Arc Welding Continued

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Arc Welding Continued
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Arc Welding Processes

• Learning Activities
• Look Up Keywords
• View Slides
• Read Notes,
• Listen to lecture
• View High Speed Videos
• Do demo on web
• Do on-line
• workbook

• Lesson Objectives
• When you finish this lesson you will understand
• The similarities and difference between the
  remaining arc welding processes
• Advantages and disadvantages of these arc
  welding processes
• Need to select between the processes

Keywords Gas Tungsten Arc Welding (GTAW),
Straight Polarity(SEN), Reverse Polarity (REP),
Plasma Arc Welding (PAW), Keyhole, Electrogas
(EGW), Electroslag Welding (ESW), Stud Welding,
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Gas Tungsten Arc Welding (GTAW or TIG)
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Effects of Polarity
Gas Tungsten Arc Welding
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Advantages
Gas Tungsten Arc Welding

• Superior quality welds, generally free from
  spatter, porosity, or other defects
• Precise control of arc and fusion characteristics
• Weld almost all metals
• Used with or without filler wire
• Easily automated
• Used in all positions
• Intricate geometries weldable

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Disadvantages
Gas Tungsten Arc Welding

• Less economical than consumable electrode
  processes for sections thicker than 3/8 inch
• Lowest deposition rate of all arc processes
• Tungsten inclusions
• Higher operator skill Required
• Sensitive to drafts

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Questions?

• Turn to the person sitting next to you and
  discuss (1 min.)
• In all the previous arc welding processes metal
  wire or electrodes material melts and droplets of
  metal deposit on the weldment. Some of that
  metal as it goes through the arc ionized into
  metal ions and electrons which conduct the
  electricity through the arc. In GTAW there are
  no metal ions (or very few metal ions) in the arc
  since the tungsten electrode is non-consumable.
  What carries the current in the GTAW arc?

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Plasma Arc Welding
Linnert, Welding Metallurgy, AWS, 1994
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AWS Welding Handbook Ed 8 Vol 1 1987
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Stinchcomb, Welding Technology Today, Prentice
Hall, 1989
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Advantages

• Greater Energy Concentration
• Improved arc stability over other processes
• Higher heat content, Higher travel speeds
• Greater penetration capabilities
• Finer sections can be welded with low current
  PAW than GTAW

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Disadvantages

• Operator skill required is slightly greater than
  for GTAW
• Equipment more expensive
• Orifice replacement necessary

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Videos
Take a moment this evening to view the High Speed
Videos of Arc Welding Processes on the Video
Page of the WE300 Website
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Questions?

• Turn to the person sitting next to you and
  discuss (1 min.)
• The keyhole mode of welding is used because the
  weld speed can be very fast where molten metal
  flows around the hole and collides and solidifies
  in the rear of the hole. What might happen to
  the shape of the trailing weld pool if the speed
  was increased too fast?

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Electrogas
Flux cored Shielding
AWS Welding Handbook Ed 8 Vol 1 1987
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Electrogas
AWS Welding Handbook Ed 8 Vol 1 1987
External Shielding Gas
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Electroslag
AWS Welding Handbook Ed 8 Vol 1 1987
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Advantages

• Used for thick weldments
• Produces sound welds
• Increased cost effectiveness as thickness
  increases

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Disadvantages

• Once started, the weld must continue
• Coarse grained Heat Affected Zone

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Questions?

• Turn to the person sitting next to you and
  discuss (1 min.)
• If insufficient cooling water is supplied to the
  shoes on electroslag welding what is likely to
  happen
• a.) the shoe will warp and liquid steel will flow
  out
• b.) the shoe will melt and water will be absorbed
  by the weld metal later causing delayed or cold
  cracking.
• c.) an explosion will occur

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Cary, Modern Welding Technology, 1989
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Cary, Modern Welding Technology, 1989
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Cary, Modern Welding Technology, 1989
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Demonstration
Do the Arc Weld Demonstration from the
Demonstration Web Page on the WE300 Website