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<p>The welding tests of Q500qENH weathering steel were carried out using a DC1000-K1387-3 submerged arc welding machine, combined with optical microscopy, electron backscatter diffraction, Charpy impact testing, and other technologies to investigate the microstructure, toughness, and their evolution rules in welded joints under different heat inputs. Results indicated that while the microstructural composition of the weld metal (WM) and heat-affected zone (HAZ) remained consistent across energy inputs, higher welding energy led to coarser grains, reduced martensite/austenite (M/A) content, increased M/A volume, and a transition from equiaxed to irregular grain morphologies. The welded joints exhibited hardness values ranging from 212 to 258 HV, demonstrating favorable hardness compatibility with the base metal. At 20&#xa0;kJ/cm, the − 40&#xa0;°C impact energy in all regions exceeded 60&#xa0;J, accompanied by a yield strength of 573&#xa0;MPa and a yield-to-tensile strength ratio of 0.81, indicative of optimal mechanical properties. The primary factors causing the decrease in impact energy with increasing heat input were identified as grain coarsening, dimensional growth of M/A constituents, and the formation of irregular large-scale M/A phases.</p>

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Research on Microstructure and Properties of Q500qENH Heat-Affected Zone under Different Energy Inputs

  • 期刊论文

  • 发表日期：

    2025年6月23日

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  • Bowen Li,
  • Cuncai Peng,
  • Wang Li,
  • Cairu Gao,
  • Hongyan Wu,
  • Xiuhua Gao,
  • Linxiu Du

摘要

The welding tests of Q500qENH weathering steel were carried out using a DC1000-K1387-3 submerged arc welding machine, combined with optical microscopy, electron backscatter diffraction, Charpy impact testing, and other technologies to investigate the microstructure, toughness, and their evolution rules in welded joints under different heat inputs. Results indicated that while the microstructural composition of the weld metal (WM) and heat-affected zone (HAZ) remained consistent across energy inputs, higher welding energy led to coarser grains, reduced martensite/austenite (M/A) content, increased M/A volume, and a transition from equiaxed to irregular grain morphologies. The welded joints exhibited hardness values ranging from 212 to 258 HV, demonstrating favorable hardness compatibility with the base metal. At 20 kJ/cm, the − 40 °C impact energy in all regions exceeded 60 J, accompanied by a yield strength of 573 MPa and a yield-to-tensile strength ratio of 0.81, indicative of optimal mechanical properties. The primary factors causing the decrease in impact energy with increasing heat input were identified as grain coarsening, dimensional growth of M/A constituents, and the formation of irregular large-scale M/A phases.