| Project/Area Number |
63550545
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
溶接工学
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| Research Institution | Tohoku University |
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Principal Investigator |
SATO Yoshihiro (1989-1990) Tohoku University, Department of Materials Ppocessing, Research Associate, 工学部, 助手 (00170796)
粉川 博之 (1988) 東北大学, 工学部, 助教授 (10133050)
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| Co-Investigator(Kenkyū-buntansha) |
KIGUCHI Ryuji Tohoku University, Department of Materials Processing, Research Associate, 工学部, 助手 (60005410)
KOKAWA Hiroyuki Tohoku University, Department of Materials Processing, Associate Professor, 工学部, 助教授 (10133050)
佐藤 嘉洋 東北大学, 工学部, 助手 (00170796)
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| Project Period (FY) |
1988 – 1990
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| Project Status |
Completed (Fiscal Year 1990)
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| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1990: ¥200,000 (Direct Cost: ¥200,000)
Fiscal Year 1989: ¥200,000 (Direct Cost: ¥200,000)
Fiscal Year 1988: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Keywords | STEEL WELDMENT / MICROSTRUCTURE / MECHANICAL PROPERTY / STAINLESS STEEL / PRECIPIATES / TRANSFORMATION / INTERGRANULAR CORROSION / COHERENCY / 溶接熱影響部 / 炭化物析出 / ウェルドディケイ / 規則粒界 / クロム欠乏層 / 粒界制御 / レ-ザ-ビ-ム溶接 / 電子ビ-ム / 金属組織学 / 溶接金属 / 急速凝固 / 高温変態挙動 / シグマ相 / アーク溶接 / 組織学 / 結晶学 |
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| Research Abstract |
In order to make clear the relationships between metallographic structure and various properties of steel weldments, several steels were welded in different atmospheres and the microstructures were observed. Also mechanical and corrosion tests were performed for the weldments. The results are as follows.
(1) A mild steel was arc-welded in pressurized Ar-CO_2 gas mixture atmospheres. The microstructure of weld metal depended on the atmospheric pressure and gas composition, and affected strongly the mechanical properties. An oxygen content of weld metal showed an optimum toughness.
(2) Purified iron and iron alloys were arc-welded in various atmospheres containing oxygen to study the oxygen absorption and deoxidation mechanism during arc welding process. The oxide inclusions formed in the weld metal were observed to have fundamental informations, because they play very important roles in formation of the microstructure of steel welds.
(3) Delta-ferrite transformations and their crystallogra
… More
phic characteristics in a type 304L austenitic stainless steel weld metal at elevated temperatures were observed mainly by transmission electron microscopy. The morphology change and sigma precipitation strongly depended on the initial ferrite structure in the weld metal. Incoherent boundary between ferrite and austenite resulted easily in sigma precipitation. These facts suggested that the boundary coherency affects strongly on the transformation in the weld metal.
(4) Grain boundary carbide precipitation and intergranular corrosion in the weld heat affected zone of a type 304 stainless steel were investigated using optical, scanning and transmission electron microscopy to discuss effects of grain boundary atomic structure on precipitation and corrosion from a crystallographic viewpoint. The results suggested that grain boundary carbide precipitation and corrosion in stainless steel weld HAZ depend sensitively on the crystallographic character of grain boundaries, and that weld decay in austenitic stainless steel can be prevented by increasing the percentage of ordered boundaries in the material. Less
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