Investigation on the weldability of a Zr-Ti microalloyed X120 linepipe

Three-wire submerged arc welding was utilized to weld a newly developed Zr-Ti microalloyed X120 linepipe with heat input of 21 kJ/cm. The microstructure in the heat-affected zone （HAZ）, predominantly consisted of bainite, was examined by means of optical and scanning electron microscope. The average Vickers hardness of grain coarsening heat-affected zone （GCHAZ） is about 290 HV0. 2. The lowest Vickers hardness in HAZ is about 265 HV0. 2. No obvious softening occurred in HAZ. The average impact toughness at -30 ℃ in HAZ was 186 -191 J. The tested results indicated that HAZ of newly developed Zr-Ti microalloyed X120 linepipe steel had high strength and excellent low temperature toughness which met the requirements of API 5L standard.