The zinc content of European steel mill dusts is mostly recovered in the so called Waelz process. The iron containing by-product Waelz slag is generated in the extent of 700 kg per ton of treated steel mill dust. Its application as construction material is limited to landfill sites, because of its leachable components of heavy metals as well as salts. The cycle of materials is to be closed in recovering the iron in a slag reduction. Optimum conditions concerning temperature, refractory material, type of coke/carbon and surcharges were investigated in experiments by using a hot metal bath that was melted in an induction furnace. On the one hand the slag becomes a stable material while its heavy metal content can be reduced and zinc and lead refer to the off-gas. On the other hand the iron alloy is characterized by high contents of copper, chromium and sulphur. An integration of such a process in an existing Waelz plant could reduce unfavorable high energy consumption via hot charging of waelz slag directly from the Waelz furnace. An insertion of the offgas into the existing offgas treatment plant allows recovering zinc and lead contents from the Waelz slag.