INFLUENCE OF GTA WELDING THERMAL CYCLES ON HSLA-100 STEEL PLATE

Autogenous gas-tungsten are (GTA) welds were performed on U.S. Navy HS LA-100 steel with heat inputs of 0.7, 1.1 and 2.2 kJ/mm. The absence o f weld metal and underbead HAZ cracking illustrated the advantage of l ow carbon steel for both weld wire and base plate. The maximum microha rdness values in the coarse grain HAZ next to the fusion line were fou nd to be well below 375 HV, which is usually considered to be the hard ness value above which severe hydrogen induced cold cracking can be ob served in this type of steel. Optical, scanning and transmission elect ron microscopy studies of the HAZ microstructure were correlated with the continuous cooling transformation diagram for this steel, and good agreement between the observed and predicted microstructures was obta ined. Unfortunately, the autogenous weld metal yield strength appeared to be somewhat lower than Navy specifications. It is therefore sugges ted that a more highly alloyed weld consumable than HSLA-100 be employ ed to maintain the weld metal yield strength at least equal to that of the base plate. Copyright (C) 1996 Canadian Institute of Mining and M etallurgy.