Mechanical properties of the heat affected zone of an X100 grade pipeline steel

The microstructure and mechanical properties of an X100 grade pipeline steel were investigated by the thermal simulation tests performed on a Gleeble-3500 thermal simulator. The results show that the steel has excellent weldability. Even if the weld heat input gets 40 kJ mm(-1), the low impact toughness energy in welding coarse grain heat affected zone (CGHAZ) is still higher than 200 J. Yet, an embrittlement zone emerges in inter-critical HAZ (ICHAZ) at the peak temperature of 750 degrees C, and the lowest strength appears in fine grained HAZ (FGHAZ) at the peak temperature of 950 degrees C. Moreover, the strength and toughness decrease with the increase of heat input.