루르슈탈-헤레우스（RH）의 체적 확장에 따른 탈탄 효과 = Decarbonization Effect due to Enlarged Volume of Ruhrstahl Heraeus（RH）Degasser

다국어 초록 (Multilingual Abstract)

RH（Ruhrstahl-Heraeus） refining has been the subject of numerous studies due to its many advantages. However, research on the decarburization process associated with the enlargement of the lower volume of the RH degasser is currently lacking. Therefore, this study enlarged the lower volume of the RH degasser used in the field from 7,376m3（CRH） to 8,164m3（ERH） and evaluated the effects on the decarburization time, carbon content, and mechanical properties of ultra-low carbon steel according to the circulation gas flow rate of 190 Nm3/h, 230 Nm3/h, and 250 Nm3/h. Furthermore, under actual operating conditions using a 320 ton RH degasser, the molten steel circulation rate and the decarburization reaction were evaluated within both the conventional RH degasser （CRH） and the enlarged RH degasser （ERH） by varying the up-snorkel diameter and the circulation gas flow rate. The results of this evaluation were then compared with the carbon concentration results obtained from the experiments. Additionally, during the RH degassing process for Ti-added ultra-low carbon steel, the study aimed to enhance cleanliness by controlling the total inclusion content to 0.003 wt% or less. It also aimed to prevent nozzle clogging during continuous casting by controlling the TiO2 content in complex inclusions to 20 wt% or less. Decarburization in the ERH increased as the circulation gas flow rate （190 Nm3/h, 230 Nm3/h, and 250 Nm3/h） increased. The optimal circulation gas flow rate was determined to be 230 Nm3/h, considering factors such as the lifespan of the up-snorkel and the RH refractories.The decarburization time required to reach the target carbon content of 0.003 wt% for ultra-low carbon steel was 12.4 minutes for the CRH and 10.8 minutes for the ERH, representing a 1.6 minute reduction achieved by the ERH. The enlarged lower volume of the RH degasser （ERH） allowed for this 1.6 minute reduction in the RH process decarburization time, leading to production cost savings.

목차 (Table of Contents)

• 제1장 서론 1
• 1.1 RH 정련 공정 기술 개발 역사 2
• 1.2 탈탄 5
• 1.3 탈가스 9
• 1.4 균질화 12
• 1.5 스노클（상승 및 하강관） 설계 최적화 14
• 1.6 진공 시스템 개선 17
• 1.7 공정 제어 시스템 개발 19
• 1.8 대형 RH 탈기기 21
• 1.9 첨단 정련 기술 23
• 1.10 본 연구의 목적 및 필요성 27
• 1.11 본 연구의 구성 28
• 참고문헌 29
• 제2장 탄소량 및 기계적 특성 34
• 2.1 서언 35
• 2.2 실험방법 37
• 2.3 결과 및 고찰 41
• 2.3.1 환류 가스 유량에 따른 탄소량 41
• 2.3.2 환류 시간에 따른 개재물 47
• 2.3.3 기계적 특성 56
• 2.3.4 개재물 관찰 62
• 2.4 고찰 66
• 2.4 결언 67
• 참고문헌 69
• 제3장 상승관 직경에 따른 탈탄 반응 76
• 3.1 서언 77
• 3.2 평가 방법 80
• 3.3 결과 및 고찰 84
• 3.4 결언 98
• 참고문헌 99
• 제4장 Ti 첨가량에 따른 청정도 102
• 4.1 서언 103
• 4.2 재료 및 실험방법 105
• 4.3 결과 및 고찰 107
• 4.4 결언 124
• 참고문헌 125
• 제5장 결론 129
• 발표 논문 131
• 감사의 글 133