METHOD OF RESISTANCE SPOT WELDING Russian patent published in 2017 - IPC B23K11/11 B23K11/16 

FIELD: metallurgy.

SUBSTANCE: method can be used for resistance spot welding of high-strength steel sheets, having the carbon content of at least 0.15 wt % and the tensile strength of at least 980 MPa. The joint is obtained by spot welding, which includes the current I₁ supply for the welding spot core formation, cooling without the welding current supply and the heat treatment for the welding spot core metal release, when the current I₂is supplied. The ratio of the current I₂ to the current I₁ is choosen from 0.5 upto 0.8. The cooling process time tc is selected in the range from 0.8×tmin upto 2.5×tmin, where tmin is calculated in accordance with the steel sheets thickness H, using the equation tmin = 0.2×H². The heat treatment time t2 is selected in the range from 0.7×tmin upto 2.5×tmin. The applied pressure value at the welding spot joint cooling stage is greater than the pressure at the core formation stage. The electrodes pressure is maintained during the cooling stage and until the heat treatment is complete.

EFFECT: obtaining the high and stable characteristics to resist the delayed fracture, while simultaneous suppressing of the hardness decrease during tempering.

2 cl, 4 dwg, 3 tbl, 3 ex