Metall. Res. Technol.
Volume 118, Number 2, 2021
|Number of page(s)||11|
|Published online||25 March 2021|
The critical influence of La content on the microstructure-toughness relationship in the simulated coarse-grained heat-affected zone of high-strength low-alloy steels
The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology,
430081, PR China
2 School of Mechanical and Electrical Engineering, Foshan Polytechnic, Foshan 528237, PR China
3 Band (Foshan) Metallic Composite Materials Co. Ltd., Foshan 528000, Guangdong, PR China
Accepted: 10 February 2021
The present study was envisaged to investigate the role of La content on the particle, microstructure and toughness in the simulated coarse-grained heat-affected zone (CGHAZ) of high-strength low-alloy steels. Three steels with La content of 0.016 wt.%, 0.046 wt.% and 0.093 wt.% were prepared and simulated in a 100 kJ/cm heat input welding thermal cycle. Subsequently, the particle and microstructure of selected specimens were characterized and the impact absorb energy was measured at −20 °C. The results indicated that the La2O2S inclusions in 0.016 wt.%-La steel were gradually modified to LaS-LaP in 0.046 wt.%-La steel and to LaP in 0.093 wt.%-La steel. A higher fraction of acicular ferrite was obtained in the simulated CGHAZ of 0.016 wt.%-La steel, since the inclusion of La2O2S was more powerful to induce the formation of acicular ferrite. Furthermore, the fraction of M-A constituents in the simulated CGHAZ increased with increasing La content. The impact toughness in the simulated CGHAZ of 0.016 wt.%-La steel was the highest, owing to the high fraction of the fine-grained acicular ferrite and low fraction of M-A constituent.
Key words: HSLA steels / lanthanum / microstructure / grain refinement / impact toughness
© EDP Sciences, 2021
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