Transmission Electron Microscopy of Longitudinal Double Submerged Arc Weld (LDSAW) of X-120M Steel Line Pipe
This paper deals with the development of submerged arc welding wires for longitudinal double submerged arc welded (LDSAW) line pipe weld through transmission electron microscopy (TEM). The experimental procedure in the paper describes the test coupons preparation for submerged arc welding (SAW) with various combinations of wire and flux with varying level of alloying element. Microstructural characterization by transmission electron microscopy has been carried out to establish the desired microstructure in the weld of LDSAW for manufacturing the API-5L X-120M line pipes. The TEM micrographs for shows the lath type ferrite and bainitic type ferrite with high dislocation density. The lath type ferrite and bainitic type ferrite with high dislocation density also have fine precipitates in the ferrite matrix having orientation relationship. The weld metal suitable for X-120M have the microstructure of mainly bainitic and martensitic with high dislocation density and coarse precipitates in the matrix. The bainitic and martensitic microstructure have excellent fracture toughness down to -20 °C at this strength level (X-120M).
B.S.S. Daniel and G.P. Chaudhari
J. D. S. Chandel and N. L. Singh, "Transmission Electron Microscopy of Longitudinal Double Submerged Arc Weld (LDSAW) of X-120M Steel Line Pipe", Advanced Materials Research, Vol. 585, pp. 460-464, 2012