Al–Si alloyed uncoated hot stamping steels for enhanced oxidation resistance

Abstract

Hot stamping steels are extensively used in the production of lightweight automobile bodies, which are crucial for reducing carbon emissions. Although significant advancements have been made in the development of Si–Cr alloyed uncoated hot stamping steels to mitigate high-temperature oxidation, a gap remains in the literature regarding Al–Si alloyed uncoated steels. Specifically, there is a need for systematic investigation into their oxidation resistance. In this study, we designed Al–Si alloyed uncoated hot stamping steels based on the 22MnB5 composition system and characterized the scales formed under a simulated hot stamping thermal cycle. Our results indicate that the formation of dense Al2O3, SiO2, and Fe2SiO4 phases, driven by the presence of Al and Si, inhibits FeO formation, thereby enhancing oxidation resistance. Notably, the scale thickness decreases with increasing Al content, reaching just 3.5 μm at 0.48% Al, which is substantially lower than the 46 μm observed in 22MnB5 steel. However, due to compressive stress in the scale during its growth process, oxide ridges form when the Al content exceeds approximately 0.1%. Therefore, maintaining an optimal Al content of around 0.1% is recommended to prevent the formation of oxide ridges and prolong the lifespan of hot stamping moulds. This research not only addresses a critical gap in the literature but also offers a cost-effective strategy for enhancing the oxidation resistance of hot stamping steels, contributing to the broader goals of lightweight vehicle design and carbon emission reduction.

Keywords

• Hot stamping steel
• Oxidation resistance
• Al–Si alloyed
• Vehicles lightweighting
• Carbon neutrality