Due to the increasing demand of steel production, the reduction of primary ressources and the challenge on the environmental footprint, recycling scrap materials for the steel production is necessary. However, use of recycled materials implies to introduce solute elements and thus to increase the amount of alloying elements in the material. While, there is a real potential of using scrap materials, the presence and concentration of these tramp elements must be considered in the process, since it affects process- and product-relevant issues such as the formation of precipitates, shift of phase transformation temperatures, or segregation at grain boundaries. In order to consider the role of tramp elements in scrap alloy materials, we use thermodynamic modeling of Fe-base multi-component systems with the impurities of Cu, Sn, As, Bi, and Zn and we analyse the effect of respective tramp elements on the equilibrium phase stabilities and thermodynamic properties. We show a number of examples of the use of Calphad methodology for the assessment of the effects of residual elements. Among these, we discuss the limits for the formation and development of uncontrolled phases due to impurities, the influence on phase transformations, as well as expected segregation during steel casting. In the framework of applied Calphad to practical metallurgy, we also propose solutions of how to tackle the effect of residual elements by adjusting the chemical composition of the given alloy, i.e. by modulating the amount of an alloy element already present in the steel. Finally, also challenges of the Calphad methodology for interpretations of the influence of tramp elements for alloy materials are discussed.