Welding method for ultrahigh-strength structural steel with yield strength of 1400 MPa

The invention relates to a welding method of ultrahigh-strength structural steel with the yield strength of 1400 MPa, which is used for preventing cold cracks after welding, and is used for welding the ultrahigh-strength structural steel with the yield strength of 1400 MPa by selecting proper manners of groove processing, cleaning pretreatment, demagnetization, spot welding, low-speed welding (high linear energy) and cooling. A welding joint has good obdurability and cold crack resistance, the yield strength of a welding seam is larger than or equal to 1050 MPa, the impact energy of the welding seam, a fusion zone and a heat affected zone at the temperature of minus 40 DEG C is larger than 25 J, meanwhile, the structural steel contains a large amount of martensite, magnetism of a steel plate of the structural steel can have obvious attraction force on a welding wire, electric arcs are unstable, and through degaussing treatment, the electric arcs are not stable. According to the ultrahigh-strength steel plate