Fe-Mn-Al-C계 경량철강의 미세조직 및 기계적 물성 변화에 미치는 냉각속도의 영향

• Published in: 대한금속·재료학회지, 55(12) Vol. 55; no. 12; pp. 825 - 835
• Main Authors: 박준영, Jun Young Park, 박성준, Seong-jun Park, 이재현, Jae-hyun Lee, 문준오, Joonoh Moon, 이태호, Tae-ho Lee, 정경재, Kyeong Jae Jeong, 한흥남, Heung Nam Han, 신종호, Jong-ho Shin
• Format: Journal Article
• Language: Korean
• Published: 대한금속재료학회 05.12.2017; 대한금속·재료학회
• Subjects: cooling rate; light-weight steel; microstructure; β-Mn; κ-carbide; 재료공학
• ISSN: 1738-8228; 2288-8241
• DOI: 10.3365/KJMM.2017.55.12.825

The effects of cooling after solution heat treatment on the microstructure and mechanical properties of light-weight steels were investigated using Fe-30Mn-xAl-0.9C alloys containing 9.0-12.8 wt% Al. Lab-scale specimens (thickness: 10 mm) of the alloys were cooled by different cooling rates from -337 to -0.053 ℃/s using water, air, and furnace cooling. As the cooling rate decreased, hardness of the alloys increased due to precipitation of κ-carbides. However, reduction of the cooling rate induced the growth of intergranular κ-carbides. This resulted in the decrease of impact absorbed energy of the alloys at room temperature, and exhibited intergranular brittle fracture behavior. The 12.8 wt% Al alloy cooled at the slowest cooling rate in particular showed the formation of β-Mn. To estimate the cooling rates of large-scale slabs of light-weight steels, finite element simulations were conducted. The cooling rates at the center of the slab under air and water cooling (free convection) were calculated to be -0.049 and -0.15 ℃/s, respectively. The results indicated that water cooling could prevent the excessive formation of κ-carbides/β-Mn during fabrication of large-scale slabs of alloys containing an Al content lower than 10.5 wt%. (Received September 1, 2017; Accepted September 20, 2017)