2006 Fiscal Year Final Research Report Summary
Rheocast of lead-free bismuth bronze and phosphorus bronze utilizing high fluidity slurry manufactured by repeated extrusion process
| Project/Area Number |
17560653
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Metal making engineering
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| Research Institution | Toyama Prefectural University |
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Principal Investigator |
UETANI Yasuhiro Toyama Prefectural University, Faculty of Engineering, Associate Professor (60099405)
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| Project Period (FY) |
2005 – 2006
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| Keywords | lead-free bismuth bronze / phosphorus bronze / semi-solid slurry / rheocast / granular structure / tensile property / 粒状組織 / 引張特性 |
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| Research Abstract |
Semi-solid slurry with fine solid granules for rheocasting was made from lead-free bismuth bronze and phosphorus bronze by passing the low-superheat melt through an opening between a rotating regular octagonal rotor and a circumscribed chill block. At first, we mainly investigated the effect of rotational speed on the structure of a solidified small ingot of lead-free bismuth bronze. The ingot structures changed from the dendrite of rotor-free condition to the rosette at the rotational speed of 50rpm and to the granular with a mean grain size of about 50μm at higher than100rpm. If the slurry made at 100rpm was rheocast to a disk shape by the use of a high pressure casting machine, the disk had almost uniform granular structures from the center to the edge regions. However, the tensile elongation and strength were very low because of the existence of brittle fine dendrite-like structure regions which were generated by rapid cooling of liquid phases during rheocasting. They were drastically improved by lowering cooling rate to suppress the generation of fine dendrite structure regions, especially in the elongation showing much higher than that of conventional squeeze cast sample. On the other hand, the rotor process also produced semi-solid slurry phosphorus bronze with mean granule size of less than 40μm at almost the same processing conditions. When rheocasting utilizing the semi-solid slurry had been carried out at slower cooling rate, the formed sample had a fine grain structure with mean grain size of 30μm. We expect this reocast sample of phosphorus bronze have an excellent tensile property especially in the much higher elongation than that of the conventional castings.
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Research Products
(2 results)
