1996 Fiscal Year Final Research Report Summary
Development of High Temperature Stress-Strain Test for Multi-Layred Materials
| Project/Area Number |
06555219
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 試験 |
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| Research Field |
Metal making engineering
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| Research Institution | Tohoku University |
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Principal Investigator |
EMI Toshihiko Inst.for Advanced Materials Processing, Tohoku University, Professor, 素材工学研究所, 教授 (30250822)
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| Co-Investigator(Kenkyū-buntansha) |
FUJII Tetsuya Kawasaki Steel Corp., 鉄鋼プロセス部長
SHIBATA Hiroyuki Inst.for Advanced Materials Processing, Tohoku University, Research Associate, 素材工学研究所, 助手 (50250824)
SATO Shunichi Inst.for Advanced Materials Processing, Tohoku University, Associate Professor, 素材工学研究所, 助教授 (30162431)
SUZUKI Mimiko Inst.for Advanced Materials Processing, Tohoku University, Associate Professor, 素材工学研究所, 助教授 (10261471)
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| Project Period (FY) |
1994 – 1996
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| Keywords | multi-layred materials / hot tensile test / temperature gradient field / solidified steel shell / peritectic medium carbon steel / continuous casting / longitudinal facial crack / critical strain for crack formation |
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| Research Abstract |
In present study, convenient and simple temperature gradient tensile and bending tests were developed with which mechanical properties of materials which exhibit multi-layr structure under temperature gradient, e.g., steels in casting mold and the critical strain for the crack formation can be determined at better accuracy with rectangular test-pieces.
(1) Results of present tests agree well with those by thermal elastic plastic stress analysis where finite element code is employed with corresponding stress-strain data measured in isothermal temperature field at different temperatures. The present tests can replace, therefore, the troublesome tensile tests as well as the complicated thermal elastic plastic stress analysis, and capable of determining mechanical properties of multi-layred materials (or materials under temperature gradient) reliably by one test.
(2) The fracture strength of solidifying steel shells determined by the temperature gradient test agrees well with that by a subme
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rged split chill tensile test to measure in-situ the fracture strength of solidifying steel shells. The fracture strength of ultra low and low carbon steel shells with thinner thickness is lower than that of medium and high carbon steels.
(3) Internal cracks were found to form at the hot side of test-piece during straining. The critical strain was independent of test methods, measured from 0.6% to 2.1% and decreased with increasing carbon content and grain boundary segregation. Surface cracks arising in high speed casting of peritectic medium carbon (0.09-0.16mass%C) steel slabs is not caused by low fracture strength of the steels. A cause of cracking for these steels is, therefore, considered that the shell deformation occurs as a consequence of shell shrinkage due to delta/gamma transformation during initial solidification. The shrinkage induces surface roughness of the shell, resulting in anomalous decrease of heat transfer from the shell to mold, often causing uneven shell growth and surface cracks on the shell. Less
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