2004 Volume 44 Issue 9 Pages 1560-1567
Copper and sulfur are the major residual elements or impurities in scrap steel. The direct near net shape casting is an attractive process for scrap recycling. In the present paper, the precipitation and orientation relationship with matrix of copper sulfide in a strip casting steel were investigated by transmission electron microscopy. Nano-scale copper sulfides less than 50 nm with a face-centered cubic structure (Digenite) were found precipitating throughout the grains. These tiny copper sulfides have a cube-cube orientation relationship with the body-centered cubic α-Fe matrix, which is (001)Cu2S//(001)α-Fe and [110]Cu2S//[110]α-Fe. Thermodynamic and kinetic analysis was conducted to compare the Cu2S precipitation to the MnS precipitation in γ-Fe and α-Fe. The calculation shows the nucleation of Cu2S is dominant in the γ-Fe at low temperature and in the α-Fe compared with that of MnS. The high cooling rate during strip casting and the complete coherent relationship with the matrix result in the present nano-scale copper sulfides.
