저탄소 미량합금강의 미세조직에 미치는 고온변형의 효과 = Research Effects of Austenitization Temperature and Hot Deformation on Microstructure of Microalloyed Low Carbon Steels

다국어 초록 (Multilingual Abstract)

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다국어 초록 (Multilingual Abstract)

As a research for developing fine-grained high strength low carbon steels, the effects of austenitization temperature and hot deformation on microstructure was investigated in 0.15 wt% carbon steels with microalloying elements such as Nb and Ti. When the steels were reheated at 1250℃, Nb containing steel showed very coarse austenite grain size of 200㎛ whereas Nb-Ti steel did fine one of 70㎛ because Ti carbonitrides could suppress the austenite grain growth. In case of 50% reduction at 850℃, the austenite grains in the Nb steel partially recrystallized while those in the Nb-Ti steel fully recrystallized probably due to finer prior austenite grains. For the Nb-Ti steel, ferrite grain size was not sensitively changed with austenitization temperature and compression strain and, severe deformation of 80% reduction was not essentially necessary to refine ferrite grains to about 3㎛ which could be obtained through lighter deformation of 40% reduction.