The present study is aimed at understanding the effect of rate of heat extraction on macrosegregation during solidification of binary Fe–1wt%C alloy. For a constant superheat and geometry, the effect of cooling rate is studied by imposing constant heat fluxes, along the vertical wall of a rectangular cavity, in the range of 5 kW/m² to 6 000 kW/m². The effect of variation of heat flux on various transport fields such as double-diffusive convection, thermal and solutal fields and resultant solutal in-homogeneity are analyzed in detail. Its effect on final macrosegregation is discussed in terms of global extent of segregation (GES) and overall macrosegregation pattern in the casting. GES initially decreases with an increase in heat flux up to 10kW/m². Between heat flux of 10 and 100 kW/m², GES goes through a maximum. Beyond 100 kW/m², GES decreases with an increase in heat flux. The variation in GES with heat flux is explained in terms of thermosolutal convection, mush structure and solidification time.