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<p>Laser hybrid welding presents several challenges when used to weld thick steels. A typical weld is divided into the arc-dominated and laser-dominated zone. These zones lead to variations in the mechanical properties of the weld. The laser-dominated zone is of particular importance regarding mechanical properties, notably Charpy impact toughness, due to the high cooling rates and the absence of filler wire. The low heat input of the laser can lead to martensitic microstructure causing hardening and deterioration of impact toughness. The high heat input of the arc can lead to grain coarsening and even loss of impact toughness. This study examines the influence of heat input on the cooling rates, microstructure and mechanical properties of single-pass laser hybrid welded steels of S355J2 and EH36 with thicknesses up to 30&#xa0;mm. The experiments were performed with a 20-kW fibre laser and a contactless electromagnetic weld backing in the butt-joint configuration in 1G welding position. The cooling time was measured in three different locations near the fusion lines corresponding to different heights of the seam using a special configuration with pyrometers, collimators and optical fibres. The test specimens for the Charpy impact testing and tensile testing were extracted in three different depths. The experiments indicated that a heat input of 1.6&#xa0;kJ/mm–2&#xa0;kJ/mm, 2&#xa0;kJ/mm–2.4&#xa0;kJ/mm and 3.7&#xa0;kJ/mm were recommended when single-pass laser hybrid welding of 20-, 25-, and 30-mm-thick structural steels regarding the minimum requirements of the mechanical properties, respectively.</p>

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Influence of heat input on cooling rates and mechanical properties of laser hybrid welded thick structural steels

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年1月30日

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  • Fatma Akyel,
  • Ömer Üstündag,
  • Nasim Bakir,
  • Christian Brunner-Schwer,
  • Andrey Gumenyuk,
  • Michael Rethmeier

摘要

Laser hybrid welding presents several challenges when used to weld thick steels. A typical weld is divided into the arc-dominated and laser-dominated zone. These zones lead to variations in the mechanical properties of the weld. The laser-dominated zone is of particular importance regarding mechanical properties, notably Charpy impact toughness, due to the high cooling rates and the absence of filler wire. The low heat input of the laser can lead to martensitic microstructure causing hardening and deterioration of impact toughness. The high heat input of the arc can lead to grain coarsening and even loss of impact toughness. This study examines the influence of heat input on the cooling rates, microstructure and mechanical properties of single-pass laser hybrid welded steels of S355J2 and EH36 with thicknesses up to 30 mm. The experiments were performed with a 20-kW fibre laser and a contactless electromagnetic weld backing in the butt-joint configuration in 1G welding position. The cooling time was measured in three different locations near the fusion lines corresponding to different heights of the seam using a special configuration with pyrometers, collimators and optical fibres. The test specimens for the Charpy impact testing and tensile testing were extracted in three different depths. The experiments indicated that a heat input of 1.6 kJ/mm–2 kJ/mm, 2 kJ/mm–2.4 kJ/mm and 3.7 kJ/mm were recommended when single-pass laser hybrid welding of 20-, 25-, and 30-mm-thick structural steels regarding the minimum requirements of the mechanical properties, respectively.