| Project/Area Number |
01550561
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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 | Osaka University |
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Principal Investigator |
SHINOZAKI Kenji Osaka University, Faculty of Engineering, Research Associate, 工学部, 助手 (70154218)
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| Co-Investigator(Kenkyū-buntansha) |
NAKAO Yoshikuni Osaka University, Faculty of Engineering, Professor, 工学部, 教授 (20029086)
SAIDA Kazuyuki Osaka University, Faculty of Engineering, Research Associate, 工学部, 助手 (30178470)
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| Project Period (FY) |
1989 – 1990
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| Project Status |
Completed (Fiscal Year 1990)
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| Budget Amount *help |
¥2,800,000 (Direct Cost: ¥2,800,000)
Fiscal Year 1990: ¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 1989: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Keywords | Ni-base superalloy / Solidification crack / Liquation crack / Multipass weld metal / Microsegregation / Ductility-dip crack / Reheated weld metal |
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| Research Abstract |
This paper was carried out in order to make clear the cracking mechanism of microfissure in multipass weld metal of Ni-base super-alloys. Metallographic and fractographic examinations were performed to the fracture surface of microfissure. Moreover, the effects of P, Si and S on hot cracking susceptibilities in reheated weld metal of 70%Ni-Cr-Fe ternary alloys were evaluated in order to make clear the effects of these impurity elements on hot cracking susceptibilities in multipass weld metal of Ni-base welding rods. Main results obtained are as follows.
(1) A detail fractographic examination has made clear that microfissure in multipass weld metal was liquation crack or ductility-dip crack occurring at reheated weld metal.
(2) The liquation cracking susceptibilities in reheated weld metal of 70%Ni-Cr-Fe ternary alloys were too low and they increased with an increase in impurity elements. Ductility-dip cracking susceptibilities of materials containing S were much higher than those containing P and Si. Especially cracking susceptibilities of 0%Cr and 20%Cr alloys containing 0.007%S were higher than those of 5%Cr and 10%Cr alloys.
(3) There was the suitable Cr content for reducing the ductility-dip cracking susceptibility because of contrary effects due to grain boundary carbide, hardness and grain boundary segregation of S.
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