In‐Depth Oxide Scale Growth Analysis of B and Ti Microalloyed AISI 304 in Oxygen‐Containing Furnace Atmospheres and CH4 Burn‐Simulating Furnace Atmospheres

Abstract

The effects of boron and titanium microalloying on scale‐layer formation and structure on AISI 304 austenitic stainless steel are studied. The research is focused on a steel slab's oxide scale formation in a reheat furnace prior to hot rolling. The studied boron microalloying amounts are 7, 35, and 55 ppm and the studied titanium microalloying amounts are <100 and 400 ppm. In‐depth temperature and atmosphere tests span from 1100 to 1300 °C for an O2‐containing atmosphere and 1100 to 1250 °C in an H2O‐containing atmosphere, both using 25 °C increments. Research shows that microalloying 55 ppm B reduces scale growth at above 1175 °C in an H2O atmosphere, all microalloying elements show significant scale growth reduction at 1175 °C in an O2 atmosphere, microalloying 35 and 55 ppm B increases scale growth amounts at above 1225 °C in an O2 atmosphere, while microalloying 400 ppm Ti reduced it. The inhibiting effect on scale growth that results from boron microalloying is tied to silicon oxide infiltration of the steel substrate.