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<p>This study investigates the microstructure and impact performance of laser-MAG hybrid welded T-joints in 12-mm 945 shipbuilding steel under various heat input conditions. The variations in microstructure and impact properties of the welded joints are analyzed, including changes in grain size within the heat-affected zone (HAZ) under different heat inputs. Impact tests are conducted on the T-joints using a drop weight impact tester, and the process of impact and acceleration data during impact are recorded using high-speed cameras and an accelerometer. The fracture energy of the welded joints under different heat inputs is analyzed, and the microstructure and fracture characteristics of the impact fracture surfaces are observed through SEM scanning. The results show that the critical drop height for the 12-mm&#xa0;T-joints is 725&#xa0;mm. With an increase in heat input, the grain size of the welded joint, especially within the HAZ, increases, leading to a decrease in mechanical properties. The impact test on the 12-mm&#xa0;T-joints shows that at a heat input of 11.5&#xa0;kJ/cm, the fracture energy is 2518.8&#xa0;J, while at a heat input of 14.8&#xa0;kJ/cm, the fracture energy is 2084.2&#xa0;J, representing a 17.25% reduction in fracture impact energy. The fracture modes of the welded joints under different heat input conditions are identified as ductile fractures, and T-joints with lower heat input within the allowable process parameter range exhibit better resistance to impact.</p>

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Study on Microstructure and Impact Performance of 945 Steel Laser-MAG Hybrid Welded T-Joints under Different Heat Inputs

  • 期刊论文

  • 发表日期：

    2025年12月16日

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  • Bingwen Zhao,
  • Yong Zhao,
  • Juan Fu,
  • Feiyun Wang,
  • Deyang Zhang,
  • Xueyan Yang,
  • Yinjun Liu

摘要

This study investigates the microstructure and impact performance of laser-MAG hybrid welded T-joints in 12-mm 945 shipbuilding steel under various heat input conditions. The variations in microstructure and impact properties of the welded joints are analyzed, including changes in grain size within the heat-affected zone (HAZ) under different heat inputs. Impact tests are conducted on the T-joints using a drop weight impact tester, and the process of impact and acceleration data during impact are recorded using high-speed cameras and an accelerometer. The fracture energy of the welded joints under different heat inputs is analyzed, and the microstructure and fracture characteristics of the impact fracture surfaces are observed through SEM scanning. The results show that the critical drop height for the 12-mm T-joints is 725 mm. With an increase in heat input, the grain size of the welded joint, especially within the HAZ, increases, leading to a decrease in mechanical properties. The impact test on the 12-mm T-joints shows that at a heat input of 11.5 kJ/cm, the fracture energy is 2518.8 J, while at a heat input of 14.8 kJ/cm, the fracture energy is 2084.2 J, representing a 17.25% reduction in fracture impact energy. The fracture modes of the welded joints under different heat input conditions are identified as ductile fractures, and T-joints with lower heat input within the allowable process parameter range exhibit better resistance to impact.