In recent years, demands for saving energy and reducing GHG emissions have been greatly increasing the development of automobile steel sheets. It is necessary to develop higher strength steel sheets to meet the above-mentioned requirements. Resistance spot welding is widely used in advanced high strength steels (AHSS). However, there are still many welding problems to be solved. The critical one is the weld defects which will decrease nugget strength and cause brittle fractures. Therefore, the only way to get good quality of weld nugget is depending on an optimal welding sequence to avoid welding defects.
|
| Fig. Weld nuggets after (a) general and (b) optimal welding sequences |