高温合金电磁软接触近净成形定向凝固研究

传统高温合金叶片类铸件制备过程中，熔体长时间受到陶瓷模壳材料的污染，性能难以提高，借助于电磁软接触成形技术中的电磁压力使高温合金熔体呈半悬浮状态，减少了熔体与磁模结晶器的接触面积和时间，提高了合金熔炼和成形的纯净度，同时将该技术和定向凝固技术相结合开发了一种实现高温合金复杂形状电磁软接触成形定向凝固的工艺，并探讨了该工艺下3种结晶器材料（陶瓷、磁模和石墨）中磁感应强度的分布规律，结果表明，石墨套高度对磁模结晶器磁感应强度的大小和分布以及熔体温度场有很大影响。通过调整上下线圈功率和抽拉速度等工艺参数成功地制备了大小两种近叶片形状的高温合金电磁软接触成形的定向凝固样件。．

Electromagnetic soft-contact confinement and directional solidification of near-net shape castings of superalloys

The properties of turbine blade castings of superalloys are often dissatisfactor because the melts of superalloys are contaminated by the ceramic mold materials. By electromagnetic soft contact confinement process, the melts of superalloys are half suspended by electromagnetic pressure, which decreases the contacting area and time between the melts and the magnetic mold material. Simultaneously, the purification of liquid metals is improved. Combining electromagnetic soft contact confinement and directional solidification processes, the new technique for manufacturing near net shape castings of superalloys is proposed and the ceramic, magnetic mold and graphite materials affect the magnetic flux density distribution in the coil is investigated. It is shown that the height of graphite not only affects the magnetic flux density, but also the temperature field distribution in the melts. By selecting suitable technological parameters, such as the upper and lower coil powers, pulling rate etc., two near net shape turbine blade castings with directionally solidified microstructures are successfully manufactured by electromagnetic soft contact confinement process.