Transcript unit_27_smaw_gmaw - Waterford High School Mr.Douglas

Unit 27
Arc Welding Mild Steel and
GMAW/GTAW Welding
Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED.
Safety Procedures
• Welding area should consist of
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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
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Safety Procedures (continued)
• Personal protection
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#10 shade lens with safety glasses or a flip-up lens
Fire-resistant coveralls
High leather shoes
Leather gloves
Cover all exposed skin
Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED.
Setting Up
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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
Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED.
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
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Running a Bead
• Electrode angle
– 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
Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED.
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
Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED.
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
Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED.
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
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Pipe
• When welding pipe
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Use E6013
Generally welded without grinding
Maintain same arc length used for straight areas
Flatten ends first
Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED.
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
Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED.
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
Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED.
GMAW Safety (continued)
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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
Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED.
GMAW Equipment
• Most equipment is semiautomatic
• Components
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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
Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED.
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
Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED.
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
Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED.
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
Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED.
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
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Automated and Robotic
Welding
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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
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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
Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED.