Submerged arc welding method for ultrafast cooled steel with lower yield strength (Rel) being 500 MPa

A submerged arc welding method for ultrafast cooled steel with the lower yield strength (Rel) being 500 MPa includes the steps that the steel cooled at the cooling speed not lower than 60 DEG C/s is adopted, wherein the Rel is greater than or equal to 480 MPa, the tensile strength (Rm) ranges from 610 MPa to 770 MPa, the thickness does not exceed 40 mm, welding grooves are in a double-V shape, and the truncated edge ranges from 4 mm to 6 mm; backing welding is carried out without preheating before welding, wherein the Rm of a wire for welding is 685 MPa, the welding linear power input is 13 kJ/cm-30 kJ/cm, and a weakly basic sintered flux is adopted; filling submerged arc welding is conducted in the upper V-shaped groove and the lower V-shaped groove, wherein a weakly basic sintered flux is adopted, the Rm of a wire for welding is 600 MPa, and the welding linear power input is 13 kJ/cm-30 kJ/cm. According to the submerged arc welding method, obvious softening cannot occur in a welding heat affected zone, and back gouging is not needed for the back surface; besides, the impact toughness KV2 at the temperature of minus 40 DEG C of a welded joint is greater than or equal to 80 J, the strength (Rm) of the welded joint is greater than or equal to 610 MPa, and the submerged arc welding requirement of the fast cooled steel is met completely.