harpy V-notch impact tests on 5.5mm thick, hot-rolled Dual-Phase 590 (DP590) steel plate were evalu-atedattemperaturesrangingfrom90
◦
Cto
−
120
◦
C.Similartestson2.0mmthickDP590HDGIsteelplatewere also conducted at room temperature. Splitting or secondary cracks was observed on the fracturedsurfaces. The mechanisms of the splitting were then investigated. Fracture surfaces were analyzed byoptical microscope (OM) and scanning electron microscope (SEM). Composition of the steel plates wasdetermined by electron probe microanalysis (EPMA). Micro Vickers hardness of the steel plates was alsosurveyed. Results show that splitting occurred on the main fractured surfaces of hot-rolled steel speci-mens at various testing temperatures. At temperatures above the ductile–brittle-transition-temperature(DBTT),
−
95
◦
C,wherethefractureispredominantlyductile,thelengthandamountofsplittingdecreasedwith increasing temperature. At temperatures lower than the DBTT, where the fracture is predominantlybrittle, both the length and width of the splitting are insignificant. Splitting in HDGI steel plates onlyappeared in specimens of T-L direction. The analysis revealed that splitting in hot-rolled plate is causedbysilicateandcarbideinclusionswhilesplittinginHDGIplateresultsfromstripmicrostructureduetoitshighcontentofmanganeseandlowcontentofsilicon.ThemicroVickershardnessofeithertheinclusionsor the strip microstructures is higher than that of the respective base steel
harpy V-notch impact tests on 5.5mm thick, hot-rolled Dual-Phase 590 (DP590) steel plate were evalu-atedattemperaturesrangingfrom90
◦
Cto
−
120
◦
C.Similartestson2.0mmthickDP590HDGIsteelplatewere also conducted at room temperature. Splitting or secondary cracks was observed on the fracturedsurfaces. The mechanisms of the splitting were then investigated. Fracture surfaces were analyzed byoptical microscope (OM) and scanning electron microscope (SEM). Composition of the steel plates wasdetermined by electron probe microanalysis (EPMA). Micro Vickers hardness of the steel plates was alsosurveyed. Results show that splitting occurred on the main fractured surfaces of hot-rolled steel speci-mens at various testing temperatures. At temperatures above the ductile–brittle-transition-temperature(DBTT),
−
95
◦
C,wherethefractureispredominantlyductile,thelengthandamountofsplittingdecreasedwith increasing temperature. At temperatures lower than the DBTT, where the fracture is predominantlybrittle, both the length and width of the splitting are insignificant. Splitting in HDGI steel plates onlyappeared in specimens of T-L direction. The analysis revealed that splitting in hot-rolled plate is causedbysilicateandcarbideinclusionswhilesplittinginHDGIplateresultsfromstripmicrostructureduetoitshighcontentofmanganeseandlowcontentofsilicon.ThemicroVickershardnessofeithertheinclusionsor the strip microstructures is higher than that of the respective base steel
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