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<p>Due to the precipitation of δ ferrite at the fusion line (FL), the tensile strength of the laser weld of Al-Si coated 22MnB5 steel fails to reach the level of the base material (BM). A method for improving the tensile strength at a low cost is introduced in this paper. The external magnetic field-assisted welding technology was adopted to prepare tailor welded blanks (TWB) of Al-Si coated steel. A numerical simulation model was established to study the changes in the flow field of the molten pool and the distribution of coating elements. Under the magnetic field, thermoelectric currents and induced currents generate Lorentz forces, which alter the molten pool flow field by deflecting liquid metal flow and creating vortices. This enhanced flow accelerates fluid velocity at the molten pool periphery, thereby promoting Al element diffusion while preventing Al element aggregation at the FL. Ultimately, a homogeneous Al distribution is achieved throughout the fusion zone (FZ). The δ-ferrite in the FZ is eliminated, and the microstructure transforms into fully lath martensite (LM). The average hardness increased from 442.8 HV to 487.3 HV. The tensile strength increased from 1209&#xa0;MPa to 1568&#xa0;MPa, and the fracture mechanism transitioned from a combination of ductile and brittle fracture to predominantly ductile fracture. The tensile strength is increased to the level of the base material without removing the coating or adding alloying elements.</p> Graphical Abstract <p></p>

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The Improvement Effect of Magnetic Field on Microstructure and Properties of the Al-Si Coated Steel Laser Weld

  • 期刊论文

  • 发表日期：

    2026年2月26日

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  • Fei Teng,
  • Hongshuang Di,
  • Yuyang Liu,
  • Sitong Li,
  • Pengcheng Huan,
  • Qiyuan Chen,
  • Xiaonan Wang

摘要

Due to the precipitation of δ ferrite at the fusion line (FL), the tensile strength of the laser weld of Al-Si coated 22MnB5 steel fails to reach the level of the base material (BM). A method for improving the tensile strength at a low cost is introduced in this paper. The external magnetic field-assisted welding technology was adopted to prepare tailor welded blanks (TWB) of Al-Si coated steel. A numerical simulation model was established to study the changes in the flow field of the molten pool and the distribution of coating elements. Under the magnetic field, thermoelectric currents and induced currents generate Lorentz forces, which alter the molten pool flow field by deflecting liquid metal flow and creating vortices. This enhanced flow accelerates fluid velocity at the molten pool periphery, thereby promoting Al element diffusion while preventing Al element aggregation at the FL. Ultimately, a homogeneous Al distribution is achieved throughout the fusion zone (FZ). The δ-ferrite in the FZ is eliminated, and the microstructure transforms into fully lath martensite (LM). The average hardness increased from 442.8 HV to 487.3 HV. The tensile strength increased from 1209 MPa to 1568 MPa, and the fracture mechanism transitioned from a combination of ductile and brittle fracture to predominantly ductile fracture. The tensile strength is increased to the level of the base material without removing the coating or adding alloying elements.

Graphical Abstract