Q/T 처리된 FeCrMoVC강의 석출강화를 고려한 기계적 특성 예측 모델링 = The Mechanical Properties Prediction Modeling Considering Precipitation Hardening for Quenched and Tempered FeCrMoVC Steel

다국어 초록 (Multilingual Abstract)

In recent years, as global warming has intensified, environmental preservation and saving of energy resources have become more important. Therefore, advanced countries are setting stricter fuel economy regulations. As a result, the automotive industry continues to make efforts to improve fuel efficiency through vehicle weight reduction. For this purpose, we are increasing the ratio of advanced high strength steel (AHSS), which is stronger than conventional steel, However, high strength steels become difficult to process. Therefore, research on high strength tool steels used for machining such advanced high strength steels is being actively carried out. The steel composition Fe84.3Cr4.3Mo4.6V2.2C4.6 subjected to preparation conditions typically used for manufacturing of bulk metallic glasses. This steel in the as-cast state exhibits superior mechanical properties. However, Microstructure and mechanical property for cold work process have not been reported. Therefore, in this study, Cold work process was conducted to FeCrMoVC steel and conducted QT treatment. Tempering temperature and holding time were varied to control the formation of carbides. Also the samples were austenitized at different temperatures in order to change the prior austenite grain size which influenced the martensite transformation kinetics and final mechanical properties. The quantitative changes of carbides in solution treatment conditions and tempering conditions were predicted using MatCalc. Based on the calculated values, we have proposed a constitutive equation model that can predict the mechanical properties. Unlike existing models, tensile behavior prediction model considering precipitation strengthening of each type of precipitate was studied.

목차 (Table of Contents)

• 1. 서 론 1
• 2. 이론적 배경 5
• 2.1 냉간 공구강의 열처리 방법 5
• 2.2 냉간 공구강의 주요 합금 원소 9
• 2.3 공구강의 석출 탄화물 10
• 2.4 기계적 성질 예측 모델 13
• 3. 실험 방법 18
• 3.1 시편 제조 및 열처리 18
• 3.2 미세조직 관찰 18
• 3.3 기계적 성질 평가 19
• 4. 실험 결과 및 고찰 25
• 4.1 미세조직에 미치는 템퍼링온도와 용체화온도의 영향 25
• 4.2 기계적 성질에 미치는 템퍼링온도와 용체화온도의 영향 29
• 5. 석출강화를 고려한 인장 거동 예측 모델 개발 32
• 5.1 열처리 공정에 따른 탄화물 석출 거동 정량 예측 32
• 5.2 석출강화 효과가 고려된 인장 거동 예측 모델 제안 40
• 5.3 제안된 모델의 정확성 평가 45
• 6. 결론 48
• 참고문헌 50