WO2017217515A1 - 脆性亀裂伝播停止特性に優れる溶接構造体 - Google Patents
脆性亀裂伝播停止特性に優れる溶接構造体 Download PDFInfo
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- WO2017217515A1 WO2017217515A1 PCT/JP2017/022212 JP2017022212W WO2017217515A1 WO 2017217515 A1 WO2017217515 A1 WO 2017217515A1 JP 2017022212 W JP2017022212 W JP 2017022212W WO 2017217515 A1 WO2017217515 A1 WO 2017217515A1
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- fillet
- joined
- welded
- doubler
- joint
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B73/00—Building or assembling vessels or marine structures, e.g. hulls or offshore platforms
- B63B73/40—Building or assembling vessels or marine structures, e.g. hulls or offshore platforms characterised by joining methods
- B63B73/43—Welding, e.g. laser welding
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/02—Seam welding; Backing means; Inserts
- B23K9/0206—Seam welding; Backing means; Inserts of horizontal seams in assembling vertical plates, a welding unit being adapted to travel along the upper horizontal edge of the plates
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K31/00—Processes relevant to this subclass, specially adapted for particular articles or purposes, but not covered by only one of the preceding main groups
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/0026—Arc welding or cutting specially adapted for particular articles or work
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/02—Seam welding; Backing means; Inserts
Definitions
- the present invention relates to a welded steel structure welded using a thick steel plate, such as a large container ship or a bulk carrier, and more particularly, the propagation of a brittle crack generated from a thick steel plate base material or a welded joint.
- the present invention relates to a welded structure excellent in brittle crack propagation stopping characteristics, which can be stopped before reaching a large-scale fracture of an object.
- Container ships and bulk carriers have a structure that has few partition walls in the hold and a large opening at the top of the ship, for example, unlike tankers, to improve loading capacity and cargo handling efficiency. Yes. Therefore, in container ships and bulk carriers, it is necessary to increase the strength or thickness of the hull skin, in particular.
- TEU wenty feet Equivalent Unit
- TEU represents the number of containers converted into a 20-foot container and represents an indicator of the loading capacity of a container ship.
- thick steel plates with a thickness of 50 mm or more and a yield strength of 390 N / mm class 2 or more tend to be used.
- Non-Patent Document 1 reports the results of an experimental study on the brittle crack propagation behavior of welds in steel plates for shipbuilding with a thickness of less than 50 mm.
- this non-patent document 1 the propagation path and propagation behavior of a brittle crack forcibly generated in a welded portion are experimentally investigated, and if the fracture toughness of the welded portion is ensured to some extent.
- a plurality of examples in which brittle cracks propagate along the welded part have been confirmed. This suggests that there is no possibility that brittle fracture will propagate straight along the weld.
- Non-Patent Document 2 For this reason, in a hull structure to which a thick high-strength steel plate having a thickness of 50 mm or more is applied, ensuring safety is a big problem. In addition, Non-Patent Document 2 also points out that a thick steel plate having special brittle crack propagation stop characteristics is required in order to stop the propagation of the generated brittle cracks.
- Patent Document 1 in a welded structure that is preferably a hull outer plate having a thickness of 50 mm or more, an aggregate is arranged so as to intersect the butt weld, and fillet welding is performed. A joined welded structure is described.
- the surface layer portion and the back layer portion have an average equivalent particle diameter of 0.5 to 5 ⁇ m over a thickness of 3 mm or more, and are parallel to the plate thickness surface.
- a steel sheet having a microstructure with an X-ray plane intensity ratio of (100) crystal planes of 1.5 or more is used.
- Patent Document 2 describes a welded structure having a fillet welded joint formed by fillet welding a joining member (web) to a member to be joined (flange) and having excellent brittle crack propagation stop characteristics. .
- an unwelded portion is left on the butt surface of the web in the fillet welded joint cross section with the flange, the width of the unwelded portion, and the left and right sides of the fillet welded portion.
- the width of the unwelded portion is adjusted so that the ratio of the leg length to the sum of the web plate thickness, X, satisfies the brittle crack propagation stop performance Kca of the member to be joined (flange) and a special relational expression.
- Patent Documents 3 to 5 also describe a welded structure having a fillet welded joint obtained by welding a joining member (web) to a member to be joined (flange) and having excellent brittle crack propagation stopping characteristics. ing.
- the end face of a joining member is abutted against the surface of a member to be joined having a plate thickness of 50 mm or more, and at least a welding leg length or welding width formed by joining the joining member and the member to be joined by fillet welding.
- One side is a welded structure having a fillet welded joint of 16 mm or less, and a cross-section of the fillet welded joint is formed on the surface where the end face of the joining member in the fillet welded joint and the surface of the joined member meet.
- the Charpy impact test fracture surface transition temperature vTrs of the fillet weld metal in the fillet welded joint is related to the plate thickness tf of the joined member.
- Patent Document 4 discloses a welding leg length or welding width in which an end face of a joining member is abutted against a surface of a joined member having a thickness of 50 mm or more, and the joining member and the joined member are joined by fillet welding.
- a cross-section of the fillet welded joint is a welded structure having at least one fillet welded joint of 16 mm or less, where the end face of the joining member in the fillet welded joint and the surface of the joined member are abutted.
- the welded material has an unwelded portion of 95% or more of the plate thickness tw of the joining member, and the Charpy impact test fracture surface transition temperature vTrs of the fillet weld metal in the fillet welded joint is equal to the plate thickness tf of the joined member.
- vTrs (° C) ⁇ ⁇ 1.5 tf + 90 and / or Charpy impact test temperature of fillet weld metal absorbed energy vE ⁇ 20 (J) at ⁇ 20 ° C.
- the thickness tf of the joined member In the case of 50 ⁇ tf (mm) ⁇ 53, vE ⁇ 2 In the case of 0 ⁇ 5.75 and tf (mm)> 53, vE ⁇ 20 (J) ⁇ 2.75 tf ⁇ 140 is satisfied, the fillet weld metal is included, and in addition, the brittle crack propagation stop toughness Kca is A welded structure is described which is composed of a steel plate having a common temperature of 2500 N / mm 2/3 or more. And by setting it as such a welded structure, it is supposed that a brittle crack can be stopped by a fillet welded part or the base material of a joining member.
- Patent Document 5 discloses a welding leg length or welding width in which an end face of a joining member is abutted against a surface of a joined member having a plate thickness of 50 mm or more, and the joining member and the joined member are joined by fillet welding.
- At least one of which is a welded structure having a fillet welded joint of 16 mm or less, wherein both the joining member and the joined member have a butt weld joint, and the weld metal of the butt weld joint is vTrs ⁇ 65 ° C or less and / or toughness of 140J or more at vE- 20 , the weld end surface of the butt weld joint of the joint member in the fillet welded joint is the weld surface of the butt weld joint of the member to be joined And the butt-welded surface has an unwelded portion of 95% or more of the plate thickness tw of the joining member at the cross-section of the butt-welded joint of the fillet welded joint.
- vTrs (° C.) ⁇ ⁇ 1.5 tf + 90 and / or absorbed temperature vE ⁇ 20 at Charpy impact test temperature of fillet weld metal: ⁇ 20 ° C. J) is in relation to the thickness tf of the bonded member, in the case of 50 ⁇ tf (mm) ⁇ 53 is, vE -20 ⁇ 5.75, in the case of tf (mm)> 53 is, vE -20 ( J) A welded structure with fillet weld metal that satisfies ⁇ 2.75 tf-140 is described.
- a brittle crack can be stopped by the fillet weld part or the base material of a joining member. Further, by adopting such a welded structure, a brittle crack generated from the welded member welded portion, or a brittle crack generated from the welded member welded portion, the fillet welded portion or the welded portion of the joined member or the joined member It is said that propagation can be prevented at the welded part.
- Japanese Patent Laid-Open No. 2004-232052 JP 2007-326147 A Japanese Patent No.5395985 Japanese Patent No.53657661 Japanese Patent No. 5408396
- the aggregate which is a reinforcing material used in the technique described in Patent Document 1
- Patent Document 2 indicates that brittle cracks generated in a joining member (hereinafter also referred to as a web), structural discontinuity, and brittle crack propagation stop of a joined member (hereinafter also referred to as a flange). It is a technology that tries to prevent it in combination with performance.
- Non-Patent Document 3 in general, a brittle crack generated in a member to be welded (flange) of a fillet welded joint is stopped in the joint member (web) and stopped in the joint member (web). It has been experimentally confirmed that it is difficult compared to stopping propagation of the brittle crack that has been caused by the member to be joined (flange).
- the joining member (web) is more than the case where the fracture driving force (stress intensity factor) when a crack enters the T-joint part enters the member to be joined (flange). ) Is likely to be larger.
- the leg length of the fillet welded part is large in the field work, so ensuring the strength of the fillet welded part (securing the fillet leg length)
- To achieve both brittle crack prevention performance (restricted to fillet leg length of 16 mm or less) requires a lot of labor for construction management at the site and increases additional costs such as rework.
- the present invention solves the above-described problems of the prior art, propagates brittle cracks generated in the member to be joined (flange) to the joining member (web), and joins member of the brittle crack generated in the joining member (web) ( It is an object of the present invention to provide a welded structure excellent in brittle crack propagation stopping characteristics that can stop (prevent) any propagation to a flange) before reaching a large-scale fracture.
- the present inventors diligently studied a method for reducing the variation in the leg length of the fillet weld in the construction of the fillet weld that stops the brittle crack.
- the basic welded structure is changed from the conventional fillet welded structure to a fillet welded structure with a doubler member in which a doubler member is disposed between the joining member and the member to be joined.
- the idea was to stop at the fillet weld metal part of the member to be joined. With this fillet welded structure, it is possible to weld the fillet welded portion that stops brittle cracks in the factory.
- the present inventors further studied various factors affecting the brittle crack propagation stop characteristics in the fillet welded structure with a doubler member.
- a discontinuous portion is secured on the overlapping surface of the member to be joined (flange) and the doubler member, and the member to be joined is joined.
- the energy release rate (crack growth driving force) at the tip of the brittle crack increases and the brittle crack becomes difficult to stop.
- the prevention (stop) of the propagation of brittle cracks generated from the joining member (web) is often easier than the prevention (stop) of the propagation of brittle cracks generated from the joined member (flange),
- the prevention (stop) of the propagation of brittle cracks generated from the joining member (web) is the member to be joined (flange) It has also been found that it becomes more severe than the prevention (stop) of the propagation of brittle cracks generated from the crack.
- the present invention has been completed based on the above findings and further studies.
- the gist of the present invention is as follows. (1) With a doubler member provided with a fillet welded joint in which the end surface of the joining member is butt welded and joined to the surface of the doubler member, and the doubler member is fillet welded to the surface of the joined member having a thickness of 50 mm or more A fillet welded structure in which the surface of the doubler member in the fillet welded joint and the surface of the member to be joined are overlapped with the plate width Wd of the doubler member in the cross section of the fillet welded joint.
- the doubler member has 95% or more unwelded portion, and the doubler member satisfies the following formula (1a) in the ratio td / Wd between the plate thickness td and the plate width Wd. Further, the fillet weld of the fillet welded joint The metal is subjected to the Charpy impact test fracture surface transition temperature vTrs (° C.) of the fillet weld metal corresponding to the fillet leg length or weld width L, and the thickness tf and fillet leg length or weld width L of the joined member. In relation to the following formula (1b) or A welded structure excellent in brittle crack propagation stopping characteristics, which is a fillet weld metal satisfying the formula (1c).
- the joining member has a butt weld joint portion, and the joining member is disposed so that the butt weld joint portion of the joint member intersects the butt weld joint portion of the joined member (2 ) Welded structure according to the above.
- Both the propagation of the brittle cracks generated in the joining member (web) to the joined member (flange) can be stopped or prevented before reaching a large-scale fracture. Therefore, according to the present invention, it is possible to avoid the risk of large-scale brittle fracture such as hull separation in steel structures, particularly large container ships and bulk carriers, and to ensure the safety of the hull structure. It has a great effect and has a remarkable industrial effect.
- the present invention by adjusting the size of the doubler member and the toughness of the fillet weld metal at the time of construction, it is easily brittle without using a special steel plate and without sacrificing safety. There is also an effect that it is possible to manufacture a welded structure having excellent crack propagation stopping characteristics.
- the welded structure of the present invention is formed by abutting the end face of the joining member 1 against the surface of the doubler member 10, joining the joining member 1 and the doubler member 10, and the joined member 2 having a plate thickness of 50 mm or more. It is a welded structure provided with a fillet welded joint that is superposed on the surface and joined by fillet welding.
- This welded structure includes a fillet weld joint having a fillet weld metal 5 having a weld leg length 3 or a weld width 13 of L mm, and the doubler member 10 of the fillet weld joint and the member to be joined (flange) 2 are overlapped.
- the unwelded part 4 which becomes a structure discontinuous part is made to exist in a mating surface.
- a structural discontinuity may be included in the butted surface where the end surface of the joining member 1 is butted against the surface of the doubler member 10.
- FIG. 1A shows a case where the joining member (web) 1 is attached upright with respect to the joined member (flange) 2, but the present invention is not limited to this.
- the joining member (web) 1 may be attached to the joined member (flange) 2 at an angle ⁇ .
- the welded structure of the present invention has the unwelded portion 4 where the structure is discontinuous on the overlapping surface of the doubler member 10 and the member to be joined (flange) 2.
- the overlapping surface of the doubler member 10 and the member to be joined (flange) 2 becomes a propagation surface of the brittle crack, and therefore, in the present invention, the unwelded portion 4 is present on the overlapping surface.
- the energy release rate (crack propagation driving force) of the brittle crack tip that has propagated through the joining member (web) 1 or the joined member (flange) 2 is reduced, Brittle cracks tend to stop. Therefore, in the present invention, the fillet weld metal 5 that retains toughness greater than or equal to a predetermined value is formed, and brittle cracks are stopped at the fillet weld metal 5.
- the member to be joined (flange) 2 is a steel plate joined by a butt weld joint 22, and the joining member (web) is filleted so as to intersect the welded portion (butt weld joint portion) 22 of the butt weld joint.
- a welded welded fillet as shown in FIG. 2 or a joining member (web) 1 and a joined member (flange) 2 are both steel plates having butt welded joint portions 12 and 22, and the joined member (flange). In the fillet welded joint as shown in FIG.
- the unwelded part (structure discontinuous part) 4 is made to exist in the overlapping surface of the to-be-joined member and doubler member in a fillet weld part.
- FIG. 2A shows the appearance of the fillet weld joint
- FIG. 2B shows the cross-sectional shape of the butt weld joint portion 22
- FIG. 3 shows a case where both the joining member (web) 1 and the member to be joined (flange) 2 are steel plates having butt weld joint portions 12 and 22, and the butt weld joint portion of the member to be joined (flange) 2.
- intersect is shown.
- FIG. 3A shows the appearance of the fillet weld joint
- FIG. 3B shows the joint cross-sectional shape of the butt weld joint portions 12 and 22.
- a welded structure may be manufactured by butt welding flange steel plates and web steel plates, and fillet welding the obtained butt weld joints via a doubler member.
- a set of web steel sheets before butt welding is tack welded to the doubler member on the flange surface, then the web steel sheets are butt welded together, and the resulting butt weld joint is welded to the flange to produce a welded structure. May be.
- the dimension of the unwelded portion 4 in the fillet welded joint cross section is 95% or more of the doubler member width Wd in order to suppress the propagation of brittle cracks.
- the dimension (width B) 16 of the unwelded portion 4 is less than 95% of the doubler member width Wd, the plastic deformation in the fillet weld metal is suppressed, and the vicinity of the crack tip of the brittle crack that has entered the fillet weld metal has high stress. Thus, it becomes difficult to stop or prevent brittle cracks.
- the dimension (width B) 16 of the unwelded portion 4 is limited to 95% or more of the doubler member width Wd in order to suppress the propagation of brittle cracks.
- they are 96% or more and 100% or less.
- the ratio between the plate thickness td of the doubler member and the plate width Wd of the doubler member, td / Wd is expressed by the following equation (1a): td / Wd ⁇ 2 (1a)
- td / Wd ⁇ 2 (1a)
- the plate thickness td of the doubler member and the plate width Wd of the doubler member do not satisfy the formula (1a)
- stopping or preventing the propagation of the brittle cracks generated from the joining member (web) is more effective for the joined member (flange).
- the propagation of the brittle cracks generated from the joining member (web) and the joined member (flange) cannot be stopped or prevented together.
- the lower limit value of td / Wd is preferably 0.2.
- the fillet weld metal does not satisfy the above-described formula (1b) or (1c), the fillet weld metal has insufficient toughness, and the to-be-joined member (flange) or joined member (web) The brittle crack that has been generated and propagated cannot be prevented by the fillet weld metal part.
- the fillet weld metal prevents both the brittle cracks that occurred in the joined members (flange) and the brittle cracks that occurred in the joined members (web). can do.
- the welded structure of the present invention is provided with the above-described fillet welded joint.
- FIGS. 4 (a), (b), (c) and FIGS. 4 (a), 4 (b), (c) and Large welded joints of actual structure sizes having the shapes shown in FIGS. 5 (a), 5 (b), and 5 (c) were produced.
- 4A, 4B, and 4C show cases where brittle cracks are generated and propagated from a member to be joined (flange), and
- FIGS. 5A, 5B, and 5C show joining members (webs). ) Assumes the case where brittle cracks are generated and propagated.
- the unwelded portion 4 as shown in FIG.
- the member to be joined (flange) in the case of FIG. 4 is a thick steel plate (base material only) (FIG. 4A) or a thick steel plate having a butt weld joint (FIG. 4B).
- a thick steel plate (base material only) (FIGS. 4A and 4B), or a thick steel plate having a butt weld joint (FIG. 4C).
- the joining member (web) of the case of FIG. 5 is a thick steel plate (base material only) (FIG. 5 (a)) or a thick steel plate having a butt weld joint (FIG. 5 (b)).
- the butt weld joint was produced by one-pass high heat input electrogas arc welding (one electrode EGW, two electrodes EGW, SEGARC, two electrodes SEGARC) or multilayer CO 2 welding.
- the fillet welded joint is a fillet welded joint having various toughness, fillet weld metal with various fillet leg lengths or weld widths by changing welding conditions such as welding material, welding heat input, shield gas, etc. did.
- the fillet leg length and the welding width are both average values on both sides.
- the toughness of fillet weld metal is determined by taking Charpy impact test specimens (10 mm thick) from butt welded joints produced under the same conditions as fillet weld metal or fillet welds, and breaking in accordance with the provisions of JIS Z 2242.
- the surface transition temperature vTrs (° C.) was determined.
- an ultra-large structural model test body shown in FIGS. 4 and 5 was produced, and a brittle crack propagation stop test was performed.
- 4 has a plate thickness of the same thickness as that of the member to be joined (flange) 2 by tack welding 8 below the member to be joined (flange) 2 of the large fillet weld joint 9 with doubler.
- the steel plate was welded.
- the ultra-large structural model test body of FIG. 5 is a temporary welding 8 below the joining member (web) 1 of the large fillet welded joint 9 with a doubler, and a steel plate having the same thickness as that of the joining member (web) 1. Welded.
- tip of the machine notch 7 was processed so that it might become the base material of the joining member (web) 1 or the to-be-joined member (flange) 2, the BOND part of the butt-weld joint parts 12 and 22, or the weld metal WM.
- a mechanical notch was hit to generate a brittle crack, and it was investigated whether the propagated brittle crack stopped at the fillet weld. All tests were conducted under the conditions of a test stress of 100 to 283 N / mm 2 and a temperature of ⁇ 10 ° C.
- the test stress of 100 N / mm 2 is the average value of the stress that constantly acts on the hull, and the test stress of 257 N / mm 2 is the maximum allowable stress of the 390 N / mm 2 class steel plate with the yield strength applied to the hull.
- test stress 283 N / mm 2 is a value corresponding to the maximum allowable stress of the yield strength 460 N / mm 2 grade steel plate applied to the hull.
- the temperature –10 ° C is the design temperature of the ship. The obtained results are shown in Table 2-1 and Table 2-2.
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Abstract
Description
この非特許文献1では、溶接部で強制的に発生させた脆性亀裂の伝播経路、伝播挙動を実験的に調査し、溶接部の破壊靱性がある程度確保されていれば、溶接残留応力の影響により脆性亀裂は溶接部から母材側に逸れてしまうことが多いという結果が記載されているが、溶接部に沿って脆性亀裂が伝播した例も複数例確認されている。このことは、脆性破壊が溶接部に沿って直進伝播する可能性が無いとは言い切れないことを示唆している。
また、非特許文献2には、とくに発生した脆性亀裂の伝播停止のために、特別な脆性亀裂伝播停止特性を有する厚鋼板を必要とするとの指摘もある。
この特許文献1に記載された技術では、骨材(補強材)として、表層部および裏層部で3mm以上の厚みにわたり0.5~5μmの平均円相当粒径を有しさらに板厚面に平行な面で(100)結晶面のX線面強度比が1.5以上である、ミクロ組織を有する鋼板を用いるとしている。このようなミクロ組織を有する鋼板を補強材として隅肉溶接した構造とすることにより、突合せ溶接継手部に脆性亀裂が発生しても、補強材である骨材で脆性破壊を停止でき、溶接構造体が破壊するような致命的な損傷を防止できるとしている。
この特許文献2に記載された溶接構造体では、隅肉溶接継手断面におけるウェブの、フランジとの突合せ面に未溶着部を残存させ、その未溶着部の幅と、隅肉溶接部の左右の脚長とウェブ板厚との和との比、Xが、被接合部材(フランジ)の脆性亀裂伝播停止性能Kcaと特別な関係式を満足するように、未溶着部の幅を調整する。これにより、被接合部材(フランジ)として板厚:50mm以上の厚物材を用いたとしても、接合部材(ウェブ)で発生した脆性亀裂の伝播を、隅肉溶接部のウェブとフランジの突合せ面で停止させ、被接合部材(フランジ)への脆性亀裂の伝播を阻止することができるとしている。
そして、このような溶接構造体であれば、被接合部材で発生した脆性亀裂を、大規模破壊に至る前に隅肉溶接金属で伝播阻止することができるとしている。
そして、このような溶接構造体とすることにより、脆性亀裂は、隅肉溶接部または接合部材の母材で伝播停止できるとしている。
そして、このような溶接構造体とすることにより、脆性亀裂は、隅肉溶接部または接合部材の母材で停止できるとしている。
また、このような溶接構造体とすることにより、被接合部材溶接部から発生した脆性亀裂、または接合部材溶接部から発生した脆性亀裂を、隅肉溶接部あるいは接合部材の溶接部または被接合部材の溶接部で伝播阻止することができるとしている。
この理由は明確には解明されていないが、一因としてT継手部に亀裂が突入するときの破壊駆動力(応力拡大係数)が被接合部材(フランジ)に突入する場合よりも接合部材(ウェブ)に突入する場合のほうが大きくなることが考えられる。
また、部材の板厚が80mm未満の場合であっても、現場での実施工においては、隅肉溶接部の脚長のバラツキが大きいため、隅肉溶接部の強度確保(隅肉脚長確保)と脆性亀裂阻止性能の確保(隅肉脚長16mm以下に制限)とを両立させることは、現場での施工管理上多大な労力を要すると共に、手直し等の追加コストがかさむという問題があった。
その結果、基本溶接構造を従来の隅肉溶接構造から、接合部材と被接合部材との間に、ダブラー部材を配設したダブラー部材付き隅肉溶接構造とし、脆性亀裂の伝播は、ダブラー部材と被接合部材の隅肉溶接金属部で阻止することに想到した。この隅肉溶接構造であれば、脆性亀裂を停止させる隅肉溶接部の施工を工場内で溶接することができる。また、これにより、隅肉溶接部の脚長のばらつきを所定の範囲内とすることが容易となり、現場での実施工コストの大幅な低減に繋がることを知見した。
そして、これにより、施工管理が厳しい現場で行う、接合部材とダブラー部材との接合は、接合部材の端面をダブラー部材の表面に突き合わせて、施工管理の容易な溶接条件(部分溶込み、完全溶込み等)で施工できるようになることを知見した。
その結果、被接合部材(フランジ)から発生した脆性亀裂の伝播を阻止(停止)するには、被接合部材(フランジ)とダブラー部材との重ね合せ面に不連続部を確保すると共に、被接合部材(フランジ)の板厚tf(mm)が大きくなると脆性亀裂先端のエネルギー解放率(亀裂進展駆動力)が増加し、脆性亀裂が停止しにくくなることに鑑みて、被接合部材(フランジ)の板厚tf(mm)に関連した、隅肉溶接部の靭性向上が必須となることに想到した。
そしてさらに、隅肉溶接部の脚長もしくは溶着幅が長くなると、脆性亀裂の伝播が容易となるため、隅肉溶接脚長(もしくは溶着幅)に応じて隅肉溶接金属の靭性を確保する必要があることも知見した。
本発明は、上記の知見に基づき、さらに検討を加えて完成されたものである。
(1)接合部材の端面が、ダブラー部材の表面に突き合わせ溶接接合され、かつ前記ダブラー部材が板厚50mm以上の被接合部材の表面に隅肉溶接接合された隅肉溶接継手を備えるダブラー部材付き隅肉溶接構造体であって、前記隅肉溶接継手における前記ダブラー部材の表面と前記被接合部材の表面とを重ね合わせた面に、前記隅肉溶接継手の断面でダブラー部材の板幅Wdの95%以上の未溶着部を有し、さらに前記ダブラー部材が、板厚tdと板幅Wdとの比td/Wdが下記(1a)式を満足し、さらに前記隅肉溶接継手の隅肉溶接金属を、該隅肉溶接金属のシャルピー衝撃試験破面遷移温度vTrs(℃)が、隅肉脚長もしくは溶着幅Lに対応して、前記被接合部材の板厚tfと隅肉脚長もしくは溶着幅Lとの関係で下記(1b)式または下記(1c)式を満足する隅肉溶接金属とする、脆性亀裂伝播停止特性に優れる溶接構造体。
記
td/Wd<2 ‥‥(1a)
L≧20mmの場合、 vTrs≦-5L+65-1.5(tf-75) ‥‥(1b)
L<20mmの場合、 vTrs≦-35-1.5(tf-75) ‥‥(1c)
ここで、vTrs:隅肉溶接金属のシャルピー衝撃試験破面遷移温度(℃)、
tf:被接合部材の板厚(mm)、
td:ダブラー部材の板厚(mm)、
Wd:ダブラー部材の板幅(mm)、
L:隅肉脚長もしくは溶着幅(mm)
従って、本発明によれば、鋼構造物、とくに、大型コンテナ船やバルクキャリアーなどにおける船体分離などの大規模な脆性破壊の危険性を回避することができ、船体構造の安全性を確保するうえで大きな効果をもたらし、産業上格段の効果を奏する。
本発明の溶接構造体は、接合部材1の端面をダブラー部材10の表面に突き合わせ、接合部材1とダブラー部材10とを接合してなり、かつダブラー部材10を板厚50mm以上の被接合部材2の表面に重ね合わせ、隅肉溶接により接合されてなる隅肉溶接継手を備えた溶接構造体である。この溶接構造体は、溶接脚長3もしくは溶着幅13がLmmの隅肉溶接金属5を有する隅肉溶接継手を備え、該隅肉溶接継手のダブラー部材10と被接合部材(フランジ)2との重ね合わせ面には、構造不連続部となる、未溶着部4を存在させる。なお、本発明溶接構造体では、接合部材1の端面をダブラー部材10の表面に突き合わせた突合せ面には、構造不連続部を含めてもよい。
そこで、本発明では、所定以上の靭性を保持する隅肉溶接金属5を形成し、脆性亀裂を、隅肉溶接金属5で停止させる。
そのため、本発明では隅肉溶接部における被接合部材とダブラー部材との重ね合せ面に未溶着部(構造の不連続部)4を存在させるのである。
また、溶接構造体の製造方法はとくに限定する必要はなく、常用の製造方法がいずれも適用できる。例えば、フランジ用鋼板同士、ウェブ用鋼板同士を突合せ溶接し、得られた突合せ溶接継手をダブラー部材を介して隅肉溶接して溶接構造体を製造してもよい。また、突合せ溶接前の一組のウェブ用鋼板をフランジ表面のダブラー部材に仮付溶接しついでウェブ用鋼板同士を突合せ溶接し、得られた突合せ溶接継手をフランジに溶接して溶接構造体を製造してもよい。
td/Wd<2 ‥‥(1a)
を満足するように、ダブラー部材の寸法を調整する。ダブラー部材の板厚tdとダブラー部材の板幅Wdが(1a)式を満足しない場合には、接合部材(ウェブ)から発生した脆性亀裂の伝播の停止ないし阻止の方が、被接合部材(フランジ)から発生した脆性亀裂の伝播の停止ないし阻止よりも厳しくなり、接合部材(ウェブ)および被接合部材(フランジ)から発生した脆性亀裂の伝播をともに、停止ないし阻止することができなくなる。
なお、td/Wdがあまりに小さくなると、ダブラー部材の縦方向剛性が低下する問題が生じるので、td/Wdの下限値は0.2とすることが好ましい。
L≧20mmの場合、 vTrs≦-5L+65-1.5(tf-75) ‥‥(1b)
L<20mmの場合、 vTrs≦-35-1.5(tf-75) ‥‥(1c)
(ここで、vTrs:隅肉溶接金属のシャルピー衝撃試験破面遷移温度(℃)、tf:被接合部材の板厚(mm)、L:隅肉脚長もしくは溶着幅(mm))
を満足するように隅肉溶接金属の靭性を調整する。なお、Lは隅肉脚長、溶着幅のうち小さい方を用いる。
なお、本発明の溶接構造体は、上記した隅肉溶接継手を備えるものであり、例えば、船舶の船体外板をフランジとし、隔壁をウェブとする船体構造、あるいはデッキをフランジとし、ハッチをウェブとする船体構造などに適用可能である。
表1-1および表1-2に示す板厚の厚鋼板を接合部材(ウェブ)、ダブラー部材および被接合部材(フランジ)として用いて、図4(a)、(b)、(c)および図5(a)、(b)、(c)に示す形状の実構造サイズの大型溶接構造継手を作製した。図4(a)、(b)、(c)は、被接合部材(フランジ)から脆性亀裂が発生・伝播するケース、図5(a)、(b)、(c)は、接合部材(ウェブ)から脆性亀裂が発生・伝播するケースを想定したものである。なお、作製した隅肉溶接継手では、ダブラー部材10と被接合部材2との突合わせ面に、図1(a)に示すような未溶着部4を、未溶着部の比率Y(=(未溶着部の幅B/ダブラー部材の板幅Wd))を変化させて、存在させた。なお、接合部材(ウェブ)とダブラー部材の突合せ面には未溶着部は残留させなかった。
そして、機械ノッチ7の先端を、接合部材(ウェブ)1または被接合部材(フランジ)2の母材、突合せ溶接継手部12、22のBOND部または溶接金属WMとなるように加工した。
いずれの試験も、試験応力100~283N/mm2、温度:-10℃の条件で実施した。試験応力100N/mm2は、船体に定常的に作用する応力の平均的な値であり、試験応力257N/mm2は、船体に適用されている降伏強度390N/mm2級鋼板の最大許容応力相当の値、試験応力283N/mm2は、船体に適用されている降伏強度460N/mm2級鋼板の最大許容応力相当の値である。温度-10℃は船舶の設計温度である。
得られた結果を表2-1および表2-2に示す。
一方、本発明の範囲を外れる比較例では、脆性亀裂を被接合部材(フランジ)から伝播させた場合において、または脆性亀裂を接合部材(フランジ)から伝播させた場合において、あるいは両方の場合において、脆性亀裂は隅肉溶接部で停止することなく伝播し、隅肉溶接金属で脆性亀裂の伝播を阻止することができなかった。
2 被接合部材(フランジ)
3 脚長
4 未溶着部
5 隅肉溶接金属
7 機械ノッチ
8 仮付け溶接
9 ダブラー部材付き大型隅肉溶接継手
10 ダブラー部材
12 ウェブ突合せ溶接継手部
13 溶着幅
16 未溶着幅(B)
22 フランジ突合せ溶接継手部
θ 交差角
Claims (3)
- 接合部材の端面が、ダブラー部材の表面に突き合わせ溶接接合され、かつ前記ダブラー部材が板厚50mm以上の被接合部材の表面に隅肉溶接接合された隅肉溶接継手を備えるダブラー部材付き隅肉溶接構造体であって、前記隅肉溶接継手における前記ダブラー部材の表面と前記被接合部材の表面とを重ね合わせた面に、前記隅肉溶接継手の断面でダブラー部材の板幅Wdの95%以上の未溶着部を有し、さらに前記ダブラー部材が、板厚tdと板幅Wdとの比td/Wdが下記(1a)式を満足し、さらに前記隅肉溶接継手の隅肉溶接金属を、該隅肉溶接金属のシャルピー衝撃試験破面遷移温度vTrs(℃)が、隅肉脚長もしくは溶着幅Lに対応して、前記被接合部材の板厚tfと隅肉脚長もしくは溶着幅Lとの関係で下記(1b)式または下記(1c)式を満足する隅肉溶接金属とする、脆性亀裂伝播停止特性に優れる溶接構造体。
記
td/Wd<2 ‥‥(1a)
L≧20mmの場合、 vTrs≦-5L+65-1.5(tf-75)
‥‥(1b)
L<20mmの場合、 vTrs≦-35-1.5(tf-75) ‥‥(1c)
ここで、vTrs:隅肉溶接金属のシャルピー衝撃試験破面遷移温度(℃)、
tf:被接合部材の板厚(mm)、
td:ダブラー部材の板厚(mm)、
Wd:ダブラー部材の板幅(mm)、
L:隅肉脚長もしくは溶着幅(mm) - 前記被接合部材が、前記接合部材に交差する向きに突合せ溶接継手部を有する請求項1に記載の溶接構造体。
- 前記接合部材が突合せ溶接継手部を有し、該接合部材の突合せ溶接継手部が前記被接合部材の突合せ溶接継手部と交差するように該接合部材を配設してなる請求項2に記載の溶接構造体。
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