Role of Carbon Content on Microstructure Evolution and Impact Toughness in Coarse-Grained Heat-Affected Zone of High-Strength Steel

The effect of carbon content in the base metals high-strength steel on microstructure and impact toughness simulated welding focusing a coarse-grained heat-affected zone (CGHAZ) at different heat inputs was systematically investigated by using scanning electron microscopy (SEM) back-scattering diffraction (EBSD). Charpy test confirmed that there an optimal input, which caused CGHAZ to obtain highest toughness. input is ~20 kJ/cm remains unchanged with increase from 0.04 0.12 wt.%. However, decreases each input. Microstructure characterization showed wt.% gradually changed lath bainite (LB) granular (GB) while it martensite (LM) LB then GB for carbon. Although density high-angle grain boundaries (HAGBs) obtained 20 high-carbon sample higher than low-carbon sample, its lower, related parallel structure bundles morphology austenite penetration.