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Volume 41 (2003)
- Issue 6 Pages 292-
- Issue 5 Pages 216-
- Issue 4 Pages 150-
- Issue 3 Pages 96-
- Issue 2 Pages 48-
- Issue 1 Pages 4-
Predecessor
Volume 41, Issue 4
Displaying 1-4 of 4 articles from this issue
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Original Paper
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-Assessment of Integrity for Fracture of Weld Joints-Susumu HONGOH, Shuji YAMAMOTO, Kouji MICHIBA, Taketo YAMAKAWA, Hideki ...Article type: Original paper
2003 Volume 41 Issue 4 Pages 150-159
Published: 2003
Released on J-STAGE: August 20, 2003
JOURNAL FREE ACCESSTaking into consideration of terms and conditions which could actually be assumed in utilization of LNG piping made of Invar alloy, assessment of integrity for fracture of weld joints was examined synthetically. Consequently, the following conclusions were obtained.
As a cause of crack initiation that could be assumed during the time of construction and operation, a weld crack, a fatigue crack and a stress corrosion cracking were mentioned. As for the weld crack and the stress corrosion cracking, the prevention method on construction was already established. Moreover, under the design stress to be assumed, it became clear that the fatigue crack did not result in initiating with sufficient degree of safety. Therefore, it was thought that the possibility of the crack initiation was very small.
Supposing that the crack arose in a certain reason despite fully preventing the crack initiation, the possibility of resulting in structural collapse by both brittle and ductile fracture was examined. Since percent ductile fracture on Charpy impact test pieces was 100%, it could be judged that there was no possibility of brittle fracture. Furthermore, since there was sufficient degree of safety about elastic-plastic fracture toughness, JIC, as compared with J which was determined from the design conditions of LNG piping, it could be said that the possibility of ductile fracture was very small.
Comparison with the maximum allowable crack size and the detectability of the defects in radiographic testing was performed. The former was much larger compared with the latter, and the detrimental defects in actual construction could be discovered certainly.View full abstractDownload PDF (327K) -
-Multi-pass GTAW process for thick joint of Fe-36%Ni alloy-Susumu HONGOH, Shuji YAMAMOTO, Kazuhiro OGAWA, Masahito IKEBE, Shinji ...Article type: Original paper
2003 Volume 41 Issue 4 Pages 160-167
Published: 2003
Released on J-STAGE: August 20, 2003
JOURNAL FREE ACCESSAuthors have carried out investigations on multi-pass GTAW process for 9. 5mm thick Invar alloy. In the welding of Invar alloy, use of the filler wire of base metal compositions resulted in the occurrence of ductility-dip cracks in weld metal. Authors' previous study had clarified that addition of Nb and C was effective to prevent the crack. Based on that result appropriate compositions of Nb and C were investigated through welding tests and a filler wire containing 0. 8%Nb and 0. 2%C was established for multi-pass GTAW process of Invar alloy. In the welding of U-shaped groove configuration, however, higher dilution rate of base metal at weld root lowered Nb and C contents and caused cracks in that area. To keep the amount of NbC at grain boundaries beyond the necessary level for preventing cracks, new filler wire of higher Nb content (1. 6%) was applied to the deposition at the root. Finally, to complete U-shaped groove by GTAW process, two filler wires of different Nb and C contents were used properly. By applying this deposition method, crack-free GTAW joints of Invar alloy with sufficient mechanical properties especially in respect of Charpy absorbed energy were made. Moreover, abovementioned combined use of filler wires were validated also in the welding of dissimilar joint between Invar alloy and 304 stainless steel. As the result of those investigations, authors have established multi-pass GTAW process for Invar alloy LNG piping that assures crack free weld metal with sufficient low temperature toughness under wide range of welding conditions.View full abstractDownload PDF (297K) -
Kiyomi ARAKI, Shinichi DESHIMARU, Hiroshi KONDOU, Takeshi KOHRIYAMAArticle type: Original paper
2003 Volume 41 Issue 4 Pages 168-175
Published: 2003
Released on J-STAGE: August 20, 2003
JOURNAL FREE ACCESSHeavy section steel plates have been usually manufactured in ingot casting process for the requirement of good internal properties. We have newly applied the combined forging and plate rolling process using continuous casting slabs in place of ingot casting process for the economical point of view. The applying of this manufacturing process was possible both homogeneous and sound internal properties of steel plates. The forging method with reduction in widthwise and thickness wise direction of slabs was greatly effective for annihilation of center porosities. By the application of this process, the excellent internal properties can be obtained in the manufacture of heavy section steel plates with thickness of up to 240mm which means the reduction ratio of thickness from a strand cast slab to plate: 1.29. The properties at the center of plate thickness could be greatly improved by increase of slab reheating time before forging due to easy diffusion of center segregation elements in continuous casting slabs.
This combined forging and plate rolling process was approved as special practices mitigating the reduction ratio limitation on ASME 2002 Addenda SA-20⁄SA-20M (Standard specification for general requirements for steel plates for pressure vessels).View full abstractDownload PDF (238K)
Review
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Toshiyuki SAWAArticle type: Technical report
2003 Volume 41 Issue 4 Pages 176-181
Published: 2003
Released on J-STAGE: August 20, 2003
JOURNAL FREE ACCESSFive accidents on mechanical structures which the author investigated and their sources were described. (1) Two workers were killed by soil collapse due to a rupture of bolted joints in sheet pile structures. (2) Drive recklessly of tractor due to brake trouble. (3) Leakage accident of LPG internal fluid from bolted pipe flange connection due to earthquake. (4) Gas explosion from buried pipe line. (5) An accident where two workers were killed by a rupture of chains in operation. As conclusions, the author pointed out that engineers hand to pay a lot of attentions to the design and the instruction for structures. Especially, it is pointed out that a technology for bolted joints is important in practice.View full abstractDownload PDF (191K)
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