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Arc Welding Continued

Arc Welding Continued. 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:

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Arc Welding Continued

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  1. Arc Welding Continued

  2. 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,

  3. Gas Tungsten Arc Welding (GTAW or TIG)

  4. Gas Tungsten Arc Welding Effects of Polarity

  5. 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

  6. 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

  7. 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?

  8. Plasma Arc Welding Linnert, Welding Metallurgy, AWS, 1994

  9. AWS Welding Handbook Ed 8 Vol 1 1987

  10. Stinchcomb, Welding Technology Today, Prentice Hall, 1989

  11. 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

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

  13. Videos Take a moment this evening to view the High Speed Videos of Arc Welding Processes on the “Video Page” of the WE300 Website

  14. 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?

  15. Electrogas Flux cored Shielding AWS Welding Handbook Ed 8 Vol 1 1987

  16. Electrogas AWS Welding Handbook Ed 8 Vol 1 1987 External Shielding Gas

  17. Electroslag AWS Welding Handbook Ed 8 Vol 1 1987

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

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

  20. 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

  21. Cary, Modern Welding Technology, 1989

  22. Cary, Modern Welding Technology, 1989

  23. Cary, Modern Welding Technology, 1989

  24. Demonstration Do the “Arc Weld Demonstration” from the Demonstration Web Page on the WE300 Website

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