2000 Fiscal Year Final Research Report Summary
Creation of Easy-to-Recycle Sintered Steels. Replacement of Copper Addition to Boron.
| Project/Area Number |
11450276
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| Research Category |
Grant-in-Aid for Scientific Research (B).
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Material processing/treatments
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| Research Institution | Hiroshima University |
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Principal Investigator |
KUROKI Hidenori Faculty of Engineering, Hiroshima University, Professor, 工学部, 教授 (80037853)
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| Co-Investigator(Kenkyū-buntansha) |
SUZUKI Hiroyuki Faculty of Engineering, Hiroshima University, Research Associate, 工学部, 助手 (90284158)
SHINOZAKI Kenji Faculty of Engineering, Hiroshima University, Associate Professor, 工学部, 助教授 (70154218)
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| Project Period (FY) |
1999 – 2000
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| Keywords | recycle / sintered material / boron / Fe-B-C eutectic / mechanical property |
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| Research Abstract |
A boron of 0.03-0.125mass% and a carbon of 0-1mass% are simultaneously added in iron powder to promote sintering by forming a eutectic melt of Fe-B-C during heating. Sintering conditions are varied in temperature of 1380-1440 K and in holding time of 0-180 min. The dimensional change during sintering is observed by a dilatometer. The presence of eutectic melt during sintering has been verified by the observation with optical microscope and SEM.The tensile strength and elongation of sintered materials are measured. Some specimens are subjected to post-sintering heat treatment of quenching and annealing to improve mechanical properties.
The results are as follows.
(1) The simultaneous addition of boron and carbon in iron powder forms eutectic melt at and above 1410 K.The differential dilatometric curve of Fe-0.05mass%B-1.0mass%C material coincides well to that of conventional copper added sintered steel. The coincidence would be the result of the occurrence of nearly the same amount of eutectic melt as well as the expansion of ferrite with the solid solution of carbon.
(2) The eutectic forms three dimensional network between iron particles. With slow cooling rate, the boundary with eutectic behaves as the precipitating site of Fe_3C during γ-α phase transformation. Therefore, the outer part of iron particles becomes ferrite and only the center part of the particles forms pearlite.
(3) The tensile strength of both boron and carbon doped materials mainly depends on the amount of pearlite or ferrite, which vary with the effective amount of carbon, than the amount of the eutectic. The excessive addition of boron reduces effective amount of carbon. With a boron of 0.1mass% or more, the strength decreases.
(4) Fe-0.05mass%B-1.0mass%C material can sinter at 1440 K with a microstructure consists of the eutectic and pearlite with a small amount of ferrite, which results good mechanical properties. The strength of this material can be improved by quenching and annealing.
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Research Products
(4 results)
