【摘要】 为了进一步提高真空熔铸高温合金铸件的的质量,本文系统研究了在K417高温合金真空熔铸过程中施加由工频交流电磁场和恒稳直流电磁场组成的复合磁场对高温合金铸件凝固组织的影响。实验结果表明:在浇注完毕后同时施加60A旋转电磁场和290 A恒稳直流电磁场的工艺条件下,由于恒稳直流电磁场在金属液面处产生的电磁制动效应可以抑制施加旋转电磁场所引起的金属液面的波动,因此既可以避免因金属液液面波动太大而使铸件缩孔恶化的情况出现,又可以大幅提高旋转电磁场在金属液凝固过程中的作用范围和效果,最终得到细小等轴晶比例达到99%、缩孔明显改善的优质高温合金铸件。更多还原

【Abstract】 The effect of superposed rotary and dc electro-magnetic fields,powered by currents of 60 and 290 A. respectively,on the microstructures of the solidified super-alloy( K417) in vacuum investment casting was experimentally investigated. The preliminary results show that the superposition of rotary and dc electromagnetic fields in solidifying liquid super-alloy significantly heightened the positive impact and reduced the negative influence of the rotary magnetic field on microstructure formation in the bulk and on the surface of the super-alloy casting. For example,the dc electromagnetic field effectively suppressed the micro-ripples on the liquid metal surface originated form the eddy current,resulting in a considerable reduction of shrinkage porosity and an incrased fraction of fine equiaxed grains up to 99% in the solidified super-alloy casting. Possible mechanisms responsible for the improvement were also tentatively discussed.更多还原