CD - Capacitor discharge stud welding
Capacitor discharge stud welding with contact
- The capacitor battery will be charged according to chosen charging voltage.
- The stud (with ignition tip) is placed onto the work piece and pressed by a spring in the welding gun onto the work piece (contact). The current circuit is closed.
- After triggering the welding process, the rapidly increasing current evaporates the ignition tip and ignites the arc.
- Stud and work piece are melted.
- The stud is moved forward to the plate.
- The arc is cut as soon as the stud touches the work piece
- The molten zones are joining and solidifying.
- Welding time is ≤ 3 msec.
- Recommended plate thickness should be 1/10 d, but not less than 0.5 mm.
Capacitor discharge stud welding with gap
Gap welding is different from the procedure described above: Before welding starts, the stud is positioned in a defined and adjustable distance above the work piece (gap). After triggering the welding process, the stud is accelerated by a spring to the plate surface. If there is contact between the ignition tip on the work piece, the process continues as described above. Welding time is approx. 1 msec; thus e.g. welding of aluminum becomes feasible without using a shielding gas atmosphere. Recommended plate thickness should be 1/10 d, but not less than 0.5 mm.
ARC - Drawn arc stud welding
Drawn arc stud welding with ceramic ferrule or shielding gas
Figure: Motion sequence at a use of a ceramic ferrule
- The stud is inserted into the chuck and - if necessary - equipped with a ceramic ferrule
- The stud is placed onto the work piece
- A lift mechanism in the welding gun or welding head lifts the stud. A secondary arc (pilot arc) of low current is ignited between stud tip and work piece
- Then the ignition of the main arc is carried out between stud tip and work piece
- Stud and work piece are melted
- At the end of the adjusted welding time the stud is moved to the work piece, the two molten zones join. The power source is switched off, the weld pool solidifies and cools down
SC - Short Cycle
Short cycle drawn arc stud welding
- Welding sequence is as with drawn arc stud welding (ARC) with the exception of higher current and shorter welding time (≤ 100 msec).
- This variant is suitable for stud diameters of up to 12 mm to thin plates.
- As the process up to 8 mm is often used without weld pool protection, studs with upset flange are used. In this way, a higher tensile strength of the weld zone is achieved in the welded area than in the stud shaft in spite of the existence of pores.
- From 8 mm stud diameter upwards, a shielding gas should be used to avoid pore formation.
ISO - Insulation technique - Welding processes for insulation
Cupped head pin welding ISO Plus (HVAC)
The welding process of cupped head pin welding corresponds with the contact-type capacitor discharge drawn-arc stud welding (CD).
Fire-resistant insulation with ARC-insulation pins (FRI)
The welding process of ARC-insulation pin welding corresponds with short cycle drawn arc stud welding (SC).