Enhanced low-temperature toughness of laser-arc hybrid welding of Q450NQR1 high-strength weathering steel via beam oscillation

Abstract

Suppressed low-temperature toughness mismatch between the fusion zone (FZ) and base metal (BM) was achieved in a Q450NQR1 high-strength weathering steel joint by employing laser-arc hybrid welding (LAHW) with beam oscillation (O-LAHW), thereby avoiding the heat aggregation of conventional LAHW at the center of the molten pool. The O-LAHWed joint exhibited a higher content of acicular ferrite in the FZ, increasing it by 8% compared with the LAHWed joint, reaching the maximum value of 61%. Meanwhile, the O-LAHWed joint demonstrates higher ultimate tensile strength (775 MPa), yield strength (697 MPa), and impact absorption energy (175 J for FZ, at − 40 °C) compared to LAHWed joints, with increases of 3%, 9%, and 35%, respectively. That is, O-LAHW can significantly improve the impact toughness at low temperatures and exhibit a low-temperature toughness matching degree of 118% with BM, surpassing the metal active-gas arc-welded joints reported in the existing literature by more than one time. The key factor contributing to the improved low-temperature toughness of the FZ was the interlocked microstructure with a high dislocation density promoted by the beam stirring effect.

Keywords

Weathering steel / Laser-arc hybrid welding (LAHW) / Laser beam oscillation / Microstructure / Low-temperature impact toughness

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Funding

National Natural Science Foundation of China(52275335)

Postdoctoral Fellowship Program of CPSF(GZB20230231)

China Postdoctoral Science Foundation(2023M731173)

RIGHTS & PERMISSIONS

Shanghai University and Periodicals Agency of Shanghai University and Springer-Verlag GmbH Germany, part of Springer Nature