difference-between-arc-welding-and-gas-welding

1. Fundamentals of Heat Generation

Arc welding relies on an electric arc struck between an electrode and the workpiece to generate intense, concentrated heat for fusion. In contrast, gas welding (oxy-fuel welding) burns a fuel gas (e.g., acetylene) mixed with oxygen to produce a flame that melts the base and filler materials.

2. Heat Source Characteristics and Temperature Profiles

  • Arc Welding

    • Heat source: Electric arc (DC or AC)

    • Arc temperature: 5 000–6 500 °C

    • Heat density: Very high, localized

  • Gas Welding

    • Heat source: Combustion flame (acetylene + O₂)

    • Flame temperature: 3 200–3 600 °C

    • Heat density: Lower, broader footprint

High arc temperatures translate into deeper penetration and narrower heat-affected zones (HAZ), while gas welding yields shallower fusion and wider HAZ.

3. Equipment Components and Setup

Component Arc Welding Gas Welding
Power source Welding power supply (transformer/inverter) None
Electrodes/filler Consumable rods (SMAW/MIG) or non-consumable tungsten (TIG) Filler rods (solid or cored)
Shielding Flux coating or inert gases (Ar, CO₂) Flame chemistry regulates oxidation
Torch/mouthpiece Welding gun or electrode holder Oxy-fuel torch with mixing chamber
Gas cylinders Protective gases (for MIG/TIG only) Oxygen and fuel gas (e.g., acetylene)
Safety gear Welding helmet, fume extraction, gloves Goggles, flame-resistant clothing, gloves
 
4. Process Parameters and Heat Input

Controlling heat input (HI) is critical for microstructure and distortion. HI for arc welding is calculated as:

HI (kJ/mm)=V×I×60S×1000×η\text{HI (kJ/mm)} = \frac{V \times I \times 60}{S \times 1000} \times \eta

Where

  • VV: arc voltage (V)

  • II: current (A)

  • SS: travel speed (mm/min)

  • η\eta: process efficiency (typically 0.6–0.8 for SMAW/MIG)

Gas welding heat input is governed by flame setting and torch speed, lacking a direct electrical formula but adjustable via oxygen/fuel ratio and torch travel.

5. Weld Pool Dynamics and Metallurgical Effects

  • Penetration and Fusion Arc welding’s high heat density yields deep fusion and a narrow weld bead. Gas welding produces a wider, shallower weld pool with slower solidification.

  • Heat-Affected Zone (HAZ) Arc welding’s narrow HAZ concentrates microstructural changes (grain coarsening) over a small region. Gas welding spreads heat, enlarging the HAZ and raising distortion risk.

  • Microstructure Rapid cooling in arc welds can form martensitic or fine bainitic structures in steels. Gas welds cool more slowly, promoting coarser ferrite–pearlite mixtures.

6. Electrode and Filler Material Selection

  • Arc Welding

    • SMAW: Rutile or basic electrodes for mild/low-alloy steel

    • MIG/TIG: Solid wires or rods—SS316, ER70S-6, ER4043 (Al)

    • Flux-cored: High-strength or all-position applications

  • Gas Welding

    • Solid rods: ER70S-2 for mild steel; ER4043 for aluminum

    • Bronze/copper-silicon for brazing steel

    • Flux-coated rods to improve wetting and slag control

Filler choice impacts weld chemistry, mechanical properties, and susceptibility to defects.

7. Shielding, Flux, and Oxidation Control

  • Arc Welding uses inert (Ar, He) or active (CO₂) shielding gases, or flux coatings, to exclude atmospheric nitrogen and oxygen—preventing porosity and embrittlement.

  • Gas Welding Flame provides limited protection; neutral flames (1:1 O₂:C₂H₂) minimize oxidation, but fore- or oxidizing flames adjust penetration and flame chemistry.

8. Mechanical Properties, Defects, and Quality Control

Aspect Arc Welding Gas Welding
Tensile strength Often > 450 MPa with proper electrodes Typically 350–450 MPa
Common defects Porosity, undercut, lack of fusion Incomplete fusion, slag inclusion, oxidation
Distortion risk Lower (narrow HAZ) Higher (wider HAZ)
Residual stress Concentrated; may require PWHT Distributed; often self-relieves
 

Non-destructive testing (UT, radiography) and post-weld heat treatment (PWHT) are more common in arc-welded structures.

9. Application Domains

  • Arc Welding:

    • Structural steel fabrication (beams, columns)

    • Shipbuilding, pipelines, pressure vessels

    • Automotive frames (MIG), aerospace components (TIG)

  • Gas Welding:

    • Sheet metal repairs, HVAC tubing

    • Brazing and soldering light alloys

    • Field repairs where power is unavailable

10. Safety and Environmental Considerations

  • Arc Welding

    • Hazards: UV/IR radiation, ozone, metal fumes

    • Controls: Helmets with auto-darkening filters, ventilation, respirators

  • Gas Welding

    • Hazards: Fire/explosion (gas leaks), CO exposure

    • Controls: Flashback arrestors, proper cylinder storage, flame-resistant PPE

11. Productivity and Cost Factors

  • Equipment Investment

    • Arc rigs (inverter-based): $1 500–$5 000

    • Oxy-fuel setup: $300–$1 200

  • Deposition Rate

    • MIG: up to 10 kg/hr

    • Gas welding: ~2 kg/hr

  • Operating Costs

    • Electricity vs. fuel gas consumption

    • Consumables pricing (electrodes vs. rods and flux)

12. Method Selection Criteria

  1. Material Type & Thickness

  2. Required Weld Strength & Toughness

  3. Distortion Tolerance

  4. Mobility & Field Conditions

  5. Operator Skill Level

  6. Cost & Throughput Targets

Conclusion

Arc welding and gas welding each excel in specific niches. Arc welding delivers high-strength joints, deep penetration, and high productivity for thick metals under controlled conditions. Gas welding remains invaluable for thin sections, on-site repairs, and brazing operations where power access is limited. Selecting the optimal method hinges on balancing metallurgical requirements, mechanical performance, cost, and environmental constraints.

QTE Technologies offers a wide range of welding machines from renowned brands. We are an international MRO provider proudly serving customers in over 180 countries. Established in 2010, we supply over 1 million products across every industry and engineering discipline. Additionally, you can reach us anytime via 24×7 chat support, phone, WhatsApp or email. Discover what our valued customers have to say about our services on our dedicated review page.

Post Author By QTE Technologies Editorial Staff (with a solid background in both technical and creative writing - accumulated 15+ years of experience).