Fracture resistance mechanism of high strength structural steel Q690GJ treated by intercritical quenching process

doi:10.13251/j.issn.0254-6051.2021.12.041

Abstract

Abstract: Effects of QT (quenching+tempering) and QLT (quenching+intercritical quenching+tempering) process on microstructure and low temperature toughness of high strength structural steel Q690GJ were investigated. The microstructure of the low temperature impact specimen and the NDT (nil-ductility transition) specimen was analyzed by means of optical microscopy and scanning electronic microscopy. The results show that the low temperature toughness of the steel treated by QLT process is obviously better than that treated by QT process. The microstructure obtained by QLT process is lath martensite+retained austenite. More stable retained austenite that responsible for the enhanced plastic formability before crack initiation is transformed through intercritical quenching. While, chaotic martensite lath bundles formed by QLT process effectively prevent crack propagation. Then the low temperature toughness and NDT temperature of the steel is improved and reduced, respectively by QLT process.

Key words: high strength structural steel Q690GJ, intercritical quenching, nil-ductility transition temperature, low temperature toughness

CLC Number:

TG142.1

Deng Wei, Qin Xiaomei. Fracture resistance mechanism of high strength structural steel Q690GJ treated by intercritical quenching process[J]. Heat Treatment of Metals, 2021, 46(12): 247-251.

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