Importance of Advanced High-Strength Steels and Electronic Units on the Recycling of Automobiles: A Review

With increasing environmental concerns by government and industry, automobile manufacturers are constantly striving to reduce the carbon footprint of their vehicles. An effective way to reduce emissions during life time use is to reduce the weight of the vehicle itself.1 However, the safety of passengers is still paramount and under strict regulation. Thus, advanced high strength steels (AHSS), which offer yield strengths over 300 Mpa and tensile strengths exceeding 600 Mpa, are becoming more prominent in vehicle manufacturing.2 The category of AHSS covers steel types such as dual phase (DP), transformation induced plasticity (TRIP), complex phase (CP) and martensitic steels (MART), all of which draw their enhanced properties from alloying additions.1 Thus, with increased volumes of AHSS, there is a rising concern over the recyclability of this specialty material in automobiles. Current practices cannot separate AHSS from plain carbon or low alloyed steel; this can result in contamination of new product produced from this scrap source. Demand for the recycling of AHSS will continue to increase in the future, and designing a process that is both feasible and effective is essential to the future use of this material. Likewise, the market for electronics used in automobiles has skyrocketed since 1980, increasing by 5.9% every year.3 Originally used only in stand-alone systems such as radios, electronics are now used to monitor and control almost every aspect of an automobile including personal comfort, automobile safety features, and engine control functions.4 When automobiles produced with these advanced electronic systems are recycled at their end-of-life (EOL), the materials contained in the wiring and circuit boards may prove to be a valuable output of the recycling process. The ever increasing cost of precious metals will likely be the driving force for the development of an adequate separation technique as current recycling practices do not address the challenges in isolation of electronics from the bulk of automotive shredder residue. As such, the work of two senior capstone design project teams at Missouri S&T have been funded under a FeMET Design Grant from the AIST Foundation and AISI to investigate the effects of AHSS and electrical components on the recyclability of automobiles and explore techniques for separation of these two materials from a scrap stream