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<p>Using different welding heat inputs on 1000 MPa grade hydropower steel for gas shielded welding experiments, research on different heat input under 1000 MPa hydropower steel welded joints microstructure, hardness, strength and toughness of the law of change, through the highest hardness experiments to measure the highest hardness of the experimental steel under different conditions. The results show that the hardness of the heat-affected zone of the specimen plate decreases by 11 and 9 HV after preheating at 100 °C and increasing heat input, respectively. A large number of inclusions were present in the weld metal (WM), which partly acted as point for non-uniform nucleation of acicular ferrite (AF). With the increase in heat input, the WM microstructure AF is coarsened, the size of granular bainite (GB) is coarsened, the percentage of high misorientation grain boundaries (HAGB) in WM microstructure decreases from 73.7 to 60.9%, and the KAM value decreases. Diffusion of alloying elements in the vicinity of the fusion zone (FZ) and GB phase transition in the fine grain heat affected zone (FGHAZ) leads to a decrease in microhardness. The tensile strength of welded joints decreases with increasing welding heat input, and the strength requirements are met using a heat input of 10 ~ 16 kJ/cm. The impact absorption work of welded joints at − 60 °C is to meet the mechanical properties of hydroelectric power station 1000 MPa grade steel plate requirements more than 47 J.</p>

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Effect of welding heat input on microstructure evolution and mechanical properties of welded joints of 1000 MPa steel for hydropower engineering

  • 期刊论文

  • 发表日期：

    2025年2月13日

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  • Qiuju Bu,
  • Fan Wang,
  • Xiuhua Gao,
  • Guoqing Feng,
  • Zhiyong Chang,
  • Xincheng Chen

摘要

Using different welding heat inputs on 1000 MPa grade hydropower steel for gas shielded welding experiments, research on different heat input under 1000 MPa hydropower steel welded joints microstructure, hardness, strength and toughness of the law of change, through the highest hardness experiments to measure the highest hardness of the experimental steel under different conditions. The results show that the hardness of the heat-affected zone of the specimen plate decreases by 11 and 9 HV after preheating at 100 °C and increasing heat input, respectively. A large number of inclusions were present in the weld metal (WM), which partly acted as point for non-uniform nucleation of acicular ferrite (AF). With the increase in heat input, the WM microstructure AF is coarsened, the size of granular bainite (GB) is coarsened, the percentage of high misorientation grain boundaries (HAGB) in WM microstructure decreases from 73.7 to 60.9%, and the KAM value decreases. Diffusion of alloying elements in the vicinity of the fusion zone (FZ) and GB phase transition in the fine grain heat affected zone (FGHAZ) leads to a decrease in microhardness. The tensile strength of welded joints decreases with increasing welding heat input, and the strength requirements are met using a heat input of 10 ~ 16 kJ/cm. The impact absorption work of welded joints at − 60 °C is to meet the mechanical properties of hydroelectric power station 1000 MPa grade steel plate requirements more than 47 J.