The effect of thermomechanical welding on the microstructure and mechanical properties of S700MC steel welds

Peng Wang*, Felipe Martins Gomes, Fernando Gustavo Warchomicka, Wolfgang Ernst, Rudolf Vallant, M. C. Poletti, Norbert Enzinger

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Grain refinement by plastic deformation during conventional TIG welding can help to compensate for the loss of mechanical properties of welded joints. The thermomechanical welding (TMW) tests were performed on S700MC steel with different combinations of TIG arc energy and high frequency hammering over three target cooling times (t8/5 = 5s, 15s, and 25s). Additionally, the effect of initial microstructures on the weld joint quality was analysed by testing three materials conditions: hot-rolled (as-received) and cold-rolled with 10% and 30% thickness reductions, respectively. The effects of plastic deformation and the mechanical vibration on the grain refinement were studied separately. Optical microscopy, electron backscattered diffraction, and Vickers hardness were used to characterise the weld microstructure heterogeneity. The weld width and depth and the mean grain size were correlated as the function of cooling time t8/5. The results show that the weld dimensions increase with increasing the t8/5. The weld microstructures transformed from the mixed martensite and bainite into mixed ferrite and bainite with increasing the t8/5 time, and the related mean grain size increased gradually. The TMW welds exhibit smaller grains compared to TIG welds due to the coupled effects of mechanical vibration and plastic deformation. The mechanical vibration contributes to weld metal homogenisation, accelerating TiN precipitation in the fusion zone. The proposed TMW process can refine the weld microstructure of S700MC steel, enhancing its mechanical properties.
Original languageEnglish
Article number10.1007/s40194-024-01711-x
Pages (from-to)1053-1069
Number of pages17
JournalWelding in the World
Volume68
Issue number5
Early online date15 Feb 2024
DOIs
Publication statusPublished - May 2024

Keywords

  • Grain refinement
  • Heat-affected zone softening
  • Mechanical vibration
  • S700MC steel
  • Thermomechanical welding (TMW)

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys

Fields of Expertise

  • Advanced Materials Science

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