偏析部組成相当材の組織と靱性

概要

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The microstructure and toughness of steels corresponding to the chemical composition of the segregated zone in the plate by continuous casting process or in the ingot by non-continuous process were investigated by means of microstructural observations and notch tensile tests to clarify the degree of embrittlement of the segregated zone. The nil-ductility transition temperature (NDTT) in notch tensile tests of the martensite-bainite duplex structure due to the high manganese and high phosphorus contents is above +200℃, while that of the ferrite-pearlite structure containing low manganese contents with even high phosphorus contents is below -100℃. Therefore, the embrittlement caused by the independent increase of phosphorus content is comparatively small, whereas the one caused by the formation of low-temperature transformed structure due to the increase of both manganese and phosphorus contents is large. Here the embrittlement becomes small by tempering at 650℃ even when the low-temperature transformed structure is formed. The fracture mode is transferred from cleavage to intergranular with the increase of phophorus content, which bring about lower fracture strength.
社団法人日本鉄鋼協会の論文
1980-08-01