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<p>In response to the high standards demanded by marine engineering equipment for the strength and toughness of high-strength steel welded joints, this study systematically explores the effects and synergistic interactions of key alloy elements such as Mn, Ni, and Cu on the microstructural evolution mechanism, phase transformation behavior, and comprehensive mechanical properties of submerged arc welding deposited metal in 440&#xa0;MPa grade high-strength low-alloy marine steel. Three welding wires with gradient variations in Mn, Ni, and Cu contents were designed and fabricated, followed by deposition experiments combined with OM, SEM, and TEM characterizations to analyze macroscopic morphology, microstructural constituents, and their evolution. Complementary JmatPro simulations of CCT curves and transformation temperatures further elucidated the relationships between alloying, microstructure, and properties. Mechanical testing revealed that increasing Mn, Ni, and Cu contents effectively promoted acicular ferrite (AF), significantly reduced proeutectoid ferrite (PF), ferrite side plates (FSP), and brittle M-A constituents, while refining and optimizing ferrite lath morphology, resulting in a denser and more homogeneous structure. Thermodynamic analysis indicated enhanced austenite stability and increased hardenability due to the alloying additions. The weld metal produced by wire #3 exhibited superior properties, including a yield strength of 523&#xa0;MPa, tensile strength of 615&#xa0;MPa, yield-to-tensile ratio of 0.85, and a high absorbed impact energy of 163 J at -40℃, with fracture mode transitioning to ductile dimples and quasi-cleavage. Overall, moderate additions of Mn, Ni, and Cu synergistically refined the microstructure and enhanced toughness, enabling wire #3 (Mn = 1.27%, Ni = 1.17%, Cu = 0.15%) to achieve optimal strength-toughness matching with the base metal, thereby fulfilling the demanding safety and reliability requirements of welded joints in harsh marine environments.</p>

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Study on the influence mechanism of alloying elements on the microstructure and mechanical properties of deposited metal of high-strength offshore steel

  • 期刊论文

  • 发表日期：

    2025年12月22日

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  • Deyang Gong,
  • Jianyun He,
  • Haiyang Dai,
  • Siyu Zhang

摘要

In response to the high standards demanded by marine engineering equipment for the strength and toughness of high-strength steel welded joints, this study systematically explores the effects and synergistic interactions of key alloy elements such as Mn, Ni, and Cu on the microstructural evolution mechanism, phase transformation behavior, and comprehensive mechanical properties of submerged arc welding deposited metal in 440 MPa grade high-strength low-alloy marine steel. Three welding wires with gradient variations in Mn, Ni, and Cu contents were designed and fabricated, followed by deposition experiments combined with OM, SEM, and TEM characterizations to analyze macroscopic morphology, microstructural constituents, and their evolution. Complementary JmatPro simulations of CCT curves and transformation temperatures further elucidated the relationships between alloying, microstructure, and properties. Mechanical testing revealed that increasing Mn, Ni, and Cu contents effectively promoted acicular ferrite (AF), significantly reduced proeutectoid ferrite (PF), ferrite side plates (FSP), and brittle M-A constituents, while refining and optimizing ferrite lath morphology, resulting in a denser and more homogeneous structure. Thermodynamic analysis indicated enhanced austenite stability and increased hardenability due to the alloying additions. The weld metal produced by wire #3 exhibited superior properties, including a yield strength of 523 MPa, tensile strength of 615 MPa, yield-to-tensile ratio of 0.85, and a high absorbed impact energy of 163 J at -40℃, with fracture mode transitioning to ductile dimples and quasi-cleavage. Overall, moderate additions of Mn, Ni, and Cu synergistically refined the microstructure and enhanced toughness, enabling wire #3 (Mn = 1.27%, Ni = 1.17%, Cu = 0.15%) to achieve optimal strength-toughness matching with the base metal, thereby fulfilling the demanding safety and reliability requirements of welded joints in harsh marine environments.