Flux Core Welding

Definition

• Flux core welding is an arc welding process that uses a tubular wire electrode with a flux-filled inner core.
• Officially referred to as Flux Cored Arc Welding (FCAW) by the American Welding Society.
• Equipment similar to MIG (Gas Metal Arc Welding) is used in flux core welding.

Key Components

• Wire Electrode: Fed through a wire feed unit, often requiring knurled rollers to grip the tubular wire without damage.
• Electric Arc: Forms between the wire electrode and the workpiece, heating both above their melting point to coalesce and solidify.
• Base Metal: The parts to be joined.
• Filler Metal: Metal that comes from the melting wire electrode.

Welding Process

• Flux core welding is a consumable electrode process, adding filler metal to the joint.
• The flux's role varies based on the type of flux-cored process:
  • Self Shielded (FCAW-S)
  • Gas Shielded (FCAW-G)

Types of Flux Core Welding

Self Shielded (FCAW-S)

• Contains flux protecting the molten weld pool, creating a protective cloud against gases (N2, O2).
• Advantages:
  • No need for gas shielding equipment.
  • Less sensitivity to drafts and breezes.

Gas Shielded (FCAW-G)

• Relies on secondary shielding gas for protection.
• Uses high-pressure gas cylinders (similar to MIG/TIG).
• Common gases:
  • Pure CO2
  • CO2/Argon blends
• Advantages:
  • Cost-effective CO2 for shielding.
  • High deposition rate achievable.

Slag Formation

• Both processes form a thin layer of slag that protects the weld as it cools, ensuring a consistent low-profile shape.

Machine Controls

• Most machine controls are set on the machine, including:
  • Polarity
  • Wire speed
  • Voltage
• Current: Typically Direct Current (DC).

Polarity Settings

• Self Shielded Flux Core:
  • Electrode: Negative
  • Workpiece: Positive
  • Term: DCEN (Direct Current Electrode Negative)
• Gas Shielded Flux Core:
  • Electrode: Positive
  • Workpiece: Negative
  • Term: DCEP (Direct Current Electrode Positive)

Summary

• Flux core welding is an electric arc welding process using a consumable tubular wire electrode with flux material.
• Filler material is automatically added as the electrode melts.
• Two primary types: self shielded (protection by flux) and gas shielded (protection by gas).
• Always check manufacturer recommendations for settings.