Welding Methods For Weld Studs

There are three main arc welding processes for weld studs.

The first one is stable‑arc stud welding, also known as arc stud welding. A stable and continuous electric arc is generated between the stud end and the workpiece. As a heat source, the arc forms a molten pool on the base material of the workpiece, and meanwhile produces a molten layer and plastic zone at the stud end. Held inside the welding gun, the stud is pressed into the molten pool by spring force or other mechanical forces from the gun. Part or all of the molten metal is squeezed out of the pool and flows into the ceramic ferrule forming groove, forming a recrystallized plastic joint or a mixed metallurgical joint with both recrystallization and recrystallization‑phase transformation. Power sources for this process are generally arc‑welding rectifiers (controllable and non‑controllable) with drooping volt‑ampere characteristics, welding inverters or DC arc‑welding generators. The arc discharge is stable and continuous, similar to shielded metal arc welding.

The second process is unstable‑arc stud welding, namely capacitor‑energy‑storage stud welding, also called capacitance discharge stud welding. It uses a capacitor bank as the power supply for arc generation. Welding is completed by instantaneous capacitor discharge between the stud end and the workpiece. Capacitor discharge creates an unsteady arc condition with abrupt changes in arc voltage and welding current, and the welding process is uncontrollable. Studs applied in this process require a pre‑fabricated pointed tip at the center of the stud end, so it is also referred to as peak discharge stud welding.

The third arc‑based stud welding method is short‑cycle stud welding, also named short‑time stud welding. Its welding arc is modulated in current waveform. The welding procedure consists of two phases: a pilot arc with low current and a main welding arc with high current. It is a short‑duration controllable arc stud‑welding technology. Power supply for short‑cycle stud welding usually adopts two parallel power sources to supply power sequentially for the pilot arc and the main welding arc. Available combinations include two arc‑welding rectifiers (controllable or non‑controllable), or a rectifier matched with a capacitor bank. Inverter‑type power supplies can work without dual‑power parallel configuration.