Abstract:A new method is proposed to evaluate the process parameters by the solid-liquid interface position, thermal gradient angle and the axial thermal gradient. The effects of the process parameters on the solid-liquid interface position, thermal gradient angle and the axial thermal gradient were simulated by ProCAST using LMC(Liquid Metal Cooling) and HRS(High Rate Solidification) processes. The results show that HRS process is little affected by the mold thickness, the dominant heat transfer factor in HRS is radiation from the mold surface, and the dominant heat transfer factor in LMC either mold thermal conductivity or mold-metal interface heat transfer; increasing furnace temperature is beneficial to increase the axial thermal gradient; the withdrawal rate is the most important process parameter which significantly affects the thermal field during solidification, as the withdrawal rate increases, the axial thermal gradient first increases and then decreases, therefore, it is necessary to apply different withdrawal rates for different alloys. After holding 10min at different pouring temperatures, a uniform temperature is achieved, and it has slight influence on the subsequent solidification. It has been put forward that the solid-liquid interface position, thermal gradient angle and the axial thermal gradient can be utilized as a serial of efficient analysis standards for optimization of process conditions independent of casting geometry.
[1] 刘林.高温合金精密铸造技术研究进展[J].铸造,2012, 61(11):1273-1285. LIU L. The progress of investment casting of nickle-based superalloy[J]. Foundry, 2012, 61(11):1273-1285.
[2] MURRAY B T, WHEELER A A, GLICKSMAN M E.Simulation of experimentally observed dendritic growth behavior using a phase-field model[J]. Journal of Crystal Growth,1995, 154:386-400.
[3] KONTER M, THUMAANN M. Material and manufacturing of advanced industrial gas turbine component[J]. Journal of Materials Processing Technology, 2001, 117(3): 386-390.
[4] ZHANG J, LOU L H. Directional solidification assisted by liquid metal cooling[J]. Journal of Materials Science and Technology, 2007, 23: 289-300.
[5] 杨亮,李嘉荣,金海鹏,等.DD6单晶精铸薄壁试样定向凝固过程数值模拟[J].材料工程,2014,(11):15-22. YANG L,LI J R,JIN H P, et al. Numerical simulation of directional solidification process of DD6 single crystal superalloy thin-walled specimen[J]. Journal of Materials Engineering, 2014, (11): 15-22.
[6] KERMANPUR A, VARAHRAM N, DAVAMI P, et al. Thermal and grain-structure simulation in a land-based turbine blade directionally solidified with the liquid metal cooling process[J]. Metallurgical and Materials Transactions, 2000, 31(6): 1293-1304.
[7] ELLIOTT A J,TIN S, KING W T,et a1.Directional solidification of large superalloy castings with radiation and liquid-metal cooling: a comparative assessment[J]. Metallurgical and Materials Transactions A, 2004, 35: 3221-3231.
[8] BRUNDIDGE C L, VANDRASKEK D, WANG B, et al. Structure refinement by a liquid metal cooling solidification process for single-crystal nickel-base superalloys[J]. Metallurgical and Materials Transactions A, 2012, 43(3): 965-976.
[9] BRUNDIDGE C L, MILLER J D, POLLOCK T M. Development of dendritic structure in the liquid-metal-cooled, directional-solidification process[J]. Metallurgical and Materials Transactions, 2011, 42A: 2723-2732.
[10] 唐宁,闫学伟,许庆彦,等. 基于ProCAST二次开发的叶片LMC凝固特征模拟[J]. 铸造, 2014,63(4): 347-351. TANG N, YAN X W, XU Q Y, et al. Numerical simulation of solidification characteristics of blades by LMC based on secondary development of ProCAST[J]. Foundry, 2014, 63(4): 347-351.
[11] 卢玉章,王大伟,张健,等. 液态金属冷却法制备单晶铸件凝固过程的实验与模拟[J]. 铸造, 2009,58(3):245-248. LU Y Z,WANG D W,ZHANG J, et al. Numerical simulation and experimental observation of single crystal castings processed by liquid metal cooling technique[J]. Foundry, 2009, 58(3): 245-248.
[12] 卢玉章,申健,张健,等.液态金属冷却法制备大尺寸定向燃机叶片凝固过程的实验与模拟[C]//第十二届全国青年材料科学技术研讨会论文集, 南京: 中国材料研究学会,2009:1-9.
[13] 熊继春,李嘉荣,韩梅,等. 浇注温度对DD6单晶高温合金凝固组织的影响[J].材料工程,2009,(2): 43-46. XIONG J C, LI J R,HAN M, et al. Effects of poring temperature on the solidification microstructure of single crystal superalloy DD6[J]. Journal of Materials Engineering, 2009, (2): 43-46.
[14] MILLER J D, POLLOCK T M. Process simulation for the directional solidification of a tri-crystal ring segment via the bridgman and liquid-metal-cooling processes[J]. Metallurgical and Materials Transactions, 2012, 43A: 2411-2425.
[15] 卢玉章, 席会杰,申健,等. 液态金属冷却法制备重型燃机定向结晶空心叶片凝固过程的实验与模拟[J].金属学报,2015,51(5):603-611. LU Y Z, XI H J, SHEN J, et al. Simulation and experiment of the solidification for directionally solidified industrial gas turbine hollow blades prepared by liquid metal cooling[J]. Acta Metallurgica Sinica, 2015, 51(5): 603-611.