| Abstract Scope |
Electric arc furnace (EAF) steel making provides for energy, cost, and emissions reductions for steelmakers due to processing flexibility and scrap utilization when compared to the basic oxygen furnace (BOF). However, scrap recovery rates are limited due to the increasing accumulation of residual elements such as copper in the steel scrap stream. EAF charges must often be diluted with iron to achieve chemical specifications for a given grade. However, iron dilution has traditionally been associated with higher energy consumption and carbon emissions. While copper’s role in steelmaking up through thermomechanical processing is well understood, its effect on subsequent weldability is not as thoroughly researched. In this work, we examine the effects of increased copper content on the microstructure, mechanical properties, and weldability of resistance spot welded and autogenous laser welded low carbon sheet steels with copper contents up to 0.85 wt %. The results show that copper content significantly affects microstructure evolution in the sheet base material where higher copper contents lead to finer microstructures, higher strength, and lower ductility. Increased copper content led to increasing occurrence of expulsion during resistance spot welding due to higher base metal electrical resistance. However, copper content did not negatively influence solidification cracking susceptibility during autogenous laser welding. For both resistance spot welding and autogenous laser welding, the mechanical performance of weldments matched that of the base metal, where higher copper contents result in higher strength but lower ductility. The results of this work show that quite high copper contents can be accommodated in low carbon sheets steels, but base metal processing and welding parameters much be adjusted to account for the effects of copper on microstructure evolution and physical properties, which provides a positive outlook for 100% scrap based steels. |