HIsarna is a revolutionary step towards production of green steel. Due to the complex nature of the process the control of various facets of HIsarna is difficult. One of these facets is the slag-composition control, or more specifically slag-basicity. In this thesis an optimal sequential decision making strategy has been developed using the Bellman Optimality rule and Value-Iteration. The algorithm has been evaluated at length in order to refine the design choices and decison tree based classification has been used to make the output interpretable for a wider audience. Simulations show the effectiveness of the proposed strategy over the existing control techniques.