Arc Welding Mild Steel and GMAW/GTAW Welding Unit 27 Arc Welding Mild Steel and GMAW/GTAW Welding

Safety Procedures Welding area should consist of metal benches booths made of fireproof or fire-resistant materials fire extinguishers for class a, b, and c fires safety equipment, first-aid kit, and wool fire blanket buckets of water no oil, grease, paper, sawdust, rags, or other flammable materials

Safety Procedures (continued) Personal protection #10 shade lens with safety glasses or a flip-up lens Fire-resistant coveralls High leather shoes Leather gloves Cover all exposed skin

Setting Up Pick appropriate electrode Eliminate fire hazards Gather all necessary materials Make sure the welding machine has suitable welding cables Put on safety clothing including helmet Select your amperage Be sure the metal is clean and free of any oil, grease, or rust Strike the arc

Beads A bead is produced by handling the electrode so that there is a proper mix of base and filler metal Stringer bead: made without weaving Weaving: moving the electrode back and forth (side to side) to create a wider bead

Running a Bead Electrode angle Obtain correct arc length Lean slightly in the direction of travel; usually a 75° to 80° angle (or 10° to 15° from vertical) Obtain correct arc length Move across metal at a uniform travel speed Check for correct amperage setting (semicircles should be wider than they are long) If weaving for the first time, start using a circular pattern

Butt Welds Butt joint: pieces placed end to end or edge to edge Leave a gap between the two pieces that is about the thickness of the electrode core Be sure all slag is removed between beads to ensure a solid weld without voids

Fillet Welds Fillet joint: two parts come together to form a 90-degree angle Be sure to prepare the vertical piece so the weld metal will fuse both pieces completely Follow a procedure similar to butt welds Remember that heat rises, so watch the top piece for overheating

Welding Positions Horizontal: moving horizontally across a vertical piece of metal Vertical: moving up or down across vertical piece of metal (weaving is not recommended) Overhead: the metal is positioned above the welder

Pipe When welding pipe Use E6013 Generally welded without grinding Maintain same arc length used for straight areas Flatten ends first

GMAW Welding GMAW: Gas Metal Arc Welding Uses short-circuit arc method to transfer weld material Uses thin welding rods, low current, and low voltage Welding wire is fed automatically at a constant speed Produces a short arc between base metal and wire Ideal for exhaust system work installing trailer hitches and truck bumpers repairing mechanical supports

GMAW Safety Follow manufacturer’s recommendations Check all cables and be sure equipment is properly grounded Wear protective clothing Use approved helmet Never touch electrical connections or wires while switch is on Never weld in wet locations

GMAW Safety (continued) No flammable materials in clothing pockets Handle hot metal with pliers or tongs Weld only in well-ventilated areas Do not do your own repair work on welding equipment When finished, be sure equipment is turned off and safely stored

GMAW Equipment Most equipment is semiautomatic Components shielding gas supplied by a regulator wire speed/feed control spool of electrode wire welder connected to electrical power supply work cable and clamp assembly welding gun and cable assembly

GTAW Welding GTAW: Gas Tungsten Arc Welding Used to weld very light, thin metals Originally used DC current, today most use AC current (which provides a better weld) Slower than GMAW welding Similar in some ways to oxyacetylene welding

GTAW Safety Use the same safety procedures as GMAW welding Wear hearing protection when utilizing pulsed-power and high-current settings Never touch the tungsten electrode with body parts or the filler rod Keep the settings within the limits set by the manufacturer

GTAW Equipment Three major components power supply welding gun gas cylinder with flow meter AC welding is primarily used for nonferrous metals Cups available in variety of sizes and flow rates Foot control also available Electrodes available in 1/16-, 3/32-, and 1/8-inch diameters

Plasma Arc Welding Creates an ionized gas called plasma Plasma conducts electricity and produces very intense heat in a small, concentrated area Metal melts and fuses together quickly Provides a very stable arc Makes use of low amperage currents, which allow the welding of very small instruments

Automated and Robotic Welding Newest process in welding Uses computer control and robots Used on assembly lines Very efficient and produces high-quality welds Very expensive and reserved for high-output productions

Important Terms Pad: practice metal Crater: a low spot in the metal where the force of the arc has pushed out molten metal Pass: one bead or layer of filler metal Root pass: the first and most important welding pass