Differences Between Electroslag Welding and Submerged Arc Welding

1. Arc Generation Mechanism
Electroslag Welding (ESW): The arc is initiated by current passing through a muffle arc interrupter, melting the base metal and filler wire to form the weld.
Submerged Arc Welding (SAW): The arc is generated by introducing current via an electrode coil between the workpiece and the wire.

2. Arc Sustainment
ESW: Uses a tungsten electrode to strike the arc, which requires frequent replacement due to electrode melting.
SAW: Employs an automatically fed electrode that remains intact, allowing continuous arc stability.

3. Weld Contamination Levels
ESW: High-temperature arc spatter generates excessive slag and porosity. Slag pools produce hydrogen compounds and hard inclusions.
SAW: Minimal contamination due to flux shielding, ensuring cleaner welds.

4. Welding Speed
SAW: High mechanization enables faster welding speeds.
ESW: Slower for thick plates due to operational complexity.

5. Application Scope
SAW: Preferred for high-quality structural steel welding (e.g., pipelines, H-beams).
ESW: Effective for thick plates (>25mm) and component repairs.

6. Flux Differences
a. Heat Source:
SAW: Arc heat.
ESW: Slag pool resistance heat.
b. Flux Roles:
SAW: Mechanical protection and metallurgical refinement.
ESW: Thermal conduction, protection, and impurity removal.
c. Flux Composition:
SAW: Includes molten salts, organics, and reactive gases (e.g., HJ431).
ESW: Composed of marble, quartz, fluorite, titanium dioxide, and cellulose.

7. Porosity Resistance
ESW outperforms SAW in porosity prevention due to:
a. Slag Protection: Dense slag layer blocks atmospheric gas intrusion.
b. Material Purity: ESW flux and wires are optimized for deoxidation and desulfurization.
c. Thermal Control: Slow vertical solidification (minutes vs. SAW's seconds) allows gas escape.
d. Process Stability: Lower current density (0.2–0.3 A/mm²vs SAW's 1–2 A/mm²) reduces spatter.
e. Industrial Data:
ESW porosity rate: <0.05% in nuclear vessels.
SAW porosity rate: 0.1–0.3% under similar conditions.
Key Technical Terms:
Muffle Arc Interrupter: Device for initiating ESW arcs.
Hydrogen Compounds: Byproducts in ESW slag (e.g., HF, H2).
Flux Shielding: SAW's primary contamination barrier.