Proceedings of the Third International Conference on Metals & Hydrogen P44

Hydrogen distribution in multi-layer welds of steel S960QL

Thomas Schaupp (1)1 , Michael Rhode (1)1 , Hamza Yahyaoui (2)2 , Thomas Kannengiesser (1)1

  • (1) 1

    Bundesanstalt für Materialforschung und -prüfung (BAM), Division 9.4 “Weld Mechanics”, Unter den Eichen 87, 12205 Berlin, Germany

  • (2) 2

    Bundesanstalt für Materialforschung und –prüfung (BAM), Germany


High-strength low-alloyed (HSLA) steels with yield strength ≥ 690 MPa have increasing importance in steel construction and civil engineering. However, weld processing of those steels is a major challenge. The susceptibility for degradation of mechanical properties of weld joints significantly increases in presence of hydrogen and can result in hydrogen assisted cracking (HAC). Generally, risk for HAC increases with increasing yield strength of HSLA steels. To minimize the incidence of HAC, it is essential to gain knowledge about both the (1) absorbed hydrogen amount and its distribution in the weld seam and (2) options to lower the amount of introduced hydrogen. Existing standards recommend heat treatment procedures (interpass temperature or post weld heat treatment) to reduce the diffusible hydrogen concentration in weldments. In this context, different weld seam geometries should be considered. For HSLA steel fabrication weld processing with seam opening angles of 45° to 60° is typical. Modern weld technologies allow welding with seam opening angles of 30° - reduced welding time and costs. In the present study, the hydrogen distribution in multi-layer welds of a 960 MPa HSLA steel was analysed. Influence of different seam opening angles as well as heat input, interpass temperature and post weld heat treatments were investigated. The welded samples were quenched in ice water immediately after welding and subsequently stored in liquid nitrogen. After defined warming up, small specimens were machined from the weld seam by water jet cutting. The diffusible hydrogen concentration was measured by carrier gas hot extraction with coupled mass spectrometer. The results showed, that low heat input and post weld heat treatment procedures can lower hydrogen concentrations in welds. Furthermore, a gradient of the hydrogen concentration was identified with increasing weld pool depth. By varying the seam opening angles different hydrogen concentrations were measured.


  • Hydrogen concentration
  • Welding
  • High-strength Steel
  • Heat treatment
  • Carrier gas hot extraction