AMP_06_September_2021

A D V A N C E D M A T E R I A L S & P R O C E S S E S | S E P T E M B E R 2 0 2 1 2 4 I n recent years, aluminum alloys have become the dominant material for structural and safety components in electric vehicles (EVs)—including battery enclosures—due to their low density and acceptable strength. Tra- ditionally, the aluminum alloys best suited to EVs are 5000 and 6000 series alloys [1] . Despite their light weight and re- cyclability benefits, aluminum alloys have a crucial disadvantage if the heat generated by the battery cells raises the battery enclosure temperature above 600°F (315°C). With over 300 seconds of exposure at 600°F (315°C) or higher, the yield strength of the aluminumalloy drops by more than 70%, especially in parts that are in direct contact with bat- tery cells. Further, in critical situations of fire at about 2200°F (1205°C), battery enclosures fail within approximately 5 sec, creating a paramount safety con- cern for EV occupants. Alternatives to aluminum alloys include thermoplas- tics and composite materials, but these are not often used in battery enclosures due to high cost and challenges with performance in temperatures above 600°F (315°C). A patented, cold-rolled high- strength steel for cold stamping (Cold- Stamp-Steel) [2] has been developed to address the challenges presented by conventional materials. For production of EV structural and safety components, ColdStamp-Steel offers high strength at moderate ductility and possesses a higher strength-to-weight ratio than commercial cold-rolled steels and high- strength aluminum alloys. DESCRIPTION ColdStamp-Steel is a low alloy steel with the total alloying elements (other than carbon) < 3.0 wt%. The steel is hardened by quenching and temper- ing at temperatures of 300° to 1060°F (150° to 571°C). The manufacturing pro- cess principally consists of the follow- ing steps: melting of molten pig iron in HIGH-STRENGTH STEEL FOR ELECTRIC VEHICLES A new high-strength steel developed for cold stamping addresses the challenges presented by materials traditionally used to manufacture electric vehicle components. TECHNICAL SPOTLIGHT Electric vehicle lithiumbattery pack featuring an aluminumenclosure.