Fe-Mn-Al-C계 경량철강의 미세조직 및 기계적 물성 변화에 미치는 냉각속도의 영향 |
박준영1, 박성준1, 이재현1, 문준오1, 이태호1, 정경재2, 한흥남2, 신종호3 |
1재료연구소 철강재료연구실 2서울대학교 재료공학부 3두산중공업 주단기술고도화팀 |
Effect of Cooling Rate on the Microstructure and Mechanical Properties of Fe-Mn-Al-C Light-Weight Steels |
Jun Young Park1, Seong-Jun Park1, Jae-Hyun Lee1, Joonoh Moon1, Tae-Ho Lee1, Kyeong Jae Jeong2, Heung Nam Han2, Jong-Ho Shin3 |
1Ferrous Alloy Department, Korea Institute of Materials Science, Changwon 51508, Republic of Korea 2Department of Materials Science and Engineering and Research Institute of Advanced Materials, Seoul National 3Casting & Forging Technology Development Team, Doosan Heavy Industries & Construction, Changwon 51711, |
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Received: 1 September 2017; Accepted: 20 September 2017. Published online: 4 December 2017. |
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ABSTRACT |
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%. |
Keywords:
light-weight steel, microstructure, cooling rate, κ-carbide, β-Mn |
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