Preparation of 5N grade tantalum by electron beam melting

The commercial Na-reduced tantalum powder was purified using electron beam melting (EBM) by four successive melt cycles. Nearly 60 impurity elements (Li to U) in the tantalum was analyzed using glow discharge mass spectrometry (GDMS). Vickers hardness on the surface of the electron beam (EB)-melted tantalum piece was decreased by ∼43% after first melting and the change in hardness was feeble in the subsequent melt cycles, indicating a quick vaporization of impurities during the first melt cycle itself. The behaviour of Na, K, S, Ti, Mo, Zr, Nb, W, C, N, and O impurities in tantalum at the end of each melt cycle were analyzed and found to be in ppm/ppb level. The overall purity of tantalum by EBM was increased from 2N8 to 5N at the end of three melt cycles. GDMS analysis results on EB-melted tantalum, showed excellent removal effect of interstitial and metallic impurities. The metallic and gaseous impurities present in high purity of tantalum prepared by EBM and plasma arc melting (PAM) were compared. The removal degree of impurities in tantalum using EBM was much higher, when compared to Ar/Ar-H₂ plasma arc melting.