Features (Research) of the Effect of Microstructure on Large Diameter Pipe Welded Joint Impact Strength

In this work control welded joints of plates made of pipeline steel type 07KhG2B of strength class K60 are studied, obtained in a laboratory multi-arc welding stand and samples processed according to welding thermal cycles in a Gleeble 3180 test complex. It is shown that modeling and simulation techniques used make it possible to calculate the thermal cycle and form a structure in a steel sample that is as close as possible to the structure of the HAZ of a real welded joint. Studies carried out show general features of the effect of microstructure on specimen impact strength with a simulated HAZ microstructure and specimens from an actual welded joint in terms of the effect of matrix structure, large particles of titanium and niobium carbonitride phases, and MA-constituents. It is shown that the toughness of specimens with a simulated HAZ overheating area microstructure correspond to the worst test results of a real welded joint in the zone (GOST 6996) and the fusion line (DNV-OS-F101). This result confirms the validity of applying the simulated test technique for evaluating steel weldability.