High Toughness Independent of Low‐Medium Heat Inputs in Coarse‐Grain Heat‐Affected Zone of a Designed HSLA Steel

In the present work, low‐medium heat inputs of 15, 30, and 50 kJ cm −1 are adopted to simulate Coarse‐Grain Heat‐Affected Zones (CGHAZ) of a designed HSLA steel by Gleeble‐3500 thermal simulator. Microstructures are characterized by optical microscope (OM), scanning electron microscope (SEM), and transmission electron microscope (TEM). Charpy impact tests are performed to evaluate toughness of CGHAZs. Results show that impact toughness (−50 °C) of CGHAZs with heat inputs of 15, 30, and 50 kJ cm −1 is 156.18, 172.86, and 181.49 J, respectively. Toughness stays in high level though heat input varies within low‐medium range. Evolution of microstructures is investigated and micro‐mechanisms of high toughness in all of the three heat inputs are discussed in detail. An original alloy design for HSLA steels with high toughness CGHAZ is proposed as well.