1. Arc Welding Processes

2. Lesson Objectives When you finish this lesson you will be able to: Explain similarities and difference between some of the various arc welding processes Explain flux and gas shielding methods Explain advantages and disadvantages of the arc welding processes Select between the processes Learning Activities 1.Read Handbook Pp 1-16, 2.Look up Keywords 3.View Slides; 4.Read Notes, 5.Listen to 6. lecture 7.Do on-line workbook 8.Do homework Keywords Welding Flux, Inert Shielding Gas, Shielded Metal Arc Welding (SMAW), Gas Metal Arc Welding (GMAW), Metal Transfer Mode

3. Linnert, Welding Metallurgy, AWS, 1994

4. Arc Welding Processes Welding processes that employ an electric arc are the most prevalent in industry –Shielded Metal Arc Welding –Gas Metal Arc Welding –Flux Cored Arc Welding –Submerged Arc Welding –Gas Tungsten Arc Welding These processes are associated with molten metal Electric Arc

5. Linnert, Welding Metallurgy, AWS, 1994

6. Protection of the Molten Weld Pool Molten metal reacts with the atmosphere –Oxides and nitrides are formed –Discontinuities such as porosity –Poor weld metal properties All arc welding processes employ some means of shielding the molten weld pool from the air

7. Welding Flux Three forms –Granular –Electrode wire coating –Electrode core Fluxes melt to form a protective slag over the weld pool Other purposes –Contain scavenger elements to purify weld metal –Contain metal powder added to increase deposition rate –Add alloy elements to weld metal –Decompose to form a shielding gas

8. Shielding Gas Shielding gas forms a protective atmosphere over the molten weld pool to prevent contamination Inert shielding gases, argon or helium, keep out oxygen, nitrogen, and other gases Active gases, such as oxygen and carbon dioxide, are sometimes added to improve variables such as arc stability and spatter reduction Argon HeliumOxygen Carbon Dioxide