2015 Volume 101 Issue 12 Pages 636-644
The copper distribution ratio between the Na2S flux and silver, LCu(flux-Ag) (=[mass% Cu](in flux) / [mass% Cu](in Ag)), was measured at 1473 K in order to know the copper capacity of Na2S flux. As the greatest value, LCu(flux-Ag) = 42 was obtained. By combining the LCu(flux-Ag) value with the distribution ratio of copper between the silver and the carbon-saturated iron, LCu(Ag-Fe), the distribution ratio of copper between the Na2S flux and carbon-saturated iron, LCu(flux-Fe), is derived to be 330 at 1473 K. Moreover, the sulfurization removal of copper in iron silver phase into Na2S flux has been tried at 1473 K. Silver can keep iron from being sulfurized, which enables to maintain the high copper capacity of the Na2S flux. For this reason, the LCu value increases with an increase of sulfur potential. Copper removal proceeds at lower 0.1mass%Cu, and the Cu content decreased to 0.06mass%. The silver phase prevents the sulfur dissolution into the iron, and the sulfur content of iron can be kept lower ( [mass%S]in Fe-C < 0.007-0.02).