Simplified models of micro-segregation are in common use in academia and industry. An issue regarding the accuracy of these approaches is addressed, before describing extensions required for the sponsor (Corus/Tata). It is shown that the adopted growth rate law of the solid is of equal importance as the diffusivity and the partition coefficient. By making the growth rate part of the solution rather than arbitrarily imposed (e.g. parabolic growth), dramatic errors are avoided. This approach has now been extended to the peritectic transformation in steel. Also included are dendrite arm coarsening and predictions of the solute profiles across the solid and their sub-solidus homogenization. The results of this streamlined model compare very well with experimental data and Finite Difference model calculations despite operating orders of magnitude more quickly.