ELECTRIC ARC WELDING DEEPAK-KUMAR C4902A-07

Introduction Electric arc welding A group of fusion welding processes that use an electric arc to produce the heat required for melting the metal. Electric arc is about 9,000 All fusion welding process have thee requirements. Heat Shielding Filler metal The method used to meet these three requirements is the primary difference between arc welding processes.

Arc Welding Requirements Filler Material Process Heat Shielding Stick Electrode SMAW Electric Arc Inert Gas (Flux) Electric Arc Inert Gas (Cylinder) Wire Electrode GMAW

Arc Welding Power Supplies The current for arc welder can be supplied by line current or by an alternator/generator. The amount of heat is determined by the current flow (amps) The ease of starting and harshness of the arc is determined by the electrical potential (volts). Welding current adjustments can include: Amperage Voltage Polarity High frequency current Wave form

Five Common Output Currents For Arc Welding 1. AC (Alternating Current) 2. DC (Direct Current) 3. ACHF (Alternating Current-High Frequency) 4. PC (Pulsed Current) 5. Square wave

TYPES OF JOINTS Five (5) joints: Corner Butt Lap Edge T

1. Surface Welds Surface welds are welds were a material has been applied to the surface of another material. May or may not be blended with the work piece. Two common applications are for hard surfacing and padding.

2. Groove Welds Groove welds are used to fuse the sides or ends of two pieces of metal. The primary use of groove welds is to complete butt joints.

3. Fillet Welds Fillet welds have a triangular cross section and are used to fuse two faces of metal that are at a 90 degree angle to each other. Lap Joint Outside Corner T Joint

Joints, Welds & Positions Arc Welding Positions Flat Horizontal Vertical Up Vertical Down Overhead

Weld Nomenclature Bead Penetration Base metal Reinforcement Joint Angle Bead Root Face Excessive Penetration Root Opening

Weld Nomenclature-cont. Reinforcement Toe Face Throat Leg Toe Root Leg

Common Defects and Causes Description Cause(s) The depth of the weld is less than specifications. Excessive heat Excessive speed. The weld metal is not completely fused to base metal or passes are not completely fused. Incorrect angle Incorrect manipulation Insufficient heat Weld material flows over, but is not fused with the base metal. Slow speed

Common Defects and Causes--cont. Description Cause(s) Weld bead does not extend to the desired depth. Low heat Long arc Incorrect joint design Small indentions in the surface of the weld Excessive gas in the weld zone. Moisture Rust Dirt Accelerated cooling Small voids throughout the weld material.

Common Defects and Causes--cont. Description Cause(s) Usually visible cracks on the surface or through the weld Accelerated cooling Constrained joint Small weld volume Cracks in the transition zone between the weld and base metal Induced hydrogen Incompatible electrode or wire Accelerated cooling Misshapen and/or uneven ripples Inconstant speed Incorrect manipulation Incorrect welder settings