Effect of simulated cooling time on microstructure and toughness of CGHAZ in novel high-strength low-carbon construction steel

Abstract

Influences of cooling time (welding heat input) on microstructure, impact toughness and the fracture mechanism of the weakest CGHAZ (coarse-grained heat-affected zone) in a novel high-strength low-carbon microalloyed construction steel were studied for the purpose of laying a theoretical foundation for developing welding support technologies. When the cooling time (t_8/5) was increased, the microstructure changed from dot shape M-A constituents and lath martensite/bainite to slender and blocky M-A constituents and coarse granular bainite. Accordingly, the impact toughness deteriorated. Large blocky M-A constituents seriously reduced the impact absorbed energy during crack initiation. For coarse bainite, the high-misorientation boundary almost disappeared. Therefore, crack initiation energy determines the cleavage fracture micromechanism of high heat input construction steel.

KEYWORDS:

• High-strength low-carbon construction steel
• CGHAZ
• misorientation grain boundary
• M-A constituents
• impact toughness

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Junjun Cui http://orcid.org/0000-0002-6781-2965

Additional information

Funding

This work was financially supported by the National Natural Science Foundation of China (grant number 51904071), the Fundamental Research Funds for the Central Universities (grant number N180703011), the Postdoctoral Science Foundation of Northeastern University (CN) (grant number 20190302), the Key Research and Development Program of Hebei Province (CN) (grant number 18211019D) and Technical Development Program between HBIS Company Limited and NEU (CN) (Contract No. 2019040200044).