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<p>In this study, patterns of the formation of microstructures in laser welded joints of the X80 low-carbon steel plates were investigated, varying both their thicknesses from 1.3 up to 8.0&#xa0;mm and heat input from 0.072 up to 0.375&#xa0;kJ/mm. The microhardness levels were measured at room temperature, while the impact toughness (KCV) values were determined in the range from + 20 down to − 70&#xa0;°C. At the plate thickness of 1.3&#xa0;mm, a predominantly martensitic microstructure with a small proportion of bainite was observed in the weld metal, but it was predominantly bainitic with an insignificant content of martensite at 8.0&#xa0;mm. The average microhardness levels increased from 230&#xa0;HV for the plate thickness of 8.0&#xa0;mm up to 295&#xa0;HV for 1.3&#xa0;mm. For the plate thicknesses of 1.3 and 3.0&#xa0;mm, the welded joints were fractured viscously in the entire studied temperature range, while the failure type was ductile-brittle when testing the 8.0&#xa0;mm ones at the temperature of − 40 and completely brittle at − 70&#xa0;°C. The reason was associated with the heterogeneity of the microstructure and the presence of phases characterized by different microhardness levels.</p> Graphical Abstract <p></p>

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Effect of Plate Thickness and Heat Input on Microstructure and Impact Toughness of Laser Welded Joints of X80 Low-Carbon Steel

  • 期刊论文

  • 发表日期：

    2025年11月3日

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  • A. I. Gordienko,
  • I. V. Vlasov,
  • A. G. Malikov

摘要

In this study, patterns of the formation of microstructures in laser welded joints of the X80 low-carbon steel plates were investigated, varying both their thicknesses from 1.3 up to 8.0 mm and heat input from 0.072 up to 0.375 kJ/mm. The microhardness levels were measured at room temperature, while the impact toughness (KCV) values were determined in the range from + 20 down to − 70 °C. At the plate thickness of 1.3 mm, a predominantly martensitic microstructure with a small proportion of bainite was observed in the weld metal, but it was predominantly bainitic with an insignificant content of martensite at 8.0 mm. The average microhardness levels increased from 230 HV for the plate thickness of 8.0 mm up to 295 HV for 1.3 mm. For the plate thicknesses of 1.3 and 3.0 mm, the welded joints were fractured viscously in the entire studied temperature range, while the failure type was ductile-brittle when testing the 8.0 mm ones at the temperature of − 40 and completely brittle at − 70 °C. The reason was associated with the heterogeneity of the microstructure and the presence of phases characterized by different microhardness levels.

Graphical Abstract