1996 Volume 14 Issue 2 Pages 285-291
Resin composite type vibration damping steel sheet (VDSS) is composed of two skin steel sheets and the core damping resin. To spot-weld VDSS, an electrical contact must be needed between the two skin sheets by using a shunting circuit because the core resin is an electrically insulator. In this mothod of spot welding, it is considered that time to exclusion of resin between upper and lower skin sheets affects both weld quality and working efficiency.
In this study, the relationship between time to exclusion of resin and material-, welding-conditions were clarified by investigating the mechanism of resin exclusion in shunt welding. The proposed mechanism was considered as follows : In the initial stage of welding, the temperature elevated first around the electrode which has curved tip face and the core resin started to melt. As electrode-skin sheet contact area is gradually enlarged by heat generation, finally this brings about the contact between upper and lower skin sheets.
In this model, time to exclusion is proportional to melting point of resin and inversely proportional to the square of shunt current. The core resin thickness and the radius of electrode face curvature affect exclusion time as a parameter of electrode-skin contact diameter.
This model was well corresponded with the experimental results. From these results, it was revealed that the thin resin thickness as material conditions and the short distance between welding and shunting points as welding conditions were important to obtain good weldability.