと、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、粒界とも組織を粗大化する傾向があり、好ましくない。本発明はこのNによる溶接金属に対する悪影響が許容できる鋼板中含有量として、鋼板のN量は上限を0.015%とする。 N is combined with Al and Ti and effectively works to refine the austenite grains and contributes to the improvement of the toughness of the steel sheet, but in order to clarify the effect, it is necessary to contain 0.001% or more, but excessively contained If it does, solid solution N will increase and it will lead to the deterioration of the toughness of a steel plate. Further, if the N amount of the steel sheet is excessively high, the N amount of the weld metal also becomes excessive, and B and nitride are formed to reduce the amount of solid solution B effective for refining the structure. Both tend to coarsen the structure, which is not preferable. In the present invention, the upper limit of the N content of the steel sheet is 0.015% as the content in the steel sheet that can tolerate the adverse effect of N on the weld metal.
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 is an impurity element and is preferably reduced as much as possible with respect to the properties of the steel sheet and the weld metal. However, the upper limit is set to 0.02% as an allowable amount from the viewpoint of securing toughness.
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。 Since S is also an impurity element and deteriorates both the ductility and toughness of the steel plate and the weld metal, reduction is necessary. As the upper limit that is practically acceptable without significant deterioration in ductility and toughness, the content is 0.01% or less.
Oは、鋼板においては不純物元素であり、酸化物による悪影響で鋼板の延性、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、靱性を劣化させる場合も懸念されるため、0.01%以下に制限する。 O is an impurity element in a steel sheet, and is not preferable because it adversely affects the ductility and toughness of the steel sheet due to the adverse effects of oxides. Further, since there is a concern that the amount of O of the weld metal is excessively increased to similarly deteriorate the ductility and toughness of the weld metal, the content is limited to 0.01% or less.
以上が、本発明で使用する鋼板の基本成分であるが、本発明では、さらに、鋼板の強度を調整する等の目的で、鋼板中に、さらに、Ti、B、Mo、Ni、Cr、W、Cu、Nb、V、及び、Taの1種または2種以上を以下の含有量の範囲で含有することができる。 The above are the basic components of the steel sheet used in the present invention. In the present invention, Ti, B, Mo, Ni, Cr, W are further added to the steel sheet for the purpose of adjusting the strength of the steel sheet. Cu, Nb, V, and Ta can be contained in the following content range.
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り、また希釈によって溶接金属に含有されることによって、溶接金属の組織微細化にも効果を発揮するが、これらの効果を発揮できるためには鋼板中に0.002%以上の含有が必要である。一方、鋼板中の含有量が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せ、また、溶接材料の組成によっては溶接金属中の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、上限を0.05%とする。 Ti is an element effective in improving the toughness of steel sheets by refining austenite grains by the formation of TiN, and it also has an effect on refining the structure of weld metal by being contained in the weld metal by dilution. In order to exhibit the above effect, the steel sheet needs to contain 0.002% or more. On the other hand, if the content in the steel sheet exceeds 0.05%, coarse oxides and nitrides are formed to deteriorate the toughness and ductility of the steel sheet, and depending on the composition of the welding material, the Ti content in the weld metal Therefore, the upper limit is made 0.05%.
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、鋼板にBが適正量含有されていると、希釈によって溶接金属中にも含有されて溶接金属の粒界フェライト抑制に効果がある。これらの効果を明確に発揮するためには、Bは鋼板中に0.0003%以上含有する必要がある。一方、0.015%を超えて鋼板中に含有させると、鋼片製造時や鋼板製造時の加熱段階で粗大な析出物を形成する場合が多いため、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生じる危険性も増加する。そのため、本発明においては、Bの範囲を0.0003〜0.015%とする。 B is an element that enhances hardenability in a very small amount and is effective for increasing the strength of a steel sheet. Further, when an appropriate amount of B is contained in the steel plate, it is also contained in the weld metal by dilution, and is effective in suppressing the grain boundary ferrite of the weld metal. In order to clearly exhibit these effects, B needs to be contained in the steel sheet in an amount of 0.0003% or more. On the other hand, if it is included in the steel sheet in excess of 0.015%, a coarse precipitate is often formed in the heating stage at the time of steel slab production or steel sheet production, so the effect of improving the hardenability becomes insufficient. In addition, there is an increased risk of toughness degradation due to cracks and precipitates in the steel slab. Therefore, in the present invention, the range of B is set to 0.0003 to 0.015%.
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、鋼板にMoが適正量含有されていると、希釈によって溶接金属中にも含有されて溶接金属の焼入性を高めて粒界フェライト抑制、アシキュラーフェライト微細化に効果がある。明瞭な効果を生じるためには0.01%以上必要である。一方、Moが1.5%を超えて過剰に含有されると、強度が過度に高くなって鋼板の靭性を劣化させるため、本発明においては、鋼板中のMoの含有量を0.01〜1.5%とする。 Mo is an element effective for improving the strength of a steel sheet by improving hardenability and precipitation strengthening. Further, when a proper amount of Mo is contained in the steel sheet, it is also contained in the weld metal by dilution, and the hardenability of the weld metal is enhanced, which is effective in suppressing grain boundary ferrite and refining acicular ferrite. In order to produce a clear effect, 0.01% or more is necessary. On the other hand, when Mo is contained excessively exceeding 1.5%, the strength is excessively increased and the toughness of the steel sheet is deteriorated. Therefore, in the present invention, the Mo content in the steel sheet is 0.01 to 1.5%.
CrもMoとほぼ同様の効果と作用を有するため、Moと同様の理由により、鋼板中の含有量は0.01〜1.5%に限定する。 Since Cr has substantially the same effect and action as Mo, the content in the steel sheet is limited to 0.01 to 1.5% for the same reason as Mo.
WもMo、Crと様の効果と作用を有するため、同様の理由により、鋼板中の含有量は0.01〜1.5%に限定する。 Since W has the same effects and actions as Mo and Cr, the content in the steel sheet is limited to 0.01 to 1.5% for the same reason.
Niは、本質的にマトリクスの靭性を高めることが可能な元素であり、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が、鋼板の靱性向上に効果を発揮するためには鋼板中に0.01%以上含有させる必要がある。含有量が多くなると強度、靭性は向上するが、6%を超えて含有させても効果が飽和するため、経済性も考慮して、上限を6%とする。 Ni is an element that can essentially increase the toughness of the matrix, and can be improved at the same time in strength and toughness without depending largely on the microstructure. Therefore, Ni is a very effective element in both steel sheets and weld metals. In order to exhibit the effect of improving the toughness of the steel plate, it is necessary to contain 0.01% or more in the steel plate. When the content increases, the strength and toughness are improved, but even if the content exceeds 6%, the effect is saturated, so the upper limit is made 6% in consideration of economy.
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るが、効果を発揮するためには、0.01%以上含有させる必要がある。一方、1.5%超含有させると、熱間加工性に問題を生じるため、また、溶接金属の耐高温割れ性を劣化させるため、鋼板中のCu含有量は0.01〜1.5%に限定する。 Cu is an element effective for improving the strength of the steel sheet mainly by improving the hardenability and strengthening the solid solution, but in order to exert the effect, it is necessary to contain 0.01% or more. On the other hand, if the content exceeds 1.5%, there is a problem in hot workability, and the hot cracking resistance of the weld metal is deteriorated, so the Cu content in the steel sheet is 0.01 to 1.5%. Limited to.
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が、効果を発揮するためには、0.002%以上は必要である。ただし、0.1%を超えて過剰に含有させると、鋼板の靭性を劣化させ、かつ、希釈によって溶接金属中にも過剰なNb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Nb含有量は0.002〜0.1%の範囲に限定する。 Nb is an element effective for increasing the strength of a steel sheet in a small amount by precipitation strengthening and transformation strengthening, and also effective for improving the toughness of the steel sheet by refining the heated austenite grain size. 0.002% or more is necessary. However, if it is excessively contained exceeding 0.1%, the toughness of the steel sheet is deteriorated, and there is also a concern that excessive Nb is contained in the weld metal due to dilution, and the toughness of the weld metal is deteriorated. In the present invention, the Nb content in the steel sheet is limited to a range of 0.002 to 0.1%.
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、0.002%以上は必要である。ただし、0.5%を超えて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、希釈によって溶接金属中にも過剰なV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V含有量は0.002〜0.5%の範囲に限定する。 V is an element which is effective for increasing the strength of a steel sheet in a small amount mainly by precipitation strengthening, and 0.002% or more is necessary to exert the effect. However, if it is contained excessively exceeding 0.5%, coarse precipitates are formed and the toughness of the steel sheet is deteriorated, and excessive V is also contained in the weld metal due to dilution, and the toughness of the weld metal. In the present invention, the V content in the steel sheet is limited to a range of 0.002 to 0.5%.
Taも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、0.002%以上は必要である。ただし、0.5%を超えて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、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含有量は0.002〜0.5%の範囲に限定する。 Ta is an element that is effective for increasing the strength of a steel sheet in a small amount mainly by precipitation strengthening, and 0.002% or more is necessary to exert the effect. However, if it exceeds 0.5% and contains excessively, coarse precipitates are formed and the toughness of the steel sheet is deteriorated, and excessive Ta is also contained in the weld metal due to dilution, and the toughness of the weld metal In the present invention, the Ta content in the steel sheet is limited to a range of 0.002 to 0.5%.
発明では、上記鋼板成分に加え、さらに、鋼板の延性を改善する目的で、Ca、MgおよびREMの1種または2種以上含有させることができる。該選択可能な元素においても、各々の組成範囲について、下記のように限定する必要がある。 In the invention, in addition to the steel plate component, one or more of Ca, Mg and REM can be contained for the purpose of improving the ductility of the steel plate. Also in the selectable element, it is necessary to limit each composition range as follows.
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。酸化物を微細化させて溶接継手の熱影響部靭性の向上にも有効に働く。その効果を発揮するための下限の含有量は、鋼板中の含有量でいずれも0.0002%である。一方、過剰に含有すると、硫化物や酸化物の粗大化を生じ、延性、靭性、さらに疲労特性の劣化を招くため、また、希釈によって溶接金属中に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、鋼板中の含有量の上限をいずれも0.01%とする。 Ca, Mg, and REM are all effective in improving ductility by suppressing the extension of sulfide during hot rolling. It effectively works to improve the heat affected zone toughness of welded joints by refining oxides. The lower limit content for exhibiting the effect is 0.0002% in terms of the content in the steel sheet. On the other hand, excessive inclusion causes coarsening of sulfides and oxides, leading to deterioration of ductility, toughness, and fatigue characteristics. Also, excessive inclusion in the weld metal due to dilution inhibits weldability. Therefore, the upper limit of the content in the steel sheet is 0.01%.
以上が本発明で使用する鋼板の化学組成における限定理由である。 The above is the reason for limitation in the chemical composition of the steel sheet used in the present invention.
次に、フラックスの組成の限定理由を以下に述べる。大入熱サブマージアーク溶接においては溶接金属の組成、組織に対して、フラックスの寄与が大きいため、安定的に高い溶接金属靱性を達成するためには、溶接ワイヤや鋼板だけでなく、フラックス組成も適正化する必要がある。すなわち、本発明においては、質量%で、SiO2:10〜25%、MgO:5〜20%、CaO:5〜15%、CaF2:1〜10%、Al2O3:5〜25%、TiO2:2〜20%、Fe:10〜25%、B2O3:0.1%〜2.5%、からなり、さらに必要に応じて、Mo:1〜5%、Ni:1〜5%、の1種または2種を含有する必要がある。 Next, the reasons for limiting the flux composition will be described below. In high heat input submerged arc welding, the flux contributes greatly to the composition and structure of the weld metal. To achieve stable and high weld metal toughness, not only the welding wire and steel plate but also the flux composition It needs to be optimized. That is, in the present invention, 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 to 20%, Fe: 10 to 25%, B 2 O 3 : 0.1% to 2.5%, Mo: 1 to 5%, Ni: 1 if necessary It is necessary to contain -5% of 1 type or 2 types.
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。 SiO 2 is the most important component for improving the conformability of the bead toe in high heat input submerged arc welding and forming a good weld bead. In order to obtain this effect, 10% of SiO 2 is added to the flux. % Or more. On the other hand, if the SiO 2 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 is contained in the flux in an amount of 5% or more in order to improve the fire resistance of the slag 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 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, CaO 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。 CaF 2 is effective in improving toughness. To obtain this effect, the flux contains 1% or more of CaF 2 . On the other hand, since CaF 2 has a low melting point and excessively exceeds 10%, high heat input submerged arc welding impairs the smoothness of the beads and results in poor beads, so the upper limit of the CaF 2 content in the flux is limited. 10%.
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。 Al 2 O 3 has an effect of improving the slag peelability, and in order to obtain this effect, the flux contains 5% or more of Al 2 O 3 . On the other hand, when the Al 2 O 3 content exceeds 25%, a convex bead is formed and the bead shape is poor. Therefore, the upper limit of the Al 2 O 3 content in the flux is set to 25%.
TiO2はビード表面の平滑性向上及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。 TiO 2 is effective in improving the smoothness and toughness of the bead surface. To obtain these effects, TiO 2 is contained in the flux in an amount of 2% or more. On the other hand, if the TiO 2 content exceeds 20%, the rising angle of the bead toe portion becomes large and the bead shape is deteriorated. In addition, TiO 2 is excessively present in the weld metal and adversely affects the toughness. Therefore, the upper limit of the TiO 2 content in the flux is set to 20%.
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 is effective in improving the welding efficiency and reducing the welding heat input. In order to obtain these effects, Fe in the flux is contained by 10% or more. 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0.1%以上、好ましくは0.6%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。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。 B 2 O 3 precipitates a B compound such as BN at the interface of the Ti oxide formed in the weld metal, further promotes the ability of the Ti oxide to form fine acicular ferrite. As a segregation to austenite grain boundaries, it has the effect of suppressing the formation of coarse grain boundary ferrite. In order to use these functions and refine the weld metal structure, it is necessary to contain B 2 O 3 in the flux in an amount of 0.1% or more, preferably 0.6% 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, the addition of B to the weld metal is basically performed in the form of B 2 O 3 from the flux, and in addition to this, B is added from the welding wire as needed. Add to weld metal. On the other hand, when the content of B 2 O 3 in the flux exceeds 2.5%, the surface side weld metal is sintered 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 permeability is excessively increased, and 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 the B 2 O 3 content in the flux is defined 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。 In the present invention, the reason why the form of B in the flux is B 2 O 3 is that B 2 O 3 has a better yield of B in the weld metal than the form of metal B or other B compounds. It is.
本発明においては、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 in the following ranges as selective components. .
Moは、他の焼入性向上元素に比べて、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、焼入性向上元素中で、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及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 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 hardenability improving 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. Further, Ni is the only hardenability-enhancing element and has the only solid solution toughening effect and can essentially improve toughness. The higher the Ni content, 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及び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。 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 effect 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.
一方、Mo及び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及び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。 On the other hand, if the content of each of Mo and Ni exceeds 5%, depending on the welding wire composition and steel plate 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及び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及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、本発明の目的及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 object and technical idea of the present invention, but does not deviate from the object 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.
次に溶接ワイヤの成分組成の限定理由を説明する。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及び機械的特性への寄与が大きい。このため、溶接金属の組成を限定して表面側から裏面側まで均一に高靭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。なお、本発明の2電極片面1パス大入熱サブマージアーク溶接においては、第1電極と第2電極とに異なるワイヤ径の溶接ワイヤ用いることが要点となっているが、ワイヤ組成については、第1電極と第2電極とが各々本発明の化学組成範囲内であれば、第1電極と第2電極とは化学組成が同一のものであっても異なったものでも本発明の効果を損ねるものではない。 Next, the reason for limiting the component composition of the welding wire will be described. In the 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. Therefore, in order to limit the composition of the weld metal and achieve high toughness uniformly from the front surface side to the back surface side, it is necessary to optimize not only the flux and the steel plate but also the composition of the welding wire as follows: is there. In the two-electrode single-sided one-pass large heat input submerged arc welding according to the present invention, it is important to use welding wires having different wire diameters for the first electrode and the second electrode. If the first electrode and the second electrode are each within the chemical composition range of the present invention, the first electrode and the second electrode may impair the effects of the present invention regardless of whether the chemical composition is the same or different. is not.
溶接ワイヤの組成は、質量%で、C:0.02〜0.2%、Si:0.01〜1%、Mn:0.5〜2.5%、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%以下に制限することを基本要件とし、必要に応じて、Ni:0.1〜6%、Cu:0.01〜1.5%、Cr:0.01〜1.5%、Mo:0.1〜3%、W:0.01〜2%、Nb:0.002〜0.05%、V:0.005〜0.5%、Ta:0.002〜0.2%、及び、B:0.001〜0.05%の1種または2種以上を含有し、さらに、必要に応じて、Ca:0.0002〜0.01%、Mg:0.0002〜0.01%、及び、REM:0.0002〜0.01%、の1種または2種以上を含有することを特徴とする。 The composition of the welding wire is mass%, C: 0.02 to 0.2%, Si: 0.01 to 1%, Mn: 0.5 to 2.5%, 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 Limiting is a basic requirement, and if necessary, Ni: 0.1 to 6%, Cu: 0.01 to 1.5%, Cr: 0.01 to 1.5%, Mo: 0.1 to 0.1% 3%, W: 0.01-2%, Nb: 0.002-0.05%, V: 0.005-0.5%, Ta: 0.002-0.2%, and B: 0 0.001 to 0.05% of one kind or two or more kinds, and, if necessary, Ca: 0.0002 to 0.01%, Mg: 0.0002 to 0.01%, and REM : 0.0002 ~ .01%, characterized in that it contains one or more.
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 is a component that improves the strength of the weld metal, and in particular, 0.02% or more is contained in the welding wire in order to ensure a tensile strength of 500 to 800 MPa as a weld metal for high-strength 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 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0.5%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0.5%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 has a strength improvement and deoxidation action of the weld metal. If the content in the welding wire is less than 0.5%, sufficient deoxidation action and sufficient strength of the weld metal cannot be obtained. Since the oxygen content of the weld metal is increased, the toughness of the weld metal is deteriorated. Therefore, the lower limit of the Mn content in the wire is set to 0.5%. 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%.
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 acts as a deoxidizing element and is an element effective for controlling the amount of oxygen in the weld metal. In order to effectively contribute to 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及び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、これらの効果を十分に確保するため、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 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 a B compound such as BN and Fe 23 (C, B) 6. Precipitating at the Ti oxide interface makes it possible to enhance the ability to produce fine acicular ferrite. 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。これらの効果を得るためには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、及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 is an unavoidable 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. In addition, B is fixed as a nitride, which inhibits the transformation of proeutectoid ferrite (grain boundary ferrite) at the austenite grain boundary due to the segregation of grain boundaries 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 is an unavoidable impurity element, and P in the weld metal deteriorates the toughness of the weld metal. Therefore, the P content in the welding wire is preferably reduced 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も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 is also 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.
酸素(O)も、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。 Oxygen (O) is also an unavoidable impurity element in the welding wire, and if the O content is excessive, the productivity of the welding wire is hindered, and the O content in the weld metal is increased and welding is performed. This is not preferable because it deteriorates the ductility and toughness of the 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Ni、Cu、Cr、Mo、W、Nb、V、Taおよび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, in order to adjust the mechanical properties of the weld metal, particularly strength and toughness, one of Ni, Cu, Cr, Mo, W, Nb, V, Ta and B is further added. Two or more species can be contained in the welding wire within a predetermined range.
Niは、焼入性向上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有効な元素である。これらの作用効果を十分に発現するためにNiを溶接ワイヤ中に含有させる場合は、0.1%以上含有させる必要がある。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。 Ni has the only solid solution toughening effect among the hardenability improving 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 an effective element for achieving uniform toughness in the entire thickness range of the weld metal. In order to fully express these effects, when Ni is contained in the welding wire, it is necessary to contain 0.1% or more. 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%.
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及び強度・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 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 manufacturability of the welding wire is deteriorated, so the upper limit of the Cu content is 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は、Moと同様、焼入性向上に有効な元素であり、溶接金属の強度向上のために溶接ワイヤ中にCrを含有させる場合には、0.01%以上含有する必要がある。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, like Mo, is an element effective for improving hardenability. When Cr is contained in the welding wire in order to improve the strength of the weld metal, it is necessary to contain 0.01% or more. 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%.
Moは、他の焼入性向上元素に比べて、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有効な元素である。該作用効果を期待して溶接ワイヤ中にMoを含有させる場合は、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。 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 improving 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 element that is particularly effective for uniformizing the toughness of the entire range of the weld metal. When Mo is contained in the welding wire in anticipation of the effect, it is necessary to contain 0.1% or more. 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 limited. 3%.
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を含有させる場合、効果を発揮させるためには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 is qualitatively an element having the same effect as Cr, and when W is contained in the welding wire in order to improve the strength of the weld metal, 0.01% or more is contained in order to exert the effect. It is preferable to do this. 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は、溶接金属の焼入性向上及び析出強化により、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 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 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 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溶接ワイヤ中にTaを含有させる場合は、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。 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. When Ta is contained in the welding wire in order to reliably exhibit this effect, 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 set to 0.2%.
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。 B segregates at the austenite grain boundaries as solid solution B in the weld metal, suppresses the formation of coarse grain boundary ferrite, precipitates as a B compound such as BN at the same time as the Ti oxide, and interacts with the Ti oxide. This has the effect of promoting the formation of fine acicular ferrite. 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.
本発明では、Bは基本的にフラックスから添加するが、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ことも可能である。その場合、効果を確実に発揮するためには、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。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。 In the present invention, B is basically added from the flux, but it is also possible to supplementarily add B from the welding wire into the weld metal in order to obtain the effect of B stably. In that case, in order to exhibit an effect reliably, it is preferable to make B content in a welding wire 0.001% or more. 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%.
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ため、必要に応じて溶接ワイヤに含有させることができる。これらの効果を発揮するためには、溶接ワイヤ中のCa、Mg及びREMの1種または2種以上の含有量は、各々0.0002%以上とすることが好ましい。一方、Ca、Mg及びREMの1種または2種以上の含有量が0.01%を超えて過剰なると、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及びREMの1種または2種以上の含有量の上限を0.01%とする。 Since Ca, Mg, and REM are effective elements for changing the sulfide structure in the weld metal, reducing the size of the sulfide and oxide, and improving the ductility and toughness of the weld metal, It can be contained in the welding wire as required. 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% or more. On the other hand, if the content of one or more of Ca, Mg and REM exceeds 0.01%, the sulfides and oxides in the weld metal are coarsened, and the ductility and toughness of the weld metal deteriorate. In addition, since the weld bead shape and weldability may be deteriorated, the upper limit of the content of one or more of Ca, Mg and REM in the welding wire is set to 0.01%. .
以上が本発明の要件についての限定理由であるが、さらに、実施例により、本発明の作用、効果を説明する。 The above is the reason for limiting the requirements of the present invention. Further, the operation and effects of the present invention will be described with reference to examples.
図1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2電極片面1パス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に示す溶接金属中央の鋼板表面下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。 As shown in FIG. 1, a joint is formed by abutting a steel plate having a component composition shown in Table 1 with a plate thickness shown in Table 1 that has been grooved in advance at the end of the steel plate. 2 electrode single-sided 1-pass large heat input submerged arc welding was performed under the welding conditions shown in Table 4 using welding wires having the composition shown in Table 3. 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 plate at the center of the weld metal 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.
表1において、鋼板A1〜A8が本発明範囲内の化学組成を有する鋼板、鋼板B1〜B4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A1〜A9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B1〜B5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A1−a〜A9−bが本発明範囲内の化学組成を有するワイヤ、ワイヤB1−a〜B5−b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。なお、ワイヤについては、同一のインゴットから異なるワイヤ径(4〜8mm)のワイヤに伸線加工しており、ワイヤ記号の−の左側の記号が同一のものは同一のインゴットから加工したことを示している。ワイヤの化学組成はワイヤ伸線加工後の分析値である。 In Table 1, steel plates A1 to A8 are steel plates having a chemical composition within the range of the present invention, and steel plates B1 to B4 are steel plates having a chemical composition outside the range of the present invention. In Table 2, fluxes A1 to A9 are fluxes having a chemical composition within the scope of the present invention, and fluxes B1 to B5 are fluxes having a chemical composition outside the scope of the present invention. Furthermore, in Table 3, wires A1-a to A9-b are wires having a chemical composition within the scope of the present invention, and wires B1-a to B5-b are wires having a chemical composition outside the scope of the present invention. Note that the wire is drawn from the same ingot to a wire having a different wire diameter (4 to 8 mm), and the same symbol on the left side of the wire symbol-indicates that the wire is machined from the same ingot. ing. The chemical composition of the wire is an analytical value after wire drawing.
表4に示すように、様々に鋼板、フラックス、ワイヤを組み合わせて継手を作製し、そのときの溶接金属中央の鋼板表面下7mm、板厚中心部、裏面上7mmの靭性を0℃におけるシャルピー衝撃吸収エネルギーで評価した。また、継手のX線透過試験、断面組織観察等により、溶接欠陥の有無を調査した。表4のうち、継手A1〜A33が本発明を満足している継手であり、溶接金属のいずれの位置においても70Jよりも十分高い吸収エネルギーが得られ、かつ、溶接金属の表面側〜裏面側で安定して高靭性が得られていることが明らかである。 As shown in Table 4, various steel plates, fluxes, and wires are combined to produce a joint. At that time, the toughness of 7 mm below the steel plate surface, the center of the plate thickness, and 7 mm above the back surface at the center of the weld metal is Charpy impact at 0 ° C. Evaluation was based on absorbed energy. In addition, the presence or absence of welding defects was investigated by X-ray transmission tests of joints, cross-sectional structure observations, and the like. Among Table 4, joints A1 to A33 are joints satisfying the present invention. Absorbed energy sufficiently higher than 70J is obtained at any position of the weld metal, and the front side to the back side of the weld metal. It is clear that high toughness is obtained stably.
一方、表4において、継手B1〜B18は本発明の要件を満足していない継手であり、下記に説明するように、溶接金属全体の靭性レベルが低いか、あるいは、溶接金属の一部の位置で靭性が低下するか、あるいは/及び、溶接欠陥が生じて継手の健全性が損なわれている。 On the other hand, in Table 4, joints B1 to B18 are joints that do not satisfy the requirements of the present invention, and as described below, the toughness level of the entire weld metal is low, or the position of a part of the weld metal Therefore, the toughness is lowered or / and weld defects are generated, and the soundness of the joint is impaired.
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 B2, since the P amount of the steel plate is excessive, the P 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B3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 B3, 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B4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、溶接金属における固溶B量が十分でなく、合金組成の調整により表面下7mmでは比較的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 B4, since the N amount of the steel plate is excessive, the N amount of the weld metal is also excessive. Therefore, the amount of solute B in the weld metal is not sufficient, and it is relatively good at 7 mm below the surface by adjusting the alloy composition. Although fine toughness is obtained, the structure is not sufficiently refined at the thickness 7 mm from the center of the plate thickness to the back surface, and the toughness is greatly deteriorated compared to 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B5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 B5 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B6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本発明よりも劣る。また、溶接金属に高温割れも観察され、継手としての健全性も劣る。 In the joint B6, 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 to that of the present invention regardless of the position of the weld metal. Moreover, a hot crack is also observed in the weld metal, and the soundness as a joint is inferior.
継手B7は、フラックス中のTiO2とともにMo量が過大であるために、溶接金属中のTi、Mo量が過大となり、そのため、粗大な析出物が増加し、かつ、溶接金属が過剰に硬化するため、溶接金属の靭性が溶接金属の位置によらず本発明よりも劣る。 In the joint B7, the amount of Mo is excessive together with the TiO2 in the flux, so the amount of Ti and Mo in the weld metal is excessive, so that coarse precipitates increase and the weld metal hardens excessively. The toughness of the weld metal is inferior to that of the present invention regardless of the position of the weld metal.
継手B8は、TiO2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Ti、Ni量とも過大となり、その結果、粗大な析出物が増加し、かつ、溶接金属強度が過度に高くなり、溶接金属の靭性が溶接金属の位置によらず十分でない。 In the joint B8, since the content of Ni in the flux in addition to TiO2 is excessive, both the amount of Ti and Ni in the weld metal are excessive. As a result, coarse precipitates increase and the weld metal strength is increased. It becomes excessively high and the toughness of the weld metal is not sufficient regardless of the position of the weld metal.
継手B9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、溶接金属中にTiO2が過剰に存在し、粗大なTiO2も多くなり、そのため、溶接金属の靱性も位置によらず劣化している。 Since the amount of TiO2 in the flux is excessive, the joint B9 is not preferable because the rising angle of the bead toe is increased and the bead shape is deteriorated. Further, TiO2 is excessively present in the weld metal and coarse TiO2 is also increased, so that the toughness of the weld metal is deteriorated regardless of the position.
継手B10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 B10, 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B11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ため、好ましくない。 In the joint B11, 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. Since it is inferior, it is not preferable.
継手B12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 B12, since the P amount of the welding wire is excessive, the P amount of the weld metal is also excessive, and therefore the toughness of the weld metal is inferior regardless of the position of the weld metal.
継手B13は、溶接ワイヤのTi含有量が過大であるために、溶接金属中のTi量も過大となり、そのため、溶接金属中に粗大なTi析出物が生じ、溶接金属の靭性劣化が著しい。 In the joint B13, since the Ti content of the welding wire is excessive, the amount of Ti in the weld metal also becomes excessive. Therefore, coarse Ti precipitates are generated in the weld metal, and the toughness of the weld metal is remarkably deteriorated.
継手B14は、溶接ワイヤにTiが含有されていないため、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 B14, since the welding wire does not contain Ti, 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B15は、表面側の靭性は比較的良好であるが、溶接ワイヤ径が同一であるため、溶接金属表面側から裏面側にいくに従って冷却速度が小さくなるため、裏面側にいくほど組織が粗大化している。そのため、表面側から裏面側にいくほど靭性が低下し、裏面上7mmにおける吸収エネルギーは低くなっており、好ましくない。 The joint B15 has relatively good toughness on the surface side, but since the welding wire diameter is the same, the cooling rate decreases from the weld metal surface side to the back surface side, so the structure becomes coarser toward the back surface side. It has become. For this reason, the toughness decreases with increasing distance from the front surface side to the back surface side, and the absorbed energy at 7 mm on the back surface is low, which is not preferable.
継手B16は、第1電極は第2電極に比べて細径とはなっているが、第1電極のワイヤ断面積が第2電極のワイヤ断面積に比べて十分小さくなっておらず、そのため、本発明の効果が十分発揮されない。従って、継手B17と同様、表面側から裏面側にいくほど靭性が低下し、裏面上7mmにおける吸収エネルギーは低くなっており、好ましくない。 In the joint B16, the first electrode has a smaller diameter than the second electrode, but the wire cross-sectional area of the first electrode is not sufficiently smaller than the wire cross-sectional area of the second electrode. The effect of the present invention is not sufficiently exhibited. Therefore, as with the joint B17, the toughness decreases as it goes from the front surface side to the back surface side, and the absorbed energy at 7 mm on the back surface is low, which is not preferable.
継手B17は、逆に第1電極のワイヤ断面積が第2電極のワイヤ断面積に比べて過小であるため、ビード断面形状が不良となり、高温割れが生じているため、好ましくない。 On the other hand, the joint B17 is not preferable because the wire cross-sectional area of the first electrode is excessively smaller than the wire cross-sectional area of the second electrode, and the bead cross-sectional shape becomes poor and high-temperature cracking occurs.
継手B18は、第2電極のワイヤ径が過小であるため、溶接金属の靭性は良好であるものの、融合不良が生じており、継手健全性が損なわれるため、好ましくない。 In the joint B18, since the wire diameter of the second electrode is excessively small, the weld metal has good toughness, but poor fusion occurs and the soundness of the joint is impaired.
以上の実施例の結果から、本発明によれば、板厚が40mm以上の厚手高張力鋼板を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70J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 thick high-tensile steel plate having a thickness of 40 mm or more is welded with a heat input of 400 kJ / cm or more and single-sided high-pass submerged arc welding on one side, the weld metal It is clear that excellent toughness of 70 J or more can be obtained uniformly over the entire thickness range from the front surface side to the back surface side with 2 mmV notch Charpy absorbed energy.
Claims (6)
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%、
B2O3:0.1%〜2.5%からなるフラックスと、
質量%で、
C:0.02〜0.2%、
Si:0.01〜1%、
Mn:0.5〜2.5%、
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第1電極および第2電極の溶接ワイヤを用い、第2電極の溶接ワイヤの直径が6〜8mmであり、かつ第2電極の溶接ワイヤの断面積に対する第1電極の溶接ワイヤの断面積の比率が35〜75%である条件で溶接することを特徴とする溶接金属の靱性に優れた2電極片面1パス大入熱サブマージアーク溶接方法。 When one-sided one-pass welding of steel plates with a thickness of 40 mm or more by two-electrode submerged arc welding,
% By mass
C: 0.02 to 0.2%,
Si: 0.01 to 1%,
Mn: 0.1 to 2.5%
Al: 0.002 to 0.1%,
N: 0.001 to 0.015% is contained,
P: 0.02% or less,
S: 0.01% or less,
O: limited to 0.01% or less,
A steel plate with the balance being Fe and inevitable impurities,
% By mass
SiO 2 : 10 to 25%,
MgO: 5 to 20%,
CaO: 5 to 15%,
CaF 2 : 1 to 10%,
Al 2 O 3 : 5 to 25%,
TiO 2 : 2 to 20%,
Fe: 10 to 25%,
B 2 O 3 : a flux composed of 0.1% to 2.5%,
% By mass
C: 0.02 to 0.2%,
Si: 0.01 to 1%,
Mn: 0.5 to 2.5%
Al: 0.002 to 0.1%,
Ti: 0.005 to 0.3%,
N: 0.001 to 0.015% contained,
P: 0.02% or less,
S: 0.01% or less,
O: Limiting to 0.01% or less, using the welding wire of the first electrode and the second electrode, the balance being Fe and inevitable impurities, the diameter of the welding wire of the second electrode is 6 to 8 mm, and the second Welding is performed under the condition that the ratio of the cross-sectional area of the welding wire of the first electrode to the cross-sectional area of the welding wire of the electrode is 35 to 75%. Submerged arc welding method.
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%、
Ni:0.01〜6%、
Cu:0.01〜1.5%、
Nb:0.002〜0.1%、
V:0.002〜0.5%、及び、
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に記載の溶接金属の靱性に優れた2電極片面1パス大入熱サブマージアーク溶接方法。 The steel sheet is in mass%, and
Ti: 0.002 to 0.05%,
B: 0.0003 to 0.015%,
Mo: 0.01 to 1.5%,
Cr: 0.01 to 1.5%
W: 0.01 to 1.5%
Ni: 0.01-6%,
Cu: 0.01 to 1.5%,
Nb: 0.002 to 0.1%,
V: 0.002-0.5% and
Ta: 0.002 to 0.5% of 1 type or 2 types or more, The two-electrode single-sided single-pass large heat input submerged arc welding method with excellent toughness of the weld metal according to claim 1 .
Ca:0.0002〜0.01%
Mg:0.0002〜0.01%、及び、
REM:0.0002〜0.01%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2電極片面1パス大入熱サブマージアーク溶接方法。 The steel sheet is in mass%, and
Ca: 0.0002 to 0.01%
Mg: 0.0002 to 0.01%, and
REM: 0.0002-0.01% of 1 type or 2 types or more are contained, The 2 electrode single side | surface 1 pass large heat input submerged arc excellent in the toughness of the weld metal of Claim 1 or 2 characterized by the above-mentioned. Welding method.
Mo:1〜5%、及び、
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2電極片面1パス大入熱サブマージアーク溶接方法。 The flux is mass%, and
Mo: 1-5%, and
Ni: 1-5% of 1 type or 2 types are contained, The 2 electrode single side | surface 1 pass large heat input submerged arc welding method excellent in the toughness of the weld metal in any one of Claims 1-3 characterized by the above-mentioned. .
Ni:0.1〜6%、
Cu:0.01〜1.5%、
Cr:0.01〜1.5%、
Mo:0.1〜3%、
W:0.01〜2%、
Nb:0.002〜0.05%、
V:0.005〜0.5%、
Ta:0.002〜0.2%、及び、
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2電極片面1パス大入熱サブマージアーク溶接方法。 The welding wire is in% by mass;
Ni: 0.1 to 6%,
Cu: 0.01 to 1.5%,
Cr: 0.01 to 1.5%
Mo: 0.1 to 3%,
W: 0.01-2%
Nb: 0.002 to 0.05%,
V: 0.005 to 0.5%,
Ta: 0.002 to 0.2%, and
B: One type or two or more types of 0.001 to 0.05% are contained. The two-electrode single-sided one-pass large-diameter excellent in weld metal toughness according to any one of claims 1 to 4 Thermal submerged arc welding method.
Ca:0.0002〜0.01%、
Mg:0.0002〜0.01%、及び、
REM:0.0002〜0.01%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1〜5の何れかに記載の溶接金属の靱性に優れた2電極片面1パス大入熱サブマージアーク溶接方法。 The welding wire is in% by mass;
Ca: 0.0002 to 0.01%,
Mg: 0.0002 to 0.01%, and
REM: 1 type or 2 types or more of 0.0002-0.01% is contained, The 2 electrode single side | surface 1 pass large insertion excellent in the toughness of the weld metal in any one of Claims 1-5 characterized by the above-mentioned Thermal submerged arc welding method.
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Cited By (2)
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CN101817130A (en) * | 2010-04-06 | 2010-09-01 | 天津大桥焊材集团有限公司 | Fire and weather resistant steel welding rod at the level of 50 kilograms and preparation method thereof |
CN102581520A (en) * | 2012-04-10 | 2012-07-18 | 山东大学 | Thin-layer slag protecting medicinal powder for welding high strength steel |
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JP2008264812A (en) * | 2007-04-18 | 2008-11-06 | Kobe Steel Ltd | Groove filler for submerged-arc welding |
JP5551990B2 (en) * | 2010-05-25 | 2014-07-16 | 株式会社神戸製鋼所 | High strength weld metal with excellent CTOD characteristics |
JP5874068B2 (en) * | 2012-01-27 | 2016-03-01 | 株式会社神戸製鋼所 | Flux for single-sided submerged arc welding |
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JPH0899178A (en) * | 1994-09-30 | 1996-04-16 | Kobe Steel Ltd | Submerged arc welding method for one side surface |
JP2000167670A (en) * | 1998-12-08 | 2000-06-20 | Kawasaki Steel Corp | Fillet welding method of high strength thick plate steel |
JP2002018595A (en) * | 2000-07-03 | 2002-01-22 | Nippon Steel Corp | One side submerged arc welding method for steel for low temperature use |
JP2004001028A (en) * | 2002-05-31 | 2004-01-08 | Nippon Steel Corp | Method for high heat input submerged-arc welding |
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Publication number | Priority date | Publication date | Assignee | Title |
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CN101817130A (en) * | 2010-04-06 | 2010-09-01 | 天津大桥焊材集团有限公司 | Fire and weather resistant steel welding rod at the level of 50 kilograms and preparation method thereof |
CN102581520A (en) * | 2012-04-10 | 2012-07-18 | 山东大学 | Thin-layer slag protecting medicinal powder for welding high strength steel |
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