Types of Welding - 4 Welding Methods

Resistance welding is a fusion process which takes place between two metals under a certain load and heat without any demand of additional materials. The heat required during welding process is generated from the electrical resistance of the materials.

There are four types of welding methods in resistance welding: Spot Welding, Projection Welding, Seam Welding, & Flash Butt or Butt Welding.

Flash Butt or Butt Welding requires no overlapping of the joining metals among them. There are four types of Output Current solutions. Capacitor Discharge DC is not applicable in Seam Welding and Flash Butt / Butt Welding methods due to its intrinsic nature of instantaneity on current flow time.
Resistance Welding can be divided into four welding methods and four output current solutions.
Spot Welding / Projection Welding / Seam Welding / Flash Butt Welding

Electrical Output Methods used in Welding

Single Phase AC is the most common type of output solution, electric current levels return to zero every half cycle creating a “no current flow” period and inducing an intermittent heating reaction. AC welding machines with constant current Controllers supply primary voltage compensation and primary/secondary constant current feedback control which automatically adjusts power fluctuations.
DC Current Capacitor Discharging. The capacitor stores energy in its own electric field and returns energy to the circuit whenever required. The stored energy is rapidly discharged to the transformer producing a flow of electrical current for welding. Capacitor Discharge solution is the best suited welding application for hot rolled sheet or thick steel sheet with multiple embossments.
Three Phase Rectifier-DC Output. Widely applied before the emergence of Three Phase DC Inverters, this method uses a three-phase balanced AC input operating at 50 or 60Hz and converts it to DC. This method saves 40% of energy in comparison to a Single Phase AC solution.
Three Phase Inverter. Utilizes three-phase balanced input, current wave is fully rectified to DC and switched to 1000Hz to produce AC supply to primary transformers. The current is then rectified into DC for welding operation.
  Three Phase Inverter DC solution has the following advantages:

1.No “blank period” in the current wave form. Heat produced is continuous and efficient. The fast feedback control (roughly 0.1 milliseconds) ensures stable welding quality and controls welding splash.

2.High frequency means high current density, which easily generates the required welding heat in the shortest time interval, thus welding is completed in a faster approach with minimum power consumption.

3.High-frequency switching technology reduces 60-70% of power consumption compared to Single Phase AC solutions.

4.High-frequency transformers make wide-range welding possible. Traditional AC transformers may induce insufficient current dispensation leading to poor welding quality.