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급냉 연속 주조된 페라이트 스테인레스강 판재의 조직 및 인장성질에 미치는 Cr 함량의 영향
오명석,전병완,이태행,조성석 ( Myeong Suck Oh,Byeong Whan Jeon,Tae Haeng Lee,Seong Seock Gho ) 한국주조공학회 1988 한국주조공학회지 Vol.8 No.1
Using the twin-roller type melt-quenching technique, we investigated the effect of Cr content on the microstructure and tensile properties of ferritic stainless steels, whose thickness is 0.5㎜ has been investigated. In this experiment, the three kinds of ferritic stainless steels has been used. The predicted cooling rates of melt-quenched ferritic stainless steels were not changed, even the Cr content increases up, to 25%. The metastable phase of the melt-quenched ferritic stainless steels were changed depending upon the car Cr content. In case of 17% Cr steel, the metastable phase was martensite and in case of 20 and 25% Cr steel, the metastable phase was austenite. After heat treatment, the tensile properties of the melt-quenched stainless steels are better than those of conventional ferritic stainless steels.
급냉응고한 오스테나이트계 스테인레스강의 조직 및 인장 성질에 미치는 조성의 영향
조성석,오명석 대한금속재료학회(대한금속학회) 1987 대한금속·재료학회지 Vol.25 No.12
Using a twin-roller type melt-quenching technique we investigated the effect of chemical composition on the microstructure and tensile properties of austenitic stainless steels. For three austenitic stainless steels, 0.5㎜ thick sheets were produced. For Cr-eq./Ni-eq.< 1.35, solidification typically takes place by primary austenite formation whereas if the ratio is greater than 1.35, primary ferrite formation is the solidification mode. As the Cr-eq./Ni-eq. ratio increases, the cooling rate of melt-quenched austenitic stainless steels slighlly decreases. In a melt-quenched AISI 304 (Cr-eq./Ni-eq. ratio: 1.7), the ferrite to austenite transformation was suppressed, resulting in residual ferrite. Secondary dendrite arm spacing of melt-quenched austenitic stainless steels was about 2-3㎛ . After heat treatment, the tensile properties of the melt-quenched stainless steels are bettor than those of conventional austenitic stainless steels.
급냉 응고된 AISI 304 스텐레스강의 조직 및 인장성질에 미치는 두께의 영향
조성석,오명석,최필규 대한금속재료학회(대한금속학회) 1987 대한금속·재료학회지 Vol.25 No.12
Using twin-roller type melt-quenching technique, the effect of thickness on the microstructure and the tensile properties of AISI 304 stainless steel were investigated by optical microscope, X-ray diffractometer and tensile test. In AISI 304 stainless steel, sheets whose thickness was 0.3-1.0 ㎜ could be produced. As the thickness increased, the cooling rate of melt-quenched AISI 304 stainless steel decreased. The microstructure of 0.8 ㎜-thick sheet consisted of columnar grains which formed near the sheet surface and equiaxed grains which formed near the center of the sheet cross-section. As the thickness increased in melt-quenched AISI 304 stainless steel, the Vickers hardness, 0.2% proof stress and tensile strength increased whereas the elongation decreased.
超急冷 Ni_60B_40 合金의 構造 및 熱的 安定性에 관한 硏究(Ⅰ)
具滋洛,吳明錫,林榮彦,조성석 충남대학교 공업교육연구소 1981 論文集 Vol.4 No.2
The phase transformation and structure of rapidly quenched Ni_60B_40 alloy has been studied by x-ray diffraction and electrical resistivity measurements. The first step in the transformation of rapidly quenched Ni_60B_40 alloy was found to be Am+O-Ni_4B_3+m-Ni_4B_3 → O-Ni_4B_3+m-Ni_4B_3. The mechanism of transformation has been determined by the initially present microcrystallites in the amorphous matrix. The diffusional growth has three steps of growth of a disc with constant thickness, thickening of a disc and growth in axial direction only. The activation energy for crystallization is 43㎉/mole in the first step, 57㎉/mole in the second step and 55㎉/mole in the third step.