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The significant influence of the welding heat input on the microstructural evolution, precipitation behavior and resultant properties of the coarse grained heat affected zone (CGHAZ) in low carbon Nb-V-Ti-N quaternary microalloyed steel was comparatively studied on a Gleeble 3800 thermomechanical simulator. Metallographic investigations revealed that the dominant microstructure transformed from lath bainite (LB) at heat input of 50 kJ/cm to intragranular acicular ferrite (IAF) at 100 kJ/cm, to IAF and intragranular polygonal ferrite (IPF) at 150 kJ/cm and to IPF, IAF and grain boundary ferrite (GBF) at 200 kJ/cm. In addition, Ti- and Nb-enriched submicron-scale precipitates promoted IAF and IPF nucleation with an orientation relationship 01 1 − MC / / 1 − 11 Ferrite and effectively pinned grain boundaries; V-enriched nanoscale precipitates acted as obstacles for dislocation movement, consequently improving CGHAZ performance. Moreover, the impact absorbed energy at 20 °C and −20 °C first increased from 216 ± 4.3J and 58 ± 2.7J to 219 ± 3.7J and 64 ± 3.0J, respectively, and then decreased to 184 ± 7.5J and 45 ± 2.1J, respectively, when the heat input increased from 50 kJ/cm to 200 kJ/cm. The maximum value was obtained at heat input of 100 kJ/cm, which was primarily attributed to the largest amount of high angle grain boundaries originating from IAF. The microhardness slightly reduced as heat input increased from 50 kJ/cm to 100 kJ/cm and did not obviously decrease as heat input varied from 100 to 200 kJ/cm, which was directly related to the microstructure constituents and nanoscale precipitates. Furthermore, the optimal heat input to obtain a good combination of strength and toughness was 100 kJ/cm, and Nb-V-Ti-N microalloyed steel was suitable for high heat input welding. • The low carbon Nb-V-Ti-N microalloyed steel is suitable for high heat input welding. • The optimum welding heat input is 100 kJ/cm to obtain a strengthened and toughened CGHAZ. • The submicron Nb- and Ti-enriched particles promote intragranular ferrite nucleation and pin grain boundary. • The orientation relationship between nucleation site and the induced ferrite grain is 01 1 − MC / / 1 − 11 Ferrite. • The nanoscale V-enriched precipitates act as obstacles for dislocation movement. [ABSTRACT FROM AUTHOR]