Circular boron steel: a case study on high performance materials for a zero emission automobile industry

\nThe European automotive sector is under pressure to transform into a zero net emission industry. This involves lightweight, highly efficient vehicles, but also zero emission structural materials. At the same time, a steel industry with automotion as its main customer faces a similar conundrum; it is only natural that this synergy is explored. One of the possible ways this need can be solved is by producing the high performance sheet steel consumed by the Auto industry through scrap-intensive Electric Arc Furnace (EAF) routes, saving an approximate 1.5 tCO2/tsteel compared through the integrated steelmaking route. However, in order to do this, the effect of Residual or Tramp elements inherited from the scrap needs to be considered into the downstream process and use phase. In this scenario, hot stamping of Boron steel sheet presents itself as an excellent use case. This process has become a mainstay in lightweight, high performance safety cage components in passenger cars. It is also gaining traction into light transport vehicles and trucks, and all future trends point to stable usage in the future. Transformed through hot stamping, boron steel shows incredible flexibility to cover different usage scenarios, all while having a simple chemical composition and reasonable cost. And as an added benefit, forming at high temperature bypasses many of the difficulties posited by the presence of residuals affecting springback and formability. This work shows a preliminary study on the concept of circular boron steel for automotive applications, produced by EAF instead of blast furnace. First, sources of scrap commonly used in steelmaking are analyzed to determine the residual elements and inclusions present in this raw material. From this study, studies have been performed to determine the effect on the steel CCT of the residuals with highest impact (in this case, Mo, Cr and Cu). Finally, an industrial cast has been produced and rolled into 4 mm thick sheet, such as it is being used in components like bumpers or in light trucks. Subject to common heat treatments, this material has shown performance on par with commercial, blast furnace products. Results show that scrap-intensive EAF production of Boron steel is possible, and that the impact of moderate amounts of residual elements can be acceptable in this application.\n