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<p>Laser welding of thin Al-Si coated press-hardened steel (PHS) faces critical challenges because of Al segregation and the formation of soft ferrite phases, which degrade weld quality. This work proposes an integrated approach combining laser beam oscillation with a low-alloy filler wire, aiming to optimize thermal distribution and promote material mixing. Three oscillation modes (no oscillation, linear oscillation, and circular oscillation) were systematically investigated through experiments and thermo-fluid numerical simulations. In the no-oscillation mode, rapid solidification resulted in insufficient mixing and pronounced Al segregation, yielding a high ferrite fraction (~ 32%) and fracture along the fusion line during tensile testing. Linear oscillation improved melt flow and Al dilution, reducing the ferrite fraction to ~ 26% and enhancing mechanical properties. However, residual ferrite near the fusion line remained a weak zone during tensile testing. In contrast, the circular oscillation mode generated vortex-like flows that homogenized the molten pool, improving Al dilution, and further decreased the ferrite fraction to ~ 20%. Consequently, welds produced with circular oscillation exhibited markedly improved mechanical properties, with fracture occurring in the base metal.</p>

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Enhancing Weld Quality of Thin Al-Si Coated Press-Hardened Steel Via Laser Beam Oscillation

  • 期刊论文

  • 发表日期：

    2025年11月11日

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  • S. Guo,
  • F. R. Wang,
  • Z. Y. Zhang,
  • Z. Q. Jin,
  • Z. X. Li,
  • H. L. Yi,
  • G. M. Xie

摘要

Laser welding of thin Al-Si coated press-hardened steel (PHS) faces critical challenges because of Al segregation and the formation of soft ferrite phases, which degrade weld quality. This work proposes an integrated approach combining laser beam oscillation with a low-alloy filler wire, aiming to optimize thermal distribution and promote material mixing. Three oscillation modes (no oscillation, linear oscillation, and circular oscillation) were systematically investigated through experiments and thermo-fluid numerical simulations. In the no-oscillation mode, rapid solidification resulted in insufficient mixing and pronounced Al segregation, yielding a high ferrite fraction (~ 32%) and fracture along the fusion line during tensile testing. Linear oscillation improved melt flow and Al dilution, reducing the ferrite fraction to ~ 26% and enhancing mechanical properties. However, residual ferrite near the fusion line remained a weak zone during tensile testing. In contrast, the circular oscillation mode generated vortex-like flows that homogenized the molten pool, improving Al dilution, and further decreased the ferrite fraction to ~ 20%. Consequently, welds produced with circular oscillation exhibited markedly improved mechanical properties, with fracture occurring in the base metal.