Abstract:In order to further understand the debismuthizing mechanism with calcium and magnesium, the influence of adding amount of calcium on the bismuth removal from lead was examined. A part of the debismuthizing dross samples were studied by electron probe microanalysis (EPMA). The results show that the calculated bismuthide governing debismuthizing process is Ca₃Mg₇Bi₈, which may be a mixture of Ca₃Bi₂, CaBi, CaBi₃ and Mg₃Bi₂. And the bismuthide formed during the debismuthizing process exists in two states: one is free bismuthide in the matrix of dross, and the other is symbiotic with Pb-Ca phase.

Key words: debismuthizing mechanism; Kroll-Betterton process; Ca₃Mg₇Bi₈; Pb-Ca phase; Bi-Ca-Mg phase