Microstructure and crystallographic texture of high frequency electric resistance welded X65 pipeline steel

Microstructure and crystallographic texture and their correlation with impact toughness of high-frequency electric resistance welded (HF-ERW) X65 Grade pipeline steel have been investigated. X65 base metal after HF-ERW has formed a typical hourglass-shaped weld joint with four different regions, including the thermomechanical-affected zone (TMAZ), fine-grained heat affected zone (FGHAZ), coarse-grained heat affected zone (CGHAZ), and bondline (Weld Zone). X65 base metal shows prominent (113) [110] and (112) [110] texture components due to thermomechanical-controlled processing. TMAZ depicted random texture with a minor in-tensity of Cube component (001)[110] due to the partial recrystallization during welding. In the FGHAZ and CGHAZ, near the bondline, the base metal texture has been converted to rotated Goss (110) [110], Goss (110) [001], and rotated cube (001) [110] due to the recrystallization of the austenite and the shear deformation in the austenite temperature range. A high density of {100} and {110} cleavage planes is observed in the CGHAZ, which is often found to be the fracture location for the impact toughness testing.

Automated summary

The microstructure and crystallographic texture of HF-ERW X65 Grade pipeline steel are studied in relation to its impact toughness. After HF-ERW, the X65 base metal forms a weld joint with four distinct regions, including the TMAZ, FGHAZ, CGHAZ, and Weld Zone. Different texture components are observed in these regions due to the thermomechanical-controlled processing and recrystallization. The CGHAZ, where a high density of cleavage planes is found, is frequently associated with fracture in impact toughness testing.