JP4319886B2 - Large heat input butt weld joint with brittle fracture resistance - Google Patents
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本発明は、溶接構造体、特に、板厚５０ｍｍ未満の船体構造用鋼板で、その降伏強度が４００ＭＰａ以上になるまで高強度化することに伴い、その突合せ溶接継手部の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くなる、船舶溶接構造体の耐脆性破壊発生特性を有する大入熱突合せ溶接継手に関する。 The present invention is welded structure, in particular, hull structural steel thickness of less than 50 mm, with to high strength until the yield strength is more than 400 MPa, and V notch Charpy test results of the butt weld joint portion The present invention relates to a large heat input butt weld joint having brittle fracture resistance of a ship welded structure, in which a correlation with a deep notch test result cannot be obtained.
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。その理由としては、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、溶接継手部の脆性破壊に係る指標として用いられている破壊靭性値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, and further, the steel sheet structure becomes coarse due to the influence of welding heat, and the brittleness of the welded joint part. For example, the fracture toughness value Kc used as an index related to fracture is decreased.
それ故、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よりも高くすることが、溶接継手を形成する上での基本であり、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。 Therefore, in order to prevent the deformation and strain from concentrating on the welded joint, the strength and hardness of the weld metal is higher than that of the base metal, which is the basis for forming the welded joint. When selecting a metal, the joint design is overmatched by comparison with the strength of the base material.
溶接継手における破壊靭性値を評価する試験としては、幅４００ｍｍの試験片の中央部にて、溶接継手の最脆弱部と想定される位置に、長さ２４０ｍｍの切欠きを機械加工した試験片を用いるディープノッチ試験がある。 As a test for evaluating the fracture toughness value in a welded joint, a test piece obtained by machining a notch having a length of 240 mm at a position assumed to be the weakest part of a welded joint at the center of a test piece having a width of 400 mm. There is a deep notch test to use.
そして、これまで、この試験により、主として板厚５０ｍｍ以下の船体構造用鋼板の溶接継手における破壊靭性値を評価、その結果に基づいて、船体構造用鋼板に必要な性能・特性が論じられてきた。 So far, this test has mainly evaluated the fracture toughness value of welded joints of hull structural steel plates with a thickness of 50 mm or less, and based on the results, the performance and characteristics necessary for hull structural steel plates have been discussed. .
その結果、溶接部の破壊靭性値を考慮した船体構造用鋼板として、脆性破壊特性と疲労特性に優れた鋼板（ＴＭＣＰ鋼板）が開発されている（例えば、特許文献１）。 As a result, a steel plate (TMCP steel plate) excellent in brittle fracture characteristics and fatigue properties has been developed as a hull structural steel sheet considering the fracture toughness value of the welded part (for example, Patent Document 1).
これまで、大入熱溶接が適用される鋼構造物では、板厚５０ｍｍ程度のＴＭＣＰ鋼板等が使用されていたが、近年、構造物の大型化のニーズが高まり、その結果、高強度鋼でも大入熱溶接を適用しようとする傾向が高まってきた。 Until now, in steel structures to which high heat input welding is applied, TMCP steel sheets with a thickness of about 50 mm have been used. However, in recent years, there has been a growing need for larger structures, and as a result, even high-strength steels There has been an increasing tendency to apply high heat input welding.
例えば、現在、実用化されている船体構造用鋼板の強度の上限は、降伏強さで３９０ＭＰａレベルであり、鋼構造物の大きさがさらに増大すると、必然的に、板厚の厚い鋼板を用いることとなるが、鋼板の板厚が増大し過ぎると、溶接施工上の工数が増えて建造コストが上がったり、コンテナー船そのものの重量が増える等、工業的な問題が生じる。 For example, the upper limit of the strength of hull structural steel plates currently in practical use is 390 MPa in terms of yield strength. When the size of steel structures further increases, inevitably thick steel plates are used. However, if the plate thickness of the steel plate increases too much, there will be industrial problems such as an increase in the number of man-hours for welding construction, increasing the construction cost, and increasing the weight of the container ship itself.
溶接構造物の大型化が進み、使用する鋼板の板厚が増大するに伴い、設計応力が高い高張力厚鋼板を用いることが要望されている。 As the size of the welded structure increases and the plate thickness of the steel plate used increases, it is desired to use a high-tensile steel plate having a high design stress.
そこで、本発明者は、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、降伏強度が４００ＭＰａクラスで、板厚５０ｍｍ以下の船体構造用高強度鋼板を突合せ溶接した大入熱溶接継手の性能について調査した。 Accordingly, the present inventor has proposed that the welded joint portion can be a portion having the highest possibility of fracture occurrence, so that the high strength steel plate is butt-welded with a high strength steel plate for ship structures having a yield strength of 400 MPa class and a thickness of 50 mm or less. The performance of the heat welded joint was investigated.
その結果、降伏強度が４００ＭＰａクラスで、板厚５０ｍｍ以下の船体構造用高強度鋼板を突合せ溶接した大入熱溶接継手は、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, a high heat input welded joint with a yield strength of 400 MPa class and a butt weld of a high-strength steel plate for a hull structure having a thickness of 50 mm or less shows a good result in a V-notch Charpy impact test, which is a small test, It was found that the deep notch test, which is a large fracture test, does not necessarily show a good fracture toughness value Kc.
そこで、本発明は、上記知見を踏まえ、板厚５０ｍｍ未満の船体構造用鋼板で、その降伏強度が４００ＭＰａ以上になるまで高強度化することに伴い、その突合せ溶接継手部の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くなる、船舶溶接構造体の突合せ溶接継手に、大入熱突合せ溶接を適用する場合において、破壊靭性値Ｋｃが十分に高い溶接継手を形成することを課題とする。 The present invention is based on the above findings, in the hull structural steel thickness of less than 50 mm, with to high strength until the yield strength is more than 400 MPa, V-notch Charpy test results of the butt weld joint portion When a large heat input butt weld is applied to a butt welded joint of a ship welded structure, which can no longer be correlated with a deep notch test result, a weld joint with a sufficiently high fracture toughness value Kc should be formed. Let it be an issue.
本発明者は、上記課題を解決するため、母材と溶接継手の機械的性質について調査した。その結果、本発明者は、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を溶接継手形成上の基本とし、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従来の継手設計にとらわれない、新規な継手設計技術を見出した。 In order to solve the above problems, the present inventor investigated the mechanical properties of the base material and the welded joint. As a result, in order to prevent deformation and strain from concentrating on the weld joint, the present inventor has made the weld metal strength and hardness higher than the base metal strength and hardness in forming the weld joint. When selecting weld metal, we found a new joint design technology that is not confined to the conventional joint design that is overmatched by comparison with the base metal strength.
即ち、大入熱突合せ溶接継手の継手設計において、溶接金属の硬さを母材の硬さの７０％以上１１０％以下となるように制御し（アンダーマッチングとなる継手設計）、溶接金属の幅を、母材板厚の７０％以下とすることにより、アンダーマッチングによる継手強度の低下を防止できることを見出した。 That is, in the joint design of a high heat input butt weld joint, the hardness of the weld metal is controlled to be 70% or more and 110% or less of the hardness of the base metal (joint design for undermatching), and the width of the weld metal. Was found to be able to prevent a decrease in joint strength due to undermatching by making it 70% or less of the base material plate thickness.
そして、上記知見に基づいて、板厚５０ｍｍ未満の船体構造用鋼板で、その降伏強度が４００ＭＰａ以上になるまで高強度化することに伴い、その突合せ溶接継手部の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くなる、大入熱突合せ溶接において、破壊靭性値Ｋｃの高い溶接継手を具現化する技術として本発明を完成した。 Then, based on the above finding, in the hull structural steel thickness of less than 50 mm, with to high strength until the yield strength is more than 400 MPa, V notch Charpy test results and deep notch of the butt weld joint portion The present invention has been completed as a technique for realizing a welded joint having a high fracture toughness value Kc in high heat input butt welding, in which a correlation with the test results cannot be obtained.
本発明の要旨は、以下のとおりである。 The gist of the present invention is as follows.
（１） 板厚５０ｍｍ未満の船体構造用鋼板で、その降伏強度が４００ＭＰａ以上になるまで高強度化することに伴い、その突合せ溶接継手部の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くなる、船舶溶接構造体の突合せ溶接継手において、
（ａ）溶接金属の硬さ（板厚中央部硬さ）が熱影響を受けていない母材の硬さ（板厚方向平均硬さ）の７０％以上１１０％以下であり、かつ、
（ｂ）溶接金属の幅（表面、裏面及び板厚中心の平均値）が母材板厚の７０％以下である
ことを特徴とする耐脆性破壊発生特性を有する大入熱突合せ溶接継手。
(1) hull structural steel thickness of less than 50 mm, the correlation between the yield strength due to be high strength until the above 400 MPa, V notch Charpy test results and deep notch test results of the butt weld joint portion In butt welded joints for ship welded structures where the relationship cannot be obtained,
(A) The hardness of the weld metal (plate thickness center portion hardness) is 70% or more and 110% or less of the hardness (average thickness in the plate thickness direction) of the base material not affected by heat , and
(B) A high heat input butt-welded joint having brittle fracture resistance, wherein the width of the weld metal (average value of the front, back and center of plate thickness) is 70% or less of the base metal plate thickness.
（２） 板厚５０ｍｍ未満の船体構造用鋼板で、その降伏強度が４００ＭＰａ以上になるまで高強度化することに伴い、その突合せ溶接継手部の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くなる、船舶溶接構造体の突合せ溶接継手において、
（ａ）溶接金属の硬さ（板厚中央部硬さ）が熱影響を受けていない母材の硬さ（板厚方向平均硬さ）の７０％以上１１０％以下であり、
（ｂ）溶接金属の幅（表面、裏面及び板厚中心の平均値）が母材板厚の７０％以下であり、かつ、
（ｃ）熱影響を受けていない母材の硬さ（板厚方向平均硬さ）の９５％以下の硬さに軟化している溶接熱影響部領域の幅が５ｍｍ以上である
ことを特徴とする耐脆性破壊発生特性を有する大入熱突合せ溶接継手。
(2) in hull structural steel thickness of less than 50 mm, the correlation between the yield strength due to be high strength until the above 400 MPa, V notch Charpy test results and deep notch test results of the butt weld joint portion In butt welded joints for ship welded structures where the relationship cannot be obtained,
(A) The hardness of the weld metal (plate thickness central portion hardness) is 70% or more and 110% or less of the hardness (average thickness in the plate thickness direction) of the base material not affected by heat ,
(B) the width of the weld metal (the average value of the front, back and center of plate thickness) is 70% or less of the base metal plate thickness, and
(C) The width of the weld heat-affected zone softened to 95% or less of the hardness (average thickness in the thickness direction) of the base material not affected by heat is 5 mm or more. Large heat input butt welded joints with brittle fracture resistance.
（３） 板厚５０ｍｍ未満の船体構造用鋼板で、その降伏強度が４００ＭＰａ以上になるまで高強度化することに伴い、その突合せ溶接継手部の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くなる、船舶溶接構造体の突合せ溶接継手において、
（ａ）溶接金属の硬さ（板厚中央部硬さ）が熱影響を受けていない母材の硬さ（板厚方向平均硬さ）の７０％以上１１０％以下であり、
（ｃ）熱影響を受けていない母材の硬さ（板厚方向平均硬さ）の９５％以下の硬さに軟化している溶接熱影響部領域の幅が５ｍｍ以上であり、かつ、
（ｄ）溶接溶融線と接する溶接熱影響部の旧オーステナイト粒径が２００μｍ以下である
ことを特徴とする耐脆性破壊発生特性を有する大入熱突合せ溶接継手。
(3) in the hull structural steel thickness of less than 50 mm, the correlation between the yield strength due to be high strength until the above 400 MPa, V notch Charpy test results and deep notch test results of the butt weld joint portion In butt welded joints for ship welded structures where the relationship cannot be obtained,
(A) The hardness of the weld metal (plate thickness central portion hardness) is 70% or more and 110% or less of the hardness (average thickness in the plate thickness direction) of the base material not affected by heat ,
(C) the width of the weld heat affected zone softened to 95% or less of the hardness (average thickness in the thickness direction) of the base material not affected by heat is 5 mm or more, and
(D) A high heat input butt-welded joint having brittle fracture resistance, characterized in that the prior austenite grain size of the weld heat affected zone in contact with the weld melt line is 200 μm or less.
（４） 板厚５０ｍｍ未満の船体構造用鋼板で、その降伏強度が４００ＭＰａ以上になるまで高強度化することに伴い、その突合せ溶接継手部の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くなる、船舶溶接構造体の突合せ溶接継手において、
（ａ）溶接金属の硬さ（板厚中央部硬さ）が熱影響を受けていない母材の硬さ（板厚方向平均硬さ）の７０％以上１１０％以下であり、
（ｂ）溶接金属の幅（表面、裏面及び板厚中心の平均値）が母材板厚の７０％以下であり、
（ｃ）熱影響を受けていない母材の硬さ（板厚方向平均硬さ）の９５％以下の硬さに軟化している溶接熱影響部領域の幅が５ｍｍ以上であり、かつ、
（ｄ）溶接溶融線と接する溶接熱影響部の旧オーステナイト粒径が２００μｍ以下である
ことを特徴とする耐脆性破壊発生特性を有する大入熱突合せ溶接継手。
(4) in the hull structural steel thickness of less than 50 mm, the correlation between the yield strength due to be high strength until the above 400 MPa, V notch Charpy test results and deep notch test results of the butt weld joint portion In butt welded joints for ship welded structures where the relationship cannot be obtained,
(A) The hardness of the weld metal (plate thickness central portion hardness) is 70% or more and 110% or less of the hardness (average thickness in the plate thickness direction) of the base material not affected by heat ,
(B) the width of the weld metal (the average value of the front surface, back surface and center of plate thickness) is 70% or less of the base metal plate thickness;
(C) the width of the weld heat affected zone softened to 95% or less of the hardness (average thickness in the thickness direction) of the base material not affected by heat is 5 mm or more, and
(D) A high heat input butt-welded joint having brittle fracture resistance, characterized in that the prior austenite grain size of the weld heat affected zone in contact with the weld melt line is 200 μm or less.
本発明によれば、板厚５０ｍｍ未満の船体構造用鋼板で、その降伏強度が４００ＭＰａ以上になるまで高強度化することに伴い、その突合せ溶接継手部の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くなる、船舶溶接構造体の突合せ溶接継手において、破壊靭性値Ｋｃが十分に高い溶接継手を形成することができる。 According to the present invention, in the hull structural steel thickness of less than 50 mm, with to high strength until the yield strength is more than 400 MPa, V notch Charpy test results and deep notch test results of the butt weld joint portion In the butt welded joint of the ship welded structure, the welded joint having a sufficiently high fracture toughness value Kc can be formed.
これまで、溶接継手の設計は、溶接継手部に変形や歪が集中することを阻止するために、溶接金属の強度や硬さを、母材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。 Up to now, the design of welded joints has been based on making the strength and hardness of the weld metal higher than the base metal in order to prevent deformation and strain from concentrating on the welded joint. The strength was selected to be overmatched compared to the base material strength.
そこで、本発明者は、降伏強さで４００ＭＰａクラスの鋼板を試作し、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で、溶接継手を製作し、ディープノッチ試験でその機械的性質を評価した。 Therefore, the present inventor made a prototype 400 MPa class steel sheet with yield strength, manufactured a welded joint with a welding material selected so that the weld metal was overmatched, and evaluated its mechanical properties by a deep notch test. did.
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は、−２０℃の試験温度で９０Ｊ以上の十分な値を示し、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以下と極めて低い値を示し、結局、これらの試験結果は、従来から用いている「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。 As a result, in the V-notch Charpy test of the welded joint part, the above welded joint shows a sufficient value of 90 J or more at a test temperature of −20 ° C., and the fracture surface transition temperature is also a very good value of −20 ° C. In spite of the above, in the deep notch test, the fracture toughness value Kc shows an extremely low value of 2000 N / mm 1.5 or less, and as a result, these test results are the results of the “V-notch Charpy test results and deep It was found that there was a great departure from "correlation with notch test results".
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、溶接金属とＨＡＺ（溶接熱影響部）の境界であること、及び、
（ii）破壊の発生した部分の微視組織は、シャルピー試験片で観察された破壊発生部の微視組織と同一であること、
を突き止め、
（iii）ディープノッチ試験とシャルピー試験においては、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が著しく異なること、
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 and HAZ (welding heat affected zone), and
(Ii) The microstructure of the fractured part is the same as the microstructure of the fractured part observed on the Charpy specimen.
Ascertain
(Iii) In the deep notch test and the Charpy test, the local stress distribution form that becomes the driving force of fracture is significantly different.
Foresee.
そして、両者における上記局所応力分布を３次元有限要素法で解析した結果、降伏強度が４００ＭＰａ以上の高強度鋼になると、板厚方向での拘束度（力）が著しく増大し、破壊靭性値は、溶接部で最も降伏強度の高い領域で発生する局所応力に支配されて、溶接金属の強度が母材やＨＡＺ（溶接熱影響部）の強度よりも高いと、局所応力が溶接金属とＨＡＺとの境界で著しく増大すること、即ち、局所応力の上記境界での著しい増大を抑制するには、溶接金属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。 And as a result of analyzing the local stress distribution in both by the three-dimensional finite element method, when the yield strength becomes high strength steel of 400 MPa or more, the restraint degree (force) in the plate thickness direction is remarkably increased, and the fracture toughness value is If the strength of the weld metal is higher than that of the base metal or HAZ (welding heat affected zone), it is governed by the local stress generated in the region with the highest yield strength in the weld zone. It has been found that the strength of the weld metal needs to be as low as possible in order to suppress a significant increase at the boundary, that is, to suppress a significant increase in local stress at the boundary.
ここで、上記解析結果をもとに、溶接金属の硬さ（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結果、図１中「●」に示すように、溶接金属の硬さを母材の硬さの１１０％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ることを知見した。 Here, based on the above analysis results, the hardness (Hv (WM)) of the weld metal is variously changed, the fracture toughness value Kc is measured, and the Kc measurement value is expressed as “the hardness of the weld metal [Hv (WM). )] / Hardness [Hv (BM)] ”of the base metal, and as a result, as shown by“ ● ”in FIG. 1, the hardness of the weld metal is suppressed to 110% or less of the hardness of the base material. It has been found that this can prevent a decrease in fracture toughness value due to an increase in local stress.
このように、溶接金属の硬さを、母材の硬さより低くすることが、溶接継手の破壊靭性値を向上させるために必要であることを知見したが、溶接金属の硬さを低下させると、一方で、溶接継手の強度（引張強さ）を確保できず、構造物や構造体として致命的な問題を引き起こすことにもなる。 As described above, it was found that the hardness of the weld metal is lower than the hardness of the base metal in order to improve the fracture toughness value of the welded joint, but when the hardness of the weld metal is reduced. However, on the other hand, the strength (tensile strength) of the welded joint cannot be ensured, resulting in a fatal problem as a structure or structure.
そこで、溶接継手においても母材の強度と同程度の強度を確保するために必要な溶接金属の強度の下限を実験的に検討した。その結果、図２に示すように、溶接金属の幅（ビード幅）の影響が顕著であるところ、該幅を板厚の７０％以下に限定すれば、溶接金属の硬さを母材の硬さの７０％まで低減しても、溶接継手の強度（引張強さ）を確保できることを見出した。 Therefore, the lower limit of the strength of the weld metal necessary for securing the same strength as that of the base metal in the welded joint was experimentally examined. As a result, as shown in FIG. 2, when the influence of the width (bead width) of the weld metal is significant, if the width is limited to 70% or less of the plate thickness, the hardness of the weld metal is reduced to the hardness of the base metal. It has been found that the strength (tensile strength) of the welded joint can be ensured even when the thickness is reduced to 70%.
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向上させることが重要である。 As described above, in order to ensure the predetermined fracture toughness value Kc in the welded joint, it is important not to increase the local stress in the weld melt line (FL) which is the most fragile part of the welded joint. At the same time, it is important to improve the microscopic brittle fracture resistance in the vicinity of the FL.
ＦＬ近傍で脆性破壊が発生するメカニズムを調査、検討した結果、旧オーステナイト周辺に生成する初析フェライトや、旧オーステナイト内部にラス状に生成する上部ベーナイトやフェライトサイドプレート等が破壊の起点となることを突き止め、旧オーステナイト粒径を小さく抑制することにより、耐脆性破壊発生特性を改善することができることを知見した。 As a result of investigating and investigating the mechanism of brittle fracture near FL, pro-eutectoid ferrite generated around the former austenite, upper bainite and ferrite side plate generated in the lath form inside the former austenite, etc. It has been found that the brittle fracture resistance can be improved by suppressing the prior austenite grain size.
本発明者の実験結果によれば、溶接溶融線（ＦＬ）と接する溶接熱影響部（ＨＡＺ）の旧オーステナイト粒径を２００μｍ以下に抑制することが好ましい。 According to the experiment results of the present inventors, it is preferable to suppress the prior austenite grain size of the weld heat affected zone (HAZ) in contact with the weld melting line (FL) to 200 μm or less.
また、本発明者は、溶接金属に接する溶接溶融線（ＦＬ）における局所応力の発生ないし分布は、溶接金属の硬さに支配されるが、ＦＬに接しているＨＡＺ領域において“軟化している領域”が大きい場合には、ＦＬの局所応力が緩和される傾向にあることを見出した。 Further, the present inventor has found that the generation or distribution of local stress in the weld melt line (FL) in contact with the weld metal is governed by the hardness of the weld metal, but is “softened” in the HAZ region in contact with the FL. It was found that when the “region” is large, the local stress of FL tends to be relaxed.
本発明者の実験結果によれば、ＨＡＺ軟化幅が５ｍｍ以上存在した場合に、上記緩和現象が認められたので、ＨＡＺ軟化幅は５ｍｍ以上とすることが好ましい。ＨＡＺの硬さが母材の硬さより低ければ、原理的に局所応力は低減するが、本発明者の実験結果によれば、局所応力低減効果が明確に認められるのは、ＨＡＺの硬さが、母材の硬さよりも５％以上低くなっている場合であった。 According to the experiment results of the present inventor, when the HAZ softening width is 5 mm or more, the above relaxation phenomenon is observed. Therefore, the HAZ softening width is preferably 5 mm or more. If the hardness of the HAZ is lower than the hardness of the base material, the local stress is reduced in principle. However, according to the experiment results of the present inventor, the local stress reduction effect is clearly recognized because the hardness of the HAZ is In this case, the hardness was 5% or more lower than the hardness of the base material.
それ故、本発明においては、熱影響を受けていない母材部の硬さの９５％以下の硬さに軟化している溶接熱影響部（ＨＡＺ）領域の幅を５ｍｍ以上とすることが好ましい。 Therefore, in the present invention, it is preferable that the width of the weld heat affected zone (HAZ) region softened to a hardness of 95% or less of the hardness of the base material portion not affected by heat is 5 mm or more. .
本発明で用いる船舶溶接構造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。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。 The steel plate for ship welding structure used in the present invention may be those produced from welding structural steel of known chemical composition. 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.
また、溶接材料も本発明で規定する溶接金属の硬さが得られる限り、特にその成分組成を限定するものではないが、本発明では、例えば、溶接材料の化学成分として、Ｃ：０．０１〜０．０６％、Ｓｉ：０．２〜１．０％、Ｍｎ：０．５〜２．５％、Ｎｉ≦４．０％、Ｍｏ≦０．３０％、Ａｌ≦０．３％、Ｍｇ≦０．３０％、Ｔｉ：０．０２〜０．２５％、Ｂ≦０．０５０％を含有し、さらに、使用する鋼材の化学成分を考慮して、溶接材料を適宜選択して用いることが望ましい。 Further, the component composition of the welding material is not particularly limited as long as the hardness of the weld metal specified in the present invention can be obtained. However, in the present invention, for example, as a chemical component of the welding material, C: 0.01 -0.06%, Si: 0.2-1.0%, Mn: 0.5-2.5%, Ni≤4.0%, Mo≤0.30%, Al≤0.3%, Mg ≦ 0.30%, Ti: 0.02 to 0.25%, B ≦ 0.050%, and further considering the chemical composition of the steel material to be used, it is possible to appropriately select and use a welding material desirable.
また、溶接方法も、本発明で規定する溶接ビード（溶接金属）幅が得られる限り、特に限定するものではなく、通常のエレクトロガス溶接（ＥＧ）、揺動エレクトロガス溶接（ＶＥＧＡ）、ＣＯ2溶接などのアーク溶接などが用いられる。レーザー溶接や電子ビーム溶接は、溶接ビードの幅の制御が容易であり、溶接材料を用いて溶接金属の硬さを制御することにより本発明で適用できる。 Further, welding methods, as long as the weld bead (weld metal) width defined in the present invention can be obtained, not particularly limited, conventional electro-gas welding (EG), rocking electro-gas welding (VEG A), CO Arc welding such as 2 welding is used. Laser welding and electron beam welding are easy to control the width of the weld bead, and can be applied in the present invention by controlling the hardness of the weld metal using a welding material.
ただし、溶接材料を用いずにレーザー溶接や電子ビーム溶接する場合は、母材の溶融、凝固のみで溶接金属となるため、溶接金属の硬さが母材部よりも高くなりやすいので溶接金属の硬さ制御の点から好ましくない。 However, when laser welding or electron beam welding is performed without using a welding material, the weld metal is easily melted and solidified, so that the weld metal hardness tends to be higher than the base metal part. It is not preferable from the point of hardness control.
以下、本発明を、実施例に基いて説明するが、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 condition example adopted to confirm the feasibility and effects of the present invention, and the present invention is the one condition example. 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２５ｍｍ〜５０ｍｍの厚鋼板を準備し、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に示す。
Example 1
Thick steel plates having a thickness of 25 mm to 50 mm were prepared, and the characteristics and performance of welded joints were tested and investigated. The results are shown in Table 1.
溶接方法について、ＶＥＧＡは、揺動エレクトロガス溶接である。ＥＧは、通常のエレクトロガス溶接である。ＳＡＷは、潜弧溶接である。ＣＯ2は炭酸ガス溶接である。それぞれの溶接条件は、表２に示した。 Welding method, VEG A is a rocking electro-gas welding. EG is normal electrogas welding. SAW is submerged arc welding. CO 2 is carbon dioxide welding. The respective welding conditions are shown in Table 2.
なお、鋼材の開先形状は、ＶＥＧＡ、ＥＧ溶接の場合は、開先角度２０°のＶ字開先とし、ルートギャップは８ｍｍとし、ＳＡＷ溶接の場合は、開先角度４０°のＹ字開先とし、ルートギャップは２ｍｍとした。 The groove shape of the steel material is a V-shaped groove with a groove angle of 20 ° for VEG A and EG welding, a root gap of 8 mm, and a Y-shape with a groove angle of 40 ° for SAW welding. The groove was a groove and the root gap was 2 mm.
Ｈｖ（ＢＭ）は、１０ｋｇ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、１０ｋｇ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 of 10 kg. Hv (WM) is a hardness value measured by a 10 kg indentation at the center of the plate thickness of the weld metal.
ビード幅は、溶接金属の表面、裏面、及び、板厚中心の３点で測定した平均値である。 The bead width is an average value measured at three points of the front surface, the back surface, and the center of the plate thickness of the weld metal.
ＨＡＺ軟化幅は、母材の硬さより５％軟化したＨＡＺ領域を、溶接溶融線から母材方向へ測定した時の領域の幅である。 The HAZ softening width is a width of a region when a HAZ region softened by 5% from the hardness of the base material is measured from the weld melt line toward the base material.
ＨＡＺの旧γ粒径は、溶接溶融線に接するＨＡＺでの旧オーステナイト粒を円相当径で表記したものである。 The former γ grain size of HAZ is a representation of the former austenite grains in HAZ that are in contact with the weld melting line in terms of equivalent circle diameter.
溶接継手の性能に関し、破面遷移温度ｖＴrs（℃）は、溶接継手の最脆弱部である溶接溶融線（ＦＬ）が試験片の板厚中央となるように採取した試験片を用い、試験温度を変化させて求めた結果である。 Regarding the performance of welded joints, the fracture surface transition temperature vTrs (° C) is determined by using a test piece taken so that the weld melt line (FL), which is the weakest part of the welded joint, is at the center of the thickness of the test piece. This is the result obtained by changing.
破壊靭性値Ｋｃ（Ｎ／ｍｍ1.5）は、前述のディープノッチ試験において、−２０℃の試験温度で求めた値であり、「＞」印を付記した値は、試験片の切欠き部で十分変形して、延性き裂の痕跡が確認されたものであり、試験片幅が４００ｍｍであるため、それ以上のＫｃ値を計測できなかったものである。 The fracture toughness value Kc (N / mm 1.5 ) is a value obtained at a test temperature of −20 ° C. in the above-described deep notch test, and the value marked with “>” is sufficient at the notch of the test piece. Deformation was confirmed and a trace of a ductile crack was confirmed. Since the specimen width was 400 mm, a Kc value higher than that could not be measured.
継手引張強度（ＭＰａ）は、ＮＫＵ１号試験片を作製して、継手引張試験を行った結果であり、破断した強度を示すものである。 The joint tensile strength (MPa) is a result of producing a NKU No. 1 test piece and conducting a joint tensile test, and indicates a fracture strength.
表１に示すように、本発明例のＮｏ．１、２、６、７、９〜１４は、各種条件が本発明で規定する範囲内にあるものであり、Ｋｃ値及び継手引張強度ともに十分な値を示している。Ｎｏ．４、８は、板厚が５０ｍｍであるので、参考例である。 As shown in Table 1, No. of the present invention example. 1 , 2 , 6 , 7 , and 9 to 14 are those in which various conditions are within the range defined by the present invention, and both the Kc value and the joint tensile strength are sufficient values. No. Nos. 4 and 8 are reference examples because the plate thickness is 50 mm.
これに対して、比較例Ｎｏ．１５〜１７は、Ｈｖ(ＷＭ)/Ｈｖ(ＢＭ)が、本発明で規定する所定値を超えているため、シャルピー試験によるｖＴrsが、本発明例のＮｏ．１〜１４と同程度のレベルにあるにもかかわらず、Ｋｃ値が低いものである。 In contrast, Comparative Example No. In Nos. 15 to 17, since Hv (WM) / Hv (BM) exceeds a predetermined value defined in the present invention, vTrs by the Charpy test is No. of the present invention. Despite being at the same level as 1 to 14, the Kc value is low.
比較例Ｎｏ．１８は、Ｈｖ(ＷＭ)/Ｈｖ(ＢＭ)が、本発明で規定する所定値より小さいため、シャルピー試験によるｖＴrsが、本発明例のＮｏ．１〜１４と同程度のレベルであることに対応し、Ｋｃ値が十分な値であるが、継手引張強度が低いものである。 Comparative Example No. No. 18, because Hv (WM) / Hv (BM) is smaller than the predetermined value defined in the present invention, vTrs by the Charpy test is No. of the present invention example. Corresponding to the level of 1 to 14, the Kc value is a sufficient value, but the joint tensile strength is low.
比較例Ｎｏ．２０は、ビード幅が、本発明で規定する所定値を超えているため、継手引張強度が低いものである。 Comparative Example No. 20 has a low joint tensile strength because the bead width exceeds a predetermined value defined in the present invention.
本発明によれば、板厚５０ｍｍ未満の船体構造用鋼板で、その降伏強度が４００ＭＰａ以上になるまで高強度化することに伴い、その突合せ溶接継手部の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くなる、大入熱突合せ溶接継手において、万一、溶接欠陥が存在したり、又は、疲労亀裂が発生、成長しても、脆性破壊が発生し難いので、船舶溶接構造体が破壊するような致命的な損傷、損壊を防止することができる。 According to the present invention, in the hull structural steel thickness of less than 50 mm, with to high strength until the yield strength is more than 400 MPa, V notch Charpy test results and deep notch test results of the butt weld joint portion In a high heat input butt welded joint where no correlation can be obtained, it is unlikely that brittle fracture will occur even if there are weld defects or fatigue cracks are generated and grown. It can prevent fatal damage and destruction that destroys the body.
よって、本発明は、溶接構造体の安全性を顕著に高めるという顕著な効果を奏し、産業上の利用価値の高い発明である。 Therefore, the present invention has a remarkable effect of significantly increasing the safety of the welded structure, and is an invention having high industrial utility value.
Claims (4)
（ａ）溶接金属の硬さ（板厚中央部硬さ）が熱影響を受けていない母材の硬さ（板厚方向平均硬さ）の７０％以上１１０％以下であり、かつ、
（ｂ）溶接金属の幅（表面、裏面及び板厚中心の平均値）が母材板厚の７０％以下である
ことを特徴とする耐脆性破壊発生特性を有する大入熱突合せ溶接継手。 Hull structural steel thickness of less than 50 mm, with to high strength until the yield strength is more than 400 MPa, obtained correlation between the V-notch Charpy test results and deep notch test results of the butt weld joint portion In the butt welded joint of ship welded structures,
(A) The hardness of the weld metal (plate thickness center portion hardness) is 70% or more and 110% or less of the hardness (average thickness in the plate thickness direction) of the base material not affected by heat , and
(B) A high heat input butt-welded joint having brittle fracture resistance, wherein the width of the weld metal (average value of the front, back and center of plate thickness) is 70% or less of the base metal plate thickness.
（ａ）溶接金属の硬さ（板厚中央部硬さ）が熱影響を受けていない母材の硬さ（板厚方向平均硬さ）の７０％以上１１０％以下であり、
（ｂ）溶接金属の幅（表面、裏面及び板厚中心の平均値）が母材板厚の７０％以下であり、かつ、
（ｃ）熱影響を受けていない母材の硬さ（板厚方向平均硬さ）の９５％以下の硬さに軟化している溶接熱影響部領域の幅が５ｍｍ以上である
ことを特徴とする耐脆性破壊発生特性を有する大入熱突合せ溶接継手。 Hull structural steel thickness of less than 50 mm, with to high strength until the yield strength is more than 400 MPa, obtained correlation between the V-notch Charpy test results and deep notch test results of the butt weld joint portion In the butt welded joint of ship welded structures,
(A) The hardness of the weld metal (plate thickness central portion hardness) is 70% or more and 110% or less of the hardness (average thickness in the plate thickness direction) of the base material not affected by heat ,
(B) the width of the weld metal (the average value of the front, back and center of plate thickness) is 70% or less of the base metal plate thickness, and
(C) The width of the weld heat-affected zone softened to 95% or less of the hardness (average thickness in the thickness direction) of the base material not affected by heat is 5 mm or more. Large heat input butt welded joints with brittle fracture resistance.
（ａ）溶接金属の硬さ（板厚中央部硬さ）が熱影響を受けていない母材の硬さ（板厚方向平均硬さ）の７０％以上１１０％以下であり、
（ｃ）熱影響を受けていない母材の硬さ（板厚方向平均硬さ）の９５％以下の硬さに軟化している溶接熱影響部領域の幅が５ｍｍ以上であり、かつ、
（ｄ）溶接溶融線と接する溶接熱影響部の旧オーステナイト粒径が２００μｍ以下である
ことを特徴とする耐脆性破壊発生特性を有する大入熱突合せ溶接継手。 Hull structural steel thickness of less than 50 mm, with to high strength until the yield strength is more than 400 MPa, obtained correlation between the V-notch Charpy test results and deep notch test results of the butt weld joint portion In the butt welded joint of ship welded structures,
(A) The hardness of the weld metal (plate thickness central portion hardness) is 70% or more and 110% or less of the hardness (average thickness in the plate thickness direction) of the base material not affected by heat ,
(C) the width of the weld heat affected zone softened to 95% or less of the hardness (average thickness in the thickness direction) of the base material not affected by heat is 5 mm or more, and
(D) A high heat input butt-welded joint having brittle fracture resistance, characterized in that the prior austenite grain size of the weld heat affected zone in contact with the weld melt line is 200 μm or less.
（ａ）溶接金属の硬さ（板厚中央部硬さ）が熱影響を受けていない母材の硬さ（板厚方向平均硬さ）の７０％以上１１０％以下であり、
（ｂ）溶接金属の幅（表面、裏面及び板厚中心の平均値）が母材板厚の７０％以下であり、
（ｃ）熱影響を受けていない母材の硬さ（板厚方向平均硬さ）の９５％以下の硬さに軟化している溶接熱影響部領域の幅が５ｍｍ以上であり、かつ、
（ｄ）溶接溶融線と接する溶接熱影響部の旧オーステナイト粒径が２００μｍ以下である
ことを特徴とする耐脆性破壊発生特性を有する大入熱突合せ溶接継手。 Hull structural steel thickness of less than 50 mm, with to high strength until the yield strength is more than 400 MPa, obtained correlation between the V-notch Charpy test results and deep notch test results of the butt weld joint portion In the butt welded joint of ship welded structures,
(A) The hardness of the weld metal (plate thickness central portion hardness) is 70% or more and 110% or less of the hardness (average thickness in the plate thickness direction) of the base material not affected by heat ,
(B) the width of the weld metal (the average value of the front surface, back surface and center of plate thickness) is 70% or less of the base metal plate thickness;
(C) the width of the weld heat affected zone softened to 95% or less of the hardness (average thickness in the thickness direction) of the base material not affected by heat is 5 mm or more, and
(D) A high heat input butt-welded joint having brittle fracture resistance, characterized in that the prior austenite grain size of the weld heat affected zone in contact with the weld melt line is 200 μm or less.
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| CN104475935A (en) * | 2014-11-24 | 2015-04-01 | 南京钢铁股份有限公司 | Field welding method for CO2-corrosion-resistant pipeline steel |
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| JP4761746B2 (en) * | 2004-09-22 | 2011-08-31 | 新日本製鐵株式会社 | Evaluation method of brittle fracture resistance of large heat input butt welded joints for ship hulls |
| 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 |
| JP4903107B2 (en) * | 2007-09-28 | 2012-03-28 | Ｊｆｅスチール株式会社 | Welded joint |
| CN102601502B (en) * | 2012-04-01 | 2014-03-26 | 哈尔滨工业大学 | Re-nanocrystallization welding device for nanometer bainite steel and method |
| 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 |
| CN103706917B (en) * | 2013-12-25 | 2015-10-28 | 青岛武船重工有限公司 | A kind of FCB that prevents welds the terminal heating means producing terminal crackle |
| CN107309527A (en) * | 2017-06-30 | 2017-11-03 | 蓬莱巨涛海洋工程重工有限公司 | The Large Heat Input Welding technique of marine engineering large thick steel plate under a kind of low temperature |
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| CN104475935A (en) * | 2014-11-24 | 2015-04-01 | 南京钢铁股份有限公司 | Field welding method for CO2-corrosion-resistant pipeline steel |
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