METHOD FOR WELDING OF THE SPACING GRATES OF THE FUEL ELEMENTS OF NUCLEAR REACTORS Russian patent published in 2005 - IPC

FIELD: nuclear power engineering.

SUBSTANCE: the method of resistance spot welding, mainly of the spacing grates of nuclear reactors, is realized by a modulated unipolar pulse of the welding current. In this case the current-conducting section is produced at the constant force of compression of welding electrodes. The contact resistance of this section is lesser than the contact resistance of cold articles, but greater than the contact resistance of the articles, welded by means of the current with the greater amplitude and lesser duration, than welding current. The stabilization of the contact resistance is realized without formation of the cast core in the section of the welding circuit of "electrode-electrode" by means of passing the current at the lesser amplitude than welding current. The article welding with production of the cast core is realized when passing the current at the amplitude, sufficient for formation of the cast core of given dimensions and further passing of the current at the lesser amplitude through a welded article. Monitoring of the instantaneous values of voltage during the welding process is carried out. The monitoring results are used for article rejection. The rejected articles are rewelded by means of a more power current pulses without removing the welding force. The duration of the part of the welding current pulse at the constant amplitude, ensuring the stabilization of the contact resistance is chosen as sufficient one for reaching the voltage constancy in the welding circuit. The parameters of the part of the welding current, passing through the produced cast core after decreasing its maximum value of duration and amplitude, correspond to the parameters of the part of stabilization of the contact resistance. Monitoring the disappearance the contact resistance of "article-article" is realized by comparison of the amplitude values of voltages during the indicated parts of the welding current pulse. The existence of the cast core is determined by the voltage change rate during the horizontal part with the maximum amplitude of the welding current.

EFFECT: increased reliability of the welded spacing grates of the fuel elements of nuclear reactors.

1 cl, 4 dwg