표제지
국문초록
목차
Ⅰ. 서론 12
Ⅱ. 이론적 배경 19
2-1. 활동도 계수 및 상호작용계수의 열역학적 의미 19
2-2. 용융 Ag 중 Mn의 열역학적 성질 도출 원리 및 방법 24
2-3. 고상 Fe 중 Mn의 열역학적 성질 도출 원리 및 방법 29
2-4. 고상 Fe 중 S의 열역학적 성질 도출 원리 및 방법 31
2-5. 강 중 MnS 석출거동과 용해도적 33
Ⅲ. 실험 방법 35
3-1. 용융 Ag와 MnO간 평형실험 조건 35
3-2. 고상 Fe와 용융 Ag간 Mn의 분배평형 실험 조건 37
3-3. 고상 Fe와 S간 평형실험 조건 39
3-4. 평형실험을 위한 시편 제작 41
3-5. 활동도 계수 및 상호작용계수 도출을 위한 평형실험 방법 45
3-5-1. 용융 Ag와 MnO간 평형실험 방법 45
3-5-2. γ-Fe내 Mn의 활동도 계수와 자기상호작용계수 도출을 위한 평형실험 방법 47
3-5-3. γ-Fe 내 Mn과 S의 상호작용계수 도출을 위한 평형실험 방법 52
3-5-4. Fe와 Ag내 용질의 농도 분석 54
Ⅳ. 실험 결과 및 고찰 57
4-1. 평형실험 후 용질원소의 농도 구배 확인 57
4-2. 용융 Ag 내 Mn의 활동도 계수와 상호작용계수 도출 59
4-2-1. 실험 후 MnO 압분체와 Ag 계면의 XRD 분석 59
4-2-2. 용융 Ag내 Mn의 활동도 계수와 자기 상호작용계수 도출 61
4-3. γ-Fe상 내 용질의 활동도 계수 및 상호작용계수 도출 66
4-3-1. γ-Fe상 내 Mn의 활동도 계수와 자기 상호작용계수 도출 66
4-3-2. γ-Fe상 내 Mn과 S의 상호작용계수 도출 69
4-4. γ-Fe상 내 MnS의 용해도적 71
Ⅴ. 결론 76
참고문헌 78
ABSTRACT 83
Table. 3-1-1. Partial pressure conditions of the gases used in the experiment 36
Table. 3-2-1. Equilibrium time(t) for x=50㎛ 38
Table. 3-3-1. Solubility of Mn in γ-Fe, coexisting with solid sulfide 40
Table. 3-3-2. Calculated partial pressure ratio 40
Table. 3-4-1. Composition of Ag-Mn alloy 42
Table. 3-4-2. Composition of Fe-Mn alloy 42
Table. 4-2-1. The contents of Mn in extracted samples in equilibrium experimental at 1373K 63
Table. 4-2-2. Comparison of activity coefficients of present result with reference at 1373K 64
Table. 4-3-1. Analysis result of γ-Fe and molten Ag phases for determining εMnMn in γ-Fe at 1373K[이미지참조] 67
Table. 4-3-2. Comparison of molten steel and present study result 68
Table. 4-3-3. Comparison of molten steel and present study result 70
Table. 4-4-1. Values of interaction coefficients eij (a) at 1373K(*: eij at 1873K) (b) at 1873K[이미지참조] 74
Table. 4-4-2. Solubility product of MnS in Fe in literatures⁴⁴-⁴⁷ 75
Fig 1-1. Effect of Mn on the size of the austenite phase field 15
Fig 1-2. Ellingham diagram for some metal sulphides 16
Fig 1-3. SEM image and corresponding EDS maps of typical inclusion 17
Fig 1-4. FESEM morphology of the surfaces perpendicular to the necking parts 17
Fig 1-5. Schematic illustration of the triggering of pitting corrosion in stainless steel. 18
Fig 1-6. Schematic illustration of heterogeneous nucleation for acicular ferrite by non-metallic inclusions in steel. 18
Fig. 2-1-1. Acticity of i as function of mole fraction of i 22
Fig. 2-1-2. Schematic illustration of interaction parameter in non-ideal solution 23
Fig. 2-2-1. Phase diagram of Fe-Ag alloy 27
Fig. 2-2-2. Schematic of control of oxygen partial pressure 28
Fig. 3-2-1. Diffusion coefficient of Mn in γ-Fe as a function of Temperature 38
Fig. 3-4-1. Thickness control fixture 43
Fig. 3-4-2. Procedure of thickness control of Fe-Mn alloy 43
Fig. 3-4-3. SEM image of the specimen after grinding by thickness control fixture 44
Fig. 3-5-1. Schematic diagram of the experimental apparatus molten Ag in Mn 46
Fig. 3-5-2. Specimen after equilibrium experiment for 24h 46
Fig. 3-5-3. Schematic diagram of the experimental apparatus γ-Fe and molten Ag 49
Fig. 3-5-4. Photograph showing specimens and Ti sponge in alumina crucible before equilibrium experiment 49
Fig. 3-5-5. Specimen after equilibrium experiment for 96h 50
Fig. 3-5-6. Schematic diagram of the experimental apparatus 50
Fig. 3-5-7. Specimen after equilibrium experiment for 96h in ampoule 51
Fig. 3-5-8. Specimen diagram of the experimental apparatus 53
Fig. 3-5-9. Specimen after equilibrium experiment for 72h 53
Fig. 3-5-10. Schematic illustration of the chemical separation for dissolution of Fe in HCl(aq) and Ag in HNO₃(aq) 56
Fig. 3-5-11. Procedure of chemical analysis for Fe and Ag phases 56
Fig. 4-1-1. SEM micrographs of cross section between γ-Fe and Ag 58
Fig. 4-2-1. XRD analysis results of MnO pellet and Ag 60
Fig. 4-2-2. Relationship between the activity and mole fraction of Mn in molten Ag at 1373K 63
Fig. 4-2-3. Temperature dependence of activity coefficient of Mn in molten Ag 64
Fig. 4-2-4. (a) Determination of εMnMn in molten Ag at 1373K (b) difference of εMnMn and measured values[이미지참조] 65
Fig. 4-3-1. Relationship between left-hand side of Eq (37) and XMninFe(s) in γ-Fe at 1373K[이미지참조] 68
Fig. 4-3-2. Determination of the interaction parameter of sulfur in γ-Fe-Mn alloy at 1373K 70
Fig. 4-4-1. Solubility product of MnS in γ-Fe at 1373K 74
Fig. 4-4-2. Comparison of solubility product at 1373K with literatures 75