In this work an analytical solution of general validity is used to explain mechanism of the silicon influence on the absolute chill tendency (CT) and chill (w) of cast iron. It is found that CTcan be related to nucleation potential of graphite (N_v), growth parameter (μ) of eutectic cells, temperature range (△T_(sc)), where △T_(SC)=T_S-T_C (T_s is graphite eutectic equilibrium temperature and T_c is cementite eutectic formation temperature) and the pre-eutectic austenite volume fraction (f_γ). It has been shown that silicon additions: 1) impede the growth of graphite eutectic cells through decreasing graphite eutectic growth coefficient μ, 2) expands the temperature range △T_(sc), 3) increases the nucleation potential of graphite N_v, 4) lowers the pre-eutectic austenite volume fraction, f_γ and in consequence the absolute chilling tendency CT decreases. The minimum wall thicknesses for chilled castings, or chill widths, win wedge shaped castings is related to CT and as Si contents increases, the chill widths, w value decreases.
展开▼
