Transcript No Slide Title

Arc Welding Continued
Arc Welding Processes
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
Learning Activities
1. Look Up Keywords
2. View Slides;
3. Read Notes,
4. Listen to lecture
5. View High Speed
Videos
6. Do demo on web
7. Do on-line
workbook
Keywords:
Gas Tungsten Arc Welding (GTAW), Straight Polarity(SEN),
Reverse Polarity (REP), Plasma Arc Welding (PAW), Keyhole,
Electrogas (EGW), Electroslag Welding (ESW), Stud Welding,
Gas Tungsten Arc Welding
(GTAW or TIG)
Gas Tungsten Arc Welding
Effects of Polarity
Gas Tungsten Arc Welding
Advantages
• 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
Gas Tungsten Arc Welding
Disadvantages
• 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
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?
Linnert, Welding Metallurgy,
AWS, 1994
AWS Welding Handbook
Ed 8 Vol 1 1987
Stinchcomb, Welding Technology
Today, Prentice Hall, 1989
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
Disadvantages
• Operator skill required is slightly greater than
for GTAW
• Equipment more expensive
• Orifice replacement necessary
Take a moment this evening to view the High Speed
Videos of Arc Welding Processes on the “Video
Page” of the WE300 Website
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?
Flux cored Shielding
AWS Welding Handbook
Ed 8 Vol 1 1987
External Shielding Gas
AWS Welding Handbook
Ed 8 Vol 1 1987
AWS Welding Handbook
Ed 8 Vol 1 1987
Advantages
• Used for thick weldments
• Produces sound welds
• Increased cost effectiveness as thickness increases
Disadvantages
• Once started, the weld must continue
• Coarse grained Heat Affected Zone
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
Cary, Modern Welding
Technology, 1989
Cary, Modern Welding
Technology, 1989
Cary, Modern Welding
Technology, 1989
Do the “Arc Weld Demonstration” from the
Demonstration Web Page on the WE300
Website