Improvement of resistance spot weldability for dual-phase (DP600) steels using servo gun

Dual-phase (DP) steel is a kind of advanced high-strength steels (AHSS) developed specifically for automotive application due to its excellent formability and better crash absorption than other conventional AHSS. Resistance spot welding (RSW) is the dominant sheet metal joining method in automobile industry, whereas the weldability of dual-phase steel using conventional air gun is not so excellent for the weld lobe diagram under constant electrode force is too narrow. However, this disadvantage can be easily overcome by servo gun's electrode force control function. This paper mainly relates how to improve weldability of dual-phase steel by adjusting electrode force during spot welding process. By modifying the electrode force using an orthogonal experimental design method, the result shows that the width of weld lobe diagram of dual-phase steel can be nearly doubled.