Electric Welding: Types, Components and Applications

Welding Processes

All welding processes fall into two main categories:

1. Fusion Welding

Electric Energy-Based:
  • Carbon arc welding
  • Metal arc welding
  • Electron beam welding
  • Electroslag welding
  • Electrogas welding
Chemical Energy-Based:
  • Gas welding
  • Thermit welding

2. Non-Fusion Welding: 

Chemical Energy-Based:
  • Forge welding
  • Gas non-fusion welding
Mechanical Energy-Based:
  • Explosive welding
  • Friction welding
  • Ultrasonic welding
Electrical Energy-Based:
  • Resistance welding
  • Arc welding

Selection Criteria for Welding Process:

  • Type of metals to be joined
  • Cost considerations
  • Nature of the product
  • Production techniques

Use of Electricity in Welding

Electricity generates localized heat for melting materials, forming a weld joint.
The two most common methods are:
  1. Resistance Welding – Current passes through the joint’s resistance, generating heat (I²Rt).
  2. Arc Welding – Electricity conducts as an arc between two metallic surfaces.

Types of Arc Welding:

  • Shielded Metal Arc Welding (SMAW) / Manual Metal Arc (MMA): Uses a flux-coated electrode.
  • Gas Metal Arc Welding (GMAW) / MIG Welding: Uses a wire electrode and shielding gas.
  • Gas Tungsten Arc Welding (GTAW) / TIG Welding: Uses a tungsten electrode and inert gas.
  • Submerged Arc Welding (SAW): Uses a granular flux for shielding.
  • Flux-Cored Arc Welding (FCAW): Uses a tubular wire filled with flux.
  • Plasma Arc Welding (PAW): Uses a constricted arc and plasma gas.

Types of Resistance Welding:

  • Spot Welding: Common for joining sheet metals.
  • Seam Welding: Produces continuous welds along a seam.
  • Projection Welding: Uses projections on one of the workpieces.
  • Flash Welding: Ends of the pieces are heated by arcing and then forged together.
  • Upset Welding: Similar to flash welding but without visible arcing.

Other Electric Welding Types:

  • Electroslag Welding (ESW): Uses molten slag to melt the filler and base metal.
  • Electron Beam Welding (EBW): Uses a focused beam of electrons in a vacuum.
  • Laser Beam Welding (LBW): Uses a laser beam as the heat source.

Formation and Characteristics of Electric Arc

An electric arc forms when current passes between two electrodes separated by a small gap.
Process:
  • The electrode briefly touches the workpiece, creating a short circuit.
  • When withdrawn (~3–6 mm), current flows as a spark, ionizing the air gap.
  • Ionized air conducts current, forming an arc
Heat Distribution:
  • Anode (Positive): ~⅔ of heat (3500–4000°C).
  • Cathode (Negative): ~⅓ of heat.
  • In DC welding, the electrode burns faster when connected to the positive side.

Effect of Arc Length

A short arc length is essential for quality welds due to:
  • Concentrated heat on the workpiece
  • Stable arc (reduced magnetic blow)
  • Protection from atmospheric contamination
Issues with Long Arc Length:
  • Poor penetration and fusion
  • Unstable arc (prone to extinguishing)
  • Weld contamination (oxygen/nitrogen absorption)
  • Weak, porous, and spattered welds

Arc Blow

A deflection of the arc caused by magnetic fields, common in DC welding.
Effects:
  • Incomplete fusion
  • Bead porosity
  • Excessive spatter
Solutions:
  • Use AC welding (cancels magnetic fields)
  • Adjust ground connection position
  • Reduce current or electrode size
  • Shorten arc length

Polarity in DC Welding

Reverse Polarity (DCRP – Electrode Positive):
  • Electrode burns faster.
  • Shallow, wide weld bead.
  • Used with thick, heavily coated electrodes.
Straight Polarity (DCSP – Electrode Negative):
  • Workpiece is hottest.
  • Narrow, deep penetration.
  • Used with bare/medium-coated electrodes.
Note: AC welding alternates polarity, combining DCRP and DCSP effects.

Advantages of Coated Electrodes

  • Stabilizes the arc (ionizing agents like sodium/potassium)
  • Removes impurities (flux action)
  • Forms protective slag (prevents contamination, ensures even cooling)
  • Compensates for lost alloying elements
  • Increases melting rate
  • Reduces spatter
  • Enables AC welding (shielding gases maintain ionization)
Storage Tip: Keep electrodes dry to prevent efficiency loss.

Arc Welding Machines

Welding requires specialized machines to:
  • Convert AC to DC (if needed)
  • Reduce supply voltage
  • Provide high welding current safely
Types of Welding Machines:
  • DC Welding Machines:
  • Motor-generator sets
  • AC transformers with rectifiers
  • AC Welding Machines

V-I Characteristics of DC Welding Machines:

  • Drooping Arc Voltage (DAV): High open-circuit voltage, drops during welding (ideal for manual welding).
  • Constant Arc Voltage (CAV): Stable voltage (suitable for semi-automatic/automatic welding).
  • Rising Arc Voltage (RAV): Maintains constant arc gap (best for fully automatic processes).
    V-I Characteristics of DC Welding Machines

DC Motor-Generator Welding Machines

Advantages:
  • Portable
  • Adjustable polarity
  • Works on most metals
  • Supports various electrodes
Disadvantages:
  • High initial/maintenance cost
  • Noisy operation
  • Prone to arc blow

AC Rectified Welding Unit

  • Uses a transformer + rectifier (silicon diodes).
  • No moving parts (long lifespan).
Ideal for:
  • Pipe welding
  • Non-ferrous metals
  • Thin-gauge steel
  • AC Welding Machines
  • Step-down transformer with adjustable reactor.
Advantages:
  • Low cost & maintenance
  • No arc blow
Disadvantages:
  • Fixed polarity
  • Unsuitable for cast iron/non-ferrous metals

FAQs on Welding Processes

Q1. What are the main types of welding processes?
Welding processes are mainly divided into Fusion Welding and Non-Fusion Welding. Fusion welding involves melting of base metals (e.g., arc welding, gas welding), while non-fusion welding joins metals without melting them (e.g., friction welding, resistance welding).

Q2. What is the difference between fusion and non-fusion welding?
In fusion welding, heat melts the base materials to create a joint, whereas non-fusion welding joins materials using pressure or mechanical energy without melting the base metals.

Q3. Which welding processes use electric energy?
Electric energy-based welding includes arc welding, resistance welding, electron beam welding, electroslag welding, and laser beam welding. These methods generate heat via electrical resistance or arc discharge.

Q4. What are the different types of arc welding processes?
The major types of arc welding are:
  • Shielded Metal Arc Welding (SMAW)
  • Gas Metal Arc Welding (GMAW / MIG)
  • Gas Tungsten Arc Welding (GTAW / TIG)
  • Submerged Arc Welding (SAW)
  • Flux-Cored Arc Welding (FCAW)
  • Plasma Arc Welding (PAW)

Q5. What are the types of resistance welding?
Resistance welding types include:
  • Spot Welding
  • Seam Welding
  • Projection Welding
  • Flash Welding
  • Upset Welding

Q6. How does electricity help in welding?
Electricity generates localized heat either through resistance (I²Rt) or an electric arc between electrodes, which melts the base materials and forms a weld joint.

Q7. What is arc blow in welding and how to prevent it?
Arc blow is the deflection of the welding arc due to magnetic fields, common in DC welding. To prevent it:
  • Use AC welding
  • Shorten arc length
  • Adjust ground clamp position
  • Use lower current or smaller electrodes

Q8. What is the role of electrode polarity in DC welding?
  • DCRP (Reverse Polarity): Electrode positive, more heat at electrode, shallow wide welds
  • DCSP (Straight Polarity): Electrode negative, deeper welds, more heat at workpiece
  • AC Welding: Alternates polarity, combines both effects

Q9. Why are coated electrodes used in arc welding?
Coated electrodes help in:
  • Arc stabilization
  • Slag formation (protects weld)
  • Alloying compensation
  • Reducing spatter
  • Enabling AC welding by maintaining ionization

Q10. What are the advantages of DC welding machines?
DC welding machines offer:
  • Adjustable polarity
  • Compatibility with various metals
  • Suitability for different electrodes
However, they may be expensive, noisy, and prone to arc blow.

Q11. What are the benefits of using AC welding machines?
AC machines are:
  • Cost-effective
  • Low-maintenance
  • Free from arc blow
But they have fixed polarity and are less effective on cast iron or non-ferrous metals.

Q12. How is arc length important in welding quality?
A short arc length ensures:
  • Concentrated heat
  • Stable arc
  • Better protection from atmospheric gases
Whereas a long arc can cause:
  • Poor penetration
  • Porosity
  • Spatter and contamination

Q13. What is electroslag welding used for?
Electroslag welding is used for thick section welding in vertical positions. It utilizes molten slag to melt the base and filler metal for deep penetration.

Q14. What are common criteria for selecting a welding process?
Key factors include:
  • Type of metals
  • Welding cost
  • Product design
  • Production speed and technique
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