| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1997: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1996: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
Modified heat treatment effects on the microstructure, tensile properties, slow bend and impact toughness, fracture toughness and fatigue properties of Fe-0.6C-1.5Si-0.8Mn steel have been studied with the aim of developing the mechanical properties of environmental conscious material Fe-C-Si-Mn steel through mixed-structure control As a result of the investigation, Fe-C-Si-Mn TRIP (533K-IQ-Aus) steel has been suggested whereby the mechanical properties were improved. The results are summarized as follows : (1) The microstructure of modified heat treated steels consisted of triple phases of carbide-free upper bainite, retained austenite and tempered martensite. The results are summarized : (2) Compared to the Con-Aus, the 533KIQ-Aus significantly improved total elongation by twice with increased strength : (3) From the result of true-stress-strain diagram, X-ray analysis of the carbon content in the retained austenite (gamma) and determination of mechanical stability of the gamma, a rem
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arkable increase in elongation of the 533KIQ-Aus steel can be attributed to the fact that as a result of low temperature aging of gamma, transformation-induced plasticity (TRIP) occurred effectively during plastic deformation : (4) There was little difference between the slow bend and Charpy impact energies of the 533KIQ-Aus and Con Aus steels : (5) Compared to the Con-Aus, the 533KIQ-Aus increased J_<IC> but the 493KIQ-Aus decreased : (6) An increase in J_<IC> of the 533KIQ-Aus steel was due to the fact that stress relief at the crack tip occurred through TRIP : (7) The decrease in the 493KIQ-Aus steel was due to the embrittling effect of tempered martensite introduced by interrupted quenching : (8) Compared to the Con Aus steel, the 533KIQ-Aus steel increased fatigue stress by one-half and decreased notch sensitivity : (9) The 493KIQ-Aus steel increased fatigue stress by two-half compared with that of the Con Aus steel but significantly decreased notch sensitivity : (10) There was little difference between crack propagation rate of the 533K and Con-Aus steels. Less
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