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| Microstructure and property evolution of coarse-grained heat-affected zone in 960 MPa high-strength steel with low yield ratio |
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Received:October 10, 2024
Revised:October 21, 2024
Accepted:October 28, 2024
Published Online:April 30, 2026
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| DOI：10.3969/j.issn.1005-7854.2025.06.022 |
| KeyWord:high-strength steel with low yield ratio;welding thermal simulation;coarse-grained heat-affected zone;heat input;microstructure and properties |
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| 1.State Key Laboratory of Metallic Materials for Marine Equipment and Applications, Anshan 114009, Liaoning, China;2.Ansteel Beijing Research Institute Co. Ltd., Beijing 102200, China;3.Iron & Steel Research Institute of Angang Group, Anshan 114009, Liaoning, China |
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| Abstract: |
| With the increasing scale of steel structures, high-strength steels with low yield ratio are being increasingly applied. The coarse-grained heat-affected zone (CGHAZ) formed during the welding of high-strength steel often constitutes a performance weak area in the joint, thus requiring significant attention. This study investigates a newly developed 15 mm thick 960 MPa grade high-strength trial steel with low yield ratio. Using a Gleeble-3800 thermal simulation tester to prepare simulated samples, the evolution of microstructure and properties in the CGHAZ under different welding heat inputs was examined via optical microscopy, scanning electron microscopy, microhardness testing, and impact testing. The results indicate that at lower heat inputs, the CGHAZ microstructure consists mainly of lath martensite (LM) and lath bainite (LB). As heat input increases, the LM content gradually decreases while the LB content increases. When the heat input exceeds 20 kJ·cm?1, granular bainite (GB) appears and grain growth becomes pronounced. The Vickers hardness of the CGHAZ generally decreases with increasing heat input, whereas the impact absorbed energy at 0 ℃ shows an overall increasing trend. The CGHAZ exhibits relatively balanced performance at a heat input of 20 kJ·cm?1. |
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