Physics of Welding Continued

Lesson Objectives When you finish this lesson you will understand: Wire melting modes Power Supply Characteristics Interactions between the arc and the power supplies Principles of Magnetic Arc Blow Learning Activities 1.Look up Keywords 2.View Slides; 3.Read Notes, 4.Listen to lecture 5.View Hi-speed Videos 6.Do on-line workbook 7.Do Excel Tutorial Keywords Metal Transfer, Short Circuit Transfer, Pulsed Arc, Power Supply Characteristics, Open Circuit Voltage, Closed Circuit Current, Constant Voltage Power Supply, Constant Current Power Supply, Drooping Characteristic, Self Regulating Arc,Magnetic Arc Blow

Physics of Welding Heat Input Concepts Energy Sources Arc Characteristics Wire Melting

GMAW Modes of Metal Transfer Spray Globular Short CircuitingPulsed Spray Gas Metal Arc Welding

Ave I

Pulsed Arc Tandom Arc

View the Arc Welding High Speed Videos from the Video Web Page on the WE300 Website

Turn to the person sitting next to you and discuss (1 min.): From the chart showing the effect on metal transfer by changes in shielding gas it is seen that an addition of 2% oxygen to tan argon GMAW using DCEP caused the arc to stop wandering and have good spray transfer. Can you explain from a physical point of view what might have happened?

Welding Arcs and Machines

Open-Circuit Voltage

Short-Circuit Current

Electrical Stability of the Arc

Manual Arc Control

Manual Arc Control Inputs

Self-Regulation of the Arc

Processes Using Constant Current Processes Using Constant Voltage SMAW GTAW PAW Processes where humans control arc length by hand GMAW FCAW SAW Processes that use constant velocity wire feeding

Turn to the person sitting next to you and discuss (1 min.): In the V-I Characteristic Curves, there are two places where the Arc current and voltage are the same as the power supply current and voltage, one point is stable and the other is unstable. Why is the unstable point unstable?

Magnetic Arc Blow

Magnetic Flux Concentration

Next Class Period You will Have a Homework Assignment which will require the use of an Excel Spreadsheet. You should review your knowledge of Excel or click on the digging deeper tutorial. Excel Tutorial