Abstract
In the previous paper, empirical formulas that estimate shear tensile foce of spot weld and dimensions of nugget cross-section from both welding conditions (welding current, arc voltage, arc time) and upper plate thickness were obtained for CO2 arc spot welds in steel. These empirical formulas are valid when the gap between upper plate and lower plate is zero. However, in practice, some gap will exist in the weld joint because the force applied to press the plates together is weak.
In this paper, in order to study how the gap affects shear tensile force of weld joint and dimensions of nugget, arc spot weld joints were made using different gaps and the nugget dimensions and shear tensile force were measured. These experimental results were compared with values estimated using the empirical formulas, and the maximum gap width that could be allowed in practice was obtained.
The results are summarized as follows;
1) When the gap exceeds 1 mm, button dia. decreases with increasing gap width.
2) Nugget dia. increases with increasing gap width.
3) Shear tensile force of weld joint increases with increasing gap width. However, when the gap becomes wide and a hole appears in the center of the button, it decreases suddenly.
4) The relationship between the practically allowable gap width and the upper plate thickness has been shown graphically.
