Untitled Quiz

Welding Processes

• Welding is a fabrication process that joins materials using heat or pressure, or both, to produce coalescence.
• Welding Classifications:
  • Arc welding
    • Gas-metal arc welding (GMAW)
    • Gas tungsten arc welding (GTAW)
    • Shielded metal arc welding (SMAW)
    • Submerged arc welding (SAW)
  • Solid-state welding (SSW)
  • Brazing
  • Soldering
  • Thermal Spraying
  • Allied Processes
    • Oxy-fuel gas welding
    • Electric arc spraying
  • Cutting
    • Arc cutting
    • Chemical-flux cutting
    • Oxy-fuel gas cutting
    • Plasma arc cutting
    • Laser-beam cutting
    • Other

Shielded Metal Arc Welding (SMAW)

• Most common type of arc welding.
• Uses a consumable covered electrode (metal wire).
• Electrode includes a core wire surrounded by a flux coating.
• Flux melts to protect the weld area from contamination.
• Electrode also melts and combines with molten base metal as filler.

SMAW Principle and Equipment

• Electrode and workpiece form an electrical circuit.
• Two cables from power source: one to the workpiece, one to the electrode holder.
• Striking the arc: electrode slightly touches the workpiece, then pulled back.
• Initiates arc and melting, with electrode droplets moving to the weld pool.

SMAW Equipment Components

• Welding generator (DC or AC transformer)
• Two cables (one for workpiece, one for electrode)
• Ground clamp
• Electrode holder
• Protective shield
• Gloves
• Wire brush
• Chipping hammer

SMAW Polarity

• Polarity refers to the direction of current flow in a DC electrical circuit.
• Two types for DC circuit:
  • Direct current straight polarity (DCSP)
  • Direct current reverse polarity (DCRP)
• Workpiece connected to the positive side.
• Electrode attached to the negative side in DCSP.
• More power at the work end of the arc with less at electrode end in DCSP.
• In DCRP, the work is negative and the
• Electrode is positive.
• Electrode receives more of the heating effect in DCRP.

SMAW Alternating Current (AC)

• AC combines deep penetration and shallow penetration characteristics.
• Penetration depth is approximately halfway between DCSP and DCRP.

Types of Welding Joints

• Butt joint: Joining two aligned members.
• Corner joint: Joining two members at a right angle.
• Edge joint: Joining edges of two or more members lying on the same plane.
• Lap joint: One member laid over another.
• Tee joint: Two members at right angles, joined by one piece.

Types of Welds

• Fillet weld:

• Used to fill in corners, laps, and tees.

• Approximate shape of a right triangle.

• Most common type in arc and oxy-fuel welding.

• Requires minimal edge preparation.

• Groove Weld:

• Requires part edges shaped into groove for weld penetration.

• Grooved shapes include square, bevel, V, U, and J, in single or double sides.

• Most closely associated with butt joints.

Welding Defects

• Slag inclusions
• Gas porosity
• Incomplete fusion
• Incomplete penetration
• Excessive penetration
• Spatter
• Cracks
• Undercut
• Underfill

Welding Terminology

• Filler Material: Material added to space between the joint during welding
• Welding Rod: Filler metal that does not conduct electricity.
• Electrode: Conducts current from electrode holder to the metal being welded. Consumable or non-consumable.
• Consumable Electrode: Provides a current path and filler metal.
• Non-Consumable Electrode: Used as a conductor for current in certain welding styles.
• Flux: Material used to dissolve oxides and release slag. (Powder,liquid, or paste form.)
• Deposited Metal: Material in weld created by electrode or filler wire.
• Base Metal: The original piece that is welded, soldered or cut.
• Weld Metal: Portion of a weld melted during welding.
• Weld Pool: Area of a weld where the base metal has reached its melting point.
• Heat-affected zone (HAZ): Area near weld that hasn't melted, but structure or properties are changed.