Increasing the recycling rate is the most efficient way to improve the carbon foot print of steel making. Remelting scrap in the electric arc furnace (EAF) requires only 20% of the energy that is needed in the primary iron-ore-reduction route. However, the cleanliness of the EAF process is often not sufficient to fulfil the demanding specifications of flat products, e.g. in the packaging or automotive industry. Furthermore, the gradual accumulation of impurities from the scrap, like Cu or Sn, may cause hot shortness during forming or embrittlement of the final product. Therefore, establishment of a circular steel economy requires, impurity-tolerant recycling steel grades. In the present study, it has been shown that adding between 0.5 and 2 wt.% Cu in low- and medium carbon steel as well as in the quench and tempering steel 42CrMo4 (AISI 4140, produced by vacuum induction melting) led to an improvement of the static and cyclic mechanical properties. A tailored solutionizing and ageing heat treatment results in the precipitation of nano-sized, semi coherent Cu precipitates that were identified by means of atom probe tomography and that result in a substantial strength increase. The results are discussed aiming at an optimized chemistry and treatment of new impurity-tolerant steel grades for a circular economy.