Shunting during spot welding - Sheet Metal Chassis

During spot welding, the current flowing outside the main welding circuit is called shunt. Shunting reduces the current flowing through the welding area, resulting in insufficient heating, resulting in a significant decline in the strength of the solder joint and affecting the welding quality.

The factors affecting the degree of diversion mainly include the following aspects:

(1) Thickness of weldment and spacing of welds. With the increase of solder joint spacing, the shunt resistance increases and the shunt degree decreases. When the conventional point spacing of 30 ~ 50mm is used, the shunt current accounts for 25% ~ 40% of the total current, and the shunt degree decreases with the decrease of the thickness of the weldment.

(2) Surface condition of weldment. When there are oxides or foreign matters on the surface of the weldment, the contact resistance between the two weldments increases, and the current through the welding area decreases, that is, the shunt degree increases. The workpiece can be pickled, sandblasted or polished.