Failure analysis and improvement of bending cracking of low alloy Q345B steel treated by ultra-fast cooling process

doi:10.13251/j.issn.0254-6051.2020.01.046

Abstract

Abstract: Fracture morphology, microstructure and inclusions of bending cracking of Q345B steel treated by ultra-fast cooling process were systematically analyzed by scanning electron microscopy. The results show that a lot of large-size inclusions are observed in the Q345B steel which causes the crack initiation during bending deformation. However, the hard-phase microstructure including network cementite and granular bainite are produced during ultra-fast cooling process reduces the plasticity and toughness of the Q345B steel and promotes further the crack propagation. By extending refining time of LF process, controlling ultra-fast cooling rate and increasing the final cooling temperature, the inclusion size in the steel is greatly reduced, and the microstructure is transformed into ferrite and pearlite, thus the bending resistance of the Q345B steel is improved greatly.

Key words: Q345B steel, ultra-fast cooling, bending cracking, network cementite, inclusions

CLC Number:

TG115

Yu Chunming, Zhang Jiming. Failure analysis and improvement of bending cracking of low alloy Q345B steel treated by ultra-fast cooling process[J]. HTM, 2020, 45(1): 239-244.

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