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 µm 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 γ-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.