TWO-PASS WELDING METHOD WITH DOUBLE ANNEALING FOR JOINING HIGH-STRENGTH STEEL Russian patent published in 2022 - IPC C21D9/50 B23K11/06 B23K11/30 

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, namely to the welding of automotive high-strength steel (AHSS). The method for joining automotive high-strength steels (AHSS) includes providing the first surface of a sheet or strip and the second surface of a sheet or strip of high-strength AHSS steels with compositions having a carbon equivalent (Ceq) of at least 0.45, creating an overlap by superimposing the first surface on the specified second surface, welding them to form a weld, cooling the weld to a temperature between the temperatures Ac3 and Mf of the specified steels, heating the weld at a rate of at least 10°C/s to a temperature between the temperatures Ms and Ac1 of the steels, cooling the weld to a temperature below the temperature of Ms steels, heating the weld at a rate of at least 10°C/s to a temperature between the temperatures of Ms and Ac1 steels and cooling the weld to room temperature. Ceq is defined as: Ceq = C + A(C) ⋅ [Si/24 + Mn/6 + Cu/15 + Ni/20 + (Cr + Mo + Nb + V)/5 + 5B], with A(C) = 0.75 + 0.25 tanh [20(C - 0.12)], where the amount of each of the elements: C, Si, Mn, Cu, Ni, Cr, Mo, Nb, V and B is expressed in wt. %, and tanh is a hyperbolic tangent.

EFFECT: formation of a high-quality weld is ensured, which is not destroyed when passed on a continuous annealing line.

8 cl, 16 dwg, 6 tbl