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Korean Journal of Metals and Materials > Volume 55(2); 2017 > Article
Korean Journal of Metals and Materials 2017;55(2): 132-138. doi: https://doi.org/10.3365/KJMM.2017.55.2.132
Alloy 738 초내열합금 4 mm 두께 각관의 정밀주조 시 수축공 및 수축변위 해석 및 분석
박명일1,2, 김경민2, 이영철2, 이정석3, 이재현3, 유재현4, 박상후4, 최윤석1,5,*
1부산대학교 수송기기하이테크소재부품학과
2㈜성일터빈 기술연구소
3창원대학교 공과대학 신소재공학부
4부산대학교 공과대학 기계공학부
5부산대학교 공과대학 재료공학부
Numerical and Experimental Analysis on the Cavity Formation and Shrinkage for Investment Cast Alloy 738 4 mm-Thick Rectangular Tube
Myeong-Il Park1,2, Kyeong-Min Kim2, Yeong-Chul Lee2, Jung-Seok Lee3, Jae-Hyun Lee3, Jae-Hyun Yoo4, Sang-Hu Park4, Yoon Suk Choi1,5,*
1Department of Advanced Materials and Parts of Transportation Systems, Pusan National University, Busan, Republic of Korea
2R&D Center, Sung Il Turbine Co., Ltd., Busan, Republic of Korea
3Department of Materials Science and Engineering, Changwon National University, Changwon, Republic of Korea
4School of Mechanical Engineering, Pusan National University, Busan 46241, Republic of Korea
5School of Materials Science and Engineering, Pusan National University, Busan 46241, Republic of Korea
Correspondence  Yoon Suk Choi ,Tel: +82-51-510-2382, Email: choiys@pusan.ac.kr
Received: 7 September 2016;  Accepted: 12 November 2016.  Published online: 2 February 2017.
Investment casting for the thin (4 mm thick) rectangular tube (40 mm wide, 80 mm high and 200 mm long) was carried out numerically and experimentally for Alloy 738, which is a precipitation-hardened Ni-base superalloy. Two types of rectangular tubes, one with a regular array (10 mm by 10 mm square array) of protruded rods (3 mm in diameter and 3mm in height) embedded on the outer surface and the other with just smooth surface, were investment-cast at the same time through the side feeding mold design. The investment casting simulation predicted the presence of cavities, particularly in the area away from the gate for both types of rectangular tubes. In particular, for the rectangular tube with embedded protruded rods cavities were found mainly in the areas between the protruded rods. This simulation result was qualitatively consistent with the experimental observation from the X-ray analysis. Also, both prediction and experiment showed that the dimensional shrinkage (particularly in the longitudinal direction) of the investment-cast rectangular tube is reduced by having protruded rods embedded on the outer surface. Additional numerical attempts were made to check how the amount of cavities and dimensional shrinkage change by varying the preheating temperature and the thickness of the mold. The results predicted that the amount of cavities and the dimensional shrinkage are significantly reduced by increasing the preheating temperature of the mold by 200 ℃. However, an increase in mold thickness from 10 mm to 12 mm showed almost no difference in cavity population and a slight decrease in dimensional shrinkage.
Keywords: Alloy 738, Ni-base superalloy, investment casting, shrinkage, cavity, simulation
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