Microstructure–Property Correlation in High-Strength Formable Steel with Varying Nb-Si Content

High-strength formable quality (HSFQ) steel grades, steel A (0.038Nb, 0.031Si), steel B (0.034 Nb, 0.27Si),
and steel C (0.044Nb, 0.26Si), with varying Nb and Si content has been investigated. The microstructure,
texture, precipitation, mechanical properties and corrosion behavior of these steel grades have been explored.
Very fine grain size in the range of 2.7-3.6 lm was obtained in all these steel grades through
controlled hot rolling. However, a significant variation in the crystallographic texture and precipitation
behavior in these steels was observed. A higher volume fraction of gamma fiber texture components and uniformly
distributed fine Nb(C, N) precipitates were obtained in steel B as compared to steel A and C. This
resulted in better properties in steel B with relatively high PSE (product of strength–elongation), high
uniform elongation, and high hole expansion ratio. The corrosion properties of the steels were also evaluated,
and steel B showed better corrosion resistance among the three grades. Considering the overall
performance and properties of these steel grades, steel B with an optimum Nb and Si content is found to
have better property and performance among the three grades.