JP4761746B2 - Evaluation method of brittle fracture resistance of large heat input butt welded joints for ship hulls - Google Patents
Evaluation method of brittle fracture resistance of large heat input butt welded joints for ship hulls Download PDFInfo
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本発明は、船体用大入熱突合せ溶接継手の耐脆性破壊発生特性評価方法に関し、特に、板厚が５０ｍｍ以上１００ｍｍ以下で、降伏強度が３９０ＭＰａ級ないし７９６ＭＰａ級の高強度鋼板を大入熱突合せ溶接して構成した船体用溶接構造体における溶接継手の耐脆性破壊発生特性を評価する方法に関する。 The present invention relates to a method for evaluating brittle fracture occurrence characteristics of a large heat input butt welded joint for a hull, and in particular, a high heat input butt for a high strength steel plate having a thickness of 50 mm to 100 mm and a yield strength of 390 MPa to 796 MPa. The present invention relates to a method for evaluating the brittle fracture resistance characteristics of a welded joint in a welded structure for a hull constructed by welding.
溶接構造体において、最も破壊発生の可能性の高い部位は、溶接継手部である。その理由として、溶接時に溶接欠陥が生じ、この欠陥が、破壊の起点となる応力集中部となる可能性が高いこと、さらに、溶接熱の影響により鋼板組織が粗大化し、溶接継手部の耐脆性破壊に対する抵抗値である破壊靭性値Ｋｃが低下すること等が挙げられる。 In the welded structure, a portion having the highest possibility of occurrence of fracture is a welded joint. The reason for this is that a weld defect occurs during welding, and this defect is likely to become a stress concentration part that becomes the starting point of fracture.In addition, the steel sheet structure becomes coarse due to the influence of welding heat, and the brittle resistance of the welded joint part. For example, the fracture toughness value Kc, which is a resistance value against fracture, may be reduced.
それ故、溶接構造体の安全性を確保するためには、溶接継手部の破壊靭性値Ｋｃを正しく評価する必要があり、その評価試験として、溶接継手部の残留応力が厳しく作用する中央切欠き付き広幅引張試験が提案され、これまで広く用いられている。 Therefore, in order to ensure the safety of the welded structure, it is necessary to correctly evaluate the fracture toughness value Kc of the welded joint. As an evaluation test, a central notch in which the residual stress of the welded joint acts severely. A wide-width tensile test has been proposed and has been widely used.
この試験をディープノッチ試験と称し、線形破壊力学に基づいて、溶接継手部における脆性破壊の発生限界値を破壊靭性値Ｋｃとして評価する。 This test is referred to as a deep notch test, and the occurrence limit value of brittle fracture in a welded joint is evaluated as the fracture toughness value Kc based on linear fracture mechanics.
ディープノッチ試験は、図４に示すように、溶接金属２を中央に抱える標準的には幅４００ｍｍの試験片１の中央部において、溶接継手の最脆弱部と想定される位置に、標準的には長さ２４０ｍｍの切欠き３を機械加工で形成した試験片を、矢印方向に引張る試験である。
As shown in FIG. 4, the deep notch test is typically performed at a position assumed to be the weakest part of the welded joint in the central part of the
即ち、ディープノッチ試験においては、大きな試験片、大きな試験機が必要で、費用も多大に要するので、溶接施工時の品質管理や鋼材出荷試験には、その代替試験として、Ｖノッチシャルピー衝撃試験が広く用いられている。 That is, in the deep notch test, a large test piece and a large testing machine are required, and the cost is very high. Therefore, the V-notch Charpy impact test is used as an alternative test in quality control and steel material shipment test during welding. Widely used.
例えば、船級協会で規定する材料規格は、シャルピー試験特性値（試験温度での吸収エネルギーｖＥ値又は破面遷移温度vＴrs）と、ディープノッチ試験で得られる破壊靭性値Ｋｃとの相関関係の上に成り立っている（非特許文献１、参照）。 For example, the material standard specified by the classification society is based on the correlation between the Charpy test characteristic value (absorbed energy vE value or fracture surface transition temperature vTrs at the test temperature) and the fracture toughness value Kc obtained in the deep notch test. (See Non-Patent Document 1).
そして、これまで、上記相関関係に従い、主として板厚５０ｍｍ以下の船体構造用鋼板の溶接継手の破壊靭性値を評価し、その結果に基づいて、船体用鋼板に必要な性能・特性が論じられてきた。 And until now, according to the above correlation, the fracture toughness value of welded joints of hull structural steel plates with a plate thickness of 50 mm or less was mainly evaluated, and based on the results, performance and characteristics required for hull steel plates have been discussed. It was.
その結果、溶接部の破壊靭性値を考慮した船体用鋼板として、脆性破壊特性と疲労特性に優れた鋼板（ＴＭＣＰ［Thermo-Mechanical Control Process］鋼板）が開発され（特許文献１、参照）、板厚５０ｍｍ程度のＴＭＣＰ鋼板が、大型タンカーや６０００ＴＥＵ（Twenty-foot Equivalent Units）以下のコンテナー船の建造に使用されているが、近年、６０００ＴＥＵ以上の大型コンテナー船の建造ニーズが高まり、板厚６０ｍｍや、それ以上の板厚の鋼板も、船体構造用鋼板として実用化されている。 As a result, steel plates with excellent brittle fracture characteristics and fatigue properties (TMCP [Thermo-Mechanical Control Process] steel plates) were developed as steel plates for ship hulls considering the fracture toughness values of welds (see Patent Document 1). TMCP steel plates with a thickness of about 50 mm are used for construction of large tankers and container ships of 6000 TEU (Twenty-foot Equivalent Units) or less. , even more the thickness of the steel sheet, it has been put to practical use as a hull structural steel.
しかし、現在、実用化されている船体構造用鋼板の強度は、降伏強さで３９０ＭＰａレベルである。即ち、降伏強さが３９０ＭＰａ以上で、かつ、板厚が５０ｍｍ以上の鋼板において、シャルピー試験結果とディープノッチ試験結果との相関関係は十分解明されておらず、板厚５０ｍｍ以上の高強度鋼板を溶接した構造体における溶接継手の機械的特性を評価し、溶接継手の品質を管理するためには、従来知見を適用できるか否かを含めて検討する必要がある。 However, the strength of the steel plate for ship hull structure that is currently in practical use is 390 MPa level in terms of yield strength. That is, in a steel sheet having a yield strength of 390 MPa or more and a plate thickness of 50 mm or more, the correlation between the Charpy test result and the deep notch test result has not been sufficiently elucidated. In order to evaluate the mechanical characteristics of the welded joint in the welded structure and manage the quality of the welded joint, it is necessary to consider whether or not the conventional knowledge can be applied.
通常、溶接継手部に変形や歪が集中するのを阻止するために、溶接金属の強度や硬さを母材の強度や硬さよりも高くすることが、溶接継手部の設計指針における基本であり、溶接金属を選定する際には、母材強度との比較でオーバーマッチングとなる継手設計がなされている。しかし、上記継手設計が、板厚５０ｍｍ以上の高強度鋼板を溶接した構造体における溶接継手の設計に適用できるか否かについても検討する必要がある。 Usually, in order to prevent deformation and strain from concentrating on the welded joint, the strength and hardness of the weld metal should be higher than the strength and hardness of the base metal in the design guidelines for the welded joint. When selecting a weld metal, a joint design that is overmatched by comparison with the strength of the base metal is made. However, it is necessary to consider whether the joint design can be applied to the design of a welded joint in a structure in which a high-strength steel plate having a thickness of 50 mm or more is welded.
溶接構造物の大型化が進み、例えば、６０００ＴＥＵを超えるコンテナ船の建造においては、板厚５０ｍｍ以上で、かつ、設計応力が高い高張力厚鋼板を用い建造することが要望されている。 For example, in the construction of a container ship exceeding 6000 TEU, it is desired to use a high-tensile steel plate having a plate thickness of 50 mm or more and a high design stress.
そこで、本発明者らは、溶接継手部が最も破壊発生の可能性の高い部位になり得ることから、板厚５０ｍｍ以上の高強度鋼板を突合せ溶接して形成した溶接継手の性能・特性について調査した。 Accordingly, the present invention monaural is welded since the joint can become likely site of the most fracture, investigated the performance and characteristics of the welded joint formed by butt welding the above high-strength steel sheet thickness 50mm did.
その結果、上記溶接継手（大入熱溶接継手）の性能・特性は、小型試験であるＶノッチシャルピー衝撃試験で良好な結果を示しても、大型破壊試験であるディープノッチ試験では、必ずしも良好な破壊靭性値Ｋｃを示さないことを知見した。 As a result, the performance and characteristics of the above-mentioned welded joint (high heat input welded joint) are not necessarily good in the deep notch test, which is a large fracture test, even if the V-notch Charpy impact test, which is a small test, shows good results. It was found that the fracture toughness value Kc was not shown.
即ち、これまで、降伏強さ３９０ＭＰa級、板厚５０ｍｍ以下の鋼板を突合せ溶接した場合の溶接継手の性能・特性において確認されていた“シャルピー試験結果と破壊靭性値Ｋｃとの相関関係”が成立しないことを知見した。 In other words, the “correlation between Charpy test results and fracture toughness value Kc”, which has been confirmed so far in the performance and characteristics of welded joints when butt-welding steel sheets with a yield strength of 390 MPa and a thickness of 50 mm or less, is established. I found out that I would not.
そこで、本発明は、上記知見を踏まえ、板厚が５０ｍｍ以上１００ｍｍ以下で、降伏強度が３９０ＭＰａ級ないし７９６ＭＰａ級の船体用高強度鋼板を大入熱突合せ溶接する場合に、破壊靭性値Ｋｃが十分に高い溶接継手の形成を確実にするための特性評価方法を提供することを課題とする。 Therefore, based on the above findings, the present invention has a sufficient fracture toughness value Kc when high-heat butt welding is performed on high-strength steel plates for ship hulls having a thickness of 50 mm to 100 mm and a yield strength of 390 MPa to 796 MPa. Another object of the present invention is to provide a characteristic evaluation method for ensuring the formation of a high weld joint.
従来、溶接継手の設計においては、溶接継手部に変形や歪が集中するのを阻止するため、溶接金属の強度や硬さを、母材の強度や硬さよりも高くすること（オーバーマッチング）を基本としていたが、本発明者らは、前述した“シャルピー試験結果と破壊靭性値Ｋｃとの相関関係”が成立しないとの知見を踏まえ、従来のオーバーマッチングに問題があると発想し、該発想の下に上記課題を解決するため、溶接継手部の破壊靭性値Ｋｃを支配する因子について系統的に調査した。 Conventionally, when designing welded joints, the strength and hardness of the weld metal must be made higher than the strength and hardness of the base metal (overmatching) in order to prevent deformation and strain from concentrating on the welded joint. Based on the knowledge that the above-mentioned “correlation between the Charpy test result and the fracture toughness value Kc” is not established, the present inventors have thought that there is a problem with the conventional overmatching and the idea In order to solve the above problems, systematic investigation was conducted on factors governing the fracture toughness value Kc of the welded joint.
その結果、降伏強度が４６０ＭＰａ級で、板厚が５０ｍｍ以上の高強度鋼板を大入熱突合せ溶接する場合においては、溶接金属の硬さが、シャルピー試験特性値と破壊靭性値Ｋｃとの相関関係に大きく影響することを見出した。 As a result, the yield strength at 460MPa class, when the plate thickness is large heat input butt welding the above high strength steel sheet 50mm is the hardness of the weld metal, the correlation between the Charpy test characteristic values and fracture toughness value Kc It has been found that it greatly affects
即ち、大入熱突合せ溶接継手においては、溶接金属の硬さと母材の硬さとの関係が、溶接継手のフュージョンライン部での破壊靭性値Ｋｃに大きな影響を及ぼすという事実を発見し、従来知られていた“Ｖノッチシャルピー衝撃試験結果と破壊靭性値との相関関係”が、溶接金属の硬さの影響を大きく受けるということを知見した。 That is, in the high heat input butt welded joint, the fact that the relationship between the hardness of the weld metal and the hardness of the base material has a great influence on the fracture toughness value Kc at the fusion line portion of the welded joint has been discovered. It was found that the “correlation between the V-notch Charpy impact test result and the fracture toughness value” was greatly affected by the hardness of the weld metal.
そして、上記知見に基づき、溶接金属の硬さとシャルピー衝撃試験結果の両者から予測破壊靭性値Ｋｃ値と要求Ｋｃ値に基づき、大入熱突合せ溶接継手の破壊靭性値を検証する手法を確立し、本発明を完成した。本発明の要旨は、以下のとおりである。 And based on the above knowledge, based on the predicted fracture toughness value Kc value and the required Kc value from both the hardness of the weld metal and the Charpy impact test result, a method for verifying the fracture toughness value of the high heat input butt weld joint is established, The present invention has been completed. The gist of the present invention is as follows.
（１）板厚が５０ｍｍ以上１００ｍｍ以下で、降伏強度が３９０ＭＰａ級ないし７９６ＭＰａ級の高強度鋼板を大入熱突合せ溶接した船体用溶接構造体における溶接継手であって、Ｖノッチシャルピー試験結果とディープノッチ試験結果との相関関係が得られない場合のある、船体用大入熱突合せ溶接継手の機械的特性を評価する方法において、
（ａ）溶接金属の板厚中央部の硬さＨｖ（ＷＭ）を測定し、
（ｂ）Ｖノッチシャルピー衝撃試験により溶接継手部の吸収エネルギーｖＥと遷移温度vＴrsを測定し、
（ｃ）上記実測Ｈｖ（ＷＭ）値が、熱影響を受けていない母材の板厚方向平均硬さＨｖ（ＢＭ）の１．１倍以下を満たすこと、及び、上記実測ｖＥ値が、（船体用構造体設計温度−１０）℃での測定値で５３Ｊ以上を満たすことを確認し、
（ｄ）実測遷移温度vＴrsに基づく予測破壊靭性値Ｋｃ値が２０００Ｎ／ｍｍ 1.5 超であることを評価することを特徴とする、船体用大入熱突合せ溶接継手の耐脆性破壊発生特性評価方法。
(1) thickness is at least 50mm 100mm or less, the yield strength is a welded joint in 390MPa class to hull welding structure and large heat input butt welded high strength steel sheet 796MPa grade, V notch Charpy test results and deep In a method for evaluating the mechanical properties of a large heat input butt welded joint for a hull, which may not be correlated with the notch test result ,
(A) Measure the hardness Hv (WM) of the central portion of the weld metal thickness ,
(B) The absorbed energy vE and transition temperature vTrs of the welded joint are measured by a V-notch Charpy impact test,
(C) The measured Hv (WM) value satisfies 1.1 times or less of the thickness direction average hardness Hv (BM) of the base material not affected by heat , and the measured vE value is ( It is confirmed that the design value of the hull structure design temperature −10) ° C. satisfies 53J or more .
(D) A method for evaluating brittle fracture occurrence characteristics of a large heat input butt weld joint for a hull, characterized by evaluating that a predicted fracture toughness value Kc value based on measured transition temperature vTrs is more than 2000 N / mm 1.5 .
（２）前記実測Ｈｖ（ＷＭ）値が、２１０以下を満たすことを確認することを特徴とする、前記（１）に記載の船体用大入熱突合せ溶接継手の耐脆性破壊発生特性評価方法。 (2) The method for evaluating brittle fracture resistance characteristics of a large heat input butt weld joint for a hull according to (1), wherein the measured Hv (WM) value satisfies 210 or less.
本発明によれば、板厚が５０ｍｍ以上１００ｍｍ以下で、降伏強度が３９０ＭＰａ級ないし７９６ＭＰａ級の船体用高強度鋼板を突合せ溶接した溶接継手であって、Ｖノッチシャルピー試験結果とディープノッチ試験結果との相関関係が得られない場合のある、船体用大入熱突合せ溶接継手において、適正な溶接方法、溶接材料、鋼材を選定することにより、厚手高強度鋼板を用いて建造する船体用溶接構造物の脆性破壊に対する抵抗特性を従来以上に確保することができる。 According to the present invention, a welded joint obtained by butt welding high-strength steel plates for ship hulls having a thickness of 50 mm or more and 100 mm or less and a yield strength of 390 MPa to 796 MPa , In a large heat input butt welded joint for ship hulls, a welded structure for ship hulls constructed using thick, high-strength steel sheets by selecting appropriate welding methods, welding materials, and steel materials. The resistance characteristic against brittle fracture can be ensured more than before.
これまで、溶接継手の設計においては、溶接継手部に変形や歪が集中することを阻止するため、溶接金属（ＷＭ）の強度や硬さを、母材（ＢＭ）の強度や硬さよりも高くすることが基本であり、溶接材料は、その強度が母材の強度と比較してオーバーマッチングとなるよう選定されていた。 Until now, in the design of welded joints, the strength and hardness of the weld metal (WM) is higher than the strength and hardness of the base metal (BM) in order to prevent deformation and strain from concentrating on the welded joint. The welding material has been selected so that its strength is overmatched compared to the strength of the base material.
「高強度厚鋼板の溶接継手を設計する場合、このオーバーマッチングに問題がある」と本発明者らが発想したことは前述したとおりであるが、この問題の実態を解明するため、本発明者らは、降伏強さで４６０ＭＰａ級の鋼板を用い、溶接金属がオーバーマッチングとなるように選定した溶接材料を用いて溶接継手を形成し、ディープノッチ試験で、その機械的性質を評価した。 "When designing welded joints of high strength thick steel plate, there is a problem with this overmatching" but to what the present inventors have conceived is as described above, in order to elucidate the actual conditions of this problem, the present inventors Luo, with 460MPa grade steel sheet yield strength, using a selected weld material as the weld metal is over matching form a welded joint, a deep notch test, to evaluate its mechanical properties.
その結果、上記溶接継手は、溶接継手部のＶノッチシャルピー試験で、−２０℃（試験温度）で９０Ｊ以上の十分な吸収エネルギー値を示し、かつ、破面遷移温度も−２０℃と極めて良好な値を示したにもかかわらず、ディープノッチ試験では、破壊靭性値Ｋｃが２０００Ｎ／ｍｍ1.5以下で、極めて低い値を示した。 As a result, the welded joint showed a sufficient absorbed energy value of 90 J or more at −20 ° C. (test temperature) in the V-notch Charpy test of the welded joint, and the fracture surface transition temperature was also very good at −20 ° C. In spite of showing a good value, in the deep notch test, the fracture toughness value Kc was 2000 N / mm 1.5 or less, showing an extremely low value.
結局、これらの試験結果から、従来のオーバーマッチング方式に従って高強度厚鋼板の溶接継手を設計した場合、溶接継手の性能・特性は、従来知られている“Ｖノッチシャルピー試験結果とディープノッチ試験結果との相関関係”から大きく逸脱することが判明した。 After all, from these test results, when designing welded joints of high-strength thick steel plates according to the conventional overmatching method, the performance and characteristics of the welded joints are known as “V-notch Charpy test results and deep notch test results. Was found to deviate significantly from the "correlation with".
そこで、ディープノッチ試験での破壊発生点を詳細に調査した結果、
（ｉ）破壊の発生位置は、溶接金属（ＷＭ）と溶接熱影響部（ＨＡＺ）の境界（溶接溶融線［ＦＬ］）であること、及び、
（ii）破壊の発生した部分の微視的組織は、シャルピー試験片で観察された破壊発生部の微視的組織と同じであること、
を突き止め、さらに、
（iii）ディープノッチ試験とシャルピー試験において、破壊のドライビングフォースとなる局所応力の分布形態を３次元有限要素法で解析した結果，両分布形態は著しく異なること、
を予見した。
Therefore, as a result of investigating the failure occurrence point in the deep notch test in detail,
(I) The occurrence position of the fracture is the boundary between the weld metal (WM) and the weld heat affected zone (HAZ) (weld fusion line [FL]), and
(Ii) The microscopic structure of the fractured part is the same as the microscopic structure of the fractured part observed on the Charpy specimen.
As well as
(Iii) In the deep notch test and the Charpy test, as a result of analyzing the distribution form of local stress, which becomes the driving force of fracture, by the three-dimensional finite element method, both distribution forms are remarkably different.
Foresee.
図１は、板厚７０ｍｍの試験片につき、溶接金属（ＷＭ）と溶接熱影響部（ＨＡＺ）との境界部（ＦＬ）、及び、溶接熱影響部（ＨＡＺ）にノッチを設け、ノッチ先端でのＣＴＯＤ（Crack Tip Opening Displacement:亀裂端開口変位）が０．０５ｍｍになる場合のノッチ先端から亀裂進展方向に離れた各位置における亀裂開口応力分布をＦＥＭ（３次元有限要素法）で解析した結果の一例を示す。 FIG. 1 shows a test piece having a thickness of 70 mm, in which notches are provided at the boundary (FL) between the weld metal (WM) and the weld heat affected zone (HAZ), and at the weld heat affected zone (HAZ). Analysis of crack opening stress distribution at each position distant from the notch tip in the crack propagation direction when the CTOD (Crack Tip Opening Displacement) is 0.05 mm, using FEM (3D Finite Element Method) An example is shown.
この図から、（iv）板厚が５０ｍｍを超え７０ｍｍ程度になると、板厚方向での拘束度（力）が著しく増大して、溶接金属（ＷＭ）の強度が、母材（ＢＭ）や溶接熱影響部（ＨＡＺ）の強度よりも高いと（ＷＭ−Ｈの場合）、局所応力が、溶接金属（ＷＭ）と溶接熱影響部（ＨＡＺ）との境界で著しく増大することが解る（図中、□［ＷＭ−Ｈ］及び黒四角［ＷＭ−Ｌ］、参照）。 From this figure, (iv) When the plate thickness exceeds 50 mm and reaches about 70 mm, the degree of restraint (force) in the plate thickness direction increases remarkably, and the strength of the weld metal (WM) is increased by the base material (BM) and welding. It can be seen that when the strength is higher than the heat affected zone (HAZ) (in the case of WM-H), the local stress significantly increases at the boundary between the weld metal (WM) and the weld heat affected zone (HAZ) (in the figure). , □ [WM-H] and black square [WM-L], see).
一方、溶接金属（ＷＭ）の強度が、母材（ＢＭ）や溶接熱影響部（ＨＡＺ）の強度よりも高い場合（ＷＭ−Ｈの場合）であっても、溶接熱影響部（ＨＡＺ）では、局所的な応力は増大せず、溶接金属（ＷＭ）の強度が低い場合（ＷＭ−Ｌの場合）とほぼ同じになる。 On the other hand, even when the strength of the weld metal (WM) is higher than that of the base material (BM) or the weld heat affected zone (HAZ) (in the case of WM-H), the weld heat affected zone (HAZ) The local stress does not increase and is almost the same as when the strength of the weld metal (WM) is low (in the case of WM-L).
このことから、Ｋｃ値が低下する理由は、溶接金属（ＷＭ）の強度が、母材（ＢＭ）や溶接熱影響部（ＨＡＺ）の強度よりも高い場合（ＷＭ−Ｈの場合）に、溶接金属（ＷＭ）と溶接熱影響部（ＨＡＺ）との境界で、局所的な応力が増大するためであると考えられる。 From this, the reason why the Kc value decreases is that when the strength of the weld metal (WM) is higher than the strength of the base metal (BM) or the weld heat affected zone (HAZ) (in the case of WM-H), welding is performed. This is probably because local stress increases at the boundary between the metal (WM) and the weld heat affected zone (HAZ).
即ち、上記解析の結果、本発明者らは、（ｖ）溶接金属（ＷＭ）と溶接熱影響部（ＨＡＺ）との境界での局所応力の著しい増大を抑制し、Ｋｃ値を向上させるためには、溶接金属（ＷＭ）の強度をできるだけ低くすることが必要であることを見出した。 That is, the result of the analysis, the present invention monaural, in order to improve a significant increase was suppressed, Kc value of the local stress at the boundary between the (v) the weld metal (WM) and weld heat affected zone (HAZ) Found that the strength of the weld metal (WM) needs to be as low as possible.
ここで、上記解析結果を踏まえ、溶接金属（ＷＭ）の硬さ（Ｈｖ（ＷＭ））を種々変化させて破壊靭性値Ｋｃを測定し、Ｋｃ測定値を“溶接金属の硬さ［Ｈｖ（ＷＭ）］／母材の硬さ［Ｈｖ（ＢＭ）］”に対してプロットした。 Here, based on the above analysis results, the fracture toughness value Kc is measured by changing the hardness (Hv (WM)) of the weld metal (WM) in various ways, and the measured Kc value is expressed as “hardness of weld metal [Hv (WM)”. )] / Base material hardness [Hv (BM)] ".
その結果、本発明者らは、図２中「●」に示すように、溶接金属の硬さ［Ｈｖ（ＷＭ）］を、“母材の硬さ［Ｈｖ（ＢＭ）］×１．１以下”に抑制すれば、局所的な応力の増大による破壊靭性値の低下を防止できて、５０００Ｎ／ｍｍ1.5程度の破壊靭性値を確保できることを知見した。 As a result, the present invention monaural, as shown in FIG. 2 "●", the hardness of the weld metal [Hv (WM)], "hardness of the base metal [Hv (BM)] × 1.1 or less It has been found that if it is suppressed to "", a decrease in fracture toughness value due to an increase in local stress can be prevented, and a fracture toughness value of about 5000 N / mm 1.5 can be secured.
特に、ＹＰが３９０ＭＰａ以上の高強度鋼においては、局所応力の増大がより顕著となるので、上記程度の破壊靭性値を確保するため、溶接金属の硬さ［Ｈｖ（ＷＭ）］を、数値をもって“２１０以下”に限定することが望ましい。 In particular, in the YP is 390M P a more high strength steel, because the increase in local stress becomes more remarkable, in order to ensure the fracture toughness value of about the hardness of the weld metal [Hv (WM)], It is desirable to limit the numerical value to “210 or less”.
このように、溶接金属の硬さ［Ｈｖ（ＷＭ）］を、母材の硬さ［Ｈｖ（ＢＭ）］の１．１倍以下になるように低くすることが、溶接継手において、微視的組織で支配される破壊特性（靭性）に見合った破壊靭性値Ｋｃ、即ち、少なくとも２０００Ｎ／ｍｍ1.5を超えるＫｃ値、好ましくは３５８０Ｎ／ｍｍ1.5を超えるＫｃ値、より好ましくは４３５４Ｎ／ｍｍ1.5以上のＫｃ値を確保するために必要であることを知見した。 In this way, in the welded joint, it is microscopic to reduce the hardness [Hv (WM)] of the weld metal so that it is 1.1 times or less the hardness [Hv (BM)] of the base metal. fracture properties governed organization fracture toughness value Kc commensurate with (toughness), i.e., Kc value exceeding at least 2000N / mm 1.5, preferably Kc value exceeding 3580N / mm 1.5, more preferably 4354N / mm 1.5 or more It was found that it is necessary for securing the Kc value.
ここで、確保すべき“少なくとも２０００Ｎ／ｍｍ1.5超”（本発明で“破壊靭性値Ｋｃが２０００Ｎ／ｍｍ1.5超”と規定）の破壊靭性値Ｋｃは、日本海事協会が、船体用鋼溶接構造物を設計する場合において定める船体設計温度（−１０℃：船舶の最低使用温度）に準拠し、−１０℃（基準温度）での値とする。 Here, the fracture toughness value Kc of “at least 2000 N / mm 1.5 ” (specified in the present invention as “fracture toughness value Kc is more than 2000 N / mm 1.5 ”) is determined by the Japan Maritime Association. In accordance with the hull design temperature (−10 ° C .: minimum ship operating temperature) determined when designing an object, the value is −10 ° C. (reference temperature).
なお、好ましいＫｃ値３５８０Ｎ／ｍｍ1.5は、疲労き裂を導入した試験片で評価した場合に必要な値であり、また、より好ましいＫｃ値４３５４Ｎ／ｍｍ1.5は、切り欠き先端幅が０．１ｍｍ程度である試験片で評価した場合に必要な値である。 A preferable Kc value of 3580 N / mm 1.5 is a value necessary for evaluation with a test piece into which a fatigue crack has been introduced. A more preferable Kc value of 4354 N / mm 1.5 is a notch tip width of 0.1 mm. This is a necessary value when an evaluation is made with a test piece having a degree.
また、下記式（１）〜（３）に従えば、シャルピー試験結果（vＥ）に基づいてＫｃ値を推定できるので、推定Ｋｃ値を併せて図２に示した。 In addition, according to the following formulas (1) to (3), the Kc value can be estimated based on the Charpy test result (vE), so the estimated Kc value is also shown in FIG.
Ｋｃ（Ｔ）＝５.６σｙ0・exp（ｋ0（１／iＴk−１／Ｔ）） …（１）
iＴk＝（０.００３２１σｙ0＋０.３９１）vＴrs＋Ａ√ｔ＋Ｘ …（２）
ｋ0＝Ｃ・iＴk−Ｄ …（３）
ここで、σｙ0：室温での降伏強さ(kg/ｍｍ2)
ｔ：板厚(ｍｍ)、Ｔ：試験温度
Ａ：板厚効果に係る係数で、１．５≦Ａ≦３．５
Ｘ：切り欠き先鋭度に係る係数で、−２０≦Ｘ≦８０
Ｃ：ｋ０に係る係数で、４≦Ｃ≦８９
Ｄ：ｋ０に係る係数で、１００≦Ｄ≦６００
Kc (T) = 5.6σy 0 · exp (k 0 (1 /
iTk = (0.0031σy 0 +0.391) vTrs + A√t + X (2)
k 0 = C · iTk−D (3)
Where σy 0 : yield strength at room temperature (kg / mm 2 )
t: Plate thickness (mm), T: Test temperature
A: a coefficient related to the plate thickness effect, 1.5 ≦ A ≦ 3.5
X: coefficient related to notch sharpness, −20 ≦ X ≦ 80
C: coefficient related to k 0 , 4 ≦ C ≦ 89
D: Coefficient associated with k 0 , 100 ≦ D ≦ 600
上記式（２）及び（３）は、Ｋｃとシャルピー特性との相関式である。Ａは、力学的に決定される板厚効果に係る係数であり、通常、１．５〜３．５であるが、推定精度の点から、２．５〜３．０が好ましい。Ｘは、鋼板の製造方法や溶接継ぎ手における溶接方法に依存する定数であり、通常、−２０〜８０であるが、ＴＭＣＰ鋼では、１５〜７０が好ましい。 The above equations (2) and (3) are correlation equations between Kc and Charpy characteristics. A is a coefficient related to the plate thickness effect determined dynamically, and is usually 1.5 to 3.5, but is preferably 2.5 to 3.0 from the viewpoint of estimation accuracy. X is a constant depending on the steel plate production method and the welding method in the weld joint, and is usually -20 to 80, but 15 to 70 is preferable for TMCP steel.
上記式（３）は、Ｋｃと試験温度の関係において基準となる値を表す式である。Ｃ及びＤは、鋼材の製造方法や溶接方法、組織等により定まる定数であり、通常、Ｃは４〜８９、Ｄは１００〜６００であるが、ＴＭＣＰ鋼を適用する点から、Ｃは６．５〜７．０が好ましく、また、Ｄは４００〜５００が好ましい。 The above expression (3) is an expression representing a reference value in the relationship between Kc and the test temperature. C and D are constants determined by the manufacturing method, welding method, structure, etc. of the steel material. Normally, C is 4 to 89 and D is 100 to 600. However, from the point of applying TMCP steel, C is 6. 5 to 7.0 are preferable, and D is preferably 400 to 500.
なお、上記式（２）及び（３）において、最も好ましい値は、Ａ＝２．７４、Ｘ＝６６.１、Ｃ＝６.６５、Ｄ＝４４０である。 In the above formulas (2) and (3), the most preferable values are A = 2.74, X = 66.1, C = 6.65, and D = 440.
本発明で用いた式（２）及び（３）は、従来からＫｃとシャルピー特性との相関関係を表す式として知られているものである。しかし、この式は実験式であり、鋼材の強度や溶接方法によって大きな影響を受けることも広く知られている事実である。これまでには、船体用鋼板としては存在しなかった降伏点３９０ＭＰａ以上の鋼板や、板厚が５０ｍｍ以上の鋼板において、Ｋｃとシャルピーの相関関係を系統的に調査した事実はない。 Expressions (2) and (3) used in the present invention are conventionally known as expressions representing the correlation between Kc and Charpy characteristics. However, this equation is an empirical equation, and it is a well-known fact that it is greatly affected by the strength of steel and the welding method. So far, there is no fact that the correlation between Kc and Charpy has been systematically investigated in a steel plate having a yield point of 390 MPa or more and a steel plate having a thickness of 50 mm or more, which has not existed as a steel plate for ship hulls.
本発明によって、はじめて、降伏点３９０ＭＰａ以上の鋼板で、かつ、板厚が５０ｍｍ以上の鋼板においても、Ｋｃとシャルピーの相関関係を、上記式の形を適用できることを突き止め、上記適用範囲で適用し得る定数又は係数の範囲及び適正値を明らかにしたのである。 According to the present invention, for the first time, even in a steel plate having a yield point of 390 MPa or more and a steel plate having a thickness of 50 mm or more, the correlation between Kc and Charpy can be applied and the above formula can be applied. The range of constants or coefficients to be obtained and the appropriate values were clarified.
推定Ｋｃ値とＨｖ（ＷＭ）／Ｈｖ（ＢＭ）の間に相関関係はないが、“Ｈｖ（ＷＭ）／Ｈｖ（ＢＭ）≦１．１”の範囲で、推定Ｋｃ値と測定Ｋｃ値はほぼ対応関係にあるので、本発明者は、該対応関係について詳細に調査した。その結果を図３に示す。 Although there is no correlation between the estimated Kc value and Hv (WM) / Hv (BM), the estimated Kc value and the measured Kc value are almost in the range of “Hv (WM) / Hv (BM) ≦ 1.1”. Since there is a correspondence relationship, the inventor investigated the correspondence relationship in detail. The result is shown in FIG.
図３に示すように、“Ｈｖ（ＷＭ）／Ｈｖ（ＢＭ）≦１．１”において、シャルピー試験結果（vＥ）に基づく推定Ｋｃ値と測定Ｋｃ値は対応する。このことは、上記硬さ比範囲においては、従来のＶノッチシャルピー衝撃試験の結果で、大入熱突合せ溶接継手の耐脆性破壊発生特性を評価できることを意味している。 As shown in FIG. 3, in “Hv (WM) / Hv (BM) ≦ 1.1”, the estimated Kc value based on the Charpy test result (vE) corresponds to the measured Kc value. This means that the brittle fracture resistance of the high heat input butt welded joint can be evaluated by the result of the conventional V-notch Charpy impact test in the above hardness ratio range.
即ち、溶接継手において所定の破壊靭性値Ｋｃを確保するためには、溶接継手の最脆弱部である溶接溶融線（ＦＬ）において局所応力が増大しないようにすることが肝要であることは前述したが、同時に、ＦＬ近傍での微視的な耐脆性破壊発生特性を確保する必要があり、その評価は、“Ｈｖ（ＷＭ）／Ｈｖ（ＢＭ）≦１．１”であれば、従来のＶノッチシャルピー衝撃試験により可能であることを知見した。 That is, in order to ensure the predetermined fracture toughness value Kc in the welded joint, it is important to prevent the local stress from increasing in the weld melt line (FL) which is the most fragile part of the welded joint. However, at the same time, it is necessary to secure microscopic brittle fracture resistance in the vicinity of the FL, and if the evaluation is “Hv (WM) / Hv (BM) ≦ 1.1”, the conventional V It was found that it was possible by the notch Charpy impact test.
本発明において、溶接金属の硬さ［Ｈｖ（ＷＭ）］は、“Ｈｖ（ＷＭ）／Ｈｖ（ＢＭ）≦１．１”を満たす必要があるが、降伏点４６０ＭＰａ級で板厚５０ｍｍ以上の船体用高強度構造用厚鋼板を突合せ溶接し、溶接部において、２０００Ｎ／ｍｍ1.5を超えるＫｃ値、好ましくは３５８０Ｎ／ｍｍ1.5を超えるＫｃ値、より好ましくは４３５４Ｎ／ｍｍ1.5以上のＫｃ値を確保するには、溶接金属の硬さを２１０以下にする必要がある。 In the present invention, the hardness [Hv (WM)] of the weld metal needs to satisfy “Hv (WM) / Hv (BM) ≦ 1.1”, but the hull having a yield point of 460 MPa class and a plate thickness of 50 mm or more. use high strength structural steel plate by butt welding, the welding unit, Kc value exceeding 2000N / mm 1.5, preferably Kc value exceeding 3580N / mm 1.5, more preferably to ensure 4354N / mm 1.5 or more Kc value For this, the hardness of the weld metal needs to be 210 or less.
溶接構造物においては、線形破壊力学を用いて、設計応力σDと想定欠陥寸法ａより要求破壊靭性値：Ｋｑ＝σD√(πａ)を容易に算出できる。それ故、ＫｑとＫｃを比較してＫｑ≦Ｋｃであれば、溶接構造物は脆性亀裂の発生に対して安全であると評価できる。 In a welded structure, the required fracture toughness value: Kq = σ D √ (πa) can be easily calculated from the design stress σ D and the assumed defect size a using linear fracture mechanics. Therefore, if Kq and Kc are compared and Kq ≦ Kc, it can be evaluated that the welded structure is safe against the occurrence of brittle cracks.
例えば、船体用構造用鋼板の要求靭性値等の規格が、上記のような評価思想に基づいて成り立っている（非特許文献１、参照）。そして、−１０℃（日本海事協会が定めた船体設計温度に準拠する基準温度）で、Ｋｑ≦Ｋｃであることが求められる。 For example, standards such as required toughness values of structural steel plates for ship hulls are based on the above evaluation concept (see Non-Patent Document 1). And it is calculated | required that it is Kq <= Kc at -10 degreeC (reference temperature based on the hull design temperature which the Japan Maritime Association established).
そこで、本発明においては、（ａ１）溶接金属の硬さＨｖ（ＷＭ）と母材の硬さＨｖ（ＢＭ）の比Ｈｖ（ＷＭ）／Ｈｖ（ＢＭ）が１．１以下、又は、（ａ２）溶接金属の硬さＨｖ（ＷＭ）が２１０以下の場合において、（ｂ２）溶接部の破壊靭性値Ｋｃが下記式を満たすこととする。
Ｋｃ≧Ｋｑ＝σD√（πａ）（σD：設計応力、ａ：想定欠陥寸法）
Therefore, in the present invention, (a1) the ratio Hv (WM) / Hv (BM) of the hardness Hv (WM) of the weld metal to the hardness Hv (BM) of the base metal is 1.1 or less , or (a2 ) When the hardness Hv (WM) of the weld metal is 210 or less, (b2) the fracture toughness value Kc of the welded portion satisfies the following formula.
Kc ≧ Kq = σ D √ (πa) (σ D : design stress, a: assumed defect size)
なお、破壊靭性値Ｋｃは、前述したように、日本海事協会が定める船体設計温度（−１０℃）に準拠して、−１０℃での値である。 Note that the fracture toughness value Kc is a value at −10 ° C. in accordance with the hull design temperature (−10 ° C.) determined by the Japan Maritime Association, as described above.
ここで、想定欠陥寸法（ａ）は、溶接した際に生じる欠陥や、それを起点にして成長した疲労亀裂などの欠陥が溶接継手に存在すると想定して定めた欠陥の寸法値である。 Here, the assumed defect size (a) is a size value of a defect determined on the assumption that a defect generated when welding and a defect such as a fatigue crack grown from the defect exist in the welded joint.
本発明において対象とする溶接構造用高強度鋼板は、高強度であればよく、この限りで強度や用途に制限はないが、本発明は、降伏点３９０ＭＰａ級ないし７９６ＭＰａ級の船体用溶接構造用鋼板の大入熱突合せ溶接において、耐脆性破壊発生特性に優れた溶接継手を形成することができる。 The high-strength steel sheet for welded structure that is the subject of the present invention is not particularly limited as long as it has high strength, and the present invention does not limit the strength or use, but the present invention is a welded structure for ship bodies having a yield point of 390 MPa class to 796 MPa class In high heat input butt welding of steel sheets for welding, a welded joint having excellent brittle fracture resistance can be formed.
本発明の溶接継手が、確かに所要の破壊靭性値Ｋｃを備えているか否かは、ディープノッチ試験により破壊靭性値を測定することにより確認できる。 Whether or not the welded joint of the present invention has the required fracture toughness value Kc can be confirmed by measuring the fracture toughness value by a deep notch test.
しかし、ディープノッチ試験は、前述したように、シャルピー試験に比べ大掛かりな試験であり、試験片を作製するのにも手間がかかり、必要な時に迅速に対応し難いのが難点である。 However, as described above, the deep notch test is a larger test than the Charpy test, and it takes time and effort to produce a test piece, and it is difficult to respond quickly when necessary.
そこで、本発明者らは、Ｈｖ（ＷＭ）／Ｈｖ（ＢＭ）≦１．１において、シャルピー試験結果（ｖＥ）に基づく予測Ｋｃ値と測定Ｋｃ値は対応し（図３、参照）、このことは、上記範囲においては、従来のＶノッチシャルピー衝撃試験の結果で、大入熱突合せ溶接継手の耐脆性破壊発生特性を評価できるとの知見に基づいて、耐脆性破壊発生特性を、Ｖノッチシャルピー衝撃試験の結果で評価する方法を発明した。 Therefore, the present inventors correspond to the predicted Kc value based on the Charpy test result (vE) and the measured Kc value when Hv (WM) / Hv (BM) ≦ 1.1 (see FIG. 3). In the above range, based on the knowledge that the brittle fracture occurrence characteristics of high heat input butt welded joints can be evaluated based on the results of conventional V-notch Charpy impact tests, We invented a method to evaluate the impact test results.
本発明の評価方法は、
（ａ）溶接金属（ＷＭ）の硬さＨｖ（ＷＭ）を測定し、
（ｂ）Ｖノッチシャルピー衝撃試験により溶接継手部の吸収エネルギーｖＥと遷移温度vＴrsを測定し、
（ｃ）上記実測Ｈｖ（ＷＭ）値が要求Ｈｖ値を満たすこと、及び、上記実測ｖＥが要求ｖＥ値を満たすことを確認し、
（ｄ）実測遷移温度vＴrsに基づく予測破壊靭性値Ｋｃが要求Ｋｃ値であることを評価する。
The evaluation method of the present invention is:
(A) Measure the hardness Hv (WM) of the weld metal (WM),
(B) The absorbed energy vE and transition temperature vTrs of the welded joint are measured by a V-notch Charpy impact test,
(C) Confirm that the measured Hv (WM) value satisfies the required Hv value and that the measured vE satisfies the required vE value;
(D) It is evaluated that the predicted fracture toughness value Kc based on the measured transition temperature vTrs is the required Kc value.
上記評価を有効に実施するためには、母材の硬さＨｖ（ＢＭ）×１．１以下、又は、要求Ｈｖ値を２１０以下と設定し、かつ、要求ｖＥ値を、（船体用構造体設計温度［−１０℃］−１０）℃での測定値で５３Ｊ以上と設定することが好ましい。 In order to effectively carry out the above evaluation , the hardness of the base material Hv (BM) × 1.1 or less, or the required Hv value is set to 210 or less, and the required vE value is set to (structure for hull) Design temperature [−10 ° C.] − 10) It is preferable to set the measured value at 53 ° C. to 53 J or more.
上記要求Ｋｃ値は、溶接構造物の用途や鋼板強度に応じて、適宜、数値で設定する。また、線形破壊力学のＫｑ＝σD√（πａ）（σD：設計応力、ａ：想定欠陥寸法）に基づいて設定してもよい。 The required Kc value is appropriately set as a numerical value according to the use of the welded structure and the steel plate strength. Alternatively, it may be set based on Kq = σ D √ (πa) (σ D : design stress, a: assumed defect size) of linear fracture mechanics.
そして、破壊靭性値Ｋｃを、測定した吸収エネルギーｖＥに基づいて下記式（１）〜（３）で算定し、該破壊靭性値Ｋｃが要求Ｋｃ値であるか否かを評価する。 Then, the fracture toughness value Kc is calculated by the following formulas (1) to (3) based on the measured absorbed energy vE, and it is evaluated whether or not the fracture toughness value Kc is a required Kc value.
Ｋｃ（Ｔ）＝５．６σｙ0・ｅｘｐ（ｋ0（１／iＴk−１／Ｔ）） …（１）
iＴk＝（０．００３２１σｙ0＋０．３９１）vＴrs＋Ａ√ｔ＋Ｘ …（２）
ｋ0＝Ｃ・iＴk−Ｄ …（３）
但し、σｙ0：室温での降伏強さ（ｋｇ／ｍｍ2）、ｔ：板厚（ｍｍ）、Ｔ：試験温度
ここで、σｙ0：室温での降伏強さ（ｋｇ／ｍｍ2）
ｔ：板厚（ｍｍ）、
Ｔ：試験温度
Ａ：板厚効果に係る係数で、１．５≦Ａ≦３．５
Ｘ：切り欠き先鋭度に係る係数で、−２０≦Ｘ≦８０
Ｃ：ｋ0に係る係数で、４≦Ｃ≦８９
Ｄ：ｋ0に係る係数で、１００≦Ｄ≦６００
Kc (T) = 5.6σy 0 · exp (k 0 (1 /
iTk = (0.00321σy 0 +0.391) vTrs + A√t + X (2)
k 0 = C · iTk−D (3)
However, .sigma.y 0: yield strength at room temperature (kg / mm 2), t : sheet thickness (mm), T: test temperature
In here, .sigma.y 0: yield strength at room temperature (kg / mm 2)
t: plate thickness (mm),
T: Test temperature
A: a coefficient related to the plate thickness effect, 1.5 ≦ A ≦ 3.5
X: coefficient related to notch sharpness, −20 ≦ X ≦ 80
C: coefficient related to k 0 , 4 ≦ C ≦ 89
D: Coefficient related to k 0 , 100 ≦ D ≦ 600
上記式（２）及び（３）の技術的意味、及び、定数Ａ、Ｘ、Ｃ及びＤの通常の範囲、好ましい範囲、さらに、最も好ましい値については、前述したとおりである。 The technical meanings of the above formulas (2) and (3), and the normal ranges, preferred ranges, and most preferred values of the constants A, X, C, and D are as described above.
このように、シャルピー衝撃試験の結果に基づいて、大入熱突合せ溶接継手の耐脆性破壊発生特性を、ディープノッチ試験に比べ迅速かつ簡便に評価することができる。 Thus, based on the result of the Charpy impact test, the brittle fracture resistance of the high heat input butt welded joint can be evaluated quickly and easily compared to the deep notch test.
本発明で用いる船体用の高強度鋼板は、公知の成分組成の溶接用構造用鋼から製造したものでよい。 The high-strength steel plate for a hull used in the present invention may be manufactured from a structural steel for welding having a known component composition.
例えば、質量％で、Ｃ：０．０２〜０．２０％、Ｓｉ：０．０１〜１．０％、Ｍｎ：０．３〜２．０％、Ａｌ：０．００１〜０．２０％、Ｎ：０．０２％以下、Ｐ：０．０１％以下、Ｓ：０．０１％以下を基本成分とし、母材強度や継手靭性の向上等、要求される性質に応じて、Ｎｉ、Ｃｒ、Ｍｏ、Ｃｕ、Ｗ、Ｃｏ、Ｖ、Ｎｂ、Ｔｉ、Ｚｒ、Ｔａ、Ｈｆ、ＲＥＭ、Ｙ、Ｃａ、Ｍｇ、Ｔｅ、Ｓｅ、Ｂの内の１種又は２種以上を含有した鋼が好ましい。 For example, in mass%, C: 0.02 to 0.20%, Si: 0.01 to 1.0%, Mn: 0.3 to 2.0%, Al: 0.001 to 0.20%, N: 0.02% or less, P: 0.01% or less, S: 0.01% or less as basic components, depending on required properties such as improvement of base material strength and joint toughness, Ni, Cr, Steels containing one or more of Mo, Cu, W, Co, V, Nb, Ti, Zr, Ta, Hf, REM, Y, Ca, Mg, Te, Se, and B are preferred.
鋼板の板厚は、本発明では、板厚が５０ｍｍ以上１００ｍｍ以下の大型船用の高強度鋼板に適用するのが好ましい。 In the present invention, the plate thickness of the steel plate is preferably applied to a high-strength steel plate for large ships having a plate thickness of 50 mm or more and 100 mm or less .
以下、本発明を、実施例に基づいて説明するが、実施例における条件は、本発明の実施可能性及び効果を確認するために採用した一条件例であり、本発明は、該一条件例に限定されるものではない。 Hereinafter, the present invention will be described based on examples, but the conditions in the examples are one example of conditions adopted to confirm the feasibility and effects of the present invention, and the present invention is examples of the one condition. It is not limited to.
本発明は、本発明の要旨を逸脱せず、本発明の目的を達成する限りにおいて、種々の条件ないし条件の組合せを採用し得るものである。 The present invention can adopt various conditions or combinations of conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.
（実施例１）
板厚５０ｍｍ〜１００ｍｍの厚鋼板を準備し、各種の溶接方法で形成した溶接継手の特徴及び性能を試験、調査した。その結果を表１及び表２（表１の続き）に示す。
Example 1
Thick steel plates with a thickness of 50 mm to 100 mm were prepared, and the characteristics and performance of welded joints formed by various welding methods were tested and investigated. The results are shown in Table 1 and Table 2 (continuation of Table 1).
表１中「継手種類」欄において、ＳＥＧ−ＡＲＣは簡易エレクトロガス溶接、ＥＧは通常のエレクトロガス溶接、ＳＭＡＷは、被覆アーク溶接、ＳＡＷは潜弧溶接、ＶＥＧＡ２は、２電極の立向きエレクトロガスアーク溶接である。 In Table 1, in the “Joint type” column, SEG-ARC is simple electrogas welding, EG is normal electrogas welding, SMAW is covered arc welding, SAW is submerged arc welding, and VEGA2 is a two-electrode vertical electrogas arc. It is welding.
Ｈｖ（ＢＭ）は、荷重１０ｋｇｆ（＝９８Ｎ）の圧痕により測定した母材の板厚方向における硬さの平均値である。Ｈｖ（ＷＭ）は、溶接金属の板厚中央部において、荷重１０ｋｇｆ（＝９８Ｎ）の圧痕により測定した硬さの値である。 Hv (BM) is an average value of the hardness in the thickness direction of the base material measured by an indentation with a load of 10 kgf (= 98 N) . Hv (WM) is a hardness value measured by an indentation with a load of 10 kgf (= 98 N) at the center of the plate thickness of the weld metal.
溶接継手において、板厚の表面下１ｍｍ（表１で“Ｓ”と表示）、板厚の１／４（表１で“Ｑ”と表示）、及び、板厚の１／２（表１で“Ｃ”と表示）の位置で試験片を採取し、溶接金属、溶接溶融線（ＦＬ）、及び、ＦＬからＨＡＺ側の１ｍｍ、３ｍｍ、５ｍｍの各部位に切欠きが一致するように切欠を形成しシャルピー試験片を作製した。 In the welded joint, 1 mm below the surface of the plate thickness (indicated as “S” in Table 1), 1/4 of the plate thickness (indicated as “Q” in Table 1), and 1/2 of the plate thickness (in Table 1) Specimen is taken at the position of “C” and notches are placed so that the notches are aligned with the weld metal, weld melt line (FL), and 1mm, 3mm and 5mm on the HAZ side from FL. A Charpy test piece was formed.
上記シャルピー試験片につき、試験温度を変化させてシャルピー試験を実施し、vＴrsが最も高温にあった部位の値をvＴrsとして表に示した。その値を用い、下記式に従い、推定破壊靭性値Ｋｃ（ＦＣ）及びＫｃ（ＭＮ）を算定した。 The Charpy test piece was subjected to a Charpy test while changing the test temperature, and the value of the region where vTrs was at the highest temperature was shown in the table as vTrs. Using that value, estimated fracture toughness values Kc (FC) and Kc (MN) were calculated according to the following formula.
iＴk＝（０.００３２１σｙ0＋０.３９１）vＴrs＋２．７４√ｔ＋Ｘ
ｋ0＝Ｃ・iＴk−Ｄ
Ｋc（Ｔ）＝５.６σｙ0・exp（ｋ0（１／iＴk−１／Ｔ））
ここで、Ｔは試験温度（Ｋ）、σｙ0は室温での降伏強さ、ｔは板厚であり。Ｃ、Ｄは定数で、Ｃ＝６.６５、Ｄ＝４４０である。
iTk = (0.0031σy 0 +0.391) vTrs + 2.74√t + X
k 0 = C · iTk−D
Kc (T) = 5.6σy 0 · exp (k 0 (1 /
Here, T is the test temperature (K), σy 0 is the yield strength at room temperature, and t is the plate thickness. C and D are constants, and C = 6.65 and D = 440.
溶接構造物の溶接継手に存在する疲労亀裂や割れ等の欠陥は、その先端半径がゼロであることを前提とするので、前述したＫｃ値は、本来、疲労亀裂付きの中央亀裂付き引張試験片を用いて求められるＫｃ値であり、その値が、前述したように継手設計に使用される。このＫｃ値を、次に説明するＫｃ（ＭＮ）と区別するため、Ｋｃ（ＦＣ）と称する。 Since defects such as fatigue cracks and cracks existing in welded joints of welded structures are based on the assumption that the tip radius is zero, the above-mentioned Kc value is originally a tensile test piece with a central crack with fatigue cracks. The Kc value obtained by using this value, and this value is used for joint design as described above. This Kc value is referred to as Kc (FC) in order to distinguish it from Kc (MN) described below.
しかしながら、大型引張試験に疲労亀裂を導入することは多大な費用と時間を必要とし、能率的でないので、通常は、先端幅が０．１ｍｍの機械切欠付きの中央切欠付き引張試験片を用いて、破壊靭性値Ｋｃを求める。このＫｃをＫｃ（ＭＮ）と称する。 However, introducing fatigue cracks in large tensile tests is very costly and time consuming and is not efficient, so we typically use a center notched tensile test specimen with a mechanical notch with a 0.1 mm tip width. The fracture toughness value Kc is obtained. This Kc is referred to as Kc (MN).
溶接金属の硬さが本発明の範囲内に制御したことを前提に、Ｋｃ（ＭＮ）を求めるときは、Ｘ＝５６．１とし、Ｋｃ（ＦＣ）を求めるときは、Ｘ＝６６．１とすれば、実験結果とＫｃ推定値との間に良好な相関関係を与えることを実験的に確認したので、Ｘについては、上記値を用いた。 On the premise that the hardness of the weld metal is controlled within the range of the present invention, when obtaining Kc (MN), X = 56.1, and when obtaining Kc (FC), X = 66.1. Then, since it was experimentally confirmed that a good correlation was given between the experimental result and the estimated Kc value, the above value was used for X.
破壊靭性値Ｋｃ（Ｎ／ｍｍ1.5）は、ディープノッチ試験において、表２に示す所定の試験温度で求めた値である。 The fracture toughness value Kc (N / mm 1.5 ) is a value obtained at a predetermined test temperature shown in Table 2 in the deep notch test.
表２において、ディープノッチ試験結果である実測Ｋｃ値と推定Ｋｃ値を比較する際には、推定Ｋｃ（ＭＮ）値を参照すればよい。また、推定Ｋｃ（ＭＮ）値に対応する疲労亀裂の場合の推定Ｋｃ値が、推定Ｋｃ（ＦＣ）値である。 In Table 2, when comparing the measured Kc value, which is the result of the deep notch test, with the estimated Kc value, the estimated Kc (MN) value may be referred to. Moreover, the estimated Kc value in the case of the fatigue crack corresponding to the estimated Kc (MN) value is the estimated Kc (FC) value.
なお、前記（１）〜（３）式は、降伏強さが３９０ＭＰａ級の鋼材の溶接継手におけるＫｃ値とシャルピー特性値との相関関係を基盤として、さらに、板厚７０ｍｍ程度（厚手材）でかつ降伏強さが４６０ＭＰａ級程度までの高強度鋼の溶接継手に係る数多くのシャルピー試験結果とディープノッチ試験結果に基づいて相関性を検討して決定した定数を係数とする式であるから、上記式も本発明の範囲内のものである。 The above formulas (1) to (3) are based on the correlation between the Kc value and the Charpy characteristic value in a welded joint of a steel material having a yield strength of 390 MPa class, and the plate thickness is about 70 mm (thick material). And since the yield strength is an expression having a coefficient as a constant determined by examining the correlation based on many Charpy test results and deep notch test results related to welded joints of high-strength steel up to about 460 MPa class, The formula is also within the scope of the present invention.
表２に示すように、本発明例のＮｏ．１〜１３は、Ｈｖ（ＷＭ）／Ｈｖ（ＢＭ）の値が１．１以下、または、Ｈｖ（ＷＭ）が２１０以下であり、推定Ｋｃ（ＭＮ）値及び推定Ｋｃ（ＦＣ）値が、実測Ｋｃ値と略一致している。このことから、シャルピー試験結果に基づいて溶接継手の破壊靭性値を推定して、溶接継手の耐脆性破壊発生特性を管理、確認し、溶接構造物の安全性を確保することができる。 As shown in Table 2, No. of the present invention example. 1 to 13, Hv (WM) / Hv (BM) value is 1.1 or less, or Hv (WM) is 210 or less, and the estimated Kc (MN) value and the estimated Kc (FC) value are measured. It is approximately the same as the Kc value. From this, it is possible to estimate the fracture toughness value of the welded joint based on the Charpy test result, manage and confirm the brittle fracture resistance of the welded joint, and ensure the safety of the welded structure.
これに対し、比較例Ｎｏ．１４〜２５は、Ｈｖ(ＷＭ)／Ｈｖ(ＢＭ)が、本発明で規定する１．１を超えていて、推定Ｋｃ（ＭＮ）値及び推定Ｋｃ（ＦＣ）値が、実測Ｋｃ値と大きく異なり、実測Ｋｃ値は、推定Ｋｃ値よりも大きく低下している。 In contrast, Comparative Example No. 14 to 25, Hv (WM) / Hv (BM) exceeds 1.1 defined in the present invention, and the estimated Kc (MN) value and the estimated Kc (FC) value are greatly different from the actually measured Kc value. The measured Kc value is significantly lower than the estimated Kc value.
即ち、Ｈｖ(ＷＭ)／Ｈｖ(ＢＭ)が本発明で規定する範囲外の場合、シャルピー試験結果で溶接継手の品質・特性を管理しても、破壊靭性値は、実際には大きく低下していることになるので、溶接構造物の安全性を管理、確認したことにはならず、危険である。 That is, when Hv (WM) / Hv (BM) is outside the range specified in the present invention, even if the quality and characteristics of the welded joint are controlled by the Charpy test results, the fracture toughness value actually decreases greatly. Therefore, the safety of the welded structure is not managed and confirmed, which is dangerous.
本発明によれば、板厚が５０ｍｍ以上１００ｍｍ以下で、降伏強度が３９０ＭＰａ級ないし７９６ＭＰａ級の船体用高強度鋼板を突合せ溶接した溶接継手において、適正な溶接方法、溶接材料、鋼材を選定することにより、厚手高強度鋼板を用いて建造する船体用溶接構造物の脆性破壊に対する抵抗特性を確保することができる。 According to the present invention, an appropriate welding method, welding material, and steel material are selected for a welded joint obtained by butt welding high- strength steel sheets for ship hulls having a thickness of 50 mm to 100 mm and a yield strength of 390 MPa to 796 MPa. Accordingly, it is possible to secure a resistance characteristic against brittle fracture of the hull for welded structure to build using a thickness Tedaka strength steel sheet.
したがって、万一、溶接継手に溶接欠陥が存在したり、疲労亀裂が発生し、成長しても、脆性破壊が発生し難い船体用溶接構造体を確実に提供することができる。 Therefore, even if a weld defect exists in a welded joint or a fatigue crack is generated and grows, a welded structure for a hull that hardly causes brittle fracture can be provided reliably.
よって、本発明は、船体用溶接構造体の安全性を顕著に高めるので、産業上の利用価値の高い発明である。 Therefore, the present invention remarkably enhances the safety of the welded structure for a hull , and thus is an invention with high industrial utility value.
１ 試験片
２ 溶接金属
３ 切欠き
1
Claims (2)
（ａ）溶接金属の板厚中央部の硬さＨｖ（ＷＭ）を測定し、
（ｂ）Ｖノッチシャルピー衝撃試験により溶接継手部の吸収エネルギーｖＥと遷移温度vＴrsを測定し、
（ｃ）上記実測Ｈｖ（ＷＭ）値が、熱影響を受けていない母材の板厚方向平均硬さＨｖ（ＢＭ）の１．１倍以下を満たすこと、及び、上記実測ｖＥ値が、（船体用構造体設計温度−１０）℃での測定値で５３Ｊ以上を満たすことを確認し、
（ｄ）実測遷移温度vＴrsに基づく予測破壊靭性値Ｋｃ値が２０００Ｎ／ｍｍ1.5超であることを評価することを特徴とする、船体用大入熱突合せ溶接継手の耐脆性破壊発生特性評価方法。 A welded joint in a welded structure for ship hull welded with high-strength butt-welded high-strength steel sheets with a thickness of 50mm to 100mm and a yield strength of 390MPa to 796MPa. Results of V-notch Charpy test and deep notch test In a method for evaluating the mechanical properties of a large heat input butt welded joint for a hull, which may not be correlated with
(A) Measure the hardness Hv (WM) of the central portion of the weld metal thickness,
(B) The absorbed energy vE and transition temperature vTrs of the welded joint are measured by a V-notch Charpy impact test,
(C) The measured Hv (WM) value satisfies 1.1 times or less of the thickness direction average hardness Hv (BM) of the base material not affected by heat, and the measured vE value is ( It is confirmed that the design value of the hull structure design temperature −10) ° C. satisfies 53J or more.
(D) A method for evaluating brittle fracture occurrence characteristics of a large heat input butt weld joint for a hull, characterized by evaluating that a predicted fracture toughness value Kc value based on measured transition temperature vTrs is more than 2000 N / mm 1.5 .
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| WO2007108139A1 (en) * | 2006-03-22 | 2007-09-27 | Nippon Steel Corporation | High heat input butt-welded joint excelling in brittle fracturing resisting performance and method of verifying brittle fracturing resisting performance of high heat input butt-welded joint |
| JP5144053B2 (en) * | 2006-05-12 | 2013-02-13 | Ｊｆｅスチール株式会社 | Welded structure with excellent brittle crack propagation stop properties |
| JP4546995B2 (en) | 2007-01-05 | 2010-09-22 | 新日本製鐵株式会社 | Butt multipass weld joint and welded structure with excellent brittle crack propagation characteristics |
| JP4995066B2 (en) | 2007-01-05 | 2012-08-08 | 新日本製鐵株式会社 | Butt multipass weld joint and welded structure with excellent brittle crack propagation characteristics |
| GB2460362B (en) * | 2007-02-27 | 2011-09-07 | Exxonmobil Upstream Res Co | Corrosion resistant alloy weldments in carbon steel structures and pipelines to accommodate high axial plastic strains |
| JP4935767B2 (en) * | 2008-06-19 | 2012-05-23 | トヨタ自動車株式会社 | Fracture strength measurement method |
| JPWO2010038305A1 (en) | 2008-10-03 | 2012-02-23 | 三菱重工業株式会社 | Evaluation index setting method and program thereof |
| JP5212280B2 (en) * | 2009-07-03 | 2013-06-19 | 株式会社Ｉｈｉ | Destructive specimen |
| JP5962578B2 (en) * | 2013-05-01 | 2016-08-03 | Ｊｆｅスチール株式会社 | Joint strength evaluation method for soft welded joints |
| WO2023095528A1 (en) * | 2021-11-29 | 2023-06-01 | Ｊｆｅスチール株式会社 | Method for evaluating brittle crack arrest performance of thick steel plate |
| JP7252525B1 (en) * | 2021-11-29 | 2023-04-05 | Ｊｆｅスチール株式会社 | Evaluation method of brittle crack arrestability of steel plate |
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| JP4528089B2 (en) * | 2003-10-22 | 2010-08-18 | 新日本製鐵株式会社 | Large heat input butt welded joints for ship hulls with brittle fracture resistance |
| JP4319886B2 (en) * | 2003-10-22 | 2009-08-26 | 新日本製鐵株式会社 | Large heat input butt weld joint with brittle fracture resistance |
| JP4394996B2 (en) * | 2004-03-30 | 2010-01-06 | 新日本製鐵株式会社 | Welded joints with excellent brittle fracture resistance |
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