Abstract: Production of steels with complex bainitic microstructures is becoming more common in industry. Modern experimental techniques utilizing high resolution scanning electron microscopy and electron backscatter diffraction (EBSD) can provide quantitative assessment of the complex microstructures produced. EBSD measurements were performed on a series of high strength low alloy (HSLA) steels with approximately 0.06 wt pct C and various microalloying additions, including vanadium, niobium, and titanium, which were isothermally transformed to bainite immediately after simulated austenite conditioning and accelerated cooling. The effect of microalloying additions on the conditioning of austenite and bainite formation as well as isothermal transformation temperature were related to boundary misorientation angle distributions and bainitic ferrite variant selection. In the base composition and steels with only vanadium additions, decreasing transformation temperature generally increases the peaks at high misorientation angles. However, niobium additions change the austenite conditioning response and produce less change in misorientation angle distributions with transformation temperature.
Authors: Julian K. Benz and Steven W. Thompson
Keywords: Bainitic Steels, Linepipe, Thermomechanical Processing, EBSD, Misorientation Angle