Aluminum and Vanadium Competition for Nitrogen in CSP Sheet Steels

摘要

Aluminum nitride precipitation has been studied extensively in steels but is less well understood in thin slab cast than in conventional sheet products. In microalloyed steels, it is expected that A1N precipitation may influence the nitrogen content that remains to form other microalloy carbonitrides, such as V(C,N) or Nb(C,N). The lower slab reheating temperature in the compact strip production process may be relevant in this context as it promotes AlN formation prior to hot-rolling. In this study the effect of aluminum level on microalloying response was characterized via mechanical testing, metallography, and electron microscopy for two vanadium-microalloyed steels that differ in aluminum content. The steels were examined in the hot-rolled condition, as well as after cold-rolling and simulated batch or continuous annealing. The results suggest that reduced levels of aluminum are associated with increased strength levels and slower recrystallization after cold rolling, due to an interesting competition between Al and V for the available N. A1N is found in the high Al steel, while V(C,N) is found at lower Al levels.