Pipeline welding is an integral part of oil and gas exploration industries. Often the weld failures are observed due to lack of weld quality, improper heat treatment and poor workmanship. Further, the use of new materials in pipeline industry puts focus on a better understanding of requirements for welding and reducing the failures in future. This necessitates the need for development and design of suitable welding fluxes for joining of these materials. In this paper an attempt is made to analyse the effect of commercial submerged arc welding flux and laboratory prepared agglomerated submerged arc welding fluxes (of basic, rutile basic and rutile acidic type) on the weldability, microstructural evolution as well as the structural integrity issues in API X70 line pipe steel welds. The mechanical and microstructural behaviour of weld joints was observed for submerged arc welding fluxes. The maximum tensile strength of 613 N/mm2 was observed for weld joint prepared using commercial flux (C.F). While in case of agglomerated fluxes the maximum value of tensile strength observed was 561 N/mm2 for F15B basic flux. Impact toughness for all the weld joints was evaluated both at room temperature and at −65 °C. For the weld as well as the heat-affected zone, the maximum impact toughness (160 J and 436 J) was observed for basic flux F5B at room temperature while at −65 °C (16 J and 30 J) impact toughness was obtained which was similar to that obtained with commercial flux. Microhardness of commercial weld joint (232 HV) is maximum as compared to the other weld joints. Maximum microhardness of 222 HV was observed for weld joint fabricated with flux F15B. Flux F15B shows a maximum value of microhardness (218 HV) for the heat-affected zone. Weld joints fabricated by using F3RA and F19RA fluxes exhibit high susceptibility to hydrogen induced cracking as compared to the remaining weld joints. The crack sensitivity ratio (CSR %) is high for weld specimen F3RA (54.64%) and F19RA (50.26%) while weld specimen fabricated using (F5B and C.F) fluxes show minimum crack sensitivity ratio (27.54% & 30.97%) respectively. The high susceptibility towards hydrogen induced cracking may be attributed to the very low value of carbon equivalent as compared to the remaining weld joints. © 2018 Elsevier Ltd